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Sample records for actinic flux measurements

  1. Aerosol properties derived from spectral actinic flux measurements

    NASA Astrophysics Data System (ADS)

    Stark, H.; Schmidt, K. S.; Pilewskie, P.; Cozic, J.; Wollny, A. G.; Brock, C. A.; Baynard, T.; Lack, D.; Parrish, D. D.; Fehsenfeld, F. C.

    2008-12-01

    Measurement of aerosol properties is very important for understanding climate change. Aerosol optical properties influence solar radiation throughout the troposphere. According to the Working Group I report of the intergovernmental panel for climate change [IPCC, 2007], aerosols have a direct radiative forcing of - 0.5±0.4 W/m2 with a medium to low level of scientific understanding. This relatively large uncertainty indicates the need for more frequent and precise measurements of aerosol properties. We will show how actinic flux measurements can be used to derive important optical aerosol parameters such as aerosol optical thickness and depth, surface albedo, angstrom exponent, radiative forcing by clouds and aerosols, aerosol extinction, and others. The instrument used for this study is a combination of two spectroradiometers measuring actinic flux in the ultraviolet and visible radiation range from 280 to 690 nm with a resolution of 1 nm. Actinic flux is measured as the radiation incident on a spherical surface with sensitivity independent of direction. In contrast, irradiance is measured as the radiation incident on a plane surface, which depends on the cosine of the incident angle. Our goal is to assess the capabilities of using spectral actinic flux measurements to derive various aerosol properties. Here we will compare 1) actinic flux measurements to irradiance measurements from the spectral solar flux radiometer (SSFR), 2) derived aerosol size distributions with measurements from a white light optical particle counter (WLOPC) and ultra high sensitivity aerosol size spectrometer (UHSAS), and 3) derived aerosol optical extinction with measurements from a cavity ringdown aerosol extinction spectrometer (CRD-AES). These comparisons will utilize data from three recent field campaigns over New England and the Atlantic Ocean (ICARTT 2004), Texas and the Gulf of Mexico during (TexAQS/GoMACCS 2006), and Alaska and the Arctic Ocean (ARCPAC 2008) when the instruments

  2. Actinic flux measurements and photolysis frequencies enhancements near clouds during DC3 and TORERO

    NASA Astrophysics Data System (ADS)

    Hall, S. R.; Ullmann, K.; Schmidt, S.; Kindel, B. C.; Hair, J. W.

    2012-12-01

    Spectrally resolved up and down-welling actinic flux was measured from aircraft during the Deep Convective Clouds & Chemistry Experiment (DC3) and Tropical Ocean Troposphere Exchange of reactive halogen species and oxygenated VOC (TORERO) field campaigns. The measurements were made on the NASA DC-8 and NSF/NCAR G-V aircraft with the Charged coupled device Actinic Flux Spectroradiometer (CAFS)and the HIAPER Airborne Radiation Package (HARP), respectively. Improvements in this instrumentation and the data analysis provide for fast, accurate measurements from the aircraft. Photolysis frequencies calculated from the actinic flux show significant enhancements above clouds. The upwelling signal is enhanced by the high reflectivity of the cloud below. The downwelling is also enhanced due to backscatter of reflected light from the cloud top. Under specific conditions, including high sun and highly reflective clouds, upwelling actinic radiation may exceed the downwelling even with clear skies above. These conditions may have occurred during TORERO and DC3 resulting in regions of highly active photochemistry.

  3. Investigation of the 3-D actinic flux field in mountainous terrain

    NASA Astrophysics Data System (ADS)

    Wagner, J. E.; Angelini, F.; Blumthaler, M.; Fitzka, M.; Gobbi, G. P.; Kift, R.; Kreuter, A.; Rieder, H. E.; Simic, S.; Webb, A.; Weihs, P.

    2011-11-01

    During three field campaigns spectral actinic flux was measured from 290-500 nm under clear sky conditions in Alpine terrain and the associated O3- and NO2-photolysis frequencies were calculated and the measurement products were then compared with 1-D- and 3-D-model calculations. To do this 3-D-radiative transfer model was adapted for actinic flux calculations in mountainous terrain and the maps of the actinic flux field at the surface, calculated with the 3-D-radiative transfer model, are given. The differences between the 3-D- and 1-D-model results for selected days during the campaigns are shown, together with the ratios of the modeled actinic flux values to the measurements. In many cases the 1-D-model overestimates actinic flux by more than the measurement uncertainty of 10%. The results of using a 3-D-model generally show significantly lower values, and can underestimate the actinic flux by up to 30%. This case study attempts to quantify the impact of snow cover in combination with topography on spectral actinic flux. The impact of snow cover on the actinic flux was ~ 25% in narrow snow covered valleys, but for snow free areas there were no significant changes due snow cover in the surrounding area and it is found that the effect snow-cover at distances over 5 km from the point of interest was below 5%. Overall the 3-D-model can calculate actinic flux to the same accuracy as the 1-D-model for single points, but gives a much more realistic view of the surface actinic flux field in mountains as topography and obstruction of the horizon are taken into account.

  4. Investigation of the 3-D actinic flux field in mountainous terrain

    PubMed Central

    Wagner, J.E.; Angelini, F.; Blumthaler, M.; Fitzka, M.; Gobbi, G.P.; Kift, R.; Kreuter, A.; Rieder, H.E.; Simic, S.; Webb, A.; Weihs, P.

    2011-01-01

    During three field campaigns spectral actinic flux was measured from 290–500 nm under clear sky conditions in Alpine terrain and the associated O3- and NO2-photolysis frequencies were calculated and the measurement products were then compared with 1-D- and 3-D-model calculations. To do this 3-D-radiative transfer model was adapted for actinic flux calculations in mountainous terrain and the maps of the actinic flux field at the surface, calculated with the 3-D-radiative transfer model, are given. The differences between the 3-D- and 1-D-model results for selected days during the campaigns are shown, together with the ratios of the modeled actinic flux values to the measurements. In many cases the 1-D-model overestimates actinic flux by more than the measurement uncertainty of 10%. The results of using a 3-D-model generally show significantly lower values, and can underestimate the actinic flux by up to 30%. This case study attempts to quantify the impact of snow cover in combination with topography on spectral actinic flux. The impact of snow cover on the actinic flux was ~ 25% in narrow snow covered valleys, but for snow free areas there were no significant changes due snow cover in the surrounding area and it is found that the effect snow-cover at distances over 5 km from the point of interest was below 5%. Overall the 3-D-model can calculate actinic flux to the same accuracy as the 1-D-model for single points, but gives a much more realistic view of the surface actinic flux field in mountains as topography and obstruction of the horizon are taken into account. PMID:26412915

  5. Investigation of the three-dimensional actinic flux field in mountainous terrain

    NASA Astrophysics Data System (ADS)

    Wagner, J. E.; Angelini, F.; Blumthaler, M.; Fitzka, M.; Gobbi, J. P.; Kift, R.; Kreuter, A.; Rieder, H. E.; Webb, A.; Weihs, P.

    2010-09-01

    Spectrally resolved high quality actinic flux measurements between 290 nm and 500 nm have been performed in complex Alpine terrain under clear sky conditions. A three-dimensional Monte Carlo radiative transfer model was adapted for actinic flux calculations in mountainous terrain. This model is used to study the impact of topography and surface albedo on surface spectral actinic flux and no2- and o3-photolysis rates. This approach leads to surface maps of actinic flux and photolysis rates. The typical high spatial variability due to altitude, snow cover and shading affects is very well reproduced in the model. By running the model in three modes (realistic, without topography, with albedo zero) one gets a good estimation of the impact of topography and surface albedo.

  6. Measuring F-actin properties in dendritic spines

    PubMed Central

    Koskinen, Mikko; Hotulainen, Pirta

    2014-01-01

    During the last decade, numerous studies have demonstrated that the actin cytoskeleton plays a pivotal role in the control of dendritic spine shape. Synaptic stimulation rapidly changes the actin dynamics and many actin regulators have been shown to play roles in neuron functionality. Accordingly, defects in the regulation of the actin cytoskeleton in neurons have been implicated in memory disorders. Due to the small size of spines, it is difficult to detect changes in the actin structures in dendritic spines by conventional light microscopy imaging. Instead, to know how tightly actin filaments are bundled together, and how fast the filaments turnover, we need to use advanced microscopy techniques, such as fluorescence recovery after photobleaching (FRAP), photoactivatable green fluorescent protein (PAGFP) fluorescence decay and fluorescence anisotropy. Fluorescence anisotropy, which measures the Förster resonance energy transfer (FRET) between two GFP fluorophores, has been proposed as a method to measure the level of actin polymerization. Here, we propose a novel idea that fluorescence anisotropy could be more suitable to study the level of actin filament bundling instead of actin polymerization. We validate the method in U2OS cell line where the actin structures can be clearly distinguished and apply to analyze how actin filament organization in dendritic spines changes during neuronal maturation. In addition to fluorescence anisotropy validation, we take a critical look at the properties and limitations of FRAP and PAGFP fluorescence decay methods and offer our proposals for the analysis methods for these approaches. These three methods complement each other, each providing additional information about actin dynamics and organization in dendritic spines. PMID:25140131

  7. Heat flux measurements

    NASA Technical Reports Server (NTRS)

    Liebert, Curt H.; Weikle, Donald H.

    1989-01-01

    A new automated, computer controlled heat flux measurement facility is described. Continuous transient and steady-state surface heat flux values varying from about 0.3 to 6 MW/sq m over a temperature range of 100 to 1200 K can be obtained in the facility. An application of this facility is the development of heat flux gauges for continuous fast transient surface heat flux measurement on turbine blades operating in space shuttle main engine turbopumps. The facility is useful for durability testing at fast temperature transients.

  8. Measuring Actin Flow in 3D Cell Protrusions

    PubMed Central

    Chiu, Chi-Li; Digman, Michelle A.; Gratton, Enrico

    2013-01-01

    Actin dynamics is important in determining cell shape, tension, and migration. Methods such as fluorescent speckle microscopy and spatial temporal image correlation spectroscopy have been used to capture high-resolution actin turnover dynamics within cells in two dimensions. However, these methods are not directly applicable in 3D due to lower resolution and poor contrast. Here, we propose to capture actin flow in 3D with high spatial-temporal resolution by combining nanoscale precise imaging by rapid beam oscillation and fluctuation spectroscopy techniques. To measure the actin flow along cell protrusions in cell expressing actin-eGFP cultured in a type I collagen matrix, the laser was orbited around the protrusion and its trajectory was modulated in a clover-shaped pattern perpendicularly to the protrusion. Orbits were also alternated at two positions closely spaced along the protrusion axis. The pair cross-correlation function was applied to the fluorescence fluctuation from these two positions to capture the flow of actin. Measurements done on nonmoving cellular protrusion tips showed no pair-correlation at two orbital positions indicating a lack of flow of F-actin bundles. However, in some protrusions, the pair-correlation approach revealed directional flow of F-actin bundles near the protrusion surface with flow rates in the range of ∼1 μm/min, comparable to results in two dimensions using fluorescent speckle microscopy. Furthermore, we found that the actin flow rate is related to the distance to the protrusion tip. We also observed collagen deformation by concomitantly detecting collagen fibers with reflectance detection during these actin motions. The implementation of the nanoscale precise imaging by rapid beam oscillation method with a cloverleaf-shaped trajectory in conjunction with the pair cross-correlation function method provides a quantitative way of capturing dynamic flows and organization of proteins during cell migration in 3D in conditions of

  9. Quantitative fluorescent speckle microscopy (QFSM) to measure actin dynamics.

    PubMed

    Mendoza, Michelle C; Besson, Sebastien; Danuser, Gaudenz

    2012-10-01

    Quantitative fluorescent speckle microscopy (QFSM) is a live-cell imaging method to analyze the dynamics of macromolecular assemblies with high spatial and temporal resolution. Its greatest successes were in the analysis of actin filament and adhesion dynamics in the context of cell migration and microtubule dynamics in interphase and the meiotic/mitotic spindle. Here, focus is on the former application to illustrate the procedures of FSM imaging and the computational image processing that extracts quantitative information from these experiments. QFSM is advantageous over other methods because it measures the movement and turnover kinetics of the actin filament (F-actin) network in living cells across the entire field of view. Experiments begin with the microinjection of fluorophore-labeled actin into cells, which generate a low ratio of fluorescently labeled to endogenously unlabeled actin monomers. Spinning disk confocal or wide-field imaging then visualizes fluorophore clusters (two to eight actin monomers) within the assembled F-actin network as speckles. QFSM software identifies and computationally tracks and utilizes the location, appearance, and disappearance of speckles to derive network flows and maps of the rate of filament assembly and disassembly. PMID:23042526

  10. 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).

  11. Influence of clouds on the spectral actinic flux density in the lower troposphere (INSPECTRO): overview of the field campaigns

    NASA Astrophysics Data System (ADS)

    Thiel, S.; Ammannato, L.; Bais, A.; Bandy, B.; Blumthaler, M.; Bohn, B.; Engelsen, O.; Gobbi, G. P.; Gröbner, J.; Jäkel, E.; Junkermann, W.; Kazadzis, S.; Kift, R.; Kjeldstad, B.; Kouremeti, N.; Kylling, A.; Mayer, B.; Monks, P. S.; Reeves, C. E.; Schallhart, B.; Scheirer, R.; Schmidt, S.; Schmitt, R.; Schreder, J.; Silbernagl, R.; Topaloglou, C.; Thorseth, T. M.; Webb, A. R.; Wendisch, M.; Werle, P.

    2008-03-01

    Ultraviolet radiation is the key factor driving tropospheric photochemistry. It is strongly modulated by clouds and aerosols. A quantitative understanding of the radiation field and its effect on photochemistry is thus only possible with a detailed knowledge of the interaction between clouds and radiation. The overall objective of the project INSPECTRO was the characterization of the three-dimensional actinic radiation field under cloudy conditions. This was achieved during two measurement campaigns in Norfolk (East Anglia, UK) and Lower Bavaria (Germany) combining space-based, aircraft and ground-based measurements as well as simulations with the one-dimensional radiation transfer model UVSPEC and the three-dimensional radiation transfer model MYSTIC. During both campaigns the spectral actinic flux density was measured at several locations at ground level and in the air by up to four different aircraft. This allows the comparison of measured and simulated actinic radiation profiles. In addition satellite data were used to complete the information of the three dimensional input data set for the simulation. A three-dimensional simulation of actinic flux density data under cloudy sky conditions requires a realistic simulation of the cloud field to be used as an input for the 3-D radiation transfer model calculations. Two different approaches were applied, to derive high- and low-resolution data sets, with a grid resolution of about 100 m and 1 km, respectively. The results of the measured and simulated radiation profiles as well as the results of the ground based measurements are presented in terms of photolysis rate profiles for ozone and nitrogen dioxide. During both campaigns all spectroradiometer systems agreed within ±10% if mandatory corrections e.g. stray light correction were applied. Stability changes of the systems were below 5% over the 4 week campaign periods and negligible over a few days. The J(O1D) data of the single monochromator systems can be

  12. Influence of clouds on the spectral actinic flux density in the lower troposphere (INSPECTRO): overview of the field campaigns

    NASA Astrophysics Data System (ADS)

    Thiel, S.; Ammannato, L.; Bais, A.; Bandy, B.; Blumthaler, M.; Bohn, B.; Engelsen, O.; Gobbi, G. P.; Gröbner, J.; Jäkel, E.; Junkermann, W.; Kazadzis, S.; Kift, R.; Kjeldstad, B.; Kouremeti, N.; Kylling, A.; Mayer, B.; Monks, P. S.; Reeves, C. E.; Schallhart, B.; Scheirer, R.; Schmidt, S.; Schmitt, R.; Schreder, J.; Silbernagl, R.; Topaloglou, C.; Thorseth, T. M.; Webb, A. R.; Wendisch, M.; Werle, P.

    2007-09-01

    Ultraviolet radiation is the key factor driving tropospheric photochemistry. It is strongly modulated by clouds and aerosols. A quantitative understanding of the radiation field and its effect on photochemistry is thus only possible with a detailed knowledge of the interaction between clouds and radiation. The overall objective of the project INSPECTRO was the characterization of the three-dimensional actinic radiation field under cloudy conditions. This was achieved during two measurement campaigns in Norfolk (East Anglia, UK) and Lower Bavaria (Germany) combining space-based, aircraft and ground-based measurements as well as simulations with the one-dimensional radiation transfer model UVSPEC and the three-dimensional radiation transfer model MYSTIC. During both campaigns the spectral actinic flux density was measured at several locations at ground level and in the air by up to four different aircraft. This allows the comparison of measured and simulated actinic radiation profiles. In addition satellite data were used to complete the information of the three dimensional input data set for the simulation. A three-dimensional simulation of actinic flux density data under cloudy sky conditions requires a realistic simulation of the cloud field to be used as an input for the 3-D radiation transfer model calculations. Two different approaches were applied, to derive high- and low-resolution data sets, with a grid resolution of about 100 m and 1 km, respectively. The results of the measured and simulated radiation profiles as well as the results of the ground based measurements are presented in terms of photolysis rate profiles for ozone and nitrogen dioxide. During both campaigns all spectroradiometer systems agreed within ±10% if mandatory corrections e.g. stray light correction were applied. Stability changes of the systems were below 5% over the 4 week campaign periods and negligible over a few days. The J(O1D) data of the single monochromator systems can be

  13. Fast two-stream method for computing diurnal-mean actinic flux in vertically inhomogeneous atmospheres

    NASA Technical Reports Server (NTRS)

    Filyushkin, V. V.; Madronich, S.; Brasseur, G. P.; Petropavlovskikh, I. V.

    1994-01-01

    Based on a derivation of the two-stream daytime-mean equations of radiative flux transfer, a method for computing the daytime-mean actinic fluxes in the absorbing and scattering vertically inhomogeneous atmosphere is suggested. The method applies direct daytime integration of the particular solutions of the two-stream approximations or the source functions. It is valid for any duration of period of averaging. The merit of the method is that the multiple scattering computation is carried out only once for the whole averaging period. It can be implemented with a number of widely used two-stream approximations. The method agrees with the results obtained with 200-point multiple scattering calculations. The method was also tested in runs with a 1-km cloud layer with optical depth of 10, as well as with aerosol background. Comparison of the results obtained for a cloud subdivided into 20 layers with those obtained for a one-layer cloud with the same optical parameters showed that direct integration of particular solutions possesses an 'analytical' accuracy. In the case of the source function interpolation, the actinic fluxes calculated above the one-layer and 20-layer clouds agreed within 1%-1.5%, while below the cloud they may differ up to 5% (in the worst case). The ways of enhancing the accuracy (in a 'two-stream sense') and computational efficiency of the method are discussed.

  14. Heat-Flux-Measuring Facility

    NASA Technical Reports Server (NTRS)

    Liebert, Curt H.; Weikle, Donald H.

    1990-01-01

    Apparatus simulates conditions in turbine engines. Automated facility generates and measures transient and steady-state heat fluxes at flux densities from 0.3 to 6 MW/m(Sup2) and temperatures from 100 to 1,200 K. Positioning arm holds heat-flux gauge at focal point of arc lamp. Arm previously chilled gauge in liquid nitrogen in Dewar flask. Cooling water flows through lamp to heat exchanger. Used to develop heat-flux gauges for turbine blades and to test materials for durability under rapidly changing temperatures.

  15. Measuring surface fluxes in CAPE

    NASA Technical Reports Server (NTRS)

    Kanemasu, E. T.; D-Shah, T.; Nie, Dalin

    1992-01-01

    Two stations (site 1612 and site 2008) were operated by the University of Georgia group from 6 July 1991 to 18 August 1991. The following data were collected continuously: surface energy fluxes (i.e., net radiation, soil heat fluxes, sensible heat flux and latent heat flux), air temperature, vapor pressure, soil temperature (at 1 cm depth), and precipitation. Canopy reflectance and light interception data were taken three times at each site between 6 July and 18 August. Soil moisture content was measured twice at each site.

  16. The influence of the spatial resolution of topographic input data on the accuracy of 3-D UV actinic flux and irradiance calculations

    NASA Astrophysics Data System (ADS)

    Weihs, P.; Wagner, J. E.; Schreier, S. F.; Rieder, H. E.; Angelini, F.; Blumthaler, M.; Fitzka, M.; Gobbi, G. P.; Kift, R.; Kreuter, A.; Simic, S.; Webb, A. R.

    2012-03-01

    The aim of this study is to investigate the influence of the spatial resolution of a digital elevation map (DEM) on the three-dimensional (3-D) radiative transfer performance for both spectral ultraviolet (UV) irradiance and actinic flux at 305 nm. Model simulations were performed for clear sky conditions for three case studies: the first and second one using three sites in the Innsbruck area and the third one using three sites at the Sonnblick observatory and surrounding area. It was found that the DEM resolution may change the altitude at some locations by up to 500 m, resulting in changes in the sky obscured by the horizon of up to 15%. The geographical distribution of UV irradiance and actinic flux shows that with larger pixel size, uncertainties in UV irradiance and actinic flux determination of up to 100% are possible. These large changes in incident irradiance and actinic flux with changing pixel size are strongly connected to shading effects. The effect of the DEM pixel size on irradiance and actinic flux was studied at the six locations, and it was found that significant increases in irradiance and actinic flux with increasing DEM pixel size occurred at one valley location at high solar zenith angles in the Innsbruck area as well as for one steep valley location in the Sonnblick area. This increase in irradiance and actinic flux with increasing DEM resolution is most likely to be connected to shading effects affecting the reflections from the surroundings.

  17. The influence of the spatial resolution of topographic input data on the accuracy of 3-D UV actinic flux and irradiance calculations

    NASA Astrophysics Data System (ADS)

    Weihs, P.; Wagner, J. E.; Schreier, S. F.; Rieder, H. E.; Angelini, F.; Blumthaler, M.; Fitzka, M.; Gobbi, G. P.; Kift, R.; Kreuter, A.; Simic, S.; Webb, A. R.

    2011-10-01

    The aim of this study was to investigate the influence of the spatial resolution of a digital elevation map (DEM) on the three-dimensional (3-D) radiative transfer performance for both spectral ultraviolet (UV) irradiance and actinic flux at 305 nm. Model simulations were performed for clear sky conditions for three case studies: the first and second one using three sites in the Innsbruck area and the third one using three sites at the Sonnblick Observatory and surrounding area. It was found that DEM resolution may change the altitude at some locations by up to 500 m, resulting in changes in the sky obscured by the horizon of up to 15%. The geographical distribution of UV irradiance and actinic flux shows that with larger pixel size, uncertainties in UV irradiance and actinic flux determination of up to 100% are possible. These large changes in incident irradiance and actinic flux with changing pixel size are strongly connected to shading effects. The effect of DEM pixel size on irradiance and actinic flux was studied at the six locations, and it was found that significant increases in irradiance and actinic flux with increasing DEM pixel size occurred at one valley location at high solar zenith angles in the Innsbruck area as well as for one steep valley location in the Sonnblick area. This increase in irradiance and actinic flux with increasing DEM resolution is most likely to be connected to shading effects affecting the reflections from the surroundings.

  18. Association between tensin 1 and p130Cas at focal adhesions links actin inward flux to cell migration

    PubMed Central

    Zhao, Zhihai; Tan, Song Hui; Machiyama, Hiroaki; Kawauchi, Keiko; Araki, Keigo; Hirata, Hiroaki; Sawada, Yasuhiro

    2016-01-01

    ABSTRACT Cell migration is a highly dynamic process that plays pivotal roles in both physiological and pathological processes. We have previously reported that p130Cas supports cell migration through the binding to Src as well as phosphorylation-dependent association with actin retrograde flow at focal adhesions. However, it remains elusive how phosphorylated Cas interacts with actin cytoskeletons. We observe that the actin-binding protein, tensin 1, co-localizes with Cas, but not with its phosphorylation-defective mutant, at focal adhesions in leading regions of migrating cells. While a truncation mutant of tensin 1 that lacks the phosphotyrosine-binding PTB and SH2 domains (tensin 1-SH2PTB) poorly co-localizes or co-immunoprecitates with Cas, bacterially expressed recombinant tensin 1-SH2PTB protein binds to Cas in vitro in a Cas phosphorylation-dependent manner. Furthermore, exogenous expression of tensin 1-SH2PTB, which is devoid of the actin-interacting motifs, interferes with the Cas-driven cell migration, slows down the inward flux of Cas molecules, and impedes the displacement of Cas molecules from focal adhesions. Taken together, our results show that tensin 1 links inwardly moving actin cytoskeletons to phosphorylated Cas at focal adhesions, thereby driving cell migration. PMID:27029899

  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. 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...

  1. Apparatus for measuring a flux of neutrons

    DOEpatents

    Stringer, James L.

    1977-01-01

    A flux of neutrons is measured by disposing a detector in the flux and applying electronic correlation techniques to discriminate between the electrical signals generated by the neutron detector and the unwanted interfering electrical signals generated by the incidence of a neutron flux upon the cables connecting the detector to the electronic measuring equipment at a remote location.

  2. 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.

  3. 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.

  4. Diamagnetic flux measurement in Aditya tokamak

    SciTech Connect

    Kumar, Sameer; Jha, Ratneshwar; Lal, Praveen; Hansaliya, Chandresh; Gopalkrishna, M. V.; Kulkarni, Sanjay; Mishra, Kishore

    2010-12-15

    Measurements of diamagnetic flux in Aditya tokamak for different discharge conditions are reported for the first time. The measured diamagnetic flux in a typical discharge is less than 0.6 mWb and therefore it has required careful compensation for various kinds of pick-ups. The hardware and software compensations employed in this measurement are described. We introduce compensation of a pick-up due to plasma current of less than 20 kA in short duration discharges, in which plasma pressure gradient is supposed to be negligible. The flux measurement during radio frequency heating is also presented in order to validate compensation.

  5. 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.

  6. 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.

  7. 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.

  8. Eddy Correlation Flux Measurement System Handbook

    SciTech Connect

    Cook, D. R.

    2016-01-01

    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. The instruments used are: • a fast-response, three-dimensional (3D) wind sensor (sonic anemometer) to obtain the orthogonal wind components and the speed of sound (SOS) (used to derive the air temperature) • an open-path infrared gas analyzer (IRGA) to obtain the water vapor density and the CO2 concentration, and • an open-path infrared gas analyzer (IRGA) to obtain methane density and methane flux at one SGP EF and at the NSA CF. The ECOR systems are deployed at the locations where other methods for surface flux measurements (e.g., energy balance Bowen ratio [EBBR] systems) are difficult to employ, primarily at the north edge of a field of crops. A Surface Energy Balance System (SEBS) has been installed collocated with each deployed ECOR system in SGP, NSA, Tropical Western Pacific (TWP), ARM Mobile Facility 1 (AMF1), and ARM Mobile Facility 2 (AMF2). The surface energy balance system consists of upwelling and downwelling solar and infrared radiometers within one net radiometer, a wetness sensor, and soil measurements. The SEBS measurements allow the comparison of ECOR sensible and latent heat fluxes with the energy balance determined from the SEBS and provide information on wetting of the sensors for data quality purposes. The SEBS at one SGP and one NSA site also support upwelling and downwelling PAR measurements to qualify those two locations as Ameriflux sites.

  9. Radiative flux measurements in the troposphere

    NASA Technical Reports Server (NTRS)

    Valero, F. P. J.; Gore, W. J. Y.; Giver, L. P. M.

    1982-01-01

    A new airborne radiometric system with a time resolution as high as 60 msec has been designed for measuring radiative fluxes in the atmosphere. To verify the instrument performance, the solar constant at the top of the atmosphere has been calculated using the radiative flux densities measured in the troposphere, and the result obtained has been found to agree with the standard value to within 4%. Total heating rates of 0.175 and 0.377 K/h have been determined for hazy and foggy atmospheres, respectively, and aerosol heating rates of 0.065 and 0.235 K/h have been deduced from the total heating rates.

  10. Dual neutron flux/temperature measurement sensor

    DOEpatents

    Mihalczo, John T.; Simpson, Marc L.; McElhaney, Stephanie A.

    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.

  11. Velocity of movement of actin filaments in in vitro motility assay. Measured by fluorescence correlation spectroscopy.

    PubMed Central

    Borejdo, J; Burlacu, S

    1992-01-01

    We have measured the velocity of actin filaments in in vitro motility assay by fluorescence correlation spectroscopy. In this method, one measures fluctuations in the number of filaments in an open sample volume. The number of filaments was calculated from measurements of fluorescence of rhodamine-phalloidin bound to F-actin. Sample volume was defined by a diaphragm placed in front of the photomultiplier. Fluctuations arise when actin filaments enter and leave the sample volume due to translations driven by mechanochemical interactions with myosin heads which are immobilized on a glass surface. The average velocity of the translation of filaments determined by the correlation method, (Vc), was equal to the diameter of the diaphragm divided by the half-time of the relaxation of fluctuations. The average number of moving filaments determined by correlation method, (Nc), was inversely proportional to the relative fluctuations. By the fluctuation method it was possible to determine the average velocity of over 800 moving filaments in less than 4 min. There was good agreement between (Vc) and (Nc) and the average velocity and the average number of moving filaments determined manually. To be able to apply correlation measurements to an experimental problem, neither (Vc) nor (Nc) must depend on the position of observation of filaments. We first confirmed that this was indeed the case. We then applied the method to investigate the dependence of motility on the ATPase activity of myosin heads. ATPase activity was varied by mixing intact heads with heads which were labeled with different thiol reagents. It was found that the motion was drastically influenced by the reagent used for modification. When the reagent was N-ethyl-maleimide, 1.5% modification was sufficient to completely inhibit the motion. When the reagent was 5-iodoacetamidofluorescein, motion declined hyperbolically with the fraction of modified heads. Images FIGURE 2 FIGURE 4 FIGURE 11 PMID:1534696

  12. Actinic Keratosis

    MedlinePlus

    ... rashes clinical tools newsletter | contact Share | Actinic Keratosis (Solar Keratosis) Information for adults A A A Actinic ... the touch. Overview Actinic keratoses, also known as solar keratoses, are small rough or scaly areas of ...

  13. Instruments for measuring radiant thermal fluxes

    NASA Technical Reports Server (NTRS)

    Gerashenko, O. A.; Sazhina, S. A.

    1974-01-01

    An absolute two-sided radiometer, designed on the principle of replacing absorbed radiant energy with electrical energy, is described. The sensitive element of the detector is a thermoelectric transducer of thermal flux. The fabrication technology, methods of measurement, technical characteristics, and general operation of the instrument are presented.

  14. Interplanetary magnetic flux - Measurement and balance

    NASA Technical Reports Server (NTRS)

    Mccomas, D. J.; Gosling, J. T.; Phillips, J. L.

    1992-01-01

    A new method for determining the approximate amount of magnetic flux in various solar wind structures in the ecliptic (and solar rotation) plane is developed using single-spacecraft measurements in interplanetary space and making certain simplifying assumptions. The method removes the effect of solar wind velocity variations and can be applied to specific, limited-extent solar wind structures as well as to long-term variations. Over the 18-month interval studied, the ecliptic plane flux of coronal mass ejections was determined to be about 4 times greater than that of HFDs.

  15. Plasma momentum meter for momentum flux measurements

    DOEpatents

    Zonca, Fulvio; Cohen, Samuel A.; Bennett, Timothy; Timberlake, John R.

    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. Whole Cell Model of Actin Diffusion and Reaction based on Single Molecule Speckle Microscopy Measurements

    NASA Astrophysics Data System (ADS)

    McMillen, Laura; Vavylonis, Dimitrios; Vavylonis Group Team

    It is debated whether transport of actin across the cell by diffusion alone is sufficiently fast to account for the rapid reorganization of actin filaments at the leading edge of motile cells. In order to investigate this question, we created a 3D model of the whole cell that includes reaction and diffusion of actin using a particle Monte Carlo method. For the lamellipodium of the simulated cell we use the model by Smith et al. Biophys. J 104:247 (2013), which includes two diffuse pools of actin, one which is slowly diffusing and the other which diffuses more quickly, as well as a pool of filamentous actin undergoing retrograde flow towards the cell center. We adjusted this model to fit a circular geometry around the whole cell. We also consider actin in the cell center which is either diffusing or in stationary filamentous form, representing cortical actin or actin in stress fibers. The local rates of polymerization and the lifetime distributions of polymerized actin were estimated from single molecule speckle microscopy experiments by the group of N. Watanabe. With this model we are able to simulate prior experiments that monitored the redistribution of actin after photoactivation or fluorescence recovery after photobleaching in various parts of the cell. We find that transport by diffusion is sufficient to fit these data, without the need for an active transport mechanism, however significant concentration gradients may develop at steady state.

  17. 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.

  18. Observational biases in flux magnification measurements

    NASA Astrophysics Data System (ADS)

    Hildebrandt, H.

    2016-02-01

    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 multiband photometric mock catalogues of Lyman-break galaxies in a CFHTLenS (Canada France Hawaii Telescope Lensing Survey)-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 source sample in different photometric bands is to magnification including the same observational effects. Again we find significant deviations from simple analytical estimates. We also discover a wavelength-dependence of the magnitude-shift effect when applied to a colour-selected noisy source sample. Such an effect can mimic the reddening by dust in the lens. It has to be disentangled from the dust extinction before the magnitude shift/colour-excess can be used to measure the distribution of either dark matter or extragalactic dust. Using simulations like the ones presented here these observational effects can be studied and eventually removed from observations making precise measurements of flux magnification possible.

  19. Quantitative Analysis of Approaches to Measure Cooperative Phosphate Release in Polymerized Actin

    PubMed Central

    Burnett, Mark M.; Carlsson, Anders E.

    2012-01-01

    We use stochastic simulations that treat several experimental probes of actin dynamics to explore the extent to which phosphate dissociation in filamentous actin may be cooperative. Phosphate time-courses from polymerization and copolymerization experiments of ATP- and ADP-actin are studied, including the effects of variations in filament-number concentration as well as single-filament depolymerization time-courses. We find that highly cooperative models are consistent with the treated experimental data. We also find that some types of experiments that are believed to provide strong constraints on the cooperativity of actin hydrolysis models do not provide such constraints. PMID:23283236

  20. 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...

  1. Untangling Autophagy Measurements: All Fluxed Up

    PubMed Central

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

    2015-01-01

    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 as 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 in data interpretation, in order to illustrate the challenges. Finally we will discuss methods to assess autophagy in vivo and in patients. PMID:25634973

  2. Actinic keratosis

    MedlinePlus

    Solar keratosis; Sun-induced skin changes - keratosis; Keratosis - actinic (solar) ... Some actinic keratoses become squamous cell skin cancer . Have your health care provider look at all skin growths as soon as you find them. Your provider will ...

  3. Measuring fast calcium fluxes in cardiomyocytes.

    PubMed

    Golebiewska, Urszula; Scarlata, Suzanne

    2011-01-01

    Cardiomyocytes have multiple Ca(2+) fluxes of varying duration that work together to optimize function (1,2). Changes in Ca(2+) activity in response to extracellular agents is predominantly regulated by the phospholipase Cβ- Gα(q;) pathway localized on the plasma membrane which is stimulated by agents such as acetylcholine (3,4). We have recently found that plasma membrane protein domains called caveolae(5,6) can entrap activated Gα(q;)(7). This entrapment has the effect of stabilizing the activated state of Gα(q;) and resulting in prolonged Ca(2+) signals in cardiomyocytes and other cell types(8). We uncovered this surprising result by measuring dynamic calcium responses on a fast scale in living cardiomyocytes. Briefly, cells are loaded with a fluorescent Ca(2+) indicator. In our studies, we used Ca(2+) Green (Invitrogen, Inc.) which exhibits an increase in fluorescence emission intensity upon binding of calcium ions. The fluorescence intensity is then recorded for using a line-scan mode of a laser scanning confocal microscope. This method allows rapid acquisition of the time course of fluorescence intensity in pixels along a selected line, producing several hundreds of time traces on the microsecond time scale. These very fast traces are transferred into excel and then into Sigmaplot for analysis, and are compared to traces obtained for electronic noise, free dye, and other controls. To dissect Ca(2+) responses of different flux rates, we performed a histogram analysis that binned pixel intensities with time. Binning allows us to group over 500 traces of scans and visualize the compiled results spatially and temporally on a single plot. Thus, the slow Ca(2+) waves that are difficult to discern when the scans are overlaid due to different peak placement and noise, can be readily seen in the binned histograms. Very fast fluxes in the time scale of the measurement show a narrow distribution of intensities in the very short time bins whereas longer Ca(2+) waves

  4. Flux measurements using the BATSE spectroscopic detectors

    NASA Technical Reports Server (NTRS)

    Mcnamara, Bernard

    1993-01-01

    Among the Compton Gama-Ray Observatory instruments, the BATSE Spectroscopic Detectors (SD) have the distinction of being able to detect photons of energies less than about 20 keV. This is an interesting energy range for the examination of low mass X-ray binaries (LMXB's). In fact, Sco X-1, the prototype LMXB, is easily seen even in the raw BATSE spectroscopic data. The all-sky coverage afforded by these detectors offers a unique opportunity to monitor this source over time periods never before possible. The aim of this investigation was to test a number of ways in which both continous and discrete flux measurements can be obtained using the BATSE spectroscopic datasets. A instrumental description of a SD can be found in the Compton Workshop of Apr. 1989, this report will deal only with methods which can be used to analyze its datasets. Many of the items discussed below, particularly in regard to the earth occultation technique, have been developed, refined, and applied by the BATSE team to the reduction of BATSE LAD data. Code written as part of this project utilizes portions of that work. The following discussions will first address issues related to the reduction of SD datasets using the earth occultation technique. It will then discuss methods for the recovery of the flux history of strong sources while they are above the earth's limb. The report will conclude with recommended reduction procedures.

  5. 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.

  6. Large Area Lunar Dust Flux Measurement Instrument

    NASA Technical Reports Server (NTRS)

    Corsaro, R.; Giovane, F.; Liou, Jer-Chyi; Burchell, M.; Stansbery, Eugene; Lagakos, N.

    2009-01-01

    The instrument under development is designed to characterize the flux and size distribution of the lunar micrometeoroid and secondary ejecta environment. When deployed on the lunar surface, the data collected will benefit fundamental lunar science as well as enabling more reliable impact risk assessments for human lunar exploration activities. To perform this task, the instrument requirements are demanding. It must have as large a surface area as possible to sample the very sparse population of the larger potentially damage-inducing micrometeorites. It must also have very high sensitivity to enable it to measure the flux of small (<10 micron) micrometeorite and secondary ejecta dust particles. To be delivered to the lunar surface, it must also be very low mass, rugged and stow compactly. The instrument designed to meet these requirements is called FOMIS. It is a large-area thin film under tension (i.e. a drum) with multiple fiber optic displacement (FOD) sensors to monitor displacements of the film. This sensor was chosen since it can measure displacements over a wide dynamic range: 1 cm to sub-Angstrom. A prototype system was successfully demonstrated using the hypervelocity impact test facility at the University of Kent (Canterbury, UK). Based on these results, the prototype system can detect hypervelocity (approx.5 km/s) impacts by particles as small as 2 microns diameter. Additional tests using slow speeds find that it can detect secondary ejecta particles (which do not penetrate the film) with momentums as small as 15 pico-gram 100m/s, or nominally 5 microns diameter at 100 m/s.

  7. 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...

  8. Measurement of local high-level, transient surface heat flux

    NASA Technical Reports Server (NTRS)

    Liebert, Curt H.

    1988-01-01

    This study is part of a continuing investigation to develop methods for measuring local transient surface heat flux. A method is presented for simultaneous measurements of dual heat fluxes at a surface location by considering the heat flux as a separate function of heat stored and heat conducted within a heat flux gage. Surface heat flux information is obtained from transient temperature measurements taken at points within the gage. Heat flux was determined over a range of 4 to 22 MW/sq m. It was concluded that the method is feasible. Possible applications are for heat flux measurements on the turbine blade surfaces of space shuttle main engine turbopumps and on the component surfaces of rocket and advanced gas turbine engines and for testing sensors in heat flux gage calibrators.

  9. AmeriFlux Measurement Component (AMC) Handbook

    SciTech Connect

    Reichl, K.; Biraud, S. C.

    2016-01-01

    An AMC system was installed at the Atmospheric Radiation Measurement (ARM) Climate Research Facility’s North Slope Alaska (NSA) Barrow site, also known as NSA C1 at the ARM Data Archive, in August 2012. A second AMC system was installed at the third ARM Mobile Facility deployment at Oliktok Point, also known as NSA M1. This in situ system consists of 12 combination soil temperature and volumetric water content (VWC) reflectometers and one set of upwelling and downwelling PAR sensors, all deployed within the fetch of the Eddy Correlation Flux Measurement System. Soil temperature and VWC sensors placed at two depths (10 and 30 cm below the vegetation layer) at six locations (or microsites) allow soil property inhomogeneity to be monitored across a landscape. The soil VWC and temperature sensors used at NSA C1 are the Campbell Scientific CS650L and the sensors at NSA M1 use the Campbell Scientific CS655. The two sensors are nearly identical in function, and vendor specifications are based on the CS650 unless otherwise stated.

  10. 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.

  11. A comparison of new measurements of total monoterpene flux with improved measurements of speciated monoterpene flux

    NASA Astrophysics Data System (ADS)

    Lee, A.; Schade, G. W.; Holzinger, R.; Goldstein, A. H.

    2005-02-01

    Many monoterpenes have been identified in forest emissions using gas chromatography (GC). Until now, it has been impossible to determine whether all monoterpenes are appropriately measured using GC techniques. We used a proton transfer reaction mass spectrometer (PTR-MS) coupled with the eddy covariance (EC) technique to measure mixing ratios and fluxes of total monoterpenes above a ponderosa pine plantation. We compared PTR-MS-EC results with simultaneous measurements of eight speciated monoterpenes, β-pinene, α-pinene, 3-carene, d-limonene, β-phellandrene, α-terpinene, camphene, and terpinolene, made with an automated, in situ gas chromatograph with flame ionization detectors (GC-FID), coupled to a relaxed eddy accumulation system (REA). Monoterpene mixing ratios and fluxes measured by PTR-MS averaged 30±2.3% and 31±9.2% larger than by GC-FID, with larger mixing ratio discrepancies between the two techniques at night than during the day. Two unidentified peaks that correlated with β-pinene were resolved in the chromatograms and completely accounted for the daytime difference and reduced the nighttime mixing ratio difference to 20±2.9%. Measurements of total monoterpenes by PTR-MS-EC indicated that GC-FID-REA measured the common, longer-lived monoterpenes well, but that additional terpenes were emitted from the ecosystem that represented an important contribution to the total mixing ratio above the forest at night.

  12. A comparison of new measurements of total monoterpene flux with improved measurements of speciated monoterpene flux

    NASA Astrophysics Data System (ADS)

    Lee, A.; Schade, G. W.; Holzinger, R.; Goldstein, A. H.

    2004-12-01

    Many monoterpenes have been identified in forest emissions using gas chromatography (GC). Until now, it has been impossible to determine whether all monoterpenes are appropriately measured using GC techniques. We used a proton transfer reaction mass spectrometer (PTR-MS) coupled with the eddy covariance (EC) technique to measure mixing ratios and fluxes of total monoterpenes above a ponderosa pine plantation. We compared PTR-MS-EC results with simultaneous measurements of eight speciated monoterpenes, β-pinene, α-pinene, 3-carene, d-limonene, β-phellandrene, α-terpinene, camphene, and terpinolene, made with an automated, in situ gas chromatograph with flame ionization detectors (GC-FID), coupled to a relaxed eddy accumulation system (REA). Monoterpene mixing ratios and fluxes measured by PTR-MS averaged 30±2.3% and 31±9.2% larger than by GC-FID, with larger differences at night than during the day. Four unidentified peaks that correlated with β-pinene were resolved in the chromatograms and completely accounted for the daytime difference and reduced the nighttime difference to 19±3.4%. Measurements of total monoterpenes by PTR-MS-EC indicated that GC-FID-REA measured the common, longer-lived monoterpenes well, but that additional monoterpenes were emitted from the ecosystem that represented an important contribution to the total mixing ratio above the forest at night, and that must have been oxidized during the day before they escaped the forest canopy.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. Regulation of water flow by actin-binding protein-induced actin gelatin.

    PubMed Central

    Ito, T; Suzuki, A; Stossel, T P

    1992-01-01

    Actin filaments inhibit osmotically driven water flow (Ito, T., K.S. Zaner, and T.P. Stossel. 1987. Biophys. J. 51: 745-753). Here we show that the actin gelation protein, actin-binding protein (ABP), impedes both osmotic shrinkage and swelling of an actin filament solution and reduces markedly the concentration of actin filaments required for this inhibition. These effects depend on actin filament immobilization, because the ABP concentration that causes initial impairment of water flow by actin filaments corresponds to the gel point measured viscometrically and because gelsolin, which noncovalently severs actin filaments, solates actin gels and restores water flow in a solution of actin cross-linked by ABP. Since ABP gels actin filaments in the periphery of many eukaryotic cells, such actin networks may contribute to physiological cell volume regulation. PMID:1318095

  18. 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.

  19. A technique for simultaneous measurement of force and overlap between single muscle filaments of myosin and actin.

    PubMed

    Kalganov, Albert; Novinger, Rowan; Rassier, Dilson E

    2010-12-17

    In this study, we show a method for direct measurements of force and simultaneous visualization of isolated muscle filaments. Single actin filaments isolated from chicken skeletal muscle and single thick filaments isolated from Mussels were imaged using fluorescence and dark field microscopy, respectively. Force generated by the filaments was measured using micro-fabricated cantilevers. Force values were in the range observed previously with myosin filaments and molecules. The results suggest that the technique can be used to investigate many issues of interest and debate in the field of muscle biophysics. PMID:21081114

  20. Actinic keratosis

    MedlinePlus

    ... example, if you work outdoors) Had many severe sunburns early in life Are older Symptoms Actinic keratosis ... and tanning salons. Other things to know about sun exposure: Sun exposure is stronger in or near surfaces ...

  1. Actinic Cheilitis

    MedlinePlus

    ... is a precancerous condition related to cumulative lifetime sun exposure. The lower lip is most often affected. Individuals ... Wearing barrier clothing (eg, wide-brimmed hats) and sunscreen-containing lip balms can aid in preventing actinic ...

  2. Non-contact heat flux measurement using a transparent sensor

    NASA Technical Reports Server (NTRS)

    Ng, Daniel; Spuckler, Charles M.

