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1

Lava discharge rates from satellite-measured heat flux  

Microsoft Academic Search

A commonly used method to convert lava flow area to volume flux using low spatial resolution satellite data rests on two primary assumptions, that: (1) volume flux is related to flow area, and (2) lava surfaces cool exponentially with time and distance from the source. Field data show that both assumptions are valid. The ensuing relationship is an empirical one

Andrew J. L. Harris; Stephen M. Baloga

2009-01-01

2

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

Microsoft Academic Search

Absolute fission rate measurements using modified National Bureau of Standards fission chambers were performed in the Fast Flux Test Facility at two core locations for isotopic deposits of 眾淹h, 眾袋, 眾U, 眾U, 眾Np, 眾Pu, 盒Pu, and 硃Pu. Monitor chamber results at a third location were analyzed to support other experiments involving passive dosimeter fission rate determinations.

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

1981-01-01

3

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

Microsoft Academic Search

Absolute fission rate measurements using modified National Bureau of Standards fission chambers were performed in the Fast Flux Test Facility at two core locations for isotopic deposits of 眾淹h, 眾袋, 眾U, 眾U, 眾Np, 眾Pu, 盒Pu, and 硃Pu. Monitor chamber results at a third location were analyzed to support other experiments involving passive dosimeter fission rate determinations.

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

1981-01-01

4

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

SciTech Connect

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

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

1981-05-01

5

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

SciTech Connect

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

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

1981-05-01

6

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

NASA Astrophysics Data System (ADS)

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

Hern嘁dez-Pajares, M.; Garc檃-Rigo, A.; Juan, J. M.; Sanz, J.; Monte, E.; Arag鏮-霍gel, A.

2012-12-01

7

Isoprene emission rates and fluxes measured above a Mediterranean oak ( Quercus pubescens) forest  

NASA Astrophysics Data System (ADS)

The present work, carried out as part of the European fiEld experimentS to COnstrain Models of atmospheric Pollution and Transport of Emissions project (ESCOMPTE), brings a new contribution to the inventory of the main natural hydrocarbons sources that are liable to participate in the production of ozone. The measurement campaign was conducted in Montmeyan, a site close to Marseilles (France), with the aim of quantifying the terpenic emission pattern and the behaviour of Quercus pubescens, an important Mediterranean tree species. Biogenic emissions by Q. pubescens were determined by the enclosure of an intact branch of this tree in a Teflon cuvette. The total monoterpenic emission rates thus recorded were found to reach maximum values ranged between 40 and 350 ?g g Dry Weight-1 h -1. Emissions were correlated strongly with leaf temperature and Photosynthetic Active Radiation (PAR). The fluxes were also determined by extrapolating the results of the enclosure method and by using aerodynamic gradient method. They reach around 73 mg m -2 h -1 with the first method and 55 mg m -2 h -1 with the second one. The obtained values fit with a maximal ratio of 2.

Simon, V.; Dumergues, L.; Bouchou, P.; Torres, L.; Lopez, A.

2005-03-01

8

Pulse flux measuring device  

DOEpatents

A device for measuring particle flux comprises first and second photodiode detectors for receiving flux from a source and first and second outputs for producing first and second signals representing the flux incident to the detectors. The device is capable of reducing the first output signal by a portion of the second output signal, thereby enhancing the accuracy of the device. Devices in accordance with the invention may measure distinct components of flux from a single source or fluxes from several sources.

Riggan, William C. (Albuquerque, NM)

1985-01-01

9

Measurement of surface emission flux rates for volatile organic compounds at Technical Area 54  

SciTech Connect

The survey described in this report was conducted to estimate the mass of volatile organic compounds venting to the atmosphere from active and inactive waste disposal sites at Technical Area 54. A large number of nonintrusive passive sample collection devices were placed on the ground surface for 72 hours to characterize an area of approximately 150 acres. Results provided an indication of the boundary location of the known volatile organic plume, plume constituents, and isolated high concentration areas. The data from this survey enhanced existing data from a limited number of monitor wells currently used for plume surveillance. Results indicate that the estimated mass emission to the atmosphere is orders of magnitude lower than what is considered a small flux rate at a spill site or a Resource Conservation and Recovery Act landfill and is far below the threshold limit established by the State of New Mexico as an air quality concern.

Trujillo, V.; Morgenstern, M.; Krier, D. [Los Alamos National Lab., NM (United States); Gilkeson, R. [Weirich and Associates, Albuquerque, NM (United States)

1998-06-01

10

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

EPA Science Inventory

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

11

Radiative flux measurements in the troposphere  

SciTech Connect

The results of radiative flux-density measurements in the troposphere, made using an especially designed radiometer mounted on a Cessna 402B aircraft, are reported. The radiometer incorporates several well-known principles that result in highly accurate determinations of radiative fluxes in the atmosphere. Heating rates for gases and for aerosols are calculated, using measurements and radiosonde data. Instrument performance is verified by calculating the solar constant at the top of the atmosphere, using the radiative flux densities measured in the troposphere. Total heating rates of 0.175 and 0.377 K h/sup -1/ are determined for hazy and foggy atmospheres, respectively. Aerosol heating rates of 0.065 and 0.235 K h/sup -1/ are deduced from the total heating rates. Environmental noise measurements during data acquisition are presented. The solar constant value of 1387 +- 21 W m/sup -2/ derived from the experiments agrees within 4% of the standard value.

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

1982-03-01

12

Radiative flux measurements in the troposphere  

Microsoft Academic Search

The results of radiative flux-density measurements in the troposphere, made using an especially designed radiometer mounted on a Cessna 402B aircraft, are reported. The radiometer incorporates several well-known principles that result in highly accurate determinations of radiative fluxes in the atmosphere. Heating rates for gases and for aerosols are calculated, using measurements and radiosonde data. Instrument performance is verified by

Francisco P. J. Valero; Warren J. Y. Gore; Lawrence P. M. Giver

1982-01-01

13

Cosmic Ray Neutron Flux Measurements  

NASA Astrophysics Data System (ADS)

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)

Dayananda, Mathes

2009-11-01

14

Gas flux Estimates: Problems of Scaling from one Volcano and Instantaneous Measurements to Decadal-Millenial Rates for Whole Arc Systems.  

NASA Astrophysics Data System (ADS)

We have remote sensing tools to measure volcanic SO2 releases to the atmosphere by volcanoes in terms of kg/s-1 (Rodriguez et al, this session) but to use these data to develop estimates of arc gas release rates to compare with subduction zone rates (subduction factory) is far from straightforward. We have investigated this by considering how to convert the last 20 years of SO2 remote sensing at one Guatemalan volcano to a millenial gas release rate. We have chosen Fuego Volcano as a focal point because much is known about its activity (eruption rates and times) and magma characteristics (composition, intensive parameters, melt inclusion analyses), and because its behavior over the past 500 years consists of frequent eruptions and continual gas emissions. A steady-state rate conversion (20 x 50 = 1000) for Fuego may nonetheless be a basis for considering the whole arc, because it tends to release its volatiles readily. Even with this kind of open vent behavior and abundant helpful lab data we need to use speculative assumptions to get a result. One of these speculations involves excess gas release: Fuego is well known to exhibit this, but data collected in many geochemical studies of Fuego suggest it is highly variable. Lacking understanding of the process which causes the excess leaves us puzzled how to generalize it, even for only one volcanic system. Evaluating the rest of the arc and computing a flux per unit of arc length seems much more difficult than evaluating Fuego alone. Other volcanoes in the arc tend to retain their volatiles (in part for later release) and are therefore not well-estimated from sparse measurements. Another question is whether the relatively constant activity representative exhibited by Fuego is representative of arc activity. Volcanoes with compositional variability and long reposes require integration of robust data over periods much longer than 20 years to determine an accurate rate. Other examples of open vent volcanoes (eg Pacaya) do not seem to behave at all like Fuego. Hydrothermal systems and unerupted magma are further complications. Each volcano in the arc has its own unique story to add to the mix of the arc history. A few examples are explained in detail (Tacana, Santa Maria, Pacaya, Agua).

Rose, W. I.; Carn, S. A.; Bluth, G. J.

2002-05-01

15

Effect of plasma flux composition on the nitriding rate of stainless steel  

Microsoft Academic Search

The total ion flux and nitriding rate for stainless steel specimens exposed to a modulated electron beam generated argon-nitrogen plasma were measured as a function of distance from the electron beam axis. The total ion flux decreased linearly with distance, but the nitriding rate increased under certain conditions, contrary to other ion flux\\/nitriding rate comparisons published in the literature. Variation

C. Muratore; S. G. Walton; D. Leonhardt; R. F. Fernsler; D. D. Blackwell; R. A. Meger

2004-01-01

16

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...

17

Metabolic Rate Measurement System.  

National Technical Information Service (NTIS)

The Metabolic Rate Measurement System (MRMS) is an uncomplicated and accurate apparatus for measuring oxygen consumption and carbon dioxide production of a test subject. From this one can determine the subject's metabolic rate for a variety of conditions,...

K. Koester W. Crosier

1980-01-01

18

Novel Instrumentation for Methane Flux Measurements  

NASA Astrophysics Data System (ADS)

We describe the development and testing of a new compact, rugged and inexpensive instrument for measurements of methane flux in ambient air. The instrument is based on a new technology called Off-Axis Integrated Cavity Output Spectroscopy (Off-Axis ICOS). This novel instrument measures methane with high sensitivity, accuracy (<2 ppbv at 1 Hz), and specificity in real time (no cross interferences). The instrument combines inexpensive, robust telecommunications-grade room-temperature diode laser operating at 1.65 microns with Off-Axis ICOS to yield an instrument capable of continuously recording data in the field with high precision (better than 0.2% uncertainty at a 10-Hz rate). We will discuss the measurement strategy in detail and present recent results demonstrating real-time measurements without the need for any user intervention. Ongoing efforts to demonstrate the instrument's capabilities to record measurements with high precision and accuracy without calibration over extended periods as well as testing of the instrument at field sites in the AmeriFlux and FLUXNET networks, and NOAA/CMDL will also be discussed. By significantly increasing the accuracy and precision of methane flux measurements, the Off-Axis ICOS instrument will enhance local, regional and global studies of global warming and facilitate controlled multi-year studies and comparisons between field sites. These studies, which could involve using the instruments aboard airplanes to enable coverage over large distances and to correlate with satellite images, will help track and quantify the global carbon cycle on small and large spatial scales, and enable atmospheric chemists to generate more reliable models of climate change and determine environmental impact.

Owano, T.; Baer, D.; Gupta, M.; Ricci, K.; O'Keefe, A.

2004-12-01

19

Gas flux Estimates: Problems of Scaling from one Volcano and Instantaneous Measurements to Decadal-Millenial Rates for Whole Arc Systems  

Microsoft Academic Search

We have remote sensing tools to measure volcanic SO2 releases to the atmosphere by volcanoes in terms of kg\\/s-1 (Rodriguez et al, this session) but to use these data to develop estimates of arc gas release rates to compare with subduction zone rates (subduction factory) is far from straightforward. We have investigated this by considering how to convert the last

W. I. Rose; S. A. Carn; G. J. Bluth

2002-01-01

20

Atmospheric sulfur flux rates to and from Israel.  

PubMed

Both field measurements and model simulation studies have shown that Israel is the recipient of long range transported air pollutants that originated over various parts of Europe. The present paper presents results of aircraft measurements aimed at quantitizing the sulfur flux arriving at Israel's western coast from Europe and the Israeli pollution contribution to the air masses leaving its eastern borders towards Jordan. During the research flights, measurements of sulfur dioxide and sulfate particulates and meteorological data were recorded. Two different legs were performed for each research flight: one over the Mediterranean Sea, west of the coast and the second along the Jordan Valley. All flights were carried out at a height of approximately 300 m above ground level. A total of 14 research flights were performed covering the summer and autumn seasons. The results indicate that the influx of sulfur arriving at the Israeli coast from Europe varied in the range of 1-30 mg S/h, depending on the measuring season. The particulate sulfate level in the incoming LRT air masses was at least 50% of the total sulfur content. The contribution of the local pollutant sources to the outgoing easterly fluxes also varies strongly according to season. During the early and late summer, the Israeli sources contributed an average of 25 mg S/h to the total pollution flux as compared to only approximately 9 mg S/h during the autumn period. Synoptic analysis indicates that conditions during the summer in Israel favor the accumulation of pollution species above the Mediterranean basin from upwind European sources. This season features a shallow mixed layer and weak zonal flow leads to poor ventilation rates, inhibiting an efficient dispersion of these pollutants while being transported eastward. Under these conditions, in flux, local contribution and the total out-flux of these pollutants are elevated as opposed to during other seasons. During the fall, the eastern Mediterranean region is usually subjected to weak easterly winds, interrupted at times by strong westerly wind flows inducing higher ventilation rates. These meteorological conditions and the lack of major emitting sources eastwards of Israel result in lower sulfur budgets to and from Israel for this season. An estimate of the yearly flux showed that approximately 0.06 tg S arrived at the Israeli coast from the west. This is approximately 15% of the estimated pollution leaving Europe towards the eastern edge of the Mediterranean basin. The local contribution to the out-flux towards Jordan was calculated to be 0.13 tg S per year, almost all of the sulfur air pollutants emitted in Israel. PMID:12150434

Matvev, Valeri; Dayan, Un; Tass, Iran; Peleg, Mordechai

2002-05-27

21

Atmospheric neutrino flux measurement using upgoing muons  

Microsoft Academic Search

We report on the first measurement of the flux of upgoing muons resulting from interactions of atmospheric neutrinos in the rock below MACRO. The ratio of the observed to the expected number of events integrated over all nadir angles is 0.73 .09stat. .06sys. .12theor.. The flux of upgoing muons as a function of nadir angle is presented

S. Ahlen; M. Ambrosio; R. Antolini; G. Auriemma; R. Baker; A. Baldini; G. C. Barbarino; B. C. Barish; G. Battistoni; R. Bellotti; C. Bemporad; P. Bernardini; H. Bilokon; V. Bisi; C. Bloise; C. Bower; S. Bussino; F. Cafagna; M. Calicchio; D. Campana; M. Carboni; M. Castellano; S. Cecchini; F. Cei; P. Celio; V. Chiarella; R. Cormack; A. Corona; S. Coutu; G. De Cataldo; H. Dekhissi; C. De Marzo; E. Diehl; I. De Mitri; M. De Vincenzi; A. Di Credico; O. Erriquez; C. Favuzzi; C. Forti; P. Fusco; G. Giacomelli; G. Giannini; N. Giglietto; M. Grassi; P. Green; A. Grillo; F. Guarino; P. Guarnaccia; C. Gustavino; A. Habig; K. Hanson; A. Hawthorne; R. Heinz; J. T. Hong; E. Iarocci; E. Katsavounidis; E. Kearns; S. Kyriazopoulou; E. Lamanna; D. S. Levin; P. Lipari; G. Liu; R. Liu; N. P. Longley; M. J. Longo; Y. Lu; G. Ludlam; G. Mancarella; G. Mandrioli; A. Margiotta-Neri; A. Marin; A. Marini; D. Martello; A. Marzari-Chiesa; M. N. Mazziotta; D. G. Michael; S. Mikheyev; L. Miller; M. Mittelbrunn; P. Monacelli; T. Montaruli; M. Monteno; S. Mufson; J. Musser; D. Nicol; R. Nolty; S. Nutter; C. Okada; C. Orth; G. Osteria; O. Palamara; S. Parlati; V. Patera; L. Patrizii; R. Pazzi; C. W. Peck; J. Petrakis; S. Petrera; N. D. Pignatano; P. Pistilli; V. Popa; A. Rain; J. Reynoldson; F. Ronga; A. Sanzgiri; F. Sartogo; C. Satriano; L. Satta; E. Scapparone; K. Scholberg; A. Sciubba; P. Serra-Lugaresi; M. Severi; M. Sitta; P. Spinelli; M. Spinetti; M. Spurio; R. Steinberg; J. L. Stone; L. R. Sulak; A. Surdo; G. Tarl; V. Togo; V. Valente; C. W. Walter; R. Webb; W. Worstell

1995-01-01

22

Calving fluxes and basal melt rates of Antarctic ice shelves.  

PubMed

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

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

2013-09-15

23

Methods for Comparing Relative Flux Rates of Two or More Biological Molecules in Vivo Through a Single Protocol.  

National Technical Information Service (NTIS)

The invention relates to techniques for measuring and comparing relative molecular flux rates of different biological molecules by administering isotope-labeled water to one or more tissues or individuals and comparing the molecular flux rates of two or m...

M. K. Hellerstein

2006-01-01

24

Eddy Correlation Flux Measurement System (ECOR) Handbook  

SciTech Connect

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.

Cook, DR

2011-01-31

25

Measuring Evolutionary Rates  

NASA Astrophysics Data System (ADS)

We have been using extensive data sets of time series photometry acquired over the last three decades to measure the rate of change of the pulsation periods of white dwarf stars, which in turn measure their evolutionary rates. The evolution of an isolated white dwarf is dominated by cooling. However, hot pre white dwarfs also show significant radius evolutionary rates. After 30 years of observations we finally measured the cooling rate of a DAV, G117-B15A, in good agreement with the theoretical predictions. But other periodicities for G 117-B15A, and a similar DAV, R 548, show faster rates of period changes. We also observe faster evolutionary rates in other classes of white dwarf variables, e.g., the DOV PG1 159-035 and the DBV GD 358. These fast changes are not explained by the theoretical models to date.

Kepler, S. O.; Costa, J. E. S.; Mukadam, A.; Mullally, F.; Winget, D. E.; Nather, R. E.; Sullivan, D.

2005-07-01

26

Measuring fast calcium fluxes in cardiomyocytes.  

PubMed

Cardiomyocytes have multiple Ca(2+) fluxes of varying duration that work together to optimize function (1,2). Changes in Ca(2+) activity in response to extracellular agents is predominantly regulated by the phospholipase C?- G?(q;) pathway localized on the plasma membrane which is stimulated by agents such as acetylcholine (3,4). We have recently found that plasma membrane protein domains called caveolae(5,6) can entrap activated G?(q;)(7). This entrapment has the effect of stabilizing the activated state of G?(q;) and resulting in prolonged Ca(2+) signals in cardiomyocytes and other cell types(8). We uncovered this surprising result by measuring dynamic calcium responses on a fast scale in living cardiomyocytes. Briefly, cells are loaded with a fluorescent Ca(2+) indicator. In our studies, we used Ca(2+) Green (Invitrogen, Inc.) which exhibits an increase in fluorescence emission intensity upon binding of calcium ions. The fluorescence intensity is then recorded for using a line-scan mode of a laser scanning confocal microscope. This method allows rapid acquisition of the time course of fluorescence intensity in pixels along a selected line, producing several hundreds of time traces on the microsecond time scale. These very fast traces are transferred into excel and then into Sigmaplot for analysis, and are compared to traces obtained for electronic noise, free dye, and other controls. To dissect Ca(2+) responses of different flux rates, we performed a histogram analysis that binned pixel intensities with time. Binning allows us to group over 500 traces of scans and visualize the compiled results spatially and temporally on a single plot. Thus, the slow Ca(2+) waves that are difficult to discern when the scans are overlaid due to different peak placement and noise, can be readily seen in the binned histograms. Very fast fluxes in the time scale of the measurement show a narrow distribution of intensities in the very short time bins whereas longer Ca(2+) waves show binned data with a broad distribution over longer time bins. These different time distributions allow us to dissect the timing of Ca(2+)fluxes in the cells, and to determine their impact on various cellular events. PMID:22143396

Golebiewska, Urszula; Scarlata, Suzanne

2011-11-29

27

Advances in the Surface Renewal Flux Measurement Method  

NASA Astrophysics Data System (ADS)

The measurement of ecosystem-scale energy and mass fluxes between the planetary surface and the atmosphere is crucial for understanding geophysical processes. Surface renewal is a flux measurement technique based on analyzing the turbulent coherent structures that interact with the surface. It is a less expensive technique because it does not require fast-response velocity measurements, but only a fast-response scalar measurement. It is therefore also a useful tool for the study of the global cycling of trace gases. Currently, surface renewal requires calibration against another flux measurement technique, such as eddy covariance, to account for the linear bias of its measurements. We present two advances in the surface renewal theory and methodology that bring the technique closer to becoming a fully independent flux measurement method. The first advance develops the theory of turbulent coherent structure transport associated with the different scales of coherent structures. A novel method was developed for identifying the scalar change rate within structures at different scales. Our results suggest that for canopies less than one meter in height, the second smallest coherent structure scale dominates the energy and mass flux process. Using the method for resolving the scalar exchange rate of the second smallest coherent structure scale, calibration is unnecessary for surface renewal measurements over short canopies. This study forms the foundation for analysis over more complex surfaces. The second advance is a sensor frequency response correction for measuring the sensible heat flux via surface renewal. Inexpensive fine-wire thermocouples are frequently used to record high frequency temperature data in the surface renewal technique. The sensible heat flux is used in conjunction with net radiation and ground heat flux measurements to determine the latent heat flux as the energy balance residual. The robust thermocouples commonly used in field experiments underestimate the sensible heat flux, yielding results that are less than 50% of the sensible heat flux measured with finer sensors. We present the methodology for correcting the thermocouple signal to avoid underestimating the heat flux at both the smallest and the second smallest coherent structure scale.

Shapland, T. M.; McElrone, A.; Paw U, K. T.; Snyder, R. L.

2011-12-01

28

Particle flux measurements with pump limiters  

SciTech Connect

The pressure buildup in pump limiters is a function of the incident particle flux, the pump limiter geometry, particle-surface interactions, and, under certain conditions, nonlinear effects due to interactions of the neutral gas with the incoming plasma. At sufficiently low density and for short pump limiter throat, the pressure observed in the pump limiter chamber is a direct measure of the particle flux at the limiter slot. This paper discusses a simple model for the correlation between particle flux and pump limiter pressure. In addition, some estimates are presented on the thermalization of fast neutrals in the pump limiter duct and its implications for ''enhanced particle collection.''

Mioduszewski, P.

1986-01-01

29

Experimental Flux Measurements on a Network Scale  

PubMed Central

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 plants 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 13C-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.

Schwender, Jorg

2011-01-01

30

Noninvasive measurement of pulmonary transvascular protein flux in normal man.  

PubMed

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

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

1980-11-01

31

Factors that influence methylmercury flux rates from wetland sediments.  

PubMed

Sediments are thought to be an important source of methylmercury (MeHg) to the water column of wetlands. We measured sediment MeHg pore water concentrations as a function of depth in four wetlands to determine the concentration gradient and used it determine sediment-water flux of MeHg. Fluxes of MeHg ranged from -1.60 to 10.02 ng m(-2) day(-1) and were shown to be a function of 1) redox conditions at the sediment-water interface, 2) oxygen gradient above the sediment surface, 3) water temperature, and 4) pore water and water column-dissolved sulphide. MeHg water column concentration in each of the four wetlands was positively correlated with MeHg concentrations present in surface sediment and pore water, and with the calculated sediment-water MeHg flux rate. In addition to MeHg, ethylmercury (EtHg) was detected in the sediment in all four wetlands, but not in the pore water or the water column. EtHg levels in sediment exceeded MeHg concentrations in two of the wetlands. This demonstrates that Hg ethylation is a significant part of the Hg cycle in some aquatic environments. PMID:16410019

Holmes, Jonathan; Lean, David

2006-01-10

32

Dual neutron flux/temperature measurement sensor  

DOEpatents

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

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

1994-10-04

33

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

Microsoft Academic Search

This paper concerns the application of a process-based model (MOCA, Modelling of Carbon Assessment) as an useful tool for estimating gas exchange, and integrating the empirical algorithms for calculation of monoterpene fluxes, in a Mediterranean maquis of central Italy (Castelporziano, Rome). Simulations were carried out for a range of hypothetical but realistic canopies of the evergreen Quercus ilex (holm oak),

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

2009-01-01

34

Fast Neutron Flux Measurement through Neutron Activation  

Microsoft Academic Search

Neutron activation of various materials is often used to detect the fluence from a neutron source. In this report silver sleeves were placed around individual Geiger-Mueller tubes, and set in a polyethylene box to measure the neutron flux from a D-D fusion pinch. The silver is neutron activated from the DPF neutrons which are moderated by the polyethylene box, and

Jim Ferguson

2002-01-01

35

Plasma momentum meter for momentum flux measurements  

DOEpatents

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.

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

1993-01-01

36

Plasma momentum meter for momentum flux measurements  

DOEpatents

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 [minus]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 an intense magnetic field and pulsed plasma environment.

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

1991-01-01

37

Plasma momentum meter for momentum flux measurements  

DOEpatents

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 {minus}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 an intense magnetic field and pulsed plasma environment.

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

1991-12-31

38

Plasma momentum meter for momentum flux measurements  

SciTech Connect

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.

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

1993-01-01

39

Least-Squares Fitting Methods for Estimating the Winding Rate in Twisted Magnetic-Flux Tubes  

NASA Astrophysics Data System (ADS)

We investigate least-squares fitting methods for estimating the winding rate of field lines about the axis of twisted magnetic-flux tubes. These methods estimate the winding rate by finding the values for a set of parameters that correspond to the minimum of the discrepancy between vector magnetic-field measurements and predictions from a twisted flux-tube model. For the flux-tube model used in the fitting, we assume that the magnetic field is static, axisymmetric, and does not vary in the vertical direction. Using error-free, synthetic vector magnetic-field data constructed with models for twisted magnetic-flux tubes, we test the efficacy of fitting methods at recovering the true winding rate. Furthermore, we demonstrate how assumptions built into the flux-tube models used for the fitting influence the accuracy of the winding-rate estimates. We identify the radial variation of the winding rate within the flux tube as one assumption that can have a significant impact on the winding-rate estimates. We show that the errors caused by making a fixed, incorrect assumption about the radial variation of the winding rate can be largely avoided by fitting directly for the radial variation of the winding rate. Other assumptions that we investigate include the lack of variation of the field in the azimuthal and vertical directions in the magnetic-flux tube model used for the fitting, and the inclination, curvature, and location of the flux-tube axis. When the observed magnetic field deviates substantially from the flux-tube model used for the fitting, we find that the winding-rate estimates can be unreliable. We conclude that the magnetic-flux tube models used in this investigation are probably too simple to yield reliable estimates for the winding rate of the field lines in solar magnetic structures in general, unless additional information is available to justify the choice of flux-tube model used for the fitting.

Crouch, A. D.

2012-12-01

40

Satellite beacon measurements of protonospheric fluxes  

NASA Astrophysics Data System (ADS)

The ionospheric and protonospheric regions of the plasmasphere, which are dominated by the O(+) and H(+) ionic species, respectively, interact by means of proton fluxes within tubes of magnetic force. The present study is concerned with the determination of these fluxes by the beacon satellite technique as used in the ATS-6 experiment in relation to three observing sites: Boulder, Colorado; Lancaster, U.K.; and Fairbanks, Alaska. From plasmasphere models based on solutions of the time dependent O(+) and H(+) momentum and continuity equations, it is shown that the time differential of the residual content as measured at Lancaster provides a good estimate of the protonospheric flux at 4000 km altitude in the L = 1.8 magnetic shell under quiet geomagnetic conditions. The effect of the neutral thermospheric wind on the protonospheric flux is also investigated. Fluxes determined by the beacon technique for the period from September 1975 to July 1976 are shown, and these are compared with typical results derived from other techniques.

Poulter, E. M.; Hargreaves, J. K.; Bailey, G. J.; Moffett, R. J.

1981-12-01

41

Remote measurement of energy and carbon flux from wildfires in ...  

Treesearch

... Photo and Video Gallery, Publications, Recreational Activities, Research and ... Description: Temperature, intensity, spread, and dimensions of fires burning in ... first in situ airborne measurements of sensible heat and carbon fluxes in fire plumes ... These estimators provide a means to determine rates of fuel consumption...

42

Allometric scaling of flight energetics in orchid bees: evolution of flux capacities and flux rates  

Microsoft Academic Search

The evolution of metabolic pathways involved in energy production was studied in the flight muscles of 28 species of orchid bees. Previous work revealed that wingbeat frequencies and mass-specific metabolic rates decline in parallel by threefold as body mass increases interspecifically over a 20-fold range. We investigated the correlated evolution of metabolic rates during hovering flight and the flux capacities,

Charles-A. Darveau; Peter W. Hochachka; David W. Roubik; Raul K. Suarez

2005-01-01

43

Cutaneous heat flux models do not reliably predict metabolic rates of marine mammals.  

PubMed

Heat flux models have been used to predict metabolic rates of marine mammals, generally by estimating conductive heat transfer through their blubber layer. Recently, Kvadsheim et al. (1997) found that such models tend to overestimate metabolic rates, and that such errors probably result from the asymmetrical distribution of blubber. This problem may be avoided if reliable estimates of heat flux through the skin of the animals are obtained by using models that combine calculations of conductive heat flux through the skin and fur, and convective heat flux from the surface of the animal to the environment. We evaluated this approach based on simultaneous measurements of metabolic rates and of input parameters necessary for heat flux calculations, as obtained from four harp seals (Phoca groenlandica) resting in cold water. Heat flux estimates were made using two free convection models (double-flat-plate and cylindrical geometry) and one forced convection model (single-flat-plate geometry). We found that heat flux estimates generally underestimated metabolic rates, on average by 26-58%, and that small variations in input parameters caused large variations in these estimates. We conclude that cutaneous heat flux models are too inaccurate and sensitive to small errors in input parameters to provide reliable estimates of metabolic rates of marine mammals. PMID:11082302

Boily, P; Kvadsheim, P H; Folkow, L P

2000-12-01

44

Measuring Your Peak Flow Rate  

MedlinePLUS

... Asthma > Taking Control of Asthma Measuring Your Peak Flow Rate A peak flow meter is a portable, inexpensive, ... for asthma management. Why Should I Measure My Flow Rate? Your peak flow rates can show you if ...

45

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

46

Measurements of Dephasing in Superconducting Flux Qubits  

NASA Astrophysics Data System (ADS)

The time over which a superposition of qubit states maintains phase coherence is an important figure of merit for a qubit. One technique for measuring this dephasing time is the Ramsey fringe, consisting of two ?/2 pulses detuned from resonance. Varying the time between the pulses produces a damped oscillatory fringe, with the frequency equal to the detuning from resonance and the decay time given by the dephasing time. The dephasing time can also be extracted from measurements of the spectroscopic linewidths for different excitation amplitudes. We report measurements using both techniques in a superconducting flux qubit, giving dephasing times of the order of 10 ns. We present the variation of the dephasing time with various parameters, such as qubit level splitting, readout SQUID operating point, and temperature. We compare our results with expected levels of low frequency noise in the qubit environment and discuss possible methods for enhancing the coherence, including spin echo pulse sequences.

Wu, C.-E.

2005-03-01

47

Multi-spectra Cosmic Ray Flux Measurement  

NASA Astrophysics Data System (ADS)

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). )

He, Xiaochun; Dayananda, Mathes

2010-02-01

48

Integrated leak rate test of the FFTF (Fast Flux Test Facility) containment vessel  

Microsoft Academic Search

The third integrated leak rate test (ILRT) performed at the Fast Flux Test Facility (FFTF) demonstrated that effective leak rate measurements could be obtained at a pressure of 2 psig. In addition, innovative data reduction methods demonstrated the ability to accurately account for diurnal variations in containment pressure and temperature. Further development of methods used in this test indicate significant

M. L. Grygiel; R. H. Davis; D. L. Polzin; W. D. Yule

1987-01-01

49

Derivation of water vapor fluxes from Lidar measurements  

NASA Astrophysics Data System (ADS)

Two techniques are described by which the flux of water vapor can be derived from concentration measurements made by a Raman-Lidar. Monin-Obukhov similarity theory and dissipation techniques are used as the basis for these methods. The resulting fluxes are compared to fluxes from standard point instruments. The techniques described are appropriate for measuring the flux of any scalar quantity using Lidar measurements in the inner region of the boundary layer.

Eichinger, W. E.; Cooper, D. I.; Holtkamp, D. B.; Karl, R. R.; Quick, C. R.; Tiee, J. J.

1993-02-01

50

Plasma momentum meter for momentum flux measurements  

DOEpatents

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.

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

1993-08-24

51

Magnetic flux transport in the Dungey cycle: A survey of dayside and nightside reconnection rates  

NASA Astrophysics Data System (ADS)

Changes in the open flux content of the ionospheric polar cap, estimated from auroral, radar, and low-Earth orbit particle measurements, are used to determine dayside and nightside reconnection rates during 73 hours of observation spread over nine intervals. We identify 25 episodes of nightside reconnection and examine statistically the rates and durations of reconnection, as well as possible triggers for the onset of reconnection, such as changes in solar wind ram pressure or orientation of the interplanetary magnetic field. Approximately half of the events can possibly be identified with a trigger, the other half appearing spontaneous. On average 0.3 GWb of open flux are closed in each event, with average durations and reconnection rates being 70 min and 85 kV. We find no evidence for a low background rate of nightside reconnection between these events and conclude that substorms and other large reconnection bursts provide the major or only source of flux closure on the nightside.

Milan, S. E.; Provan, G.; Hubert, B.

2007-01-01

52

Sensitivity of Radiative Fluxes and Heating Rates To Cloud Microphysics  

NASA Astrophysics Data System (ADS)

We have investigated the sensitivity of modeled radiative fluxes to the specification of cloud microphysical parameterizations using a single-column model and measure- ments from the Atmospheric Radiation Measurement (ARM) Program. The single- column model was run for the three-month period of June-August, 2000 at the ARM Southern Great Plains and Tropical Western Pacific sites. At each site, the model was forced using 0-24 hour forecast products from the global spectral model of the U. S. National Centers for Environmental Prediction. Several model runs were performed, each with a different package of cloud microphysical parameterizations. The temporal evolution of modeled cloud amount as well as surface radiative fluxes from a control run compare well with ARM measurements at the Southern Great Plains site. The re- alism of the control run results at the Tropical West Pacific site is more difficult to evaluate due to the limited spatial resolution of the ARM observations there. Both surface and top-of-atmosphere radiative fluxes are sensitive to the scheme used to specify the ice particle effective radius. We also find that the inclusion of ice particle fallout can have a significant effect on the amount and location of high cirrus clouds. A particularly interesting finding is that the variance of the modeled ice particle effective radius is considerably smaller than that suggested by ARM cloud radar measurements at the Southern Great Plains site. This was the case for all four tested parameterizations of ice particle effective radius. Our preliminary results suggest that this theoretical underestimate of the ice particle effective radius variance can have significant effects on the modeled radiative fluxes due to the highly non-linear nature of cloud-radiation interactions.

Iacobellis, S. F.; Somerville, R. C. J.; McFarquhar, G. M.

53

PATHFINDER ATOMIC POWER PLANT DETAILED FLUX MEASUREMENTS IN SUPERHEATER CELLS  

Microsoft Academic Search

Experiments were conducted in the Allis-Chalmers Critical Experimental ; Facility to determine the regionaverage thermal flux and flux shape in a unit ; Pathfinder superheater cell. Accuiate values are necessary in order to calculate ; superheater constants. Measurements were made using Cu-Mn wires (radial traverse ; for regionaverage) and Al-U foils (sectioned for region-average) and foilettes ; (for flux detail).

H. F. Finn; R. H. Vollmer

1962-01-01

54

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

NASA Astrophysics Data System (ADS)

We measured the integrated low frequency flux noise (~1 m?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.

Mao, Bo; Qiu, Wei; Han, Siyuan

2008-11-01

55

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

NASA Astrophysics Data System (ADS)

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

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

2008-07-01

56

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

NASA Astrophysics Data System (ADS)

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, ?-pinene, ?-pinene, 3-carene, d-limonene, ?-phellandrene, ?-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 302.3% and 319.2% 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 ?-pinene were resolved in the chromatograms and completely accounted for the daytime difference and reduced the nighttime mixing ratio difference to 202.9%. 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.

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

2005-02-01

57

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

NASA Astrophysics Data System (ADS)

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, ?-pinene, ?-pinene, 3-carene, d-limonene, ?-phellandrene, ?-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 302.3% and 319.2% larger than by GC-FID, with larger differences at night than during the day. Four unidentified peaks that correlated with ?-pinene were resolved in the chromatograms and completely accounted for the daytime difference and reduced the nighttime difference to 193.4%. 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.

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

2004-12-01

58

Flux Rope Acceleration and Enhanced Magnetic Reconnection Rate  

SciTech Connect

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

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

2003-03-25

59

Heat flux microsensor measurements and calibrations  

NASA Astrophysics Data System (ADS)

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.

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

1992-09-01

60

Comparison of calculated internal tide energy flux with microstructure measurements  

NASA Astrophysics Data System (ADS)

A comparison of the model-derived vertical energy flux from the internal tide with micro-structure measurements is undertaken. The latter data set originates from two field surveys during the Brazil Basin Tracer Release experiment (BBTRE1, BBTRE2) as well as from a third field cruise of the LArval Dispersal along the Deep East-Pacific Rise project (LADDER3). The model for estimating the time-dependent vertical energy flux is based on linear wave theory, and takes into account the the finite depth of the ocean, the spatial variations of the bathymetry and the spatio-temporal variations of the barotropic tide. The temporal average of the vertical energy flux over a limited period (a few days) immediately before the observational time is compared with the depth-integrated observed energy dissipation rate. A rather good correlation was found between the theoretical predictions and the microstructure data from the BBTRE2 field survey, while the comparison made for the BBTRE1 survey yields a low correlation, The model-based estimates of the vertical energy flux are of the correct order of magnitude, and imply that about one third of the internal wave energy dissipates locally. In the case of LADDER3, the comparison between the observations and the model predictions shows a significant correlation, whereas the modelled energy flux is much higher than the observed dissipation, implying a very low dissipation efficiency. A possible explanation is that the sharp topography at the East-Pacific Rise consists of a few isolated seamounts, which should mean that the general background level of internal wave energy is low. If nonlinear wave interaction is essential for wave dissipation, the wave dissipation should then be less local in this region than in the eastern Brazil Basin, with very extended rough topography.

Falahat, Saeed; Nycander, Jonas

2013-04-01

61

Evaluation of contaminant flux rates from sediments of Sinclair Inlet, WA, using a benthic flux sampling device. Final report  

SciTech Connect

A Benthic Flux Sampling Device (BFSD) was demonstrated on site to determine the mobility of contaminants in sediments off the Puget Sound Naval Shipyard (PSNS) in Sinclair Inlet, WA. Quantification of toxicant flux from the sediments will support ongoing assessment studies and facilitate the design of appropriate remediation strategies, if required. In general, where release of contaminants was found, the measured rates do not represent a significant source relative to other major inputs such as sewer discharges, nonpoint source runoff, and marinas. They may, however, represent an exposure pathway for benthic biota with a subsequent potential for toxicological effects and/or bioaccumulation. Environmental assessment, CIVAPP:Toxicity, CIVAPP:Marine chemistry, Hazardous waste.

Chadwick, D.B.; Lieberman, S.H.; Reimers, C.E.; Young, D.

1993-02-01

62

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

NASA Astrophysics Data System (ADS)

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 帠-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 % higher than the during the rest of the year, but the variability is generally very high. Short-term flux minima are mainly due to precipitation events. First results will be shown of the parameterization of the 222Radon and CO2 fluxes with the groundwater level, soil temperature and humidity, rain events and atmospheric pressure changes.

