Fluxes and exchange rates of radon and oxygen across an air-sea interface

International Nuclear Information System (INIS)

Duenas, C.; Fernandez, M.C.; La Torre, M. de

1986-01-01

The flux of 222 Rn and O 2 from shallow water off the Bay of Malaga has been measured. The mean value of flux of 222 Rn is evaluated to be 74 atoms/m 2 · s. The Bay is a weak source of oxygen to the atmosphere, where the net production of oxygen is found to be 1.82 mol/m 2 · y. Moreover, the gas exchange rates of 222 Rn and O 2 across the air-sea interface has been determined by the radon method. The gas exchange rates and the wind speed have been estimated. (author)

A detailed analysis of inviscid flux splitting algorithms for real gases with equilibrium or finite-rate chemistry

Science.gov (United States)

Shuen, Jian-Shun; Liou, Meng-Sing; Van Leer, Bram

1989-01-01

The extension of the known flux-vector and flux-difference splittings to real gases via rigorous mathematical procedures is demonstrated. Formulations of both equilibrium and finite-rate chemistry for real-gas flows are described, with emphasis on derivations of finite-rate chemistry. Split-flux formulas from other authors are examined. A second-order upwind-based TVD scheme is adopted to eliminate oscillations and to obtain a sharp representation of discontinuities.

Determination of radon flux rates in a uranium mine (Cluff Lake, Saskatchewan)

International Nuclear Information System (INIS)

1989-12-01

The Atomic Energy Control Board contracted SENES Consultants Limited to design and implement a field program at Amok Limited's Cluff Lake uranium mine, with the overall objective of obtaining reliable radon flux data applicable for use in the VENTRAD computer model. The VENTRAD model was developed to model underground mine ventilation systems. To avoid the uncertainties inherent in localized flux measurements made on small surfaces, radon flux measurements were determined through measurement of incremental changes in the concentration of radon between the incoming and outgoing air in selected areas of the underground workings. The locations were selected throughout the mine in both ore and sterile rock. Average radon flux rates measured during three field campaigns were as follows: sterile rock decline 4 pCi/m 2 .second; sterile rock mainway 25 pCi/m 2 .second; worked-out stope 100 pCi/m 2 .second; active work stope 240 pCi/m 2 .second; and work face 14,000 pCi/m 2 .second. Data collected during the three field programs were used to validate the VENTRAD computer model. The results of the validation exercise suggest close agreement between predicted and measured air flow rates and radon concentrations were overestimated for areas immediately impacted by auxiliary ventilation fans and ore transfer mill holes which connect the ore extraction and haulage levels of the mine

Correlation between TCA cycle flux and glucose uptake rate during respiro-fermentative growth of Saccharomyces cerevisiae.

Science.gov (United States)

Heyland, Jan; Fu, Jianan; Blank, Lars M

2009-12-01

Glucose repression of the tricarboxylic acid (TCA) cycle in Saccharomyces cerevisiae was investigated under different environmental conditions using (13)C-tracer experiments. Real-time quantification of the volatile metabolites ethanol and CO(2) allowed accurate carbon balancing. In all experiments with the wild-type, a strong correlation between the rates of growth and glucose uptake was observed, indicating a constant yield of biomass. In contrast, glycerol and acetate production rates were less dependent on the rate of glucose uptake, but were affected by environmental conditions. The glycerol production rate was highest during growth in high-osmolarity medium (2.9 mmol g(-1) h(-1)), while the highest acetate production rate of 2.1 mmol g(-1) h(-1) was observed in alkaline medium of pH 6.9. Under standard growth conditions (25 g glucose l(-1) , pH 5.0, 30 degrees C) S. cerevisiae had low fluxes through the pentose phosphate pathway and the TCA cycle. A significant increase in TCA cycle activity from 0.03 mmol g(-1) h(-1) to about 1.7 mmol g(-1) h(-1) was observed when S. cerevisiae grew more slowly as a result of environmental perturbations, including unfavourable pH values and sodium chloride stress. Compared to experiments with high glucose uptake rates, the ratio of CO(2) to ethanol increased more than 50 %, indicating an increase in flux through the TCA cycle. Although glycolysis and the ethanol production pathway still exhibited the highest fluxes, the net flux through the TCA cycle increased significantly with decreasing glucose uptake rates. Results from experiments with single gene deletion mutants partially impaired in glucose repression (hxk2, grr1) indicated that the rate of glucose uptake correlates with this increase in TCA cycle flux. These findings are discussed in the context of regulation of glucose repression.

The Effect of Cumulus Cloud Field Anisotropy on Domain-Averaged Solar Fluxes and Atmospheric Heating Rates

Science.gov (United States)

Hinkelman, Laura M.; Evans, K. Franklin; Clothiaux, Eugene E.; Ackerman, Thomas P.; Stackhouse, Paul W., Jr.

2006-01-01

Cumulus clouds can become tilted or elongated in the presence of wind shear. Nevertheless, most studies of the interaction of cumulus clouds and radiation have assumed these clouds to be isotropic. This paper describes an investigation of the effect of fair-weather cumulus cloud field anisotropy on domain-averaged solar fluxes and atmospheric heating rate profiles. A stochastic field generation algorithm was used to produce twenty three-dimensional liquid water content fields based on the statistical properties of cloud scenes from a large eddy simulation. Progressively greater degrees of x-z plane tilting and horizontal stretching were imposed on each of these scenes, so that an ensemble of scenes was produced for each level of distortion. The resulting scenes were used as input to a three-dimensional Monte Carlo radiative transfer 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. The mechanisms by which anisotropy interacts with solar fluxes were investigated by comparisons to independent pixel approximation and tilted independent pixel approximation computations for the same scenes. Cumulus anisotropy was found to most strongly impact solar radiative transfer by changing the effective cloud fraction, i.e., the cloud fraction when the field is projected on a surface perpendicular to the direction of the incident solar beam.

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

Science.gov (United States)

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

2007-01-01

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

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

Science.gov (United States)

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

2011-11-11

Mechanistic models of glucose stimulated insulin secretion (GSIS) established in minimal media in vitro, may not accurately describe the complexity of coupling metabolism with insulin secretion that occurs in vivo. As a first approximation, we have evaluated metabolic pathways in a typical growth media, DMEM as a surrogate in vivo medium, for comparison to metabolic fluxes observed under the typical experimental conditions using the simple salt-buffer of KRB. Changes in metabolism in response to glucose and amino acids and coupling to insulin secretion were measured in INS-1 832/13 cells. Media effects on mitochondrial function and the coupling efficiency of oxidative phosphorylation were determined by fluorometrically measured oxygen consumption rates (OCRs) combined with (31)P NMR measured rates of ATP synthesis. Substrate preferences and pathways into the TCA cycle, and the synthesis of mitochondrial 2nd messengers by anaplerosis were determined by (13)C NMR isotopomer analysis of the fate of [U-(13)C] glucose metabolism. Despite similar incremental increases in insulin secretion, the changes of OCR in response to increasing glucose from 2.5 to 15mM 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. Copyright © 2011 Elsevier Inc. All

Dry-out heat fluxes of falling film and low-mass flux upward-flow in heated tubes

International Nuclear Information System (INIS)

Koizumi, Yasuo; Ueda, Tatsuhiro; Matsuo, Teruyuki; Miyota, Yukio

1998-01-01

Dry-out heat fluxes were investigated experimentally for a film flow falling down on the inner surface of vertical heated-tubes and for a low mass flux forced-upward flow in the tubes using R 113. This work followed the study on those for a two-phase natural circulation system. For the falling film boiling, flow state observation tests were also performed, where dry-patches appearing and disappearing repeatedly were observed near the exit end of the heated section at the dry-out heat flux conditions. Relation between the dry-out heat flux and the liquid film flow rate is analyzed. The dry-out heat fluxes of the low mass flux upflow are expressed well by the correlation proposed in the previous work. The relation for the falling film boiling shows a similar trend to that for the upflow boiling, however, the dry-out heat fluxes of the falling film are much lower, approximately one third, than those of the upward flow. (author)

Forward flux sampling calculation of homogeneous nucleation rates from aqueous NaCl solutions.

Science.gov (United States)

Jiang, Hao; Haji-Akbari, Amir; Debenedetti, Pablo G; Panagiotopoulos, Athanassios Z

2018-01-28

We used molecular dynamics simulations and the path sampling technique known as forward flux sampling to study homogeneous nucleation of NaCl crystals from supersaturated aqueous solutions at 298 K and 1 bar. Nucleation rates were obtained for a range of salt concentrations for the Joung-Cheatham NaCl force field combined with the Extended Simple Point Charge (SPC/E) water model. The calculated nucleation rates are significantly lower than the available experimental measurements. The estimates for the nucleation rates in this work do not rely on classical nucleation theory, but the pathways observed in the simulations suggest that the nucleation process is better described by classical nucleation theory than an alternative interpretation based on Ostwald's step rule, in contrast to some prior simulations of related models. In addition to the size of NaCl nucleus, we find that the crystallinity of a nascent cluster plays an important role in the nucleation process. Nuclei with high crystallinity were found to have higher growth probability and longer lifetimes, possibly because they are less exposed to hydration water.

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

International Nuclear Information System (INIS)

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

2011-01-01

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

Solar Flux Deposition And Heating Rates In Jupiter's Atmosphere

Science.gov (United States)

Perez-Hoyos, Santiago; Sánchez-Lavega, A.

2009-09-01

We discuss here the solar downward net flux in the 0.25 - 2.5 µm 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 2.5±0.5 Wm-2 at the 6 bar level. The maximum solar heating is 0.04±0.01 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 0.04±0.02 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.

American National Standard: neutron and gamma-ray flux-to-dose rate factors

International Nuclear Information System (INIS)

Anon.

1977-01-01

This Standard presents data recommended for computing biological dose rates due to neutron and gamma-ray radiation fields. Neutron flux-to-dose-rate conversion factors for energies from 2.5 x 10 -8 to 20 MeV are given; the energy range for the gamma-ray conversion factors is 0.01 to 15 MeV. Specifically, this Standard is intended for use by shield designers to calculate wholebody dose rates to radiation workers and the general public. Establishing dose-rate limits is outside the scope of this Standard. Use of this Standard in cases where the dose equivalents are far in excess of occupational exposure guidelines is not recommended

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

Energy Technology Data Exchange (ETDEWEB)

Cline, Gary W., E-mail: gary.cline@yale.edu [The Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06520 (United States); Department of Surgery, University of Minnesota-Twin Cities, Minneapolis, MN 55455 (United States); Pongratz, Rebecca L.; Zhao, Xiaojian [The Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06520 (United States); Papas, Klearchos K. [Department of Surgery, University of Minnesota-Twin Cities, Minneapolis, MN 55455 (United States)

2011-11-11

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

Heat flux from magmatic hydrothermal systems related to availability of fluid recharge

Science.gov (United States)

Harvey, M. C.; Rowland, J.V.; Chiodini, G.; Rissmann, C.F.; Bloomberg, S.; Hernandez, P.A.; Mazot, A.; Viveiros, F.; Werner, Cynthia A.

2015-01-01

Magmatic hydrothermal systems are of increasing interest as a renewable energy source. Surface heat flux indicates system resource potential, and can be inferred from soil CO2 flux measurements and fumarole gas chemistry. Here we compile and reanalyze results from previous CO2 flux surveys worldwide to compare heat flux from a variety of magma-hydrothermal areas. We infer that availability of water to recharge magmatic hydrothermal systems is correlated with heat flux. Recharge availability is in turn governed by permeability, structure, lithology, rainfall, topography, and perhaps unsurprisingly, proximity to a large supply of water such as the ocean. The relationship between recharge and heat flux interpreted by this study is consistent with recent numerical modeling that relates hydrothermal system heat output to rainfall catchment area. This result highlights the importance of recharge as a consideration when evaluating hydrothermal systems for electricity generation, and the utility of CO2 flux as a resource evaluation tool.

Convective Heat Transfer Scaling of Ignition Delay and Burning Rate with Heat Flux and Stretch Rate in the Equivalent Low Stretch Apparatus

Science.gov (United States)

Olson, Sandra

2011-01-01

To better evaluate the buoyant contributions to the convective cooling (or heating) inherent in normal-gravity material flammability test methods, we derive a convective heat transfer correlation that can be used to account for the forced convective stretch effects on the net radiant heat flux for both ignition delay time and burning rate. The Equivalent Low Stretch Apparatus (ELSA) uses an inverted cone heater to minimize buoyant effects while at the same time providing a forced stagnation flow on the sample, which ignites and burns as a ceiling fire. Ignition delay and burning rate data is correlated with incident heat flux and convective heat transfer and compared to results from other test methods and fuel geometries using similarity to determine the equivalent stretch rates and thus convective cooling (or heating) rates for those geometries. With this correlation methodology, buoyant effects inherent in normal gravity material flammability test methods can be estimated, to better apply the test results to low stretch environments relevant to spacecraft material selection.

Mass transfer inside a flux hood for the sampling of gaseous emissions from liquid surfaces - Experimental assessment and emission rate rescaling

Science.gov (United States)

Prata, Ademir A.; Lucernoni, Federico; Santos, Jane M.; Capelli, Laura; Sironi, Selena; Le-Minh, Nhat; Stuetz, Richard M.

2018-04-01

This study assesses the mass transfer of compounds inside the US EPA flux hood, one of the enclosure devices most commonly employed for the direct measurement of atmospheric emissions from liquid surfaces in wastewater treatment plants (WWTPs). Experiments comprised the evaporation of water and the volatilisation of a range of volatile organic compounds (VOCs). Special attention was given to the evaluation of the mass transfer coefficients in the microenvironment created by the flux hood and the effects of concentration build up in the hood's headspace. The VOCs emission rates and the water evaporation rates generally increased with the sweep air flow rate, as did the mass transfer coefficients for all compounds. The emission of compounds whose volatilisation is significantly influenced by the gas phase was greatly affected by concentration build up, whereas this effect was not significant for liquid phase-controlled compounds. The gas-film mass transfer coefficient (kG) estimated inside the US EPA flux hood was of the same order as the respective kG reported in the literature for wind tunnel-type devices, but the emission rates measured by the flux hood can be expected to be lower, due to the concentration build-up. Compared against an emission model for the passive surfaces in WWTPs, the mass transfer of acetic acid (representing a gas phase-dominated compound) inside the US EPA flux hood was equivalent to conditions of wind speeds at 10 m height (U10) of 0.27, 0.51 and 0.99 m s-1, respectively, for sweep air flow rates of 2, 5 and 10 L min-1. On the other hand, for higher wind speeds, the emission rates of gas phase-controlled compounds obtained with the flux hood can be considerably underestimated: for instance, at U10 = 5 m s-1, the emission rates of acetic acid inside the flux hood would be approximately 23, 12 and 6 times lower than the emission rates in the field, for sweep air flow rates of 2, 5 and 10 L min-1, respectively. A procedure is presented in

A redetermination of the Barnes-Evans relation for surface flux in the V band

International Nuclear Information System (INIS)

Eaton, J.A.; Poe, C.H.

1984-01-01

Paying especial attention to the errors, we have redetermined the relation between visual flux at the star and color for stars with measured angular diameters. For stars cooler than the sun this is given both as a group of four polynomials in (V-R) for various parts of the range (V-R) >or approx.0.2, which start to recognize the fine structure in the flux-color relation, and as a straight line fitted to the data for 0,7 ≤ (V-R) ≤ 2.5. For stars hotter than the sun we give a table of surface flux vs. spectral type and (B-I) color. For stars later than the sun this flux-color relation is still defined almost entirely by giants. The conclusion that visual surface flux is a single function of (V-R) for all luminosity classes remains weak because of the small number of dwarfs and supergiants with angular diameters, likely systematic errors in the angular diameters of supergiants and the relatively large errors of individual angular diameters. The flux-color relation is combined with independent scales of bolometric corrections to give effective temperatures. We find that our results agree moderately well with those of Code et al. (1976), on which they are primarily based, for the hotter stars. However, they imply significant revisions of both the temperature and bolometric-correction scales for cool stars. 94 refs., 5 figs., 4 tabs. (author)

Statistical analysis of error rate of large-scale single flux quantum logic circuit by considering fluctuation of timing parameters

International Nuclear Information System (INIS)

Yamanashi, Yuki; Masubuchi, Kota; Yoshikawa, Nobuyuki

2016-01-01

The relationship between the timing margin and the error rate of the large-scale single flux quantum logic circuits is quantitatively investigated to establish a timing design guideline. We observed that the fluctuation in the set-up/hold time of single flux quantum logic gates caused by thermal noises is the most probable origin of the logical error of the large-scale single flux quantum circuit. The appropriate timing margin for stable operation of the large-scale logic circuit is discussed by taking the fluctuation of setup/hold time and the timing jitter in the single flux quantum circuits. As a case study, the dependence of the error rate of the 1-million-bit single flux quantum shift register on the timing margin is statistically analyzed. The result indicates that adjustment of timing margin and the bias voltage is important for stable operation of a large-scale SFQ logic circuit.

Statistical analysis of error rate of large-scale single flux quantum logic circuit by considering fluctuation of timing parameters

Energy Technology Data Exchange (ETDEWEB)

Yamanashi, Yuki, E-mail: yamanasi@ynu.ac.jp [Department of Electrical and Computer Engineering, Yokohama National University, Tokiwadai 79-5, Hodogaya-ku, Yokohama 240-8501 (Japan); Masubuchi, Kota; Yoshikawa, Nobuyuki [Department of Electrical and Computer Engineering, Yokohama National University, Tokiwadai 79-5, Hodogaya-ku, Yokohama 240-8501 (Japan)

2016-11-15

The relationship between the timing margin and the error rate of the large-scale single flux quantum logic circuits is quantitatively investigated to establish a timing design guideline. We observed that the fluctuation in the set-up/hold time of single flux quantum logic gates caused by thermal noises is the most probable origin of the logical error of the large-scale single flux quantum circuit. The appropriate timing margin for stable operation of the large-scale logic circuit is discussed by taking the fluctuation of setup/hold time and the timing jitter in the single flux quantum circuits. As a case study, the dependence of the error rate of the 1-million-bit single flux quantum shift register on the timing margin is statistically analyzed. The result indicates that adjustment of timing margin and the bias voltage is important for stable operation of a large-scale SFQ logic circuit.

Simulation of Silver Thin Films' Growth and Influence of Deposition Rate on Final Grain Size under Angle Flux and Standard Situation

Directory of Open Access Journals (Sweden)

Maryam Jamshidnejad

2011-01-01

Full Text Available In this paper, a 2D stimulation model, FACET, is used for investigation of the relation between micro structure and deposition conditions such as substrate temperature, deposition rate and deposition angle of Ag thin films. It is observed that by increasing the deposition rate in standard conditions providing that the temperature of substrate is low, the average of final grain size is decreased. While, in deposition with angle flux the average of final grain size is increased.

Gap-related trapped magnetic flux dependence between single and combined bulk superconductors

International Nuclear Information System (INIS)

Deng, Z.; Miki, M.; Felder, B.; Tsuzuki, K.; Shinohara, N.; Uetake, T.; Izumi, M.

2011-01-01

Highlights: → Rectangular YBCO bulks to realize a compact combination. → The gap effect was added to consider in the trapped flux density mapping. → The trapped-flux dependence between single and combined bulks is gap related. → It is possible to estimate the total magnetic flux of bulk combinations. - Abstract: Aiming at examining the trapped-flux dependence between single and combined bulk superconductors for field-pole applications, three rectangular Y 1.65 Ba 2 Cu 3 O 7-x (YBCO) bulks with a possibly compact combination were employed to investigate the trapped-flux characteristics of single and combined bulks with a field-cooling magnetization (FCM) method. A gap-related dependence was found between them. At lower gaps of 1 mm and 5 mm, the peak trapped fields and total magnetic flux of combined bulks are both smaller than the additive values of each single bulk, which can be ascribed to the demagnetization influences of the field around the bulk generated by the adjacent ones. While, at larger gaps like 10 mm, the situation becomes reversed. The combined bulks can attain bigger peak trapped fields as well as total magnetic flux, which indicates that the magnetic field by the bulk combination can reach higher gaps, thanks to the bigger magnetic energy compared with the single bulk. The presented results show that, on one hand, it is possible to estimate the total trapped magnetic flux of combined bulks by an approximate additive method of each single bulk while considering a demagnetization factor; on the other hand, it also means that the performance of combined bulks will be superior to the addition of each single bulk at larger gaps, thus preferable for large-scaled magnet applications.

Gap-related trapped magnetic flux dependence between single and combined bulk superconductors

Energy Technology Data Exchange (ETDEWEB)

Deng, Z., E-mail: zgdeng@gmail.co [Laboratory of Applied Physics, Department of Marine Electronics and Mechanical Engineering, Tokyo University of Marine Science and Technology, Tokyo 135-8533 (Japan); Miki, M.; Felder, B.; Tsuzuki, K.; Shinohara, N.; Uetake, T.; Izumi, M. [Laboratory of Applied Physics, Department of Marine Electronics and Mechanical Engineering, Tokyo University of Marine Science and Technology, Tokyo 135-8533 (Japan)

2011-05-15

Highlights: {yields} Rectangular YBCO bulks to realize a compact combination. {yields} The gap effect was added to consider in the trapped flux density mapping. {yields} The trapped-flux dependence between single and combined bulks is gap related. {yields} It is possible to estimate the total magnetic flux of bulk combinations. - Abstract: Aiming at examining the trapped-flux dependence between single and combined bulk superconductors for field-pole applications, three rectangular Y{sub 1.65}Ba{sub 2}Cu{sub 3}O{sub 7-x} (YBCO) bulks with a possibly compact combination were employed to investigate the trapped-flux characteristics of single and combined bulks with a field-cooling magnetization (FCM) method. A gap-related dependence was found between them. At lower gaps of 1 mm and 5 mm, the peak trapped fields and total magnetic flux of combined bulks are both smaller than the additive values of each single bulk, which can be ascribed to the demagnetization influences of the field around the bulk generated by the adjacent ones. While, at larger gaps like 10 mm, the situation becomes reversed. The combined bulks can attain bigger peak trapped fields as well as total magnetic flux, which indicates that the magnetic field by the bulk combination can reach higher gaps, thanks to the bigger magnetic energy compared with the single bulk. The presented results show that, on one hand, it is possible to estimate the total trapped magnetic flux of combined bulks by an approximate additive method of each single bulk while considering a demagnetization factor; on the other hand, it also means that the performance of combined bulks will be superior to the addition of each single bulk at larger gaps, thus preferable for large-scaled magnet applications.

HOOKED FLARE RIBBONS AND FLUX-ROPE-RELATED QSL FOOTPRINTS

Energy Technology Data Exchange (ETDEWEB)

Zhao, Jie; Li, Hui [Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, CAS, Nanjing 210008 (China); Gilchrist, Stuart A.; Aulanier, Guillaume; Schmieder, Brigitte; Pariat, Etienne, E-mail: nj.lihui@pmo.ac.cn [LESIA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Univ. Paris 06, Univ. Paris-Diderot, Sorbonne Paris Cité, 5 place Jules Janssen, F-92195 Meudon (France)

2016-05-20

We studied the magnetic topology of active region 12158 on 2014 September 10 and compared it with the observations before and early in the flare that begins at 17:21 UT (SOL2014-09-10T17:45:00). Our results show that the sigmoidal structure and flare ribbons of this active region observed by the Solar Dynamics Observatory /Atmospheric Imaging Assembly can be well reproduced from a Grad–Rubin nonlinear force-free field extrapolation method. Various inverse-S- and inverse-J-shaped magnetic field lines, which surround a coronal flux rope, coincide with the sigmoid as observed in different extreme-ultraviolet wavelengths, including its multithreaded curved ends. Also, the observed distribution of surface currents in the magnetic polarity where it was not prescribed is well reproduced. This validates our numerical implementation and setup of the Grad–Rubin method. The modeled double inverse-J-shaped quasi-separatrix layer (QSL) footprints match the observed flare ribbons during the rising phase of the flare, including their hooked parts. The spiral-like shape of the latter may be related to a complex pre-eruptive flux rope with more than one turn of twist, as obtained in the model. These ribbon-associated flux-rope QSL footprints are consistent with the new standard flare model in 3D, with the presence of a hyperbolic flux tube located below an inverse-teardrop-shaped coronal QSL. This is a new step forward forecasting the locations of reconnection and ribbons in solar flares and the geometrical properties of eruptive flux ropes.

