Science.gov

Sample records for accurate flux measurements

  1. A flux monitoring method for easy and accurate flow rate measurement in pressure-driven flows.

    PubMed

    Siria, Alessandro; Biance, Anne-Laure; Ybert, Christophe; Bocquet, Lydéric

    2012-03-01

    We propose a low-cost and versatile method to measure flow rate in microfluidic channels under pressure-driven flows, thereby providing a simple characterization of the hydrodynamic permeability of the system. The technique is inspired by the current monitoring method usually employed to characterize electro-osmotic flows, and makes use of the measurement of the time-dependent electric resistance inside the channel associated with a moving salt front. We have successfully tested the method in a micrometer-size channel, as well as in a complex microfluidic channel with a varying cross-section, demonstrating its ability in detecting internal shape variations.

  2. The Heat Output of the Waimangu, Waiotapu-Waikite and Reporoa Geothermal Systems (NZ): Do Chloride Fluxes Provide an Accurate Measure?

    SciTech Connect

    Bibby, H.M.; Glover, R.B.; Whiteford, P.C.

    1995-01-01

    Geothermal waters from the Waimangu, Waiotapu-Waikite and Reporoa geothermal systems find their way into three separate watersheds. The heat flow data from each of these drainage areas have been assessed making it possible to compare the heat outputs from two independent methods: direct heat measurements and the chloride flux method. For both the Waiotapu/Reporoa Valley drainage and the Waikite drainage a discrepancy exists between the two assessments, with the heat output observed at the surface (Waiotapu-540 {+-} 110 MW; Waikite-80 MW) nearly double of that calculated from the chloride flux (300 MW; 36 MW respectively). It appears that much of the throughput of chloride does not reach the surface within the area which was monitored and the basic assumption on which the method is based has been violated. For Waimangu the direct heat output is assessed as 510 {+-} 60 MW. However the ratio of enthalpy to chloride concentration of the source fluid is not well determined. Depending on the ratio chosen the heat output could lie between 360 and 800 MW. Although the chloride flux is accurately known, the heat output cannot be measured accurately without well determined data on the source fluid at depth.

  3. Accurate measurements of vadose zone fluxes using automated equilibrium tension plate lysimeters: A synopsis of results from the Spydia research facility, New Zealand.

    NASA Astrophysics Data System (ADS)

    Wöhling, Thomas; Barkle, Greg; Stenger, Roland; Moorhead, Brian; Wall, Aaron; Clague, Juliet

    2014-05-01

    Automated equilibrium tension plate lysimeters (AETLs) are arguably the most accurate method to measure unsaturated water and contaminant fluxes below the root zone at the scale of up to 1 m². The AETL technique utilizes a porous sintered stainless-steel plate to provide a comparatively large sampling area with a continuously controlled vacuum that is in "equilibrium" with the surrounding vadose zone matric pressure to ensure measured fluxes represent those under undisturbed conditions. This novel lysimeter technique was used at an intensive research site for investigations of contaminant pathways from the land surface to the groundwater on a sheep and beef farm under pastoral land use in the Tutaeuaua subcatchment, New Zealand. The Spydia research facility was constructed in 2005 and was fully operational between 2006 and 2011. Extending from a central access caisson, 15 separately controlled AETLs with 0.2 m² surface area were installed at five depths between 0.4 m and 5.1 m into the undisturbed volcanic vadose zone materials. The unique setup of the facility ensured minimum interference of the experimental equipment and external factors with the measurements. Over the period of more than five years, a comprehensive data set was collected at each of the 15 AETL locations which comprises of time series of soil water flux, pressure head, volumetric water contents, and soil temperature. The soil water was regularly analysed for EC, pH, dissolved carbon, various nitrogen compounds (including nitrate, ammonia, and organic N), phosphorus, bromide, chloride, sulphate, silica, and a range of other major ions, as well as for various metals. Climate data was measured directly at the site (rainfall) and a climate station at 500m distance. The shallow groundwater was sampled at three different depths directly from the Spydia caisson and at various observation wells surrounding the facility. Two tracer experiments were conducted at the site in 2009 and 2010. In the 2009

  4. 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.

  5. 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...

  6. Accurate thickness measurement of graphene

    NASA Astrophysics Data System (ADS)

    Shearer, Cameron J.; Slattery, Ashley D.; Stapleton, Andrew J.; Shapter, Joseph G.; Gibson, Christopher T.

    2016-03-01

    Graphene has emerged as a material with a vast variety of applications. The electronic, optical and mechanical properties of graphene are strongly influenced by the number of layers present in a sample. As a result, the dimensional characterization of graphene films is crucial, especially with the continued development of new synthesis methods and applications. A number of techniques exist to determine the thickness of graphene films including optical contrast, Raman scattering and scanning probe microscopy techniques. Atomic force microscopy (AFM), in particular, is used extensively since it provides three-dimensional images that enable the measurement of the lateral dimensions of graphene films as well as the thickness, and by extension the number of layers present. However, in the literature AFM has proven to be inaccurate with a wide range of measured values for single layer graphene thickness reported (between 0.4 and 1.7 nm). This discrepancy has been attributed to tip-surface interactions, image feedback settings and surface chemistry. In this work, we use standard and carbon nanotube modified AFM probes and a relatively new AFM imaging mode known as PeakForce tapping mode to establish a protocol that will allow users to accurately determine the thickness of graphene films. In particular, the error in measuring the first layer is reduced from 0.1-1.3 nm to 0.1-0.3 nm. Furthermore, in the process we establish that the graphene-substrate adsorbate layer and imaging force, in particular the pressure the tip exerts on the surface, are crucial components in the accurate measurement of graphene using AFM. These findings can be applied to other 2D materials.

  7. Accurate thickness measurement of graphene.

    PubMed

    Shearer, Cameron J; Slattery, Ashley D; Stapleton, Andrew J; Shapter, Joseph G; Gibson, Christopher T

    2016-03-29

    Graphene has emerged as a material with a vast variety of applications. The electronic, optical and mechanical properties of graphene are strongly influenced by the number of layers present in a sample. As a result, the dimensional characterization of graphene films is crucial, especially with the continued development of new synthesis methods and applications. A number of techniques exist to determine the thickness of graphene films including optical contrast, Raman scattering and scanning probe microscopy techniques. Atomic force microscopy (AFM), in particular, is used extensively since it provides three-dimensional images that enable the measurement of the lateral dimensions of graphene films as well as the thickness, and by extension the number of layers present. However, in the literature AFM has proven to be inaccurate with a wide range of measured values for single layer graphene thickness reported (between 0.4 and 1.7 nm). This discrepancy has been attributed to tip-surface interactions, image feedback settings and surface chemistry. In this work, we use standard and carbon nanotube modified AFM probes and a relatively new AFM imaging mode known as PeakForce tapping mode to establish a protocol that will allow users to accurately determine the thickness of graphene films. In particular, the error in measuring the first layer is reduced from 0.1-1.3 nm to 0.1-0.3 nm. Furthermore, in the process we establish that the graphene-substrate adsorbate layer and imaging force, in particular the pressure the tip exerts on the surface, are crucial components in the accurate measurement of graphene using AFM. These findings can be applied to other 2D materials.

  8. Quantifying Methane Fluxes Simply and Accurately: The Tracer Dilution Method

    NASA Astrophysics Data System (ADS)

    Rella, Christopher; Crosson, Eric; Green, Roger; Hater, Gary; Dayton, Dave; Lafleur, Rick; Merrill, Ray; Tan, Sze; Thoma, Eben

    2010-05-01

    Methane is an important atmospheric constituent with a wide variety of sources, both natural and anthropogenic, including wetlands and other water bodies, permafrost, farms, landfills, and areas with significant petrochemical exploration, drilling, transport, or processing, or refining occurs. Despite its importance to the carbon cycle, its significant impact as a greenhouse gas, and its ubiquity in modern life as a source of energy, its sources and sinks in marine and terrestrial ecosystems are only poorly understood. This is largely because high quality, quantitative measurements of methane fluxes in these different environments have not been available, due both to the lack of robust field-deployable instrumentation as well as to the fact that most significant sources of methane extend over large areas (from 10's to 1,000,000's of square meters) and are heterogeneous emitters - i.e., the methane is not emitted evenly over the area in question. Quantifying the total methane emissions from such sources becomes a tremendous challenge, compounded by the fact that atmospheric transport from emission point to detection point can be highly variable. In this presentation we describe a robust, accurate, and easy-to-deploy technique called the tracer dilution method, in which a known gas (such as acetylene, nitrous oxide, or sulfur hexafluoride) is released in the same vicinity of the methane emissions. Measurements of methane and the tracer gas are then made downwind of the release point, in the so-called far-field, where the area of methane emissions cannot be distinguished from a point source (i.e., the two gas plumes are well-mixed). In this regime, the methane emissions are given by the ratio of the two measured concentrations, multiplied by the known tracer emission rate. The challenges associated with atmospheric variability and heterogeneous methane emissions are handled automatically by the transport and dispersion of the tracer. We present detailed methane flux

  9. AN ACCURATE FLUX DENSITY SCALE FROM 1 TO 50 GHz

    SciTech Connect

    Perley, R. A.; Butler, B. J. E-mail: BButler@nrao.edu

    2013-02-15

    We develop an absolute flux density scale for centimeter-wavelength astronomy by combining accurate flux density ratios determined by the Very Large Array between the planet Mars and a set of potential calibrators with the Rudy thermophysical emission model of Mars, adjusted to the absolute scale established by the Wilkinson Microwave Anisotropy Probe. The radio sources 3C123, 3C196, 3C286, and 3C295 are found to be varying at a level of less than {approx}5% per century at all frequencies between 1 and 50 GHz, and hence are suitable as flux density standards. We present polynomial expressions for their spectral flux densities, valid from 1 to 50 GHz, with absolute accuracy estimated at 1%-3% depending on frequency. Of the four sources, 3C286 is the most compact and has the flattest spectral index, making it the most suitable object on which to establish the spectral flux density scale. The sources 3C48, 3C138, 3C147, NGC 7027, NGC 6542, and MWC 349 show significant variability on various timescales. Polynomial coefficients for the spectral flux density are developed for 3C48, 3C138, and 3C147 for each of the 17 observation dates, spanning 1983-2012. The planets Venus, Uranus, and Neptune are included in our observations, and we derive their brightness temperatures over the same frequency range.

  10. 38 CFR 4.46 - Accurate measurement.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2010-07-01 2010-07-01 false Accurate measurement. 4... RATING DISABILITIES Disability Ratings The Musculoskeletal System § 4.46 Accurate measurement. Accurate measurement of the length of stumps, excursion of joints, dimensions and location of scars with respect...

  11. 38 CFR 4.46 - Accurate measurement.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2013-07-01 2013-07-01 false Accurate measurement. 4... RATING DISABILITIES Disability Ratings The Musculoskeletal System § 4.46 Accurate measurement. Accurate measurement of the length of stumps, excursion of joints, dimensions and location of scars with respect...

  12. 38 CFR 4.46 - Accurate measurement.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2011-07-01 2011-07-01 false Accurate measurement. 4... RATING DISABILITIES Disability Ratings The Musculoskeletal System § 4.46 Accurate measurement. Accurate measurement of the length of stumps, excursion of joints, dimensions and location of scars with respect...

  13. 38 CFR 4.46 - Accurate measurement.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2014-07-01 2014-07-01 false Accurate measurement. 4... RATING DISABILITIES Disability Ratings The Musculoskeletal System § 4.46 Accurate measurement. Accurate measurement of the length of stumps, excursion of joints, dimensions and location of scars with respect...

  14. 38 CFR 4.46 - Accurate measurement.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 1 2012-07-01 2012-07-01 false Accurate measurement. 4... RATING DISABILITIES Disability Ratings The Musculoskeletal System § 4.46 Accurate measurement. Accurate measurement of the length of stumps, excursion of joints, dimensions and location of scars with respect...

  15. Accurate documentation and wound measurement.

    PubMed

    Hampton, Sylvie

    This article, part 4 in a series on wound management, addresses the sometimes routine yet crucial task of documentation. Clear and accurate records of a wound enable its progress to be determined so the appropriate treatment can be applied. Thorough records mean any practitioner picking up a patient's notes will know when the wound was last checked, how it looked and what dressing and/or treatment was applied, ensuring continuity of care. Documenting every assessment also has legal implications, demonstrating due consideration and care of the patient and the rationale for any treatment carried out. Part 5 in the series discusses wound dressing characteristics and selection.

  16. Accurate Mass Measurements in Proteomics

    SciTech Connect

    Liu, Tao; Belov, Mikhail E.; Jaitly, Navdeep; Qian, Weijun; Smith, Richard D.

    2007-08-01

    To understand different aspects of life at the molecular level, one would think that ideally all components of specific processes should be individually isolated and studied in details. Reductionist approaches, i.e., studying one biological event at a one-gene or one-protein-at-a-time basis, indeed have made significant contributions to our understanding of many basic facts of biology. However, these individual “building blocks” can not be visualized as a comprehensive “model” of the life of cells, tissues, and organisms, without using more integrative approaches.1,2 For example, the emerging field of “systems biology” aims to quantify all of the components of a biological system to assess their interactions and to integrate diverse types of information obtainable from this system into models that could explain and predict behaviors.3-6 Recent breakthroughs in genomics, proteomics, and bioinformatics are making this daunting task a reality.7-14 Proteomics, the systematic study of the entire complement of proteins expressed by an organism, tissue, or cell under a specific set of conditions at a specific time (i.e., the proteome), has become an essential enabling component of systems biology. While the genome of an organism may be considered static over short timescales, the expression of that genome as the actual gene products (i.e., mRNAs and proteins) is a dynamic event that is constantly changing due to the influence of environmental and physiological conditions. Exclusive monitoring of the transcriptomes can be carried out using high-throughput cDNA microarray analysis,15-17 however the measured mRNA levels do not necessarily correlate strongly with the corresponding abundances of proteins,18-20 The actual amount of functional proteins can be altered significantly and become independent of mRNA levels as a result of post-translational modifications (PTMs),21 alternative splicing,22,23 and protein turnover.24,25 Moreover, the functions of expressed

  17. 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...

  18. 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.

  19. 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.

  20. Modified chemiluminescent NO analyzer accurately measures NOX

    NASA Technical Reports Server (NTRS)

    Summers, R. L.

    1978-01-01

    Installation of molybdenum nitric oxide (NO)-to-higher oxides of nitrogen (NOx) converter in chemiluminescent gas analyzer and use of air purge allow accurate measurements of NOx in exhaust gases containing as much as thirty percent carbon monoxide (CO). Measurements using conventional analyzer are highly inaccurate for NOx if as little as five percent CO is present. In modified analyzer, molybdenum has high tolerance to CO, and air purge substantially quenches NOx destruction. In test, modified chemiluminescent analyzer accurately measured NO and NOx concentrations for over 4 months with no denegration in performance.

  1. Accurately measuring volcanic plume velocity with multiple UV spectrometers

    USGS Publications Warehouse

    Williams-Jones, G.; Horton, K.A.; Elias, T.; Garbeil, H.; Mouginis-Mark, P. J.; Sutton, A.J.; Harris, A.J.L.

    2006-01-01

    A fundamental problem with all ground-based remotely sensed measurements of volcanic gas flux is the difficulty in accurately measuring the velocity of the gas plume. Since a representative wind speed and direction are used as proxies for the actual plume velocity, there can be considerable uncertainty in reported gas flux values. Here we present a method that uses at least two time-synchronized simultaneously recording UV spectrometers (FLYSPECs) placed a known distance apart. By analyzing the time varying structure of SO2 concentration signals at each instrument, the plume velocity can accurately be determined. Experiments were conducted on Ki??lauea (USA) and Masaya (Nicaragua) volcanoes in March and August 2003 at plume velocities between 1 and 10 m s-1. Concurrent ground-based anemometer measurements differed from FLYSPEC-measured plume speeds by up to 320%. This multi-spectrometer method allows for the accurate remote measurement of plume velocity and can therefore greatly improve the precision of volcanic or industrial gas flux measurements. ?? Springer-Verlag 2006.

  2. Errors in airborne flux measurements

    NASA Astrophysics Data System (ADS)

    Mann, Jakob; Lenschow, Donald H.

    1994-07-01

    We present a general approach for estimating systematic and random errors in eddy correlation fluxes and flux gradients measured by aircraft in the convective boundary layer as a function of the length of the flight leg, or of the cutoff wavelength of a highpass filter. The estimates are obtained from empirical expressions for various length scales in the convective boundary layer and they are experimentally verified using data from the First ISLSCP (International Satellite Land Surface Climatology Experiment) Field Experiment (FIFE), the Air Mass Transformation Experiment (AMTEX), and the Electra Radome Experiment (ELDOME). We show that the systematic flux and flux gradient errors can be important if fluxes are calculated from a set of several short flight legs or if the vertical velocity and scalar time series are high-pass filtered. While the systematic error of the flux is usually negative, that of the flux gradient can change sign. For example, for temperature flux divergence the systematic error changes from negative to positive about a quarter of the way up in the convective boundary layer.

  3. Preparation and accurate measurement of pure ozone.

    PubMed

    Janssen, Christof; Simone, Daniela; Guinet, Mickaël

    2011-03-01

    Preparation of high purity ozone as well as precise and accurate measurement of its pressure are metrological requirements that are difficult to meet due to ozone decomposition occurring in pressure sensors. The most stable and precise transducer heads are heated and, therefore, prone to accelerated ozone decomposition, limiting measurement accuracy and compromising purity. Here, we describe a vacuum system and a method for ozone production, suitable to accurately determine the pressure of pure ozone by avoiding the problem of decomposition. We use an inert gas in a particularly designed buffer volume and can thus achieve high measurement accuracy and negligible degradation of ozone with purities of 99.8% or better. The high degree of purity is ensured by comprehensive compositional analyses of ozone samples. The method may also be applied to other reactive gases. PMID:21456766

  4. Accurate measurement of unsteady state fluid temperature

    NASA Astrophysics Data System (ADS)

    Jaremkiewicz, Magdalena

    2016-07-01

    In this paper, two accurate methods for determining the transient fluid temperature were presented. Measurements were conducted for boiling water since its temperature is known. At the beginning the thermometers are at the ambient temperature and next they are immediately immersed into saturated water. The measurements were carried out with two thermometers of different construction but with the same housing outer diameter equal to 15 mm. One of them is a K-type industrial thermometer widely available commercially. The temperature indicated by the thermometer was corrected considering the thermometers as the first or second order inertia devices. The new design of a thermometer was proposed and also used to measure the temperature of boiling water. Its characteristic feature is a cylinder-shaped housing with the sheath thermocouple located in its center. The temperature of the fluid was determined based on measurements taken in the axis of the solid cylindrical element (housing) using the inverse space marching method. Measurements of the transient temperature of the air flowing through the wind tunnel using the same thermometers were also carried out. The proposed measurement technique provides more accurate results compared with measurements using industrial thermometers in conjunction with simple temperature correction using the inertial thermometer model of the first or second order. By comparing the results, it was demonstrated that the new thermometer allows obtaining the fluid temperature much faster and with higher accuracy in comparison to the industrial thermometer. Accurate measurements of the fast changing fluid temperature are possible due to the low inertia thermometer and fast space marching method applied for solving the inverse heat conduction problem.

  5. Beta ray flux measuring device

    DOEpatents

    Impink, Jr., Albert J.; Goldstein, Norman P.

    1990-01-01

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

  6. Accurate shear measurement with faint sources

    SciTech Connect

    Zhang, Jun; Foucaud, Sebastien; Luo, Wentao E-mail: walt@shao.ac.cn

    2015-01-01

    For cosmic shear to become an accurate cosmological probe, systematic errors in the shear measurement method must be unambiguously identified and corrected for. Previous work of this series has demonstrated that cosmic shears can be measured accurately in Fourier space in the presence of background noise and finite pixel size, without assumptions on the morphologies of galaxy and PSF. The remaining major source of error is source Poisson noise, due to the finiteness of source photon number. This problem is particularly important for faint galaxies in space-based weak lensing measurements, and for ground-based images of short exposure times. In this work, we propose a simple and rigorous way of removing the shear bias from the source Poisson noise. Our noise treatment can be generalized for images made of multiple exposures through MultiDrizzle. This is demonstrated with the SDSS and COSMOS/ACS data. With a large ensemble of mock galaxy images of unrestricted morphologies, we show that our shear measurement method can achieve sub-percent level accuracy even for images of signal-to-noise ratio less than 5 in general, making it the most promising technique for cosmic shear measurement in the ongoing and upcoming large scale galaxy surveys.

  7. Apparatus for accurately measuring high temperatures

    DOEpatents

    Smith, Douglas D.

    1985-01-01

    The present invention is a thermometer used for measuring furnace temperaes in the range of about 1800.degree. to 2700.degree. C. The thermometer comprises a broadband multicolor thermal radiation sensor positioned to be in optical alignment with the end of a blackbody sight tube extending into the furnace. A valve-shutter arrangement is positioned between the radiation sensor and the sight tube and a chamber for containing a charge of high pressure gas is positioned between the valve-shutter arrangement and the radiation sensor. A momentary opening of the valve shutter arrangement allows a pulse of the high gas to purge the sight tube of air-borne thermal radiation contaminants which permits the radiation sensor to accurately measure the thermal radiation emanating from the end of the sight tube.

  8. Apparatus for accurately measuring high temperatures

    DOEpatents

    Smith, D.D.

    The present invention is a thermometer used for measuring furnace temperatures in the range of about 1800/sup 0/ to 2700/sup 0/C. The thermometer comprises a broadband multicolor thermal radiation sensor positioned to be in optical alignment with the end of a blackbody sight tube extending into the furnace. A valve-shutter arrangement is positioned between the radiation sensor and the sight tube and a chamber for containing a charge of high pressure gas is positioned between the valve-shutter arrangement and the radiation sensor. A momentary opening of the valve shutter arrangement allows a pulse of the high gas to purge the sight tube of air-borne thermal radiation contaminants which permits the radiation sensor to accurately measure the thermal radiation emanating from the end of the sight tube.

  9. Fast and Accurate Exhaled Breath Ammonia Measurement

    PubMed Central

    Solga, Steven F.; Mudalel, Matthew L.; Spacek, Lisa A.; Risby, Terence H.

    2014-01-01

    This exhaled breath ammonia method uses a fast and highly sensitive spectroscopic method known as quartz enhanced photoacoustic spectroscopy (QEPAS) that uses a quantum cascade based laser. The monitor is coupled to a sampler that measures mouth pressure and carbon dioxide. The system is temperature controlled and specifically designed to address the reactivity of this compound. The sampler provides immediate feedback to the subject and the technician on the quality of the breath effort. Together with the quick response time of the monitor, this system is capable of accurately measuring exhaled breath ammonia representative of deep lung systemic levels. Because the system is easy to use and produces real time results, it has enabled experiments to identify factors that influence measurements. For example, mouth rinse and oral pH reproducibly and significantly affect results and therefore must be controlled. Temperature and mode of breathing are other examples. As our understanding of these factors evolves, error is reduced, and clinical studies become more meaningful. This system is very reliable and individual measurements are inexpensive. The sampler is relatively inexpensive and quite portable, but the monitor is neither. This limits options for some clinical studies and provides rational for future innovations. PMID:24962141

  10. Highly accurate articulated coordinate measuring machine

    DOEpatents

    Bieg, Lothar F.; Jokiel, Jr., Bernhard; Ensz, Mark T.; Watson, Robert D.

    2003-12-30

    Disclosed is a highly accurate articulated coordinate measuring machine, comprising a revolute joint, comprising a circular encoder wheel, having an axis of rotation; a plurality of marks disposed around at least a portion of the circumference of the encoder wheel; bearing means for supporting the encoder wheel, while permitting free rotation of the encoder wheel about the wheel's axis of rotation; and a sensor, rigidly attached to the bearing means, for detecting the motion of at least some of the marks as the encoder wheel rotates; a probe arm, having a proximal end rigidly attached to the encoder wheel, and having a distal end with a probe tip attached thereto; and coordinate processing means, operatively connected to the sensor, for converting the output of the sensor into a set of cylindrical coordinates representing the position of the probe tip relative to a reference cylindrical coordinate system.

  11. Cosmic Ray Neutron Flux Measurements

    NASA Astrophysics Data System (ADS)

    Dayananda, Mathes

    2009-11-01

    Cosmic rays are high-energetic particles originating from outer space that bombard the upper atmosphere of the Earth. Almost 90% of cosmic ray particles consist of protons, electrons and heavy ions. When these particles hit the Earth's atmosphere, cascade of secondary particles are formed. The most abundant particles reach to the surface of the Earth are muons, electrons and neutrons. In recent years many research groups are looking into potential applications of the effects of cosmic ray radiation at the surface of the Earth [1, 2]. At Georgia State University we are working on a long-term measurement of cosmic ray flux distribution. This study includes the simultaneous measurement of cosmic ray muons, neutrons and gamma particles at the Earth surface in downtown Atlanta. The initial effort is focusing on the correlation studies of the cosmic ray particle flux distribution and the atmospheric weather conditions. In this presentation, I will talk about the development of a cosmic ray detector using liquid scintillator and the preliminary results. [4pt] [1] K.Borozdin, G.Hogan, C.Morris, W.Priedhorsky, A.Saunders, L.Shultz, M.Teasdale, ``Radiographic imaging with cosmic-ray muons'', Nature, Vol.422, p.277, Mar.2003[0pt] [2] Svensmark Henrik, Physical Review 81, 3, (1998)

  12. 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.

  13. 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.

  14. 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...

  15. A unique, accurate LWIR optics measurement system

    NASA Astrophysics Data System (ADS)

    Fantone, Stephen D.; Orband, Daniel G.

    2011-05-01

    A compact low-cost LWIR test station has been developed that provides real time MTF testing of IR optical systems and EO imaging systems. The test station is intended to be operated by a technician and can be used to measure the focal length, blur spot size, distortion, and other metrics of system performance. The challenges and tradeoffs incorporated into this instrumentation will be presented. The test station performs the measurement of an IR lens or optical system's first order quantities (focal length, back focal length) including on and off-axis imaging performance (e.g., MTF, resolution, spot size) under actual test conditions to enable the simulation of their actual use. Also described is the method of attaining the needed accuracies so that derived calculations like focal length (EFL = image shift/tan(theta)) can be performed to the requisite accuracy. The station incorporates a patented video capture technology and measures MTF and blur characteristics using newly available lowcost LWIR cameras. This allows real time determination of the optical system performance enabling faster measurements, higher throughput and lower cost results than scanning systems. Multiple spectral filters are also accommodated within the test stations which facilitate performance evaluation under various spectral conditions.

  16. Modified algesimeter provides accurate depth measurements

    NASA Technical Reports Server (NTRS)

    Turner, D. P.

    1966-01-01

    Algesimeter which incorporates a standard sensory needle with a sensitive micrometer, measures needle point depth penetration in pain tolerance research. This algesimeter provides an inexpensive, precise instrument with assured validity of recordings in those biomedical areas with a requirement for repeated pain detection or ascertaining pain sensitivity.

  17. EMR Gage Would Measure Coal Thickness Accurately

    NASA Technical Reports Server (NTRS)

    King, J. D.; Rollwitz, W. L.

    1982-01-01

    Laboratory tests indicate electron magnetic resonance (EMR) would be effective in measuring thickness of coal overlying rock substrate. In prototype dual-frequency EMR system, Sample is irradiated by two radio frequencies. Signals are mixed, producing sum and difference output frequencies that are detected by receiver. Magnetic field is varied to scan resonant spot through sample. In system designed for field use, electromagnet is U-shaped, so that sample can be adjacent to, rather than inside the probe. Same coil is used for transmitting and receiving.

  18. 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.

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

    PubMed

    Barnes, C; Tibbitts, T; Sager, J; Deitzer, G; Bubenheim, D; Koerner, G; Bugbee, B

    1993-12-01

    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.

  20. Accurate Measurement of Bone Density with QCT

    NASA Technical Reports Server (NTRS)

    Cleek, Tammy M.; Beaupre, Gary S.; Matsubara, Miki; Whalen, Robert T.; Dalton, Bonnie P. (Technical Monitor)

    2002-01-01

    The objective of this study was to determine the accuracy of bone density measurement with a new OCT technology. A phantom was fabricated using two materials, a water-equivalent compound and hydroxyapatite (HA), combined in precise proportions (QRM GrnbH, Germany). The phantom was designed to have the approximate physical size and range in bone density as a human calcaneus, with regions of 0, 50, 100, 200, 400, and 800 mg/cc HA. The phantom was scanned at 80, 120 and 140 KVp with a GE CT/i HiSpeed Advantage scanner. A ring of highly attenuating material (polyvinyl chloride or teflon) was slipped over the phantom to alter the image by introducing non-axi-symmetric beam hardening. Images were corrected with a new OCT technology using an estimate of the effective X-ray beam spectrum to eliminate beam hardening artifacts. The algorithm computes the volume fraction of HA and water-equivalent matrix in each voxel. We found excellent agreement between expected and computed HA volume fractions. Results were insensitive to beam hardening ring material, HA concentration, and scan voltage settings. Data from all 3 voltages with a best fit linear regression are displays.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Accurately measuring MPI broadcasts in a computational grid

    SciTech Connect

    Karonis N T; de Supinski, B R

    1999-05-06

    An MPI library's implementation of broadcast communication can significantly affect the performance of applications built with that library. In order to choose between similar implementations or to evaluate available libraries, accurate measurements of broadcast performance are required. As we demonstrate, existing methods for measuring broadcast performance are either inaccurate or inadequate. Fortunately, we have designed an accurate method for measuring broadcast performance, even in a challenging grid environment. Measuring broadcast performance is not easy. Simply sending one broadcast after another allows them to proceed through the network concurrently, thus resulting in inaccurate per broadcast timings. Existing methods either fail to eliminate this pipelining effect or eliminate it by introducing overheads that are as difficult to measure as the performance of the broadcast itself. This problem becomes even more challenging in grid environments. Latencies a long different links can vary significantly. Thus, an algorithm's performance is difficult to predict from it's communication pattern. Even when accurate pre-diction is possible, the pattern is often unknown. Our method introduces a measurable overhead to eliminate the pipelining effect, regardless of variations in link latencies. choose between different available implementations. Also, accurate and complete measurements could guide use of a given implementation to improve application performance. These choices will become even more important as grid-enabled MPI libraries [6, 7] become more common since bad choices are likely to cost significantly more in grid environments. In short, the distributed processing community needs accurate, succinct and complete measurements of collective communications performance. Since successive collective communications can often proceed concurrently, accurately measuring them is difficult. Some benchmarks use knowledge of the communication algorithm to predict the

  6. Accurate Fiber Length Measurement Using Time-of-Flight Technique

    NASA Astrophysics Data System (ADS)

    Terra, Osama; Hussein, Hatem

    2016-06-01

    Fiber artifacts of very well-measured length are required for the calibration of optical time domain reflectometers (OTDR). In this paper accurate length measurement of different fiber lengths using the time-of-flight technique is performed. A setup is proposed to measure accurately lengths from 1 to 40 km at 1,550 and 1,310 nm using high-speed electro-optic modulator and photodetector. This setup offers traceability to the SI unit of time, the second (and hence to meter by definition), by locking the time interval counter to the Global Positioning System (GPS)-disciplined quartz oscillator. Additionally, the length of a recirculating loop artifact is measured and compared with the measurement made for the same fiber by the National Physical Laboratory of United Kingdom (NPL). Finally, a method is proposed to relatively correct the fiber refractive index to allow accurate fiber length measurement.

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. Subcanopy Flux Measurements in Forest Ecosystems

    NASA Astrophysics Data System (ADS)

    Wolf, S.; Paul-Limoges, E.; Baldocchi, D. D.

    2015-12-01

    Eddy-covariance measurements of carbon dioxide, water vapour and energy provide direct evidence for the biosphere-atmosphere exchange at the ecosystem scale. Such continuous measurements are typically performed in the atmospheric surface layer above the canopy and integrate fluxes over the entire ecosystem within the footprint. Forest ecosystems, however, have complex vertical structures composed of several layers with different functional properties that are represented to a limited extend by above canopy measurements. Concurrent eddy-covariance measurements below canopy (subcanopy) can provide valuable insights on (1) understory processes, (2) their contributions to total ecosystem fluxes, and (3) the partitioning of component fluxes. Accordingly, there is a large potential for including standardized subcanopy forest measurements into large-scale measurement networks such as FLUXNET. However, our understanding of the performance and limitations for such measurements is still very limited. To gain a better understanding of subcanopy measurements, we conducted (I) a survey across FLUXNET on their availability, and (II) a literature review on published subcanopy measurements. Subsequently, we are preparing a standardized synthesis dataset on subcanopy measurements within FLUXNET. We will present the results from our survey, summarize the current process understanding, and discuss research priorities for concurrent below and above canopy eddy-covariance measurements.

  12. 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.

  13. Denoising surface renewal flux density measurements

    NASA Astrophysics Data System (ADS)

    Shapland, T.; Paw U, K.; Snyder, R. L.; McElrone, A.; Calderon Orellana, A.; Williams, L.

    2012-12-01

    When combined with net radiation and ground heat flux density measurements, surface renewal sensible heat flux density measurements can be used to obtain latent heat flux density, and therefore evapotranspiration, via the energy balance residual. Surface renewal is based on analyzing the energy and mass budget of air parcels that interact with plant canopies. The air parcels are manifested as ramp-like shapes in turbulent scalar time series data, and the amplitude and period of the ramps are used to calculate the flux densities. The root mean square error between calibrated surface renewal and eddy covariance is generally twice the root mean square error between two eddy covariance systems. In this presentation, we evaluate the efficacy of various methods for reducing the random error in surface renewal sensible heat flux density measurements. These methods include signal de-spiking, conventional low-pass filtering, wavelet-based filtering, ramp signal to noise thresholds, ramp period scaling, novel rearrangements of the Van Atta procedure (Arch Mech 29:161-171, 1977) for resolving the ramp amplitude and ramp period, sensor replication, and optimization of sensor placement.

  14. Regional airborne flux measurements in Europe

    NASA Astrophysics Data System (ADS)

    Gioli, B.; Miglietta, F.; Vaccari, F. P.; Zaldei, A.; Hutjes, R. W. A.

    2003-04-01

    The problem of identifying the spatial and temporal distribution of sources and sinks of atmospheric CO2 is the subject of considerable scientific and political debate. Even if it is now possible to estimate within reasonable accuracy the sink strength of European forests at the local scale, difficulties still exist in determining the partitioning of the sinks at the global and regional scales. The aim of the EU-project RECAB (Regional Assessment of the Carbon Balance in Europe) that is coordinated by Alterra, Wageningen (NL), is to bridge the gap between local scale flux measurements and continental scale inversion models by a generic modelling effort and measurement program, focussing on a limited number of selected regions in Europe for which previous measurements exists. This required the establishment of a European facility for airborne measurement of surface fluxes of CO2 at very low altitude, and a research aircraft capable of performing airborne eddy covariance measurements has been acquired by this project and used on several occasions at the different RECAB sites. The aircraft is the italian Sky Arrows ERA (Environmental Research Aircraft) equipped with the NOAA/ARA Mobile Flux Platform (MFP), and a commercial open-path infrared gas analyser. Airborne eddy covariance measurements were made from June 2001 onwards in Southern Spain near Valencia (June and December 2001), in Central Germany near Jena (July 2001), in Sweden near Uppsala (August 2001), in The Netherlands near Wageningen (January and July 2002) and in Italy near Rome (June 2002). Flux towers were present at each site to provide a validation of airborne eddy covariance measurements. This contribution reports some validation results based on the comparison between airborne and ground based flux measurements and some regional scale results for different locations and different seasons, in a wide range of meteorological and ecological settings.

  15. Accurate Insertion Loss Measurements of the Juno Patch Array Antennas

    NASA Technical Reports Server (NTRS)

    Chamberlain, Neil; Chen, Jacqueline; Hodges, Richard; Demas, John

    2010-01-01

    This paper describes two independent methods for estimating the insertion loss of patch array antennas that were developed for the Juno Microwave Radiometer instrument. One method is based principally on pattern measurements while the other method is based solely on network analyzer measurements. The methods are accurate to within 0.1 dB for the measured antennas and show good agreement (to within 0.1dB) of separate radiometric measurements.

  16. Accurately measuring dynamic coefficient of friction in ultraform finishing

    NASA Astrophysics Data System (ADS)

    Briggs, Dennis; Echaves, Samantha; Pidgeon, Brendan; Travis, Nathan; Ellis, Jonathan D.

    2013-09-01

    UltraForm Finishing (UFF) is a deterministic sub-aperture computer numerically controlled grinding and polishing platform designed by OptiPro Systems. UFF is used to grind and polish a variety of optics from simple spherical to fully freeform, and numerous materials from glasses to optical ceramics. The UFF system consists of an abrasive belt around a compliant wheel that rotates and contacts the part to remove material. This work aims to accurately measure the dynamic coefficient of friction (μ), how it changes as a function of belt wear, and how this ultimately affects material removal rates. The coefficient of friction has been examined in terms of contact mechanics and Preston's equation to determine accurate material removal rates. By accurately predicting changes in μ, polishing iterations can be more accurately predicted, reducing the total number of iterations required to meet specifications. We have established an experimental apparatus that can accurately measure μ by measuring triaxial forces during translating loading conditions or while manufacturing the removal spots used to calculate material removal rates. Using this system, we will demonstrate μ measurements for UFF belts during different states of their lifecycle and assess the material removal function from spot diagrams as a function of wear. Ultimately, we will use this system for qualifying belt-wheel-material combinations to develop a spot-morphing model to better predict instantaneous material removal functions.

  17. 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.

  18. Estimating the gas transfer velocity: a prerequisite for more accurate and higher resolution GHG fluxes (lower Aare River, Switzerland)

    NASA Astrophysics Data System (ADS)

    Sollberger, S.; Perez, K.; Schubert, C. J.; Eugster, W.; Wehrli, B.; Del Sontro, T.

    2013-12-01

    Currently, carbon dioxide (CO2) and methane (CH4) emissions from lakes, reservoirs and rivers are readily investigated due to the global warming potential of those gases and the role these inland waters play in the carbon cycle. However, there is a lack of high spatiotemporally-resolved emission estimates, and how to accurately assess the gas transfer velocity (K) remains controversial. In anthropogenically-impacted systems where run-of-river reservoirs disrupt the flow of sediments by increasing the erosion and load accumulation patterns, the resulting production of carbonic greenhouse gases (GH-C) is likely to be enhanced. The GH-C flux is thus counteracting the terrestrial carbon sink in these environments that act as net carbon emitters. The aim of this project was to determine the GH-C emissions from a medium-sized river heavily impacted by several impoundments and channelization through a densely-populated region of Switzerland. Estimating gas emission from rivers is not trivial and recently several models have been put forth to do so; therefore a second goal of this project was to compare the river emission models available with direct measurements. Finally, we further validated the modeled fluxes by using a combined approach with water sampling, chamber measurements, and highly temporal GH-C monitoring using an equilibrator. We conducted monthly surveys along the 120 km of the lower Aare River where we sampled for dissolved CH4 (';manual' sampling) at a 5-km sampling resolution, and measured gas emissions directly with chambers over a 35 km section. We calculated fluxes (F) via the boundary layer equation (F=K×(Cw-Ceq)) that uses the water-air GH-C concentration (C) gradient (Cw-Ceq) and K, which is the most sensitive parameter. K was estimated using 11 different models found in the literature with varying dependencies on: river hydrology (n=7), wind (2), heat exchange (1), and river width (1). We found that chamber fluxes were always higher than boundary

  19. Accurate aircraft wind measurements using the global positioning system (GPS)

    SciTech Connect

    Dobosy, R.J.; Crawford, T.L., McMillen, R.T., Dumas, E.J.

    1996-11-01

    High accuracy measurements of the spatial distribution of wind speed are required in the study of turbulent exchange between the atmosphere and the earth. The use of a differential global positioning system (GPS) to determine the sensor velocity vector component of wind speed is discussed in this paper. The results of noise and rocking testing are summarized, and fluxes obtained from the GPS-based methods are compared to those measured from systems on towers and airplanes. The GPS-based methods provided usable measurements that compared well with tower and aircraft data at a significantly lower cost. 21 refs., 1 fig., 2 tabs.

  20. Interactive Database of Pulsar Flux Density Measurements

    NASA Astrophysics Data System (ADS)

    Koralewska, O.; Krzeszowski, K.; Kijak, J.; Lewandowski, W.

    2012-12-01

    The number of astronomical observations is steadily growing, giving rise to the need of cataloguing the obtained results. There are a lot of databases, created to store different types of data and serve a variety of purposes, e. g. databases providing basic data for astronomical objects (SIMBAD Astronomical Database), databases devoted to one type of astronomical object (ATNF Pulsar Database) or to a set of values of the specific parameter (Lorimer 1995 - database of flux density measurements for 280 pulsars on the frequencies up to 1606 MHz), etc. We found that creating an online database of pulsar flux measurements, provided with facilities for plotting diagrams and histograms, calculating mean values for a chosen set of data, filtering parameter values and adding new measurements by the registered users, could be useful in further studies on pulsar spectra.

  1. Monitoring circuit accurately measures movement of solenoid valve

    NASA Technical Reports Server (NTRS)

    Gillett, J. D.

    1966-01-01

    Solenoid operated valve in a control system powered by direct current issued to accurately measure the valve travel. This system is currently in operation with a 28-vdc power system used for control of fluids in liquid rocket motor test facilities.

  2. Instrument accurately measures small temperature changes on test surface

    NASA Technical Reports Server (NTRS)

    Harvey, W. D.; Miller, H. B.

    1966-01-01

    Calorimeter apparatus accurately measures very small temperature rises on a test surface subjected to aerodynamic heating. A continuous thin sheet of a sensing material is attached to a base support plate through which a series of holes of known diameter have been drilled for attaching thermocouples to the material.

  3. A Simple and Accurate Method for Measuring Enzyme Activity.

    ERIC Educational Resources Information Center

    Yip, Din-Yan

    1997-01-01

    Presents methods commonly used for investigating enzyme activity using catalase and presents a new method for measuring catalase activity that is more reliable and accurate. Provides results that are readily reproduced and quantified. Can also be used for investigations of enzyme properties such as the effects of temperature, pH, inhibitors,…

  4. Device accurately measures and records low gas-flow rates

    NASA Technical Reports Server (NTRS)

    Branum, L. W.

    1966-01-01

    Free-floating piston in a vertical column accurately measures and records low gas-flow rates. The system may be calibrated, using an adjustable flow-rate gas supply, a low pressure gage, and a sequence recorder. From the calibration rates, a nomograph may be made for easy reduction. Temperature correction may be added for further accuracy.

  5. Toward more accurate loss tangent measurements in reentrant cavities

    SciTech Connect

    Moyer, R. D.

    1980-05-01

    Karpova has described an absolute method for measurement of dielectric properties of a solid in a coaxial reentrant cavity. His cavity resonance equation yields very accurate results for dielectric constants. However, he presented only approximate expressions for the loss tangent. This report presents more exact expressions for that quantity and summarizes some experimental results.

  6. Calibrating X-ray Imaging Devices for Accurate Intensity Measurement

    SciTech Connect

    Haugh, M. J.

    2011-07-28

    The purpose of the project presented is to develop methods to accurately calibrate X-ray imaging devices. The approach was to develop X-ray source systems suitable for this endeavor and to develop methods to calibrate solid state detectors to measure source intensity. NSTec X-ray sources used for the absolute calibration of cameras are described, as well as the method of calibrating the source by calibrating the detectors. The work resulted in calibration measurements for several types of X-ray cameras. X-ray camera calibration measured efficiency and efficiency variation over the CCD. Camera types calibrated include: CCD, CID, back thinned (back illuminated), front illuminated.

  7. Calibration Techniques for Accurate Measurements by Underwater Camera Systems.

    PubMed

    Shortis, Mark

    2015-12-07

    Calibration of a camera system is essential to ensure that image measurements result in accurate estimates of locations and dimensions within the object space. In the underwater environment, the calibration must implicitly or explicitly model and compensate for the refractive effects of waterproof housings and the water medium. This paper reviews the different approaches to the calibration of underwater camera systems in theoretical and practical terms. The accuracy, reliability, validation and stability of underwater camera system calibration are also discussed. Samples of results from published reports are provided to demonstrate the range of possible accuracies for the measurements produced by underwater camera systems.