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

2009-04-01

63

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

64

Measuring biogenic carbon flux in the ocean  

SciTech Connect

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

Boyd, P. [Univ. of Otago, Dunedin (New Zealand); Newton, P. [Commissariat a l`Energie Atomique, Gif-sur-Yvette (France)

1997-01-24

65

Ambient Neutron Flux Measurements at Kimballton Underground Research Facility (KURF)  

NASA Astrophysics Data System (ADS)

It is important to accurately measure the ambient neutron flux at the Kimballton Underground Research Facility (KURF) in Virginia for the low background experiments housed there, some of which are associated with the Majorana project. This paper presents initial results for measurements of the neutron flux at KURF, which will be compared to those from other sites around the world.

Kaleko, David; Henning, Reyco; Tornow, Werner

2009-10-01

66

Statistical Correlation of the Rate of Failures on Geosynchronous Satellites with Fluxes of Energetic Electrons and Protons  

Microsoft Academic Search

A statistical comparison of failures on geosynchronous satellites in the maximum and during the decline of the 22nd solar cycle (19891994) with space weather parameters is carried out. A positive correlation of the rate of failures with the flux of relativistic electrons on the geosynchronous orbit and with the proton flux measured before the bow shock front is revealed. The

N. V. Romanova; V. A. Pilipenko; N. V. Yagova; A. V. Belov

2005-01-01

67

Solar Flux Deposition And Heating Rates In Jupiter's Atmosphere  

NASA Astrophysics Data System (ADS)

We discuss here the solar downward net flux in the 0.25 - 2.5 痠 range in the atmosphere of Jupiter and the associated heating rates under a number of vertical cloud structure scenarios focusing in the effect of clouds and hazes. Our numerical model is based in the doubling-adding technique to solve the radiative transfer equation and it includes gas absorption by CH4, NH3 and H2, in addition to Rayleigh scattering by a mixture of H2 plus He. Four paradigmatic Jovian regions have been considered (hot-spots, belts, zones and Polar Regions). The hot-spots are the most transparent regions with downward net fluxes of 2.50.5 Wm-2 at the 6 bar level. The maximum solar heating is 0.040.01 K/day and occurs above 1 bar. Belts and zones characterization result in a maximum net downward flux of 0.5 Wm-2 at 2 bar and 0.015 Wm-2 at 6 bar. Heating is concentrated in the stratospheric and tropospheric hazes. Finally, Polar Regions are also explored and the results point to a considerable stratospheric heating of 0.040.02 K/day. In all, these calculations suggest that the role of the direct solar forcing in the Jovian atmospheric dynamics is limited to the upper 1 - 2 bar of the atmosphere except in the hot-spot areas. Acknowledgments: This work has been funded by Spanish MEC AYA2006-07735 with FEDER support and Grupos Gobierno Vasco IT-464-07.

Perez-Hoyos, Santiago; S嫕chez-Lavega, A.

2009-09-01

68

IR thermography heat flux measurement in fire safety applications  

NASA Astrophysics Data System (ADS)

The paper deals with heat flux measurement possibilities in fire safety applications. The paper presents two methods for radiation heat flux measurement - the thermography source-target measurement method, and the radiation contact target measurement method. Both the methods were used simultaneously for radiation heat flux measurement during a fire experiment on a high-density polyethylene plastic box storage stack. The theoretical background, experimental set-up, application example, and comparison of both methods are presented in this paper. Dependence of heat flux magnitude on a distance and direction from a heat source is evaluated. The possible safety risks ensuing from high temperatures inside the burning stack, and therefore high heat fluxes near the stack, are discussed.

vantner, Michal; Vac璭ov, Petra; Honner, Milan

2012-07-01

69

Measuring nitrate fluxes to assess estuarine eutrophication  

Microsoft Academic Search

Summary form only given.The availability of nitrate sensors has enabled integration of these instruments into real-time profiling buoys and, when coupled with current meters, allows for calculation of nitrate fluxes into and out of estuaries. As the United States' estuaries are increasingly experiencing eutrophication this technological development is timely. We report on the use of nitrate sensors on our profiling

J. Newton; A. Devol; W. Ruef

2009-01-01

70

Rating scales and Rasch measurement.  

PubMed

Assessments with ratings in ordered categories have become ubiquitous in health, biological and social sciences. Ratings are used when a measuring instrument of the kind found in the natural sciences is not available to assess some property in terms of degree - for example, greater or smaller, better or worse, or stronger or weaker. The handling of ratings has ranged from the very elementary to the highly sophisticated. In an elementary form, and assumed in classical test theory, the ratings are scored with successive integers and treated as measurements; in a sophisticated form, and used in modern test theory, the ratings are characterized by probabilistic response models with parameters for persons and the rating categories. Within modern test theory, two paradigms, similar in many details but incompatible on crucial points, have emerged. For the purposes of this article, these are termed the statistical modeling and experimental measurement paradigms. Rather than reviewing a compendium of available methods and models for analyzing ratings in detail, the article focuses on the incompatible differences between these two paradigms, with implications for choice of model and inferences. It shows that the differences have implications for different roles for substantive researchers and psychometricians in designing instruments with rating scales. To illustrate these differences, an example is provided. PMID:21958102

Andrich, David

2011-10-01

71

A new approach of surface flux measurements using DTS  

NASA Astrophysics Data System (ADS)

Estimation of surface fluxes is a difficult task, especially over lakes. Determining latent heat flux (evaporation), sensible heat flux and ground heat flux involves measurements and (or calculations) of net radiation, air temperature, water temperature, wind speed and relative humidity. This research presents a new method to measure surface fluxes by means of Distributed Temperature Sensing (DTS). From 0.5 m above lake level to 1.5 m under lake level DTS was applied to measure temperature. Using a PVC hyperboloid construction, a floating standalone measuring device was developed. This new setup distinguished itself by the open construction, so it is almost insensitive to direct radiation. While most of the lake ground heat changes occur very close to the lake surface, most measuring methods only obtain rough results. With this construction it was possible to create a spiral shaped fiber-optic cable setup, with which a vertical spatial resolution of 0.02 m and a temporal resolution of 1 min was obtained. The new method was tested in the deep Lake Kinneret (Israel) from 6 October, 2011 to 11 October, 2011and in the shallow Lake Binaba (Ghana) from 24 October, 2011 to 28 October, 2011. This study shows that with the developed method it is possible to capture the energy fluxes within the top water layer with a high resolution. When the old low resolution method was compared with the new high resolution method, it could be concluded that the impact of the surface fluxes in the upper layer is high on the energy balance on a daily scale. During the measuring period it was possible to use the temperature measured by the DTS to determine the sensible heat flux, the latent heat flux and the ground heat flux of both lakes.

van Emmerik, T. H. M.; Wenker, K. J. R.; Rimmer, A.; de Jong, S. A. P.; Lechinsky, Y.; van de Giesen, N. C.

2012-04-01

72

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

PubMed

Thrombin is released as a soluble enzyme from the surface of platelets and tissue-factor-bearing cells to trigger fibrin polymerization during thrombosis under flow conditions. Although isotropic fibrin polymerization under static conditions involves protofibril extension and lateral aggregation leading to a gel, factors regulating fiber growth are poorly quantified under hemodynamic flow due to the difficulty of setting thrombin fluxes. A membrane microfluidic device allowed combined control of both thrombin wall flux (10(-13) to 10(-11) nmol/mum(2) s) and the wall shear rate (10-100 s(-1)) of a flowing fibrinogen solution. At a thrombin flux of 10(-12) nmol/mum(2) s, both fibrin deposition and fiber thickness decreased as the wall shear rate increased from 10 to 100 s(-1). Direct measurement and transport-reaction simulations at 12 different thrombin flux-wall shear rate conditions demonstrated that two dimensionless numbers, the Peclet number (Pe) and the Damkohler number (Da), defined a state diagram to predict fibrin morphology. For Da < 10, we only observed thin films at all Pe. For 10 < Da < 900, we observed either mat fibers or gels, depending on the Pe. For Da > 900 and Pe < 100, we observed three-dimensional gels. These results indicate that increases in wall shear rate quench first lateral aggregation and then protofibril extension. PMID:20371335

Neeves, K B; Illing, D A R; Diamond, S L

2010-04-01

73

First eddy covariance flux measurements by PTR-TOF  

NASA Astrophysics Data System (ADS)

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

Mller, M.; Graus, M.; Ruuskanen, T. M.; Schnitzhofer, R.; Bamberger, I.; Kaser, L.; Titzmann, T.; H顤tnagl, L.; Wohlfahrt, G.; Karl, T.; Hansel, A.

2009-12-01

74

First eddy covariance flux measurements by PTR-TOF  

NASA Astrophysics Data System (ADS)

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

Mller, M.; Graus, M.; Ruuskanen, T. M.; Schnitzhofer, R.; Bamberger, I.; Kaser, L.; Titzmann, T.; H顤tnagl, L.; Wohlfahrt, G.; Karl, T.; Hansel, A.

2010-03-01

75

Rotor Losses Measurements in an Axial Flux Permanent Magnet Machine  

Microsoft Academic Search

MMF space harmonics and slot openings produce considerable rotor losses in permanent magnet (PM) machines, especially if fractional-slot windings are adopted. This paper aims to measure the rotor losses of a 12-slot 10-pole axial flux phase modulation machine. Both MMF space harmonics and slot open- ings are considered. The prototype is an axial flux machine with open slots, equipped with

Luigi Alberti; Emanuele Fornasiero; Nicola Bianchi; Silverio Bolognani

2011-01-01

76

Evaluation of the flux gradient technique for measurement of ozone surface fluxes over snowpack at Summit, Greenland  

NASA Astrophysics Data System (ADS)

A multi-step procedure for investigating ozone surface fluxes over polar snow by the tower gradient method was developed and evaluated. These measurements were then used to obtain five months (April-August 2004) of turbulent ozone flux data at the Summit research camp located in the center of the Greenland ice shield. Turbulent fluxes were determined by the gradient method incorporating tower measurements of (a) ozone gradients measured by commercial ultraviolet absorption analyzers, (b) ambient temperature gradients using aspirated thermocouple sensors, and (c) wind speed gradients determined by cup anemometers. All gradient instruments were regularly inter-compared by bringing sensors or inlets to the same measurement height. The developed protocol resulted in an uncertainty on the order of 0.1 ppbv for 30-min averaged ozone gradients that were used for the ozone flux calculations. This protocol facilitated a lower sensitivity threshold for the ozone flux determination of ∼8 10-3?g m-2 s-1, respectively ∼0.01 cm s-1 for the ozone deposition velocity for typical environmental conditions encountered at Summit. Uncertainty in the 30-min ozone exchange measurements (evaluated by the Monte Carlo statistical approach) was on the order of 10-2 cm s-1. This uncertainty typically accounted to ~20-100% of the ozone exchange velocities that were determined. These measurements are among the most sensitive ozone deposition determinations reported to date. This flux experiment allowed for measurements of the relatively low ozone uptake rates encountered for polar snow, and thereby the study of their environmental and spring-versus-summer dependencies.

Bocquet, F.; Helmig, D.; van Dam, B. A.; Fairall, C. W.

2011-10-01

77

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

SciTech Connect

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

Porch, W.; Barnes, F.; Buchwald, M.; Clements, W.; Cooper, D.; Hoard, D. (Los Alamos National Lab., NM (United States)); Doran, C.; Hubbe, J.; Shaw, W. (Pacific Northwest Lab., Richland, WA (United States)); Coulter, R.; Martin, T. (Argonne National Lab., IL (United States)); Kunkel, K. (Illinois State Water Survey, Champaign, IL (United States))

1991-01-01

78

Model for GCR-particle fluxes in stony meteorites and production rates of cosmogenic nuclides  

SciTech Connect

A model is presented for the differential fluxes of galactic-cosmic-ray (GCR) particles with energies above 1 MeV inside any spherical stony meteorite as a function of the meteorite's radius and the sample's depth. This model is based on the Reedy-Arnold equations for the energy-dependent fluxes of GCR particles in the moon and is an extension of flux parameters that were derived for several meteorites of various sizes. This flux is used to calculate the production rates of many cosmogenic nuclides as a function of radius and depth. The peak production rates for most nuclides made by the reactions of energetic GCR particles occur near the centers of meteorites with radii of 40 to 70 g cm/sup -2/. Although the model has some limitations, it reproduces well the basic trends for the depth-dependent production of cosmogenic nuclides in stony meteorites of various radii. These production profiles agree fairly well with measurements of cosmogenic nuclides in meteorites. Some of these production profiles are different than those calculated by others. The chemical dependence of the production rates for several nuclides varies with size and depth. 25 references, 8 figures.

Reedy, R.C.

1984-01-01

79

Measurement of Outgoing Radiative Fluxes from Ultra Long Duration Balloons  

NASA Astrophysics Data System (ADS)

Top of Atmosphere TOA radiative fluxes W m 2 are critical to our understanding of the physics of the present climate and it is variability Recognizing this importance NASA has measured the shortwave 0 2--4 mu m fluxes reflected by the Earth-atmosphere system and longwave 4--100 mu m fluxes emitted by the Earth-atmosphere systme for almost 40 years Outgoing flux can be measured directly from satellite using wide field of view radiometers with a footprint of a few thousand kilometers In order to provide fluxes more commensurate with the increasingly fine resolution of climate models Earth radiation budget satellite the Cloud and Earth s Radiant Energy System CERES on Terra and Aqua is based entirely on narrow filed of view scanner to measure directional radiances W m 2 sr Therefore we have to rely on empirical angular directional models to convert radiance to flux which is the principle source of uncertainty in instantaneous fluxes estimated from Earth radiation budget satellites Unlike other retrieved variables emph in situ validation of outgoing fluxes has been nearly impossible for lack of platforms that operate for long periods at the top of atmosphere The NASA Ultra Long Duration Balloon ULDB program opens a new avenue for direct measurement of the Earth radiation budget Radiative transfer model shows that the outgoing flux differences between ULDB flight altitude and TOA is less than 1 W m 2 Therefore it provides a unique platform to validate the satellite retrieved TOA radiative fluxes An Earth radiation balloon package has

Su, W.; Dutton, E.; Charlock, T.; Wiscombe, W.

80

Flux Measurements of Volatile Organic Compounds from an Urban Landscape  

SciTech Connect

Direct measurements of volatile organic compound (VOC) emissions that include all anthropogenic and biogenic emission sources in urban areas are a missing requirement to evaluate emission inventories and constrain current photochemical modelling practices. Here we demonstrate the use of micrometeorological techniques coupled with fast-response sensors to measure urban VOC fluxes from a neighborhood of Mexico City, where the spatial variability of surface cover and roughness is high. Fluxes of olefins, methanol, acetone, toluene and C2-benzenes were measured and compared with the local gridded emission inventory. VOC fluxes exhibited a clear diurnal pattern with a strong relationship to vehicular traffic. Recent photochemical modeling results suggest that VOC emissions are significantly underestimated in Mexico City1, but the measured VOC fluxes described here indicate that the official emission inventory2 is essentially correct. Thus, other explanations are needed to explain the photochemical modelling results.

Velasco, E.; Lamb, Brian K.; Pressley, S.; Allwine, Eugene J.; Westberg, Halvor; Jobson, B Tom T.; Alexander, M. Lizabeth; Prazeller, Peter; Molina, Luisa; Molina, Mario J.

2005-10-19

81

Measuring Regional CO2 Fluxes Using a Lagrangian Approach  

NASA Astrophysics Data System (ADS)

The difficulty of measuring regional fluxes of CO2 has limited our understanding of the global carbon budget and the processes controlling carbon exchange across politically relevant spatial scales. A Lagrangian experiment was conducted over Iowa on June 19, 2007 as part of the North American Carbon Program's Mid-Continent Intensive using a light-weight, cost-effective aircraft to measure a net drawdown of CO2 concentration within the boundary layer. The drawdown is related to photosynthetic uptake when emission footprints are considered using a combination of emission inventories from the Vulcan project and HYSPLIT source contributions. Entrainment through the top of the boundary layer is measured directly using turbulence measurements from an onboard probe capable of measuring winds in 3-dimensions. Results show a total average CO2 flux of -5.30.7 ?mol m-2 s-1. The average flux from fossil fuels over the measurement area is 2.80.4 ?mol m-2 s-1. Thus, the CO2 flux attributable to the vegetation is -8.10.8 ?mol m-2 s-1. The magnitude of the vegetative flux is comparable to other studies using the Lagrangian approach, but it is smaller than tower- based eddy covariance fluxes over the same period and measurement area. Sensitivities to analysis procedures and discrepancies between aircraft and tower-based measurements are discussed. We describe an aircraft Lagrangian experiment that offers direct, reliable, and cost-effective means for measuring CO2 fluxes at regional scales that can be used to compare to ecosystem models or to satellite measurements.

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

2008-12-01

82

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

SciTech Connect

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

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

2010-03-31

83

Design of a differential radiometer for atmospheric radiative flux measurements  

SciTech Connect

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.

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

1994-11-01

84

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

NASA Astrophysics Data System (ADS)

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

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

2008-02-01

85

Hybrid heat flux measurement system for solar central receiver evaluation  

Microsoft Academic Search

A hybrid heat flux measurement system has been designed, built and mounted on top of the SSPS-CRS tower at the Plataforma Solar de Almer燰 (PSA) to measure the incident solar power that is concentrated by a heliostat field on the flat aperture of a central receiver. This device is composed of two measurement systems, one direct and the other indirect.

J. Ballestr璯; R. Monterreal

2004-01-01

86

Standard measuring system for calibration of magnetic flux density gradiometers  

Microsoft Academic Search

A standard measuring system (setup) has been developed at VNIIM to be used for the calibration of magnetic flux density gradient (MFDG) coils, sensors and magnetic gradiometers (MG). This measurement standard is based on the calculable quartz coil used for the reproduction of gradient which is uniform in a specified working space. It also includes measuring equipment to compare coils,

V. N. Khorev; V. Y. Shifrin; S. A. Shubin; P. G. Park

2010-01-01

87

Measurements of the Solar Neutrino Flux from Super-Kamiokande{close_quote}s First 300 Days  

SciTech Connect

The first results of the solar neutrino flux measurement from Super-Kamiokande are presented. The results shown here are obtained from data taken between 31 May 1996, and 23 June 1997. Using our measurement of recoil electrons with energies above 6.5thinspthinspMeV, we infer the total flux of {sup 8}B solar neutrinos to be 2.42{plus_minus}0.06(stat){sup +0.10}{sub {minus}0.07}(syst){times}10{sup 6} thinspcm{sup {minus}2}thinsp s{sup {minus}1} . This result is consistent with the Kamiokande measurement and is 36{percent} of the flux predicted by the BP95 solar model. The flux is also measured in 1.5 month subsets and shown to be consistent with a constant rate. {copyright} {ital 1998} {ital The American Physical Society }

Fukuda, Y.; Hayakawa, T.; Ichihara, E.; Inoue, K.; Ishihara, K.; Ishino, H.; Itow, Y.; Kajita, T.; Kameda, J.; Kasuga, S.; Kobayashi, K.; Kobayashi, Y.; Koshio, Y.; Martens, K.; Miura, M.; Nakahata, M.; Nakayama, S.; Okada, A.; Oketa, M.; Okumura, K.; Ota, M.; Sakurai, N.; Shiozawa, M.; Suzuki, Y.; Takeuchi, Y.; Totsuka, Y.; Yamada, S. [Institute for Cosmic Ray Research, University of Tokyo, Tanashi, Tokyo 188-8502 (Japan); Earl, M.; Habig, A.; Hong, J.T.; Kearns, E.; Kim, S.B.; Masuzawa, M.; Messier, M.D.; Scholberg, K.; Stone, J.L.; Sulak, L.R.; Walter, C.W. [Department of Physics, Boston University, Boston, Massachusetts 02215 (United States); Goldhaber, M. [Physics Department, Brookhaven National Laboratory, Upton, New York 11973 (United States); Barszczak, T.; Gajewski, W.; Halverson, P.G.; Hsu, J.; Kropp, W.R.; Price, L.R.; Reines, F.; Sobel, H.W.; Vagins, M.R.; Haines, T.J.; Kielczewska, D. [Department of Physics and Astronomy, University of California, Irvine, Irvine, California 92697-4575 (United States); Ganezer, K.S.; Keig, W.E. [Department of Physics, California State University, Dominguez Hills, Carson, California 90747 (United States); Ellsworth, R.W. [Department of Physics, George Mason University, Fairfax, Virginia 22030 (United States); Tasaka, S. [Department of Physics, Gifu University, Gifu, Gifu 501-1193 (Japan); Flanagan, J.W.; Kibayashi, A.; Learned, J.G.; Matsuno, S.; Stenger, V.; Takemori, D. [Department of Physics and Astronomy, University of Hawaii, Honolulu, Hawaii 96822 (United States); Ishii, T.; Kanzaki, J.; Kobayashi, T.; Nakamura, K.; Nishikawa, K.; Oyama, Y.; Sakai, A.; Sakuda, M.; Sasaki, O. [Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801 (Japan); Echigo, S.; Kohama, M.; Suzuki, A.T. [Department of Physics, Kobe University, Kobe, Hyogo 657-8501 (Japan); Haines, T.J. [Physics Division, P-23, Los Alamos National Laboratory (United States)

1998-08-01

88

Absolute flux measurement at HIGS using Compton backscattering  

Microsoft Academic Search

The High Intensity gamma-ray Source (HIgammaS) at FELL\\/TUNL is developing a program to study many aspects of nuclear physics presently using 2-to-50 MeV gamma-rays. In many cases these experiments require absolute gamma-flux monitoring and determination. This project presents a technique to indirectly measure the absolute gamma-ray flux by placing a thin scattering foil in the gamma-beam and then detecting the

B. Fallin; M. W. Ahmed; B. Perdue; A. Sabourov; T. Sheard; W. Tornow; A. P. Tonchev; H. R. Weller; J. Li; I. V. Pinaev; Y. Wu; R. M. Prior; M. Spraker; J. Chen; G. Feldman

2003-01-01

89

The air density correction to eddy flux measurements  

Microsoft Academic Search

Under the usual assumptions for the atmospheric surface layer, we show that air density fluctuations, particularly those due\\u000a to temperature fluctuations associated with a heat flux, result in a small mean vertical wind velocity. Because of this, there\\u000a can be a significant correction to eddy flux measurements of passive scalars, for example CO2, whose average concentration is very large compared

E. P. Jones; S. D. Smith

1978-01-01

90

High flux-fluence measurements in fast reactors  

Microsoft Academic Search

Characterization of irradiation environments for fuels and materials tests in fast reactors requires determination of the neutron flux integrated over times as long as several years. An accurate integration requires, therefore, passive dosimetry monitors with long half-life or stable products which can be conveniently measured. In addition, burn-up, burn-in, and burn-out effects must be considered in high flux situations and

E. P. Lippincott; J. A. Ulseth

1977-01-01

91

FluxPro: Real time monitoring and simulation system for eddy covariance flux measurement  

NASA Astrophysics Data System (ADS)

To cope with unusual weather changes on crop cultivation in a field level, prompt and precise monitoring of photosynthesis and evapotranspiration, and those fast and reliable forecasting are indispensable. So we have developed FluxPro which is simultaneous operating system of the monitoring and the forecasting. The monitoring subsystem provides vapor and CO2 fluxes with uncertainty to understand the live condition of photosynthesis and evapotranspiration by open-path eddy covariance flux measurement (EC) system and self-developed EC tolerance analysis scheme. The forecasting subsystem serves the predicted fluxes with anomaly based on model parameter assimilation to estimate the hourly or daily water consumption and carbon assimilation during a week by multi-simulation package consisting of various models from simple to complicate. FluxPro is helpful not only to detect a critical condition of growing crop in terms of photosynthesis and evapotranspiration but also to decide time and amount of launching control for keeping those optimization condition when an unusual weather event is arisen. In our presentation, we will demonstrate the FluxPro operated at tangerine orchard in Jeju, Korea.

Kim, W.; Seo, H.; Mano, M.; Ono, K.; Miyata, A.; Yokozawa, M.

2010-12-01

92

Regional carbon dioxide fluxes from aircraft measurements in southwest France  

NASA Astrophysics Data System (ADS)

In 2007, the CarboEurope-IP Regional Component organised the second edition of the CERES measurement campaign in the southwest of France. This was a follow-up of the initial campaign in 2005. CERES'07 consisted of two intensive observational periods (IOPs), of which one in spring and the other one in summer. During both IOPs, ground stations, tall towers, radiosondes and a number of aircrafts were used, including our own environmental research aircraft (ERA). The ERA is a small aircraft flying at low altitudes and low air speeds, equipped to measure fluxes of carbon dioxide, latent heat and sensible heat using the eddy-correlation technique. In addition, instruments are on board for measuring ground temperature, net radiation and photosynthetically active radiation (PAR). Flux data obtained with the ERA during CERES'07 have been analyzed and will be presented here. In the data analysis, we present regional fluxes of carbon dioxide focussing at seasonal trends in relation to landscape elements. To achieve this, flight tracks were split into homogeneous segments based on land cover, topography and soil type. During both IOPs, weather conditions were constant. This gives us the possibility to average data in each segment across all flights, though the issue of diurnal variation in surface fluxes and radiation still remains. In short, the analysis strategy on our airborne flux data from CERES'07 will be addressed in this presentation together with its results focussing at drivers for these fluxes at landscape scale.

Vellinga, O. S.; Hutjes, R. W. A.; Elbers, J. A.

2009-04-01

93

Precise, Facile Initial Rate Measurements  

PubMed Central

Progress curve analysis has been used sparingly in studies of enzyme-catalyzed reactions due largely to the complexity of the integrated rate expressions used in data analysis. Using an experimental design that simplifies the analysis, the advantages and limitations of progress curve experiments are explored in a study of four different enzyme-catalyzed reactions. The approach involves relatively simple protocols, requires 2025% of the materials, and provides 10- to 20-fold signal enhancements compared to analogous initial rate studies. Product inhibition, which complicates integrated rate analysis, was circumvented using cloned, purified enzymes that remove the products and draw the reaction forward. The resulting progress curves can be transformed into the equivalent of thousands of initial rate and [S] measurements and, due to the absence of product inhibition, are plotted in the familiar, linear double-reciprocal format. Allowing product to accumulate during a reaction produces a continuously changing substrate/product ratio that can be used as the basis for obtaining product inhibition constants and to distinguish among the three classical inhibition mechanisms. Algebraic models describing the double-reciprocal patterns obtained from such inhibition studies are presented. The virtual continuum of substrate concentrations that occurs during a progress curve experiment provides a nearly errorless set of relative concentrations that results in remarkably precise data; kinetic constant standard deviations are on the order of 0.5%.

Tang, Qingxiu; Leyh, Thomas S.

2010-01-01

94

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...

95

Preliminary measurements of heat flux in a subsonic gun simulator  

Microsoft Academic Search

Preliminary measurements of heat flux have been obtained in a subsonic gun simulator with thin film resistance thermometry for an inert, single phase flow expanding behind a projectile from an initial pressure of 8 bars and resulting in an exit projectile velocity of 40 m\\/s. The results show that heat transfer measurements at locations swept by the projectile are possible

A. F. Bicen; M. Schmidt; J. H. Whitelaw

1987-01-01

96

Measurement of a surface heat flux and temperature  

Microsoft Academic Search

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

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

1994-01-01

97

Intercomparison of gas analyzers for methane flux measurements  

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

98

Uncertainty of calorimeter measurements at NREL's high flux solar furnace  

SciTech Connect

The uncertainties of the calorimeter and concentration measurements at the High Flux Solar Furnace (HFSF) at the National Renewable Energy Laboratory (NREL) are discussed. Two calorimeter types have been used to date. One is an array of seven commercially available circular foil calorimeters (gardon or heat flux gages) for primary concentrator peak flux (up to 250 W/cm{sup 2}). The second is a cold-water calorimeter designed and built by the University of Chicago to measure the average exit power of the reflective compound parabolic secondary concentrator used at the HFSF (over 3.3 kW across a 1.6cm{sup {minus}2} exit aperture, corresponding to a flux of about 2 kW/cm{sup 2}). This paper discussed the uncertainties of the calorimeter and pyrheliometer measurements and resulting concentration calculations. The measurement uncertainty analysis is performed according to the ASME/ANSI standard PTC 19.1 (1985). Random and bias errors for each portion of the measurement are analyzed. The results show that as either the power or the flux is reduced, the uncertainties increase. Another calorimeter is being designed for a new, refractive secondary which will use a refractive material to produce a higher average flux (5 kW/cm{sup 2}) than the reflective secondary. The new calorimeter will use a time derivative of the fluid temperature as a key measurement of the average power out of the secondary. A description of this calorimeter and test procedure is also presented, along with a pre-test estimate of major sources of uncertainty. 8 refs., 4 figs., 3 tabs.

Bingham, C.E.

1991-12-01

99

Some Rate-Dependent Aspects of Flux Jumping in Nb25% Zr Tubes  

Microsoft Academic Search

A series of experiments have been performed on rate dependence of flux jumping in tubular samples of Nb-25% Zr using pulsed magnetic fields. The field H1 for which the first flux jump occurred was studied as a function of the rate of change of field H˙1 at the time of the flux jump. The range of H˙1 was 101

F. Rothwarf; D. Ford; G. Articola; Gail P. Segal; Y. B. Kim

1968-01-01

100

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

PubMed Central

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

2011-01-01

101

New Method for Estimation of Aeolian Sand Transport Rate Using Ceramic Sand Flux Sensor (UD-101)  

PubMed Central

In this study, a new method for the estimation of aeolian sand transport rate was developed; the method employs a ceramic sand flux sensor (UD-101). UD-101 detects wind-blown sand impacting on its surface. The method was devised by considering the results of wind tunnel experiments that were performed using a vertical sediment trap and the UD-101. Field measurements to evaluate the estimation accuracy during the prevalence of unsteady winds were performed on a flat backshore. The results showed that aeolian sand transport rates estimated using the developed method were of the same order as those estimated using the existing method for high transport rates, i.e., for transport rates greater than 0.01 kg m?1 s?1.

Udo, Keiko

2009-01-01

102

Air-sea flux of bromoform: Controls, rates, and implications  

Microsoft Academic Search

Bromoform (CHBr3) is the largest single source of atmospheric organic bromine and therefore of importance as a source of reactive halogens to the troposphere and lower stratosphere. The sea-to-air flux, originating with macroalgal and planktonic sources, is the main source for atmospheric bromoform. We review bromoform's contribution to atmospheric chemistry, its atmospheric and oceanic distributions and its oceanic sources and

Birgit Quack; D. W. R. Wallace

2003-01-01

103

Blazar flaring rates measured with GLAST  

NASA Astrophysics Data System (ADS)

We derive the minimum observing time scales to detect a blazar at a given flux level with the LAT on the Gamma-ray Large Area Space Telescope (GLAST) in the scanning and pointing modes. Based upon Phase 1 observations with EGRET, we predict the GLAST detection rate of blazar flares at different flux levels. With some uncertainty given the poor statistics of bright blazars, we predict that a blazar flare with integral flux ?20010 -8 photons (>100 MeV) cm -2 s -1, which are the best candidates for Target of Opportunity pointings and extensive temporal and spectral studies, should occur every few days.

Dermer, C. D.; Dingus, B. L.

2004-04-01

104

Measurement of Decoherence Time in a Flux Qubit  

NASA Astrophysics Data System (ADS)

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

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

2006-09-01

105

Absolute flux measurement at HIGS using Compton backscattering  

NASA Astrophysics Data System (ADS)

The High Intensity ?-ray Source (HI?S) at FELL/TUNL is developing a program to study many aspects of nuclear physics presently using 2-to-50 MeV ?-rays. In many cases these experiments require absolute ?-flux monitoring and determination. This project presents a technique to indirectly measure the absolute ?-ray flux by placing a thin scattering foil in the ?-beam and then detecting the Compton-scattered ?-rays at a particular scattering angle using a HPGe detector. The fluxes of these Compton-scattered ?-rays are low (i.e., 10^3 ?/s) in comparison to the direct flux of the beam ( 10^6 ?/s). In addition the Compton-scattered energies are in the energy range of 2 to 5 MeV for ?-ray beam energies below 10 MeV, which are relatively easy to measure with a HPGe detector with very high energy resolution. Recent experimental results from the flux measurements at HI?S will be presented.

Fallin, B.; Ahmed, M. W.; Perdue, B.; Sabourov, A.; Sheard, T.; Tornow, W.; Tonchev, A. P.; Weller, H. R.; Li, J.; Pinaev, I. V.; Wu, Y.; Prior, R. M.; Spraker, M.; Chen, J.; Feldman, G.

2003-10-01

106

Direct Measurement of Turbulent Particle and Gas Fluxes by Eddy Covariance Technique  

NASA Astrophysics Data System (ADS)

Direct Measurement of Turbulent Particle and Gas Fluxes by Eddy Covariance Technique Fumiyoshi KONDO (The University of Tokyo) Frank GRIESSBAUM (Universit酹 Mnster) Osamu TSUKAMOTO (Okayama University) Mitsuo UEMATSU (The University of Tokyo) The oceans play major key roles in global energy transport, element cycles, and atmospheric radiation balance. The study of the processes at the interface of ocean and atmosphere is essential to develop profound understanding of the mechanisms driving ocean-atmosphere interaction and climate. Eddy covariance technique is the only direct measurement of air-sea particle and gas fluxes. This technique has little assumption (constant flux layer and steady state), and may evaluate small spatial and temporal particle and gas fluxes. For these reasons, we hope that the eddy covariance technique investigates uncertain processes that control the air-sea particle (aerosol) and gas (CO2) fluxes. The understanding of processes controlling both the CO2 uptake to the ocean and the oceans as major source of aerosols is vital for quantifying the role of the global oceans in the climate system. We developed the simultaneous measurement system of turbulent particle and gas fluxes by eddy covariance technique and installed with ship motion correction system on the top of the foremast of R/V Hakuho-Maru and Mirai. The turbulent flux system on the top of the foremast consisted of a sonic anemometer-thermometer (Gill, HS-50), an infrared CO2/H2O gas analyzer (LI-COR, LI-7500), a water-based condensation particle counter (TSI, WCPC3785), and Fog Monitor (Droplet Measurement, FM-100). The ship motion correction system consisted of a three-axis accelerometer and a three-axis rate gyro (Systron Donner, MotionPak II). The sonic anemometer measures three-dimensional wind components relative to the ship including apparent wind velocity due to the ship motion. Then, the ship motion correction system measures the ship motions by time integral of accelerometer and rate gyro. The turbulent flux system on the top of the foremast is capable to simultaneously measure the turbulent flux of the CO2 and H2O gases, fine aerosols (5 nm - 3 ?m diameters), and fog water droplets (2 ?m - 50 ?m diameters). Analog and digital output signals from both systems are sampled at 10 Hz by a PC-based data logging systems. In this study, we will present the direct flux measurement system and discuss results of air-sea particle and CO2 fluxes directly evaluated by the eddy covariance technique over the open ocean.

Kondo, F.; Griessbaum, F.; Tsukamoto, O.; Uematsu, M.

2010-12-01

107

{sup 36}Cl measurements of the unsaturated zone flux at Yucca Mountain  

SciTech Connect

Determining the unsaturated zone percolation rate, or flux, is an extremely important site characterization issue for the proposed Yucca Mountain nuclear waste repository. A new technique that measures the {sup 36}Cl content of tuff from the Exploratory Shaft will be used to calculate flux through the unsaturated zone over longer times than could be measured by the more conventional {sup 14}C method. Measurements of the {sup 36}Cl "bomb pulse" in soil samples from Yucca Mountain have been used to confirm that infiltration is not an important recharge mechanism. 5 refs., 3 figs.

Norris, A.E.; Wolfsberg, K.; Gifford, S.K.

1985-12-31

108

Flux Rope Acceleration and Enhanced Magnetic Reconnection Rate  

Microsoft Academic Search

A physical mechanism of flares, in particular for the flare rise phase, has emerged from our 2-1\\/2D resistive MHD simulations. The dynamical evolution of current sheet formation and magnetic reconnection and flux rope acceleration subject to continuous, slow increase of magnetic shear in the arcade are studied by employing a non-uniform anomalous resistivity in the reconnecting current sheet under gravity.

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

2003-01-01

109

Analysis of particles and carbon dioxide concentrations and fluxes in an urban area: Correlation with traffic rate and local micrometeorology  

NASA Astrophysics Data System (ADS)

Number particle concentrations and fluxes were measured, synchronously with CO 2 concentrations and fluxes, in an urban area. Measurements were taken with an eddy-correlation station located near the busiest road of the town of Lecce (Italy). Upward fluxes dominate completely over deposition and the area behaved as a source of aerosol and CO 2 with an average particle flux F N = 71,100 #/cm 2 s (median 64,000 #/cm 2 s) and an average CO 2 flux F C = 0.76 mg/m 2 s (median 0.46 mg/m 2 s). Pronounced diurnal and weekly cycles of F N and F C were observed, well correlated with measured traffic rate, T R, indicating that traffic is the main source of CO 2 and particles in the area. Biogenic cycle on CO 2 fluxes and concentrations was also distinguishable, decreasing the correlation between F N and F C. The relationships between particle and CO 2 fluxes with T R, friction velocity and atmospheric stability were analysed. Measured F N/ T R increased when friction velocity increased and, correspondingly, number concentration decreased. Particle fluxes showed a dependence on the atmospheric stability. These dependencies were used to derive an empirical parameterisation of aerosol concentration and fluxes, based on T R and micrometeorological parameters, that could be used to estimate traffic emissions, in real operating conditions, for applications in dispersion and climate modelling. Measured F C/ T R showed a limited correlation with friction velocity and stability, because of the influence of the biogenic cycle, thereby micrometeorological parameters were not used in the parameterisation of F C.

Contini, D.; Donateo, A.; Elefante, C.; Grasso, F. M.

2012-01-01

110

A PROBLEM WITH FLUX CHAMBER MEASUREMENTS OF BIOGENIC SULFUR EMISSIONS  

EPA Science Inventory

Problems associated with identifying and quantifying factors that influence liquid-phase controlled evolution of hydrogen sulfide and organic sulfides through the air-water interface are briefly reviewed. It was found that at present flux chamber measurements of the release of th...

111

TECHNIQUE FOR GROSS FLUX MEASUREMENTS IN THE OMR CRITICAL ASSEMBLY  

Microsoft Academic Search

A technique was developed for measuring the gross neutron flux ; distributions in the OMR Critical Assembly using Mn-alloy wires. Manganese-alloy ; (Mn-20% cu - l9%Ni) wire segments, one-half inch long, are loaded into Al or Cd ; tubing, which is then placed in a stainless steel tube inserted in the desired ; location in the critical assembly. After irradiation,

Tuttle

1959-01-01

112

CorerReactors for Contaminant Flux Measurement in Sediments  

Microsoft Academic Search

disturbance to the sediment. This apparatus has been used in our laboratory for a number of years (Jones and Design details and operating instructions are provided for a sedi- Jung, 1996; Jung et al., 1997) and has generated useful ment corer that can be converted into a reactor for the measurement of the fluxes of contaminants from sediments to overlying

R. F. Jung; D. R. Jones; G. E. Batley

2003-01-01

113

Preliminary Measurements of Heat Flux in a Subsonic Gun Simulator.  