    1993-01-01

    A working non-contact heat flux sensor was demonstrated using a transparent material (sapphire) and a multiwavelength pyrometer. The pyrometer is used to measure the temperatures of the two surfaces of the sensor from the spectrum of radiation originating from them. The heat conducted through the material is determined from the temperature difference of the two surfaces and the thermal conductivity of the material. The measured heat flux is equal to the incident heat flux within experimental error indicating that no calibration would be necessary. A steady state heat flux of 100 kW/sq m was easily achieved.

  3. The measurement of surface heat flux using the Peltier effect

    SciTech Connect

    Shewen, E.C. ); Hollands, K.G.T., Raithby, G.D. )

    1989-08-01

    Calorimetric methods for measuring surface heat flux use Joulean heating to keep the surface isothermal. This limits them to measuring the heat flux of surfaces that are hotter than their surroundings. Presented in this paper is a method whereby reversible Peltier effect heat transfer is used to maintain this isothermality, making it suitable for surfaces that are either hotter or colder than the surroundings. The paper outlines the theory for the method and describes physical models that have been constructed, calibrated, and tested. The tested physical models were found capable of measuring heat fluxes with an absolute accuracy of 1 percent over a wide range of temperature (5-50C) and heat flux (15-500 W/m{sup 2}), while maintaining isothermality to within 0.03 K. A drawback of the method is that it appears to be suited only for measuring the heat flux from thick metallic plates.

  4. Real-time diamagnetic flux measurements on ASDEX Upgrade.

    PubMed

    Giannone, L; Geiger, B; Bilato, R; Maraschek, M; Odstrčil, T; Fischer, R; Fuchs, J C; McCarthy, P J; Mertens, V; Schuhbeck, K H

    2016-05-01

    Real-time diamagnetic flux measurements are now available on ASDEX Upgrade. In contrast to the majority of diamagnetic flux measurements on other tokamaks, no analog summation of signals is necessary for measuring the change in toroidal flux or for removing contributions arising from unwanted coupling to the plasma and poloidal field coil currents. To achieve the highest possible sensitivity, the diamagnetic measurement and compensation coil integrators are triggered shortly before plasma initiation when the toroidal field coil current is close to its maximum. In this way, the integration time can be chosen to measure only the small changes in flux due to the presence of plasma. Two identical plasma discharges with positive and negative magnetic field have shown that the alignment error with respect to the plasma current is negligible. The measured diamagnetic flux is compared to that predicted by TRANSP simulations. The poloidal beta inferred from the diamagnetic flux measurement is compared to the values calculated from magnetic equilibrium reconstruction codes. The diamagnetic flux measurement and TRANSP simulation can be used together to estimate the coupled power in discharges with dominant ion cyclotron resonance heating. PMID:27250425

  5. Quantifying the "chamber effect" in CO2 flux measurements

    NASA Astrophysics Data System (ADS)

    Vihermaa, Leena; Childs, Amy; Long, Hazel; Waldron, Susan

    2014-05-01

    The significance of aquatic CO2 emissions has received attention in recent years. For example annual aquatic emissions in the Amazon basin have been estimated as 500 Mt of carbon1. Methods for determining the flux rates include eddy covariance flux tower measurements, flux estimates calculated from partial pressure of CO2 (pCO2) in water and the use floating flux chambers connected to an infra-red gas analyser. The flux chamber method is often used because it is portable, cheaper and allows smaller scale measurements. It is also a direct method and hence avoids problems related to the estimation of the gas transfer coefficient that is required when fluxes are calculated from pCO2. However, the use of a floating chamber may influence the flux measurements obtained. The chamber shields the water underneath from effects of wind which could lead to lower flux estimates. Wind increases the flux rate by i) causing waves which increase the surface area for efflux, and ii) removing CO2 build up above the water surface, hence maintaining a higher concentration gradient. Many floating chambers have an underwater extension of the chamber below the float to ensure better seal to water surface and to prevent any ingress of atmospheric air when waves rock the chamber. This extension may cause additional turbulence in flowing water and hence lead to overestimation of flux rates. Some groups have also used a small fan in the chamber headspace to ensure thorough mixing of air in the chamber. This may create turbulence inside the chamber which could increase the flux rate. Here we present results on the effects of different chamber designs on the detected flux rates. 1Richey et al. 2002. Outgassing from Amazonian rivers and wetlands as a large tropical source of atmospheric CO2. Nature 416: 617-620.

  6. 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

  7. 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.

  8. Footprint prediction of scalar fluxes - Reliability and implications for airborne flux measurements over the FIFE site

    NASA Technical Reports Server (NTRS)

    Schuepp, P. H.; Desjardins, R. L.; Macpherson, J. I.; Leclerc, M. Y.

    1990-01-01

    Estimates of the location and extension of the upwind ground area that affects flux observations most directly are examined to determine the reliability of airborne versus near-ground flux measurements. The theoretical issues regarding the 'footprint' are examined, and specific observations are analyzed by studying the data over a grid regarding sensible heat, latent heat, CO2, and greenness. The grid is footprint-corrected to correlate better with independently observed surface characteristics, and an optimized footprint is developed that satisfies the relationships between the observed variables. Optimized mapping of the surface flux is given which demonstrates the importance of considering local advection to correlate airborne and ground-based flux observations. The technique is particularly applicable to situations in which significant variations in the surface flux density exist.

  9. 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)

  10. Validating CERES Radiative Fluxes in the Arctic with Airborne Radiative Flux Measurements from the ARISE Campaign

    NASA Astrophysics Data System (ADS)

    Corbett, J.; Bucholtz, A.; Kato, S.; Rose, F. G.; Smith, W. L., Jr.

    2015-12-01

    The Clouds and the Earth's Radiant Energy System (CERES) instruments on board NASA's Terra, Aqua, and Soumi-NPP satellites provide the only measurements of reflected solar shortwave and emitted longwave radiative flux over the Arctic. Various methods have shown the uncertainty of CERES fluxes over sea ice to be higher than other scene types. However validation against an independent radiative flux measurement has never been attempted. We present here an attempt to better quantify the uncertainty of time-and-space averaged CERES flux measurements using airborne measurements from the Arctic Radiation - IceBridge Sea Ice Experiment (ARISE). The ARISE campaign took place during September of 2014 based out of Fairbanks, Alaska, with most of the measurements taken in the vicinity of the sea ice edge between 125°W and 150°W, and 71°N to 77°N. For six of the flights, measurements were taken in a lawnmower type pattern over either 100 x 200 km box regions at a constant altitude of >6 km, or 100 x 100 km box regions at an altitude of between 200 m to 500 m. They were designed to resemble the CERES Level 3 spatial averaging grids, and were located and timed to coincide with a high number of CERES overpasses. On board the aircraft were a set of upward and downward facing shortwave and longwave broadband radiometers (BBR), along with other instruments measuring meteorological conditions and cloud properties. We have compared the broadband radiative fluxes from BBR with those from CERES for the three days where the aircraft was flying the high altitude pattern. We use the Fu-Liou radiative transfer model to account for differences in the measurement altitude between BBR and CERES. We will present results of the comparisons between the computed fluxes and the measured longwave and shortwave radiative fluxes.

  11. Measurements of EUV coronal holes and open magnetic flux

    SciTech Connect

    Lowder, C.; Qiu, J.; Leamon, R.; Liu, Y.

    2014-03-10

    Coronal holes are regions on the Sun's surface that map the footprints of open magnetic field lines. We have developed an automated routine to detect and track boundaries of long-lived coronal holes using full-disk extreme-ultraviolet (EUV) images obtained by SOHO/EIT, SDO/AIA, and STEREO/EUVI. We measure coronal hole areas and magnetic flux in these holes, and compare the measurements with calculations by the potential field source surface (PFSS) model. It is shown that, from 1996 through 2010, the total area of coronal holes measured with EIT images varies between 5% and 17% of the total solar surface area, and the total unsigned open flux varies between (2-5)× 10{sup 22} Mx. The solar cycle dependence of these measurements is similar to the PFSS results, but the model yields larger hole areas and greater open flux than observed by EIT. The AIA/EUVI measurements from 2010-2013 show coronal hole area coverage of 5%-10% of the total surface area, with significant contribution from low latitudes, which is under-represented by EIT. AIA/EUVI have measured much enhanced open magnetic flux in the range of (2-4)× 10{sup 22} Mx, which is about twice the flux measured by EIT, and matches with the PFSS calculated open flux, with discrepancies in the location and strength of coronal holes. A detailed comparison between the three measurements (by EIT, AIA-EUVI, and PFSS) indicates that coronal holes in low latitudes contribute significantly to the total open magnetic flux. These low-latitude coronal holes are not well measured with either the He I 10830 line in previous studies, or EIT EUV images; neither are they well captured by the static PFSS model. The enhanced observations from AIA/EUVI allow a more accurate measure of these low-latitude coronal holes and their contribution to open magnetic flux.

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

    NASA Astrophysics Data System (ADS)

    LaDelfe, Peter C.; Weber, Paul G.; Rodriguez, C. William

    1995-02-01

    The hemispherical optimized net radiometer (HONER) is an instrument under development at the Los Alamos National Laboratory as part of the Atmospheric Radiation measurements/Unmanned Aerospace Vehicles (ARM/UAV) program. HONER is a radiometer which will either measure directly the difference between the total upwelling and downwelling fluxes or the individual fluxes and will provide a means of measuring the atmospheric radiative flux divergence. Unlike existing instruments which only 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 the two relevant spectral bands; one covering the solar dominated region from less than 0.4 micrometer to approximately 4 micrometers and the other covering the region from approximately 4 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 describe the basic design and operation of the sensor head and the on-board reference sources as well as the means of the initial deployment on a UAV. This instrument can also be used in ground-based, space, or other airborne applications.

  13. Actinic reticuloid

    SciTech Connect

    Marx, J.L.; Vale, M.; Dermer, P.; Ragaz, A.; Michaelides, P.; Gladstein, A.H.

    1982-09-01

    A 58-year-old man has his condition diagnosed as actinic reticuloid on the basis of clinical and histologic findings and phototesting data. He had clinical features resembling mycosis fungoides in light-exposed areas. Histologic findings disclosed a bandlike infiltrate with atypical mononuclear cells in the dermis and scattered atypical cells in the epidermis. Electron microscopy disclosed mononuclear cells with bizarre, convoluted nuclei, resembling cerebriform cells of Lutzner. Phototesting disclosed a diminished minimal erythemal threshold to UV-B and UV-A. Microscopic changes resembling actinic reticuloid were reproduced in this patient 24 and 72 hours after exposure to 15 minimal erythemal doses of UV-B.

  14. 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.

  15. Determining Maximum Glycolytic Capacity Using Extracellular Flux Measurements

    PubMed Central

    Mookerjee, Shona A.; Nicholls, David G.; Brand, Martin D.

    2016-01-01

    Measurements of glycolytic rate and maximum glycolytic capacity using extracellular flux analysis can give crucial information about cell status and phenotype during normal operation, development of pathology, differentiation, and malignant transformation. They are also of great use when assessing the effects of chemical or drug treatments. Here, we experimentally define maximum glycolytic capacity, demonstrate how it differs from glycolytic rate, and provide a protocol for determining the basal glycolytic rate and maximum glycolytic capacity in cells using extracellular flux measurements. The results illustrate the power of extracellular flux analysis to describe the energetics of adherent cells in culture in a fully quantitative way. PMID:27031845

  16. Measurement of magnetic fluctuation-induced particle flux (invited)

    SciTech Connect

    Ding, W. X.; Brower, D. L.; Yates, T. Y.

    2008-10-15

    Magnetic field fluctuation-induced particle transport has been directly measured in the high-temperature core of the MST reversed field pinch plasma. Measurement of radial particle transport is achieved by combining various interferometry techniques, including Faraday rotation, conventional interferometry, and differential interferometry. It is observed that electron convective particle flux and its divergence exhibit a significant increase during a sawtooth crash. In this paper, we describe the basic techniques employed to determine the particle flux.

  17. Measuring Regional CO2 Fluxes Using a Lagrangian Approach

    NASA Astrophysics Data System (ADS)

    Martins, D. K.; Sweeney, C.; Stirm, B. H.; Shepson, P. B.

    2008-12-01

    The difficulty of measuring regional fluxes of CO2 has limited our understanding of the global carbon budget and the processes controlling carbon exchange across politically relevant spatial scales. A Lagrangian experiment was conducted over Iowa on June 19, 2007 as part of the North American Carbon Program's Mid-Continent Intensive using a light-weight, cost-effective aircraft to measure a net drawdown of CO2 concentration within the boundary layer. The drawdown is related to photosynthetic uptake when emission footprints are considered using a combination of emission inventories from the Vulcan project and HYSPLIT source contributions. Entrainment through the top of the boundary layer is measured directly using turbulence measurements from an onboard probe capable of measuring winds in 3-dimensions. Results show a total average CO2 flux of -5.3±0.7 μmol m-2 s-1. The average flux from fossil fuels over the measurement area is 2.8±0.4 μmol m-2 s-1. Thus, the CO2 flux attributable to the vegetation is -8.1±0.8 μmol m-2 s-1. The magnitude of the vegetative flux is comparable to other studies using the Lagrangian approach, but it is smaller than tower- based eddy covariance fluxes over the same period and measurement area. Sensitivities to analysis procedures and discrepancies between aircraft and tower-based measurements are discussed. We describe an aircraft Lagrangian experiment that offers direct, reliable, and cost-effective means for measuring CO2 fluxes at regional scales that can be used to compare to ecosystem models or to satellite measurements.

  18. 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.

  19. A simple laboratory system for diffusive radon flux measurements

    NASA Astrophysics Data System (ADS)

    Kranrod, C.; Chanyotha, S.; Tonlublao, S.; Burnett, W. C.

    2015-05-01

    This study designed a simple, custom-made system to estimate the diffusive radon flux from solid materials (e.g., sediments, soils, building materials). Determination of the radon flux is based on the measurement of the radon activity in the air over time inside a closed loop system. For sediments, the system consists of wet sediment and water inside a gas-tight flask connected in a closed loop to a drying system and a radon analyzer (Durridge RAD7). The flux is determined based on an initial slope method in which the slope of radon activities vs. time plot during the first 12 h is evaluated. The slope is then multiplied by the total air volume and divided by the exposed sediment area to obtain the radon flux. The minimal thickness or mass of wet sediment should be about 4 cm or (equivalent to approximately 150 g of wet sediment) to obtain a reliable radon diffusive flux in this study.

  20. Contaminant discharge and uncertainty estimates from passive flux meter measurements

    NASA Astrophysics Data System (ADS)

    Klammler, Harald; Hatfield, Kirk; GuimarãEs da Luz, Joana AngéLica; Annable, Michael D.; Newman, Mark; Cho, Jaehyun; Peacock, Aaron; Stucker, Valerie; Ranville, James; Cabaniss, Steven A.; Rao, P. S. C.

    2012-02-01

    The passive flux meter (PFM) measures local cumulative water and contaminant fluxes at an observation well. Conditional stochastic simulation accounting for both spatial correlation and data skewness is introduced to interpret passive flux meter observations in terms of probability distributions of discharges across control planes (transects) of wells. An estimator of the effective number of independent data is defined and applied in the development of two significantly simpler approximate methods for estimating discharge distributions. One method uses a transformation of the t statistic to account for data skewness and the other method is closely related to the classic bootstrap. The approaches are demonstrated with passive flux meter data from two field sites (a trichloroethylene [TCE] plume at Ft. Lewis, WA, and a uranium plume at Rifle, CO). All methods require that the flux heterogeneity is sufficiently represented by the data and maximum differences in discharge quantile estimates between methods are ˜7%.

  1. 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.

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

    NASA Astrophysics Data System (ADS)

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

    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.

  3. 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

  4. Radiative flux measurements in the stratosphere

    NASA Technical Reports Server (NTRS)

    Valero, Francisco P. J.

    1990-01-01

    The objective is to determine how the stratospheric tropospheric exchange of water vapor is affected by the interaction of solar (visible) and planetary (infrared) radiation with tropical cumulonimbus anvils. This research involves field measurements from the ER-2 aircraft as well as radiative transfer modelling to determine heating and cooling rates and profiles that directly affect the exchange between the troposphere and the stratosphere.

  5. Cosmological flux noise and measured noise power spectra in SQUIDs

    PubMed Central

    Beck, Christian

    2016-01-01

    The understanding of the origin of 1/f magnetic flux noise commonly observed in superconducting devices such as SQUIDs and qubits is still a major unsolved puzzle. Here we discuss the possibility that a significant part of the observed low-frequency flux noise measured in these devices is ultimately seeded by cosmological fluctuations. We consider a theory where a primordial flux noise field left over in unchanged form from an early inflationary or quantum gravity epoch of the universe intrinsically influences the phase difference in SQUIDs and qubits. The perturbation seeds generated by this field can explain in a quantitatively correct way the form and amplitude of measured low-frequency flux noise spectra in SQUID devices if one takes as a source of fluctuations the primordial power spectrum of curvature fluctuations as measured by the Planck collaboration. Our theoretical predictions are in excellent agreement with recent low-frequency flux noise measurements of various experimental groups. Magnetic flux noise, so far mainly considered as a nuisance for electronic devices, may thus contain valuable information about fluctuation spectra in the very early universe. PMID:27320418

  6. Cosmological flux noise and measured noise power spectra in SQUIDs

    NASA Astrophysics Data System (ADS)

    Beck, Christian

    2016-06-01

    The understanding of the origin of 1/f magnetic flux noise commonly observed in superconducting devices such as SQUIDs and qubits is still a major unsolved puzzle. Here we discuss the possibility that a significant part of the observed low-frequency flux noise measured in these devices is ultimately seeded by cosmological fluctuations. We consider a theory where a primordial flux noise field left over in unchanged form from an early inflationary or quantum gravity epoch of the universe intrinsically influences the phase difference in SQUIDs and qubits. The perturbation seeds generated by this field can explain in a quantitatively correct way the form and amplitude of measured low-frequency flux noise spectra in SQUID devices if one takes as a source of fluctuations the primordial power spectrum of curvature fluctuations as measured by the Planck collaboration. Our theoretical predictions are in excellent agreement with recent low-frequency flux noise measurements of various experimental groups. Magnetic flux noise, so far mainly considered as a nuisance for electronic devices, may thus contain valuable information about fluctuation spectra in the very early universe.

  7. Cosmological flux noise and measured noise power spectra in SQUIDs.

    PubMed

    Beck, Christian

    2016-01-01

    The understanding of the origin of 1/f magnetic flux noise commonly observed in superconducting devices such as SQUIDs and qubits is still a major unsolved puzzle. Here we discuss the possibility that a significant part of the observed low-frequency flux noise measured in these devices is ultimately seeded by cosmological fluctuations. We consider a theory where a primordial flux noise field left over in unchanged form from an early inflationary or quantum gravity epoch of the universe intrinsically influences the phase difference in SQUIDs and qubits. The perturbation seeds generated by this field can explain in a quantitatively correct way the form and amplitude of measured low-frequency flux noise spectra in SQUID devices if one takes as a source of fluctuations the primordial power spectrum of curvature fluctuations as measured by the Planck collaboration. Our theoretical predictions are in excellent agreement with recent low-frequency flux noise measurements of various experimental groups. Magnetic flux noise, so far mainly considered as a nuisance for electronic devices, may thus contain valuable information about fluctuation spectra in the very early universe. PMID:27320418

  8. Measurement of thermal fluxes in power plant components

    SciTech Connect

    Stradomskii, M.V.; Fedorova, O.V.; Maksimov, E.A.

    1985-12-01

    The authors present a method of recovering the thermal flux acting on a sensing element with respect to measurements of sensing element signals. The solution of such problems is prompted by the need for information on the actual values of the energy density entering parts of various power plants. The dynamics of temperatures at the sensing element surfaces in a thermal flux data unit is shown during start up from cold of a power plant. The variation in time of the thermal flux density is also shown as calculated by the proposed method.

  9. 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.

  10. Effects of F/G-actin ratio and actin turn-over rate on NADPH oxidase activity in microglia

    PubMed Central

    2010-01-01

    Background Most in vivo studies that have addressed the role of actin dynamics in NADPH oxidase function in phagocytes have used toxins to modulate the polymerization state of actin and mostly effects on actin has been evaluated by end point measurements of filamentous actin, which says little about actin dynamics, and without consideration for the subcellular distribution of the perturbed actin cytoskeleton. Results Here, we in addition to toxins use conditional expression of the major actin regulatory protein LIM kinase-1 (LIMK1), and shRNA knock-down of cofilin to modulate the cellular F/G-actin ratio in the Ra2 microglia cell line, and we use Fluorescence Recovery after Photobleaching (FRAP) in β-actin-YFP-transduced cells to obtain a dynamic measure of actin recovery rates (actin turn-over rates) in different F/G-actin states of the actin cytoskeleton. Our data demonstrate that stimulated NADPH oxidase function was severely impaired only at extreme actin recovery rates and F/G-actin ratios, and surprisingly, that any moderate changes of these parameters of the actin cytoskeleton invariably resulted in an increased NADPH oxidase activity. Conclusion moderate actin polymerization and depolymerization both increase the FMLP and PMA-stimulated NADPH oxidase activity of microglia, which is directly correlated with neither actin recovery rate nor F/G- actin ratio. Our results indicate that NADPH oxidase functions in an enhanced state of activity in stimulated phagocytes despite widely different states of the actin cytoskeleton. PMID:20825680

  11. Passive hyporheic flux meter - measuring nitrate flux to the reactive sites in the river bed

    NASA Astrophysics Data System (ADS)

    Kunz, Julia Vanessa; Borchardt, Dietrich; Rode, Michael; Annable, Michael

    2015-04-01

    Most European lowland rivers are afflicted by high nitrate loads, modified morphology and discharge regulations, resulting in restricted capacity to retain nitrate. In those nutrient saturated rivers, sediment bound denitrification is the only process by which nitrate is removed from the system. Despite the importance of the hyporheic zone in nutrient reduction we are lacking detailed information on the transport to and retention at those reactive sites. Passive flux meters have successfully been used to measure contaminant transport to aquifers (eg Cho and Annable 2007). Here we present how a modification of those samplers can be used to quantify nitrate flux to and intermediate storage patterns in the interstices of an agriculturally impacted river. Installed in the river bed sediments, water flux and nutrient quantities passing through the device are recorded. While the amount of water flux serves as an index for connectivity of the hyporheic zone (exchange surface-subsurface water) the nitrate flux through the device can be seen as the portion of nitrate subjected to denitrification. The generated data on solute behavior in hyporheic zones are the missing puzzle to in-stream nitrate dynamics. Complementing flume and tracer experiments our approach depicts how discharge, morphology and sediment characteristics control the denitrification rate via the connectivity of the hyporheic zone. Passive hyporheic flux meter are a novel method to directly asses the quantity of removed nitrate by an in situ experiment.

  12. Distributed Sensible Heat Flux Measurements for Wireless Sensor Networks

    NASA Astrophysics Data System (ADS)

    Huwald, H.; Brauchli, T.; Lehning, M.; Higgins, C. W.

    2015-12-01

    The sensible heat flux component of the surface energy balance is typically computed using eddy covariance or two point profile measurements while alternative approaches such as the flux variance method based on convective scaling has been much less explored and applied. Flux variance (FV) certainly has a few limitations and constraints but may be an interesting and competitive method in low-cost and power limited wireless sensor networks (WSN) with the advantage of providing spatio-temporal sensible heat flux over the domain of the network. In a first step, parameters such as sampling frequency, sensor response time, and averaging interval are investigated. Then we explore the applicability and the potential of the FV method for use in WSN in a field experiment. Low-cost sensor systems are tested and compared against reference instruments (3D sonic anemometers) to evaluate the performance and limitations of the sensors as well as the method with respect to the standard calculations. Comparison experiments were carried out at several sites to gauge the flux measurements over different surface types (gravel, grass, water) from the low-cost systems. This study should also serve as an example of spatially distributed sensible heat flux measurements.

  13. Flux measurement and modeling in a typical mediterranean vineyard

    NASA Astrophysics Data System (ADS)

    Marras, Serena; Bellucco, Veronica; Pyles, David R.; Falk, Matthias; Sirca, Costantino; Duce, Pierpaolo; Snyder, Richard L.; Tha Paw U, Kyaw; Spano, Donatella

    2014-05-01

    Vineyard ecosystems are typical in the Mediterranean area, since wine is one of the most important economic sectors. Nevertheless, only a few studies have been conducted to investigate the interactions between this kind of vegetation and the atmosphere. These information are important both to understand the behaviour of such ecosystems in different environmental conditions, and are crucial to parameterize crop and flux simulation models. Combining direct measurements and modelling can obtain reliable estimates of surface fluxes and crop evapotranspiration. This study would contribute both to (1) directly measure energy fluxes and evapotranspiration in a typical Mediterranean vineyard, located in the South of Sardinia (Italy), through the application of the Eddy Covariance micrometeorological technique and to (2) evaluate the land surface model ACASA (Advanced-Canopy-Atmosphere-Soil Algorithm) in simulating energy fluxes and evapotranspiration over vineyard. Independent datasets of direct measurements were used to calibrate and validate model results during the growing period. Statistical analysis was performed to evaluate model performance and accuracy in predicting surface fluxes. Results will be showed as well as the model capability to be used for future studies to predict energy fluxes and crop water requirements under actual and future climate.

  14. 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.

  15. Absolute photon-flux measurements in the vacuum ultraviolet

    NASA Technical Reports Server (NTRS)

    Samson, J. A. R.; Haddad, G. N.

    1974-01-01

    Absolute photon-flux measurements in the vacuum ultraviolet have extended to short wavelengths by use of rare-gas ionization chambers. The technique involves the measurement of the ion current as a function of the gas pressure in the ion chamber. The true value of the ion current, and hence the absolute photon flux, is obtained by extrapolating the ion current to zero gas pressure. Examples are given at 162 and 266 A. The short-wavelength limit is determined only by the sensitivity of the current-measuring apparatus and by present knowledge of the photoionization processes that occur in the rate gases.

  16. Auroral Energy and Energy Flux Measurements using GUVI

    NASA Astrophysics Data System (ADS)

    Holley, K. E.; McHarg, M. G.; Paxton, L.; Zhang, Y.; Morrison, D.

    2003-12-01

    We present estimates of the average characteristic energy and energy flux of energetic precipitating auroral particles. These estimates are derived from irradiance data measured on the Global Ultraviolet Imager (GUVI) flying on the TIMED satellite. We will present both the average and standard deviation of global maps of the energy and energy flux during the first year of GUVI data. We will compare results of the GUVI derived measurements to previous estimates of Hardy who used in-situ particle measurements from the Defense Meteorological Support Satellite (DMSP) program.

  17. Uncertainties Associated with Flux Measurements Due to Heterogeneous Contaminant Distributions

    EPA Science Inventory

    Mass flux and mass discharge measurements at contaminated sites have been applied to assist with remedial management, and can be divided into two broad categories: point-scale measurement techniques and pumping methods. Extrapolation across un-sampled space is necessary when usi...

  18. Monitoring of MNSR operation by measuring subcritical photoneutron flux.

    PubMed

    Haddad, Kh; Alsomel, N

    2011-03-01

    Passive nondestructive assay methods are used to monitor the reactor's operation. It is required for nuclear regulatory, calculation validation and safeguards purposes. So, it plays a vital role in the safety and security of the nuclear plants. The possibility of MNSR operation monitoring by measuring the subcritical state photoneutron flux were investigated in this work. The photoneutron flux is induced by the fuels hard gamma radiation in the beryllium reflector. Theoretical formulation and experimental tests were performed. The results show that within a specified cooling time range, the photoneutron flux is induced by a single dominant hard gamma emitter such as (117)Cd (activation product) and (140)Ba ((140)La fission product). This phenomenon was utilized to monitor the cooling time and the operation neutron flux during the last campaign. Thus a passive nondestructive assay method is proposed with regard to the reactor operation's monitoring. PMID:21168337

  19. Direct measurements of CO2 flux in the Greenland Sea

    NASA Astrophysics Data System (ADS)

    Lauvset, Siv K.; McGillis, Wade R.; Bariteau, Ludovic; Fairall, C. W.; Johannessen, Truls; Olsen, Are; Zappa, Christopher J.

    2011-06-01

    During summer 2006 eddy correlation CO2 fluxes were measured in the Greenland Sea using a novel system set-up with two shrouded LICOR-7500 detectors. One detector was used exclusively to determine, and allow the removal of, the bias on CO2 fluxes due to sensor motion. A recently published correction method for the CO2-H2O cross-correlation was applied to the data set. We show that even with shrouded sensors the data require significant correction due to this cross-correlation. This correction adjusts the average CO2 flux by an order of magnitude from -6.7 × 10-2 mol m-2 day-1 to -0.61 × 10-2 mol m-2 day-1, making the corrected fluxes comparable to those calculated using established parameterizations for transfer velocity.

  20. 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.

  1. Measurement of Decoherence Time in a Flux Qubit

    NASA Astrophysics Data System (ADS)

    Harrabi, K.; Yoshihara, F.; Nakamura, Y.; Tsai, J. S.

    2006-09-01

    We present a measurement of the relaxation and the dephasing times in a flux qubit. In order to improve coherence of the qubit, two external parameters were optimized: the applied flux through the qubit loop and the bias current of the SQUID which serves as a readout device of the qubit state. At the optimal point the dephasing time measured with spin-echo technique was twice longer than the energy relaxation time. By changing one of the two bias parameters while keeping the other at the optimal value, one can separate the contribution of the noise in each parameter to the decoherence of the qubit.

  2. Calorimeter probes for measuring high thermal flux. [in arc jets

    NASA Technical Reports Server (NTRS)

    Russell, L. D.

    1979-01-01

    Expendable, slug-type calorimeter probes were developed for measuring high heat-flux levels of 10-30 kW/sq cm in electric-arc jet facilities. The probes were constructed with thin tungsten caps mounted on Teflon bodies. The temperature of the back surface of the tungsten cap is measured, and its time rate of change gives the steady-state absorbed heat flux as the calorimeter probe heats to destruction when inserted into the arc jet. Design, construction, test, and performance data are presented.

  3. 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.

  4. Measuring diffuse neutrino fluxes with IceCube

    NASA Astrophysics Data System (ADS)

    Kowalski, Marek

    2005-05-01

    In this paper the sensitivity of a future kilometre-sized neutrino detector to detect and measure the diffuse flux of high energy neutrinos is evaluated. Event rates in established detection channels, such as muon events from charged current νμ interactions or cascade events from νe and ντ interaction, are calculated using a detailed Monte Carlo simulation. Neutrino fluxes as expected from prompt charm decay in the atmosphere or from astrophysical sources such as Active Galactic Nuclei are modelled assuming power laws. The ability to measure the normalization and slope of these spectra is then analysed. It is found that the cascade channel generally has a high sensitivity for the detection and characterization of the diffuse flux, when compared to what is expected for the upgoing- and downgoing-muon channels. A flux at the level of the Waxman Bahcall upper bound should be detectable in all channels separately while a combination of the information of the different channels will allow detection of a flux more than one order of magnitude lower. Neutrinos from the prompt decay of charmed mesons in the atmosphere should be detectable in future measurements for all but the lowest predictions.

  5. Aerosol flux measurements above a mixed forest at Borden, Ontario

    NASA Astrophysics Data System (ADS)

    Gordon, M.; Staebler, R. M.; Liggio, J.; Vlasenko, A.; Li, S.-M.; Hayden, K.

    2010-10-01

    Aerosol fluxes were measured above a mixed forest by Eddy Covariance (EC) with a Fast Mobility Particle Sizer (FMPS) at the Borden Forest Research Station in Ontario, Canada between 13 July and 12 August 2009. The FMPS, mounted at a height of 33 m (approximately 10 m above the canopy top) and housed in a temperature controlled enclosure, measured size-resolved particle concentrations for 3 to 410 nm at a rate of 1 Hz. For the size range 20fluxes were upward. The exchange velocity is between -0.5 and 2.0 mm s-1, with median values near 0.5 mm s-1 for all sizes between 24 and 280 nm. The net production rate of particles is highest for 75 nm particles and is near 0.4×106 m-2 s-1. Results indicate a decoupling of the above and below canopy spaces, whereby particles are stored in the canopy space at night, and are then diluted with cleaner air above during the day. Chemically speciated flux measurements from a previous study at the same location using a Quadrupole Aerosol Mass Spectrometer (Q-AMS) demonstrate a tendency towards downward fluxes, which may be due to an organic particle component which can not be resolved by the flux mode of the Q-AMS.

  6. 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.

  7. Measurement of neutrino flux from neutrino-electron elastic scattering

    DOE PAGESBeta

    Park, J.; Aliaga, L.; Altinok, O.; Bellantoni, L.; Bercellie, A.; Betancourt, M.; Bodek, A.; Bravar, A.; Budd, H.; Cai, T.; et al

    2016-06-10

    In muon-neutrino elastic scattering on electrons is an observable neutrino process whose cross section is precisely known. Consequently a measurement of this process in an accelerator-based νμ beam can improve the knowledge of the absolute neutrino flux impinging upon the detector; typically this knowledge is limited to ~10% due to uncertainties in hadron production and focusing. We also isolated a sample of 135±17 neutrino-electron elastic scattering candidates in the segmented scintillator detector of MINERvA, after subtracting backgrounds and correcting for efficiency. We show how this sample can be used to reduce the total uncertainty on the NuMI νμ flux frommore » 9% to 6%. Finally, our measurement provides a flux constraint that is useful to other experiments using the NuMI beam, and this technique is applicable to future neutrino beams operating at multi-GeV energies.« less

  8. Measurement of neutrino flux from neutrino-electron elastic scattering

    NASA Astrophysics Data System (ADS)

    Park, J.; Aliaga, L.; Altinok, O.; Bellantoni, L.; Bercellie, A.; Betancourt, M.; Bodek, A.; Bravar, A.; Budd, H.; Cai, T.; Carneiro, M. F.; Christy, M. E.; Chvojka, J.; da Motta, H.; Dytman, S. A.; Díaz, G. A.; Eberly, B.; Felix, J.; Fields, L.; Fine, R.; Gago, A. M.; Galindo, R.; Ghosh, A.; Golan, T.; Gran, R.; Harris, D. A.; Higuera, A.; Kleykamp, J.; Kordosky, M.; Le, T.; Maher, E.; Manly, S.; Mann, W. A.; Marshall, C. M.; Martinez Caicedo, D. A.; McFarland, K. S.; McGivern, C. L.; McGowan, A. M.; Messerly, B.; Miller, J.; Mislivec, A.; Morfín, J. G.; Mousseau, J.; Naples, D.; Nelson, J. K.; Norrick, A.; Nuruzzaman; Osta, J.; Paolone, V.; Patrick, C. E.; Perdue, G. N.; Rakotondravohitra, L.; Ramirez, M. A.; Ray, H.; Ren, L.; Rimal, D.; Rodrigues, P. A.; Ruterbories, D.; Schellman, H.; Solano Salinas, C. J.; Tagg, N.; Tice, B. G.; Valencia, E.; Walton, T.; Wolcott, J.; Wospakrik, M.; Zavala, G.; Zhang, D.; Miner ν A Collaboration

    2016-06-01

    Muon-neutrino elastic scattering on electrons is an observable neutrino process whose cross section is precisely known. Consequently a measurement of this process in an accelerator-based νμ beam can improve the knowledge of the absolute neutrino flux impinging upon the detector; typically this knowledge is limited to ˜10 % due to uncertainties in hadron production and focusing. We have isolated a sample of 135 ±17 neutrino-electron elastic scattering candidates in the segmented scintillator detector of MINERvA, after subtracting backgrounds and correcting for efficiency. We show how this sample can be used to reduce the total uncertainty on the NuMI νμ flux from 9% to 6%. Our measurement provides a flux constraint that is useful to other experiments using the NuMI beam, and this technique is applicable to future neutrino beams operating at multi-GeV energies.

  9. Comparison between elementary flux modes analysis and 13C-metabolic fluxes measured in bacterial and plant cells

    PubMed Central

    2011-01-01

    Background 13C metabolic flux analysis is one of the pertinent ways to compare two or more physiological states. From a more theoretical standpoint, the structural properties of metabolic networks can be analysed to explore feasible metabolic behaviours and to define the boundaries of steady state flux distributions. Elementary flux mode analysis is one of the most efficient methods for performing this analysis. In this context, recent approaches have tended to compare experimental flux measurements with topological network analysis. Results Metabolic networks describing the main pathways of central carbon metabolism were set up for a bacteria species (Corynebacterium glutamicum) and a plant species (Brassica napus) for which experimental flux maps were available. The structural properties of each network were then studied using the concept of elementary flux modes. To do this, coefficients of flux efficiency were calculated for each reaction within the networks by using selected sets of elementary flux modes. Then the relative differences - reflecting the change of substrate i.e. a sugar source for C. glutamicum and a nitrogen source for B. napus - of both flux efficiency and flux measured experimentally were compared. For both organisms, there is a clear relationship between these parameters, thus indicating that the network structure described by the elementary flux modes had captured a significant part of the metabolic activity in both biological systems. In B. napus, the extension of the elementary flux mode analysis to an enlarged metabolic network still resulted in a clear relationship between the change in the coefficients and that of the measured fluxes. Nevertheless, the limitations of the method to fit some particular fluxes are discussed. Conclusion This consistency between EFM analysis and experimental flux measurements, validated on two metabolic systems allows us to conclude that elementary flux mode analysis could be a useful tool to complement 13C

  10. Low Permafrost Methane Emissions from Arctic Airborne Flux Measurements

    NASA Astrophysics Data System (ADS)

    Sachs, T.; Serafimovich, A.; Metzger, S.; Kohnert, K.; Hartmann, J.

    2014-12-01

    One of the most pressing questions with regard to climate feedback processes in a warming Arctic is the regional-scale greenhouse gas release from Arctic permafrost areas. Ground-based eddy covariance (EC) measurements provide continuous in-situ observations of the surface-atmosphere exchange of energy and matter. However, these observations are rare in the Arctic permafrost zone and site selection is bound by logistical constraints among others. Consequently, these observations cover only small areas that are not necessarily representative of the region of interest. Airborne measurements can overcome this limitation by covering distances of hundreds of kilometers over time periods of a few hours. The Airborne Measurements of Methane Fluxes (AIRMETH) campaigns are designed to quantitatively and spatially explicitly address this question. During the AIRMETH-2012 and AIRMETH-2013 campaigns aboard the research aircraft POLAR 5 we measured turbulent exchange of energy, methane, and (in 2013) carbon dioxide along thousands of kilometers covering the North Slope of Alaska and the Mackenzie Delta, Canada. Time-frequency (wavelet) analysis, footprint modeling, and machine learning techniques are used to (i) determine spatially resolved turbulence statistics, fluxes, and contributions of biophysical surface properties, and (ii) extract regionally valid functional relationships between environmental drivers and the observed fluxes. These environmental response functions (ERF) are used to explain spatial flux patterns and - if drivers are available in temporal resolution - allow for spatio-temporal scaling of the observations. This presentation will focus on 2012 methane fluxes on the North Slope of Alaska and the relevant processes on the regional scale and provide an updated 100 m resolution methane flux map of the North Slope of Alaska.

  11. Multiple-Point Mass Flux Measurement System Using Rayleigh Scattering

    NASA Technical Reports Server (NTRS)

    Mielke, Amy F.; Elam, Kristie A.; Clem, Michelle M.

    2009-01-01

    A multiple-point Rayleigh scattering diagnostic is being developed to provide mass flux measurements in gas flows. Spectroscopic Rayleigh scattering is an established flow diagnostic that has the ability to provide simultaneous density, temperature, and velocity measurements. Rayleigh scattered light from a focused 18 Watt continuous-wave laser beam is directly imaged through a solid Fabry-Perot etalon onto a CCD detector which permits spectral analysis of the light. The spatial resolution of the measurements is governed by the locations of interference fringes, which can be changed by altering the etalon characteristics. A prototype system has been used to acquire data in a Mach 0.56 flow to demonstrate feasibility of using this system to provide mass flux measurements. Estimates of measurement uncertainty and recommendations for system improvements are presented

  12. 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...

  13. 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...

  14. Some Recent Secondary Production Measurements for Neutrino Flux Determination

    NASA Astrophysics Data System (ADS)

    Mills, Geoffrey B.

    2011-12-01

    Recent measurements of meson production in proton-nucleus interactions have made possible reliable neutrino flux determinations at modern neutrino experiments. This article discusses preliminary results from the HARP, MIP, and E910 are discussed along with some of their implications for the MINOS, K2K, and MiniBooNE neutrino experiments.

  15. 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

  16. 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.

  17. Ultra High Precision Laser Monitor for Oxygen Eddy Flux Measurements

    NASA Astrophysics Data System (ADS)

    Nelson, David; Herndon, Scott; McManus, Barry; Roscioli, Rob; Jervis, Dylan; Zahniser, Mark

    2016-04-01

    Atmospheric oxygen provides one of the most powerful tracers to study the carbon cycle through its close interaction with carbon dioxide. Keeling and co-workers demonstrated this at the global scale by using small variations in atmospheric oxygen content to disentangle oceanic and terrestrial carbon sinks. It would be very exciting to apply similar ideas at the ecosystem level to improve our understanding of biosphere-atmosphere exchange and our ability to predict the response of the biosphere and atmosphere to climate change. The eddy covariance technique is perhaps the most effective approach available to quantify the exchange of gases between these spheres. Therefore, eddy covariance flux measurements of oxygen would be extremely valuable. However, this requires a fast response (0.1 seconds), high relative precision (0.001% or 10 per meg) oxygen sensor. We report recent progress in developing such a sensor using a high resolution visible laser to probe the oxygen A-band electronic transition. We have demonstrated precision of 1 ppmv or 5 per meg for a 100 second measurement duration. This sensor will enable oxygen flux measurements using eddy covariance. In addition, we will incorporate a second laser in this instrument to simultaneously determine the fluxes of oxygen, carbon dioxide and water vapor within the same sampling cell. This will provide a direct, real time measurement of the ratio of the flux of oxygen to that of carbon dioxide. This ratio is expected to vary on short time scales and small spatial scales due to the differing stoichiometry of processes producing and consuming carbon dioxide. Thus measuring the variations in the ratio of oxygen and carbon dioxide fluxes will provide mechanistic information to improve our understanding of the crucial exchange of carbon between the atmosphere and biosphere.

  18. 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.

  19. 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.

  20. Measuring Response Of Propellant To Oscillatory Heat Flux

    NASA Technical Reports Server (NTRS)

    Strand, Leon D.; Schwartz, Ken; Burns, Shawn P.

    1990-01-01

    Apparatus for research in combustion of solid propellants measures oscillatory response of rate of burning to oscillating thermal radiation from modulated CO2 laser. Determines response to rate of burning to equivalent oscillation in pressure. Rod of propellant mounted in burner assembly including waveguide at one end and infrared window at other end. Microwave Doppler velocimeter measures motion of combustion front. Microwave, laser-current, and heat-flux signals processed into and recorded in forms useful in determining desired response of propellent.

  1. Thermal Accommodation Coefficients Based on Heat-Flux Measurements

    NASA Astrophysics Data System (ADS)

    Gallis, Michael A.; Trott, Wayne M.; Torczynski, John R.; Rader, Daniel J.

    2006-11-01

    A new method to determine the thermal accommodation coefficient of gases on solid surfaces based on heat-flux measurements is presented. An experimental chamber and supporting diagnostics have been developed that allow accurate heat-flux measurements between two parallel plates. The heat flux is inferred from temperature-difference measurements across the plates using precision thermistors, where the plate temperatures are set with two carefully controlled thermal baths. The resulting heat flux is used in a recently derived semi-empirical formula to determine the thermal accommodation coefficient. This formula has the advantage of eliminating the ˜8% discrepancy between molecular simulations and the predictions of the more approximate Sherman-Lees formula used in most studies. Nitrogen, argon, and helium on stainless steel with various finishes and on other silicon-based surfaces are examined. The thermal accommodation coefficients thus determined indicate that the Maxwell gas-surface interaction model can adequately represent all of the experimental observations. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  2. High-Fidelity Measurements of Long-Lived Flux Qubits

    NASA Astrophysics Data System (ADS)

    Hover, David; Macklin, Chris; O'Brien, Kevin; Sears, Adam; Yoder, Jonilyn; Gudmundsen, Ted; Kerman, Jamie; Bolkhovsky, Vladimir; Tolpygo, Sergey; Fitch, George; Weir, Terry; Kamal, Archana; Gustavsson, Simon; Yan, Fei; Birenbaum, Jeff; Siddiqi, Irfan; Orlando, Terry; Clarke, John; Oliver, Will

    2015-03-01

    We report on high-fidelity dispersive measurements of a long-lived flux qubit using a Josephson superconducting traveling wave parametric amplifier (JTWPA). A capacitively shunted flux qubit that incorporates high-Q MBE aluminum will have longer relaxation and dephasing times when compared to a conventional flux qubit, while also maintaining the large anharmonicity necessary for complex gate operations. The JTWPA relies on a Josephson junction embedded transmission line to deliver broadband, nonreciprocal gain with large dynamic range. 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

  3. Reducing measurement scale mismatch to improve surface energy flux estimation

    NASA Astrophysics Data System (ADS)

    Iwema, Joost; Rosolem, Rafael; Rahman, Mostaquimur; Blyth, Eleanor; Wagener, Thorsten

    2016-04-01

    Soil moisture importantly controls land surface processes such as energy and water partitioning. A good understanding of these controls is needed especially when recognizing the challenges in providing accurate hyper-resolution hydrometeorological simulations at sub-kilometre scales. Soil moisture controlling factors can, however, differ at distinct scales. In addition, some parameters in land surface models are still often prescribed based on observations obtained at another scale not necessarily employed by such models (e.g., soil properties obtained from lab samples used in regional simulations). To minimize such effects, parameters can be constrained with local data from Eddy-Covariance (EC) towers (i.e., latent and sensible heat fluxes) and Point Scale (PS) soil moisture observations (e.g., TDR). However, measurement scales represented by EC and PS still differ substantially. Here we use the fact that Cosmic-Ray Neutron Sensors (CRNS) estimate soil moisture at horizontal footprint similar to that of EC fluxes to help answer the following question: Does reduced observation scale mismatch yield better soil moisture - surface fluxes representation in land surface models? To answer this question we analysed soil moisture and surface fluxes measurements from twelve COSMOS-Ameriflux sites in the USA characterized by distinct climate, soils and vegetation types. We calibrated model parameters of the Joint UK Land Environment Simulator (JULES) against PS and CRNS soil moisture data, respectively. We analysed the improvement in soil moisture estimation compared to uncalibrated model simulations and then evaluated the degree of improvement in surface fluxes before and after calibration experiments. Preliminary results suggest that a more accurate representation of soil moisture dynamics is achieved when calibrating against observed soil moisture and further improvement obtained with CRNS relative to PS. However, our results also suggest that a more accurate

  4. 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.