HOOKED FLARE RIBBONS AND FLUX-ROPE-RELATED QSL FOOTPRINTS

International Nuclear Information System (INIS)

Zhao, Jie; Li, Hui; Gilchrist, Stuart A.; Aulanier, Guillaume; Schmieder, Brigitte; Pariat, Etienne

2016-01-01

We studied the magnetic topology of active region 12158 on 2014 September 10 and compared it with the observations before and early in the flare that begins at 17:21 UT (SOL2014-09-10T17:45:00). Our results show that the sigmoidal structure and flare ribbons of this active region observed by the Solar Dynamics Observatory /Atmospheric Imaging Assembly can be well reproduced from a Grad–Rubin nonlinear force-free field extrapolation method. Various inverse-S- and inverse-J-shaped magnetic field lines, which surround a coronal flux rope, coincide with the sigmoid as observed in different extreme-ultraviolet wavelengths, including its multithreaded curved ends. Also, the observed distribution of surface currents in the magnetic polarity where it was not prescribed is well reproduced. This validates our numerical implementation and setup of the Grad–Rubin method. The modeled double inverse-J-shaped quasi-separatrix layer (QSL) footprints match the observed flare ribbons during the rising phase of the flare, including their hooked parts. The spiral-like shape of the latter may be related to a complex pre-eruptive flux rope with more than one turn of twist, as obtained in the model. These ribbon-associated flux-rope QSL footprints are consistent with the new standard flare model in 3D, with the presence of a hyperbolic flux tube located below an inverse-teardrop-shaped coronal QSL. This is a new step forward forecasting the locations of reconnection and ribbons in solar flares and the geometrical properties of eruptive flux ropes.

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

Science.gov (United States)

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

2014-05-01

rates. All three EC systems showed 30 min. flux values varying around zero nmol m-2 s-1. This noise was considerably lower in the EC systems that used QCL analysers. The maximum daily averages of the uncorrected fluxes from two of the EC systems reached 0.26 (ICOS/HS50) and 0.28 (QCL/R3) nmol m-2 s-1.Spectral correction increased the flux estimates up to, e.g., 180% equivalent to 0.54 nmol m-2 s-1. The flux estimates from the soil chambers were with one exception higher than the flux estimates obtained from the EC systems with highest daily averages ranging from 0.1 up to 2 nmol m-2 s-1. These large differences were unexpected, because at least two of the EC systems were shown to accurately measure fluxes at such higher levels at another InGOS campaign in a fertilised Scottish grazed meadow. We use spectral analysis to examine the raw data for the effects of sensor noise on the flux estimates and discuss strategies on how to correct or account for it. Furthermore possible causes for the observed differences between the observed EC and chamber flux estimates will be discussed.

Integrated leak rate test of the FFTF [Fast Flux Test Facility] containment vessel

International Nuclear Information System (INIS)

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

1987-04-01

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 savings in the time and effort required to perform an ILRT on Liquid Metal Reactor Systems with consequent reduction in test costs

Critical flux determination by flux-stepping

DEFF Research Database (Denmark)

Beier, Søren; Jonsson, Gunnar Eigil

2010-01-01

In membrane filtration related scientific literature, often step-by-step determined critical fluxes are reported. Using a dynamic microfiltration device, it is shown that critical fluxes determined from two different flux-stepping methods are dependent upon operational parameters such as step...... length, step height, and.flux start level. Filtrating 8 kg/m(3) yeast cell suspensions by a vibrating 0.45 x 10(-6) m pore size microfiltration hollow fiber module, critical fluxes from 5.6 x 10(-6) to 1.2 x 10(-5) m/s have been measured using various step lengths from 300 to 1200 seconds. Thus......, such values are more or less useless in itself as critical flux predictors, and constant flux verification experiments have to be conducted to check if the determined critical fluxes call predict sustainable flux regimes. However, it is shown that using the step-by-step predicted critical fluxes as start...

MURLI, 1-D Flux, Reaction Rate in Cylindrical Geometry Thermal Reactor Lattice by Transport

International Nuclear Information System (INIS)

Huria, H.C.

1985-01-01

1 - Description of problem or function: MURLI is an integral transport theory code to calculate fluxes and reaction rates in one- dimensional cylindrical geometry lattice cells of a thermal reactor. For a specified buckling, it computes k-effective using few-group diffusion theory and a few-group collapsed set of Cross sections. The code can optionally be used to solve a first order differential equation for the number density of fissile, fertile and fission product nuclei as a function of time, and to recalculate fluxes, reaction rates and k-effective at different stages of burnup. A 27-group cross section data library is included. There are four pseudo-fission products each associated with the decay chains of plutonium and uranium isotopes in addition to Rh-105, Xe-135, Np-239, U-236, Am-241, Am-242 and Am-243. There is also data for one lumped pseudo-fission product. 2 - Method of solution: Multiple collision probabilities and escape probabilities are calculated for each cylindrical shell region assuming protons are born uniformly and isotropically over the entire region volume. The equations of integral transport theory can then be solved for neutron flux. The first order differential burnup equation is solved by a fourth order Runge-Kutta method. 3 - Restrictions on the complexity of the problem: There are maxima of 8 fissionable elements, 8 resonant elements, and 20 spatial regions

A new lattice hydrodynamic model based on control method considering the flux change rate and delay feedback signal

Science.gov (United States)

Qin, Shunda; Ge, Hongxia; Cheng, Rongjun

2018-02-01

In this paper, a new lattice hydrodynamic model is proposed by taking delay feedback and flux change rate effect into account in a single lane. The linear stability condition of the new model is derived by control theory. By using the nonlinear analysis method, the mKDV equation near the critical point is deduced to describe the traffic congestion. Numerical simulations are carried out to demonstrate the advantage of the new model in suppressing traffic jam with the consideration of flux change rate effect in delay feedback model.

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

International Nuclear Information System (INIS)

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

1984-01-01

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

Compilation of neutron flux density spectra and reaction rates in different neutron fields. V.3

International Nuclear Information System (INIS)

Ertek, C.

1980-04-01

Upon the recommendation of the International Working Group of Reactor Radiation Measurements (IWGRRM) a compilation of documents containing neutron flux density spectra and the reaction rates obtained by activiation and fission foils in different neutron fields is presented

Compilation of neutron flux density spectra and reaction rates in different neutron fields

International Nuclear Information System (INIS)

Ertek, C.

1979-07-01

Upon the recommendation of International Working Group of Reactor Radiation Measurements (IWGRRM), the compilation of neutron flux density spectra and the reaction rates obtained by activation and fission foils in different neutron fields is presented. The neutron fields considered are as follows: 1/E; iron block; LWR core and pressure vessel; LMFBR core and blanket; CTR first wall and blanket; fission spectrum

Sinking rates and ballast composition of particles in the Atlantic Ocean: implications for the organic carbon fluxes to the deep ocean

Science.gov (United States)

Fischer, G.; Karakaş, G.

2009-01-01

The flux of materials to the deep sea is dominated by larger, organic-rich particles with sinking rates varying between a few meters and several hundred meters per day. Mineral ballast may regulate the transfer of organic matter and other components by determining the sinking rates, e.g. via particle density. We calculated particle sinking rates from mass flux patterns and alkenone measurements applying the results of sediment trap experiments from the Atlantic Ocean. We have indication for higher particle sinking rates in carbonate-dominated production systems when considering both regional and seasonal data. During a summer coccolithophorid bloom in the Cape Blanc coastal upwelling off Mauritania, particle sinking rates reached almost 570 m per day, most probably due the fast sedimentation of densely packed zooplankton fecal pellets, which transport high amounts of organic carbon associated with coccoliths to the deep ocean despite rather low production. During the recurring winter-spring blooms off NW Africa and in opal-rich production systems of the Southern Ocean, sinking rates of larger particles, most probably diatom aggregates, showed a tendency to lower values. However, there is no straightforward relationship between carbonate content and particle sinking rates. This could be due to the unknown composition of carbonate and/or the influence of particle size and shape on sinking rates. It also remains noticeable that the highest sinking rates occurred in dust-rich ocean regions off NW Africa, but this issue deserves further detailed field and laboratory investigations. We obtained increasing sinking rates with depth. By using a seven-compartment biogeochemical model, it was shown that the deep ocean organic carbon flux at a mesotrophic sediment trap site off Cape Blanc can be captured fairly well using seasonal variable particle sinking rates. Our model provides a total organic carbon flux of 0.29 Tg per year down to 3000 m off the NW African upwelling

Oxygen permeation flux through La1-ySryFeO3 limited by the carbon monoxide oxidation rate

NARCIS (Netherlands)

van Hassel, B.A.; van Hassel, B.A.; ten Elshof, Johan E.; Bouwmeester, Henricus J.M.

1995-01-01

The oxygen permeation flux through La1-ySryFeO3-δ (y = 0.1, 0.2) in a large oxygen partial pressure gradient (air/CO, CO2 mixture) was found to be limited by the carbon monoxide oxidation rate at the low oxygen partial pressure side of the membrane. The oxygen permeation flux through the membrane

Wintertime Air-Sea Gas Transfer Rates and Air Injection Fluxes at Station Papa in the NE Pacific

Science.gov (United States)

McNeil, C.; Steiner, N.; Vagle, S.

2008-12-01

In recent studies of air-sea fluxes of N2 and O2 in hurricanes, McNeil and D'Asaro (2007) used a simplified model formulation of air-sea gas flux to estimate simultaneous values of gas transfer rate, KT, and air injection flux, VT. The model assumes air-sea gas fluxes at high to extreme wind speeds can be explained by a combination of two processes: 1) air injection, by complete dissolution of small bubbles drawn down into the ocean boundary layer by turbulent currents, and 2) near-surface equilibration processes, such as occurs within whitecaps. This analysis technique relies on air-sea gas flux estimates for two gases, N2 and O2, to solve for the two model parameters, KT and VT. We present preliminary results of similar analysis of time series data collected during winter storms at Station Papa in the NE Pacific during 2003/2004. The data show a clear increase in KT and VT with increasing NCEP derived wind speeds and acoustically measured bubble penetration depth.

Flux flow and flux creep in thick films of YBCO. [Y-Ba-Cu-O

Energy Technology Data Exchange (ETDEWEB)

Rickets, J.; Vinen, W.F.; Abell, J.S.; Shields, T.C. (Superconductivity Research Group, Univ. of Birmingham (United Kingdom))

1991-12-01

The results are described of new experiments designed to study flux creep and flux flow along a single flux percolation path in thick films of YBCO. The flux flow regime is studied by a four-point resistive technique using pulsed currents, and the flux creep regime by observing the rate at which flux enters a superconducting loop in parallel with the resistance that is associated with the flux percolation path. (orig.).

Role of land use change in landslide-related sediment fluxes in tropical mountain regions

Science.gov (United States)

Guns, M.; Vanacker, V.; Demoulin, A.

2012-04-01

Tropical mountain regions are characterised by high denudation rates. Landslides are known to be recurrent phenomena in active mountain belts, but their contribution to the overall sedimentary fluxes is not yet well known. Previous studies on sedimentary cascades have mostly focused on natural environments, without considering the impact of human and/or anthropogenic disturbances on sedimentary budgets. In our work, we hypothesise that human-induced land use change might alter the sediment cascade through shifts in the landslide magnitude-frequency relationship. We have tested this assumption in the Virgen Yacu catchment (approximately 11km2), in the Ecuadorian Cordillera Occidental. Landslide inventories and land use maps were established based on a series of sequential aerial photos (1963, 1977, 1984 and 1989), a HR Landsat image (2001) and a VHR WorldView2 image (2010). Aerial photographs were ortho-rectified, and coregistred with the WorldView2 satellite image. Field campaigns were realised in 2010 and 2011 to collect field-based data on landslide type and geometry (depth, width and length). This allowed us to establish an empirical relationship between landslide area and volume, which was then applied to the landslide inventories to estimate landslide-related sediment production rates for various time periods. The contribution of landslides to the overall sediment flux of the catchment was estimated by comparing the landslide-related sediment production to the total sediment yield. The empirical landslide area-volume relationship established here for the Ecuadorian Andes is similar to that derived for the Himalayas. It suggests that landslides are the main source of sediment in this mountainous catchment. First calculations indicate that human-induced land use change alters the magnitude-frequency relationship through strong increase of small landslides.

Neutron and Gamma Fluxes and dpa Rates for HFIR Vessel Beltline Region (Present and Upgrade Designs)

Energy Technology Data Exchange (ETDEWEB)

Blakeman, E.D.

2001-01-11

The Oak Ridge National Laboratory (ORNL) High Flux Isotope Reactor (HFIR) is currently undergoing an upgrading program, a part of which is to increase the diameters of two of the four radiation beam tubes (HB-2 and HB-4). This change will cause increased neutron and gamma radiation dose rates at and near locations where the tubes penetrate the vessel wall. Consequently, the rate of radiation damage to the reactor vessel wall at those locations will also increase. This report summarizes calculations of the neutron and gamma flux (particles/cm{sup 2}/s) and the dpa rate (displacements/atom/s) in iron at critical locations in the vessel wall. The calculated dpa rate values have been recently incorporated into statistical damage evaluation codes used in the assessment of radiation induced embrittlement. Calculations were performed using models based on the discrete ordinates methodology and utilizing ORNL two-dimensional and three-dimensional discrete ordinates codes. Models for present and proposed beam tube designs are shown and their results are compared. Results show that for HB-2, the dpa rate in the vessel wall where the tube penetrates the vessel will be increased by {approximately}10 by the proposed enlargement. For HB-4, a smaller increase of {approximately}2.6 is calculated.

Design basis for creep of zirconium alloy components in a fast neutron flux

International Nuclear Information System (INIS)

Ross-Ross, P.A.; Fidleris, V.

1975-01-01

The chalk River Nuclear Laboratory's experience with the creep of zirconium alloys in a neutron flux is described. Fast neutron flux changes the creep behaviour of zirconium alloys and new design criteria for in-reactor applications are needed. From experimental results empirical relations describing the effects of neutron flux, stress, temperature, time and anisotropy on creep rate were established. The relations are applied to the design of pressure tubes. (author)

Design basis for creep of zirconium alloy components in a fast neutron flux

International Nuclear Information System (INIS)

Ross-Ross, P.A.; Fidleris, V.

1974-01-01

The Chalk River Nuclear Laboratory's experience with the creep of zirconium alloys in a neutron flux is described. Fast neutron flux changes the creep behavior of zirconium alloys and new design criteria for in-reactor applications are needed. From experimental results empirical relations describing the effects of neutron flux, stress, temperature, time, and anisotropy on creep rate were established. The relations are applied to the design of pressure tubes. (author)

Efficiency of nitrate uptake in spinach : impact of external nitrate concentration and relative growth rate on nitrate influx and efflux

NARCIS (Netherlands)

Ter Steege, MW; Stulen, [No Value; Wiersema, PK; Posthumus, F; Vaalburg, W

1999-01-01

Regulation of nitrate influx and efflux in spinach (Spinacia oleracea L., cv. Subito), was studied in short-term label experiments with N-13- and N-15-nitrate. Nitrate fluxes were examined in relation to the N demand for growth, defined as relative growth rate (RGR) times plant N concentration.

Carbon Flux of Down Woody Materials in Forests of the North Central United States

International Nuclear Information System (INIS)

Woodall, C.W.

2010-01-01

Across large scales, the carbon (C) flux of down woody material (DWM) detrital pools has largely been simulated based on forest stand attributes (e.g., stand age and forest type). The annual change in forest DWM C stocks and other attributes (e.g., size and decay class changes) was assessed using a forest inventory in the north central United States to provide an empirical assessment of strategic-scale DWM C flux. Using DWM inventory data from the USDA Forest Service's Forest Inventory and Analysis program, DWM C stocks were found to be relatively static across the study region with an annual flux rate not statistically different from zero. Mean C flux rates across the study area were -0.25, -0.12, -0.01, and -0.04 (Mg/ha/yr) for standing live trees, standing dead trees, coarse woody debris, and fine woody debris, respectively. Flux rates varied in their both magnitude and status (emission/sequestration) by forest types, latitude, and DWM component size. Given the complex dynamics of DWM C flux, early implementation of inventory re measurement, and relatively low sample size, numerous future research directions are suggested.

Bursts of Pc 1-2 related to flux transfer events

International Nuclear Information System (INIS)

Arnoldy, R.L.; Cahill, L.J. Jr.; Engebretson, M.J.

1987-01-01

Instances of sporadic reconnection of geomagnetic and interplanetary magnetic field lines have been measured by space-craft passing through the dayside magnetopause region (Russell and Elphic 1979; Rijnbeek et al. 1984). The ionospheric signature of the reconnection events (flux transfer events) is a topic of current interest in that if one is evident then ground magnetic field data can be used to monitor the rate of dayside reconnection and conditions under which it occurs in a manner not possible with rapidly moving spacecraft. The proposed ground magnetic signature of a flux transfer event (FTE) is a large amplitude one-cycle Pc 5 (150-600 second period) pulse produced by a large vortex of ionospheric Hall current generated by the field-aligned current in the helical flux tube that has reconnected (Lee 1986). The intent of this article is to provide further data on the possible ground magnetic signatures of FTE (Lanzerotti el al. 1986) as measured by the induction antennas that the University of New Hampshire and the University of Minnesota have operated at high latitudes in the Antarctic and Greenland. With a high-frequency cut-off of 5 hertz, the induction magnetometers can measure Pc 1-2 waves (0.1-5.0 hertz) which cannot be seen by fluxgate instruments. Indeed, Pc 1-2 waves are frequently observed on the ground coincident with the Pc 5 FTE signature which provides some interesting new perspectives on these events

Oxygen, nitrogen and sulphide fluxes in the Black Sea

Directory of Open Access Journals (Sweden)

S.K. KONOVALOV

2000-12-01

Full Text Available The fluxes and production/consumption rates of oxygen, nitrate, ammonium and sulphide are estimated in the paper utilising results of the 1.5-dimensional stationary model of vertical exchange in the Black Sea (Samodurov & Ivanov, 1998. The profiles of the vertical flux and rate of production/consumption of these substances have revealed a number of intriguing features in the biogeochemical nature of the Black Sea. An approximate redox balance of the counter-fluxes of nitrate and ammonium into the sub-oxic zone has been revealed confirming that intensive denitrification may be the primary loss of nitrogen in the Black Sea. A low ratio of the nitrate stock to the flux of nitrate from the oxycline confirms the possibility of prominent changes in the distribution of nitrate on the time scale of a year. The ratio of the nitrate to oxygen vertical flux has revealed a lack of nitrate in the oxycline above the nitrate maximum. The lateral (related to the "Bosporus plume" flux of oxygen in the layer of the main pycnocline appears to be very important for the existing biogeochemical structure of the Black sea water column being the reason of sulphide consumption inside the anoxic zone and changes in the ammonium-sulphide stoichiometry of the anoxic zone, the primary reason of the existence of the sub-oxic layer and the basic reason of relative stability of the sulphide onset.

Quasi-biennial periodicity in the solar neutrino flux and its relation to the solar structure

International Nuclear Information System (INIS)

Sakurai, K.

1981-01-01

By analysing the observed results on the neutrino flux from the Sun for the years 1970-1978, it is shown that the production rate of the neutrinos at the central core of the Sun had been varying with a period almost equal to 26 months for these years. This so-called 'quasi-biennial' periodicity in this rate suggests that the physical state of the central core of the Sun must have been modulated with this period through the variation of physical parameters as temperature and the chemial composition at the central core of the Sun. An idea to interpret this observed periodicity is thus proposed by taking the variations of these parameters into consideration. Some supporting evidence on this periodicity can be found on the variations of the solar activity as the relative sunspot numbers and the equatorial rotation speed of the Sun. (orig.)

Measurement of a thermal neutron flux using air activation; Mesure de flux de neutrons thermiques par activation d'air

Energy Technology Data Exchange (ETDEWEB)

Guyonvarh, M; Lecomte, P; Le Meur, R [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1967-07-01

It is necessary to know, in irradiation loops, the thermal neutron flux after the irradiation device has been introduced and without being obliged to wait for the discharge of this device. In order to measure the flux and to control it continuously, one possible method is to place in the flux a coiled steel tube through which air passes. By measuring the activity of argon 41, and with a knowledge of the flow rate and the temperature of the air, it is possible to calculate the flux. An air-circulation flux controller is described and the relationship between the flux and the count rate is established The accuracy of an absolute measurement is about 14 per cent; that of a relative measurement is about 3 per cent. The measurement can be carried out equally well whether the reactor is operating at maximum or at low power. The measurement range goes from 10{sup 9} to lO{sup 15} n.cm{sup -2}.sec{sup -1}, and it would be possible after a few modifications to measure fluxes between 10{sup 5} and 10{sup 15} n.cm{sup -2}.sec{sup -1}. Finally, the method is very safe to operate: there is little risk of irradiation because of the low specific activity of the argon-41 formed, and no risk of contamination because the decay product of argon-41 is stable. This method, which is now being used in loops, is thus very practical. (authors) [French] Sur des boucles d'irradiation il est necessaire de connaitre le flux de neutrons thermiques apres mise en place du dispositif d'irradiation et sans etre oblige d'attendre le detournement de ce dispositif. Pour mesurer le flux et le controler en permanence, une methode consiste a placer sous flux un serpentin en acier dans lequel on fait circuler de l'air. La mesure d'activite d'argon 41 permet de calculer le flux, connaissant le debit et la temperature de l'air. Un controleur de flux par circulation d'air est decrit et la relation entre le flux et le taux de comptage est etablie. La precision d'une mesure absolue est de l'ordre de 14 pour

Organic carbon mass accumulation rate regulates the flux of reduced substances from the sediments of deep lakes

Directory of Open Access Journals (Sweden)

T. Steinsberger

2017-07-01

Full Text Available The flux of reduced substances, such as methane and ammonium, from the sediment to the bottom water (Fred is one of the major factors contributing to the consumption of oxygen in the hypolimnia of lakes and thus crucial for lake oxygen management. This study presents fluxes based on sediment porewater measurements from different water depths of five deep lakes of differing trophic states. In meso- to eutrophic lakes Fred was directly proportional to the total organic carbon mass accumulation rate (TOC-MAR of the sediments. TOC-MAR and thus Fred in eutrophic lakes decreased systematically with increasing mean hypolimnion depth (zH, suggesting that high oxygen concentrations in the deep waters of lakes were essential for the extent of organic matter mineralization leaving a smaller fraction for anaerobic degradation and thus formation of reduced compounds. Consequently, Fred was low in the 310 m deep meso-eutrophic Lake Geneva, with high O2 concentrations in the hypolimnion. By contrast, seasonal anoxic conditions enhanced Fred in the deep basin of oligotrophic Lake Aegeri. As TOC-MAR and zH are based on more readily available data, these relationships allow estimating the areal O2 consumption rate by reduced compounds from the sediments where no direct flux measurements are available.

Coronal and heliospheric magnetic flux circulation and its relation to open solar flux evolution

Science.gov (United States)

Lockwood, Mike; Owens, Mathew J.; Imber, Suzanne M.; James, Matthew K.; Bunce, Emma J.; Yeoman, Timothy K.

2017-06-01

Solar cycle 24 is notable for three features that can be found in previous cycles but which have been unusually prominent: (1) sunspot activity was considerably greater in the northern/southern hemisphere during the rising/declining phase; (2) accumulation of open solar flux (OSF) during the rising phase was modest, but rapid in the early declining phase; (3) the heliospheric current sheet (HCS) tilt showed large fluctuations. We show that these features had a major influence on the progression of the cycle. All flux emergence causes a rise then a fall in OSF, but only OSF with foot points in opposing hemispheres progresses the solar cycle via the evolution of the polar fields. Emergence in one hemisphere, or symmetric emergence without some form of foot point exchange across the heliographic equator, causes poleward migrating fields of both polarities in one or both (respectively) hemispheres which temporarily enhance OSF but do not advance the polar field cycle. The heliospheric field observed near Mercury and Earth reflects the asymmetries in emergence. Using magnetograms, we find evidence that the poleward magnetic flux transport (of both polarities) is modulated by the HCS tilt, revealing an effect on OSF loss rate. The declining phase rise in OSF was caused by strong emergence in the southern hemisphere with an anomalously low HCS tilt. This implies the recent fall in the southern polar field will be sustained and that the peak OSF has limited implications for the polar field at the next sunspot minimum and hence for the amplitude of cycle 25.type="synopsis">type="main">Plain Language SummaryThere is growing interest in being able to predict the evolution in solar conditions on a better basis than past experience, which is necessarily limited. Two of the key features of the solar magnetic cycle are that the polar fields reverse just after the peak of each sunspot cycle and that the polar field that has accumulated by the time of each sunspot minimum is a good

About Merging Threshold and Critical Flux Concepts into a Single One: The Boundary Flux

Directory of Open Access Journals (Sweden)

Marco Stoller

2014-01-01

Full Text Available In the last decades much effort was put in understanding fouling phenomena on membranes. One successful approach to describe fouling issues on membranes is the critical flux theory. The possibility to measure a maximum value of the permeate flux for a given system without incurring in fouling issues was a breakthrough in membrane process design. However, in many cases critical fluxes were found to be very low, lower than the economic feasibility of the process. The knowledge of the critical flux value must be therefore considered as a good starting point for process design. In the last years, a new concept was introduced, the threshold flux, which defines the maximum permeate flow rate characterized by a low constant fouling rate regime. This concept, more than the critical flux, is a new practical tool for membrane process designers. In this paper a brief review on critical and threshold flux will be reported and analyzed. And since the concepts share many common aspects, merged into a new concept, called the boundary flux, the validation will occur by the analysis of previously collected data by the authors, during the treatment of olive vegetation wastewater by ultrafiltration and nanofiltration membranes.