National Technical Information Service (NTIS)

Preliminary measurements of heat flux have been obtained in a subsonic gun simulator with thin film resistance thermometry for an inert, single phase flow expanding behind a projectile from an initial pressure of 8 bars and resulting in an exit projectile...

A. F. Bicen M. Schmidt J. H. Whitelaw

1987-01-01

114

Estimation of wet surface evaporation from sensible heat flux measurements  

Microsoft Academic Search

A new method is proposed to estimate wet surface evaporation by means of measurements of sensible heat flux and of air temperature, relative humidity, and wind speed at one level only. This formulation is made possible by the linearization of the Bowen ratio, a common assumption in other methods, such as Penman's model and its derivatives. The method will be

Nikki Vercauteren; Elie Bou-Zeid; Hendrik Huwald; Marc B. Parlange; Wilfried Brutsaert

2009-01-01

115

Measurement of a Surface Heat Flux and Temperature.  

National Technical Information Service (NTIS)

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. ...

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

1994-01-01

116

Single-cell flux measurement by continuous fluorescence microphotolysis  

Microsoft Academic Search

Continuous fluorescence microphotolysis (CFM) was adapted to flux measurements in single cells. The principle of the method is simple: Cells are equilibrated with a fluorescent solute, an individual cell is continuously irradiated by a laser beam focussed down to approximately the diameter of the cell, and fluorescence originating from the irradiated cell is monitored. In this procedure irradiation irreversibly photolyzes

M. Scholz; K. Schulten; R. Peters

1985-01-01

117

Radio Sources: 3.3mm Flux and Variability Measurements.  

National Technical Information Service (NTIS)

Graphical and tabular summaries of 3.3-mm (90-GHz) flux measurements of 35 discrete galactic and extragalactic sources are presented, including results of extensive monitoring of nine sources. Variability at 3.3-mm is certain for NGC 1068, NGC 1275, 3C120...

E. E. Epstein J. W. Montgomery M. M. Dworetsky W. G. Fogarty

1971-01-01

118

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

SciTech Connect

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.

Eklund, B. [Radian Corp., Austin, TX (United States)

1995-03-15

119

A Novel Detector for High Neutron Flux Measurements  

SciTech Connect

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

Singo, T. D.; Wyngaardt, S. M. [Department of Physics, University of Stellenbosch, Private bag X1, Matieland, Stellenbosch (South Africa); Papka, P. [Department of Physics, University of Stellenbosch, Private bag X1, Matieland, Stellenbosch (South Africa); Nuclear Physics group, iThemba labs, P. O. Box 722, Somerset West 7129 (South Africa); Dobson, R. T. [Department of Mechanical and Mechatronic Engineering, University of Stellenbosch, Private bag X1, Matieland, Stellenbosch (South Africa)

2010-01-05

120

Ecosystem photosynthesis inferred from measurements of carbonyl sulphide flux  

NASA Astrophysics Data System (ADS)

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.

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

2013-03-01

121

Surface Flux Measurements at King Sejong Station in West Antarctica  

NASA Astrophysics Data System (ADS)

The Antarctic Peninsula is important in terms of global warming research due to pronounced increase of air temperature over the last century. The first eddy covariance system was established and turbulent fluxes of heat, water vapor, CO2 and momentum have been measured at King Sejong Station (62 \\deg 13鱦S, 58 \\deg 47鱦W) located in the northern edge of the Antarctic Peninsula since December in 2002. Our objectives are to better understand the interactions between the Antarctic land surface and the atmosphere and to test the feasibility of the long-term operation of eddy covariance system under extreme weather conditions. Various lichens cover the study area and the dominant species is Usnea fasciata-Himantormia. Based on the analyses on turbulent statistics such as integral turbulence characteristics of vertical velocity (w) and heat (T), stationarity test and investigation of correlation coefficient, they follow the Monin-Obukhov similarity and eddy covariance flux data were reliable. About 50 % of total retrieved sensible heat flux data could be used for further analysis. We will report on seasonal variations of energy and mass fluxes and environmental variables. In addition, factors controlling these fluxes will be presented. Acknowledgement: This study was supported by 〉Environmental Monitoring on Human Impacts at the King Sejong Station, Antarctica︵ (Project PP04102 of Korea Polar Research Institute) and 〉Eco-technopia 21 project︵ (Ministry of Environment of Korea).

Choi, T.; Lee, B.; Lee, H.; Shim, J.

2004-12-01

122

Solar Flux Estimated from Electron Density and Ion Composition Measurements in the Lower Thermosphere.  

National Technical Information Service (NTIS)

Appropriate models of solar flux in X-rays and Extreme Ultra Violet (XEUV) bands are presented in the light of the present status of ion chemistry in the region 90 to 130 km and reliable measurements of reaction rates, electron density, and ion compositio...

P. Chakrabarty D. K. Chakrabarty A. K. Saha

1977-01-01

123

Maize Residue Decomposition Measurement Using Soil Surface Carbon Dioxide Fluxes and Natural Abundance of Carbon13  

Microsoft Academic Search

organic matter content and nutrient cycling. We hypothesized that mation obtained is mostly relevant to aboveground crop natural abundance 13 C analyses could be used with soil CO2 flux measurements to quantify the short-term decomposition rates of residues. The natural abundance of 13 C has also been maize (Zea mays L.) residues under undisturbed field conditions. For used to study

Philippe Rochette; Denis A. Angers; Lawrence B. Flanagan

1999-01-01

124

Connecting extracellular metabolomic measurements to intracellular flux states in yeast  

PubMed Central

Background Metabolomics has emerged as a powerful tool in the quantitative identification of physiological and disease-induced biological states. Extracellular metabolome or metabolic profiling data, in particular, can provide an insightful view of intracellular physiological states in a noninvasive manner. Results We used an updated genome-scale metabolic network model of Saccharomyces cerevisiae, iMM904, to investigate how changes in the extracellular metabolome can be used to study systemic changes in intracellular metabolic states. The iMM904 metabolic network was reconstructed based on an existing genome-scale network, iND750, and includes 904 genes and 1,412 reactions. The network model was first validated by comparing 2,888 in silico single-gene deletion strain growth phenotype predictions to published experimental data. Extracellular metabolome data measured in response to environmental and genetic perturbations of ammonium assimilation pathways was then integrated with the iMM904 network in the form of relative overflow secretion constraints and a flux sampling approach was used to characterize candidate flux distributions allowed by these constraints. Predicted intracellular flux changes were consistent with published measurements on intracellular metabolite levels and fluxes. Patterns of predicted intracellular flux changes could also be used to correctly identify the regions of the metabolic network that were perturbed. Conclusion Our results indicate that integrating quantitative extracellular metabolomic profiles in a constraint-based framework enables inferring changes in intracellular metabolic flux states. Similar methods could potentially be applied towards analyzing biofluid metabolome variations related to human physiological and disease states.

Mo, Monica L; Palsson, Bernhard ?; Herrgard, Markus J

2009-01-01

125

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

126

Biogenic silica fluxes and accumulation rates in the Gulf of California  

SciTech Connect

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

Thunell, R.C.; Pride, C.J.; Tappa, E. (Univ. of South Carolina, Columbia, SC (United States)); Muller-Karger, F.E. (Univ. of South Florida, St. Petersburg, FL (United States))

1994-04-01

127

A mobile detector for measurements of the atmospheric muon flux  

NASA Astrophysics Data System (ADS)

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

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

2011-04-01

128

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

SciTech Connect

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

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

1996-06-01

129

Upward shower rates at neutrino telescopes directly determine the neutrino flux  

SciTech Connect

We show that the rate for upward showers from an isotropic cosmic neutrino flux at neutrino telescopes like IceCube is independent of the neutrino-nucleon cross section. For bins that span a relatively narrow range in energy, neither scaling the cross section, nor changing its power-law energy behavior affects the upward shower rate, which depends only on the flux. The neutrino flux can be completely known since its spectral shape can be determined by comparing the rates in neighboring bins. We also show that the downward shower rate varies linearly with cross section with a proportionality constant determined by the energy dependence of the cross section, independent of the power-law behavior of the flux. The normalization and energy dependence of the cross section can be found by comparing the downward rates in neighboring bins.

Hussain, S. [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Marfatia, D.; McKay, D. W. [Department of Physics and Astronomy, University of Kansas, Lawrence, KS 66045 (United States)

2008-05-15

130

Hepatic, gut, and renal substrate flux rates in patients with hepatic cirrhosis.  

PubMed Central

The roles of liver, kidney, and gut in maintaining fuel homeostasis were studied in 28 patients with severe hepatic cirrhosis, 25 of whom had alcohol-induced cirrhosis. Hepatic, portal, and renal blood flow rates were measured and combined with substrate concentration differences across liver, gut, and kidney to calculate the net flux of free fatty acids, ketone bodies, triglycerides, and glucose with selected glucose precursors, including glycerol, lactate, pyruvate, and amino acids. Data from the catheterization studies were related to hepatic histology, glycogen content, and activities of gluconeogenic enzymes and compared with data obtained from control patients. The effects of food deprivation on net flux of fuels across the liver, gut, and kidney were assessed after overnight and after 3d of fasting. Activities of gluconeogenic enzymes were normal, but hepatic glycogen content was diminished in cirrhotic livers, probably as a consequence of extensive hepatic fibrosis. Extrahepatic splanchnic tissues (gut) had only a small influence on total splanchnic flux rates of carbohydrates, lipids and, amino acids. In cirrhotic patients, there was no mean renal glucose contribution to the bloodstream after an overnight or after a 3-d fast. After an overnight fast hepatic glucose production in patients with cirrhosis was diminished as a result of low-rate glycogenolysis. Hepatic gluconeogenesis and ketogenesis were increased. This pattern of hepatic metabolism mimics that seen in "normal" patients after more advanced stages of starvation. After 3 d of starvation, patients with hepatic cirrhosis have hepatic gluconeogenic and ketogenic profiles comparable to those of normal patients undergoing starvation of similar duration. Nevertheless, the total number of caloric equivalents derived from ketone bodies plus glucose corrected for recycled lactate and pyruvate added to the bloodstream by the cirrhotic livers that could be terminally oxidized by peripheral tissues was less than the contributions made by the normal livers, both after and overnight and after a 3-d fast.

Owen, O E; Reichle, F A; Mozzoli, M A; Kreulen, T; Patel, M S; Elfenbein, I B; Golsorkhi, M; Chang, K H; Rao, N S; Sue, H S; Boden, G

1981-01-01

131

Measurement of a surface heat flux and temperature  

NASA Astrophysics Data System (ADS)

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

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

1994-04-01

132

Measurement of the 8B Solar Neutrino Flux with KamLAND  

SciTech Connect

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

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

2011-06-04

133

Flux Control Analysis of the Rate of Photosynthetic CO 2 Assimilation  

Microsoft Academic Search

Metabolic flux control analysis offers an opportunity to understand how fluxes are determined and thus how they can be increased.\\u000a Enzymes are assigned a control coefficient (usually between zero and one) which is a measure of the degree to which the flux\\u000a is sensitive to small changes in enzyme concentration. This chapter examines research on the application of control analysis

Ian E. Woodrow

134

Measurements of the thermal neutrons flux near the EAS core  

NASA Astrophysics Data System (ADS)

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.

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

2013-02-01

135

Estimating terrestrial uranium and thorium by antineutrino flux measurements.  

PubMed

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

Dye, Stephen T; Guillian, Eugene H

2008-01-02

136

MARIE Dose and Flux Measurements in Mars Orbit  

NASA Astrophysics Data System (ADS)

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

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

137

DIRECT MEASUREMENT OF HEAT FLUX FROM COOLING LAKE THERMAL IMAGERY  

SciTech Connect

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.

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

2007-12-19

138

Initial Tile Temperature and Heat Flux Measurements in NSTX  

NASA Astrophysics Data System (ADS)

Due to their compact nature, spherical tori are projected to experience higher peak heat flux than conventional aspect ratio tokamaks of comparable heating power. For NSTX, it has been predicted[1,2] that the peak heat flux in double-null divertor configuration could reach between 10-15 MW/m2, and single-null operation would result in even higher peak heat flux. To test these predictions and support physics operations, two infrared television cameras (Inframetrics 525) have been installed on NSTX to monitor real-time tile heating and surface heat flux. The data are analyzed in real-time with a frame grabber (IMAXX) and software, and these data are also archived on videotape for future analysis. The first set of measurements will focus on thermal emission from the RF antenna, the center stack, and divertor regions. Initial data and comparison with the earlier predictions will be presented. 1 R.Maingi, et. al., "Estimates of Scrape-Off Layer and Divertor Parameters in NSTX", Proc. 1996 Intl Workshop on the Spherical Torus, Abingdon, U.K., Dec. 4-6, 1996. 2 R. Maingi, et. al., "2-D Edge Plasma Transport Calculations for NSTX", Proc. 1997 Intl Workshop on the Spherical Torus, St. Petersburg, Russia, Sept. 3-5, 1997.

Maingi, Rajesh; Kugel, Henry; Roquemore, Lane; Lasnier, Charles; Johnson, Dave

1999-11-01

139

EISCAT observations of pump-enhanced plasma temperature and optical emission excitation rate as a function of power flux  

NASA Astrophysics Data System (ADS)

We analyze optical emissions and enhanced electron temperatures induced by high power HF radio waves as a function of power flux using the EISCAT heater with a range of effective radiated powers. The UHF radar was used to measure the electron temperatures and densities. The Digital All Sky Imager was used to record the 630.0 nm optical emission intensities. We quantify the HF flux loss due to self-absorption in the D-region (typically 3-11 dB) and refraction in the F-region to determine the flux which reaches the upper-hybrid resonance height. We find a quasi-linear relationship between the HF flux and both the temperature enhancement and the optical emission excitation rate with a threshold at 37.5 ?Wm-2. On average 70% of the HF flux at the upper-hybrid resonance height goes in to heating the electrons for fluxes above the threshold compared to 40% for fluxes below the threshold.

Bryers, C. J.; Kosch, M. J.; Senior, A.; Rietveld, M. T.; Yeoman, T. K.

2012-09-01

140

Radioastronomical measurement of ultrahigh-energy cosmic particle fluxes  

NASA Astrophysics Data System (ADS)

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

Filonenko, A. D.

2012-08-01

141

Impact of CO2 measurement bias on CarbonTracker surface flux estimates  

NASA Astrophysics Data System (ADS)

For over 20 years, atmospheric measurements of CO2 dry air mole fractions have been used to derive estimates of CO2 surface fluxes. Historically, only a few research laboratories made these measurements. Today, many laboratories are making CO2 observations using a variety of analysis techniques and, in some instances, using different calibration scales. As a result, the risk of biases in individual CO2 mole fraction records, or even in complete monitoring networks, has increased over the last decades. Ongoing experiments comparing independent, well-calibrated measurements of atmospheric CO2 show that biases can and do exist between measurement records. Biases in measurements create artificial spatial and temporal CO2 gradients, which are then interpreted by an inversion system, leading to erroneous flux estimates. Here we evaluate the impact of a constant bias introduced into the National Oceanic and Atmospheric Administration (NOAA) quasi-continuous measurement record at the Park Falls, Wisconsin (LEF), tall tower site on CarbonTracker flux estimates. We derive a linear relationship between the magnitude of the introduced bias at LEF and the CarbonTracker surface flux responses. Temperate North American net flux estimates are most sensitive to a bias at LEF in our CarbonTracker inversion, and its linear response rate is 68 Tg C yr-1 (10% of the estimated North American annual terrestrial uptake) for every 1 ppm of bias in the LEF record. This sensitivity increases when (1) measurement biases approached assumed model errors and (2) fewer other measurement records are available to anchor the flux estimates despite the presence of bias in one record. Flux estimate errors are also calculated beyond North America. For example, biospheric uptake in Europe and boreal Eurasia combined increases by 25 Tg C yr-1 per ppm CO2 to partially compensate for changes in the North American flux totals. These results illustrate the importance of well-calibrated, high-precision CO2 dry air mole fraction measurements, as well as the value of an effective strategy for detecting bias in measurements. This study stresses the need for a monitoring network with the necessary density to anchor regional, continental, and hemispheric fluxes more tightly and to lessen the impact of potentially undetected biases in observational networks operated by different national and international research programs.

Masarie, K. A.; P嬡ron, G.; Andrews, A.; Bruhwiler, L.; Conway, T. J.; Jacobson, A. R.; Miller, J. B.; Tans, P. P.; Worthy, D. E.; Peters, W.

2011-09-01

142

Grasland Stable Isotope Flux Measurements: Three Isotopomers of Carbon Dioxide Measured by QCL Spectroscopy  

Microsoft Academic Search

To improve our understanding of greenhouse gas dynamics of managed ecosystems such as grasslands, we not only need to investigate the effects of management (e.g., grass cuts) and weather events (e.g., rainy days) on carbon dioxide fluxes, but also need to increase the time resolution of our measurements. Thus, for the first time, we assessed respiration and assimilation fluxes with

M. J. Zeeman; B. Tuzson; W. Eugster; R. A. Werner; N. Buchmann; L. Emmenegger

2007-01-01

143

Ion fluxes across the pitcher walls of three Bornean Nepenthes pitcher plant species: flux rates and gland distribution patterns reflect nitrogen sequestration strategies  

PubMed Central

Nepenthes pitcher plant species differ in their prey capture strategies, prey capture rates, and pitcher longevity. In this study, it is investigated whether or not interspecific differences in nutrient sequestration strategy are reflected in the physiology and microstructure of the pitchers themselves. Using a non-invasive technique (MIFE), ion fluxes in pitchers of Nepenthes ampullaria Jack, Nepenthes bicalcarata Hook.f., and Nepenthes rafflesiana Jack were measured. Scanning electron microscopy was also used to characterize the distribution of glandular and other structures on the inner pitcher walls. The results demonstrate that nutrient sequestration strategy is indeed mirrored in pitcher physiology and microstructure. Species producing long-lived pitchers with low prey capture rates (N. ampullaria, N. bicalcarata) showed lower rates of NH4+ uptake than N. rafflesiana, a species producing short-lived pitchers with high capture rates. Crucially, species dependent upon aquatic commensals (N. ampullaria, N. bicalcarata) actively manipulated H+ fluxes to maintain less acid pitcher fluid than found in typical species; in addition, these species lacked the lunate cells and epicuticular waxes characteristic of typical insectivorous congeners. An unexpected finding was that ion fluxes occurred in the wax-covered, non-glandular zones in N. rafflesiana. The only candidates for active transport of aqueous ions in these zones appear to be the epidermal cells lying beneath the lunate cells, as these are the only sites not visibly coated with epicuticular waxes.

Moran, Jonathan A.; Hawkins, Barbara J.; Gowen, Brent E.; Robbins, Samantha L.

2010-01-01

144

A measurement of the neutrino-induced muon flux at the MACRO detector  

NASA Astrophysics Data System (ADS)

Data from the MACRO detector was utilized to perform a measurement of the neutrino-induced muon flux in the high energy range ~ 100 GeV. This measurement comprises a large sample (403.6 events after all fidelity cuts and background subtraction) from an exposure time of 4 years. This is contrasted with an expected event rate of 540 upward muons from a detailed Monte Carlo simulation of MACRO using as input the atmospheric neutrino flux of the Bartol group. This gives a ratio of 0.76 +/- 0.04(stat.) +/- 0.16(syst.) measured versus expected. Recent results from other experiments worldwide, most notably the Super-Kamioka collaboration in Japan, have exposed similar discrepancies in the measured versus expected fluxes of underground muons. A consistent explanation of these effects is that the neutrino flux undergoes flavor oscillations between source and detector. For simple two-flavor mixing, a mixing angle of sin2 2? ~ 1 and a mass-squared difference in the range 0.001 < ?m2 < 0.01 eV2 best fits the observed muon neutrino flux.

Hanson, Kael Dylan

2000-09-01

145

Initial assessment of multi-scale measures of C02 and H20flux in the Siberian taiga  

Microsoft Academic Search

We measured C02 and HzO fluxes between undis- turbed Larix gmelinii forest and the atmosphere at a remote Eastern Siberian site in July 1993. Scaled-up leaf-level porom- eter measurements agreed with those derived from the eddy correlation technique for the canopy fluxes of COz and HzO. Patch-scale measurements of ecosystem C02 exchange agreed in turn with regional CO2 exchange rates

D. Y. HOLLINGER; F. M. KELLIHER; E.-D. SCHULZE; N. N. VYGODSKAYA; A. VARLAGIN

146

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

Microsoft Academic Search

Nitrous oxide (N2O) 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 N2O detection. The N2O mixing ratio was sampled at a rate of 10 Hz synchronously with the three-dimensional wind data,

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

1995-01-01

147

ACTIVE: a program to calculate and plot reaction rates from ANISN calculated fluxes  

SciTech Connect

The ACTIVE code calculates spatial heating rates, tritium production rates, neutron reaction rates, and energy spectra from particle fluxes calculated by ANISN. ACTIVE has a variety of input options including the capability to plot all calculated spatial distributions. The code was primarily designed for use with fusion first wall/blanket systems, but could be applied to any one-dimensional problem.

Judd, J.L.

1981-12-01

148

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

SciTech Connect

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

Markham, J.R.; Smith, W.W.; Haigis, J.R. [Advanced Fuel Research, Inc., East Hartford, CT (United States)] [and others

1996-02-01

149

Corer-reactors for contaminant flux measurement in sediments.  

PubMed

Design details and operating instructions are provided for a sediment corer that can be converted into a reactor for the measurement of the fluxes of contaminants from sediments to overlying waters. The corer-reactor permits measurements, under controlled laboratory conditions, on intact, largely undisturbed sediment cores, without significantly perturbing the physical and chemical conditions found in the field. The design can be constructed in-house for around US dollar 240 (A dollar 400) (excluding motor and corer lid), making it a relatively inexpensive system. PMID:14535336

Jung, R F; Jones, D R; Batley, G E

150

Oxygen flux implications of observed nitrogen removal rates in subsurface-flow treatment wetlands.  

PubMed

Nitrification, an oxygen-requiring microbial process, is generally considered the rate-limiting step for N removal in subsurface-flow constructed wetlands treating organic wastewaters. We used a simplified model of sequential N transformations and sinks to infer required rates of oxygen supply at 5 stages along experimental wetland mesocosms supplied with four different organic wastewaters with contrasting ratios of COD: N and forms of N. Mass balances of water-borne organic, ammoniacal and nitrate N, and plant and sediment N uptake showed average net rates of N mineralisation ranging from 0.22-0.53 g m(-2) d(-1), nitrification 0.56-2.15 g m(-2) d(-1), denitrification 0.47-1.99 g m(-2) d(-1) (60-84% of measured N removal) and plant assimilation 0.28-0.47 g m(-2) d(-1). The nitrogenous oxygen demand (NOD) required to support the observed nitrification rates alone was high compared to expected fluxes from surficial and plant-mediated oxygen transfer. In the presence of high levels of degradable organic matter (COD removal rates up to 66 g m(-2) d(-1)), heterotrophs with significantly higher oxygen affinities and energy yields are expected to outcompete nitrifiers for available oxygen. Problems with commonly held assumptions on the nature of coupled nitrification-denitrification in treatment wetlands are discussed. PMID:14621164

Tanner, C C; Kadlec, R H

2003-01-01

151

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

NASA Astrophysics Data System (ADS)

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

Wittich, Peter

2000-12-01

152

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

SciTech Connect

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.

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

2003-05-20

153

Extraction of the atmospheric neutrino fluxes from experimental event rate data  

NASA Astrophysics Data System (ADS)

Precise knowledge of the atmospheric neutrino fluxes is a key ingredient in the interpretation of the results from any atmospheric neutrino experiment. In the standard atmospheric neutrino data analysis, these fluxes are theoretical inputs obtained from sophisticated numerical calculations. In this contribution, we present an alternative approach to the determination of the atmospheric neutrino fluxes based on the direct extraction from the experimental data on neutrino event rates. The extraction is achieved by means of a combination of artificial neural networks as interpolants and Monte Carlo methods.

Gonzalez-Garcia, M. C.; Maltoni, M.; Rojo, J.

2007-06-01

154

System having unmodulated flux locked loop for measuring magnetic fields  

DOEpatents

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.

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

2006-08-15

155

Accuracy of the relaxed eddy-accumulation technique, evaluated using CO2 flux measurements  

NASA Astrophysics Data System (ADS)

A system capable of measuring the fluxes of trace gases was developed. It is based on a simpler version of the eddy-accumulation technique (EA), known as the relaxed eddy-accumulation technique (REA). It accumulates air samples associated with updrafts and downdrafts at a constant flow rate in two containers for later analysis of the trace gas mean concentration. The flux integration is based on the durations of updraft and downdraft events, rather than on the vertical wind velocity ( W) as is the case for EA and eddy-correlation (EC) techniques. The flux, calculated by the REA technique, is equal to the difference in the mean concentration of the trace gas of interest between the upward and downward moving eddies, multiplied by the standard deviation of the vertical wind velocity and an empirical coefficient. CO2 fluxes measured for 162 half-hour periods over a soybean field by both EC and REA techniques showed excellent agreement (coefficient of determination, R 2=0.92). The slope (0.985) and the intercept (-0.042 mg m-2 s-1) were not significantly different from 1 and 0, respectively, at the 5% level; and the standard error of estimate was 0.074 mg m-2 s-1. It is also shown that the empirical coefficient can be calculated from either latent or sensible heat fluxes. A model describing the effect on this empirical coefficient of not sampling around W equal to zero is proposed.

Pattey, E.; Desjardins, R. L.; Rochette, P.

1993-12-01

156

Image migration: measured retrieval rates  

NASA Astrophysics Data System (ADS)

When the Indianapolis Veterans Affairs Medical Center changed Picture Archiving and Communication Systems (PACS) vendors, we chose to use "on demand" image migration as the more cost effective solution. The legacy PACS stores the image data on optical disks in multi-platter jukeboxes. The estimated size of the legacy image data is about 5 terabytes containing studies from ~1997 to ~2003. Both the legacy and the new PACS support a manual DICOM query/retrieve. We implemented workflow rules to determine when to fetch the relevant priors from the legacy PACS. When a patient presents for a new radiology study, we used the following rules to initiate the manual DICOM query/retrieve. For general radiography we retrieved the two most recent prior examinations and for the modalities MR and CT we retrieved the clinically relevant prior examinations. We monitored the number of studies retrieved each week for about a 12 month period. For our facility which performs about 70,000 radiology examinations per year, we observed an essentially constant retrieval rate of slightly less than 50 studies per week. Some explanations for what may be considered an anomalous result maybe related to the fact that we are a tertiary care facility and a teaching hospital.

Witt, Robert M.

2007-03-01

157

Wind tunnel measurements of pollutant turbulent fluxes in urban intersections  

NASA Astrophysics Data System (ADS)

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

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

2012-01-01

158

Atmospheric VOC Flux Measurements using PTR-MS  

NASA Astrophysics Data System (ADS)

The largest fraction of organic carbon in the atmosphere exists in form of volatile organic compounds (VOC). Highly time-resolved, quantitative measurements of VOC using Proton-transfer-reaction mass spectrometry (PTR-MS) have significantly helped to improve our understanding of the surface atmosphere exchange of VOC over the past decade. This presentation will focus on recent progress in constraining the exchange of VOC on the ecosystem and regional scale. The life cycle of organic carbon is ultimately controlled by emission and deposition processes at the surface. Uncertainties in budgets of VOC and potential ramifications for organic aerosol production in the atmosphere will be discussed based on a synthesis of direct VOC flux measurements performed in a range of different ecosystems. These direct flux measurements will be used to address some outstanding questions concerning (1) the amount of reactive biogenic organic aerosol precursors, (2) the magnitude of deposition processes and (3) the lifetime of reactive biogenic organic aerosol precursors in the atmosphere.

Karl, T.

2011-12-01

159

An analysis of the random error affecting CO2 fluxes measured by eddy covariance  

Microsoft Academic Search

This study focuses on random errors associated with eddy covariance flux measurements. This error is heteroscedastic, increases linearly with the flux magnitude and the error on CO2 flux decreases with increasing wind speed. As random errors accumulate in quadrature, they are less critical than systematic errors as far as flux sums are concerned. On the other hand it may affect

Q. Laffineur; B. Heinesch; M. Aubinet

2009-01-01

160

Performance measurements at the fast flux test facility  

SciTech Connect

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

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

1987-01-01

161

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

Microsoft Academic Search

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

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

2003-01-01

162

A STROBOSCOPIC DEVICE FOR MEASURING REVOLUTION RATES  

Microsoft Academic Search

An inexpensive device for measuring rotation rates can be made by mounting two paper discs on rotating axes. If the rate of one is known, the rate of the other can be determined by finding the ratio between the two speeds stroboscopically. One disc may be put in place of a record in a good phonograph. The rate of revolution

Benjamin Franklin Zuehl

1922-01-01

163

Grasland Stable Isotope Flux Measurements: Three Isotopomers of Carbon Dioxide Measured by QCL Spectroscopy  

NASA Astrophysics Data System (ADS)

To improve our understanding of greenhouse gas dynamics of managed ecosystems such as grasslands, we not only need to investigate the effects of management (e.g., grass cuts) and weather events (e.g., rainy days) on carbon dioxide fluxes, but also need to increase the time resolution of our measurements. Thus, for the first time, we assessed respiration and assimilation fluxes with high time resolution (5Hz) stable isotope measurements at an intensively managed farmland in Switzerland (Chamau, 400m ASL). Two different methods were used to quantify fluxes of carbon dioxide and associated fluxes of stable carbon isotopes: (1) the flux gradient method, and (2) the eddy covariance method. During a week long intensive measurement campaign, we (1) measured mixing ratios of carbon dioxide isotopomers (12C16O2, 12C16O18O, 13C16O2) with a Quantum Cascade Laser (QCL, Aerodyne Inc.) spectroscope and (2) collected air samples for isotope analyses (13C/12C) and (18O/16O) of carbon dioxide by Isotope Ratio Mass Spectrometry (IRMS, Finnigan) every two hours, concurrently along a height profile (z = 0.05; 0.10; 0.31; 2.15m). In the following week, the QCL setup was used for closed-path eddy covariance flux measurement of the carbon dioxide isotopomers, with the air inlet located next to an open-path Infra Red Gas Analyzers (IRGA, LiCor 7500) used simultaneously for carbon dioxide measurements. During this second week, an area of grass inside the footprint was cut and harvested after several days. The first results of in-field continuous QCL measurements of carbon dioxide mixing ratios and their stable isotopic ratios show good agreement with IRGA measurements and isotope analysis of flask samples by IRMS. Thus, QCL spectroscopy is a very promising tool for stable isotope flux investigations.

Zeeman, M. J.; Tuzson, B.; Eugster, W.; Werner, R. A.; Buchmann, N.; Emmenegger, L.

2007-12-01

164

Simultaneous coastal measurements of ozone deposition fluxes and iodine-mediated particle emission fluxes with subsequent CCN formation  

NASA Astrophysics Data System (ADS)

Here we present the first observations of simultaneous ozone deposition fluxes and ultrafine particle emission fluxes over an extensive infra-littoral zone. Fluxes were measured by the eddy covariance technique at the Station Biologique de Roscoff, on the coast of Brittany, north-west France. This site overlooks a very wide (3 km) littoral zone controlled by very deep tides (9.6 m) exposing extensive macroalgae beds available for significant iodine mediated photochemical production of ultrafine particles. The aspect at the Station Biologique de Roscoff provides an extensive and relatively flat, uniform fetch within which micrometeorological techniques may be utilized to study links between ozone deposition to macroalgae (and sea water) and ultrafine particle production. Ozone deposition to seawater at high tide was significantly slower (vd[O3]=0.3020.095 mm s-1) than low tidal deposition. A statistically significant difference in the deposition velocities to macroalgae at low tide was observed between night time (vd[O3]=1.000.10 mm s-1) and daytime (vd[O3]=2.050.16s-1) when ultrafine particle formation results in apparent particle emission. Very high emission fluxes of ultrafine particles were observed during daytime periods at low tides ranging from 50 000 particles cm-2 s-1 to greater than 200 000 particles cm-2 s-1 during some of the lowest tides. These emission fluxes exhibited a significant relationship with particle number concentrations comparable with previous observations at another location. Apparent particle growth rates were estimated to be in the range 17-150 nm h-1 for particles in the size range 3-10 nm. Under certain conditions, particle growth may be inferred to continue to greater than 120 nm over tens of hours; sizes at which they may readily behave as cloud condensation nuclei (CCN) under reasonable supersaturations that may be expected to pertain at the top of the marine boundary layer. These results link direct depositional loss and photochemical destruction of ozone to the formation of particles and hence CCN from macroalgal emissions at a coastal location.

Whitehead, J. D.; McFiggans, G.; Gallagher, M. W.; Flynn, M. J.

2009-09-01

165

Simultaneous coastal measurements of ozone deposition fluxes and iodine-mediated particle emission fluxes with subsequent CCN formation  

NASA Astrophysics Data System (ADS)

Here we present the first observations of simultaneous ozone deposition fluxes and ultrafine particle emission fluxes over an extensive infra-littoral zone. Fluxes were measured by the eddy covariance technique at the Station Biologique de Roscoff, on the coast of Brittany, north-west France. This site overlooks a very wide (3 km) littoral zone controlled by very deep tides (9.6 m) exposing extensive macroalgae beds available for significant iodine mediated photochemical production of ultrafine particles. The aspect at the Station Biologique de Roscoff provides an extensive and relatively flat, uniform fetch within which micrometeorological techniques may be utilized to study links between ozone deposition to macroalgae (and sea water) and ultrafine particle production. Ozone deposition to seawater at high tide was significantly slower (vd[O3]=0.3020.095 mm s-1) than low tidal deposition. A statistically significant difference in the deposition velocities to macroalgae at low tide was observed between night time (vd[O3]=1.000.10 mm s-1) and daytime (vd[O3]=2.050.16 mm s-1) when ultrafine particle formation results in apparent particle emission. Very high emission fluxes of ultrafine particles were observed during daytime periods at low tides ranging from 50 000 particles cm-2 s-1 to greater than 200 000 particles cm-2 s-1 during some of the lowest tides. These emission fluxes exhibited a significant relationship with particle number concentrations comparable with previous observations at another location. Apparent particle growth rates were estimated to be in the range 17-150 nm h-1 for particles in the size range 3-10 nm. Under certain conditions, particle growth may be inferred to continue to greater than 120 nm over tens of hours; sizes at which they may readily behave as cloud condensation nuclei (CCN) under reasonable supersaturations that may be expected to pertain at the top of the marine boundary layer. These results link direct depositional loss and photochemical destruction of ozone to the formation of particles and hence CCN from macroalgal emissions at a coastal location.

Whitehead, J. D.; McFiggans, G.; Gallagher, M. W.; Flynn, M. J.

2010-01-01

166

Measuring Star Formation Rates in Blue Galaxies.  

National Technical Information Service (NTIS)

The problems associated with measurements of star formation rates in galaxies are briefly reviewed, and specific models are presented for determinations of current star formation rates from H alpha and Far Infrared (FIR) luminosities. The models are appli...

J. S. Gallagher D. A. Hunter

1987-01-01

167

CO2 flux measurements in volcanic areas using the dynamic concentration method: Influence of soil permeability  

Microsoft Academic Search

In order to evaluate the influence of soil permeability on soil CO2 flux measurements performed with the dynamic concentration method, several tests were carried out using soils characterized by different permeability values and flow rates. A special device was assembled in the laboratory to create a one-dimensional gas flow through a soil of known permeability. Using the advective-diffusion theory, a

M. Camarda; S. Gurrieri; M. Valenza

2006-01-01

168

Heat flux measurements for use in physiological and clothing research  

NASA Astrophysics Data System (ADS)

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.

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

2013-07-01

169

O2-MAVS: An instrument for measuring oxygen flux  

Microsoft Academic Search

With the awareness that the surface ocean is becoming more acidic due to the uptake of anthropogenic CO2 and that the resulting decrease in carbonate ion concentration is contributing to a decline in the calcification rate of many organisms, there is a pressing need to develop methods that can easily and reliably measure the calcification rates of these organisms under

Wade R. McGillis; Chris Langdon; A. J. Williams; Brice Loose

2009-01-01

170

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)

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.

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

2005-12-01

171

Measurements of ozone vertical flux to ocean and forest  

NASA Astrophysics Data System (ADS)

Ozone flux has been measured from aircraft by the eddy correlation technique over the Gulf of Mexico, the north Pacific Ocean, and a Gulf Coast pine forest. Measurements over the Gulf were obtained in polluted air over relatively warm water, while the north Pacific observations were obtained in pristine air over relatively cold water with nearly neutral stratification. Values of the surface resistance to ozone were about 1800 s/m over both ocean surfaces and 50 s/m over the forest, with an accuracy within 15%. Photochemical production of ozone during midmorning with clear skies over the Gulf of Mexico was 0.2-0.3 ng/cu m per sec, which is an order of magnitude less than that observed over northeastern Colorado.

Lenschow, D. H.; Stankov, B. B.; Pearson, R., Jr.

1982-10-01

172

A capacitive probe with shaped probe bias for ion flux measurements in depositing plasmas.  

PubMed

The application of a pulse shaped biasing method implemented to a capacitive probe is described. This approach delivers an accurate and simple way to determine ion fluxes in diverse plasma mixtures. To prove the reliability of the method, the ion probe was used in a different configuration, namely, a planar Langmuir probe. In this configuration, the ion current was directly determined from the I-V characteristic and compared with the ion current measured with the pulse shaped ion probe. The results from both measurements are in excellent agreement. It is demonstrated that the capacitive probe is able to perform spatially resolved ion flux measurements under high deposition rate conditions (2-20 nm/s) in a remote expanding thermal plasma in Ar/NH(3)/SiH(4) mixture. PMID:19045910

Petcu, M C; Bronneberg, A C; Sarkar, A; Blauw, M A; Creatore, M; van de Sanden, M C M

2008-11-01

173

HANARO core channel flow-rate measurement.  

National Technical Information Service (NTIS)

HANARO core consists of 23 hexagonal flow tubes and 16 cylindrical flow tubes. To get the core flow distribution, we used 6 flow-rate measuring dummy fuel assemblies (instrumented dummy fuel assemblies). The differential pressures were measured and conver...

H. I. Kim H. T. Chae D. S. Im S. D. Kim

1996-01-01

174

Measurements of neutron fluxes in the LSM underground laboratory  

NASA Astrophysics Data System (ADS)

A good particle candidate for Cold Dark Matter (CDM) is the supersymmetric neutralino or more generally a weakly interacting massive particle (WIMP). The expected interaction rate of WIMPs with the detector medium in direct detection experiments is below 0.01 events/kg/day. This makes a good knowledge of the background conditions highly important, especially with ever increasing sensitivity of the detectors. One major component of the background is related to energetic neutrons induced by cosmic muons. However, the flux of low energy and thermal neutrons typically from spontaneous fission and (?, n) reactions in the rock surrounding underground experiments gives also valuable information about the overall environmental activity. Detailed studies carried out in the framework of the EDELWEISS experiment are presented.