  5. Actin dynamics: from nanoscale to microscale.

    PubMed

    Carlsson, Anders E

    2010-01-01

    The dynamic nature of actin in cells manifests itself constantly. Polymerization near the cell edge is balanced by depolymerization in the interior, externally induced actin polymerization is followed by depolymerization, and spontaneous oscillations of actin at the cell periphery are frequently seen. I discuss how mathematical modeling relates quantitative measures of actin dynamics to the rates of underlying molecular level processes. The dynamic properties addressed include the rate of actin assembly at the leading edge of a moving cell, the disassembly rates of intracellular actin networks, the polymerization time course in externally stimulated cells, and spontaneous spatiotemporal patterns formed by actin. Although several aspects of actin assembly have been clarified by increasingly sophisticated models, our understanding of rapid actin disassembly is limited, and the origins of nonmonotonic features in externally stimulated actin polymerization remain unclear. Theory has generated several concrete, testable hypotheses for the origins of spontaneous actin waves and cell-edge oscillations. The development and use of more biomimetic systems applicable to the geometry of a cell will be key to obtaining a quantitative understanding of actin dynamics in cells. PMID:20462375

  6. Luminous-flux measurements by an absolute integrating sphere

    NASA Astrophysics Data System (ADS)

    Rastello, Maria Luisa; Miraldi, Elio; Pisoni, Paolo

    1996-08-01

    We present an original implementation of the absolute-sphere method recently proposed by Ohno. The luminous-flux unit, the lumen, is realized by means of an integrating sphere with an opening calibrated by a luminous-intensity standard placed outside. The adapted experimental setup permits one to measure luminous-flux values between 5 and 2500 lm with a significant improvement with respect to the simulated performances reported in the literature. Traditionally, the luminous-flux unit, the lumen, is realized by goniophotometric techniques in which the luminous-intensity distribution is measured and integrated over the whole solid angle. Thus sphere results are compared with those obtained with the Istituto Elettrotecnico Nazionale goniophotometer. In particular, a set of standards, characterized by luminous-flux values of approximately 2000 lm, has been calibrated with both techniques. We highlight some of the problems encountered. Experimental results show that the agreement between the two methods is within the estimated uncertainty and suggest promising areas for future research.

  7. 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.

  8. 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

  9. Measurement of a surface heat flux and temperature

    NASA Astrophysics Data System (ADS)

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

    1994-04-01

    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

  10. 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

  11. 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

  12. Actinic Prurigo.

    PubMed

    Rodríguez-Carreón, Alma Angélica; Rodríguez-Lobato, Erika; Rodríguez-Gutiérrez, Georgina; Cuevas-González, Juan Carlos; Mancheno-Valencia, Alexandra; Solís-Arias, Martha Patricia; Vega-Memije, María Elisa; Hojyo-Tomoka, María Teresa; Domínguez-Soto, Luciano

    2015-01-01

    Actinic prurigo is an idiopathic photodermatosis that affects the skin, as well as the labial and conjunctival mucosa in indigenous and mestizo populations of Latin America. It starts predominantly in childhood, has a chronic course, and is exacerbated with solar exposure. Little is known of its pathophysiology, including the known mechanisms of the participation of HLA-DR4 and an abnormal immunologic response with increase of T CD4+ lymphocytes. The presence of IgE, eosinophils, and mast cells suggests that it is a hypersensitivity reaction (likely type IVa or b). The diagnosis is clinical, and the presence of lymphoid follicles in the mucosal histopathologic study of mucosa is pathognomonic. The best available treatment to date is thalidomide, despite its secondary effects. PMID:26861426

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

    NASA Astrophysics Data System (ADS)

    Görres, Carolyn-Monika; Kammann, Claudia; Ceulemans, Reinhart

    2016-03-01

    Recent technological advances have enabled the wider application of automated chambers for soil greenhouse gas (GHG) flux measurements, several of them commercially available. However, few studies addressed the 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 until August 2014, the two systems monitored in parallel soil respiration (SR) fluxes at a recently harvested poplar (Populus) 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 data sets of the LI-8100A and the AGPS were 520 and 433 g CO2 m-2 respectively. For the closed canopy phase (1 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; and (iv) a possible overestimation of nighttime SR fluxes by the LI-8100A. Additionally, increased root growth was observed within the LI-8100A collars but not within the AGPS collars, which might have also contributed to the observed differences. 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

  14. 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

  15. [Actinic Keratosis].

    PubMed

    Dejaco, D; Hauser, U; Zelger, B; Riechelmann, H

    2015-07-01

    Actinic keratosis is a cutaneous lesion characterized by proliferation of atypical epidermal keratinocytes due to prolonged exposure to exogenous factors such as ultraviolet radiation. AKs are in-situ-squamous cell carcinomas (PEC) of the skin. AK typically presents as erythematous, scaly patch or papule (classic AK), occasionally as thick, adherent scale on an erythematous base. Mostly fair-skinned adults are affected. AKs typically occur in areas of frequent sun exposure (balding scalp, face, "H-region", lateral neck, décolleté, dorsum of the hand and lower extremities). Actinic Cheilitis is the term used for AKs appearing on the lips. The diagnosis of AK is based on clinical examination including inspection and palpation. The typical palpable rough surface of AK often precedes a visible lesion. Dermoscopy may provide additional information. If diagnosis is uncertain and invasion suspected, biopsy and histopathologic evaluation should be performed. The potential for progression to invasive PECs mandates therapeutic intervention. Treatment options include topical and systemic therapies. Topical therapies are classified into physical, medical and combined physical-chemical approaches and a sequential combination of treatment modalities is possible. Topical-physical cryotherapy is the treatment of choice for isolated, non-hypertrophic AK. Topical-medical treatment, e. g. 5-fluoruracil (5FU) cream or Imiquomod or Ingenolmebutat application is used for multiple, non-hypertrophic AKs. For hypertrophic AKs, a dehorning pretreatment with salicinated vaseline is recommended. Isolated hypertrophic AKs often need cryotherapy with prolonged freezing time or several consecutive applications. Sequentially combined approaches are recommended for multiple, hypertrophic AKs. Photodynamic therapy (PDT) as example for a combined physical-chemical approach is an established treatment for multiple, non-hypertrophic and hypertrophic AKs. Prevention includes avoidance of sun and

  16. Aerosol flux measurements above a mixed forest at Borden, Ontario

    NASA Astrophysics Data System (ADS)

    Gordon, M.; Staebler, R. M.; Liggio, J.; Vlasenko, A.; Li, S.-M.; Hayden, K.

    2011-07-01

    Aerosol fluxes were measured above a mixed forest by Eddy Covariance (EC) with a Fast Mobility Particle Sizer (FMPS) at the Borden Forest Research Station in Ontario, Canada between 13 July and 12 August 2009. Chemically speciated flux measurements were made at a height of 29 m at the same location between 19 July and 2 August, 2006 using a Quadrupole Aerosol Mass Spectrometer (Q-AMS). The Q-AMS measured an average sulphate deposition velocity of 0.3 mm s-1 and an average nitrate deposition velocity of 4.8 mm s-1. The FMPS, mounted at a height of 33 m (approximately 10 m above the canopy top) and housed in a temperature controlled enclosure, measured size-resolved particle concentrations from 3 to 410 nm diameter at a rate of 1 Hz. For the size range 18 < D < 452 nm, 60 % of fluxes were upward. The exchange velocity was between -0.5 and 2.0 mm s-1, with median values near 0.5 mm s-1 for all sizes between 22 and 310 nm. The size distribution of the apparent production rate of particles at 33 m peaked at a diameter of 75 nm. Results indicate a decoupling of the above and below canopy spaces, whereby particles are stored in the canopy space at night, and are then diluted with cleaner air above during the day.

  17. Estimating terrestrial uranium and thorium by antineutrino flux measurements

    PubMed Central

    Dye, Stephen T.; Guillian, Eugene H.

    2008-01-01

    Uranium and thorium within the Earth produce a major portion of terrestrial heat along with a measurable flux of electron antineutrinos. These elements are key components in geophysical and geochemical models. Their quantity and distribution drive the dynamics, define the thermal history, and are a consequence of the differentiation of the Earth. Knowledge of uranium and thorium concentrations in geological reservoirs relies largely on geochemical model calculations. This article describes the methods and criteria to experimentally determine average concentrations of uranium and thorium in the continental crust and in the mantle by using site-specific measurements of the terrestrial antineutrino flux. Optimal, model-independent determinations involve significant exposures of antineutrino detectors remote from nuclear reactors at both a midcontinental and a midoceanic site. This would require major, new antineutrino detection projects. The results of such projects could yield a greatly improved understanding of the deep interior of the Earth. PMID:18172211

  18. An Alpha-Gamma Counter for Absolute Neutron Flux Measurement

    NASA Astrophysics Data System (ADS)

    Yue, A.; Greene, G.; Dewey, M.; Gilliam, D.; Nico, J.; Laptev, A.

    2012-03-01

    An alpha-gamma counter was used to measure the absolute neutron flux of a monochromatic cold neutron beam to sub-0.1,% precision. Simultaneously, the counter was used to calibrate a thin neutron flux monitor based on neutron absorption on ^6Li to the same precision. This monitor was used in the most precise beam-based measurement of the neutron lifetime, where the limiting systematic effect was the uncertainty in the neutron counting efficiency (0.3,%). The counter uses a thick target of ^10B-enriched boron carbide to completely absorb the beam. The rate of absorbed neutrons is determined by counting 478 keV gamma rays from neutron capture on ^10B with calibrated high-purity germanium detectors. The calibration results and the implications for the neutron lifetime will be discussed.

  19. 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.

  20. Corrections of Heat Flux Measurements on Launch Vehicles

    NASA Technical Reports Server (NTRS)

    Reinarts, Thomas R.; Matson, Monique L.; Walls, Laurie K.

    2002-01-01

    Knowledge of aerothermally induced convective heat transfer is important in the design of thermal protection systems for launch vehicles. Aerothermal models are typically calibrated via the data from circular, in-flight, flush-mounted surface heat flux gauges exposed to the thermal and velocity boundary layers of the external flow. Typically, copper or aluminum Schmidt- Boelter gauges, which take advantage of the one-dimensional Fourier's law of heat conduction, are used to measure the incident heat flux. This instrumentation, when surrounded by low-conductivity insulation, has a wall temperature significantly lower than the insulation. As a result of this substantial disturbance to the thermal boundary layer, the heat flux incident on the gauge tends to be considerably higher than it would have been on the insulation had the calorimeter not been there. In addition, radial conductive heat transfer from the hotter insulation can cause the calorimeter to indicate heat fluxes higher than actual. An overview of an effort to develop and calibrate gauge correction techniques for both of these effects will be presented.

  1. 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.

  2. 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.

  3. 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

  4. 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

  5. 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.

  6. 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

  7. 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

  8. 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

  9. High-Energy Neutron Spectra and Flux Measurements Below Ground

    NASA Astrophysics Data System (ADS)

    Roecker, Caleb; Bernstein, Adam; Marleau, Peter; Vetter, Kai

    2016-03-01

    High-energy neutrons are a ubiquitous and often poorly measured background. Below ground, these neutrons could potentially interfere with antineutrino based reactor monitoring experiments as well as other rare-event neutral particle detectors. We have designed and constructed a transportable fast neutron detection system for measuring neutron energy spectra and flux ranging from tens to hundreds of MeV. The spectrometer uses a multiplicity technique in order to have a higher effective area than traditional transportable high-energy neutron spectrometers. Transportability ensures a common detector-related systematic bias for future measurements. The spectrometer is composed of two Gd containing plastic scintillator detectors arranged around a lead spallation target. A high-energy neutron may interact in the lead producing many secondary neutrons. The detector records the correlated secondary neutron multiplicity. Over many events, the response can be used to infer the incident neutron energy spectrum and flux. As a validation of the detector response, surface measurements have been performed; results confirm agreement with previous experiments. Below ground measurements have been performed at 3 depths (380, 600, and 1450 m.w.e.); results from these measurements will be presented.

  10. 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.

  11. Doppler lidar measurement of profiles of turbulence and momentum flux

    NASA Technical Reports Server (NTRS)

    Eberhard, Wynn L.; Cupp, Richard E.; Healy, Kathleen R.

    1989-01-01

    A short-pulse CO2 Doppler lidar with 150-m range resolution measured vertical profiles of turbulence and momentum flux. Example measurements are reported of a daytime mixed layer with strong mechanical mixing caused by a wind speed of 15 m/sec, which exceeded the speed above the capping inversion. The lidar adapted an azimuth scanning technique previously demonstrated by radar. Scans alternating between two elevation angles allow determination of mean U-squared, V-squared, and W-squared. Expressions were derived to estimate the uncertainty in the turbulence parameters. A new processing method, partial Fourier decomposition, has less uncertainty than the filtering used earlier.

  12. 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

  13. Optimizing laboratory-based radon flux measurements for sediments.

    PubMed

    Chanyotha, Supitcha; Kranrod, Chutima; Kritsananuwat, Rawiwan; Lane-Smith, Derek; Burnett, William C

    2016-07-01

    Radon flux via diffusion from sediments and other materials may be determined in the laboratory by circulating air through the sample and a radon detector in a closed loop. However, this approach is complicated by the necessity of having to determine the total air volume in the system and accounting for any small air leaks that can arise if using extended measurement periods. We designed a simple open-loop configuration that includes a measured mass of wet sediment and water inside a gas-tight reaction flask connected to a drying system and a radon-in-air analyzer. Ambient air flows through two charcoal columns before entering the reaction vessel to eliminate incoming radon. After traveling through the reaction flask, the air passes the drier and the radon analyzer and is then vented. After some time, the radon activity will reach a steady state depending upon the airflow rate. With this approach, the radon flux via diffusion is simply the product of the steady-state radon activity (Bq/m(3)) multiplied by the airflow rate (mL/min). We demonstrated that this setup could produce good results for materials that produce relatively high radon fluxes. We also show that a modified closed system approach, including radon removal of the incoming air by charcoal filtration in a bypass, can produce very good results including samples with very low emission rates. PMID:27064564

  14. A measurement of the antiproton flux in the cosmic rays

    NASA Technical Reports Server (NTRS)

    Buffington, A.; Schindler, S. M.

    1981-01-01

    A balloon-borne instrument has been used to detect cosmic-ray antiprotons. These are identified topologically by the appearance of annihilation prongs in a thick lead-plate spark chamber. The initial recording of the data is enriched in potential antimatter events by a selective trigger. After a small subtraction for background, 14 identified antiprotons yield a flux of 1.7 plus or minus 0.00005 antiproton/(sq m ster sec MeV) between 130 and 320 MeV at the top of the atmosphere. When combined with higher energy antiproton flux measurements, this result indicates that the antiprotons have a spectrum whose shape is the same as that of the protons, but with a magnitude reduced by a factor of 1/3000.

  15. 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.

  16. Momentum flux measurements using an impact thrust stand

    NASA Astrophysics Data System (ADS)

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

    2004-11-01

    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 evaluated 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.

  17. Assessment of CO2 flux measurements in different soil types

    NASA Astrophysics Data System (ADS)

    Xia, L.; Szlavecz, K.; Musaloiu, R.; Cupchup, J.; Pitz, S.

    2008-12-01

    Accurate measurements of soil CO2 efflux are extraordinarily challenging due to the very properties of CO2 transport in a porous medium of soil. The most commonly used method today is the chamber method, which provides direct measurements of CO2 efflux at the soil surface, but it can not measure the soil CO2 flux continuously. In order to develop new measurement methods in soil CO2 efflux, small solid-state CO2 sensors have been used to continuously to monitor soil CO2 profiles by burying these sensors at different soil depths. Using this method we compared soil CO2 efflux of four different soil types: forests soil, grassland soil (collected in Maryland) commercial potting soil and pure sand as control. CO2 concentration varied between 500 ppm in sand and 8000 ppm in forest soil at depth 12 cm. CO2 flux had the following order: Forest (0.3~0.4 mg CO2 m-2 s-1), potting soil (0.1~0.14 mg CO2 m-2 s-1 ), grassland (0.03~0.05 mg CO2 m-2 s-1), sand ( 0 mg CO2 m-2 s-1 ). Exponential relationship between temperature and CO2 flux was established for forest soil and potting soil only. Leaf litter, often thick layer in many terrestrial ecosystems and a significant source of CO2 production, is not part of the of the diffusivity models. We are currently conducting experiments which include the effect of leaf litter and soil invertebrates into soil respiration.

  18. 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.

  19. 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

  20. 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.

  1. 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.

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

    DOEpatents

    Ganther, Jr., Kenneth R.; Snapp, Lowell D.

    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.

  3. Wind tunnel measurements of pollutant turbulent fluxes in urban intersections

    NASA Astrophysics Data System (ADS)

    Carpentieri, Matteo; Hayden, Paul; Robins, Alan G.

    2012-01-01

    Wind tunnel experiments have been carried out at the EnFlo laboratory to measure mean and turbulent tracer fluxes in geometries of real street canyon intersections. The work was part of the major DAPPLE project, focussing on the area surrounding the intersection between Marylebone Road and Gloucester Place in Central London, UK. Understanding flow and dispersion in urban streets is a very important issue for air quality management and planning, and turbulent mass exchange processes are important phenomena that are very often neglected in urban modelling studies. The adopted methodology involved the combined use of laser Doppler anemometry and tracer concentration measurements. This methodology was applied to quantify the mean and turbulent flow and dispersion fields within several street canyon intersections. Vertical profiles of turbulent tracer flux were also measured. The technique, despite a number of limitations, proved reliable and allowed tracer balance calculations to be undertaken in the selected street canyon intersections. The experience gained in this work will enable much more precise studies in the future as issues affecting the accuracy of the experimental technique have been identified and resolved.

  4. Performance measurements at the fast flux test facility

    SciTech Connect

    Baumhardt, R.J.; Newland, D.J.; Praetorius, P.R.

    1987-01-01

    In 1984, Fast Flux Test Facility (FFTF) management recognized the need to develop a measurement system that would quantify the operational performance of the FFTF and the human resources needed to operate it. Driven by declining budgets and the need to safely manage a manpower rampdown at FFTF, an early warning system was developed. Although the initiating event for the early warning system was the need to safely manage a manpower rampdown, many related uses have evolved. The initial desired objective for the FFTF performance measurements was to ensure safety and control of key performance trends. However, the early warning system has provided a more quantitative, supportable basis upon which to make decisions. From this initial narrow focus, efforts in the FFTF plant and supporting organizations are leading to measurement of and, subsequently, improvements in productivity. Pilot projects utilizing statistical process control have started with longer range productivity improvement.

  5. 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

  6. 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.

  7. Quantifying Representation and Using Representation Weights to Interpolate Flux Tower Measurements across the United States

    NASA Astrophysics Data System (ADS)

    Hargrove, W. W.; Hoffman, F. M.

    2003-12-01

    We are using a new multivariate statistical technique to quantitatively divide the lower 48 United States into a series of flux-relevant ecoregions. On the basis of these flux-relevant ecoregions, we will quantify the representativeness of the existing network of AmeriFlux towers, showing how well each ecoregion is represented by the current stations in the AmeriFlux network. Quantifying AmeriFlux representation will indicate the best locations where additional AmeriFlux towers should be placed. Using a "paint-by-number" approach, we are attempting to use the flux ecoregions as the statistical basis for extrapolating measurements made at the 52 actively-reporting AmeriFlux towers into a continuous 1-km grid across the United States seasonally. We will use the similarity of the suite of flux-relevant ecosystem characteristics to modify existing flux measurements and estimate fluxes within unmeasured flux ecoregions. Weights calculated for each environmental gradient will allow us to mix new "paint-by-number" colors, extending the process beyond the palette of existing flux measurements. The map of 2000 to 5000 flux ecoregions will produce a highly-resolved national map of estimated fluxes, and will be equivalent to creating thousands of new "virtual" flux towers across the nation. Once flux ecoregions and representation weights have been determined, it may be possible to use them to obtain an interpolated grid of the estimated flux at any point in time across the United States.

  8. 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.

  9. Standardization of flux chamber and wind tunnel flux measurements for quantifying 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 inaccuracy caused by inappropriate air velocity or sweep air flow...

  10. 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

  11. 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.

  12. 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

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

    SciTech Connect

    Veselinović, N. Dragić, A. Maletić, D. Joković, D. Savić, M. Banjanac, R. Udovičić, V. Aničin, 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.

  14. Absolute measurement of the extreme UV solar flux

    NASA Technical Reports Server (NTRS)

    Carlson, R. W.; Ogawa, H. S.; Judge, D. L.; Phillips, E.

    1984-01-01

    A windowless rare-gas ionization chamber has been developed to measure the absolute value of the solar extreme UV flux in the 50-575-A region. Successful results were obtained on a solar-pointing sounding rocket. The ionization chamber, operated in total absorption, is an inherently stable absolute detector of ionizing UV radiation and was designed to be independent of effects from secondary ionization and gas effusion. The net error of the measurement is + or - 7.3 percent, which is primarily due to residual outgassing in the instrument, other errors such as multiple ionization, photoelectron collection, and extrapolation to the zero atmospheric optical depth being small in comparison. For the day of the flight, Aug. 10, 1982, the solar irradiance (50-575 A), normalized to unit solar distance, was found to be 5.71 + or - 0.42 x 10 to the 10th photons per sq cm sec.

  15. Measurement of geothermal flux through poorly consolidated sediments

    USGS Publications Warehouse

    Sass, J.H.; Munroe, R.J.; Lachenbruch, A.H.

    1968-01-01

    In many regions, crystalline rocks are covered by hundreds of meters of unconsolidated and poorly consolidated sediments. Estimates of heat flux within these sediments using standard continental techniques (temperature and conductivity measurements at intervals of 10 to 30 meters) are unreliable, mainly because of the difficulty in obtaining and preserving representative lengths of core. However, it is sometimes feasible to use what amounts to an oceanographic technique by making closely spaced temperature and conductivity measurements within short cored intervals. This is demonstrated in a borehole at Menlo Park, California (37??27???N, 122??10???W, elevation 16 meters), where heat flows determined over 12 separate 1-meter intervls al lie within 10% of their mean value; 2.2 ??cal/cm2 sec. ?? 1968.

  16. 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

  17. 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...

  18. 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.

  19. Eddy covariance measurements of methane fluxes over grazed native and improved prairies in Oklahoma

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Although several studies have reported eddy covariance (EC) measurements at several tallgrass prairie sites to investigate the dynamics of carbon and water vapor fluxes, the EC measurements of methane (CH4) fluxes over grazed tallgrass prairie sites are lacking. CH4 fluxes were measured during the 2...

  20. Improvements to measuring water flux in the vadose zone.

    PubMed

    Masarik, Kevin C; Norman, John M; Brye, Kristofor R; Baker, John M

    2004-01-01

    Evaluating the impact of land use practices on ground water quality has been difficult because few techniques are capable of monitoring the quality and quantity of soil water flow below the root zone without disturbing the soil profile and affecting natural flow processes. A recently introduced method, known as equilibrium tension lysimetry, was a major improvement but it was not a true equilibrium since it still required manual intervention to maintain proper lysimeter suction. We addressed this issue by developing an automated equilibrium tension lysimeter (AETL) system that continuously matches lysimeter tension to soil-water matric potential of the surrounding soil. The soil-water matric potential of the bulk soil is measured with a heat-dissipation sensor, and a small DC pump is used to apply suction to a lysimeter. The improved automated approach reported here was tested in the field for a 12-mo period. Powered by a small 12-V rechargeable battery, the AETLs were able to continuously match lysimeter suction to soil-water matric potential for 2-wk periods with minimal human attention, along with the added benefit of collecting continuous soil-water matric potential data. We also demonstrated, in the laboratory, methods for continuous measurement of water depth in the AETL, a capability that quantifies drainage on a 10-min interval, making it a true water-flux meter. Equilibrium tension lysimeters have already been demonstrated to be a reliable method of measuring drainage flux, and the further improvements have created a more effective device for studying water drainage and chemical leaching through the soil matrix. PMID:15224955

  1. "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.

  2. 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.

  3. Bacterial lipopolysaccharide induces actin reorganization, intercellular gap formation, and endothelial barrier dysfunction in pulmonary vascular endothelial cells: concurrent F-actin depolymerization and new actin synthesis.

    PubMed

    Goldblum, S E; Ding, X; Brann, T W; Campbell-Washington, J

    1993-10-01

    Bacterial lipopolysaccharide (LPS) influences pulmonary vascular endothelial barrier function in vitro. We studied whether LPS regulates endothelial barrier function through actin reorganization. Postconfluent bovine pulmonary artery endothelial cell monolayers were exposed to Escherichia coli 0111:B4 LPS 10 ng/ml or media for up to 6 h and evaluated for: 1) transendothelial 14C-albumin flux, 2) F-actin organization with fluorescence microscopy, 3) F-actin quantitation by spectrofluorometry, and 4) monomeric G-actin levels by the DNAse 1 inhibition assay. LPS induced increments in 14C-albumin flux (P < 0.001) and intercellular gap formation at > or = 2-6 h. During this same time period the endothelial F-actin pool was not significantly changed compared to simultaneous media controls. Mean (+/- SE) G-actin (micrograms/mg total protein) was significantly (P < 0.002) increased compared to simultaneous media controls at 2, 4, and 6 h but not at 0.5 or 1 h. Prior F-actin stabilization with phallicidin protected against the LPS-induced increments in G-actin (P = 0.040) as well as changes in barrier function (P < 0.0001). Prior protein synthesis inhibition unmasked an LPS-induced decrement in F-actin (P = 0.0044), blunted the G-actin increment (P = 0.010), and increased LPS-induced changes in endothelial barrier function (P < 0.0001). Therefore, LPS induces pulmonary vascular endothelial F-actin depolymerization, intercellular gap formation, and barrier dysfunction. Over the same time period, LPS increased total actin (P < 0.0001) and new actin synthesis (P = 0.0063) which may be a compensatory endothelial cell response to LPS-induced F-actin depolymerization. PMID:8408232

  4. 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.

  5. 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...

  6. Passive flux sampler for measurement of formaldehyde emission rates

    NASA Astrophysics Data System (ADS)

    Shinohara, Naohide; Fujii, Minoru; Yamasaki, Akihiro; Yanagisawa, Yukio

    A new passive flux sampler (PFS) was developed to measure emission rates of formaldehyde and to determine emission sources in indoor environments. The sampler consisted of a glass Petri dish containing a 2,4-dinitrophenyl hydrazine (DNPH)-impregnated sheet. At the start of sampling, the PFS was placed with the open face of the dish on each of the indoor materials under investigation, such as flooring, walls, doors, closets, desks, beds, etc. Formaldehyde emitted from a source material diffused through the inside of the PFS and was adsorbed onto the DNPH sheet. The formaldehyde emission rates could be determined from the quantities adsorbed. The lower determination limits were 9.2 and 2.3 μg m -2 h -1 for 2- and 8-h sampling periods. The recovery rate and the precision of the PFS were 82.9% and 8.26%, respectively. The emission rates measured by PFS were in good agreement with the emission rates measured by the chamber method ( R2=0.963). This shows that it is possible to take measurements of the formaldehyde emission rates from sources in a room and to compare them. In addition, the sampler can be used to elucidate the emission characteristics of a source by carrying out emission measurements with different air-layer thicknesses inside the PFS and at different temperatures. The dependency of the emission rate on the thickness of the air layer inside the PFS indicated whether the internal mass transfer inside the source material or the diffusion in the gas-phase boundary layer controlled the formaldehyde emission rate from a material. In addition, as a pilot study, the formaldehyde emission rates were measured, and the largest emission source of formaldehyde could be identified from among several suspected materials in a model house by using the PFS.

  7. Yeast dynamic metabolic flux measurement in nutrient-rich media by HPLC and accelerator mass spectrometry.

    PubMed

    Stewart, Benjamin J; Navid, Ali; Turteltaub, Kenneth W; Bench, Graham

    2010-12-01

    Metabolic flux, the flow of metabolites through networks of enzymes, represents the dynamic productive output of cells. Improved understanding of intracellular metabolic fluxes will enable targeted manipulation of metabolic pathways of medical and industrial importance to a greater degree than is currently possible. Flux balance analysis (FBA) is a constraint-based approach to modeling metabolic fluxes, but its utility is limited by a lack of experimental measurements. Incorporation of experimentally measured fluxes as system constraints will significantly improve the overall accuracy of FBA. We applied a novel, two-tiered approach in the yeast Saccharomyces cerevisiae to measure nutrient consumption rates (extracellular fluxes) and a targeted intracellular flux using a (14)C-labeled precursor with HPLC separation and flux quantitation by accelerator mass spectrometry (AMS). The use of AMS to trace the intracellular fate of (14)C-glutamine allowed the calculation of intracellular metabolic flux through this pathway, with glutathione as the metabolic end point. Measured flux values provided global constraints for the yeast FBA model which reduced model uncertainty by more than 20%, proving the importance of additional constraints in improving the accuracy of model predictions and demonstrating the use of AMS to measure intracellular metabolic fluxes. Our results highlight the need to use intracellular fluxes to constrain the models. We show that inclusion of just one such measurement alone can reduce the average variability of model predicted fluxes by 10%. PMID:21062031

  8. 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...

  9. Using passive capillary lysimeter water flux measurements to improve flow predictions in variably saturated soils.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Passive capillary lysimeters (PCLs) are uniquely suited for measuring water fluxes in variably-saturated soils. The objective of this work was to compare PCL flux measurements with simulated fluxes obtained with a calibrated unsaturated flow model. The Richards equation-based model was calibrated us...

  10. 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...

  11. Structural Transitions of F-Actin:Espin Bundles

    NASA Astrophysics Data System (ADS)

    Purdy, Kirstin; Bartles, James; Wong, Gerard

    2006-03-01

    Espin is an actin bundling protein involved in the formation of the parallel bundles of filamentous actin in hair cell stereocilia. Mutations in espin are implicated in deafness phenotypes in mice and humans. We present measurements of the F-actin structures induced by wild type and by mutated espin obtained via small angle x-ray scattering and fluorescence microscopy. We found that wild type espin induced a paracrystalline hexagonal array of twisted F-actin, whereas the mutated espin only condensed the F-actin into a nematic-like phase. The possibility of coexisting nematic and bundled actin in mixtures containing both mutant and wild type espins was also investigated.

  12. 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.

  13. Architecture and Connectivity Govern Actin Network Contractility.

    PubMed

    Ennomani, Hajer; Letort, Gaëlle; Guérin, Christophe; Martiel, Jean-Louis; Cao, Wenxiang; Nédélec, François; De La Cruz, Enrique M; Théry, Manuel; Blanchoin, Laurent

    2016-03-01

    Actomyosin contractility plays a central role in a wide range of cellular processes, including the establishment of cell polarity, cell migration, tissue integrity, and morphogenesis during development. The contractile response is variable and depends on actomyosin network architecture and biochemical composition. To determine how this coupling regulates actomyosin-driven contraction, we used a micropatterning method that enables the spatial control of actin assembly. We generated a variety of actin templates and measured how defined actin structures respond to myosin-induced forces. We found that the same actin filament crosslinkers either enhance or inhibit the contractility of a network, depending on the organization of actin within the network. Numerical simulations unified the roles of actin filament branching and crosslinking during actomyosin contraction. Specifically, we introduce the concept of "network connectivity" and show that the contractions of distinct actin architectures are described by the same master curve when considering their degree of connectivity. This makes it possible to predict the dynamic response of defined actin structures to transient changes in connectivity. We propose that, depending on the connectivity and the architecture, network contraction is dominated by either sarcomeric-like or buckling mechanisms. More generally, this study reveals how actin network contractility depends on its architecture under a defined set of biochemical conditions. PMID:26898468

  14. Stochastic model of profilin-actin polymerization

    NASA Astrophysics Data System (ADS)

    Horan, Brandon; Vavylonis, Dimitrios

    A driving factor in cell motility and other processes that involve changes of cell shape is the rapid polymerization of actin subunits into long filaments. This process is regulated by profilin, a protein which binds to actin subunits and regulates elongation of actin filaments. Whether profilin stimulates polymerization by coupling to hydrolysis of ATP-bound actin is debated. Previous studies have proposed indirect coupling to ATP hydrolysis using rate equations, but did not include the effects of fluctuations that are important near the critical concentration. We developed stochastic simulations using the Gillespie algorithm to study single filament elongation at the barbed end in the presence of profilin. We used recently measured rate constants and estimated the rate of profilin binding to the barbed end such that detailed balance is satisfied. Fast phosphate release at the tip of the filament was accounted for. The elongation rate and length diffusivity as functions of profilin and actin concentration were calculated and used to extract the critical concentrations of free actin and of total actin. We show under what conditions profilin leads to an increase in the critical concentration of total actin but a decrease in the critical concentration of free actin.

  15. 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.

  16. An easy-to-use single-molecule speckle microscopy enabling nanometer-scale flow and wide-range lifetime measurement of cellular actin filaments.

    PubMed

    Yamashiro, Sawako; Mizuno, Hiroaki; Watanabe, Naoki

    2015-01-01

    Single-molecule speckle (SiMS) microscopy has been a powerful method to analyze actin dynamics in live cells by tracking single molecule of fluorescently labeled actin. Recently we developed a new SiMS method, which is easy-to-use for inexperienced researchers and achieves high spatiotemporal resolution. In this method, actin labeled with fluorescent DyLight dye on lysines is employed as a probe. Electroporation-mediated delivery of DyLight-actin (DL-actin) into cells enables to label cells with 100% efficiency at the optimal density. DL-actin labels cellular actin filaments including formin-based structures with improved photostability and brightness compared to green fluorescent protein-actin. These favorable properties of DL-actin extend time window of the SiMS analysis. Furthermore, the new SiMS method enables nanometer-scale displacement analysis with a low localization error of ±8-8.5 nm. With these advantages, our new SiMS microscopy method will help researchers to investigate various actin remodeling processes. In this chapter, we introduce the methods for preparation of DL-actin probes, electroporation to deliver DL-actin, the SiMS imaging and data analysis. PMID:25640423

  17. A Summary of Mass Flux Measurements in Solid 4He

    NASA Astrophysics Data System (ADS)

    Hallock, R. B.; Ray, M. W.; Vekhov, Y.

    2012-11-01

    Here we provide a summary and brief review of some of the work done with solid 4He at the University of Massachusetts Amherst below a sample pressure of 28 bar. The motivation for the work has been to attempt to pass 4He atoms through solid 4He without directly applying mechanical pressure to the solid itself. The specific technique chosen is limited to pressures near the melting curve and was initially designed to provide a yes/no answer to the question of whether or not it might be possible to observe such a mass flux. The thermo-mechanical effect and direct mass injection have been separately used to create chemical potential differences between two reservoirs of superfluid 4He connected to each other through superfluid-filled Vycor rods in series with solid 4He, which is in the hcp region of the phase diagram. The thermo-mechanical effect is a more versatile approach. And, in a particular symmetric application it is designed to provide a mass flux with little or no net increase in the density of the solid. Our observations, off but near the melting curve, have included: (1) the presence of an increasing DC flux of atoms through the solid-filled cell with decreasing temperature below ≈650 mK and no flux above this temperature; (2) the presence of a flux minimum and flux instability in the vicinity of 75-80 mK, with a flux increase at lower temperatures; (3) the temperature dependence of the flux above 100 mK and the dependence of the flux on the net driving chemical potential difference provide interesting insights on the possible mechanism that leads to the flux above 100 mK. The most recent data suggest that whatever is responsible for the flux in solid 4He, at least for T>100 mK, may be an example of a Bosonic Luttinger liquid.

  18. SIERRA-Flux: measuring regional surface fluxes of carbon dioxide, methane, and water vapor from an unmanned aircraft system

    NASA Astrophysics Data System (ADS)

    Fladeland, M. M.; Yates, E. L.; Bui, T. P.; Dean-Day, J. M.; Kolyer, R.; Schiro, K.; Berthold, R.; Iraci, L. T.; Loewenstein, M.

    2011-12-01

    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 more 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. In a series of flights in June of 2011, the NASA SIERRA carried a payload consisting of the NASA Ames Meteorological Measurement System (MMS) and a fast response (10Hz) CO2, CH4, and H2O vapor analyzer in order to demonstrate the feasibility of measuring fluxes from unmanned aircraft and to characterize accuracy and precision based upon ground measurements. The flights were conducted in Railroad Valley, NV in order to provide a simple model for understanding biases and uncertainties. This paper describes the system specifications, provides preliminary data compared against coincident ground measurements, and discusses future applications of the system.

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

    SciTech Connect

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

    1983-03-01

    This report recommends 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 month measurement methodology are then presented based on the inherent difficulties of measuring average radon flux over a cover using the recommended instrumentation.

  20. 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.

  1. Measurements of Urban Area-Wide CO2 and CH4 Fluxes as part of the Indianapolis Flux Experiment (INFLUX)

    NASA Astrophysics Data System (ADS)

    Shepson, P.; Callahan, B.; Cambaliza, M. L.; Davis, K. J.; Hardesty, R.; Iraci, L. T.; Gurney, K. R.; Karion, A.; Lauvaux, T.; McGowan, L. E.; Miles, N. L.; Moser, B.; Newberger, T.; Possolo, A.; Razlivanov, I. N.; Richardson, S.; Samarov, D. V.; Sarmiento, D.; Stirm, B.; Sweeney, C.; Turnbull, J. C.; Whetstone, J. R.

    2012-12-01

    The Indianapolis Flux Experiment (INFLUX) was created in order to develop and evaluate methods for the measurement of greenhouse gas emission fluxes from urban environments. Such methods are important for a variety of reasons, including that more than half the global population now resides in cities, and because it is likely that many CO2 emissions reductions strategies will be implemented on local, largely urban, scales. INFLUX is using Indianapolis as a test case for measurements of urban scale greenhouse gas fluxes, because it is a fairly isolated urban environment with tractable meteorology, and a well-developed emission inventory (Vulcan/Hestia). INFLUX aims to quantify and reduce the uncertainty limits for such flux determinations, and to define the uncertainties for individual and combined approaches. The project currently combines a network of towers (currently 10 with 12 possible by the end of 2012) at which CO, CO2 and CH4 are measured, along with periodic flask sampling for 14CO2 and ~50 other trace gases and isotopes. Aircraft-based measurements of CO2, CH4 and H2O, along with flask samples for a variety of gases including 14CO2 are conducted from a light twin aircraft that enables flux measurements using the on-board turbulence/wind measurements via mass balance or eddy covariance methods. As of August of 2012 INFLUX has a Total Carbon Column Observing Network (TCCON) Fourier Transform Spectrometer at a downwind site, measuring column total CO2, CH4, H2O (and other greenhouse gases). The data from these tower, TCCON and aircraft measurements are then used in an inverse-modeling approach, using the Weather Research and Forecast model with chemistry (WRF-Chem) and the Lagrangian Particle Dispersion Model (LDPM) to yield estimates of the urban area flux at 1 km2 resolution. When aggregated these fluxes can be compared to estimates derived from aircraft mass-balance estimates, and the 14CO2 and CO data are used to extract the fossil fuel component of the

  2. 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.

  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. Improving surface energy balance closure by reducing errors in soil heat flux measurement

    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. Although relatively simple to use, the flux plate method is susceptible to significant errors. Two of the most common errors are heat flow divergence around the plate and fa...

  5. Actin-Regulator Feedback Interactions during Endocytosis.

    PubMed

    Wang, Xinxin; Galletta, Brian J; Cooper, John A; Carlsson, Anders E

    2016-03-29

    Endocytosis mediated by clathrin, a cellular process by which cells internalize membrane receptors and their extracellular ligands, is an important component of cell signaling regulation. Actin polymerization is involved in endocytosis in varying degrees depending on the cellular context. In yeast, clathrin-mediated endocytosis requires a pulse of polymerized actin and its regulators, which recruit and activate the Arp2/3 complex. In this article, we seek to identify the main protein-protein interactions that 1) cause actin and its regulators to appear in pulses, and 2) determine the effects of key mutations and drug treatments on actin and regulator assembly. We perform a joint modeling/experimental study of actin and regulator dynamics during endocytosis in the budding yeast Saccharomyces cerevisiae. We treat both a stochastic model that grows an explicit three-dimensional actin network, and a simpler two-variable Fitzhugh-Nagumo type model. The models include a negative-feedback interaction of F-actin onto the Arp2/3 regulators. Both models explain the pulse time courses and the effects of interventions on actin polymerization: the surprising increase in the peak F-actin count caused by reduced regulator branching activity, the increase in F-actin resulting from slowing of actin disassembly, and the increased Arp2/3 regulator lifetime resulting from latrunculin treatment. In addition, they predict that decreases in the regulator branching activity lead to increases in accumulation of regulators, and we confirmed this prediction with experiments on yeast harboring mutations in the Arp2/3 regulators, using quantitative fluorescence microscopy. Our experimental measurements suggest that the regulators act quasi-independently, in the sense that accumulation of a particular regulator is most strongly affected by mutations of that regulator, as opposed to the others. PMID:27028652

  6. Real-time soil flux measurements and calculations with CRDS + Soil Flux Processor: comparison among flux algorithms and derivation of whole system error

    NASA Astrophysics Data System (ADS)

    Alstad, K. P.; Venterea, R. T.; Tan, S. M.; Saad, N.

    2015-12-01

    Understanding chamber-based soil flux model fitting and measurement error is key to scaling soils GHG emissions and resolving the primary uncertainties in climate and management feedbacks at regional scales. One key challenge is the selection of the correct empirical model applied to soil flux rate analysis in chamber-based experiments. Another challenge is the characterization of error in the chamber measurement. Traditionally, most chamber-based N2O and CH4 measurements and model derivations have used discrete sampling for GC analysis, and have been conducted using extended chamber deployment periods (DP) which are expected to result in substantial alteration of the pre-deployment flux. The development of high-precision, high-frequency CRDS analyzers has advanced the science of soil flux analysis by facilitating much shorter DP and, in theory, less chamber-induced suppression of the soil-atmosphere diffusion gradient. As well, a new software tool developed by Picarro (the "Soil Flux Processor" or "SFP") links the power of Cavity Ring-Down Spectroscopy (CRDS) technology with an easy-to-use interface that features flexible sample-ID and run-schemes, and provides real-time monitoring of chamber accumulations and environmental conditions. The SFP also includes a sophisticated flux analysis interface which offers a user-defined model selection, including three predominant fit algorithms as default, and an open-code interface for user-composed algorithms. The SFP is designed to couple with the Picarro G2508 system, an analyzer which simplifies soils flux studies by simultaneously measuring primary GHG species -- N2O, CH4, CO2 and H2O. In this study, Picarro partners with the ARS USDA Soil & Water Management Research Unit (R. Venterea, St. Paul), to examine the degree to which the high-precision, high-frequency Picarro analyzer allows for much shorter DPs periods in chamber-based flux analysis, and, in theory, less chamber-induced suppression of the soil

  7. 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...

  8. Design and operation - Surface flux measurements in FIFE

    NASA Technical Reports Server (NTRS)

    Kanemasu, E. T.; Verma, Shashi B.; Fritschen, L. J.; Gurney, R. J.; Hsu, A. T.

    1990-01-01

    A general overview of the structure, technology, and methodology of the investigation of surface flux is presented for the First International Satellite Land-Surface Climatology Project Field Experiment. The paper examines the placement of stations, choice of constants, instruments, and micrometeorological techniques, the information system, and comparisons between the data from the sensors and data from different sites. The differences between sites are generally small, and a similarity is noted in the magnitude of fluxes across all sites.

  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. Actin in Herpesvirus Infection

    PubMed Central

    Roberts, Kari L.; Baines, Joel D.

    2011-01-01

    Actin is important for a variety of cellular processes, including uptake of extracellular material and intracellular transport. Several emerging lines of evidence indicate that herpesviruses exploit actin and actin-associated myosin motors for viral entry, intranuclear transport of capsids, and virion egress. The goal of this review is to explore these processes and to highlight potential future directions for this area of research. PMID:21994736

  11. The Interaction of Caldesmon with the COOH Terminus of Actin*

    PubMed Central

    Crosbie, Rachelle; Adams, Susan; Chalovich, Joseph M.; Reisler, Emil

    2005-01-01

    Caldesmon interacts with the NH2-terminal region of actin. It is now shown in airfuge centrifugation experiments that modification of the penultimate cysteine residue of actin significantly weakens its binding to caldesmon both in the presence and absence of tropomyosin. Furthermore, as revealed by fluorescence measurements, caldesmon increases the exposure of the COOH-terminal region of actin to the solvent. This effect of caldesmon, like its inhibitory effect on actomyosin ATPase activity, is enhanced in the presence of tropomyosin. Proteolytic removal of the last three COOH-terminal residues of actin, containing the modified cysteine residue, restores the normal binding between caldesmon and actin. These results establish a correlation between the binding of caldesmon to actin and the conformation of the COOH-terminal region of actin and suggest an indirect rather than direct interaction between caldesmon and this part of actin. PMID:1939062

  12. Actin from Saccharomyces cerevisiae.

    PubMed Central

    Greer, C; Schekman, R

    1982-01-01

    Inhibition of DNase I activity has been used as an assay to purify actin from Saccharomyces cerevisiae (yeast actin). The final fraction, obtained after a 300-fold purification, is approximately 97% pure as judged by sodium dodecyl sulfate-gel electrophoresis. Like rabbit skeletal muscle actin, yeast actin has a molecular weight of about 43,000, forms 7-nm-diameter filaments when polymerization is induced by KCl or Mg2+, and can be decorated with a proteolytic fragment of muscle myosin (heavy meromyosin). Although heavy meromyosin ATPase activity is stimulated by rabbit muscle and yeast actins to approximately the same Vmax (2 mmol of Pi per min per mumol of heavy meromyosin), half-maximal activation (Kapp) is obtained with 14 micro M muscle actin, but requires approximately 135 micro M yeast actin. This difference suggests a low affinity of yeast actin for muscle myosin. Yeast and muscle filamentous actin respond similarly to cytochalasin and phalloidin, although the drugs have no effect on S. cerevisiae cell growth. Images PMID:6217414

  13. Actin Rings of Power.

    PubMed

    Schwayer, Cornelia; Sikora, Mateusz; Slováková, Jana; Kardos, Roland; Heisenberg, Carl-Philipp

    2016-06-20

    Circular or ring-like actin structures play important roles in various developmental and physiological processes. Commonly, these rings are composed of actin filaments and myosin motors (actomyosin) that, upon activation, trigger ring constriction. Actomyosin ring constriction, in turn, has been implicated in key cellular processes ranging from cytokinesis to wound closure. Non-constricting actin ring-like structures also form at cell-cell contacts, where they exert a stabilizing function. Here, we review recent studies on the formation and function of actin ring-like structures in various morphogenetic processes, shedding light on how those different rings have been adapted to fulfill their specific roles. PMID:27326928

  14. 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, Damien Johann; Jahnke, Annika; MacLeod, Matthew

    2016-04-01

    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 simulate 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 neither strongly affected by the length of sample duration nor the use of a fixed value for the transfer coefficient.