Interpreting the variations in atmospheric methane fluxes observed above a restored wetland

DEFF Research Database (Denmark)

Herbst, Mathias; Friborg, Thomas; Ringgaard, Rasmus

2011-01-01

The eddy flux of methane (CH4) was measured over 14 months above a restored wetland in western Denmark. The average annual daily CH4 flux was 30.2mgm-2 d-1, but the daily emission rates varied considerably over time. Several factors were identified that explained some of this variation. (1) Grazing...... that the variability in the CH4 fluxes strongly affects the greenhouse gas sink strength of the restored wetland.......4 flux to soil temperature at 20cm depth was found for most of the study period, but not for parts of the summer season that coincided with a low water level in the river flowing through the wetland. (4) Additional variations in the CH4 emission rates were related to the spatial heterogeneity...

Gap-related trapped magnetic flux dependence between single and combined bulk superconductors

Science.gov (United States)

Deng, Z.; Miki, M.; Felder, B.; Tsuzuki, K.; Shinohara, N.; Uetake, T.; Izumi, M.

2011-05-01

Aiming at examining the trapped-flux dependence between single and combined bulk superconductors for field-pole applications, three rectangular Y 1.65Ba 2Cu 3O 7-x (YBCO) bulks with a possibly compact combination were employed to investigate the trapped-flux characteristics of single and combined bulks with a field-cooling magnetization (FCM) method. A gap-related dependence was found between them. At lower gaps of 1 mm and 5 mm, the peak trapped fields and total magnetic flux of combined bulks are both smaller than the additive values of each single bulk, which can be ascribed to the demagnetization influences of the field around the bulk generated by the adjacent ones. While, at larger gaps like 10 mm, the situation becomes reversed. The combined bulks can attain bigger peak trapped fields as well as total magnetic flux, which indicates that the magnetic field by the bulk combination can reach higher gaps, thanks to the bigger magnetic energy compared with the single bulk. The presented results show that, on one hand, it is possible to estimate the total trapped magnetic flux of combined bulks by an approximate additive method of each single bulk while considering a demagnetization factor; on the other hand, it also means that the performance of combined bulks will be superior to the addition of each single bulk at larger gaps, thus preferable for large-scaled magnet applications.

Measurement and simulation of thermal neutron flux distribution in the RTP core

Science.gov (United States)

Rabir, Mohamad Hairie B.; Jalal Bayar, Abi Muttaqin B.; Hamzah, Na'im Syauqi B.; Mustafa, Muhammad Khairul Ariff B.; Karim, Julia Bt. Abdul; Zin, Muhammad Rawi B. Mohamed; Ismail, Yahya B.; Hussain, Mohd Huzair B.; Mat Husin, Mat Zin B.; Dan, Roslan B. Md; Ismail, Ahmad Razali B.; Husain, Nurfazila Bt.; Jalil Khan, Zareen Khan B. Abdul; Yakin, Shaiful Rizaide B. Mohd; Saad, Mohamad Fauzi B.; Masood, Zarina Bt.

2018-01-01

The in-core thermal neutron flux distribution was determined using measurement and simulation methods for the Malaysian’s PUSPATI TRIGA Reactor (RTP). In this work, online thermal neutron flux measurement using Self Powered Neutron Detector (SPND) has been performed to verify and validate the computational methods for neutron flux calculation in RTP calculations. The experimental results were used as a validation to the calculations performed with Monte Carlo code MCNP. The detail in-core neutron flux distributions were estimated using MCNP mesh tally method. The neutron flux mapping obtained revealed the heterogeneous configuration of the core. Based on the measurement and simulation, the thermal flux profile peaked at the centre of the core and gradually decreased towards the outer side of the core. The results show a good agreement (relatively) between calculation and measurement where both show the same radial thermal flux profile inside the core: MCNP model over estimation with maximum discrepancy around 20% higher compared to SPND measurement. As our model also predicts well the neutron flux distribution in the core it can be used for the characterization of the full core, that is neutron flux and spectra calculation, dose rate calculations, reaction rate calculations, etc.

Observation of the thunderstorm-related ground cosmic ray flux variations by ARGO-YBJ

Science.gov (United States)

Bartoli, B.; Bernardini, P.; Bi, X. J.; Cao, Z.; Catalanotti, S.; Chen, S. Z.; Chen, T. L.; Cui, S. W.; Dai, B. Z.; D'Amone, A.; Danzengluobu; De Mitri, I.; D'Ettorre Piazzoli, B.; Di Girolamo, T.; Di Sciascio, G.; Feng, C. F.; Feng, Zhaoyang; Feng, Zhenyong; Gao, W.; Gou, Q. B.; Guo, Y. Q.; He, H. H.; Hu, Haibing; Hu, Hongbo; Iacovacci, M.; Iuppa, R.; Jia, H. Y.; Labaciren; Li, H. J.; Liu, C.; Liu, J.; Liu, M. Y.; Lu, H.; Ma, L. L.; Ma, X. H.; Mancarella, G.; Mari, S. M.; Marsella, G.; Mastroianni, S.; Montini, P.; Ning, C. C.; Perrone, L.; Pistilli, P.; Salvini, P.; Santonico, R.; Shen, P. R.; Sheng, X. D.; Shi, F.; Surdo, A.; Tan, Y. H.; Vallania, P.; Vernetto, S.; Vigorito, C.; Wang, H.; Wu, C. Y.; Wu, H. R.; Xue, L.; Yang, Q. Y.; Yang, X. C.; Yao, Z. G.; Yuan, A. F.; Zha, M.; Zhang, H. M.; Zhang, L.; Zhang, X. Y.; Zhang, Y.; Zhao, J.; Zhaxiciren; Zhaxisangzhu; Zhou, X. X.; Zhu, F. R.; Zhu, Q. Q.; D'Alessandro, F.; ARGO-YBJ Collaboration

2018-02-01

A correlation between the secondary cosmic ray flux and the near-earth electric field intensity, measured during thunderstorms, has been found by analyzing the data of the ARGO-YBJ experiment, a full coverage air shower array located at the Yangbajing Cosmic Ray Laboratory (4300 m a. s. l., Tibet, China). The counting rates of showers with different particle multiplicities (m =1 , 2, 3, and ≥4 ) have been found to be strongly dependent upon the intensity and polarity of the electric field measured during the course of 15 thunderstorms. In negative electric fields (i.e., accelerating negative charges downwards), the counting rates increase with increasing electric field strength. In positive fields, the rates decrease with field intensity until a certain value of the field EFmin (whose value depends on the event multiplicity), above which the rates begin increasing. By using Monte Carlo simulations, we found that this peculiar behavior can be well described by the presence of an electric field in a layer of thickness of a few hundred meters in the atmosphere above the detector, which accelerates/decelerates the secondary shower particles of opposite charge, modifying the number of particles with energy exceeding the detector threshold. These results, for the first time to our knowledge, give a consistent explanation for the origin of the variation of the electron/positron flux observed for decades by high altitude cosmic ray detectors during thunderstorms.

A punctual flux estimator and reactions rates optimization in neutral particles transport calculus by the Monte Carlo method

International Nuclear Information System (INIS)

Authier, N.

1998-12-01

One of the questions asked in radiation shielding problems is the estimation of the radiation level in particular to determine accessibility of working persons in controlled area (nuclear power plants, nuclear fuel reprocessing plants) or to study the dose gradients encountered in material (iron nuclear vessel, medical therapy, electronics in satellite). The flux and reaction rate estimators used in Monte Carlo codes give average values in volumes or on surfaces of the geometrical description of the system. But in certain configurations, the knowledge of punctual deposited energy and dose estimates are necessary. The Monte Carlo estimate of the flux at a point of interest is a calculus which presents an unbounded variance. The central limit theorem cannot be applied thus no easy confidence level may be calculated. The convergence rate is then very poor. We propose in this study a new solution for the photon flux at a point estimator. The method is based on the 'once more collided flux estimator' developed earlier for neutron calculations. It solves the problem of the unbounded variance and do not add any bias to the estimation. We show however that our new sampling schemes specially developed to treat the anisotropy of the photon coherent scattering is necessary for a good and regular behavior of the estimator. This developments integrated in the TRIPOLI-4 Monte Carlo code add the possibility of an unbiased punctual estimate on media interfaces. (author)

The variation of methane flux rates from boreal tree species at the beginning of the growing season

Science.gov (United States)

Haikarainen, Iikka; Halmeenmäki, Elisa; Machacova, Katerina; Pihlatie, Mari

2016-04-01

Boreal forests are considered as net sink for atmospheric methane (CH4) because of the CH4 oxidizing bacteria in the aerobic soil layer. However, within the last decades it has become more evident that trees play an important role in the global CH4 budget by offering pathways for anaerobically produced CH4 from deeper soil layers to the atmosphere. Furthermore, trees may also act as independent sources of CH4. To confirm magnitude, variability and the origin of the tree mediated CH4 emissions more research is needed, especially in boreal forests which have been in a minority in such investigation. We measured tree stem and shoot CH4 exchange of three boreal tree species at the beginning of the growing season (13.4.-13.6.2015) at SMEAR II station in Hyytiälä, located in southern Finland (61° 51'N, 24° 17'E, 181 asl). The fluxes were measured from silver birch (Betula pendula), downy birch (B. pubescens) and Norway spruce (Picea abies) on two sites with differing soil type and characteristics (paludified and mineral soil), vegetation and forest structure by using the static chamber technique. Scaffold towers were used for measurements at multiple stem heights and shoots. The aim was to study the vertical profile of CH4 fluxes at stem and shoot level and compare these fluxes among the studied species, and to observe temporal changes in CH4 flux over the beginning of the growing season. We found that all the trees emitted CH4 from their stems and shoots. Overall, the birches showed higher emissions compared to the spruces. The emission rates were considerably larger in the lower parts of the birch stems than upper parts, and these emissions increased during the growing season. The spruces had more variation in the stem CH4 flux, but the emission rates of the upper parts of the stem exceeded the birch emissions at the same height. The shoot fluxes of all the studied trees indicated variable CH4 emissions without a clear pattern regarding the vertical profile and

Turbulent fluxes by "Conditional Eddy Sampling"

Science.gov (United States)

Siebicke, Lukas

2015-04-01

Turbulent flux measurements are key to understanding ecosystem scale energy and matter exchange, including atmospheric trace gases. While the eddy covariance approach has evolved as an invaluable tool to quantify fluxes of e.g. CO2 and H2O continuously, it is limited to very few atmospheric constituents for which sufficiently fast analyzers exist. High instrument cost, lack of field-readiness or high power consumption (e.g. many recent laser-based systems requiring strong vacuum) further impair application to other tracers. Alternative micrometeorological approaches such as conditional sampling might overcome major limitations. Although the idea of eddy accumulation has already been proposed by Desjardin in 1972 (Desjardin, 1977), at the time it could not be realized for trace gases. Major simplifications by Businger and Oncley (1990) lead to it's widespread application as 'Relaxed Eddy Accumulation' (REA). However, those simplifications (flux gradient similarity with constant flow rate sampling irrespective of vertical wind velocity and introduction of a deadband around zero vertical wind velocity) have degraded eddy accumulation to an indirect method, introducing issues of scalar similarity and often lack of suitable scalar flux proxies. Here we present a real implementation of a true eddy accumulation system according to the original concept. Key to our approach, which we call 'Conditional Eddy Sampling' (CES), is the mathematical formulation of conditional sampling in it's true form of a direct eddy flux measurement paired with a performant real implementation. Dedicated hardware controlled by near-real-time software allows full signal recovery at 10 or 20 Hz, very fast valve switching, instant vertical wind velocity proportional flow rate control, virtually no deadband and adaptive power management. Demonstrated system performance often exceeds requirements for flux measurements by orders of magnitude. The system's exceptionally low power consumption is ideal

Extraction of the atmospheric neutrino fluxes from experimental event rate data

NARCIS (Netherlands)

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

2007-01-01

The 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

The causal relation between turbulent particle flux and density gradient

Energy Technology Data Exchange (ETDEWEB)

Milligen, B. Ph. van; Martín de Aguilera, A.; Hidalgo, C. [CIEMAT - Laboratorio Nacional de Fusión, Avda. Complutense 40, 28040 Madrid (Spain); Carreras, B. A. [BACV Solutions, 110 Mohawk Road, Oak Ridge, Tennessee 37830 (United States); García, L.; Nicolau, J. H. [Universidad Carlos III, 28911 Leganés, Madrid (Spain)

2016-07-15

A technique for detecting the causal relationship between fluctuating signals is used to investigate the relation between flux and gradient in fusion plasmas. Both a resistive pressure gradient driven turbulence model and experimental Langmuir probe data from the TJ-II stellarator are studied. It is found that the maximum influence occurs at a finite time lag (non-instantaneous response) and that quasi-periodicities exist. Furthermore, the model results show very long range radial influences, extending over most of the investigated regions, possibly related to coupling effects associated with plasma self-organization. These results clearly show that transport in fusion plasmas is not local and instantaneous, as is sometimes assumed.

Determination of neutron flux densities in WWR-S reactor core

International Nuclear Information System (INIS)

Tomasek, F.

1989-04-01

The method is described of determining neutron flux densities and neutron fluences using activation detectors. The basic definitions and relations for determining reaction rates, fluence and neutron flux as well as the characteristics of some reactions and of sitable activation detectors are reported. The flux densities were determined of thermal and fast neutrons and of gamma quanta in the WWR-S reactor core. The data measured in the period 1984-1987 are tabulated. Cross sections for the individual reactions were determined from spectra measurements processed using program SAND-II and cross section library ENDF-B IV. Neutron flux densities were also measured for the WWR-S reactor vertical channels. (E.J.). 10 figs., 8 tabs., 111 refs

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

Science.gov (United States)

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

2013-12-01

Fluid flow through marine sediments and oceanic crust impacts seawater chemistry as well as diagenetic, thermal, seismic, and magmatic processes at plate boundaries, creates ore and gas hydrate deposits at and below seafloor, and establishes and maintains deep microbial ecosystems. However, steady-state fluid flow rates, as well as the temporal and spatial variability of fluid flow and composition are poorly constrained in many marine environments. A new, low-cost instrument deployable by ROV or submersible, named the Mosquito, was recently developed to provide continuous, long-term and campaign style monitoring of fluid flow rate and contemporaneous solute fluxes at multiple depths below the sea floor. The Mosquito consists of a frame that houses several osmotic pumps (Osmo-Samplers [OS]) connected to coils of tubing that terminate with an attachment to long thin titanium (Ti) needles, all of which are mounted to a release plate. The OS's consist of an acrylic housing which contains a brine chamber (BC) and a distilled water chamber (DWC) separated by semi permeable membranes. The osmotic gradient between the chambers drives the flow of distilled water into the BC. The DWC is connected to the Teflon tubing coil and a Ti needle, both of which are also filled with distilled water, thus the OS pulls fluid from the base of the needle through the tubing coil. One central Ti needle is attached to a custom-made tracer injection assembly, filled with a known volume of tracer, which is triggered, injecting a point source in the sediment. On a typical Mosquito, 4 needles are mounted vertically at varying depths with respect to the tracer injection needle, and 4 needles are mounted at equal depth but set at variable horizontal distances away from the tracer injection. Once the Mosquito has been placed on the seafloor, the release plate is manually triggered pushing the Ti needles into the sediment, then the tracer injection assembly is actuated. As the tracer is advected

From elementary flux modes to elementary flux vectors: Metabolic pathway analysis with arbitrary linear flux constraints

Science.gov (United States)

Klamt, Steffen; Gerstl, Matthias P.; Jungreuthmayer, Christian; Mahadevan, Radhakrishnan; Müller, Stefan

2017-01-01

Elementary flux modes (EFMs) emerged as a formal concept to describe metabolic pathways and have become an established tool for constraint-based modeling and metabolic network analysis. EFMs are characteristic (support-minimal) vectors of the flux cone that contains all feasible steady-state flux vectors of a given metabolic network. EFMs account for (homogeneous) linear constraints arising from reaction irreversibilities and the assumption of steady state; however, other (inhomogeneous) linear constraints, such as minimal and maximal reaction rates frequently used by other constraint-based techniques (such as flux balance analysis [FBA]), cannot be directly integrated. These additional constraints further restrict the space of feasible flux vectors and turn the flux cone into a general flux polyhedron in which the concept of EFMs is not directly applicable anymore. For this reason, there has been a conceptual gap between EFM-based (pathway) analysis methods and linear optimization (FBA) techniques, as they operate on different geometric objects. One approach to overcome these limitations was proposed ten years ago and is based on the concept of elementary flux vectors (EFVs). Only recently has the community started to recognize the potential of EFVs for metabolic network analysis. In fact, EFVs exactly represent the conceptual development required to generalize the idea of EFMs from flux cones to flux polyhedra. This work aims to present a concise theoretical and practical introduction to EFVs that is accessible to a broad audience. We highlight the close relationship between EFMs and EFVs and demonstrate that almost all applications of EFMs (in flux cones) are possible for EFVs (in flux polyhedra) as well. In fact, certain properties can only be studied with EFVs. Thus, we conclude that EFVs provide a powerful and unifying framework for constraint-based modeling of metabolic networks. PMID:28406903

Relative measurement of the fluxes of thermal, resonant and rapid neutrons in reactor G1; Mesures relatives des flux thermique, resonnant et rapide dans le reacteur G1

Energy Technology Data Exchange (ETDEWEB)

Carle, R; Mazancourt, T de [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1957-07-01

We sought to determine the behavior of the thermal, resonant and rapid neutron fluxes in the multiplier-reflector transition region, in the two principal directions of the system. We have also measured the variation of these different fluxes in the body of the multiplier medium in a canal filled with graphite and in an empty canal. The results are given in the form of curves representing: - the variation of the ratio of the thermal flux to the rapid flux in axial and radial transitions - the behavior of the thermal and resonant fluxes and the variation of their ratio in the same regions. (author) [French] Nous avons cherche a determiner le comportement des differents flux, thermique, resonnant et rapide a la transition milieu multiplicateur-reflecteur dans les deux directions principales du reseau. Nous avons egalement mesure la variation de ces differents flux au sein du milieu multiplicateur dans un canal rempli de graphite et dans un canal vide. Les resultats sont donnes sous forme de courbe representant: - La variation du rapport du flux thermique au flux rapide aux transitions axiale et radiale - L'allure des flux thermique et resonnant et la variation de leur rapport dans les memes regions. (auteur)

The Effect of Growth Temperature and V/III Flux Ratio of MOCVD Antimony Based Semiconductors on Growth Rate and Surface Morphology

Directory of Open Access Journals (Sweden)

Ramelan Ari Handono

2017-01-01

Full Text Available Epitaxial Alx Ga1-x Sb layers on GaSb and GaAs substrates have been grown by atmospheric pressure metalorganic chemical vapor deposition using TMAl, TMGa and TMSb. Nomarski microscope and a profiler were employed to examine the surface morphology and growth rate of the samples. We report the effect of growth temperature and V/III flux ratio on growth rate and surface morphology. Growth temperatures in the range of 520°C and 680°C and V/III ratios from 1 to 5 have been investigated. A growth rate activation energy of 0.73 eV was found. At low growth temperatures between 520 and 540°C, the surface morphology is poor due to antimonide precipitates associated with incomplete decomposition of the TMSb. For layers grown on GaAs at 580°C and 600°C with a V/III ratio of 3 a high quality surface morphology is typical, with a mirror-like surface and good composition control. It was found that a suitable growth temperature and V/III flux ratio was beneficial for producing good AlGaSb layers. Undoped AlGaSb grown at 580°C with a V/III flux ratio of 3 at the rate of 3.5 μm/hour shows p-type conductivity with smooth surface morphology

Relative measurement of the fluxes of thermal, resonant and rapid neutrons in reactor G1; Mesures relatives des flux thermique, resonnant et rapide dans le reacteur G1

Energy Technology Data Exchange (ETDEWEB)

Carle, R.; Mazancourt, T. de [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1957-07-01

We sought to determine the behavior of the thermal, resonant and rapid neutron fluxes in the multiplier-reflector transition region, in the two principal directions of the system. We have also measured the variation of these different fluxes in the body of the multiplier medium in a canal filled with graphite and in an empty canal. The results are given in the form of curves representing: - the variation of the ratio of the thermal flux to the rapid flux in axial and radial transitions - the behavior of the thermal and resonant fluxes and the variation of their ratio in the same regions. (author) [French] Nous avons cherche a determiner le comportement des differents flux, thermique, resonnant et rapide a la transition milieu multiplicateur-reflecteur dans les deux directions principales du reseau. Nous avons egalement mesure la variation de ces differents flux au sein du milieu multiplicateur dans un canal rempli de graphite et dans un canal vide. Les resultats sont donnes sous forme de courbe representant: - La variation du rapport du flux thermique au flux rapide aux transitions axiale et radiale - L'allure des flux thermique et resonnant et la variation de leur rapport dans les memes regions. (auteur)

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

Science.gov (United States)

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

2002-12-01

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

BRIGITTE, Dose Rate and Heat Source and Energy Flux for Self-Absorbing Rods

International Nuclear Information System (INIS)

Jegu, M.; Clement, M.

1978-01-01

1 - Nature of physical problem solved: Calculation of dose rate, heat sources or energy flux. The sources are self-absorbing radioactive rods. The shielding consists of blocks of which the cross section can be defined. 2 - Method of solution: Exponential attenuation and build-up factor between source points and detector points. Source integration with error estimate. Automatic or controlled build-up with monitor print-out. 3 - Restrictions on the complexity of the problem: Number of energy points, regions, detector points, abscissa points of the rod, vertical position of the rod, are all limited to ten. The maximum total number of vertical steps is 124

Incision and Landsliding Lead to Coupled Increase in Sediment Flux and Grain Size Export

Science.gov (United States)

Roda-Boluda, D. C.; Brooke, S.; D'Arcy, M. K.; Whittaker, A. C.; Armitage, J. J.

2017-12-01

The rates and grain sizes of sediment fluxes modulate the dynamics and timing of landscape response to tectonics, and dictate the depositional patterns of sediment in basins. Over the last decades, we have gained a good quantitative understanding on how sediment flux and grain size may affect incision and basin stratigraphy. However, we comparably still have limited knowledge on how these variables change with varying tectonic rates. To address this question, we have studied 152 catchments along 8 normal fault-bounded ranges in southern Italy, which are affected by varying fault slip rates and experiencing a transient response to tectonics. Using a data set of 38 new and published 10Be erosion rates, we calibrate a sediment flux predictive equation (BQART), in order to estimate catchment sediment fluxes. We demonstrate that long-term sediment flux is governed by fault slip rates and the tectonically-controlled transient incision, and that sediment flux estimates from the BQART, steady-state assumptions, and incised volumes are highly correlated. This is supported by our 10Be erosion rates, which are controlled by fault slip and incision rates, and the associated landsliding. Based on a new landslide inventory, we show that erosion rate differences are likely due to differences in incision-related landslide activity across these catchments, and that landslides are a major component of sediment fluxes. From a data set of >13000 grain size counts on hillslope grain size supply and fluvial sediment at catchment outlets, we observe that landslides deliver material 20-200% coarser than other sediment sources, and that this coarse supply has an impact on the grain size distributions being exported from the catchments. Combining our sediment flux and grain size data sets, we are able to show that for our catchments, and potentially also for any areas that respond to changes in climate or tectonics via enhanced landsliding, sediment flux and grain size export increase

The potential influence of multiple scattering on longwave flux and heating rate simulations with clouds

Science.gov (United States)

Kuo, C. P.; Yang, P.; Huang, X.; Feldman, D.; Flanner, M.; Kuo, C.; Mlawer, E. J.