Eitel, Klaus; Edelweiss Collaboration

2012-07-01

175

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

Microsoft Academic Search

Among the parameters affecting carbon transfer to the ocean interior, particle sinking rates vary three orders of magnitude and thus more than primary production, f-ratios, or particle carbon contents [e.g., Boyd, P.W., Trull, T.W., 2006. Understanding the export of marine biogenic particles: is there consensus? Progress in Oceanography 4, 276312, doi:10.1016\\/j.pocean.2006.10.007]. Very few data have been obtained from the mesopelagic

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

2008-01-01

176

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

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

177

Measurements for the JASPER Program Flux Monitor Experiment  

SciTech Connect

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

Muckenthaler, F.J.; Spencer, R.R.; Hunter, H.T.; Hull, J.L. [Oak Ridge National Lab., TN (United States); Shono, A. [Power Reactor and Nuclear Fuel Development Corp., Oarai, Ibaraki (Japan). Oarai Engineering Center

1993-02-01

178

Measurement of the Atmospheric ?e Flux in IceCube  

NASA Astrophysics Data System (ADS)

We report the first measurement of the atmospheric electron neutrino flux in the energy range between approximately 80 GeV and 6 TeV, using data recorded during the first year of operation of IceCubes DeepCore low-energy extension. Techniques to identify neutrinos interacting within the DeepCore volume and veto muons originating outside the detector are demonstrated. A sample of 1029 events is observed in 281 days of data, of which 49666(stat)88(syst) are estimated to be cascade events, including both electron neutrino and neutral current events. The rest of the sample includes residual backgrounds due to atmospheric muons and charged current interactions of atmospheric muon neutrinos. The flux of the atmospheric electron neutrinos is consistent with models of atmospheric neutrinos in this energy range. This constitutes the first observation of electron neutrinos and neutral current interactions in a very large volume neutrino telescope optimized for the TeV energy range.

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

2013-04-01

179

Improvements to measuring water flux in the vadose zone.  

PubMed

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

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

180

Ultrasonic measurement of solid propellant burning rate  

Microsoft Academic Search

Considering the inadequacy of current methods for measuring the burning rate of solid propellants, an ultrasonic device has been developed that measures the grain thickness at a rate up to 5000 Hz. Satisfactory results have been obtained on specimens up to 40 mm thick in steady or slowly varying conditions, such as erosive combustion. Composite, double base and autopyrolyzing propellants

P. Kuentzmann; J.-C. Demarais; F. Cauty

1979-01-01

181

Measurements of hydrocarbon airsurface exchange rates over maize  

Microsoft Academic Search

Vertical gradients of volatile organic compounds (VOCs) were measured over a maize (Zea mays) field, in its early growth period, during May 1995, in the Lower Coastal Plains of North Carolina. These measurements were combined with micrometeorological flux measurements to determine emission flux measurements for various VOCs. This measurement program was part of project NOVA (Natural emissions of Oxidant precursors:

M. Das; Daiwen Kanga; V. P. Aneja; W. Lonneman; D. R. Cook; M. L. Wesely

2003-01-01

182

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...

183

Sensitivity of shortwave radiative flux density, forcing, and heating rate to the aerosol vertical profile  

Microsoft Academic Search

The effect of the aerosol vertical distribution on the solar radiation profiles for idealized and measured profiles of extinction and single-scattering albedo (SSA) during the May 2003 Atmospheric Radiation Measurement Aerosol Intensive Observation Period (AIOP) is investigated using the rapid radiative transfer model shortwave code. Calculated profiles of downwelling and upwelling solar flux density during the AIOP are compared with

Hong Guan; Beat Schmid; Anthony Bucholtz; Robert Bergstrom

2010-01-01

184

Simulation of the eddy accumulation method for measuring pollutant fluxes  

SciTech Connect

A numerical simulation of the eddy accumulation technique for measuring pollutant fluxes has been used to test the sensitivity of the method to errors from various sources including sensor orientation, sampling limitations and chemical resolution. The tests were conducted using artificial pollutant concentration signals derived from actual meteorological data, in order to avoid the possibility of including unwanted errors by employing a poor quality pollutant signal. It is found that to detect a pollutant deposition velocity of 0.1 cm/sec it is necessary to maintain the linear sampling characteristics over a dynamic range corresponding to two orders of magnitude of vertical wind speed to maintain sampling zero offsets to less than 0.02 sigma of equivalent standard vertical velocity and to resolve chemical concentration differences amounting to about 0.4 percent in typical conditions. 5 references.

Hicks, B.B.; Mcmillen, R.T.

1984-04-01

185

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

National Technical Information Service (NTIS)

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 dis...

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

1983-01-01

186

Rates, Fluxes, and Cycling in the Earth System: What Do We Know, What Are We Teaching?  

Microsoft Academic Search

Earth system science provides exciting new insights into the dynamics of the Earth. This approach emphasizes a special focus on the processes, pathways, and interfaces across different subsystems; the transfer of mass and energy throughout the Earth system; and the influence of biota and humanity on Earth processes (AGU, 1997). Consequently, rates, fluxes and global cycling are all concepts that

D. W. Mogk; C. A. Manduca

2004-01-01

187

Studies on refractivity structure constant, eddy dissipation rate, and momentum flux at a tropical latitude  

Microsoft Academic Search

VHF and UHF Doppler radars provide a unique database to estimate the refractivity structure constant Cn2, eddy dissipation rate ?, and vertical flux of horizontal momentum. Using the data collected from the Indian MST radar, these parameters are studied at a tropical latitude. The refractivity turbulence structure constant is estimated from the backscattered power of the received echoes. Cn2 (radar)

D. Narayana Rao; P. Kishore; T. Narayana Rao; S. Vijaya Bhaskara Rao; K. Krishna Reddy; M. Yarraiah; M. Hareesh

1997-01-01

188

FFTF (Fast Flux Test Facility) Integrated Leak Rate Test Computer System  

Microsoft Academic Search

The Fast Flux Test Facility (FFTF) is a liquid-metal-cooled test reactor located on the Hanford Site. The FFTF is the only reactor of this type designed and operated with the intent of meeting the licensing requirements of the Nuclear Regulatory Commission (NRC). Unique characteristics of the FFTF that present special challenges related to leak rate testing include thin wall containment

Hubbard

1987-01-01

189

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

NASA Astrophysics Data System (ADS)

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

Neubauer, Mark Stephen

2001-11-01

190

Direct measurements of the helium photoionization rate from sounding rockets  

NASA Astrophysics Data System (ADS)

A method of directly measuring the absolute helium photoionization rate coefficient independent of detailed solar EUV spectra and photoionization cross sections has been demonstrated. Three such measurements were obtained using windowless rare-gas ionization cells operated in an optically thin mode. The cells were launched on Nike/Terrier boosted Black Brant sounding rockets from the White Sands Missile Range in 1983, 1989, and 1990. The rate coefficients were determined for altitudes from 150 to 330 km and were extrapolated to give values of 11.110-8s-1+/-11%, 21.310-8s-1+/-16%, and 13.210-8s-1+/-11% at the ``top'' of the Earth's atmosphere. The solar activity levels were characterized by absolute F10.7 values of 119, 172, and 142 (10-22Wm-2Hz-1), respectively. The top of the atmosphere solar EUV flux values inferred from the measured ionization rates were found to be consistent with absolute flux measurements obtained simultaneously with a neon ionization cell operated in the optically thick mode.

Ogawa, H. S.; Phillips, E.; Judge, D. L.

1997-06-01

191

A Cytochrome c Oxidase Model Catalyzes Oxygen to Water Reduction Under Rate-Limiting Electron Flux  

Microsoft Academic Search

We studied the selectivity of a functional model of cytochrome c oxidase's active site that mimics the coordination environment and relative locations of Fea3, CuB, and Tyr244. To control electron flux, we covalently attached this model and analogs lacking copper and phenol onto self-assembled monolayer-coated gold electrodes. When the electron transfer rate was made rate limiting, both copper and phenol

James P. Collman; Neal K. Devaraj; Richard A. Decr嶧u; Ying Yang; Yi-Long Yan; Wataru Ebina; Todd A. Eberspacher; Christopher E. D. Chidsey

2007-01-01

192

Ambrym Basaltic Volcano (Vanuatu Arc): Volatile Fluxes, Magma Degassing Rate and Chamber Depth  

NASA Astrophysics Data System (ADS)

Basaltic magma continuously erupts and degases during lava lake and/or Strombolian explosive activity at Marum and Benbow cones, the two active vents of Ambrym arc volcano in Vanuatu (800 m asl), generating a huge volcanic plume. Here we report the first complete budget for the volatile emissions of major, trace and radioactive species, as well as the first data for dissolved volatiles in the erupted basalt (Fo83-74 olivine-hosted melt inclusions, MIs), which allows us to assess the depth and degassing rate of the magma reservoir feeding Ambrym volcano. Real-time multi-gas measurements, coupled with lab analysis of filtered-pack plume samples, demonstrate that gas emissions from Marum and Benbow cones are uniform in their water content (90 mol%), SO2/HCl (5), SO2/HF (11) and trace metals/SO2 ratios but differ in their CO2/SO2 ratio (5.6 and 1.0, respectively), suggesting a deeper (CO2-enriched) gas derivation at Marum. Airborne measurements of SO2 flux (8000 tons/day) and the bulk plume CO2/SO2 ratio (3.7) verify that Marum cone produces 60% of the overall emissions, while Benbow only 40%. Ambrym ranks among the strongest volcanic emitters on Earth not only for SO2 (this work and a), but also for H2O, CO2, HCl, HF and HBr (2x105, 2x104, 800, 180 and 7 tons/day, respectively), for several volatile to mildly-volatile trace elements (Se, As, Sn, Tl, Cu, Pb, Rb, Cd, Ag) and for radioactive 210Po (~8.5% of the global volcanic flux). The aphyric nature of the basalt and the quite low dissolved wt% of H2O (?1.5), CO2 (?0.1) and S (?0.15) in MIs of Fo83-olivine point to shallow melt entrapment in a gas-rich magma reservoir emplaced at ~3.6 km depth beneath the caldera. This depth is in good agreement with inference from available VLPT-seismic data (b). The magma degassing rate - from 2.7x108 kg/d (based on S data) to 1.3x109 kg/d (using the Pbs output, melt content and vapour-melt partition coefficient) - largely exceeds the production of ash (~106 kg/d) and likely lava blocks, and indicates extensive separate gas flow across the shallow plumbing system of this basaltic volcano during its current (standard) stage of activity. (a) Bani et al., Bull. Volcanol., May 2009; (b) Legrand et al., Geophys. Res. Lett., 32, 2005.

Allard, P.; Aiuppa, A.; Bani, P.; Metrich, N.; Bertagnini, A.; Gauthier, P. G.; Parello, F.; Sawyer, G. M.; Shinohara, H.; Bagnato, E.; Mariet, C.; Garaebiti, E.; Pelletier, B.

2009-12-01

193

Effect on Autochamber Flux Measurements in an Ombrotrophic Peatland from Atmospheric Turbulence and Deployment Time  

NASA Astrophysics Data System (ADS)

Accurate quantification of soil-atmosphere gas exchange is essential for understanding the magnitude and controls of soil respiration as well as modelling the effects of various perturbations on soil carbon dynamics. We investigated the influence of atmospheric turbulence and chamber deployment time on CO2 and CH4 fluxes measured by closed, dynamic automatic chambers in the ombrotrophic Mer Bleue peatland near Ottawa, Canada. With a short deployment time of 2.5 minutes, autochamber CH4 flux exhibited a strong diurnal pattern that was highly and negatively correlated with friction velocity. We also found a significant, negative relationship between friction velocity and CO2 concentration gradient in the top 20 cm surface peat. This demonstrated a mass flow of gas from peat pore space to the atmosphere under highly turbulent conditions. Consequently, it is hypothesized that the transient low gas fluxes obtained could be due to insufficient time allowed for re-establishment of a diffusive concentration gradient with short duration deployment. On the other hand, the high CO2 and CH4 effluxes measured under calm conditions were possibly artefacts of chamber closure and headspace mixing by fans that enhanced near surface gas emissions when concentration gradients were large. Results of a test with a 30-minute deployment time showed that CO2 and CH4 efflux rates reached a constant rate after about 13 minutes of chamber closure. Methane fluxes calculated using the headspace concentration after this duration had no significant relationship with friction velocity and exhibited little diurnal variation. The above results suggest there is considerable potential bias in chamber flux measurements under both high and low turbulence conditions when sampling porous soils with a short deployment time. This bias is expected to be of particular concern in ecosystems with highly porous and aerated soils like those at Mer Bleue which has a relatively low water table (30 cm or more) and a peat soil with a porosity of more than 94% in the top 30 cm though we suspect it also exists to a lesser extent in other less porous soils. In these situations, the time required to reach a steady rate of increase in headspace concentration should be determined for each site to minimize bias in calculated fluxes.

Lai, D.; Roulet, N. T.; Dalva, M.; Humphreys, E. R.; Moore, T. R.

2010-12-01

194

The measurement of thermal neutron flux depression for determining the concentration of boron in blood.  

PubMed

Boron neutron capture therapy (BNCT) is a form of targeted radiotherapy that relies on the uptake of the capture element boron by the volume to be treated. The treatment procedure requires the measurement of boron in the patient's blood. The investigation of a simple and inexpensive method for determining the concentration of the capture element 10B in blood is described here. This method, neutron flux depression measurement, involves the determination of the flux depression of thermal neutrons as they pass through a boron-containing sample. It is shown via Monte Carlo calculations and experimental verification that, for a maximum count rate of 1 x 10(4) counts/s measured by the detector, a 10 ppm 10B sample of volume 20 ml can be measured with a statistical precision of 10% in 32 +/- 2 min. For a source activity of less than 1.11 x 10(11) Bq and a maximum count rate of less than 1 x 10(4) counts/s, a 10 ppm 10B sample of volume 20 ml can be measured with a statistical precision of 10% in 58 +/- 3 min. It has also been shown that this technique can be applied to the measurement of the concentration of any element with a high thermal neutron cross section such as 157Gd. PMID:11277219

Brooke, S L; Green, S; Charles, M W; Beddoe, A H

2001-03-01

195

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

SciTech Connect

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.

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

2001-09-19

196

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

SciTech Connect

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

West, Michael D.; Charles, Christine; Boswell, Rod W. [Space Plasma, Power and Propulsion Group, Research School of Physics and Engineering, Australian National University, Canberra ACT 0200 (Australia)

2009-05-15

197

A Summary of Mass Flux Measurements in Solid 4He  

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

198

How large is the subducted water flux? New constraints on mantle regassing rates  

NASA Astrophysics Data System (ADS)

Estimates of the subducted water (H2O) flux have been used to discuss the regassing of the mantle over Earth history. However, these estimates vary widely, and some are large enough to have reduced the volume of water in the global ocean by a factor of two over the Phanerozoic. In light of uncertainties in the hydration state of subducting slabs, magma production rates and mantle source water contents, we use a Monte Carlo simulation to set limits on long-term global water cycling and the return flux of water to the deep Earth. Estimates of magma production rates and water contents in primary magmas generated at ocean islands, mid-ocean ridges, arcs and back-arcs are paired with estimates of water entering trenches via subducting oceanic slab in order to construct a model of the deep Earth water cycle. The simulation is constrained by reconstructions of Phanerozoic sea level change, which suggest that ocean volume is near steady-state, though a sea level decrease of up to 360 m may be supported. We provide limits on the return flux of water to the deep Earth over the Phanerozoic corresponding to a near steady-state exosphere (0-100 meter sea level decrease) and a maximum sea level decrease of 360 m. For the near steady-state exosphere, the return flux is 1.4 - 2.0- 0.3+ 0.4 1013 mol/yr, corresponding to 2-3% serpentinization in 10 km of lithospheric mantle. The return flux that generates the maximum sea level decrease over the Phanerozoic is 3.5- 0.3+ 0.4 1013 mol/yr, corresponding to 5% serpentinization in 10 km of lithospheric mantle. Our estimates of the return flux of water to the mantle are up to 7 times lower than previously suggested. The imbalance between our estimates of the return flux and mantle output flux leads to a low rate of increase in bulk mantle water content of up to 24 ppm/Ga.

Parai, R.; Mukhopadhyay, S.

2012-02-01

199

``Designing Lagrangian experiments to measure regional-scale trace gas fluxes''  

NASA Astrophysics Data System (ADS)

Knowledge of trace gas fluxes at the land surface is essential for understanding the impact of human activities on the composition and radiative balance of the atmosphere. An ability to derive fluxes at the regional scale (on the order of 102-104 km2), at the scale of ecosystems and political borders, is crucial for policy and management responses. Lagrangian ("air mass-following") aircraft experiments have potential for providing direct estimates of regional-scale fluxes by measuring concentration changes in air parcels as they travel over the landscape. Successful Lagrangian experiments depend critically on forecasts of air parcel locations, rate of dispersion of air parcels, and proper assessment of forecast errors. We describe an operational tool to forecast air parcel locations and dispersion and to guide planning of flights for air mass-following experiments using aircraft. The tool consists of a particle dispersion model driven by mesoscale model forecasts from operational centers. The particle model simulates time-reversed motions of air parcels from specified locations, predicting the source regions which influence these locations. Forecast errors are incorporated into planning of Lagrangian experiments using statistics of wind errors derived by comparison with radiosonde data, as well as the model-to-model spread in forecast results. We illustrate the tool's application in a project designed to infer regional CO2 fluxesthe CO2 Budget and Rectification Airborne study, discuss errors in the forecasts, and outline future steps for further improvement of the tool.

Lin, J. C.; Gerbig, C.; Wofsy, S. C.; Chow, V. Y.; Gottlieb, E.; Daube, B. C.; Matross, D. M.

2007-07-01

200

Evapotranspiration fluxes over mixed vegetation areas measured from large aperture scintillometer  

Microsoft Academic Search

Routine measurement of spatially averaged surface fluxes of sensible heat (H) in river basins is now feasible. These fluxes, when combined with net radiation estimates, can be used to derive areally averaged actual evapotranspiration (ET). The scintillation method is shown to be promising method for estimating areally averaged sensible heat fluxes. The large aperture scintillometer (LAS) is an optical device

H. M. Hemakumara; Lalith Chandrapala; Arnold F. Moene

2003-01-01

201

In situ measurements of saltwater flux through tidal passes of Lake Pontchartrain estuary by Hurricanes Gustav and Ike in September 2008  

NASA Astrophysics Data System (ADS)

Storm surge induced saltwater flux through multiple inlets has never been documented. This article reports in situ measurements of saltwater flux through major tidal passes by two consecutive storm surges impacting Lake Pontchartrain estuary in Louisiana during the first two weeks in September 2008. The main peak of inward saltwater flux lasted for 1.9 days during the flood, followed by more than 8 days of outward salt flux. The salt flux rate reached close to 200 tons/sec through the northern channel and 16 tons/sec through the southern channel. Outward flux of salt during Gustav amounted to more than 16 million tons during the receding stage, more than twice of that measured for the flux into the lake. Apparently, overland inundation, which was not measured, caused this biased estimate of influx of salt. Hurricane Ike, however, did not cause such a dramatic difference in influx and outflux of salt.

Li, Chunyan; Weeks, Eddie; Rego, Joao L.

2009-10-01

202

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

NASA Astrophysics Data System (ADS)

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

Hinkelman, Laura M.

203

How representative are instantaneous evaporative fraction measurements of daytime fluxes?  

NASA Astrophysics Data System (ADS)

Sun-synchronous optical and thermal remote sensing is a promising technique to provide instantaneous ET (evapotranspiration) estimates during satellite overpass. The common approach to extrapolate the instantaneous estimates to values for daily or longer periods relies on the assumption that the EF (evaporative fraction, defined as the ratio of latent heat flux to surface available energy) remains nearly constant during daytime. However, there is still no consensus on the validity of the self-preservation of the EF. We use FLUXNET (a global network of eddy covariance stations) measurements to examine this self-preservation, and the conditions under which it can hold. It is found that the instantaneous EF could represent daytime EF under clear sky conditions, especially between 11:00 and 14:00 LT (local time) for all stations. However, the results show that the EF is more variable during cloudy sky conditions, so that an increase in cloud cover results in an increase in the variability of the EF during daytime.

Peng, J.; Borsche, M.; Liu, Y.; Loew, A.

2013-10-01

204

Wide Range Neutron Flux Measuring Channel for Aerospace Application  

NASA Astrophysics Data System (ADS)

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.

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

2008-01-01

205

How representative are instantaneous evaporative fraction measurements for daytime fluxes?  

NASA Astrophysics Data System (ADS)

Sun synchronous optical remote sensing is a promising technique to provide instantaneous ET (Evapotranspiration) estimates during satellite overpass. The common approach to extrapolate the instantaneous estimates to values for daily or longer periods relies on the assumption that the EF (Evaporative Fraction, defined as the ratio of latent heat flux to surface available energy) remains nearly constant during daytime. However, there is still no consensus on the validity of the self preservation of EF. We used FLUXNET (a global network of eddy covariance stations) measurements to examine this self preservation, and the conditions under which it can hold. It is found here that the instantaneous EF could represent daytime EF under clear-sky conditions especially between 11:00 and 14:00 LT for all the stations. However, the EF is more unstable during cloudy skies. The increase in cloud cover would result in the increase in the variability of EF during daytime. Future works will focus on the evaluation of this EF constant assumption using real remote sensing data over different surface and climate conditions.

Peng, J.; Borsche, M.; Liu, Y.; Loew, A.

2013-02-01

206

Ionized metal flux fraction measurements in HiPIMS discharges  

NASA Astrophysics Data System (ADS)

Using a biased quartz crystal microbalance in combination with a gridded electrode, the ionized metal flux fraction in a high power impulse magnetron sputtering (HiPIMS) discharge operated with a titanium target has been investigated. The average discharge power was controlled by varying three different parameters; initial target voltage, pulse width and pulse frequency. The average discharge power was varied from 0.3 to 1.3 kW and irrespective of the power control method used an associated decrease in the flux fraction (from 50% to 30%) was observed. The mechanisms responsible for this decrease in the time-averaged flux fraction of metal ions are discussed.

Poolcharuansin, P.; Bowes, M.; Petty, T. J.; Bradley, J. W.

2012-08-01

207

Effect of magnetic field strength on deposition rate and energy flux in a dc magnetron sputtering system  

SciTech Connect

Variations in the magnetic field strongly affect the plasma parameters in a magnetron sputtering system. This in turn affects the throughput as well as the energy flux to the substrate. The variation in the magnetic field in this study, for a dc magnetron process, is achieved by shifting the magnet assembly slightly away from the target. Measurements of the plasma parameters show that while the electron density at the substrate increases with decrease in magnetic field, the electron temperature decreases. The cooling of the electron temperature is consistent with results reported elsewhere. The deposition rate per input magnetron power is found to increase slightly with the decrease in magnetic field for the process conditions considered in this study. Results suggest that the energy flux to the substrate tends to show a general decrease with the shift in the magnet assembly.

Ekpe, Samuel D.; Jimenez, Francisco J.; Field, David J.; Davis, Martin J.; Dew, Steven K. [Department of Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta T6G 2V4 (Canada); NUCRYST Pharmaceuticals, 10102-114 st., Fort Saskatchewan, Alberta T8L 3W4 (Canada); Department of Electrical and Computer Engineering, University of Alberta, Edmonton, Alberta T6G 2V4 (Canada)

2009-11-15

208

Methane uptake in grassland soils: Concentration profiles, flux measurements, and modeling  

SciTech Connect

Aerobic soil uptake of atmospheric methane varies between 1-3 kg CH[sub 4][minus]C ha[sup [minus]1] y[sup [minus]1] across diverse ecosystems, and accounts for 5-10% or more of the total CH[sub 4] sink. The controls over these rates are unclear, but diffusion rates often appear limiting. We developed a diagenetic model to couple measurements of methane uptake rates with distribution of methane within the soil atmosphere and to predict zones of active microbial oxidation. Flux rates predicted from the model were higher than those measured using static chambers, but also indicated maximum CH[sub 4] uptake rates occurred in the 10-20 cm soil layer. Laboratory incubations confirmed that this zone was the most above CH[sub 4], oxidizing layer. We are evaluating two alternative hypotheses to explain why oxidation is faster in subsurface horizons: (1) higher soil moisture in this zone is more favorable than at the surface; and (2) rapid N mineralization in the surface soils may inhibit CH[sub 4] oxidation. If the subsurface maximum is typical of other ecosystems, it suggests that diffusion rates generally limit uptake rates and may thus explain the remarkably low variation of uptake rates observed within and among ecosystems.

Valentine, D.W. (Colorado State Univ., Fort Collins (United States)); Mosier, A.R.; Lober, R.W. (USDA-ARS, Fort Collins, CO (United States)); Doran, J.W. (USDA-ARS, Lincoln, NE (United States))

1993-06-01

209

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

National Technical Information Service (NTIS)

Cloud formation and its relation to climate change is the greatest weakness in current numerical climate models. Surface heat flux in some cases causes clouds to form and in other to dissipate and the differences between these cases are subtle enough to m...

W. Porch F. Barnes M. Buchwald W. Clements D. Cooper

1991-01-01

210

Airborne aerosol flux measurements with eddy correlation above the ocean in a coastal environment  

Microsoft Academic Search

This work is a first pilot study of particle eddy correlation flux measurements from an aircraft using a condensation particle counter. The study reports aerosol flux measurements from an airplane conducted at approximately 33m altitude above the ocean in the coastal region of Monterey Bay. The systematic and random uncertainties of such measurements are evaluated. Covariance was calculated for 200s

G. Buzorius; J. Kalogiros; V. Varutbangkul

2006-01-01

211

DECAY RATES, NITROGEN FLUXES, AND DECOMPOSER COMMUNITIES OF SINGLE AND MIXED-SPECIES FOLIAR LITTER1 V  

Microsoft Academic Search

Decomposition rates, N fluxes, and abundances of decomposer organisms were quantified in mixed-species litterbags (containing leaves of two or three of the following tree species: Acer rubrum, Cornus florida, and Quercus prinus) and in litterbags containing leaves of a single species. Data from single-species litterbags were used to generate predicted decay rates, N fluxes, and abundances of decomposer organisms for

JOHN M. BiAm; ROBERT W. PARMELEE; MICHAEL H. BEARE

212

Late Weichselian and Holocene sediment flux and sedimentation rates in Andfjord and V嶓sfjord, North Norway  

Microsoft Academic Search

Late Weichselian and Holocene sediment flux and sedimentation rates in a continental-shelf trough, Andfjord, and its inshore continuation, V嶓sfjord, North Norway, have been analysed. The study is based on sediment cores and high-resolution acoustic data. Andfjord was deglaciated between 14.6 and 13 14C kyr BP (17.5 and 15.6 calibrated (cal.) kyr BP), the V嶓sfjord basin before 12.5 14C kyr BP

Liv Plassen; Tore O. Vorren

2002-01-01

213

A Problem with Flux Chamber Measurements of Biogenic Sulfur Emissions.  

National Technical Information Service (NTIS)

Problems associated with identifying and quantifying factors that influence liquid-phase controlled evolution of hydrogen sulfide and organic sulfides through the air-water interface are briefly reviewed. It was found that at present flux chamber measurem...

D. R. Hitchcock

1979-01-01

214

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...

215

PHOTON FLUX DETERMINATION FOR A PRECISION MEASUREMENT OF THE NEUTRAL PION LIFETIME  

SciTech Connect

The Jefferson Lab Hall B PrimEx Collaboration is using tagged photons to perform a 1.4% level measurement of the absolute cross section for the photo-production of neutral pions in the Coulomb field of a nucleus as a test of Chiral Perturbation Theory. Such a high precision pushes the limits of the photon tagging technique in regards to the determination of the absolute photon flux. A multifaceted approach to this problem has included measuring the absolute tagging ratios with a Total Absorption Counter (TAC) as well as relative tagging ratios with a Pair Spectrometer (PS), and determining the rate of the tagging counters using multi-hit TDC s and a clock trigger. This enables the determination of the absolute tagged photon flux for the PrimEx experiment with uncertainty of ? 1.0%, which is unprecedented. In view of the stringent constraints on the required precision of the photon flux for this experiment, periodicmeasurements of the pair production cross section were perform

Teymurazyan, Aram

2007-12-01

216

Measurements of BVOC fluxes Above Mixed Hardwood Forest Canopy During the 2009 CABINEX Field Campaign  

NASA Astrophysics Data System (ADS)

Biological volatile organic compounds (BVOCs) such as isoprene and monoterpenes are emitted in large amounts from North American forests. Quantification of the flux of (BVOCs) is therefore critical in the evaluation of the impact of these compounds on the concentration of oxidants and on the production of secondary organic aerosol. A disjunct eddy accumulation (DEA) sampler system has been constructed for the measurement of BVOC fluxes. Unlike the traditional relaxed eddy accumulation (REA) and eddy covariance (EC) systems which measure continuously, the relatively new technique of disjunct sampling differs by taking short, separate samples. Ambient airflow is directed into cartridges containing sorbant materials at sampling rates proportional to the magnitude of the vertical wind. The cartridges are changed after a suitable accumulation period. Compounds accumulated on the cartridges can then be quantified by thermal desorption of the BVOCs into a gas chromatograph. Data presented will describe laboratory tests to validate the disjunct sampling procedure as well as the magnitude of fluxes of isoprene and monoterpenes from mixed hardwood forest at the University of Michigan Biological Station (Pellston, MI) during the 2009 CABINEX field campaign.

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

2010-12-01

217

Flux tubes in the solar wind from Cluster measurements  

NASA Astrophysics Data System (ADS)

Recent studies of solar wind turbulence suggest that tangential discontinuities in the interplanetary medium can introduce significant intermittency and these discontinuities may be a natural manifestation of flux-tube-like structures in the solar wind. Because the existence of these flux tubes can affect our understanding of the solar wind MHD turbulence, it is necessary that we verify their existence and are able to identify them individually. Using the magnetic field data from FGM instrument onboard Cluster spacecraft, we examine the existence of flux tubes in the solar wind. Cluster/FGM has a high time resolution of magnetic field data and the orbits of Cluster also traverse through various dynamic regions, including the solar wind, Earth's magnetosheath and magnetotail, making Cluster's dataset ideal for studying the differences between, for example, solar wind turbulence and those inside the magnetosphere (e.g. turbulence in plasma sheet). Using a recent data analysis by Li, [2007a,b], we show that flux tubes exist in the solar wind, but not inside Earth's magnetotial. The existence of flux-tube-like structures in the solar wind implies that current studies of solar wind MHD turbulence must be carefully re-examined because these flux tubes will inneviatablly cause intermittency and affect turbulence power spectrum.

Li, G.; Lee, E.; Parks, G.

2007-12-01

218

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

NASA Astrophysics Data System (ADS)

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.

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

2013-10-01

219

Ways of measuring rates of recurrent events.  

PubMed Central

Recurrent events are common in medical research, yet the best ways to measure their occurrence remain controversial. Moreover, the correct statistical techniques to compare the occurrence of such events across populations or treatment groups are not widely known. In both observational studies and randomised clinical trials one natural and intuitive measure of occurrence is the event rate, defined as the number of events (possibly including multiple events per person) divided by the total person-years of experience. This is often a more relevant and clinically interpretable measure of disease burden in a population than considering only the first event that occurs. Appropriate statistical tests to compare such event rates among treatment groups or populations require the recognition that some individuals may be especially likely to experience recurrent events. Straightforward approaches are available to account for this tendency in crude and stratified analyses. Recently developed regression models can appropriately examine the association of several variables with rates of recurrent events.

Glynn, R. J.; Buring, J. E.

1996-01-01

220

Lidar based particulate flux measurements of agricultural field operations  

NASA Astrophysics Data System (ADS)

Ground based remote sensing technologies such as scanning lidar systems (light detection and ranging) are increasingly being used to characterize ambient aerosols due to key advantages (i.e., wide area of regard (10 km2), fast response time, high spatial resolution (<10 m) and high sensitivity). Scanning lidar allows for 3D imaging of atmospheric motion and aerosol variability. Space Dynamics Laboratory at Utah State University, in conjunction with the USDA-ARS, has developed and successfully deployed a three-wavelength lidar system called Aglite to characterize particles in diverse settings. Aglite generates near real-time imagery of particle size distribution and size-segregated mass concentration in addition to the ability to calculate whole facility emission rates. Based on over nine years of field and laboratory experience, we present concentration and emission rate results from various measurements in military and civilian deployments.

Wojcik, Michael D.; Martin, Randal S.; Moore, Kori; Hatfield, Jerry L.; Prueger, John H.

2012-05-01

221

Measurement of total ion flux in vacuum Arc discharges  

SciTech Connect

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

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

2004-04-12

222

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

Microsoft Academic Search

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

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

1997-01-01

223

Effects of heat and water vapor transport on eddy covariance measurement of CO2 fluxes  

Microsoft Academic Search

Flux densities of carbon dioxide were measured over an arid, vegetation-free surface by eddy covariance techniques and by a heat budget-profile method, in which CO2 concentration gradients were specified in terms of mixing ratios. This method showed negligible fluxes of CO2, consistent with the bareness of the experimental site, whereas the eddy covariance measurements indicated large downward fluxes of CO2.

R. Leuning; O. T. Denmead; A. R. G. Lang; E. Ohtaki

1982-01-01

224

Optical measurement of temperature dissipation rates (TDR)  

Microsoft Academic Search

We present the results of a laboratory experiment in which the turbulent properties of fluid flow were measured using optical methods. As a source of turbulence we used a thermally isolated tank (0.3x0.3x0.3 m) which is capable of generating turbulent convective flow with a Rayleigh number of 10^9. The temperature dissipation rate (TDR) was measured optically by examining scattered light

Darek J. Bogucki; Robert Ecke; Andrzej Domaradzki; R. C. Truman

1999-01-01

225

Steam quality and flow rate measurement  

SciTech Connect

This patent describes a method for determining both the quality and quantity of steam containing both vapor and liquid being injected into a hydrocarbon bearing formation in a thermal recovery process. It comprises positioning a bladed rotating member attached to a motor-generator combination downhole adjacent the hydrocarbon formation; measuring the voltage generated by the rotation of the rotating member; positioning a network of bristles across the borehole to contact the wall of the borehole and intercept substantially all of the liquid flowing along the borehole wall; measuring the total drag force due to liquid and vapor flow as the bristles are lowered into the borehole; measuring the total drag force due to liquid and vapor flow as the bristles are withdrawn from the borehole; determining the vapor flow by comparing the measured voltage with predetermined voltage versus vapor flow rate for the rotating member motor/generator combination; and determining the quantity of liquid flowing along the wall of the borehole by utilizing the measured drag forces and predetermined drag force versus vapor flow rate and liquid flow rate measurements.

Wicks, M. III; Moore, B.B.

1992-03-10

226

[Volatile organic compounds (VOCs) emitted from wood furniture--estimation of emission rate by passive flux sampler].  

PubMed

The aim of this study was to evaluate aldehydes and other volatile organic compounds (VOCs) emission from furniture, which may cause hazardous influence on human being such as sick building/sick house syndrome. In this study, VOCs emitted from six kinds of wood furniture, including three set of dining tables and three beds, were analyzed by large chamber test method (JIS A 1911). Based on the emission rates of total VOCs (TVOC), the impacts on the indoor TVOC was estimated by the simulation model with volume of 20 m3 and ventilation frequency of 0.5 times/h. The estimated increment of formaldehyde were exceeded the guideline value (100 microg/m3) in one set of dining table and one bed. The estimated TVOC increment values were exceeded the provisional target value for indoor air (400 microg/m3) in two sets of dining tables and two beds. These results revealed that VOC emissions from wood furniture may influence significantly indoor air quality. Also, in this study, to establish the alternative method for large chamber test methods, emission rates from representative five areas of furniture unit were evaluated by passive sampling method using flux sampler and emission rate from full-sized furniture was predicted. Emission rates predicted by flux passive sampler were 10-106% (formaldehyde) and 8-141% (TVOC) of the data measured using large chamber test, respectively. PMID:22259847

Jinno, Hideto; Tanaka-Kagawa, Toshiko; Furuta, Mitsuko; Shibatsuji, Masayoshi; Nishimura, Tetsuji

2011-01-01

227

High Resolution Measurement of the Glycolytic Rate  

PubMed Central

The glycolytic rate is sensitive to physiological activity, hormones, stress, aging, and malignant transformation. Standard techniques to measure the glycolytic rate are based on radioactive isotopes, are not able to resolve single cells and have poor temporal resolution, limitations that hamper the study of energy metabolism in the brain and other organs. A new method is described in this article, which makes use of a recently developed FRET glucose nanosensor to measure the rate of glycolysis in single cells with high temporal resolution. Used in cultured astrocytes, the method showed for the first time that glycolysis can be activated within seconds by a combination of glutamate and K+, supporting a role for astrocytes in neurometabolic and neurovascular coupling in the brain. It was also possible to make a direct comparison of metabolism in neurons and astrocytes lying in close proximity, paving the way to a high-resolution characterization of brain energy metabolism. Single-cell glycolytic rates were also measured in fibroblasts, adipocytes, myoblasts, and tumor cells, showing higher rates for undifferentiated cells and significant metabolic heterogeneity within cell types. This method should facilitate the investigation of tissue metabolism at the single-cell level and is readily adaptable for high-throughput analysis.

Bittner, Carla X.; Loaiza, Anitsi; Ruminot, Ivan; Larenas, Valeria; Sotelo-Hitschfeld, Tamara; Gutierrez, Robin; Cordova, Alex; Valdebenito, Rocio; Frommer, Wolf B.; Barros, L. Felipe

2010-01-01

228

Studies on refractivity structure constant, eddy dissipation rate, and momentum flux at a tropical latitude  

NASA Astrophysics Data System (ADS)

VHF and UHF Doppler radars provide a unique database to estimate the refractivity structure constant Cn2, eddy dissipation rate ?, and vertical flux of horizontal momentum. Using the data collected from the Indian MST radar, these parameters are studied at a tropical latitude. The refractivity turbulence structure constant is estimated from the backscattered power of the received echoes. Cn2 (radar) and Cn2 (model), derived from radiosonde observations, are compared, and a fairly good agreement is seen. Diurnal and seasonal variations of Cn2 are also presented. The eddy dissipation rate is estimated from the radar echoes employing the power and spectral width methods. A fairly good agreement is seen between the two methods. Values of ? are found to vary from 10-6 to 10-3 m2 s-3 in a height range of 4-19 km. Cn2 and ? are observed to be minimum during a moderate jet stream wind of 50-60 m s-1. Vertical flux of horizonal momentum is computed using the symmetrical two-beam method. Significant fluxes of westward and northward momentum are observed, and the values lie in the range of -1 to +1 m2 s-2. The implied accelarations are also estimated. The results presented are largely consistent with the results available in the literature.

Rao, D. Narayana; Kishore, P.; Rao, T. Narayana; Rao, S. Vijaya Bhaskara; Reddy, K. Krishna; Yarraiah, M.; Hareesh, M.