  15. Measurement of photon flux with a miniature gas ionization chamber in a Material Testing Reactor

    NASA Astrophysics Data System (ADS)

    Fourmentel, D.; Filliatre, P.; Villard, J. F.; Lyoussi, A.; Reynard-Carette, C.; Carcreff, H.

    2013-10-01

    Nuclear heating measurements in Material Testing Reactors (MTR) are crucial for the design of the experimental devices and the prediction of the temperature of the hosted samples. Nuclear heating in MTR materials (except fuel) is mainly due to the energy deposition by the photon flux. Therefore, the photon flux is a key input parameter for the computer codes which simulate nuclear heating and temperature reached by samples/devices under irradiation. In the Jules Horowitz MTR under construction at the CEA Cadarache, the maximal expected nuclear heating levels will be about 15 to 18 W g-1 and it will be necessary to assess this parameter with the best accuracy. An experiment was performed at the OSIRIS reactor to combine neutron flux, photon flux and nuclear heating measurements to improve the knowledge of the nuclear heating in MTR. There are few appropriate sensors for selective measurement of the photon flux in MTR even if studies and developments are ongoing. An experiment, called CARMEN-1, was conducted at the OSIRIS MTR and we used in particular a gas ionization chamber based on miniature fission chamber design to measure the photon flux. In this paper, we detail Monte-Carlo simulations to analyze the photon fluxes with ionization chamber measurements and we compare the photon flux calculations to the nuclear heating measurements. These results show a good accordance between photon flux measurements and nuclear heating measurement and allow improving the knowledge of these parameters.

  16. 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.

  17. 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.

  18. New technique of the local heat flux measurement in combustion chambers of steam boilers

    NASA Astrophysics Data System (ADS)

    Taler, Jan; Taler, Dawid; Sobota, Tomasz; Dzierwa, Piotr

    2011-12-01

    A new method for measurement of local heat flux to water-walls of steam boilers was developed. A flux meter tube was made from an eccentric tube of short length to which two longitudinal fins were attached. These two fins prevent the boiler setting from heating by a thermal radiation from the combustion chamber. The fins are not welded to the adjacent water-wall tubes, so that the temperature distribution in the heat flux meter is not influenced by neighbouring water-wall tubes. The thickness of the heat flux tube wall is larger on the fireside to obtain a greater distance between the thermocouples located inside the wall which increases the accuracy of heat flux determination. Based on the temperature measurements at selected points inside the heat flux meter, the heat flux absorbed by the water-wall, heat transfer coefficient on the inner tube surface and temperature of the water-steam mixture was determined.

  19. Airborne eddy correlation gas flux measurements - Design criteria for optical techniques

    NASA Technical Reports Server (NTRS)

    Ritter, John A.; Sachse, Glen W.; Anderson, Bruce E.

    1993-01-01

    Although several methods exist for the determination of the flux of an atmospheric species, the airborne eddy correlation method has the advantage of providing direct flux measurements that are representative of regional spatial domains. The design criteria pertinent to the construction of chemical instrumentation suitable for use in airborne eddy correlation flux measurements are discussed. A brief overview of the advantages and limitations of the current instrumentation used to obtain flux measurements for CO, CH4, O3, CO2, and water vapor are given. The intended height of the measurement within the convective boundary layer is also shown to be an important design criteria. The sensitivity, or resolution, which is required in the measurement of a scalar species to obtain an adequate species flux measurement is discussed. The relationship between the species flux resolution and the more commonly stated instrumental resolution is developed and it is shown that the standard error of the flux estimate is a complicated function of the atmospheric variability and the averaging time that is used. The use of the recently proposed intermittent sampling method to determine the species flux is examined. The application of this technique may provide an opportunity to expand the suite of trace gases for which direct flux measurements are possible.

  20. Use of CMOS imagers to measure high fluxes of charged particles

    NASA Astrophysics Data System (ADS)

    Servoli, L.; Tucceri, P.

    2016-03-01

    The measurement of high flux charged particle beams, specifically at medical accelerators and with small fields, poses several challenges. In this work we propose a single particle counting method based on CMOS imagers optimized for visible light collection, exploiting their very high spatial segmentation (> 3 106 pixels/cm2) and almost full efficiency detection capability. An algorithm to measure the charged particle flux with a precision of ~ 1% for fluxes up to 40 MHz/cm2 has been developed, using a non-linear calibration algorithm, and several CMOS imagers with different characteristics have been compared to find their limits on flux measurement.

  1. 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

  2. Thermal flux measurements in hypersonic flows: A review

    NASA Astrophysics Data System (ADS)

    Wendt, J. F.; Balageas, D.; Neumann, R. D.

    1993-04-01

    This contribution reviews the papers presented in the Session on 'Heat Flux' and 'Thermography' at a NATO Advanced Research Workshop entitled 'New Trends in Instrumentation for Hypersonic Research', 27 April-1 May, 1992, Le Fauga, France. The present status and problem areas associated with specific methods are discussed and recommendations for future research and development are presented.

  3. DYNAMIC FLUX CHAMBER SYSTEMS FOR FUMIGANT EMISSION MEASUREMENTS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Assessment of effective field practices on emission reductions from soil fumigation relies on continuous and reliable emission data. Dynamic (flow through) flux chambers can provide continuous sampling for fumigants volatilized from the soil surface. The objective of this project was to design and c...

  4. 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

  5. MARIE Dose and Flux Measurements in Mars Orbit

    NASA Technical Reports Server (NTRS)

    Zeitlin, C.; Cleghorn, T.; Cucinotta, F. A.; Saganti, P.; Andersen, V.; Lee, K. T.; Pinsky, L. S.; Turner, R.; Atwell, W.

    2004-01-01

    We present results from the Martian Radiation Environment Experiment (MARIE), aboard the 2001 Mars Odyssey spacecraft in orbit around Mars. MARIE operated successfully from March 2002 through October 2003. At the time of this writing, the instrument is off due to a loss of communications during an extremely intense Solar Particle Event. Efforts to revive MARIE are planned for Spring 2004, when Odyssey's role as a communications relay for the MER rovers is completed. During the period of successful operation, MARIE returned the first detailed energetic charged particle data from Mars. Due to limitations of the instrument, normalizing MARIE data to flux or dose is not straightforward - several large corrections are needed. Thus normalized results (like dose or flux) have large uncertainties and/or significant model-dependence. The problems in normalization are mainly due to inefficiency in detecting high-energy protons (signal-to-noise problems force the trigger threshold to be higher than optimal), to the excessively high gains employed in the signal processing electronics (many ions deposit energy sufficient to saturate the electronics, and dE/dx information is lost), and to artifacts associated with the two trigger detectors (incomplete registration of dE/dx). Despite these problems, MARIE is efficient for detecting helium ions with kinetic energies above about 30 MeV/nucleon, and for detecting high-energy ions (energies above about 400 MeV/nucleon) with charges from 5 to 10. Fluxes of these heavier ions can be compared to fluxes obtained from the ACE/CRIS instrument, providing at least one area of direct comparison between data obtained at Earth and at Mars; this analysis will be presented as a work in progress. We will also present dose-rate data, with a detailed explanation of the many sources of uncertainty in normalization. The results for both flux and dose will be compared to predictions of the HZETRN model of the GCR.

  6. The altitude variation of the ionospheric photoelectron flux A comparison of theory and measurement

    NASA Technical Reports Server (NTRS)

    Richards, P. G.; Torr, D. G.

    1985-01-01

    The 145 to 300-km altitude variation of the measured photoelectron flux in the 13 to 18 eV, 28 to 34 eV, and 50 to 55 eV energy regions are compared with the variations expected from theory. There is a strong linear relationship between the measured photoelectron flux and the attenuation of the solar EUV flux at these energies. Therefore, the photoelectron flux is sensitive to changes in the solar zenith angle, neutral density scale height, and total neutral density. However, contrary to previous assertions, the photoelectron flux at most energies is not sensitive to the relative densities of the neutral constituents. In addition, good agreement between theory and measurement is obtained. By using the concept of photoelectron production frequencies, the usually complex evaluation of the local equilibrium photoelectron flux is reduced to a trivial calculation so that the steps in the calculation can be readily verified.

  7. 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...

  8. 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...

  9. Calculating the detection limits of chamber-based greenhouse gas flux measurements

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Chamber-based measurement of greenhouse gas emissions from soil is a common technique. However, when changes in chamber headspace gas concentrations are small over time, determination of the flux can be problematic. Several factors contribute to the reliability of measured fluxes, including: samplin...

  10. A bottom-up perspective of the net land methanol flux: synthesis of global eddy covariance flux measurements

    NASA Astrophysics Data System (ADS)

    Wohlfahrt, Georg; Amelynck, Crist; Ammann, Christof; Arneth, Almut; Bamberger, Ines; Goldstein, Allen; Hansel, Armin; Heinesch, Bernhard; Holst, Thomas; Hörtnagl, Lukas; Karl, Thomas; Neftel, Albrecht; McKinney, Karena; Munger, William; Schade, Gunnar; Schoon, Niels

    2014-05-01

    Methanol (CH3OH) is, after methane, the second most abundant VOC in the troposphere and globally represents nearly 20% of the total biospheric VOC emissions. With typical concentrations of 1-10 ppb in the continental boundary layer, methanol plays a crucial role in atmospheric chemistry, which needs to be evaluated in the light of ongoing changes in land use and climate. Previous global methanol budgets have approached the net land flux by summing up the various emission terms (namely primary biogenic and anthropogenic emissions, plant decay and biomass burning) and by subtracting dry and wet deposition, resulting in a net land flux in the range of 75-245 Tg y-1. The data underlying these budget calculations largely stem from small-scale leaf gas exchange measurements and while recently column-integrated remotely sensed methanol concentrations have become available for constraining budget calculations, there have been few attempts to contrast model calculations with direct net ecosystem-scale methanol flux measurements. Here we use eddy covariance methanol flux measurements from 8 sites in Europe and North America to study the magnitude of and controls on the diurnal and seasonal variability in the net ecosystem methanol flux. In correspondence with leaf-level literature, our data show that methanol emission and its strong environmental and biotic control (by temperature and stomatal conductance) prevailed at the more productive (agricultural) sites and at a perturbed forest site. In contrast, at more natural, less productive sites substantial deposition of methanol occurred, in particular during periods of surface wetness. These deposition processes are poorly represented by currently available temperature/light and/or production-driven modelling algorithms. A new framework for modelling the bi-directional land-atmosphere methanol exchange is proposed which accounts for the production of methanol in leaves, the regulation of leaf methanol emission by stomatal

  11. Flux Measurements of Trace Gases, Aerosols and Energy from the Urban Core of Mexico City

    NASA Astrophysics Data System (ADS)

    Velasco, E.; Molina, L.; Lamb, B.; Pressley, S.; Grivicke, R.; Westberg, H.; Jobson, T.; Allwine, E.; Coons, T.; Jimenez, J.; Nemitz, E.; Alexander, L. M.; Worsnop, D.; Ramos, R.

    2007-05-01

    As part of the MILAGRO field campaign in March 2006 we deployed a flux system in a busy district of Mexico City surrounded by congested avenues. The flux system consisted of a tall tower instrumented with fast-response sensors coupled with eddy covariance (EC) techniques to measure fluxes of volatile organic compounds (VOCs), CO2, CO, aerosols and energy. The measured fluxes represent direct measurements of emissions that include all major and minor emission sources from a typical residential and commercial district. In a previous study we demonstrated that the EC techniques are valuable tools to evaluate emissions inventories in urban areas, and understand better the atmospheric chemistry and the role that megacities play in global change. We measured fluxes of olefins using a Fast Olefin Sensor (FOS) and the EC technique, fluxes of aromatic and oxygenated VOCs by Proton Transfer Reaction-Mass Spectroscopy (PTR-MS) and the disjunct eddy covariance (DEC) technique, fluxes of CO2 and H2O with an open path Infrared Gas Analyzer (IRGA) and the EC technique, fluxes of CO using a modified gradient method and a commercial CO instrument, and fluxes of aerosols (organics, nitrates and sulfates) using an Aerodyne Aerosol Mass Spectrometer (AMS) and the EC technique. In addition we used a disjunct eddy accumulation (DEA) system to extend the number of VOCs. This system collected whole air samples as function of the direction of the vertical wind component, and the samples were analyzed on site using gas chromatography / flame ionization detection (GC-FID). We also measured fluxes of sensible and latent heat by EC and the radiation components with a net radiometer. Overall, these flux measurements confirm the results of our previous flux measurements in Mexico City in terms of the magnitude, composition, and distribution. We found that the urban surface is a net source of CO2 and VOCs. The diurnal patterns show clear anthropogenic signatures, with important contributions from

  12. Direct dynamin–actin interactions regulate the actin cytoskeleton

    PubMed Central

    Gu, Changkyu; Yaddanapudi, Suma; Weins, Astrid; Osborn, Teresia; Reiser, Jochen; Pollak, Martin; Hartwig, John; Sever, Sanja

    2010-01-01

    The large GTPase dynamin assembles into higher order structures that are thought to promote endocytosis. Dynamin also regulates the actin cytoskeleton through an unknown, GTPase-dependent mechanism. Here, we identify a highly conserved site in dynamin that binds directly to actin filaments and aligns them into bundles. Point mutations in the actin-binding domain cause aberrant membrane ruffling and defective actin stress fibre formation in cells. Short actin filaments promote dynamin assembly into higher order structures, which in turn efficiently release the actin-capping protein (CP) gelsolin from barbed actin ends in vitro, allowing for elongation of actin filaments. Together, our results support a model in which assembled dynamin, generated through interactions with short actin filaments, promotes actin polymerization via displacement of actin-CPs. PMID:20935625

  13. Flux measurements in a nuclear research reactor by using an aluminum nitride detector

    NASA Astrophysics Data System (ADS)

    Moon, B. S.; Yoo, D. S.; Hwang, I. K.; Chung, C. E.; Holcomb, D. E.

    2007-08-01

    A small polycrystalline aluminium nitride detector with a thickness of 381 μm was used to measure a 200,000 Ci Co 60 source and to measure the flux in a research reactor where the neutron flux is about 10 14/cm 2 s, which is nearly the same order as in the commercial power plant. If the applied voltage is greater than or equal to 2000 V and if the measurements are done in a short period of time so that the heat energy does not build up in the aluminium nitride, then the measured electric current is linearly proportional to the input flux. It is assumed of course that the energy spectrum of the input flux remains constant. This linearity relation is illustrated by the results of a measurement in which the reactor power has been controlled so that the flux becomes a step function.

  14. Neutrophil actin dysfunction is a genetic disorder associated with partial impairment of neutrophil actin assembly in three family members.

    PubMed Central

    Southwick, F S; Dabiri, G A; Stossel, T P

    1988-01-01

    A male infant with a severe neutrophil motility disorder and poorly polymerizable actin in PMN extracts was reported over a decade ago to have neutrophil actin dysfunction (NAD) (1974. N. Engl. J. Med. 291:1093-1099). Polymerized actin (F-actin) content of fixed and permeabilized intact neutrophils from the father, mother, and sister of the NAD index case have been measured using nitrobenzoxadiazole-phallacidin, a fluorescent compound which binds specifically to actin filaments. F-actin content of unstimulated PMN from all three family members was significantly lower than unstimulated control PMN (mean 23.6 +/- 0.4 SEM fluorescent units vs. 32.6 +/- 0.6 for controls). After stimulation with the chemotactic peptide FMLP, maximal F-actin content of NAD family member PMN was below that of controls (52.7 +/- 1.3 vs. 72.6 +/- 1.8). F-actin content of detergent insoluble cytoskeletons after stimulation with FMLP was also significantly lower in PMN from NAD family members as compared with controls (21 +/- 6% vs. 73 +/- 8%). PMN extracts from the father and mother, when treated with 0.6 M KCl, polymerized half as much actin as controls. Whereas diisopropylfluorophosphate treatment of normal PMN decreased actin polymerizability in cell extracts, this treatment increased the assembly of actin in parental PMN extract. Addition of purified actin to NAD extracts failed to reveal an abnormal actin polymerization inhibitory activity, and no obvious structural defect in actin purified from the father's PMNs was noted by HPLC and two dimensional thin layer chromatography of tryptic digests. The present studies of actin assembly in intact PMNs confirm that NAD is associated with a true defect in PMN actin assembly and is a genetic disorder that is recessively inherited. Images PMID:3183050

  15. SkyLine and SkyGas: Novel automated technologies for automatic GHG flux measurements

    NASA Astrophysics Data System (ADS)

    Ineson, Philip; Stockdale, James

    2014-05-01

    1. Concerns for the future of the Earth's climate centre around the anthropogenically-driven continuing increases in atmospheric concentrations of the major 'greenhouse gases' (GHGs) which include CO2, CH4 and N2O. A major component of the global budgets for all three of these gases is the flux between the atmosphere and terrestrial ecosystems. 2. Currently, these fluxes are poorly quantified, largely due to technical limitations associated with making these flux measurements. Whilst eddy covariance systems have greatly improved such measurements at the ecosystem scale, flux measurements at the plot scale are commonly made using labour intensive traditional 'cover box' approaches; technical limitations have frequently been a bottle-neck in producing adequate and appropriate GHG flux data necessary for making land management decisions. For example, there are almost no night time flux data for N2O fluxes, and frequently such data are only measured over bare soil patches. 3. We have been addressing the design of novel field equipment for the automation of GHG flux measurements at the chamber and plot scale and will present here some of the technical solutions we have developed. These solutions include the development of the SkyLine and SkyGas approaches which resolve many of the common problems associated with making high frequency, sufficiently replicated GHG flux measurements under field conditions. 4. Unlike most other automated systems, these technologies 'fly' a single chamber to the measurement site, rather than have multiple replicated chambers and analysers. We will present data showing how such systems can deliver high time and spatial resolution flux data, with a minimum of operator intervention and, potentially, at relatively low per plot cost. We will also show how such measurements can be extended to monitoring fluxes from freshwater features in the landscape.

  16. Orthogonal (transverse) arrangements of actin in endothelia and fibroblasts

    PubMed Central

    Curtis, Adam; Aitchison, Gregor; Tsapikouni, Theodora

    2006-01-01

    Though actin filaments running across the cell (transverse actin) have been occasionally reported for epithelial cells in groups and for cells growing on fibres, there has been no report heretofore of transverse actin in cells grown on planar substrata. This paper describes evidence in support of this possibility derived from actin staining, polarization microscopy and force measurements. The paper introduces two new methods for detecting the orientation and activity of contractile elements in cells. The orthogonal actin is most obvious in cells grown on groove ridge structures, but can be detected in cells grown on flat surfaces. PMID:17015307

  17. Determination of solar proton fluxes and energies at high solar latitudes by UV radiation measurements

    NASA Technical Reports Server (NTRS)

    Witt, N.; Blum, P. W.; Ajello, J. M.

    1981-01-01

    The latitudinal variation of the solar proton flux and energy causes a density increase at high solar latitudes of the neutral gas penetrating the heliosphere. Measurements of the neutral density by UV resonance radiation observations from interplanetary spacecraft thus permit deductions on the dependence of the solar proton flux on heliographic latitude. Using both the results of Mariner 10 measurements and of other off-ecliptic solar wind observations, the values of the solar proton fluxes and energies at polar heliographic latitudes are determined for several cases of interest. The Mariner 10 analysis, together with IPS results, indicate a significant decrease of the solar proton flux at polar latitudes.

  18. Measuring sand flux on Mars using HiRISE Images

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    As wind is the major agent of sediment transport on Mars, a quantitative estimate of aeolian processes is therefore essential to assess recent geological evolution and current climate. We adapted the Co-registration of Optically Sensed Image and Correlation (COSI-Corr) toolbox to the MRO HiRISE imager specifications to produce a dense map of the ripples migration on the surface of the Martian dunes on the Nili Patera area. The ripple migration rate, along with an estimate of the ripple height, were used to derive the sand flux, a key quantity that controls the style and rate of landscape evolution. Using the dunes shape, size, and height, which were extracted from a DEM of the dune field, we show that the dunes are near steady state, and we observe that dune migration rate varies inversely with size and position within the dune field. The time scale associated with the formation and evolution of the Nili Patera dune field, estimated from comparing the sand volume with the sand flux and the dunes migration rates with the length scale of the dune field, is on the order of 10s to 100s of thousands Earth years. However, sand fluxes at the dune crests are 0.7 - 4.8 m3 m-1 per Earth year, which is comparable to that of dunes in Victoria Valley, Antarctica. This implies that rates of landscape modification from aeolian abrasion on Mars may be comparable to that on Earth.

  19. 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.

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

    DOEpatents

    Duncan, Robert V.

    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.

  1. Accurate measurement of poleward microtubule flux in the spindle of Drosophila S2 cells.

    PubMed

    Munzarova, Alina; Popova, Julia; Razuvaeva, Alena; Shloma, Victor; Gatti, Maurizio; Omelyanchuk, Leonid

    2016-09-01

    The spindle microtubule (MT) flux is the continuous translocation of MTs toward the spindle poles caused by MT polymerization at plus ends coupled to depolymerization at minus ends. Poleward flux is observed in both mitotic and meiotic spindles; it is evolutionarily conserved and contributes to the regulation of spindle length and anaphase chromosome movement. MT photobleaching is a tool frequently used to measure poleward flux. Spindles containing fluorescently tagged tubulin are photobleached to generate a non-fluorescent stripe, which moves toward the spindle poles allowing a measure of the flux. However, this method only permits rapid measurements of the flux, because the fluorescence of the bleached stripe recovers rapidly due to the spindle MT turnover. Here, we describe a modification of the current photobleaching-based method for flux measurement. We photobleached two large areas at the opposite sides of the metaphase plate in spindles of Drosophila S2 cells expressing Cherry-tagged tubulin, leaving unbleached only the area near the chromosomes. We then measured the speed with which the fluorescent MTs move toward the poles. We found that this method allows a measure of the flux over a two- to threefold longer time than the "single stripe" method, providing a reliable evaluation of the flux rate. PMID:27317357

  2. Anthropogenic and Biogenic Features of Long-Term Measured CO Flux in North Downtown Houston, Texas.

    PubMed

    Park, Changhyoun; Schade, Gunnar W

    2016-01-01

    Long-term urban carbon cycle studies remain rare despite the importance of carbon for energy, air quality, and climate change. To study spatial and temporal variations of energy and carbon fluxes in a subtropical urban environment, eddy covariance flux measurements were conducted north of downtown Houston, TX, using a tall radio-tower installation. The results of the first 2 yr of measurements show that both concentrations and fluxes of CO display typical seasonal and diurnal variations in urban areas. The seasonal variation of net CO flux is driven by steady anthropogenic emissions dominated by car traffic and human respiration, moderated by the local deciduous tree foliage. Weekday-weekend differences were observed in carbon fluxes, but not concentrations, while diurnal changes were dominated by rush-hour peaks from traffic and vegetation influences. Interestingly, CO and CO concentrations, but not CO flux, exhibited long-term declines, especially comparing pre- and post-Hurricane Ike periods. A directional analysis of CO fluxes revealed that the highest fluxes typically occurred from northwest directions, most likely due to emissions from small industrial sources. Car traffic as carbon source was revealed via correlations of CO with CO during the morning rush hours, and of CO flux with traffic counts during winter time. The influence of urban vegetation on net CO fluxes was identified via correlations with daytime photosynthetically active radiation due to photosynthesis, and with nighttime temperatures due to ecosystem respiration. The study site is a net source of CO throughout all seasons. PMID:26828181

  3. Combined FTIR-micrometeorological techniques for long term measurements of greenhouse gas fluxes from agriculture

    NASA Astrophysics Data System (ADS)

    Petersen, A. K.; Griffith, D.; Harvey, M.; Naylor, T.; Smith, M.

    2009-04-01

    The exchange of trace gases between the biosphere and the atmosphere affects the atmospheric concentrations of gases such as methane, carbon dioxide, nitrous oxide, carbon monoxide, ammonia, volatile organic compounds, nitrogen dioxide and others. The quantification of the exchange between a biogenic system and the atmosphere is necessary for the evaluation of the impact of these interactions. This is of special interest for agricultural systems which can be sources or sinks of trace gases, and the measurement of the fluxes is necessary when evaluating both the environmental impact of agricultural activities and the impact of atmospheric pollution on agricultural production and sustainability. With the exception of CO2, micrometeorological measurements of the fluxes of greenhouse gases from agricultural activities are still mostly possible only in campaign mode due to the complexity and logistical requirements of the existing measurement techniques. This limitation precludes studies of fluxes which run for longer periods, for example over full seasonal or growing cycles for both animal- and crop-based agriculture. We have developed an instrument system for long-term flux measurements through a combination of micrometeorological flux measurement techniques such as Relaxed Eddy Accumulation (REA) and Flux-Gradient (FG) with the high precision multi-species detection capabilities of FTIR spectroscopy. The combined technique is capable of simultaneous flux measurements of N2O, CH4 and CO2 at paddock to regional scales continuously, over longer terms (months, seasonal cycles, years). The system was tested on a 3 weeks field campaign in NSW, Australia on a flat, homogeneous circular grass paddock with grazing cattle. The flux of the atmospheric trace gas CO2 was measured with three different micrometeorological techniques: Relaxed Eddy Accumulation, Flux-Gradient, and Eddy Correlation. Simultaneously, fluxes of CH4 and N2O were measured by REA and FG technique.

  4. Actin Mechanics and Fragmentation*

    PubMed Central

    De La Cruz, Enrique M.; Gardel, Margaret L.

    2015-01-01

    Cell physiological processes require the regulation and coordination of both mechanical and dynamical properties of the actin cytoskeleton. Here we review recent advances in understanding the mechanical properties and stability of actin filaments and how these properties are manifested at larger (network) length scales. We discuss how forces can influence local biochemical interactions, resulting in the formation of mechanically sensitive dynamic steady states. Understanding the regulation of such force-activated chemistries and dynamic steady states reflects an important challenge for future work that will provide valuable insights as to how the actin cytoskeleton engenders mechanoresponsiveness of living cells. PMID:25957404

  5. Actin Polymerization is Stimulated by Actin Crosslinking Protein Palladin

    PubMed Central

    Gurung, Ritu; Yadav, Rahul; Brungardt, Joseph G.; Orlova, Albina; Egelman, Edward H.; Beck, Moriah R.

    2016-01-01

    The actin scaffold protein palladin regulates both normal cell migration and invasive cell motility, processes that require the coordinated regulation of actin dynamics. However, the potential effect of palladin on actin dynamics has remained elusive. Here we show that the actin binding immunoglobulin-like domain of palladin, which is directly responsible for both actin binding and bundling, also stimulates actin polymerization in vitro. Palladin eliminated the lag phase that is characteristic of the slow nucleation step of actin polymerization. Furthermore, palladin dramatically reduced depolymerization, slightly enhanced the elongation rate, and did not alter the critical concentration. Microscopy and in vitro crosslinking assays reveal differences in actin bundle architecture when palladin is incubated with actin before or after polymerization. These results suggest a model whereby palladin stimulates a polymerization-competent form of G-actin, akin to metal ions, either through charge neutralization or conformational changes. PMID:26607837

  6. A simple method for measuring the relative force exerted by myosin on actin filaments in the in vitro motility assay: evidence that tropomyosin and troponin increase force in single thin filaments.

    PubMed Central

    Bing, W; Knott, A; Marston, S B

    2000-01-01

    We have studied the effect of an internal load on the movement of actin filaments over a bed of heavy meromyosin (HMM) in the in vitro motility assay. Immobilized alpha-actinin can bind to actin filaments reversibly and ultimately stop the filaments from moving. Above a critical concentration of alpha-actinin, thin filament velocity rapidly diminished to zero. The fraction of thin motile filaments decreased linearly to zero with increasing alpha-actinin concentration. The concentration of alpha-actinin needed to stop all filaments from moving (0.8 microg/ml with actin) was very consistent both within and between experiments. In the present study we have defined the 'index of retardation' as the concentration of alpha-actinin needed to stop all filament movement, and we propose that this index is a measure of the isometric force exerted by HMM on actin filaments. When we measured the effect of immobilized alpha-actinin on motility in the presence of 10 mM P(i) we found that the index of retardation was 0.62+/-0.07 (n=3) times that in the absence of P(i). This observation is in agreement with the reduction of isometric tension in chemically-skinned muscle due to P(i). In a series of comparative experiments we observed that tropomyosin and troponin increase the index of retardation and that the degree of increase depends upon the tropomyosin isoform studied. The index of retardation of actin is increased 1.8-fold by skeletal-muscle tropomyosin, and 3-fold by both cardiac-muscle and smooth-muscle tropomyosin. In the presence of troponin the index of retardation is 2.9-3.4-fold greater than that of actin with all tropomyosin isoforms. PMID:10970781

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

    DOE R&D Accomplishments Database

    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.

    2009-07-10

    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}.

  8. 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}.

  9. Demonstration of HNO3 Eddy Flux Measurements at the Boulder Atmospheric Observatory Using Active Passivation

    NASA Astrophysics Data System (ADS)

    Roscioli, J. R.; Herndon, S. C.; Zahniser, M. S.; Nelson, D. D.; Zaragoza, J.; Pollack, I. B.; Fischer, E. V.

    2015-12-01

    Eddy flux measurements of "sticky" molecules have historically proven difficult due to strong interactions with instrument surfaces. A novel approach has been developed to improve these response times, enabling flux measurements of nitric acid (HNO3) and and ammonia (NH3). Deliberate addition of the vapor of perfluorinated acids and bases into a sample stream serves to eject existing surface-bound sample molecules and passivate instrument surfaces. HNO3 response times for an Aerodyne quantum cascade laser absorption spectrometer (QCLAS) improve by a factor of 60-fold when actively passivating. This approach was used during field measurements of HNO3 fluxes at the Boulder Atmospheric Observatory, where an actively passivated inertial inlet at 8 m height yielded HNO3 deposition fluxes of 0.5 - 2 nmol/m2/sec. The dependence of the deposition flux upon urban vs rural outflow is discussed.

  10. 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%.

  11. Sensible heat bias in open-path eddy covariance carbon dioxide flux measurements

    NASA Astrophysics Data System (ADS)

    Sonnentag, O.; Helbig, M.; Karoline, W.; Humphreys, E.; Quinton, W. L.; Bogoev, I.

    2015-12-01

    The widely observed differences between net carbon dioxide (CO2) flux estimates derived from eddy covariance systems deploying open- and closed-path infrared gas analyzers (IRGAs) pose a major challenge for site intercomparison studies. Our limited knowledge about potential systematic biases in the derivation of CO2 flux estimates by these two types of systems hampers our ability to detect significant differences in CO2 flux measurements made at contrasting ecosystems. Here we explore potential systematic biases in CO2 fluxes measured with two open-path IRGAs. Comparison of fluxes from open- (EC150 & IRGASON, Campbell Scientific Inc.) and (en)closed-path IRGAs (LI7000 & LI7200, LI-COR Biosciences) at a northern peatland and a northern boreal forest site revealed consistent differences in CO2 flux estimates across a wide range of environmental conditions. These differences directly scaled with the magnitude of the sensible heat flux indicating a selectively systematic bias in open-path CO2 flux measurements due to the temperature sensitivity of the CO2 density measurements. We present two empirical correction procedures: the "direct" approach requires data from a limited period of concurrent CO2 flux measurements by open- and closed-path IRGA-based eddy covariance systems, whereas the second approach only requires wintertime CO2 flux data from the open-path IRGA. The "direct" approach effectively removes the bias in the open-path CO2 flux measurements and results in remaining differences with the closed-path CO2 fluxes smaller than 0.5 µmol m-2 s-1. In contrast, the "wintertime" approach seems to overcompensate for the sensible heat effects with differences remaining between 0.9 µmol m-2 s-1 and 1.8 µmol m-2 s-1. When a high-frequency air temperature is used to compensate for the temperature sensitivity of the CO2 density measurements, open- and closed-path CO2 flux agree within ±0.5 µmol m-2 s-1, similar to the "direct" post-processing correction. These

  12. 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.

  13. A comparison of measured and modeled turbulent fluxes over snow based on site characteristics

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sensible and latent heat and mass flux represent a significant component of the snowcover energy and mass balance in mountain environments. Though these fluxes are computed in energy balance snow models, limited measurements exist for comparison or validation in complex, mountainous sites. Sensibl...

  14. An assessment of corrections for eddy covariance measured turbulent fluxes over snow in mountain environments

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Snow-covered complex terrain is an extremely important runoff generating landscape in high altitude and latitude environments, yet is often considered non-viable for eddy covariance measurements of turbulent fluxes. Turbulent flux data are useful for evaluating the coupled snow cover mass and energ...

  15. 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.

  16. 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.

  17. Measurement of the Magnetic Flux Noise Spectrum in Superconducting Xmon Transmon Quantum Bits

    NASA Astrophysics Data System (ADS)

    Chiaro, Ben; Sank, D.; Kelly, J.; Chen, Z.; Campbell, B.; Dunsworth, A.; O'Malley, P.; Neill, C.; Quintana, C.; Vainsencher, A.; Wenner, J.; Barends, R.; Chen, Y.; Fowler, A.; Jeffrey, E.; Migrant, A.; Mutus, J.; Roushan, P.; White, T.; Martinis, J. M.

    Dephasing induced by magnetic flux noise limits the performance of modern superconducting quantum processors. We measure the flux noise power spectrum in planar, frequency-tunable, Xmon transmon quantum bits (qubits), with several SQUID loop geometries. We extend the Ramsey Tomography Oscilloscope (RTO) technique by rapid sampling up to 1 MHz, without state reset, to measure the flux noise power spectrum between 10-2 and 105 Hz. The RTO measurements are combined with idle gate randomized benchmarking and Ramsey decay to give a more complete picture of dephasing in SQUID-based devices.

  18. 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

  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

  20. Actin Automata with Memory

    NASA Astrophysics Data System (ADS)

    Alonso-Sanz, Ramón; Adamatzky, Andy

    Actin is a globular protein which forms long polar filaments in eukaryotic. The actin filaments play the roles of cytoskeleton, motility units, information processing and learning. We model actin filament as a double chain of finite state machines, nodes, which take states “0” and “1”. The states are abstractions of absence and presence of a subthreshold charge on actin units corresponding to the nodes. All nodes update their state in parallel to discrete time. A node updates its current state depending on states of two closest neighbors in the node chain and two closest neighbors in the complementary chain. Previous models of actin automata consider momentary state transitions of nodes. We enrich the actin automata model by assuming that states of nodes depend not only on the current states of neighboring node but also on their past states. Thus, we assess the effect of memory of past states on the dynamics of acting automata. We demonstrate in computational experiments that memory slows down propagation of perturbations, decrease entropy of space-time patterns generated, transforms traveling localizations to stationary oscillators, and stationary oscillations to still patterns.

  1. A framework to utilize turbulent flux measurements for mesoscale models and remote sensing applications

    NASA Astrophysics Data System (ADS)

    Babel, W.; Huneke, S.; Foken, T.

    2011-05-01

    Meteorologically measured fluxes of energy and matter between the surface and the atmosphere originate from a source area of certain extent, located in the upwind sector of the device. The spatial representativeness of such measurements is strongly influenced by the heterogeneity of the landscape. The footprint concept is capable of linking observed data with spatial heterogeneity. This study aims at upscaling eddy covariance derived fluxes to a grid size of 1 km edge length, which is typical for mesoscale models or low resolution remote sensing data. Here an upscaling strategy is presented, utilizing footprint modelling and SVAT modelling as well as observations from a target land-use area. The general idea of this scheme is to model fluxes from adjacent land-use types and combine them with the measured flux data to yield a grid representative flux according to the land-use distribution within the grid cell. The performance of the upscaling routine is evaluated with real datasets, which are considered to be land-use specific fluxes in a grid cell. The measurements above rye and maize fields stem from the LITFASS experiment 2003 in Lindenberg, Germany and the respective modelled timeseries were derived by the SVAT model SEWAB. Contributions from each land-use type to the observations are estimated using a forward lagrangian stochastic model. A representation error is defined as the error in flux estimates made when accepting the measurements unchanged as grid representative flux and ignoring flux contributions from other land-use types within the respective grid cell. Results show that this representation error can be reduced up to 56 % when applying the spatial integration. This shows the potential for further application of this strategy, although the absolute differences between flux observations from rye and maize were so small, that the spatial integration would be rejected in a real situation. Corresponding thresholds for this decision have been estimated as

  2. A direct passive method for measuring water and contaminant fluxes in porous media

    NASA Astrophysics Data System (ADS)

    Hatfield, Kirk; Annable, Michael; Cho, Jaehyun; Rao, P. S. C.; Klammler, Harald

    2004-12-01

    This paper introduces a new direct method for measuring water and contaminant fluxes in porous media. The method uses a passive flux meter (PFM), which is essentially a self-contained permeable unit properly sized to fit tightly in a screened well or boring. The meter is designed to accommodate a mixed medium of hydrophobic and/or hydrophilic permeable sorbents, which retain dissolved organic/inorganic contaminants present in the groundwater flowing passively through the meter. The contaminant mass intercepted and retained on the sorbent is used to quantify cumulative contaminant mass flux. The sorptive matrix is also impregnated with known amounts of one or more water soluble 'resident tracers'. These tracers are displaced from the sorbent at rates proportional to the groundwater flux; hence, in the current meter design, the resident tracers are used to quantify cumulative groundwater flux. Theory is presented and quantitative tools are developed to interpret the water flux from tracers possessing linear and nonlinear elution profiles. The same theory is extended to derive functional relationships useful for quantifying cumulative contaminant mass flux. To validate theory and demonstrate the passive flux meter, results of multiple box-aquifer experiments are presented and discussed. From these experiments, it is seen that accurate water flux measurements are obtained when the tracer used in calculations resides in the meter at levels representing 20 to 70 percent of the initial condition. 2,4-Dimethyl-3-pentanol (DMP) is used as a surrogate groundwater contaminant in the box aquifer experiments. Cumulative DMP fluxes are measured within 5% of known fluxes. The accuracy of these estimates generally increases with the total volume of water intercepted.

  3. Eddy covariance carbonyl sulfide flux measurements with a quantum cascade laser absorption spectrometer

    NASA Astrophysics Data System (ADS)

    Gerdel, Katharina; Spielmann, Felix M.; Hammerle, Albin; Wohlfahrt, Georg

    2016-04-01

    Carbonyl sulfide (COS) is the most abundant sulfur containing trace gas present in the troposphere at concentrations of around 500 ppt. Recent interest in COS by the ecosystem-physiological community has been sparked by the fact that COS co-diffuses into plant leaves pretty much the same way as carbon dioxide (CO2) does, but in contrast to CO2, COS is not known to be emitted by plants. Thus uptake of COS by vegetation has the potential to be used as a tracer for canopy gross photosynthesis, which cannot be measured directly, however represents a key term in the global carbon cycle. Since a few years, quantum cascade laser absorption spectrometers (QCLAS) are commercially available with the precision, sensitivity and time response suitable for eddy covariance (EC) flux measurements. While there exist a handful of published reports on EC flux measurements in the recent literature, no rigorous investigation of the applicability of QCLAS for EC COS flux measurements has been carried out so far, nor have been EC processing and QA/QC steps developed for carbon dioxide and water vapor flux measurements within FLUXNET been assessed for COS. The aim of this study is to close this knowledge gap, to discuss critical steps in the post-processing chain of COS EC flux measurements and to devise best-practice guidelines for COS EC flux data processing. To this end we collected EC COS (and CO2, H2O and CO) flux measurements above a temperate mountain grassland in Austria over the vegetation period 2015 with a commercially available QCLAS. We discuss various aspects of EC data post-processing, in particular issues with the time-lag estimation between sonic anemometer and QCLAS signals and QCLAS time series detrending, as well as QA/QC, in particular flux detection limits, random flux uncertainty, the interaction of various processing steps with common EC QA/QC filters (e.g. detrending and stationarity tests), u*-filtering, etc.

  4. An inter-comparison of surface energy flux measurement systems used during FIFE, 1987

    NASA Technical Reports Server (NTRS)

    Nie, D.; Kanemasu, E. T.; Fritschen, L. J.; Weaver, H.; Smith, E. A.; Verma, S. B.; Field, R. T.; Kustas, W.; Stewart, J. B.

    1990-01-01

    During the first International Satellite Land Surface Climatology Program Field Experiment (FIFE-87), surface energy fluxes were measured at 22 flux sites by nine groups of scientists using different measuring systems. A rover Bowen ratio station was taken to nearly all the flux stations to serve as a reference for estimating the instrument related differences. The rover system was installed within a few meters from the host instrument of a site. Net radiation, Bowen ratio, and latent heat fluxes were compared between the rover and the host for the stations visited. Linear regression analysis was used to examine the relationship between rover measurements and host measurements. These inter-comparisons are needed to examine the influence of instrumentation on measurement uncertainty. Highly significant effects of instrument type were detected from these comparisons. Instruments of the same type showed average differences of less than 5 percent for net radiation, 10 percent for Bowen ratio, and 6 percent for latent heat flux. The corresponding average differences for different types of instruments can be up to 10, 30, and 20 percent respectively. The Didcot net radiometer gave higher net radiation while the Swissteco type showed lower values, as compared to the corrected REBS model. The 4-way components methed and the Thornswaite type give similar values to the REBS. The SERBS type Bowen ratio systems exhibit slightly lower Bowen ratios and thus higher latent heat fluxes, compared to the AZET systems. Eddy correlation systems showed slightly lower latent heat flux in comparison to the Bowen ratio systems.

  5. Measurement of LNAPL flux using single-well intermittent mixing tracer dilution tests.

    PubMed

    Smith, Tim; Sale, Tom; Lyverse, Mark

    2012-01-01

    The stability of subsurface Light Nonaqueous Phase Liquids (LNAPLs) is a key factor driving expectations for remedial measures at LNAPL sites. The conventional approach to resolving LNAPL stability has been to apply Darcy's Equation. This paper explores an alternative approach wherein single-well tracer dilution tests with intermittent mixing are used to resolve LNAPL stability. As a first step, an implicit solution for single-well intermittent mixing tracer dilution tests is derived. This includes key assumptions and limits on the allowable time between intermittent mixing events. Second, single-well tracer dilution tests with intermittent mixing are conducted under conditions of known LNAPL flux. This includes a laboratory sand tank study and two field tests at active LNAPL recovery wells. Results from the sand tank studies indicate that LNAPL fluxes in wells can be transformed into formation fluxes using corrections for (1) LNAPL thicknesses in the well and formation and (2) convergence of flow to the well. Using the apparent convergence factor from the sand tank experiment, the average error between the known and measured LNAPL fluxes is 4%. Results from the field studies show nearly identical known and measured LNAPL fluxes at one well. At the second well the measured fluxes appear to exceed the known value by a factor of two. Agreement between the known and measured LNAPL fluxes, within a factor of two, indicates that single-well tracer dilution tests with intermittent mixing can be a viable means of resolving LNAPL stability. PMID:22489832

  6. The Molecular Evolution of Actin

    PubMed Central

    Hightower, Robin C.; Meagher, Richard B.

    1986-01-01

    We have investigated the molecular evolution of plant and nonplant actin genes comparing nucleotide and amino acid sequences of 20 actin genes. Nucleotide changes resulting in amino acid substitutions (replacement substitutions) ranged from 3–7% for all pairwise comparisons of animal actin genes with the following exceptions. Comparisons between higher animal muscle actin gene sequences and comparisons between higher animal cytoplasmic actin gene sequences indicated <3% divergence. Comparisons between plant and nonplant actin genes revealed, with two exceptions, 11–15% replacement substitution. In the analysis of plant actins, replacement substitution between soybean actin genes SAc1, SAc3, SAc4 and maize actin gene MAc1 ranged from 8–10%, whereas these members within the soybean actin gene family ranged from 6–9% replacement substitution. The rate of sequence divergence of plant actin sequences appears to be similar to that observed for animal actins. Furthermore, these and other data suggest that the plant actin gene family is ancient and that the families of soybean and maize actin genes have diverged from a single common ancestral plant actin gene that originated long before the divergence of monocots and dicots. The soybean actin multigene family encodes at least three classes of actin. These classes each contain a pair of actin genes that have been designated kappa (SAc1, SAc6), lambda (SAc2, SAc4) and mu (SAc3, SAc7). The three classes of soybean actin are more divergent in nucleotide sequence from one another than higher animal cytoplasmic actin is divergent from muscle actin. The location and distribution of amino acid changes were compared between actin proteins from all sources. A comparison of the hydropathy of all actin sequences, except from Oxytricha, indicated a strong similarity in hydropathic character between all plant and nonplant actins despite the greater number of replacement substitutions in plant actins. These protein sequence

  7. 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.