2017-12-01

Clouds, which cover approximately 67% of the globe, serve as one of the major modulators in adjusting radiative energy on the Earth. Since rigorous radiative transfer computations including multiple scattering are costly, only absorption is considered in the longwave spectral bands in the radiation sub-models of the general circulation models (GCMs). Quantification of the effect of ignoring longwave scattering for flux and heating rate simulations is performed by using the GCM version of the Longwave Rapid Radiative Transfer Model (RRTMG_LW) with an implementation with the 16-stream Discrete Ordinates Radiative Transfer (DISORT) Program for a Multi-Layered Plane-Parallel Medium in conjunction with the 2010 CCCM products that merge satellite observations from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO), the CloudSat, the Clouds and the Earth's Radiant Energy System (CERES) and the Moderate Resolution Imaging Spectrometer (MODIS). One-year global simulations show that neglecting longwave scattering overestimates upward flux at the top of the atmosphere (TOA) and underestimates downward flux at the surface by approximately 2.63 and 1.15 W/m2, respectively. Furthermore, when longwave scattering is included in the simulations, the tropopause is cooled by approximately 0.018 K/day and the surface is heated by approximately 0.028 K/day. As a result, the radiative effects of ignoring longwave scattering and doubling CO2 are comparable in magnitude.

Metabolite Depletion Affects Flux Profiling of Cell Lines

DEFF Research Database (Denmark)

Nilsson, A.; Haanstra, J. R.; Teusink, B.

2018-01-01

Quantifying the rate of consumption and release of metabolites (i.e., flux profiling) has become integral to the study of cancer. The fluxes as well as the growth of the cells may be affected by metabolite depletion during cultivation.......Quantifying the rate of consumption and release of metabolites (i.e., flux profiling) has become integral to the study of cancer. The fluxes as well as the growth of the cells may be affected by metabolite depletion during cultivation....

Methane and Carbon Dioxide Concentrations and Fluxes in Amazon Floodplains

Science.gov (United States)

Melack, J. M.; MacIntyre, S.; Forsberg, B.; Barbosa, P.; Amaral, J. H.

2016-12-01

Field studies on the central Amazon floodplain in representative aquatic habitats (open water, flooded forests, floating macrophytes) combine measurements of methane and carbon dioxide concentrations and fluxes to the atmosphere over diel and seasonal times with deployment of meteorological sensors and high-resolution thermistors and dissolved oxygen sondes. A cavity ringdown spectrometer is used to determine gas concentrations, and floating chambers and bubble collectors are used to measure fluxes. To further understand fluxes, we measured turbulence as rate of dissipation of turbulent kinetic energy based on microstructure profiling. These results allow calculations of vertical mixing within the water column and of air-water exchanges using surface renewal models. Methane and carbon dioxide fluxes varied as a function of season, habitat and water depth. High CO2 fluxes at high water are related to high pCO2; low pCO2 levels at low water result from increased phytoplankton uptake. CO2 fluxes are highest at turbulent open water sites, and pCO2 is highest in macrophyte beds. Fluxes and pCH4 are high in macrophyte beds.

Grazing effects on ecosystem CO2 fluxes differ among temperate steppe types in Eurasia.

Science.gov (United States)

Hou, Longyu; Liu, Yan; Du, Jiancai; Wang, Mingya; Wang, Hui; Mao, Peisheng

2016-07-01

Grassland ecosystems play a critical role in regulating CO2 fluxes into and out of the Earth's surface. Whereas previous studies have often addressed single fluxes of CO2 separately, few have addressed the relation among and controls of multiple CO2 sub-fluxes simultaneously. In this study, we examined the relation among and controls of individual CO2 fluxes (i.e., GEP, NEP, SR, ER, CR) in three contrasting temperate steppes of north China, as affected by livestock grazing. Our findings show that climatic controls of the seasonal patterns in CO2 fluxes were both individual flux- and steppe type-specific, with significant grazing impacts observed for canopy respiration only. In contrast, climatic controls of the annual patterns were only individual flux-specific, with minor grazing impacts on the individual fluxes. Grazing significantly reduced the mean annual soil respiration rate in the typical and desert steppes, but significantly enhanced both soil and canopy respiration in the meadow steppe. Our study suggests that a reassessment of the role of livestock grazing in regulating GHG exchanges is imperative in future studies.

Transient critical heat flux under flow coast-down in vertical annulus with non-uniform heat flux distribution

International Nuclear Information System (INIS)

Moon, S.K.; Chun, S.Y.; Choi, K.Y.; Yang, S.K.

2001-01-01

An experimental study on transient critical heat flux (CHF) under flow coast-down has been performed for water flow in a non-uniformly heated vertical annulus under low flow and a wide range of pressure conditions. The objectives of this study are to systematically investigate the effect of the flow transient on the CHF and to compare the transient CHF with steady state CHF. The transient CHF experiments have been performed for three kinds of flow transient modes based on the coast-down data of the Kori 3/4 nuclear power plant reactor coolant pump. Most of the CHFs occurred in the annular-mist flow regime. Thus, it means that the possible CHF mechanism might be the liquid film dryout in the annular-mist flow regime. For flow transient mode with the smallest flow reduction rate, the time-to-CHF is the largest. At the same inlet subcooling, system pressure and heat flux, the effect of the initial mass flux on the critical mass flux can be negligible. However, the effect of the initial mass flux on the time-to-CHF becomes large as the heat flux decreases. Usually, the critical mass flux is large for slow flow reduction. There is a pressure effect on the ratio of the transient CHF data to steady state CHF data. Some conventional correlations show relatively better CHF prediction results for high system pressure, high quality and slow transient modes than for low system pressure, low quality and fast transient modes. (author)

Meromorphic flux compactification

Energy Technology Data Exchange (ETDEWEB)

Damian, Cesar [Departamento de Ingeniería Mecánica, Universidad de Guanajuato,Carretera Salamanca-Valle de Santiago Km 3.5+1.8 Comunidad de Palo Blanco,Salamanca (Mexico); Loaiza-Brito, Oscar [Departamento de Física, Universidad de Guanajuato,Loma del Bosque No. 103 Col. Lomas del Campestre C.P 37150 León, Guanajuato (Mexico)

2017-04-26

We present exact solutions of four-dimensional Einstein’s equations related to Minkoswki vacuum constructed from Type IIB string theory with non-trivial fluxes. Following https://www.doi.org/10.1007/JHEP02(2015)187; https://www.doi.org/10.1007/JHEP02(2015)188 we study a non-trivial flux compactification on a fibered product by a four-dimensional torus and a two-dimensional sphere punctured by 5- and 7-branes. By considering only 3-form fluxes and the dilaton, as functions on the internal sphere coordinates, we show that these solutions correspond to a family of supersymmetric solutions constructed by the use of G-theory. Meromorphicity on functions constructed in terms of fluxes and warping factors guarantees that flux and 5-brane contributions to the scalar curvature vanish while fulfilling stringent constraints as tadpole cancelation and Bianchi identities. Different Einstein’s solutions are shown to be related by U-dualities. We present three supersymmetric non-trivial Minkowski vacuum solutions and compute the corresponding soft terms. We also construct a non-supersymmetric solution and study its stability.

Meromorphic flux compactification

International Nuclear Information System (INIS)

Damian, Cesar; Loaiza-Brito, Oscar

2017-01-01

We present exact solutions of four-dimensional Einstein’s equations related to Minkoswki vacuum constructed from Type IIB string theory with non-trivial fluxes. Following https://www.doi.org/10.1007/JHEP02(2015)187; https://www.doi.org/10.1007/JHEP02(2015)188 we study a non-trivial flux compactification on a fibered product by a four-dimensional torus and a two-dimensional sphere punctured by 5- and 7-branes. By considering only 3-form fluxes and the dilaton, as functions on the internal sphere coordinates, we show that these solutions correspond to a family of supersymmetric solutions constructed by the use of G-theory. Meromorphicity on functions constructed in terms of fluxes and warping factors guarantees that flux and 5-brane contributions to the scalar curvature vanish while fulfilling stringent constraints as tadpole cancelation and Bianchi identities. Different Einstein’s solutions are shown to be related by U-dualities. We present three supersymmetric non-trivial Minkowski vacuum solutions and compute the corresponding soft terms. We also construct a non-supersymmetric solution and study its stability.

Metabolic Flux Analysis of Shewanella spp. Reveals Evolutionary Robustness in Central Carbon Metabolism

Energy Technology Data Exchange (ETDEWEB)

Tang, Yinjie J.; Martin, Hector Garcia; Dehal, Paramvir S.; Deutschbauer, Adam; Llora, Xavier; Meadows, Adam; Arkin, Adam; Keasling, Jay D.

2009-08-19

Shewanella spp. are a group of facultative anaerobic bacteria widely distributed in marine and fresh-water environments. In this study, we profiled the central metabolic fluxes of eight recently sequenced Shewanella species grown under the same condition in minimal med-ium with [3-13C] lactate. Although the tested Shewanella species had slightly different growth rates (0.23-0.29 h31) and produced different amounts of acetate and pyruvate during early exponential growth (pseudo-steady state), the relative intracellular metabolic flux distributions were remarkably similar. This result indicates that Shewanella species share similar regulation in regard to central carbon metabolic fluxes under steady growth conditions: the maintenance of metabolic robustness is not only evident in a single species under genetic perturbations (Fischer and Sauer, 2005; Nat Genet 37(6):636-640), but also observed through evolutionary related microbial species. This remarkable conservation of relative flux profiles through phylogenetic differences prompts us to introduce the concept of metabotype as an alternative scheme to classify microbial fluxomics. On the other hand, Shewanella spp. display flexibility in the relative flux profiles when switching their metabolism from consuming lactate to consuming pyruvate and acetate.

The relation between radio flux density and ionizing ultra-violet flux for HII regions and supernova remnants in the Large Magellanic cloud

Directory of Open Access Journals (Sweden)

Filipović M.D.

2003-01-01

Full Text Available We present a comparison between the Parkes radio surveys (Filipović et al 1995 and Vacuum Ultra-Violet (VUV surveys (Smith et al. 1987 of the Large Magellanic Clouds (LMC. We have found 72 sources in common in the LMC which are known HII regions (52 and supernova remnants (SNRs (19. Some of these radio sources are associated with two or more UV stellar associations. A comparison of the radio flux densities and ionizing UV flux for HII regions shows a very good correlation, as expected from theory. Many of the Magellanic Clouds (MCs SNRs are embedded in HII regions, so there is also a relation between radio and UV which we attribute to the surrounding HII regions.

Nonlinear radiative heat flux and heat source/sink on entropy generation minimization rate

Science.gov (United States)

Hayat, T.; Khan, M. Waleed Ahmed; Khan, M. Ijaz; Alsaedi, A.

2018-06-01

Entropy generation minimization in nonlinear radiative mixed convective flow towards a variable thicked surface is addressed. Entropy generation for momentum and temperature is carried out. The source for this flow analysis is stretching velocity of sheet. Transformations are used to reduce system of partial differential equations into ordinary ones. Total entropy generation rate is determined. Series solutions for the zeroth and mth order deformation systems are computed. Domain of convergence for obtained solutions is identified. Velocity, temperature and concentration fields are plotted and interpreted. Entropy equation is studied through nonlinear mixed convection and radiative heat flux. Velocity and temperature gradients are discussed through graphs. Meaningful results are concluded in the final remarks.

Effect of chamber enclosure time on soil respiration flux: A comparison of linear and non-linear flux calculation methods

DEFF Research Database (Denmark)

Kandel, Tanka P; Lærke, Poul Erik; Elsgaard, Lars

2016-01-01

One of the shortcomings of closed chamber methods for soil respiration (SR) measurements is the decreased CO2 diffusion rate from soil to chamber headspace that may occur due to increased chamber CO2 concentrations. This feedback on diffusion rate may lead to underestimation of pre-deployment flu......One of the shortcomings of closed chamber methods for soil respiration (SR) measurements is the decreased CO2 diffusion rate from soil to chamber headspace that may occur due to increased chamber CO2 concentrations. This feedback on diffusion rate may lead to underestimation of pre...... was placed on fixed collars, and CO2 concentration in the chamber headspace were recorded at 1-s intervals for 45 min. Fluxes were measured in different soil types (sandy, sandy loam and organic soils), and for various manipulations (tillage, rain and drought) and soil conditions (temperature and moisture......) to obtain a range of fluxes with different shapes of flux curves. The linear method provided more stable flux results during short enclosure times (few min) but underestimated initial fluxes by 15–300% after 45 min deployment time. Non-linear models reduced the underestimation as average underestimation...

Diffuse fluxes of cosmic high-energy neutrinos

International Nuclear Information System (INIS)

Stecker, F.W.

1979-01-01

Production spectra of high-energy neutrinos from galactic cosmic-ray interactions with interstellar gas and extragalactic ultrahigh-energy cosmic-ray interactions with microwave blackbody photons are presented and discussed. These production processes involve the decay of charged pions and are thus related to the production of cosmic γ-rays from the decay of neutral pions. Estimates of the neutrino fluxes from various diffuse cosmic sources are then made, and the reasons for significant differences with previous estimates are discussed. Small predicted event rates for a DUMAND type detection system, combined with a possible significant flux of prompt neutrinos from the atmosphere above 50 TeV, may make the study of diffuse extraterrestrial neutrinos more difficult than previously thought

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

Directory of Open Access Journals (Sweden)

A. Fraser

2013-06-01

posterior methane fluxes by incorporating them into GEOS-Chem and sampling the model at the location and time of 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 to 0.23 and the biases decreasing by a mean of 0.4 ppb (range: −8.9 to 8.4 ppb.

Effects of quartz on crystallization behavior of mold fluxes and microstructural characteristics of flux film.

Science.gov (United States)

Lei, Liu; Xiuli, Han; Mingduo, Li; Di, Zhang

2018-01-01

Mold fluxes are mainly prepared using cement clinker, quartz, wollastonite, borax, fluorite, soda ash and other mineral materials. Quartz, as one of the most common and essential materials, was chosen for this study to analyze itseffects on crystallization temperature, critical cooling rate, crystal incubation time, crystallization ratio and phases of flux film. We used the research methods of process mineralogy with the application of the single hot thermocouple technique, heat flux simulator, polarizing microscope, X-ray diffraction, etc. Results: By increasing the quartz content from 16 mass% to 24 mass%, the crystallization temperature, critical cooling rate and crystallization ratio of flux film decreased, and the crystal incubation time was extended. Meanwhile, the mineralogical structure of the flux film changed, with a large amount of wollastonite precipitation and a significant decrease in the cuspidine content until it reached zero. This showed a steady decline in the heat transfer control capacity of the flux film. The reason for the results above is that, by increasing the quartz content, the silicon-oxygen tetrahedron network structure promoted a rise in viscosity and restrained ion migration, inhibiting crystal nucleation and growth, leading to the weakening of the crystallization and a decline in the crystallization ratio.

Source-to-incident flux relation for a tokamak fusion test reactor blanket module

International Nuclear Information System (INIS)

Imel, G.R.

1982-01-01

The source-to-incident 14-MeV flux relation for a blanket module on the Tokamak Fusion Test Reactor is derived. It is shown that assumptions can be made that allow an analytical expression to be derived, using point kernel methods. In addition, the effect of a nonuniform source distribution is derived, again by relatively simple point kernel methods. It is thought that the methodology developed is valid for a variety of blanket modules on tokamak reactors

Integrated leak rate testing of the fast flux test facility reactor containment building

International Nuclear Information System (INIS)

James, E.B.; Farabee, O.A.; Bliss, R.J.

1978-01-01

The initial Integrated Leak Rate Test (ILRT) of the Fast Flux Test Facility containment building was performed from May 27 to June 2, 1978. The test was conducted in air with systems vented and with the containment recirculating coolers in operation. 10 psig and 5 psig tests were run using the absolute pressure test method. The measured leakage rates were .033% Vol/24 hr. and -.0015% Vol/24 hrs. respectively. Subsequent verification tests at both 10 psig and 5 psig proved that the test equipment was operating properly and it was sensitive enough to detect leaks at low pressures. This ILRT was performed at a lower pressure than any previous ILRT on a reactor containment structure in the United States. While the initial design requirements for ice condenser containments called for a part pressure test at 6 psig, the tests were waived due to the apparent statistical problems of data analysis and the repeatability of the data itself at such low pressure. In contrast to this belief, both the 5 and 10 psig ILRT's were performed in a successful manner at FFTF

CREME96 and Related Error Rate Prediction Methods

Science.gov (United States)

Adams, James H., Jr.

2012-01-01

Predicting the rate of occurrence of single event effects (SEEs) in space requires knowledge of the radiation environment and the response of electronic devices to that environment. Several analytical models have been developed over the past 36 years to predict SEE rates. The first error rate calculations were performed by Binder, Smith and Holman. Bradford and Pickel and Blandford, in their CRIER (Cosmic-Ray-Induced-Error-Rate) analysis code introduced the basic Rectangular ParallelePiped (RPP) method for error rate calculations. For the radiation environment at the part, both made use of the Cosmic Ray LET (Linear Energy Transfer) spectra calculated by Heinrich for various absorber Depths. A more detailed model for the space radiation environment within spacecraft was developed by Adams and co-workers. This model, together with a reformulation of the RPP method published by Pickel and Blandford, was used to create the CR ME (Cosmic Ray Effects on Micro-Electronics) code. About the same time Shapiro wrote the CRUP (Cosmic Ray Upset Program) based on the RPP method published by Bradford. It was the first code to specifically take into account charge collection from outside the depletion region due to deformation of the electric field caused by the incident cosmic ray. Other early rate prediction methods and codes include the Single Event Figure of Merit, NOVICE, the Space Radiation code and the effective flux method of Binder which is the basis of the SEFA (Scott Effective Flux Approximation) model. By the early 1990s it was becoming clear that CREME and the other early models needed Revision. This revision, CREME96, was completed and released as a WWW-based tool, one of the first of its kind. The revisions in CREME96 included improved environmental models and improved models for calculating single event effects. The need for a revision of CREME also stimulated the development of the CHIME (CRRES/SPACERAD Heavy Ion Model of the Environment) and MACREE (Modeling and

Tropical Gravity Wave Momentum Fluxes and Latent Heating Distributions

Science.gov (United States)

Geller, Marvin A.; Zhou, Tiehan; Love, Peter T.

2015-01-01

Recent satellite determinations of global distributions of absolute gravity wave (GW) momentum fluxes in the lower stratosphere show maxima over the summer subtropical continents and little evidence of GW momentum fluxes associated with the intertropical convergence zone (ITCZ). This seems to be at odds with parameterizations forGWmomentum fluxes, where the source is a function of latent heating rates, which are largest in the region of the ITCZ in terms of monthly averages. The authors have examined global distributions of atmospheric latent heating, cloud-top-pressure altitudes, and lower-stratosphere absolute GW momentum fluxes and have found that monthly averages of the lower-stratosphere GW momentum fluxes more closely resemble the monthly mean cloud-top altitudes rather than the monthly mean rates of latent heating. These regions of highest cloud-top altitudes occur when rates of latent heating are largest on the time scale of cloud growth. This, plus previously published studies, suggests that convective sources for stratospheric GW momentum fluxes, being a function of the rate of latent heating, will require either a climate model to correctly model this rate of latent heating or some ad hoc adjustments to account for shortcomings in a climate model's land-sea differences in convective latent heating.

An improved flux-split algorithm applied to hypersonic flows in chemical equilibrium

Science.gov (United States)

Palmer, Grant

1988-01-01

An explicit, finite-difference, shock-capturing numerical algorithm is presented and applied to hypersonic flows assumed to be in thermochemical equilibrium. Real-gas chemistry is either loosely coupled to the gasdynamics by way of a Gibbs free energy minimization package or fully coupled using species mass conservation equations with finite-rate chemical reactions. A scheme is developed that maintains stability in the explicit, finite-rate formulation while allowing relatively high time steps. The codes use flux vector splitting to difference the inviscid fluxes and employ real-gas corrections to viscosity and thermal conductivity. Numerical results are compared against existing ballistic range and flight data. Flows about complex geometries are also computed.

Carbon Dioxide and Methane Flux Related to Forest Type and Managed and Unmanaged Conditions in the Great Dismal Swamp, USA

Science.gov (United States)

Gutenberg, L. W.; Krauss, K.; Qu, J. J.; Hogan, D. M.; Zhu, Z.; Xu, C.

2017-12-01

The Great Dismal Swamp in Virginia and North Carolina, USA, has been greatly impacted by human use and management for the last few hundred years through logging, ditching, and draining. Today, the once dominant cedar, cypress and pocosin forest types are fragmented due to logging and environmental change. Maple-gum forest has taken over more than half the remaining area of the swamp ecosystem, which is now a National Wildlife Refuge and State Park. The peat soils and biomass store a vast quantity of carbon compared with the size of the refuge, but this store is threatened by fire and drying. This study looks at three of the main forest types in the GDS— maple-sweet gum, tall pine pocosin, and Atlantic white cedar— in terms of their carbon dioxide and methane soil flux. Using static chambers to sample soil gas flux in locally representative sites, we found that cedar sites showed a higher carbon dioxide flux rate as the soil temperature increased than maple sites, and the rate of carbon dioxide flux decreased as soil moisture increased faster in cedar sites than in maple sites. Methane flux increased as temperature increased for pocosin, but decreased with temperature for cedar and maple. All of the methane fluxes increased as soil moisture increased. Cedar average carbon dioxide flux was statistically significantly different from both maple and pocosin. These results show that soil carbon gas flux depends on soil moisture and temperature, which are factors that are changing due to human actions, as well as on forest type, which is also the result of human activity. Some of these variables may be adjustable by the managers of the land. Variables other than forest type, temperature and soil moisture/inundation may also play a role in influencing soil flux, such as stand age, tree height, composition of the peat and nutrient availability, and source of moisture as some sites are more influenced by groundwater from ditches and some more by rainfall depending on the

Method of Relative Magnitudes for Calculating Magnetic Fluxes in Electrical Machine

Directory of Open Access Journals (Sweden)

Oleg A.

2018-03-01

Full Text Available Introduction: The article presents the study results of the model of an asynchronous electric motor carried out by the author within the framework of the Priorities Research Program “Research and development in the priority areas of development of Russia’s scientific and technical complex for 2014–2020”. Materials and Methods: A model of an idealized asynchronous machine (with sinusoidal distribution of magnetic induction in air gap is used in vector control systems. It is impossible to create windings for this machine. The basis of the new calculation approach was the Conductivity of Teeth Contours Method, developed at the Electrical Machines Chair of the Moscow Power Engineering Institute (MPEI. Unlike this method, the author used not absolute values, but relative magnitudes of magnetic fluxes. This solution fundamentally improved the method’s capabilities. The relative magnitudes of the magnetic fluxes of the teeth contours do not required the additional consideration for exact structure of magnetic field of tooth and adjacent slots. These structures are identical for all the teeth of the machine and differ only in magnitude. The purpose of the calculations was not traditional harmonic analysis of magnetic induction distribution in air gap of machine, but a refinement of the equations of electric machine model. The vector control researchers used only the cos(θ function as a value of mutual magnetic coupling coefficient between the windings. Results: The author has developed a way to take into account the design of the windings of a real machine by using imaginary measuring winding with the same winding design as a real phase winding. The imaginary winding can be placed in the position of any machine windings. The calculation of the relative magnetic fluxes of this winding helped to estimate the real values of the magnetic coupling coefficients between the windings, and find the correction functions for the model of an idealized

Energy fluxes and their relations within energy plants

International Nuclear Information System (INIS)

Grazzini, Giuseppe; Milazzo, Adriano

2007-01-01

Analysing how energy is delivered from its primary sources to final users, it may be seen that the evolution of technology, driven by economic considerations, has mainly rewarded those systems that have intense energy fluxes through their main sections. On the other hand, renewable energy sources are prevented from being widespread by their low energy density. If a high energy flux is a recognized target for energy use, one may try to characterise the various devices encountered along the energy path according to the concentration obtained of the energy flow. In this way, apart from measuring the energy loss suffered within a given device, it can be decided if this loss is adequate with respect to the gain in terms of energy density

APPLE-3: improvement of APPLE for neutron and gamma-ray flux, spectrum and reaction rate plotting code, and of its code manual

International Nuclear Information System (INIS)

Kawasaki, Hiromitu; Maki, Koichi; Seki, Yasushi.