1997-07-01

229

Systematic experiments on turbulent premixed Bunsen flames including turbulent flux measurements  

SciTech Connect

The existence of good experimental data for turbulent premixed flames is of interest for the development and validation of numerical models. In this paper special focus is laid on the systematic variation of either the fuel-air ratio with fixed flow rate or varied flow and turbulence with fixed composition. In total, 15 different turbulent Bunsen flames are investigated. With the planar conditioned particle image velocimetry (CPIV) technique, simultaneous access is given to the flow, turbulence, and flame position data, using PIV for flow and turbulence and the density jump at the instantaneous flame front for reaction progress variable and density. This allows the fast determination of a large amount of statistical data such as Reynolds- and Favre-averaged mean reaction progress and velocities, which are needed for the density-weighted sets of equations used in the numerical codes. Additionally, conditioned and unconditioned mean velocities and velocity fluctuations can be determined and the turbulent flux terms of the reaction progress variable can be measured directly. Thus, a comprehensive data set is presented, which can be used for validation studies. The measured turbulent flux is compared with two models, the gradient diffusion assumption and a relation proposed by Veynante et al. that accounts for the competition between gas-dynamic expansion and turbulent mixing. While the former approach fails, the latter shows reasonable agreement for the radial flux and also accounts for the trend observed for the varied flow or flame conditions. The axial turbulent flux near the tip of the flame is not fully resolved. (author)

Pfadler, Sebastian; Leipertz, Alfred [Erlangen Graduate School in Advanced Optical Technologies (SAOT) and Lehrstuhl fuer Technische Thermodynamik (LTT), Friedrich-Alexander Universitaet Erlangen-Nuernberg, Am Weichselgarten 8, 91058 Erlangen (Germany); Dinkelacker, Friedrich [Lehrstuhl fuer Thermodynamik und Verbrennung, Universitaet Siegen, Paul-Bonatz-Str. 9-11, 57068 Siegen (Germany)

2008-03-15

230

A calorimeter for measuring liquid evaporation rates  

Microsoft Academic Search

Describes a simple calorimetric procedure which allows the measurement of evaporation rates of liquids over a range of temperatures and hydrodynamic conditions. The method is rapid, its accuracy is about +or-3% and it may be used with small volumes of sample (100 mu l and less). Results obtained for a representative group of substances are presented.

C. A. Reading; A. Reiser

1977-01-01

231

Surface acoustic wave measurements of evaporation rate  

Microsoft Academic Search

Measurements of the surface acoustic wave (SAW) attenuation versus time have been performed in liquids with a relatively high evaporation rate (acetone, ethyl acetate, etc.). The linear dependence of the SAW attenuation versus time has been observed. The possibility of determining the unknown molecular mass of the liquid from the SAW attenuation versus time dependence is presented. The special experimental

Pavol Kotial

1996-01-01

232

Burning Rate Measurement of Solid Propellants  

Microsoft Academic Search

An improved technique for measuring the burning rate of experimental propellants is described. By using a thick -in. i.d. Lucite cylinder to hold the propellant grain, none of the usual inhibition problems are encountered. In addition, since the Lucite does not char on burning, the technique is ideally suited for high speed window bomb photography. Although this technique was developed

Lawrence Spenadel

1961-01-01

233

Continuous Measurement of Solid Propellant Burning Rates  

Microsoft Academic Search

An experimental system is presented for the direct and continuous measurement of the burning rates of solid rocket propellants under conditions closely approximating those of a solid rocket motor. The system involves a positioning type servomechanism which moves a sample of solid propellant within a two dimensional rocket motor such that the receding burning surface of the sample is maintained

J. R. Osborn; R. J. Burick; R. F. Panella

1966-01-01

234

Measurements and Phenomenological Modeling of Magnetic FluxBuildup in Spheromak Plasmas  

SciTech Connect

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

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

2007-12-14

235

Flux density measurements and peculiarities of radio emission of pulsars at 102 and 111 MHz  

Microsoft Academic Search

At present time more than 1000 pulsars are discovered. But flux density and energy measurements were basically obtained at frequencies 400, 610 and 1400 MHz. For detail consideration of pulsar spectra and its connection with pulsar parameters the multifrequency measurements of the flux densities in all radio waves are required. At frequency about 100 MHz maximum of radio emission is

O. I. Malov

2000-01-01

236

Eddy correlation measurements of the air\\/sea flux of dimethylsulfide over the North Pacific Ocean  

Microsoft Academic Search

Shipboard measurements of air\\/sea fluxes and sea surface concentrations of dimethylsulfide (DMS) were made over the tropical and midlatitude North Pacific Ocean. Atmospheric pressure chemical ionization mass spectrometry was used to measure DMS levels in ambient air and in air equilibrated with surface seawater drawn from a depth of 5 m. Air\\/sea fluxes were obtained using eddy covariance. Corrections and

C. A. Marandino; W. J. De Bruyn; S. D. Miller; E. S. Saltzman

2007-01-01

237

FLUX MEASUREMENTS OF OZONE AND NITRIC ACID AT COASTAL AND MID-CONTINENTAL SITES  

EPA Science Inventory

A system for measuring the turbulent fluxes of ozone, nitric acid, and other gases was operated at two sites in 1994. hese direct measurements of fluxes are for comparison with those calculated for National Dry Deposition Network sites using an inferential model approach. zone fl...

238

Study on methodology of LED's luminous flux measurement with integrating sphere  

Microsoft Academic Search

Errors are introduced when using traditional methods for measuring the total luminous flux of LEDs since an LED is quite different from traditional light sources in terms of physical size, flux level, spectrum and spatial distribution. This paper uses commercial lighting simulation software named Tracepro to simulate the self-absorption effect when using traditional integrating sphere methods to measure the total

Mu-Qing Liu; Xiao-Li Zhou; Wen-Yi Li; Yu-Yang Chen; Wan-Lu Zhang

2008-01-01

239

Growing season total gaseous mercury (TGM) flux measurements over an Acer rubrum L. stand  

Microsoft Academic Search

Relaxed eddy accumulation (REA) measurements of the total gaseous mercury (TGM) flux measurements were taken over a deciduous forest predominantly composed of Red Maple (Acer rubrum L.) during the growing season of 2004 and the second half of the growing season of 2005. The magnitudes of the flux estimates were in the range of published results from other micrometeorological mercury

Jesse O. Bash; David R. Miller

2009-01-01

240

Solar Actinic Flux Spectroradiometry: A Technique for Measuring Photolysis Frequencies in the Atmosphere  

Microsoft Academic Search

A spectroradiometer has been developed for direct measurement of the solar actinic UV flux (scalar intensity) and determination of photolysis frequencies in the atmosphere. The instrument is based on a scanning double monochromator with an entrance optic that exhibits an isotropic angular response over a solid angle of 2 sr. Actinic flux spectra are measured at a resolution of 1

Andreas Hofzumahaus; Alexander Kraus; Martin Meller

1999-01-01

241

Measurement of 8B Solar Neutrino Flux and Energy Spectrum at Super-Kamiokande  

Microsoft Academic Search

The latest Super-Kamiokande measurement of 8B solar neutrino flux and recoil electron energy spectrum are presented. The highlights of our results are the day vs night flux asymmetry, which differs from zero at the 1.3 sigma level, and the energy spectrum measurement, which shows no significant distortion compared to the BP98 standard solar model.

Gene Guillian

2001-01-01

242

What Do Magnetic Resonance-Based Measurements of Pi->ATP Flux Tell Us About Skeletal Muscle Metabolism?  

PubMed Central

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.

Kemp, Graham J.; Brindle, Kevin M.

2012-01-01

243

Turbulent heat flux to the ice shelf base: Microstructure measurements in the oceanic boundary layer  

NASA Astrophysics Data System (ADS)

Basal melting of Antarctic ice shelves plays an important role in ice sheet dynamics, as ice shelf loss allows the flow of inland glaciers to accelerate. Observed ice shelf thinning leads to suggestions of an increasing basal melt rate, yet given the inaccessibility of the ice shelf-ocean interface, the melt rate, vertical heat flux and processes that drive them are rarely quantified directly. Microstructure shear and conductivity observations from a tethered profiler were made beneath Larsen C Ice Shelf in December 2011 and repeated along with microstructure temperature beneath George VI Ice Shelf in January 2012. Such measurements at the ice-ocean interface within the cavity of an ice shelf are unprecedented. CTD and 3D current velocity measurements were also made at both sites, and radar measurements showed that the ice base was melting. Mean potential temperature in the upper ocean beneath Larsen C Ice Shelf was 77m C above the in situ freezing point. Eddy diffusivities immediately beneath the ice base of up to 10-4 m2s-1 were calculated from shear derived dissipation rates of turbulent kinetic energy between 10-9 and 10-7 Wkg-1. Associated mean heat flux of 0.7 Wm-2 leads to an underestimation of the observed melt rate by at least an order of magnitude. Sharp interfaces dividing mixed layers of O(4m) thickness were detected in both CTD and microstructure measurements within a thermohaline staircase beneath George VI Ice Shelf. Temperature differences of ~0.05 C occurred across the steps and temperature at the ice base was 2 C warmer than in situ freezing point. Stability calculations confirmed that this was a primarily double diffusive environment. Turbulent mixing was strong in some layers and weak in others, with shear and thermal variance-derived dissipation rates of turbulent kinetic energy varying between 10-10 (close to the shear probe noise limit) and 10-7 Wkg-1. Vertical diffusion of heat is thought to provide the primary contribution to vertical heat flux where turbulent mixing is weak. We use the first direct microstructure profiles taken through hot water-drilled access boreholes in these two different environments to gain insight into the processes involved in the transport of heat from the upper ocean to the ice shelf base.

Venables, Emily; Nicholls, Keith; Makinson, Keith

2013-04-01

244

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

NASA Astrophysics Data System (ADS)

As part of the MILAGRO field campaign in March 2006 we deployed a flux system in a busy district of Mexico City surrounded by congested avenues. The flux system consisted of a tall tower instrumented with fast-response sensors coupled with eddy covariance (EC) techniques to measure fluxes of volatile organic compounds (VOCs), CO2, CO, aerosols and energy. The measured fluxes represent direct measurements of emissions that include all major and minor emission sources from a typical residential and commercial district. In a previous study we demonstrated that the EC techniques are valuable tools to evaluate emissions inventories in urban areas, and understand better the atmospheric chemistry and the role that megacities play in global change. We measured fluxes of olefins using a Fast Olefin Sensor (FOS) and the EC technique, fluxes of aromatic and oxygenated VOCs by Proton Transfer Reaction-Mass Spectroscopy (PTR-MS) and the disjunct eddy covariance (DEC) technique, fluxes of CO2 and H2O with an open path Infrared Gas Analyzer (IRGA) and the EC technique, fluxes of CO using a modified gradient method and a commercial CO instrument, and fluxes of aerosols (organics, nitrates and sulfates) using an Aerodyne Aerosol Mass Spectrometer (AMS) and the EC technique. In addition we used a disjunct eddy accumulation (DEA) system to extend the number of VOCs. This system collected whole air samples as function of the direction of the vertical wind component, and the samples were analyzed on site using gas chromatography / flame ionization detection (GC-FID). We also measured fluxes of sensible and latent heat by EC and the radiation components with a net radiometer. Overall, these flux measurements confirm the results of our previous flux measurements in Mexico City in terms of the magnitude, composition, and distribution. We found that the urban surface is a net source of CO2 and VOCs. The diurnal patterns show clear anthropogenic signatures, with important contributions from vehicular traffic. The DEA results for individual hydrocarbons show that the alkane fluxes are considerably higher than alkene fluxes, which is consistent with ambient concentration measurements and with the emission inventory for Mexico City. CO fluxes, estimated from a modified gradient technique, were more than 10% of the measured CO2 fluxes (on a molar basis) which is much higher than is generally expected for combustion efficiencies in mobile and other sources. Investigation of this result is underway. The energy balance distribution and radiative parameters observed are similar to distributions and parameters reported for other urban sites.

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

2007-05-01

245

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

SciTech Connect

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

Abe, S.; Furuno, K.; Gando, A.; Gando, Y.; Ichimura, K.; Ikeda, H.; Kibe, Y.; Kimura, W.; Kishimoto, Y.; Minekawa, Y.; Mitsui, T.; Morikawa, T.; Nagai, N.; Nakajima, K.; Nakamura, M.; Narita, K.; Shimizu, I.; Shimizu, Y.; Shirai, J.; Suekane, F. [Research Center for Neutrino Science, Tohoku University, Sendai 980-8578 (Japan)

2011-09-15

246

Measuring the Rate of Lava Effusion by InSAR  

NASA Astrophysics Data System (ADS)

The rate at which lava emerges from a volcano is a fundamental property of the dynamics of the eruption. Intensive field measurements can capture this. However, for many, often cloud-covered, volcanoes with long-lived eruptions, spaceborne InSAR provides a potentially useful source of information. Repeated DEM creation at intervals allows the changing thickness of the lava flow field to be measured and incremental changes to calculate the volumetric lava flux rate. ERS data from (i) an andesitic lava dome eruption at Soufri re Hills, Montserrat , and (ii) a basaltic andesite lava flow-field at Arenal volcano, Costa Rica illustrate the method. There are two main limitations. Firstly, flowing or otherwise thermo- mechanically unstable surfaces that are active between interferogram pair acquisitions leads to decorrelation. This effect is particularly difficult on lava domes where the surface is extremely dynamic. Compound lava flow-fields are more tractable. Secondly, very slight motions on flows that have "stopped" can be confused with topography in repeat-pass interferograms. The InSAR-measured rate of lava effusion at Arenal fits well with rates calculated by other methods over the last 30 years. Radar systems best suited to this task should be L-band, have short orbit repeat intervals and moderate perpendicular baselines.

Wadge, G.

2004-06-01

247

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

SciTech Connect

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

Bakwin, P.S.; Wofsy, S.C.; Fan, Songmiao; Fitzjarrald, D.R. (Harvard Univ., Cambridge, MA (United States) New York State Univ., Albany (United States))

1992-10-01

248

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

USGS Publications Warehouse

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

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

2005-01-01

249

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

NASA Astrophysics Data System (ADS)

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.

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

2010-05-01

250

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

251

Airborne measurements of mass, momentum, and energy fluxes for the boardman-arm regional flux experiment-1991. Preliminary data release. Technical memo  

SciTech Connect

During 2 - 19 June 1991 the Atmospheric Turbulence and Diffusion Division of NOAA measured flux densities of mass, momentum, and energy from an airplane in support of DOE's Atmospheric Radiation Measurement (ARM) program. Over 507 horizontal flux transects were completed, along with 24 vertical atmospheric profiles, during the 93 flight hours. Flux transects passed over both irrigated farmland and steppe. The report describes the variation in wind, radiation, and surface temperature, along with exchange of mass (CO2, H2O, and O3), momentum, and energy as observed along the transects. Airborne measurements are compared with those from flux towers in wheat, corn, and steppe. In general, the measurements correspond well. The largest difference occurs at the steppe tower, with stronger heat fluxes reported by the tower. This discrepancy increases as heat flux increases. The cause may be a significant vertical flux divergence or an inconsistant specification of the mean state.

Crawford, T.L.; Dobosy, R.J.; Birdwell, K.R.

1993-04-01

252

Measuring strength at ultrahigh strain rates.  

SciTech Connect

The strain rate sensitivity of materials is measured through a combination of quasistatic, Hopkinson bar, and pressure-shear experiments. The pressure-shear technique has largely been limited to strain rates of order 1E6 1/s. Recent advances in laser and magnetically driven ramp loading have made it possible to achieve significantly higher rates, 1E5-1E8 1/s, under uniaxial strain compression. Strength in these experiments can be calculated by comparing the loading response to the hydrostatic (pressure-density) response of the material for the same density and temperature [Fowles, 1961]. This must be done accounting for the heating due to plastic work in the experiments. Experimental uniaxial strain data for aluminum for strain rates up to 1E8 1/s are examined and compared with existing data. The results are consistent with conventional views of the strain rate sensitivity of aluminum. However, when one considers the higher mean stress (pressure) present in the uniaxial strain experiments and, to a lesser extent, the pressure-shear experiments, one finds the material remains rate insensitive to about 1E7 1/s, two orders of magnitude higher than previously thought. Important caveats about determining strength in this manner will be discussed, and recommendations for future work will be made.

Vogler, Tracy John

2010-03-01

253

Advances in upscaling of eddy covariance measurements of carbon and water fluxes  

NASA Astrophysics Data System (ADS)

Eddy covariance flux towers provide continuous measurements of ecosystem-level net exchange of carbon, water, energy, and other trace gases between land surface and the atmosphere. The upscaling of flux observations from towers to broad regions provides a new and independent approach for quantifying these fluxes over regions, continents, or the globe. The seven contributions of this special section reflect the most recent advances in the upscaling of fluxes from towers to these broad regions. The section mainly stems from presentations at the recent North American Carbon Program (NACP), FLUXNET, and AGU meetings. These studies focus on different aspects of upscaling: (1) assessing the representativeness of flux networks; (2) upscaling fluxes from towers to broad spatial scales; (3) examining the magnitude, distribution, and interannual variability of fluxes over regions, continents, or the globe; and (4) evaluating the impacts of spatial heterogeneity and parameter variability on flux estimates. Collectively, this special issue provides a timely update on upscaling science and also generates gridded flux data that can be used for model evaluations. Future upscaling studies are expected to advance toward incorporating the impacts of disturbance on ecosystem carbon dynamics, quantifying uncertainties associated with gridded flux estimates, and comparing various upscaling methods and the resulting gridded flux fields.

Xiao, Jingfeng; Chen, Jiquan; Davis, Kenneth J.; Reichstein, Markus

2012-03-01

254

Daytime Chamber Measurements Miss Substantial Nighttime Methane Spikes Captured by Flux Tower  

NASA Astrophysics Data System (ADS)

Methane emissions from natural wetlands are estimated to range from 105 to 278 Tg per year, making wetlands the Earth's largest natural source of methane to the atmosphere. It is well established that methane production from a wetland varies spatially and temporally with parameters such as topography, soil temperature, and soil moisture content. Numerous studies on methane emission from wetlands have been performed using static chamber measurements. While this method measures methane emission directly from a known location, it may not capture spatial heterogeneity for the landscape of interest and the choice of chamber locations may lead to non-representative estimates of methane emissions. Furthermore, these emission estimates are limited in their temporal resolution due to the amount of time required to install and sample the chambers. Few studies have compared, from a wetland, both static chamber methane measurements and continuous measurements from a flux tower. In this work we analyzed methane emissions based on both techniques using data from the 1996 BOREAS project. The mean daytime methane emission rate from chamber measurements was greater than the mean from the tower, which suggests that a small number of chambers may be inadequate to describe spatial heterogeneity. Surprisingly, the nighttime methane emissions, measured with the flux tower, were often an order of magnitude greater than emissions recorded during the day by either method. Thus, the use of only daytime measurements would lead to a substantial underestimation of total methane emissions from the wetland. We will evaluate several potential explanations for heightened nighttime emissions and evaluate how this affects our efforts to reconcile static chamber measurements with ecosystem-wide estimates based on tower methods.

Godwin, C. M.; Markfort, C. D.; McNamara, P.

2011-12-01

255

Measuring light-emitting diodes with a scanner for radiant flux and colour characterization  

NASA Astrophysics Data System (ADS)

Due to the performance requirements of displays and lighting applications, there is a great need to measure the radiant flux and colour of light-emitting diodes (LEDs) simultaneously in a high throughput format. We evaluate the feasibility of obtaining reliable colour and radiant flux values of LEDs with a low-cost office flatbed document scanner under factory settings versus conventional measurements. Colour purity was evaluated against a spectrometer and a digital camera, while radiant flux was evaluated against photodiodes. Scanner colour rendition of red, green and yellow LEDs was of variable quality. The scanner showed better correlation to conventional radiant flux measurements, with linear least-squares agreement between 0.934 and 0.985. A scanner represents a low cost and high throughput means of evaluating LEDs with simultaneous measures of both electroluminescent flux and emission colour with operational time.

Naquin, Clint A.; Hasan, Omar A.; Liou, Wei-Ting; Lee, Roxanne R.; Halbert, Armand J.; Phung, Anthony T.; Liu, An-Ting; Bursa, Emin J.; Shen, Yulong; Taylor, David W.; Slinker, Jason D.

2013-05-01

256

In situ measurements of calcium carbonate dissolution rates in deep-sea sediments  

Microsoft Academic Search

Benthic fluxes of alkalinity, carbon dioxide, and oxygen have been measured using an in situ incubation chamber at three sites (MANOP Sites C and S and PACFLUX Site SC) in the central equatorial north Pacific. At two carbonate-rich sites (C and SC), a budget for oxygen, alkalinity, and TCO fluxes indicate a net CaCO dissolution rate of approximately 0.4 mmol

W. M. Berelson; D. E. Hammond; G. A. Cutter

1990-01-01

257

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

NASA Astrophysics Data System (ADS)

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

Obara, Shin'ya; Tanno, Itaru

258

Measured carbon dioxide emissions from Oldoinyo Lengai and the skewed distribution of passive volcanic fluxes  

Microsoft Academic Search

Airborne measurements of CO2 released from Oldoinyo Lengai, the only carbonatite-erupting volcano in the world, reveal a CO2 flux of 0.055 1012 mol\\/yr. This flux is substantially smaller than that of Mount Etna (1 1012 mol\\/yr), which accounts for over half of the global carbon flux attributed to subaerial volcanoes (1 2 1012 mol\\/yr). We propose that

Susan L. Brantley; Kevin W. Koepenick

1995-01-01

259

Accurate Measurement of Glomerular Filtration Rate  

Microsoft Academic Search

\\u000a Measurement of the glomerular filtration rate (GFR) in patients with chronic renal disease has recently assumed increasing\\u000a importance. Responsibility for this evolutionary change can be directly traced to our understanding of the limitations of\\u000a plasma creatinine and creatinine clearance as markers of GFR (1,2) and the need for accurate and precise quantitation of GFR as potential therapies for progressive renal

Jeffrey G. Mulhern; Ronald D. Perrone

260

Ultrasonic rate measurement of multiphase flow  

SciTech Connect

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

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

1993-01-01

261

Measuring radiative capture rates at DRAGON  

NASA Astrophysics Data System (ADS)

The DRAGON recoil separator facility is located at the ISAC facility at TRIUMF, Vancouver. It is designed to measure radiative alpha and proton capture reactions of astrophysical importance in inverse kinematics. The Supernanogan ion source at ISAC provides stable beams of high intensities. The DRAGON collaboration has taken advantage of this over the last years by measuring several reactions requiring high-intensity stable oxygen beams. In particular,the ^17O(p,?) and ^16O(?,?) reaction rates were recently measured. The former reaction is part of the hot CNO cycle, and strongly influences the abundance of ^18F in classical novae. Because of its relatively long lifetime, ^18F is a possible target for satellite-based gamma-ray spectroscopy. The ^16O(?,?) reaction plays a role in steady-state helium burning in massive stars, where it follows the ^12C(?,?) reaction. At astrophysically relevant energies, the reaction proceeds exclusively via direct capture, resulting in a low rate. In both cases, the unique capabilities of DRAGON enabled determination not only of the total reaction rates, but also of decay branching ratios. Results from both experiments will be presented.

Hager, U.; Davids, B.; Fallis, J.; Greife, U.; Hutcheon, D. A.; Rojas, A.; Ruiz, C.

2013-04-01

262

Ultrasonic rate measurement of multiphase flow  

NASA Astrophysics Data System (ADS)

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

Dannert, David A.; Horne, Roland N.

1993-01-01

263

Evaluation of a closed tunnel for field scale measurements of N2O fluxes at the soil-atmosphere interface  

NASA Astrophysics Data System (ADS)

Measuring N2O emissions from soils is challenging as they are notoriously variable in space and time. A vast majority of measurements to quantify N2O emissions are conducted using chamber techniques. Since chambers usually cover a rather small surface area (<1 m2), the method has its limitations, particularly in tackling the spatial variability of N2O emissions with reasonable effort. Alternatively, micrometeorological methods like flux-gradient and eddy covariance (EC) techniques are increasingly applied to measure N2O fluxes at an ecosystem level. However, uncertainties remain since those methods are affected by the stability of the atmosphere and limited to detect small emission rates precisely. Therefore, we tested and evaluated the applicability of a closed measuring tunnel to upscale N2O fluxes from a fallow field applying open-path FTIR spectroscopy for N2O concentration measurements. The tunnel covered an area of about 500 m2 and is particularly appropriate for stable atmospheric conditions. Hence, we hypothesized that the tunnel is a potentially gap-filling method between chamber and micrometeorological techniques, since it provides the possibility to integrate N2O fluxes over the field scale but also enables reliable measurements during calm meteorological conditions. The N2O fluxes obtained by the tunnel were compared with simultaneous closed chamber based measurements at the same plot where each chamber covered an area of 0.045 m2. To calculate N2O fluxes from the change of N2O concentrations during deployment, we used three non-linear approaches and compared as well as assessed their suitability for our measuring devices. Two of these approaches, the recently published NDFE (Livingston et al., 2006) and HMR (Pedersen et al., 2010), were only shown to be suitable for classical closed chambers. Hence, we further aimed to calculate N2O fluxes by inverse modelling which takes into account the specific geometry of the measuring tunnel and the static conditions in the tunnel atmosphere during deployment. Among the three approaches, the inverse modelling approach was shown to be most appropriate for the calculation of N2O fluxes at the soil-atmosphere interface. Consequently, we concluded that an up-scaling of N2O fluxes using a measuring tunnel provides reliable results. During a two-year campaign the chamber measurements showed a tremendous spatial and temporal variation of N2O emissions including an uptake of N2O. This finding is in agreement with a huge number of studies on N2O emissions from soils. On the other hand, the simultaneous field scale tunnel measurements were substantially less variable in time. No N2O uptake was measured, and the tunnel N2O fluxes were considerably lower than small scale chamber fluxes. Obviously, sporadic very high N2O fluxes at hot spots caused the overestimation of N2O fluxes up-scaled from the chamber measurements.

Sch輎er, K.; B飆tcher, J.; Weymann, D.; von der Heide, C.; Duijnisveld, W.

2011-12-01

264

Measuring the energy flux at the substrate position during magnetron sputter deposition processes  

NASA Astrophysics Data System (ADS)

In this work, the energetic conditions at the substrate were investigated in dc magnetron sputtering (DCMS), pulsed dc magnetron sputtering (pDCMS), and high power impulse magnetron sputtering (HiPIMS) discharges by means of an energy flux diagnostic based on a thermopile sensor, the probe being set at the substrate position. Measurements were performed in front of a titanium target for a highly unbalanced magnetic field configuration. The average power was always kept to 400 W and the probe was at the floating potential. Variation of the energy flux against the pulse peak power in HiPIMS was first investigated. It was demonstrated that the energy per deposited titanium atom is the highest for short pulses (5 ?s) high pulse peak power (39 kW), as in this case, the ion production is efficient and the deposition rate is reduced by self-sputtering. As the argon pressure is increased, the energy deposition is reduced as the probability of scattering in the gas phase is increased. In the case of the HiPIMS discharge run at moderate peak power density (10 kW), the energy per deposited atom was found to be lower than the one measured for DCMS and pDCMS discharges. In these conditions, the HiPIMS discharge could be characterized as soft and close to a pulsed DCMS discharge run at very low duty cycle. For the sake of comparison, measurements were also carried out in DCMS mode with a balanced magnetron cathode, in the same working conditions of pressure and power. The energy flux at the substrate is significantly increased as the discharge is generated in an unbalanced field.

Cormier, P.-A.; Balhamri, A.; Thomann, A.-L.; Dussart, R.; Semmar, N.; Mathias, J.; Snyders, R.; Konstantinidis, S.

2013-01-01

265

Improved radon-flux-measurement system for uranium-tailings pile measurement  

SciTech Connect

The Pacific Northwest Laboratory (PNL) is developing cover technology for uranium mill tailings that will inhibit the diffusion of radon to the atmosphere. As part of this cover program, an improved radon flux measurement system has been developed. The radon measurement system is a recirculating, pressure-balanced, flow-through system that uses activated carbon at ambient temperatures to collect the radon. With the system, an area of 0.93 m/sup 2/ is sampled for periods ranging from 1 to 12 h. The activated carbon is removed from the radon trap and the collected radon is determined by counting the /sup 214/Bi daughter product. Development of the system included studies to determine the efficiency of activated carbon, relative calibration measurements and field measurements made during 1980 at the inactive tailings pile in Grand Junction, Colorado. Results of these studies are presented.

Freeman, H.D.

1981-10-01

266

Surface turbulent flux measurements over the Loess Plateau for a semi-arid climate change study  

NASA Astrophysics Data System (ADS)

In order to provide high quality data for climate change studies, the data quality of turbulent flux measurements at the station of SACOL (Semi-Arid Climate & Environment Observatory of Lanzhou University), which is located on a semi-arid grassland over the Loess Plateau in China, has been analyzed in detail. The effects of different procedures of the flux corrections on CO2, momentum, and latent and sensible heat fluxes were assessed. The result showed that coordinate rotation has a great influence on the momentum flux but little on scalar fluxes. For coordinate rotation using the planar fit method, different regression planes should be determined for different wind direction sectors due to the heterogeneous nature of the ground surface. Sonic temperature correction decreased the sensible heat flux by about 9%, while WPL correction (correction for density fluctuations) increased the latent heat flux by about 10%. WPL correction is also particularly important for CO2 fluxes. Other procedures of flux corrections, such as the time delay correction and frequency response correction, do not significantly influence the turbulent fluxes. Furthermore, quality tests on stationarity and turbulence development conditions were discussed. Parameterizations of integral turbulent characteristics (ITC) were tested and a specific parameterization scheme was provided for SACOL. The ITC test on turbulence development conditions was suggested to be applied only for the vertical velocity. The combined results of the quality tests showed that about 62%-65% of the total data were of high quality for the latent heat flux and CO2 flux, and as much as about 76% for the sensible heat flux. For the momentum flux, however, only about 35% of the data were of high quality.

Zuo, Jinqing; Huang, Jianping; Wang, Jiemin; Zhang, Wu; Bi, Jianrong; Wang, Guoyin; Li, Weijing; Fu, Peijian

2009-07-01

267

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

USGS Publications Warehouse

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

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

1998-01-01

268

Contribution of Soil Surface CO2 Efflux to Boreal Forest Net Ecosystem Flux: Measurements and Modeling  

NASA Astrophysics Data System (ADS)

The aims of the study are to assess the contribution of measured soil surface CO2 efflux to boreal forest net ecosystem flux and to test whether modeled component fluxes such as leaf and surface soil fluxes are consistent with the net flux measured from a tower over a forest stand. Net ecosystem flux was measured continuously in a boreal Scots pine forest in eastern Finland (62 52'N, 30 49'E) during the growing period in 2000. Height and diameter of trees in this 50-year-old stand ranged from 10 to 13 m and from 9 to 12 cm, respectively, for 80 % of trees. Eddy-flux measurements were made at the top of a 32-m tower, about 20 m above the canopy. Wind velocity and virtual temperature were measured with a three-axis sonic anemometer. CO2 fluctuations at 32 m were continuously monitored with a CO2 analyzer. Raw data were sampled at 10 Hz and 1/2 hr fluxes calculated. Soil surface CO2 efflux was measured on the top of a feather moss or lichen cover with an IRGA and four automated open dynamic chambers, each equipped with a PAR sensor and air temperature probe. Chambers of 19 cm diameter were made of transparent PMMA. Measurements were made twice per hr, lasting 1 min each. Periods considered in this study included both early and late season conditions, since data from the automated soil surface efflux measurements were available from May to June as well as from August to September. In this study, we aim to compare the measured soil surface CO2 efflux with simultaneously measured net ecosystem flux. The performance of the automated chambers will be tested by comparing with simultaneous measurements from a dark closed static chamber at the same site. A simple regression model, using soil surface temperature as an independent variable, will be built using the static dark chamber data from the previous years. A rough correction for the carbon uptake of moss will be made. This model could be validated later with automated measurements. To investigate further the components of the net ecosystem flux, we are planning to use a process-based model on forest ecosystem functioning to estimate flux from the canopy. Canopy structure will be described in the model using results from needle mass sampling in the same stand. The physiological responses of shoots to environmental factors such as light, temperature, and soil moisture are derived from measurements or estimates made at the site or from studies on Scots pine at a nearby site. These modeled component fluxes from tree canopies and soil surface will be compared with the measured net ecosystem flux for the sample periods.

Niinisto, S. M.; Kellomaki, S.

2001-05-01

269

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

SciTech Connect

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}.

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

270

Measurement of the cosmic ray and neutrino-induced muon flux at the Sudbury neutrino observatory  

SciTech Connect

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 unoscillated portion of the neutrino flux. A total of 514 muonlike events are measured between -1{<=}cos{theta}{sub zenith}{<=}0.4 in a total exposure of 2.30x10{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))x10{sup -10} {mu}/s/cm{sup 2}.

Aharmim, B.; Farine, J.; Fleurot, F.; Hallman, E. D.; Krueger, A.; Luoma, S.; Schwendener, M. H.; Virtue, C. J. [Department of Physics and Astronomy, Laurentian University, Sudbury, Ontario P3E 2C6 (Canada); Ahmed, S. N.; Cai, B.; Chen, M.; Evans, H. C.; Ewan, G. T.; Guillian, E.; Harvey, P. J.; Kos, M.; Kraus, C.; Leslie, J. R.; MacLellan, R.; Mak, H. B. [Department of Physics, Queen's University, Kingston, Ontario K7L 3N6 (Canada)] (and others)

2009-07-01

271

Measurement of the cosmic ray and neutrino-induced muon flux at the Sudbury neutrino observatory  

NASA Astrophysics Data System (ADS)

Results are reported on the measurement of the atmospheric neutrino-induced muon flux at a depth of 2 kilometers below the Earths 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 unoscillated portion of the neutrino flux. A total of 514 muonlike events are measured between -1?cos??zenith?0.4 in a total exposure of 2.301014cm2s. The measured flux normalization is 1.220.09 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??zenith>0.4 is measured to be (3.310.01(stat)0.09(sys))10-10?/s/cm2.

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. T. M.; Graham, K.; Grant, D. R.; Guillian, E.; Habib, S.; Hahn, R. L.; Hallin, A. L.; Hallman, E. D.; Hargrove, C. K.; Harvey, P. J.; Hazama, R.; 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.; Krger, 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.; Gann, G. D. Orebi; 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.; Tei?, G.; Tolich, N.; Tsui, T.; van de Water, R. G.; Vandevender, B. A.; Virtue, C. J.; Waller, D.; Waltham, C. E.; Tseung, H. Wan Chan; 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.

2009-07-01

272

Direct Retrieval of Radiative Flux-Divergence and Radiative Forcing from Satellite Spectral Measurements.  

NASA Astrophysics Data System (ADS)

We explore the concept of a retrieval of the thermal infrared radiative flux divergence and cooling rate profile using top-of-atmosphere spectral radiance measurements and demonstrate that the retrieval of this quantity can be performed directly. We show that the inversion encountered in this problem is sensitive to the initial atmospheric state vector assumed a priori. However, the direct approach has specific advantageous in terms of accuracy and computational speed, as compared to the conventional indirect approach using the retrieved atmospheric state vector coupled with a line-by-line radiative transfer model in cooling rate calculations. Furthermore, we show that the spectrally-resolved radiative forcing at the tropopause can be derived directly from the retrieved flux-divergence profile. As a test case, we carried out retrieval in the strong cooling band associated with the 15 ?m band of CO2 employing the Atmospheric Infrared Sounder (AIRS, 2002-present) on board the Aqua satellite, along with validation campaign data and underflight Scanning High-Resolution Interferometer (S-HIS) zenith and nadir spectra taken aboard a high-altitude aircraft. Retrieval sensitivity analyses have been performed for AIRS and the Infrared Interferometer Sounder (IRIS-D, 1970-1971) instruments. It is anticipated that the large changes in stratospheric temperature and CO2 values between the two missions would lead to detectable changes in the CO2 radiative forcing at the tropopause so long as the IRIS-D instrument could be appropriately characterized.

Feldman, D.; Liou, K.; Yung, Y.; Tobin, D.; Berk, L.

2005-12-01

273

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

SciTech Connect

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.

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

2011-04-01

274

Measured and simulated nitrogen fluxes after field application of food-processing and municipal organic wastes.  

PubMed

The aims of this study were to (i) assess N fluxes (mineralization, volatilization, denitrification, leaching) caused by spreading various organic wastes from food-processing industries during a field experiment, and (ii) to identify the main factors affecting N transformation processes after field spreading. Experimental treatments including the spreading of six types of waste and a control soil were set up in August 2000 and studied for 22 mo under bare soil conditions. Ammonia and nitrous oxide emissions, and nitrogen mineralization were measured in experimental devices and extrapolated to field conditions or computed in calculation models. The ammonia emissions varied from 80 to 580 g kg(-1) NH4+-N applied, representing 0 to 90 g N kg(-1) total N applied. Under these meteorologically favorable conditions (dry and warm weather), waste pH was the main factor affecting volatilization rates. Cumulated N2O-N fluxes were estimated at 2 to 5 g kg(-1) total N applied, which was quite low due to the low soil water content during the experimental period; water-filled pore space (WFPS) was confirmed as the main factor affecting N2O fluxes. Nitrogen mineralization from wastes represented 126 to 723 g N kg(-1) organic N added from the incorporation date to 14 May 2001 and was not related to the organic C to organic N ratio of wastes. Nitrogen lost by leaching during the equivalent period ranged from 30 to 890 g kg(-1) total N applied. The highest values were obtained for wastes having the highest inorganic N content and mineralization rates. PMID:19141817

Parnaudeau, V; G幯ermont, S; H幯ault, C; Farrugia, A; Robert, P; Nicolardot, B

2009-01-13

275

An Analysis of Airborne Measurements of Vertical Water Vapor Flux During BOMEX  

Microsoft Academic Search

The initial analysis of the water vapor flux measurements taken onboard a NOAA DC-6 during the Barbados Oceanographic and Meteorological Experiment (BOMEX) is presented. The flux of water vapor seems to be constant in the lower subcloud layer. Day-to-day variations, as well as variations within a day are apparent in the evaporation data. Spatial variations of evaporation also seem to

B. R. Bean; R. Gilmer; R. L. Grossman; R. McGavin; C. Travis

1972-01-01

276

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

Microsoft Academic Search

All the available nightside electron data obtained during circular orbits at Mars from the Phobos-2 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

N. Shutte; K. Gringauz; P. Kir嫮y; G. Kotova; A. F. Nagy; H. Rosenbauer; K. Szeg; M. Verigin

1995-01-01

277

Flux chamber measurements of anomalous CO2 emission from the flanks of Mammoth Mountain, California  

Microsoft Academic Search

The CO2 fluxes involved in the mass mortality of large stands of timber on the flanks of Mammoth Mountain in California's Sierra Nevada were measured and spatial and temporal inhomogeneities observed. Our estimate of the integrated flux over the total area of tree-kill is on the order of 400 t day?1. Small scale spatial variability most likely reflects varying degrees

T. A. Rahn; J. E. Fessenden; M. Wahlen

1996-01-01

278

New Epstein Frame for Core Loss Measurements at High Frequencies and High Flux Densities  

Microsoft Academic Search

This paper presents a new Epstein frame capable of core loss measurements on laminations subjected to high frequencies and high flux densities. The lamination characterization at high frequencies and high flux densities is mandatory in loss calculation procedure for high speed novel designs. The new 200- turn frame is compared with the 352-turn industrial standard frame and the recently developed

Marubini J. Manyage; Pragasen Pillay

2008-01-01

279

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

280

Study of Evaporation Rate of Water in Hydrophobic Confinement using Forward Flux Sampling  

NASA Astrophysics Data System (ADS)

Drying of hydrophobic cavities is of interest in understanding biological self assembly, protein stability and opening and closing of ion channels. Liquid-to-vapor transition of water in confinement is associated with large kinetic barriers which preclude its study using conventional simulation techniques. Using forward flux sampling to study the kinetics of the transition between two hydrophobic surfaces, we show that a) the free energy barriers to evaporation scale linearly with the distance between the two surfaces, d; b) the evaporation rates increase as the lateral size of the surfaces, L increases, and c) the transition state to evaporation for sufficiently large L is a cylindrical vapor cavity connecting the two hydrophobic surfaces. Finally, we decouple the effects of confinement geometry and surface chemistry on the evaporation rates.