  8. A True Eddy Accumulation - Eddy Covariance hybrid for measurements of turbulent trace gas fluxes

    NASA Astrophysics Data System (ADS)

    Siebicke, Lukas

    2016-04-01

    Eddy covariance (EC) is state-of-the-art in directly and continuously measuring turbulent fluxes of carbon dioxide and water vapor. However, low signal-to-noise ratios, high flow rates and missing or complex gas analyzers limit it's application to few scalars. True eddy accumulation, based on conditional sampling ideas by Desjardins in 1972, requires no fast response analyzers and is therefore potentially applicable to a wider range of scalars. Recently we showed possibly the first successful implementation of True Eddy Accumulation (TEA) measuring net ecosystem exchange of carbon dioxide of a grassland. However, most accumulation systems share the complexity of having to store discrete air samples in physical containers representing entire flux averaging intervals. The current study investigates merging principles of eddy accumulation and eddy covariance, which we here refer to as "true eddy accumulation in transient mode" (TEA-TM). This direct flux method TEA-TM combines true eddy accumulation with continuous sampling. The TEA-TM setup is simpler than discrete accumulation methods while avoiding the need for fast response gas analyzers and high flow rates required for EC. We implemented the proposed TEA-TM method and measured fluxes of carbon dioxide (CO2), methane (CH4) and water vapor (H2O) above a mixed beech forest at the Hainich Fluxnet and ICOS site, Germany, using a G2301 laser spectrometer (Picarro Inc., USA). We further simulated a TEA-TM sampling system using measured high frequency CO2 time series from an open-path gas analyzer. We operated TEA-TM side-by-side with open-, enclosed- and closed-path EC flux systems for CO2, H2O and CH4 (LI-7500, LI-7200, LI-6262, LI-7700, Licor, USA, and FGGA LGR, USA). First results show that TEA-TM CO2 fluxes were similar to EC fluxes. Remaining differences were similar to those between the three eddy covariance setups (open-, enclosed- and closed-path gas analyzers). Measured TEA-TM CO2 fluxes from our physical

  9. A scintillating fission detector for neutron flux measurements

    SciTech Connect

    Stange, Sy; Esch, Ernst I; Burgett, Eric A; May, Iain; Muenchausen, Ross E; Taw, Felicia; Tovesson, Fredrik K

    2010-01-01

    Neutron flux monitors are commonly used for a variety of nuclear physics applications. A scintillating neutron detector, consisting of a liquid scintillator loaded with fissionable material, has been developed, characterized, and tested in the beam line at the Los Alamos Neutron Science Center, and shows a significant improvement in neutron sensitivity compared with a conventional fission chamber. Recent research on nanocomposite-based scintillators for gamma-ray detection indicates that this approach can be extended to load nanoparticles of fissionable material into a scintillating matrix, with up to three orders of magnitude higher loading than typical fission chambers. This will result in a rugged, cost-efficient detector with high efficiency, a short signal rise time, and the ability to be used in low neutron-flux environments. Initial efforts to utilize the luminescence of uranyl oxide to eliminate the need for wavelength-shifting dyes were unsuccessful. Excitation of uranyl compounds has been reported at wavelengths ranging from 266 nm to 532 nm. However, neither the 300 nm emission of toluene, nor the 350 nm emission of PPO, nor the 410 nm emission of POPOP resulted in significant excitation of and emission by uranyl oxide. As indicated by UV/visible spectroscopy, light emitted at these wavelengths was absorbed by the colored solution. {sup 235}U remains the most attractive candidate for a fissionable scintillator, due to its high fission cross-section and lack of a threshold fission energy, but all solutions containing molecular uranium compounds will be colored, most more highly than the U{sup 6+} compounds used here. Research is therefore continuing toward the fabrication of uranium nanoparticles, in which, due to Rayleigh scattering, the coloration should be less pronounced. The characterization of the thorium-loaded liquid scintillator and the fabrication of the 100 mL detectors for use at LANSCE demonstrated the feasibility of loading fissionable

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

    NASA Astrophysics Data System (ADS)

    Velasco, E.; Pressley, S.; Grivicke, R.; Allwine, E.; Coons, T.; Foster, W.; Jobson, B. T.; Westberg, H.; Ramos, R.; Hernández, F.; Molina, L. T.; Lamb, B.

    2009-10-01

    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 chemistry and the role that cities play in regional and global chemical cycles. As part of the MCMA-2003 study, we demonstrated the feasibility of using eddy covariance techniques to measure fluxes of selected volatile organic compounds (VOCs) and CO2 from a residential district of Mexico City (Velasco et al., 2005a, b). During the MILAGRO/MCMA-2006 field campaign, a second flux measurement study was conducted in a different district of Mexico City to corroborate the 2003 flux measurements, to expand the number of species measured, and to obtain additional data for evaluation of the local emissions inventory. Fluxes of CO2 and olefins were measured by the conventional EC technique using an open path CO2 sensor and a Fast Isoprene Sensor calibrated with a propylene standard. In addition, fluxes of toluene, benzene, methanol and C2-benzenes were measured using a virtual disjunct EC method with a Proton Transfer Reaction Mass Spectrometer. The flux measurements were analyzed in terms of diurnal patterns and vehicular activity and were compared with the most recent gridded local emissions inventory. In both studies, the results showed that the urban surface of Mexico City is a net source of CO2 and VOCs with significant contributions from vehicular traffic. Evaporative emissions from commercial and other anthropogenic activities were significant sources of toluene and methanol. The results show that the emissions inventory is in reasonable agreement with measured olefin and CO2 fluxes, while C2-benzenes and toluene emissions from evaporative sources are overestimated in the inventory. It appears that methanol emissions from mobile sources occur, but are not reported in the mobile emissions inventory.

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

    NASA Astrophysics Data System (ADS)

    Velasco, E.; Pressley, S.; Grivicke, R.; Allwine, E.; Coons, T.; Foster, W.; Jobson, T.; Westberg, H.; Ramos, R.; Hernández, F.; Molina, L. T.; Lamb, B.

    2009-03-01

    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 chemistry and the role that cities play in regional and global chemical cycles. As part of the MCMA-2003 study, we demonstrated the feasibility of using eddy covariance techniques to measure fluxes of selected volatile organic compounds (VOCs) and CO2 from a residential district of Mexico City (Velasco et al., 2005a, b). During the MILAGRO/MCMA-2006 field campaign, a second flux measurement study was conducted in a different district of Mexico City to corroborate the 2003 flux measurements, to expand the number of species measured, and to obtain additional data for evaluation of the local emissions inventory. Fluxes of CO2 and olefins were measured by the conventional EC technique using an open path CO2 sensor and a Fast Isoprene Sensor calibrated with a propylene standard. In addition, fluxes of toluene, benzene, methanol and C2-benzenes were measured using a virtual disjunct EC method with a Proton Transfer Reaction Mass Spectrometer. The flux measurements were analyzed in terms of diurnal patterns and vehicular activity and were compared with the most recent gridded emissions inventory. In both studies, the results showed that the urban surface of Mexico City is a net source of CO2 and VOCs with significant contributions from vehicular traffic. Evaporative emissions from commercial and other anthropogenic activities were significant sources of toluene and methanol. The data show that the emissions inventory is in reasonable agreement with measured olefin and CO2 fluxes, while C2-benzenes and toluene emissions from evaporative sources are overestimated in the inventory. It appears that methanol emissions from mobile sources occur, but are not present in the mobile emissions inventory.

  12. The Thermal Conductivity Measurements of Solid Samples by Heat Flux Differantial Scanning Calorimetry

    NASA Astrophysics Data System (ADS)

    Kök, M.; Aydoǧdu, Y.

    2007-04-01

    The thermal conductivity of polyvinylchloride (PVC), polysytrene (PS) and polypropylene (PP) were measured by heat flux DSC. Our results are in good agreement with the results observed by different methods.

  13. Length regulation of mechanosensitive stereocilia depends on very slow actin dynamics and filament-severing proteins.

    PubMed

    Narayanan, Praveena; Chatterton, Paul; Ikeda, Akihiro; Ikeda, Sakae; Corey, David P; Ervasti, James M; Perrin, Benjamin J

    2015-01-01

    Auditory sensory hair cells depend on stereocilia with precisely regulated lengths to detect sound. Since stereocilia are primarily composed of crosslinked, parallel actin filaments, regulated actin dynamics are essential for controlling stereocilia length. Here we assessed stereocilia actin turnover by monitoring incorporation of inducibly expressed β-actin-GFP in adult mouse hair cells in vivo and by directly measuring β-actin-GFP turnover in explants. Stereocilia actin incorporation is remarkably slow and restricted to filament barbed ends in a small tip compartment, with minimal accumulation in the rest of the actin core. Shorter rows of stereocilia, which have mechanically gated ion channels, show more variable actin turnover than the tallest stereocilia, which lack channels. Finally, the proteins ADF and AIP1, which both mediate actin filament severing, contribute to stereocilia length maintenance. Altogether, the data support a model whereby stereocilia actin cores are largely static, with dynamic regulation at the tips to maintain a critical length. PMID:25897778

  14. 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.

  15. Temperature measurements during high flux ion beam irradiations.

    PubMed

    Crespillo, M L; Graham, J T; Zhang, Y; Weber, W J

    2016-02-01

    A systematic study of the ion beam heating effect was performed in a temperature range of -170 to 900 °C using a 10 MeV Au(3+) ion beam and a Yttria stabilized Zirconia (YSZ) sample at a flux of 5.5 × 10(12) cm(-2) s(-1). Different geometric configurations of beam, sample, thermocouple positioning, and sample holder were compared to understand the heat/charge transport mechanisms responsible for the observed temperature increase. The beam heating exhibited a strong dependence on the background (initial) sample temperature with the largest temperature increases occurring at cryogenic temperatures and decreasing with increasing temperature. Comparison with numerical calculations suggests that the observed heating effect is, in reality, a predominantly electronic effect and the true temperature rise is small. A simple model was developed to explain this electronic effect in terms of an electrostatic potential that forms during ion irradiation. Such an artificial beam heating effect is potentially problematic in thermostated ion irradiation and ion beam analysis apparatus, as the operation of temperature feedback systems can be significantly distorted by this effect. PMID:26931879

  16. Measurement of momentum flux using two meteor radars in Indonesia

    NASA Astrophysics Data System (ADS)

    Matsumoto, Naoki; Shinbori, Atsuki; Riggin, Dennis M.; Tsuda, Toshitaka

    2016-03-01

    Two nearly identical meteor radars were operated at Koto Tabang (0.20° S, 100.32° E), West Sumatra, and Biak (1.17° S, 136.10° E), West Papua, in Indonesia, separated by approximately 4000 km in longitude on the Equator. The zonal and meridional momentum flux, u'w' and v'w', where u, v, and w are the eastward, northward, and vertical wind velocity components, respectively, were estimated at 86 to 94 km altitudes using the meteor radar data by applying a method proposed by Hocking (2005). The observed u'w' at the two sites agreed reasonably well at 86, 90, and 94 km during the observation periods when the data acquisition rate was sufficiently large enough. Variations in v'w' were consistent between 86, 90, and 94 km altitudes at both sites. The climatological variation in the monthly averaged u'w' and v'w' was investigated using the long-term radar data at Koto Tabang from November 2002 to November 2013. The seasonal variations in u'w' and v'w' showed a repeatable semiannual and annual cycles, respectively. u'w' showed eastward values in February-April and July-September and v'w' was northward in June to August at 90-94 km, both of which were generally anti-phase with the mean zonal and meridional winds, having the same periodicity. Our results suggest the usefulness of the Hocking method.

  17. Temperature measurements during high flux ion beam irradiations

    DOE PAGESBeta

    Crespillo, Miguel L.; Graham, Joseph T.; Zhang, Yanwen; Weber, William J.

    2016-02-16

    A systematic study of the ion beam heating effect was performed in a temperature range of –170 to 900 °C using a 10 MeV Au3+ ion beam and a Yttria stabilized Zirconia (YSZ) sample at a flux of 5.5 × 1012 cm–2 s–1. Different geometric configurations of beam, sample, thermocouple positioning, and sample holder were compared to understand the heat/charge transport mechanisms responsible for the observed temperature increase. The beam heating exhibited a strong dependence on the background (initial) sample temperature with the largest temperature increases occurring at cryogenic temperatures and decreasing with increasing temperature. Comparison with numerical calculations suggestsmore » that the observed heating effect is, in reality, a predominantly electronic effect and the true temperature rise is small. Furthermore, a simple model was developed to explain this electronic effect in terms of an electrostatic potential that forms during ion irradiation. Such an artificial beam heating effect is potentially problematic in thermostated ion irradiation and ion beamanalysis apparatus, as the operation of temperature feedback systems can be significantly distorted by this effect.« less

  18. Temperature measurements during high flux ion beam irradiations

    NASA Astrophysics Data System (ADS)

    Crespillo, M. L.; Graham, J. T.; Zhang, Y.; Weber, W. J.

    2016-02-01

    A systematic study of the ion beam heating effect was performed in a temperature range of -170 to 900 °C using a 10 MeV Au3+ ion beam and a Yttria stabilized Zirconia (YSZ) sample at a flux of 5.5 × 1012 cm-2 s-1. Different geometric configurations of beam, sample, thermocouple positioning, and sample holder were compared to understand the heat/charge transport mechanisms responsible for the observed temperature increase. The beam heating exhibited a strong dependence on the background (initial) sample temperature with the largest temperature increases occurring at cryogenic temperatures and decreasing with increasing temperature. Comparison with numerical calculations suggests that the observed heating effect is, in reality, a predominantly electronic effect and the true temperature rise is small. A simple model was developed to explain this electronic effect in terms of an electrostatic potential that forms during ion irradiation. Such an artificial beam heating effect is potentially problematic in thermostated ion irradiation and ion beam analysis apparatus, as the operation of temperature feedback systems can be significantly distorted by this effect.

  19. 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.

  20. Eddy flux and leaf-level measurements of biogenic VOC emissions from mopane woodland of Botswana

    NASA Astrophysics Data System (ADS)

    Greenberg, J. P.; Guenther, A.; Harley, P.; Otter, L.; Veenendaal, E. M.; Hewitt, C. N.; James, A. E.; Owen, S. M.

    2003-07-01

    Biogenic volatile organic compound (BVOC) emissions were measured in a mopane woodland near Maun, Botswana in January-February 2001 as part of SAFARI 2000. This landscape is comprised of more than 95% of one woody plant species, Colophospermum mopane (Caesalpinaceae). Mopane woodlands extend over a broad area of southern Africa. A leaf cuvette technique was used to determine the emission capacities of the major vegetation and the temperature and light dependence of the emissions. In addition, relaxed eddy accumulation (REA) measurements of BVOC fluxes were made on a flux tower, where net CO2 emissions were also measured simultaneously. Large light-dependent emissions of terpenes (mostly α-pinene and D-limonene) were observed from the mopane woodland. The diurnal BVOC emissions were integrated and compared with the CO2 flux. Monoterpene flux exceeded 3000 μg C m-2 h-1 during the daytime period, comparable to isoprene fluxes and much higher than terpene fluxes measured in most areas. The terpene flux constituted approximately 25% of the diurnal net carbon exchange (CO2) during the experimental period. Other BVOC emissions may also contribute to the carbon exchange.

  1. Chemotaxis and Actin Oscillations

    NASA Astrophysics Data System (ADS)

    Bodenschatz, Eberhard; Hsu, Hsin-Fang; Negrete, Jose; Beta, Carsten; Pumir, Alain; Gholami, Azam; Tarantola, Marco; Westendorf, Christian; Zykov, Vladimir

    Recently, self-oscillations of the cytoskeletal actin have been observed in Dictyostelium, a model system for studying chemotaxis. Here we report experimental results on the self-oscillation mechanism and the role of regulatory proteins and myosin II. We stimulate cells rapidly and periodically by using photo un-caging of the chemoattractant in a micro-fluidic device and measured the cellular responses. We found that the response amplitude grows with stimulation strength only in a very narrow region of stimulation, after which the response amplitude reaches a plateau. Moreover, the frequency-response is not constant but rather varies with the strength of external stimuli. To understand the underlying mechanism, we analyzed the polymerization and de-polymerization time in the single cell level. Despite of the large cell-to-cell variability, we found that the polymerization time is independent of external stimuli and the de-polymerization time is prolonged as the stimulation strength increases. Our conclusions will be summarized and the role of noise in the signaling network will be discussed. German Science Foundation CRC 937.

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

    NASA Astrophysics Data System (ADS)

    Ganju, Neil K.; Schoellhamer, David H.

    2006-08-01

    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.

  3. 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

  4. Measurement of Solar pp-neutrino flux with Borexino: results and implications

    NASA Astrophysics Data System (ADS)

    Smirnov, O. Yu; Agostini, M.; Appel, S.; Bellini, G.; Benziger, J.; Bick, D.; Bonfini, G.; Bravo, D.; Caccianiga, B.; Calaprice, F.; Caminata, A.; Cavalcante, P.; Chepurnov, A.; D'Angelo, D.; Davini, S.; Derbin, A.; Di Noto, L.; Drachnev, I.; Etenko, A.; Fomenko, K.; Franco, D.; Gabriele, F.; Galbiati, C.; Ghiano, C.; Giammarchi, M.; Goeger-Neff, M.; Goretti, A.; Gromov, M.; Hagner, C.; Hungerford, E.; Ianni, Aldo; Ianni, Andrea; Jedrzejczak, K.; Kaiser, M.; Kobychev, V.; Korablev, D.; Korga, G.; Kryn, D.; Laubenstein, M.; Lehnert, B.; Litvinovich, E.; Lombardi, F.; Lombardi, P.; Ludhova, L.; Lukyanchenko, G.; Machulin, O.; Manecki, S.; Maneschg, W.; Marcocci, S.; Meroni, E.; Meyer, M.; Miramonti, L.; Misiaszek, M.; Montuschi, M.; Mosteiro, P.; Muratova, V.; Neumair, B.; Oberauer, L.; Obolensky, M.; Ortica, F.; Pallavicini, M.; Papp, L.; Perasso, L.; Pocar, A.; Ranucci, G.; Razeto, A.; Re, A.; Romani, A.; Roncin, R.; Rossi, N.; Schönert, S.; Semenov, D.; Simgen, H.; Skorokhvatov, M.; Sotnikov, A.; Sukhotin, S.; Suvorov, Y.; Tartaglia, R.; Testera, G.; Thurn, J.; Toropova, M.; Unzhakov, E.; Vishneva, A.; Vogelaar, R. B.; von Feilitzsch, F.; Wang, H.; Weinz, S.; Winter, J.; Wojcik, M.; Wurm, M.; Yokley, Z.; Zaimidoroga, O.; Zavatarelli, S.; Zuber, K.; Zuzel, G.

    2016-02-01

    Measurement of the Solar pp-neutrino flux completed the measurement of Solar neutrino fluxes from the pp-chain of reactions in Borexino experiment. The result is in agreement with the prediction of the Standard Solar Model and the MSW/LMA oscillation scenario. A comparison of the total neutrino flux from the Sun with Solar luminosity in photons provides a test of the stability of the Sun on the 105 years time scale, and sets a strong limit on the power production by the unknown energy sources in the Sun.

  5. Nightside electron flux measurements at Mars by the Phobos-2 HARP instrument

    NASA Technical Reports Server (NTRS)

    Shutte, N.; Gringauz, K.; Kiraly, P.; Kotova, G.; Nagy, A. F.; Rosenbauer, H.; Szego, K.; Verigin, M.

    1995-01-01

    All the available nightside electron data obtained during circular orbits at Mars from the Phobos-2 Hyperbolic Retarded Potential Analyzer (HARP) instrument have been examined in detail and are summarized in this paper. An electron flux component with energies exceeding that of the unperturbed solar wind was observed inside the magnetosheath, indicating the presence of acceleration mechanism(s). The character of the electron fluxes measured in the magnetotail cannot be classified in any simple manner, however, there is a correlation between the electron fluxes measured well inside this region and the unperturbed solar wind ram pressure.

  6. 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.

  7. How Well Can We Measure the Vertical Wind Speed? Implications for Fluxes of Energy and Mass

    NASA Astrophysics Data System (ADS)

    Kochendorfer, John; Meyers, Tilden P.; Frank, John; Massman, William J.; Heuer, Mark W.

    2012-11-01

    Sonic anemometers are capable of measuring the wind speed in all three dimensions at high frequencies (10-50 Hz), and are relied upon to estimate eddy-covariance-based fluxes of mass and energy over a wide variety of surfaces and ecosystems. In this study, wind-velocity measurement errors from a three-dimensional sonic anemometer with a non-orthogonal transducer orientation were estimated for over 100 combinations of angle-of-attack and wind direction using a novel technique to measure the true angle-of-attack and wind speed within the turbulent atmospheric surface layer. Corrections to the vertical wind speed varied from -5 to 37% for all angles-of-attack and wind directions examined. When applied to eddy-covariance data from three NOAA flux sites, the wind-velocity corrections increased the magnitude of CO2 fluxes, sensible heat fluxes, and latent heat fluxes by ≈11%, with the actual magnitude of flux corrections dependent upon sonic anemometer, surface type, and scalar. A sonic anemometer that uses vertically aligned transducers to measure the vertical wind speed was also tested at four angles-of-attack, and corrections to the vertical wind speed measured using this anemometer were within ±1% of zero. Sensible heat fluxes over a forest canopy measured using this anemometer were 15% greater than sensible heat fluxes measured using a sonic anemometer with a non-orthogonal transducer orientation. These results indicate that sensors with a non-orthogonal transducer orientation, which includes the majority of the research-grade three-dimensional sonic anemometers currently in use, should be redesigned to minimize sine errors by measuring the vertical wind speed using one pair of vertically aligned transducers.

  8. Eddy Covariance Measurements of Methane Fluxes over Arable Land in Southern Ontario

    NASA Astrophysics Data System (ADS)

    Brown, S. E.; Wagner-Riddle, C.

    2013-12-01

    Aerobic soils are the only biological sink for atmospheric methane. Although the sinks are relatively small (~ -1 to -5 ng/m2s), this can translate to a significant quantity of methane consumption over large areas. The degree of sink strength can vary over time and space with changing soil moisture and texture, as well as variations in agricultural practices. Chamber measurements currently provide the majority of information on methane flux values for arable land. Improvements in high-frequency trace gas instrumentation allows for easier eddy covariance flux measurements for methane, thus providing the opportunity for flux measurements over a larger integrated area than chambers. A Picarro G2311-f gas analyzer was recently acquired to measure CH4 and CO2 fluxes for a corn field in Southern Ontario treated with manure. The analyzer employs cavity ring-down spectroscopy to measure gas concentrations and integrates sonic anemometry for eddy covariance measurements. Since methane flux values are small for agricultural soils, noise tests assessed the detection limits of the Picarro system in order to differentiate between instrument noise and fluxes close to zero. A spectral response test characterized the analyzer's capacity to resolve flux values by using a random noise generator to simulate different sized eddies passing by an eddy covariance system. Measurements of CH4 and CO2 commenced in spring of 2013 and continued throughout the growing season and post-harvest. Models will be developed to gap-fill the time series to calculate the net CO2 and CH4 budgets for the corn field. Results from the instrument characterization tests and preliminary results from the flux measurements will be presented.

  9. Factors affecting the measurement of mercury emissions from soils with flux chambers

    NASA Astrophysics Data System (ADS)

    WallschläGer, Dirk; Turner, Ralph R.; London, Jacqueline; Ebinghaus, Ralf; Kock, Hans H.; Sommar, Jonas; Xiao, Zifan

    1999-09-01

    Air-surface exchange of mercury (Hg) above an arid geothermal area was measured with three parallel flux chamber experiments. The different experimental designs were intercompared with each other, with regard to the magnitude of the measured Hg fluxes and their response to environmental changes. Qualitatively, the measured Hg fluxes agreed well throughout the diurnal cycle, and in their response to environmental events and experimental manipulations, but quantitatively, there were significant discrepancies between the individual flux results. On average, the three designs yielded Hg fluxes agreeing within a factor of 2, but even more pronounced differences were observed during midday high emission periods and during apparent nighttime deposition events. The chamber flushing rate appears to have a very significant impact on the measured fluxes and on the response behavior to environmental change. This study demonstrates that both experimental differences and small-scale regional variability introduce large uncertainty in the estimation of natural Hg air-surface exchange by different flux chamber techniques. Also, the impact of environmental parameters on Hg air-surface exchange was studied. Rain events led to a strong increase in the Hg emissions, even when the covered soil remained dry, suggesting that the apparent chamber footprint is larger than the actually covered area. Exclusion of sunlight led to decreases in Hg emissions. Statistical analysis revealed the strongest correlations between the measured Hg fluxes and radiation and wind speed. Weaker correlations were observed with air and soil temperature and wind direction (probably due to local Hg sources). Fluxes were also inversely correlated with relative humidity.

  10. Dual-channel red/blue fluorescence dosimetry with broadband reflectance spectroscopic correction measures protoporphyrin IX production during photodynamic therapy of actinic keratosis

    NASA Astrophysics Data System (ADS)

    Kanick, Stephen Chad; Davis, Scott C.; Zhao, Yan; Hasan, Tayyaba; Maytin, Edward V.; Pogue, Brian W.; Chapman, M. Shane

    2014-07-01

    Dosimetry for aminolevulinic acid (ALA)-induced protoporphyrin IX (PpIX) photodynamic therapy of actinic keratosis was examined with an optimized fluorescence dosimeter to measure PpIX during treatment. While insufficient PpIX generation may be an indicator of incomplete response, there exists no standardized method to quantitate PpIX production at depths in the skin during clinical treatments. In this study, a spectrometer-based point probe dosimeter system was used to sample PpIX fluorescence from superficial (blue wavelength excitation) and deeper (red wavelength excitation) tissue layers. Broadband white light spectroscopy (WLS) was used to monitor aspects of vascular physiology and inform a correction of fluorescence for the background optical properties. Measurements in tissue phantoms showed accurate recovery of blood volume fraction and reduced scattering coefficient from WLS, and a linear response of PpIX fluorescence versus concentration down to 1.95 and 250 nM for blue and red excitations, respectively. A pilot clinical study of 19 patients receiving 1-h ALA incubation before treatment showed high intrinsic variance in PpIX fluorescence with a standard deviation/mean ratio of >0.9. PpIX fluorescence was significantly higher in patients reporting higher pain levels on a visual analog scale. These pilot data suggest that patient-specific PpIX quantitation may predict outcome response.

  11. Mathematical Modeling and In-Situ Measurements of Soil CO2/O2 Flux Dynamics

    NASA Astrophysics Data System (ADS)

    Turcu, V. E.; Or, D.

    2002-12-01

    Gaseous exchange between soil and atmosphere consist primarily of CO2 and O2 fluxes induced by concentration gradients resulting from respiration within the soil profile. Despite their crucial role in the biosphere, dynamics of CO2/O2 concentrations in soil and surface fluxes are rarely measured continuously. A new gradient-based method for continuous monitoring of soil CO2/O2 concentrations was tested in the laboratory and in the field and compared to closed-chamber measurements. In situ measurements were made in different plant communities within a semi-arid ecosystem. A one-dimensional vertical model for soil CO2/O2 fluxes that considers bio-geo-chemical and environmental factors within the basic governing equations for gaseous transport in porous media was developed. Comparisons between model simulations and continuous in-situ measurements of CO2 and O2 concentrations (and fluxes) were in reasonable agreement. Simultaneous measurements of soil CO2 and O2 concentrations provide insights on soil respiration characteristics such as the respiratory quotient (CO2/O2) that ranged from 0.7 to 1.2 and tended to remain remarkably stable under particular experimental conditions. Conversion of measured concentration gradients into surface fluxes was critically dependent on proper estimation of water content profile that affects soil diffusion coefficients. Continuous monitoring in the soil is particularly important following rainfall events where spatial (vertical) and temporal patterns of gaseous fluxes are complex and are unobservable by common surface chamber methods.

  12. 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.

  13. Using "snapshot" measurements of CH4 fluxes from peatlands to estimate annual budgets: interpolation vs. modelling.

    NASA Astrophysics Data System (ADS)

    Green, Sophie M.; Baird, Andy J.

    2016-04-01

    There is growing interest in estimating annual budgets of peatland-atmosphere carbon dioxide (CO2) and methane (CH4) exchanges. Such budgeting is required for calculating peatland carbon balance and the radiative forcing impact of peatlands on climate. There have been multiple approaches used to estimate CO2 budgets; however, there is a limited literature regarding the modelling of annual CH4 budgets. Using data collected from flux chamber tests in an area of blanket peatland in North Wales, we compared annual estimates of peatland-atmosphere CH4 emissions using an interpolation approach and an additive and multiplicative modelling approach. Flux-chamber measurements represent a snapshot of the conditions on a particular site. In contrast to CO2, most studies that have estimated the time-integrated flux of CH4 have not used models. Typically, linear interpolation is used to estimate CH4 fluxes during the time periods between flux-chamber measurements. It is unclear how much error is involved with such a simple integration method. CH4 fluxes generally show a rise followed by a fall through the growing season that may be captured reasonably well by interpolation, provided there are sufficiently frequent measurements. However, day-to-day and week-to-week variability is also often evident in CH4 flux data, and will not necessarily be properly represented by interpolation. Our fits of the CH4 flux models yielded r2 > 0.5 in 38 of the 48 models constructed, with 55% of these having a weighted rw2 > 0.4. Comparison of annualised CH4 fluxes estimated by interpolation and modelling reveals no correlation between the two data sets; indeed, in some cases even the sign of the flux differs. The difference between the methods seems also to be related to the size of the flux - for modest annual fluxes there is a fairly even scatter of points around the 1:1 line, whereas when the modelled fluxes are high, the corresponding interpolated fluxes tend to be low. We consider the

  14. 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.

  15. 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.

  16. Sounding rocket measurement of the absolute solar EUV flux utilizing a silicon photodiode

    NASA Technical Reports Server (NTRS)

    Ogawa, H. S.; Mcmullin, D.; Judge, D. L.; Canfield, L. R.

    1990-01-01

    A newly developed stable and high quantum efficiency silicon photodiode was used to obtain an accurate measurement of the integrated absolute magnitude of the solar extreme UV photon flux in the spectral region between 50 and 800 A. The adjusted daily 10.7-cm solar radio flux and sunspot number were 168.4 and 121, respectively. The unattenuated absolute value of the solar EUV flux at 1 AU in the specified wavelength region was 6.81 x 10 to the 10th photons/sq cm per s. Based on a nominal probable error of 7 percent for National Institute of Standards and Technology detector efficiency measurements in the 50- to 500-A region (5 percent on longer wavelength measurements between 500 and 1216 A), and based on experimental errors associated with the present rocket instrumentation and analysis, a conservative total error estimate of about 14 percent is assigned to the absolute integral solar flux obtained.

  17. Ir Thermographic Measurements of Temperatures and Heat Fluxes in Hypersonic Plasma Flow

    NASA Astrophysics Data System (ADS)

    Cardone, G.; Tortora, G.; del Vecchio, A.

    2005-02-01

    The technological development achieved in instruments and methodology concerning both flights and ground hypersonic experiment (employed in space plane planning) goes towards an updating and a standardization of the heat flux technical measurements. In fact, the possibility to simulate high enthalpy flow relative to reentry condition by hypersonic arc-jet facility needs devoted methods to measure heat fluxes. Aim of this work is to develop an experimental numerical technique for the evaluation of heat fluxes over Thermal Protection System (TPS) by means of InfraRed (IR) thermographic temperature measurements and a new heat flux sensor (IR-HFS). We tackle the numerical validation of IR-HFS, apply the same one to the Hyflex nose cap model and compare the obtained results with others ones obtained by others methodology.

  18. Flux measurements of CA II H and K emission. [from stellar chromospheres

    NASA Technical Reports Server (NTRS)

    Vaughan, A. H.; Preston, G. W.; Wilson, O. C.

    1978-01-01

    A four-channel photon-counting spectrophotometer (designated HKP-2) is described which is designed for measuring stellar chromospheric calcium emission. The HKP-2 is calibrated, and its performance and accuracy evaluated, by observing 63 of Wilson's (1968) program stars on the same nights with both the HKP-2 and a coude scanner designated HKP-1. The results of the observations are discussed in terms of the calibration of mean H-K flux indices, variations in individual stellar fluxes, the flux ratio for H and K, and the instrument color index. It is shown that the HKP-2 provides satisfactory performance in the measurement of stellar chromospheric emission in a manner closely analogous to the method of Wilson and that a single observation yields a color index as well as flux indices for H and K that can be calibrated and transferred unambiguously to Wilson's system of measurement.

  19. 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.

  20. 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 μg 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

  1. Intranuclear Actin Regulates Osteogenesis

    PubMed Central

    Sen, Buer; Xie, Zhihui; Uzer, Gunes; Thompson, William R.; Styner, Maya; Wu, Xin; Rubin, Janet

    2016-01-01

    Depolymerization of the actin cytoskeleton induces nuclear trafficking of regulatory proteins and global effects on gene transcription. We here show that in mesenchymal stem cells (MSCs), cytochalasin D treatment causes rapid cofilin-/importin-9-dependent transfer of G-actin into the nucleus. The continued presence of intranuclear actin, which forms rod-like structures that stain with phalloidin, is associated with induction of robust expression of the osteogenic genes osterix and osteocalcin in a Runx2-dependent manner, and leads to acquisition of osteogenic phenotype. Adipogenic differentiation also occurs, but to a lesser degree. Intranuclear actin leads to nuclear export of Yes-associated protein (YAP); maintenance of nuclear YAP inhibits Runx2 initiation of osteogenesis. Injection of cytochalasin into the tibial marrow space of live mice results in abundant bone formation within the space of 1 week. In sum, increased intranuclear actin forces MSC into osteogenic lineage through controlling Runx2 activity; this process may be useful for clinical objectives of forming bone. PMID:26140478

  2. 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.

  3. 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.

  4. 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.

  5. Testing the Need for Replication of Eddy Covariance Carbon Dioxide Flux Measurements over Agricultural Fields

    NASA Astrophysics Data System (ADS)

    Taylor, A. M.; Amiro, B. D.; Gervais, M.

    2015-12-01

    The eddy covariance method directly measures carbon dioxide (CO2) fluxes for long periods of time and with footprints up to hundreds of meters in size. Any ecosystem process that alters how gases and energy move between the atmosphere and soil/vegetation can affect these fluxes. Eddy covariance is vulnerable to systematic errors and uncertainy, particular through relying on assumptions about surface characteristics. Additionally, spatial variation within a site can cause more uncertainty in these measurements and lack of replication in many eddy covariance studies makes statistical analysis of carbon fluxes challenging. We tested if there are significant differences between co-located and simultaneous CO2 flux measurements over a uniform crop surface, and if the differences increase if we measure different flux footprint areas over the same field. During the summer of 2014, three matched instrumented 2.5-m high towers were co-located and then periodically separated by moving at 50 m intervals along a north-south transect on an alfalfa/trefoil field and a spring wheat field in Southern Manitoba, Canada to compare CO­2 fluxes. Georeferenced leaf area index measurements were taken in 50 m grid of each field to establish uniformity of the source/sink within a footprint. Diurnal differences of similar magnitude in the CO2 ­fluxes were found in both the co-located experiment and the spatially separated intervals. Despite rigorous calibration during the experiment, some differences were caused by the measurement systems rather than by variation within the field. Interpretation of the spatial variation in leaf area index is being used to determine the contribution caused by difference in source/sink contributions to the flux footprint areas when the towers were spatially separated.

  6. The truth is out there: measured, calculated and modelled benthic fluxes.

    NASA Astrophysics Data System (ADS)

    Pakhomova, Svetlana; Protsenko, Elizaveta

    2016-04-01

    In a modern Earth science there is a great importance of understanding the processes, forming the benthic fluxes as one of element sources or sinks to or from the water body, which affects the elements balance in the water system. There are several ways to assess benthic fluxes and here we try to compare the results obtained by chamber experiments, calculated from porewater distributions and simulated with model. Benthic fluxes of dissolved elements (oxygen, nitrogen species, phosphate, silicate, alkalinity, iron and manganese species) were studied in the Baltic and Black Seas from 2000 to 2005. Fluxes were measured in situ using chamber incubations (Jch) and at the same time sediment cores were collected to assess the porewater distribution at different depths to calculate diffusive fluxes (Jpw). Model study was carried out with benthic-pelagic biogeochemical model BROM (O-N-P-Si-C-S-Mn-Fe redox model). It was applied to simulate biogeochemical structure of the water column and upper sediment and to assess the vertical fluxes (Jmd). By the behaviour at the water-sediment interface all studied elements can be divided into three groups: (1) elements which benthic fluxes are determined by the concentrations gradient only (Si, Mn), (2) elements which fluxes depend on redox conditions in the bottom water (Fe, PO4, NH4), and (3) elements which fluxes are strongly connected with organic matter fate (O2, Alk, NH4). For the first group it was found that measured fluxes are always higher than calculated diffusive fluxes (1.5flux. In this case bioturbation, bioirrigation and advection should be taken into account. For the second group measured fluxes can be both much lower (practically absent) and much higher than calculated diffusive fluxes (0.01

  7. 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...

  8. Excitable actin dynamics in lamellipodial protrusion and retraction.

    PubMed

    Ryan, Gillian L; Petroccia, Heather M; Watanabe, Naoki; Vavylonis, Dimitrios

    2012-04-01

    Many animal cells initiate crawling by protruding lamellipodia, consisting of a dense network of actin filaments, at their leading edge. We imaged XTC cells that exhibit flat lamellipodia on poly-L-lysine-coated coverslips. Using active contours, we tracked the leading edge and measured the total amount of F-actin by summing the pixel intensities within a 5-μm band. We observed protrusion and retraction with period 130-200 s and local wavelike features. Positive (negative) velocities correlated with minimum (maximum) integrated actin concentration. Approximately constant retrograde flow indicated that protrusions and retractions were driven by fluctuations of the actin polymerization rate. We present a model of these actin dynamics as an excitable system in which a diffusive, autocatalytic activator causes actin polymerization; F-actin accumulation in turn inhibits further activator accumulation. Simulations of the model reproduced the pattern of actin polymerization seen in experiments. To explore the model's assumption of an autocatalytic activation mechanism, we imaged cells expressing markers for both F-actin and the p21 subunit of the Arp2/3 complex. We found that integrated Arp2/3-complex concentrations spike several seconds before spikes of F-actin concentration. This suggests that the Arp2/3 complex participates in an activation mechanism that includes additional diffuse components. Response of cells to stimulation by fetal calf serum could be reproduced by the model, further supporting the proposed dynamical picture. PMID:22500749

  9. CO2, CH4 and particles flux measurements in Florence, Italy

    NASA Astrophysics Data System (ADS)

    Gioli, Beniamino; Toscano, Piero; Zaldei, Alessandro; Fratini, Gerardo; Miglietta, Franco

    2013-04-01

    We report a synthesis of seven years of eddy covariance (EC) flux measurements in the city of Florence, Italy. The measurement site is located in a densely urbanized area in the central city area, where fluxes are governed by anthropogenic emissions, considering the lack of green-space in the flux footprint. EC flux measurements of CO2 are made long-term since seven years, while short-term campaigns have been aimed at measuring CH4 and particles fluxes. CO2 and CH4 densities are measured with fast open-path sensors, while particles in the range 0.32 - 7.00 µm optical diameter are measured with a custom-built optical counter. CO2 long-term fluxes are always a net source, with a small inter-annual variability associated with a high seasonality, ranging from 39 to 172% of the mean annual value in summer and winter respectively. CH4 fluxes to the atmosphere are relevant, representing about 8% of CO2-equivalent emissions, and do not exhibit any significant seasonality. Relative contributions of road traffic and domestic heating to observed emissions has been estimated through multi-variate analysis combined with inventorial data and emission proxies such as traffic counters and gas network flow rates, revealing that domestic heating accounts for more than 80% of observed CO2 fluxes. Heating and road traffic are instead responsible for only 14% of observed CH4 fluxes, while the major residual part is likely dominated by gas network leakages. Particles flux data show a smaller seasonal trend and a pronounced weekend decrease, highlighting that the contribution of heating to particle emissions is relatively small compared to road traffic. Dynamics at hourly time scales during week and week-end days allows the analysis of the coupled role of emission strength and atmospheric processes such as advection and entrainment in regulating atmospheric concentrations. This set of observations highlights the potential of urban EC flux measurements as a validation tool for

  10. 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.

  11. Seasonality of Overstory and Understory Fluxes in a Semi-Arid Oak Savanna: What can be Learned from Comparing Measured and Modeled Fluxes?

    NASA Astrophysics Data System (ADS)

    Raz-Yaseef, N.; Sonnentag, O.; Kobayashi, H.; Chen, J. M.; Verfaillie, J. G.; Ma, S.; Baldocchi, D. D.

    2011-12-01

    Semi-arid climates experience large seasonal and inter-annual variability in radiation and precipitation, creating natural conditions adequate to study how year-to-year changes affect atmosphere-biosphere fluxes. Especially, savanna ecosystems, that combine tree and below-canopy components, create a unique environment in which phenology dramatically changes between seasons. We used a 10-year flux database in order to define seasonal and interannual variability of climatic inputs and fluxes, and evaluate model capability to reproduce observed variability. This is based on the perception that model capability to construct the deviation, and not the average, is important in order to correctly predict ecosystem sensitivity to climate change. Our research site is a low density and low LAI (0.8) semi-arid savanna, located at Tonzi Ranch, Northern California. In this system, trees are active during the warm season (Mar - Oct), and grasses are active during the wet season (Dec - May). Measurements of carbon and water fluxes above and below the tree canopy using eddy covariance and supplementary measurements have been made since 2001. Fluxes were simulated using bio-meteorological process-oriented ecosystem models: BEPS and 3D-CAONAK. Models were partly capable of reproducing fluxes on daily scales (R2=0.66). We then compared model outputs for different ecosystem components and seasons, and found distinct seasons with high correlations while other seasons were purely represented. Comparison was much higher for ET than for GPP. The understory was better simulated than the overstory. CANOAK overestimated spring understory fluxes, probably due to the capability to directly calculated 3D radiative transfer. BEPS underestimated spring understory fluxes, following the pre-description of grass die-off. Both models underestimated peak spring overstory fluxes. During winter tree dormant, modeled fluxes were null, but occasional high fluxes of both ET and GPP were measured following

  12. Myosins, Actin and Autophagy.

    PubMed

    Kruppa, Antonina J; Kendrick-Jones, John; Buss, Folma

    2016-08-01

    Myosin motor proteins working together with the actin cytoskeleton drive a wide range of cellular processes. In this review, we focus on their roles in autophagy - the pathway the cell uses to ensure homeostasis by targeting pathogens, misfolded proteins and damaged organelles for degradation. The actin cytoskeleton regulated by a host of nucleating, anchoring and stabilizing proteins provides the filament network for the delivery of essential membrane vesicles from different cellular compartments to the autophagosome. Actin networks have also been implicated in structurally supporting the expanding phagophore, moving autophagosomes and enabling efficient fusion with the lysosome. Only a few myosins have so far been shown to play a role in autophagy. Non-muscle myosin IIA functions in the early stages delivering membrane for the initial formation of the autophagosome, whereas myosin IC and myosin VI are involved in the final stages providing specific membranes for autophagosome maturation and its fusion with the lysosome. PMID:27146966

  13. 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 μm). 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 μm to 2.5 μm 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

  14. 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.

  15. Standardization of flux chamber and wind tunnel flux measurements for quantifying volatile organic compound and ammonia emissions from area sources at animal feeding operations

    NASA Astrophysics Data System (ADS)

    Parker, David; Ham, Jay; Woodbury, Bryan; Cai, Lingshuang; Spiehs, Mindy; Rhoades, Marty; Trabue, Steve; Casey, Ken; Todd, Rick; Cole, Andy

    2013-02-01

    A variety of portable 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 air velocity or sweep air flow rates that are either too low or too high to simulate field conditions. There is a need for correction factors to standardize flux chamber and wind tunnel measurements. In this manuscript, we present results of water evaporative flux and VOC flux measurements with the EPA flux chamber and a small wind tunnel. In the EPA flux chamber, water evaporative flux was positively correlated with sweep air flow rate (SAFR) between 1 and 20 L min-1 (r2 = 0.981-0.999) and negatively correlated with sweep air relative humidity between 0 and 80% (r2 = 0.982-0.992). Emissions of gas-film controlled compounds like NH3 and VOC at AFOs were positively correlated with evaporation rates between 0.6 and 2.8 mm d-1. We demonstrate a simple methodology for standardizing and comparing different chamber types by measuring water evaporation within the chamber using a gravimetric mass balance approach under controlled laboratory conditions. A water evaporative flux ratio correction factor (EFRCF) was used to improve the accuracy of field-measured VOC and NH3 chamber flux measurements. In a field study, both the EPA flux chamber (SAFR = 5 L min-1) and small wind tunnel (SAFR = 1 L min-1) underestimated the true field emissions of VOC, with EFRCFs of 2.42 and 3.84, respectively. EFRCFs are recommended for all but the driest of soil and manure conditions.

  16. Measuring and modeling near surface reflected and emitted radiation fluxes at the FIFE site

    NASA Technical Reports Server (NTRS)

    Blad, Blaine L.; Norman, John M.; Walter-Shea, Elizabeth; Starks, Patrick; Vining, Roel; Hays, Cynthia

    1988-01-01

    Research was conducted during the four Intensive Field Campaigns (IFC) of the FIFE project in 1987. The research was done on a tall grass prairie with specific measurement sites on and near the Konza Prairie in Kansas. Measurements were made to help meet the following objectives: determination of the variability in reflected and emitted radiation fluxes in selected spectral wavebands as a function of topography and vegetative community; development of techniques to account for slope and sun angle effects on the radiation fluxes; estimation of shortwave albedo and net radiation fluxes using the reflected and emitted spectral measurements described; estimation of leaf and canopy spectral properties from calculated normalized differences coupled with off-nadir measurements using inversion techniques; estimation of plant water status at several locations with indices utilizing plant temperature and other environmental parameters; and determination of relationships between estimated plant water status and measured soil water content. Results are discussed.

  17. A direct measurement of the energy flux density in plasma surface interaction

    NASA Astrophysics Data System (ADS)

    Dussart, Remi; Thomann, Anne-Lise; Semmar, Nadjib; Pichon, Laurianne; Bedra, Larbi; Mathias, Jacky; Tessier, Yves; Lefaucheux, Philippe

    2008-10-01

    The energy flux transferred from a plasma to a surface is a key issue for materials processing (sputtering, etching). We present direct measurements made with a Heat Flux Microsensor (HFM) in an Ar plasma interacting with the surface of the sensor. The HFM is a thermopile of about one thousand metal couples mounted in parallel. An Inductively Coupled Plasma in Argon was used to make the experiments. Langmuir probe and tuneable laser diode absorption measurements were carried out to estimate the contribution of ions, neutrals (conduction) and metastables. In order to evaluate the ability of the HFM to measure the part due to chemical reactions, a Si surface in contact with the HFM was submitted to an SF6 plasma. The direct measurements are in good agreement with the estimation we made knowing the etch rate and the enthalpy of the reaction. Finally, tests were performed on a sputtering reactor. Additional energy flux provided by condensing atoms (Pt) was also measured.

  18. Radon flux measurements on Gardinier and Royster phosphogypsum piles near Tampa and Mulberry, Florida

    SciTech Connect

    Hartley, J.N.; Freeman, H.D.