1991-03-01

A code APPLE was produced in 1976 for calculating and plotting tritium breeding ratio and tritium production rate distributions. That code was improved as 'APPLE-2' in 1982, to calculate and plot not only tritium breeding ratio but also distributions of neutron and gamma-ray fluxes, their spectra, nuclear heating rates and other reaction rates, and dose rate distributions during operation and after shutdown in 1982. The code APPLE-2 can calculate and plot these nuclear properties derived from neutron and gamma-ray fluxes by ANISN (one dimensional transport code), DOT3.5 (two dimensional transport code) and MORSE (three dimensional Monte Carlo code). We revised the code APPLE-2 as 'APPLE-3' by adding many functions to the APPLE-2 code in accordance with users' requirements proposed in recent progress of fusion reaction nuclear design. With minor modification of APPLE-2, a number of inconsistencies have been found between the code manual and the input data in the code. In the present report, the new functions added to APPLE-2 and improved users' manual are explained. (author)

Flux of Cadmium through Euphausiids

International Nuclear Information System (INIS)

Benayoun, G.; Fowler, S.W.; Oregioni, B.

1976-01-01

Flux of the heavy metal cadmium through the euphausiid Meganyctiphanes norvegica was examined. Radiotracer experiments showed that cadmium can be accumulated either directly from water or through the food chain. When comparing equilibrium cadmium concentration factors based on stable element measurements with those obtained from radiotracer experiments, it is evident that exchange between cadmium in the water and that in euphausiid tissue is a relatively slow process, indicating that, in the long term, ingestion of cadmium will probably be the more important route for the accumulation of this metal. Approximately 10% of cadmium ingested by euphausiids was incorporated into internal tissues when the food source was radioactive Artemia. After 1 month cadmium, accumulated directly from water, was found to be most concentrated in the viscera with lesser amounts in eyes, exoskeleton and muscle, respectively. Use of a simple model, based on the assumption that cadmium taken in by the organism must equal cadmium released plus that accumulated in tissue, allowed assessment of the relative importance of various metabolic parameters in controlling the cadmium flux through euphausiids. Fecal pellets, due to their relatively high rate of production and high cadmium content, accounted for 84% of the total cadmium flux through M. norvegica. Comparisons of stable cadmium concentrations in natural euphausiid food and the organism's resultant fecal pellets indicate that the cadmium concentration in ingested material was increased nearly 5-fold during its passage through the euphausiid. From comparisons of all routes by which cadmium can be released from M. norvegica to the water column, it is concluded that fecal pellet deposition represents the principal mechanism effecting the downward vertical transport of cadmium by this species. (author)

Role of recycling flux in gas fuelling in the Large Helical Device

International Nuclear Information System (INIS)

Miyazawa, J.; Masuzaki, S.; Yamada, H.

2004-01-01

The 'effective' fuelling efficiency of hydrogen gas puffing ranges from 10% to 50% in the Large Helical Device. A local increase in neutral particle pressure at the gas puff port was measured in the experiment. The pressure increase rate corresponds to ∼ 10% of the gas puff flux. The other 90% of the gas puff flux increases the density and/or the plasma outflow. A particle balance model reveals that the recycling flux estimated from the particle flux on the divertor plates increases during the gas puffing. It is shown that the high effective fuelling efficiency is possibly due to the large recycling flux. At the limit of small recycling flux, the effective fuelling efficiency decreases to ∼10%. In the helium gas puff discharge, the effective fuelling efficiency is larger than the hydrogen gas puffing and approaches 100%. This can be related to the large recycling coefficient of more than 0.95. (author)

The role of soil weathering and hydrology in regulating chemical fluxes from catchments (Invited)

Science.gov (United States)

Maher, K.; Chamberlain, C. P.

2010-12-01

Catchment-scale chemical fluxes have been linked to a number of different parameters that describe the conditions at the Earth’s surface, including runoff, temperature, rock type, vegetation, and the rate of tectonic uplift. However, many of the relationships relating chemical denudation to surface processes and conditions, while based on established theoretical principles, are largely empirical and derived solely from modern observations. Thus, an enhanced mechanistic basis for linking global solute fluxes to both surface processes and climate may improve our confidence in extrapolating modern solute fluxes to past and future conditions. One approach is to link observations from detailed soil-based studies with catchment-scale properties. For example, a number of recent studies of chemical weathering at the soil-profile scale have reinforced the importance of hydrologic processes in controlling chemical weathering rates. An analysis of data from granitic soils shows that weathering rates decrease with increasing fluid residence times and decreasing flow rates—over moderate fluid residence times, from 5 days to 10 years, transport-controlled weathering explains the orders of magnitude variation in weathering rates to a better extent than soil age. However, the importance of transport-controlled weathering is difficult to discern at the catchment scale because of the range of flow rates and fluid residence times captured by a single discharge or solute flux measurement. To assess the importance of transport-controlled weathering on catchment scale chemical fluxes, we present a model that links the chemical flux to the extent of reaction between the soil waters and the solids, or the fluid residence time. Different approaches for describing the distribution of fluid residence times within a catchment are then compared with the observed Si fluxes for a limited number of catchments. This model predicts high solute fluxes in regions with high run-off, relief, and

Influence of the current-phase relation on the critical-current-applied-magnetic-flux dependence in parallel-connected Josephson junctions

International Nuclear Information System (INIS)

Tsang, W.; Van Duzer, T.

1976-01-01

The form of the current-phase relations for the Josephson junctions is shown to have a significant influence on the relation I/sub c/(theta/sub a/) between critical current and applied flux for two junctions connected in parallel in a superconducting circuit. The observed one-flux-quantum periodicity and inversion symmetry of the I/sub c/(theta/sub a/) relation are shown to result from the fact that the current-phase, i-phi, relations of the junctions satisfy i (phi+2mπ) =i (phi) and i (-phi) =-i (phi), respectively. It is also shown that if the current-phase relations for the two junctions are different, an asymmetry appears in the I/sub c/(theta/sub a/)

KoFlux: Korean Regional Flux Network in AsiaFlux

Science.gov (United States)

Kim, J.

2002-12-01

AsiaFlux, the Asian arm of FLUXNET, held the Second International Workshop on Advanced Flux Network and Flux Evaluation in Jeju Island, Korea on 9-11 January 2002. In order to facilitate comprehensive Asia-wide studies of ecosystem fluxes, the meeting launched KoFlux, a new Korean regional network of long-term micrometeorological flux sites. For a successful assessment of carbon exchange between terrestrial ecosystems and the atmosphere, an accurate measurement of surface fluxes of energy and water is one of the prerequisites. During the 7th Global Energy and Water Cycle Experiment (GEWEX) Asian Monsoon Experiment (GAME) held in Nagoya, Japan on 1-2 October 2001, the Implementation Committee of the Coordinated Enhanced Observing Period (CEOP) was established. One of the immediate tasks of CEOP was and is to identify the reference sites to monitor energy and water fluxes over the Asian continent. Subsequently, to advance the regional and global network of these reference sites in the context of both FLUXNET and CEOP, the Korean flux community has re-organized the available resources to establish a new regional network, KoFlux. We have built up domestic network sites (equipped with wind profiler and radiosonde measurements) over deciduous and coniferous forests, urban and rural rice paddies and coastal farmland. As an outreach through collaborations with research groups in Japan, China and Thailand, we also proposed international flux sites at ecologically and climatologically important locations such as a prairie on the Tibetan plateau, tropical forest with mixed and rapid land use change in northern Thailand. Several sites in KoFlux already begun to accumulate interesting data and some highlights are presented at the meeting. The sciences generated by flux networks in other continents have proven the worthiness of a global array of micrometeorological flux towers. It is our intent that the launch of KoFlux would encourage other scientists to initiate and

Increasing flux rate to shorten leaching period and ramp-up production

Science.gov (United States)

Ngantung, Billy; Agustin, Riska; Ravi'i

2017-01-01

J Resources Bolaang Mongondow (JBRM) has operated a dynamic heap leach in its Bakan Gold Mine since late 2013. After successfully surpassing its name plate capacity of 2.6 MT/annum in 2014, the clayey and transition ore become the next operational challenge. The presence of transition and clayey ore requires longer leaching period, hence reducing the leach pad capacity which then caused reduced production. Maintaining or even increasing production with such longer leaching ore types can be done by expanding the leach pad area which means an additional capital investment, and/or shortening the leaching cycle which compromise a portion of gold extraction. JBRM has been successfully increasing the leach pad production from 2.6 MT/annum to 3.8 MT/annum, whilst improving the gold extraction from around 70% to around 80%. This was achieved by managing the operation of the leach pad which is shortening the leach cycle by identifying and combining the optimal flux rate application versus the tonne processed in each cell, at no capital investment for expanding the cell capacity.

Effects of insulin on perfused liver from streptozotocin-diabetic and untreated rats: 13C NMR assay of pyruvate kinase flux

International Nuclear Information System (INIS)

Cohen, S.M.

1987-01-01

The effects of insulin in vitro on perfused liver from streptozotocin-diabetic rats and their untreated littermates during gluconeogenesis from either [3- 13 C]alanine + ethanol or [2- 13 C]pyruvate + NH 4 Cl + ethanol were studied by 13 C NMR. A 13 C NMR determination of the rate of pyruvate kinase flux under steady-state conditions of active gluconeogenesis was developed; this assay includes a check on the reuse of recycled pyruvate. The preparations studied provided gradations of pyruvate kinase flux within the confines of the assay's requirement of active gluconeogenesis. By this determination, the rate of pyruvate kinase flux was 0.74 +/- 0.04 of the gluconeogenic rate in liver from 24-h-fasted controls; in liver from 12-h fasted controls, relative pyruvate kinase flux increased to 1.0 +/- 0.2. In diabetic liver, this flux was undetectable by the authors NMR method. Insulin's hepatic influence in vitro was greatest in the streptozotocin model of type 1 diabetes: upon treatment of diabetic liver with 7 nM insulin in vitro, a partial reversal of many of the differences noted between diabetic and control liver was demonstrated by 13 C NMR. A major effect of insulin in vitro upon diabetic liver was the induction of a large increase in the rate of pyruvate kinase flux, bringing relative and absolute fluxes up to the levels measured in 24-h-fasted controls. By way of comparison, the effects of ischemia on diabetic liver were studied by 13 C NMR to test whether changes in allosteric effectors under these conditions could also increase pyruvate kinase flux. A large increase in this activity was demonstrated in ischemic diabetic liver

Magnetic relaxation, flux pinning and critical currents in superconductors

International Nuclear Information System (INIS)

Lichtenberger, K.S.

1991-01-01

A systematic study of the magnetic flux pinning properties in superconductors has been undertaken in an attempt to understand the differences between the flux creep behavior of classical superconductors and high-temperature superconductors (HTSC's). In HTSC's, the ratio of the effective flux pinning energy to the thermal energy, U 0 /kT, is much smaller than that of conventional superconductors, often approaching unity. This results in much larger creep rates in HTSC's than in conventional superconductors. It is necessary to find suitable models that describe flux creep in both classical superconductors and HTSC's. Results show that while these two classes of materials are quantitatively very different, a single pinning barrier mode adequately describes both, within the proper region of the H-T plane. The model is applied to a variety of superconductors and the results are contrasted. Although the H-T plane appears to be very different HTSC's than for conventional superconductors, qualitatively the same physics describes both. In HTSC's, near the upper critical field there exists a relatively wide region of superconducting fluctuations, followed successively by regions of thermodynamic reversibility, thermally assisted flux, flux creep, and finally rigid flux lattice where little, if any, motion of the flux lattice occurs. All of these regions are also present in conventional superconductors, but often much more difficult, especially the irreversibility transition and the fluctuation region. The central finding of the flux creep analysis is that the region of flux creep is defined as a band in the H-T plane in which 2 ≤ U 0 /kT ≤ 100, and that the flux creep model applies best within this band

Calculation of the transmutation rates of Tc-99, I-129 and Cs-135 in the High Flux Reactor, in the Phenix Reactor and in a light water reactor

International Nuclear Information System (INIS)

Bultman, J.

1992-04-01

Transmutation of long-lived fission products is of interest for the reduction of the possible dose to the population resulting from long-term leakage of nuclear waste from waste disposals. Three isotopes are of special interest: Tc-99, I-129 and Cs-135. Therefore, experiments on transmutation of these isotopes in nuclear reactors are planned. In the present study, the possible transmutation rates and mass reductions are determined for experiments in High Flux Reactor (HFR) located in Petten (Netherlands) and in Phenix (France). Also, rates were determined for a standard Light Water Reactor (LWR). The transmutation rates of the 3 fission products will be much higher in HFR than in Phenix reactor, as both total flux and effective cross sections are higher. For thick targets the effective half lives are approximately 3, 2 and 7 years for Tc-99, I-129 and Cs-135 irradiation respectively in HFR and 22, 16 and 40 years for Tc-99, I-129 and Cs-135 irradiation in Phenix reactor. The transmutation rates in LWR are low. Only the relatively large power of LWR guarantees a large total mass reduction. Especially transmutation of Cs-135 will be very difficult in Phenix and LWR, clearly shown by the very long effective half lives of 40 and 100 years, respectively. (author). 7 refs.; 5 figs.; 7 tabs

A process-based 222radon flux map for Europe and its comparison to long-term observations

Science.gov (United States)

Karstens, U.; Schwingshackl, C.; Schmithüsen, D.; Levin, I.

2015-11-01

Detailed 222radon (222Rn) flux maps are an essential pre-requisite for the use of radon in atmospheric transport studies. Here we present a high-resolution 222Rn flux map for Europe, based on a parameterization of 222Rn production and transport in the soil. The 222Rn exhalation rate is parameterized based on soil properties, uranium content, and modelled soil moisture from two different land-surface reanalysis data sets. Spatial variations in exhalation rates are primarily determined by the uranium content of the soil, but also influenced by soil texture and local water-table depth. Temporal variations are related to soil moisture variations as the molecular diffusion in the unsaturated soil zone depends on available air-filled pore space. The implemented diffusion parameterization was tested against campaign-based 222Rn soil profile measurements. Monthly 222Rn exhalation rates from European soils were calculated with a nominal spatial resolution of 0.083° × 0.083° and compared to long-term direct measurements of 222Rn exhalation rates in different areas of Europe. The two realizations of the 222Rn flux map, based on the different soil moisture data sets, both realistically reproduce the observed seasonality in the fluxes but yield considerable differences for absolute flux values. The mean 222Rn flux from soils in Europe is estimated to be 10 mBq m-2 s-1 (ERA-Interim/Land soil moisture) or 15 mBq m-2 s-1 (GLDAS (Global Land Data Assimilation System) Noah soil moisture) for the period 2006-2010. The corresponding seasonal variations with low fluxes in winter and high fluxes in summer range in the two realizations from ca. 7 to ca. 14 mBq m-2 s-1 and from ca. 11 to ca. 20 mBq m-2 s-1, respectively. These systematic differences highlight the importance of realistic soil moisture data for a reliable estimation of 222Rn exhalation rates. Comparison with observations suggests that the flux estimates based on the GLDAS Noah soil moisture model on average better

A process-based 222radon flux map for Europe and its comparison to long-term observations

International Nuclear Information System (INIS)

Karstens, U.; Schwingshackl, C.; Schmithuesen, D.; Levin, I.

2015-01-01

Detailed 222 radon ( 222 Rn) flux maps are an essential pre-requisite for the use of radon in atmospheric transport studies. Here we present a high-resolution 222 Rn flux map for Europe, based on a parameterization of 222 Rn production and transport in the soil. The 222 Rn exhalation rate is parameterized based on soil properties, uranium content, and modelled soil moisture from two different land-surface reanalysis data sets. Spatial variations in exhalation rates are primarily determined by the uranium content of the soil, but also influenced by soil texture and local water-table depth. Temporal variations are related to soil moisture variations as the molecular diffusion in the unsaturated soil zone depends on available air-filled pore space. The implemented diffusion parameterization was tested against campaign-based 222 Rn soil profile measurements. Monthly 222 Rn exhalation rates from European soils were calculated with a nominal spatial resolution of 0.083 x 0.083 and compared to long-term direct measurements of 222 Rn exhalation rates in different areas of Europe. The two realizations of the 222 Rn flux map, based on the different soil moisture data sets, both realistically reproduce the observed seasonality in the fluxes but yield considerable differences for absolute flux values. The mean 222 Rn flux from soils in Europe is estimated to be 10 mBq m -2 s -1 (ERA-Interim/Land soil moisture) or 15 mBq m -2 s -1 (GLDAS (Global Land Data Assimilation System) Noah soil moisture) for the period 2006-2010. The corresponding seasonal variations with low fluxes in winter and high fluxes in summer range in the two realizations from ca. 7 to ca. 14 mBq m -2 s -1 and from ca. 11 to ca. 20 mBq m -2 s -1 , respectively. These systematic differences highlight the importance of realistic soil moisture data for a reliable estimation of 222 Rn exhalation rates. Comparison with observations suggests that the flux estimates based on the GLDAS Noah soil moisture model on

Mesoscopic fluctuations in biharmonically driven flux qubits

Science.gov (United States)

Ferrón, Alejandro; Domínguez, Daniel; Sánchez, María José

2017-01-01

We investigate flux qubits driven by a biharmonic magnetic signal, with a phase lag that acts as an effective time reversal broken parameter. The driving induced transition rate between the ground and the excited state of the flux qubit can be thought of as an effective transmittance, profiting from a direct analogy between interference effects at avoided level crossings and scattering events in disordered electronic systems. For time scales prior to full relaxation, but large compared to the decoherence time, this characteristic rate has been accessed experimentally by Gustavsson et al. [Phys. Rev. Lett. 110, 016603 (2013)], 10.1103/PhysRevLett.110.016603 and its sensitivity with both the phase lag and the dc flux detuning explored. In this way, signatures of universal conductance fluctuationslike effects have been analyzed and compared with predictions from a phenomenological model that only accounts for decoherence, as a classical noise. Here we go beyond the classical noise model and solve the full dynamics of the driven flux qubit in contact with a quantum bath employing the Floquet-Born-Markov master equation. Within this formalism, the computed relaxation and decoherence rates turn out to be strongly dependent on both the phase lag and the dc flux detuning. Consequently, the associated pattern of fluctuations in the characteristic rates display important differences with those obtained within the mentioned phenomenological model. In particular, we demonstrate the weak localizationlike effect in the average values of the relaxation rate. Our predictions can be tested for accessible but longer time scales than the current experimental times.

Magnetic Flux Conversion in the DIII-D Steady-State Hybrid Scenario

Science.gov (United States)

Taylor, N. Z.; Luce, T. C.; La Haye, R. J.; Petty, C. C.; Nazikian, R.

2017-10-01

The hybrid is a promising high confinement scenario for ITER. The broader current profile aids discharge sustainment by raising qmin > 1 thereby avoiding sawtooth-triggered 2/1 tearing modes. In DIII-D hybrid scenario discharges, the rate of poloidal magnetic energy consumption is more than the rate of energy flow from the poloidal field coils. This is evidence that there is a conversion of toroidal flux to poloidal flux, which may be responsible for the anomalous broadening of the current profile known as flux pumping. The rate of poloidal flux being provided and consumed was tracked with coil and kinetic flux states. During long stationary intervals (1.5 seconds) with constant stored magnetic energy, a significant flux state deficit rate >10 mV was observed. The inequality in the evolution of the flux states was observed in hybrids that were 100% non-inductive and with successful RMP ELM suppression. Work supported by the US DOE under DE-FC02-04ER54698 and DE-AC05-06OR23100.

Sodium Flux Growth of Bulk Gallium Nitride

Science.gov (United States)

Von Dollen, Paul Martin

This dissertation focused on development of a novel apparatus and techniques for crystal growth of bulk gallium nitride (GaN) using the sodium flux method. Though several methods exist to produce bulk GaN, none have been commercialized on an industrial scale. The sodium flux method offers potentially lower cost production due to relatively mild process conditions while maintaining high crystal quality. But the current equipment and methods for sodium flux growth of bulk GaN are generally not amenable to large-scale crystal growth or in situ investigation of growth processes, which has hampered progress. A key task was to prevent sodium loss or migration from the sodium-gallium growth melt while permitting N2 gas to access the growing crystal, which was accomplished by implementing a reflux condensing stem along with a reusable sealed capsule. The reflux condensing stem also enabled direct monitoring and control of the melt temperature, which has not been previously reported for the sodium flux method. Molybdenum-based materials were identified from a corrosion study as candidates for direct containment of the corrosive sodium-gallium melt. Successful introduction of these materials allowed implementation of a crucible-free containment system, which improved process control and can potentially reduce crystal impurity levels. Using the new growth system, the (0001) Ga face (+c plane) growth rate was >50 mum/hr, which is the highest bulk GaN growth rate reported for the sodium flux method. Omega X-ray rocking curve (?-XRC) measurements indicated the presence of multiple grains, though full width at half maximum (FWHM) values for individual peaks were 1020 atoms/cm3, possibly due to reactor cleaning and handling procedures. This dissertation also introduced an in situ technique to correlate changes in N2 pressure with dissolution of nitrogen and precipitation of GaN from the sodium-gallium melt. Different stages of N2 pressure decay were identified and linked to

Factors Controlling Nitrogen Fluxes in Groundwater in Agricultural Areas

Science.gov (United States)

Liao, L.; Green, C. T.; Bekins, B. A.; Bohlke, J. K.

2010-12-01

Predictions of effects of land use changes on water quality require identification of the relative importance of geochemical and hydrologic factors. To understand the factors controlling the transport of nitrogen in groundwater, vertical fluxes of water and solutes were estimated for 13 aquifers in agricultural areas located in California, Iowa, Maryland, Minnesota, Mississippi, Nebraska, North Carolina, Texas, and Wisconsin. The aquifers are overlain by unsaturated zones with thicknesses ranging from 2.5 to 100 m. Precipitation ranges from 19 to 132 cm/yr and irrigation ranges from 0 to 120 cm/yr. Main crop types include corn, soybeans, forage, wheat, and cotton. A 1-dimensional mathematical model was developed to estimate vertical N transport in response to N inputs on the land surface from chemical fertilizer, manure and atmospheric deposition. Simulated vertical profiles of O2, NO3-, N2 from denitrification, Cl- and atmospheric age tracers were matched to observations by adjusting parameters for recharge rate, unsaturated zone travel time, N leaching ratio (defined as leaching fraction of N reaching water table of N input at land surface), Cl- leaching ratio, O2 reduction rate and denitrification rate. Results indicated that vertical NO3 fluxes below the water table were affected by both geochemical and physical factors. High vertical NO3 fluxes below the water table are associated with high N input at the land surface. Values of Cl- leaching ratios were less than 1 (0.42 to 1) likely as a result of runoff and exported harvested crops. N leaching ratios were lower (0.1 to 0.6), consistent with additional N losses such as denitrification and volatilization. The sites with high leaching ratios for both N and Cl tended to be those with high recharge rates and low ET loss, defined as the fraction of applied water lost to ET. Modeled zero-order denitrification rates in the saturated zone varied within an order of magnitude with a maximum rate of 1.6 mg

Can we relate respiration rates of bark and wood with tissue nitrogen concentrations and branch-level CO2 fluxes across woody species?

Science.gov (United States)

Eller, A. S.; Wright, I.; Cernusak, L. A.

2013-12-01

Respiration from above-ground woody tissue is generally responsible for 5-15% of ecosystem respiration (~ 30% of total above-ground respiration). The CO2 respired by branches comes from both the sapwood and the living layers within the bark, but because there is considerable movement of respired CO2 within woody tissues (e.g. in the transpiration stream), and because the bark can present a considerable barrier to CO2 diffusion, it can be difficult to interpret measured CO2 efflux from intact branches in relation to the respiration rates of the component tissues, and to relative mass allocation to each. In this study we investigated these issues in 15 evergreen tree and shrub species native to the Sydney area in eastern Australia. We measured CO2 efflux and light-dependent refixation of respired CO2 in photosynthetic bark from the exterior surfaces of branches (0.5-1.5 cm in diameter), and measured the tissue-specific respiration rates of the bark and wood from those same branches. We also measured the nitrogen content and tissue density of the wood and bark to determine: 1) Among species, what is the relationship between %N and tissue respiration? 2) How is photosynthetic refixation of CO2 related to respiration and %N in the bark and underlying wood? and 3) What is the relationship between branch CO2 efflux and the respiration rates of the underlying wood and bark that make up the branch? Across the 15 species %N was a better predictor of respiration in wood than in bark. CO2 efflux measured from the exterior of the stem in the dark was positively correlated with photosynthetic refixation and explained ~40% of the variation in rates of refixation. Refixation rates were not strongly related to bark or wood %N. Differences among species in CO2 efflux rates were not well explained by differences in bark or wood %N and there was a stronger relationship between bark respiration and CO2 efflux than between wood respiration and CO2 efflux. These results suggest that the

On the relation between neoclassical transport and turbulent transport

International Nuclear Information System (INIS)

Shaing, K.C.