  8. Calibration Techniques for Accurate Measurements by Underwater Camera Systems

    PubMed Central

    Shortis, Mark

    2015-01-01

    Calibration of a camera system is essential to ensure that image measurements result in accurate estimates of locations and dimensions within the object space. In the underwater environment, the calibration must implicitly or explicitly model and compensate for the refractive effects of waterproof housings and the water medium. This paper reviews the different approaches to the calibration of underwater camera systems in theoretical and practical terms. The accuracy, reliability, validation and stability of underwater camera system calibration are also discussed. Samples of results from published reports are provided to demonstrate the range of possible accuracies for the measurements produced by underwater camera systems. PMID:26690172

  9. Calibration Techniques for Accurate Measurements by Underwater Camera Systems.

    PubMed

    Shortis, Mark

    2015-01-01

    Calibration of a camera system is essential to ensure that image measurements result in accurate estimates of locations and dimensions within the object space. In the underwater environment, the calibration must implicitly or explicitly model and compensate for the refractive effects of waterproof housings and the water medium. This paper reviews the different approaches to the calibration of underwater camera systems in theoretical and practical terms. The accuracy, reliability, validation and stability of underwater camera system calibration are also discussed. Samples of results from published reports are provided to demonstrate the range of possible accuracies for the measurements produced by underwater camera systems. PMID:26690172

  10. A method for accurate temperature measurement using infrared thermal camera.

    PubMed

    Tokunaga, Tomoharu; Narushima, Takashi; Yonezawa, Tetsu; Sudo, Takayuki; Okubo, Shuichi; Komatsubara, Shigeyuki; Sasaki, Katsuhiro; Yamamoto, Takahisa

    2012-08-01

    The temperature distribution on a centre-holed thin foil of molybdenum, used as a sample and heated using a sample-heating holder for electron microscopy, was measured using an infrared thermal camera. The temperature on the heated foil area located near the heating stage of the heating holder is almost equal to the temperature on the heating stage. However, during the measurement of the temperature at the edge of the hole of the foil located farthest from the heating stage, a drop in temperature should be taken into consideration; however, so far, no method has been developed to locally measure the temperature distribution on the heated sample. In this study, a method for the accurate measurement of temperature distribution on heated samples for electron microscopy is discussed.

  11. 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

  12. Accurate measurements of dynamics and reproducibility in small genetic networks

    PubMed Central

    Dubuis, Julien O; Samanta, Reba; Gregor, Thomas

    2013-01-01

    Quantification of gene expression has become a central tool for understanding genetic networks. In many systems, the only viable way to measure protein levels is by immunofluorescence, which is notorious for its limited accuracy. Using the early Drosophila embryo as an example, we show that careful identification and control of experimental error allows for highly accurate gene expression measurements. We generated antibodies in different host species, allowing for simultaneous staining of four Drosophila gap genes in individual embryos. Careful error analysis of hundreds of expression profiles reveals that less than ∼20% of the observed embryo-to-embryo fluctuations stem from experimental error. These measurements make it possible to extract not only very accurate mean gene expression profiles but also their naturally occurring fluctuations of biological origin and corresponding cross-correlations. We use this analysis to extract gap gene profile dynamics with ∼1 min accuracy. The combination of these new measurements and analysis techniques reveals a twofold increase in profile reproducibility owing to a collective network dynamics that relays positional accuracy from the maternal gradients to the pair-rule genes. PMID:23340845

  13. Accurate Runout Measurement for HDD Spinning Motors and Disks

    NASA Astrophysics Data System (ADS)

    Jiang, Quan; Bi, Chao; Lin, Song

    As hard disk drive (HDD) areal density increases, its track width becomes smaller and smaller and so is non-repeatable runout. HDD industry needs more accurate and better resolution runout measurements of spinning spindle motors and media platters in both axial and radial directions. This paper introduces a new system how to precisely measure the runout of HDD spinning disks and motors through synchronously acquiring the rotor position signal and the displacements in axial or radial directions. In order to minimize the synchronizing error between the rotor position and the displacement signal, a high resolution counter is adopted instead of the conventional phase-lock loop method. With Laser Doppler Vibrometer and proper signal processing, the proposed runout system can precisely measure the runout of the HDD spinning disks and motors with 1 nm resolution and 0.2% accuracy with a proper sampling rate. It can provide an effective and accurate means to measure the runout of high areal density HDDs, in particular the next generation HDDs, such as, pattern media HDDs and HAMR HDDs.

  14. Measurement of Atomic-Oxygen Flux Distribution

    NASA Astrophysics Data System (ADS)

    Hisashiba, Takuya; Kuroda, Kazutaka; Masui, Hirokazu; Iwata, Minoru; Toyoda, Kazuhiro; Cho, Mengu

    Since material surfaces on the outside of spacecraft are exposed directly to the space environment, material having high tolerance to atomic oxygen, ultraviolet rays and radiation are preferred for long time spacecraft operation. In order to examine the influence of atomic oxygen (AO) on space grade materials, an atomic oxygen simulation chamber was developed. A system was developed that generates AO using a laser detonation method. A CO2 gas laser (5 J) irradiates the oxygen gas in a vacuum chamber (2 MPa) to dissociate the molecular oxygen into atomic. The velocity of AO can be controlled based on the timing between the laser and the gas pulse valve that injects oxygen gas into the chamber. The AO velocity generated by this system is measured using a QMASS (Quadruple Mass Spectrometer) and found to be 8 km/s. It was necessary to measure the AO flux distribution in the chamber at the location where the material samples are exposed to AO. The AO flux distribution was evaluated by measuring the mass gain on a QCM (QuartzCrystal Microbalance) coated with a silver film upon exposure to the AO.

  15. Precise and accurate isotopic measurements using multiple-collector ICPMS

    NASA Astrophysics Data System (ADS)

    Albarède, F.; Telouk, Philippe; Blichert-Toft, Janne; Boyet, Maud; Agranier, Arnaud; Nelson, Bruce

    2004-06-01

    New techniques of isotopic measurements by a new generation of mass spectrometers equipped with an inductively-coupled-plasma source, a magnetic mass filter, and multiple collection (MC-ICPMS) are quickly developing. These techniques are valuable because of (1) the ability of ICP sources to ionize virtually every element in the periodic table, and (2) the large sample throughout. However, because of the complex trajectories of multiple ion beams produced in the plasma source whether from the same or different elements, the acquisition of precise and accurate isotopic data with this type of instrument still requires a good understanding of instrumental fractionation processes, both mass-dependent and mass-independent. Although physical processes responsible for the instrumental mass bias are still to be understood more fully, we here present a theoretical framework that allows for most of the analytical limitations to high precision and accuracy to be overcome. After a presentation of unifying phenomenological theory for mass-dependent fractionation in mass spectrometers, we show how this theory accounts for the techniques of standard bracketing and of isotopic normalization by a ratio of either the same or a different element, such as the use of Tl to correct mass bias on Pb. Accuracy is discussed with reference to the concept of cup efficiencies. Although these can be simply calibrated by analyzing standards, we derive a straightforward, very general method to calculate accurate isotopic ratios from dynamic measurements. In this study, we successfully applied the dynamic method to Nd and Pb as examples. We confirm that the assumption of identical mass bias for neighboring elements (notably Pb and Tl, and Yb and Lu) is both unnecessary and incorrect. We further discuss the dangers of straightforward standard-sample bracketing when chemical purification of the element to be analyzed is imperfect. Pooling runs to improve precision is acceptable provided the pooled

  16. Accurate measurement method for tube's endpoints based on machine vision

    NASA Astrophysics Data System (ADS)

    Liu, Shaoli; Jin, Peng; Liu, Jianhua; Wang, Xiao; Sun, Peng

    2016-08-01

    Tubes are used widely in aerospace vehicles, and their accurate assembly can directly affect the assembling reliability and the quality of products. It is important to measure the processed tube's endpoints and then fix any geometric errors correspondingly. However, the traditional tube inspection method is time-consuming and complex operations. Therefore, a new measurement method for a tube's endpoints based on machine vision is proposed. First, reflected light on tube's surface can be removed by using photometric linearization. Then, based on the optimization model for the tube's endpoint measurements and the principle of stereo matching, the global coordinates and the relative distance of the tube's endpoint are obtained. To confirm the feasibility, 11 tubes are processed to remove the reflected light and then the endpoint's positions of tubes are measured. The experiment results show that the measurement repeatability accuracy is 0.167 mm, and the absolute accuracy is 0.328 mm. The measurement takes less than 1 min. The proposed method based on machine vision can measure the tube's endpoints without any surface treatment or any tools and can realize on line measurement.

  17. Accurate frequency noise measurement of free-running lasers.

    PubMed

    Schiemangk, Max; Spiessberger, Stefan; Wicht, Andreas; Erbert, Götz; Tränkle, Günther; Peters, Achim

    2014-10-20

    We present a simple method to accurately measure the frequency noise power spectrum of lasers. It relies on creating the beat note between two lasers, capturing the corresponding signal in the time domain, and appropriately postprocessing the data to derive the frequency noise power spectrum. In contrast to methods already established, it does not require stabilization of the laser to an optical reference, i.e., a second laser, to an optical cavity or to an atomic transition. It further omits a frequency discriminator and hence avoids bandwidth limitation and nonlinearity effects common to high-resolution frequency discriminators.

  18. Multi-spectra Cosmic Ray Flux Measurement

    NASA Astrophysics Data System (ADS)

    He, Xiaochun; Dayananda, Mathes

    2010-02-01

    The Earth's upper atmosphere is constantly bombarded by rain of charged particles known as primary cosmic rays. These primary cosmic rays will collide with the atmospheric molecules and create extensive secondary particles which shower downward to the surface of the Earth. In recent years, a few studies have been done regarding to the applications of the cosmic ray measurements and the correlations between the Earth's climate conditions and the cosmic ray fluxes [1,2,3]. Most of the particles, which reach to the surface of the Earth, are muons together with a small percentage of electrons, gammas, neutrons, etc. At Georgia State University, multiple cosmic ray particle detectors have been constructed to measure the fluxes and energy distributions of the secondary cosmic ray particles. In this presentation, we will briefly describe these prototype detectors and show the preliminary test results. Reference: [1] K.Borozdin, G.Hogan, C.Morris, W.Priedhorsky, A.Saunders, L.Shultz, M.Teasdale, Nature, Vol.422, 277 (2003). [2] L.V. Egorova, V. Ya Vovk, O.A. Troshichev, Journal of Atmospheric and Terrestrial Physics 62, 955-966 (2000). [3] Henrik Svensmark, Phy. Rev. Lett. 81, 5027 (1998). )

  19. Technological Basis and Scientific Returns for Absolutely Accurate Measurements

    NASA Astrophysics Data System (ADS)

    Dykema, J. A.; Anderson, J.

    2011-12-01

    The 2006 NRC Decadal Survey fostered a new appreciation for societal objectives as a driving motivation for Earth science. Many high-priority societal objectives are dependent on predictions of weather and climate. These predictions are based on numerical models, which derive from approximate representations of well-founded physics and chemistry on space and timescales appropriate to global and regional prediction. These laws of chemistry and physics in turn have a well-defined quantitative relationship with physical measurement units, provided these measurement units are linked to international measurement standards that are the foundation of contemporary measurement science and standards for engineering and commerce. Without this linkage, measurements have an ambiguous relationship to scientific principles that introduces avoidable uncertainty in analyses, predictions, and improved understanding of the Earth system. Since the improvement of climate and weather prediction is fundamentally dependent on the improvement of the representation of physical processes, measurement systems that reduce the ambiguity between physical truth and observations represent an essential component of a national strategy for understanding and living with the Earth system. This paper examines the technological basis and potential science returns of sensors that make measurements that are quantitatively tied on-orbit to international measurement standards, and thus testable to systematic errors. This measurement strategy provides several distinct benefits. First, because of the quantitative relationship between these international measurement standards and fundamental physical constants, measurements of this type accurately capture the true physical and chemical behavior of the climate system and are not subject to adjustment due to excluded measurement physics or instrumental artifacts. In addition, such measurements can be reproduced by scientists anywhere in the world, at any time

  20. Accurate Sound Velocity Measurement in Ocean Near-Surface Layer

    NASA Astrophysics Data System (ADS)

    Lizarralde, D.; Xu, B. L.

    2015-12-01

    Accurate sound velocity measurement is essential in oceanography because sound is the only wave that can propagate in sea water. Due to its measuring difficulties, sound velocity is often not measured directly but instead calculated from water temperature, salinity, and depth, which are much easier to obtain. This research develops a new method to directly measure the sound velocity in the ocean's near-surface layer using multi-channel seismic (MCS) hydrophones. This system consists of a device to make a sound pulse and a long cable with hundreds of hydrophones to record the sound. The distance between the source and each receiver is the offset. The time it takes the pulse to arrive to each receiver is the travel time.The errors of measuring offset and travel time will affect the accuracy of sound velocity if we calculated with just one offset and one travel time. However, by analyzing the direct arrival signal from hundreds of receivers, the velocity can be determined as the slope of a straight line in the travel time-offset graph. The errors in distance and time measurement result in only an up or down shift of the line and do not affect the slope. This research uses MCS data of survey MGL1408 obtained from the Marine Geoscience Data System and processed with Seismic Unix. The sound velocity can be directly measured to an accuracy of less than 1m/s. The included graph shows the directly measured velocity verses the calculated velocity along 100km across the Mid-Atlantic continental margin. The directly measured velocity shows a good coherence to the velocity computed from temperature and salinity. In addition, the fine variations in the sound velocity can be observed, which is hardly seen from the calculated velocity. Using this methodology, both large area acquisition and fine resolution can be achieved. This directly measured sound velocity will be a new and powerful tool in oceanography.

  1. 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.

  2. A spectroscopic transfer standard for accurate atmospheric CO measurements

    NASA Astrophysics Data System (ADS)

    Nwaboh, Javis A.; Li, Gang; Serdyukov, Anton; Werhahn, Olav; Ebert, Volker

    2016-04-01

    Atmospheric carbon monoxide (CO) is a precursor of essential climate variables and has an indirect effect for enhancing global warming. Accurate and reliable measurements of atmospheric CO concentration are becoming indispensable. WMO-GAW reports states a compatibility goal of ±2 ppb for atmospheric CO concentration measurements. Therefore, the EMRP-HIGHGAS (European metrology research program - high-impact greenhouse gases) project aims at developing spectroscopic transfer standards for CO concentration measurements to meet this goal. A spectroscopic transfer standard would provide results that are directly traceable to the SI, can be very useful for calibration of devices operating in the field, and could complement classical gas standards in the field where calibration gas mixtures in bottles often are not accurate, available or stable enough [1][2]. Here, we present our new direct tunable diode laser absorption spectroscopy (dTDLAS) sensor capable of performing absolute ("calibration free") CO concentration measurements, and being operated as a spectroscopic transfer standard. To achieve the compatibility goal stated by WMO for CO concentration measurements and ensure the traceability of the final concentration results, traceable spectral line data especially line intensities with appropriate uncertainties are needed. Therefore, we utilize our new high-resolution Fourier-transform infrared (FTIR) spectroscopy CO line data for the 2-0 band, with significantly reduced uncertainties, for the dTDLAS data evaluation. Further, we demonstrate the capability of our sensor for atmospheric CO measurements, discuss uncertainty calculation following the guide to the expression of uncertainty in measurement (GUM) principles and show that CO concentrations derived using the sensor, based on the TILSAM (traceable infrared laser spectroscopic amount fraction measurement) method, are in excellent agreement with gravimetric values. Acknowledgement Parts of this work have been

  3. 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

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

    NASA Astrophysics Data System (ADS)

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

    2005-12-01

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

  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. Accurate measurement of RF exposure from emerging wireless communication systems

    NASA Astrophysics Data System (ADS)

    Letertre, Thierry; Monebhurrun, Vikass; Toffano, Zeno

    2013-04-01

    Isotropic broadband probes or spectrum analyzers (SAs) may be used for the measurement of rapidly varying electromagnetic fields generated by emerging wireless communication systems. In this paper this problematic is investigated by comparing the responses measured by two different isotropic broadband probes typically used to perform electric field (E-field) evaluations. The broadband probes are submitted to signals with variable duty cycles (DC) and crest factors (CF) either with or without Orthogonal Frequency Division Multiplexing (OFDM) modulation but with the same root-mean-square (RMS) power. The two probes do not provide accurate enough results for deterministic signals such as Worldwide Interoperability for Microwave Access (WIMAX) or Long Term Evolution (LTE) as well as for non-deterministic signals such as Wireless Fidelity (WiFi). The legacy measurement protocols should be adapted to cope for the emerging wireless communication technologies based on the OFDM modulation scheme. This is not easily achieved except when the statistics of the RF emission are well known. In this case the measurement errors are shown to be systematic and a correction factor or calibration can be applied to obtain a good approximation of the total RMS power.

  8. Accurate measure by weight of liquids in industry

    SciTech Connect

    Muller, M.R.

    1992-12-12

    This research's focus was to build a prototype of a computerized liquid dispensing system. This liquid metering system is based on the concept of altering the representative volume to account for temperature changes in the liquid to be dispensed. This is actualized by using a measuring tank and a temperature compensating displacement plunger. By constantly monitoring the temperature of the liquid, the plunger can be used to increase or decrease the specified volume to more accurately dispense liquid with a specified mass. In order to put the device being developed into proper engineering perspective, an extensive literature review was undertaken on all areas of industrial metering of liquids with an emphasis on gravimetric methods.

  9. Accurate measure by weight of liquids in industry. Final report

    SciTech Connect

    Muller, M.R.

    1992-12-12

    This research`s focus was to build a prototype of a computerized liquid dispensing system. This liquid metering system is based on the concept of altering the representative volume to account for temperature changes in the liquid to be dispensed. This is actualized by using a measuring tank and a temperature compensating displacement plunger. By constantly monitoring the temperature of the liquid, the plunger can be used to increase or decrease the specified volume to more accurately dispense liquid with a specified mass. In order to put the device being developed into proper engineering perspective, an extensive literature review was undertaken on all areas of industrial metering of liquids with an emphasis on gravimetric methods.

  10. Electron Microprobe Analysis Techniques for Accurate Measurements of Apatite

    NASA Astrophysics Data System (ADS)

    Goldoff, B. A.; Webster, J. D.; Harlov, D. E.

    2010-12-01

    Apatite [Ca5(PO4)3(F, Cl, OH)] is a ubiquitous accessory mineral in igneous, metamorphic, and sedimentary rocks. The mineral contains halogens and hydroxyl ions, which can provide important constraints on fugacities of volatile components in fluids and other phases in igneous and metamorphic environments in which apatite has equilibrated. Accurate measurements of these components in apatite are therefore necessary. Analyzing apatite by electron microprobe (EMPA), which is a commonly used geochemical analytical technique, has often been found to be problematic and previous studies have identified sources of error. For example, Stormer et al. (1993) demonstrated that the orientation of an apatite grain relative to the incident electron beam could significantly affect the concentration results. In this study, a variety of alternative EMPA operating conditions for apatite analysis were investigated: a range of electron beam settings, count times, crystal grain orientations, and calibration standards were tested. Twenty synthetic anhydrous apatite samples that span the fluorapatite-chlorapatite solid solution series, and whose halogen concentrations were determined by wet chemistry, were analyzed. Accurate measurements of these samples were obtained with many EMPA techniques. One effective method includes setting a static electron beam to 10-15nA, 15kV, and 10 microns in diameter. Additionally, the apatite sample is oriented with the crystal’s c-axis parallel to the slide surface and the count times are moderate. Importantly, the F and Cl EMPA concentrations are in extremely good agreement with the wet-chemical data. We also present EMPA operating conditions and techniques that are problematic and should be avoided. J.C. Stormer, Jr. et al., Am. Mineral. 78 (1993) 641-648.

  11. Radio Astronomers Set New Standard for Accurate Cosmic Distance Measurement

    NASA Astrophysics Data System (ADS)

    1999-06-01

    A team of radio astronomers has used the National Science Foundation's Very Long Baseline Array (VLBA) to make the most accurate measurement ever made of the distance to a faraway galaxy. Their direct measurement calls into question the precision of distance determinations made by other techniques, including those announced last week by a team using the Hubble Space Telescope. The radio astronomers measured a distance of 23.5 million light-years to a galaxy called NGC 4258 in Ursa Major. "Ours is a direct measurement, using geometry, and is independent of all other methods of determining cosmic distances," said Jim Herrnstein, of the National Radio Astronomy Observatory (NRAO) in Socorro, NM. The team says their measurement is accurate to within less than a million light-years, or four percent. The galaxy is also known as Messier 106 and is visible with amateur telescopes. Herrnstein, along with James Moran and Lincoln Greenhill of the Harvard- Smithsonian Center for Astrophysics; Phillip Diamond, of the Merlin radio telescope facility at Jodrell Bank and the University of Manchester in England; Makato Inoue and Naomasa Nakai of Japan's Nobeyama Radio Observatory; Mikato Miyoshi of Japan's National Astronomical Observatory; Christian Henkel of Germany's Max Planck Institute for Radio Astronomy; and Adam Riess of the University of California at Berkeley, announced their findings at the American Astronomical Society's meeting in Chicago. "This is an incredible achievement to measure the distance to another galaxy with this precision," said Miller Goss, NRAO's Director of VLA/VLBA Operations. "This is the first time such a great distance has been measured this accurately. It took painstaking work on the part of the observing team, and it took a radio telescope the size of the Earth -- the VLBA -- to make it possible," Goss said. "Astronomers have sought to determine the Hubble Constant, the rate of expansion of the universe, for decades. This will in turn lead to an

  12. Absolute flux measurements for swift atoms

    NASA Technical Reports Server (NTRS)

    Fink, M.; Kohl, D. A.; Keto, J. W.; Antoniewicz, P.

    1987-01-01

    While a torsion balance in vacuum can easily measure the momentum transfer from a gas beam impinging on a surface attached to the balance, this measurement depends on the accommodation coefficients of the atoms with the surface and the distribution of the recoil. A torsion balance is described for making absolute flux measurements independent of recoil effects. The torsion balance is a conventional taut suspension wire design and the Young modulus of the wire determines the relationship between the displacement and the applied torque. A compensating magnetic field is applied to maintain zero displacement and provide critical damping. The unique feature is to couple the impinging gas beam to the torsion balance via a Wood's horn, i.e., a thin wall tube with a gradual 90 deg bend. Just as light is trapped in a Wood's horn by specular reflection from the curved surfaces, the gas beam diffuses through the tube. Instead of trapping the beam, the end of the tube is open so that the atoms exit the tube at 90 deg to their original direction. Therefore, all of the forward momentum of the gas beam is transferred to the torsion balance independent of the angle of reflection from the surfaces inside the tube.

  13. Accurate measurement of liquid transport through nanoscale conduits

    PubMed Central

    Alibakhshi, Mohammad Amin; Xie, Quan; Li, Yinxiao; Duan, Chuanhua

    2016-01-01

    Nanoscale liquid transport governs the behaviour of a wide range of nanofluidic systems, yet remains poorly characterized and understood due to the enormous hydraulic resistance associated with the nanoconfinement and the resulting minuscule flow rates in such systems. To overcome this problem, here we present a new measurement technique based on capillary flow and a novel hybrid nanochannel design and use it to measure water transport through single 2-D hydrophilic silica nanochannels with heights down to 7 nm. Our results show that silica nanochannels exhibit increased mass flow resistance compared to the classical hydrodynamics prediction. This difference increases with decreasing channel height and reaches 45% in the case of 7 nm nanochannels. This resistance increase is attributed to the formation of a 7-angstrom-thick stagnant hydration layer on the hydrophilic surfaces. By avoiding use of any pressure and flow sensors or any theoretical estimations the hybrid nanochannel scheme enables facile and precise flow measurement through single nanochannels, nanotubes, or nanoporous media and opens the prospect for accurate characterization of both hydrophilic and hydrophobic nanofluidic systems. PMID:27112404

  14. Slim hole MWD tool accurately measures downhole annular pressure

    SciTech Connect

    Burban, B.; Delahaye, T. )

    1994-02-14

    Measurement-while-drilling of downhole pressure accurately determines annular pressure losses from circulation and drillstring rotation and helps monitor swab and surge pressures during tripping. In early 1993, two slim-hole wells (3.4 in. and 3 in. diameter) were drilled with continuous real-time electromagnetic wave transmission of downhole temperature and annular pressure. The data were obtained during all stages of the drilling operation and proved useful for operations personnel. The use of real-time measurements demonstrated the characteristic hydraulic effects of pressure surges induced by drillstring rotation in the small slim-hole annulus under field conditions. The interest in this information is not restricted to the slim-hole geometry. Monitoring or estimating downhole pressure is a key element for drilling operations. Except in special cases, no real-time measurements of downhole annular pressure during drilling and tripping have been used on an operational basis. The hydraulic effects are significant in conventional-geometry wells (3 1/2-in. drill pipe in a 6-in. hole). This paper describes the tool and the results from the field test.

  15. Accurate measurement of liquid transport through nanoscale conduits

    NASA Astrophysics Data System (ADS)

    Alibakhshi, Mohammad Amin; Xie, Quan; Li, Yinxiao; Duan, Chuanhua

    2016-04-01

    Nanoscale liquid transport governs the behaviour of a wide range of nanofluidic systems, yet remains poorly characterized and understood due to the enormous hydraulic resistance associated with the nanoconfinement and the resulting minuscule flow rates in such systems. To overcome this problem, here we present a new measurement technique based on capillary flow and a novel hybrid nanochannel design and use it to measure water transport through single 2-D hydrophilic silica nanochannels with heights down to 7 nm. Our results show that silica nanochannels exhibit increased mass flow resistance compared to the classical hydrodynamics prediction. This difference increases with decreasing channel height and reaches 45% in the case of 7 nm nanochannels. This resistance increase is attributed to the formation of a 7-angstrom-thick stagnant hydration layer on the hydrophilic surfaces. By avoiding use of any pressure and flow sensors or any theoretical estimations the hybrid nanochannel scheme enables facile and precise flow measurement through single nanochannels, nanotubes, or nanoporous media and opens the prospect for accurate characterization of both hydrophilic and hydrophobic nanofluidic systems.

  16. Accurate measurement of liquid transport through nanoscale conduits.

    PubMed

    Alibakhshi, Mohammad Amin; Xie, Quan; Li, Yinxiao; Duan, Chuanhua

    2016-01-01

    Nanoscale liquid transport governs the behaviour of a wide range of nanofluidic systems, yet remains poorly characterized and understood due to the enormous hydraulic resistance associated with the nanoconfinement and the resulting minuscule flow rates in such systems. To overcome this problem, here we present a new measurement technique based on capillary flow and a novel hybrid nanochannel design and use it to measure water transport through single 2-D hydrophilic silica nanochannels with heights down to 7 nm. Our results show that silica nanochannels exhibit increased mass flow resistance compared to the classical hydrodynamics prediction. This difference increases with decreasing channel height and reaches 45% in the case of 7 nm nanochannels. This resistance increase is attributed to the formation of a 7-angstrom-thick stagnant hydration layer on the hydrophilic surfaces. By avoiding use of any pressure and flow sensors or any theoretical estimations the hybrid nanochannel scheme enables facile and precise flow measurement through single nanochannels, nanotubes, or nanoporous media and opens the prospect for accurate characterization of both hydrophilic and hydrophobic nanofluidic systems. PMID:27112404

  17. 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.

  18. New simple method for fast and accurate measurement of volumes

    NASA Astrophysics Data System (ADS)

    Frattolillo, Antonio

    2006-04-01

    A new simple method is presented, which allows us to measure in just a few minutes but with reasonable accuracy (less than 1%) the volume confined inside a generic enclosure, regardless of the complexity of its shape. The technique proposed also allows us to measure the volume of any portion of a complex manifold, including, for instance, pipes and pipe fittings, valves, gauge heads, and so on, without disassembling the manifold at all. To this purpose an airtight variable volume is used, whose volume adjustment can be precisely measured; it has an overall capacity larger than that of the unknown volume. Such a variable volume is initially filled with a suitable test gas (for instance, air) at a known pressure, as carefully measured by means of a high precision capacitive gauge. By opening a valve, the test gas is allowed to expand into the previously evacuated unknown volume. A feedback control loop reacts to the resulting finite pressure drop, thus contracting the variable volume until the pressure exactly retrieves its initial value. The overall reduction of the variable volume achieved at the end of this process gives a direct measurement of the unknown volume, and definitively gets rid of the problem of dead spaces. The method proposed actually does not require the test gas to be rigorously held at a constant temperature, thus resulting in a huge simplification as compared to complex arrangements commonly used in metrology (gas expansion method), which can grant extremely accurate measurement but requires rather expensive equipments and results in time consuming methods, being therefore impractical in most applications. A simple theoretical analysis of the thermodynamic cycle and the results of experimental tests are described, which demonstrate that, in spite of its simplicity, the method provides a measurement accuracy within 0.5%. The system requires just a few minutes to complete a single measurement, and is ready immediately at the end of the process. The

  19. Assessing temporal flux of plant hormones in stored processing potatoes using high definition accurate mass spectrometry

    PubMed Central

    Ordaz-Ortiz, José Juan; Foukaraki, Sofia; Terry, Leon Alexander

    2015-01-01

    Plant hormones are important molecules which at low concentration can regulate various physiological processes. Mass spectrometry has become a powerful technique for the quantification of multiple classes of plant hormones because of its high sensitivity and selectivity. We developed a new ultrahigh pressure liquid chromatography–full-scan high-definition accurate mass spectrometry method, for simultaneous determination of abscisic acid and four metabolites phaseic acid, dihydrophaseic acid, 7′-hydroxy-abscisic acid and abscisic acid glucose ester, cytokinins zeatin, zeatin riboside, gibberellins (GA1, GA3, GA4 and GA7) and indole-3-acetyl-L-aspartic acid. We measured the amount of plant hormones in the flesh and skin of two processing potato cvs. Sylvana and Russet Burbank stored for up to 30 weeks at 6 °C under ambient air conditions. Herein, we report for the first time that abscisic acid glucose ester seems to accumulate in the skin of potato tubers throughout storage time. The method achieved a lowest limit of detection of 0.22 ng g−1 of dry weight and a limit of quantification of 0.74 ng g−1 dry weight (zeatin riboside), and was able to recover, detect and quantify a total of 12 plant hormones spiked on flesh and skin of potato tubers. In addition, the mass accuracy for all compounds (<5 ppm) was evaluated. PMID:26504563

  20. Radio Astronomers Set New Standard for Accurate Cosmic Distance Measurement

    NASA Astrophysics Data System (ADS)

    1999-06-01

    A team of radio astronomers has used the National Science Foundation's Very Long Baseline Array (VLBA) to make the most accurate measurement ever made of the distance to a faraway galaxy. Their direct measurement calls into question the precision of distance determinations made by other techniques, including those announced last week by a team using the Hubble Space Telescope. The radio astronomers measured a distance of 23.5 million light-years to a galaxy called NGC 4258 in Ursa Major. "Ours is a direct measurement, using geometry, and is independent of all other methods of determining cosmic distances," said Jim Herrnstein, of the National Radio Astronomy Observatory (NRAO) in Socorro, NM. The team says their measurement is accurate to within less than a million light-years, or four percent. The galaxy is also known as Messier 106 and is visible with amateur telescopes. Herrnstein, along with James Moran and Lincoln Greenhill of the Harvard- Smithsonian Center for Astrophysics; Phillip Diamond, of the Merlin radio telescope facility at Jodrell Bank and the University of Manchester in England; Makato Inoue and Naomasa Nakai of Japan's Nobeyama Radio Observatory; Mikato Miyoshi of Japan's National Astronomical Observatory; Christian Henkel of Germany's Max Planck Institute for Radio Astronomy; and Adam Riess of the University of California at Berkeley, announced their findings at the American Astronomical Society's meeting in Chicago. "This is an incredible achievement to measure the distance to another galaxy with this precision," said Miller Goss, NRAO's Director of VLA/VLBA Operations. "This is the first time such a great distance has been measured this accurately. It took painstaking work on the part of the observing team, and it took a radio telescope the size of the Earth -- the VLBA -- to make it possible," Goss said. "Astronomers have sought to determine the Hubble Constant, the rate of expansion of the universe, for decades. This will in turn lead to an

  1. 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.

  2. 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.

  3. A novel technique for highly accurate gas exchange measurements

    NASA Astrophysics Data System (ADS)

    Kalkenings, R. K.; Jähne, B. J.

    2003-04-01

    The Heidelberg Aeolotron is a circular wind-wave facility for investigating air-sea gas exchange. In this contribution a novel technique for measuring highly accurate transfer velocities k of mass transfer will be presented. Traditionally, in mass balance techniques the constant of decay for gas concentrations over time is measured. The major drawback of this concept is the long time constant. At low wind speeds and a water height greater than 1 m the period of observation has to be several days. In a gas-tight facility such as the Aeolotron, the transfer velocity k can be computed from the concentration in the water body and the change of concentration in the gas space. Owing to this fact, transfer velocities are gained while greatly reducing the measuring times to less than one hour. The transfer velocity k of a tracer can be parameterized as k=1/β \\cdot u_* \\cdot Sc^n, with the Schmidt Number Sc, shear velocity u_* and the dimensionless transfer resistance β. The Schmidt Number exponent n can be derived from simultaneous measurements of different tracers. Since these tracers are of different Schmidt number, the shear velocity is not needed. To allow for Schmidt numbers spanning a hole decade, in our experiments He, H_2, N_2O and F12 are used. The relative accuracy of measuring the transfer velocity was improved to less than 2%. In 9 consecutive experiments conducted at a wind speed of 6.2 m/s, the deviation of the Schmidt number exponent was found to be just under 0.02. This high accuracy will allow precisely determining the transition of the Schmidt number exponent from n=2/3 to n=0.5 from a flat to wavy water surface. In order to quantify gas exchange not only the wind speed is important. Surfactants have a pronounced effect on the wave field and lead to a drastic reduction in the transfer velocity. In the Aeolotron measurements were conducted with a variety of measuring devices, ranging from an imaging slope gauge (ISG) to thermal techniques with IR

  4. Measurement of Fracture Geometry for Accurate Computation of Hydraulic Conductivity

    NASA Astrophysics Data System (ADS)

    Chae, B.; Ichikawa, Y.; Kim, Y.

    2003-12-01

    Fluid flow in rock mass is controlled by geometry of fractures which is mainly characterized by roughness, aperture and orientation. Fracture roughness and aperture was observed by a new confocal laser scanning microscope (CLSM; Olympus OLS1100). The wavelength of laser is 488nm, and the laser scanning is managed by a light polarization method using two galvano-meter scanner mirrors. The system improves resolution in the light axis (namely z) direction because of the confocal optics. The sampling is managed in a spacing 2.5 μ m along x and y directions. The highest measurement resolution of z direction is 0.05 μ m, which is the more accurate than other methods. For the roughness measurements, core specimens of coarse and fine grained granites were provided. Measurements were performed along three scan lines on each fracture surface. The measured data were represented as 2-D and 3-D digital images showing detailed features of roughness. Spectral analyses by the fast Fourier transform (FFT) were performed to characterize on the roughness data quantitatively and to identify influential frequency of roughness. The FFT results showed that components of low frequencies were dominant in the fracture roughness. This study also verifies that spectral analysis is a good approach to understand complicate characteristics of fracture roughness. For the aperture measurements, digital images of the aperture were acquired under applying five stages of uniaxial normal stresses. This method can characterize the response of aperture directly using the same specimen. Results of measurements show that reduction values of aperture are different at each part due to rough geometry of fracture walls. Laboratory permeability tests were also conducted to evaluate changes of hydraulic conductivities related to aperture variation due to different stress levels. The results showed non-uniform reduction of hydraulic conductivity under increase of the normal stress and different values of

  5. History and progress on accurate measurements of the Planck constant.

    PubMed

    Steiner, Richard

    2013-01-01

    The measurement of the Planck constant, h, is entering a new phase. The CODATA 2010 recommended value is 6.626 069 57 × 10(-34) J s, but it has been a long road, and the trip is not over yet. Since its discovery as a fundamental physical constant to explain various effects in quantum theory, h has become especially important in defining standards for electrical measurements and soon, for mass determination. Measuring h in the International System of Units (SI) started as experimental attempts merely to prove its existence. Many decades passed while newer experiments measured physical effects that were the influence of h combined with other physical constants: elementary charge, e, and the Avogadro constant, N(A). As experimental techniques improved, the precision of the value of h expanded. When the Josephson and quantum Hall theories led to new electronic devices, and a hundred year old experiment, the absolute ampere, was altered into a watt balance, h not only became vital in definitions for the volt and ohm units, but suddenly it could be measured directly and even more accurately. Finally, as measurement uncertainties now approach a few parts in 10(8) from the watt balance experiments and Avogadro determinations, its importance has been linked to a proposed redefinition of a kilogram unit of mass. The path to higher accuracy in measuring the value of h was not always an example of continuous progress. Since new measurements periodically led to changes in its accepted value and the corresponding SI units, it is helpful to see why there were bumps in the road and where the different branch lines of research joined in the effort. Recalling the bumps along this road will hopefully avoid their repetition in the upcoming SI redefinition debates. This paper begins with a brief history of the methods to measure a combination of fundamental constants, thus indirectly obtaining the Planck constant. The historical path is followed in the section describing how the

  6. Measurements of Continuum Flux in Solar Flares

    NASA Astrophysics Data System (ADS)

    Kotrč, P.; Heinzel, P.; Procházka, O.

    2016-04-01

    A broad-band diagnostics of chromospheric flare plasma needs to analyze spectra covering many spectral lines and various continuum features. The flare spectra are well detected on the background of the solar disk, but the detection of flare line emission from the Sun-as-a-star in optical is much more difficult due to a strong background radiation. When the flare/background radiation contrast is strong enough to be detected, we need a device for measuring the flux from a selected part of the flaring region. Here we present technical demands for such an instrument and its brief description. This device denoted as Image Selector is a post-focus instrument installed at the horizontal solar telescope HSFA2 of the Ondřejov observatory, described by Kotrč (2009). Its core consists of a system of diaphragms, imaging Hα telescope and a fast spectrometer with dispersion of 3 px per Å but with cadency reaching up to 50 frames per second. The first solar flares observed recently by this novel technique provide quite interesting results. Our analysis of the data proves that the described device is sufficiently sensitive to detect variations in the Balmer continuum during solar flares.

  7. 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.

  8. Accurate MTF measurement in digital radiography using noise response

    PubMed Central

    Kuhls-Gilcrist, Andrew; Jain, Amit; Bednarek, Daniel R.; Hoffmann, Kenneth R.; Rudin, Stephen

    2010-01-01

    an average of 20%. Deviations of the experimental results largely followed the trend seen in the simulation results, suggesting that differences between the two methods could be explained as resulting from the inherent inaccuracies of the edge-response measurement technique used in this study. Aliasing of the correlated noise component was shown to have a minimal effect on the measured MTF for the three detectors studied. Systems with significant aliasing of the correlated noise component (e.g., a-Se based detectors) would likely require a more sophisticated fitting scheme to provide accurate results. Conclusions: Results indicate that the noise-response method, a simple technique, can be used to accurately measure the MTF of digital x-ray detectors, while alleviating the problems and inaccuracies associated with use of precision test objects, such as a slit or an edge. PMID:20229882

  9. Automatic classification and accurate size measurement of blank mask defects

    NASA Astrophysics Data System (ADS)

    Bhamidipati, Samir; Paninjath, Sankaranarayanan; Pereira, Mark; Buck, Peter

    2015-07-01

    complexity of defects encountered. The variety arises due to factors such as defect nature, size, shape and composition; and the optical phenomena occurring around the defect. This paper focuses on preliminary characterization results, in terms of classification and size estimation, obtained by Calibre MDPAutoClassify tool on a variety of mask blank defects. It primarily highlights the challenges faced in achieving the results with reference to the variety of defects observed on blank mask substrates and the underlying complexities which make accurate defect size measurement an important and challenging task.

  10. 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.

  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.

    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.

  12. 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.

  13. 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.

  14. Accurate body composition measures from whole-body silhouettes

    PubMed Central

    Xie, Bowen; Avila, Jesus I.; Ng, Bennett K.; Fan, Bo; Loo, Victoria; Gilsanz, Vicente; Hangartner, Thomas; Kalkwarf, Heidi J.; Lappe, Joan; Oberfield, Sharon; Winer, Karen; Zemel, Babette; Shepherd, John A.

    2015-01-01

    Purpose: Obesity and its consequences, such as diabetes, are global health issues that burden about 171 × 106 adult individuals worldwide. Fat mass index (FMI, kg/m2), fat-free mass index (FFMI, kg/m2), and percent fat mass may be useful to evaluate under- and overnutrition and muscle development in a clinical or research environment. This proof-of-concept study tested whether frontal whole-body silhouettes could be used to accurately measure body composition parameters using active shape modeling (ASM) techniques. Methods: Binary shape images (silhouettes) were generated from the skin outline of dual-energy x-ray absorptiometry (DXA) whole-body scans of 200 healthy children of ages from 6 to 16 yr. The silhouette shape variation from the average was described using an ASM, which computed principal components for unique modes of shape. Predictive models were derived from the modes for FMI, FFMI, and percent fat using stepwise linear regression. The models were compared to simple models using demographics alone [age, sex, height, weight, and body mass index z-scores (BMIZ)]. Results: The authors found that 95% of the shape variation of the sampled population could be explained using 26 modes. In most cases, the body composition variables could be predicted similarly between demographics-only and shape-only models. However, the combination of shape with demographics improved all estimates of boys and girls compared to the demographics-only model. The best prediction models for FMI, FFMI, and percent fat agreed with the actual measures with R2 adj. (the coefficient of determination adjusted for the number of parameters used in the model equation) values of 0.86, 0.95, and 0.75 for boys and 0.90, 0.89, and 0.69 for girls, respectively. Conclusions: Whole-body silhouettes in children may be useful to derive estimates of body composition including FMI, FFMI, and percent fat. These results support the feasibility of measuring body composition variables from simple

  15. Accurate and fast fiber transfer delay measurement based on phase discrimination and frequency measurement

    NASA Astrophysics Data System (ADS)

    Dong, J. W.; Wang, B.; Gao, C.; Wang, L. J.

    2016-09-01

    An accurate and fast fiber transfer delay measurement method is demonstrated. As a key technique, a simple ambiguity resolving process based on phase discrimination and frequency measurement is used to overcome the contradiction between measurement accuracy and system complexity. The system achieves a high measurement accuracy of 0.2 ps with a 0.1 ps measurement resolution and a large dynamic range up to 50 km as well as no dead zone.

  16. 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.

  17. Disjunct eddy accumulation flux measurements of individual VOCs from an urban environment

    NASA Astrophysics Data System (ADS)

    Velasco, Erik; Pressley, Shelley; Grivicke, Rasa; Allwine, Eugene; Jobson, B. Tom; Westberg, Hal; Molina, Luisa T.; Lamb, Brian

    2010-05-01

    As part of the MILAGRO-2006 study a flux tower was deployed at urban Mexico City to measure turbulent fluxes of trace gases. Fluxes of individual volatile organic compounds (VOCs) were measured using a disjunct eddy accumulation (DEA) sampler with ionization detector/gas chromatography (GC-FID) analysis. The DEA method partitions the air into two reservoirs based on the magnitude and direction of the vertical wind speed. The VOCs concentrations in both reservoirs are analyzed and used to determine the fluxes with the vertical wind velocities. Although this method is not as precise as other micrometeorological techniques, such as the eddy covariance method, it provides the ability to directly measure the fluxes of an extended number of individual species using off-line sensors without relying on similarity scaling or empirical parameters. According to our knowledge these measurements constitute the first time that the DEA method was applied in an urban environment. A comparison of the DEA fluxes of selected aromatic and olefinic species measured in parallel by the more accurate eddy covariance and disjunct eddy covariance techniques coupled with fast-response analytical sensors evidenced a flux under-prediction by the DEA method. However, this under-prediction was consistent and constant for the species compared, allowing an analysis of the DEA fluxes in terms of relative magnitudes and ratios. It was found that fluxes of alkane species were the dominant VOCs fluxes, which is consistent with ambient concentration measurements and the local emissions inventory. Among the top 20 mean VOCs fluxes measured during daytime, 11 corresponded to alkanes, followed by 5 aromatics, 2 olefins, 1 alkyne and 1 oxygenated.

  18. Heat flux measurement in SSME turbine blade tester

    NASA Astrophysics Data System (ADS)

    Liebert, Curt H.

    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. Heat flux measurement in SSME turbine blade tester

    NASA Astrophysics Data System (ADS)

    Liebert, Curt 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.

  20. Heat flux measurement in SSME turbine blade tester

    NASA Technical Reports Server (NTRS)

    Liebert, Curt H.

    1990-01-01

    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.