    1986-01-01

    As part of the planned Environmental Protection Agency (EPA) radon flux monitoring program for the Florida phosphogypsum piles, Pacific Northwest Laboratory (PNL), under contract to the EPA, constructed 50 large-area passive radon collection devices and demonstrated their use at two phosphogypsum piles near Tampa and Mulberry, Florida. The passive devices were also compared to the PNL large-area flow-through system. The main objectives of the field tests were to demonstrate the use of the large-area passive radon collection devices to EPA and PEI personnel and to determine the number of radon flux measurement locations needed to estimate the average radon flux from a phosphogypsum pile. This report presents the results of the field test, provides recommendations for long-term monitoring, and includes a procedure for making the radon flux measurements.

  19. 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.

  20. Combined FTIR-micrometeorological techniques for long term flux measurements of greenhouse gases and their applicability for 13CO2 fluxes

    NASA Astrophysics Data System (ADS)

    Warneke, Thorsten; Caldow, Chris; Griffith, David

    2010-05-01

    Fourier Transform InfraRed (FTIR) spectrometry has been deployed for continuous long term flux measurements on a flat, homogeneous circular grass paddock in New South Wales, Australia. The rationale for using FTIR spectrometry is its capability to measure many species simultaneously. The flux measurement techniques combined with FTIR - spectrometry in this study were Disjunct Eddy Accumulation (DEA) and Flux-Gradient (FG). The fluxes of CO2 derived from the FTIR-DEA and FTIR-FG measurements agree well and have been validated by Eddy Covariance Licor measurements. Variations in the observed fluxes could be attributed to temperature increase and water availability over the 5 months measurement period. In addition to CO2, CH4, CO and N2O FTIR-spectrometry is also capable to measure 13CO2. The isotopic fluxes of CO2 allow to separate net ecosystem exchange of CO2 into its gross one-way component fluxes, ecosystem respiration and photosynthesis. It has been shown that it is possible to measure the isoflux of CO2.

  1. 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

  2. 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

  3. Interfacial flux in wetlands predicted using surface divergence measurements

    NASA Astrophysics Data System (ADS)

    Poindexter, Cristina; Variano, Evan A.

    2012-11-01

    Surface divergence has been shown to be a robust predictor of the air-water gas transfer velocity, k. We used this surface divergence model to investigate the effects of wind on k in wetlands with emergent vegetation. We used fluoropolymer tubes to represent plant stems in a laboratory tank equipped with a wind tunnel. The fluoropolymer material provided optical access to the water flows directly around the ``stems'' for PIV. The k values predicted by the surface divergence model from PIV-derived near surface divergence fields in the tank matched directly-measured k values in the tank. The surface divergence fields also illustrated a mechanism for wind-induced gas transfer in wetlands with emergent vegetation. We observed an area of high surface divergence surrounding each stem and order of magnitude lower surface divergence in areas away from any stems. Thus we expect a nearly linear relationship between stem density and k (if average wind speed in the emergent canopy is held constant). The agreement between modeled and measured k values in this low-Reynolds-number, obstructed flow provides further support for the universality of the surface divergence model for k. The results also permit improved prediction of k in wetlands.

  4. 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

  5. CO2 Flux Measurement Uncertainty Estimates for NACP

    NASA Astrophysics Data System (ADS)

    Barr, A.; Hollinger, D.; Richardson, A. D.

    2009-12-01

    We evaluated the uncertainties in eddy-covariance net ecosystem exchange NEE, total ecosystem respiration RE and gross primary production GPP associated with (a) random measurement error and (b) uncertainties in the u* (friction velocity) threshold u*Th for all site-years in the NACP site-level synthesis. The analyses required automated evaluation of the u*Th filter used to identify and reject bad NEE measurements during low-turbulence periods at night. The u*Th detection algorithm was adapted from Papale et al. (2006), modified to use a standard change-point detection algorithm. Uncertainty in the u*Th was estimated by bootstrapping, conducted annually with 1,000 draws per site-year, then pooling all years and calculating the lower and upper 95% confidence intervals from the median and 2.5 and 97.5 percentiles of the pooled u*Th values. Random uncertainties in NEE, RE and GPP were estimated following Richardson et al. (2007). The NEE random uncertainty characteristic curve, which characterizes random uncertainty in NEE as a function of NEE, was estimated for each site-year based on the differences between the measured data and the output of a simple and robust gap-filling model. The estimation procedure began with synthetic NEE data generated by the gap-filling model, introduced gaps (as in the measured data after u*Th filtering), added synthetic noise (defined by the NEE random uncertainty characteristic curve using a Monte-Carlo approach), then filled the gaps in the noisy, gappy synthetic data. The process was repeated 1,000 times for each site-year, and the random uncertainty was estimated from median and the 2.5 and 97.5 percentiles of the gap-filled data. The uncertainties in NEE, RE and GPP associated with uncertainties in the u*Th were evaluated by running the gap-filling routine at 1,000 u*Th values, drawn randomly from the pooled annual bootstrapping estimates. This produced 1,000 realizations of the gap-filled NEE, RE and GPP time series. The

  6. Measurement of total ion flux in vacuum Arc discharges

    SciTech Connect

    Anders, Andre; Oks, Efim M.; Yushkov, Georgy Yu.; Brown, Ian G.

    2004-04-12

    A vacuum arc ion source was modified allowing us to collections from arc plasma streaming through an anode mesh. The mesh had ageometric transmittance of 60 percent, which was taken into account as acorrection factor. The ion current from twenty-two cathode materials wasmeasured at an arc current of 100 A. The ion current normalized by thearc current was found to depend on the cathode material, with valuesinthe range from 5 percent to 11 percent. The normalized ion current isgenerally greater for light elements than for heavy elements. The ionerosion rates were determined fromvalues of ion currentand ion chargestates, which were previously measured in the same experimental system.The ion erosion rates range from 12-94 mu g/C.

  7. 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.

  8. Spatially resolved flux measurements of NOx from London suggest significantly higher emissions than predicted by inventories.

    PubMed

    Vaughan, Adam R; Lee, James D; Misztal, Pawel K; Metzger, Stefan; Shaw, Marvin D; Lewis, Alastair C; Purvis, Ruth M; Carslaw, David C; Goldstein, Allen H; Hewitt, C Nicholas; Davison, Brian; Beevers, Sean D; Karl, Thomas G

    2016-07-18

    To date, direct validation of city-wide emissions inventories for air pollutants has been difficult or impossible. However, recent technological innovations now allow direct measurement of pollutant fluxes from cities, for comparison with emissions inventories, which are themselves commonly used for prediction of current and future air quality and to help guide abatement strategies. Fluxes of NOx were measured using the eddy-covariance technique from an aircraft flying at low altitude over London. The highest fluxes were observed over central London, with lower fluxes measured in suburban areas. A footprint model was used to estimate the spatial area from which the measured emissions occurred. This allowed comparison of the flux measurements to the UK's National Atmospheric Emissions Inventory (NAEI) for NOx, with scaling factors used to account for the actual time of day, day of week and month of year of the measurement. The comparison suggests significant underestimation of NOx emissions in London by the NAEI, mainly due to its under-representation of real world road traffic emissions. A comparison was also carried out with an enhanced version of the inventory using real world driving emission factors and road measurement data taken from the London Atmospheric Emissions Inventory (LAEI). The measurement to inventory agreement was substantially improved using the enhanced version, showing the importance of fully accounting for road traffic, which is the dominant NOx emission source in London. In central London there was still an underestimation by the inventory of 30-40% compared with flux measurements, suggesting significant improvements are still required in the NOx emissions inventory. PMID:27098421

  9. 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

  10. Probe measurements of hydrogen fluxes during discharge cleaning in JFT-2M

    NASA Astrophysics Data System (ADS)

    JFT-2M Team; Maeda, H.; Susuki, K.; Hasegawa, K.; Honda, A.; Ishibori, I.; Kashiwa, Y.; Kazawa, M.; Kikuchi, K.; Ohuchi, K.; Okano, F.; Sato, E.; Shibata, T.; Tani, T.; Uno, S.; Hoshino, K.; Kasai, S.; Kawakami, T.; Kawashima, K.; Matsuda, T.; Matsumoto, H.; Miura, Y.; Mori, M.; Nakazawa, I.; Odajima, K.; Ogawa, H.; Ogawa, T.; Ohasa, K.; Ohtsuka, H.; Sengoku, S.; Shoji, T.; Suzuki, N.; Tamai, H.; Uesugi, Y.; Yamamoto, T.; Yamauchi, T.; Matsuzaki, Y.

    1989-04-01

    Thermal desorption spectroscopy (TDS) has been applied during discharge cleaning in the JFT-2M tokamak to measure hydrogen fluxes. The TDS carbon sample, thickness 0.13 mm, was heated to 1000°C by direct current and the temperature distribution of the sample surface measured by infrared thermography. The probe was exposed to three types of plasma: Taylor-type discharge cleaning (TDC), ECR discharge cleaning (ECR-DC), and glow discharge cleaning (GDC). The TDS spectra show peak desorption at around 800°C. The hydrogen flux, obtained by integration of the TDS spectrum, decreases exponentially in the radial direction with decay length 7.4 cm and 5.8 cm in TDC and ECR-DC, respectively. The relation between hydrogen fluxes and water vapour production was investigated. In TDC, the amount of water vapour depends more strongly on the electron temperature of the plasma than on the hydrogen flux. In ECR-DC, the production of water vapour increases approximately linearly with the hydrogen-flux. In GDC, hydrogen fluxes were measured by TDS but no water vapour could be detected in the residual gases during the discharge.

  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 uncertainties in quantifying aeolian mass flux: evidence from wind tunnel and field site data.

    PubMed

    Poortinga, Ate; Keijsers, Joep G S; Maroulis, Jerry; Visser, Saskia M

    2014-01-01

    Aeolian sediment traps are widely used to estimate the total volume of wind-driven sediment transport, but also to study the vertical mass distribution of a saltating sand cloud. The reliability of sediment flux estimations from such measurements are dependent upon the specific configuration of the measurement compartments and the analysis approach used. In this study, we analyse the uncertainty of these measurements by investigating the vertical cumulative distribution and relative sediment flux derived from both wind tunnel and field studies. Vertical flux data was examined using existing data in combination with a newly acquired dataset; comprising meteorological data and sediment fluxes from six different events, using three customized catchers at Ameland beaches in northern Netherlands. Fast-temporal data collected in a wind tunnel shows that the median transport height has a scattered pattern between impact and fluid threshold, that increases linearly with shear velocities above the fluid threshold. For finer sediment, a larger proportion was transported closer to the surface compared to coarser sediment fractions. It was also shown that errors originating from the distribution of sampling compartments, specifically the location of the lowest sediment trap relative to the surface, can be identified using the relative sediment flux. In the field, surface conditions such as surface moisture, surface crusts or frozen surfaces have a more pronounced but localized effect than shear velocity. Uncertainty in aeolian mass flux estimates can be reduced by placing multiple compartments in closer proximity to the surface. PMID:25071984

  13. Fluxpro As a Realtime Monitoring and Surveillance System for Eddy Covariance Flux Measurement

    NASA Astrophysics Data System (ADS)

    Kim, W.

    2014-12-01

    To understand how terrestrial ecosystems respond to global climate change, colleagues have globally measured the energy, water and carbon dioxide flux densities (F) over various vegetations by the eddy covariance (EC) method. However, the process of F calculation and the method of quality control and quality assurance (QCQA) are complex and site specific. Moreover, instantly maintaining remote EC flux measurement sites against instrumentation problems and administrative difficulties is laborious. To overcome these issues, particularly those of realtime F monitoring and prompt site management, FluxPro was created. FluxPro is consisted of three functional systems: 1) gathering system that transports EC measurements from various sites to the FluxPro management server; 2) cooking system that computes F and its frictional uncertainty (ɛ) together with micrometeorological variables (V); and 3) serving system that presents the above two results as charts to be distributed over the internet in realtime. Consequently, FluxPro could become an appropriate system in realtime-multi-site management, since it not only to automatically monitors F with ɛ and V but also continuously surveils EC sites, providing copious information and an email alert system.

  14. 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

  15. Measurement uncertainties in quantifying aeolian mass flux: evidence from wind tunnel and field site data

    PubMed Central

    Keijsers, Joep G.S.; Maroulis, Jerry; Visser, Saskia M.

    2014-01-01

    Aeolian sediment traps are widely used to estimate the total volume of wind-driven sediment transport, but also to study the vertical mass distribution of a saltating sand cloud. The reliability of sediment flux estimations from such measurements are dependent upon the specific configuration of the measurement compartments and the analysis approach used. In this study, we analyse the uncertainty of these measurements by investigating the vertical cumulative distribution and relative sediment flux derived from both wind tunnel and field studies. Vertical flux data was examined using existing data in combination with a newly acquired dataset; comprising meteorological data and sediment fluxes from six different events, using three customized catchers at Ameland beaches in northern Netherlands. Fast-temporal data collected in a wind tunnel shows that the median transport height has a scattered pattern between impact and fluid threshold, that increases linearly with shear velocities above the fluid threshold. For finer sediment, a larger proportion was transported closer to the surface compared to coarser sediment fractions. It was also shown that errors originating from the distribution of sampling compartments, specifically the location of the lowest sediment trap relative to the surface, can be identified using the relative sediment flux. In the field, surface conditions such as surface moisture, surface crusts or frozen surfaces have a more pronounced but localized effect than shear velocity. Uncertainty in aeolian mass flux estimates can be reduced by placing multiple compartments in closer proximity to the surface. PMID:25071984

  16. Wind Tunnel Measurement of Turbulent and Advective Scalar Fluxes: A Case Study on Intersection Ventilation

    PubMed Central

    Kukačka, Libor; Nosek, Štĕpán; Kellnerová, Radka; Jurčáková, Klára; Jaňour, Zbyněk

    2012-01-01

    The objective of this study is to determine processes of pollution ventilation in the X-shaped street intersection in an idealized symmetric urban area for the changing approach flow direction. A unique experimental setup for simultaneous wind tunnel measurement of the flow velocity and the tracer gas concentration in a high temporal resolution is assembled. Advective horizontal and vertical scalar fluxes are computed from averaged measured velocity and concentration data within the street intersection. Vertical advective and turbulent scalar fluxes are computed from synchronized velocity and concentration signals measured in the plane above the intersection. All the results are obtained for five approach flow directions. The influence of the approach flow on the advective and turbulent fluxes is determined. The contribution of the advective and turbulent flux to the ventilation is discussed. Wind direction with the best dispersive conditions in the area is found. The quadrant analysis is applied to the synchronized signals of velocity and concentration fluctuation to determine events with the dominant contribution to the momentum flux and turbulent scalar flux. PMID:22649290

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

    SciTech Connect

    Garrett, Alfred J.; Kurzeja, Robert J.; Villa-Aleman, Eliel; Bollinger, James S.; Pendergast, Malcolm M.

    2013-06-01

    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 σ 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 σ. 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 σ 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 σ and q" of 0.45 and 0.76, respectively. Values of q" computed from a function of σ and friction velocity u* derived from turbulent boundary layer theory had higher correlations with measured values of q" (0.84 and 0.89). Finally, 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.

  18. 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...

  19. 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...

  20. 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.

  1. The Importance of the Spatial Density of Satellite Measurements for the Retrieval of Spatial Flux Patterns

    NASA Astrophysics Data System (ADS)

    Marshall, J.; Nuñez Ramirez, T. G.; Kiemle, C.; Butz, A.; Hasekamp, O. P.; Ehret, G.; Heimann, M.

    2014-12-01

    Initial results from GOSAT flux inversions of column-integrated carbon dioxide suggest a significant redistribution of surface fluxes compared to inversions using only surface-based inversions as an observational constraint. New evidence suggests that this redistribution of fluxes is a robust feature, and is related to the increased spatial density of the measurements made available by remote sensing. However GOSAT's rather large measurement footprint and sparse sampling still provide poor coverage over many areas of the globe, particularly regions characterized by consistent cloud cover, such as the tropics, and all passive near-infrared sensors suffer from a seasonal sampling bias due to limited sunlight during high latitude winter. As such, errors in the pattern of retrieved fluxes may still be significant. Active sensors based on lidar do not suffer from the same seasonal (or diurnal) sampling biases, and their exceptionally small instantaneous field of view (~150 m) promises to greatly improve the spatial coverage of the measurements over partially cloudy regions. Using the case of MERLIN, a planned joint French-German lidar mission designed to measure XCH4, the implications of this increased spatial coverage is considered in an inverse modelling framework, and compared to presently available measurement coverage from the surface-based network and GOSAT. The gain in knowledge about the absolute size of the regional methane fluxes, particularly in currently undersampled regions such as the Arctic permafrost zones and tropical wetlands, is quantified.

  2. Measurements and modelling of turbulent fluxes at two glaciers in British Columbia, Canada

    NASA Astrophysics Data System (ADS)

    Radic, V.; Fitzpatrick, N.; Tessema, M.; Menounos, B.; Shea, J. M.; Dery, S. J.

    2015-12-01

    The most physically-based method to simulate surface glacier melting is by surface energy balance models since they account for radiative and turbulent heat exchanges occurring at the snow or ice surface. Direct measurements of turbulent fluxes, however, are uncommon given the complexity of making reliable measurements of turbulent energy exchange on alpine glaciers. Most studies thus rely on the bulk aerodynamic method used to parametrize turbulent fluxes; an approach that may be inaccurate due to poorly specified empirical coefficients, such as the transfer coefficient and roughness lengths. Here we present direct measurements of turbulent energy fluxes for two alpine glaciers in British Columbia: Castle Glacier in the Interior Mountains for ablation seasons 2010 and 2012, and Nordic Glacier in Canadian Rockies for ablation season 2014. On both glaciers the turbulent heat fluxes may account for up to 35% of energy available for daily melt. Using eddy-covariance method we derive the roughness lengths for momentum, temperature and humidity, and evaluate the performance of bulk method with different parametrizations for transfer coefficient in simulating the turbulent fluxes. Finally, we estimate the transfer coefficient directly from our measurements, and investigate its dependence on meteorological variables measured at the glaciers.

  3. A new low-power, open-path instrument for measuring methane flux by eddy covariance

    NASA Astrophysics Data System (ADS)

    McDermitt, D.; Burba, G.; Xu, L.; Anderson, T.; Komissarov, A.; Riensche, B.; Schedlbauer, J.; Starr, G.; Zona, D.; Oechel, W.; Oberbauer, S.; Hastings, S.

    2011-02-01

    This paper describes a new low-power instrument for measuring methane flux by eddy covariance method at sites without grid power. Design and field performance of the LI-7700 Methane Analyzer (LI-COR Biosciences) are examined in this study. The instrument uses 8 W of power in steady-state operation and employs a tunable diode laser in an open Herriott cell configuration with 0.47 m base path and 30 m optical path length. Methane number density is measured using wavelength modulation spectroscopy (WMS) with 2f detection. Typical signal noise is <5 ppb rms at 10 Hz. Corrections for variations in temperature, pressure and water vapor are described. Data losses due to mirror contamination and condensation are minimized by a radiation shield and automatic mirror cleaning system and are shown to be small. Measured spectra and co-spectra are shown to follow the Kaimal model at deployment sites meeting classical criteria, and to follow sensible heat flux co-spectra from the sonic anemometer in most other cases, including difficult ones. Measured fluxes are similar in magnitude to those expected from the literature, and zero flux was measured during both summer and winter at a site known to have fluxes at or very near zero.

  4. Ammonia fluxes for beech forest in the leaf fall transition period - measurements and modeling

    NASA Astrophysics Data System (ADS)

    Hansen, K.; Sørensen, L.; Hertel, O.; Geels, C.; Skjøth, C. A.; Jensen, B.; Boegh, E.

    2012-12-01

    Deposition of atmospheric reactive nitrogen represents uncertainties for the prediction of future greenhouse gas exchange between land surfaces and the atmosphere. This is because the mechanisms describing nutritional effects are not well developed in climate and ecosystems models. Improving the understanding of biochemical feed-back mechanisms in the climate system and quantifying the magnitude of the NH3 flux in the biosphere-atmosphere system is therefore essential. In particular, more knowledge of the bi-directional ammonia (NH3) exchange between natural ecosystems and the atmosphere is needed. We investigated the NH3 exchange for deciduous forests in relation to leaf fall by studying the atmospheric NH3 fluxes throughout a 25 days period during autumn 2010 (21 October - 14 November) for the Danish beech (Fagus sylvatica) forest, Lille Bøgeskov. Vegetation status was observed using plant area index (PAI) and leaf area index (LAI). The atmospheric NH3 fluxes were measured using the relaxed eddy accumulation (REA) method and compared to NH3 denuder measurements. Model calculations were obtained using the Danish Ammonia MOdelling System (DAMOS). We found that 57.7% of the fluxes measured showed emission and 19.5% deposition. The mean NH3 flux was 0.087±0.19 μg NH3-N m-2 s-1. Measurements indicate a clear tendency of the flux going from negative (deposition) to positive (emission) fluxes of up to 0.96±0.40 μg NH3-N m-2 s-1 throughout the measurement period. In the leaf fall period (23 October - 8 November) the measured atmospheric NH3 concentration was increasing in relation to the increasing forest NH3 flux. The mean NH3 concentration was well simulated in DAMOS before leaf fall, but was underestimated following leaf fall. The results indicate that there is a missing contribution to atmospheric NH3 concentration from vegetative surfaces related to leaf fall of a relatively large magnitude in the model. This points to the need for representing forest leaf fall

  5. Electrophoresis and orientation of F-actin in agarose gels.

    PubMed Central

    Borejdo, J; Ortega, H

    1989-01-01

    F-Actin was electrophoresed on agarose gels. In the presence of 2 mM MgCl2 and above pH 8.5 F-actin entered 1% agarose; when the electric field was 2.1 V/cm and the pH was 8.8, F-actin migrated through a gel as a single band at a rate of 2.5 mm/h. Labeling of actin with fluorophores did not affect its rate of migration, but an increase in ionic strength slowed it down. After the electrophoresis actin was able to bind phalloidin and heavy meromyosin (HMM) and it activated Mg2+-dependent ATPase activity of HMM. The mobility of F-actin increased with the rise in pH. Acto-S-1 complex was also able to migrate in agarose at basic pH, but at a lower rate than F-actin alone. The orientation of fluorescein labeled F-actin and of fluorescein labeled S-1 which formed rigor bonds with F-actin was measured during the electrophoresis by the fluorescence detected linear dichroism method. The former showed little orientation, probably because the dye was mobile on the surface of actin, but we were able to measure the orientation of the absorption dipole of the dye bound to S-1 which was attached to F-actin, and found that it assumed an orientation largely parallel to the direction of the electric field. These results show that actin can migrate in agarose gels in the F form and that it is oriented during the electrophoresis. Images FIGURE 1 FIGURE 3 FIGURE 4 PMID:2528384

  6. 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.

  7. DESIGN AND IMPLEMENTATION OF A TRANSPORTABLE SYSTEM FOR DIRECT MEASUREMENT OF DRY DEPOSITION FLUXES

    EPA Science Inventory

    Dry deposition of air pollutants is expensive and difficult to measure. icks et al. (1985) proposed the dry deposition inferential model determines dry deposition fluxes as the product of a measured concentration and a modeled deposition velocity. eposition velocity is calculated...

  8. 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

  9. 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

  10. Measuring diurnal cycles of plant transpiration fluxes in the Arctic with an automated clear chamber

    NASA Astrophysics Data System (ADS)

    Cohen, L. R.; Raz Yaseef, N.; Curtis, J. B.; Rahn, T. A.; Young, J. M.; Newman, B. D.

    2013-12-01

    Evapotranspiration is an important greenhouse gas and a major component of the hydrological cycle, but methodological challenges still limit our knowledge of this flux. Measuring evapotranspiration is even more difficult when aiming to partition plant transpiration and soil evaporation. Information on this process for arctic systems is very limited. In order to decrease this gap, our objective was to directly measure plant transpiration in Barrow, Alaska (71.3°N 156.7°W). A commercial system allows measuring carbon soil respiration fluxes with an automated clear chamber connected to an infrared gas-analyzer (Licor 8100), and while it simultaneously measures water concentrations, it is not calibrated to measure vapor fluxes. We calibrated the clear chamber against a previously established method based on a Licor 6400 soil chamber, and we developed a code to calculate fluxes. We performed laboratory comparisons in New Mexico and field comparisons in the Arctic, suggesting that this is a valid tool for a large range of climates. In the field we found a strong correlation between the two instruments with R2 of 0.79. Even with 24 hours of daylight in the Arctic, the system captures a clear diurnal transpiration flux, peaking at 0.9 mmol m-2 s-1 and showing no flux at the lowest points. This new method should be a powerful approach for long term measurements of specific vegetation types or surface features. Such Data can also be used to help understand controls on larger scale eddy covariance tower measurements of evapotranspiration.

  11. FT-IR measurements of emissivity and temperature during high flux solar processing

    SciTech Connect

    Markham, J.R.; Smith, W.W.; Haigis, J.R.

    1996-02-01

    The experimental capability to generate and utilize concentrated solar flux has been demonstrated at a number of facilities in the US. To advance this research area, the National Renewable Energy Laboratory (NREL) has designed and constructed a versatile High Flux Solar Furnace (HFSF). Research is ongoing in areas of material processing, high temperature and UV enhanced detoxification, chemical synthesis, high flux optics, solar pumped lasers, and high heating rate processes. Surface modifications via concentrated solar flux, however, are currently performed without the means to accurately monitor the temperature of the surface of interest. Thermoelectric and pyrometric devices are not accurate due to limitations in surface contact and knowledge of surface emissivity, respectively, as well as interference contributed by the solar flux. In this article, the authors present a noncontact optical technique that simultaneously measures the directional spectral emissivity, and temperature of the surface during solar processing. A Fourier Transform Infrared (FT-IR) spectrometer is coupled to a processing chamber at NREL`s HFSF with a fiber-optic radiation transfer assembly. The system measures directional emission and hemispherical-directional reflectance in a spectral region that lacks contribution from solar flux. From these radiative property measurements during solar processing, the spectral emittance and temperature at the measurement point can be obtained. The methodology, validation measurements, and in-situ measurements during solar processing of materials are presented. Knowledge of surface temperature during solar processing is an important parameter for process control. Based on validation measurements for spectral emittance, the temperature error associated with the novel instrument is less than {+-} 5% for surfaces of mid-range emittance.

  12. Airborne flux measurements of trace species in an Arctic boundary layer

    NASA Technical Reports Server (NTRS)

    Ritter, John A.; Barrick, John D. W.; Sachse, Glen W.; Gregory, Gerald L.; Woerner, Mary A.; Watson, Catherine E.; Hill, Gerald F.; Collins, James E., Jr.

    1992-01-01

    In situ airborne flux values for O3, CO, an CH4 over selected wetlands of Alaska are reported, and airborne CH4 flux measurements are presented for the first time. The source/sink distribution over the Yukon-Kuskokwim Delta (YKD) is qualitatively correlated with surface vegetation type. The CH4 source strength over the YKD ranged from 25 to 85 mg/sq m/d. A spatially averaged, seasonally adjusted source strength of 51 mg/sq m/d was established for the YKD. Indirect CH4 flux estimates obtained over the Alaskan North Slope indicate a much lower source strength. The global CH4 emission from tundra are estimated to be 44 Tg/a at an upper limit. Airborne CO flux measurements over the YKD indicate low negative flux values over the coastal areas, while some positive fluxes were observed in the inland sparsely forested regions. An inspection of the cospectrum of CO with vertical velocity for sample runs in coastal areas indicate the possibility of in situ photochemical destruction/production of CO.

  13. Method for improving line flux and redshift measurements with narrowband filters

    NASA Astrophysics Data System (ADS)

    Zabl, J.; Freudling, W.; Møller, P.; Milvang-Jensen, B.; Nilsson, K. K.; Fynbo, J. P. U.; Le Fèvre, O.; Tasca, L. A. M.

    2016-05-01

    Context. High redshift star-forming galaxies are discovered routinely because of a flux excess in narrowband filters caused by an emission line. In most cases, the width of such filters is broader than typical line widths, and the throughput of the filters varies substantially within the bandpass. This leads to substantial uncertainties in redshifts and fluxes that are derived from the observations with one specific narrowband filter. Aims: The uncertainty in measured line parameters can be sharply reduced by using repeated observations of the same target field with filters that have overlapping passbands but differ slightly in central wavelength or wavelength dependence of the effective filter curve. Such data are routinely collected with some large field imaging cameras that use multiple detectors and a separate filter for each of the detectors. An example is the European Southern Observatory's VISTA InfraRed CAMera (VIRCAM). Methods: We developed a method of determining more accurate redshift and line flux estimates from the ratio of apparent fluxes measured from observations in different narrowband filters and several matching broadband filters. A parameterized model of the line and continuum flux is used to predict the flux ratios as a function of redshift based on the known filter curves. These model predictions are then used to determine the most likely redshift and line flux. Results: We tested the obtainable quality of parameter estimation for the example of Hα in the VIRCAM NB118 filters both on simulated and actual observations where the latter were based on the UltraVISTA DR2 data set. We combined the narrowband data with deep broadband data in Y, J, and H. We find that with this method, the errors in the measured lines fluxes can be reduced up to almost an order of magnitude. Conclusions: We conclude that existing narrowband data can be used to derive accurate line fluxes if the observations include images taken with sufficiently different filter

  14. Long-term micrometeorological measurements of nitrous oxide fluxes from agro-ecosystems (Invited)

    NASA Astrophysics Data System (ADS)

    Wagner-Riddle, C.; Brown, S.; Snider, D.

    2013-12-01

    Year-round measurements of nitrous oxide fluxes are needed in order to better characterize emissions from agro-ecosystems, and devise mitigation strategies for emission reduction. This is particularly the case for agroecosystems in cold regions where freezing and thawing of soil often results in enhanced fluxes. In addition, nitrogen fertilizer application at crop planting in the spring will also result in emission events with high temporal variability. Micrometeorological methods do not interfere with soil conditions and hence, can be used quasi-continuously (at hourly to half-hourly intervals) to capture the highly intermittent nature of N2O emission episodes. Simultaneous flux measurements on multiple plots is desirable so that the effect of soil management practices on N2O emissions can be characterized. We have conducted several studies deploying the flux-gradient technique to measure surface N2O fluxes at a long-term in Elora, ON, Canada, a site established in 2000 with the objective of improving our understanding of how management affects N2O emissions. The experimental area consists of four 1.5-4 ha plots within a level and aerodynamically homogeneous 30-ha area, and half-hourly flux is measured sequentially providing up to 12 values per plot per day. A total of 521 monthly N2O emission rates were measured over the 2000-2013 period for a range of crops (e.g. soybeans, corn, wheat) and management (e.g. no-tillage, conventional). The aggregated analysis shows that extreme flux events tend to be concentrated in February/March and May/Jun/Jul (Fig. 1). The main thaw events tend to occur in February and March, and they events contribute on average 30% to the annual nitrous oxide emission total. Timely rains after fertilizer application at crop planting in May provide high soil water content for denitrification to take place and also lead to high emission events. Sixty-six percent of the annual emission occurred from Jan to Jun on average at this site. Emissions

  15. Quantitative comparison of fluxes of solar protons measured outside and inside the earth's magnetosphere

    NASA Astrophysics Data System (ADS)

    Klimenko, V. V.

    1981-09-01

    Fluxes of flare protons for the events of September 24, 1977, May 7, 1978, and September 23, 1978, are compared on the basis of measurements made inside and outside the magnetosphere; data from the Raduga, GMS, Prognoz-6, Venera-11, and IMP 7 and 8 spacecraft are used. Differential energy spectra of solar particles obtained from the maximum values of their intensities are presented along with the temporal variations of the integral proton fluxes for the same events. At the maximum, there is a systematic increase of particle fluxes inside the magnetosphere (I1) as compared to the fluxes outside the magnetosphere (I2), and the I1/I2 ratio varies from event to event.

  16. Long-term CH3Br and CH3Cl flux measurements in temperate salt marshes

    NASA Astrophysics Data System (ADS)

    Blei, E.; Heal, M. R.; Heal, K. V.

    2010-08-01

    Fluxes of CH3Br and CH3Cl and their relationship with potential drivers such as sunlight, temperature and soil moisture, were monitored at fortnightly to monthly intervals for more than two years at two contrasting temperate salt marsh sites in Scotland. Manipulation experiments were conducted to further investigate possible links between drivers and fluxes. Mean (± 1 sd) annually and diurnally-weighted net emissions from the two sites were found to be 300 ± 44 ng m-2 h-1 for CH3Br and 662 ± 266 ng m-2 h-1 for CH3Cl. A tentative scale-up indicates that salt marshes account for 0.5-3.2% and 0.05-0.33%, respectively, of currently-estimated total global production of these two gases, in line with previous findings from this and other research groups, but consistently lower than past global scale-up estimates from Southern Californian salt marshes. Fluxes followed both seasonal and diurnal trends with highest fluxes during summer days and lowest (negative) fluxes during winter nights. Statistical analysis generally did not demonstrate a strong link between temperature or sunlight levels and methyl halide fluxes, although it is likely that temperatures have a weak direct influence on emissions, and both certainly have indirect influence via the annual and daily cycles of the vegetation. CH3Cl flux magnitudes from different measurement locations depended on the plant species enclosed whereas such dependency was not discernible for CH3Br fluxes. In 14 out of 19 collars CH3Br and CH3Cl net fluxes were significantly correlated. The CH3Cl/CH3Br net-emission mass ratio was 2.2, a magnitude lower than mass ratios of global methyl halide budgets (~22) or emissions from tropical rainforests (~60). This is likely due to preference for CH3Br production by the relatively high bromine content in the salt marsh plant material.

  17. 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.

  18. Estimation of Ammonia Flux Over A Semi-natural Grassland Based On Profile Measurements

    NASA Astrophysics Data System (ADS)

    Weidinger, T.; Horváth, L.; Mészáros, R.; Kugler, Sz.; Pintér, K.

    Ammonia flux measurements have been started at the end of December, 1999 over a semi-natural grassland. The concentration profile of ammonia was determined by a three-channel AMANDA denuder system. The inlets of AMANDA were settled at 50, 100 and 200 cm heights above the grass. The duration of one cycle of measurement (3 levels) was 7.5 minutes. Half an hour averages were used to calculate the ammo- nia flux. Around 100 measurement day records have been collected during the years of 2000 and 2001. Turbulent flux of ammonia was determined by profile method. Meteorological parameters were simultaneously measured using a sonic anemome- ter, and a Bowen-ratio system. Data were collected using 30 minute averaging time. Momentum-, sensible-, latent- and soil heat fluxes were also calculated from the mea- surements. An extensive analysis of dataset, such as ammonia exchange between the semi-natural grassland and the near surface layer during different meteorological con- ditions are presented in this study. Effects of various natural and anthropogenic sources (volatilization from livestock wastes, fertilization) on ammonia flux are also analysed.

  19. Eddy covariance measurements of nitric oxide flux within an Amazonian rain forest

    NASA Astrophysics Data System (ADS)

    Rummel, , U.; Ammann, , C.; Gut, , A.; Meixner, , F. X.; Andreae, M. O.

    2002-10-01

    NO flux measurements by the eddy covariance technique were performed within a tropical rain forest 1 m and 11 m above the forest floor. A fast-response chemiluminescence NO analyzer with a sampling tube of 25 m length was used for the gas measurements. Nighttime similarity between the cospectra of sensible heat and the NO flux offered the possibility to quantify the high-frequency attenuation of the NO eddy covariance by spectral analysis. Integrated flux correction factors of about 21% for the system at 1 m and 5% for the one at 11 m above ground were calculated by transfer functions adopted from the literature and confirmed experimentally. For an independent validation the results of the eddy covariance system were compared with the NO soil emissions obtained by dynamic chambers. For nighttime averages, good agreement within 10% was found. The obtained NO fluxes were 3.5 ± 0.14 and 4.8 ± 0.39 ng N m-2 s-1 for the two investigated periods at 1 and 11 m heights, respectively. During the day, chemical reaction with ozone entrained from aloft reduced the fraction of the soil-emitted NO that reached the measuring height of the eddy covariance system. The average flux showed a reduction of 48% at 1 m and 92% at 11 m height compared to the corresponding soil emission measured by the chamber system.

  20. Flux threshold measurements of He-ion beam induced nanofuzz formation on hot tungsten surfaces

    NASA Astrophysics Data System (ADS)

    Meyer, F. W.; Hijazi, H.; Bannister, M. E.; Unocic, K. A.; Garrison, L. M.; Parish, C. M.

    2016-02-01

    We report measurements of the energy dependence of flux thresholds and incubation fluences for He-ion induced nano-fuzz formation on hot tungsten surfaces at UHV conditions over a wide energy range using real-time sample imaging of tungsten target emissivity change to monitor the spatial extent of nano-fuzz growth, corroborated by ex situ SEM and FIB/SEM analysis, in conjunction with accurate ion-flux profile measurements. The measurements were carried out at the multicharged ion research facility (MIRF) at energies from 218 eV to 8.5 keV, using a high-flux deceleration module and beam flux monitor for optimizing the decel optics on the low energy MIRF beamline. The measurements suggest that nano-fuzz formation proceeds only if a critical rate of change of trapped He density in the W target is exceeded. To understand the energy dependence of the observed flux thresholds, the energy dependence of three contributing factors: ion reflection, ion range and target damage creation, were determined using the SRIM simulation code. The observed energy dependence can be well reproduced by the combined energy dependences of these three factors. The incubation fluences deduced from first visual appearance of surface emissivity change were (2-4) × 1023 m-2 at 218 eV, and roughly a factor of 10 less at the higher energies, which were all at or above the displacement energy threshold. The role of trapping at C impurity sites is discussed.

  1. Flux of organic compounds from grass measured by relaxed eddy accumulation technique.

    PubMed

    Olofsson, Marcus; Ek-Olausson, Birgitta; Ljungström, Evert; Langer, Sarka

    2003-12-01

    Fluxes of some Volatile Organic Compounds (VOC) from grass were measured at a golf course in western Sweden, using the Relaxed Eddy Accumulation (REA) technique. The sampling was done by collecting VOC onto adsorbent tubes and the analysis was performed by thermal desorption followed by GC/MS. High emissions were observed after cutting. Transient fluxes of (Z)-3-hexenyl acetate (0.51 microg m(-2) s(-1)), (Z)-3-hexen-1-ol (0.14 microg m(-2) s(-1)) and (Z)-3-hexenal (0.40 microg m(-2) s(-1)) were measured, even at low temperatures. The REA technique requires a relatively large fetch area that is sometimes not available. Therefore, a procedure for correcting measured fluxes from a limited fetch is suggested. PMID:14710940

  2. 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

  3. 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

  4. 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

  5. Observing the Arctic Carbon Feedback: Regional scale methane flux measurements over the Alaskan North Slope using airplane flux observations and in situ measurements of δ13CH4.

    NASA Astrophysics Data System (ADS)

    Healy, C. E.; Sayres, D. S.; Dobosy, R.; Dumas, E. J.; Munster, J. B.; Kochendorfer, J.; Wilkerson, J.; Baker, B.; Dubey, M. K.; Anderson, J. G.

    2015-12-01

    One of the most powerful positive feedback mechanisms to anthropogenic climate change postulated is the increase in carbon emissions from polar-regions. Warmer temperatures at the poles is predicted to increase the rate of methanogensesis in thawing permafrost soils as well as destabilize the network of arctic marine and terrestrial methane hydrates. Recent estimates put the quantity of organic carbon stored in soils in the northern permafrost zone around 1,700 Pg of C, which is well in excess of the maximum carbon emissions necessary to limit global average temperature increase to only 2 C° (260-410 Pg of C between 2011 and 2100 as CO2). However, many climate models used to forecast changes in average global temperature and inform policy decisions do not take into account arctic carbon feedback. This is largely due in part to the daunting observational challenge presented by observing methane fluxes in the Arctic. An ideal measurement system must be able to distinguish between biological and anthropogenic methane sources, have the ability to cover large spatial ranges, and have the sensitivity to distinguish changes from season to season, and year to year. The FOCAL platform has been engineered to address these challenges and help bridge the gap in spatial coverage between ground based and inverse modelling studies. It consists of a small aircraft equipped with the best atmospheric turbulence (BAT) probe, and gas sensors for in situ measurements of CH4, CO2, δ13CH4, δ13CO2 to make regional scale surface eddy-covariance flux measurements of methane and carbon dioxide as well as their stable isotopologues. We will present data from the initial FOCAL flight series in August 2013 based out of Deadhorse, AK, including CH4 concentration and running flux data, as well as in situ δ13CH4 observations to gain mechanistic insight. With the FOCAL platform we were able to dramatically extend regional coverage of methane flux observations beyond what can normally be observe

  6. 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

  7. 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

  8. Shaped scintillation detector systems for measurements of gamma ray flux anisotropy

    NASA Technical Reports Server (NTRS)

    Trombka, J. I.; Vette, J. I.; Stecker, F. W.; Eller, E. L.; Wildes, W. T.

    1973-01-01

    The detection efficiencies of cylindrical detectors for various gamma ray photon angular distributions were studied in the energy range from .10 Mev to 15 Mev. These studies indicate that simple detector systems on small satellites can be used to measure flux anisotropy of cosmic gamma rays and the angular distribution of albedo gamma rays produced in planetary atmospheres. The results indicate that flat cylindrical detectors are most suitable for measuring flux anisotropy because of their angular response function. A general method for calculating detection efficiencies for such detectors is presented.

  9. 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.

  10. Development of a laser remote sensing instrument to measure sub-aerial volcanic CO2 fluxes

    NASA Astrophysics Data System (ADS)

    Queisser, Manuel; Burton, Mike

    2016-04-01

    A thorough quantification of volcanic CO2 fluxes would lead to an enhanced understanding of the role of volcanoes in the geological carbon cycle. This would enable a more subtle understanding of human impact on that cycle. Furthermore, variations in volcanic CO2 emissions are a key to understanding volcanic processes such as eruption phenomenology. However, measuring fluxes of volcanic CO2 is challenging as volcanic CO2 concentrations are modest compared with the ambient CO2 concentration (~400 ppm) . Volcanic CO2 quickly dilutes with the background air. For Mt. Etna (Italy), for instance, 1000 m downwind from the crater, dispersion modelling yields a signal of ~4 ppm only. It is for this reason that many magmatic CO2 concentration measurements focus on in situ techniques, such as direct sampling Giggenbach bottles, chemical sensors, IR absorption spectrometers or mass spectrometers. However, emission rates are highly variable in time and space. Point measurements fail to account for this variability. Inferring 1-D or 2-D gas concentration profiles, necessary to estimate gas fluxes, from point measurements may thus lead to erroneous flux estimations. Moreover, in situ probing is time consuming and, since many volcanoes emit toxic gases and are dangerous as mountains, may raise safety concerns. In addition, degassing is often diffuse and spatially extended, which makes a measurement approach with spatial coverage desirable. There are techniques that allow to indirectly retrieve CO2 fluxes from correlated SO2 concentrations and fluxes. However, they still rely on point measurements of CO2 and are prone to errors of SO2 fluxes due to light dilution and depend on blue sky conditions. Here, we present a new remote sensing instrument, developed with the ERC project CO2Volc, which measures 1-D column amounts of CO2 in the atmosphere with sufficient sensitivity to reveal the contribution of magmatic CO2. Based on differential absorption LIDAR (DIAL) the instrument measures

  11. Precision measurements of e+, e_, e++e_ fluxes with AMS-02

    NASA Astrophysics Data System (ADS)

    Pizzolotto, Cecilia

    2016-05-01

    The Alpha Magnetic Spectrometer (AMS-02) is a large acceptance particle physics detector installed on board the International Space Station (ISS) since May 19th 2011 to search for primordial anti-matter, for indirect signals of dark matter and to perform a high statistic and long duration measurement of the spectra of primary charged cosmic rays. Precise measurements of the electron and positron fluxes and of the total e++e_ flux are presented. These AMS results provide a deeper understanding of the nature of high energy cosmic rays and can shed more light on the nature of dark matter.

  12. 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.

  13. Human cytoplasmic actin proteins are encoded by a multigene family

    SciTech Connect

    Engel, J.; Gunning, P.; Kedes, L.

    1982-06-01

    The authors characterized nine human actin genes that they isolated from a library of cloned human DNA. Measurements of the thermal stability of hybrids formed between each cloned actin gene and ..cap alpha..-, ..beta..-, and ..gamma..-actin mRNA demonstrated that only one of the clones is most homologous to sarcomeric actin mRNA, whereas the remaining eight clones are most homologous to cytoplasmic actin mRNA. By the following criteria they show that these nine clones represent nine different actin gene loci rather than different alleles or different parts of a single gene: (i) the restriction enzyme maps of the coding regions are dissimilar; (ii) each clone contains sufficient coding region to encode all or most of an entire actin gene; and (iii) each clone contains sequences homologous to both the 5' and 3' ends of the coding region of a cloned chicken ..beta..-actin cDNA. They conclude, therefore, that the human cytoplasmic actin proteins are encoded by a multigene family.

  14. Electrostatics control actin filament nucleation and elongation kinetics.

    PubMed

    Crevenna, Alvaro H; Naredi-Rainer, Nikolaus; Schönichen, André; Dzubiella, Joachim; Barber, Diane L; Lamb, Don C; Wedlich-Söldner, Roland

    2013-04-26

    The actin cytoskeleton is a central mediator of cellular morphogenesis, and rapid actin reorganization drives essential processes such as cell migration and cell division. Whereas several actin-binding proteins are known to be regulated by changes in intracellular pH, detailed information regarding the effect of pH on the actin dynamics itself is still lacking. Here, we combine bulk assays, total internal reflection fluorescence microscopy, fluorescence fluctuation spectroscopy techniques, and theory to comprehensively characterize the effect of pH on actin polymerization. We show that both nucleation and elongation are strongly enhanced at acidic pH, with a maximum close to the pI of actin. Monomer association rates are similarly affected by pH at both ends, although dissociation rates are differentially affected. This indicates that electrostatics control the diffusional encounter but not the dissociation rate, which is critical for the establishment of actin filament asymmetry. A generic model of protein-protein interaction, including electrostatics, explains the observed pH sensitivity as a consequence of charge repulsion. The observed pH effect on actin in vitro agrees with measurements of Listeria propulsion in pH-controlled cells. pH regulation should therefore be considered as a modulator of actin dynamics in a cellular environment. PMID:23486468

  15. Magnetic Field-line Length and Twist Distributions within Interplanetary Flux Fopes from Wind Spacecraft Measurements

    NASA Astrophysics Data System (ADS)

    Hu, Q.; Qiu, J.; Krucker, S.; Wang, L.; Wang, B.; Chen, Y.; Moestl, C.