2005-01-01

It is demonstrated through the flux-force relationship in the neoclassical theory that when neoclassical transport fluxes are improved, the damping rate of the radial electric field of the zonal flow is reduced. This, in turn, leads to improved turbulent transport fluxes. Thus, two seemingly unrelated transport fluxes are intimately connected through the momentum equation, and the neoclassical flux-force relation. This also implies a method to improve turbulent transport by improving neoclassical fluxes

Losses in magnetic flux compression generators: Part 2, Radiation losses

International Nuclear Information System (INIS)

Fowler, C.M.

1988-06-01

This is the second monograph devoted to the analysis of flux losses in explosive driven magnetic flux compression generators. In the first monograph, flux losses from magnetic field penetration into conductor walls was studied by conventional diffusion theory. In the present report flux loss by radiation from the outer conductor walls is treated. Flux leakage rates through walls of finite thickness are first obtained by diffusion theory. It is shown, for normal wall thicknesses, that flux leakage is determined essentially by the wall conductance, defined as the product of wall thickness and wall conductivity. This remains true when the wall thickness is reduced to zero at unchanged conductance. In this case the wall is said to be coalesced. Solutions for a cavity bounded by a perfect conductor on one side and a coalesced wall on the other are then obtained using the complete Maxwell wave equations in both the cavity and free space beyond the coalesced wall. Several anomalies, noted earlier, that arise from diffusion analysis are resolved by the wave treatment. Conditions for the validity of the diffusion treatment are noted, and an expression is obtained within the framework of diffusion theory for energy radiated into space from the cavity walls. The free space wave equations are solved by using the method of characteristics in both the cavity and free space regions. An extension of the characteristic method to situations where the constitutive relations are non-linear is outlined in an appendix. For a special class of these relations, Riemann-like invariants are determined explicitly and used to solve a particular example

Seasonal variations of nitrous oxide fluxes and soil denitrification rates in subtropical freshwater and brackish tidal marshes of the Min River estuary.

Science.gov (United States)

Wang, Xuming; Hu, Minjie; Ren, Hongchang; Li, Jiabing; Tong, Chuan; Musenze, Ronald S

2018-03-01

Estuarine tidal marshes provide favorable conditions for nitrous oxide (N 2 O) production. Saltwater intrusion caused by sea-level rise would exert complex effects on the production and emission of N 2 O in estuarine tidal marshes; however, few studies have been conducted on its effects on N 2 O emissions. Salinity gradients are a common occurrence in estuarine tidal marshes. Studies on production and emission of N 2 O in tidal marshes with different salinities may elucidate the impact of saltwater intrusion on the emission of greenhouse gases. This study explores the seasonal variations of N 2 O fluxes and soil denitrification rates in freshwater (Daoqingzhou wetland) and brackish (Shanyutan wetland) tidal marshes dominated by Cyperus malaccensis var. brevifolius (shichito matgrass) in the Min River estuary, southeastern China. N 2 O fluxes in both marshes showed strong temporal variability. The highest N 2 O fluxes were observed in the hot and wet summer months, whereas the lowest fluxes were observed in the cold winter and autumn months. N 2 O fluxes from the freshwater marsh (48.81±9.01μgm -2 h -1 ) were significantly higher (ptidal wetlands and exert a negative feedback on the climate system. Copyright © 2017 Elsevier B.V. All rights reserved.

Relating hyporheic fluxes, residence times, and redox-sensitive biogeochemical processes upstream of beaver dams

Science.gov (United States)

Briggs, Martin A.; Lautz, Laura; Hare, Danielle K.

2013-01-01

Abstract. Small dams enhance the development of patchy microenvironments along stream corridors by trapping sediment and creating complex streambed morphologies. This patchiness drives intricate hyporheic flux patterns that govern the exchange of O2 and redox-sensitive solutes between the water column and the stream bed. We used multiple tracer techniques, naturally occurring and injected, to evaluate hyporheic flow dynamics and associated biogeochemical cycling and microbial reactivity around 2 beaver dams in Wyoming (USA). High-resolution fiber-optic distributed temperature sensing was used to collect temperature data over 9 vertical streambed profiles and to generate comprehensive vertical flux maps using 1-dimensional (1-D) heat-transport modeling. Coincident with these locations, vertical profiles of hyporheic water were collected every week and analyzed for dissolved O2, pH, dissolved organic C, and several conservative and redox-sensitive solutes. In addition, hyporheic and net stream aerobic microbial reactivity were analyzed with a constant-rate injection of the biologically sensitive resazurin (Raz) smart tracer. The combined results revealed a heterogeneous system with rates of downwelling hyporheic flow organized by morphologic unit and tightly coupled to the redox conditions of the subsurface. Principal component analysis was used to summarize the variability of all redox-sensitive species, and results indicated that hyporheic water varied from oxic-stream-like to anoxic-reduced in direct response to the hydrodynamic conditions and associated residence times. The anaerobic transition threshold predicted by the mean O2 Damko

Notes on neutron flux measurement

International Nuclear Information System (INIS)

Alcala Ruiz, F.

1984-01-01

The main purpose of this work is to get an useful guide to carry out topical neutron flux measurements. Although the foil activation technique is used in the majority of the cases, other techniques, such as those based on fission chambers and self-powered neutron detectors, are also shown. Special interest is given to the description and application of corrections on the measurement of relative and absolute induced activities by several types of detectors (scintillators, G-M and gas proportional counters). The thermal arid epithermal neutron fluxes, as determined in this work, are conventional or effective (West cots fluxes), which are extensively used by the reactor experimentalists; however, we also give some expressions where they are related to the integrated neutron fluxes, which are used in neutron calculations. (Author) 16 refs

Flux-Enabled Exploration of the Role of Sip1 in Galactose Yeast Metabolism

Directory of Open Access Journals (Sweden)

Christopher M. Shymansky

2017-05-01

Full Text Available 13C metabolic flux analysis (13C MFA is an important systems biology technique that has been used to investigate microbial metabolism for decades. The heterotrimer Snf1 kinase complex plays a key role in the preference Saccharomyces cerevisiae exhibits for glucose over galactose, a phenomenon known as glucose repression or carbon catabolite repression. The SIP1 gene, encoding a part of this complex, has received little attention, presumably, because its knockout lacks a growth phenotype. We present a fluxomic investigation of the relative effects of the presence of galactose in classically glucose-repressing media and/or knockout of SIP1 using a multi-scale variant of 13C MFA known as 2-Scale 13C metabolic flux analysis (2S-13C MFA. In this study, all strains have the galactose metabolism deactivated (gal1Δ background so as to be able to separate the metabolic effects purely related to glucose repression from those arising from galactose metabolism. The resulting flux profiles reveal that the presence of galactose in classically glucose-repressing conditions, for a CEN.PK113-7D gal1Δ background, results in a substantial decrease in pentose phosphate pathway (PPP flux and increased flow from cytosolic pyruvate and malate through the mitochondria toward cytosolic branched-chain amino acid biosynthesis. These fluxomic redistributions are accompanied by a higher maximum specific growth rate, both seemingly in violation of glucose repression. Deletion of SIP1 in the CEN.PK113-7D gal1Δ cells grown in mixed glucose/galactose medium results in a further increase. Knockout of this gene in cells grown in glucose-only medium results in no change in growth rate and a corresponding decrease in glucose and ethanol exchange fluxes and flux through pathways involved in aspartate/threonine biosynthesis. Glucose repression appears to be violated at a 1/10 ratio of galactose-to-glucose. Based on the scientific literature, we may have conducted our experiments

Flux cutting in superconductors

International Nuclear Information System (INIS)

Campbell, A M

2011-01-01

This paper describes experiments and theories of flux cutting in superconductors. The use of the flux line picture in free space is discussed. In superconductors cutting can either be by means of flux at an angle to other layers of flux, as in longitudinal current experiments, or due to shearing of the vortex lattice as in grain boundaries in YBCO. Experiments on longitudinal currents can be interpreted in terms of flux rings penetrating axial lines. More physical models of flux cutting are discussed but all predict much larger flux cutting forces than are observed. Also, cutting is occurring at angles between vortices of about one millidegree which is hard to explain. The double critical state model and its developments are discussed in relation to experiments on crossed and rotating fields. A new experiment suggested by Clem gives more direct information. It shows that an elliptical yield surface of the critical state works well, but none of the theoretical proposals for determining the direction of E are universally applicable. It appears that, as soon as any flux flow takes place, cutting also occurs. The conclusion is that new theories are required. (perspective)

Metabolic-flux dependent regulation of microbial physiology.

Science.gov (United States)

Litsios, Athanasios; Ortega, Álvaro D; Wit, Ernst C; Heinemann, Matthias

2018-04-01

According to the most prevalent notion, changes in cellular physiology primarily occur in response to altered environmental conditions. Yet, recent studies have shown that changes in metabolic fluxes can also trigger phenotypic changes even when environmental conditions are unchanged. This suggests that cells have mechanisms in place to assess the magnitude of metabolic fluxes, that is, the rate of metabolic reactions, and use this information to regulate their physiology. In this review, we describe recent evidence for metabolic flux-sensing and flux-dependent regulation. Furthermore, we discuss how such sensing and regulation can be mechanistically achieved and present a set of new candidates for flux-signaling metabolites. Similar to metabolic-flux sensing, we argue that cells can also sense protein translation flux. Finally, we elaborate on the advantages that flux-based regulation can confer to cells. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

FluxPyt: a Python-based free and open-source software for 13C-metabolic flux analyses.

Science.gov (United States)

Desai, Trunil S; Srivastava, Shireesh

2018-01-01

13 C-Metabolic flux analysis (MFA) is a powerful approach to estimate intracellular reaction rates which could be used in strain analysis and design. Processing and analysis of labeling data for calculation of fluxes and associated statistics is an essential part of MFA. However, various software currently available for data analysis employ proprietary platforms and thus limit accessibility. We developed FluxPyt, a Python-based truly open-source software package for conducting stationary 13 C-MFA data analysis. The software is based on the efficient elementary metabolite unit framework. The standard deviations in the calculated fluxes are estimated using the Monte-Carlo analysis. FluxPyt also automatically creates flux maps based on a template for visualization of the MFA results. The flux distributions calculated by FluxPyt for two separate models: a small tricarboxylic acid cycle model and a larger Corynebacterium glutamicum model, were found to be in good agreement with those calculated by a previously published software. FluxPyt was tested in Microsoft™ Windows 7 and 10, as well as in Linux Mint 18.2. The availability of a free and open 13 C-MFA software that works in various operating systems will enable more researchers to perform 13 C-MFA and to further modify and develop the package.

An analysis of pavement heat flux to optimize the water efficiency of a pavement-watering method

International Nuclear Information System (INIS)

Hendel, Martin; Colombert, Morgane; Diab, Youssef; Royon, Laurent

2015-01-01

Pavement-watering as a technique of cooling dense urban areas and reducing the urban heat island effect has been studied since the 1990's. The method is currently considered as a potential tool for and climate change adaptation against increasing heat wave intensity and frequency. However, although water consumption necessary to implement this technique is an important aspect for decision makers, optimization of possible watering methods has only rarely been conducted. An analysis of pavement heat flux at a depth of 5 cm and solar irradiance measurements is proposed to attempt to optimize the watering period, cycle frequency and water consumption rate of a pavement-watering method applied in Paris over the summer of 2013. While fine-tuning of the frequency can be conducted on the basis of pavement heat flux observations, the watering rate requires a heat transfer analysis based on a relation established between pavement heat flux and solar irradiance during pavement insolation. From this, it was found that watering conducted during pavement insolation could be optimized to 30-min cycles and water consumption could be reduced by more than 80% while reducing the cooling effect by less than 13%. - Highlights: • The thermal effects of pavement-watering were investigated in Paris, France. • Pavement-watering was found to significantly affect pavement heat flux 5 cm deep. • When insolated, a linear relation was found between heat flux and solar radiation. • Pavement-watering did not alter its slope, but introduced a negative intercept. • Subsequent improvements of the watering period, frequency and rate are proposed

DEVELOPMENT OF FLUORINE-FREE MOULD FLUX APPLIED IN LOW CARBON STEEL

Directory of Open Access Journals (Sweden)

Jayme Alves de Souza Junior

2012-12-01

Full Text Available ract The mould flux is a mixture of non-metallic oxides that, in contact with liquid steel melts, becomes a liquid slag which the mainly function is to lubricate and control heat transfer between mould and strand during the continuous casting process. The mould flux without fluoride has the advantage of decreasing the wear of machine and the SEN in comparison to common mould flux. The application in Continuous Casting of Slabs has been a great challenge in relation to the operational viability together with internal and surface quality of slabs. Another differential is the decrease of environmental issues on account of the contamination of secondary cooling water by the fluorides. It is considered that properties of mould flux as chemical composition, viscosity, softening, melting flowing temperatures, fusion rate, etc, should be suitable to the chemical composition and the mechanical properties at elevated temperatures of steel and also the operational parameters such as casting temperature, casting speed, mould frequency, among others. This work presents a preliminary analysis in relation to operational viability, analysis of surface quality of slabs, measurements of fluorides content in the water of secondary cooling of machine. In addition to that, the analyses of operational features as measurements of wear of SEN, mould flux consumption, slag pool and behavior of thermocouples of detection system break outs (MSD are considered.

Flux flow and flux dynamics in high-Tc superconductors

International Nuclear Information System (INIS)

Bennett, L.H.; Turchinskaya, M.; Swartzendruber, L.J.; Roitburd, A.; Lundy, D.; Ritter, J.; Kaiser, D.L.

1991-01-01

Because high temperature superconductors, including BYCO and BSSCO, are type 2 superconductors with relatively low H(sub c 1) values and high H(sub c 2) values, they will be in a critical state for many of their applications. In the critical state, with the applied field between H(sub c 1) and H(sub c 2), flux lines have penetrated the material and can form a flux lattice and can be pinned by structural defects, chemical inhomogeneities, and impurities. A detailed knowledge of how flux penetrates the material and its behavior under the influence of applied fields and current flow, and the effect of material processing on these properties, is required in order to apply, and to improve the properties of these superconductors. When the applied field is changed rapidly, the time dependence of flux change can be divided into three regions, an initial region which occurs very rapidly, a second region in which the magnetization has a 1n(t) behavior, and a saturation region at very long times. A critical field is defined for depinning, H(sub c,p) as that field at which the hysteresis loop changes from irreversible to reversible. As a function of temperature, it is found that H(sub c,p) is well described by a power law with an exponent between 1.5 and 2.5. The behavior of H(sub c,p) for various materials and its relationship to flux flow and flux dynamics are discussed

Calving fluxes and basal melt rates of Antarctic ice shelves

NARCIS (Netherlands)

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

2013-01-01

Iceberg calving has been assumed to be the dominant cause of mass loss for the Antarctic ice sheet, with previous estimates of the calving flux exceeding 2,000 gigatonnes per year1, 2. More recently, the importance of melting by the ocean has been demonstrated close to the grounding line and near

Effect of tunnel cross section on gas temperatures and heat fluxes in case of large heat release rate

International Nuclear Information System (INIS)

Fan, Chuan Gang; Li, Ying Zhen; Ingason, Haukur; Lönnermark, Anders

2016-01-01

Highlights: • The effect of tunnel cross section together with ventilation velocity was studied. • Ceiling temperature varies clearly with tunnel height, but little with tunnel width. • Downstream temperature decreases with increasing tunnel dimensions. • HRR is an important factor that influences decay rate of excess gas temperature. • An equation considering both tunnel dimensions and HRR was developed. - Abstract: Tests with liquid and solid fuels in model tunnels (1:20) were performed and analysed in order to study the effect of tunnel cross section (width and height) together with ventilation velocity on ceiling gas temperatures and heat fluxes. The model tunnel was 10 m long with varying width (0.3 m, 0.45 m and 0.6 m) and height (0.25 m and 0.4 m). Test results show that the maximum temperature under the ceiling is a weak function of heat release rate (HRR) and ventilation velocity for cases with HRR more than 100 MW at full scale. It clearly varies with the tunnel height and is a weak function of the tunnel width. With a lower tunnel height, the ceiling is closer to the base of continuous flame zone and the temperatures become higher. Overall, the gas temperature beneath the ceiling decreases with the increasing tunnel dimensions, and increases with the increasing longitudinal ventilation velocity. The HRR is also an important factor that influences the decay rate of excess gas temperature, and a dimensionless HRR integrating HRR and other two key parameters, tunnel cross-sectional area and distance between fuel centre and tunnel ceiling, was introduced to account for the effect. An equation for the decay rate of excess gas temperature, considering both the tunnel dimensions and HRR, was developed. Moreover, a larger tunnel cross-sectional area will lead to a smaller heat flux.

Comparison of nonflare solar soft x ray flux with 10.7-cm radio flux

International Nuclear Information System (INIS)

Donnelly, R.F.

1982-01-01

The similarities and differences of the nonflare solar 1- to 8-A X ray flux and the daily 10.7-cm Ottawa solar radio flux are examined. The radio flux is shown to be much less sensitive than the soft X ray flux on the average to the coronal emission of active regions located near or beyond the solar chromospheric limb relative to regions near the center of the solar disk. This is caused by the solar soft X ray emission's being optically thin while much of the 10.7-cm active region emission is from optical depths of tauapprox.1. The radio flux includes a large quiet sun flux which is emitted mostly from the tenuous chromosphere-corona transition region (Tapprox.10 4 --10 6 0 K) and partly from the cooler portions of the quiet corona Tapprox.1.5 x 10 6 0 K. Conversely, the solar soft X ray flux has a very small quiet sun component

Comparison of the 1D flux theory with a 2D hydrodynamic secondary settling tank model.

Science.gov (United States)

Ekama, G A; Marais, P

2004-01-01

The applicability of the 1D idealized flux theory (1DFT) for design of secondary settling tanks (SSTs) is evaluated by comparing its predicted maximum surface overflow (SOR) and solids loading (SLR) rates with that calculated from the 2D hydrodynamic model SettlerCAD using as a basis 35 full scale SST stress tests conducted on different SSTs with diameters from 30 to 45m and 2.25 to 4.1 m side water depth, with and without Stamford baffles. From the simulations, a relatively consistent pattern appeared, i.e. that the 1DFT can be used for design but its predicted maximum SLR needs to be reduced by an appropriate flux rating, the magnitude of which depends mainly on SST depth and hydraulic loading rate (HLR). Simulations of the sloping bottom shallow (1.5-2.5 m SWD) Dutch SSTs tested by STOWa and the Watts et al. SST, all with doubled SWDs, and the Darvill new (4.1 m) and old (2.5 m) SSTs with interchanged depths, were run to confirm the sensitivity of the flux rating to depth and HLR. Simulations with and without a Stamford baffle were also done. While the design of the internal features of the SST, such as baffling, have a marked influence on the effluent SS concentration for underloaded SSTs, these features appeared to have only a small influence on the flux rating, i.e. capacity, of the SST, In the meantime until more information is obtained, it would appear that from the simulations so far that the flux rating of 0.80 of the 1DFT maximum SLR recommended by Ekama and Marais remains a reasonable value to apply in the design of full scale SSTs--for deep SSTs (4 m SWD) the flux rating could be increased to 0.85 and for shallow SSTs (2.5 m SWD) decreased to 0.75. It is recommended that (i) while the apparent interrelationship between SST flux rating and depth suggests some optimization of the volume of the SST, that this be avoided and that (ii) the depth of the SST be designed independently of the surface area as is usually the practice and once selected, the

Validation of absolute axial neutron flux distribution calculations with MCNP with 197Au(n,γ)198Au reaction rate distribution measurements at the JSI TRIGA Mark II reactor.

Science.gov (United States)

Radulović, Vladimir; Štancar, Žiga; Snoj, Luka; Trkov, Andrej

2014-02-01

The calculation of axial neutron flux distributions with the MCNP code at the JSI TRIGA Mark II reactor has been validated with experimental measurements of the (197)Au(n,γ)(198)Au reaction rate. The calculated absolute reaction rate values, scaled according to the reactor power and corrected for the flux redistribution effect, are in good agreement with the experimental results. The effect of different cross-section libraries on the calculations has been investigated and shown to be minor. Copyright © 2013 Elsevier Ltd. All rights reserved.

The Russian Landing Rate, Central Bank’s Policy Related Rate and Intermediation Premium

Directory of Open Access Journals (Sweden)

Chu V. Nguyen

2017-04-01

Full Text Available This paper illustrates asymmetries in the Russian intermediation premium as measured by the spread between the commercial lending rate and the Central Bank’s policy related rate. Empirical results have shown that the Russian intermediation premium adjusts to the threshold faster when the Central Bank’s policy related rates increase relative to lending rates as opposed to when the Central Bank’s policy related rates move in the opposite direction. The findings of this paper suggest that during the period when the Russian Federation faced formidable challenges from a sharp decline in oil prices and reduced access to international capital markets due to Western sanctions, the Central Bank of Russia was not effective in utilizing countercyclical monetary policy to achieve macroeconomic objectives and commercial banks exhibited predatory pricing behavior.

Non-geometric fluxes and mixed-symmetry potentials

NARCIS (Netherlands)

Bergshoeff, E.A.; Penas, V.A.; Riccioni, F.; Risoli, S.

2015-01-01

We discuss the relation between generalised fluxes and mixed-symmetry potentials. We refer to the fluxes that cannot be described even locally in the framework of supergravity as ‘non-geometric’. We first consider the NS fluxes, and point out that the non-geometric R flux is dual to a mixed-symmetry

Flight muscle enzymes and metabolic flux rates during hovering flight of the nectar bat, Glossophaga soricina: further evidence of convergence with hummingbirds.

Science.gov (United States)

Suarez, R K; Welch, K C; Hanna, S K; Herrera M, L G

2009-06-01

Given their high metabolic rates, nectarivorous diet, and ability to directly fuel their energetically-expensive flight using recently-ingested sugar, we tested the hypothesis that Pallas long tongued nectar bats (Glossophaga soricina) possess flight muscles similar to those of hummingbirds with respect to enzymatic flux capacities in bioenergetic pathways. In addition, we compared these biochemical capacities with flux rates achieved in vivo during hovering flight. Rates of oxygen consumption (V(O(2))) were measured during hover-feeding and used to estimate rates of ATP turnover, glucose and long-chain fatty acid oxidation per unit mass of flight muscle. Enzyme V(max) values at key steps in glucose and fatty acid oxidation obtained in vitro from pectoralis muscle samples exceed those found in the locomotory muscles of other species of small mammals and resemble data obtained from hummingbird flight muscles. The ability of nectar bats and hummingbirds to hover in fed and fasted states, fueled almost exclusively by carbohydrate or fat, respectively, allowed the estimation of fractional velocities (v/V(max)) at both the hexokinase and carnitine palmitoyltransferase-2 steps in glucose and fatty acid oxidation, respectively. The results further support the hypothesis of convergent evolution in biochemical and physiological traits in nectar bats and hummingbirds.

Lymph flux rates from various lymph sacs in the cane toad Rhinella marina: an experimental evaluation of the roles of compliance, skeletal muscles and the lungs in the movement of lymph.

Science.gov (United States)

Hillman, Stanley S; Hedrick, Michael S; Drewes, Robert C; Withers, Philip C

2010-09-15

A new method for quantitatively determining lymph flux from various lymphatic sacs of an anuran, the cane toad, was developed. This method used the dye dilution principle of C(i)V(i)=C(f)V(f) following injection of Evans Blue into specific lymph sacs and measuring its appearance in the venous circulation. The apparent lymph volume was 57 ml kg(-1). The greatest rate of lymph return (0.5-0.8 ml kg(-1) min(-1)) and best linear fit of Evans Blue appearance in the circulation with time followed injections into the subvertebral lymph sac, which has direct connections to both the anterior and posterior pairs of lymphatic hearts. Rate of lymph flux from the pair of posterior lymph hearts was three times greater than the anterior pair. Rates of lymph flux were only influenced by injection volume in the crural lymph sacs, implicating lymph sac compliance as the source of the pressure for lymph movement from these sacs. Femoral lymph sac fluxes were decreased by 60% following ablation of the tendons of the sphincter ani cloacalis, abdominal crenators and piriformis. This supports a role for these muscles in generating the pressure for vertical lymph movement. Femoral lymph sac fluxes were also decreased by 70% by the insertion of a coil in the subvertebral lymph sac, preventing normal compression and expansion of this sac by the lungs. This supports a role for lung ventilation in generating the pressure for vertical movement of lymph. Contrary to previous hypotheses, fluxes from the brachial sac were not influenced by insertion of the coil into the subvertebral sac. A haemorrhage equivalent to 50% of the blood volume did not change lymph flux rates from the femoral lymph sacs. These data provide the first experimental evidence that actual lymph fluxes in the cane toad Rhinella marina depend on lymph sac compliance, contraction of specific skeletal muscles and lung ventilation to move lymph laterally and vertically to the dorsally located lymphatic hearts.