  1. No galaxy left behind: accurate measurements with the faintest objects in the Dark Energy Survey

    NASA Astrophysics Data System (ADS)

    Suchyta, E.; Huff, E. M.; Aleksić, J.; Melchior, P.; Jouvel, S.; MacCrann, N.; Ross, A. J.; Crocce, M.; Gaztanaga, E.; Honscheid, K.; Leistedt, B.; Peiris, H. V.; Rykoff, E. S.; Sheldon, E.; Abbott, T.; Abdalla, F. B.; Allam, S.; Banerji, M.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Burke, D. L.; Rosell, A. Carnero; Kind, M. Carrasco; Carretero, J.; Cunha, C. E.; D'Andrea, C. B.; da Costa, L. N.; DePoy, D. L.; Desai, S.; Diehl, H. T.; Dietrich, J. P.; Doel, P.; Eifler, T. F.; Estrada, J.; Evrard, A. E.; Flaugher, B.; Fosalba, P.; Frieman, J.; Gerdes, D. W.; Gruen, D.; Gruendl, R. A.; James, D. J.; Jarvis, M.; Kuehn, K.; Kuropatkin, N.; Lahav, O.; Lima, M.; Maia, M. A. G.; March, M.; Marshall, J. L.; Miller, C. J.; Miquel, R.; Neilsen, E.; Nichol, R. C.; Nord, B.; Ogando, R.; Percival, W. J.; Reil, K.; Roodman, A.; Sako, M.; Sanchez, E.; Scarpine, V.; Sevilla-Noarbe, I.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Swanson, M. E. C.; Tarle, G.; Thaler, J.; Thomas, D.; Vikram, V.; Walker, A. R.; Wechsler, R. H.; Zhang, Y.; DES Collaboration

    2016-03-01

    Accurate statistical measurement with large imaging surveys has traditionally required throwing away a sizable fraction of the data. This is because most measurements have relied on selecting nearly complete samples, where variations in the composition of the galaxy population with seeing, depth, or other survey characteristics are small. We introduce a new measurement method that aims to minimize this wastage, allowing precision measurement for any class of detectable stars or galaxies. We have implemented our proposal in BALROG, software which embeds fake objects in real imaging to accurately characterize measurement biases. We demonstrate this technique with an angular clustering measurement using Dark Energy Survey (DES) data. We first show that recovery of our injected galaxies depends on a variety of survey characteristics in the same way as the real data. We then construct a flux-limited sample of the faintest galaxies in DES, chosen specifically for their sensitivity to depth and seeing variations. Using the synthetic galaxies as randoms in the Landy-Szalay estimator suppresses the effects of variable survey selection by at least two orders of magnitude. With this correction, our measured angular clustering is found to be in excellent agreement with that of a matched sample from much deeper, higher resolution space-based Cosmological Evolution Survey (COSMOS) imaging; over angular scales of 0.004° < θ < 0.2°, we find a best-fitting scaling amplitude between the DES and COSMOS measurements of 1.00 ± 0.09. We expect this methodology to be broadly useful for extending measurements' statistical reach in a variety of upcoming imaging surveys.

  2. No Galaxy Left Behind: Accurate Measurements with the Faintest Objects in the Dark Energy Survey

    DOE PAGES

    Suchyta, E.

    2016-01-27

    Accurate statistical measurement with large imaging surveys has traditionally required throwing away a sizable fraction of the data. This is because most measurements have have relied on selecting nearly complete samples, where variations in the composition of the galaxy population with seeing, depth, or other survey characteristics are small. We introduce a new measurement method that aims to minimize this wastage, allowing precision measurement for any class of stars or galaxies detectable in an imaging survey. We have implemented our proposal in Balrog, a software package which embeds fake objects in real imaging in order to accurately characterize measurement biases.more » We also demonstrate this technique with an angular clustering measurement using Dark Energy Survey (DES) data. We first show that recovery of our injected galaxies depends on a wide variety of survey characteristics in the same way as the real data. We then construct a flux-limited sample of the faintest galaxies in DES, chosen specifically for their sensitivity to depth and seeing variations. Using the synthetic galaxies as randoms in the standard LandySzalay correlation function estimator suppresses the effects of variable survey selection by at least two orders of magnitude. Now our measured angular clustering is found to be in excellent agreement with that of a matched sample drawn from much deeper, higherresolution space-based COSMOS imaging; over angular scales of 0.004° < θ < 0.2 ° , we find a best-fit scaling amplitude between the DES and COSMOS measurements of 1.00 ± 0.09. We expect this methodology to be broadly useful for extending the statistical reach of measurements in a wide variety of coming imaging surveys.« less

  3. The Design of a Calorimeter to Measure Concentrated Solar Flux

    NASA Astrophysics Data System (ADS)

    Sefkow, Elizabeth Anne Bennett

    A water-cooled, cavity calorimeter was designed to accurately measure concentrated solar thermal power produced by the University of Minnesota's solar simulator. The cavity is comprised of copper tubing bent into spiral and helical coils for the base and cylindrical walls, respectively. Insulation surrounds the cavity to reduce heat transfer to the ambient, and a water- cooled aperture cover is positioned at the open end of the cavity. The calorimeter measures the heat gain of water flowing through the system as radiant energy is passed through the aperture. Chilled water flows through the tubing, and the energy incident on the cavity surface is conducted through the wall and convected to the flowing water. The energy increase in the water can be observed by an increase in fluid temperature. A Monte Carlo ray tracing method is used to predict the incident flux distribution and corresponding power on the surfaces of the cavity. These values are used to estimate the thermal losses of the system, and it is found that they account for less that 1% of the total power passed through the aperture. The overall uncertainty of the calorimeter is found by summing the measured uncertainty and the estimated heat loss and is found to be +/-2.5% for 9.2 kW of power output and +/-3.4% for 3 kW.

  4. 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.

  5. 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

  6. 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.

  7. Accurate Measurements of Aerosol Hygroscopic Growth over a Wide Range in Relative Humidity.

    PubMed

    Rovelli, Grazia; Miles, Rachael E H; Reid, Jonathan P; Clegg, Simon L

    2016-06-30

    Using a comparative evaporation kinetics approach, we describe a new and accurate method for determining the equilibrium hygroscopic growth of aerosol droplets. The time-evolving size of an aqueous droplet, as it evaporates to a steady size and composition that is in equilibrium with the gas phase relative humidity, is used to determine the time-dependent mass flux of water, yielding information on the vapor pressure of water above the droplet surface at every instant in time. Accurate characterization of the gas phase relative humidity is provided from a control measurement of the evaporation profile of a droplet of know equilibrium properties, either a pure water droplet or a sodium chloride droplet. In combination, and by comparison with simulations that account for both the heat and mass transport governing the droplet evaporation kinetics, these measurements allow accurate retrieval of the equilibrium properties of the solution droplet (i.e., the variations with water activity in the mass fraction of solute, diameter growth factor, osmotic coefficient or number of water molecules per solute molecule). Hygroscopicity measurements can be made over a wide range in water activity (from >0.99 to, in principle, <0.05) on time scales of <10 s for droplets containing involatile or volatile solutes. The approach is benchmarked for binary and ternary inorganic solution aerosols with typical uncertainties in water activity of <±0.2% at water activities >0.9 and ∼±1% below 80% RH, and maximum uncertainties in diameter growth factor of ±0.7%. For all of the inorganic systems examined, the time-dependent data are consistent with large values of the mass accommodation (or evaporation) coefficient (>0.1). PMID:27285052

  8. 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.

  9. Flux gradient measurements from a catamaran buoy in SEMAPHORE

    SciTech Connect

    Katsaros, K.B.; Drennan, W.M.; Donelan, M.A.

    1994-12-31

    During the SEMAPHORE Structure des Echanges Mer Atmosphere Proprietes des Heterogeneities de L`Ocean leur Repartition (Structure of Exchanges with the Marine Atmosphere, Properties of Heterogeneities of the Ocean and their Repartition) experiment in the fall of 1993, a large catamaran buoy, the MENTOR, was set adrift in the Azores region. The purpose of the buoy was to provide measurements for testing flux-profile relations over the sea, and to measure the influence of sea state on the turbulent fluxes and atmospheric profiles and the effects of atmospheric and radiative fluxes on near surface temperature structure in the ocean. In addition, the buoy measurements were to provide an anchor point for calibrating mesoscale bulk surface flux estimates over the SEMAPHORE domain and to provide intercomparison data for dissipation estimates of fluxes from the R/V Le Suroit.

  10. 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.

  11. Validation of two innovative methods to measure contaminant mass flux in groundwater.

    PubMed

    Goltz, Mark N; Close, Murray E; Yoon, Hyouk; Huang, Junqi; Flintoft, Mark J; Kim, Sehjong; Enfield, Carl

    2009-04-15

    The ability to quantify the mass flux of a groundwater contaminant that is leaching from a source area is critical to enable us to: (1) evaluate the risk posed by the contamination source and prioritize cleanup, (2) evaluate the effectiveness of source remediation technologies or natural attenuation processes, and (3) quantify a source term for use in models that may be applied to predict maximum contaminant concentrations in downstream wells. Recently, a number of new methods have been developed and subsequently applied to measure contaminant mass flux in groundwater in the field. However, none of these methods has been validated at larger than the laboratory-scale through a comparison of measured mass flux and a known flux that has been introduced into flowing groundwater. A couple of innovative flux measurement methods, the tandem circulation well (TCW) and modified integral pumping test (MIPT) methods, have recently been proposed. The TCW method can measure mass flux integrated over a large subsurface volume without extracting water. The TCW method may be implemented using two different techniques. One technique, the multi-dipole technique, is relatively simple and inexpensive, only requiring measurement of heads, while the second technique requires conducting a tracer test. The MIPT method is an easily implemented method of obtaining volume-integrated flux measurements. In the current study, flux measurements obtained using these two methods are compared with known mass fluxes in a three-dimensional, artificial aquifer. Experiments in the artificial aquifer show that the TCW multi-dipole and tracer test techniques accurately estimated flux, within 2% and 16%, respectively; although the good results obtained using the multi-dipole technique may be fortuitous. The MIPT method was not as accurate as the TCW method, underestimating flux by as much as 70%. MIPT method inaccuracies may be due to the fact that the method assumptions (two-dimensional steady

  12. 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.

  13. 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.

  14. Method accurately measures mean particle diameters of monodisperse polystyrene latexes

    NASA Technical Reports Server (NTRS)

    Kubitschek, H. E.

    1967-01-01

    Photomicrographic method determines mean particle diameters of monodisperse polystyrene latexes. Many diameters are measured simultaneously by measuring row lengths of particles in a triangular array at a glass-oil interface. The method provides size standards for electronic particle counters and prevents distortions, softening, and flattening.

  15. Problems with Accurate Atomic Lfetime Measurements of Multiply Charged Ions

    SciTech Connect

    Trabert, E

    2009-02-19

    A number of recent atomic lifetime measurements on multiply charged ions have reported uncertainties lower than 1%. Such a level of accuracy challenges theory, which is a good thing. However, a few lessons learned from earlier precision lifetime measurements on atoms and singly charged ions suggest to remain cautious about the systematic errors of experimental techniques.

  16. Accurate Measurements of Spectral Reflectance in Picasso's Guernica Painting.

    PubMed

    de Luna, Javier Muñoz; Fernandez-Balbuena, Antonio Alvarez; Vázquez, Daniel; Melgosa, Manuel; Durán, Humberto; García, Jorge; Muro, Carmen

    2016-01-01

    The use of non-invasive spectral measurements to control the conservation status is a part of the preventive conservation of artworks which nowadays is becoming increasingly interesting. This paper describes how to use a spectral measuring device and an illumination system specifically designed for such a task in a very large dimension artwork painting (7.8 m wide × 3.5 m high). The system, controlled by a Cartesian robot, allows spectral measurements in a spectral range of 400-780 nm. The measured data array has a total of 2201 circular regions with 5.5 mm spot diameter placed on a square grid. Colorimetric calculations performed from these spectral measurements may be used to characterize color shifts related to reflectance changes in specific areas of the paint. A color shifting from the expected gray has been shown.

  17. Accurate Measurements of Spectral Reflectance in Picasso's Guernica Painting.

    PubMed

    de Luna, Javier Muñoz; Fernandez-Balbuena, Antonio Alvarez; Vázquez, Daniel; Melgosa, Manuel; Durán, Humberto; García, Jorge; Muro, Carmen

    2016-01-01

    The use of non-invasive spectral measurements to control the conservation status is a part of the preventive conservation of artworks which nowadays is becoming increasingly interesting. This paper describes how to use a spectral measuring device and an illumination system specifically designed for such a task in a very large dimension artwork painting (7.8 m wide × 3.5 m high). The system, controlled by a Cartesian robot, allows spectral measurements in a spectral range of 400-780 nm. The measured data array has a total of 2201 circular regions with 5.5 mm spot diameter placed on a square grid. Colorimetric calculations performed from these spectral measurements may be used to characterize color shifts related to reflectance changes in specific areas of the paint. A color shifting from the expected gray has been shown. PMID:26767640

  18. PRESAGE 3D dosimetry accurately measures Gamma Knife output factors

    NASA Astrophysics Data System (ADS)

    Klawikowski, Slade J.; Yang, James N.; Adamovics, John; Ibbott, Geoffrey S.

    2014-12-01

    Small-field output factor measurements are traditionally very difficult because of steep dose gradients, loss of lateral electronic equilibrium, and dose volume averaging in finitely sized detectors. Three-dimensional (3D) dosimetry is ideal for measuring small output factors and avoids many of these potential challenges of point and 2D detectors. PRESAGE 3D polymer dosimeters were used to measure the output factors for the 4 mm and 8 mm collimators of the Leksell Perfexion Gamma Knife radiosurgery treatment system. Discrepancies between the planned and measured distance between shot centers were also investigated. A Gamma Knife head frame was mounted onto an anthropomorphic head phantom. Special inserts were machined to hold 60 mm diameter, 70 mm tall cylindrical PRESAGE dosimeters. The phantom was irradiated with one 16 mm shot and either one 4 mm or one 8 mm shot, to a prescribed dose of either 3 Gy or 4 Gy to the 50% isodose line. The two shots were spaced between 30 mm and 60 mm apart and aligned along the central axis of the cylinder. The Presage dosimeters were measured using the DMOS-RPC optical CT scanning system. Five independent 4 mm output factor measurements fell within 2% of the manufacturer’s Monte Carlo simulation-derived nominal value, as did two independent 8 mm output factor measurements. The measured distances between shot centers varied by ±0.8 mm with respect to the planned shot displacements. On the basis of these results, we conclude that PRESAGE dosimetry is excellently suited to quantify the difficult-to-measure Gamma Knife output factors.

  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. Comparison of surface fluxes and boundary-layer measurements at Arctic terrestrial sites

    NASA Astrophysics Data System (ADS)

    Grachev, Andrey; Uttal, Taneil; Persson, Ola; Stone, Robert; Crepinsek, Sara; Albee, Robert; Makshtas, Alexander; Kustov, Vasily; Repina, Irina; Artamonov, Arseniy

    2014-05-01

    Observational evidence suggests that atmospheric energy fluxes are a major contributor to the decrease of the Arctic pack ice, seasonal land snow cover and the warming of the surrounding land areas and permafrost layers. To better understand the atmosphere-surface exchange mechanisms, improve models, and to diagnose climate variability in the Arctic, accurate measurements are required of all components of the net surface energy budget and the carbon dioxide cycle over representative areas and over multiple years. This study analyzes and discusses variability of surface fluxes and basic meteorological parameters based on measurements made at several long-term research observatories near the coast of the Arctic Ocean located in USA (Barrow), Canada (Eureka), and Russia (Tiksi). Tower-based eddy covariance and solar radiation measurements provide a long-term near continuous temporal record of hourly average mass and energy fluxes respectively. The turbulent fluxes of the momentum, sensible heat, water vapor, and carbon dioxide are supported by additional atmospheric and surface/snow/permafrost measurements (mean wind speed, air temperature and humidity, upwelling and downwelling short-wave and long-wave atmospheric and surface radiation, snow depth, surface albedo, soil heat flux, active layer temperature profiles etc.) In this study we compare annual cycles of surface fluxes including solar radiation and other ancillary data to describe four seasons in the Arctic including spring onset of melt and fall onset of snow accumulation. Particular interest is a transition through freezing point, i.e. during transition from winter to spring and from summer to fall, when the carbon dioxide and/or water vapor turbulent fluxes change their direction. According to our data, in a summer period observed temporal variability of the carbon dioxide flux was generally in anti-phase with water vapor flux (downward CO2 flux and upward H2O flux). On average the turbulent flux of carbon

  1. Magnetic field models of nine CP stars from "accurate" measurements

    NASA Astrophysics Data System (ADS)

    Glagolevskij, Yu. V.

    2013-01-01

    The dipole models of magnetic fields in nine CP stars are constructed based on the measurements of metal lines taken from the literature, and performed by the LSD method with an accuracy of 10-80 G. The model parameters are compared with the parameters obtained for the same stars from the hydrogen line measurements. For six out of nine stars the same type of structure was obtained. Some parameters, such as the field strength at the poles B p and the average surface magnetic field B s differ considerably in some stars due to differences in the amplitudes of phase dependences B e (Φ) and B s (Φ), obtained by different authors. It is noted that a significant increase in the measurement accuracy has little effect on the modelling of the large-scale structures of the field. By contrast, it is more important to construct the shape of the phase dependence based on a fairly large number of field measurements, evenly distributed by the rotation period phases. It is concluded that the Zeeman component measurement methods have a strong effect on the shape of the phase dependence, and that the measurements of the magnetic field based on the lines of hydrogen are more preferable for modelling the large-scale structures of the field.

  2. An accurate and simple method for measurement of paw edema.

    PubMed

    Fereidoni, M; Ahmadiani, A; Semnanian, S; Javan, M

    2000-01-01

    Several methods for measuring inflammation are available that rely on the parameters changing during inflammation. The most commonly used methods estimate the volume of edema formed. In this study, we present a novel method for measuring the volume of pathologically or artificially induced edema. In this model, a liquid column is placed on a balance. When an object is immersed, the liquid applies a force F to attempt its expulsion. Physically, F is the weight (W) of the volume of liquid displaced by that part of the object inserted into the liquid. A balance is used to measure this force (F=W).Therefore, the partial or entire volume of any object, for example, the inflamed hind paw of a rat, can be calculated thus, using the specific gravity of the immersion liquid, at equilibrium mass/specific gravity=volume (V). The extent of edema at time t (measured as V) will be V(t)-V(o). This method is easy to use, materials are of low cost and readily available. It is important that the rat paw (or any object whose volume is being measured) is kept from contacting the wall of the column containing the fluid whilst the value on the balance is read.

  3. 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.

  4. Determining Maximum Glycolytic Capacity Using Extracellular Flux Measurements.

    PubMed

    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

  5. Determining Maximum Glycolytic Capacity Using Extracellular Flux Measurements.

    PubMed

    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.

  6. 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

  7. 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.

  8. Pool size measurements facilitate the determination of fluxes at branching points in non-stationary metabolic flux analysis: the case of Arabidopsis thaliana.

    PubMed

    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.

  9. 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

  10. Measuring Fisher information accurately in correlated neural populations.

    PubMed

    Kanitscheider, Ingmar; Coen-Cagli, Ruben; Kohn, Adam; Pouget, Alexandre

    2015-06-01

    Neural responses are known to be variable. In order to understand how this neural variability constrains behavioral performance, we need to be able to measure the reliability with which a sensory stimulus is encoded in a given population. However, such measures are challenging for two reasons: First, they must take into account noise correlations which can have a large influence on reliability. Second, they need to be as efficient as possible, since the number of trials available in a set of neural recording is usually limited by experimental constraints. Traditionally, cross-validated decoding has been used as a reliability measure, but it only provides a lower bound on reliability and underestimates reliability substantially in small datasets. We show that, if the number of trials per condition is larger than the number of neurons, there is an alternative, direct estimate of reliability which consistently leads to smaller errors and is much faster to compute. The superior performance of the direct estimator is evident both for simulated data and for neuronal population recordings from macaque primary visual cortex. Furthermore we propose generalizations of the direct estimator which measure changes in stimulus encoding across conditions and the impact of correlations on encoding and decoding, typically denoted by Ishuffle and Idiag respectively.

  11. Highly Accurate Photogrammetric Measurements of the Planck Reflectors

    NASA Astrophysics Data System (ADS)

    Amiri Parian, J.; Gruen, Armin; Cozzani, Alessandro

    2006-06-01

    The Planck mission of the European Space Agency (ESA) is designed to image the anisotropies of the Cosmic Background Radiation Field over the whole sky. To achieve this aim, sophisticated reflectors are used as part of the Planck telescope receiving system. The system consists of secondary and primary reflectors which are sections of two different ellipsoids of revolution with mean diameters of 1 and 1.6 meters. Deformations of the reflectors which influence the optical parameters and the gain of receiving signals are investigated in vacuum and at very low temperatures. For this investigation, among the various high accuracy measurement techniques, photogrammetry was selected. With respect to the photogrammetric measurements, special considerations had to be taken into account in design steps, measurement arrangement and data processing to achieve very high accuracies. The determinability of additional parameters of the camera under the given network configuration, datum definition, reliability and precision issues as well as workspace limits and propagating errors from different sources are considered. We have designed an optimal photogrammetric network by heuristic simulation for the flight model of the primary and the secondary reflectors with relative precisions better than 1:1000000 and 1:400000 to achieve the requested accuracies. A least squares best fit ellipsoid method was developed to determine the optical parameters of the reflectors. In this paper we will report about the procedures, the network design and the results of real measurements.

  12. Air toxics being measured more accurately, controlled more effectively

    SciTech Connect

    1995-04-01

    In response to the directives of the Clean Air Act Amendments, Argonne National Laboratory is developing new or improved pollutant control technologies for industries that burn fossil fuels. This research continues Argonne`s traditional support for the US DOE Flue Gas Cleanup Program. Research is underway to measure process emissions and identify new and improved control measures. Argonne`s emission control research has ranged from experiments in the basic chemistry of pollution-control systems, through laboratory-scale process development and testing to pilot-scale field tests of several technologies. Whenever appropriate, the work has emphasized integrated or combined control systems as the best approach to technologies that offer low cost and good operating characteristics.

  13. Inflation model building with an accurate measure of e -folding

    NASA Astrophysics Data System (ADS)

    Chongchitnan, Sirichai

    2016-08-01

    It has become standard practice to take the logarithmic growth of the scale factor as a measure of the amount of inflation, despite the well-known fact that this is only an approximation for the true amount of inflation required to solve the horizon and flatness problems. The aim of this work is to show how this approximation can be completely avoided using an alternative framework for inflation model building. We show that using the inverse Hubble radius, H =a H , as the key dynamical parameter, the correct number of e -folding arises naturally as a measure of inflation. As an application, we present an interesting model in which the entire inflationary dynamics can be solved analytically and exactly, and, in special cases, reduces to the familiar class of power-law models.

  14. Accurate Measurement of Heat Capacity by Differential Scanning Calorimetry

    NASA Technical Reports Server (NTRS)

    1984-01-01

    Experience with high quality heat capacity measurement by differential scanning calorimetry is summarized and illustrated, pointing out three major causes of error: (1) incompatible thermal histories of the sample, reference and blank runs; (2) unstable initial and final isotherms; (3) incompatible differences between initial and final isotherm amplitudes for sample, reference and blank runs. Considering these problems, it is shown for the case of polyoxymethylene that accuracies in heat capacity of 0.1 percent may be possible.

  15. ACCURATE TEMPERATURE MEASUREMENTS IN A NATURALLY-ASPIRATED RADIATION SHIELD

    SciTech Connect

    Kurzeja, R.

    2009-09-09

    Experiments and calculations were conducted with a 0.13 mm fine wire thermocouple within a naturally-aspirated Gill radiation shield to assess and improve the accuracy of air temperature measurements without the use of mechanical aspiration, wind speed or radiation measurements. It was found that this thermocouple measured the air temperature with root-mean-square errors of 0.35 K within the Gill shield without correction. A linear temperature correction was evaluated based on the difference between the interior plate and thermocouple temperatures. This correction was found to be relatively insensitive to shield design and yielded an error of 0.16 K for combined day and night observations. The correction was reliable in the daytime when the wind speed usually exceeds 1 m s{sup -1} but occasionally performed poorly at night during very light winds. Inspection of the standard deviation in the thermocouple wire temperature identified these periods but did not unambiguously locate the most serious events. However, estimates of sensor accuracy during these periods is complicated by the much larger sampling volume of the mechanically-aspirated sensor compared with the naturally-aspirated sensor and the presence of significant near surface temperature gradients. The root-mean-square errors therefore are upper limits to the aspiration error since they include intrinsic sensor differences and intermittent volume sampling differences.

  16. Mobil unit provides fast and accurate Btu measurements

    SciTech Connect

    Lansing, J. )

    1991-05-01

    Southern California Gas Co. (SoCalGas) provides service to more than four million customers in a 23,000-plus square mile area. Some 95% of these customers fall under the residential category and the remaining customers are industrial and commercial. To ensure Btu value received from the supplier and delivered to the user is accounted for properly, SoCalGas has divided its service area into 47 districts according to the gas Btu content. The company obtains the information by collecting approximately 200 sample cylinders each week from field monitoring points and transporting them to one of four laboratories for analysis. For collecting the information from each lab site, SoCalGas uses a computerized Gas Quality Measurement System (GQMS) that utilizes a Hewlett-Packard 1000 computer. Information on all the gas sample analysis is transmitted each day to the company's measurement office. About two- thirds of the lab work is performed in Los Angeles and the remaining at three satellite laboratories. Sample points are strategically located to monitor gas entering each district. By measuring gas volumes at these key points, a volume- weighted average can be determined and the customers' monthly bills then can be adjusted for gas energy content by this volume-weighted four-week average. The engineering department uses sample-cylinder analysis data to establish and maintain correct Btu boundaries. However, the time it takes for this information to be processed makes it difficult for engineering to process the data.

  17. 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.

  18. Radiant Flux of Near Field in Temperature Measurements

    SciTech Connect

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

    2008-04-15

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

  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. 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.

  1. 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

  2. Blood-Pressure Measuring System Gives Accurate Graphic Output

    NASA Technical Reports Server (NTRS)

    1965-01-01

    The problem: To develop an instrument that will provide an external (indirect) measurement of arterial blood pressure in the form of an easily interpreted graphic trace that can be correlated with standard clinical blood-pressure measurements. From sphygmograms produced by conventional sphygmographs, it is very difficult to differentiate the systolic and diastolic blood-pressure pulses and to correlate these indices with the standard clinical values. It is nearly impossible to determine these indices when the subject is under physical or emotional stress. The solution: An electronic blood-pressure system, basically similar to conventional ausculatory sphygmomanometers, employing a standard occluding cuff, a gas-pressure source, and a gas-pressure regulator and valve. An electrical output transducer senses cuff pressure, and a microphone positioned on the brachial artery under the occluding cuff monitors the Korotkoff sounds from this artery. The output signals present the conventional systolic and diastolic indices in a clear, graphical display. The complete system also includes an electronic timer and cycle-control circuit.

  3. Accurate measurement of intestinal transit in the rat

    SciTech Connect

    Miller, M.S.; Galligan, J.J.; Burks, T.F.

    1981-11-01

    A new method for quantifying intestinal transit was evaluated by comparison with two other popular techniques. The distribution of radiochromium (51Cr) throughout the small intestine of rats previously treated with saline (1.0 ml/kg s.c.), capsaicin (10 mg/kg s.c.), hexamethonium (20 mg/kg i.p.), D-ala2-met-enkephalinamide (1.0 microgram i.c.v.), or neostigmine (0.1 mg/kg i.p.) was quantified by (1) measuring the most distal intestinal segment reached by chromium, (2) calculating the slope produced by linear regression analysis on cumulative percent chromium that had passed through each segment, and (3) determining the geometric center of the distribution of chromium throughout the small intestine. It was concluded that the geometric center methods for quantifying intestinal transit provides the most sensitive and reliable measure of intestinal transit. Less sensitive techniques often fail to detect important effects of drugs on intestinal transit.

  4. Accurate blood flow measurements: are artificial tracers necessary?

    PubMed

    Poelma, Christian; Kloosterman, Astrid; Hierck, Beerend P; Westerweel, Jerry

    2012-01-01

    Imaging-based blood flow measurement techniques, such as particle image velocimetry, have become an important tool in cardiovascular research. They provide quantitative information about blood flow, which benefits applications ranging from developmental biology to tumor perfusion studies. Studies using these methods can be classified based on whether they use artificial tracers or red blood cells to visualize the fluid motion. We here present the first direct comparison in vivo of both methods. For high magnification cases, the experiments using red blood cells strongly underestimate the flow (up to 50% in the present case), as compared to the tracer results. For medium magnification cases, the results from both methods are indistinguishable as they give the same underestimation of the real velocities (approximately 33%, based on in vitro reference measurements). These results suggest that flow characteristics reported in literature cannot be compared without a careful evaluation of the imaging characteristics. A method to predict the expected flow averaging behavior for a particular facility is presented.

  5. Accurate on line measurements of low fluences of charged particles

    NASA Astrophysics Data System (ADS)

    Palla, L.; Czelusniak, C.; Taccetti, F.; Carraresi, L.; Castelli, L.; Fedi, M. E.; Giuntini, L.; Maurenzig, P. R.; Sottili, L.; Taccetti, N.

    2015-03-01

    Ion beams supplied by the 3MV Tandem accelerator of LABEC laboratory (INFN-Firenze), have been used to study the feasibility of irradiating materials with ion fluences reproducible to about 1%. Test measurements have been made with 7.5 MeV 7Li2+ beams of different intensities. The fluence control is based on counting ions contained in short bursts generated by chopping the continuous beam with an electrostatic deflector followed by a couple of adjustable slits. Ions are counted by means of a micro-channel plate (MCP) detecting the electrons emitted from a thin layer of Al inserted along the beam path in between the pulse defining slits and the target. Calibration of the MCP electron detector is obtained by comparison with the response of a Si detector.

  6. An approach for the accurate measurement of social morality levels.

    PubMed

    Liu, Haiyan; Chen, Xia; Zhang, Bo

    2013-01-01

    In the social sciences, computer-based modeling has become an increasingly important tool receiving widespread attention. However, the derivation of the quantitative relationships linking individual moral behavior and social morality levels, so as to provide a useful basis for social policy-making, remains a challenge in the scholarly literature today. A quantitative measurement of morality from the perspective of complexity science constitutes an innovative attempt. Based on the NetLogo platform, this article examines the effect of various factors on social morality levels, using agents modeling moral behavior, immoral behavior, and a range of environmental social resources. Threshold values for the various parameters are obtained through sensitivity analysis; and practical solutions are proposed for reversing declines in social morality levels. The results show that: (1) Population size may accelerate or impede the speed with which immoral behavior comes to determine the overall level of social morality, but it has no effect on the level of social morality itself; (2) The impact of rewards and punishment on social morality levels follows the "5∶1 rewards-to-punishment rule," which is to say that 5 units of rewards have the same effect as 1 unit of punishment; (3) The abundance of public resources is inversely related to the level of social morality; (4) When the cost of population mobility reaches 10% of the total energy level, immoral behavior begins to be suppressed (i.e. the 1/10 moral cost rule). The research approach and methods presented in this paper successfully address the difficulties involved in measuring social morality levels, and promise extensive application potentials.

  7. An Approach for the Accurate Measurement of Social Morality Levels

    PubMed Central

    Liu, Haiyan; Chen, Xia; Zhang, Bo

    2013-01-01

    In the social sciences, computer-based modeling has become an increasingly important tool receiving widespread attention. However, the derivation of the quantitative relationships linking individual moral behavior and social morality levels, so as to provide a useful basis for social policy-making, remains a challenge in the scholarly literature today. A quantitative measurement of morality from the perspective of complexity science constitutes an innovative attempt. Based on the NetLogo platform, this article examines the effect of various factors on social morality levels, using agents modeling moral behavior, immoral behavior, and a range of environmental social resources. Threshold values for the various parameters are obtained through sensitivity analysis; and practical solutions are proposed for reversing declines in social morality levels. The results show that: (1) Population size may accelerate or impede the speed with which immoral behavior comes to determine the overall level of social morality, but it has no effect on the level of social morality itself; (2) The impact of rewards and punishment on social morality levels follows the “5∶1 rewards-to-punishment rule,” which is to say that 5 units of rewards have the same effect as 1 unit of punishment; (3) The abundance of public resources is inversely related to the level of social morality; (4) When the cost of population mobility reaches 10% of the total energy level, immoral behavior begins to be suppressed (i.e. the 1/10 moral cost rule). The research approach and methods presented in this paper successfully address the difficulties involved in measuring social morality levels, and promise extensive application potentials. PMID:24312189

  8. 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.

  9. Analysis of actinic flux profiles measured from an ozonesonde balloon

    NASA Astrophysics Data System (ADS)

    Wang, P.; Allaart, M.; Knap, W. H.; Stammes, P.

    2015-04-01

    A green light sensor has been developed at KNMI to measure actinic flux profiles using an ozonesonde balloon. In total, 63 launches with ascending and descending profiles were performed between 2006 and 2010. The measured uncalibrated actinic flux profiles are analysed using the Doubling-Adding KNMI (DAK) radiative transfer model. Values of the cloud optical thickness (COT) along the flight track were taken from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) Cloud Physical Properties (CPP) product. The impact of clouds on the actinic flux profile is evaluated on the basis of the cloud modification factor (CMF) at the cloud top and cloud base, which is the ratio between the actinic fluxes for cloudy and clear-sky scenes. The impact of clouds on the actinic flux is clearly detected: the largest enhancement occurs at the cloud top due to multiple scattering. The actinic flux decreases almost linearly from cloud top to cloud base. Above the cloud top the actinic flux also increases compared to clear-sky scenes. We find that clouds can increase the actinic flux to 2.3 times the clear-sky value at cloud top and decrease it to about 0.05 at cloud base. The relationship between CMF and COT agrees well with DAK simulations, except for a few outliers. Good agreement is found between the DAK-simulated actinic flux profiles and the observations for single-layer clouds in fully overcast scenes. The instrument is suitable for operational balloon measurements because of its simplicity and low cost. It is worth further developing the instrument and launching it together with atmospheric chemistry composition sensors.

  10. Device for accurately measuring mass flow of gases

    DOEpatents

    Hylton, James O.; Remenyik, Carl J.

    1994-01-01

    A device for measuring mass flow of gases which utilizes a substantially buoyant pressure vessel suspended within a fluid/liquid in an enclosure. The pressure vessel is connected to a weighing device for continuously determining weight change of the vessel as a function of the amount of gas within the pressure vessel. In the preferred embodiment, this pressure vessel is formed from inner and outer right circular cylindrical hulls, with a volume between the hulls being vented to the atmosphere external the enclosure. The fluid/liquid, normally in the form of water typically with an added detergent, is contained within an enclosure with the fluid/liquid being at a level such that the pressure vessel is suspended beneath this level but above a bottom of the enclosure. The buoyant pressure vessel can be interconnected with selected valves to an auxiliary pressure vessel so that initial flow can be established to or from the auxiliary pressure vessel prior to flow to or from the buoyant pressure vessel.

  11. Device for accurately measuring mass flow of gases

    DOEpatents

    Hylton, J.O.; Remenyik, C.J.

    1994-08-09

    A device for measuring mass flow of gases which utilizes a substantially buoyant pressure vessel suspended within a fluid/liquid in an enclosure is disclosed. The pressure vessel is connected to a weighing device for continuously determining weight change of the vessel as a function of the amount of gas within the pressure vessel. In the preferred embodiment, this pressure vessel is formed from inner and outer right circular cylindrical hulls, with a volume between the hulls being vented to the atmosphere external the enclosure. The fluid/liquid, normally in the form of water typically with an added detergent, is contained within an enclosure with the fluid/liquid being at a level such that the pressure vessel is suspended beneath this level but above a bottom of the enclosure. The buoyant pressure vessel can be interconnected with selected valves to an auxiliary pressure vessel so that initial flow can be established to or from the auxiliary pressure vessel prior to flow to or from the buoyant pressure vessel. 5 figs.

  12. 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.

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

    PubMed

    Beck, Christian

    2016-06-20

    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.

  14. 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

  15. 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

  16. 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.

  17. The Airborne Measurements of Methane Fluxes (AIRMETH) Arctic Campaign (Invited)

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    One of the most pressing questions with regard to climate feedback processes in a warming Arctic is the regional-scale methane release from Arctic permafrost areas. The Airborne Measurements of Methane Fluxes (AIRMETH) campaign is designed to quantitatively and spatially explicitly address this question. Ground-based eddy covariance (EC) measurements provide continuous in-situ observations of the surface-atmosphere exchange of methane. 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. Here, we present the potential of environmental response functions (ERFs) for quantitatively linking methane flux observations in the atmospheric surface layer to meteorological and biophysical drivers in the flux footprints. For this purpose thousands of kilometers of AIRMETH data across the Alaskan North Slope are utilized, with the aim to extrapolate the airborne EC methane flux observations to the entire North Slope. The data were collected aboard the research aircraft POLAR 5, using its turbulence nose boom and fast response methane and meteorological sensors. After thorough data pre-processing, Reynolds averaging is used to derive spatially integrated fluxes. To increase spatial resolution and to derive ERFs, we then use wavelet transforms of the original high-frequency data. This enables much improved spatial discretization of the flux observations, and the quantification of continuous and biophysically relevant land cover properties in the flux footprint of each observation. A machine learning technique is then employed to extract and quantify the functional relationships between the methane flux observations and the meteorological and

  18. Measurement and modelling of methane fluxes from UK peatlands

    NASA Astrophysics Data System (ADS)

    Levy, P. E.; Gray, A.

    2012-12-01

    Nearly 5000 chamber measurements of CH4 flux were collated from 21 sites across the UK, covering a range of soil and vegetation types, to derive a parsimonious model that explains as much of the variability as possible, with the least input requirements. Less than half of the observed variability in instantaneous fluxes could be explained by the independent variables measured. Measurement error is one reason for this, and here we analyse several of the uncertainties inherent in these measurements, including the choice of model used to calculate the flux. Other reasons include the stochastic nature of some of the transport processes and the poor correspondence between the independent variables measured and the actual variables influencing the processes underlying methane production, transport and oxidation. Alternative measurement methods are considered which may circumvent some of these problems. When temporal variation was removed, and the fluxes averaged at larger spatial scales, simple models explained up to ~75 % of the variance in CH4 fluxes. Soil carbon, peat depth, soil moisture and pH together provided the best sub-set of explanatory variables. To estimate the impact of changes in peatland water table on CH4 emissions in the UK, an emission factor of +0.4 g CH4 m-2 y-1 per cm increase in water table was derived from the data. As an alternative approach, vegetation species composition provides a long-term integrator of environmental conditions, which may correlate with methane flux. Here, we used a "weighted averaging" approach to predict methane flux from plant species composition at a range of sites in the UK, continental Europe and Canada. Species were classified into functional groups, defined by a number of qualitative traits considered relevant to methane dynamics. We compared the results based on this functional classification with those based on the original species composition data with a purely taxonomic classification.

  19. 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.

  20. 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.

  1. Trapped Proton Fluxes at Low Earth Orbits Measured by the PAMELA Experiment

    NASA Astrophysics Data System (ADS)

    Adriani, O.; Barbarino, G. C.; Bazilevskaya, G. A.; Bellotti, R.; Boezio, M.; Bogomolov, E. A.; Bongi, M.; Bonvicini, V.; Bottai, S.; Bruno, A.; Cafagna, F.; Campana, D.; Carbone, R.; Carlson, P.; Casolino, M.; Castellini, G.; De Donato, C.; De Santis, C.; De Simone, N.; Di Felice, V.; Formato, V.; Galper, A. M.; Karelin, A. V.; Koldashov, S. V.; Koldobskiy, S.; Krutkov, S. Y.; Kvashnin, A. N.; Leonov, A.; Malakhov, V.; Marcelli, L.; Martucci, M.; Mayorov, A. G.; Menn, W.; Mergé, M.; Mikhailov, V. V.; Mocchiutti, E.; Monaco, A.; Mori, N.; Munini, R.; Osteria, G.; Palma, F.; Panico, B.; Papini, P.; Pearce, M.; Picozza, P.; Ricci, M.; Ricciarini, S. B.; Sarkar, R.; Scotti, V.; Simon, M.; Sparvoli, R.; Spillantini, P.; Stozhkov, Y. I.; Vacchi, A.; Vannuccini, E.; Vasilyev, G. I.; Voronov, S. A.; Yurkin, Y. T.; Zampa, G.; Zampa, N.; Zverev, V. G.

    2015-01-01

    We report an accurate measurement of the geomagnetically trapped proton fluxes for kinetic energy above ~70 MeV performed by the PAMELA mission at low Earth orbits (350 ÷ 610 km). Data were analyzed in the frame of the adiabatic theory of charged particle motion in the geomagnetic field. Flux properties were investigated in detail, providing a full characterization of the particle radiation in the South Atlantic Anomaly region, including locations, energy spectra, and pitch angle distributions. PAMELA results significantly improve the description of the Earth's radiation environment at low altitudes, placing important constraints on the trapping and interaction processes, and can be used to validate current trapped particle radiation models.

  2. 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.

  3. Measuring flux of soil fumigants using the aerodynamic and dynamic flux chamber methods.

    PubMed

    van Wesenbeeck, I J; Knuteson, J A; Barnekow, D E; Phillips, A M

    2007-01-01

    Methods for measuring and estimating flux density of soil fumigants under field conditions are important for the purpose of providing inputs to air dispersion models and for comparing the effects of management practices on emission reduction. The objective of this study was to measure the flux of 1,3-dichloropropene (1,3-D) and chloropicrin at a site in Georgia (GA) using the aerodynamic method and the dynamic flux chamber (FC) method. A secondary objective was to compare the effects of high density polyethylene (HDPE), and virtually impermeable film (VIF) tarps on fumigant flux at a site in Florida (FL). Chloropicrin and 1,3-D were applied by surface drip application of In-Line soil fumigant on vegetable beds covered by low density polyethylene (LDPE), HDPE, or VIF. The surface drip fumigation using In-Line and LDPE tarp employed in this study resulted in volatilization of 26.5% of applied 1,3-D and 11.2% of the applied chloropicrin at the GA site, as determined using the aerodynamic method. Estimates of mass loss obtained from dynamic FCs were 23.6% for 1,3-D and 18.0% for chloropicrin at the GA site. Flux chamber trials at the FL site indicate significant additional reduction in flux density, and cumulative mass loss when VIF tarp is used. This study supports the use of dynamic FCs as a valuable tool for estimating gas flux density from agricultural soils, and evaluating best management practices for reducing fumigant emissions to the atmosphere.

  4. 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...

  5. Field Comparison of Methods for Measuring Soil CO2 Flux

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A variety of techniques are available for measurement of soil carbon dioxide (CO2) flux in the field, and each method has inherent advantages and disadvantages. On five dates in October, 2005 we measured soil CO2 emissions in a central Iowa soybean field using: i)eddy covariance, ii)a commercially a...

  6. 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.

  7. 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

  8. Flux measurements of biogenic VOCs during ECHO 2003

    NASA Astrophysics Data System (ADS)

    Spirig, C.; Neftel, A.; Ammann, C.; Dommen, J.; Grabmer, W.; Thielmann, A.; Schaub, A.; Beauchamp, J.; Wisthaler, A.; Hansel, A.

    2004-10-01

    Within the framework of the AFO 2000 project ECHO, two PTR-MS instruments were operated in combination with sonic anemometers to determine biogenic VOC fluxes from a mixed deciduous forest site in North-Western Germany using the eddy covariance (EC) technique. The measurement site was characterised by a forest of inhomogeneous composition, complex canopy structure, limited extension in certain wind directions and frequent calm wind conditions during night time. As a consequence, a considerable fraction of the measurements did not qualify for flux calculations by EC and had to be discarded. The validated results show light and temperature dependent emissions of isoprene and monoterpenes from this forest, with average emissions (normalised to 30°C and 1000 µmoles m-2 s-1 PAR) of 1.5 and 0.39 µg m-2 s-1, respectively. Emissions of methanol reached on average 0.087 µg m-2 s-1 during daytime, but fluxes were too small to be detected during night time. Upward fluxes of the isoprene oxidation products methyl vinyl ketone (MVK) and methacrolein (MACR) were also found, being two orders of magnitude lower than those of isoprene. The observed fluxes are consistent with upscalings from leaf-level emission measurements of representative tree species in this forest and, in the case of MVK and MACR, can plausibly be explained by chemical production through oxidation of isoprene within the canopy. Calculations with an analytical footprint model indicate that the observed isoprene fluxes correlate with the fraction of oaks within the footprints of the flux measurement.