Sharma, Sumit; Debenedetti, Pablo G.

2012-02-01

281

Annual Southern Ocean heat flux measured for first time  

NASA Astrophysics Data System (ADS)

The Southern Ocean makes up nearly a quarter of the global ocean by surface area and plays a powerful role in regulating Earth's climate by affecting ocean and atmospheric circulation patterns. Modeled representations of the Southern Ocean, however, are plagued by uncertainty. Obtaining direct observations of Southern Ocean properties with which to confirm the modeled estimates is difficult in such hostile polar conditions. To help overcome this shortfall, the Southern Ocean Flux Station (SOFS), the first moored sensor array to ever be successfully deployed in the Southern Ocean, was set up south of Australia.

Schultz, Colin

2012-10-01

282

Remote Measurement of Heat Flux from Power Plant Cooling Lakes  

SciTech Connect

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

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

2013-01-01

283

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

SciTech Connect

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

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

2004-04-27

284

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

PubMed

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

Smith, Tim; Sale, Tom; Lyverse, Mark

2012-04-10

285

Methane flux, vertical gradient and mixing ratio measurements in a tropical forest  

NASA Astrophysics Data System (ADS)

Measurements of CH4 mixing ratio, vertical gradients and turbulent fluxes were carried out in a tropical forest (Reserva Biol鏬ica Cuieiras), about 60 km north of Manaus, Brazil. The methane mixing ratio and flux measurements were performed at a height of 53 m (canopy height 35 m). In addition, vertical CH4 gradients were measured within the canopy using custom made air samplers at levels of 2, 16 and 36 m above ground. The methane gradients within the canopy reveal that there is a continuous methane source at the surface. No clear evidence for aerobic methane emission from the canopy was found. The methane fluxes above the canopy are small but consistently show an upward flux with a maximum early in the morning, and the measured fluxes are in agreement with what is expected from the positive CH4 gradient in the canopy. In the morning hours, a strong canopy venting peak is observed for both CH4 and CO2, but for CO2 this peak is then superimposed by photosynthetic uptake, whereas the peak lasts longer for CH4. Monthly averaged diurnal cycles of the CH4 mixing ratio show a decrease during daytime and increase during nighttime. The magnitude of the difference in CH4 mixing ratio between day and night gradually increases throughout the wet season. The fluxes required to explain the nighttime increase are in agreement with the nighttime fluxes measured above the canopy, which implies that the CH4 increase in the nighttime boundary layer originates from local sources.

Querino, C. A. S.; Smeets, C. J. P. P.; Vigano, I.; Holzinger, R.; Moura, V.; Gatti, L. V.; Martinewski, A.; Manzi, A. O.; de Arajo, A. C.; R鐼kmann, T.

2011-02-01

286

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

SciTech Connect

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.

Nakos, James Thomas

2010-12-01

287

Independent Measurement of the Total Active B8 Solar Neutrino Flux Using an Array of He3 Proportional Counters at the Sudbury Neutrino Observatory  

Microsoft Academic Search

The Sudbury Neutrino Observatory (SNO) used an array of He3 proportional counters to measure the rate of neutral-current interactions in heavy water and precisely determined the total active (nux) B8 solar neutrino flux. This technique is independent of previous methods employed by SNO. The total flux is found to be 5.54-0.31+0.33(stat)-0.34+0.36(syst)106cm-2s-1, in agreement with previous measurements and standard solar models.

B. Aharmim; S. N. Ahmed; J. F. Amsbaugh; A. E. Anthony; J. Banar; N. Barros; E. W. Beier; A. Bellerive; B. Beltran; M. Bergevin; S. D. Biller; K. Boudjemline; M. G. Boulay; T. J. Bowles; M. C. Browne; T. V. Bullard; T. H. Burritt; B. Cai; Y. D. Chan; D. Chauhan; M. Chen; B. T. Cleveland; G. A. Cox-Mobrand; C. A. Currat; X. Dai; H. Deng; J. Detwiler; M. Dimarco; P. J. Doe; G. Doucas; P.-L. Drouin; C. A. Duba; F. A. Duncan; M. Dunford; E. D. Earle; S. R. Elliott; H. C. Evans; G. T. Ewan; J. Farine; H. Fergani; F. Fleurot; R. J. Ford; J. A. Formaggio; M. M. Fowler; N. Gagnon; J. V. Germani; A. Goldschmidt; J. T. M. Goon; K. Graham; E. Guillian; S. Habib; R. L. Hahn; A. L. Hallin; E. D. Hallman; A. A. Hamian; G. C. Harper; P. J. Harvey; R. Hazama; K. M. Heeger; W. J. Heintzelman; J. Heise; R. L. Helmer; R. Henning; A. Hime; C. Howard; M. A. Howe; M. Huang; P. Jagam; B. Jamieson; N. A. Jelley; K. J. Keeter; J. R. Klein; L. L. Kormos; M. Kos; A. Krger; C. Kraus; C. B. Krauss; T. Kutter; C. C. M. Kyba; R. Lange; J. Law; I. T. Lawson; K. T. Lesko; J. R. Leslie; J. C. Loach; R. MacLellan; S. Majerus; H. B. Mak; J. Maneira; R. Martin; K. McBryde; N. McCauley; A. B. McDonald; S. McGee; C. Mifflin; G. G. Miller; M. L. Miller; B. Monreal; J. Monroe; B. Morissette; A. Myers; B. G. Nickel; A. J. Noble; N. S. Oblath; H. M. O'Keeffe; R. W. Ollerhead; G. D. Orebi Gann; S. M. Oser; R. A. Ott; S. J. M. Peeters; A. W. P. Poon; G. Prior; S. D. Reitzner; K. Rielage; B. C. Robertson; R. G. H. Robertson; E. Rollin; M. H. Schwendener; J. A. Secrest; S. R. Seibert; O. Simard; J. J. Simpson; L. Sinclair; P. Skensved; M. W. E. Smith; T. D. Steiger; L. C. Stonehill; G. Tesic; P. M. Thornewell; N. Tolich; T. Tsui; C. D. Tunnell; T. van Wechel; R. van Berg; B. A. Vandevender; C. J. Virtue; T. J. Walker; B. L. Wall; D. Waller; H. Wan Chan Tseung; J. Wendland; J. B. Wilhelmy; J. F. Wilkerson; J. R. Wilson; J. M. Wouters; A. Wright; M. Yeh; F. Zhang; K. Zuber

2008-01-01

288

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

PubMed Central

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

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

2011-01-01

289

Eddy covariance flux measurements of pollutant gases in urban Mexico City  

NASA Astrophysics Data System (ADS)

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

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

2009-10-01

290

Eddy covariance flux measurements of pollutant gases in urban Mexico City  

NASA Astrophysics Data System (ADS)

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

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

2009-03-01

291

Scrape-off layer power flux measurements in the Tore Supra tokamak  

NASA Astrophysics Data System (ADS)

A new method to measure power flux in strongly magnetized plasmas is described, while the flaws inherent in standard Langmuir probe techniques are demonstrated. Instead of small cylindrical pins which overestimate the ion current density by several 100%, a concave probe has been developed which is immune to sheath expansion, and which inherently provides accurate measurements. A retarding field analyzer directly measures the ion component of the power flux by means of an integral method that eliminates the need to calculate the heat transmission factor. Evidence shows that strong secondary electron emission from surfaces with non-oblique magnetic field incidence angles is ubiquitous in the scrape-off layer of the Tore Supra tokamak. This results in sheath collapse, causing the power flux to be dominated by the electrons. The radially integrated power flux measured by the probes agrees well with the power convected to the limiter.

Gunn, J. P.; Dejarnac, R.; Devynck, P.; Fedorczak, N.; Fuchs, V.; Gil, C.; Ko?an, M.; Komm, M.; Kubi?, M.; Lunt, T.; Monier-Garbet, P.; Pascal, J.-Y.; Saint-Laurent, F.

2013-07-01

292

Study on methodology of LED's luminous flux measurement with integrating sphere  

NASA Astrophysics Data System (ADS)

Errors are introduced when using traditional methods for measuring the total luminous flux of LEDs since an LED is quite different from traditional light sources in terms of physical size, flux level, spectrum and spatial distribution. This paper uses commercial lighting simulation software named Tracepro to simulate the self-absorption effect when using traditional integrating sphere methods to measure the total luminous flux of LEDs and then presents a modified method for the measurement. The LED under investigation or a specially designed narrow beam standard lamp is placed on the interior wall of the sphere in our method. The results show that the measurement method presented here can lead to better precision in the evaluation of the total luminous flux of LEDs.

Liu, Mu-Qing; Zhou, Xiao-Li; Li, Wen-Yi; Chen, Yu-Yang; Zhang, Wan-Lu

2008-07-01

293

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

NASA Astrophysics Data System (ADS)

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

K闥, M.; Aydo?du, Y.

2007-04-01

294

Annual sediment flux estimates in a tidal strait using surrogate measurements  

NASA Astrophysics Data System (ADS)

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.

Ganju, N.; Schoellhamer, D.

2006-08-01

295

Estimating regional methane surface fluxes: the relative importance of surface and GOSAT mole fraction measurements  

NASA Astrophysics Data System (ADS)

We use an ensemble Kalman filter (EnKF), together with the GEOS-Chem chemistry transport model, to estimate regional monthly methane (CH4) fluxes for the period June 2009-December 2010 using proxy dry-air column-averaged mole fractions of methane (XCH4) from GOSAT (Greenhouse gases Observing SATellite) and/or NOAA ESRL (Earth System Research Laboratory) and CSIRO GASLAB (Global Atmospheric Sampling Laboratory) CH4 surface mole fraction measurements. Global posterior estimates using GOSAT and/or surface measurements are between 510-516 Tg yr-1, which is less than, though within the uncertainty of, the prior global flux of 529 25 Tg yr-1. We find larger differences between regional prior and posterior fluxes, with the largest changes (75 Tg yr-1) occurring in Temperate Eurasia. In non-boreal regions the error reductions for inversions using the GOSAT data are at least three times larger (up to 45%) than if only surface data are assimilated, a reflection of the greater spatial coverage of GOSAT, with the two exceptions of latitudes > 60 associated with a data filter and over Europe where the surface network adequately describes fluxes on our model spatial and temporal grid. We use CarbonTracker and GEOS-Chem XCO2 model output to investigate model error on quantifying proxy GOSAT XCH4 (involving model XCO2) and inferring methane flux estimates from surface mole fraction data and show similar resulting fluxes, with differences reflecting initial differences in the proxy value. Using a series of observing system simulation experiments (OSSEs) we characterize the posterior flux error introduced by non-uniform atmospheric sampling by GOSAT. We show that clear-sky measurements can theoretically reproduce fluxes within 5% of true values, with the exception of South Africa and Tropical South America where, due to a large seasonal cycle in the number of measurements because of clouds and aerosols, fluxes are within 17% and 19% of true fluxes, respectively. We evaluate our posterior methane fluxes by incorporating them into GEOS-Chem and sampling the model at the location and time of independent surface CH4 measurements from the AGAGE (Advanced Global Atmospheric Gases Experiment) network and column XCH4 measurements from TCCON (Total Carbon Column Observing Network). The posterior fluxes modestly improve the model agreement with AGAGE and TCCON data relative to prior fluxes, with the correlation coefficients (r2) increasing by a mean of 0.04 (range: -0.17, 0.23) and the biases decreasing by a mean of 0.4 ppb (range: -8.9, 8.4 ppb).

Fraser, A.; Palmer, P. I.; Feng, L.; Boesch, H.; Cogan, A.; Parker, R.; Dlugokencky, E. J.; Fraser, P. J.; Krummel, P. B.; Langenfelds, R. L.; O'Doherty, S.; Prinn, R. G.; Steele, L. P.; van der Schoot, M.; Weiss, R. F.

2012-12-01

296

Scaling up flux measurements for the boreal forest using aircraft-tower combinations  

NASA Astrophysics Data System (ADS)

Fluxes of carbon dioxide, water vapor, sensible heat, and momentum obtained over the boreal forest from the Twin Otter aircraft and six tower-based systems are compared. These measurements were collected as part of the Boreal Ecosystem-Atmosphere Study (BOREAS) during three intensive field campaigns between May 25 and September 17, 1994. The representativeness of the tower-based measurements collected during BOREAS is discussed. Even though the net radiation from aircraft- and tower-based systems agreed well, in general, the aircraft tended to observe larger latent heat and smaller sensible heat fluxes than the towers. The CO2 fluxes from the aircraft were substantially less than from the tower, while the differences were relatively small for the momentum fluxes. The relationships between aircraft and tower-based flux measurements obtained by making repeated runs past various towers are used to scale up tower-based fluxes to a 1616 km2 area near Prince Albert, Saskatchewan. It is demonstrated that except for a couple of cases primarily due to rapidly changing radiation conditions, this combination of measurements provides regional flux estimates of momentum, CO2, and sensible and latent heat similar to those obtained by flying a grid pattern over the area.

Desjardins, R. L.; MacPherson, J. I.; Mahrt, L.; Schuepp, P.; Pattey, E.; Neumann, H.; Baldocchi, D.; Wofsy, S.; Fitzjarrald, D.; McCaughey, H.; Joiner, D. W.

1997-12-01

297

A stochastic model for estimating groundwater and contaminant discharges from fractured rock passive flux meter measurements  

NASA Astrophysics Data System (ADS)

Estimation of water and contaminant discharges is an important hydrological problem. Fractured rock aquifers are recognized as highly complex flow and transport systems, and the fractured rock passive flux meter (FRPFM) is a recently tested device to simultaneously measure cumulative water and contaminant mass fluxes in fractures intersecting an observation well (boring). Furthermore, the FRPFM is capable of indicating orientations and directions of flow in hydraulically active ("flowing") fractures. The present work develops a discharge estimator for when FRPFM measurements of fracture fluxes in the direction perpendicular to a transect (control plane) along one or more observation wells are available. In addition, estimation uncertainty in terms of a coefficient of variation is assessed based on a Monte Carlo approach under normalized conditions. Sources of uncertainty considered are spatially random fracture trace locations, random trace lengths, and orientations as well as variability of trace average fluxes (including smooth spatial trends), variability of local fluxes within traces, and flux measurement errors. Knowledge about the trace length distribution, which is commonly not available from borehole surveys, is not required for discharge estimation. However, it does affect the uncertainty assessment, and equations for upper uncertainty bounds are given as an alternative. In agreement with general statistical inference, it is found that discharge uncertainty decreases proportionally with the number of fluxes measured. Results are validated, and an example problem illustrates practical application and performance.

Acar, 畤lem; Klammler, Harald; Hatfield, Kirk; Newman, Mark A.; Annable, Michael D.; Cho, Jaehyun; Parker, Beth L.; Cherry, John A.; Pehme, Pete; Quinn, Patryk; Kroeker, Ryan

2013-03-01

298

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

NASA Astrophysics Data System (ADS)

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 ?-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 ?g 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.

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

2003-07-01

299

Measurements of the Solar Neutrino Flux From Super-Kamiokande's First 300 Days  

Microsoft Academic Search

The results of the solar neutrino flux measurements from data taken by Super-Kamiokande between the 31st of May, 1996 and the 23rd of June, 1997 are presented. Using our measurement of recoil electrons with energies above 6.5 MeV\\/c^2, we infer the flux of all ^8 B solar neutrinos to be 2.420.06(stat.)^+0.10_-0.07(syst.)10^6\\/cm^2\\/s, which is 36% of the flux predicted by the

Robert Sanford; T. Hayakawa; E. Ichihara; K. Inoue; K. Ishihara; H. Ishino; Y. Itow; T. Kajita; J. Kameda; S. Kasuga; K. Kobayashi; Y. Kobayashi; Y. Koshio; K. Martens; M. Miura; M. Nakahata; S. Nakayama; A. Okada; M. Oketa; K. Okumura; M. Ota; N. Sakurai; M. Shiozawa; Y. Suzuki; Y. Takeuchi; Y. Totsuka; S. Yamada; M. Earl; A. Habig; J. T. Hong; E. Kearns; S. B. Kim; M. Masuzawa; M. D. Messier; K. Scholberg; J. L. Stone; L. R. Sulak; C. W. Walter; M. Goldhaber; T. Barszczak; W. Gajewski; P. G. Halverson; J. Hsu; W. R. Kropp; L. R. Price; F. Reines; H. W. Sobel; M. R. Vagins; K. S. Ganezer; W. E. Keig; R. W. Ellsworth; S. Tasaka; J. W. Flanagan; A. Kibayashi; J. G. Learned; S. Matsuno; V. Stenger; D. Takemori; T. Ishii; J. Kanzaki; T. Kobayashi; K. Nakamura; K. Nishikawa; Y. Oyama; A. Sakai; M. Sakuda; O. Sasaki; S. Echigo; M. Kohama; A. T. Suzuki; T. J. Haines; E. Blaufuss; R. Svoboda; M. L. Chen; Z. Conner; J. A. Goodman; G. W. Sullivan; M. Mori; J. Hill; C. K. Jung; C. Mauger; C. McGrew; E. Sharkey; B. Viren; C. Yanagisawa; W. Doki; T. Ishizuka; Y. Kitaguchi; H. Koga; K. Miyano; H. Okazawa; C. Saji; M. Takahata; A. Kusano; Y. Nagashima; M. Takita; T. Yamaguchi; M. Yoshida; M. Etoh; K. Fujita; A. Hasegawa; T. Hasegawa; S. Hatakeyama; T. Iwamoto; T. Kinebuchi; M. Koga; T. Maruyama; H. Ogawa; F. Tsushima; M. Koshiba; M. Nemoto; K. Nishijima; T. Futagami; Y. Hayato; Y. Kanaya; K. Kaneyuki; Y. Watanabe; D. Kielczewska; R. Doyle; J. George; A. Stachyra; L. Wai; J. Wilkes; K. Young

1998-01-01

300

Fluxes of energetic protons and electrons measured on board the Oersted satellite  

Microsoft Academic Search

The Charged Particle Detector (CPD) on board the Oersted satellite (649 km perigee, 865 km apogee and 96.48 inclination) currently measures energetic protons and electrons. The measured peak fluxes of E>1 MeV electrons are found to confirm the predictions of AE8-MAX, though they occur at a geographical position relatively shifted in the SAA. The fluxes of protons are one order

J. Cabrera; M. Cyamukungu; P. Stauning; A. Leonov; P. Leleux; J. Lemaire; G. Gr嶲oire

2005-01-01

301

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

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

302

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

SciTech Connect

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

Olson, D.A.

1989-10-01

303

Recent Measurements of Ice Flux From Outlet Glaciers of the South Shetlands and Antarctic Peninsula  

NASA Astrophysics Data System (ADS)

One of the most significant events in the evolution of the Antarctic climate and cryosphere was the pronounced glacial erosion in the late Cenozoic that led to the considerable depth and landward sloping profile of the continental shelf, affecting both ice sheet dynamics and the oceanographic processes that drive circulation on the shelf. Understanding how changes in glacial conditions during the LGM may have led to enhanced glacial erosion, however, requires us to first identify the factors that control the amount and rate of glacier erosion in Antarctica today. The bays and fjords of the Antarctic Peninsula contain a rich history of climate change recorded both in proxy climate data (e.g., forams, oxygen isotopes) and in sediment accumulation rates that reflect changes in glacial erosion and sediment transfer. Prior studies revealed large variations in the rate of sediment accumulation across the Peninsula, with a general trend of decreasing sedimentation from north to south and west to east, attributed to climate-driven differences in glacier dynamics. Little is known to date, however, about the individual dynamics of the glaciers in these fjords, and the variability in their sediment delivery, particularly as many of them start to accelerate and retreat (Cook et al., 2005; Rignot, 1998; Angelis and Skvarca, 2003). As part of a study concerning the factors controlling rates of glacial erosion and sedimentation across climatic regimes, the cross-sectional area at the ELA of 16 tidewater glaciers in the South Shetland Islands and the western coast of the Antarctic Peninsula were measured in April 2007. The cross-section area of each glacier is then combined with the mean surface velocity, measured remotely using SAR interferometry, to reconstruct the contemporary ice flux through these glacier systems. The study area spans almost 4 of latitude and 8 of mean annual temperature, encompassing both sub-polar and polar regimes, from Maxwell Bay, South Shetland Islands (6210' S) to Beascochea Bay, Graham Coast (6531' S). For the sub-polar glaciers (2 of 16), where the ELA was significantly above sea level, the cross-sectional area at the ELA was measured using ice-penetrating radar. Velocity stakes were also measured at the ELA of these glaciers to ground-truth the satellite measurements of surface velocity. For the remaining polar glaciers, whose ELAs are at sea-level, multi-beam swath bathymetry was used from aboard the RV/IB Nathaniel B. Palmer together with estimates of ice cliff heights to determine the cross-sectional area of the calving front. The variability in ice flux across the sub-polar and polar climatic regimes of the western Antarctic Peninsula reported here will be compared to bathymetric data and sediment accumulation rates derived from 210-Pb and 14-C chronology in the adjacent fjords, as they become available, to examine the influence of both climate and ice flux on the rate of glacial erosion and sedimentation, and to infer potential changes in sediment delivery to the shelf as the region warms.

Koppes, M.; Hallet, B.; Rignot, E.; Jaffrey, M.

2007-12-01

304

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

305

Disjunct Eddy Accumulation Measurements of Organic Nitrate Fluxes Over a Forest Site in Northern Michigan  

NASA Astrophysics Data System (ADS)

Fluxes of organic nitrates have been measured at the PROPHET tower site in northern Michigan by the technique of disjunct eddy accumulation (DEA). This relatively new method involves conditional sampling into up and down cartridge-based reservoirs, from a disjunct sample container. In this experiment, air parcels containing target species were sampled at rates proportional to the magnitude and direction of the vertical wind vector. One disjunct sample was taken every 30 seconds by drawing ambient air into analysis tubes containing a sorbent material (Tenax-TA) for a period of one hour. These sorbet tubes were then analyzed by thermal desorption/GC-ECD. The performance of the DEA instrument and GC during their first field deployment is evaluated and the overall flux for several organic nitrate molecules will be reported. Using these data and the gas phase concentrations, dry deposition velocities of these organic nitrates can be calculated and will be discussed here. The potential role and relative importance (compared to other sources of nitrogen) of these molecules in biosphere-atmosphere exchange within a nitrogen limited forest will also be discussed.

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

2004-12-01

306

The Zero-Flux DC Current Transformer a High Precision Bipolar Wide-Band Measuring Device  

Microsoft Academic Search

A current-carrying conductor is surrounded by a pair of ring cores. A sense winding on one core provides flux rate feedback to a power amplifier which drives the ampere-turn compensating current through a common compensating winding. The other core serves as a second-harmonic modulator to establish zero-flux operation and thus to ensure a perfect, temperature-independent current balance. A specially-developed burden

H. C. Appelo; M. Groenenboom; J. Lisser

1977-01-01

307

Sizes of nanobubbles from nucleation rate measurements  

NASA Astrophysics Data System (ADS)

In homogeneous bubble nucleation, the critical nucleus typically has nanometer dimensions. The volume V of a critical bubble can be determined from the simple equation (partial W/partial p)_T=V, where W is the reversible work of nucleus formation and p is the ambient pressure of the liquid phase in which bubble formation is occurring. The relation, W/kT=-ln J+ln A, where J is the steady state nucleation rate and A is the weakly pressure-dependent kinetic prefactor, allows V to be determined from rate measurements. The original derivation of this equation for V from the nucleation theorem was limited to one-component, ideal gas bubbles with a gas density much smaller than that of the ambient liquid. [D. Kashchiev, Nucleation: basic theory with applications (Butterworth-Heinemann, Oxford, 2000) p. 226.] The result is actually much more general, and it will be shown that it applies to multi-component, nonideal gas bubbles, provided the same density inequality holds. When the bubble phase and liquid densities are comparable, a more complicated, but also general and rigorous result is found.

Wilemski, G.

2003-03-01

308

Modeling thermal behavior and work flux in finite-rate systems with radiation  

Microsoft Academic Search

We apply thermodynamic analysis in modeling, simulation and optimization of radiation engines as non-linear energy converters. We also perform critical analysis of available data for photon flux and photon density that leads to exact numerical value of photon flux constant. Basic thermodynamic principles lead to expressions for converters efficiency and generated work in terms of driving energy flux in the

Stanislaw Sieniutycz; Piotr Kuran

2006-01-01

309

A passive flux sampler for measuring ammonia volatilization form manure storage facilities  

SciTech Connect

An integrated horizontal flux technique was tested for quantification of ammonia (NH{sub 3}) emission from manure storage. The method is based on a simple and inexpensive passive flux sampler consisting of two disconnectable glass tubes, coated on the inside with oxalic acid. The flux sampler is mounted at a minimum of three heights, 20 to 100 cm above the storage, on each of four masts, placed perpendicular to each other around the storage. The samplers continuously integrate the horizontal flux of NH{sub 3} at the various heights. After analysis of the Nh{sub 3} content in the tubes facing the storage (exposed tubes) and surroundings (background tubes), the vertical flux of NH{sub 3} from the storage can be obtained by application of mass balance equations (micrometeorological mass balance technique). For the measurements of NH{sub 3} volatilization from slurry tanks or lagoons the technique is useful, because it is not affected by heterogenity in wind profiles and the masts with the passive flux samplers are placed on the periphery of the slurry store. The flux samplers were able to accurately quantify NH{sub 3} volatilization from slurry tanks. From above the rim of the slurry tank the horizontal net flux decline exponential with height. This may facilitate the calculation of the vertical flux of NH{sub 3}. Bypass of NH{sub 3} between exposed and background tubes may occur during periods with high wind velocities (>10 m s{sup {minus}1}) or when more than one-fifth of the oxalate in the exposed tube has reacted. However, if bypass occurs, a good estimate of NH{sub 3} volatilization can still be obtained by addition of exposed and background tubes, because the NH{sub 3} flux from storage are usually much greater than the flux from surroundings. 19 refs., 5 figs., 4 tabs.

Sommer, S.G.; Sibbesen, E.; Olesen, J.E. [Danish Inst. of Plant and Soil Science, Tjele (Germany); Nielsen, T. [Danish Agricultural Advisory Centre, Arhus (Germany); Schjorring, J.K. [Royal Veterinary and Agricultural Univ., Copenhagen (Germany)

1996-03-01

310

Whole-body calcium flux rates in cichlid teleost fish Oreochromis mossambicus adapted to freshwater  

SciTech Connect

Radiotracer techniques were used to measure influx and efflux rates of CaS in freshwater-adapted Oreochromis mossambicus. The influx rate of CaS is related to body weight (W) as Fin = 50W0.805 nmol CaS /h. For a 20-g fish the calculated influx rate was 558 nmol CaS /h, and this was attributed largely to extraintestinal uptake since the drinking rate was estimated to be only 28 microliter water/h, which corresponds to an intake of 22.4 nmol CaS /h. The CaS efflux rate was calculated using the initial rate of appearance of radiotracer in the ambient water and the specific activity of plasma CaS . Tracer efflux rates were constant over 6-8 h, which indicated that there was no substantial loss of tracer in either the urine or the feces because this would have resulted in random bursts of tracer loss. Efflux rates then primarily represent integumentary and presumably branchial efflux rates. The efflux rate of CaS is related to body weight as Fout = 30W0.563 nmol CaS /h, which means an efflux rate of 162 nmol CaS /h for a 20-g fish. The net whole-body CaS influx, calculated as Fnet = Fin - Fout, was 396 nmol/h for a 20-g fish, which proves that the ambient water is an important source of CaS .

Flik, G.; Fenwick, J.C.; Kolar, Z.; Mayer-Gostan, N.; Wendelaar Bonga, S.E.

1985-10-01

311

Determination of longwave heat flux at the air-sea interface using measurements from buoy platforms  

SciTech Connect

A theory for pyrgeometer operation is utilized for determining downwelling longwave radiation. Errors in downwelling longwave radiation measurements are due to differences in pyrgeometer body and dome temperatures compared to that of the atmosphere. Additionally, incident shortwave radiation fluxes may be important. Using the present theory along with laboratory and field observations, it appears that downwelling longwave heat fluxes can be measured with errors less than 6 W/sq m. Longwave heat flux observations from surface buoys deployed in four different oceanic regions suggest that (1) incoming longwave measurements from buoys are repeatable, (2) uncertainties in radiometer calibration are significant and systematic, and (3) pyrgeometers are affected by direct and indirect solar heating. A hybrid measurement method for the determination of net longwave heat flux at the air-sea interface is described. The authors recommend improvement in calibration procedures as well as development of a radiometer to be used as a transfer standard to compare with in situ measurements. Uncertainties in sea surface skin temperature and emissivity are contributors to the error in the net longwave heat flux. However, a targeted error limit goal of +/- 10 W/sq m for the monthly mean net longwave heat flux appears to be achievable.

Dickey, T.D.; Manov, D.V.; Weller, R.A.; Siegel, D.A. [Univ. of Southern California, Los Angeles, CA (United States)]|[Woods Hole Oceanographic Institution, Woods Hole, MA (United States)]|[Univ. of California, Santa Barbara, CA (United States)

1994-08-01

312

Methane flux, vertical gradient and mixing ratio measurements in a tropical forest  

NASA Astrophysics Data System (ADS)

Measurements of CH4 mixing ratio, vertical gradients and turbulent fluxes were carried out in a tropical forest (Reserva Biol鏬ica Cuieiras), about 60 km north of Manaus, Brazil. The methane mixing ratio and flux measurements were performed at a height of 53 m (canopy height 35 m). In addition, vertical CH4 gradients were measured within the canopy using custom made air samplers at levels of 2, 16 and 36 m above ground. The methane gradients within the canopy reveal that there is a continuous methane source at the surface. No clear evidence for aerobic methane emission from the canopy was found. The methane fluxes above the canopy are small but consistently upwards with a maximum early in the morning. The measured fluxes are in agreement with the observed CH4 gradient in the canopy. In the morning hours, a strong canopy venting peak is observed for both CH4 and CO2, but for CO2 this peak is then superimposed by photosynthetic uptake, whereas the peak lasts longer for CH4. Monthly averaged diurnal cycles of the CH4 mixing ratio show a decrease during daytime and increase during nighttime. The magnitude of the difference in CH4 mixing ratio between day and night gradually increases throughout the wet season. The fluxes required to explain the nighttime increase are in agreement with the nighttime fluxes measured above the canopy, which implies that the CH4 increase in the nighttime boundary layer originates from local sources.

Querino, C. A. S.; Smeets, C. J. P. P.; Vigano, I.; Holzinger, R.; Moura, V.; Gatti, L. V.; Martinewski, A.; Manzi, A. O.; de Arajo, A. C.; R鐼kmann, T.

2011-08-01

313

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)

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 precipitation events, likely produced by an adverse measurement effect. This analysis enabled to pinpoint specific areas where models break, and stress that model capability to reproduce fluxes vary among seasons and ecosystem components. The combined response was such, that comparison decreases when ecosystem fluxes were partitioned between overstory and understory fluxes. Model performance decreases with time scale; while performance was high for some seasons, models were less capable of reproducing the high variability in understory fluxes vs. the conservative overstory fluxes on annual scales. Discrepancies were not always a result of models' faults; comparison largely improved when measurements of overstory fluxes during precipitation events were excluded. Conclusions raised from this research enable to answer the critical question of the level and type of details needed in order to correctly predict ecosystem respond to environmental and climatic change.

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

2011-12-01

314

Precision measurement of the 7Be solar neutrino flux and its day-night asymmetry with Borexino  

NASA Astrophysics Data System (ADS)

Borexino measures the 7Be solar neutrino flux on 740 live days of data-taking to be 461.5+1.6-1.5 events/(day 100 tons) which corresponds to an equivalent unoscillated flux on Earth of (3.110.10+0.11-0.10)109sec -1 cm-2. This result excludes the no-oscillation hypothesis at 5 ? and provides a precise measurement of the survival probability Pee in the vacuum dominated oscillation regime Pee = 0.510.07. Borexino also measures the day-night asymmetry of the 7Be neutrino rate with a total error of 1.4% and finds it to be consistent with zero. This result is in agreement with the MSW-LMA hypothesis and disfavours at more than 8.5 ? the so-called LOW region of the oscillation parameter space.

Caccianiga, Barbara; Bellini, G.; Benziger, J.; Bick, D.; Bonetti, S.; Bonfini, G.; Bravo, D.; Buizza Avanzini, M.; Caccianiga, B.; Cadonati, L.; Calaprice, F.; Carraro, C.; Cavalcante, P.; Chavarria, A.; D'Angelo, D.; Davini, S.; Derbin, A.; Etenko, A.; Fomenko, K.; Franco, D.; Galbiati, C.; Gazzana, S.; Ghiano, C.; Giammarchi, M.; Goeger-Neff, M.; Goretti, A.; Grandi, L.; Guardincerri, E.; Hardy, S.; Ianni, Aldo; Ianni, Andrea; Korablev, D.; Korga, G.; Koshio, Y.; Kryn, D.; Laubenstein, M.; Lewke, T.; Litvinovich, E.; Loer, B.; Lombardi, P.; Lombardi, L.; Ludhova, L.; Machulin, I.; Manecki, S.; Maneschg, W.; Manuzio, G.; Meindl, Q.; Meroni, E.; Miramonti, L.; Misiaszek, M.; Montanari, D.; Mosteiro, P.; Muratova, V.; Oberauer, L.; Obolensky, M.; Ortica, F.; Otis, K.; Pallavicini, M.; Papp, L.; Perasso, L.; Perasso, S.; Pocar, A.; Quirk, J.; Raghavan, R. S.; Ranucci, G.; Razeto, A.; Re, A.; Romani, A.; Sabelnikov, A.; Saldanha, R.; Salvo, C.; Sch霵ert, S.; Simgen, H.; Skorokhvatov, M.; Smirnov, O.; Sotnikov, A.; Sukhotin, S.; Suvorov, Y.; Tartaglia, R.; Testera, G.; Vignaud, D.; Vogelaar, R. B.; von Feilitzsch, F.; Winter, J.; Wojcik, M.; Wright, A.; Wurm, M.; Xu, J.; Zaimidoroga, O.; Zavatarelli, S.; Zuzel, G.; Borexino Collaboration

2012-07-01

315

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

NASA Astrophysics Data System (ADS)

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

Liu, H.; Feng, J.

2009-12-01

316

Tests of A Displaced-beam Small Aperture Laser Scintillometer To Determine Surface Fluxes and Dissipation Rate of Tke  

Microsoft Academic Search

Comparisons between surface fluxes of sensible heat and momentum derived from a displaced-beam small aperture scintillometer (DBSAS) and eddy-correlation mea- surements (or flux-profile methods) will be presented. Furthermore, similar compar- isons for the dissipation rate of turbulent kinetic energy and temperatures structure parameter will be shown. Although the results are very promising, some systematic de- viations are observed. The cause

H. A. R. de Bruin; O. K. Hartogensis; F. Beyrich; W. M. L. Meininger; A.-S. Smedman

2002-01-01

317

Remotely sensed dune celerity and sand flux measurements of the world's fastest barchans (Bod幨, Chad)  

NASA Astrophysics Data System (ADS)

Quantifying sand flux with field measurements is an expensive and time-consuming process. We here present an alternative approach using the COSI-Corr software package for Earth surface deformation detection. Using pairs of ASTER satellite images, we detected dune migration in the Bod幨 depression of northern Chad over time intervals of one month to 6.5 years. The displacement map can be used to automatically distinguish dunes from interdunes, which is a crucial step towards calculating sand flux. We interpolated a surface between the interdune areas and subtracted it from a digital elevation model, thus obtaining dune heights and volumes. Multiplying height with celerity yields a pixel-by-pixel estimate of the sand flux. We applied this method to large diatomite dunes in the Bod幨, confirming that these are some of the world's fastest moving barchans. Plotting dune height against inverse celerity reveals sand flux at the dune crest of >200 m3/m/yr. Average dune sand flux values for the eastern and western Bod幨 are 76 and 99 m3/m/yr, respectively. The contribution of the dunes to the total area-averaged sand flux is 24-29 m3/m/yr, which is ~10% of the saltation flux determined by previously published field measurements.

Vermeesch, Pieter; Drake, Nick

2008-12-01

318

Sensible Heat Flux Measurements Near A Cold Surface.  

National Technical Information Service (NTIS)

A unidirectional sonic anemometer with a fine-wire thermocouple in conjunction with a hot film anemometer were employed to measure the turbulent fluctuating velocities of W', U', and the fluctuating temperature T'. Covariances were evaluated to compute th...

Y. Yen

1995-01-01

319

Reconciling main belt asteroid spectral flux density measurements with a self-consistent thermophysical model  

NASA Astrophysics Data System (ADS)

Thermophysical models consistent with Earth's Moon and infrared and submillimeter measurements obtained during the Rosetta fly-by of Asteroid (21) Lutetia have been applied to computations of thermal fluxes from Asteroids (4) Vesta, (1) Ceres, (2) Pallas, and (10) Hygiea. Comparisons are made with Earth- and space-based flux measurements that cover the infrared-to-centimeter wavelength spectrum. The models account for diurnal and seasonal effects as well as viewing geometry at the epochs of the observational data. Model fluxes at submillimeter and longer wavelengths are computed from a radiative transfer integral that takes into account temperature gradients in the subsurface and a plausible range of lunar-like electrical properties. A surface roughness model in the form of hemispherical mini-craters is included in the evaluation of the infrared flux comparisons. Results of the infrared-to-centimeter comparisons confirm that low thermal inertia (I 5-80 J/(K m2 s0.5)) material constitutes the upper 1 cm of the four large asteroids studied. For the non-isothermal models considered, spectral emissivities near 1.0 fit the data of all four asteroids with no significant variations indicated throughout the infrared to microwave spectrum. Enhanced measured infrared flux levels (relative to a smooth surface model) of the four asteroids are constrained by a surface model with up to 50% fractional coverage of hemispherical craters, consistent with both the recent Lutetia result and historical measurements of the Moon's thermal flux characteristics.