Flux Recovery of a Forward Osmosis Membrane After a Fouling Process

Science.gov (United States)

Romero-Mangado, Jaione; Parodi, Jurek; Gamboa-Vazquez, Sonia; Stefanson, Ofir; Diaz-Cartagena, Diana C.; Flynn, Michael

2016-01-01

Wastewater treatment through forward osmosis (FO) membranes is a process that has been evaluated in the past years as an innovative technology for the Next Generation Life Support Systems. FO technologies are cost effective, and require very low energy consumption, but are subject to membrane fouling. Membrane fouling occurs when unwanted materials accumulate on the active side of the membrane during the wastewater treatment process, which leads to a decrease in membrane flux rate. The aim of this study is to identify the materials that cause flux rate reduction due to membrane fouling, as well as to evaluate the flux rate recovery after membrane treatment using commercially available antifoulants. Fourier Transform Infrared (FTIR) spectrometry results identified possible compounds that cause membrane fouling and FO testing results demonstrated flux rate recovery after membrane treatment using antifoulants.

Abundant carbon substrates drive extremely high sulfate reduction rates and methane fluxes in Prairie Pothole Wetlands.

Science.gov (United States)

Dalcin Martins, Paula; Hoyt, David W; Bansal, Sheel; Mills, Christopher T; Tfaily, Malak; Tangen, Brian A; Finocchiaro, Raymond G; Johnston, Michael D; McAdams, Brandon C; Solensky, Matthew J; Smith, Garrett J; Chin, Yu-Ping; Wilkins, Michael J

2017-08-01

Inland waters are increasingly recognized as critical sites of methane emissions to the atmosphere, but the biogeochemical reactions driving such fluxes are less well understood. The Prairie Pothole Region (PPR) of North America is one of the largest wetland complexes in the world, containing millions of small, shallow wetlands. The sediment pore waters of PPR wetlands contain some of the highest concentrations of dissolved organic carbon (DOC) and sulfur species ever recorded in terrestrial aquatic environments. Using a suite of geochemical and microbiological analyses, we measured the impact of sedimentary carbon and sulfur transformations in these wetlands on methane fluxes to the atmosphere. This research represents the first study of coupled geochemistry and microbiology within the PPR and demonstrates how the conversion of abundant labile DOC pools into methane results in some of the highest fluxes of this greenhouse gas to the atmosphere ever reported. Abundant DOC and sulfate additionally supported some of the highest sulfate reduction rates ever measured in terrestrial aquatic environments, which we infer to account for a large fraction of carbon mineralization in this system. Methane accumulations in zones of active sulfate reduction may be due to either the transport of free methane gas from deeper locations or the co-occurrence of methanogenesis and sulfate reduction. If both respiratory processes are concurrent, any competitive inhibition of methanogenesis by sulfate-reducing bacteria may be lessened by the presence of large labile DOC pools that yield noncompetitive substrates such as methanol. Our results reveal some of the underlying mechanisms that make PPR wetlands biogeochemical hotspots, which ultimately leads to their critical, but poorly recognized role in regional greenhouse gas emissions. © 2017 John Wiley & Sons Ltd.

Abundant carbon substrates drive extremely high sulfate reduction rates and methane fluxes in Prairie Pothole Wetlands

Energy Technology Data Exchange (ETDEWEB)

Dalcin Martins, Paula [Microbiology Department, The Ohio State University, Columbus OH 43210 USA; Hoyt, David W. [Environmental Molecular Sciences Laboratory, Richland WA 99350 USA; Bansal, Sheel [United States Geological Survey - Northern Prairie Wildlife Research Center, Jamestown ND 58401 USA; Mills, Christopher T. [United States Geological Survey, Crustal Geophysics and Geochemistry Science Center, Building 20, Denver Federal Center Denver CO 80225 USA; Tfaily, Malak [Environmental Molecular Sciences Laboratory, Richland WA 99350 USA; Tangen, Brian A. [United States Geological Survey - Northern Prairie Wildlife Research Center, Jamestown ND 58401 USA; Finocchiaro, Raymond G. [United States Geological Survey - Northern Prairie Wildlife Research Center, Jamestown ND 58401 USA; Johnston, Michael D. [School of Earth Sciences, The Ohio State University, Columbus OH 43210 USA; McAdams, Brandon C. [School of Earth Sciences, The Ohio State University, Columbus OH 43210 USA; Solensky, Matthew J. [United States Geological Survey - Northern Prairie Wildlife Research Center, Jamestown ND 58401 USA; Smith, Garrett J. [Microbiology Department, The Ohio State University, Columbus OH 43210 USA; Chin, Yu-Ping [School of Earth Sciences, The Ohio State University, Columbus OH 43210 USA; Wilkins, Michael J. [Microbiology Department, The Ohio State University, Columbus OH 43210 USA; School of Earth Sciences, The Ohio State University, Columbus OH 43210 USA

2017-02-23

Inland waters are increasingly recognized as critical sites of methane emissions to the atmosphere, but the biogeochemical reactions driving such fluxes are less well understood. The Prairie Pothole Region (PPR) of North America is one of the largest wetland complexes in the world, containing millions of small, shallow wetlands. The sediment pore waters of PPR wetlands contain some of the highest concentrations of dissolved organic carbon (DOC) and sulfur species ever recorded in terrestrial aquatic environments. Using a suite of geochemical and microbiological analyses we measured the impact of sedimentary carbon and sulfur transformations in these wetlands on methane fluxes to the atmosphere. This research represents the first study of coupled geochemistry and microbiology within the PPR, and demonstrates how the conversion of abundant labile DOC pools into methane results in some of the highest fluxes of this greenhouse gas to the atmosphere ever reported. Abundant DOC and sulfate additionally supported some of the highest sulfate reduction rates ever measured in terrestrial aquatic environments, which we infer to account for a large fraction of carbon mineralization in this system. Methane accumulations in zones of active sulfate reduction may be due to either the transport of free methane gas from deeper locations, or the co-occurrence of methanogenesis and sulfate reduction. If both respiratory processes are concurrent, any competitive inhibition of methanogenesis by sulfate-reducing bacteria may be lessened by the presence of large labile DOC pools that yield non-competitive substrates such as methanol. Our results reveal some of the underlying mechanisms that make PPR wetlands biogeochemical hotspots, which ultimately leads to their critical, but poorly recognized role in regional greenhouse gas emissions.

Emergence of Twisted Magnetic Flux Related Sigmoidal Brightening ...

Indian Academy of Sciences (India)

tribpo

We have examined the morphological properties of a sigmoid associated with an SXR. (soft X ray) flare. The sigmoid is cospatial with the EUV (extreme ultra violet) images and in the optical part lies along an S shaped Hα filament. The photoheliogram shows flux emergence within an existing δ type sunspot which has.

Integrated passive flux measurement in groundwater: design and performance of iFLUX samplers

Science.gov (United States)

Verreydt, Goedele; Razaei, Meisam; Meire, Patrick; Van Keer, Ilse; Bronders, Jan; Seuntjens, Piet

2017-04-01

The monitoring and management of soil and groundwater is a challenge. Current methods for the determination of movement or flux of pollution in groundwater use no direct measurements but only simulations based on concentration measurements and Darcy velocity estimations. This entails large uncertainties which cause remediation failures and higher costs for contaminated site owners. On top of that, the lack of useful data makes it difficult to get approval for a risk-based management approach which completely avoids costly remedial actions. The iFLUX technology is a key development of Dr. Goedele Verreydt at the University of Antwerp and VITO. It is supported by the passive flux measurement technology as invented by Prof. Mike Annable and his team at the University of Florida. The iFLUX technology includes an in situ measurement device for capturing dynamic groundwater quality and quantity, the iFLUX sampler, and an associated interpretation and visualization method. The iFLUX sampler is a modular passive sampler that provides simultaneous in situ point determinations of a time-averaged target compound mass flux and water flux. The sampler is typically installed in a monitoring well where it intercepts the groundwater flow and captures the compounds of interest. The sampler consists of permeable cartridges which are each packed with a specific sorbent matrix. The sorbent matrix of the water flux cartridge is impregnated with known amounts of water soluble resident tracers. These tracers are leached from the matrix at rates proportional to the groundwater flux. The measurements of the contaminants and the remaining resident tracer are used to determine groundwater and target compound fluxes. Exposure times range from 1 week to 6 months, depending on the expected concentration and groundwater flow velocity. The iFLUX sampler technology has been validated and tested at several field projects. Currently, 4 cartridges are tested and available: 1 waterflux cartridge to

THE HAWAII SCUBA-2 LENSING CLUSTER SURVEY: NUMBER COUNTS AND SUBMILLIMETER FLUX RATIOS

Energy Technology Data Exchange (ETDEWEB)

Hsu, Li-Yen; Cowie, Lennox L.; Barger, Amy J. [Institute of Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Chen, Chian-Chou [Center for Extragalactic Astronomy, Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom); Wang, Wei-Hao [Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan (China)

2016-09-20

We present deep number counts at 450 and 850 μ m using the SCUBA-2 camera on the James Clerk Maxwell Telescope. We combine data for six lensing cluster fields and three blank fields to measure the counts over a wide flux range at each wavelength. Thanks to the lensing magnification, our measurements extend to fluxes fainter than 1 mJy and 0.2 mJy at 450 μ m and 850 μ m, respectively. Our combined data highly constrain the faint end of the number counts. Integrating our counts shows that the majority of the extragalactic background light (EBL) at each wavelength is contributed by faint sources with L {sub IR} < 10{sup 12} L {sub ⊙}, corresponding to luminous infrared galaxies (LIRGs) or normal galaxies. By comparing our result with the 500 μ m stacking of K -selected sources from the literature, we conclude that the K -selected LIRGs and normal galaxies still cannot fully account for the EBL that originates from sources with L {sub IR} < 10{sup 12} L {sub ⊙}. This suggests that many faint submillimeter galaxies may not be included in the UV star formation history. We also explore the submillimeter flux ratio between the two bands for our 450 μ m and 850 μ m selected sources. At 850 μ m, we find a clear relation between the flux ratio and the observed flux. This relation can be explained by a redshift evolution, where galaxies at higher redshifts have higher luminosities and star formation rates. In contrast, at 450 μ m, we do not see a clear relation between the flux ratio and the observed flux.

An alternative method for the measurement of neutron flux

Indian Academy of Sciences (India)

A simple and easy method for measuring the neutron flux is presented. This paper deals with the experimental verification of neutron dose rate–flux relationship for a non-dissipative medium. Though the neutron flux cannot be obtained from the dose rate in a dissipative medium, experimental result shows that for ...

From COS ecosystem fluxes to GPP: integrating soil, branch and ecosystem fluxes.

Science.gov (United States)

Kooijmans, L.; Maseyk, K. S.; Vesala, T.; Mammarella, I.; Baker, I. T.; Seibt, U.; Sun, W.; Aalto, J.; Franchin, A.; Kolari, P.; Keskinen, H.; Levula, J.; Chen, H.

2016-12-01

The close coupling of Carbonyl Sulfide (COS) and CO2 due to a similar uptake pathway into plant stomata makes COS a promising new tracer that can potentially be used to partition the Net Ecosystem Exchange into gross primary production (GPP) and respiration. Although ecosystem-scale measurements have been made at several sites, the contribution of different ecosystem components to the total COS budget is often unknown. Besides that, the average Leaf Relative Uptake (LRU) ratio needs to be better determined to accurately translate COS ecosystem fluxes into GPP estimates when the simple linear correlation between GPP estimates and COS plant uptake is used. We performed two campaigns in the summer of 2015 and 2016 at the SMEAR II site in Hyytiälä, Finland to provide better constrained COS flux data for boreal forests. A combination of COS measurements were made during both years, i.e. atmospheric profile concentrations up to 125 m, eddy-covariance fluxes and soil chamber fluxes. In addition to these, branch chamber measurements were done in 2016 in an attempt to observe the LRU throughout the whole season. The LRU ratio shows an exponential correlation with photosynthetic active radiation (PAR) but is constant for PAR levels above 500 µmol m-2 s-1. Mid-day LRU values are 1.0 (aspen) and 1.5 (pine). The correlation between LRU and PAR can be explained by the fact that COS is hydrolyzed with the presence of the enzyme carbonic anhydrase, and is not light dependent, whereas the photosynthetic uptake of CO2 is. We observed nighttime fluxes on the order of 25-30 % of the daily maximum COS uptake. Soils are a small sink of COS and contribute to 3 % of the total ecosystem COS flux during daytime. In a comparison between observed and simulated fluxes from the Simple Biosphere (SiB) model, the modelled COS and CO2 ecosystem fluxes are on average 40 % smaller than the observed fluxes, however, the Ecosystem Relative Uptake (ERU) ratios are identical at a value of 1.9 ± 0

High-heat-flux testing of helium-cooled heat exchangers for fusion applications

International Nuclear Information System (INIS)

Youchison, D.L.; Izenson, M.G.; Baxi, C.B.; Rosenfeld, J.H.

1996-01-01

High-heat-flux experiments on three types of helium-cooled divertor mock-ups were performed on the 30-kW electron beam test system and its associated helium flow loop at Sandia National Laboratories. A dispersion-strengthened copper alloy (DSCu) was used in the manufacture of all the mock-ups. The first heat exchanger provides for enhanced heat transfer at relatively low flow rates and much reduced pumping requirements. The Creare sample was tested to a maximum absorbed heat flux of 5.8 MW/m 2 . The second used low pressure drops and high mass flow rates to achieve good heat removal. The GA specimen was tested to a maximum absorbed heat flux of 9 MW/m 2 while maintaining a surface temperature below 400 degree C. A second experiment resulted in a maximum absorbed heat flux of 34 MW/m 2 and surface temperatures near 533 degree C. The third specimen was a DSCu, axial flow, helium-cooled divertor mock-up filled with a porous metal wick which effectively increases the available heat transfer area. Low mass flow and high pressure drop operation at 4.0 MPa were characteristic of this divertor module. It survived a maximum absorbed heat flux of 16 MW/m 2 and reached a surface temperature of 740 degree C. Thermacore also manufactured a follow-on, dual channel porous metal-type heat exchanger, which survived a maximum absorbed heat flux of 14 MW/m 2 and reached a maximum surface temperature of 690 degree C. 11refs., 20 figs., 3 tabs

The Vietnamese lending rate, policy-related rate, and monetary policy post-1997 Asian financial crisis

Directory of Open Access Journals (Sweden)

Chu V. Nguyen

2015-12-01

Full Text Available Asymmetries in the Vietnamese lending central bank’s policy-related rate spread were documented. Empirical results revealed that the spread adjusts to the threshold faster when the central bank’s policy-related rates decrease relative to the lending rates than when the central bank’s policy-related rates move in the opposite direction. Additionally, the empirical findings indicate that Vietnamese commercial banks exhibit competitive rate setting behavior which may be attributable to graft maximization by bank’s management. The results also show bidirectional Granger causality between the Vietnamese lending rate and the central bank’s policy-related rate, indicating that the lending rate and the central bank’s policy-related rate affect each other’s movements. These results suggest that monetary authority can use its countercyclical monetary policy instruments to achieve its macroeconomics objectives. However, the estimation results of the GARCH (2, 3-in-Mean model suggest that they should intervene more frequently and by small policy measures to minimize the conditional variance of the spread to minimize the magnitude of the cycle of the lending rate.

A process-based {sup 222}radon flux map for Europe and its comparison to long-term observations

Energy Technology Data Exchange (ETDEWEB)

Karstens, U. [Max-Planck-Instistut fuer Biogeochemie, Jena (Germany); Schwingshackl, C.; Schmithuesen, D.; Levin, I. [Heidelberg Univ. (Germany). Inst. fuer Umweltphysik

2015-07-01

Detailed {sup 222}radon ({sup 222}Rn) flux maps are an essential pre-requisite for the use of radon in atmospheric transport studies. Here we present a high-resolution {sup 222}Rn flux map for Europe, based on a parameterization of {sup 222}Rn production and transport in the soil. The {sup 222}Rn exhalation rate is parameterized based on soil properties, uranium content, and modelled soil moisture from two different land-surface reanalysis data sets. Spatial variations in exhalation rates are primarily determined by the uranium content of the soil, but also influenced by soil texture and local water-table depth. Temporal variations are related to soil moisture variations as the molecular diffusion in the unsaturated soil zone depends on available air-filled pore space. The implemented diffusion parameterization was tested against campaign-based {sup 222}Rn soil profile measurements. Monthly {sup 222}Rn exhalation rates from European soils were calculated with a nominal spatial resolution of 0.083 x 0.083 and compared to long-term direct measurements of {sup 222}Rn exhalation rates in different areas of Europe. The two realizations of the {sup 222}Rn flux map, based on the different soil moisture data sets, both realistically reproduce the observed seasonality in the fluxes but yield considerable differences for absolute flux values. The mean {sup 222}Rn flux from soils in Europe is estimated to be 10 mBq m{sup -2} s{sup -1} (ERA-Interim/Land soil moisture) or 15 mBq m{sup -2} s{sup -1} (GLDAS (Global Land Data Assimilation System) Noah soil moisture) for the period 2006-2010. The corresponding seasonal variations with low fluxes in winter and high fluxes in summer range in the two realizations from ca. 7 to ca. 14 mBq m{sup -2} s{sup -1} and from ca. 11 to ca. 20 mBq m{sup -2} s{sup -1}, respectively. These systematic differences highlight the importance of realistic soil moisture data for a reliable estimation of {sup 222}Rn exhalation rates. Comparison with

Experimental Methodology for Estimation of Local Heat Fluxes and Burning Rates in Steady Laminar Boundary Layer Diffusion Flames.

Science.gov (United States)

Singh, Ajay V; Gollner, Michael J

2016-06-01

Modeling the realistic burning behavior of condensed-phase fuels has remained out of reach, in part because of an inability to resolve the complex interactions occurring at the interface between gas-phase flames and condensed-phase fuels. The current research provides a technique to explore the dynamic relationship between a combustible condensed fuel surface and gas-phase flames in laminar boundary layers. Experiments have previously been conducted in both forced and free convective environments over both solid and liquid fuels. A unique methodology, based on the Reynolds Analogy, was used to estimate local mass burning rates and flame heat fluxes for these laminar boundary layer diffusion flames utilizing local temperature gradients at the fuel surface. Local mass burning rates and convective and radiative heat feedback from the flames were measured in both the pyrolysis and plume regions by using temperature gradients mapped near the wall by a two-axis traverse system. These experiments are time-consuming and can be challenging to design as the condensed fuel surface burns steadily for only a limited period of time following ignition. The temperature profiles near the fuel surface need to be mapped during steady burning of a condensed fuel surface at a very high spatial resolution in order to capture reasonable estimates of local temperature gradients. Careful corrections for radiative heat losses from the thermocouples are also essential for accurate measurements. For these reasons, the whole experimental setup needs to be automated with a computer-controlled traverse mechanism, eliminating most errors due to positioning of a micro-thermocouple. An outline of steps to reproducibly capture near-wall temperature gradients and use them to assess local burning rates and heat fluxes is provided.

Energy and flux variations across thin auroral arcs

Directory of Open Access Journals (Sweden)

H. Dahlgren

2011-10-01

Full Text Available Two discrete auroral arc filaments, with widths of less than 1 km, have been analysed using multi-station, multi-monochromatic optical observations from small and medium field-of-view imagers and the EISCAT radar. The energy and flux of the precipitating electrons, volume emission rates and local electric fields in the ionosphere have been determined at high temporal (up to 30 Hz and spatial (down to tens of metres resolution. A new time-dependent inversion model is used to derive energy spectra from EISCAT electron density profiles. The energy and flux are also derived independently from optical emissions combined with ion-chemistry modelling, and a good agreement is found. A robust method to obtain detailed 2-D maps of the average energy and number flux of small scale aurora is presented. The arcs are stretched in the north-south direction, and the lowest energies are found on the western, leading edges of the arcs. The large ionospheric electric fields (250 mV m−1 found from tristatic radar measurements are evidence of strong currents associated with the region close to the optical arcs. The different data sets indicate that the arcs appear on the boundaries between regions with different average energy of diffuse precipitation, caused by pitch-angle scattering. The two thin arcs on these boundaries are found to be related to an increase in number flux (and thus increased energy flux without an increase in energy.

Climate Warming Can Increase Soil Carbon Fluxes Without Decreasing Soil Carbon Stocks in Boreal Forests

Science.gov (United States)

Ziegler, S. E.; Benner, R. H.; Billings, S. A.; Edwards, K. A.; Philben, M. J.; Zhu, X.; Laganiere, J.

2016-12-01

Ecosystem C fluxes respond positively to climate warming, however, the net impact of changing C fluxes on soil organic carbon (SOC) stocks over decadal scales remains unclear. Manipulative studies and global-scale observations have informed much of the existing knowledge of SOC responses to climate, providing insights on relatively short (e.g. days to years) and long (centuries to millennia) time scales, respectively. Natural climate gradient studies capture integrated ecosystem responses to climate on decadal time scales. Here we report the soil C reservoirs, fluxes into and out of those reservoirs, and the chemical composition of inputs and soil organic matter pools along a mesic boreal forest climate transect. The sites studied consist of similar forest composition, successional stage, and soil moisture but differ by 5.2°C mean annual temperature. Carbon fluxes through these boreal forest soils were greatest in the lowest latitude regions and indicate that enhanced C inputs can offset soil C losses with warming in these forests. Respiration rates increased by 55% and the flux of dissolved organic carbon from the organic to mineral soil horizons tripled across this climate gradient. The 2-fold increase in litterfall inputs to these soils coincided with a significant increase in the organic horizon C stock with warming, however, no significant difference in the surface mineral soil C stocks was observed. The younger mean age of the mineral soil C ( 70 versus 330 YBP) provided further evidence for the greater turnover of SOC in the warmer climate soils. In spite of these differences in mean radiocarbon age, mineral SOC exhibited chemical characteristics of highly decomposed material across all regions. In contrast with depth trends in soil OM diagenetic indices, diagenetic shifts with latitude were limited to increases in C:N and alkyl to O-alkyl ratios in the overlying organic horizons in the warmer relative to the colder regions. These data indicate that the

Hydrogen sulfide flux measurements from construction and demolition debris (C&D) landfills.

Science.gov (United States)

Eun, Sangho; Reinhart, Debra R; Cooper, C David; Townsend, Timothy G; Faour, Ayman

2007-01-01

Hydrogen sulfide (H2S) has been identified as a principal odorous component of gaseous emissions from construction and demolition debris (C&D) landfills. Although several studies have reported the ambient concentrations of H2S near C&D landfills, few studies have quantified emission rates of H2S. One of the most widely used techniques for measuring surface gas emission rates from landfills is the flux chamber method. Flux measurements using the flux chamber were performed at five different C&D landfills from April to August, 2003. The flux rates of H2S measured in this research were between 0.192 and 1.76 mg/(m2-d).

On flux integrals for generalized Melvin solution related to simple finite-dimensional Lie algebra

Energy Technology Data Exchange (ETDEWEB)

Ivashchuk, V.D. [VNIIMS, Center for Gravitation and Fundamental Metrology, Moscow (Russian Federation); Peoples' Friendship University of Russia (RUDN University), Institute of Gravitation and Cosmology, Moscow (Russian Federation)

2017-10-15

A generalized Melvin solution for an arbitrary simple finite-dimensional Lie algebra G is considered. The solution contains a metric, n Abelian 2-forms and n scalar fields, where n is the rank of G. It is governed by a set of n moduli functions H{sub s}(z) obeying n ordinary differential equations with certain boundary conditions imposed. It was conjectured earlier that these functions should be polynomials - the so-called fluxbrane polynomials. These polynomials depend upon integration constants q{sub s}, s = 1,.., n. In the case when the conjecture on the polynomial structure for the Lie algebra G is satisfied, it is proved that 2-form flux integrals Φ{sup s} over a proper 2d submanifold are finite and obey the relations q{sub s} Φ{sup s} = 4πn{sub s}h{sub s}, where the h{sub s} > 0 are certain constants (related to dilatonic coupling vectors) and the n{sub s} are powers of the polynomials, which are components of a twice dual Weyl vector in the basis of simple (co-)roots, s = 1,.., n. The main relations of the paper are valid for a solution corresponding to a finite-dimensional semi-simple Lie algebra G. Examples of polynomials and fluxes for the Lie algebras A{sub 1}, A{sub 2}, A{sub 3}, C{sub 2}, G{sub 2} and A{sub 1} + A{sub 1} are presented. (orig.)