  9. Heat flux measurement in a high enthalpy plasma flow

    NASA Astrophysics Data System (ADS)

    Löhle, Stefan; Battaglia, Jean-Luc; Gardarein, Jean-Laurent; Jullien, Pierre; van Ootegem, Bruno

    2008-11-01

    It is a widely used approach to measure heat flux in harsh environments like high enthalpy plasma flows, fusion plasma and rocket motor combustion chambers based on solving the inverse heat conduction problem in a semi-infinite environment. This approach strongly depends on model parameters and geometrical aspects of the sensor design. In this work the surface heat flux is determined by solving the inverse heat conduction problem using an identified system as a direct model. The identification of the system is performed using calibration measurements with modern laser technique and advanced data handling. The results of the identified thermo-physical system show that a non-integer model appears most adapted to this particular problem. It is concluded that the new method improves the heat flux sensor significantly and furthermore extend its application to very short measurement times.

  10. 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.

  11. CALIBRATION OF X-RAY IMAGING DEVICES FOR ACCURATE INTENSITY MEASUREMENT

    SciTech Connect

    Haugh, M J; Charest, M R; Ross, P W; Lee, J J; Schneider, M B; Palmer, N E; Teruya, A T

    2012-02-16

    National Security Technologies (NSTec) has developed calibration procedures for X-ray imaging systems. The X-ray sources that are used for calibration are both diode type and diode/fluorescer combinations. Calibrating the X-ray detectors is key to accurate calibration of the X-ray sources. Both energy dispersive detectors and photodiodes measuring total flux were used. We have developed calibration techniques for the detectors using radioactive sources that are traceable to the National Institute of Standards and Technology (NIST). The German synchrotron at Physikalische Technische Bundestalt (PTB) is used to calibrate silicon photodiodes over the energy range from 50 eV to 60 keV. The measurements on X-ray cameras made using the NSTec X-ray sources have included quantum efficiency averaged over all pixels, camera counts per photon per pixel, and response variation across the sensor. The instrumentation required to accomplish the calibrations is described. X-ray energies ranged from 720 eV to 22.7 keV. The X-ray sources produce narrow energy bands, allowing us to determine the properties as a function of X-ray energy. The calibrations were done for several types of imaging devices. There were back illuminated and front illuminated CCD (charge coupled device) sensors, and a CID (charge injection device) type camera. The CCD and CID camera types differ significantly in some of their properties that affect the accuracy of X-ray intensity measurements. All cameras discussed here are silicon based. The measurements of quantum efficiency variation with X-ray energy are compared to models for the sensor structure. Cameras that are not back-thinned are compared to those that are.

  12. 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.

  13. 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.

  14. 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.

  15. Densitometric tomography using the measurement of muon flux

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  16. 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.

  17. Thermal neutron flux measurements in the STAR experimental hall

    NASA Astrophysics Data System (ADS)

    Fisyak, Yuri; Tsai, Oleg; Videbæk, Flemming; Xu, Zhangbu

    2014-08-01

    We report measurements of thermal neutron fluxes at different locations in the STAR experimental hall during RHIC Run 13 with proton-proton collisions at √{s}=510 GeV. We compare these measurements to calculations based on PYTHIA as a minimum bias event generator, detailed GEANT3 simulation of the STAR detector and experimental hall, and with GCALOR as the neutron transport code. A fairly good agreement was found between simulation and measurements.

  18. 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.

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

    DOE PAGES

    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

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

    NASA Astrophysics Data System (ADS)

    Pakhomova, Svetlana; Protsenko, Elizaveta

    2016-04-01

    .) are faster than diffusion and play an important role in the benthic flux formation for these elements. For the third group measured fluxes could be often overestimated, especially for coastal shallow stations, up to 50%, because of intensive decomposition of OM and/or organisms respiration in the isolated bottom water. Values of benthic fluxes obtained by the BROM model are within the range of magnitudes measured by chamber experiments and calculated from porewater distributions (Jpw < Jmd < Jch). Using the model it is possible estimate the influence of bioturbation on elements exchange at water-sediment interface. Model has a high resolution in the upper sediment (0.1 mm) that gives the advantage of a more accurate calculation of diffusive fluxes especially for redox dependent elements. Model results showed that in 50 cm above the sediment vertical fluxes are changing largely while in chamber experiments they are averaged. As a result, each of the methods has its disadvantages and the main facing us question is - which value should be taken for calculation the balance? This research is funded by VISTA - a basic research program and collaborative partnership between the Norwegian Academy of Science and Letters and Statoil.

  1. SO2 flux measurements at Mount Etna (Sicily)

    SciTech Connect

    Caltabiano, T.; Romano, R.; Budetta, G.

    1994-06-01

    Since 1987, over 220 measurements of the SO2 flux at Mount Etna have been carried out using a correlation spectrometer (COSPEC) with different measuring techniques (mainly with COSPEC mounted on ground-based vehicle). This paper reports and analyzes the data obtained between October 1987 and December 1991. During this period, three distinct time intervals characterized by particular SO2 emission patterns were identified. The first interval (A) showed a mean SO2 flux of 5500 t/d associated with relatively quiet summit crater eruptive activity. The second interval (B) included two eruptive periods, September-October 1989 and January-February 1990, associated with high fluxes reaching 10,000-25,000 t/d. The third interval (C) started in concert with a regional earthquake (December 13, 1990) and showed first a decrease and then an increase of SO2 emissions before the onset of the major 1991-1993 flank eruption. Analysis of the data reveals a cyclic pattern to the SO2 emissions over prolonged periods; a nearly constant supply of SO2 from the volcano`s main feeder system, especially evident in the long term; a two- to fivefold increase above mean flux values (from 10,000 to 25,000 t/d) when occurring with paroxysmal eruptive activity; and minimal flux values (approximately 1000 t/d) about 1 month prior to important eruptive events.

  2. 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

  3. 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...

  4. 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.

  5. 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

  6. 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.

  7. Advances in Air-Sea Flux Measurement by Eddy Correlation

    NASA Astrophysics Data System (ADS)

    Blomquist, Byron W.; Huebert, Barry J.; Fairall, Christopher W.; Bariteau, Ludovic; Edson, James B.; Hare, Jeffrey E.; McGillis, Wade R.

    2014-09-01

    Eddy-correlation measurements of the oceanic flux are useful for the development and validation of air-sea gas exchange models and for analysis of the marine carbon cycle. Results from more than a decade of published work and from two recent field programs illustrate the principal interferences from water vapour and motion, demonstrating experimental approaches for improving measurement precision and accuracy. Water vapour cross-sensitivity is the greatest source of error for flux measurements using infrared gas analyzers, often leading to a ten-fold bias in the measured flux. Much of this error is not related to optical contamination, as previously supposed. While various correction schemes have been demonstrated, the use of an air dryer and closed-path analyzer is the most effective way to eliminate this interference. This approach also obviates density corrections described by Webb et al. (Q J R Meteorol 106:85-100, 1980). Signal lag and frequency response are a concern with closed-path systems, but periodic gas pulses at the inlet tip provide for precise determination of lag time and frequency attenuation. Flux attenuation corrections are shown to be 5 % for a cavity ring-down analyzer (CRDS) and dryer with a 60-m inlet line. The estimated flux detection limit for the CRDS analyzer and dryer is a factor of ten better than for IRGAs sampling moist air. While ship-motion interference is apparent with all analyzers tested in this study, decorrelation or regression methods are effective in removing most of this bias from IRGA measurements and may also be applicable to the CRDS.

  8. 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.

  9. 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.

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

    NASA Astrophysics Data System (ADS)

    Lammert, A.; Ament, F.

    2015-07-01

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

  11. 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

  12. 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

  13. Ecosystem photosynthesis inferred from measurements of carbonyl sulphide flux

    NASA Astrophysics Data System (ADS)

    Asaf, David; Rotenberg, Eyal; Tatarinov, Fyodor; Dicken, Uri; Montzka, Stephen A.; Yakir, Dan

    2013-03-01

    Limited understanding of carbon dioxide sinks and sources on land is often linked to the inability to distinguish between the carbon dioxide taken up by photosynthesis, and that released by respiration. Carbonyl sulphide, a sulphur-containing analogue of carbon dioxide, is also taken up by plants, and could potentially serve as a powerful proxy for photosynthetic carbon dioxide uptake, which cannot be directly measured above the leaf scale. Indeed, variations in atmospheric concentrations of carbonyl sulphide are closely related to those of carbon dioxide at regional, local and leaf scales. Here, we use eddy covariance and laser spectroscopy to estimate the net exchange of carbon dioxide and carbonyl sulphide across three pine forests, a cotton field and a wheat field in Israel. We estimate gross primary productivity--a measure of ecosystem photosynthesis--directly from the carbonyl sulphide fluxes, and indirectly from carbon dioxide fluxes. The two estimates agree within an error of +/-15%. The ratio of carbonyl sulphide to carbon dioxide flux at the ecosystem scale was consistent with the variability in mixing ratios observed on seasonal timescales in the background atmosphere. We suggest that atmospheric measurements of carbonyl sulphide flux could provide an independent constraint on estimates of gross primary productivity, key to projecting the response of the land biosphere to climate change.

  14. 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

  15. 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.

  16. Gap-filling of flux measurements over a heterogeneous urban landscape

    NASA Astrophysics Data System (ADS)

    Menzer, O.; McFadden, J.

    2012-12-01

    A small, but growing, number of urban flux towers measure surface-atmospheric exchanges of energy, water, and greenhouse gases by the eddy covariance method. Imputation of gaps in these measurements caused by low turbulence conditions and system failures is essential for obtaining annual sums of CO2 exchange and evaporation. Yet most gap-filling methods were designed for natural measurement sites such as forests and grasslands. In the urban environment, however, the assumptions on which those approaches are based are violated and well known temperature or light response models are not applicable because of urban footprint heterogeneity and localized CO2 emissions. Observation-based methods of machine learning can reveal intrinsic mechanisms by using inputs such as wind direction, footprint size, and continuous traffic data, making gap-filling results more accurate. Here, we report preliminary gap-filling results using such empirical approaches for >3 years of flux measurements from the KUOM tall tower in a suburban neighborhood of Minneapolis, Minnesota, USA. We also ran one of the most common gap-filling methods that has been used for natural systems as a baseline or null model. We found that CO2 and water vapor fluxes from the urban landscape showed higher variability than those from a nearby turfgrass lawn, in which fluxes closely followed environmental drivers of light and temperature. Higher variability was found in NEE measurements as compared to LE, due to the relatively greater heterogeneity of sources and sinks that influenced CO2 exchange in the urban landscape.

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

    NASA Astrophysics Data System (ADS)

    Zahniser, M. S.; Nelson, D. D.; Roscioli, J. R.; Herndon, S. C.; McManus, J. B.; Jervis, D.

    2015-12-01

    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. 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. Sapflow+: a four-needle heat-pulse sap flow sensor enabling nonempirical sap flux density and water content measurements.

    PubMed

    Vandegehuchte, Maurits W; Steppe, Kathy

    2012-10-01

    • To our knowledge, to date, no nonempirical method exists to measure reverse, low or high sap flux density. Moreover, existing sap flow methods require destructive wood core measurements to determine sapwood water content, necessary to convert heat velocity to sap flux density, not only damaging the tree, but also neglecting seasonal variability in sapwood water content. • Here, we present a nonempirical heat-pulse-based method and coupled sensor which measure temperature changes around a linear heater in both axial and tangential directions after application of a heat pulse. By fitting the correct heat conduction-convection equation to the measured temperature profiles, the heat velocity and water content of the sapwood can be determined. • An identifiability analysis and validation tests on artificial and real stem segments of European beech (Fagus sylvatica L.) confirm the applicability of the method, leading to accurate determinations of heat velocity, water content and hence sap flux density. • The proposed method enables sap flux density measurements to be made across the entire natural occurring sap flux density range of woody plants. Moreover, the water content during low flows can be determined accurately, enabling a correct conversion from heat velocity to sap flux density without destructive core measurements.

  19. 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

  20. 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

  1. 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

  2. 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

  3. Measuring and modeling disturbance-induced changes to flux dynamics in increasingly heterogeneous canopy environments

    NASA Astrophysics Data System (ADS)

    Maurer, K.; Bohrer, G.; He, L.; Ivanov, V. Y.; Vogel, C.; Curtis, P.

    2012-12-01

    Turbulent eddies control the flux of carbon, water and other gases between forested environments and the atmosphere. Inside the canopy, eddy correlation length is very small and surface heterogeneity due to tree-crown structures occurs at these scales. Computer simulations, particularly Large-Eddy Simulations (LES), provide the foundation to test the sensitivity of flux exchange and turbulent mixing to small scale processes, such as successional- or disturbance-driven changes to canopy structure. At the Forest Accelerated Succession ExperimenT (FASET), we disturbed 39 ha of forest by girdling all canopy-dominant early-successional aspen and birch trees, leading to a large mortality event, followed by a shift in forest structure that is typical of a more mature successional stage. Over the course of the study, we have found a divergence from pre-treatment biosphere-atmosphere gas-exchange trends between the control and disturbance sites due to changes in canopy structure and, as a consequence, biological response. We use the Regional Atmospheric Modeling System (RAMS)-based Forest Large-Eddy Simulation (RAFLES), and the more dynamic RAFLES-Ecosystem Demography (ED2) model, to investigate the consequences of increasingly heterogeneous forest environments to canopy-atmosphere exchange. RAFLES-ED2 resolves multi-layered light attenuation and vegetation and surface heat, vapor and CO2 fluxes and includes a multi-layered soil column under each atmosphere-vegetation column, as opposed to the single-layered soil-vegetation model in RAFLES. The model environment was determined by remote sensing of the actual forested area of interest using airborne Light Detection and Ranging (LiDAR) measurements and eddy-flux gas exchange measurements at two neighboring AmeriFlux eddy-flux towers, the manipulated site (US-UMd) and its undisturbed control (US-UMB) both at the University of Michigan Biological Station (UMBS) cluster site. We find more accurate surface roughness estimates and

  4. First flux surface measurements on W7-X

    NASA Astrophysics Data System (ADS)

    Pedersen, Thomas Sunn; Otte, Matthias; Biedermann, Christoph; Bozhenkov, Sergey; Braeuer, Torsten; Lazerson, Samuel; W7-X Team

    2015-11-01

    Wendelstein 7-X is rapidly approaching first plasma operation. The full operational B-field of 2.5 T has been reached using the 70 superconducting coils. The first flux surface measurements have recently been successfully performed. This talk will describe the W7-X flux surface measurement system, and show and analyze the first results from this diagnostic, which, at the time of writing this abstract, can be summarized as follows: Confirmation of the existence of nested, closed flux surfaces, first measurements of iota, and detection of the expected internal 5/6 island chain of the OP1.1 configuration. The data obtained so far agree with expectations, and provide a first confirmation of the accuracy of the coil geometry and assembly, as well as diagnostic installation. They also confirm that, with respect to the magnetic topology, plasma operation can start. Plans for, and potentially first results of, measurements of any remnant field errors, will be reported separately at this meeting.

  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.

    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.

  6. Light collection optics for measuring flux and spectrum from light-emitting devices

    DOEpatents

    McCord, Mark A.; DiRegolo, Joseph A.; Gluszczak, Michael R.

    2016-05-24

    Systems and methods for accurately measuring the luminous flux and color (spectra) from light-emitting devices are disclosed. An integrating sphere may be utilized to directly receive a first portion of light emitted by a light-emitting device through an opening defined on the integrating sphere. A light collector may be utilized to collect a second portion of light emitted by the light-emitting device and direct the second portion of light into the integrating sphere through the opening defined on the integrating sphere. A spectrometer may be utilized to measure at least one property of the first portion and the second portion of light received by the integrating sphere.

  7. Measurements of the thermal neutrons flux near the EAS core

    NASA Astrophysics Data System (ADS)

    Dzhappuev, D. D.; Volchenko, V. I.; Kudzhaev, A. U.; Mikhailova, O. I.; Petkov, V. B.; Stenkin, Yu V.; Tsyabuk, A. L.

    2013-02-01

    The characteristics of the thermal neutrons flux have been measured near the EAS core at the "Carpet-2" EAS array. The thermal neutron detectors were placed on the floor of the tunnel of the Muon Detector (MD) and showers with a core near the MD were selected. Thermal neutrons multiplicity spectrum has been obtained for these showers. Measurements of the lateral distribution function of thermal neutrons at distances of 1-16 m from the shower axis have been performed. The mean number of the recorded thermal neutrons as a function of the number of hadrons crossing the MD has been measured.

  8. 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

  9. Estimating terrestrial uranium and thorium by antineutrino flux measurements.

    PubMed

    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

  10. Estimating terrestrial uranium and thorium by antineutrino flux measurements.

    PubMed

    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.

  11. Particle and heat flux measurements in PDX edge plasmas

    NASA Astrophysics Data System (ADS)

    Budny, R.; Manos, D.

    1984-05-01

    This paper describes the use of novel combined Langmuir-calorimeter probes to measure edge plasma conditions near the midplane in PDX. The probes consisted of up to five Langmuir probes and up to two calorimeters. Single and double probe characteristics yield ne and Tc which are compared with results derived from a triple probe analysis. The calorimeters measure heat flux in the electron and ion drift directions. This paper presents time-resolved radial profiles of ne, Te, VF (floating potential),and P (heat flux) during high power neutral beam-heated, single-null discharges and circular scoop limiter discharges. The temporal dependence of these quantities displays the previously observed behavior with respect to gross discharge characteristics; however, an additional dependence on confinement mode has been observed. During the H-mode of energy confinement, a transient depression of ne, Te, and P occur in the scrape-off plasma.

  12. Fluxes through plant metabolic networks: measurements, predictions, insights and challenges.

    PubMed

    Kruger, Nicholas J; Ratcliffe, R George

    2015-01-01

    Although the flows of material through metabolic networks are central to cell function, they are not easy to measure other than at the level of inputs and outputs. This is particularly true in plant cells, where the network spans multiple subcellular compartments and where the network may function either heterotrophically or photoautotrophically. For many years, kinetic modelling of pathways provided the only method for describing the operation of fragments of the network. However, more recently, it has become possible to map the fluxes in central carbon metabolism using the stable isotope labelling techniques of metabolic flux analysis (MFA), and to predict intracellular fluxes using constraints-based modelling procedures such as flux balance analysis (FBA). These approaches were originally developed for the analysis of microbial metabolism, but over the last decade, they have been adapted for the more demanding analysis of plant metabolic networks. Here, the principal features of MFA and FBA as applied to plants are outlined, followed by a discussion of the insights that have been gained into plant metabolic networks through the application of these time-consuming and non-trivial methods. The discussion focuses on how a system-wide view of plant metabolism has increased our understanding of network structure, metabolic perturbations and the provision of reducing power and energy for cell function. Current methodological challenges that limit the scope of plant MFA are discussed and particular emphasis is placed on the importance of developing methods for cell-specific MFA.

  13. Direct measurement of heat flux from cooling lake thermal imagery

    NASA Astrophysics Data System (ADS)

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

    2008-03-01

    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, σ, derived from thermal images of the water surface over a range of heat fluxes from 400 to 1800 Wm -2. Thermal imagery and surface data were collected at two power plant cooling lakes to determine if the laboratory relationship between heat flux and σ exists in large heated bodies of water. The heat fluxes computed from the cooling lake data range from 200 to 1400 Wm -2. The linear relationship between σ 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 σ and Q is improved if a correction to the measured σ 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 σ and Q ranged from about 0.8 to 0.9.

  14. 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.

  15. Data assimilation tool to reconstruct particle flux measurements

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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

  1. 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.

  2. 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

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

    DOE PAGES

    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

  4. 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

  5. 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.

  6. 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.

  7. 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

  8. Highly accurate SNR measurement using the covariance of two SEM images with the identical view.

    PubMed

    Oho, Eisaku; Suzuki, Kazuhiko

    2012-01-01

    Quality of an SEM image is strongly influenced by the extent of noise. As a well-known method in the field of SEM, the covariance is applied to measure the signal-to-noise ratio (SNR). This method has potential ability for highly accurate measurement of the SNR, which is hardly known until now. If the precautions discussed in this article are adopted, that method can demonstrate its real ability. These precautions are strongly related to "proper acquisition of two images with the identical view," "alignment of an aperture diaphragm," "reduction of charging phenomena," "elimination of particular noises," and "accurate focusing," As necessary, characteristics in SEM signal and noise are investigated from a few standpoints. When using the maximum performance of this measurement, SNR of many SEM images obtained in a variety of the SEM operating conditions and specimens can be measured accurately.

  9. 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

  10. 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.

  11. Mars heavy ion precipitating flux as measured by MAVEN

    NASA Astrophysics Data System (ADS)

    Leblanc, F.

    2015-12-01

    Mars' atmospheric escape induced by heavy planetary ions accelerated by the solar wind and reimpacting Mars' atmosphere has been suggested to occur. The sputtering of Mars' atmosphere has been even suggested to lead to a significant cumulated loss along Mars' history. Up to now, only a limited number of observations have been possible. ASPERA-3/Mars Express observed such precipitation only during extreme solar conditions events suggesting that sputtering might be not as intense as theoretically predicted. Based on MAVEN first six months of observations, we here show that precipitation of heavy ions also occur during quiet solar conditions and that the average precipitating flux during this period is significant and globally in good agreement with predictions. From these measured precipitating flux, we propose a first estimate of the atmospheric escape induced by sputtering. Up to 8.8×105 O/cm2/s was lost by Mars' atmosphere between November 2014 and April 2015.

  12. MASS MEASUREMENTS BY AN ACCURATE AND SENSITIVE SELECTED ION RECORDING TECHNIQUE

    EPA Science Inventory

    Trace-level components of mixtures were successfully identified or confirmed by mass spectrometric accurate mass measurements, made at high resolution with selected ion recording, using GC and LC sample introduction. Measurements were made at 20 000 or 10 000 resolution, respecti...

  13. 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.

  14. Continuous measurements of methane flux in two Japanese temperate forests based on the micrometeorological and chamber methods

    NASA Astrophysics Data System (ADS)

    Yoshikawa, K.; Ueyama, M.; Takagi, K.; Kominami, Y.

    2015-12-01

    Methane (CH4) budget in forest ecosystems have not been accurately quantified due to limited measurements and considerable spatiotemporal heterogeneity. In order to quantify CH4 fluxes at temperate forest at various spatiotemporal scales, we have continuously measured CH4 fluxes at two upland forests based on the micrometeorological hyperbolic relaxed eddy accumulation (HREA) and automated dynamic closed chamber methods.The measurements have been conducted at Teshio experimental forest (TSE) since September 2013 and Yamashiro forest meteorology research site (YMS) since November 2014. Three automated chambers were installed on each site. Our system can measure CH4 flux by the micrometeorological HREA, vertical concentration profile at four heights, and chamber measurements by a laser-based gas analyzer (FGGA-24r-EP, Los Gatos Research Inc., USA).Seasonal variations of canopy-scale CH4 fluxes were different in each site. CH4 was consumed during the summer, but was emitted during the fall and winter in TSE; consequently, the site acted as a net annual CH4 source. CH4 was steadily consumed during the winter, but CH4 fluxes fluctuated between absorption and emission during the spring and summer in YMS. YMS acted as a net annual CH4 sink. CH4 uptake at the canopy scale generally decreased with rising soil temperature and increased with drying condition for both sites. CH4 flux measured by most of chambers showed the consistent sensitivity examined for the canopy scale to the environmental variables. CH4 fluxes from a few chambers located at a wet condition were independent of variations in soil temperature and moisture at both sites. Magnitude of soil CH4 uptake was higher than the canopy-scale CH4 uptake. Our results showed that the canopy-scale CH4 fluxes were totally different with the plot-scale CH4 fluxes by chambers, suggesting the considerable spatial heterogeneity in CH4 flux at the temperate forests.

  15. 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.

  16. 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.

  17. Effects of measurement resolution on the analysis of temperature time series for stream-aquifer flux estimation

    NASA Astrophysics Data System (ADS)

    Soto-López, Carlos D.; Meixner, Thomas; Ferré, Ty P. A.

    2011-12-01

    From its inception in the mid-1960s, the use of temperature time series (thermographs) to estimate vertical fluxes has found increasing use in the hydrologic community. Beginning in 2000, researchers have examined the impacts of measurement and parameter uncertainty on the estimates of vertical fluxes. To date, the effects of temperature measurement discretization (resolution), a characteristic of all digital temperature loggers, on the determination of vertical fluxes has not been considered. In this technical note we expand the analysis of recently published work to include the effects of temperature measurement resolution on estimates of vertical fluxes using temperature amplitude and phase shift information. We show that errors in thermal front velocity estimation introduced by discretizing thermographs differ when amplitude or phase shift data are used to estimate vertical fluxes. We also show that under similar circumstances sensor resolution limits the range over which vertical velocities are accurately reproduced more than uncertainty in temperature measurements, uncertainty in sensor separation distance, and uncertainty in the thermal diffusivity combined. These effects represent the baseline error present and thus the best-case scenario when discrete temperature measurements are used to infer vertical fluxes. The errors associated with measurement resolution can be minimized by using the highest-resolution sensors available. But thoughtful experimental design could allow users to select the most cost-effective temperature sensors to fit their measurement needs.

  18. TRAPPED PROTON FLUXES AT LOW EARTH ORBITS MEASURED BY THE PAMELA EXPERIMENT

    SciTech Connect

    Adriani, O.; Bongi, M.; Barbarino, G. C.; Bazilevskaya, G. A.; Bellotti, R.; Bruno, A.; Boezio, M.; Bonvicini, V.; Carbone, R.; Bogomolov, E. A.; Bottai, S.; Cafagna, F.; Campana, D.; Carlson, P.; Casolino, M.; De Donato, C.; De Santis, C.; De Simone, N.; Felice, V. Di; Castellini, G.; and others

    2015-01-20

    We report an accurate measurement of the geomagnetically trapped proton fluxes for kinetic energy above ∼70 MeV performed by the PAMELA mission at low Earth orbits (350 ÷ 610 km). Data were analyzed in the frame of the adiabatic theory of charged particle motion in the geomagnetic field. Flux properties were investigated in detail, providing a full characterization of the particle radiation in the South Atlantic Anomaly region, including locations, energy spectra, and pitch angle distributions. PAMELA results significantly improve the description of the Earth's radiation environment at low altitudes, placing important constraints on the trapping and interaction processes, and can be used to validate current trapped particle radiation models.

  19. 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.

  20. 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.

  1. 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...

  2. The effect of random and systematic measurement uncertainties on temporal and spatial upscaling of N2O fluxes

    NASA Astrophysics Data System (ADS)

    Cowan, Nicholas; Levy, Peter; Skiba, Ute

    2016-04-01

    The addition of reactive nitrogen to agricultural soils in the form of artificial fertilisers or animal waste is the largest global source of anthropogenic N2O emissions. Emission factors are commonly used to evaluate N2O emissions released after the application of nitrogen fertilisers on a global scale based on records of fertiliser use. Currently these emission factors are estimated primarily by a combination of results of experiments in which flux chamber methodology is used to estimate annual cumulative fluxes of N2O after nitrogen fertiliser applications on agricultural soils. The use of the eddy covariance method to measure N2O and estimate emission factors is also becoming more common in the flux community as modern rapid gas analyser instruments advance. The aim of the presentation is to highlight the weaknesses and potential systematic biases in current flux measurement methodology. This is important for GHG accounting and for accurate model calibration and verification. The growing interest in top-down / bottom-up comparisons of tall tower and conventional N2O flux measurements is also an area of research in which the uncertainties in flux measurements needs to be properly quantified. The large and unpredictable spatial and temporal variability of N2O fluxes from agricultural soils leads to a significant source of uncertainty in emission factor estimates. N2O flux measurements typically show poor relationships with explanatory co-variates. The true uncertainties in flux measurements at the plot scale are often difficult to propagate to field scale and the annual time scale. This results in very uncertain cumulative flux (emission factor) estimates. Cumulative fluxes estimated using flux chamber and eddy covariance methods can also differ significantly which complicates the matter further. In this presentation, we examine some effects that spatial and temporal variability of N2O fluxes can have on the estimation of emission factors and describe how

  3. 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

  4. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    Both technical and natural processes emit the greenhouse gas nitrous oxide (N2O) into the atmosphere. The abundant use of nitrogen (N) as fertiliser increases the concentration of reactive nitrogen (Nr) in the atmosphere, the hydrosphere and in the biosphere, i.e. in terrestrial and aquatic ecosystems. Surplus Nr is distributed across linkages to other spheres until most of it is emitted to the atmosphere as NO, N2O or N2. A complete estimate of the effects from human activities on N2O emissions must therefore include all emissions, the direct emissions and the indirect emissions that happen in interlinked spheres. For this it is necessary to assess the fluxes at least at the landscape scale. The episodic nature and the large spatial variability make it difficult to estimate the direct and indirect emissions in a landscape. Modelling requires not only to include the highly variable microbial processes in the ecosystems that produce N2O but as well the accurate simulation of lateral Nr fluxes and their effects on N2O fluxes in places remote from the primary Nr sources. In this context tall tower N2O flux measurements are particularly useful as they integrate over larger areas and can be run, continuously without disturbing the fluxes. On the other hand these measurements can be difficult to interpret due to difficulties to measure the small concentration fluctuations in the atmosphere at small flux rates and to accurately attribute the measured flux at the tower to the area that generates the flux, i.e. the source area. The Technical University of Denmark (DTU) has established eddy covariance N2O flux measurements on a 125 m tall tower at its Risø Campus as part of the EU research infrastructure project the 'Integrated non-CO2 Greenhouse gas Observing System' (InGOS). The eddy covariance system consisted of a N2O/CO quantum cascade laser, Los Gatos, Mountain View, CA, USA and a 3D sonic anemometer (USA-1), Metek, Elmshorn, Germany. The Risø peninsula lies at the

  6. Importance of Accurate Measurements in Nutrition Research: Dietary Flavonoids as a Case Study

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Accurate measurements of the secondary metabolites in natural products and plant foods are critical to establishing diet/health relationships. There are as many as 50,000 secondary metabolites which may influence human health. Their structural and chemical diversity present a challenge to analytic...

  7. Toward Accurate Measurement of Participation: Rethinking the Conceptualization and Operationalization of Participatory Evaluation

    ERIC Educational Resources Information Center

    Daigneault, Pierre-Marc; Jacob, Steve

    2009-01-01

    While participatory evaluation (PE) constitutes an important trend in the field of evaluation, its ontology has not been systematically analyzed. As a result, the concept of PE is ambiguous and inadequately theorized. Furthermore, no existing instrument accurately measures stakeholder participation. First, this article attempts to overcome these…

  8. 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.

  9. 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.

  10. Particle and heat flux measurements in PDX edge plasmas

    SciTech Connect

    Budny, R.; Manos, D.

    1983-12-01

    This paper describes the use of novel combined Langmuir-calorimeter probes to measure edge plasma conditions near the midplane in PDX. The probes consisted of up to five Langmuir probes and up to two calorimeters. Single and double probe characteristics yield n/sub e/ and T/sub e/ which are compared with that derived from a triple probe analysis. The calorimeters measure heat flux in the electron and ion drift directions. This paper presents time-resolved radial profiles of n/sub e/, T/sub e/, V/sub F/ (floating potential), and P (heat flux) during high power neutral beam-heated, single-null discharges and circular scoop limiter discharges. The temporal dependence of these quantities displays the previous observed behavior with respect to gross discharge characteristics; however, an additional dependence on confinement mode has been observed. During the H-mode of energy confinement, a transient depression of n/sub e/, T/sub e/, and P occurs in the scrape-off plasma.

  11. Device and method for accurately measuring concentrations of airborne transuranic isotopes

    DOEpatents

    McIsaac, C.V.; Killian, E.W.; Grafwallner, E.G.; Kynaston, R.L.; Johnson, L.O.; Randolph, P.D.

    1996-09-03

    An alpha continuous air monitor (CAM) with two silicon alpha detectors and three sample collection filters is described. This alpha CAM design provides continuous sampling and also measures the cumulative transuranic (TRU), i.e., plutonium and americium, activity on the filter, and thus provides a more accurate measurement of airborne TRU concentrations than can be accomplished using a single fixed sample collection filter and a single silicon alpha detector. 7 figs.

  12. Device and method for accurately measuring concentrations of airborne transuranic isotopes

    DOEpatents

    McIsaac, Charles V.; Killian, E. Wayne; Grafwallner, Ervin G.; Kynaston, Ronnie L.; Johnson, Larry O.; Randolph, Peter D.

    1996-01-01

    An alpha continuous air monitor (CAM) with two silicon alpha detectors and three sample collection filters is described. This alpha CAM design provides continuous sampling and also measures the cumulative transuranic (TRU), i.e., plutonium and americium, activity on the filter, and thus provides a more accurate measurement of airborne TRU concentrations than can be accomplished using a single fixed sample collection filter and a single silicon alpha detector.

  13. 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.

  14. 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.

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

    NASA Astrophysics Data System (ADS)

    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.

  16. 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.

  17. 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.

  18. Laboratory Measurement of Enthalpy Flux in High Winds

    NASA Astrophysics Data System (ADS)

    Jeong, D.; Haus, B. K.; Donelan, M. A.; Zhang, J.

    2006-12-01

    The intensity of tropical cyclones is sensitive to the rates at which enthalpy and momentum are transferred between sea and air in the high-wind core of the storm. Present models of the wind dependence of these transfer rates, does not allow for storms of greater than marginal hurricane intensity. Recent studies have shown that there is a saturation of the bulk drag coefficient in high winds, however more information on the enthalpy flux is required. In particular the role that sea spray plays in enhancing the enthalpy transfer at very high wind speeds is not known. The coefficients for sensible and latent heat transfer (Stanton and Dalton numbers) were measured in the 15-m wind-wave facility at the University of Miami's Air-Sea Interaction Saltwater Tank (ASIST). The wind speed (referred to 10m) was explored over a range of 0 to 45 m/s, covering a full range of aerodynamic conditions from smooth to fully rough. Experiments were designed with water temperatures set between 2 and 5° C above/below the air temperature, with precision thermistors (± 0.002° C) to monitor temperature and Li-Cor infra-red absorption devices to monitor specific humidity changes at upstream and downstream ends of the wave tank during the experiment. The calorimetric use of a wind-wave tank gave precise flux estimates, and experiments were repeated at different Bowen ratios to allow the separation of the heat and moisture parts of the transfer. The effect of spray on the moisture flux was reflected in the drop in temperature along the air path from upstream to downstream and this made it possible to estimate the total spray evaporated in the air column.

  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. Field-scale evaluation of the passive flux meter for simultaneous measurement of groundwater and contaminant fluxes.

    PubMed

    Annable, Michael D; Hatfield, Kirk; Cho, Jaehyun; Klammler, Harald; Parker, Beth L; Cherry, John A; Rao, P Suresh C

    2005-09-15

    A new method, passive flux meter (PFM), has been developed and field-tested for simultaneously measuring contaminant and groundwater fluxes in the saturated zone at hazardous waste sites. The PFM approach uses a sorptive permeable medium placed in either a borehole or monitoring well to intercept contaminated groundwater and release "resident" tracers. The sorbent pack is placed in a groundwater flow field for a specified exposure time and then recovered for extraction and analysis. By quantifying the mass fraction of resident tracers lost and the mass of contaminant sorbed, groundwater and contaminant fluxes are calculated. Here, we assessed the performance of PFMs at the Canadian Forces Base Borden field site in Ontario, Canada. Two field tests were conducted under imposed groundwater flow fields: (1) radial flow to a well and (2) linear flow in a test channel confined by sheet pile walls on three sides. Both tests demonstrate that the local fluxes measured by PFM and averaged overthe screen interval were within 15% of imposed groundwaterflow and within 30% of measured contaminant mass flux. Patterns in depth variations in groundwater and contaminant fluxes, determined by the PFM approach, allow for site characterization at a higher spatial resolution. These results support the PMF method as a potential innovative alternative for measuring groundwater and contaminant fluxes in screened wells.

  1. Particle Image Velocimetry Measurements in an Anatomically-Accurate Scaled Model of the Mammalian Nasal Cavity

    NASA Astrophysics Data System (ADS)

    Rumple, Christopher; Krane, Michael; Richter, Joseph; Craven, Brent

    2013-11-01

    The mammalian nose is a multi-purpose organ that houses a convoluted airway labyrinth responsible for respiratory air conditioning, filtering of environmental contaminants, and chemical sensing. Because of the complexity of the nasal cavity, the anatomy and function of these upper airways remain poorly understood in most mammals. However, recent advances in high-resolution medical imaging, computational modeling, and experimental flow measurement techniques are now permitting the study of respiratory airflow and olfactory transport phenomena in anatomically-accurate reconstructions of the nasal cavity. Here, we focus on efforts to manufacture an anatomically-accurate transparent model for stereoscopic particle image velocimetry (SPIV) measurements. Challenges in the design and manufacture of an index-matched anatomical model are addressed. PIV measurements are presented, which are used to validate concurrent computational fluid dynamics (CFD) simulations of mammalian nasal airflow. Supported by the National Science Foundation.

  2. Defining allowable physical property variations for high accurate measurements on polymer parts

    NASA Astrophysics Data System (ADS)

    Mohammadi, A.; Sonne, M. R.; Madruga, D. G.; De Chiffre, L.; Hattel, J. H.

    2016-06-01

    Measurement conditions and material properties have a significant impact on the dimensions of a part, especially for polymers parts. Temperature variation causes part deformations that increase the uncertainty of the measurement process. Current industrial tolerances of a few micrometres demand high accurate measurements in non-controlled ambient. Most of polymer parts are manufactured by injection moulding and their inspection is carried out after stabilization, around 200 hours. The overall goal of this work is to reach ±5μm in uncertainty measurements a polymer products which is a challenge in today`s production and metrology environments. The residual deformations in polymer products at room temperature after injection molding are important when micrometer accuracy needs to be achieved. Numerical modelling can give a valuable insight to what is happening in the polymer during cooling down after injection molding. In order to obtain accurate simulations, accurate inputs to the model are crucial. In reality however, the material and physical properties will have some variations. Although these variations may be small, they can act as a source of uncertainty for the measurement. In this paper, we investigated how big the variation in material and physical properties are allowed in order to reach the 5 μm target on the uncertainty.

  3. Radiometer for accurate (+ or - 1%) measurement of solar irradiance equal to 10,000 solar constants

    NASA Technical Reports Server (NTRS)

    Kendall, J. M., Sr.

    1981-01-01

    The 10,000 solar constant radiometer was developed for the accurate (+ or - 1%) measurement of the irradiance produced in the image formed by a parabolic reflector or by a multiple mirror solar installation. This radiometer is water cooled, weighs about 1 kg, and is 5 cm (2 in.) in diameter by 10 cm (4 in.) long. A sting is provided for mounting the radiometer in the solar installation capable of measuring irradiances as high as 20,000 solar constants, the instrument is self calibrating. Its accuracy depends on the accurate determination of the cavity aperture, and absorptivity of the cavity, and accurate electrical measurements. The spectral response is flat over the entire spectrum from far UV to far IR. The radiometer responds to a measurement within 99.7% of the final value within 8 s. During a measurement of the 10,000 solar constant irradiance, the temperature rise of the water is about 20 C. The radiometer has perfect cosine response up to 60 deg off the radiometer axis.

  4. "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.

  5. Surprisingly low frequency attenuation effects in long tubes when measuring turbulent fluxes at tall towers

    NASA Astrophysics Data System (ADS)

    Ibrom, Andreas; Brændholt, Andreas; Pilegaard, Kim

    2016-04-01

    The eddy covariance technique relies on the fast and accurate measurement of gas concentration fluctuations. While for some gasses robust and compact sensors are available, measurement of, e.g., non CO2 greenhouse gas fluxes is often performed with sensitive equipment that cannot be run on a tower without massively disturbing the wind field. To measure CO and N2O fluxes, we installed an eddy covariance system at a 125 m mast, where the gas analyser was kept in a laboratory close to the tower and the sampling was performed using a 150 m long tube with a gas intake at 96 m height. We investigated the frequency attenuation and the time lag of the N2O and CO concentration measurements with a concentration step experiment. The results showed surprisingly high cut-off frequencies (close to 2 Hz) and small low-pass filter induced time lags (< 0.3 s), which were similar for CO and N2O. The results indicate that the concentration signal was hardly biased during the ca 10 s travel through the tube. Due to the larger turbulence time scales at large measurement heights the low-pass correction was for the majority of the measurements < 5%. For water vapour the tube attenuation was massive, which had, however, a positive effect by reducing both the water vapour dilution correction and the cross sensitivity effects on the N2O and CO flux measurements. Here we present the set-up of the concentration step change experiment and its results and compare them with recently developed theories for the behaviour of gases in turbulent tube flows.

  6. Rotating Arc Jet Test Model: Time-Accurate Trajectory Heat Flux Replication in a Ground Test Environment

    NASA Technical Reports Server (NTRS)

    Laub, Bernard; Grinstead, Jay; Dyakonov, Artem; Venkatapathy, Ethiraj

    2011-01-01

    Though arc jet testing has been the proven method employed for development testing and certification of TPS and TPS instrumentation, the operational aspects of arc jets limit testing to selected, but constant, conditions. Flight, on the other hand, produces timevarying entry conditions in which the heat flux increases, peaks, and recedes as a vehicle descends through an atmosphere. As a result, we are unable to "test as we fly." Attempts to replicate the time-dependent aerothermal environment of atmospheric entry by varying the arc jet facility operating conditions during a test have proven to be difficult, expensive, and only partially successful. A promising alternative is to rotate the test model exposed to a constant-condition arc jet flow to yield a time-varying test condition at a point on a test article (Fig. 1). The model shape and rotation rate can be engineered so that the heat flux at a point on the model replicates the predicted profile for a particular point on a flight vehicle. This simple concept will enable, for example, calibration of the TPS sensors on the Mars Science Laboratory (MSL) aeroshell for anticipated flight environments.

  7. Practical do-it-yourself device for accurate volume measurement of breast.

    PubMed

    Tezel, E; Numanoğlu, A

    2000-03-01

    A simple and accurate method of measuring differences in breast volume based on Archimedes' principle is described. In this method, a plastic container is placed on the breast of the patient who is lying in supine position. While the breast occupies part of the container, the remaining part is filled with water and the volume is measured. This method allows the measurement of the volume differences of asymmetric breasts and also helps the surgeon to estimate the size of the prosthesis to be used in augmentation mammaplasty. PMID:10724264

  8. 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...

  9. Progress Toward Accurate Measurements of Power Consumptions of DBD Plasma Actuators

    NASA Technical Reports Server (NTRS)

    Ashpis, David E.; Laun, Matthew C.; Griebeler, Elmer L.

    2012-01-01

    The accurate measurement of power consumption by Dielectric Barrier Discharge (DBD) plasma actuators is a challenge due to the characteristics of the actuator current signal. Micro-discharges generate high-amplitude, high-frequency current spike transients superimposed on a low-amplitude, low-frequency current. We have used a high-speed digital oscilloscope to measure the actuator power consumption using the Shunt Resistor method and the Monitor Capacitor method. The measurements were performed simultaneously and compared to each other in a time-accurate manner. It was found that low signal-to-noise ratios of the oscilloscopes used, in combination with the high dynamic range of the current spikes, make the Shunt Resistor method inaccurate. An innovative, nonlinear signal compression circuit was applied to the actuator current signal and yielded excellent agreement between the two methods. The paper describes the issues and challenges associated with performing accurate power measurements. It provides insights into the two methods including new insight into the Lissajous curve of the Monitor Capacitor method. Extension to a broad range of parameters and further development of the compression hardware will be performed in future work.

  10. Reentrant albedo proton fluxes measured by the PAMELA experiment

    NASA Astrophysics Data System (ADS)

    Adriani, O.; Barbarino, G. C.; Bazilevskaya, G. A.; Bellotti, R.; Boezio, M.; Bogomolov, E. A.; Bongi, M.; Bonvicini, V.; Bottai, S.; Bruno, A.; Cafagna, F.; Campana, D.; Carlson, P.; Casolino, M.; Castellini, G.; Donato, C. De; De Santis, C.; De Simone, N.; Di Felice, V.; Formato, V.; Galper, A. M.; Karelin, A. V.; Koldashov, S. V.; Koldobskiy, S.; Krutkov, S. Y.; Kvashnin, A. N.; Leonov, A.; Malakhov, V.; Marcelli, L.; Martucci, M.; Mayorov, A. G.; Menn, W.; Mergé, M.; Mikhailov, V. V.; Mocchiutti, E.; Monaco, A.; Mori, N.; Munini, R.; Osteria, G.; Palma, F.; Panico, B.; Papini, P.; Pearce, M.; Picozza, P.; Ricci, M.; Ricciarini, S. B.; Sarkar, R.; Scotti, V.; Simon, M.; Sparvoli, R.; Spillantini, P.; Stozhkov, Y. I.; Vacchi, A.; Vannuccini, E.; Vasilyev, G. I.; Voronov, S. A.; Yurkin, Y. T.; Zampa, G.; Zampa, N.