    2014-12-01

    We report on the detailed and systematic study of field-line twist and length distributions within magnetic flux ropes embedded in Interplanetary Coronal Mass Ejections (ICMEs). In particular we will utilize energetic electron burst observations at 1 AU together with associated type III radio emissions detected by the Wind spacecraft to provide unique measurements of magnetic field-line lengths within selected ICME events. These direct measurements will be compared with flux-rope model calculations to help assess the fidelity of different models and to provide diagnostics of internal structures. The Grad-Shafranov reconstruction method will be utilized together with a constant-twist nonlinear force-free (Gold-Hoyle) flux rope model and the commonly known Lundquist (linear force-free) model to reveal the close relation between the field-line twist and length in cylindrical flux ropes, based on in-situ Wind spacecraft magnetic field and plasma measurements. We show that our initial analysis of field-line twist indicates clear deviation from the Lundquist model, but better consistency with the Gold-Hoyle model. We will also discuss the implications of our analysis of flux-rope structures on the origination and evolution processes in their corresponding solar source regions.

  16. Assessing and correcting spatial representativeness of tower eddy-covariance flux measurements

    NASA Astrophysics Data System (ADS)

    Metzger, S.; Xu, K.; Desai, A. R.; Taylor, J. R.; Kljun, N.; Blanken, P.; Burns, S. P.; Scott, R. L.

    2014-12-01

    Estimating the landscape-scale exchange of ecologically relevant trace gas and energy fluxes from tower eddy-covariance (EC) measurements is often complicated by surface heterogeneity. For example, a tower EC measurement may represent less than 1% of a grid cell resolved by mechanistic models (order 100-1000 km2). In particular for data assimilation or comparison with large-scale observations, it is hence critical to assess and correct the spatial representativeness of tower EC measurements. We present a procedure that determines from a single EC tower the spatio-temporally explicit flux field of its surrounding. The underlying principle is to extract the relationship between biophysical drivers and ecological responses from measurements under varying environmental conditions. For this purpose, high-frequency EC flux processing and source area calculations (≈60 h-1) are combined with remote sensing retrievals of land surface properties and subsequent machine learning. Methodological details are provided in our companion presentation "Towards the spatial rectification of tower-based eddy-covariance flux observations". We apply the procedure to one year of data from each of four AmeriFlux sites under different climate and ecological environments: Lost Creek shrub fen wetland, Niwot Ridge subalpine conifer, Park Falls mixed forest, and Santa Rita mesquite savanna. We find that heat fluxes from the Park Falls 122-m-high EC measurement and from a surrounding 100 km2 target area differ up to 100 W m-2, or 65%. Moreover, 85% and 24% of the EC flux observations are adequate surrogates of the mean surface-atmosphere exchange and its spatial variability across a 900 km2 target area, respectively, at 5% significance and 80% representativeness levels. Alternatively, the resulting flux grids can be summarized as probability density functions, and used to inform mechanistic models directly with the mean flux value and its spatial variability across a model grid cell. Lastly

  17. Modeling Method for Increased Precision and Scope of Directly Measurable Fluxes at a Genome-Scale.

    PubMed

    McCloskey, Douglas; Young, Jamey D; Xu, Sibei; Palsson, Bernhard O; Feist, Adam M

    2016-04-01

    Metabolic flux analysis (MFA) is considered to be the gold standard for determining the intracellular flux distribution of biological systems. The majority of work using MFA has been limited to core models of metabolism due to challenges in implementing genome-scale MFA and the undesirable trade-off between increased scope and decreased precision in flux estimations. This work presents a tunable workflow for expanding the scope of MFA to the genome-scale without trade-offs in flux precision. The genome-scale MFA model presented here, iDM2014, accounts for 537 net reactions, which includes the core pathways of traditional MFA models and also covers the additional pathways of purine, pyrimidine, isoprenoid, methionine, riboflavin, coenzyme A, and folate, as well as other biosynthetic pathways. When evaluating the iDM2014 using a set of measured intracellular intermediate and cofactor mass isotopomer distributions (MIDs),1 it was found that a total of 232 net fluxes of central and peripheral metabolism could be resolved in the E. coli network. The increase in scope was shown to cover the full biosynthetic route to an expanded set of bioproduction pathways, which should facilitate applications such as the design of more complex bioprocessing strains and aid in identifying new antimicrobials. Importantly, it was found that there was no loss in precision of core fluxes when compared to a traditional core model, and additionally there was an overall increase in precision when considering all observable reactions. PMID:26981784

  18. Experimental study on measurement and calculation of heat flux in supersonic combustor of scramjet

    NASA Astrophysics Data System (ADS)

    Zhang, Cong; Yao, Zhanli; Qin, Jiang; Bao, Wen

    2015-06-01

    An experimental measurement and calculation method which consist of thermal response model, convergence criteria and control algorithms, is proposed in this paper for the determination of heat flux in a scramjet combustor. Numerical simulations are done to evaluate the effectiveness of the proposed method, and experiments are made in the direct-connect hydrocarbon fueled scramjet combustor of Mach-6 flight for different equivalence ratios. The distribution of heat flux along the axial and circumferential directions can be obtained using the proposed method. The distribution of heat flux is uneven which is caused by the aerodynamic heating, combustion heat release and changes of section area, and the peak heat flux can be more than 2MW/m2 during the experiments. Heat flux increases with the increase in equivalence ratio for the same Mach number. And axial distribution of heat flux is uniform for different equivalence ratios. In addition, the combustion heat release area of the combustion chamber can therefore be concluded which is useful for guiding the structural design of the thermal protection system.

  19. Force of an actin spring

    NASA Astrophysics Data System (ADS)

    Shin, Jennifer; Mahadevan, L.; Matsudaira, Paul

    2003-03-01

    The acrosomal process of the horseshoe crab sperm is a novel mechanochemical molecular spring that converts its elastic stain energy to mechanical work upon the chemical activation by Ca2+. Twisted and bent, the initial state of the acrosomal bundle features a high degree of complexity in its structure and the energy is believed to be stored in the highly strained actin filaments as an elastic potential energy. When activated, the bundle relaxes from the coil of the highly twisted and bent filaments to its straight conformation at a mean velocity of 15um/s. The mean extension velocity increases dramatically from 3um/s to 27um/s when temperature of the medium is changed from 9.6C to 32C (respective viscosities of 1.25-0.75cp), yet it exhibits a very weak dependence on changes in the medium viscosity (1cp-33cp). These experiments suggest that the uncoiling of the actin spring should be limited not by the viscosity of the medium but by the unlatching events of involved proteins at a molecular level. Unlike the viscosity-limited processes, where force is directly related to the rate of the reaction, a direct measurement is required to obtain the spring force of the acrosomal process. The extending acrosomal bundle is forced to push against a barrier and its elastic buckling response is analyzed to measure the force generated during the uncoiling.

  20. 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.

  1. Water Use Patterns of Four Tropical Bamboo Species Assessed with Sap Flux Measurements.

    PubMed

    Mei, Tingting; Fang, Dongming; Röll, Alexander; Niu, Furong; Hendrayanto; Hölscher, Dirk

    2015-01-01

    Bamboos are grasses (Poaceae) that are widespread in tropical and subtropical regions. We aimed at exploring water use patterns of four tropical bamboo species (Bambusa vulgaris, Dendrocalamus asper, Gigantochloa atroviolacea, and G. apus) with sap flux measurement techniques. Our approach included three experimental steps: (1) a pot experiment with a comparison of thermal dissipation probes (TDPs), the stem heat balance (SHB) method and gravimetric readings using potted B. vulgaris culms, (2) an in situ calibration of TDPs with the SHB method for the four bamboo species, and (3) field monitoring of sap flux of the four bamboo species along with three tropical tree species (Gmelina arborea, Shorea leprosula, and Hevea brasiliensis) during a dry and a wet period. In the pot experiment, it was confirmed that the SHB method is well suited for bamboos but that TDPs need to be calibrated. In situ, species-specific parameters for such calibration formulas were derived. During field monitoring we found that some bamboo species reached high maximum sap flux densities. Across bamboo species, maximal sap flux density increased with decreasing culm diameter. In the diurnal course, sap flux densities in bamboos peaked much earlier than radiation and vapor pressure deficit (VPD), and also much earlier than sap flux densities in trees. There was a pronounced hysteresis between sap flux density and VPD in bamboos, which was less pronounced in trees. Three of the four bamboo species showed reduced sap flux densities at high VPD values during the dry period, which was associated with a decrease in soil moisture content. Possible roles of internal water storage, root pressure and stomatal sensitivity are discussed. PMID:26779233

  2. Water Use Patterns of Four Tropical Bamboo Species Assessed with Sap Flux Measurements

    PubMed Central

    Mei, Tingting; Fang, Dongming; Röll, Alexander; Niu, Furong; Hendrayanto; Hölscher, Dirk

    2016-01-01

    Bamboos are grasses (Poaceae) that are widespread in tropical and subtropical regions. We aimed at exploring water use patterns of four tropical bamboo species (Bambusa vulgaris, Dendrocalamus asper, Gigantochloa atroviolacea, and G. apus) with sap flux measurement techniques. Our approach included three experimental steps: (1) a pot experiment with a comparison of thermal dissipation probes (TDPs), the stem heat balance (SHB) method and gravimetric readings using potted B. vulgaris culms, (2) an in situ calibration of TDPs with the SHB method for the four bamboo species, and (3) field monitoring of sap flux of the four bamboo species along with three tropical tree species (Gmelina arborea, Shorea leprosula, and Hevea brasiliensis) during a dry and a wet period. In the pot experiment, it was confirmed that the SHB method is well suited for bamboos but that TDPs need to be calibrated. In situ, species-specific parameters for such calibration formulas were derived. During field monitoring we found that some bamboo species reached high maximum sap flux densities. Across bamboo species, maximal sap flux density increased with decreasing culm diameter. In the diurnal course, sap flux densities in bamboos peaked much earlier than radiation and vapor pressure deficit (VPD), and also much earlier than sap flux densities in trees. There was a pronounced hysteresis between sap flux density and VPD in bamboos, which was less pronounced in trees. Three of the four bamboo species showed reduced sap flux densities at high VPD values during the dry period, which was associated with a decrease in soil moisture content. Possible roles of internal water storage, root pressure and stomatal sensitivity are discussed. PMID:26779233

  3. Measurement of Greenhouse Gas Flux from Agricultural Soils Using Static Chambers

    PubMed Central

    Collier, Sarah M.; Ruark, Matthew D.; Oates, Lawrence G.; Jokela, William E.; Dell, Curtis J.

    2014-01-01

    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 management practices. The static chamber-based method described here is based on trapping gases emitted from the soil surface within a chamber and collecting samples from the chamber headspace at regular intervals for analysis by gas chromatography. Change in gas concentration over time is used to calculate flux. This method can be utilized to measure landscape-based flux of carbon dioxide, nitrous oxide, and methane, and to estimate differences between treatments or explore system dynamics over seasons or years. Infrastructure requirements are modest, but a comprehensive experimental design is essential. This method is easily deployed in the field, conforms to established guidelines, and produces data suitable to large-scale GHG emissions studies. PMID:25146426

  4. Simple, stable, and affordable: Towards long-term ecosystem scale flux measurements of VOCs

    NASA Astrophysics Data System (ADS)

    Rinne, J.; Karl, T.; Guenther, A.

    2016-04-01

    Biogenic volatile organic compounds (BVOC) are key players in atmospheric chemistry and climate, yet our understanding of their emission dynamics is very limited. They dominate global emissions of volatile organic compounds (VOC) with estimated rates that are an order of magnitude higher than the anthropogenic VOC emissions. Since the publication of the first global BVOC emission inventories there have been efforts to develop more realistic and process-based models of BVOC emissions. However, there are only a few ecosystem-scale BVOC flux data for evaluation and improvement of these models. Thus a reliable network of observations is urgently needed. Surface layer flux measurements by micrometeorological methods provide the most suitable data for this purpose but there are some hindrances preventing the implementation of a long-term flux measurement network.

  5. Microwave Reflectometry Measurements of Flux States of a dc SQUID Phase Qubit

    NASA Astrophysics Data System (ADS)

    Cooper, B. K.; Lewis, R. M.; Dutta, S. K.; Palomaki, T. A.; Przybysz, Anthony; Kwon, H.; Paik, Hanhee; Anderson, J. R.; Lobb, C. J.; Wellstood, F. C.

    2008-03-01

    We examine microwave reflectometry readout of a dc SQUID phase qubit. Our device is a Nb/AlOx/Nb SQUID fabricated by Hypres with loop inductance of 1.3 nH and symmetric junction critical currents of approximately 5 μA. The SQUID is current and flux biased, with one junction used as the qubit and the other used to provide isolation. The isolation junction is shunted by a large capacitor to depress its plasma frequency to about 1.5 GHz. This frequency can be shifted by flux-induced circulating current in the SQUID loop, allowing us to determine which flux state we are in by making reflectometry measurements of the resonant behavior of the isolation junction. The utility of this measurement for qubit state readout is discussed.

  6. 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

  7. Measurement of greenhouse gas flux from agricultural soils using static chambers.

    PubMed

    Collier, Sarah M; Ruark, Matthew D; Oates, Lawrence G; Jokela, William E; Dell, Curtis J

    2014-01-01

    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 management practices. The static chamber-based method described here is based on trapping gases emitted from the soil surface within a chamber and collecting samples from the chamber headspace at regular intervals for analysis by gas chromatography. Change in gas concentration over time is used to calculate flux. This method can be utilized to measure landscape-based flux of carbon dioxide, nitrous oxide, and methane, and to estimate differences between treatments or explore system dynamics over seasons or years. Infrastructure requirements are modest, but a comprehensive experimental design is essential. This method is easily deployed in the field, conforms to established guidelines, and produces data suitable to large-scale GHG emissions studies. PMID:25146426

  8. Fluxes of biogenic volatile organic compounds measured and modelled above a Norway spruce forest

    NASA Astrophysics Data System (ADS)

    Juráň, Stanislav; Fares, Silvano; Pallozzi, Emanuele; Guidolotti, Gabriele; Savi, Flavia; Alivernini, Alessandro; Calfapietra, Carlo; Večeřová, Kristýna; Křůmal, Kamil; Večeřa, Zbyněk; Cudlín, Pavel; Urban, Otmar

    2016-04-01

    Fluxes of biogenic volatile organic compounds (BVOCs) were investigated at Norway spruce forest at Bílý Kříž in Beskydy Mountains of the Czech Republic during the summer 2014. A proton-transfer-reaction-time-of-flight mass spectrometer (PTR-TOF-MS, Ionicon Analytik, Austria) has been coupled with eddy-covariance system. Additionally, Inverse Lagrangian Transport Model has been used to derive fluxes from concentration gradient of various monoterpenes previously absorbed into n-heptane by wet effluent diffusion denuder with consequent quantification by gas chromatography with mass spectrometry detection. Modelled data cover each one day of three years with different climatic conditions and previous precipitation patterns. Model MEGAN was run to cover all dataset with monoterpene fluxes and measured basal emission factor. Highest fluxes measured by eddy-covariance were recorded during the noon hours, represented particularly by monoterpenes and isoprene. Inverse Lagrangian Transport Model suggests most abundant monoterpene fluxes being α- and β-pinene. Principal component analysis revealed dependencies of individual monoterpene fluxes on air temperature and particularly global radiation; however, these dependencies were monoterpene specific. Relationships of monoterpene fluxes with CO2 flux and relative air humidity were found to be negative. MEGAN model correlated to eddy-covariance PTR-TOF-MS measurement evince particular differences, which will be shown and discussed. Bi-directional fluxes of oxygenated short-chain volatiles (methanol, formaldehyde, acetone, acetaldehyde, formic acid, acetic acid, methyl vinyl ketone, methacrolein, and methyl ethyl ketone) were recorded by PTR-TOF-MS. Volatiles of anthropogenic origin as benzene and toluene were likely transported from the most benzene polluted region in Europe - Ostrava city and adjacent part of Poland around Katowice, where metallurgical and coal mining industries are located. Those were accumulated during

  9. 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/22

  10. Symmetry breaking in actin gels - Implications for cellular motility

    NASA Astrophysics Data System (ADS)

    John, Karin; Peyla, Philippe; Misbah, Chaouqi

    2007-03-01

    The physical origin of cell motility is not fully understood. Recently minimal model systems have shown, that polymerizing actin itself can produce a motile force, without the help of motor proteins. Pathogens like Shigella or Listeria use actin to propel themselves forward in their host cell. The same process can be mimicked with polystyrene beads covered with the activating protein ActA, which reside in a solution containing actin monomers. ActA induces the growth of an actin gel at the bead surface. Initially the gel grows symmetrically around the bead until a critical size is reached. Subsequently one observes a symmetry breaking and the gel starts to grow asymmetrically around the bead developing a tail of actin at one side. This symmetry breaking is accompanied by a directed movement of the bead, with the actin tail trailing behind the bead. Force generation relies on the combination of two properties: growth and elasticity of the actin gel. We study this phenomenon theoretically within the framework of a linear elasticity theory and linear flux-force relationships for the evolution of an elastic gel around a hard sphere. Conditions for a parity symmetry breaking are identified analytically and illustrated numerically with the help of a phasefield model.

  11. Actin Dynamics in Growth Cone Motility and Navigation

    PubMed Central

    Gomez, Timothy M.; Letourneau, Paul C.

    2014-01-01

    Motile growth cones lead growing axons through developing tissues to synaptic targets. These behaviors depend on the organization and dynamics of actin filaments that fill the growth cone leading margin (peripheral (P-) domain). Actin filament organization in growth cones is regulated by actin-binding proteins that control all aspects of filament assembly, turnover, interactions with other filaments and cytoplasmic components, and participation in producing mechanical forces. Actin filament polymerization drives protrusion of sensory filopodia and lamellipodia, and actin filament connections to the plasma membrane link the filament network to adhesive contacts of filopodia and lamellipodia with other surfaces. These contacts stabilize protrusions and transduce mechanical forces generated by actomyosin activity into traction that pulls an elongating axon along the path towards its target. Adhesive ligands and extrinsic guidance cues bind growth cone receptors and trigger signaling activities involving Rho GTPases, kinases, phosphatases, cyclic nucleotides and [Ca++] fluxes. These signals regulate actin binding proteins to locally modulate actin polymerization, interactions and force transduction to steer the growth cone leading margin towards the sources of attractive cues and away from repellent guidance cues. PMID:24164353

  12. 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.

  13. Field inter-comparison of three systems for NH3 concentration and flux measurements

    NASA Astrophysics Data System (ADS)

    Voglmeier, Karl; Ammann, Christof; Neftel, Albrecht; Häni, Christoph; Richter, Undine; Brümmer, Christian

    2016-04-01

    Ambient air ammonia analyzer systems that are not only used for concentration but also for flux measurements have to meet special requirements. They either have to provide a fast response detection (c. 1 sec) for the application of the eddy covariance technique (EC) or they have to resolve relatively small horizontal or vertical concentration gradients. The Posieux intercomparison experiment in fall 2015 was designed to compare three advanced and different approaches to determine concentration and fluxes of NH3 of a grazed pasture during several weeks. The methods involved: [1] a two channel reactive N converter measuring in parallel the sum of oxidized N species with the exception of N2O and the sum of the total reactive N species. The difference of the two channels corresponds to the sum of reduced reactive N species; [2] a QC laser analyzer with a special designed inlet system that minimize wall effects and separates particles from the gas sampling stream; [3] two MiniDOAS instruments for line integrated concentration without any inlet system. The experimental setup and the environmental conditions resulted in a high temporal and spatial dynamic of NH3 concentrations and fluxes. Systems [1] and [2] are designed to perform flux measurements by the Eddy Covariance technique, whereas the DOAS technique has a temporal resolution of 1 min. Fluxes are calculated from the horizontal concentration increase across an emitting surface with back lagrangian stochastic trajectory dispersion model. We present a comparison of the measured concentrations and fluxes and discuss the advantages and limitations of the three chosen systems.

  14. 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.

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

    NASA Astrophysics Data System (ADS)

    Gaudin, Damien; Beauducel, François; Allemand, Pascal; Delacourt, Christophe; Finizola, Anthony

    2013-11-01

    Monitoring the geothermal flux of a dormant volcano is necessary both for hazard assessment and for studying hydrothermal systems. Heat from a magma body located at depth is transported by steam to the surface, where it is expelled in fumaroles if the heat flow exceeds 500 W/m2. If the heat flow is lower than 500 W/m2, steam mainly condensates in the soil close to surface and produces a thermal anomaly detectable at the surface. In this study, we propose a method to quantify low heat fluxes from temperature anomalies measured at the surface by a thermal infrared camera. Once corrected from the atmospheric and surface effects, thermal infrared images are used to compute (1) the excess of radiative flux, (2) the excess of sensible flux and (3) the steam flux from the soil to the atmosphere. These calculations require measurements of atmospheric parameters (temperature, wind velocity and humidity) and estimations of surface parameters (roughness and emissivity). This method has been tested on a low-flux fumarolic zone of the Soufrière volcano (Guadeloupe Island — Lesser Antilles), and compared to a flux estimation realized from the thermal gradient measurements into the soil. The two methods show a good agreement and a similar precision (267 ± 46 W/m2 for the thermal infrared method, and 275 ± 50 W/m2 for the vertical temperature gradient method), if surface roughness is well calibrated.

  16. Open-path tunable diode laser absorption for eddy correlation flux measurements of atmospheric trace gases

    NASA Technical Reports Server (NTRS)

    Anderson, Stuart M.; Zahniser, Mark S.

    1991-01-01

    Biogenic emissions from and dry deposition to terrestrial surfaces are important processes determining the trace gas composition of the atmosphere. An instrument has been developed for flux measurements of gases such as CH4, N2O, and O3 based on the eddy correlation technique which combines trace gas fluctuation measurements with simultaneous windfield measurements. The instrument combines a tunable diode laser infrared light source with an open-path multipass absorption cell in order to provide the fast time response and short base pathlength required for the eddy correlation method. Initial field tests using the instrument to measure methane emissions from a local wetland demonstrate the capability for high precision eddy correlation flux measurements.

  17. 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.

  18. 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.

  19. Non-linearity measurements of solar cells with an LED-based combinatorial flux addition method

    NASA Astrophysics Data System (ADS)

    Hamadani, Behrang H.; Shore, Andrew; Roller, John; Yoon, Howard W.; Campanelli, Mark

    2016-02-01

    We present a light emitting diode (LED)-based system utilizing a combinatorial flux addition method to investigate the non-linear relationship in solar cells between the output current of the cell and the incident irradiance level. The magnitude of the light flux is controlled by the supplied currents to two LEDs (or two sets of them) in a combinatorial fashion. The signals measured from the cell are arranged within a related overdetermined linear system of equations derived from an appropriately chosen Nth degree polynomial representing the relationship between the measured signals and the incident fluxes. The flux values and the polynomial coefficients are then solved for by linear least squares to obtain the best fit. The technique can be applied to any solar cell, under either monochromatic or broadband spectrum. For the unscaled solution, no reference detectors or prior calibrations of the light flux are required. However, if at least one calibrated irradiance value is known, then the entire curve can be scaled to an appropriate spectral responsivity value. Using this technique, a large number of data points can be obtained in a relatively short time scale over a large signal range.

  20. Refining Field Measurements of Methane Flux Rates from Abandoned Oil and Gas Wells

    NASA Astrophysics Data System (ADS)

    Lagron, C. S.; Kang, M.; Riqueros, N. S.; Jackson, R. B.

    2015-12-01

    Recent studies in Pennsylvania demonstrate the potential for significant methane emissions from abandoned oil and gas wells. A subset of tested wells was high emitting, with methane flux rates up to seven orders of magnitude greater than natural fluxes (up to 105 mg CH4/hour, or about 2.5LPM). These wells contribute disproportionately to the total methane emissions from abandoned oil and gas wells. The principles guiding the chamber design have been developed for lower flux rates, typically found in natural environments, and chamber design modifications may reduce uncertainty in flux rates associated with high-emitting wells. Kang et al. estimate errors of a factor of two in measured values based on previous studies. We conduct controlled releases of methane to refine error estimates and improve chamber design with a focus on high-emitters. Controlled releases of methane are conducted at 0.05 LPM, 0.50 LPM, 1.0 LPM, 2.0 LPM, 3.0 LPM, and 5.0 LPM, and at two chamber dimensions typically used in field measurements studies of abandoned wells. As most sources of error tabulated by Kang et al. tend to bias the results toward underreporting of methane emissions, a flux-targeted chamber design modification can reduce error margins and/or provide grounds for a potential upward revision of emission estimates.

  1. 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

  2. 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.

  3. Comparing computational models of slug rise at Stromboli with UV camera measurements of SO2 flux

    NASA Astrophysics Data System (ADS)

    Pering, Tom D.; McGonigle, Andrew J. S.; James, Mike R.; Tamburello, Giancarlo; Aiuppa, Alessandro

    2015-04-01

    Strombolian eruptions, particularly those at the archetypal Stromboli Volcano (Aeolian Islands, Italy) are generally accepted to be caused by the burst of gas slugs. Using computational fluid dynamic models implemented in Ansys Fluent®, with a range of conduit, magma and gas properties appropriate for current observations at Stromboli volcano, we simulate the rise of such gas slugs and demonstrate that during their ascent there is the potential for daughter bubble production from the slug base. These are bubbles which can detach from the influence of a slug to rise and burst at the surface independently. Within the models we can then estimate the amount and temporal pattern of gas released during and following individual slug burst events. This is achieved by integrating gas released near the magma surface. After correcting for atmospheric entrainment and diffusion we can then compare our modelled gas flux to our ultra-violet (UV) camera measurements of SO2 flux at Stromboli (i.e. UV measurement of gas flux is performed at least ≈ 50 m above point of slug rupture at the magma surface). The UV camera measurements identify a broad range of degassing patterns following bursts, typifying the dynamic nature and the complexities of the system at Stromboli, including a previously identified coda in gas flux spanning tens of seconds to minutes (e.g. Tamburello et al. 2012). Whilst our models only analyse a narrow range of events at Stromboli, they highlight the possibility that the production of daughter bubbles could contribute to the gas flux observed at Stromboli. In some instances, the gas flux created by bursting daughter bubbles following a burst event is of a similar time span and could explain the observed gas flux coda. It is also possible that well documented puffing events could be explained by the bursting of daughter bubbles. Indeed, the larger modelled daughter bubbles, which are apparent as well-defined peaks in gas flux within both the UV camera record

  4. Signal-to-noise issues in measuring nitrous oxide fluxes by the eddy covariance method

    NASA Astrophysics Data System (ADS)

    Cowan, Nicholas; Levy, Peter; Langford, Ben; Skiba, Ute

    2016-04-01

    Recently-developed fast-response gas analysers capable of measuring atmospheric N2O with high precision (< 50 ppt) at a rate of 10 Hz are becoming more widely available. These instruments are capable of measuring N2O fluxes using the eddy covariance method, with significantly less effort and uncertainty than previous instruments have allowed. However, there are still many issues to overcome in order to obtain accurate and reliable flux data. The signal-to-noise ratio of N2O measured using these instruments is still two to three orders of magnitude smaller than that of CO2. The low signal-to-noise ratio can lead to systematic uncertainties, in the eddy covariance method, the most significant being in the calculation of the time lag between gas analyser and anemometer by maximisation of covariance (Langford et al., 2015). When signal-to-noise ratio is relatively low, as it is with many N2O measurements, the maximisation of covariance method can systematically overestimate fluxes. However, if constant time lags are assumed, then fluxes will be underestimated. This presents a major issue for N2O eddy covariance measurements. In this presentation we will focus on the signal to noise ratio for an Aerodyne quantum cascade laser (QCL). Eddy covariance flux measurements from multiple agricultural sites across the UK were investigated for potential uncertainties. Our presentation highlights some of these uncertainties when analysing eddy covariance data and offers suggestions as to how these issues may be minimised. Langford, B., Acton, W., Ammann, C., Valach, A. and Nemitz, E.: Eddy-covariance data with low signal-to-noise ratio: time-lag determination, uncertainties and limit of detection, Atmos Meas Tech, 8(10), 4197-4213, doi:10.5194/amt-8-4197-2015, 2015.

  5. 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

  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. 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, Győző; 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.

  8. Measurements of Mass, Momentum and Energy fluxes over an ice/snow covered lake

    NASA Astrophysics Data System (ADS)

    Salgado, Rui; Potes, Miguel; Mammarella, Ivan; Provenzale, Maria

    2016-04-01

    A better understanding of the interactions between ice and snow and the atmosphere requires improved measurements of energy, mass and momentum fluxes, which continue to have a high degree of uncertainty. In this communication, observed near surface fluxes of momentum, heat and mass (H2O and CO2) over a boreal lake during a freezing period (winter 2015/2016) will be analysed and compared with observations over ice free lakes. Continuously measurements of near surface fluxes of momentum, heat and mass (H2O and CO2) are obtained with a new eddy covariance (EC) system, the Campbell Scientific's IRGASON Integrated Open-Path CO2/H2O Gas Analyzer and 3D Sonic Anemometer, over lake Vanajavesi in Finland. The measurement site is located in a tip of narrow peninsula on the lake (61.133935° N ; 24.259119° E), offering very good conditions for eddy covariance flux measurements. The EC system was installed at 2.5m height above the lake surface and was oriented against the prevailing wind direction in the site.

  9. 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...

  10. 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...

  11. Estimation of water flux in urban area using eddy covariance measurements in Riverside, Southern California

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Micrometeorological methods can direct measure the sensible and latent heat flux in specific sites and provide robust estimates of the evaporative fraction (EF), which is the fraction of available surface energy contained in latent heat. Across a vegetation coverage gradient in urban area, an empir...

  12. 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...

  13. 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...

  14. 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

  15. 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...

  16. 3D density imaging with muons flux measurements from underground galleries

    NASA Astrophysics Data System (ADS)

    Lesparre, Nolwenn; Cabrera, Justo; Marteau, Jacques

    2016-04-01

    Atmospheric muons flux measurements provide information on sub-surface density distribution, giving insights on the medium structure. We measured the muons flux from the underground galleries of the Tournemire experimental platform to image the medium between the galleries and the surface. The experiment aimed at evaluating the capacity of the method to detect the presence of discontinuities produced either by secondary strike-slip faults that present small vertical displacements or by a karstic network may be present at the level of an upper aquifer. Measurements were performed from three different sites so the trajectories of detected muons paths intersect in the medium. Such a configuration provided complementary information on the density distribution, offering the possibility to seek density variations at different depths. A specific calibration method was applied in order to interpolate the data acquired at different times with the same muons sensor. Muons flux measurements variations were then processed through a non-linear inversion, producing a 3D image of the density together with an evaluation of the different distinguished targets reliability. The density distribution showed the presence of a very low density region at the level of the upper aquifer, suggesting the presence of a karstic network hosting locally cavities. The trace of secondary strike-slip faults did not appear clearly on the image as the density contrast they produce might be too low compared to the signal to noise ratio present in the muons flux data. We propose different strategies to improve the density image accuracy.

  17. 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%).

  18. Biogenic volatile organic compound emissions during BEARPEX 2009 measured by eddy covariance and flux-gradient similarity methods

    NASA Astrophysics Data System (ADS)

    Park, J.-H.; Fares, S.; Weber, R.; Goldstein, A. H.

    2012-09-01

    The Biosphere Effects on AeRosols and Photochemistry EXperiment (BEARPEX) took place in Blodgett Forest, a Ponderosa pine forest in the Sierra Nevada Mountains of California, during summer 2009. We deployed a Proton Transfer Reaction - Mass Spectrometer (PTR-MS) to measure fluxes and concentrations of biogenic volatile organic compounds (BVOCs). Eighteen ion species including the major BVOC expected at the site were measured sequentially at 5 heights to observe their vertical gradient from the forest floor to above the canopy. Fluxes of the 3 dominant BVOCs methanol, 2-Methyl-3-butene-2-ol (MBO), and monoterpenes, were measured above the canopy by the eddy covariance method. Canopy scale fluxes were also determined by the flux-gradient similarity method (K-theory). A universal K (Kuniv) was determined as the mean of individual K's calculated from the measured fluxes divided by vertical gradients for methanol, MBO, and monoterpenes. This Kuniv was then multiplied by the gradients of each observed ion species to compute their fluxes. The flux-gradient similarity method showed very good agreement with the Eddy Covariance method. Fluxes are presented for all measured species and compared to historical measurements from the same site, and used to test emission algorithms used to model fluxes at the regional scale. MBO was the dominant emission observed followed by methanol, monoterpenes, acetone, and acetaldehyde. The flux-gradient similarity method is shown to be a useful, and we recommend its use especially in experimental conditions when fast measurement of BVOC species is not available.

  19. 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

  20. Multiple-capillary measurement of RBC speed, flux, and density with optical coherence tomography

    PubMed Central

    Lee, Jonghwan; Wu, Weicheng; Lesage, Frederic; Boas, David A

    2013-01-01

    As capillaries exhibit heterogeneous and fluctuating dynamics even during baseline, a technique measuring red blood cell (RBC) speed and flux over many capillaries at the same time is needed. Here, we report that optical coherence tomography can capture individual RBC passage simultaneously over many capillaries located at different depths. Further, we demonstrate the ability to quantify RBC speed, flux, and linear density. This technique will provide a means to monitor microvascular flow dynamics over many capillaries at different depths at the same time. PMID:24022621

  1. Rapid measurement of charged particle beam profiles using a current flux grating

    SciTech Connect

    Paul, Samit; Chowdhury, Abhishek; Bhattacharjee, Sudeep

    2015-02-15

    The principle and physics issues of charged particle beam diagnostics using a current flux grating are presented. Unidirectional array of conducting channels with interstitial insulating layers of spacing d is placed in the beam path to capture flux of charge and electronically reproduce an exact beam current profile with density variation. The role of secondary electrons due to the impinging particle beam (both electron and ion) on the probe is addressed and a correction factor is introduced. A 2-dimensional profile of the electron beam is obtained by rotating the probe about the beam axis. Finally, a comparison of measured beam profile with a Gaussian is presented.

  2. Long-term CH3Br and CH3Cl flux measurements in temperate salt marshes

    NASA Astrophysics Data System (ADS)

    Blei, E.; Heal, M. R.; Heal, K. V.

    2010-11-01

    Fluxes of CH3Br and CH3Cl and their relationship with potential drivers such as sunlight, temperature and soil moisture, were monitored at fortnightly to monthly intervals for more than two years at two contrasting temperate salt marsh sites in Scotland. Manipulation experiments were conducted to further investigate possible links between drivers and fluxes. Fluxes followed both seasonal and diurnal trends with highest fluxes during summer days and lowest (negative) fluxes during winter nights. Mean (± 1 sd) annually and diurnally-weighted net emissions from the two sites were found to be 300 ± 44 ng m-2 h-1 for CH3Br and 662 ± 266 ng m-2 h-1 for CH3Cl. The fluxes from this work are similar to findings from this and other research groups for salt marshes in cooler, higher latitude climates, but lower than values from salt marshes in the Mediterranean climate of southern California. Statistical analysis generally did not demonstrate a strong link between temperature or sunlight levels and methyl halide fluxes, although it is likely that temperatures have a weak direct influence on emissions, and both certainly have indirect influence via the annual and daily cycles of the vegetation. CH3Cl flux magnitudes from different measurement locations depended on the plant species enclosed whereas such dependency was not discernible for CH3Br fluxes. In 14 out of 18 collars with vegetation CH3Br and CH3Cl net fluxes were significantly positively correlated. The CH3Cl/CH3Br net-emission mass ratio was 2.2, a magnitude lower than mass ratios of global methyl halide budgets (~22) or emissions from tropical rainforests (~60). This is likely due to preference for CH3Br production by the relatively high bromine content in the salt marsh plant material. Extrapolation based solely on data from this study yields salt marsh contributions of 0.5-3.2% and 0.05-0.33%, respectively, of currently-estimated total global production of CH3Br and CH3Cl, but actual global contributions likely

  3. Measurement of the total boron-8 solar neutrino flux at the Sudbury Neutrino Observatory

    NASA Astrophysics Data System (ADS)

    Rusu, Vadim Liviu

    This work presents experimental measurements obtained by analyzing the first 254 live days of data from the SNO NaCl run. The electron neutrino flux was measured to be 1.66 +/- 0.10 stat.+0.07 -0.07 (syst.) x 106cm-2s-l and the non-electron neutrino flux was measured to be 3.32 +/- 0.38 stat.+0.26 -0.25 (syst.) x 106cm-2s-1. Using the above results we determined the integrated electron neutrino survival probability to be 0.33 +/- 0.04 stat.+0.02 -0.02 (syst.). This rejects maximum mixing in the solar neutrino sector at more than 3sigma using SNO data only under the assumption that the flavor changing mechanism is due to the MSW effect in the solar interior. The capability of the Sudbury Neutrino Observatory (SNO) to distinguish between the Charged-Current (CC) and Neutral-Current(NC) neutrino interactions made possible the first simultaneous measurements of the electron and non-electron solar neutrino flux, providing a direct test of the hypothesis that neutrinos change flavor as they propagate from the Sun to the Earth. Two tonnes of purified NaCl were added to the one kilotonne of heavy water target of SNO to enhance the neutron capture efficiency and detection of capture gamma-rays. Neutron capture on 35Cl often produces multiple gamma-rays, which permits a statistical separation of neutron capture and electron events based on the event isotropy, the increased statistical separation between event categories, using the degree of event isotropy, made possible a significant improvement on the measured fluxes. Moreover, the flux analysis does not require any assumption regarding the energy dependence of the flavor changing mechanism.

  4. Thermal parameters determination of battery cells by local heat flux measurements

    NASA Astrophysics Data System (ADS)

    Murashko, K. A.; Mityakov, A. V.; Pyrhönen, J.; Mityakov, V. Y.; Sapozhnikov, S. S.

    2014-12-01

    A new approach to define of the thermal parameters, such as heat capacity and through-plane thermal conductivity, of pouch-type cells is introduced. Application of local heat flux measurement with a gradient heat flux sensor (GHFS) allows determination of the cell thermal parameters in different surface points of the cell. The suggested method is not cell destructive as it does not require deep discharge of the cell or application of any charge/discharge cycles during the measurements of the thermal parameters of the cell. The complete procedure is demonstrated on a high-power lithium-ion (Li-ion) pouch cell, and it is verified on a sample with well-known thermal parameters. A comparison of the experimental results with conventional thermal characterization methods shows an acceptably low error. The dependence of the cell thermal parameters on the state of charge (SoC) and measurement points on the surface was studied by the proposed measurement approach.

  5. Precise measurement of cosmic ray fluxes with the AMS-02 experiment

    NASA Astrophysics Data System (ADS)

    Vecchi, Manuela

    2015-12-01

    The AMS-02 detector is a large acceptance magnetic spectrometer operating onboard the International Space Station since May 2011. The main goals of the detector are the search for antimatter and dark matter in space, as well as the measurement of cosmic ray composition and flux. In this document we present precise measurements of cosmic ray positrons, electrons and protons, collected during the first 30 months of operations.

  6. Measurements of x-ray spectral flux and intensity distribution of APS/CHESS undulator radiation

    SciTech Connect

    Ilinski, P.; Yun, W.; Lai, B.; Gluskin, E.; Cai, Z.

    1994-09-01

    Absolute radiation flux and polarization measurements of the APS undulators may have to be made under high thermal loading conditions. A method that may circumvent the high-heat-load problem was tested during a recent APS/CHESS undulator run. The technique makes use of a Si(Li) energy-dispersive detector to measure 5--35 keV x-rays scattered from a well-defined He gas volume at controlled pressure.

  7. Measurements of x-ray spectral flux of high brightness undulators by gas scattering

    SciTech Connect

    Ilinski, P.; Yun, W.; Lai, B.; Gluskin, E.; Cai, Z. )

    1995-02-01

    Absolute radiation flux and polarization measurements of the Advanced Photon Source (APS) undulators may have to be made under high thermal loading conditions. A method that may circumvent the high-heat-load problem was tested during a recent APS/CHESS undulator run. The technique makes use of a Si(Li) energy-dispersive detector to measure 5--35 keV x rays scattered from a well-defined He gas volume at controlled pressure.

  8. Precise measurement of cosmic ray fluxes with the AMS-02 experiment

    SciTech Connect

    Vecchi, Manuela

    2015-12-17

    The AMS-02 detector is a large acceptance magnetic spectrometer operating onboard the International Space Station since May 2011. The main goals of the detector are the search for antimatter and dark matter in space, as well as the measurement of cosmic ray composition and flux. In this document we present precise measurements of cosmic ray positrons, electrons and protons, collected during the first 30 months of operations.

  9. Molecular flux measurements in the back flow region of a nozzle plume

    NASA Technical Reports Server (NTRS)

    Chirivella, J. E.

    1973-01-01

    A series of tests were conducted to measure the mass flux in the far field of a nozzle plume in a high vacuum with emphasis on the back flow region. The measurements presented provided fairly accurate data for off-axis angles as large as 140 deg (i.e., in the back flow region). This region, since it is well behind the exit plane, is of paticular interest to those concerned with instrument contamination. Usually sensitive spacecraft surfaces are located in the region affected by the back flow. Parameters such as expansion ratio, throat diameter, nozzle lip shape, and plenum (chamber) pressure were varied, carbon dioxide and nitrogen gases were flowed and mass flux measurements were taken using quartz crystal microbalances in as many as nine different locations relative to the tests nozzle. Several conclusions with respect to the effect of nozzle and gas parameters on the amount of back flow mass flux are offered, and it was demonstrated that gaseous mass fluxes, which are not predictable by present theories, are encountered in the region behind the nozzle exit plane. This knowledge is significant if materials incompatible with the gaseous exhaust products are used in this region.

  10. 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

  11. Fluxes of polychlorinated biphenyls volatilizing from the Hudson River, New York measured using micrometeorological approaches.

    PubMed

    Sandy, Andy L; Guo, Jia; Miskewitz, Robert J; McGillis, Wade R; Rodenburg, Lisa A

    2012-01-17

    This study represents the first time that a micrometeorological technique, using turbulent transport measurements, has been used to determine the direction and magnitude of air-water exchange of polychlorinated biphenyls (PCBs). The study was conducted during July 2008 on the Hudson River estuary near the Tappan Zee Bridge, which is the site of some of the most serious PCB contamination in the world. Gas-phase ΣPCB concentrations measured at two heights above the water column averaged 1.1 ng m(-3), and concentrations were usually lower in the upper air sample, indicating net transport of PCBs from the water column to the air. Volatilization PCB fluxes were calculated using the modified Thornthwaite-Holzman equation. Values of friction velocity and atmospheric stability were calculated using the Aerodynamic Gradient and Eddy Correlation techniques. The PCB fluxes were corrected for changes in atmospheric stability using the atmospheric stability factor of water vapor (ϕ(w)) calculated from empirical formulations which ranged from 1.0 to 3.2 (neutral to stable atmospheric boundary layer conditions). Vertical ΣPCB fluxes ranged from +0.5 μg m(-2) d (-1) to +13 μg m(-2) d (-1). Mono- through tri-homologues accounted for about half of ΣPCB fluxes, with tetra- through hexa-homologue accounting for the other half. This work demonstrates the utility of a micrometeorological approach to measuring the air-water exchange of organic contaminants. PMID:22191600

  12. 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.

  13. 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

  14. Technical Note: Semi-rigid chambers for methane gas flux measurements on tree stems

    NASA Astrophysics Data System (ADS)

    Siegenthaler, Andy; Welch, Bertie; Pangala, Sunitha R.; Peacock, Michael; Gauci, Vincent

    2016-02-01

    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 and test new semi-rigid stem-flux chambers (or sleeves). We compared the CH4 permeability of the new semi-rigid chambers with that of 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 had reduced gas permeability and optimal stem gas exchange surface to total chamber volume ratio (Sc / Vtot) 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 is complicated.

  15. Measurements of absorbed heat flux and water-side heat transfer coefficient in water wall tubes

    NASA Astrophysics Data System (ADS)

    Taler, Jan; Taler, Dawid; Kowal, Andrzej

    2011-04-01

    The tubular type instrument (flux tube) was developed to identify boundary conditions in water wall tubes of steam boilers. The meter is constructed from a short length of eccentric tube containing four thermocouples on the fire side below the inner and outer surfaces of the tube. The fifth thermocouple is located at the rear of the tube on the casing side of the water-wall tube. The boundary conditions on the outer and inner surfaces of the water flux-tube are determined based on temperature measurements at the interior locations. Four K-type sheathed thermocouples of 1 mm in diameter, are inserted into holes, which are parallel to the tube axis. The non-linear least squares problem is solved numerically using the Levenberg-Marquardt method. The heat transfer conditions in adjacent boiler tubes have no impact on the temperature distribution in the flux tubes.

  16. A review of micrometeoroid flux measurements and models for low orbital altitudes of the Space Station

    NASA Technical Reports Server (NTRS)

    Susko, M.

    1984-01-01

    A review of meteoroid flux measurements and models for low orbital altitudes of the Space Station has been made in order to provide information that may be useful in design studies and laboratory hypervelocity impact tests which simulate micrometeoroids in space for design of the main wall of the Space Station. This report deals with the meteoroid flux mass model, the defocusing and shielding factors that affect the model, the probability of meteoroid penetration of the main wall of a Space Station. Whipple (1947) suggested a meteoroid bumper, a thin shield around the spacecraft at some distance from the wall, as an effective device for reducing penetration, which has been discussed in this report. The equations of the probability of meteoroid penetration, the average annual cumulative total flux, and the equations for the thickness of the main wall and the bumper are presented in this report.

  17. 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.

  18. Investigation of SOL parameters and divertor particle flux from electric probe measurements in KSTAR

    NASA Astrophysics Data System (ADS)

    Bak, J. G.; Kim, H. S.; Bae, M. K.; Juhn, J. W.; Seo, D. C.; Bang, E. N.; Shim, S. B.; Chung, K. S.; Lee, H. J.; Hong, S. H.