Keihm, Stephen; Kamp, Lucas; Gulkis, Samuel; Hofstadter, Mark; Lee, Seungwon; Janssen, Michael; Choukroun, Mathieu

2013-09-01

320

First Eddy Covariance Flux Measurements of Methanol by PTR-TOF  

NASA Astrophysics Data System (ADS)

The recently developed PTR-TOF instrument was evaluated to measure methanol fluxes using the eddy covariance method. The PTR-TOF was employed at a well characterized temperate meadow field site in the Stubai valley, Austria, to measure VOC fluxes above an intensively farmed grass land. The high time resolution of the PTR-TOF allowed storing full mass spectra up to m/z 315 with a frequency of 10 Hz. Due to the high mass resolving power of the PTR-TOF three isobaric peaks were found at a nominal mass of m/z 33. Only one of the three peaks contributed to eddy covariance fluxes. The exact mass of this peak agrees well with the exact mass of protonated methanol (m/z 33.0335). The eddy covariance methanol fluxes measured with PTR-TOF were compared to virtual disjunct eddy covariance methanol fluxes simultaneously measured with a conventional PTR-MS. The methanol fluxes from both instruments show excellent agreement.

Mller, Markus; Graus, Martin; Ruuskanen, Taina M.; Schnitzhofer, Ralf; Bamberger, Ines; Kaser, Lisa; H顤tnagel, Lukas; Wohlfahrt, Georg; Karl, Thomas; Hansel, Armin

2010-05-01

321

Measurement of ion flux and concentration in fibroblastic cells  

SciTech Connect

Techniques for the measurement of cell volume, intracellular Na and K concentrations, Na-K pump activity, /sup 86/Rb efflux, /sup 22/Na uptake, intracellular pH, /sup 45/Ca uptake and efflux, and intracellular Ca concentration have been described. The technique for washing and solubilizing the cells is similar in many of these methods. This allows several measurements to be made on the same culture. Measurement of /sup 86/Rb uptake and intracellular Na and K in the same sample has been discussed above. It is also possible to measure /sup 86/Rb uptake and (/sup 14/C)DMO distribution in a single dish. There are other possible combinations of these methods. In addition, aspects of ion transport can be measured along with the assessment of macromolecular synthesis by measuring the incorporation of labeled amino acids or thymidine into TCA-insoluble material. We have used these techniques to study the effect of such mitogens as serum, platelet-derived growth factor, vasopressin, tumor promoters, fibroblast-derived growth factor, and others on Na-K pump activity, Na uptake, intracellular pH, Ca efflux, and (Ca)i.

Mendoza, S.A.; Rozengurt, E.

1987-01-01

322

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

Microsoft Academic Search

Snow-covered complex terrain is an extremely important runoff-generating landscape in high-altitude and high-latitude environments, yet it is often considered nonviable for eddy covariance measurements of turbulent fluxes. Turbulent flux data are useful for evaluating the coupled snow cover mass and energy balance that control snow ablation and melt. In particular, detailed, multiseason analyses of eddy covariance data postprocessing requirements and

Michele L. Reba; Timothy E. Link; Danny Marks; John Pomeroy

2009-01-01

323

Determination of oceanic ozone deposition by ship-borne eddy covariance flux measurements  

Microsoft Academic Search

A fast response ozone analyzer based on the ozone-nitric oxide chemiluminescence method was integrated into the NOAA-ESRL flux system to achieve the first ship-borne, direct ozone flux measurements over the open ocean. Air was collected from an inlet at 18 m height over the ocean surface mounted to the bow-jackstaff and via a 30 m-long sampling line to the ozone

L. Bariteau; D. Helmig; C. W. Fairall; J. E. Hare; J. Hueber; E. K. Lang

2010-01-01

324

Approaches to measuring fluxes of methane and nitrous oxide between landscapes and the atmosphere  

Microsoft Academic Search

The theory, applications, strengths and weaknesses of approaches commonly used for measuring trace gas fluxes are reviewed.\\u000a Chambers, representing the smallest scale (?1m2), are the most common tools. Their operating principle is simple, they can be highly sensitive, the cost can be low and field\\u000a requirements small. Problems include leaks, stickiness of some gases, inhibition of fluxes through concentration build-up,

O. T. Denmead

2008-01-01

325

High CO 2 emissions through porous media: transport mechanisms and implications for flux measurement and fractionation  

Microsoft Academic Search

Diffuse emissions of CO2 are known to be large around some volcanoes and hydrothermal areas. Accumulation-chamber measurements of CO2 flux are increasingly used to estimate the total magmatic or metamorphic CO2 released from such areas. To assess the performance of accumulation chamber systems at fluxes one to three orders of magnitude higher than normally encountered in soil respiration studies, a

W. C Evans; M. L Sorey; B. M Kennedy; D. A Stonestrom; J. D Rogie; D. L Shuster

2001-01-01

326

Measurement of the flux and energy spectrum of cosmic-ray induced neutrons on the ground  

Microsoft Academic Search

New ground-based measurements of the cosmic-ray induced neutron flux and its energy distribution have been made at several locations across the United States using an extended-energy Bonner sphere spectrometer. The data cover over twelve decades of neutron energy, from meV to GeV. An expression to scale the flux to other locations has been developed from a fit to the altitude

M. S. Gordon; P. Goldhagen; K. P. Rodbell; T. H. Zabel; H. H. K. Tang; J. M. Clem; P. Bailey

2004-01-01

327

Surface turbulent flux measurements over the Loess Plateau for a semi-arid climate change study  

Microsoft Academic Search

In order to provide high quality data for climate change studies, the data quality of turbulent flux measurements at the station\\u000a of SACOL (Semi-Arid Climate & Environment Observatory of Lanzhou University), which is located on a semi-arid grassland over\\u000a the Loess Plateau in China, has been analyzed in detail. The effects of different procedures of the flux corrections on CO2,

Jinqing Zuo; Jianping Huang; Jiemin Wang; Wu Zhang; Jianrong Bi; Guoyin Wang; Weijing Li; Peijian Fu

2009-01-01

328

A continuous measure of gross primary production for the conterminous United States derived from MODIS and AmeriFlux data  

Microsoft Academic Search

The quantification of carbon fluxes between the terrestrial biosphere and the atmosphere is of scientific importance and also relevant to climate-policy making. Eddy covariance flux towers provide continuous measurements of ecosystem-level exchange of carbon dioxide spanning diurnal, synoptic, seasonal, and interannual time scales. However, these measurements only represent the fluxes at the scale of the tower footprint. Here we used

Jingfeng Xiao; Qianlai Zhuang; Beverly E. Law; Jiquan Chen; Dennis D. Baldocchi; David R. Cook; Ram Oren; Andrew D. Richardson; Sonia Wharton; Siyan Ma; Timothy A. Martin; Shashi B. Verma; Andrew E. Suyker; Russell L. Scott; Russell K. Monson; Marcy Litvak; David Y. Hollinger; Ge Sun; Kenneth J. Davis; Paul V. Bolstad; Sean P. Burns; Peter S. Curtis; Bert G. Drake; Matthias Falk; Marc L. Fischer; David R. Foster; Lianhong Gu; Julian L. Hadley; Gabriel G. Katul; Roser Matamala; Steve McNulty; Tilden P. Meyers; J. William Munger; Asko Noormets; Walter C. Oechel; Kyaw Tha Paw U; Hans Peter Schmid; Gregory Starr; Margaret S. Torn; Steven C. Wofsy

2010-01-01

329

On the Measurement of Soil Heat Flux to Improve Estimates of Energy Balance Closure  

NASA Astrophysics Data System (ADS)

Measurements of soil heat flux (G) are required to test for energy balance closure at many fluxnet locations. Data quality is often evaluated by comparing total available energy, composed of net radiation (Rn) and G, to the sum of latent (LE) and sensible (H) heat fluxes as measured by eddy covariance. Unfortunately, G often receives minimal attention during an experiment because other flux terms (e.g., Rn and LE) are larger or require more complex instrumentation. However, G at certain time periods can account for 10 to 30 percent of Rn, especially beneath short vegetation. Thus, errors in G can confound energy closure tests and lead to erroneous conclusions about of eddy covariance performance. Research was conducted to evaluate difference methods for automating and improving measurements of G. Automated soil heat capacity sensors were combined with heat flux plates to measure conduction and changes in heat storage at different position in the soil profile. The heat capacity sensors were also used to measure soil water content and soil temperature. Data were collected beneath turfgrass, a tallgrass prairie and a juniperous forest. Field results and numerical models were used to study the best sensor configuration and data analysis algorithms. Practical guidelines for measuring and calculating soil heat flux will be presented.

Ham, J. M.

2001-12-01

330

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

PubMed Central

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

Kukacka, Libor; Nosek, Stepan; Kellnerova, Radka; Jurcakova, Klara; Janour, Zbynek

2012-01-01

331

Effect of blood flow rate on internal filtration in a high-flux dialyzer with polysulfone membrane.  

PubMed

Internal filtration/backfiltration (IF/BF) of a dialyzer depends on several parameters. This study evaluated the effect of the blood flow rate (Q (B)) on the internal filtration flow rate (Q (IF)) measured using Doppler ultrasonography for a high-flux dialyzer with a polysulfone membrane, APS-15E. In an in vitro study, bovine blood was circulated through the dialyzer, at a Q (B) of 100-350mL/min. The clearances (CL) of creatinine, ?(2)-microglobulin, and ?(1)-microglobulin were then investigated. Q (IF) increased with the Q (B) value. A good correlation was obtained between Q (IF) and the pressure difference between the pressures at the inlet of the blood compartment and the pressure at the outlet of the dialysate compartment. The creatinine CL values strongly depended on Q (B) because molecular diffusion was dominant. The ?(2)-microglobulin CL also depended on Q (B), because its removal rate seemed to be affected by both diffusive and convective transport caused by the IF/BF. An extremely low CL value was obtained for ?(1)-microglobulin because of its low diffusivity and membrane fouling induced by proteins plugging the membrane. In conclusion, the IF/BF in the dialyzer strongly depends on Q (B). Furthermore, the dependence of the solute clearance on Q (B) decreased with increasing molecular size of the solute because of the decrease in diffusivity through the membrane. PMID:22535419

Sakiyama, Ryoichi; Ishimori, Isamu; Akiba, Takashi; Mineshima, Michio

2012-04-26

332

Field intercomparison of four methane gas analysers suitable for eddy covariance flux measurements  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

333

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

NASA Astrophysics Data System (ADS)

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

Braun, Jean-Jacques; Marechal, Jean-Christophe; Riotte, Jean; Boeglin, Jean-Loup; Bedimo Bedimo, Jean-Pierre; Ndam Ngoupayou, Jules Remy; Nyeck, Brunot; Robain, Henri; Sekhar, M.; Audry, St廧hane; Viers, J廨獽e

2012-12-01

334

Variable SO2 emission rates for Anatahan volcano, the Commonwealth of the Northern Mariana Islands: Implications for deriving arc-wide volatile fluxes from erupting volcanoes  

Microsoft Academic Search

We report new spectroscopic-derived SO2 emission rates for Anatahan volcano, Mariana Islands. Measurements of SO2 fluxes reveal large fluctuations over the 20032005 period - from 78 kg s?1 which occurred on the same day as resurgent volcanic activity (March, 2005) to 50 kg s?1 and 25 kg s?1 made days\\/weeks after the start of eruptive sequences in 2003 and 2004

D. R. Hilton; T. P. Fischer; A. J. S. McGonigle; J. M. de Moor

2007-01-01

335

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

PubMed

Renewed interest in quantifying greenhouse gas emissions from soil has led to an increase in the application of chamber-based flux measurement techniques. Despite the apparent conceptual simplicity of chamber-based methods, nuances in chamber design, deployment, and data analyses can have marked effects on the quality of the flux data derived. In many cases, fluxes are calculated from chamber headspace vs. time series consisting of three or four data points. Several mathematical techniques have been used to calculate a soil gas flux from time course data. This paper explores the influences of sampling and analytical variability associated with trace gas concentration quantification on the flux estimated by linear and nonlinear models. We used Monte Carlo simulation to calculate the minimum detectable fluxes (? = 0.05) of linear regression (LR), the Hutchinson/Mosier (H/M) method, the quadratic method (Quad), the revised H/M (HMR) model, and restricted versions of the Quad and H/M methods over a range of analytical precisions and chamber deployment times (DT) for data sets consisting of three or four time points. We found that LR had the smallest detection limit thresholds and was the least sensitive to analytical precision and chamber deployment time. The HMR model had the highest detection limits and was most sensitive to analytical precision and chamber deployment time. Equations were developed that enable the calculation of flux detection limits of any gas species if analytical precision, chamber deployment time, and ambient concentration of the gas species are known. PMID:22565252

Parkin, T B; Venterea, R T; Hargreaves, S K

336

Lidar Measurement of Boundary Layer Evolution to Determine Sensible Heat Fluxes  

NASA Astrophysics Data System (ADS)

The estimation of large scale fluxes of heat and water vapor is crucial for a number of reasons, including weather prediction, climate, agriculture, and water resources management. It is known that these fluxes are not uniform and that the distribution of the surface heat fluxes is a major factor in producing and modifying mesoscale atmospheric flows, turbulence and evaporation. Local variability in the values is the result of variations in soil type, moisture content, type of vegetative cover, and wind speed, among other factors. Obtaining high quality data requires expensive equipment that needs periodic maintenance and attention. So while point sensors cannot be extensively deployed because of cost, conventional measurements represent the surface fluxes over very limited areas. This work evaluates a method where, with a relatively simple, vertically staring lidar, larger scale estimates of the sensible heat flux can be inferred. The estimation of a spatially integrated sensible surface heat flux and the determination of regional heat fluxes over heterogeneous land surfaces is needed to address a number of problems concerning long-range and mesoscale transport models of pollutants and parameterizations in climate models.

Nichols, J. J.; Eichinger, W. E.; Cooper, D. I.; Hipps, L. E.; Holder, H. E.; Kustas, W. P.; Prueger, J. H.

2004-12-01

337

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

Microsoft Academic Search

This work presents experimental measurements obtained by analyzing the first 254 live days of data from the SNO NaCl run. The electron neutrino flux was measured to be 1.66 +\\/- 0.10 stat.+0.07 -0.07 (syst.) x 106cm-2s-l and the non-electron neutrino flux was measured to be 3.32 +\\/- 0.38 stat.+0.26 -0.25 (syst.) x 106cm-2s-1. Using the above results we determined the

Vadim Liviu Rusu

2003-01-01

338

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

NASA Astrophysics Data System (ADS)

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

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

2011-02-01

339

Results of measuring the fluxes of solar energetic particles and methods of their interpretation  

NASA Astrophysics Data System (ADS)

Reliability and credibility of the results of measurements of the fluxes of protons and heavy ions of solar energetic particles, carried out with various experimental methods, are studied, as well as the methods of description of obtained data with various model functions of energy spectra. We analyze the results of measuring the fluxes of heavy ions of solar cosmic rays with the use of solid-state track detectors in the experiments Astro (April 1981, Salyut-6 spacecraft) and Platan-3 (1988-1989, Mir orbital station) and compare them with the results of experiments VLET and CRT made onboard the IMP-8 satellite. Special emphasis is made on the analysis of results obtained with instruments SIS and ULEIS ( ACE), and of results of measuring the fluxes of helium ions by the instrument EPEAD on GOES satellites. We also discuss the problem of fitting experimental data about SCR fluxes by different functions of energy (momentum, velocity) of particles. Such an approximation is a basis for interpreting the results of measurements. Numerous systematic errors are revealed that are typical for the results of measurements of the fluxes of SCR particles, performed with different instruments onboard Earth-orbiting satellites and other space vehicles.

Baranov, D. G.; Gagarin, Yu. F.; Dergachev, V. A.; Nymmik, R. A.; Panasyuk, M. I.

2011-12-01

340

Measurements of ambient HONO concentrations and vertical HONO flux above a northern Michigan forest canopy  

NASA Astrophysics Data System (ADS)

Systems have been developed and deployed at a North Michigan forested site to measure ambient HONO and vertical HONO flux. The modified HONO measurement technique is based on aqueous scrubbing of HONO using a coil sampler, followed by azo dye derivatization and detection using a long-path absorption photometer (LPAP). A Na2CO3-coated denuder is used to generate "zero HONO" air for background correction. The lower detection limit of the method, defined by 3 times of the standard deviation of the signal, is 1 pptv for 1-min averages, with an overall uncertainty of (1 + 0.05 [HONO]) pptv. The HONO flux measurement technique has been developed based on the relaxed eddy accumulation approach, deploying a 3-D sonic anemometer and two HONO measurement systems. The overall uncertainty is estimated to be within (8 10-8 + 0.15 FHONO) mol m-2 h-1, with a 20-min averaged data point per 30 min. Ambient HONO and vertical HONO flux were measured simultaneously at the PROPHET site from 17 July to 7 August 2008. The forest canopy was found to be a net HONO source, with a mean upward flux of 0.37 10-6 moles m-2 h-1. The HONO flux reached a maximal mean of ~0.7 10-6 moles m-2 h-1 around solar noon, contributing a major fraction to the HONO source strength required to sustain the observed ambient concentration of ~70 pptv. There were no significant correlations between [NOx] and daytime HONO flux and between JNO2 [NO2] and HONO flux, suggesting that NOx was not an important precursor responsible for HONO daytime production on the forest canopy surface in this low-NOx rural environment. Evidence supports the hypothesis that photolysis of HNO3 deposited on the forest canopy surface is a major daytime HONO source.

Zhang, N.; Zhou, X.; Bertman, S.; Tang, D.; Alaghmand, M.; Shepson, P. B.; Carroll, M. A.

2012-09-01

341

Comparison of two chamber methods and eddy covariance measurements for N2O for low flux conditions  

NASA Astrophysics Data System (ADS)

Chamber measurements of N2O based on flask sampling and subsequent GC analysis in the laboratory reveal high uncertainties in particular at low flux rates. We compared automated measurements with this method to chamber measurements with a Quantum Cascade Laser (QCL, type: CW-QC-TILDAS-76-CS, Aerodyne Research Inc., Billerica, MA, USA) installed in the field and to eddy covariance (EC) measurements with a similar QCL. The comparison was conducted over a grassland located at the research farm of the Thnen Institute, Braunschweig, Germany. The QCL increased the accuracy of the chamber measurements by about factor 10. Furthermore it was possible to reduce the time of chamber closure to less than 10 minutes, allowing a relatively high number of parallel chambers with hourly repetitions. At low emissions, EC measurements were highly uncertain due to relatively high noise. Implications for long-term measurements (e. g. in the framework of research infrastructures) are discussed.

Kutsch, Werner Leo; Brmmer, Christian; Lyshede, Bjarne; Fu, Roland; Smith, Jeremy; Delorme, Jean-Pierre

2013-04-01

342

Measurement of mass flow rate using a vortex flowmeter  

Microsoft Academic Search

Conventional mass flow rate is derived from volumetric flow rate multiplied by fluid density. However the measurement accuracy is not satisfying because of density variation. Mass flowmeters that can directly measure mass flow rate have been studied and developed recently. But these flowmeters still have limits in practical application. Mass flow rate directly measured by a vortex flowmeter has been

Yongmei Huang; Hongjian Zhang; Zhiqiang Sun

2003-01-01

343

Potential and Limitations of an Electrical Low Pressure Impactor in Disjunct Eddy Covariance Aerosol Flux Measurements  

NASA Astrophysics Data System (ADS)

A micrometeorological application of an electrical low pressure impactor (ELPI) is proposed for the measurement of size-resolved particle fluxes between the surface and the atmosphere. This extends flux measurement capabilities to cover submicron particles in several size classes simultaneously. The disjunct eddy covariance system combines a sonic anemometer, an ELPI and a valve-controlled particle sampling unit. Depending on the valve setting, ambient air or filtered particle-free air is sampled and introduced into the impactor. For disjunct eddy covariance measurements, ambient air is sampled only during a very short sampling interval (~ 0.1 s) in measurement intervals of several seconds. The integrated ELPI signal is representative for the particle size distribution during the short sampling interval. This information may be correlated with fast measurements of the vertical wind speed to obtain turbulent fluxes of submicron particles simultaneously in several size classes. A prototype system has been tested in lab and field experiments in order to evaluate the technical limitations of this approach. Tests show that different valve switch cycles do not affect the concentration measurements. However, longitudinal diffusion processes within the sampling lines lead to signal dilatation. In addition, reliable measurements require a minimum number of charged particles impacting on each stage. This leads to the exclusion of some size bins in typical field applications. Nevertheless, the system showed its potential for size-resolved flux measurements under favorable conditions. Travel support by the ACCENT Access to Infrastructures program is gratefully acknowledged.

Held, A.; Niessner, R.; Bosveld, F.; Klemm, O.

2006-12-01

344

MEASUREMENT AND CALCULATION OF FAST NEUTRON FLUX IN A ZERO-ENERGY REACTOR  

Microsoft Academic Search

An activation technique for measuring relative fast neutron fluxes is ; described which has some advantages over the normal method using uranium-238 ; fission. The technique is based on the formation of rhodium-103 after inelastic ; scattering of neutrons above 100 kev. This isomer decays with a 57.4-minute half ; life giving an easily measurable gamma activity. The energy dependence

D. H. Day; W. N. Fox; M. R. Hyder

1963-01-01

345

A Gas-Capture Buoy for Measuring Bubbling Gas Flux in Oceans and Lakes  

Microsoft Academic Search

The design, calibration, and deployment of a buoy and gas-capture assembly for measuring bubbling gas flux in oceans and lakes are described. The assembly collects gas in a chamber while continuously measuring the position of the gas-water interface that forms as gas accumulates. Interface position is determined from the differential pressure between the chamber and ambient seawater. A spar buoy

Libe Washburn; Cyril Johnson; Chris C. Gotschalk; E. Thor Egland

2001-01-01

346

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

EPA Science Inventory

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

347

Flux measurements of energy and trace gases in urban Houston, Texas  

NASA Astrophysics Data System (ADS)

We describe the setup and some first year results of a new flux measurements tower in an urban area. An existing radio communications tower 4 km north of downtown Houston was equipped with micrometeorological instrumentation and trace gas sampling lines in spring 2007. Wind speed, temperature and relative humidity are recorded at five levels between 12 and 60 m above ground; 3-D wind speed measurements, solar and net radiances, and trace gas sampling are established from the 60 m level. A closed path IRGA is used for CO2 and water vapor fluxes, and independent instrumentation for criteria pollutant and VOC fluxes. Two CSI data loggers and software control the measurements, and EdiRe software is used to analyze turbulence data and compute fluxes. A project description is provided at http://atmo.tamu.edu/yellowcabtower. Surface properties as calculated from the gradient measurements show the site to be surprisingly uniform, with displacement heights between 5 and 9 m and roughness lengths between 0.4 and 0.7 m, despite urban heterogeneity. The latter is investigated through visible/near IR orthoimagery and LIDAR data, which are incorporated into a local GIS. Net radiation was also only marginally affected by surface heterogeneity. At this urban location it is balanced by roughly equal amounts of sensible heat, latent heat, and storage fluxes. Latent heat flux, however, is smaller outside the growing season, with an equivalent increase in winter storage fluxes, as expected. Significant differences are also observed with direction during summer, showing decreased Bowen ratios and lower CO2 emissions from sectors with a larger urban tree canopy cover in the footprint. The largely mature, dominantly oak urban canopy cover alleviates approximately 100 W m- 2 during typical summer days. On the other hand, anthropogenic CO2 emissions dominate over photosynthetic uptake all year round. Measured carbon fluxes peak during morning rush-hour traffic, especially when increasing stretches of the main commuter road fall into the footprint. Outside the rush hour, daytime carbon fluxes typically ranged from 0.4 to 1.6 g C m-2 h-1. A seasonal comparison shows that up to 75% of midday anthropogenic carbon flux is removed via photosynthesis in the dominant wind sector, S, which bears typical tree canopy covers of 25-50% on pervious surfaces.

Boedeker, I.; Schade, G. W.; Adams, S.; Park, C.

2008-12-01

348

High flux rates of ignimbrite and stratocone growth at Atitlan Caldera, Guatemala  

NASA Astrophysics Data System (ADS)

To understand the factors that govern the development of different volcanic edifices, recent studies have quantified eruptive volume, repose interval and crustal thickness among other parameters. Atitlan Caldera, Guatemala provides a compelling locality to contrast the age, volume and repose of several ignimbrite eruptions over the past 160 kyr including the 300 km3 Los Chocoyos ignimbrite, as well as, prolific mafic volcanism from three intracaldera stratocones. Since the caldera-forming eruption 84 kyr, 117 km3 of basaltic andesitic to dacitic lavas have been erupted from stratocones San Pedro, Toliman and Atitlan, resulting in a combined eruption rate of 1.46km3/kyr. These eruption rates are considered minimum values as preliminary 40Ar/39Ar age data suggest the cones are much younger than 84 kyr. Inclusion of the Los Chocoyos eruption increases eruption rates to 4.77 km3/kyr. Average eruption rates of the Atitlan system are an order of magnitude greater than most frontal arc complexes that are commonly characterized by cone growth due to large punctuated silicic eruptions. Although a minor proportion (<5%) of lavas erupted from San Pedro and Toliman are dacitic, the vast majority of stratocone growth occurred due to small lava flows of basaltic andesite and andesite or pyroclastic eruptions. Geochemically the lavas from stratocones San Pedro, Toliman and Atitlan are similar to four stratocones that formed prior to the Los Chocoyos and may have erupted another several hundred km3 of lava. In addition to the large volumes of mafic lava generated, three large ignimbrite eruptions that are geochemically similar to each other have occurred spaced 10s kyr apart. A large geochemical gap exists that suggests the ignimbrite is not related to the stratocone lavas by fractional crystallization. Finally, lavas must traverse ~45 km of continental crust at a very high flux rate to build large stratocones in the Atitlan system over a relatively short geologic time interval. At Atitlan Caldera, recent volcanism is not marked by large punctuated ignimbrite eruptions, but rather by continual profuse outpouring of both rhyolitic and basaltic products.

Cunningham, H. S.; Jicha, B.; Singer, B. S.

2010-12-01

349

Silicate weathering rates and solute fluxes along an erosional gradient, Middle Fork of the Feather River, CA  

NASA Astrophysics Data System (ADS)

Over geologic timescales, the weathering of silicate rocks has helped to maintain a mostly habitable planet, and it is clear that understanding rates of chemical weathering is key to accurately interpreting past changes in climate and seawater chemistry. However, the mechanisms that drive changes in weathering rates through time are incompletely described. By more closely examining the interplay between variables which control weathering, including fluid residence time, dissolution kinetics, and thermodynamic constraints, we would like to gain a more detailed understanding of these mechanisms. For example, the rate of mineral dissolution is controlled by the flux of water, the availability of fresh mineral surfaces and the proximity to thermodynamic equilibrium between the dissolving and secondary phases-once the soil or ground water reaches equilibrium, increasing mineral availability would not result in an increase in solute flux. Thus, the residence time of water and the departure from thermodynamic equilibrium are anticipated to be important controls on weathering fluxes. To gain a better understanding of the relative importance of these variables, we have studied the chemical and physical composition of solids and waters from three soil-mantled hillslope transects with different erosion rates within a tributary basin of the Middle Fork Feather River, CA. Overall, lower water contents are found in areas with higher erosion rates, and at the high erosion rate transect the solute compositions suggest that water is mostly bypassing the saprolite layer. In the solute chemistry, there is a clear trend of increasing concentration with depth for non-biologically cycled weathering components (Na, Si, etc). Other elements, such as Ca, Mg, K and Al show elevated concentrations in the surface horizons due to strong biological cycling. Calculated mineral saturation indices show that deeper waters are saturated with respect to K-feldspar and kaolinite, and slightly undersaturated with respect to albite. In general, the solute concentrations at the base of the soil profiles are similar across the three different erosion rates, indicating that the waters have reacted to a similar extent on all three transects despite widely varying moisture content, infiltration fluxes, steepness, grain size and clay content in the soils. Total chemical denudation rates (based on solute fluxes) vary across the transects according to water fluxes. This detailed study of hillslopes with different erosion rates suggests that thermodynamic equilibrium, water residence time and water flux are likely important controls on global weathering rates, even in active tectonic environments.

Kouba, C. M.; Rosen, V.; Maher, K.; Mayer, K.; Yoo, K.; Weinman, B. A.; Hurst, M. D.; Mudd, S. M.; Attal, M.

2011-12-01

350

A simple Bulk approach to improve and validate the Turbulent Fluxes derived from satellite Measurements  

NASA Astrophysics Data System (ADS)

This study presents a simple and iterative algorithm, based on the Monin-Obukhov similarity theory (Monin and Obukhov, 1954), which allows improvement and evaluation of the wind stress and latent (evaporation) and sensible heat fluxes deduced from satellite measurements. The algorithm is validated using the multiyear hourly moored buoys data from the Tropical Ocean Global Atmosphere/Tropical Atmosphere Ocean (TOGA/TAO), Pilot Research Moored Array Tropical Atlantic (PIRATA), Oceanographic Data Acquisition Systems (ODAS) and National Data Buoy Center (NDBC) observation platforms, and is compared with the turbulent fluxes from existing algorithms such as COARE3.0 (Fairall, 2003), Smith (1988), and Large and Pond (1982). These comparisons show that the mean parameters agree well with those from COARE3.0, with correlations higher than 98%. Preliminary validation results of the algorithm using the satellite variables clearly show an improvement in the estimates of the turbulent fluxes. The mean bias with the buoys flux is now about 3 W/m against -40 W/m, and correlations are more than 60% compared with 30% in the old version. The analysis also focused on the two practical aspects of the bulk approach which are of interest to the modelling community: the influence of both the iteration number and of the random variable errors on the turbulent flux estimates. It is shown that the convergence constraint has a significant influence on the coherence of three fluxes, and variable errors such as relative humidity, air and sea temperature, or wind speed can induce errors from about 10 to 100% on the turbulent flux estimates. This study has shown also that the sea surface salinity has a significant impact on the latent heat flux estimates; it can induce an increase about 5 to 10 % or a reduction of 1% of latent heat flux.

Ludos-Herv, A.; Abderrahim, B.; Jacques, S.

2006-12-01

351

Airborne flux measurements of trace species in an Arctic boundary layer  

SciTech Connect

In situ airborne flux values for O[sub 3], CO, an CH[sub 4] over selected wetlands of Alaska are reported, and airborne CH[sub 4] flux measurements are presented for the first time. The source/sink distribution over the Yukon-Kuskokwim Delta (YKD) is qualitatively correlated with surface vegetation type. The CH[sub 4] source strength over the YKD ranged from 25 to 85 mg/sq m/d. A spatially averaged, seasonally adjusted source strength of 51 mg/sq m/d was established for the YKD. Indirect CH4 flux estimates obtained over the Alaskan North Slope indicate a much lower source strength. The global CH[sub 4] emission from tundra are estimated to be 44 Tg/a at an upper limit. Airborne CO flux measurements over the YKD indicate low negative flux values over the coastal areas, while some positive fluxes were observed in the inland sparsely forested regions. An inspection of the cospectrum of CO with vertical velocity for sample runs in coastal areas indicate the possibility of in situ photochemical destruction/production of CO. 64 refs.

Ritter, J.A.; Barrick, J.D.W.; Sachse, G.W.; Gregory, G.L.; Woerner, M.A.; Watson, C.E.; Hill, G.F.; Collins, J.E. Jr. (NASA, Langley Research Center, Hampton, VA (United States) Science and Technology Corp., Hampton, VA (United States))

1992-10-01

352

Local energy dissipation rate balances local heat flux in the center of turbulent thermal convection.  

PubMed

The local kinetic energy dissipation rate ?(u,c) in Rayleigh-B幯ard convection cell was measured experimentally using the particle tracking velocimetry method, with varying Rayleigh number Ra, Prandtl number Pr, and cell height H. It is found that ?(u,c)/(?(3)H(-4))=1.0510(-4)Ra(1.550.02)Pr(1.150.38). The Ra and H dependencies of the measured results are found to be consistent with the assumption made for the bulk energy dissipation rate ?(u,bulk) in the Grossmann-Lohse model. A remarkable finding of the study is that ?(u,c) balances the directly measured local Nusselt number Nu(c) in the cell center, not only scalingwise but also in magnitude. PMID:22107524

Ni, Rui; Huang, Shi-Di; Xia, Ke-Qing

2011-10-17

353

Sampling errors in the vertical fluxes of potential temperature and moisture measured by aircraft during FIFE  

NASA Astrophysics Data System (ADS)

The First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE) was carried out over a 15 15 km area in central Kansas [Sellers et al., this issue]. The site size was constrained by land use characteristics, topography, and, importantly, the ability to field a reasonable network of surface observations of plant physiology, soil moisture, and radiative characteristics as well as surface observations of meteorological observations, including vertical fluxes of sensible heat and moisture. As described by Kelly [this issue], aircraft flying within the atmospheric boundary layer over the FIFE site played an important role: they provided direct measurements of the vertical fluxes of sensible heat and moisture above the FIFE site. Potential temperature flux and sensible heat flux differ by the constant ?dcp, where ?d is the dry air density (which is nearly constant in the atmospheric boundary layer) and cp is the specific heat of dry air at constant pressure.

Grossman, Robert L.

1992-11-01

354

Uncertainty analysis of steady state incident heat flux measurements in hydrocarbon fuel fires.  

SciTech Connect

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.

Nakos, James Thomas

2005-12-01

355

Acoustic measurement method of the volume flux of a seafloor hydrothermal plume  

NASA Astrophysics Data System (ADS)

Measuring fluxes (volume, chemical, heat, etc.) of the deep sea hydrothermal vents has been a crucial but challenging task faced by the scientific community since the discovery of the vent systems. However, the great depths and complexities of the hydrothermal vents make traditional sampling methods laborious and almost daunting missions. Furthermore, the samples, in most cases both sparse in space and sporadic in time, are hardly enough to provide a result with moderate uncertainty. In September 2010, our Cabled Observatory Vent Imaging Sonar System (COVIS, http://vizlab.rutgers.edu/AcoustImag/covis.html) was connected to the Neptune Canada underwater ocean observatory network (http://www.neptunecanada.ca) at the Main Endeavour vent field on the Endeavour segment of the Juan de Fuca Ridge. During the experiment, the COVIS system produced 3D images of the buoyant plume discharged from the vent complex Grotto by measuring the back-scattering intensity of the acoustic signal. Building on the methodology developed in our previous work, the vertical flow velocity of the plume is estimated from the Doppler shift of the acoustic signal using geometric correction to compensate for the ambient horizontal currents. A Gaussian distribution curve is fitted to the horizontal back-scattering intensity profile to determine the back-scattering intensity at the boundary of the plume. Such a boundary value is used as the threshold in a window function for separating the plume from background signal. Finally, the volume flux is obtained by integrating the resulting 2D vertical velocity profile over the horizontal cross-section of the plume. In this presentation, we discuss preliminary results from the COVIS experiment. In addition, several alternative approaches are applied to determination of the accuracy of the estimated plume vertical velocity in the absence of direct measurements. First, the results from our previous experiment (conducted in 2000 at the same vent complex using a similar methodology but a different sonar system) provide references to the consistency of the methodology. Second, the vertical flow rate measurement made in 2007 at an adjacent vent complex (Dante) using a different acoustic method (acoustic scintillation) can serve as a first order estimation of the plume vertical velocity. Third, another first order estimation can be obtained by combining the plume bending angle with the horizontal current measured by a current meter array deployed to the north of the vent field. Finally, statistical techniques are used to quantify the errors due to the ambient noises, inherent uncertainties of the methodology, and the fluctuation of the plume structure.

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

2011-12-01

356

Flux of ionizing Lyman continuum photons and the rate of star formation in the Galaxy  

SciTech Connect

Values of the ionizing radiation flux are calculated from D. Mihalas's non--LTE model atmospheres for the effective-temperature range 15,000/sup 0/K < or =T< or =55,000/sup 0/K and for log g=3.5 and 4.0. Corrections are applied for the blanketing effect. The ionizing luminosity of early-type stars is determined as a function of mass. A mass function for O stars determined from star counts yields ionizing luminosities for young clusters. In deriving the theoretical (log L, logN/sub c/) relation, where L is the luminosity of a cluster, several factors that may affect the position of the curve are taken into account: a) variations in chemical composition within the observed range (Z=0.02--0.04); b) rotation of the stars up to the critical velocity; c) variations in the exponent of the mass function. If allowance is made for these factors and for observational error, most sources (compact H II zones) fall within the correlation band in the (log L, log N/sub c/) diagram, and there is no need to resort to the hypothesis that some of the ionizing Lyman photons are absorbed by dust. For sources deviating from this correlation, there are several alternatives to the dust interpretation. The analysis provides an estimate for the rate of star formation in the Galaxy.

Avedisova, V.S.

1979-09-01

357

In situ determination and laboratory measurements of Cu fluxes in two dam sediments using DGT  

NASA Astrophysics Data System (ADS)

The technique of diffusion gradients in thin films (DGT) accumulates labile metals on a chelex resin after their diffusive transport through a hydrogel. DGT is capable to measure in-situ fluxes of metals in sediments, in response to the perturbation induced. Porewater concentration is lowered, but depending on the sediment, metal sorbed to particulate matter can either exchange with solution to maintain its concentration or not. We measured Cu fluxes in the sediments of two dams, in the field with an on-site DGT insertion technique and at the laboratory. Some experiments were also performed to measure directly fluxes in their porewaters after extraction. Results of experiments and calculations using the DIFS model allowed us to discriminate between both aquatic systems in their ability to sustain metal concentration in porewaters. The possibility of resupply was demonstrated for one sediment but particulate metal in the other sediment appeared tightly bound and not subject to release.

Roulier, J.-L.; Motte, B.

2003-05-01

358

Vector Magnetic Property Measurement in Magnetic Steel Sheets under High Magnetic Flux Density Conditions  

NASA Astrophysics Data System (ADS)

In order to develop higher torque, lower weight and smaller sized magnetic actuators for driving electrical vehicles and robot arms, designing under high magnetic field and high exciting voltage is most effective. It is therefore very important to understand vector magnetic properties in electrical steel sheets under high magnetic flux density conditions. The vector magnetic properties mean the relationship between the magnetic flux density vector and the magnetic field strength vector and it is very difficult to measure the each component under high magnetic flux density conditions because of the magnetic saturation and the magnetic anisotropy. In this paper, accurate measurement techniques of the vector magnetic properties over 1.5T and measured vector magnetic properties are reported and discussed.