    2015-05-01

    We present a precise measurement of downward going albedo proton fluxes for kinetic energy above ˜70 MeV performed by the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) experiment at an altitude between 350 and 610 km. On the basis of a trajectory tracing simulation, the analyzed protons were classified into quasi-trapped, concentrating in the magnetic equatorial region, and untrapped spreading over all latitudes, including both short-lived (precipitating) and long-lived (pseudotrapped) components. In addition, features of the penumbra region around the geomagnetic cutoff were investigated in detail. PAMELA results significantly improve the characterization of the high-energy albedo proton populations at low-Earth orbits.

  11. A novel method for measuring trace gas fluxes from tall vegetation

    NASA Astrophysics Data System (ADS)

    Keane, James; Phil, Ineson

    2014-05-01

    The nature of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) as greenhouse gases (GHGs) means that accurate measurement of their net ecosystem exchange (NEE) is extremely important to our ability to manage climate change. Manual static chambers are commonly used to measure soil fluxes of these trace gases, with landscape values extrapolated from point measurements of typically less than 1m2, at a weekly or monthly frequency. Moreover, due to the reliance upon manual sampling, data are typically biased towards day-time measurements, and use of opaque chambers halts photosynthesis. Automation of chambers, such as the Licor Li-8100 (Lincoln, NE) system, allows for measurement of soil respiration at a near-constant frequency, but does not solve the problem of measuring CH4 and N2O, neither does it allow measurements to be taken from over tall (more than 20 cm) vegetation. Eddy covariance (EC) techniques allow for high frequency measurements of CO2 and CH4 to be made at the landscape scale, and are increasingly available for N2O. However, the inability of EC to resolve to the plot scale hinders its use for manipulative experiments, and replication is rare. Additionally, stratification of the boundary layer creates difficulty in measuring night-time fluxes and it is common to discard large parts of data sets due to unsuitable wind direction or other meteorological conditions. Here we present a new technique for measuring trace gas fluxes from over tall vegetation. The system is capable of simultaneously delivering NEE of CO2, CH4 and N2O, automatically measuring at high temporal resolution (circa hourly) from replicated plots. We show the effect of green compost addition on trace gas fluxes from Miscanthus x giganteus, an important crop for bioenergy production. The ability to quantify NEE of GHGs from such crops forms an essential part of the lifecycle analysis of energy produced from biomass, which may play an important role in future mitigation of climate

  12. Accurate potential drop sheet resistance measurements of laser-doped areas in semiconductors

    SciTech Connect

    Heinrich, Martin; Kluska, Sven; Binder, Sebastian; Hameiri, Ziv; Hoex, Bram; Aberle, Armin G.

    2014-10-07

    It is investigated how potential drop sheet resistance measurements of areas formed by laser-assisted doping in crystalline Si wafers are affected by typically occurring experimental factors like sample size, inhomogeneities, surface roughness, or coatings. Measurements are obtained with a collinear four point probe setup and a modified transfer length measurement setup to measure sheet resistances of laser-doped lines. Inhomogeneities in doping depth are observed from scanning electron microscope images and electron beam induced current measurements. It is observed that influences from sample size, inhomogeneities, surface roughness, and coatings can be neglected if certain preconditions are met. Guidelines are given on how to obtain accurate potential drop sheet resistance measurements on laser-doped regions.

  13. Precise and Accurate Measurements of Strong-Field Photoionization and a Transferable Laser Intensity Calibration Standard.

    PubMed

    Wallace, W C; Ghafur, O; Khurmi, C; Sainadh U, Satya; Calvert, J E; Laban, D E; Pullen, M G; Bartschat, K; Grum-Grzhimailo, A N; Wells, D; Quiney, H M; Tong, X M; Litvinyuk, I V; Sang, R T; Kielpinski, D

    2016-07-29

    Ionization of atoms and molecules in strong laser fields is a fundamental process in many fields of research, especially in the emerging field of attosecond science. So far, demonstrably accurate data have only been acquired for atomic hydrogen (H), a species that is accessible to few investigators. Here, we present measurements of the ionization yield for argon, krypton, and xenon with percent-level accuracy, calibrated using H, in a laser regime widely used in attosecond science. We derive a transferable calibration standard for laser peak intensity, accurate to 1.3%, that is based on a simple reference curve. In addition, our measurements provide a much needed benchmark for testing models of ionization in noble-gas atoms, such as the widely employed single-active electron approximation.

  14. Precise and Accurate Measurements of Strong-Field Photoionization and a Transferable Laser Intensity Calibration Standard.

    PubMed

    Wallace, W C; Ghafur, O; Khurmi, C; Sainadh U, Satya; Calvert, J E; Laban, D E; Pullen, M G; Bartschat, K; Grum-Grzhimailo, A N; Wells, D; Quiney, H M; Tong, X M; Litvinyuk, I V; Sang, R T; Kielpinski, D

    2016-07-29

    Ionization of atoms and molecules in strong laser fields is a fundamental process in many fields of research, especially in the emerging field of attosecond science. So far, demonstrably accurate data have only been acquired for atomic hydrogen (H), a species that is accessible to few investigators. Here, we present measurements of the ionization yield for argon, krypton, and xenon with percent-level accuracy, calibrated using H, in a laser regime widely used in attosecond science. We derive a transferable calibration standard for laser peak intensity, accurate to 1.3%, that is based on a simple reference curve. In addition, our measurements provide a much needed benchmark for testing models of ionization in noble-gas atoms, such as the widely employed single-active electron approximation. PMID:27517769

  15. Precise and Accurate Measurements of Strong-Field Photoionization and a Transferable Laser Intensity Calibration Standard

    NASA Astrophysics Data System (ADS)

    Wallace, W. C.; Ghafur, O.; Khurmi, C.; Sainadh U, Satya; Calvert, J. E.; Laban, D. E.; Pullen, M. G.; Bartschat, K.; Grum-Grzhimailo, A. N.; Wells, D.; Quiney, H. M.; Tong, X. M.; Litvinyuk, I. V.; Sang, R. T.; Kielpinski, D.

    2016-07-01

    Ionization of atoms and molecules in strong laser fields is a fundamental process in many fields of research, especially in the emerging field of attosecond science. So far, demonstrably accurate data have only been acquired for atomic hydrogen (H), a species that is accessible to few investigators. Here, we present measurements of the ionization yield for argon, krypton, and xenon with percent-level accuracy, calibrated using H, in a laser regime widely used in attosecond science. We derive a transferable calibration standard for laser peak intensity, accurate to 1.3%, that is based on a simple reference curve. In addition, our measurements provide a much needed benchmark for testing models of ionization in noble-gas atoms, such as the widely employed single-active electron approximation.

  16. Are External Knee Load and EMG Measures Accurate Indicators of Internal Knee Contact Forces during Gait?

    PubMed Central

    Meyer, Andrew J.; D'Lima, Darryl D.; Besier, Thor F.; Lloyd, David G.; Colwell, Clifford W.; Fregly, Benjamin J.

    2013-01-01

    Mechanical loading is believed to be a critical factor in the development and treatment of knee osteoarthritis. However, the contact forces to which the knee articular surfaces are subjected during daily activities cannot be measured clinically. Thus, the ability to predict internal knee contact forces accurately using external measures (i.e., external knee loads and muscle EMG signals) would be clinically valuable. This study quantifies how well external knee load and EMG measures predict internal knee contact forces during gait. A single subject with a force-measuring tibial prosthesis and post-operative valgus alignment performed four gait patterns (normal, medial thrust, walking pole, and trunk sway) to induce a wide range of external and internal knee joint loads. Linear regression analyses were performed to assess how much of the variability in internal contact forces was accounted for by variability in the external measures. Though the different gait patterns successfully induced significant changes in the external and internal quantities, changes in external measures were generally weak indicators of changes in total, medial, and lateral contact force. Our results suggest that when total contact force may be changing, caution should be exercised when inferring changes in knee contact forces based on observed changes in external knee load and EMG measures. Advances in musculoskeletal modeling methods may be needed for accurate estimation of in vivo knee contact forces. PMID:23280647

  17. Accurate Determination of Torsion and Pure Bending Moment for Viscoelastic Measurements

    NASA Astrophysics Data System (ADS)

    Wang, Yun-Che; Ko, Chih-Chin; Shiau, Li-Ming

    Measurements of time-dependent material properties in the context of linear viscoelasticity, at a given frequency and temperature, require accurate determination of both loading and deformation that are subjected to the testing materials. A pendulum-type viscoelastic spectroscopy is developed to experimentally measure loss tangent and the magnitude of dynamic modulus of solid materials. The mechanical system of the device is based on the behavior of the cantilever beam, and torsion and pure bending moment are generated from the interaction between a permanent magnet and the Helmholtz coils. The strength of the magnetic interactions may be determined with a material with known mechanical properties, such as aluminum 6061T4 alloy. The sensitivity of the torque measurement is on the order of one micro N-m level. With the high accurate torque measurement and deformation detection from a laser-based displacement measurement system, viscoelastic properties of materials can be experimentally measured in different frequency regimes. Sinusoidal driving signals are adopted for measuring complex modulus in the sub-resonant regime, and dc bias driving for creep tests in the low frequency limit. At structural resonant frequencies, the full-width-at-half-maximum (FWHM) method or Lorentzian curve fitting method is adopted to extract material properties. The completion of determining material properties in the wide frequency spectrum may help to identify the deformation mechanisms of the material and to create better models for simulation work.

  18. Rapid accurate isotopic measurements on boron in boric acid and boron carbide.

    PubMed

    Duchateau, N L; Verbruggen, A; Hendrickx, F; De Bièvre, P

    1986-04-01

    A procedure is described whereby rapid and accurate isotopic measurements can be performed on boron in boric acid and boron carbide after fusion of these compounds with calcium carbonate. It allows the determination of the isotopic composition of boron in boric acid and boron carbide and the direct assay of boron or the (10)B isotope in boron carbide by isotope-dilution mass spectrometry.

  19. A Novel Multimode Waveguide Coupler for Accurate Power Measurement of Traveling Wave Tube Harmonic Frequencies

    NASA Technical Reports Server (NTRS)

    Wintucky, Edwin G.; Simons, Rainee N.

    2014-01-01

    This paper presents the design, fabrication and test results for a novel waveguide multimode directional coupler (MDC). The coupler fabricated from two dissimilar waveguides is capable of isolating the power at the second harmonic frequency from the fundamental power at the output port of a traveling-wave tube (TWT). In addition to accurate power measurements at harmonic frequencies, a potential application of the MDC is in the design of a beacon source for atmospheric propagation studies at millimeter-wave frequencies.

  20. Accurate macromolecular structures using minimal measurements from X-ray free-electron lasers.

    PubMed

    Hattne, Johan; Echols, Nathaniel; Tran, Rosalie; Kern, Jan; Gildea, Richard J; Brewster, Aaron S; Alonso-Mori, Roberto; Glöckner, Carina; Hellmich, Julia; Laksmono, Hartawan; Sierra, Raymond G; Lassalle-Kaiser, Benedikt; Lampe, Alyssa; Han, Guangye; Gul, Sheraz; DiFiore, Dörte; Milathianaki, Despina; Fry, Alan R; Miahnahri, Alan; White, William E; Schafer, Donald W; Seibert, M Marvin; Koglin, Jason E; Sokaras, Dimosthenis; Weng, Tsu-Chien; Sellberg, Jonas; Latimer, Matthew J; Glatzel, Pieter; Zwart, Petrus H; Grosse-Kunstleve, Ralf W; Bogan, Michael J; Messerschmidt, Marc; Williams, Garth J; Boutet, Sébastien; Messinger, Johannes; Zouni, Athina; Yano, Junko; Bergmann, Uwe; Yachandra, Vittal K; Adams, Paul D; Sauter, Nicholas K

    2014-05-01

    X-ray free-electron laser (XFEL) sources enable the use of crystallography to solve three-dimensional macromolecular structures under native conditions and without radiation damage. Results to date, however, have been limited by the challenge of deriving accurate Bragg intensities from a heterogeneous population of microcrystals, while at the same time modeling the X-ray spectrum and detector geometry. Here we present a computational approach designed to extract meaningful high-resolution signals from fewer diffraction measurements.

  1. 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.

  2. Accurate phase measurements for thick spherical objects using optical quadrature microscopy

    NASA Astrophysics Data System (ADS)

    Warger, William C., II; DiMarzio, Charles A.

    2009-02-01

    In vitro fertilization (IVF) procedures have resulted in the birth of over three million babies since 1978. Yet the live birth rate in the United States was only 34% in 2005, with 32% of the successful pregnancies resulting in multiple births. These multiple pregnancies were directly attributed to the transfer of multiple embryos to increase the probability that a single, healthy embryo was included. Current viability markers used for IVF, such as the cell number, symmetry, size, and fragmentation, are analyzed qualitatively with differential interference contrast (DIC) microscopy. However, this method is not ideal for quantitative measures beyond the 8-cell stage of development because the cells overlap and obstruct the view within and below the cluster of cells. We have developed the phase-subtraction cell-counting method that uses the combination of DIC and optical quadrature microscopy (OQM) to count the number of cells accurately in live mouse embryos beyond the 8-cell stage. We have also created a preliminary analysis to measure the cell symmetry, size, and fragmentation quantitatively by analyzing the relative dry mass from the OQM image in conjunction with the phase-subtraction count. In this paper, we will discuss the characterization of OQM with respect to measuring the phase accurately for spherical samples that are much larger than the depth of field. Once fully characterized and verified with human embryos, this methodology could provide the means for a more accurate method to score embryo viability.

  3. Measuring Underground Neutron Fluxes for Neutrinoless Double Beta Decay

    NASA Astrophysics Data System (ADS)

    Colletti, Katrina; Tayloe, Rex; Cooper, Robert; Garrison, Lance; Thornton, Tyler; Steele, Ethan

    2013-10-01

    The goal of this project was to measure the muon-induced neutron flux in lead at sea level using the SciBath neutral particle detector. The muon-induced neutron rate is not well known, is challenging to measure and simulate, and potentially an important background for underground experiments such as the EXO neutrinoless double beta-decay experiment. A mass of 45 kg of lead was placed on top of the detector, and muon/neutron-capture correlated events were measured. Events with accidental neutron-capture signals were subtracted as were muon/neutron-capture correlated events from spallation in the detector liquid scintillator. This procedure resulted in a neutron yield from lead at sea level of 1 . 4 (+/- 1 . 1) ×10-5n/μ (gcm-2)-1 with the typical muon energy at sea level Eμ ~ 4 GeV. We compare this to parameterizations created for underground experimental sites extrapolated up to sea level. NSF funded.

  4. How Direct Flux Measurements Can Improve Infiltration Estimates in Ephemeral Streams

    NASA Astrophysics Data System (ADS)

    Batlle-Aguilar, J.; Xie, Y.; Cook, P. G.

    2015-12-01

    In arid and semi-arid areas replenishment of groundwater resources is strongly dependent on surface water infiltration from ephemeral streams and creeks. An accurate estimation of water infiltration and aquifer recharge from these surface water features is paramount, but this task is subject to physical (streambed heterogeneity) and transient (flow variability) challenges of these watercourses. Although several methods are available to estimate stream infiltration, only a handful of them are suitable for ephemeral streams, all of which are indirect methods. In this study we performed an infiltration experiment at the transect scale in an ephemeral stream at the time it was dry, thereby obtaining direct estimates of stream infiltration. Groundwater heads measured in a transect of piezometers orthogonal to the stream identified the development of a groundwater mound laterally displaced several meters into the streambank. The experiment was modelled using the two-dimensional integrated surface-subsurface model HydroGeosphere® and calibrated with PEST using different combinations of groundwater heads and infiltration volume data. Although the model can be calibrated to produce a good match to measured groundwater heads, accurate predictions of stream infiltration can be made only if the heads used for model calibration capture the groundwater mound. The use of infiltration flux or volume during model calibration, instead, provides the best calibration results, and does not require knowledge of the position of the groundwater mound. Given that heterogeneity of streambed and streambank sediments leads to the possibility that the groundwater mound developed during flow events will be poorly characterised or perhaps missed altogether, we demonstrate that incorporating infiltration flux or volume data into the model calibration increases the ability of a model to simulate accurate estimates of stream infiltration during natural flow events.

  5. Accurate measurement of cortical bone elasticity tensor with resonant ultrasound spectroscopy.

    PubMed

    Bernard, Simon; Grimal, Quentin; Laugier, Pascal

    2013-02-01

    Resonant ultrasound spectroscopy (RUS) allows to accurately characterize the complete set of elastic constants of an anisotropic material from a set of measured mechanical resonant frequencies of a specimen. This method does not suffer from the drawbacks and limitations of the conventional sound velocity approach, but has been reported to fail to measure bone because of its strong viscoelastic damping. In this study, we take advantage of recent developments of RUS to overcome this limitation. The frequency response of a human cortical bone specimen (about 5 × 7 × 7 mm(3)) was measured between 100 and 280 kHz. Despite an important overlapping of the resonant peaks 20 resonant frequencies could be retrieved by using a dedicated signal processing method. The experimental frequencies were progressively matched to the frequencies predicted by a model of the sample whose elastic constants were adjusted. The determined diagonal elastic constants were in good agreement with concurrent sound velocity measurements performed in the principal directions of the specimen. This study demonstrates that RUS is suitable for an accurate measurement of cortical bone anisotropic elasticity. In particular, precision of measured Young and shear moduli is about 0.5%.

  6. 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.

  7. Accurate measurement of spatial noise portraits of photosensors of digital cameras

    NASA Astrophysics Data System (ADS)

    Cheremkhin, P. A.; Evtikhiev, N. N.; Krasnov, V. V.; Kulakov, M. N.; Starikov, R. S.

    2016-08-01

    Method of measurement of accurate portraits of light and dark spatial noise of photosensors is described. The method consists of four steps: creation of spatially homogeneous illumination; shooting light and dark frames; digital processing and filtering. Unlike standard technique, this method uses iterative creation of spatially homogeneous illumination by display, compensation of photosensor dark spatial noise portrait and improved procedure of elimination of dark temporal noise. Portraits of light and dark spatial noise of photosensors of a scientific digital camera were found. Characteristics of the measured portraits were compared with values of photo response and dark signal non-uniformities of camera's photosensor.

  8. Lyman continuum galaxies: Observed Lyman continuum flux measurements at z ~ 3-4 and mechanisms behind the escape

    NASA Astrophysics Data System (ADS)

    Cooke, Jeff; Ryan-Weber, Emma; Garel, Thibault; Gonzalo Diaz, C.

    2016-06-01

    Measuring the surviving Lyman continuum (LyC) flux and inferred ionizing photon escape fraction (f_esc) of Lyman break galaxies has proved challenging, in part due to the historical selection criteria based on a Lyman continuum break. A few galaxies, largely serendipitous, have been detected with measurable LyC flux but have colors inconsistent with Lyman break galaxy expectations for their specific redshifts. I will discuss our physically motivated technique that provides an accurate measure of the average f_esc for the z ~ 3 Lyman break galaxy population that has also identified a population of galaxies, termed Lyman continuum galaxies (LCGs) with high expected levels of surviving LyC flux. I will present the results of our program that uses 30-band photometry, HST imaging, and deep medium-band IR imaging from the ZFOURGE survey to select z ~ 3-4 LCGs. We obtained very deep Keck spectroscopy that has confirmed the LCG population and has directly measured the predicted level of LyC flux. In addition, our program has obtained deep Keck infrared spectroscopy to calibrate restframe optical nebular emission-line models used to predict the LyC escape fraction, with the aim to measure the f_esc of galaxies at the Epoch of Reionization where direct LyC flux detection is not possible.

  9. 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.

  10. Material interactions with the low earth orbital environment Accurate reaction rate measurements

    NASA Technical Reports Server (NTRS)

    Visentine, J. T.; Leger, L. J.

    1985-01-01

    Interactions between spacecraft surfaces and atomic oxygen within the low earth orbital (LEO) environment have been observed and measured during Space Shuttle flights over the past 3 yr. The results of these experiments have demonstrated that interaction rates for many materials proposed for spacecraft applications are high and that protective coatings must be developed to enable long-lived operation of spacecraft structures in the LEO environment. A flight experiment discussed herein uses the Space Shuttle as an orbiting exposure laboratory to obtain accurate reaction rate measurements for materials typically used in spacecraft construction. An ion-neutral mass spectrometer, installed in the Orbiter cargo bay, will measure diurnal ambient oxygen densities while material samples are exposed at low altitude (222 km) to the orbital environment. From in situ atomic oxygen density information and postflight material recession measurements, accurate reaction rates can be derived to update the Space Station materials interaction data base. Additionally, gases evolved from a limited number of material surfaces subjected to direct oxygen impingement will be identified using the mass spectrometer. These measurements will aid in mechanistic definitions of chemical reactions which cause atom-surface interactions and in validating results of upcoming degradation studies conducted in ground-based neutral beam laboratories.

  11. Accurate time-of-flight measurement of particle based on ECL-TTL Timer

    NASA Astrophysics Data System (ADS)

    Li, Deping; Liu, Jianguo; Huang, Shuhua; Gui, Huaqiao; Cheng, Yin; Wang, Jie; Lu, Yihuai

    2014-11-01

    Because of its aerodynamic diameter of the aerosol particles are stranded in different parts of different human respiratory system, thus affecting human health. Therefore, how to continue to effectively monitor the aerosol particles become increasingly concerned about. Use flight time of aerosol particle beam spectroscopy of atmospheric aerosol particle size distribution is the typical method for monitoring atmospheric aerosol particle size and particle concentration measurement , and it is the key point to accurate measurement of aerosol particle size spectra that measurement of aerosol particle flight time. In order to achieve accurate measurements of aerosol particles in time-of-flight, this paper design an ECL-TTL high-speed timer with ECL counter and TTL counter. The high-speed timer includes a clock generation, high-speed timer and the control module. Clock Generation Module using a crystal plus multiplier design ideas, take advantage of the stability of the crystal to provide a stable 500MHz clock signal is high counter. High count module design using ECL and TTL counter mix design, timing accuracy while effectively maintaining , expanding the timing range, and simplifies circuit design . High-speed counter control module controls high-speed counter start, stop and reset timely based on aerosol particles time-of-flight, is a key part of the high-speed counting. The high-speed counting resolution of 4ns, the full scale of 4096ns, has been successfully applied Aerodynamic Particle Sizer, to meet the precise measurement of aerosol particles time-of-flight.

  12. Accurate Critical Stress Intensity Factor Griffith Crack Theory Measurements by Numerical Techniques

    PubMed Central

    Petersen, Richard C.

    2014-01-01

    Critical stress intensity factor (KIc) has been an approximation for fracture toughness using only load-cell measurements. However, artificial man-made cracks several orders of magnitude longer and wider than natural flaws have required a correction factor term (Y) that can be up to about 3 times the recorded experimental value [1-3]. In fact, over 30 years ago a National Academy of Sciences advisory board stated that empirical KIc testing was of serious concern and further requested that an accurate bulk fracture toughness method be found [4]. Now that fracture toughness can be calculated accurately by numerical integration from the load/deflection curve as resilience, work of fracture (WOF) and strain energy release (SIc) [5, 6], KIc appears to be unnecessary. However, the large body of previous KIc experimental test results found in the literature offer the opportunity for continued meta analysis with other more practical and accurate fracture toughness results using energy methods and numerical integration. Therefore, KIc is derived from the classical Griffith Crack Theory [6] to include SIc as a more accurate term for strain energy release rate (𝒢Ic), along with crack surface energy (γ), crack length (a), modulus (E), applied stress (σ), Y, crack-tip plastic zone defect region (rp) and yield strength (σys) that can all be determined from load and deflection data. Polymer matrix discontinuous quartz fiber-reinforced composites to accentuate toughness differences were prepared for flexural mechanical testing comprising of 3 mm fibers at different volume percentages from 0-54.0 vol% and at 28.2 vol% with different fiber lengths from 0.0-6.0 mm. Results provided a new correction factor and regression analyses between several numerical integration fracture toughness test methods to support KIc results. Further, bulk KIc accurate experimental values are compared with empirical test results found in literature. Also, several fracture toughness mechanisms

  13. Measuring intracellular calcium fluxes in high throughput mode.

    PubMed

    Chambers, Chris; Smith, Fiona; Williams, Christine; Marcos, Sandra; Liu, Zhen Han; Hayter, Paul; Ciaramella, Giuseppe; Keighley, Wilma; Gribbon, Phil; Sewing, Andreas

    2003-06-01

    The measurement of intracellular calcium fluxes in real time is widely applied within the pharmaceutical industry to measure the activation of G-protein coupled receptors (GPCRhyp;s), either for pharmacological characterisation or to screen for new surrogate ligands. Initially restricted to G(q) coupled GPCRs, the introduction of promiscuous and chimeric G-proteins has further widened the application of these assays. The development of new calcium sensitive dyes and assays has provided sensitive, homogeneous assays which can be readily applied to high throughput screening (HTS). In this paper we describe the full automation of this assay type using a fluorometric imaging plate reader (FLIPR ) integrated into a Beckman/Sagian system to establish a simple robotic system that is well suited for the current medium throughput screening in this area of lead discovery. Using a recently completed HTS we discuss important determinants for FLIPR based screening, highlight some limitations of the current approach, and look at the requirements for future automated systems capable of keeping up with expanding compound files.

  14. A new carrier gas type for accurate measurement of N2O by GC-ECD

    NASA Astrophysics Data System (ADS)

    Wang, Yinghong; Wang, Yuesi; Ling, Hong

    2010-11-01

    The accurate measurement of concentration is the basis for determining emission sources and sinks of nitrous oxide (N2O). The detection of N2O showed that the presence of carbon dioxide (CO2) biased the N2O response when pure nitrogen (N2) was used as a carrier gas for gas chromatography (GC) equipped with an electron capture detector (GC-ECD). In this study, laboratory experiments were carried out to explore how the presence of CO2 interferes with the accurate determination of N2O. The aims were to address the extent of the influence to try and explain the underlying mechanism, and to uncover technical options for solving the problem. Three GC carrier gases are discussed: pure nitrogen (DN); a mixture of argon and methane (AM); and a high concentration CO2, which was introduced into the ECD cell with a low flow rate based on DN (DN-CO2). The results show that when DN was used, the existence of CO2 in the ECD cell greatly enhanced the response of N2O, which increased with CO2 content and remained constant when the content reached a limit. Comparisons between the three methods show that the DN method is defective for the accurate determination of N2O. The bias is caused by different electron capture mechanisms of CO2 and N2O and depends heavily on the detector temperature. New GC carrier gas types with make-up gases that can remove the CO2-induced influence, such as the DN-CO2 and DN-CH4 methods reported in this paper, are recommended for the accurate measurement of N2O.

  15. Recommendations for accurate heat capacity measurements using a Quantum Design physical property measurement system

    NASA Astrophysics Data System (ADS)

    Kennedy, Catherine A.; Stancescu, Maria; Marriott, Robert A.; White, Mary Anne

    2007-02-01

    A commercial instrument for determination of heat capacities of solids from ca. 400 K to 0.4 K, the physical property measurement system from Quantum Design, has been used to determine the heat capacities of a standard samples (sapphire [single crystal] and copper). We extend previous tests of the PPMS in three important ways: to temperatures as low as 0.4 K; to samples with poor thermal conductivity; to compare uncertainty with accuracy. We find that the accuracy of heat capacity determinations can be within 1% for 5 K < T < 300 K and 5% for 0.7 K < T < 5 K. Careful attention should be paid to the relative uncertainty for each data point, as determined from multiple measurements. While we have found that it is possible in some circumstances to obtain excellent results by measurement of samples that contribute more than ca. 1/3 to the total heat capacity, there is no "ideal" sample mass and sample geometry also is an important consideration. In fact, our studies of pressed pellets of zirconium tungstate, a poor thermal conductor, show that several samples of different masses should be determined for the highest degree of certainty.

  16. Accurate Construction of Photoactivated Localization Microscopy (PALM) Images for Quantitative Measurements

    PubMed Central

    Coltharp, Carla; Kessler, Rene P.; Xiao, Jie

    2012-01-01

    Localization-based superresolution microscopy techniques such as Photoactivated Localization Microscopy (PALM) and Stochastic Optical Reconstruction Microscopy (STORM) have allowed investigations of cellular structures with unprecedented optical resolutions. One major obstacle to interpreting superresolution images, however, is the overcounting of molecule numbers caused by fluorophore photoblinking. Using both experimental and simulated images, we determined the effects of photoblinking on the accurate reconstruction of superresolution images and on quantitative measurements of structural dimension and molecule density made from those images. We found that structural dimension and relative density measurements can be made reliably from images that contain photoblinking-related overcounting, but accurate absolute density measurements, and consequently faithful representations of molecule counts and positions in cellular structures, require the application of a clustering algorithm to group localizations that originate from the same molecule. We analyzed how applying a simple algorithm with different clustering thresholds (tThresh and dThresh) affects the accuracy of reconstructed images, and developed an easy method to select optimal thresholds. We also identified an empirical criterion to evaluate whether an imaging condition is appropriate for accurate superresolution image reconstruction with the clustering algorithm. Both the threshold selection method and imaging condition criterion are easy to implement within existing PALM clustering algorithms and experimental conditions. The main advantage of our method is that it generates a superresolution image and molecule position list that faithfully represents molecule counts and positions within a cellular structure, rather than only summarizing structural properties into ensemble parameters. This feature makes it particularly useful for cellular structures of heterogeneous densities and irregular geometries, and

  17. Particle Image Velocimetry Measurements in Anatomically-Accurate Models of the Mammalian Nasal Cavity

    NASA Astrophysics Data System (ADS)

    Rumple, C.; Richter, J.; Craven, B. A.; Krane, M.

    2012-11-01

    A summary of the research being carried out by our multidisciplinary team to better understand the form and function of the nose in different mammalian species that include humans, carnivores, ungulates, rodents, and marine animals will be presented. The mammalian nose houses a convoluted airway labyrinth, where two hallmark features of mammals occur, endothermy and olfaction. Because of the complexity of the nasal cavity, the anatomy and function of these upper airways remain poorly understood in most mammals. However, recent advances in high-resolution medical imaging, computational modeling, and experimental flow measurement techniques are now permitting the study of airflow and respiratory and olfactory transport phenomena in anatomically-accurate reconstructions of the nasal cavity. Here, we focus on efforts to manufacture transparent, anatomically-accurate models for stereo particle image velocimetry (SPIV) measurements of nasal airflow. Challenges in the design and manufacture of index-matched anatomical models are addressed and preliminary SPIV measurements are presented. Such measurements will constitute a validation database for concurrent computational fluid dynamics (CFD) simulations of mammalian respiration and olfaction. Supported by the National Science Foundation.

  18. The road towards accurate optical width measurements at the industrial level

    NASA Astrophysics Data System (ADS)

    Bodermann, Bernd; Köning, Rainer; Bergmann, Detlef; Buhr, Egbert; Hässler-Grohne, Wolfgang; Flügge, Jens; Bosse, Harald

    2013-04-01

    Optical vision systems require both unidirectional and bidirectional measurements for the calibrations and the verification of the tool performance to enable accurate measurements traceable to the SI unit Metre. However, for bidirectional measurements up to now the national metrology institutes are unable to provide internationally recognized calibrations of suitable standards. Furthermore often users are not aware of the specific difficulties of these measurements. In this paper the current status and limitations of bidirectional optical measurements at the industrial level are summarised and compared to state-of-the-art optical linewidth measurements performed at PTB on measurement objects of semiconductor industry. It turns out, that for optical widths measurements at an uncertainty level below 1 μm edge localisation schemes are required, which are based on tool and sample dependent threshold values, which usually need to be determined by a rigorous simulation of the microscopic image. Furthermore the calibration samples and structures must have a sufficient quality, e. g. high edge angle and low edge roughness and the structure materials and their material parameters have to be known. The experience obtained within the accreditation process of industrial labs for width calibrations shows that, in order to be able to achieve a desired measurement uncertainties of about 100 nm, the imaging system needs to have a monochromatic Koehler illumination, numerical aperture larger than 0.5, a magnification greater than 50x and the ability to control the deviation of the focus position to better than 100 nm.

  19. Optical coherence tomography enables accurate measurement of equine cartilage thickness for determination of speed of sound.

    PubMed

    Puhakka, Pia H; Te Moller, Nikae C R; Tanska, Petri; Saarakkala, Simo; Tiitu, Virpi; Korhonen, Rami K; Brommer, Harold; Virén, Tuomas; Jurvelin, Jukka S; Töyräs, Juha

    2016-08-01

    Background and purpose - Arthroscopic estimation of articular cartilage thickness is important for scoring of lesion severity, and measurement of cartilage speed of sound (SOS)-a sensitive index of changes in cartilage composition. We investigated the accuracy of optical coherence tomography (OCT) in measurements of cartilage thickness and determined SOS by combining OCT thickness and ultrasound (US) time-of-flight (TOF) measurements. Material and methods - Cartilage thickness measurements from OCT and microscopy images of 94 equine osteochondral samples were compared. Then, SOS in cartilage was determined using simultaneous OCT thickness and US TOF measurements. SOS was then compared with the compositional, structural, and mechanical properties of cartilage. Results - Measurements of non-calcified cartilage thickness using OCT and microscopy were significantly correlated (ρ = 0.92; p < 0.001). With calcified cartilage included, the correlation was ρ = 0.85 (p < 0.001). The mean cartilage SOS (1,636 m/s) was in agreement with the literature. However, SOS and the other properties of cartilage lacked any statistically significant correlation. Interpretation - OCT can give an accurate measurement of articular cartilage thickness. Although SOS measurements lacked accuracy in thin equine cartilage, the concept of SOS measurement using OCT appears promising.

  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. Field evaluation of polymer capacitive humidity sensors for Bowen ratio energy balance flux measurements.

    PubMed

    Savage, Michael J

    2010-01-01

    The possibility of reliable, reasonably accurate and relatively inexpensive estimates of sensible heat and latent energy fluxes was investigated using a commercial combination thin-film polymer capacitive relative humidity and adjacent temperature sensor instrument. Long-term and unattended water vapour pressure profile difference measurements using low-power combination instruments were compared with those from a cooled dewpoint mirror hygrometer, the latter often used with Bowen ratio energy balance (BREB) systems. An error analysis, based on instrument relative humidity and temperature errors, was applied for various capacitive humidity instrument models. The main disadvantage of a combination capacitive humidity instrument is that two measurements, relative humidity and temperature, are required for estimation of water vapour pressure as opposed to one for a dewpoint hygrometer. In a laboratory experiment using an automated procedure, water vapour pressure differences generated using a reference dewpoint generator were measured using a commercial model (Dew-10) dewpoint hygrometer and a combination capacitive humidity instrument. The laboratory measurement comparisons showed that, potentially, an inexpensive model combination capacitive humidity instrument (CS500 or HMP50), or for improved results a slightly more expensive model (HMP35C or HMP45C), could substitute for the more expensive dewpoint hygrometer. In a field study, in a mesic grassland, the water vapour pressure measurement noise for the combination capacitive humidity instruments was greater than that for the dewpoint hygrometer. The average water vapour pressure profile difference measured using a HMP45C was highly correlated with that from a dewpoint hygrometer with a slope less than unity. Water vapour pressure measurements using the capacitive humidity instruments were not as accurate, compared to those obtained using a dewpoint hygrometer, but the resolution magnitudes for the profile

  2. Field evaluation of polymer capacitive humidity sensors for Bowen ratio energy balance flux measurements.

    PubMed

    Savage, Michael J

    2010-01-01

    The possibility of reliable, reasonably accurate and relatively inexpensive estimates of sensible heat and latent energy fluxes was investigated using a commercial combination thin-film polymer capacitive relative humidity and adjacent temperature sensor instrument. Long-term and unattended water vapour pressure profile difference measurements using low-power combination instruments were compared with those from a cooled dewpoint mirror hygrometer, the latter often used with Bowen ratio energy balance (BREB) systems. An error analysis, based on instrument relative humidity and temperature errors, was applied for various capacitive humidity instrument models. The main disadvantage of a combination capacitive humidity instrument is that two measurements, relative humidity and temperature, are required for estimation of water vapour pressure as opposed to one for a dewpoint hygrometer. In a laboratory experiment using an automated procedure, water vapour pressure differences generated using a reference dewpoint generator were measured using a commercial model (Dew-10) dewpoint hygrometer and a combination capacitive humidity instrument. The laboratory measurement comparisons showed that, potentially, an inexpensive model combination capacitive humidity instrument (CS500 or HMP50), or for improved results a slightly more expensive model (HMP35C or HMP45C), could substitute for the more expensive dewpoint hygrometer. In a field study, in a mesic grassland, the water vapour pressure measurement noise for the combination capacitive humidity instruments was greater than that for the dewpoint hygrometer. The average water vapour pressure profile difference measured using a HMP45C was highly correlated with that from a dewpoint hygrometer with a slope less than unity. Water vapour pressure measurements using the capacitive humidity instruments were not as accurate, compared to those obtained using a dewpoint hygrometer, but the resolution magnitudes for the profile

  3. Optimum satellite orbits for accurate measurement of the earth's radiation budget, summary

    NASA Technical Reports Server (NTRS)

    Campbell, G. G.; Vonderhaar, T. H.

    1978-01-01

    The optimum set of orbit inclinations for the measurement of the earth radiation budget from spacially integrating sensor systems was estimated for two and three satellite systems. The best set of the two were satellites at orbit inclinations of 80 deg and 50 deg; of three the inclinations were 80 deg, 60 deg and 50 deg. These were chosen on the basis of a simulation of flat plate and spherical detectors flying over a daily varying earth radiation field as measured by the Nimbus 3 medium resolution scanners. A diurnal oscillation was also included in the emitted flux and albedo to give a source field as realistic as possible. Twenty three satellites with different inclinations and equator crossings were simulated, allowing the results of thousand of multisatellite sets to be intercompared. All were circular orbits of radius 7178 kilometers.

  4. 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.

  5. Soil air and soil flux measurements of 222Radon and CO2: A soil flux parametrization at Lutjewad (NL)

    NASA Astrophysics Data System (ADS)

    Neubert, R. E. M.; Kettner, E.; Palstra, S. W. L.; Hoekman, S.; van der Graaf, E. R.

    2009-04-01

    Atmospheric 222Radon concentration measurements are used as a valuable transport tracer verifying the transport part of Carbon Cycle and Greenhouse Gas models. The production rate of the radioactive noble gas 222Radon (T1•2 = 3.8 days) by radioactive decay of 226Radium in the soil is constant, the absolute quantity depending on the local soil Radium concentration. The flux of 222Radon to the atmosphere (the soil exhalation, or effective atmospheric production rate), however, is not constant. It strongly depends on soil texture, soil humidity, precipitation and other parameters, but is nearly constant if these parameters stay unchanged. Recently, an effort has been done to predict this flux rate with widely available γ-dosimetry measurements (Szegvary et al., Predicting terrestrial 222Rn-flux using gamma dose rate as a proxy, ACP 7, 2789-2795, 2007), but real 222Radon-flux measurements are sparse. 222Radon undergoes the same transport processes on the way from soil to atmosphere as any other soil-derived (greenhouse) gas. This makes 222Radon an ideal tracer to separate variations in e.g. soil CO2-production from changes in the soil-atmosphere CO2-transport, both being reflected in the total soil-atmosphere CO2-flux. At the atmospheric measurement site Lutjewad in the north of the Netherlands (53N24'18", 6E21'13", www.rug.nl/ees/onderzoek/cio/projecten/atmosphericgases) we started in 2006 with the measurements of the soil 222Radon and CO2 concentration through soil probes as well as the Radon and CO2 soil fluxes by means of an automatic soil chamber. While there are up to eight soil air measurements per day, the soil chamber is automatically closed twice per day. The station is situated directly on the Waddensea dike at an elevation of 1 m a.s.l. on seaclay soil. The groundwater table shows variations between 0.5 m and 2 m below terrain. From our measurements we find that in the dryer summer season, from April to July, the mean 222Radon-flux can be up to 40

  6. Accurate measurements of the collision stopping powers for 5 to 30 MeV electrons

    NASA Astrophysics Data System (ADS)

    MacPherson, Miller Shawn

    Accurate knowledge of electron stopping powers is crucial for accurate radiation dosimetry and radiation transport calculations. Current values for stopping powers are based on a theoretical model, with estimated uncertainties of 0.5-1% (1σ) for electron energies greater than 100 keV. This work presents the first measurements of electron collision stopping powers capable of testing the theoretical values within these stated uncertainties. A large NaI spectrometer was used to measure the change in electron energy when an absorbing disk of known thickness was placed in an electron beam. Monte Carlo simulations of the experiment were performed to account for the effects of surrounding materials. Energy differences between the calculated and measured spectra were used to determine corrections to the soft collision component of the theoretical stopping powers employed by the Monte Carlo simulations. Four different elemental materials were studied: Be, Al, Cu, and Ta. This provided a wide range of atomic numbers and densities over which to test the theory. In addition, stopping powers were measured for graphite (both standard and pyrolytic), A-150 tissue equivalent plastic, C-552 air equivalent plastic, and water. The incident electron energies ranged from 5 to 30 MeV. Generally, the measured stopping powers agree with the theoretical values within the experimental uncertainties, which range from 0.4% to 0.7% (1σ). Aluminum, however, exhibits a 0.7% discrepancy at higher electron energies. Furthermore, these measurements have established that the grain density stopping power is appropriate for graphite, contrary to the recommendations of ICRU Report 37. This removes a 0.2% uncertainty in air kerma calibrations, and impacts on dosimetric quantities determined via graphite calorimetry, such as ɛG for Fricke dosimetry and (W/ e)air for ion chamber measurements.

  7. Highly accurate isotope measurements of surface material on planetary objects in situ

    NASA Astrophysics Data System (ADS)

    Riedo, Andreas; Neuland, Maike; Meyer, Stefan; Tulej, Marek; Wurz, Peter

    2013-04-01

    Studies of isotope variations in solar system objects are of particular interest and importance. Highly accurate isotope measurements provide insight into geochemical processes, constrain the time of formation of planetary material (crystallization ages) and can be robust tracers of pre-solar events and processes. A detailed understanding of the chronology of the early solar system and dating of planetary materials require precise and accurate measurements of isotope ratios, e.g. lead, and abundance of trace element. However, such measurements are extremely challenging and until now, they never have been attempted in space research. Our group designed a highly miniaturized and self-optimizing laser ablation time-of-flight mass spectrometer for space flight for sensitive and accurate measurements of the elemental and isotopic composition of extraterrestrial materials in situ. Current studies were performed by using UV radiation for ablation and ionization of sample material. High spatial resolution is achieved by focusing the laser beam to about Ø 20μm onto the sample surface. The instrument supports a dynamic range of at least 8 orders of magnitude and a mass resolution m/Δm of up to 800—900, measured at iron peak. We developed a measurement procedure, which will be discussed in detail, that allows for the first time to measure with the instrument the isotope distribution of elements, e.g. Ti, Pb, etc., with a measurement accuracy and precision in the per mill and sub per mill level, which is comparable to well-known and accepted measurement techniques, such as TIMS, SIMS and LA-ICP-MS. The present instrument performance offers together with the measurement procedure in situ measurements of 207Pb/206Pb ages with the accuracy for age in the range of tens of millions of years. Furthermore, and in contrast to other space instrumentation, our instrument can measure all elements present in the sample above 10 ppb concentration, which offers versatile applications

  8. Wide Range Neutron Flux Measuring Channel for Aerospace Application

    SciTech Connect

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

    2008-01-21

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

  9. Radial artery blood pressure measurement in neonates: an accurate and convenient technique in clinical practice.

    PubMed

    Gevers, M; van Genderingen, H R; Lafeber, H N; Hack, W W

    1995-01-01

    To achieve accurate blood pressure measurement through radial artery catheters in infants, we previously developed an experimental high-fidelity catheter-manometer system (CMS). As this system lacks facilities for flushing and for blood sampling, we aimed to further develop this technique in order to make the system suitable for clinical practice. In addition, we aimed to develop methods to automate processing of the pressure wave forms. The high-fidelity system to be improved consisted of a 24 Gauge catheter, a threeway stopcock and a tip-manometer. We inserted this system in the catheter-manometer system as routinely used i.e. the remaining end of the stopcock was connected to the fluid-filled CMS as used routinely. This combined system became clinically applicable, since blood samples could be obtained and flushing could be performed. The measurement chain was completed by application of a modified physiological monitor and a computerized method to analyze pressure wave forms. In this manner accurate beat-to-beat pressure parameters were obtained. This technique was applied to 25 neonates admitted for intensive care and requiring arterial access. Gestational age of these infants ranged from 25-40 (median 29) weeks and birth weight ranges from 500-3375 (median 1060) grams. In all infants the technique was found to be convenient and the high-fidelity blood pressure measurements were performed without any problems. The advantage of the present system is the potential for both correct intermittent recordings of arterial wave forms in close relation to clinical condition and for the establishment of accurate radial artery beat-to-beat pressure values in clinical practice.