    2015-08-01

    The upstream scrape-off layer (SOL) profiles and downstream particle fluxes are measured with a fast reciprocating Langmuir probe assembly (FRLPA) at the outboard mid-plane and a fixed edge Langmuir probe array (ELPA) at divertor region, respectively in the KSTAR. It is found that the SOL has a two-layer structure in the outboard wall-limited (OWL) ohmic and L-mode: a near SOL (∼5 mm zone) with a narrow feature and a far SOL with a broader profile. The near SOL width evaluated from the SOL profiles in the OWL plasmas is comparable to the scaling for the L-mode divertor plasmas in the JET and AUG. In the SOL profiles and the divertor particle flux profile during the ELMy H-modes, the characteristic e-folding lengths of electron temperature, plasma density and particle flux during an ELM phase are about two times larger than ones at the inter ELM.

  19. Shortwave Radiative Fluxes, Solar-Beam Transmissions, and Aerosol Properties: TARFOX and ACE-2 Find More Absorption from Flux Radiometry than from Other Measurements

    NASA Technical Reports Server (NTRS)

    Russell, Philip B.; Redemann, J.; Schmid, B.; Livingston, J. M.; Bergstrom, R. W.; Ramirez, S. A.; Hipskind, R. Stephen (Technical Monitor)

    2001-01-01

    The Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX) and the Second Aerosol Characterization Experiment (ACE-2) made simultaneous measurements of shortwave radiative fluxes, solar-beam transmissions, and the aerosols affecting those fluxes and transmissions. Besides the measured fluxes and transmissions, other obtained properties include aerosol scattering and absorption measured in situ at the surface and aloft; aerosol single scattering albedo retrieved from skylight radiances; and aerosol complex refractive index derived by combining profiles of backscatter, extinction, and size distribution. These measurements of North Atlantic boundary layer aerosols impacted by anthropogenic pollution revealed the following characteristic results: (1) Better agreement among different types of remote measurements of aerosols (e.g., optical depth, extinction, and backscattering from sunphotometers, satellites, and lidars) than between remote and in situ measurements; 2) More extinction derived from transmission measurements than from in situ measurements; (3) Larger aerosol absorption inferred from flux radiometry than from other measurements. When the measured relationships between downwelling flux and optical depth (or beam transmission) are used to derive best-fit single scattering albedos for the polluted boundary layer aerosol, both TARFOX and ACE-2 yield midvisible values of 0.90 +/- 0.04. The other techniques give larger single scattering albedos (i.e. less absorption) for the polluted boundary layer, with a typical result of 0.95 +/- 0.04. Although the flux-based results have the virtue of describing the column aerosol unperturbed by sampling, they are subject to questions about representativeness and other uncertainties (e.g., unknown gas absorption). Current uncertainties in aerosol single scattering albedo are large in terms of climate effects. They also have an important influence on aerosol optical depths retrieved from satellite radiances

  20. Measuring the Daemon-Flux Seasonal Maxima at the Baksan Neutrino Observatory

    NASA Astrophysics Data System (ADS)

    Drobyshevski, E. M.; Drobyshevski, M. E.

    2007-08-01

    Detection of negative daemons (Dark Electric Matter Objects - presumably the multiply electrically charged Planckian objects) in low-background conditions in September 2005 and March 2006 has provided supportive evidence for the expected to occur at that times maxima in the flux of daemons with V ≈ 10-15 km/s. These objects hit the Earth from the near-Earth, almost circular heliocentric orbits (NEACHOs). The ability of some FEU-167-1 PM tubes with a thicker inner Al coating to detect directly (without a scintillator) daemon passage through them has also been employed, an effect increasing ~ 100-fold the detector efficiency. As a result, the daemon flux recorded at the maxima was increased from ~10-9 to 10-7 cm-2s-1. At the maxima, two phases in the observed flux can be discriminated. The first of them is associated with objects moving in outer NEACHOs, which catch up with the Earth and cross it. The intensity and direction of the flux during this phase which lasts about two weeks depend on the time of day and latitude of observations (therefore, synchronous measurements in the northern and southern Earth's hemispheres are desirable). In the second phase, where the flux consists primarily of few objects transferred into geocentric, Earth-surface-crossing orbits during the first phase, the daytime and latitude dependence becomes less pronounced. All the experimental results thus obtained either support the conclusions following from the daemon paradigm or find a simple interpretation within it.

  1. 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.

  2. Measuring eddy heat, constituent, and momentum fluxes with high-resolution Na and Fe Doppler lidars

    NASA Astrophysics Data System (ADS)

    Gardner, Chester S.; Liu, Alan Z.

    2014-09-01

    Vertical transport by turbulent mixing plays a fundamental role in establishing the thermal and constituent structure of the upper mesosphere and lower thermosphere (MLT). Because of observational challenges, eddy heat, constituent, and momentum fluxes, and the associated coefficients for thermal (kH), constituent (kzz), and momentum (kM), diffusion have not been well characterized in the MLT. We show that properly configured Na and Fe Doppler lidars, with sufficient resolution to observe the turbulence-induced wind, temperature, and density fluctuations, can make direct measurements of eddy fluxes throughout the mesopause region. When the horizontal (zθL with z = altitude and θL = full width at half maximum laser divergence), vertical (Δz), and temporal (Δt) resolutions of the lidar satisfy the condition LC≃ (3zθL) 2+ (0.6u>¯Δt) 2+ (1.5Δz) 2 ≤ 270 m (125 m), where u>¯ is the mean horizontal wind velocity, the observations include more than 80% (90%) of the energy in the turbulence fluctuations, and the observed fluxes and derived diffusivities will be highly representative of the actual values. For existing Na and Fe Doppler lidars, which have modest power-aperture products of about 1 W m2, long averaging times (5-20 h) are required to obtain statistically significant estimates of the eddy fluxes, kzz, kH, and kM profiles, and the turbulent Prandtl number (Pr = kM/kH) between about 85 and 100 km. These systems are capable of measuring the weekly or monthly mean flux and diffusivity profiles. Systems with power-aperture products of 5-100 W m2 or larger could be used to study the eddy fluxes generated by the dissipation and breaking of individual gravity waves to altitudes as high as the turbopause (~110 km).

  3. Direct ion flux measurements at high-pressure-depletion conditions for microcrystalline silicon deposition

    SciTech Connect

    Bronneberg, A. C.; Kang, X.; Palmans, J.; Janssen, P. H. J.; Lorne, T.; Creatore, M.; Sanden, M. C. M. van de

    2013-08-14

    The contribution of ions to the growth of microcrystalline silicon thin films has been investigated in the well-known high-pressure-depletion (HPD) regime by coupling thin-film analysis with plasma studies. The ion flux, measured by means of a capacitive probe, has been studied in two regimes, i.e., the amorphous-to-microcrystalline transition regime and a low-to-high power regime; the latter regime had been investigated to evaluate the impact of the plasma power on the ion flux in collisional plasmas. The ion flux was found not to change considerably under the conditions where the deposited material undergoes a transition from the amorphous to the microcrystalline silicon phase; for solar-grade material, an ion-to-Si deposition flux of ∼0.30 has been determined. As an upper-estimation of the ion energy, a mean ion energy of ∼19 eV has been measured under low-pressure conditions (<1 mbar) by means of a retarding field energy analyzer. Combining this upper-estimate with an ion per deposited Si atom ratio of ∼0.30, it is concluded that less than 6 eV is available per deposited Si atom. The addition of a small amount of SiH{sub 4} to an H{sub 2} plasma resulted in an increase of the ion flux by about 30% for higher power values, whereas the electron density, deduced from optical emission spectroscopy analysis, decreased. The electron temperature, also deduced from optical emission spectroscopy analysis, reveals a slight decrease with power. Although the dominant ion in the HPD regime is SiH{sub 3}{sup +}, i.e., a change from H{sub 3}{sup +} in pure hydrogen HPD conditions, the measured larger ion loss can be explained by assuming steeper electron density profiles. These results, therefore, confirm the results reported so far: the ion-to-Si deposition flux is relatively large but has neither influence on the microcrystalline silicon film properties nor on the phase transition. Possible explanations are the reported high atomic hydrogen to deposition flux ratio

  4. 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

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

    NASA Astrophysics Data System (ADS)

    Laubach, Johannes; Barthel, Matti; Fraser, Anitra; Hunt, John E.; Griffith, David W. T.

    2016-03-01

    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 (FTIR) spectrometer, which measured 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 56 % of days at one site and 73 % at the other. Both methods indicated both sites as net sources of CH4 and N2O. Mean emission rates for 1 year at the unfertilised, winter-grazed site were 8.9 (±0.79) nmol CH4 m-2 s-1 and 0.38 (±0.018) nmol N2O m-2 s-1. During the same year, mean emission rates at the irrigated, fertilised and rotationally grazed site were 8.9 (±0.79) nmol CH4 m-2 s-1 and 0.58 (±0.020) nmol N2O m-2 s-1. At this site, the N2O emissions amounted to 1.21 (±0.15) % of the nitrogen

  6. 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

  7. Airborne boundary layer flux measurements of trace species over Canadian boreal forest and northern wetland regions

    NASA Technical Reports Server (NTRS)

    Ritter, John A.; Barrick, John D. W.; Watson, Catherine E.; Sachse, Glen W.; Gregory, Gerald L.; Anderson, Bruce E.; Woerner, Mary A.; Collins, James E., Jr.

    1994-01-01

    Airborne heat, moisture, O3, CO, and CH4 flux measurements were obtained over the Hudson Bay lowlands (HBL) and northern boreal forest regions of Canada during July - August 1990. The airborne flux measurements were an integral part of the NASA/Arctic Boundary Layer Expedition (ABLE) 3B field experiment executed in collaboration with the Canadian Northern Wetlands Study (NOWES). Airborne CH4 flux measurements were taken over a large portion of the HBL. The surface level flux of CH4 was obtained from downward extrapolations of multiple-level CH4 flux measurements. Methane source strengths ranged from -1 to 31 mg m(exp -2)/d, with the higher values occurring in relatively small, isolated areas. Similar measurements of the CH4 source strength in the boreal forest region of Schefferville, Quebec, ranged from 6 to 27 mg m(exp -2)/d and exhibited a diurnal dependence. The CH4 source strengths found during the ABLE 3B expedition were much lower than the seasonally averaged source strength of 51 mg m(exp -2)/d found for the Yukon-Kuskokwim delta region of Alaska during the previous ABLE 3A study. Large positive CO fluxes (0.31 to 0.53 parts per billion by volume (ppbv) m/s) were observed over the inland, forested regions of the HBL study area, although the mechanism for the generation of these fluxes was not identified. Repetitive measurements along the same ground track at various times of day near the Schefferville site also suggested a diurnal dependence for CO emissions. Measurements of surface resistance to the uptake of O3 (1.91 to 0.80 s/cm) for the HBL areas investigated were comparable to those observed near the Schefferville site (3.40 to 1.10 s/cm). Surface resistance values for the ABLE 3B study area were somewhat less than those observed over the Yukon-Kuskokwim delta during the previous ABLE 3A study. The budgets for heat, moisture, O3, CO, and CH4 were evaluated. The residuals from these budget studies indicated, for the cases selected, a moderate net

  8. How capping protein enhances actin filament growth and nucleation on biomimetic beads

    NASA Astrophysics Data System (ADS)

    Wang, Ruizhe; Carlsson, Anders E.

    2015-12-01

    Capping protein (CP), which caps the growing ends of actin filaments, accelerates actin-based motility. Recent experiments on biomimetic beads have shown that CP also enhances the rate of actin filament nucleation. Proposed explanations for these phenomena include (i) the actin funneling hypothesis (AFH), in which the presence of CP increases the free-actin concentration, and (ii) the monomer gating model, in which CP binding to actin filament barbed ends makes more monomers available for filament nucleation. To establish how CP increases the rates of filament elongation and nucleation on biomimetic beads, we perform a quantitative modeling analysis of actin polymerization, using rate equations that include actin filament nucleation, polymerization and capping, as modified by monomer depletion near the surface of the bead. With one adjustable parameter, our simulation results match previously measured time courses of polymerized actin and filament number. The results support a version of the AFH where CP increases the local actin monomer concentration at the bead surface, but leaves the global free-actin concentration nearly constant. Because the rate of filament nucleation increases with the monomer concentration, the increased local monomer concentration enhances actin filament nucleation. We derive a closed-form formula for the characteristic CP concentration where the local free-actin concentration reaches half the bulk value, and find it to be comparable to the global Arp2/3 complex concentration. We also propose an experimental protocol for distinguishing branching nucleation of filaments from spontaneous nucleation.

  9. The Annual Cycle of Arctic Ice and Ocean Heat and Freshwater Fluxes, Measured and Modelled

    NASA Astrophysics Data System (ADS)

    Bacon, S.; Aksenov, Y.; Tsubouchi, T.

    2014-12-01

    Paucity of measurements means that quantifying and evaluating the Arctic thermal and hydrological cycles is problematic. For example: atmospheric reanalyses are not well constrained by observations; for river runoff measurements, there are un-gauged flows to consider; and until the relatively recent advent of autonomous measurement systems, ocean measurements outside the summer melt season were rare. We have assembled a complete and continuous Arctic Ocean boundary measurement array from moored installations in four ocean gateways: Fram, Davis and Bering Straits, and the Barents Sea Opening. Occasionally "patching" with coupled ice-ocean general circulation model (GCM) output is required; if so, the output water properties are validated and calibrated against climatology. This approach enables application of inverse modeling methods through the use of conservation constraints, and consequent generation of a set of 12 monthly-mean ocean (including sea ice) fluxes of freshwater and heat spanning a full calendar year. We will present results from a single annual cycle (2005-6). We have also transferred the design of the Arctic Ocean Boundary Array to the GCM environment, where we have calculated the mean annual cycles (from ca. 30-year model runs) both of net surface fluxes (atmosphere-ocean and land-ocean, including sea ice) and equivalent ice and ocean boundary fluxes of freshwater and heat, at two model resolutions (1/4 degree and 1/12 degree global mean) and for two different surface forcing data sets. We will show the resulting comparisons of the mean annual cycles of measured and modeled Arctic freshwater and heat fluxes, and also show the modeled mean annual cycle of heat and freshwater storage. We believe that the integral boundary array formed by sustained measurements in the four named ocean gateways should be a cornerstone of any Arctic environmental monitoring system.

  10. Calcium-actin waves and oscillations of cellular membranes.

    PubMed

    Veksler, Alex; Gov, Nir S

    2009-09-16

    We propose a mechanism for the formation of membrane oscillations and traveling waves, which arise due to the coupling between the actin cytoskeleton and the calcium flux through the membrane. In our model, the fluid cell membrane has a mobile but constant population of proteins with a convex spontaneous curvature, which act as nucleators of actin polymerization and adhesion. Such a continuum model couples the forces of cell-substrate adhesion, actin polymerization, membrane curvature, and the flux of calcium through the membrane. Linear stability analysis shows that sufficiently strong coupling among the calcium, membrane, and protein dynamics may induce robust traveling waves on the membrane. This result was checked for a reduced feedback scheme and is compared to the results without the effects of calcium, where permanent phase separation without waves or oscillations is obtained. The model results are compared to the published observations of calcium waves in cell membranes, and a number of testable predictions are proposed. PMID:19751660

  11. Characterization of actin filament deformation in response to actively driven microspheres propagated through entangled actin networks

    NASA Astrophysics Data System (ADS)

    Falzone, Tobias; Blair, Savanna; Robertson-Anderson, Rae

    2014-03-01

    The semi-flexible biopolymer actin is a ubiquitous component of nearly all biological organisms, playing an important role in many biological processes such as cell structure and motility, cancer invasion and metastasis, muscle contraction, and cell signaling. Concentrated actin networks possess unique viscoelastic properties that have been the subject of much theoretical and experimental work. However, much is still unknown regarding the correlation of the applied stress on the network to the induced filament strain at the molecular level. Here, we use dual optical traps alongside fluorescence microscopy to carry out active microrheology measurements that link mechanical stress to structural response at the micron scale. Specifically, we actively drive microspheres through entangled actin networks while simultaneously measuring the force the surrounding filaments exert on the sphere and visualizing the deformation and subsequent relaxation of fluorescent labeled filaments within the network. These measurements, which provide much needed insight into the link between stress and strain in actin networks, are critical for clarifying our theoretical understanding of the complex viscoelastic behavior exhibited in actin networks.

  12. 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 flux measurement? Direct flux measurements of CH4 were carried out between February and May, 2012 over a relatively densely populated, urban surface in Vancouver, Canada by means of eddy covariance (EC). The EC-system consisted of an ultrasonic anemometer (CSAT-3, Campbell Scientific Inc.) and two open-path infrared gas analyzers (Li7500 and Li7700, Licor Inc.) on a tower at 30m above the surface. The source area of the EC system is characterised by a relative homogeneous morphometry (5.3m average building height), but spatially and temporally varying emission sources, including two major intersecting arterial roads (70.000 cars drive through the 50% source area per day) and seasonal heating in predominantly single-family houses (natural gas). An inverse dispersion model (turbulent source area model), validated against large eddy simulations (LES) of the urban roughness sublayer, allows the determination of the spatial area that

  13. Initiation of methane turbulent flux measurements over a grazed grassland in Belgium

    NASA Astrophysics Data System (ADS)

    Dumortier, Pierre; Aubinet, Marc; Chopin, Henri; Debacq, Alain; Jérome, Elisabeth; Beckers, Yves; Heinesch, Bernard

    2013-04-01

    Methane fluxes emitted by a grazed meadow were measured continuously during the 2012 grazing season at the Dorinne Terrestrial Observatory (50° 18' 44" N; 4° 58' 07" E; 248 m asl.) in Belgium. Measurements were made with the eddy covariance technique, using a fast CH4 analyzer (Picarro G2311-f). Carbon dioxide fluxes (LI-7000) and various micro-meteorological and soil variables, biomass growth and stocking rate evolution were also measured at the site. The site is an intensively pastured meadow of 4.2 ha managed according to the regional usual practices where up to 30 cows are grazing simultaneously. N2O emissions are currently measured through dynamic closed chambers (Beekkerk van Ruth et al., Geophysical Research Abstracts. Vol. 15, EGU2013-3211, 2013) and the carbon budget of the site has already been investigated (Jerome et al. Geophysical Research Abstracts, Vol. 15, EGU2013-6989, 2013). As no CH4 measurements were available, CH4 fluxes were estimated on the basis of dry matter intake by the cows and a conversion factor obtained from a literature review. We want to improve this estimation by measuring CH4 fluxes, identifying their main environmental drivers and understanding diurnal and annual exchange patterns. Methane emissions were found strongly related with cattle stocking rate with a slope of 7.34±0.78 mol CH4 day-1 LSU-1. Up to now, no methane absorption has been observed, the meadow behaving as a methane emitter, even in the absence of cows. In the absence of cows, no significant relation can be established up to now between methane emissions and environmental parameters. No clear diurnal evolution is observed, neither during grazing periods nor during cow free periods. During cow presence periods, fluxes are highly variable, probably due to cow movements in and out the measurement footprint and cow digestion rhythm. Further developments are ongoing in order to improve cattle geo-localization through individual home-made GPS devices and infra

  14. 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.

  15. Experimental neutron flux measurements with a diamond detector at the QUINTA setup

    NASA Astrophysics Data System (ADS)

    Berlev, A. I.; Rodionov, N. B.; Tyutyunnikov, S. I.; Amosov, V. N.; Meshchaninov, S. A.; Yudin, I. P.

    2016-05-01

    The operational capability of a diamond detector used to measure the neutron spectrum by the response function on the QUINTA setup [1] installed at the proton beam of the phasotron [2] (Laboratory of Nuclear Problems, Joint Institute for Nuclear Research) was demonstrated in the energy interval of 2.1-20 MeV. The neutron-flux count rate was measured. The energy of neutrons was estimated at 7.4-25.7 MeV based on the diamond-detector response spectrum. The dependence of the diamond-detector response spectra on the angle between the proton beam and the line going through the detector and the center of the QUINTA setup was investigated. The angular anisotropy of the neutron flux was demonstrated. Measurements at different distances from the detector to the QUINTA setup were performed.

  16. 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 νe, + d --> p + p + e charged-current (CC) reaction.

  17. 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.

  18. Joint Measurements of Flare Flux Densities at 210 - 212 GHz by Two Different Radio Telescopes

    NASA Astrophysics Data System (ADS)

    Raulin, J.-P.; Trottet, G.; Giménez de Castro, G.; Lüthi, T.; Kaufmann, P.

    2014-04-01

    Multiple-beam observations of solar flares at submillimeter wavelengths need detection with at least four beams to derive the flux density of the emitting source, its size, and centroid position. When this condition is not fulfilled, the assumptions on the location and/or size of the emitting source have to be made in order to compute . Otherwise, only a flux density range can be estimated. We report on simultaneous flare observations at 212 and 210 GHz obtained by the Solar Submillimeter Telescope (SST) and the Bernese Multibeam Radiometer for Kosma (BEMRAK), respectively, during two solar events on 28 October 2003. For both events, BEMRAK utilized four beam information to calculate the source flux density F 210, its size and position. On the other hand, the SST observed the events with only one beam, at low solar elevation angles and during high atmospheric attenuation. Therefore, because of these poor observing conditions at 212 GHz, only a flux density range Δ F 212 could be estimated. The results show that Δ F 212 is within a factor of 2.5 of the flux density F 210. This factor can be significantly reduced ( e.g. 1.4 for one of the studied events) by an appropriate choice of the 212 GHz source position using flare observations at other wavelengths. By adopting the position and size of the 210 GHz source measured by BEMRAK, the flux density at 212 GHz, F 212b, is comparable to F 210 within the uncertainties, as expected. Therefore our findings indicate that even during poor observing conditions, the SST can provide an acceptable estimate of the flux density at 212 GHz. This is a remarkable fact since the SST and BEMRAK use quite different procedures for calibration and flux density determination. We also show that the necessary assumptions made on the size of the emitting source at 212 GHz in order to estimate its flux density are not critical, and therefore do not affect the conclusions of previous studies at this frequency.

  19. Measurement of the Reactor Antineutrino Flux and Spectrum at Daya Bay.

    PubMed

    An, F P; Balantekin, A B; Band, H R; Bishai, M; Blyth, S; Butorov, I; Cao, D; Cao, G F; Cao, J; Cen, W R; Chan, Y L; Chang, J F; Chang, L C; Chang, Y; Chen, H S; Chen, Q Y; Chen, S M; Chen, Y X; Chen, Y; Cheng, J H; Cheng, J; Cheng, Y P; Cherwinka, J J; Chu, M C; Cummings, J P; de Arcos, J; Deng, Z Y; Ding, X F; Ding, Y Y; Diwan, M V; Dove, J; Draeger, E; Dwyer, D A; Edwards, W R; Ely, S R; Gill, R; Gonchar, M; Gong, G H; Gong, H; Grassi, M; Gu, W Q; Guan, M Y; Guo, L; Guo, X H; Hackenburg, R W; Han, R; Hans, S; He, M; Heeger, K M; Heng, Y K; Higuera, A; Hor, Y K; Hsiung, Y B; Hu, B Z; Hu, L M; Hu, L J; Hu, T; Hu, W; Huang, E C; Huang, H X; Huang, X T; Huber, P; Hussain, G; Jaffe, D E; Jaffke, P; Jen, K L; Jetter, S; Ji, X P; Ji, X L; Jiao, J B; Johnson, R A; Kang, L; Kettell, S H; Kohn, S; Kramer, M; Kwan, K K; Kwok, M W; Kwok, T; Langford, T J; Lau, K; Lebanowski, L; Lee, J; Lei, R T; Leitner, R; Leung, K Y; Leung, J K C; Lewis, C A; Li, D J; Li, F; Li, G S; Li, Q J; Li, S C; Li, W D; Li, X N; Li, X Q; Li, Y F; Li, Z B; Liang, H; Lin, C J; Lin, G L; Lin, P Y; Lin, S K; Ling, J J; Link, J M; Littenberg, L; Littlejohn, B R; Liu, D W; Liu, H; Liu, J L; Liu, J C; Liu, S S; Lu, C; Lu, H Q; Lu, J S; Luk, K B; Ma, Q M; Ma, X Y; Ma, X B; Ma, Y Q; Martinez Caicedo, D A; McDonald, K T; McKeown, R D; Meng, Y; Mitchell, I; Monari Kebwaro, J; Nakajima, Y; Napolitano, J; Naumov, D; Naumova, E; Ngai, H Y; Ning, Z; Ochoa-Ricoux, J P; Olshevski, A; Pan, H-R; Park, J; Patton, S; Pec, V; Peng, J C; Piilonen, L E; Pinsky, L; Pun, C S J; Qi, F Z; Qi, M; Qian, X; Raper, N; Ren, B; Ren, J; Rosero, R; Roskovec, B; Ruan, X C; Shao, B B; Steiner, H; Sun, G X; Sun, J L; Tang, W; Taychenachev, D; Tsang, K V; Tull, C E; Tung, Y C; Viaux, N; Viren, B; Vorobel, V; Wang, C H; Wang, M; Wang, N Y; Wang, R G; Wang, W; Wang, W W; Wang, X; Wang, Y F; Wang, Z; Wang, Z; Wang, Z M; Wei, H Y; Wen, L J; Whisnant, K; White, C G; Whitehead, L; Wise, T; Wong, H L H; Wong, S C F; Worcester, E; Wu, Q; Xia, D M; Xia, J K; Xia, X; Xing, Z Z; Xu, J Y; Xu, J L; Xu, J; Xu, Y; Xue, T; Yan, J; Yang, C G; Yang, L; Yang, M S; Yang, M T; Ye, M; Yeh, M; Young, B L; Yu, G Y; Yu, Z Y; Zang, S L; Zhan, L; Zhang, C; Zhang, H H; Zhang, J W; Zhang, Q M; Zhang, Y M; Zhang, Y X; Zhang, Y M; Zhang, Z J; Zhang, Z Y; Zhang, Z P; Zhao, J; Zhao, Q W; Zhao, Y F; Zhao, Y B; Zheng, L; Zhong, W L; Zhou, L; Zhou, N; Zhuang, H L; Zou, J H

    2016-02-12

    This Letter reports a measurement of the flux and energy spectrum of electron antineutrinos from six 2.9 GWth nuclear reactors with six detectors deployed in two near (effective baselines 512 and 561 m) and one far (1579 m) underground experimental halls in the Daya Bay experiment. Using 217 days of data, 296 721 and 41 589 inverse β decay (IBD) candidates were detected in the near and far halls, respectively. The measured IBD yield is (1.55±0.04) ×10(-18)  cm(2) GW(-1) day(-1) or (5.92±0.14) ×10(-43)  cm(2) fission(-1). This flux measurement is consistent with previous short-baseline reactor antineutrino experiments and is 0.946±0.022 (0.991±0.023) relative to the flux predicted with the Huber-Mueller (ILL-Vogel) fissile antineutrino model. The measured IBD positron energy spectrum deviates from both spectral predictions by more than 2σ over the full energy range with a local significance of up to ∼4σ between 4-6 MeV. A reactor antineutrino spectrum of IBD reactions is extracted from the measured positron energy spectrum for model-independent predictions. PMID:26918980

  20. Measurement of the Reactor Antineutrino Flux and Spectrum at Daya Bay

    NASA Astrophysics Data System (ADS)

    An, F. P.; Balantekin, A. B.; Band, H. R.; Bishai, M.; Blyth, S.; Butorov, I.; Cao, D.; Cao, G. F.; Cao, J.; Cen, W. R.; Chan, Y. L.; Chang, J. F.; Chang, L. C.; Chang, Y.; Chen, H. S.; Chen, Q. Y.; Chen, S. M.; Chen, Y. X.; Chen, Y.; Cheng, J. H.; Cheng, J.; Cheng, Y. P.; Cherwinka, J. J.; Chu, M. C.; Cummings, J. P.; de Arcos, J.; Deng, Z. Y.; Ding, X. F.; Ding, Y. Y.; Diwan, M. V.; Dove, J.; Draeger, E.; Dwyer, D. A.; Edwards, W. R.; Ely, S. R.; Gill, R.; Gonchar, M.; Gong, G. H.; Gong, H.; Grassi, M.; Gu, W. Q.; Guan, M. Y.; Guo, L.; Guo, X. H.; Hackenburg, R. W.; Han, R.; Hans, S.; He, M.; Heeger, K. M.; Heng, Y. K.; Higuera, A.; Hor, Y. K.; Hsiung, Y. B.; Hu, B. Z.; Hu, L. M.; Hu, L. J.; Hu, T.; Hu, W.; Huang, E. C.; Huang, H. X.; Huang, X. T.; Huber, P.; Hussain, G.; Jaffe, D. E.; Jaffke, P.; Jen, K. L.; Jetter, S.; Ji, X. P.; Ji, X. L.; Jiao, J. B.; Johnson, R. A.; Kang, L.; Kettell, S. H.; Kohn, S.; Kramer, M.; Kwan, K. K.; Kwok, M. W.; Kwok, T.; Langford, T. J.; Lau, K.; Lebanowski, L.; Lee, J.; Lei, R. T.; Leitner, R.; Leung, K. Y.; Leung, J. K. C.; Lewis, C. A.; Li, D. J.; Li, F.; Li, G. S.; Li, Q. J.; Li, S. C.; Li, W. D.; Li, X. N.; Li, X. Q.; Li, Y. F.; Li, Z. B.; Liang, H.; Lin, C. J.; Lin, G. L.; Lin, P. Y.; Lin, S. K.; Ling, J. J.; Link, J. M.; Littenberg, L.; Littlejohn, B. R.; Liu, D. W.; Liu, H.; Liu, J. L.; Liu, J. C.; Liu, S. S.; Lu, C.; Lu, H. Q.; Lu, J. S.; Luk, K. B.; Ma, Q. M.; Ma, X. Y.; Ma, X. B.; Ma, Y. Q.; Martinez Caicedo, D. A.; McDonald, K. T.; McKeown, R. D.; Meng, Y.; Mitchell, I.; Monari Kebwaro, J.; Nakajima, Y.; Napolitano, J.; Naumov, D.; Naumova, E.; Ngai, H. Y.; Ning, Z.; Ochoa-Ricoux, J. P.; Olshevski, A.; Pan, H.-R.; Park, J.; Patton, S.; Pec, V.; Peng, J. C.; Piilonen, L. E.; Pinsky, L.; Pun, C. S. J.; Qi, F. Z.; Qi, M.; Qian, X.; Raper, N.; Ren, B.; Ren, J.; Rosero, R.; Roskovec, B.; Ruan, X. C.; Shao, B. B.; Steiner, H.; Sun, G. X.; Sun, J. L.; Tang, W.; Taychenachev, D.; Tsang, K. V.; Tull, C. E.; Tung, Y. C.; Viaux, N.; Viren, B.; Vorobel, V.; Wang, C. H.; Wang, M.; Wang, N. Y.; Wang, R. G.; Wang, W.; Wang, W. W.; Wang, X.; Wang, Y. F.; Wang, Z.; Wang, Z.; Wang, Z. M.; Wei, H. Y.; Wen, L. J.; Whisnant, K.; White, C. G.; Whitehead, L.; Wise, T.; Wong, H. L. H.; Wong, S. C. F.; Worcester, E.; Wu, Q.; Xia, D. M.; Xia, J. K.; Xia, X.; Xing, Z. Z.; Xu, J. Y.; Xu, J. L.; Xu, J.; Xu, Y.; Xue, T.; Yan, J.; Yang, C. G.; Yang, L.; Yang, M. S.; Yang, M. T.; Ye, M.; Yeh, M.; Young, B. L.; Yu, G. Y.; Yu, Z. Y.; Zang, S. L.; Zhan, L.; Zhang, C.; Zhang, H. H.; Zhang, J. W.; Zhang, Q. M.; Zhang, Y. M.; Zhang, Y. X.; Zhang, Y. M.; Zhang, Z. J.; Zhang, Z. Y.; Zhang, Z. P.; Zhao, J.; Zhao, Q. W.; Zhao, Y. F.; Zhao, Y. B.; Zheng, L.; Zhong, W. L.; Zhou, L.; Zhou, N.; Zhuang, H. L.; Zou, J. H.; Daya Bay Collaboration

    2016-02-01

    This Letter reports a measurement of the flux and energy spectrum of electron antineutrinos from six 2.9 GWt h nuclear reactors with six detectors deployed in two near (effective baselines 512 and 561 m) and one far (1579 m) underground experimental halls in the Daya Bay experiment. Using 217 days of data, 296 721 and 41 589 inverse β decay (IBD) candidates were detected in the near and far halls, respectively. The measured IBD yield is (1.55 ±0.04 ) ×10-18 cm2 GW-1 day-1 or (5.92 ±0.14 ) ×10-43 cm2 fission-1 . This flux measurement is consistent with previous short-baseline reactor antineutrino experiments and is 0.946 ±0.022 (0.991 ±0.023 ) relative to the flux predicted with the Huber -Mueller (ILL -Vogel ) fissile antineutrino model. The measured IBD positron energy spectrum deviates from both spectral predictions by more than 2 σ over the full energy range with a local significance of up to ˜4 σ between 4-6 MeV. A reactor antineutrino spectrum of IBD reactions is extracted from the measured positron energy spectrum for model-independent predictions.

  1. Measurement of the reactor antineutrino flux and spectrum at Daya Bay

    DOE PAGESBeta

    D. E. Jaffe; Bishai, M; Diwan, M.; Gill, R.; Hackenburg, R. W.; Hans, S.; Hu, L. M.; Jaffe, D. E.; Kettell, S. H.; Tang, W.; et al

    2016-02-12

    This Letter reports a measurement of the flux and energy spectrum of electron antineutrinos from six 2.9~GWth nuclear reactors with six detectors deployed in two near (effective baselines 512~m and 561~m) and one far (1,579 m) underground experimental halls in the Daya Bay experiment. Using 217 days of data, 296,721 and 41,589 inverse beta decay (IBD) candidates were detected in the near and far halls, respectively. The measured IBD yield is (1.55 ± 0.04) × 10–18 cm2/GW/day or (5.92 ± 0.14) × 10–43 cm2/fission. This flux measurement is consistent with previous short-baseline reactor antineutrino experiments and is 0.946 ± 0.022more » (0.991 ± 0.023) relative to the flux predicted with the Huber+Mueller (ILL+Vogel) fissile antineutrino model. The measured IBD positron energy spectrum deviates from both spectral predictions by more than 2σ over the full energy range with a local significance of up to ~4σ between 4-6 MeV. Furthermore, a reactor antineutrino spectrum of IBD reactions is extracted from the measured positron energy spectrum for model-independent predictions.« less

  2. A flux extraction device to measure the magnetic moment of large samples; application to bulk superconductors.

    PubMed

    Egan, R; Philippe, M; Wera, L; Fagnard, J F; Vanderheyden, B; Dennis, A; Shi, Y; Cardwell, D A; Vanderbemden, P

    2015-02-01

    We report the design and construction of a flux extraction device to measure the DC magnetic moment of large samples (i.e., several cm(3)) at cryogenic temperature. The signal is constructed by integrating the electromotive force generated by two coils wound in series-opposition that move around the sample. We show that an octupole expansion of the magnetic vector potential can be used conveniently to treat near-field effects for this geometrical configuration. The resulting expansion is tested for the case of a large, permanently magnetized, type-II superconducting sample. The dimensions of the sensing coils are determined in such a way that the measurement is influenced by the dipole magnetic moment of the sample and not by moments of higher order, within user-determined upper bounds. The device, which is able to measure magnetic moments in excess of 1 A m(2) (1000 emu), is validated by (i) a direct calibration experiment using a small coil driven by a known current and (ii) by comparison with the results of numerical calculations obtained previously using a flux measurement technique. The sensitivity of the device is demonstrated by the measurement of flux-creep relaxation of the magnetization in a large bulk superconductor sample at liquid nitrogen temperature (77 K). PMID:25725888

  3. A flux extraction device to measure the magnetic moment of large samples; application to bulk superconductors

    NASA Astrophysics Data System (ADS)

    Egan, R.; Philippe, M.; Wera, L.; Fagnard, J. F.; Vanderheyden, B.; Dennis, A.; Shi, Y.; Cardwell, D. A.; Vanderbemden, P.

    2015-02-01

    We report the design and construction of a flux extraction device to measure the DC magnetic moment of large samples (i.e., several cm3) at cryogenic temperature. The signal is constructed by integrating the electromotive force generated by two coils wound in series-opposition that move around the sample. We show that an octupole expansion of the magnetic vector potential can be used conveniently to treat near-field effects for this geometrical configuration. The resulting expansion is tested for the case of a large, permanently magnetized, type-II superconducting sample. The dimensions of the sensing coils are determined in such a way that the measurement is influenced by the dipole magnetic moment of the sample and not by moments of higher order, within user-determined upper bounds. The device, which is able to measure magnetic moments in excess of 1 A m2 (1000 emu), is validated by (i) a direct calibration experiment using a small coil driven by a known current and (ii) by comparison with the results of numerical calculations obtained previously using a flux measurement technique. The sensitivity of the device is demonstrated by the measurement of flux-creep relaxation of the magnetization in a large bulk superconductor sample at liquid nitrogen temperature (77 K).

  4. Measuring Fluxes of Mineral Nutrients and Toxicants in Plants with Radioactive Tracers

    PubMed Central

    Coskun, Devrim; Britto, Dev T.; Hamam, Ahmed M.; Kronzucker, Herbert J.

    2014-01-01

    Unidirectional influx and efflux of nutrients and toxicants, and their resultant net fluxes, are central to the nutrition and toxicology of plants. Radioisotope tracing is a major technique used to measure such fluxes, both within plants, and between plants and their environments. Flux data obtained with radiotracer protocols can help elucidate the capacity, mechanism, regulation, and energetics of transport systems for specific mineral nutrients or toxicants, and can provide insight into compartmentation and turnover rates of subcellular mineral and metabolite pools. Here, we describe two major radioisotope protocols used in plant biology: direct influx (DI) and compartmental analysis by tracer efflux (CATE). We focus on flux measurement of potassium (K+) as a nutrient, and ammonia/ammonium (NH3/NH4+) as a toxicant, in intact seedlings of the model species barley (Hordeum vulgare L.). These protocols can be readily adapted to other experimental systems (e.g., different species, excised plant material, and other nutrients/toxicants). Advantages and limitations of these protocols are discussed. PMID:25177829

  5. COMPTEL measurements of the omnidirectional high-energy neutron flux in near-earth orbit.

    PubMed

    Morris, D J; Aarts, H; Bennett, K; Lockwood, J A; McConnell, M L; Ryan, J M; Schonfelder, V; Steinle, H; Weidenspointner, G

    1998-01-01

    On four occasions, twice in 1991 (near solar maximum) and twice in 1994 (near solar minimum), one COMPTEL D1 detector module was used as an omnidirectional detector to measure the high-energy (> 12.8 MeV) neutron flux near an altitude of 450 km. The D1 modules are cylindrical, with radius 13.8 cm and depth 8 cm, and are filled with liquid scintillator (NE213A). The combined flux measurements can be fit reasonably well by a product of the Mt. Washington neutron monitor rate, a linear function in the spacecraft geocenter zenith angle, and an exponential function of the vertical geomagnetic cutoff rigidity in which the coefficient of the rigidity is a linear function of the neutron monitor rate. When pointed at the nadir, the flux is consistent with that expected from the atmospheric neutron albedo alone. When pointed at the zenith the flux is reduced by a factor of about 0.54. Thus the production of secondary neutrons in the massive (16000 kg) Compton Gamma-Ray Observatory spacecraft is negligible. Rather, the mass of the spacecraft provides shielding from the earth albedo. PMID:11542901

  6. Momentum and Heat Flux Measurements in the Exhaust of VASIMR using Helium Propellant

    NASA Technical Reports Server (NTRS)

    Chavers, D. Gregory; Chang-Diaz, Franklin R.; Irvine, Claude; Squire, Jared P.

    2003-01-01

    Interplanetary travel requires propulsion systems that can provide high specific impulse (Isp), while also having sufficient thrust to rapidly accelerate large payloads. One such propulsion system is the Variable Specific Impulse Magneto-plasma Rocket (VASIMR), which creates, heats, and ejects plasma to provide variable thrust and Isp, designed to optimally meet the mission requirements. The fraction of the total energy invested in creating the plasma, as compared to the plasma's total kinetic energy, is an important factor in determining the overall system efficiency. In VASIMR, this 'frozen flow loss' is appreciable when at high thrust, but negligible at high Isp. The loss applies to other electric thrusters as well. If some of this energy could be recovered through recombination processes, and reinjected as neutral kinetic energy, the efficiency of VASIMR, in its low Isp/high thrust mode may be improved. An experiment is being conducted to investigate the possibility of recovering some of the energy used to create the plasma by studying the flow characteristics of the charged and neutral particles in the exhaust of the thruster. This paper will cover the measurements of momentum flux and heat flux in the exhaust of the VASIMR test facility using helium as the propellant where the heat flux is comprised of both kinetic and plasma recombination energy. The flux measurements also assist in diagnosing and verifying the plasma conditions in the existing experiment.

  7. Flux measurements in the near surface layer over a non-uniform crop surface in China

    NASA Astrophysics Data System (ADS)

    Gao, Z.; Bian, L.; Liu, S.

    2005-06-01

    Eddy covariance measurements were conducted on fluxes of moisture, heat and CO2 in a near-surface layer over a non-uniform crop surface in an agricultural ecosystem in the central plain of China from 10 June to 20 July 2002. During this period, the mean canopy height was about 0.50 m. The study site consisted of grass (10% of area), bean (15%), corn (15%) and rice (60%). Based on footprint analysis, we expected >90% of the measured flux (at a height of 4 m above ground surface) to occur within the nearest 600 m of upwind area. We examined interdiurnal variations in the components of the surface energy balance and in CO2 flux. Results show that the pattern of energy partition had no obvious variation during the season. Daytime absorption of CO2 flux by the crop canopy suddenly increased after thunderstorm events. We examined the energy budget closure and found it to be around 0.85. We compared energy partitioning for all rain-free days, and found energy imbalance was more significant for the 1~3 days after rainy events and energy components almost achieve balance for the other rain-free days. It indicated that the cold or warm rainwater infiltrating into soil made problems.

  8. Isoprene Fluxes Measured By Eddy-correlation Over A Mixed Deciduous Forest In Italy

    NASA Astrophysics Data System (ADS)

    Finco, A.; Cieslik, S.

    A measuring campaign was conducted from July to September 2001 at a mixed de- ciduous forest located at a flat site (Nonantola, 4441' N; 1107' E) in the North- ern Italian plain to determine isoprene fluxes. The measuring station, operated by the CNR-ISAO (Bologna ) and CNR-IATA (Florence) was part of the CARBOEU- ROFLUX network, whose main goal is the study of the carbon balance in European forests. The flux measuring system used the eddy-correlation technique and consisted of a Gill sonic anemometer installed at 13 m a.g.l., and a LI-COR CO2/H2O analyser. For isoprene, a Hills Fast Isoprene Sensor was used.In this forest, about 50% of the trees (oaks, poplars and willows) are isoprene emitters. The canopy is very dense and homogeneous; its average height is 8 meters a.g.l. The general daily course of isoprene concentrations consisted in an increase during morning hours, followed with a sharp maximum and a rapid decrease. Maximum val- ues were quite high (around 15 ppb) in July and August, decreasing in September. During daytime, fluxes appeared to be strongly correlated with latent heat fluxes, con- firming the hypothesis of emission through stomata. The concentration decrease ob- served in the afternoon shows exponential decay, suggesting that no emission occurs after the concentration maximum, when stomata are progressively closing. A resistance analysis confirmed the above hypothesis : the role of stomatal emission appears essential, practically excluding other pathways. A mathematical investigation of the stationarity state of the lower atmosphere dur- ing the observations was made in order to draw attention on limitations of the eddy- correlation method. During nighttime, non-stationary situations are frequent, causing apparent peaks of isoprene flux, not due to an emission from the plants. The method developed permits to eliminate these biases.

  9. 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.; Blake, D.; Wiedinmyer, C.

    2008-07-01

    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-average midday toluene and benzene fluxes are calculated to be on the order of 15.5±4.0 mg/m2/h and 4.7±2.3 mg/m2/h respectively. These values argue for an underestimation of toluene and benzene emissions in current inventories used for the Mexico City Metropolitan Area (MCMA). 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) including the International airport (e.g. 3 5) and a mean flux (concentration) ratio of 3.2±0.5 (3.9±0.3) 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 (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 >90% of all BTEX sources. Our observations suggest that biomass burning emissions play a minor role for the abundance of BTEX compounds (0 10%) in the MCMA.

  10. 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 φ = 1, φ = 0.75 and φ = 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.

  11. Technique for measuring air flow and carbon dioxide flux in large, open-top chambers

    SciTech Connect

    Ham, J.M.; Owensby, C.E.; Coyne, P.I.

    1993-10-01

    Open-Top Chambers (OTCs) are commonly used to evaluate the effect of CO{sub 2},O{sub 3}, and other trace gases on vegetation. This study developed and tested a new technique for measuring forced air flow and net CO{sub 2} flux from OTCs. Experiments were performed with a 4.5-m diam. OTC with a sealed floor and a specialized air delivery system. Air flow through the chamber was computed with the Bernoulli equation using measurements of the pressure differential between the air delivery ducts and the chamber interior. An independent measurement of air flow was made simultaneously to calibrate and verify the accuracy of the Bernoulli relationship. The CO{sub 2} flux density was calculated as the product of chamber air flow and the difference in CO{sub 2} concentration between the air entering and exhausting from the OTC (C{sub in}-C{sub out}). Accuracy was evaluated by releasing CO{sub 2} within the OTC at known rates. Data were collected with OTCs at ambient and elevated CO{sub 2} ({approx}700 {mu}mol{sup -1}). Results showed the Bernoulli equation, with a flow coefficient of 0.7, accurately measured air flow in the OTC within {+-}5% regardless of flow rate and air duct geometry. Experiments in ambient OTCs showed CO{sub 2} flux density ({mu}mol m{sup -2} s{sup -1}), computed from 2-min averages of air flow and C{sub in} - C{sub out,} was typically within {+-} 10% of actual flux, provided that the exit air velocity at the top of the OTC was greater than 0.6 m s{sup -1}. Obtaining the same accuracy in CO{sub 2}-enriched OTCs required a critical exit velocity near 1.2 m s{sup -1} to minimize the incursion of ambient air and prevent contamination of exit gas sample. When flux data were integrated over time to estimate daily CO{sub 2} flux ({mu}mol m{sup -2} d{sup -1}), actual and measured values agreed to within {+-}2% for both ambient and CO{sub 2}-enriched chambers, suggesting that accurate measurements of daily net C exchange are possible with this technique.

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

    NASA Astrophysics Data System (ADS)

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

    2009-05-01

    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 0.02-0.5mN with a resolution of 15μN. 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 downstr