Maeda, Yoshitaka; Todaka, Takashi; Enokizono, Masato

359

Deposition rate enhancement in HiPIMS without compromising the ionized fraction of the deposition flux  

NASA Astrophysics Data System (ADS)

We systematically investigate and quantify different physical phenomena influencing the deposition rate, aD, of Nb coatings prepared by high power impulse magnetron sputtering (HiPIMS), and propose a straightforward approach for deposition rate enhancement through the control of the magnetron's magnetic field. The magnetic field strength at the target surface, B, of a 50 mm diameter magnetron was controlled by the application of paramagnetic spacers with different thicknesses in between the magnetron surface and the target. We found that lowering B achieved by the application of a 2.8 mm thick spacer led to an increase in aD by a factor of ?4.5 (from 10.6 to 45.2 nm min?1) when the discharge was operated at a fixed average pulse target power density (2.5 kW cm?2). However, the ionized fraction of the deposition flux onto the substrate was found to be comparable, despite a large difference in B-dependent discharge characteristics (magnetron voltage and discharge current). We show that the decrease in aD commonly observed in HiPIMS (ranging from 33% to 84% in comparison with dc magnetron sputtering in the presented experiments) is governed by different physical processes, depending on the value of B: for high B, the back-attraction of the target ions towards the target is the dominant effect, while for low B the ion back-attraction, the sub-linear dependence of the sputtering yield on the ion energy, and the variation in material transport effects are all important. Finally, we offer a theoretical background for the observed results, demonstrating that the here-presented conclusions may be applicable to HiPIMS discharges using different metal targets and different inert gases.

?apek, J.; H嫮a, M.; Zabeida, O.; Klemberg-Sapieha, J. E.; Martinu, L.

2013-05-01

360

Combined analysis of neutron and photon flux measurements for the Jules Horowitz reactor core mapping  

SciTech Connect

We study the combined analysis of nuclear measurements to improve the knowledge of the irradiation conditions in the experimental locations of the future Jules Horowitz Reactor (JHR). The goal of the present work is to measure more accurately neutron flux, photon flux and nuclear heating in the reactor. In a Material Testing Reactor (MTR), nuclear heating is a crucial parameter to design the experimental devices to be irradiated in harsh nuclear conditions. This parameter drives the temperature of the devices and of the samples. The numerical codes can predict this parameter but in-situ measurements are necessary to reach the expected accuracy. For this reason, one objective of the IN-CORE program [1] is to study the combined measurements of neutron and photon flux and their cross advanced interpretation. It should be reminded that both neutron and photon sensors are not totally selective as their signals are due to neutron and photon interactions. We intend to measure the neutron flux by three different kinds of sensors (Uranium Fission chamber, Plutonium Fission chamber and Self Powered Neutron Detector), the photon flux by two different sensors (Ionization chamber and Self Powered Gamma Detector) and the nuclear heating by two different ones (Differential calorimeter and Gamma Thermometer). For the same parameter, we expect that the use of different kinds of sensors will allow a better estimation of the aimed parameter by mixing different spectrum responses and different neutron and gamma contributions. An experimental test called CARMEN-1 is scheduled in OSIRIS reactor (CEA Saclay - France) at the end of 2011, with the goal to map irradiation locations in the reactor reflector to get a first validation of the analysis model. This article focuses on the sensor selection for CARMEN-1 experiment and to the way to link neutron and photon flux measurements in view to reduce their uncertainties but also to better assess the neutron and photon contributions to nuclear heating. (authors)

Fourmentel, D.; Villard, J. F.; Lyoussi, A. [DEN Reactor Studies Dept., French Nuclear Energy and Alternative Energies Commission, CEA Cadarache, 13108 Saint Paul-Lez-Durance (France); Reynard-Carette, C. [Laboratoire Chimie Provence LCP UMR 6264, Univ. of Provence, Centre St. Jerome, 13397 Marseille Cedex 20 (France); Bignan, G.; Chauvin, J. P.; Gonnier, C.; Guimbal, P.; Malo, J. Y. [DEN Reactor Studies Dept., French Nuclear Energy and Alternative Energies Commission, CEA Cadarache, 13108 Saint Paul-Lez-Durance (France); Carette, M.; Janulyte, A.; Merroun, O.; Brun, J.; Zerega, Y.; Andre, J. [Laboratoire Chimie Provence LCP UMR 6264, Univ. of Provence, Centre St. Jerome, 13397 Marseille Cedex 20 (France)

2011-07-01

361

CH/sub 4/ flux from biogas generators and rice paddies as measured in Sichuan, China. (Annual progress report)  

SciTech Connect

We report methane release rates from several biogas generators and from rice paddies in Sichuan, China, during four different stages of growth, using chamber techniques. The release rates from biogas generators vary greatly from pit to pit, ranging between 0.037 and 50 g/day/pit, very much depending on the seal characteristics of the pits. If this result was representative for the whole year round and all the biogas pits in China, it would result in a total annual CH/sub 4/ release of 1 x 10/sup 8/ to 1.5 x 10/sup 11/ g for the 8 million biogas pits now used in China. CH/sub 4/ flux from rice paddies varies significantly from place to place and from time to time. The measured CH/sub 4/ fluxes are larger during the seedling stage and shortly before harvest, ranging from 3.1 to 2889 mg/m/sup 2//day. During the seedling stage transport through air bubbles may have a significant contribution to the total CH/sub 4/ emission, as air bubbles are commonly seen in the seedling beds and the measured CH/sub 4/ flux is much higher at a spot with air bubbles than at a spot without air bubbles.

Wang, M.; Khalil, M.A.K.; Rasmussen, R.A.

1986-01-01

362

Ecosystem-scale measurements of nitrous oxide fluxes for an intensely grazed, fertilized grassland  

NASA Astrophysics Data System (ADS)

An eddy covariance (EC) system with a tunable diode laser trace gas analyzer was used in a field setting in Ireland to measure N2O emissions on a continuous basis over an eight-month period, spanning a range of seasonal conditions. Intensely-grazed grassland fields within the footprint area of the EC sensors were subject to chemical fertilizer and slurry applications in order to boost grassland yield, and the amounts of these applications were documented by the farmers on a monthly basis. Three major emission events, covering a timeframe of 16 days (6.6% of the measurement period) contributed to over half (51.1%) of the observed cumulative flux. Two of these events occurred during the summer, while the third occurred during the winter, with vastly different soil moisture and soil temperature conditions associated with these times of the year. The type of N applications (fertilizer vs. slurry), soil moisture and temperature status had implications for controlling the short-term rates of N2O emissions. Cumulative N2O emissions, however, were driven by fertilizer and slurry N applications, as the emission factor of approximately 3.0% displayed consistency throughout the eight-month period.

Scanlon, Todd M.; Kiely, Ger

2003-08-01

363

[High resolution measurement of concentrations and fluxes of heavy metals in pore waters by DGT].  

PubMed

Three sediment cores were collected from the Daliao River system in May 2006. The physico-chemical characteristics and heavy metal contents of sediment cores were analyzed. The vertical profiles of metals in pore water were measured by diffusive gradient in thin films (DGT) and centrifugal methods separately. The sequence of the concentrations of Cd, Co, Cr and Cu in sediment is Cr > Cu > Co > Cd. The concentrations measured by DGT were lower than that measured by centrifugal method. The average ratios of DGT measured concentrations (cDGT) to the concentrations measured by centrifugal method of Cd, Co, Cr and Cu were 0.389, 0.328, 0.863 and 0.403, respectively. This suggested that the release rates of these metals from solid phase to solution followed the sequence of Cr > Cu > Cd > Co. The fluxes of Cd, Co Cr and Cu were 1.12 x 10(-7) - 3.28 x 10(-7) nmol/(cm2 x s), 2.48 x 10(-7) - 10.40 x 10(-7) nmol/(cm2 x s), 8.80 x 10(-6) - 12.65 x 10(-6) nmol/(cm2 x s) and 6.14 x 10(-6) - 13.93 x 10(-6) nmol/(cm2 x s), respectively. The result showed that the release of Cd and Cu was mainly influenced by organic matter (OM), while Fe oxides, Mn oxides and OM were major factors controlling the transfer of Cr. The redox potential may be the major factor influencing the release of Co element. PMID:18290432

Fan, Ying-hong; Lin, Chun-ye; He, Meng-chang; Zhou, Yu-xiang; Yang, Zhi-feng

2007-12-01

364

A switched continuous-wave sonic anemometer for measuring surface heat fluxes  

NASA Astrophysics Data System (ADS)

A one-dimensional sonic anemometer system suitable for use in measuring near surface heat fluxes is described. It operates by transferring continuous sound waves in alternate directions between a matched pair of cheap ultrasonic transducers. The design and development of the anemometer is described, together with wind tunnel tests, and field experiments, in which the performances of several prototypes are compared with those of other anemometers over stubble and over forest. The results indicate that the device is suitable for measuring eddy correlation heat fluxes to an accuracy better than 5%.

Shuttleworth, W. J.; McNeil, D. D.; Moore, C. J.

1982-08-01

365

High speed infrared camera diagnostic for heat flux measurement in NSTX  

NASA Astrophysics Data System (ADS)

A new high speed infrared camera has been successfully implemented and produced first set of heat flux measurements on the lower divertor tiles in the NSTX tokamak. High spatial and temporal resolutions, 6.4 mm and 1.6-6.3 kHz, respectively, enable us to investigate detailed structure of heat flux deposition pattern caused by transient events such as edge localized modes. A comparison of the data with a slow infrared camera viewing the same region of interest shows good agreement between the two independent measurements. Data analysis for various plasma conditions is in progress.

Ahn, J.-W.; Maingi, R.; Mastrovito, D.; Roquemore, A. L.

2010-02-01

366

High speed infrared camera diagnostic for heat flux measurement in NSTX  

SciTech Connect

A new high speed infrared camera has been successfully implemented and produced first set of heat flux measurements on the lower divertor tiles in the NSTX tokamak. High spatial and temporal resolutions, 6.4 mm and 1.6-6.3 kHz, respectively, enable us to investigate detailed structure of heat flux deposition pattern caused by transient events such as edge localized modes. A comparison of the data with a slow infrared camera viewing the same region of interest shows good agreement between the two independent measurements. Data analysis for various plasma conditions is in progress.

Ahn, J.-W.; Maingi, R. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Mastrovito, D.; Roquemore, A. L. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)

2010-02-15

367

Flux measurements of volatile organic compounds at SMEAR II using surface layer gradient method  

NASA Astrophysics Data System (ADS)

Volatile organic compounds (VOCs) are mostly emitted into atmosphere from natural sources. Some of the compounds, such as monoterpenes, are highly reactive and seem to have major contributions to aerosol particle formation and growth, thus these compounds are also connected to the global climate change. Approximately 50 % of the biogenic emissions is coming from the tropical rain forests, 15-20 % from the boreal forests and the rest from the other sources like fields and oceans. In order to understand seasonal and interannual changes in VOC emissions long term emission measurements would be of great importance. However, long-term VOC emission measurements are extremely sparse. Our aim is to develop reliable and feasible method to measure ecosystem scale VOC emissions by micrometeorological methods. In the past decade the disjunct eddy covariance method with proton transfer reaction quadrupole mass spectrometry (DEC/PTR-QMS) has been the method of choise for VOC flux measurements. However, automatically data post-processing, crucial for long term measurement, remains a challenge, especially in low flux conditions. To by-pass these problems we can apply a surface layer gradient technique with PTR-QMS (SLG/PTR-QMS) for long term VOC flux measurements. In this technique fluxes are obtained using measured vertical profiles on VOC concentrations with Monin-Obukhov similarity theory. Albeit more indirect method than DEC, this classical method holds promise for long term measurement. The measurements wer conducted in Hyyti鄟 at SMEAR II station (61 51' N, 24 17' E, 180 m a.m.s.l.) since summer 2010. Hyyti鄟 represents a typical boreal region with clear snow covered winters and annual average temperature has been approximately 3.3蚓. Clear cumulative positive flux of methanol, acetaldehyde, ethanol/formic acid, acetone, MBO-fragment/isoprene, and monoterpenes were observed.

Rantala, P.; Taipale, R.; Ruuskanen, T. M.; Aalto, J.; Kajos, M. K.; Patokoski, J.; Schallhart, S.; Rinne, J.

2012-04-01

368

Solar cycle variation of trapped proton fluxes measured by LEO satellites.  

NASA Astrophysics Data System (ADS)

Now days there are few models of the Earth radiation belts proton fluxes that are used for prediction of the fluxes at the different orbits of the spacecrafts. Discrepancies in their predictions are wellknown. The AP8 model of trapped proton fluxes is based on the satellite data that were measured 1960th and 1970th during the anomalous weak 20th (in comparison with the 21st and 22d ) solar cycle and solar cycle variation is taken into account only by specifying two different models for solar maximum and solar minimum. The TPM-1 model calculates the proton fluxes for any year of solar activity and contains sub-models for quiet and active states of magnetosphere. Solar cycle variation of trapped protons measured during the 23rd solar cycle on board low orbital polar satellites Coronas-F (500 km altitude) and NPOES-15, -17 (800 km altitude) in 2001 - 2007 is considered in this report. The experimental proton fluxes measured for the drift sells L=1.14-1.2 were compared with the predictions of AP8 model for solar maximum and minimum as well as with the prediction of TPM-1 model.

Nikolaeva, Natalia; Kuznetsov, Nikolay; Panasyuk, Michail

369

Radial electrostatic flux inferred from core measurements of potential and density fluctuations  

SciTech Connect

Broadband potential fluctuations and electrostatic fluctuation induced particle flux have been measured in the core of a medium size tokamak plasma for the first time. Density fluctuations and wave numbers were simultaneously measured. Measurements indicate that radial electrostatic fluctuation induced particle flux in the core region, at the normalized radii of 0.17<{rho}<0.38, due to modes with wave numbers less than 4 cm{sup -1} is small in magnitude, is likely directed inward, and cannot account for particle flux predicted by the continuity equation and particle source codes. Estimates of electrostatic energy flux are also significantly less than values predicted via power balance analysis. Asymmetries in coherent density and potential fluctuation levels on closed flux surfaces are evident. Relative fluctuation levels {tilde n}/n and {tilde {phi}} tend to increase with radius, and the fluctuations are Boltzmann-like in the region 0.17{<=}{rho}{<=}0.38. The direction of mode propagation is in the electron diamagnetic drift direction. Corresponding phase velocities, v{sub ph}{approx}3.5x10{sup 5} cm/s, are similar to drift wave velocities.

Demers, D. R.; Schoch, P. M.; Crowley, T. P.; Connor, K. A.; Ouroua, A.

2001-04-01

370

Measurements of solar flux density distribution on a plane receiver due to a flat heliostat  

SciTech Connect

An experimental facility is designed and manufactured to measure the solar flux density distribution on a central flat receiver due to a single flat heliostat. The tracking mechanism of the heliostat is controlled by two stepping motors, one for tilt angle control and the other for azimuth angle control. A x-y traversing mechanism is also designed and mounted on a vertical central receiver plane, where the solar flux density is to be measured. A miniature solar sensor is mounted on the platform of the traversing mechanism, where it is used to measure the solar flux density distribution on the receiver surface. The sensor is connected to a data acquisition card in a host computer. The two stepping motors of the heliostat tracking mechanism and the two stepping motors of the traversing mechanism are all connected to a controller card in the same host computer. A software `TOWER` is prepared to let the heliostat track the sun, move the platform of the traversing mechanism to the points of a preselected grid, and to measure the solar flux density distribution on the receiver plane. Measurements are carried out using rectangular flat mirrors of different dimensions at several distances from the central receiver. Two types of images were identified on the receiver plane - namely, apparent (or visible) and mirror-reflected radiation images. Comparison between measurements and a mathematical model validates the mathematical model. 13 refs., 12 figs., 1 tab.

Elsayed, M.M.; Fathalah, K.A.; Al-Rabghi, O.M. [King Abdulaziz Univ., Jeddah (Saudi Arabia)

1995-06-01

371

Intercomparison of two tunable diode laser spectrometers used for eddy correlation measurements of methane flux  

NASA Astrophysics Data System (ADS)

Tunable diode laser spectroscopy has, in the last few years, become an important technique for the measurement of atmospheric trace gases and pollutants. This technique is useful not only for concentration monitoring of a particular species, but can be used to measure the flux of trace gas species released or absorbed by an area. At the present time, mainly tow types of instruments are being manufactured and used. In the summer of 1993, the Center for Laser Analytical Studies of Trace Gas Dynamics at the University of Nebraska-Lincoln made an intercomparison of these two types of tunable diode laser spectrometers as used to measure the flux and concentration of naturally produced methane. Fluxes were measured using the eddy correlation method. This method requires both a high sensitivity to the species being measured, and a fast instrument response and so was deemed a stringent test of instrument performance. The study was conducted at a prairie wetland site near Valentine, Nebraska in late July and early August, 1993. The two instruments compared were built by Unisearch Associates Inc. of Concord, Ontario, and by Campbell Scientific Inc. of Logan, Utah and were representative of the two main types in general use. The study showed that both instruments exhibited similar detectabilities, and had almost identical noise characteristics when measuring both fluxes and concentrations. The study also brought out the need for careful calibration procedures and precise thermal management of the instruments to achieve optimal performance.

Billesbach, David P.; Ullman, Frank G.; Verma, Shashi B.

1996-10-01

372

Measurement of the pep and CNO solar neutrino interaction rates in Borexino-I  

NASA Astrophysics Data System (ADS)

The Borexino detector at Laboratori Nazionali del Gran Sasso is a low-background liquid scintillator calorimeter designed to measure the flux of low-energy solar neutrinos. Thanks to the low background rate, Borexino-I, using data taken between January 2008 and May 2010, performed the first direct detection of the pep solar neutrinos together with the strongest limit to date on the CNO solar neutrino flux. The aim of this article is to provide a review of the theoretical motivations and of the analysis procedures that led to these results.

Davini, Stefano

2013-08-01

373

Eddy covariance CO2 flux measurements in nocturnal conditions: an analysis of the problem.  

PubMed

A detailed analysis of the various processes at work in stable boundary layers was made. It pointed out that two main mechanisms may affect eddy covariance measurements in stable conditions and that their impacts were different. On one hand, intermittent turbulence produces strongly nonstationary events during which the validity of turbulent transport and storage measurements is uncertain. On the other hand, during breeze and drainage flow events, significant advection takes place and competes with turbulent flux and storage. Intermittent turbulence questions both the ability of eddy covariance systems to adequately capture turbulent flux and storage and the representativeness of the measurements. Ability of the systems to capture the fluxes could be improved by adapting the averaging time period or the high pass filtering characteristics. However, beyond this, the question of representativeness of the flux remains open as the flux measured during an intermittent turbulence event represents not only the source term, but also the removal of CO2 that built up in the control volume and that cannot be simply related to the source term. In these conditions, the u* discrimination is likely to be insufficient and should be completed with a stationarity criterion. Further research should allow determining better selection criteria. Advection occurs mainly in presence of flows associated with topographical slopes (drainage flows) or with land use changes (breezes). Direct advection measurements were performed at several sites, but the results were shown to be strongly site dependent. A classification based on the general flow pattern and on the source intensity evolution along streamlines was proposed here. Five different patterns were identified that helped to classify the different observations. The classification was found to be a fairly good fit for the observations. This could serve as a tool to better understand and quantify the fluxes at sites subjected to repeatable patterns. PMID:18767616

Aubinet, Marc

2008-09-01

374

Measurements of ambient HONO concentrations and vertical HONO flux above a northern Michigan forest canopy  

NASA Astrophysics Data System (ADS)

Systems have been developed and deployed at a North Michigan forested site to measure ambient HONO and vertical HONO flux. The modified HONO measurement technique is based on aqueous scrubbing of HONO using a coil sampler, followed by azo dye derivatization and detection using an optical fiber spectrometer with a 1-m long path flow cell. A Na2CO3-coated denuder is used to generate "zero HONO" air for background correction. The lower detection limit of the method, defined by 3 times of the standard deviation of the signal, is 1 pptv for 2-min averages, with an overall uncertainty of (1 + 0.05 [HONO]) pptv. The HONO flux measurement technique has been developed based on the relaxed eddy accumulation approach, deploying a 3-D sonic anemometer and two HONO measurement systems. The overall uncertainty is estimated to be within (8 10-8 + 0.15 FHONO) mol m-2 h-1, with a 20-min averaged data point per 30 min. Ambient HONO and vertical HONO flux were measured simultaneously at the PROPHET site from 17 July to 7 August 2008. The forest canopy was found to be a net HONO source, with a mean upward flux of 0.37 10-6 moles m-2 h-1. The HONO flux reached a maximum mean of ~0.7 10-6 moles m-2 h-1 around solar noon, contributing a major fraction (~60%) to the HONO source strength required to sustain the observed ambient concentration of ~70 pptv. There was no significant correlation between NOx and daytime HONO flux, suggesting that NOx was not an important precursor responsible for HONO daytime production on the forest canopy surface in the low-NOx rural environment. Evidence suggests that photolysis of HNO3 deposited on the forest canopy surface is a major daytime HONO source.

Zhang, N.; Zhou, X.; Bertman, S.; Tang, D.; Alaghmand, M.; Shepson, P. B.; Carroll, M. A.

2012-03-01

375

Influence Of Subsurface Biosphere On Geochemical Fluxes From Diffuse Hydrothermal Fluids: Direct Measurement Of Subsurface Hydrogen Oxidation  

NASA Astrophysics Data System (ADS)

After decades of research on hydrothermal vent biogeochemistry, quantification of low-temperature diffusive geochemical fluxes remains elusive and limits our ability to place constraints on their role in global geochemical cycles. Quantifying the relative differences in geochemical composition, in particular of energy-rich compounds such as H2 and CH4, between focused high-temperature and diffuse low-temperature hydrothermal fluids can allow the estimation of metabolic rates in the underlying subsurface biosphere. Towards shortening the gap in our understanding of geochemical and microbial dynamics of the subsurface biosphere, we deployed an in situ mass spectrometer (ISMS) and low flow meter to quantify biologically relevant volatiles in a wide range of flow regimes and temperatures. Here we present coupled in situ chemical analyses and flow measurements that enable quantification of geochemical fluxes from a diversity of diffuse and focused vents along the Juan de Fuca Ridge hydrothermal system. We show that geochemical flux from diffuse vents can equal or exceed that emanating from hot, focused vents. Notably, hydrogen concentrations in fluids emerging from diffuse vents are 50% to 80% lower than predicted. We attribute the loss of hydrogen in diffuse vent fluids to microbial consumption in the subsurface, and suggest that subsurface microbial communities can significantly influence hydrothermal geochemical fluxes to the deep ocean.

Wankel, S. D.; Germanovich, L. N.; Lilley, M. D.; Genc, G.; DiPerna, C. J.; Bradley, A. S.; Olson, E. J.; Girguis, P. R.

2011-12-01

376

Flux measurements of explosive degassing using a yearlong hydroacoustic record at an erupting submarine volcano  

NASA Astrophysics Data System (ADS)

The output of gas and tephra from volcanoes is an inherently disorganized process that makes reliable flux estimates challenging to obtain. Continuous monitoring of gas flux has been achieved in only a few instances at subaerial volcanoes, but never for submarine volcanoes. Here we use the first sustained (yearlong) hydroacoustic monitoring of an erupting submarine volcano (NW Rota-1, Mariana arc) to make calculations of explosive gas flux from a volcano into the ocean. Bursts of Strombolian explosive degassing at the volcano summit (520 m deep) occurred at 1-2 min intervals during the entire 12-month hydrophone record and commonly exhibited cyclic step-function changes between high and low intensity. Total gas flux calculated from the hydroacoustic record is 5.4 0.6 Tg a-1, where the magmatic gases driving eruptions at NW Rota-1 are primarily H2O, SO2, and CO2. Instantaneous fluxes varied by a factor of 100 over the deployment. Using melt inclusion information to estimate the concentration of CO2 in the explosive gases as 6.9 0.7 wt %, we calculate an annual CO2 eruption flux of 0.4 0.1 Tg a-1. This result is within the range of measured CO2 fluxes at continuously erupting subaerial volcanoes, and represents 0.2-0.6% of the annual estimated output of CO2from all subaerial arc volcanoes, and 0.4-0.6% of the mid-ocean ridge flux. The multiyear eruptive history of NW Rota-1 demonstrates that submarine volcanoes can be significant and sustained sources of CO2 to the shallow ocean.

Dziak, R. P.; Baker, E. T.; Shaw, A. M.; Bohnenstiehl, D. R.; Chadwick, W. W.; Haxel, J. H.; Matsumoto, H.; Walker, S. L.

2012-11-01

377

An Optimal Inverse Method Using Doppler Lidar Measurements to Estimate the Surface Sensible Heat Flux  

NASA Astrophysics Data System (ADS)

Inverse methods are widely used in various fields of atmospheric science. However, such methods are not commonly used within the boundary-layer community, where robust observations of surface fluxes are a particular concern. We present a new technique for deriving surface sensible heat fluxes from boundary-layer turbulence observations using an inverse method. Doppler lidar observations of vertical velocity variance are combined with two well-known mixed-layer scaling forward models for a convective boundary layer (CBL). The inverse method is validated using large-eddy simulations of a CBL with increasing wind speed. The majority of the estimated heat fluxes agree within error with the proscribed heat flux, across all wind speeds tested. The method is then applied to Doppler lidar data from the Chilbolton Observatory, UK. Heat fluxes are compared with those from a mast-mounted sonic anemometer. Errors in estimated heat fluxes are on average 18 %, an improvement on previous techniques. However, a significant negative bias is observed (on average -63 %) that is more pronounced in the morning. Results are improved for the fully-developed CBL later in the day, which suggests that the bias is largely related to the choice of forward model, which is kept deliberately simple for this study. Overall, the inverse method provided reasonable flux estimates for the simple case of a CBL. Results shown here demonstrate that this method has promise in utilizing ground-based remote sensing to derive surface fluxes. Extension of the method is relatively straight-forward, and could include more complex forward models, or other measurements.

Dunbar, T. M.; Barlow, J. F.; Belcher, S. E.

2013-10-01

378

Methane Fluxes from a Wetland using the Flux-Gradient Technique The Measurement of Methane Flux from a Natural Wetland Pond and Adjacent Vegetated Wetlands using a TDL-Based Flux-Gradient Technique  

Microsoft Academic Search

Methane emissions were measured from a bog andlake in the Experimental Lakes Area in Northern Ontario in 1992and 1993, prior to and following flooding. Bog fluxes were smallin 1992 (0.27 mg m-2 d-1) but increased 5-fold in 1993 afterflooding. Over the bog, there was a diel cycle of nighttimeemission and daytime uptake in 1992 in contrast to constantemission in 1993.

G. C. Edwards; G. M. Dias; G. W. Thurtell; G. E. Kidd; N. T. Roulet; C. A. Kelly; J. W. M. Rudd; A. Moore; L. Halfpenny-Mitchell

2001-01-01

379

Using measured variances to compute surface fluxes and dry deposition velocities - A comparison with measurements from three surface types  

NASA Astrophysics Data System (ADS)

Fluxes of temperature, water vapor, O3, SO2 and CO2 were estimated from the measurement of their variances, taken over a wetland region in northern Ontario (Canada) during the summer of 1990, and over a deciduous forest when it was fully leafed during the summer of 1988 and when it was leafless during the winter of 1990. A set of flux-variance relations was employed, including empirical forms of universal functions that could be adjusted with some constants. Results from the present study show that these constants needed to be adjusted with site-specific data in order to achieve a closer agreement between estimated and observed fluxes. Best estimates were obtained for the fluxes of temperature and water vapor and it was found that the flux estimates of O3, SO2 and CO2 correlated better with water vapor than with temperature. For these trace gases, the flux-variance method yielded estimates of dry deposition velocities that were either comparable with or larger than those obtained from a resistance analog model. Both methods yielded values that overestimated the observed dry deposition velocities.

Padro, J.; den Hartog, G.; Neumann, H. H.; Woolridge, D.

1992-09-01

380

Measurement of cosmic ray flux in the China JinPing underground laboratory  

NASA Astrophysics Data System (ADS)

The China JinPing underground Laboratory (CJPL) is the deepest underground laboratory running in the world at present. In such a deep underground laboratory, the cosmic ray flux is a very important and necessary parameter for rare-event experiments. A plastic scintillator telescope system has been set up to measure the cosmic ray flux. The performance of the telescope system has been studied using the cosmic rays on the ground laboratory near the CJPL. Based on the underground experimental data taken from November 2010 to December 2011 in the CJPL, which has an effective live time of 171 days, the cosmic ray muon flux in the CJPL is measured to be (2.00.4)10-10/(cm2新). The ultra-low cosmic ray background guarantees an ideal environment for dark matter experiments at the CJPL.

Wu, Yu-Cheng; Hao, Xi-Qing; Yue, Qian; Li, Yuan-Jing; Cheng, Jian-Ping; Kang, Ke-Jun; Chen, Yun-Hua; Li, Jin; Li, Jian-Min; Li, Yu-Lan; Liu, Shu-Kui; Ma, Hao; Ren, Jin-Bao; Shen, Man-Bin; Wang, Ji-Min; Wu, Shi-Yong; Xue, Tao; Yi, Nan; Zeng, Xiong-Hui; Zeng, Zhi; Zhu, Zhong-Hua

2013-08-01

381

Apparatus development for measuring heat flux in a direct coal-liquefaction preheater  

NASA Astrophysics Data System (ADS)

A device is evaluated for determining heat flux in a direct coal liquefaction preheater. The heat fluxmeter determines heat flux from measurements of temperature difference across the preheater tube wall at a given plane perpendicular to the tube axis. Six fluxmeters were installed in a 5.08 m length of nominal 1 1/2 inch diameter, schedule XX pipe enclosed in stacked electric furnaces. Heat flux to a heat transfer fluid flowing through the pipe was measured and compared to values predicted by the fluxmeters. Fair agreement was observed, and the method can be used as an empirical calibration procedure for fluxmeters. A number of apparatus improvements were identified that will be incorporated in the planned experimental program.

Kornosky, R. M.; Perlmutter, M.; Fuchs, W.; Ruether, J. A.

1982-04-01

382

Measurements of turbulent heat and momentum fluxes in a mountain valley  

SciTech Connect

Measurements of heat and momentum fluxes along the valley floor of Brush Creek in Colorado are described. The measurements were taken in the fall of 1984 as part of the Department of Energy's Atmospheric Studies in Complex Terrain field program. The sensible heat flux to the ground decreased from approximately 40--60 W m{sup {minus}2} prior to midnight to about 10--25 W m{sup {minus}2} in the morning hours. Surface friction velocities {ital u}{sub *} ranged from approximately 20--15 cm s{sup {minus}1} during the corresponding time periods. Considerable site-to-site variability in flux values was found, and disturbances of the upwind flow appear to be a significant contributing cause. {copyright}1989 American Meteorological Society

Doran, J.C. (Pacific Northwest Laboratory, Richland, Washington (US)); Wesely, M.L. (Argonne National Laboratory, Argonne, Illinois); McMillen, R.T. (Atmospheric Turbulence and Diffusion Division, Air Resources Division, ERL, NOAA, Oak Ridge, Tennessee); Neff, W.D. (NOAA/ERL/Wave Propagation Laboratory, Boulder, Colorado)

1989-06-01

383

Insights into rapid explosive volcanic processes from ground- and space-based intraday SO2 flux measurements  

NASA Astrophysics Data System (ADS)

Observations of volcanic degassing yield insights into the sub-surface magmatic processes which control volcanic activity during both quiescent and eruptive phases. By combining information on volcanic gas flux with constraints on original dissolved volatile contents the volume of degassing magma can be determined. Comparisons between the volume of degassing magma, erupted volume, and ground deformation allow mass balance calculations to be performed, providing insight into the shallow volcanic plumbing system dynamics. For these reasons there is great interest in improving the quality and frequency of volcanic gas flux measurements. Ultraviolet and infrared remote sensing techniques allow determination of SO2 column amounts within volcanic plumes. By calculating SO2 column amounts in a profile orthogonal to the plume-wind direction and multiplying the integrated SO2 cross section by the wind speed the SO2 emission rate can be retrieved. There are currently three main approaches for determining volcanic SO2 fluxes; (i) ground-based mini-DOAS systems, (ii) ground-based SO2 imaging cameras, and (iii) satellite-based infrared and ultraviolet imaging. Here we examine SO2 fluxes obtained by the Flux Automatic Measurement (FLAME) network of scanning mini-DOAS instruments installed at Mt. Etna and by the MODIS instrument aboard the NASA EOS satellite AQUA during the 2006 eruption of Mt. Etna, Sicily, Italy. Mt. Etna produced a highly variable eruptive activity from the South-East crater, characterised by explosive sequences, which could be either ash-rich or ash-poor, lava effusion, partial flank collapse and periods of quiescence. We examined intraday variations in SO2 flux measured with FLAME and MODIS during both ash-rich and ash-poor explosive phases. In general, good agreement was found between the datasets. Of particular interest was the successful recalculation and validation of temporal variations in SO2 flux recorded in a single image from MODIS. By examining the temporal evolution of gas emissions our results provide insight in the eruption mechanism driving the explosive activity.

Merucci, L.; Burton, M.; Corradini, S.; Salerno, G. G.

2010-12-01

384

Instrumentation for transient gas velocity, pressure and heat flux measurements in a gun simulator  

Microsoft Academic Search

Microcomputer-based instrumentation for transient measurements of pressure, wall heat flux, and gas velocity in a Lagrangian gun simulator is described, and sample results are presented. The breech pressure was measured by a piezoelectric transducer and the surface temperature was measured by a fast-response thin-film resistance thermometer. The pressure and temperature signals were sampled by a microcomputer and transferred into memory

A. F. Bicen; J. R. Laker; M. C. Schmidt; J. H. Whitelaw

1989-01-01

385

Continuous In Situ Measurements of Near Bottom Chemistry and Sediment-Water Fluxes with the Chimney Sampler Array (CSA)  

NASA Astrophysics Data System (ADS)

The Chimney Sampler Array (CSA) was designed to measure in situ chemical and physical parameters within the benthic boundary layer plus methane and oxygen sediment-water chemical fluxes at upper slope sites in the northern Gulf of Mexico. The CSA can monitor temporal changes plus help to evaluate oceanographic and sub-seafloor processes that can influence the formation and stability of gas hydrates in underlying sediments. The CSA consists of vertical cylinders (chimneys) equipped with internal chemical sensors and with laboratory flume-calibrated washout rates. Chimney washout rates multiplied by chimney mean versus ambient concentrations allow calculation of net O2 and methane sediment-water fluxes. The CSA is emplaced on the seafloor by a ROVARD lander using a ROV for chimney deployments. The CSA presently includes two 30 cm diameter by 90 cm length cylinders that seal against the sediment with lead pellet beanbags; within each chimney cylinder are optode, conductivity and methane sensors. The CSA's data logger platform also includes pressure and turbidity sensors external to the chimneys along with an acoustic Doppler current meter to measure temporal variation in ambient current velocity and direction. The CSA was deployed aboard a ROVARD lander on 9/13/2010 in the northern Gulf of Mexico (Lat. 28 51.28440, Long. 088 29.39421) on biogeochemically active sediments within Block MC-118. A ROV was utilized for chimney deployment away from the ROVARD lander. The CSA monitored temporal changes in water column physical parameters, obtained near-bottom chemical data to compare with pore fluid and sediment core measurements and measured temporal variability in oxygen and methane sediment-water fluxes at two closely spaced stations at MC-118. A continuous, three-week data set was obtained that revealed daily cycles in chemical parameters and episodic flux events. Lower than ambient chimney dissolved O2 concentrations controlled by temporal variability in washout rates were used to calculate sediment O2 demand. Episodic events yielding turbidity spikes produced episodic spikes in chimney methane concentrations and sediment-water fluxes. The robust data set reveals new capabilities for long-term monitoring of near-bottom processes in biogeochemically active, continental margin environments.

Martens, C. S.; Mendlovitz, H. P.; White, B. L.; Hoer, D.; Sleeper, K.; Chanton, J.; Wilson, R.; Lapham, L.

2011-12-01

386

Validating Patterns in Large Scale Sensible and Latent Heat Flux Estimates from a Remote Sensing-based Model and Aircraft-based Flux Measurements  

NASA Astrophysics Data System (ADS)

A remote sensing field experiment conducted in the Southern Great Plains in 1997 (SGP97) in central Oklahoma, had aircraft-based flux observations as well as remotely sensed data collected over one of the main study sites in central Oklahoma. This agricultural region contains primarily grassland/pasture and winter wheat, which was recently harvested leaving a significant number of fields either as wheat stubble or plowed bare soil. Multi-spectral data obtained by aircraft provided high resolution (30 m) spatially-distributed vegetation cover and surface temperature information over an area approximately 10 km north-south by 30 km east-west. The spatial variations in these surface states strongly affect the partitioning of surface fluxes between sensible and latent heat. These data, together with coarser resolution (5 km) satellite data, are used in a remote sensing-based energy balance modeling system that disaggregates flux estimates to the 30 m resolution. From the aircraft-based measurements collected along the 15 km transect, "segmented" flux values over 1 km sampling intervals were computed, which were then sub-sampled using a 250 m moving window using a new scheme for estimating time-space dependence of aircraft surface fluxes. From these two estimates of the large scale heat flux patterns, a comparison is made for exploring consistency in flux distributions. This type of comparison involves estimation of the flux-footprint or source area for the aircraft flux observations in order to weight the upwind model pixels within the aircraft sensor footprint. Highest correlation between aircraft and modeled estimated heat and water vapor fluxes were obtained using different flux-footprint estimates with the source-area for heat estimated to be much closer to the aircraft flight line than for water vapor. Factors that may be contributing to these results are discussed.

Kustas, W. P.; Anderson, M. C.

2005-05-01

387

Regional inversion of CO2 ecosystem fluxes from atmospheric measurements: reliability of the uncertainty estimates  

NASA Astrophysics Data System (ADS)

The Bayesian framework of CO2 flux inversions permits estimates of the retrieved flux uncertainties. Here, the reliability of these theoretical estimates is studied through a comparison against the misfits between the inverted fluxes and independent measurements of the CO2 Net Ecosystem Exchange (NEE) made by the eddy covariance technique at local (few hectares) scale. Regional inversions at 0.5 resolution are applied for the western European domain where ~ 50 eddy covariance sites are operated. These inversions are conducted for the period 2002-2007. They use a mesoscale atmospheric transport model, a prior estimate of the NEE from a terrestrial ecosystem model and rely on the variational assimilation of in situ continuous measurements of CO2 atmospheric mole fractions. Averaged over monthly periods and over the whole domain, the misfits are in good agreement with the theoretical uncertainties for prior and inverted NEE, and pass the chi-square test for the variance at the 30% and 5% significance levels respectively, despite the scale mismatch and the independence between the prior (respectively inverted) NEE and the flux measurements. The theoretical uncertainty reduction for the monthly NEE at the measurement sites is 53% while the inversion decreases the standard deviation of the misfits by 38%. These results build confidence in the NEE estimates at the European/monthly scales and in their theoretical uncertainty from the regional inverse modelling system. However, the uncertainties at the monthly (respectively annual) scale remain larger than the amplitude of the inter-annual variability of monthly (respectively annual) fluxes, so that this study does not engender confidence in the inter-annual variations. The uncertainties at the monthly scale are significantly smaller than the seasonal variations. The seasonal cycle of the inverted fluxes is thus reliable. In particular, the CO2 sink period over the European continent likely ends later than represented by the prior ecosystem model.

Broquet, G.; Chevallier, F.; Br廩n, F.-M.; Kadygrov, N.; Alemanno, M.; Apadula, F.; Hammer, S.; Haszpra, L.; Meinhardt, F.; Morgu, J. A.; Necki, J.; Piacentino, S.; Ramonet, M.; Schmidt, M.; Thompson, R. L.; Vermeulen, A. T.; Yver, C.; Ciais, P.

2013-09-01