  10. Accurate Young's modulus measurement based on Rayleigh wave velocity and empirical Poisson's ratio

    NASA Astrophysics Data System (ADS)

    Li, Mingxia; Feng, Zhihua

    2016-07-01

    This paper presents a method for Young's modulus measurement based on Rayleigh wave speed. The error in Poisson's ratio has weak influence on the measurement of Young's modulus based on Rayleigh wave speed, and Poisson's ratio minimally varies in a certain material; thus, we can accurately estimate Young's modulus with surface wave speed and a rough Poisson's ratio. We numerically analysed three methods using Rayleigh, longitudinal, and transversal wave speed, respectively, and the error in Poisson's ratio shows the least influence on the result in the method involving Rayleigh wave speed. An experiment was performed and has proved the feasibility of this method. Device for speed measuring could be small, and no sample pretreatment is needed. Hence, developing a portable instrument based on this method is possible. This method makes a good compromise between usability and precision.

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

    NASA Astrophysics Data System (ADS)

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

    2003-08-01

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

  12. A Flexible Fringe Projection Vision System with Extended Mathematical Model for Accurate Three-Dimensional Measurement

    PubMed Central

    Xiao, Suzhi; Tao, Wei; Zhao, Hui

    2016-01-01

    In order to acquire an accurate three-dimensional (3D) measurement, the traditional fringe projection technique applies complex and laborious procedures to compensate for the errors that exist in the vision system. However, the error sources in the vision system are very complex, such as lens distortion, lens defocus, and fringe pattern nonsinusoidality. Some errors cannot even be explained or rendered with clear expressions and are difficult to compensate directly as a result. In this paper, an approach is proposed that avoids the complex and laborious compensation procedure for error sources but still promises accurate 3D measurement. It is realized by the mathematical model extension technique. The parameters of the extended mathematical model for the ’phase to 3D coordinates transformation’ are derived using the least-squares parameter estimation algorithm. In addition, a phase-coding method based on a frequency analysis is proposed for the absolute phase map retrieval to spatially isolated objects. The results demonstrate the validity and the accuracy of the proposed flexible fringe projection vision system on spatially continuous and discontinuous objects for 3D measurement. PMID:27136553

  13. A Flexible Fringe Projection Vision System with Extended Mathematical Model for Accurate Three-Dimensional Measurement.

    PubMed

    Xiao, Suzhi; Tao, Wei; Zhao, Hui

    2016-01-01

    In order to acquire an accurate three-dimensional (3D) measurement, the traditional fringe projection technique applies complex and laborious procedures to compensate for the errors that exist in the vision system. However, the error sources in the vision system are very complex, such as lens distortion, lens defocus, and fringe pattern nonsinusoidality. Some errors cannot even be explained or rendered with clear expressions and are difficult to compensate directly as a result. In this paper, an approach is proposed that avoids the complex and laborious compensation procedure for error sources but still promises accurate 3D measurement. It is realized by the mathematical model extension technique. The parameters of the extended mathematical model for the 'phase to 3D coordinates transformation' are derived using the least-squares parameter estimation algorithm. In addition, a phase-coding method based on a frequency analysis is proposed for the absolute phase map retrieval to spatially isolated objects. The results demonstrate the validity and the accuracy of the proposed flexible fringe projection vision system on spatially continuous and discontinuous objects for 3D measurement. PMID:27136553

  14. 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...

  15. Object strength--an accurate measure for small objects that is insensitive to partial volume effects.

    PubMed

    Tofts, P S; Silver, N C; Barker, G J; Gass, A

    2005-07-01

    There are currently four problems in characterising small nonuniform lesions or other objects in Magnetic Resonance images where partial volume effects are significant. Object size is over- or under-estimated; boundaries are often not reproducible; mean object value cannot be measured; and fuzzy borders cannot be accommodated. A new measure, Object Strength, is proposed. This is the sum of all abnormal intensities, above a uniform background value. For a uniform object, this is simply the product of the increase in intensity and the size of the object. Biologically, this could be at least as relevant as existing measures of size or mean intensity. We hypothesise that Object Strength will perform better than traditional area measurements in characterising small objects. In a pilot study, the reproducibility of object strength measurements was investigated using MR images of small multiple sclerosis (MS) lesions. In addition, accuracy was investigated using artificial lesions of known volume (0.3-6.2 ml) and realistic appearance. Reproducibility approached that of area measurements (in 33/90 lesion reports the difference between repeats was less than for area measurements). Total lesion volume was accurate to 0.2%. In conclusion, Object Strength has potential for improved characterisation of small lesions and objects in imaging and possibly spectroscopy.

  16. Accurate Measurements of Aircraft Engine Soot Emissions Using a CAPS PMssa Monitor

    NASA Astrophysics Data System (ADS)

    Onasch, Timothy; Thompson, Kevin; Renbaum-Wolff, Lindsay; Smallwood, Greg; Make-Lye, Richard; Freedman, Andrew

    2016-04-01

    We present results of aircraft engine soot emissions measurements during the VARIAnT2 campaign using CAPS PMssa monitors. VARIAnT2, an aircraft engine non-volatile particulate matter (nvPM) emissions field campaign, was focused on understanding the variability in nvPM mass measurements using different measurement techniques and accounting for possible nvPM sampling system losses. The CAPS PMssa monitor accurately measures both the optical extinction and scattering (and thus single scattering albedo and absorption) of an extracted sample using the same sample volume for both measurements with a time resolution of 1 second and sensitivity of better than 1 Mm-1. Absorption is obtained by subtracting the scattering signal from the total extinction. Given that the single scattering albedo of the particulates emitted from the aircraft engine measured at both 630 and 660 nm was on the order of 0.1, any inaccuracy in the scattering measurement has little impact on the accuracy of the ddetermined absorption coefficient. The absorption is converted into nvPM mass using a documented Mass Absorption Coefficient (MAC). Results of soot emission indices (mass soot emitted per mass of fuel consumed) for a turbojet engine as a function of engine power will be presented and compared to results obtained using an EC/OC monitor.

  17. Ocean Lidar Measurements of Beam Attenuation and a Roadmap to Accurate Phytoplankton Biomass Estimates

    NASA Astrophysics Data System (ADS)

    Hu, Yongxiang; Behrenfeld, Mike; Hostetler, Chris; Pelon, Jacques; Trepte, Charles; Hair, John; Slade, Wayne; Cetinic, Ivona; Vaughan, Mark; Lu, Xiaomei; Zhai, Pengwang; Weimer, Carl; Winker, David; Verhappen, Carolus C.; Butler, Carolyn; Liu, Zhaoyan; Hunt, Bill; Omar, Ali; Rodier, Sharon; Lifermann, Anne; Josset, Damien; Hou, Weilin; MacDonnell, David; Rhew, Ray

    2016-06-01

    Beam attenuation coefficient, c, provides an important optical index of plankton standing stocks, such as phytoplankton biomass and total particulate carbon concentration. Unfortunately, c has proven difficult to quantify through remote sensing. Here, we introduce an innovative approach for estimating c using lidar depolarization measurements and diffuse attenuation coefficients from ocean color products or lidar measurements of Brillouin scattering. The new approach is based on a theoretical formula established from Monte Carlo simulations that links the depolarization ratio of sea water to the ratio of diffuse attenuation Kd and beam attenuation C (i.e., a multiple scattering factor). On July 17, 2014, the CALIPSO satellite was tilted 30° off-nadir for one nighttime orbit in order to minimize ocean surface backscatter and demonstrate the lidar ocean subsurface measurement concept from space. Depolarization ratios of ocean subsurface backscatter are measured accurately. Beam attenuation coefficients computed from the depolarization ratio measurements compare well with empirical estimates from ocean color measurements. We further verify the beam attenuation coefficient retrievals using aircraft-based high spectral resolution lidar (HSRL) data that are collocated with in-water optical measurements.

  18. Accurate Measurements of the Dielectric Constant of Seawater at L Band

    NASA Technical Reports Server (NTRS)

    Lang, Roger; Zhou, Yiwen; Utku, Cuneyt; Le Vine, David

    2016-01-01

    This paper describes measurements of the dielectric constant of seawater at a frequency of 1.413 GHz, the center of the protected band (i.e., passive use only) used in the measurement of sea surface salinity from space. The objective of the measurements is to accurately determine the complex dielectric constant of seawater as a function of salinity and temperature. A resonant cylindrical microwave cavity in transmission mode has been employed to make the measurements. The measurements are made using standard seawater at salinities of 30, 33, 35, and 38 practical salinity units over a range of temperatures from 0 degree C to 35 degree C in 5 degree C intervals. Repeated measurements have been made at each temperature and salinity. Mean values and standard deviations are then computed. The total error budget indicates that the real and imaginary parts of the dielectric constant have a combined standard uncertainty of about 0.3 over the range of salinities and temperatures considered. The measurements are compared with the dielectric constants obtained from the model functions of Klein and Swift and those of Meissner and Wentz. The biggest differences occur at low and high temperatures.

  19. What Do Magnetic Resonance–Based Measurements of Pi→ATP Flux Tell Us About Skeletal Muscle Metabolism?

    PubMed Central

    Kemp, Graham J.; Brindle, Kevin M.

    2012-01-01

    Magnetic resonance spectroscopy (MRS) methods offer a potentially valuable window into cellular metabolism. Measurement of flux between inorganic phosphate (Pi) and ATP using 31P MRS magnetization transfer has been used in resting muscle to assess what is claimed to be mitochondrial ATP synthesis and has been particularly popular in the study of insulin effects and insulin resistance. However, the measured Pi→ATP flux in resting skeletal muscle is far higher than the true rate of oxidative ATP synthesis, being dominated by a glycolytically mediated Pi↔ATP exchange reaction that is unrelated to mitochondrial function. Furthermore, even if measured accurately, the ATP production rate in resting muscle has no simple relationship to mitochondrial capacity as measured either ex vivo or in vivo. We summarize the published measurements of Pi→ATP flux, concentrating on work relevant to diabetes and insulin, relate it to current understanding of the physiology of mitochondrial ATP synthesis and glycolytic Pi↔ATP exchange, and discuss some possible implications of recently reported correlations between Pi→ATP flux and other physiological measures. PMID:22826313

  20. 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...

  1. Accurate Measurements of the Dielectric Constant of Seawater at L Band

    NASA Technical Reports Server (NTRS)

    Lang, Roger H.; Utku, Cuneyt; Tarkocin, Yalcin; LeVine, David M.

    2010-01-01

    This report describes measurements of the dielectric constant of seawater at a frequency of 1.413 GHz that is at the center of the L-Sand radiometric protected frequency spectrum. Aquarius will be sensing the sea surface salinity from space in this band. The objective of the project is to refine the model function for the dielectric constant as a function of salinity and temperature so that remote sensing measurements can be made with the accuracy needed to meet the measurement goals (0.2 psu) of the Aquarius mission. The measurements were made, using a microwave cavity operated in the transmission configuration. The cavity's temperature was accurately regulated to 0.02 C by immersing it in a temperature controlled bath of distilled water and ethanol glycol. Seawater had been purchased from Ocean Scientific International Limited (OS1L) at salinities of 30, 35 and 38 psu. Measurements of these seawater samples were then made over a range of temperatures, from l0 C to 35 C in 5 C intervals. Repeated measurements were made at each temperature and salinity, Mean values and standard deviations were then computed. Total error budgets indicated that the real and imaginary parts of the dielectric constant had a relative accuracy of about l%.

  2. A New Test Rig for Accurate Nonparametric Measurement and Characterization of Thermoelectric Generators

    NASA Astrophysics Data System (ADS)

    Montecucco, Andrea; Buckle, James; Siviter, Jonathan; Knox, Andrew R.

    2013-07-01

    Thermoelectric generators (TEGs) are increasingly employed in large-scale applications, therefore accurate performance data are necessary to permit precise designs and simulations. However, there is still no standardized method to test the electrical and thermal performance of TEGs. This paper presents an innovative test system to assess device performance in the "real world." The fixture allows the hot temperature to be increased up to 800°C with minimal thermal losses and thermal shock; the clamping load can be adjusted up to 5 kN, and the temperatures are sensed by thermocouples placed directly on the TEG's surfaces. A computer program controls all the instruments in order to minimize errors and to aid accurate measurement and test repeatability. The test rig can measure four TEGs simultaneously, each one individually controlled and heated by a maximum electrical power of 2 kW. This allows testing of the effects of series and parallel connection of TEGs under mismatched conditions, e.g., dimensions, clamping force, temperature, etc. The test rig can be employed both as a performance evaluator and as a quality control unit, due to the ability to provide nonparametric testing of four TEGs concurrently. It can also be used to rapidly characterize devices of different dimensions at the same time.

  3. Generalized weighted ratio method for accurate turbidity measurement over a wide range.

    PubMed

    Liu, Hongbo; Yang, Ping; Song, Hong; Guo, Yilu; Zhan, Shuyue; Huang, Hui; Wang, Hangzhou; Tao, Bangyi; Mu, Quanquan; Xu, Jing; Li, Dejun; Chen, Ying

    2015-12-14

    Turbidity measurement is important for water quality assessment, food safety, medicine, ocean monitoring, etc. In this paper, a method that accurately estimates the turbidity over a wide range is proposed, where the turbidity of the sample is represented as a weighted ratio of the scattered light intensities at a series of angles. An improvement in the accuracy is achieved by expanding the structure of the ratio function, thus adding more flexibility to the turbidity-intensity fitting. Experiments have been carried out with an 850 nm laser and a power meter fixed on a turntable to measure the light intensity at different angles. The results show that the relative estimation error of the proposed method is 0.58% on average for a four-angle intensity combination for all test samples with a turbidity ranging from 160 NTU to 4000 NTU.

  4. Accurate and precise measurement of selenium by instrumental neutron activation analysis.

    PubMed

    Kim, In Jung; Watson, Russell P; Lindstrom, Richard M

    2011-05-01

    An accurate and precise measurement of selenium in Standard Reference Material (SRM) 3149, a primary calibration standard for the quantitative determination of selenium, has been accomplished by instrumental neutron activation analysis (INAA) in order to resolve a question arising during the certification process of the standard. Each limiting factor of the uncertainty in the activation analysis, including the sample preparation, irradiation, and γ-ray spectrometry steps, has been carefully monitored to minimize the uncertainty in the determined mass fraction. Neutron and γ-ray self-shielding within the elemental selenium INAA standards contributed most significantly to the uncertainty of the measurement. An empirical model compensating for neutron self-shielding and reducing the self-shielding uncertainty was successfully applied to these selenium standards. The mass fraction of selenium in the new lot of SRM 3149 was determined with a relative standard uncertainty of 0.6%.

  5. Highly accurate thickness measurement of multi-layered automotive paints using terahertz technology

    NASA Astrophysics Data System (ADS)

    Krimi, Soufiene; Klier, Jens; Jonuscheit, Joachim; von Freymann, Georg; Urbansky, Ralph; Beigang, René

    2016-07-01

    In this contribution, we present a highly accurate approach for thickness measurements of multi-layered automotive paints using terahertz time domain spectroscopy in reflection geometry. The proposed method combines the benefits of a model-based material parameters extraction method to calibrate the paint coatings, a generalized Rouard's method to simulate the terahertz radiation behavior within arbitrary thin films, and the robustness of a powerful evolutionary optimization algorithm to increase the sensitivity of the minimum thickness measurement limit. Within the framework of this work, a self-calibration model is introduced, which takes into consideration the real industrial challenges such as the effect of wet-on-wet spray in the painting process.

  6. Apparatus for accurate density measurements of fluids based on a magnetic suspension balance

    NASA Astrophysics Data System (ADS)

    Gong, Maoqiong; Li, Huiya; Guo, Hao; Dong, Xueqiang; Wu, J. F.

    2012-06-01

    A new apparatus for accurate pressure, density and temperature (p, ρ, T) measurements over wide ranges of (p, ρ, T) (90 K to 290 K; 0 MPa to 3 MPa; 0 kg/m3 to 2000 kg/m3) is described. This apparatus is based on a magnetic suspension balance which applies the Archimedes' buoyancy principle. In order to verify the new apparatus, comprehensive (p, ρ, T) measurements on pure nitrogen were carried out. The maximum relative standard uncertainty is 0.09% in density. The maximum standard uncertainty in temperature is 5 mK, and that in pressure is 250 Pa for 1.5 MPa and 390 Pa for 3MPa full scale range respectively. The experimental data were compared with selected literature data and good agreements were found.

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

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

  8. Home Circadian Phase Assessments with Measures of Compliance Yield Accurate Dim Light Melatonin Onsets

    PubMed Central

    Burgess, Helen J.; Wyatt, James K.; Park, Margaret; Fogg, Louis F.

    2015-01-01

    Study Objectives: There is a need for the accurate assessment of circadian phase outside of the clinic/laboratory, particularly with the gold standard dim light melatonin onset (DLMO). We tested a novel kit designed to assist in saliva sampling at home for later determination of the DLMO. The home kit includes objective measures of compliance to the requirements for dim light and half-hourly saliva sampling. Design: Participants were randomized to one of two 10-day protocols. Each protocol consisted of two back-to-back home and laboratory phase assessments in counterbalanced order, separated by a 5-day break. Setting: Laboratory or participants' homes. Participants: Thirty-five healthy adults, age 21–62 y. Interventions: N/A. Measurements and Results: Most participants received at least one 30-sec epoch of light > 50 lux during the home phase assessments (average light intensity 4.5 lux), but on average for < 9 min of the required 8.5 h. Most participants collected every saliva sample within 5 min of the scheduled time. Ninety-two percent of home DLMOs were not affected by light > 50 lux or sampling errors. There was no significant difference between the home and laboratory DLMOs (P > 0.05); on average the home DLMOs occurred 9.6 min before the laboratory DLMOs. The home DLMOs were highly correlated with the laboratory DLMOs (r = 0.91, P < 0.001). Conclusions: Participants were reasonably compliant to the home phase assessment procedures. The good agreement between the home and laboratory dim light melatonin onsets (DLMOs) demonstrates that including objective measures of light exposure and sample timing during home saliva sampling can lead to accurate home DLMOs. Clinical Trial Registration: Circadian Phase Assessments at Home, http://clinicaltrials.gov/show/NCT01487252, NCT01487252. Citation: Burgess HJ, Wyatt JK, Park M, Fogg LF. Home circadian phase assessments with measures of compliance yield accurate dim light melatonin onsets. SLEEP 2015;38(6):889–897

  9. k-Space Image Correlation Spectroscopy: A Method for Accurate Transport Measurements Independent of Fluorophore Photophysics

    PubMed Central

    Kolin, David L.; Ronis, David; Wiseman, Paul W.

    2006-01-01

    We present the theory and application of reciprocal space image correlation spectroscopy (kICS). This technique measures the number density, diffusion coefficient, and velocity of fluorescently labeled macromolecules in a cell membrane imaged on a confocal, two-photon, or total internal reflection fluorescence microscope. In contrast to r-space correlation techniques, we show kICS can recover accurate dynamics even in the presence of complex fluorophore photobleaching and/or “blinking”. Furthermore, these quantities can be calculated without nonlinear curve fitting, or any knowledge of the beam radius of the exciting laser. The number densities calculated by kICS are less sensitive to spatial inhomogeneity of the fluorophore distribution than densities measured using image correlation spectroscopy. We use simulations as a proof-of-principle to show that number densities and transport coefficients can be extracted using this technique. We present calibration measurements with fluorescent microspheres imaged on a confocal microscope, which recover Stokes-Einstein diffusion coefficients, and flow velocities that agree with single particle tracking measurements. We also show the application of kICS to measurements of the transport dynamics of α5-integrin/enhanced green fluorescent protein constructs in a transfected CHO cell imaged on a total internal reflection fluorescence microscope using charge-coupled device area detection. PMID:16861272

  10. 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.

  11. Optical aperture area determination for accurate illuminance and luminous efficacy measurements of LED lamps

    NASA Astrophysics Data System (ADS)

    Dönsberg, Timo; Mäntynen, Henrik; Ikonen, Erkki

    2016-06-01

    The measurement uncertainty of illuminance and, consequently, luminous flux and luminous efficacy of LED lamps can be reduced with a recently introduced method based on the predictable quantum efficient detector (PQED). One of the most critical factors affecting the measurement uncertainty with the PQED method is the determination of the aperture area. This paper describes an upgrade to an optical method for direct determination of aperture area where superposition of equally spaced Gaussian laser beams is used to form a uniform irradiance distribution. In practice, this is accomplished by scanning the aperture in front of an intensity-stabilized laser beam. In the upgraded method, the aperture is attached to the PQED and the whole package is transversely scanned relative to the laser beam. This has the benefit of having identical geometry in the laser scanning of the aperture area and in the actual photometric measurement. Further, the aperture and detector assembly does not have to be dismantled for the aperture calibration. However, due to small acceptance angle of the PQED, differences between the diffraction effects of an overfilling plane wave and of a combination of Gaussian laser beams at the circular aperture need to be taken into account. A numerical calculation method for studying these effects is discussed in this paper. The calculation utilizes the Rayleigh-Sommerfeld diffraction integral, which is applied to the geometry of the PQED and the aperture. Calculation results for various aperture diameters and two different aperture-to-detector distances are presented.

  12. Accurate and automatic extrinsic calibration method for blade measurement system integrated by different optical sensors

    NASA Astrophysics Data System (ADS)

    He, Wantao; Li, Zhongwei; Zhong, Kai; Shi, Yusheng; Zhao, Can; Cheng, Xu

    2014-11-01

    Fast and precise 3D inspection system is in great demand in modern manufacturing processes. At present, the available sensors have their own pros and cons, and hardly exist an omnipotent sensor to handle the complex inspection task in an accurate and effective way. The prevailing solution is integrating multiple sensors and taking advantages of their strengths. For obtaining a holistic 3D profile, the data from different sensors should be registrated into a coherent coordinate system. However, some complex shape objects own thin wall feather such as blades, the ICP registration method would become unstable. Therefore, it is very important to calibrate the extrinsic parameters of each sensor in the integrated measurement system. This paper proposed an accurate and automatic extrinsic parameter calibration method for blade measurement system integrated by different optical sensors. In this system, fringe projection sensor (FPS) and conoscopic holography sensor (CHS) is integrated into a multi-axis motion platform, and the sensors can be optimally move to any desired position at the object's surface. In order to simple the calibration process, a special calibration artifact is designed according to the characteristics of the two sensors. An automatic registration procedure based on correlation and segmentation is used to realize the artifact datasets obtaining by FPS and CHS rough alignment without any manual operation and data pro-processing, and then the Generalized Gauss-Markoff model is used to estimate the optimization transformation parameters. The experiments show the measurement result of a blade, where several sampled patches are merged into one point cloud, and it verifies the performance of the proposed method.

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

    PubMed

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

    2014-09-01

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

  14. Thermal behavior and temperature measurements of melting beryllium plasma-facing components exposed to high heat flux

    NASA Astrophysics Data System (ADS)

    Gauthier, E.; Pocheau, C.; Kovari, M.; Barnard, J. M.; Crowley, B.; Godwin, J.; Lane, C.

    2015-08-01

    The emissivity of metallic materials is low and varies with temperature and wavelength inducing errors on surface temperature measurements. High heat flux experiments on beryllium were carried out to investigate the thermal behavior of bulk Be tiles. Thermal modeling aiming at determining the surface and bulk temperatures have been performed using ANSYS®. A Be tile was exposed to heat flux with power density ranging between 1 and 7 MW/m2. Surface temperatures were measured using an infrared camera in the 3-5 μm range and two-color pyrometers, one at short wavelengths (1.5-1.7 μm) and one at mid IR range wavelengths (2-4 μm) range. Both the IR camera and two-color pyrometers do not provide accurate temperature measurements on melted Be due to changes in the emissivities and emissivity ratio induced by surface modifications.

  15. Field comparison of disjunct and conventional eddy covariance techniques for trace gas flux measurements.

    PubMed

    Rinne, J; Douffet, T; Prigent, Y; Durand, P

    2008-04-01

    A field intercomparison experiment of the disjunct eddy covariance (DEC) and the conventional eddy covariance (EC) techniques was conducted over a grass field. The half-hourly water vapor fluxes measured by the DEC were within the estimated uncertainty from the fluxes measured by the EC. On the average there was a slight overestimation (<10%) of the fluxes measured by the DEC during the day and underestimation during the night as compared to the fluxes measured by the EC. As this bias does not appear in the simulated DEC measurements it is likely to be due to instrumental problems. The insensitivity of the quality of the fluxes measured by the DEC method to the deficiencies in the gas analysis shows the robustness of this new approach for measuring the surface-atmosphere exchange of trace gases.

  16. 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.

  17. 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.

  18. Induced Dual-Nanospray: A Novel Internal Calibration Method for Convenient and Accurate Mass Measurement

    NASA Astrophysics Data System (ADS)

    Li, Yafeng; Zhang, Ning; Zhou, Yueming; Wang, Jianing; Zhang, Yiming; Wang, Jiyun; Xiong, Caiqiao; Chen, Suming; Nie, Zongxiu

    2013-09-01

    Accurate mass information is of great importance in the determination of unknown compounds. An effective and easy-to-control internal mass calibration method will dramatically benefit accurate mass measurement. Here we reported a simple induced dual-nanospray internal calibration device which has the following three advantages: (1) the two sprayers are in the same alternating current field; thus both reference ions and sample ions can be simultaneously generated and recorded. (2) It is very simple and can be easily assembled. Just two metal tubes, two nanosprayers, and an alternating current power supply are included. (3) With the low-flow-rate character and the versatility of nanoESI, this calibration method is capable of calibrating various samples, even untreated complex samples such as urine and other biological samples with small sample volumes. The calibration errors are around 1 ppm in positive ion mode and 3 ppm in negative ion mode with good repeatability. This new internal calibration method opens up new possibilities in the determination of unknown compounds, and it has great potential for the broad applications in biological and chemical analysis.

  19. Accurate label-free reaction kinetics determination using initial rate heat measurements.

    PubMed

    Ebrahimi, Kourosh Honarmand; Hagedoorn, Peter-Leon; Jacobs, Denise; Hagen, Wilfred R

    2015-01-01

    Accurate label-free methods or assays to obtain the initial reaction rates have significant importance in fundamental studies of enzymes and in application-oriented high throughput screening of enzyme activity. Here we introduce a label-free approach for obtaining initial rates of enzyme activity from heat measurements, which we name initial rate calorimetry (IrCal). This approach is based on our new finding that the data recorded by isothermal titration calorimetry for the early stages of a reaction, which have been widely ignored, are correlated to the initial rates. Application of the IrCal approach to various enzymes led to accurate enzyme kinetics parameters as compared to spectroscopic methods and enabled enzyme kinetic studies with natural substrate, e.g. proteases with protein substrates. Because heat is a label-free property of almost all reactions, the IrCal approach holds promise in fundamental studies of various enzymes and in use of calorimetry for high throughput screening of enzyme activity.

  20. Accurate label-free reaction kinetics determination using initial rate heat measurements

    PubMed Central

    Ebrahimi, Kourosh Honarmand; Hagedoorn, Peter-Leon; Jacobs, Denise; Hagen, Wilfred R.

    2015-01-01

    Accurate label-free methods or assays to obtain the initial reaction rates have significant importance in fundamental studies of enzymes and in application-oriented high throughput screening of enzyme activity. Here we introduce a label-free approach for obtaining initial rates of enzyme activity from heat measurements, which we name initial rate calorimetry (IrCal). This approach is based on our new finding that the data recorded by isothermal titration calorimetry for the early stages of a reaction, which have been widely ignored, are correlated to the initial rates. Application of the IrCal approach to various enzymes led to accurate enzyme kinetics parameters as compared to spectroscopic methods and enabled enzyme kinetic studies with natural substrate, e.g. proteases with protein substrates. Because heat is a label-free property of almost all reactions, the IrCal approach holds promise in fundamental studies of various enzymes and in use of calorimetry for high throughput screening of enzyme activity. PMID:26574737

  1. Measuring nonlinear oscillations using a very accurate and low-cost linear optical position transducer

    NASA Astrophysics Data System (ADS)

    Donoso, Guillermo; Ladera, Celso L.

    2016-09-01

    An accurate linear optical displacement transducer of about 0.2 mm resolution over a range of ∼40 mm is presented. This device consists of a stack of thin cellulose acetate strips, each strip longitudinally slid ∼0.5 mm over the precedent one so that one end of the stack becomes a stepped wedge of constant step. A narrowed light beam from a white LED orthogonally incident crosses the wedge at a known point, the transmitted intensity being detected with a phototransistor whose emitter is connected to a diode. We present the interesting analytical proof that the voltage across the diode is linearly dependent upon the ordinate of the point where the light beam falls on the wedge, as well as the experimental validation of such a theoretical proof. Applications to nonlinear oscillations are then presented—including the interesting case of a body moving under dry friction, and the more advanced case of an oscillator in a quartic energy potential—whose time-varying positions were accurately measured with our transducer. Our sensing device can resolve the dynamics of an object attached to it with great accuracy and precision at a cost considerably less than that of a linear neutral density wedge. The technique used to assemble the wedge of acetate strips is described.

  2. Invited article: Time accurate mass flow measurements of solid-fueled systems.

    PubMed

    Olliges, Jordan D; Lilly, Taylor C; Joslyn, Thomas B; Ketsdever, Andrew D

    2008-10-01

    A novel diagnostic method is described that utilizes a thrust stand mass balance (TSMB) to directly measure time-accurate mass flow from a solid-fuel thruster. The accuracy of the TSMB mass flow measurement technique was demonstrated in three ways including the use of an idealized numerical simulation, verifying a fluid mass calibration with high-speed digital photography, and by measuring mass loss in more than 30 hybrid rocket motor firings. Dynamic response of the mass balance was assessed through weight calibration and used to derive spring, damping, and mass moment of inertia coefficients for the TSMB. These dynamic coefficients were used to determine the mass flow rate and total mass loss within an acrylic and gaseous oxygen hybrid rocket motor firing. Intentional variations in the oxygen flow rate resulted in corresponding variations in the total propellant mass flow as expected. The TSMB was optimized to determine mass losses of up to 2.5 g and measured total mass loss to within 2.5% of that calculated by a NIST-calibrated digital scale. Using this method, a mass flow resolution of 0.0011 g/s or 2% of the average mass flow in this study has been achieved.

  3. Accurate Measurement of the Effects of All Amino-Acid Mutations on Influenza Hemagglutinin

    PubMed Central

    Doud, Michael B.; Bloom, Jesse D.

    2016-01-01

    Influenza genes evolve mostly via point mutations, and so knowing the effect of every amino-acid mutation provides information about evolutionary paths available to the virus. We and others have combined high-throughput mutagenesis with deep sequencing to estimate the effects of large numbers of mutations to influenza genes. However, these measurements have suffered from substantial experimental noise due to a variety of technical problems, the most prominent of which is bottlenecking during the generation of mutant viruses from plasmids. Here we describe advances that ameliorate these problems, enabling us to measure with greatly improved accuracy and reproducibility the effects of all amino-acid mutations to an H1 influenza hemagglutinin on viral replication in cell culture. The largest improvements come from using a helper virus to reduce bottlenecks when generating viruses from plasmids. Our measurements confirm at much higher resolution the results of previous studies suggesting that antigenic sites on the globular head of hemagglutinin are highly tolerant of mutations. We also show that other regions of hemagglutinin—including the stalk epitopes targeted by broadly neutralizing antibodies—have a much lower inherent capacity to tolerate point mutations. The ability to accurately measure the effects of all influenza mutations should enhance efforts to understand and predict viral evolution. PMID:27271655

  4. Accurate measurement of bromine contents in plastic samples by instrumental neutron activation analysis.

    PubMed

    Kim, I J; Lee, K S; Hwang, E; Min, H S; Yim, Y H

    2013-03-26

    Accurate measurements of bromine contents in plastic samples were made by the direct comparator instrumental neutron activation analysis (INAA). Individual factors affecting the measurements were comprehensively evaluated and compensated, including the volatility loss of bromine from standard comparators, the background bromine level in the filter papers used for preparation of the standard comparators, nuclear interference, γ-ray spectral interference and the variance among replicates of the samples. Uncertainty contributions from those factors were thoroughly evaluated and included in the uncertainty budgeting of the INAA measurement. (81)Br was chosen as the target isotope, and the INAA measurements for bromine were experimentally confirmed to exhibit good linearity within a bromine content range of 10-170 μg. The established method has been applied to the analysis of eight plastic samples: four commercially available certified reference materials (CRMs) of polyethylene and polystyrene and four acrylonitrile butadiene styrene (ABS) samples prepared as the candidate reference materials (KRISS CRM 113-01-012, -013, -014 and -015). The bromine contents of the samples were calculated at three different γ-ray energies and compared, showing good agreement. The results of the four CRMs also showed good consistency with their certified values within the stated uncertainties. Finally, the bromine contents of the ABS samples were determined with expanded uncertainties (at a 95% level of confidence) between 2.5% and 5% in a bromine content range of 25-900 mg kg(-1).

  5. Accurate Measurement of the Effects of All Amino-Acid Mutations on Influenza Hemagglutinin.

    PubMed

    Doud, Michael B; Bloom, Jesse D

    2016-01-01

    Influenza genes evolve mostly via point mutations, and so knowing the effect of every amino-acid mutation provides information about evolutionary paths available to the virus. We and others have combined high-throughput mutagenesis with deep sequencing to estimate the effects of large numbers of mutations to influenza genes. However, these measurements have suffered from substantial experimental noise due to a variety of technical problems, the most prominent of which is bottlenecking during the generation of mutant viruses from plasmids. Here we describe advances that ameliorate these problems, enabling us to measure with greatly improved accuracy and reproducibility the effects of all amino-acid mutations to an H1 influenza hemagglutinin on viral replication in cell culture. The largest improvements come from using a helper virus to reduce bottlenecks when generating viruses from plasmids. Our measurements confirm at much higher resolution the results of previous studies suggesting that antigenic sites on the globular head of hemagglutinin are highly tolerant of mutations. We also show that other regions of hemagglutinin-including the stalk epitopes targeted by broadly neutralizing antibodies-have a much lower inherent capacity to tolerate point mutations. The ability to accurately measure the effects of all influenza mutations should enhance efforts to understand and predict viral evolution. PMID:27271655

  6. Accurate measurement of bromine contents in plastic samples by instrumental neutron activation analysis.

    PubMed

    Kim, I J; Lee, K S; Hwang, E; Min, H S; Yim, Y H

    2013-03-26

    Accurate measurements of bromine contents in plastic samples were made by the direct comparator instrumental neutron activation analysis (INAA). Individual factors affecting the measurements were comprehensively evaluated and compensated, including the volatility loss of bromine from standard comparators, the background bromine level in the filter papers used for preparation of the standard comparators, nuclear interference, γ-ray spectral interference and the variance among replicates of the samples. Uncertainty contributions from those factors were thoroughly evaluated and included in the uncertainty budgeting of the INAA measurement. (81)Br was chosen as the target isotope, and the INAA measurements for bromine were experimentally confirmed to exhibit good linearity within a bromine content range of 10-170 μg. The established method has been applied to the analysis of eight plastic samples: four commercially available certified reference materials (CRMs) of polyethylene and polystyrene and four acrylonitrile butadiene styrene (ABS) samples prepared as the candidate reference materials (KRISS CRM 113-01-012, -013, -014 and -015). The bromine contents of the samples were calculated at three different γ-ray energies and compared, showing good agreement. The results of the four CRMs also showed good consistency with their certified values within the stated uncertainties. Finally, the bromine contents of the ABS samples were determined with expanded uncertainties (at a 95% level of confidence) between 2.5% and 5% in a bromine content range of 25-900 mg kg(-1). PMID:23498117

  7. Accurate measurements of ozone absorption cross-sections in the Hartley band

    NASA Astrophysics Data System (ADS)

    Viallon, J.; Lee, S.; Moussay, P.; Tworek, K.; Petersen, M.; Wielgosz, R. I.

    2015-03-01

    Ozone plays a crucial role in tropospheric chemistry, is the third largest contributor to greenhouse radiative forcing after carbon dioxide and methane and also a toxic air pollutant affecting human health and agriculture. Long-term measurements of tropospheric ozone have been performed globally for more than 30 years with UV photometers, all relying on the absorption of ozone at the 253.65 nm line of mercury. We have re-determined this cross-section and report a value of 11.27 x 10-18 cm2 molecule-1 with an expanded relative uncertainty of 0.86% (coverage factor k= 2). This is lower than the conventional value currently in use and measured by Hearn (1961) with a relative difference of 1.8%, with the consequence that historically reported ozone concentrations should be increased by 1.8%. In order to perform the new measurements of cross-sections with reduced uncertainties, a system was set up to generate pure ozone in the gas phase together with an optical system based on a UV laser with lines in the Hartley band, including accurate path length measurement of the absorption cell and a careful evaluation of possible impurities in the ozone sample by mass spectrometry and Fourier transform infrared spectroscopy. This resulted in new measurements of absolute values of ozone absorption cross-sections of 9.48 x 10-18, 10.44 x 10-18 and 11.07 x 10-18 cm2 molecule-1, with relative expanded uncertainties better than 0.7%, for the wavelengths (in vacuum) of 244.06, 248.32, and 257.34 nm respectively. The cross-section at the 253.65 nm line of mercury was determined by comparisons using a Standard Reference Photometer equipped with a mercury lamp as the light source. The newly reported value should be used in the future to obtain the most accurate measurements of ozone concentration, which are in closer agreement with non-UV-photometry based methods such as the gas phase titration of ozone with nitrogen monoxide.

  8. Accurate laser measurements of ozone absorption cross-sections in the Hartley band

    NASA Astrophysics Data System (ADS)

    Viallon, J.; Lee, S.; Moussay, P.; Tworek, K.; Petersen, M.; Wielgosz, R. I.

    2014-08-01

    Ozone plays a crucial role in tropospheric chemistry, is the third largest contributor to greenhouse radiative forcing after carbon dioxide and methane and also a toxic air pollutant affecting human health and agriculture. Long-term measurements of tropospheric ozone have been performed globally for more than 30 years with UV photometers, all relying on the absorption of ozone at the 253.65 nm line of mercury. We have re-determined this cross-section and report a value of 11.27 × 10-18 cm2 molecule-1 with an expanded relative uncertainty of 0.84 %. This is lower than the conventional value currently in use and measured by Hearn in 1961 with a relative difference of 1.8%, with the consequence that historically reported ozone concentrations should be increased by 1.8%. In order to perform the new measurements of cross sections with reduced uncertainties, a system to generate pure ozone in the gas phase together with an optical system based on a UV laser with lines in the Hartley band, including accurate path length measurement of the absorption cell and a careful evaluation of possible impurities in the ozone sample by mass spectrometry and Fourier Transform Infrared spectroscopy was setup. This resulted in new measurements of absolute values of ozone absorption cross sections of 9.48 × 10-18, 10.44 × 10-18, and 11.07 × 10-18 cm2 molecule-1, with relative expanded uncertainties better than 0.6%, for the wavelengths (in vacuum) of 244.062, 248.32, and 257.34 nm respectively. The cross-section at the 253.65 nm line of mercury was determined by comparisons using a Standard Reference Photometer equipped with a mercury lamp as the light source. The newly reported value should be used in the future to obtain the most accurate measurements of ozone concentration, which are in closer agreement with non UV photometry based methods such as the gas phase titration of ozone with nitrogen monoxide.

  9. Accurate Measurement of Velocity and Acceleration of Seismic Vibrations near Nuclear Power Plants

    NASA Astrophysics Data System (ADS)

    Arif, Syed Javed; Imdadullah; Asghar, Mohammad Syed Jamil

    In spite of all prerequisite geological study based precautions, the sites of nuclear power plants are also susceptible to seismic vibrations and their consequent effects. The effect of the ongoing nuclear tragedy in Japan caused by an earthquake and its consequent tsunami on March 11, 2011 is currently beyond contemplations. It has led to a rethinking on nuclear power stations by various governments around the world. Therefore, the prediction of location and time of large earthquakes has regained a great importance. The earth crust is made up of several wide, thin and rigid plates like blocks which are in constant motion with respect to each other. A series of vibrations on the earth surface are produced by the generation of elastic seismic waves due to sudden rupture within the plates during the release of accumulated strain energy. The range of frequency of seismic vibrations is from 0 to 10 Hz. However, there appears a large variation in magnitude, velocity and acceleration of these vibrations. The response of existing or conventional methods of measurement of seismic vibrations is very slow, which is of the order of tens of seconds. A systematic and high resolution measurement of velocity and acceleration of these vibrations are useful to interpret the pattern of waves and their anomalies more accurately, which are useful for the prediction of an earthquake. In the proposed work, a fast rotating magnetic field (RMF) is used to measure the velocity and acceleration of seismic vibrations in the millisecond range. The broad spectrum of pulses within one second range, measured by proposed method, gives all possible values of instantaneous velocity and instantaneous acceleration of the seismic vibrations. The spectrum of pulses in millisecond range becomes available which is useful to measure the pattern of fore shocks to predict the time and location of large earthquakes more accurately. Moreover, instead of average, the peak values of these quantities are helpful

  10. 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.

  11. Frequency spectra from current vs. magnetic flux density measurements for mobile phones and other electrical appliances.

    PubMed

    Straume, Aksel; Johnsson, Anders; Oftedal, Gunnhild; Wilén, Jonna

    2007-10-01

    The frequency spectra of electromagnetic fields have to be determined to evaluate human exposure in accordance to ICNIRP guidelines. In the literature, comparisons with magnetic field guidelines have been performed by using the frequency distribution of the current drawn from the battery. In the present study we compared the frequency spectrum in the range 217 Hz to 2.4 kHz of the magnetic flux density measured near the surface of a mobile phone with the frequency spectrum of the supply current. By using the multiple frequency rule, recommended in the ICNIRP guidelines, we estimated the magnetic field exposure in the two cases. Similar measurements and estimations were done for an electric drill, a hair dryer, and a fluorescent desk lamp. All the devices have a basic frequency of 50 Hz, and the frequency spectra were evaluated up to 550 Hz. We also mapped the magnetic field in 3D around three mobile phones. The frequency distributions obtained from the two measurement methods are not equal. The frequency content of the current leads to an overestimation of the magnetic field exposure by a factor up to 2.2 for the mobile phone. For the drill, the hair dryer, and the fluorescent lamp, the supply current signal underestimated the exposure by a factor up to 2.3. In conclusion, an accurate exposure evaluation requires the magnetic flux density spectrum of the device to be measured directly. There was no indication that the devices studied would exceed the reference levels at the working distances normally used.

  12. Accurate measurement of intraarterial pressure through radial artery catheters in neonates.

    PubMed

    Hack, W W; Westerhof, N; Leenhoven, T; Okken, A

    1990-07-01

    A technique is described for accurate measurement of intraarterial pressure through radial artery catheters in neonates. The technique, which can be used for short-term monitoring, uses cannulation of the radial artery with a 24-gauge Teflon catheter, connected by a Luer-Lok fitting to a three-way stopcock and a high-fidelity tip transducer. In vitro studies showed that the system is linear and the frequency response is flat (+/- 3 dB) up to 50 Hz. The technique permits gathering of high-quality pressure data and can be used in the area of neonatal clinical research for short-term monitoring. It needs to be developed further before routine application in clinical practice can be recommended.

  13. Simple yet accurate noncontact device for measuring the radius of curvature of a spherical mirror

    SciTech Connect

    Spiridonov, Maxim; Toebaert, David

    2006-09-10

    An easily reproducible device is demonstrated to be capable of measuring the radii of curvature of spherical mirrors, both convex and concave, without resorting to high-end interferometric or tactile devices. The former are too elaborate for our purposes,and the latter cannot be used due to the delicate nature of the coatings applied to mirrors used in high-power CO2 laser applications. The proposed apparatus is accurate enough to be useful to anyone using curved optics and needing a quick way to assess the values of the radii of curvature, be it for entrance quality control or trouble shooting an apparently malfunctioning optical system. Specifically, the apparatus was designed for checking 50 mm diameter resonator(typically flat or tens of meters concave) and telescope (typically some meters convex and concave) mirrors for a high-power CO2 laser, but it can easily be adapted to any other type of spherical mirror by a straightforward resizing.

  14. Simple yet accurate noncontact device for measuring the radius of curvature of a spherical mirror

    NASA Astrophysics Data System (ADS)

    Spiridonov, Maxim; Toebaert, David

    2006-09-01

    An easily reproducible device is demonstrated to be capable of measuring the radii of curvature of spherical mirrors, both convex and concave, without resorting to high-end interferometric or tactile devices. The former are too elaborate for our purposes, and the latter cannot be used due to the delicate nature of the coatings applied to mirrors used in high-power CO2 laser applications. The proposed apparatus is accurate enough to be useful to anyone using curved optics and needing a quick way to assess the values of the radii of curvature, be it for entrance quality control or trouble shooting an apparently malfunctioning optical system. Specifically, the apparatus was designed for checking 50 mm diameter resonator (typically flat or tens of meters concave) and telescope (typically some meters convex and concave) mirrors for a high-power CO2 laser, but it can easily be adapted to any other type of spherical mirror by a straightforward resizing.

  15. On the tip calibration for accurate modulus measurement by contact resonance atomic force microscopy.

    PubMed

    Passeri, D; Rossi, M; Vlassak, J J

    2013-05-01

    Accurate quantitative elastic modulus measurements using contact resonance atomic force microscopy require the calibration of geometrical and mechanical properties of the tip as well as the choice of a suitable model for describing the cantilever-tip-sample system. In this work, we demonstrate with both simulations and experiments that the choice of the model influences the results of the calibration. Neglecting lateral force results in the underestimation of the tip indentation modulus and in the overestimation of the tip-sample contact radius. We propose a new approach to the calibration and data analysis, where lateral forces and cantilever inclination are neglected (which simplifies the calculations) and the tip parameters are assumed as fictitious.

  16. Measuring solar reflectance Part I: Defining a metric that accurately predicts solar heat gain

    SciTech Connect

    Levinson, Ronnen; Akbari, Hashem; Berdahl, Paul

    2010-05-14

    Solar reflectance can vary with the spectral and angular distributions of incident sunlight, which in turn depend on surface orientation, solar position and atmospheric conditions. A widely used solar reflectance metric based on the ASTM Standard E891 beam-normal solar spectral irradiance underestimates the solar heat gain of a spectrally selective 'cool colored' surface because this irradiance contains a greater fraction of near-infrared light than typically found in ordinary (unconcentrated) global sunlight. At mainland U.S. latitudes, this metric RE891BN can underestimate the annual peak solar heat gain of a typical roof or pavement (slope {le} 5:12 [23{sup o}]) by as much as 89 W m{sup -2}, and underestimate its peak surface temperature by up to 5 K. Using R{sub E891BN} to characterize roofs in a building energy simulation can exaggerate the economic value N of annual cool-roof net energy savings by as much as 23%. We define clear-sky air mass one global horizontal ('AM1GH') solar reflectance R{sub g,0}, a simple and easily measured property that more accurately predicts solar heat gain. R{sub g,0} predicts the annual peak solar heat gain of a roof or pavement to within 2 W m{sup -2}, and overestimates N by no more than 3%. R{sub g,0} is well suited to rating the solar reflectances of roofs, pavements and walls. We show in Part II that R{sub g,0} can be easily and accurately measured with a pyranometer, a solar spectrophotometer or version 6 of the Solar Spectrum Reflectometer.

  17. Measuring solar reflectance - Part I: Defining a metric that accurately predicts solar heat gain

    SciTech Connect

    Levinson, Ronnen; Akbari, Hashem; Berdahl, Paul

    2010-09-15

    Solar reflectance can vary with the spectral and angular distributions of incident sunlight, which in turn depend on surface orientation, solar position and atmospheric conditions. A widely used solar reflectance metric based on the ASTM Standard E891 beam-normal solar spectral irradiance underestimates the solar heat gain of a spectrally selective ''cool colored'' surface because this irradiance contains a greater fraction of near-infrared light than typically found in ordinary (unconcentrated) global sunlight. At mainland US latitudes, this metric R{sub E891BN} can underestimate the annual peak solar heat gain of a typical roof or pavement (slope {<=} 5:12 [23 ]) by as much as 89 W m{sup -2}, and underestimate its peak surface temperature by up to 5 K. Using R{sub E891BN} to characterize roofs in a building energy simulation can exaggerate the economic value N of annual cool roof net energy savings by as much as 23%. We define clear sky air mass one global horizontal (''AM1GH'') solar reflectance R{sub g,0}, a simple and easily measured property that more accurately predicts solar heat gain. R{sub g,0} predicts the annual peak solar heat gain of a roof or pavement to within 2 W m{sup -2}, and overestimates N by no more than 3%. R{sub g,0} is well suited to rating the solar reflectances of roofs, pavements and walls. We show in Part II that R{sub g,0} can be easily and accurately measured with a pyranometer, a solar spectrophotometer or version 6 of the Solar Spectrum Reflectometer. (author)

  18. 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.

  19. Extracting accurate strain measurements in bone mechanics: A critical review of current methods.

    PubMed

    Grassi, Lorenzo; Isaksson, Hanna

    2015-10-01

    Osteoporosis related fractures are a social burden that advocates for more accurate fracture prediction methods. Mechanistic methods, e.g. finite element models, have been proposed as a tool to better predict bone mechanical behaviour and strength. However, there is little consensus about the optimal constitutive law to describe bone as a material. Extracting reliable and relevant strain data from experimental tests is of fundamental importance to better understand bone mechanical properties, and to validate numerical models. Several techniques have been used to measure strain in experimental mechanics, with substantial differences in terms of accuracy, precision, time- and length-scale. Each technique presents upsides and downsides that must be carefully evaluated when designing the experiment. Moreover, additional complexities are often encountered when applying such strain measurement techniques to bone, due to its complex composite structure. This review of literature examined the four most commonly adopted methods for strain measurements (strain gauges, fibre Bragg grating sensors, digital image correlation, and digital volume correlation), with a focus on studies with bone as a substrate material, at the organ and tissue level. For each of them the working principles, a summary of the main applications to bone mechanics at the organ- and tissue-level, and a list of pros and cons are provided. PMID:26099201

  20. An Accurate Method for Measuring Airplane-Borne Conformal Antenna's Radar Cross Section

    NASA Astrophysics Data System (ADS)

    Guo, Shuxia; Zhang, Lei; Wang, Yafeng; Hu, Chufeng

    2016-09-01

    The airplane-borne conformal antenna attaches itself tightly with the airplane skin, so the conventional measurement method cannot determine the contribution of the airplane-borne conformal antenna to its radar cross section (RCS). This paper uses the 2D microwave imaging to isolate and extract the distribution of the reflectivity of the airplane-borne conformal antenna. It obtains the 2D spatial spectra of the conformal antenna through the wave spectral transform between the 2D spatial image and the 2D spatial spectrum. After the interpolation from the rectangular coordinate domain to the polar coordinate domain, the spectral domain data for the variation of the scatter of the conformal antenna with frequency and angle is obtained. The experimental results show that the measurement method proposed in this paper greatly enhances the airplane-borne conformal antenna's RCS measurement accuracy, essentially eliminates the influences caused by the airplane skin and more accurately reveals the airplane-borne conformal antenna's RCS scatter properties.

  1. 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...

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  3. High-Frequency CTD Measurements for Accurate GPS/acoustic Sea-floor Crustal Deformation Measurement System

    NASA Astrophysics Data System (ADS)

    Tadokoro, K.; Yasuda, K.; Taniguchi, S.; Uemura, Y.; Matsuhiro, K.

    2015-12-01

    The GPS/acoustic sea-floor crustal deformation measurement system has developed as a useful tool to observe tectonic deformation especially at subduction zones. One of the factors preventing accurate GPS/acoustic sea-floor crustal deformation measurement is horizontal heterogeneity of sound speed in the ocean. It is therefore necessary to measure the gradient directly from sound speed structure. We report results of high-frequency CTD measurements using Underway CTD (UCTD) in the Kuroshio region. We perform the UCTD measurements on May 2nd, 2015 at two stations (TCA and TOA) above the sea-floor benchmarks installed across the Nankai Trough, off the south-east of Kii Peninsula, middle Japan. The number of measurement points is six at each station along circles with a diameter of 1.8 nautical miles around the sea-floor benchmark. The stations TCA and TOA are located on the edge and the interior of the Kuroshio current, respectively, judging from difference in sea water density measured at the two stations, as well as a satellite image of sea-surface temperature distribution. We detect a sound speed gradient of high speeds in the southern part and low speeds in the northern part at the two stations. At the TCA station, the gradient is noticeable down to 300 m in depth; the maximum difference in sound speed is +/- 5 m/s. The sound speed difference is as small as +/- 1.3 m/s at depths below 300 m, which causes seafloor benchmark positioning error as large as 1 m. At the TOA station, the gradient is extremely small down to 100 m in depth. The maximum difference in sound speed is less than +/- 0.3 m/s that is negligible small for seafloor benchmark positioning error. Clear gradient of high speed is observed to the depths; the maximum difference in sound speed is +/- 0.8-0.9 m/s, causing seafloor benchmark positioning error of several tens centimeters. The UCTD measurement is effective tool to detect sound speed gradient. We establish a method for accurate sea

  4. 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.

  5. Evaluating Earth degassing in subduction zones by measuring helium fluxes from the ocean floor

    NASA Astrophysics Data System (ADS)

    Lan, Tefang F.; Sano, Yuji; Yang, Tsanyao F.; Takahata, Naoto; Shirai, Kotaro; Pinti, Daniele L.

    2010-10-01

    Volatiles are lost from the Earth's mantle to the atmosphere, hydrosphere and the crust through subaerial and submarine volcanism. Quantifying the volatile sources bears fundamental information on a number of issues in Earth sciences, from the evolution of the atmosphere and oceans to the nature of chemical heterogeneity of the Earth's mantle. The primordial noble gas isotope 3He provides an unambiguous measure of the volatile flux from the mantle, yet so far in the ocean region; it has been only measured at a mid-ocean ridge. Here, we present original measurements of the 3He flux at the Mid-Okinawa Trough back-arc basin. The 3He flux was estimated from 3He/ 20Ne vertical profiles measured in deep-sea sediment pore water. Diffusive 3He fluxes vary from 1.6 3He atoms cm -2 s -1 at the hydrothermally active Izena Cauldron to 0.57 3He atoms cm -2 s -1 at the background site, 13 km away. These values are about 20% of the 3He flux measured at the East Pacific Rise, supporting the never-proven hypothesis that 3He mantle flux from subduction zones is a quarter of that at MOR. Measured ocean-floor 4He flux ranges from 3.3 × 10 5 to 4.8 × 10 54He atoms cm -2 s -1, higher than that measured worldwide, suggesting that 4He flux at subduction zones might have been previously underestimated.

  6. A comparison of direct measurement and model simulation of total flux of volatile organic compounds from the subsurface to the atmosphere under natural field conditions

    NASA Astrophysics Data System (ADS)

    Tillman, Fred D.; Choi, Jee-Won; Smith, James A.

    2003-10-01

    Accurate quantification of natural attenuation of volatile organic compounds (VOCs) in groundwater requires an accounting of all VOC mass-loss processes, including volatilization into soil gas with ultimate transport to land surface and the atmosphere. This paper compares two methods of estimating VOC flux to the atmosphere. The first method measures VOC flux at land surface using a vertical flux chamber (VFC). The VFC has been shown in a previous laboratory study to reliably measure organic vapor fluxes from soil to the atmosphere that are caused by either gas phase diffusion or a combination of advection plus diffusion [, 2003]. The second method simulates VOC flux using a transient, one-dimensional gas flow and transport model incorporating the effects of gas phase diffusion, equilibrium air-water partitioning of organic vapors, and unsaturated zone airflow caused by atmospheric pressure changes (i.e., barometric pumping). Flux chamber measurements were made concurrently with field data measurements required for the flow and transport model at a trichloroethene (TCE)-contaminated field site. The two methods of VOC flux estimation provided comparable results in nine sets of field comparisons with the flux chamber estimating a lower flux during most of the time periods. Sensitivity analyses of model input parameters produce upper and lower bounds on best estimate flux simulations. Average VFC measurements fall within these upper and lower bounds of combined parameter values for all nine comparison events. The ease of use, lack of a priori site knowledge and accuracy of the VFC compared with the data-intensive flow and transport model suggests that direct measurement of VOC flux from the subsurface to the atmosphere at contaminated sites could become routine practice, providing important information to decision makers about the progress of monitored natural attenuation.

  7. Maximum Mass of Strange Stars and Pulsars with the Most Accurately Measured Masses

    NASA Astrophysics Data System (ADS)

    Vartanyan, Yu. L.; Grigoryan, A. K.; Shahinyan, H. A.

    2015-06-01

    Strange quark matter (SQM) is studied using a bag model in which the transition to the SQM state takes place at energy densities of no more than twice the density in atomic nuclei. Thus, low mass neutron stars with a configuration consisting of SQM form a single family on a plot of the mass M of equilibrium superdense configurations as a function of central energy density ρ c (the M(ρ c ) curve). The bag model considered here depends on three constants: the vacuum pressure B, the quark-gluon interaction constant α c , and the strange quark mass m s . Sets of values of these constants are determined, which if used in the equation of state for SQM yield a maximal mass M max of the equilibrium quark configurations which exceeds the recently accurately determined mass of 2.01 M ⊙ for the binary radio pulsar PSR J0348+0432. The mass, radius, total baryon number, and red shift from the surface of the strange star are calculated for these configurations as a function of central energy density ρ c . The values of these integrated parameters are also calculated for each series with M max > 2.01 M ⊙ for superdense configurations with masses of 2.01, 1.97, and 1.44 solar masses, which have been determined with great accuracy from observations. It turns out that, according to the resulting equations of state, all of the three pulsars with the most accurately measured masses, may be possible candidate strange stars.

  8. Accurate, in vivo NIR measurement of skeletal muscle oxygenation through fat

    NASA Astrophysics Data System (ADS)

    Jin, Chunguang; Zou, Fengmei; Ellerby, Gwenn E. C.; Scott, Peter; Peshlov, Boyan; Soller, Babs R.

    2010-02-01

    Noninvasive near infrared (NIR) spectroscopic measurement of muscle oxygenation requires the penetration of light through overlying skin and fat layers. We have previously demonstrated a dual-light source design and orthogonalization algorithm that corrects for inference from skin absorption and fat scattering. To achieve accurate muscle oxygen saturation (SmO2) measurement, one must select the appropriate source-detector distance (SD) to completely penetrate the fat layer. Methods: Six healthy subjects were supine for 15min to normalize tissue oxygenation across the body. NIR spectra were collected from the calf, shoulder, lower and upper thigh muscles with long SD distances of 30mm, 35mm, 40mm and 45mm. Spectral preprocessing with the short SD (3mm) spectrum preceded SmO2 calculation with a Taylor series expansion method. Three-way ANOVA was used to compare SmO2 values over varying fat thickness, subjects and SD distances. Results: Overlying fat layers varied in thickness from 4.9mm to 19.6mm across all subjects. SmO2 measured at the four locations were comparable for each subject (p=0.133), regardless of fat thickness and SD distance. SmO2 (mean+/-std dev) measured at calf, shoulder, low and high thigh were 62+/-3%, 59+/-8%, 61+/-2%, 61+/-4% respectively for SD distance of 30mm. In these subjects no significant influence of SD was observed (p=0.948). Conclusions: The results indicate that for our sensor design a 30mm SD is sufficient to penetrate through a 19mm fat layer and that orthogonalization with short SD effectively removed spectral interference from fat to result in a reproducible determination of SmO2.

  9. 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.

  10. Accurate measurement of interferometer group delay using field-compensated scanning white light interferometer.

    PubMed

    Wan, Xiaoke; Wang, Ji; Ge, Jian

    2010-10-10

    Interferometers are key elements in radial velocity (RV) experiments in astronomy observations, and accurate calibration of the group delay of an interferometer is required for high precision measurements. A novel field-compensated white light scanning Michelson interferometer is introduced as an interferometer calibration tool. The optical path difference (OPD) scanning was achieved by translating a compensation prism, such that even if the light source were in low spatial coherence, the interference stays spatially phase coherent over a large interferometer scanning range. In the wavelength region of 500-560 nm, a multimode fiber-coupled LED was used as the light source, and high optical efficiency was essential in elevating the signal-to-noise ratio of the interferogram signal. The achromatic OPD scanning required a one-time calibration, and two methods using dual-laser wavelength references and an iodine absorption spectrum reference were employed and cross-verified. In an experiment measuring the group delay of a fixed Michelson interferometer, Fourier analysis was employed to process the interferogram data. The group delay was determined at an accuracy of 1×10(-5), and the phase angle precision was typically 2.5×10(-6) over the wide wavelength region.

  11. Accurately measuring volume of soil samples using low cost Kinect 3D scanner

    NASA Astrophysics Data System (ADS)

    van der Sterre, Boy-Santhos; Hut, Rolf; van de Giesen, Nick

    2013-04-01

    The 3D scanner of the Kinect game controller can be used to increase the accuracy and efficiency of determining in situ soil moisture content. Soil moisture is one of the principal hydrological variables in both the water and energy interactions between soil and atmosphere. Current in situ measurements of soil moisture either rely on indirect measurements (of electromagnetic constants or heat capacity) or on physically taking a sample and weighing it in a lab. The bottleneck in accurately retrieving soil moisture using samples is the determining of the volume of the sample. Currently this is mostly done by the very time consuming "sand cone method" in which the volume were the sample used to sit is filled with sand. We show that 3D scanner that is part of the 150 game controller extension "Kinect" can be used to make 3D scans before and after taking the sample. The accuracy of this method is tested by scanning forms of known volume. This method is less time consuming and less error-prone than using a sand cone.

  12. Accurately measuring volume of soil samples using low cost Kinect 3D scanner

    NASA Astrophysics Data System (ADS)

    van der Sterre, B.; Hut, R.; Van De Giesen, N.

    2012-12-01

    The 3D scanner of the Kinect game controller can be used to increase the accuracy and efficiency of determining in situ soil moisture content. Soil moisture is one of the principal hydrological variables in both the water and energy interactions between soil and atmosphere. Current in situ measurements of soil moisture either rely on indirect measurements (of electromagnetic constants or heat capacity) or on physically taking a sample and weighing it in a lab. The bottleneck in accurately retrieving soil moisture using samples is the determining of the volume of the sample. Currently this is mostly done by the very time consuming "sand cone method" in which the volume were the sample used to sit is filled with sand. We show that 3D scanner that is part of the $150 game controller extension "Kinect" can be used to make 3D scans before and after taking the sample. The accuracy of this method is tested by scanning forms of known volume. This method is less time consuming and less error-prone than using a sand cone.

  13. 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.

  14. 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.

  15. 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.

  16. A background correction algorithm for Van Allen Probes MagEIS electron flux measurements

    SciTech Connect

    Claudepierre, S. G.; O'Brien, T. P.; Blake, J. B.; Fennell, J. F.; Roeder, J. L.; Clemmons, J. H.; Looper, M. D.; Mazur, J. E.; Mulligan, T. M.; Spence, H. E.; Reeves, G. D.; Friedel, R. H. W.; Henderson, M. G.; Larsen, B. A.

    2015-07-14

    We describe an automated computer algorithm designed to remove background contamination from the Van Allen Probes Magnetic Electron Ion Spectrometer (MagEIS) electron flux measurements. We provide a detailed description of the algorithm with illustrative examples from on-orbit data. We find two primary sources of background contamination in the MagEIS electron data: inner zone protons and bremsstrahlung X-rays generated by energetic electrons interacting with the spacecraft material. Bremsstrahlung X-rays primarily produce contamination in the lower energy MagEIS electron channels (~30–500 keV) and in regions of geospace where multi-M eV electrons are present. Inner zone protons produce contamination in all MagEIS energy channels at roughly L < 2.5. The background-corrected MagEIS electron data produce a more accurate measurement of the electron radiation belts, as most earlier measurements suffer from unquantifiable and uncorrectable contamination in this harsh region of the near-Earth space environment. These background-corrected data will also be useful for spacecraft engineering purposes, providing ground truth for the near-Earth electron environment and informing the next generation of spacecraft design models (e.g., AE9).

  17. A background correction algorithm for Van Allen Probes MagEIS electron flux measurements

    DOE PAGES

    Claudepierre, S. G.; O'Brien, T. P.; Blake, J. B.; Fennell, J. F.; Roeder, J. L.; Clemmons, J. H.; Looper, M. D.; Mazur, J. E.; Mulligan, T. M.; Spence, H. E.; et al

    2015-07-14

    We describe an automated computer algorithm designed to remove background contamination from the Van Allen Probes Magnetic Electron Ion Spectrometer (MagEIS) electron flux measurements. We provide a detailed description of the algorithm with illustrative examples from on-orbit data. We find two primary sources of background contamination in the MagEIS electron data: inner zone protons and bremsstrahlung X-rays generated by energetic electrons interacting with the spacecraft material. Bremsstrahlung X-rays primarily produce contamination in the lower energy MagEIS electron channels (~30–500 keV) and in regions of geospace where multi-M eV electrons are present. Inner zone protons produce contamination in all MagEIS energymore » channels at roughly L < 2.5. The background-corrected MagEIS electron data produce a more accurate measurement of the electron radiation belts, as most earlier measurements suffer from unquantifiable and uncorrectable contamination in this harsh region of the near-Earth space environment. These background-corrected data will also be useful for spacecraft engineering purposes, providing ground truth for the near-Earth electron environment and informing the next generation of spacecraft design models (e.g., AE9).« less

  18. A particle-tracking approach for accurate material derivative measurements with tomographic PIV

    NASA Astrophysics Data System (ADS)

    Novara, Matteo; Scarano, Fulvio

    2013-08-01

    The evaluation of the instantaneous 3D pressure field from tomographic PIV data relies on the accurate estimate of the fluid velocity material derivative, i.e., the velocity time rate of change following a given fluid element. To date, techniques that reconstruct the fluid parcel trajectory from a time sequence of 3D velocity fields obtained with Tomo-PIV have already been introduced. However, an accurate evaluation of the fluid element acceleration requires trajectory reconstruction over a relatively long observation time, which reduces random errors. On the other hand, simple integration and finite difference techniques suffer from increasing truncation errors when complex trajectories need to be reconstructed over a long time interval. In principle, particle-tracking velocimetry techniques (3D-PTV) enable the accurate reconstruction of single particle trajectories over a long observation time. Nevertheless, PTV can be reliably performed only at limited particle image number density due to errors caused by overlapping particles. The particle image density can be substantially increased by use of tomographic PIV. In the present study, a technique to combine the higher information density of tomographic PIV and the accurate trajectory reconstruction of PTV is proposed (Tomo-3D-PTV). The particle-tracking algorithm is applied to the tracers detected in the 3D domain obtained by tomographic reconstruction. The 3D particle information is highly sparse and intersection of trajectories is virtually impossible. As a result, ambiguities in the particle path identification over subsequent recordings are easily avoided. Polynomial fitting functions are introduced that describe the particle position in time with sequences based on several recordings, leading to the reduction in truncation errors for complex trajectories. Moreover, the polynomial regression approach provides a reduction in the random errors due to the particle position measurement. Finally, the acceleration

  19. How Accurate is Your Sclerostin Measurement? Comparison Between Three Commercially Available Sclerostin ELISA Kits.

    PubMed

    Piec, Isabelle; Washbourne, Christopher; Tang, Jonathan; Fisher, Emily; Greeves, Julie; Jackson, Sarah; Fraser, William D

    2016-06-01

    Sclerostin, bone formation antagonist is in the spotlight as a potential biomarker for diseases presenting with associated bone disorders such as chronic kidney disease (CDK-MBD). Accurate measurement of sclerostin is therefore important. Several immunoassays are available to measure sclerostin in serum and plasma. We compared the performance of three commercial ELISA kits. We measured sclerostin concentrations in serum and EDTA plasma obtained from healthy young (18-26 years) human subjects using kits from Biomedica, TECOmedical and from R&D Systems. The circulating sclerostin concentrations were systematically higher when measured with the Biomedica assay (serum: 35.5 ± 1.1 pmol/L; EDTA: 39.4 ± 2.0 pmol/L; mean ± SD) as compared with TECOmedical (serum: 21.8 ± 0.7 pmol/L; EDTA: 27.2 ± 1.3 pmol/L) and R&D Systems (serum: 7.6 ± 0.3 pmol/L; EDTA: 30.9 ± 1.5 pmol/L). We found a good correlation between the assay for EDTA plasma (r > 0.6; p < 0.001) while in serum, only measurements obtained using TECOmedical and R&D Systems assays correlated significantly (r = 0.78; p < 0.001). There was no correlation between matrices results when using the Biomedica kit (r = 0.20). The variability in values generated from Biomedica, R&D Systems and TECOmedical assays raises questions regarding the accuracy and specificity of the assays. Direct comparison of studies using different kits is not possible and great care should be given to measurement of sclerostin, with traceability of reagents. Standardization with appropriate material is required before different sclerostin assays can be introduced in clinical practice. PMID:26749312

  20. How Accurate is Your Sclerostin Measurement? Comparison Between Three Commercially Available Sclerostin ELISA Kits.

    PubMed

    Piec, Isabelle; Washbourne, Christopher; Tang, Jonathan; Fisher, Emily; Greeves, Julie; Jackson, Sarah; Fraser, William D

    2016-06-01

    Sclerostin, bone formation antagonist is in the spotlight as a potential biomarker for diseases presenting with associated bone disorders such as chronic kidney disease (CDK-MBD). Accurate measurement of sclerostin is therefore important. Several immunoassays are available to measure sclerostin in serum and plasma. We compared the performance of three commercial ELISA kits. We measured sclerostin concentrations in serum and EDTA plasma obtained from healthy young (18-26 years) human subjects using kits from Biomedica, TECOmedical and from R&D Systems. The circulating sclerostin concentrations were systematically higher when measured with the Biomedica assay (serum: 35.5 ± 1.1 pmol/L; EDTA: 39.4 ± 2.0 pmol/L; mean ± SD) as compared with TECOmedical (serum: 21.8 ± 0.7 pmol/L; EDTA: 27.2 ± 1.3 pmol/L) and R&D Systems (serum: 7.6 ± 0.3 pmol/L; EDTA: 30.9 ± 1.5 pmol/L). We found a good correlation between the assay for EDTA plasma (r > 0.6; p < 0.001) while in serum, only measurements obtained using TECOmedical and R&D Systems assays correlated significantly (r = 0.78; p < 0.001). There was no correlation between matrices results when using the Biomedica kit (r = 0.20). The variability in values generated from Biomedica, R&D Systems and TECOmedical assays raises questions regarding the accuracy and specificity of the assays. Direct comparison of studies using different kits is not possible and great care should be given to measurement of sclerostin, with traceability of reagents. Standardization with appropriate material is required before different sclerostin assays can be introduced in clinical practice.

  1. Accurate and precise Pb isotope ratio measurements in environmental samples by MC-ICP-MS

    NASA Astrophysics Data System (ADS)

    Weiss, Dominik J.; Kober, Bernd; Dolgopolova, Alla; Gallagher, Kerry; Spiro, Baruch; Le Roux, Gaël; Mason, Thomas F. D.; Kylander, Malin; Coles, Barry J.

    2004-04-01

    Analytical protocols for accurate and precise Pb isotope ratio determinations in peat, lichen, vegetable, chimney dust, and ore-bearing granites using MC-ICP-MS and their application to environmental studies are presented. Acid dissolution of various matrix types was achieved using high temperature/high pressure microwave and hot plate digestion procedures. The digests were passed through a column packed with EiChrom Sr-resin employing only hydrochloric acid and one column passage. This simplified column chemistry allowed high sample throughput. Typically, internal precisions for approximately 30 ng Pb were below 100 ppm (+/-2[sigma]) on all Pb ratios in all matrices. Thallium was employed to correct for mass discrimination effects and the achieved accuracy was below 80 ppm for all ratios. This involved an optimization procedure for the 205Tl/203Tl ratio using least square fits relative to certified NIST-SRM 981 Pb values. The long-term reproducibility (+/-2[sigma]) for the NIST-SRM 981 Pb standard over a 5-month period (35 measurements) was better than 350 ppm for all ratios. Selected ore-bearing granites were measured with TIMS and MC-ICP-MS and showed good correlation (e.g., r=0.999 for 206Pb/207Pb ratios, slope=0.996, n=13). Mass bias and signal intensities of Tl spiked into natural (after matrix separation) and in synthetic samples did not differ significantly, indicating that any residual components of the complex peat and lichen matrix did not influence mass bias correction. Environmental samples with very different matrices were analyzed during two different studies: (i) lichens, vegetables, and chimney dust around a Cu smelter in the Urals, and (ii) peat samples from an ombrotrophic bog in the Faroe Islands. The presented procedure for sample preparation, mass spectrometry, and data processing tools resulted in accurate and precise Pb isotope data that allowed the reliable differentiation and identification of Pb sources with variations as small as 0

  2. Accurate 3D kinematic measurement of temporomandibular joint using X-ray fluoroscopic images

    NASA Astrophysics Data System (ADS)

    Yamazaki, Takaharu; Matsumoto, Akiko; Sugamoto, Kazuomi; Matsumoto, Ken; Kakimoto, Naoya; Yura, Yoshiaki

    2014-04-01

    Accurate measurement and analysis of 3D kinematics of temporomandibular joint (TMJ) is very important for assisting clinical diagnosis and treatment of prosthodontics and orthodontics, and oral surgery. This study presents a new 3D kinematic measurement technique of the TMJ using X-ray fluoroscopic images, which can easily obtain the TMJ kinematic data in natural motion. In vivo kinematics of the TMJ (maxilla and mandibular bone) is determined using a feature-based 2D/3D registration, which uses beads silhouette on fluoroscopic images and 3D surface bone models with beads. The 3D surface models of maxilla and mandibular bone with beads were created from CT scans data of the subject using the mouthpiece with the seven strategically placed beads. In order to validate the accuracy of pose estimation for the maxilla and mandibular bone, computer simulation test was performed using five patterns of synthetic tantalum beads silhouette images. In the clinical applications, dynamic movement during jaw opening and closing was conducted, and the relative pose of the mandibular bone with respect to the maxilla bone was determined. The results of computer simulation test showed that the root mean square errors were sufficiently smaller than 1.0 mm and 1.0 degree. In the results of clinical application, during jaw opening from 0.0 to 36.8 degree of rotation, mandibular condyle exhibited 19.8 mm of anterior sliding relative to maxillary articular fossa, and these measurement values were clinically similar to the previous reports. Consequently, present technique was thought to be suitable for the 3D TMJ kinematic analysis.

  3. An accurate mass and radius measurement for an ultracool white dwarf

    NASA Astrophysics Data System (ADS)

    Parsons, S. G.; Gänsicke, B. T.; Marsh, T. R.; Bergeron, P.; Copperwheat, C. M.; Dhillon, V. S.; Bento, J.; Littlefair, S. P.; Schreiber, M. R.

    2012-11-01

    Studies of cool white dwarfs in the solar neighbourhood have placed a limit on the age of the Galactic disc of 8-9 billion years. However, determining their cooling ages requires the knowledge of their effective temperatures, masses, radii and atmospheric composition. So far, these parameters could only be inferred for a small number of ultracool white dwarfs for which an accurate distance is known, by fitting their spectral energy distributions in conjunction with a theoretical mass-radius relation. However, the mass-radius relation remains largely untested, and the derived cooling ages are hence model dependent. Here we report direct measurements of the mass and radius of an ultracool white dwarf in the double-lined eclipsing binary SDSS J013851.54-001621.6. We find MWD = 0.529 ± 0.010 M⊙ and RWD = 0.0131 ± 0.0003 R⊙. Our measurements are consistent with the mass-radius relation and we determine a robust cooling age of 9.5 billion years for the 3570 K white dwarf. We find that the mass and radius of the low-mass companion star, Msec = 0.132 ± 0.003 M⊙ and Rsec = 0.165 ± 0.001 R⊙, are in agreement with evolutionary models. We also find evidence that this >9.5 Gyr old M5 star is still active, far beyond the activity lifetime for a star of its spectral type. This is likely caused by the high tidally enforced rotation rate of the star. The companion star is close to filling its Roche lobe and the system will evolve into a cataclysmic variable in only 70 Myr. Our direct measurements demonstrate that this system can be used to calibrate ultracool white dwarf atmospheric models.

  4. 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.

  5. Mask defect disposition: flux-area measurement of edge, contact, and OPC defects correlates to wafer and enables effective decisions

    NASA Astrophysics Data System (ADS)

    Fiekowsky, Peter; Taylor, Darren; Wang, David; Yang, Chien-Chu; Lin, Shu-Chun; Tu, L. H.; Lin, K. R.

    2001-09-01

    Lithographers' ability to set useful defect and contact specifications has almost disappeared as chip geometries have shrunk. As features sizes have decreased, measurement error has increased to 25% of the maximum allowable defect size. This has made defect disposition so difficult that many processes now require that all detected defects be repaired because the automatic defect sizing is almost meaningless, that is, the required guard band is nearly the size of the defect specification (Reynolds, BACUS 2000). Many mask processes have abandoned defect sizingin favor of stepper simulation, either using simulation microscope, such as AIMS, or software, such as NTI's VSS. However, AVI's optical Flux-Area measurement technique provides accuracy and repeatability that gives the simple, time tested defect specification technique new life. This study demonstrates high quality edge-, contact-, and OPC- defect disposition can be achieved using the Flux-Area technique. A test mask with a range of edge defects as well as mis-sized contacts and OPC defects was written. The mask defect sizing performed with the AVI is shown to be consistent on different chips using the same process. Thus it is shown that all the over-spec defects on the wafer were measured as over-spec on the mask. Results show that edge defect size on the wafer can be accurately predicted from the AVI defect area; that printed contact size is linearly proportional to the AVI measured area, on both square and irregular contacts; and that OPC defects (printed line-end separation errors) can be accurately predicted from AVI serif-area measurements on the mask. With the Flux-Area measurement technique as implemented on the AVI Photomask Metrology System, defects can be measured with long term repeatability and rms repeatability between machines of better than 10nm, 3% of a 0.3micrometers defect. This means that guard bands can often be reduced from 0.15micrometers to below 0.05micrometers .

  6. Confronting model predictions of carbon fluxes with measurements of Amazon forests subjected to experimental drought.

    PubMed

    Powell, Thomas L; Galbraith, David R; Christoffersen, Bradley O; Harper, Anna; Imbuzeiro, Hewlley M A; Rowland, Lucy; Almeida, Samuel; Brando, Paulo M; da Costa, Antonio Carlos Lola; Costa, Marcos Heil; Levine, Naomi M; Malhi, Yadvinder; Saleska, Scott R; Sotta, Eleneide; Williams, Mathew; Meir, Patrick; Moorcroft, Paul R

    2013-10-01

    Considerable uncertainty surrounds the fate of Amazon rainforests in response to climate change. Here, carbon (C) flux predictions of five terrestrial biosphere models (Community Land Model version 3.5 (CLM3.5), Ecosystem Demography model version 2.1 (ED2), Integrated BIosphere Simulator version 2.6.4 (IBIS), Joint UK Land Environment Simulator version 2.1 (JULES) and Simple Biosphere model version 3 (SiB3)) and a hydrodynamic terrestrial ecosystem model (the Soil-Plant-Atmosphere (SPA) model) were evaluated against measurements from two large-scale Amazon drought experiments. Model predictions agreed with the observed C fluxes in the control plots of both experiments, but poorly replicated the responses to the drought treatments. Most notably, with the exception of ED2, the models predicted negligible reductions in aboveground biomass in response to the drought treatments, which was in contrast to an observed c. 20% reduction at both sites. For ED2, the timing of the decline in aboveground biomass was accurate, but the magnitude was too high for one site and too low for the other. Three key findings indicate critical areas for future research and model development. First, the models predicted declines in autotrophic respiration under prolonged drought in contrast to measured increases at one of the sites. Secondly, models lacking a phenological response to drought introduced bias in the sensitivity of canopy productivity and respiration to drought. Thirdly, the phenomenological water-stress functions used by the terrestrial biosphere models to represent the effects of soil moisture on stomatal conductance yielded unrealistic diurnal and seasonal responses to drought.

  7. Accurate Permittivity Measurements for Microwave Imaging via Ultra-Wideband Removal of Spurious Reflectors

    PubMed Central

    Pelletier, Mathew G.; Viera, Joseph A.; Wanjura, John; Holt, Greg

    2010-01-01

    The use of microwave imaging is becoming more prevalent for detection of interior hidden defects in manufactured and packaged materials. In applications for detection of hidden moisture, microwave tomography can be used to image the material and then perform an inverse calculation to derive an estimate of the variability of the hidden material, such internal moisture, thereby alerting personnel to damaging levels of the hidden moisture before material degradation occurs. One impediment to this type of imaging occurs with nearby objects create strong reflections that create destructive and constructive interference, at the receiver, as the material is conveyed past the imaging antenna array. In an effort to remove the influence of the reflectors, such as metal bale ties, research was conducted to develop an algorithm for removal of the influence of the local proximity reflectors from the microwave images. This research effort produced a technique, based upon the use of ultra-wideband signals, for the removal of spurious reflections created by local proximity reflectors. This improvement enables accurate microwave measurements of moisture in such products as cotton bales, as well as other physical properties such as density or material composition. The proposed algorithm was shown to reduce errors by a 4:1 ratio and is an enabling technology for imaging applications in the presence of metal bale ties. PMID:22163668

  8. An improved method for accurate and rapid measurement of flight performance in Drosophila.

    PubMed

    Babcock, Daniel T; Ganetzky, Barry

    2014-01-01

    Drosophila has proven to be a useful model system for analysis of behavior, including flight. The initial flight tester involved dropping flies into an oil-coated graduated cylinder; landing height provided a measure of flight performance by assessing how far flies will fall before producing enough thrust to make contact with the wall of the cylinder. Here we describe an updated version of the flight tester with four major improvements. First, we added a "drop tube" to ensure that all flies enter the flight cylinder at a similar velocity between trials, eliminating variability between users. Second, we replaced the oil coating with removable plastic sheets coated in Tangle-Trap, an adhesive designed to capture live insects. Third, we use a longer cylinder to enable more accurate discrimination of flight ability. Fourth we use a digital camera and imaging software to automate the scoring of flight performance. These improvements allow for the rapid, quantitative assessment of flight behavior, useful for large datasets and large-scale genetic screens. PMID:24561810

  9. Produced water toxicity tests accurately measure the produced water toxicity in marine environments?

    SciTech Connect

    Douglas, W.S.; Veil, J.A.

    1996-10-01

    U.S. Environmental Protection Agency (EPA) Region VI has issued a general permit for offshore oil and gas discharges to the Gulf of Mexico that places numerical limits on whole effluent toxicity (WEI) for produced water. Recently proposed EPA general permits for other produced water discharges in Regions VI and X also include enforceable numerical limits on WET. Clearly, the industry will be conducting extensive produced water WET testing. Unfortunately, the WET test may not accurately measure the toxicity of the chemical constituents of produced water. Rather the mortality of test organisms may be attributable to (1) the high salinity of produced water, which causes salinity shock to the organisms, or (2) an ionic imbalance caused by excesses or deficiencies of one or more of seawater`s essential ions in the test chambers. Both of these effects are likely to be mitigated in actual offshore discharge settings, where the receiving water will be seawater and substantial dilution will be probable. Thus, the additional salinity of produced water will be rapidly assimilated, and the proper marine ionic balance will be quickly restored. Regulatory authorities should be aware of these factors when interpreting WET test results.

  10. Accurate measurement of refraction and dispersion of a solid by a double-layer interferometer.

    PubMed

    Nassif, A Y

    1997-02-01

    A silica plate of plane-parallel faces is inserted into one gap of a double-layer interferometer that transmits white light to a prism spectrograph in order to produce elliptic rings of equal chromatic order (RECO's). The silica plate is rotated and the expanding RECO's are counted at their center while this center is coincident with a standard wavelength. An analytic formula that relates the fringe count to the rotated angle enables the refractive index of the rotated plate to be accurately determined for different wavelengths. The results are fitted to a single-term Sellmeier dispersion function to find the peak wavelength of the ultraviolet absorption band and the atomic number density for such a transition. The variation of either the dispersion coefficient or the group-velocity factor with wavelength is determined from either the displacement of the RECO center across the visible spectrum if one of the double-layer interferometer's mirrors is displaced parallel to itself or from measurements on the RECO diameters. PMID:18250738

  11. 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}.

  12. 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}.

  13. 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%.

  14. Muscle function during brief maximal exercise: accurate measurements on a friction-loaded cycle ergometer.

    PubMed

    Arsac, L M; Belli, A; Lacour, J R

    1996-01-01

    A friction loaded cycle ergometer was instrumented with a strain gauge and an incremental encoder to obtain accurate measurement of human mechanical work output during the acceleration phase of a cycling sprint. This device was used to characterise muscle function in a group of 15 well-trained male subjects, asked to perform six short maximal sprints on the cycle against a constant friction load. Friction loads were successively set at 0.25, 0.35, 0.45, 0.55, 0.65 and 0.75 N.kg-1 body mass. Since the sprints were performed from a standing start, and since the acceleration was not restricted, the greatest attention was paid to the measurement of the acceleration balancing load due to flywheel inertia. Instantaneous pedalling velocity (v) and power output (P) were calculated each 5 ms and then averaged over each downstroke period so that each pedal downstroke provided a combination of v, force and P. Since an 8-s acceleration phase was composed of about 21 to 34 pedal downstrokes, this many v-P combinations were obtained amounting to 137-180 v-P combinations for all six friction loads in one individual, over the widest functional range of pedalling velocities (17-214 rpm). Thus, the individual's muscle function was characterised by the v-P relationships obtained during the six acceleration phases of the six sprints. An important finding of the present study was a strong linear relationship between individual optimal velocity (vopt) and individual maximal power output (Pmax) (n = 15, r = 0.95, P < 0.001) which has never been observed before. Since vopt has been demonstrated to be related to human fibre type composition both vopt, Pmax and their inter-relationship could represent a major feature in characterising muscle function in maximal unrestricted exercise. It is suggested that the present method is well suited to such analyses.

  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. MELIFT - A new device for accurate measurements in a snow rich environment

    NASA Astrophysics Data System (ADS)

    Dorninger, M.

    2012-04-01

    A deep snow pack, remote locations, no external power supply and very low temperatures are often the main ingredients when it comes to the deployment of meteorological stations in mountainous terrain. The accurate position of the sensor related to the snow surface is normally not known. A new device called METLIFT overcomes the problems. WMO recommends a height between 1.2 m and 2 m above ground level for the measurement of air temperature and humidity. The height above ground level is specified to take care of the possible strong vertical temperature and humidity gradients at the lowest layers in the atmosphere. Especially in snow rich and remote locations it may be hardly possible to follow this advice. Therefore most of the meteorological stations in mountainous terrain are situated at mountain tops where strong winds will blow off the snow or in valleys where a daily inspection of the sensors is possible. In other unpopulated mountainous areas, e.g. basins, plateaus, the distance of the sensor to the snow surface is not known or the sensor will be snow-covered. A new device was developed to guarantee the sensor height above surface within the WMO limits in harsh and remote environments. An ultrasonic snow height sensor measures the distance to the snow surface. If it exceeds certain limits due to snow accumulation or snow melt the lift adapts its height accordingly. The prototype of METLIFT has been installed in Lower Austria at an altitude of 1000m. The lift is 6 m high and can pull out for another 4 m. Sensor arms are mounted every meter to allow the connection of additional sensors or to measure a profile of a certain parameter of the lowest 5 m above surface. Sensors can be added easily since cable wiring is provided to each sensor arm. Horizontal winds are measured at 7 m height above surface. METLIFT is independent of external power supply. Three lead gel accumulators recharged by three solar panels provide the energy necessary for the sensors, the data

  18. 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).

  19. An intercomparison 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. L.; Smith, E. A.; Verma, S. B.; Field, R. T.; Kustas, W. P.; Stewart, J. B.

    1992-01-01

    During FIFE 1987, 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 20 of 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. Using linear regression analysis, net radiation, Bowen ratio, and latent heat fluxes were compared between the rover measurements and the host measurements. The average differences in net radiation, Bowen ratio, and latent heat flux from 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 radiation energy balance system (REBS) model. The four-way components method and the Thornthwaite type give similar values to the REBS. The surface energy radiation balance systems type Bowen ratio systems exhibit slightly lower Bowen ratios and thus higher latent heat fluxes, compared to the arid zone evapotranspiration systems. Eddy correlation systems showed slightly lower latent heat flux in comparison to the Bowen ratio systems. It is recommended that users of the flux data take these differences into account.

  20. Eddy covariance flux measurements of biogenic VOCs during ECHO 2003 using proton transfer reaction mass spectrometry

    NASA Astrophysics Data System (ADS)

    Spirig, C.; Neftel, A.; Ammann, C.; Dommen, J.; Grabmer, W.; Thielmann, A.; Schaub, A.; Beauchamp, J.; Wisthaler, A.; Hansel, A.

    2005-02-01

    Within the framework of the AFO 2000 project ECHO, two PTR-MS instruments were operated in combination with sonic anemometers to determine biogenic VOC fluxes from a mixed deciduous forest site in North-Western Germany. The measurement site was characterised by a forest of inhomogeneous composition, complex canopy structure, limited extension in certain wind directions and frequent calm wind conditions during night time. The eddy covariance (EC) technique was applied since it represents the most direct flux measurement approach on the canopy scale and is, therefore, least susceptible to these non-ideal conditions. A specific flux calculation method was used to account for the sequential multi-component PTR-MS measurements and allowing an individual delay time adjustment as well as a rigorous quality control based on cospectral analysis. The validated flux results are consistent with light and temperature dependent emissions of isoprene and monoterpenes from this forest, with average daytime emissions of 0.94 and 0.3µg m-2s-1, respectively. Emissions of methanol reached on average 0.087µg m-2s-1 during daytime, but fluxes were too small to be detected during night time. Upward fluxes of the isoprene oxidation products methyl vinyl ketone (MVK) and methacrolein (MACR) were also found, being two orders of magnitude lower than those of isoprene. Calculations with an analytical footprint model indicate that the observed isoprene fluxes correlate with the fraction of oaks within the footprints of the flux measurement.

  1. Using skin temperature gradients or skin heat flux measurements to determine thresholds of vasoconstriction and vasodilatation.

    PubMed

    House, James R; Tipton, Michael J

    2002-11-01

    Forearm-fingertip skin temperature differentials (T(sk-diff)) are used to indicate vasomotor tone, vasoconstriction defined as having occurred when T(sk-diff)> or =4 degrees C (Sessler et al. 1987, 1988a, b). This study was conducted to determine whether T(sk-diff) or finger pad heat flux (HF) can be used to predict when vasoconstriction and vasodilatation occur. Seven subjects (one female) sat in water at [mean (SD)] 40.7 (0.8) degrees C until their core temperature (T(c)) increased by 1 degrees C, ensuring vasodilatation. The water was then cooled [at a rate of 0.6 (0.1) degrees C x min(-1)] until T(c) fell to 0.5 degrees C below pretesting values, causing vasoconstriction. Subjects were then rewarmed in water [41.2 (1.0) degrees C]. Skin blood flow (SkBF) was measured using laser Doppler flowmetry (LDF) on the left second finger pad [immersed in water at 10.4 (1.4) degrees C as part of another experiment], and infrared plethysmography on the third finger pad of both hands. T(sk-diff) and HF were measured on the right upper limb, which remained in air. When vasodilated, the subjects had a stable T(sk-diff) and HF. During cooling, rapid-onset vasoconstriction occurred coincidental with large gradient changes in HF and T(sk-diff) (inflection points). In two subjects the original vasoconstriction definition (T(sk-diff)> or =4 degrees C) was not attained, in the other five this was achieved 31-51 min after vasoconstriction. During rewarming, the T(sk-diff) and HF inflection points less accurately reflected the onset of vasodilatation, although with one exception they were within 5 min of the LDF changes. We conclude that T(sk-diff) and HF inflection points predict vasoconstriction accurately, and better than T(sk-diff)> or =4 degrees C.

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

    SciTech Connect

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

    2013-10-01

    We modified our multi-channel, steady-state flow-through (SSFT), soil-CO2 flux monitoring system to include an array of inexpensive pyroelectric non-dispersive infrared detectors for full-range (0-100%) coverage of CO2 concentrations without dilution, and a larger-diameter vent tube. We then conducted field testing of this system from late July through mid-September 2010 at the Zero Emissions Research and Technology (ZERT) project site located in Bozeman, MT, and subsequently, laboratory testing at the Pacific Northwest National Laboratory (PNNL) in Richland, WA using a flux bucket filled with dry sand. In the field, an array of twenty-five SSFT and three non-steady-state (NSS) flux chambers was installed in a 10x4 m area, the long boundary of which was directly above a shallow (2-m depth) horizontal injection well located 0.5 m below the water table. Two additional chambers (one SSFT and one NSS) were installed 10 m from the well for background measurements. Volumetric soil moisture sensors were installed at each SSFT chamber to measure mean levels in the top 0.15 m of soil. A total flux of 52 kg CO2 d-1 was injected into the well for 27 d and the efflux from the soil was monitored by the chambers before, during, and for 27 d after the injection. Overall, the results were consistent with those from previous years, showing a radial efflux pattern centered on a known “hot spot”, rapid responses to changes in injection rate and wind power, evidence for movement of the CO2 plume during the injection, and nominal flux levels from the SSFT chambers that were up to 6-fold higher than those measured by adjacent NSS chambers. Soil moisture levels varied during the experiment from moderate to near saturation with the highest levels occurring consistently at the hot spot. The effects of wind on measured flux were complex and decreased as soil moisture content increased. In the laboratory, flux bucket testing with the SSFT chamber showed large measured-flux enhancement

  3. 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

  4. A new direct absorption measurement for high precision and accurate measurement of water vapor in the UT/LS

    NASA Astrophysics Data System (ADS)

    Sargent, M. R.; Sayres, D. S.; Smith, J. B.; Anderson, J.

    2011-12-01

    Highly accurate and precise water vapor measurements in the upper troposphere and lower stratosphere are critical to understanding the climate feedbacks of water vapor and clouds in that region. However, the continued disagreement among water vapor measurements (~1 - 2 ppmv) are too large to constrain the role of different hydration and dehydration mechanisms operating in the UT/LS, with model validation dependent upon which dataset is chosen. In response to these issues, we present a new instrument for measurement of water vapor in the UT/LS that was flown during the April 2011 MACPEX mission out of Houston, TX. The dual axis instrument combines the heritage and validated accuracy of the Harvard Lyman-alpha instrument with a newly designed direct IR absorption instrument, the Harvard Herriott Hygrometer (HHH). The Lyman-alpha detection axis has flown aboard NASA's WB-57 and ER2 aircraft since 1994, and provides a requisite link between the new HHH instrument and the long history of Harvard water vapor measurements. The instrument utilizes the highly sensitive Lyman-alpha photo-fragment fluorescence detection method; its accuracy has been demonstrated though rigorous laboratory calibrations and in situ diagnostic procedures. The Harvard Herriott Hygrometer employs a fiber coupled near-IR laser with state-of-the-art electronics to measure water vapor via direct absorption in a spherical Herriott cell of 10 cm length. The instrument demonstrated in-flight precision of 0.1 ppmv (1-sec, 1-sigma) at mixing ratios as low as 5 ppmv with accuracies of 10% based on careful laboratory calibrations and in-flight performance. We present a description of the measurement technique along with our methodology for calibration and details of the measurement uncertainties. The simultaneous utilization of radically different measurement techniques in a single duct in the new Harvard Water Vapor (HWV) instrument allows for the constraint of systematic errors inherent in each technique

  5. 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

  6. 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

  7. Deuterium flux measurements in the edge plasmas of PLT and PDX during auxiliary heating experiments

    SciTech Connect

    Wampler, W.R.; Cohen, S.A.; Dylla, H.F.; Manos, D.M.; Magee, C.W.

    1981-01-01

    The flux of deuterium in the plasma edge several centimeters outside the limiter has been measured using collector probes during neutral beam heating experiments on the PDX tokamak and RF heating experiments on the PLT tokamak. The dependence of the flux on the distance from the plasma was determined, and the time dependence of the flux was measured with a time resolution of 90 ms. In PDX the deuterium flux decreased rapidly with increasing distance from the plasma. The deuterium flux increased strongly when the beams came on and decreased when they turned off. The depth distribution of the deuterium in the samples, measured using SIMS, shows that when the beams are on about 30% of the deuterium incident on the probe is superthermal deuterium from the beams. In PLT the deuterium flux decreased only slightly with increasing distance from the plasma. The ICRH heating in PLT caused an increase of about 30% in the flux of deuterium to the samples and in the plasma density. In both machines the deuterium fluxes were fairly low (less than or equal to 10/sup 16/D/cm/sup 2/s) at the positions sampled.

  8. Deuterium flux measurements in the edge plasmas of PLT and PDX during auxiliary heating experiments

    SciTech Connect

    Wampler, W.R.; Cohen, S.A.; Dylla, H.F.; Manos, D.M.; Magee, C.W.

    1982-04-01

    The flux of deuterium in the plasma edge several centimeters outside the limiter has been measured using collector probes during neutral beam heating experiments on the PDX tokamak and rf heating experiments on the PLT tokamak. The dependence of the flux on the distance from the plasma was determined, and the time dependence of the flux was measured with a time resolution of 90 ms. In PDX the deuterium flux decreases rapidly with increasing distance from the plasma. The deuterium flux increased strongly when the beams came on and decreased when they turned off. The depth distribution of the deuterium in the samples, measured using SIMS, shows that when the beams are on, about 30% of the deuterium incident on the probe is superthermal deuterium from the beams. In PLT the deuterium flux decreased only slightly with increasing distance from the plasma. The ICRH heating in PLT caused an increase of about 30% in the flux of deuterium to the samples and in the plasma density. In both machines the deuterium fluxes were fairly low (< or approx. =10/sup 16/ D/cm/sup 2/s) at the positions sampled.

  9. An accurate air temperature measurement system based on an envelope pulsed ultrasonic time-of-flight technique.

    PubMed

    Huang, Y S; Huang, Y P; Huang, K N; Young, M S

    2007-11-01

    A new microcomputer based air temperature measurement system is presented. An accurate temperature measurement is derived from the measurement of sound velocity by using an ultrasonic time-of-flight (TOF) technique. The study proposes a novel algorithm that combines both amplitude modulation (AM) and phase modulation (PM) to get the TOF measurement. The proposed system uses the AM and PM envelope square waveform (APESW) to reduce the error caused by inertia delay. The APESW ultrasonic driving waveform causes an envelope zero and phase inversion phenomenon in the relative waveform of the receiver. To accurately achieve a TOF measurement, the phase inversion phenomenon was used to sufficiently identify the measurement pulse in the received waveform. Additionally, a counter clock technique was combined to compute the phase shifts of the last incomplete cycle for TOF. The presented system can obtain 0.1% TOF resolution for the period corresponding to the 40 kHz frequency ultrasonic wave. Consequently, with the integration of a humidity compensation algorithm, a highly accurate and high resolution temperature measurement can be achieved using the accurate TOF measurement. Experimental results indicate that the combined standard uncertainty of the temperature measurement is approximately 0.39 degrees C. The main advantages of this system are high resolution measurements, narrow bandwidth requirements, and ease of implementation.

  10. 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.

  11. Progress in the measurement of SSME turbine heat flux with plug-type sensors

    NASA Technical Reports Server (NTRS)

    Liebert, Curt H.

    1991-01-01

    Data reduction was completed for tests of plug-type heat flux sensors (gauges) in a turbine blade thermal cycling tester (TBT) that is located at NASA/Marshall Space Flight Center, and a typical gauge is illustrated. This is the first time that heat flux has been measured in a Space Shuttle Main Engine (SSME) Turbopump Turbine environment. The development of the concept for the gauge was performed in a heat flux measurement facility at Lewis. In this facility, transient and steady state absorbed surface heat flux information was obtained from transient temperature measurements taken at points within the gauge. A schematic of the TBT is presented, and plots of the absorbed surface heat flux measured on the three blades tested in the TBT are presented. High quality heat flux values were measured on all three blades. The experiments demonstrated that reliable and durable gauges can be repeatedly fabricated into the airfoils. The experiment heat flux data are being used for verification of SSME analytical stress, boundary layer, and heat transfer design models. Other experimental results and future plans are also presented.

  12. 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.

  13. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

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

  15. 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

  16. 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

  17. 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.

  18. Temperature measurements during high flux ion beam irradiations

    DOE PAGES

    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

  19. 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.

  20. 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.

  1. 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.

  2. Measuring planetary neutron albedo fluxes by remote gamma-ray sensing

    NASA Technical Reports Server (NTRS)

    Haines, E. L.; Metzger, A. E.

    1984-01-01

    In order to measure the planetary neutron albedo fluxes, a neutron-absorbing shield which emits gamma rays of characteristic energy and serves as a neutron detector, is added to a gamma-ray spectrometer (GRS). The gamma rays representing the neutron flux are observed against interference consisting of cosmic gamma rays, planetary continuum and line emission, and gamma rays arising from the interaction of cosmic rays with the GRS and the spacecraft. The uncertainty and minimum detection limits in neutron albedo fluxes are calculated for two missions, a lunar orbiter and a comet nucleus rendezvous. A GRS on a lunar orbiter at 100 km altitude detects a thermal neutron albedo flux as low as 0.002/sq cm/s and an expected flux of about 0.6/sq cm/s is measured with an uncertainty of 0.001/sq cm/s, for a 100 h observation period. For the comet nucleus, again in a 100 h observing period, a thermal neutron albedo flux is detected at a level of 0.006/sq cm/s and an expected flux of about 0.4/sq cm/s is measured with an uncertainty of 0.004/sq cm/s. The expanded geological capabilities made possible by this technique include improvements in H sensitivity, spatial resolution, and measurement depth; and an improved model of induced gamma-ray emission.

  3. Eddy Covariance Flux Measurements of Urban Aerosols During the MILAGRO Mexico City Field Campaign

    NASA Astrophysics Data System (ADS)

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

    2007-12-01

    Expansive urban development in the fast growing number of megacities around the world raises concerns regarding the pollution levels in such sites. The Mexico City MILAGRO 2006 (Megacity Initiative: Local and Global Research Observations) field campaign was a worldwide initiative aiming to understand sources, chemical nature and evolution of pollution in one of the largest urban developments. As part of the MILAGRO campaign, urban fluxes of aerosols and related trace gases were measured near the centre of Mexico City at 42 m above street level. Aerosol concentrations (1 min. averages) and aerosol fluxes (10 Hz, selected ion monitoring) were measured with an Aerodyne quadrupole aerosol mass spectrometer operated in an alternating 30 minute mode of ambient concentrations and fluxes. The fluxes were derived using eddy covariance calculations. The aerosol flux data were supported by additional flux measurements of CO2 and a number of gas phase VOC species using a combination of techniques, including Proton Transfer Reaction Mass Spectrometry using a disjunct eddy covariance technique and GC-FID analysis of samples from a disjunct eddy accumulation sampler. Preliminary results of aerosol concentrations and flux measurements indicate that the urban landscape is a significant source of organic aerosols.

  4. 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

  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. Effects of vegetative heterogeneity and patch-scale harvest on energy balance closure and flux measurements

    NASA Astrophysics Data System (ADS)

    Guo, X. F.; Cai, X. H.; Kang, L.; Zhu, T.; Zhang, H. S.

    2009-05-01

    Based on the micrometeorological measurements at a heterogeneous farmland in South China, this work detects the effects of vegetative heterogeneity and patch-scale harvest on the energy balance closure and turbulent fluxes. As a quality control, the integral turbulent characteristics are analyzed in the framework of Monin-Obukhov similarity theory. Spatial representativeness of the measurements is studied in terms of footprint and source area. Firstly, in two wind sectors, the nondimensional standard deviations of turbulent quantities generally agree with some foregoing studies. Discrepancies exist in the other sectors due to the instrument-induced flow distortion. Secondly, energy balance closure is examined with two types of linear regression, which confirms that mismatching source areas between the available energy and turbulent fluxes have no preference to either energy “deficit” or “surplus”. Thirdly, turbulent fluxes exhibit greater variability when they represent smaller source areas. The patch-scale harvest adjacent to the flux mast causes notable increase and decrease in the sensible heat and latent heat fluxes, respectively, while the CO2 exchange almost vanishes after the harvest. Interestingly, energy balance closure is less influenced despite the notable effects on the turbulent fluxes and Bowen ratio, implying that the energy balance closure check may mask some variability in the turbulent fluxes. Thus, to adjust the heat fluxes with a single “closure factor” for a perfect closure is dangerous at a patchy site.

  7. 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.

  8. Feedback system for divertor impurity seeding based on real-time measurements of surface heat flux in the Alcator C-Mod tokamak

    NASA Astrophysics Data System (ADS)

    Brunner, D.; Burke, W.; Kuang, A. Q.; LaBombard, B.; Lipschultz, B.; Wolfe, S.

    2016-02-01

    Mitigation of the intense heat flux to the divertor is one of the outstanding problems in fusion energy. One technique that has shown promise is impurity seeding, i.e., the injection of low-Z gaseous impurities (typically N2 or Ne) to radiate and dissipate the power before it arrives to the divertor target plate. To this end, the Alcator C-Mod team has created a first-of-its-kind feedback system to control the injection of seed gas based on real-time surface heat flux measurements. Surface thermocouples provide real-time measurements of the surface temperature response to the plasma heat flux. The surface temperature measurements are inputted into an analog computer that "solves" the 1-D heat transport equation to deliver accurate, real-time signals of the surface heat flux. The surface heat flux signals are sent to the C-Mod digital plasma control system, which uses a proportional-integral-derivative (PID) algorithm to control the duty cycle demand to a pulse width modulated piezo valve, which in turn controls the injection of gas into the private flux region of the C-Mod divertor. This paper presents the design and implementation of this new feedback system as well as initial results using it to control divertor heat flux.

  9. Feedback system for divertor impurity seeding based on real-time measurements of surface heat flux in the Alcator C-Mod tokamak.

    PubMed

    Brunner, D; Burke, W; Kuang, A Q; LaBombard, B; Lipschultz, B; Wolfe, S

    2016-02-01

    Mitigation of the intense heat flux to the divertor is one of the outstanding problems in fusion energy. One technique that has shown promise is impurity seeding, i.e., the injection of low-Z gaseous impurities (typically N2 or Ne) to radiate and dissipate the power before it arrives to the divertor target plate. To this end, the Alcator C-Mod team has created a first-of-its-kind feedback system to control the injection of seed gas based on real-time surface heat flux measurements. Surface thermocouples provide real-time measurements of the surface temperature response to the plasma heat flux. The surface temperature measurements are inputted into an analog computer that "solves" the 1-D heat transport equation to deliver accurate, real-time signals of the surface heat flux. The surface heat flux signals are sent to the C-Mod digital plasma control system, which uses a proportional-integral-derivative (PID) algorithm to control the duty cycle demand to a pulse width modulated piezo valve, which in turn controls the injection of gas into the private flux region of the C-Mod divertor. This paper presents the design and implementation of this new feedback system as well as initial results using it to control divertor heat flux.

  10. 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.

  11. Application of an energy balance correction method for turbulent flux measurements based on buoyancy

    NASA Astrophysics Data System (ADS)

    Babel, Wolfgang; Charuchittipan, Doojdao; Zhao, Peng; Biermann, Tobias; Gatzsche, Kathrin; Foken, Thomas

    2014-05-01

    The energy imbalance in flux measurements between the atmosphere and the surface is a well-known problem, but unsolved due to the complexity of possible reasons and potential error sources. In order to provide unbiased budgets, however, eddy-covariance measurements of sensible and latent heat flux should be corrected according to the closure gap. Recent studies utilising turbulent flux data and LES models suggest that the transport of the missing turbulent flux is triggered by meso-scale circulations, not detected by eddy-covariance measurements within typical averaging intervals of 30 minutes. These motions on longer timescales are driven by buoyancy, suggesting that the missing turbulent flux is a missing buoyancy flux. Based on this assumption we present an energy balance closure correction method according to the buoyancy flux. The effects are compared with the results obtained by the commonly used correction according to the Bowen ratio (Twine et al., Agr. Forest Meteorol., 2000). We show that in general both correction methods could be applied to daytime fluxes and conditions with positive Bowen ratios. Finally the corrected turbulent fluxes are compared with different simulations of SVAT-type models for Tibetan grassland sites and a central European spruce forest site. The model performance with respect to the used data correction method is linked to the different mechanism of closing the energy balance within the model. Model validation requires energy balance closure correction in case the model relies on the energy balance equation. We conclude that mechanistic model development of turbulent flux parameterisations should recognize the recent hypotheses concerning the energy balance closure rather than fitting just to the uncorrected eddy-covariance data.

  12. Comparison of calculated and measured foliar O3 flux in crop and forest species.

    PubMed

    Grulke, N E; Paoletti, E; Heath, R L

    2007-04-01

    We designed a new gas exchange system that concurrently measures foliar H2O, O3, and CO2 flux (HOC flux system) while delivering known O3 concentrations. Stomatal responses of three species were tested: snapbean, and seedlings of California black oak (deciduous broadleaf) and blue oak (evergreen broadleaf). Acute O3 exposure (120-250 ppb over an hour) was applied under moderate light and low vapor pressure deficits during near steady state conditions. The rate of stomatal closure was measured when the whole plant was placed in the dark. An adjacent leaf on each plant was also concurrently measured in an O3-free cuvette. Under some conditions, direct measurements and calculated foliar O3 flux were within the same order of magnitude; however, endogenously low gs or O3 exposure-induced depression of gs resulted in an overestimation of calculated O3 fluxes compared with measured O3 fluxes. Sluggish stomata in response to light extinction with concurrent O3 exposure, and incomplete stomatal closure likewise underestimated measured O3 flux.

  13. Measuring Bioenergetics in T Cells Using a Seahorse Extracellular Flux Analyzer.

    PubMed

    van der Windt, Gerritje J W; Chang, Chih-Hao; Pearce, Erika L

    2016-04-01

    This unit contains several protocols to determine the energy utilization of T cells in real-time using a Seahorse Extracellular Flux Analyzer (http://www.seahorsebio.com). The advantages to using this machine over traditional metabolic assays include the simultaneous measurement of glycolysis and mitochondrial respiration, in real-time, on relatively small numbers of cells, without any radioactivity. The Basic Protocol describes a standard mitochondrial stress test on the XF(e) 96, which yields information about oxidative phosphorylation and glycolysis, two energy-generating pathways. The alternate protocols provide examples of adaptations to the Basic Protocol, including adjustments for the use of the XF(e) 24. A protocol for real-time bioenergetic responses to T cell activation allows for the analysis of immediate metabolic changes after T cell receptor stimulation. Specific substrate utilization can be determined by the use of differential assay media, or the injection of drugs that specifically affect certain metabolic processes. Accurate cell numbers, purity, and viability are critical to obtain reliable results.

  14. Diamagnetic flux measurement using the PDX TF coils

    SciTech Connect

    Thomas, P.

    1983-02-01

    The diamagnetism of plasmas in PDX has been measured using the toroidal field coils as the equivalent of the conventional diamagnetic loop. The extremely low inductive coupling between the toroidal and poloidal coil systems makes the measurement feasible. The main difficulty arises from the change in the TF coil resistance due to Joule heating, compounded by the nonlinearity and sharp temperature dependence of the resistance of the joints in the TF coils. The measurement method, details of the experimental system, and illustrative results are presented.

  15. 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.

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

    PubMed

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

    2015-11-01

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

  17. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

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

  19. Atmospheric dry deposition fluxes of trace elements measured in Bursa, Turkey.

    PubMed

    Tasdemir, Yücel; Kural, Can

    2005-12-01

    Trace element dry deposition fluxes were measured using a smooth, greased, knife-edge surrogate surface (KSS) holding greased Mylar strips in Bursa, Turkey. Sampling program was conducted between October 2002 and June 2003 and 46 dry deposition samples were collected. The average fluxes of crustal metals (Mg, Ca, and Fe) were one to four orders of magnitude higher than the fluxes of anthropogenic metals. Trace element fluxes ranged from 3 (Cd) to 24,230 (Ca) microg m(-2) d(-1). The average trace element dry deposition fluxes measured in this study were similar to those measured in other urban areas. In addition, ambient air samples were also collected simultaneously with flux samples and concentrations of trace elements, collected with a TSP sampler, were between 0.7 and 4900 ng m(-3) for Cd and Ca, respectively. The overall trace element dry deposition velocities, calculated by dividing the fluxes to the particle phase concentrations ranged from 2.3+/-1.7 cm s(-1) (Pb) to 11.1+/-6.4 cm s(-1) (Ni). These values are in good agreement with the values calculated using similar techniques. The anthropogenic and crustal contributions were estimated by employing enrichment factors (EFs) calculated relative to the average crustal composition. Low EFs for dry deposition samples were calculated. This is probably due to contamination of local dust and its important contribution to the collected samples.

  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.

  1. Micrometeorological measurement and source region analysis of nitrous oxide fluxes from an agricultural soil

    NASA Astrophysics Data System (ADS)

    Wienhold, F. G.; Welling, M.; Harris, G. W.

    Nitrous oxide (N 2O) fluxes were measured by eddy correlation during a field experiment in August 1993. The measurements took place on a harvested wheat field located in northwest Sealand (Denmark). A. tunable diode laser absorption spectrometer (TDLAS) was used for N 2O detection. The N 2O mixing ratio was sampled at a rate of 10 Hz synchronously with the three-dimensional wind data, air temperature, water vapour and carbon dioxide (CO 2) concentrations. Fast Fourier transform methods were applied to analyse spectral and co-spectral power distributions and to compute the fluxes from the covariance functions. Balance of the energy budget indicated adequate frequency coverage of the flux contributions. Continuous measurements were carried out in half hour intervals during daytime and fluxes in the range of 40-120 ng N m -2 s -1 were obtained. The footprint regions for the individual measurements were estimated by Markovian trajectory simulations taking into account the atmospheric stability conditions and wind distributions inferred from the micrometeorological measurements. The influence of adjoining fields with different crops was evident in the Bowen ratio and CO 2 flux, but not noticeable in the N 2O flux. This observation is consistent with supporting analysis of the soil depth dependence of the nitrous oxide production, which indicates that the major contributions arise from levels below 0.9 m.

  2. 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.

  3. 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.

  4. Zero-Heat-Flux Thermometry for Non-Invasive Measurement of Core Body Temperature in Pigs.

    PubMed

    Guschlbauer, Maria; Maul, Alexandra C; Yan, Xiaowei; Herff, Holger; Annecke, Thorsten; Sterner-Kock, Anja; Böttiger, Bernd W; Schroeder, Daniel C

    2016-01-01

    Hypothermia is a severe, unpleasant side effect during general anesthesia. Thus, temperature surveillance is a prerequisite in general anesthesia settings during experimental surgeries. The gold standard to measure the core body temperature (Tcore) is placement of a Swan-Ganz catheter in the pulmonary artery, which is a highly invasive procedure. Therefore, Tcore is commonly examined in the urine bladder and rectum. However, these procedures are known for their inaccuracy and delayed record of temperatures. Zero-heat-flux (ZHF) thermometry is an alternative, non-invasive method quantifying Tcore in human patients by applying a thermosensoric patch to the lateral forehead. Since the porcine cranial anatomy is different to the human's, the optimal location of the patch remains unclear to date. The aim was to compare three different patch locations of ZHF thermometry in a porcine hypothermia model. Hypothermia (33.0 °C Tcore) was conducted in 11 anesthetized female pigs (26-30 kg). Tcore was measured continuously by an invasive Swan-Ganz catheter in the pulmonary artery (Tpulm). A ZHF thermometry device was mounted on three different defined locations. The smallest average difference between Tpulm and TZHF during stable temperatures was 0.21 ± 0.16 °C at location A, where the patch was placed directly behind the eye. Also during rapidly changing temperatures location A showed the smallest bias with 0.48 ± 0.29 °C. Location A provided the most reliable data for Tcore. Therefore, the ZHF thermometry patch should be placed directly behind the left temporal corner of the eye to provide a non-invasive method for accurate measurement of Tcore in pigs.

  5. Precision neutron flux measurement with a neutron beam monitor

    NASA Astrophysics Data System (ADS)

    Ino, T.; Otono, H.; Mishima, K.; Yamada, T.

    2014-07-01

    Neutron beam monitors are regularly used in various neutron beam experiments to compare two or more sets of data taken in different experimental conditions. A neutron lifetime experiment at BL05, the NOP beamline, in J-PARC requires to monitor the initial neutron intensity with an precision of 0.1% to measure the neutron lifetime with the same accuracy. The performance of a thin 3He gas neutron beam monitor used for the experiment was studied to estimate the systematic uncertainties in the neutron lifetime measurement.

  6. 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...

  7. Autonomous Instrumentation for Fast, Continuous and Accurate Isotopic Measurements of Water Vapor (δ18O, δ 2H, H2O) in the Field

    NASA Astrophysics Data System (ADS)

    Liem, J. S.; Dong, F.; Owano, T. G.; Baer, D. S.

    2010-12-01

    Stable isotopes of water vapor are powerful tracers to investigate the hydrological cycle and ecological processes. Therefore, continuous, in-situ and accurate measurements of δ18O and δ2H are critical to advance the understanding of water-cycle dynamics worldwide. Furthermore, the combination of meteorological techniques and high-frequency isotopic water measurements can provide detailed time-resolved information on the eco-physiological performance of plants and enable improved understanding of water fluxes at ecosystem scales. In this work, we present recent development and field deployment of a novel Water Vapor Isotope Measurement System (WVIMS) capable of simultaneous in situ measurements of δ18O and δ2H and water mixing ratio (H2O) with high precision, accuracy and speed (up to 10 Hz measurement rate). The WVIMS consists of an Analyzer (Water Vapor Isotope Analyzer), based on cavity enhanced laser absorption spectroscopy, and a Standard Source (Water Vapor Isotope Standard Source), based on quantitative evaporation of a liquid water standard (with known isotopic content), and operates in a dual-inlet configuration. The WVIMS automatically controls the entire sample and data collection, data analysis and calibration process to allow for continuous, autonomous unattended long-term operation. The WVIMS has been demonstrated for accurate (i.e. fully calibrated) measurements ranging from 500 ppmv (typical of arctic environments) to over 30,000 ppmv (typical of tropical environments) in air. Dual-inlet operation, which involves regular calibration with isotopic water vapor reference standards, essentially eliminates measurement drift, ensures data reliability, and allows operation over an extremely wide ambient temperature range (5-45C). This presentation will include recent measurements recorded using the WVIMS in plant growth chambers and in arctic environments. The availability of this new instrumentation provides new opportunities for detailed continuous

  8. 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.

  9. 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

  10. 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

  11. Analysis of actinic flux profiles measured from an ozone sonde balloon

    NASA Astrophysics Data System (ADS)

    Wang, P.; Allaart, M.; Knap, W. H.; Stammes, P.

    2014-12-01

    A green light sensor has been developed at KNMI to measure actinic flux profiles using an ozone sonde balloon. In total, 63 launches with ascending and descending profiles were performed between 2006 and 2010. The measured uncalibrated actinic flux profiles are analyzed using the Doubling Adding KNMI (DAK) radiative transfer model. Values of the cloud optical thickness (COT) along the flight track were taken from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) Cloud Physical Properties (CPP) product. The impact of clouds on the actinic flux profile is evaluated on the basis of the cloud modification factor (CMF) at the cloud top and cloud base, which is the ratio between the actinic fluxes for cloudy and clear-sky scenes. The impact of clouds on the actinic flux is clearly detected: the largest enhancement occurs at the cloud top due to multiple scattering. The actinic flux decreases almost linearly from cloud top to cloud base. Above the cloud top the actinic flux also increases compared to clear-sky scenes. We find that clouds can increase the actinic flux to 2.3 times of the clear-sky value at cloud top and decrease it to about 0.05 at cloud base. The relationship between CMF and COT agrees well with DAK simulations, except for a few outliers. Good agreement is found between the DAK simulated actinic flux profiles and the observations for single layer clouds in fully overcast scenes. The instrument is suitable for operational balloon measurements because of its simplicity and low cost. It is worth to further develop the instrument and launch it together with atmospheric chemistry composition sensors.

  12. Measurements of the instantaneous local heat flux in turbulent Rayleigh-Bénard convection

    NASA Astrophysics Data System (ADS)

    du Puits, Ronald; Resagk, Christian; Thess, André

    2010-07-01

    We present measurements of the instantaneous local heat flux in highly turbulent Rayleigh-Bénard (RB) convection in air (Pr=0.7) for aspect ratios in the range 1.13<=Γ<=9.00 and for Rayleigh numbers in the range 1.3×109<=Ra<=9.6×1011. The measurements have been carried out simultaneously at the surfaces of the heating and the cooling plate using a commercial sensor whose diameter is 360 times smaller than the diameter of the RB facility. We find that for all investigated values of Ra and Γ the time-averaged local heat flux at the centres of the heating and cooling plates is significantly higher than the global heat flux obtained in previous measurements. In particular, for the smallest investigated aspect ratio, Γ=1.13, the scaling exponents of the local heat fluxes as functions of the Rayleigh number are found to be considerably below those of the global heat flux obtained in experiments with cryogenic helium at Γ=1 by Niemela and Sreenivasan (2003 J. Fluid Mech. 481 355-84). Our measurements indicate that the spatial distribution of the heat flux at the heating and cooling plates is strongly nonuniform and that this nonuniformity decreases with increasing Ra and Γ. Our investigations of the time dependence of the local heat fluxes show that these quantities undergo fluctuations up to ±15% of their time-averaged values. Our work suggests that local heat flux measurements at different positions along heating and cooling plates are useful for a deeper understanding of the scaling properties of the (global) Nusselt number in RB convection.

  13. Eddy Covariance Measurements of Methane Flux Using an Open-Path Gas Analyzer

    NASA Astrophysics Data System (ADS)

    Burba, G.; Anderson, T.; Zona, D.; Schedlbauer, J.; Anderson, D.; Eckles, R.; Hastings, S.; Ikawa, H.; McDermitt, D.; Oberbauer, S.; Oechel, W.; Riensche, B.; Starr, G.; Sturtevant, C.; Xu, L.

    2008-12-01

    Methane is an important greenhouse gas with a warming potential of about 23 times that of carbon dioxide over a 100-year cycle (Houghton et al., 2001). Measurements of methane fluxes from the terrestrial biosphere have mostly been made using flux chambers, which have many advantages, but are discrete in time and space and may disturb surface integrity and air pressure. Open-path analyzers offer a number of advantages for measuring methane fluxes, including undisturbed in- situ flux measurements, spatial integration using the Eddy Covariance approach, zero frequency response errors due to tube attenuation, confident water and thermal density terms from co-located fast measurements of water and sonic temperature, and remote deployment due to lower power demands in the absence of a pump. The prototype open-path methane analyzer is a VCSEL (vertical-cavity surface-emitting laser)-based instrument. It employs an open Herriott cell and measures levels of methane with RMS noise below 6 ppb at 10 Hz sampling in controlled laboratory environment. Field maintenance is minimized by a self-cleaning mechanism to keep the lower mirror free of contamination. Eddy Covariance measurements of methane flux using the prototype open-path methane analyzer are presented for the period between 2006 and 2008 in three ecosystems with contrasting weather and moisture conditions: (1) Fluxes over a short-hydroperiod sawgrass wetland in the Florida Everglades were measured in a warm and humid environment with temperatures often exceeding 25oC, variable winds, and frequent heavy dew at night; (2) Fluxes over coastal wetlands in an Arctic tundra were measured in an environment with frequent sub-zero temperatures, moderate winds, and ocean mist; (3) Fluxes over pacific mangroves in Mexico were measured in an environment with moderate air temperatures high winds, and sea spray. Presented eddy covariance flux data were collected from a co-located prototype open-path methane analyzer, LI-7500, and

  14. Airborne system for fast measurements of upwelling and downwelling spectral actinic flux densities.

    PubMed

    Jäkel, Evelyn; Wendisch, Manfred; Kniffka, Anke; Trautmann, Thomas

    2005-01-20

    An airborne system for fast measurements of spectral actinic flux densities in the wavelength range 305-700 nm is introduced. The system is called the Actinic Flux Density Meter (AFDM). The AFDM utilizes the diode array technique and measures downwelling and upwelling spectral actinic flux densities separately with a time resolution of less than 1 s. For airborne measurements this means a spatial resolution of approximately 60 m, assuming an average aircraft velocity of 60 m/s. Thus the AFDM resolves fast changes in the actinic radiation field, which are of special importance for conditions of inhomogeneous clouds or surface reflection. Laboratory characterization measurements of the AFDM are presented, and a method to correct the nonideal angular response of the optical inlets is introduced. Furthermore, exemplar field data sampled simultaneously with spectral irradiance measurements are shown. The horizontal variability of the measured spectra of actinic flux density is quantified, and profile measurements for overcast situations are presented. Finally, the effects of clouds on the spectral actinic flux density are discussed.

  15. Evaluation of laser absorption spectroscopic techniques for eddy covariance flux measurements of ammonia.

    PubMed

    Whitehead, James D; Twigg, Marsailidh; Famulari, Daniela; Nemitz, Eiko; Sutton, Mark A; Gallagher, Martin W; Fowler, David

    2008-03-15

    An intercomparison was made between eddy covariance flux measurements of ammonia by a quantum cascade laser absorption spectrometer (QCLAS) and a lead-salt tunable diode laser absorption spectrometer (TDLAS). The measurements took place in September 2004 and again in April 2005 over a managed grassland site in Southern Scotland, U.K. These were also compared with a flux estimate derived from an "Ammonia Measurement by ANnular Denuder with online Analysis" (AMANDA), using the aerodynamic gradient method (AGM). The concentration and flux measurements from the QCLAS correlated well with those of the TDLAS and the AGM systems when emissions were high, following slurry application to the field. Both the QCLAS and TDLAS, however, underestimated the flux when compared with the AMANDA system, by 64%. A flux loss of 41% due to chemical reaction of ammonia in the QCLAS (and 37% in the TDLAS) sample tube walls was identified and characterized using laboratory tests but did not fully accountforthis difference. Recognizing these uncertainties, the agreement between the systems was nevertheless very close (R2 = 0.95 between the QCLAS and the TDLAS; R2 = 0.84 between the QCLAS and the AMANDA) demonstrating the suitability of the laser absorption methods for quantifying the temporal dynamics of ammonia fluxes.

  16. 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.

  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. 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.

  19. Comparison of static chambers to measure N2O and CH4 fluxes from soils

    NASA Astrophysics Data System (ADS)

    Pihlatie, M.

    2009-04-01

    Soil fluxes of the greenhouse gases (GHG) nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2) are often measured by closed static chambers. During a chamber enclosure the concentration of the target gas changes in the headspace of the chamber. This changes the concentration difference between the soil and the atmosphere and hence also the fluxes from the soil. We hypothesize that the magnitude how much a chamber affects the gas fluxes from the soil is chamber design specific. In addition, the use of inappropriate flux calculation methods can further lead to uncertainties in the flux estimates. To test different types of static chambers for N2O and CH4 flux measurements a chamber calibration campaign was organized at Hyytiälä Forestry Field Station in Southern Finland during August-October 2008. The overall aims of the campaign were to quantitatively assess the uncertainties and errors related to static chamber measurements. Overall 17 different static chambers were tested for five different N2O and CH4 flux levels with three different soil conditions (different moisture and porosity) in the chamber calibration system described by Pumpanen et al. (2004). Preliminary results show that most of the static chambers either over- or underestimated the N2O and CH4 fluxes. This chamber specific over- or underestimation remained near constant with different flux levels. However, the deviation varied greatly with different soil porosities. Here we will show the main results of the measurement campaign and give preliminary suggestions for ideal chamber designs, gas sampling protocol and flux calculation methods for N2O and CH4 flux measurements. References: Pumpanen, J., Kolari, P., Ilvesniemi, H., Minkkinen, K., Vesala, T., Niinistö, S., Lohila, A., Larmola, T., Morero, M., Pihlatie, M., Janssens, I., Curiel Yuste, J., Grünzweig, J. M., Reth, S., Subke, J.-A., Savage, K., Kutsch, W., Østreng, G., Ziegler, W., Anthoni, P., Lindroth, A. & Hari, P. 2004. Comparison

  20. Assessing Tower Flux Footprint Climatology and Scaling Between Remotely Sensed and Eddy Covariance Measurements

    NASA Astrophysics Data System (ADS)

    Chen, Baozhang; Black, T. Andrew; Coops, Nicholas C.; Hilker, Thomas; (Tony) Trofymow, J. A.; Morgenstern, Kai

    2009-02-01

    We describe pragmatic and reliable methods to examine the influence of patch-scale heterogeneities on the uncertainty in long-term eddy-covariance (EC) carbon flux data and to scale between the carbon flux estimates derived from land surface optical remote sensing and directly derived from EC flux measurements on the basis of the assessment of footprint climatology. Three different aged Douglas-fir stands with EC flux towers located on Vancouver Island and part of the Fluxnet Canada Research Network were selected. Monthly, annual and interannual footprint climatologies, unweighted or weighted by carbon fluxes, were produced by a simple model based on an analytical solution of the Eulerian advection-diffusion equation. The dimensions and orientation of the flux footprint depended on the height of the measurement, surface roughness length, wind speed and direction, and atmospheric stability. The weighted footprint climatology varied with the different carbon flux components and was asymmetrically distributed around the tower, and its size and spatial structure significantly varied monthly, seasonally and inter-annually. Gross primary productivity (GPP) maps at 10-m resolution were produced using a tower-mounted multi-angular spectroradiometer, combined with the canopy structural information derived from airborne laser scanning (Lidar) data. The horizontal arrays of footprint climatology were superimposed on the 10-m-resolution GPP maps. Monthly and annual uncertainties in EC flux caused by variations in footprint climatology of the 59-year-old Douglas-fir stand were estimated to be approximately 15-20% based on a comparison of GPP estimates derived from EC and remote sensing measurements, and on sensor location bias analysis. The footprint-variation-induced uncertainty in long-term EC flux measurements was mainly dependent on the site spatial heterogeneity. The bias in carbon flux estimates using spatially-explicit ecological models or tower-based remote sensing at

  1. Inverse estimation of near-field temperature and surface heat flux via single point temperature measurement

    NASA Astrophysics Data System (ADS)

    Wu, Chen-Wu; Shu, Yong-Hua; Xie, Ji-Jia; Jiang, Jian-Zheng; Fan, Jing

    2016-05-01

    A concept was developed to inversely estimate the near-field temperature as well as the surface heat flux for the transient heat conduction problem with boundary condition of the unknown heat flux. The mathematical formula was derived for the inverse estimation of the near-field temperature and surface heat flux via a single point temperature measurement. The experiments were carried out in a vacuum chamber and the theoretically predicted temperatures were justified in specific positions. The inverse estimation principle was validated and the estimation deviation was evaluated for the present configuration.

  2. Satellite measurements of Magnetospheric Poynting flux. Final report, August 1968-March 1990

    SciTech Connect

    Vickrey, J.F.; Kelley, M.C.; Knudsen, D.J.

    1990-03-09

    The first satellite observations of the Magnetospheric Poynting flux are presented for two presented for two passes of the HILAT satellite over the northern polar regions. The simultaneously measured energy input due to precipitating particles is also presented. The Poynting flux is in general agreement with an independent estimate of the Joule dissipation in the upper atmosphere. However, there are localized regions in both orbits of net upward Poynting flux, suggesting a neutral wind dynamo. Evidence for the existence of propagating Alfven waves as well as steady state current systems closed in the ionosphere are also presented.

  3. Direct measurement of the oceanic carbon monoxide flux by eddy correlation

    NASA Astrophysics Data System (ADS)

    Blomquist, B. W.; Fairall, C. W.; Huebert, B. J.; Wilson, S. T.

    2012-12-01

    This report presents results from a field trial of ship-based air-sea flux measurements of carbon monoxide (CO) by direct eddy correlation with an infrared-laser trace gas analyzer. The analyzer utilizes Off-Axis Integrated-Cavity-Output Spectroscopy (OA-ICOS) to achieve high selectivity for CO, rapid response (~2 Hz) and low noise. Over a two-day sea trial, peak daytime seawater CO concentrations were ~1.5 nM and wind speeds were consistently 10-12 m s-1. A clear diel cycle in CO flux with an early afternoon maximum was observed. An analysis of flux error suggests the effects of non-stationarity are important, and air-sea CO flux measurements are best performe