Topology of magnetic flux ropes and formation of fossil flux transfer events and boundary layer plasmas

Science.gov (United States)

Lee, L. C.; Ma, Z. W.; Fu, Z. F.; Otto, A.

1993-01-01

A mechanism for the formation of fossil flux transfer events and the low-level boundary layer within the framework of multiple X-line reconnection is proposed. Attention is given to conditions for which the bulk of magnetic flux in a flux rope of finite extent has a simple magnetic topology, where the four possible connections of magnetic field lines are: IMF to MSP, MSP to IMF, IMF to IMF, and MSP to MSP. For a sufficient relative shift of the X lines, magnetic flux may enter a flux rope from the magnetosphere and exit into the magnetosphere. This process leads to the formation of magnetic flux ropes which contain a considerable amount of magnetosheath plasma on closed magnetospheric field lines. This process is discussed as a possible explanation for the formation of fossil flux transfer events in the magnetosphere and the formation of the low-latitude boundary layer.

Powder Flux Regulation in the Laser Material Deposition Process

Science.gov (United States)

Arrizubieta, Jon Iñaki; Wegener, Maximiliam; Arntz, Kristian; Lamikiz, Aitzol; Ruiz, Jose Exequiel

In the present research work a powder flux regulation system has been designed, developed and validated with the aim of improving the Laser Material Deposition (LMD) process. In this process, the amount of deposited material per substrate surface unit area depends on the real feed rate of the nozzle. Therefore, a regulation system based on a solenoid valve has been installed at the nozzle entrance in order to control the powder flux. The powder flux control has been performed based on the machine real feed rate, which is compared with the programmed feed rate. An instantaneous velocity error is calculated and the powder flow is controlled as a function of this variation using Pulse Width Modulation (PWM) signals. Thereby, in zones where the Laser Material Deposition machine reduces the feed rate due to a trajectory change, powder accumulation can be avoided and the generated clads would present a homogeneous shape.

Advances in the Surface Renewal Flux Measurement Method

Science.gov (United States)

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

2011-12-01

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

SOIL FLUXES OF CO2, CO, NO AND N2O FROM AN OLD-PASTURE AND FROM NATIVE SAVANNA IN BRAZIL

Science.gov (United States)

We compared fluxes of CO2, CO, NO and N2O, soil microbial biomass, and N-mineralization rates in a 20-year old Brachiaria pasture and a native cerrado area (savanna in Central Brazil). In order to assess the spatial variability of CO2 fluxes, we tested the relation between elect...

The influence of plasma horizontal position on the neutron rate and flux of neutral atoms in injection heating experiment on the TUMAN-3M tokamak

Science.gov (United States)

Kornev, V. A.; Chernyshev, F. V.; Melnik, A. D.; Askinazi, L. G.; Wagner, F.; Vildjunas, M. I.; Zhubr, N. A.; Krikunov, S. V.; Lebedev, S. V.; Razumenko, D. V.; Tukachinsky, A. S.

2013-11-01

Horizontal displacement of plasma along the major radius has been found to significantly influence the fluxes of 2.45 MeV DD neutrons and high-energy charge-exchange atoms from neutral beam injection (NBI) heated plasma of the TUMAN-3M tokamak. An inward shift by Δ R = 1 cm causes 1.2-fold increase in the neutron flux and 1.9-fold increase in the charge-exchange atom flux. The observed increase in the neutron flux is attributed to joint action of several factors-in particular, improved high-energy ion capture and confinement and, probably, decreased impurity inflow from the walls, which leads to an increase in the density of target ions. A considerable increase in the flux of charge-exchange neutrals in inward-shifted plasma is due to the increased number of captured high-energy ions and, to some extent, the increased density of the neutral target. As a result of the increase in the content of high-energy ions, the central ion temperature T i (0) increased from 250 to 350 eV. The dependence of the neutron rate on major radius R 0 should be taken into account when designing compact tokamak-based neutron sources.

Tracer kinetic studies of the low density lipoprotein metabolism in the fetal rat: An example for estimation of flux rates in the nonsteady state

International Nuclear Information System (INIS)

Plonne, D.; Schlag, B.; Winkler, L.; Dargel, R.

1990-01-01

To get insight into the low density lipoprotein (LDL)-apoB flux in the rat fetus near term and in the early postnatal period, homologous apoE-free 125I-labeled LDL was injected into the umbilical vein of the rat fetus immediately after Caesarean section. Since the serum LDL-apoB spontaneously declined after birth, a time-dependent two-pool model was used to calculate the flux rates in the neonate from the specific activities of LDL-apoB up to 15 h post partum. An approximate value of LDL-apoB flux in the fetus at birth was obtained by extrapolation of the kinetic data to the time of injection of the tracer. The data revealed that the turnover of LDL-apoB in the fetus (18.6 micrograms LDL-apoB/h per g body weight) exceeded that in the adult rat (0.4 microgram/h per g body weight) by at least one order of magnitude. Even 15 h after delivery, the LDL-apoB influx amounted to 2.5 micrograms/h per g body weight. The fractional catabolic rate of LDL-apoB in the fetus at term (0.39, h-1) slightly exceeded that in the adult animal (0.15, h-1) and reached the adult level within the first 3 h after birth and remained constant thereafter. In the rat fetus, LDL-apoB flux greatly exceeds that of VLDL-apoB. The data support the view of a direct synthesis and secretion of LDL, most probably by the fetal membranes

Reduced flux motion via flux creep annealing in high- Jc single-crystal Y1Ba2Cu3O7

International Nuclear Information System (INIS)

Thompson, J.R.; Sun, Y.R.; Malozemoff, A.P.; Christen, D.K.; Kerchner, H.R.; Ossandon, J.G.; Marwick, A.D.; Holtzberg, F.

1991-01-01

We investigated the stabilization of magnetic flux in a high-temperature superconductor (a proton-irradiated Y 1 Ba 2 Cu 3 O 7 crystal), by operating with subcritical current density J. Using the thermal history to obtain an induced current density J≤J c , we observed a drastically reduced relaxation rate dM/dt (M=magnetization), after ''flux creep annealing.'' The results show that the field gradient ∼J∼M determined the relaxation rate, independent of the sample's H-T history, in agreement with recent theory

Neutron flux monitoring device

International Nuclear Information System (INIS)

Goto, Yasushi; Mitsubori, Minehisa; Ohashi, Kazunori.

1997-01-01

The present invention provides a neutron flux monitoring device for preventing occurrence of erroneous reactor scram caused by the elevation of the indication of a start region monitor (SRM) due to a factor different from actual increase of neutron fluxes. Namely, judgement based on measured values obtained by a pulse counting method and a judgment based on measured values obtained by a Cambel method are combined. A logic of switching neutron flux measuring method to be used for monitoring, namely, switching to an intermediate region when both of the judgements are valid is adopted. Then, even if the indication value is elevated based on the Cambel method with no increase of the counter rate in a neutron source region, the switching to the intermediate region is not conducted. As a result, erroneous reactor scram such as 'shorter reactor period' can be avoided. (I.S.)

In situ investigation of helium fuzz growth on tungsten in relation to ion flux, fluence, surface temperature and ion energy using infrared imaging in PSI-2

International Nuclear Information System (INIS)

Möller, S; Kachko, O; Rasinski, M; Kreter, A; Linsmeier, Ch

2017-01-01

Tungsten is a candidate material for plasma-facing components in nuclear fusion reactors. In operation it will face temperatures >800 K together with an influx of helium ions. Previously, the evolution of special surface nanostructures called fuzz was found under these conditions in a limited window of surface temperature, ion flux and ion energy. Fuzz potentially leads to lower heat load tolerances, enhanced erosion and dust formation, hence should be avoided in a fusion reactor. Here the fuzz growth is reinvestigated in situ during its growth by considering its impact on the surfaces infrared emissivity at 4 μ m wavelength with an infrared camera in the linear plasma device PSI-2. A hole in the surface serves as an emissivity reference to calibrate fuzz thickness versus infrared emissivity. Among new data on the above mentioned relations, a lower fuzz growth threshold of 815 ± 24 K is found. Fuzz is seen to grow on rough and polished surfaces and even on the hole’s side walls alike. Literature scalings for thickness, flux and time relations of the fuzz growth rate could not be reproduced, but for the temperature scaling a good agreement to the Arrhenius equation was found. (paper)

RESONANT ABSORPTION OF AXISYMMETRIC MODES IN TWISTED MAGNETIC FLUX TUBES

Energy Technology Data Exchange (ETDEWEB)

Giagkiozis, I.; Verth, G. [Solar Plasma Physics Research Centre, School of Mathematics and Statistics, University of Sheffield, Hounsfield Road, Hicks Building, Sheffield, S3 7RH (United Kingdom); Goossens, M.; Doorsselaere, T. Van [Centre for mathematical Plasma Astrophysics, Mathematics Department, KU Leuven, Celestijnenlaan 200B bus 2400, B-3001 Leuven (Belgium); Fedun, V. [Department of Automatic Control and Systems Engineering, University of Sheffield, Mappin Street, Amy Johnson Building, Sheffield, S1 3JD (United Kingdom)

2016-06-01

It has been shown recently that magnetic twist and axisymmetric MHD modes are ubiquitous in the solar atmosphere, and therefore the study of resonant absorption for these modes has become a pressing issue because it can have important consequences for heating magnetic flux tubes in the solar atmosphere and the observed damping. In this investigation, for the first time, we calculate the damping rate for axisymmetric MHD waves in weakly twisted magnetic flux tubes. Our aim is to investigate the impact of resonant damping of these modes for solar atmospheric conditions. This analytical study is based on an idealized configuration of a straight magnetic flux tube with a weak magnetic twist inside as well as outside the tube. By implementing the conservation laws derived by Sakurai et al. and the analytic solutions for weakly twisted flux tubes obtained recently by Giagkiozis et al. we derive a dispersion relation for resonantly damped axisymmetric modes in the spectrum of the Alfvén continuum. We also obtain an insightful analytical expression for the damping rate in the long wavelength limit. Furthermore, it is shown that both the longitudinal magnetic field and the density, which are allowed to vary continuously in the inhomogeneous layer, have a significant impact on the damping time. Given the conditions in the solar atmosphere, resonantly damped axisymmetric modes are highly likely to be ubiquitous and play an important role in energy dissipation. We also suggest that, given the character of these waves, it is likely that they have already been observed in the guise of Alfvén waves.

Neutron flux distribution forecasting device of reactor

International Nuclear Information System (INIS)

Uematsu, Hitoshi

1991-01-01

A neutron flux distribution is forecast by using current data obtained from a reactor. That is, the device of the present invention comprises (1) a neutron flux monitor disposed in various positions in the reactor, (2) a forecasting means for calculating and forecasting a one-dimensional neutron flux distribution relative to imaginable events by using data obtained from the neutron flux monitor and physical models, and (3) a display means for displaying the results forecast in the forecasting means to a reactor operation console. Since the forecast values for the one-dimensional neutron flux distribution relative to the imaginable events are calculated in the device of the present invention by using data obtained from the neutron flux monitor and the physical models, the data as a base of the calculation are new and the period for calculating the forecast values can be shortened. Accordingly, although there is a worry of providing some errors in the forecast values, they can be utilized sufficiently as reference data. As a result, the reactor can be operated more appropriately. (I.N.)

INES rating of radiation protection related events

International Nuclear Information System (INIS)

Hort, M.

2009-01-01

In this presentation, based on the draft Manual, a short review of the use of the INES rating of events concerning radiation protection is given, based on a new INES User's Manual edition. The presentation comprises a brief history of the scale development, general description of the scale and the main principles of the INES rating. Several examples of the use of the scale for radiation protection related events are mentioned. In the presentation, the term 'radiation protection related events' is used for radiation source and transport related events outside the nuclear installations. (authors)

Inundation and Gas Fluxes from Amazon Lakes and Wetlands

Science.gov (United States)

Melack, J. M.; MacIntyre, S.; Forsberg, B. R.; Amaral, J. H.; Barbosa, P.

2015-12-01

Inundation areas and wetland habitats for the lowland Amazon basin derived remote sensing with synthetic aperture radar are combined with measurements of greenhouse gas evasion derived from field measurements and new formulations of atmosphere-water. On-going field studies in representative aquatic habitats on the central Amazon floodplain are combining monthly measurements of carbon dioxide and methane concentrations and fluxes to the atmosphere with deployment of meteorological sensors and high-resolution thermistors and optical dissolved oxygen sensors. A real-time cavity ringdown spectrometer is being used to determine the gas concentrations; vertical profiles were obtained by using an equilibrator to extract gases from water, and floating chambers are used to assess fluxes. Gas fluxes varied as a function of season, habitat and water depth. Greatest carbon dioxide fluxes occurred during high and falling water levels. During low water, periods with high chlorophyll, indicative of phytoplankton, the flux of carbon dioxide switched from being emitted from the lake to being taken-up by the lake some of the time. The highest pCO2 concentration (5500 μatm) was about three times higher than the median (1700 μatm). Higher CO2 fluxes were observed in open water than in areas with flooded or floating vegetation. In contrast, methane fluxes were higher in vegetated regions. We measured turbulence as rate of dissipation of turbulent kinetic energy based on microstructure profiling. Comparison of these measurements with those calculated from meteorological and time series measurements validated new equations for turbulent kinetic energy dissipation (TKE) rates during moderate winds and cooling and illustrated that the highest dissipation rates occurred under heating. Measured gas exchange coefficients (k600) were similar to those based on the TKE dissipation rates and are well described using the surface renewal model. These k values are several times higher than

Flux canceling in three-dimensional radiative magnetohydrodynamic simulations

Science.gov (United States)

Thaler, Irina; Spruit, H. C.

2017-05-01

We aim to study the processes involved in the disappearance of magnetic flux between regions of opposite polarity on the solar surface using realistic three-dimensional (3D) magnetohydrodynamic (MHD) simulations. "Retraction" below the surface driven by magnetic forces is found to be a very effective mechanism of flux canceling of opposite polarities. The speed at which flux disappears increases strongly with initial mean flux density. In agreement with existing inferences from observations we suggest that this is a key process of flux disappearance within active complexes. Intrinsic kG strength concentrations connect the surface to deeper layers by magnetic forces, and therefore the influence of deeper layers on the flux canceling process is studied. We do this by comparing simulations extending to different depths. For average flux densities of 50 G, and on length scales on the order of 3 Mm in the horizontal and 10 Mm in depth, deeper layers appear to have only a mild influence on the effective rate of diffusion.

Relative measurement of the fluxes of thermal, resonant and rapid neutrons in reactor G1

International Nuclear Information System (INIS)

Carle, R.; Mazancourt, T. de

1957-01-01

We sought to determine the behavior of the thermal, resonant and rapid neutron fluxes in the multiplier-reflector transition region, in the two principal directions of the system. We have also measured the variation of these different fluxes in the body of the multiplier medium in a canal filled with graphite and in an empty canal. The results are given in the form of curves representing: - the variation of the ratio of the thermal flux to the rapid flux in axial and radial transitions - the behavior of the thermal and resonant fluxes and the variation of their ratio in the same regions. (author) [fr

SCALPLO - a universal program for plotting flux output from SCALE modules and related programs. User's manual

International Nuclear Information System (INIS)

Hersman, A.; Leege, P.F.A. de; Hoogenboom, J.E.

1992-04-01

The FORTRAN-77 program SCALPLO is being developed to make an easy and quick graphic survey of flux and/or power data calculated with SCALE modules or other core calculation or shielding codes. The basic plot functions it can perform are one- and two-dimensional plots of flux or power distributions and flux energy spectra. More specifically it can produce plots of the flux distribution in a one-dimensional geometry for one or more energy groups in one figure. It can also plot the flux distribution along a cut through a two- or three-dimensional geometry along one of the coordinate axes and it can plot a two-dimensional view of the flux distribution of a two-dimensional geometry or of a plane cut through a three-dimensional geometry. The same can be done for the power distribution in a system. Furthermore SCALPLO can plot the particle flux spectrum as a function of energy, either as group fluxes or as group fluxes per unit energy or per unit lethargy. (orig./HP)

P fluxes and exotic branes

Energy Technology Data Exchange (ETDEWEB)

Lombardo, Davide M. [Dipartimento di Fisica, Università di Roma “La Sapienza”,Piazzale Aldo Moro 2, 00185 Roma (Italy); Riccioni, Fabio [INFN - Sezione di Roma, Dipartimento di Fisica, Università di Roma “La Sapienza”,Piazzale Aldo Moro 2, 00185 Roma (Italy); Risoli, Stefano [Dipartimento di Fisica, Università di Roma “La Sapienza”,Piazzale Aldo Moro 2, 00185 Roma (Italy); INFN - Sezione di Roma, Dipartimento di Fisica, Università di Roma “La Sapienza”,Piazzale Aldo Moro 2, 00185 Roma (Italy)

2016-12-21

We consider the N=1 superpotential generated in type-II orientifold models by non-geometric fluxes. In particular, we focus on the family of P fluxes, that are related by T-duality transformations to the S-dual of the Q flux. We determine the general rule that transforms a given flux in this family under a single T-duality transformation. This rule allows to derive a complete expression for the superpotential for both the IIA and the IIB theory for the particular case of a T{sup 6}/[ℤ{sub 2}×ℤ{sub 2}] orientifold. We then consider how these fluxes modify the generalised Bianchi identities. In particular, we derive a fully consistent set of quadratic constraints coming from the NS-NS Bianchi identities. On the other hand, the P flux Bianchi identities induce tadpoles, and we determine a set of exotic branes that can be consistently included in order to cancel them. This is achieved by determining a universal transformation rule under T-duality satisfied by all the branes in string theory.

P fluxes and exotic branes

International Nuclear Information System (INIS)

Lombardo, Davide M.; Riccioni, Fabio; Risoli, Stefano

2016-01-01

We consider the N=1 superpotential generated in type-II orientifold models by non-geometric fluxes. In particular, we focus on the family of P fluxes, that are related by T-duality transformations to the S-dual of the Q flux. We determine the general rule that transforms a given flux in this family under a single T-duality transformation. This rule allows to derive a complete expression for the superpotential for both the IIA and the IIB theory for the particular case of a T 6 /[ℤ 2 ×ℤ 2 ] orientifold. We then consider how these fluxes modify the generalised Bianchi identities. In particular, we derive a fully consistent set of quadratic constraints coming from the NS-NS Bianchi identities. On the other hand, the P flux Bianchi identities induce tadpoles, and we determine a set of exotic branes that can be consistently included in order to cancel them. This is achieved by determining a universal transformation rule under T-duality satisfied by all the branes in string theory.

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

Science.gov (United States)

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

2008-07-01

Among the parameters affecting carbon transfer to the ocean interior, particle sinking rates vary three orders of magnitude and thus more than primary production, f-ratios, or particle carbon contents [e.g., Boyd, P.W., Trull, T.W., 2006. Understanding the export of marine biogenic particles: is there consensus? Progress in Oceanography 4, 276-312, doi:10.1016/j.pocean.2006.10.007]. Very few data have been obtained from the mesopelagic zone where the majority of carbon remineralization occurs and the attenuation of the sinking flux is determined. Here, we report sinking rates from ˜300 m depth for the subtropical (station ALOHA, June 2004) and subarctic (station K2, July 2005) North Pacific Ocean, obtained from short (6.5 day) deployments of an indented rotating sphere (IRS) sediment trap operating as an in situ settling column [Peterson, M.L., Wakeham, S.G., Lee, C., Askea, M.A., Miquel, J.C., 2005. Novel techniques for collection of sinking particles in the ocean and determining their settling rates. Limnology and Oceanography Methods 3, 520-532] to separate the flux into 11 sinking-rate fractions ranging from >820 to >2 m d -1 that are collected by a carousel for further analysis. Functioning of the IRS trap was tested using a novel programming sequence to check that all particles have cleared the settling column prior to the next delivery of particles by the 6-hourly rotation cycle of the IRS. There was some evidence (from the flux distribution among the cups and photomicroscopy of the collected particles) that very slow-sinking particles may have been under-collected because they were unable to penetrate the brine-filled collection cups, but good evidence for appropriate collection of fast-settling fractions. Approximately 50% of the particulate organic carbon (POC) flux was sinking at greater than 100 m d -1 at both stations. At ALOHA, more than 15% of the POC flux sank at >820 m d -1, but low fluxes make this uncertain, and precluded resolution of particles

Ballast minerals and the sinking carbon flux in the ocean: carbon-specific respiration rates and sinking velocity of marine snow aggregates

Directory of Open Access Journals (Sweden)

M. H. Iversen

2010-09-01

Full Text Available Recent observations have shown that fluxes of ballast minerals (calcium carbonate, opal, and lithogenic material and organic carbon fluxes are closely correlated in the bathypelagic zones of the ocean. Hence it has been hypothesized that incorporation of biogenic minerals within marine aggregates could either protect the organic matter from decomposition and/or increase the sinking velocity via ballasting of the aggregates. Here we present the first combined data on size, sinking velocity, carbon-specific respiration rate, and composition measured directly in three aggregate types; Emiliania huxleyi aggregates (carbonate ballasted, Skeletonema costatum aggregates (opal ballasted, and aggregates made from a mix of both E. huxleyi and S. costatum (carbonate and opal ballasted. Overall average carbon-specific respiration rate was ~0.13 d⁻¹ and did not vary with aggregate type and size. Ballasting from carbonate resulted in 2- to 2.5-fold higher sinking velocities than those of aggregates ballasted by opal. We compiled literature data on carbon-specific respiration rate and sinking velocity measured in aggregates of different composition and sources. Compiled carbon-specific respiration rates (including this study vary between 0.08 d⁻¹ and 0.20 d⁻¹. Sinking velocity increases with increasing aggregate size within homogeneous sources of aggregates. When compared across different particle and aggregate sources, however, sinking velocity appeared to be independent of particle or aggregate size. The carbon-specific respiration rate per meter settled varied between 0.0002 m⁻¹ and 0.0030 m⁻¹, and decreased with increasing aggregate size. It was lower for calcite ballasted aggregates as compared to that of similar sized opal ballasted aggregates.

Fluvial organic carbon flux from an eroding peatland catchment, southern Pennines, UK

Directory of Open Access Journals (Sweden)

R. R. Pawson

2008-03-01

Full Text Available This study investigates for the first time the relative importance of dissolved organic carbon (DOC and particulate organic carbon (POC in the fluvial carbon flux from an actively eroding peatland catchment in the southern Pennines, UK. Event scale variability in DOC and POC was examined and the annual flux of fluvial organic carbon was estimated for the catchment. At the event scale, both DOC and POC were found to increase with discharge, with event based POC export accounting for 95% of flux in only 8% of the time. On an annual cycle, exports of 35.14 t organic carbon (OC are estimated from the catchment, which represents an areal value of 92.47 g C m⁻² a⁻¹. POC was the most significant form of organic carbon export, accounting for 80% of the estimated flux. This suggests that more research is required on both the fate of POC and the rates of POC export in eroding peatland catchments.

Rates and fluxes of centennial-scale carbon storage in the fine-grained sediments from the central South Yellow Sea and Min-Zhe belt, East China Sea

Science.gov (United States)

Wang, Jianghai; Xiao, Xi; Zhou, Qianzhi; Xu, Xiaoming; Zhang, Chenxi; Liu, Jinzhong; Yuan, Dongliang

2018-01-01

The global carbon cycle has played a key role in mitigating global warming and climate change. Long-term natural and anthropogenic processes influence the composition, sources, burial rates, and fluxes of carbon in sediments on the continental shelf of China. In this study, the rates, fluxes, and amounts of carbon storage at the centennial scale were estimated and demonstrated using the case study of three fine-grained sediment cores from the central South Yellow Sea area (SYSA) and Min-Zhe belt (MZB), East China Sea. Based on the high-resolution temporal sequences of total carbon (TC) and total organic carbon (TOC) contents, we reconstructed the annual variations of historical marine carbon storage, and explored the influence of terrestrial and marine sources on carbon burial at the centennial scale. The estimated TC storage over 100 years was 1.18×108 t in the SYSA and 1.45×109 t in the MZB. The corrected TOC storage fluxes at the centennial scale ranged from 17 to 28 t/(km2·a)in the SYSA and from 56 to 148 t/(km2·a) in the MZB. The decrease of terrestrial materials and the increase of marine primary production suggest that the TOC buried in the sediments in the SYSA and MZB was mainly derived from the marine autogenetic source. In the MZB, two depletion events occurred in TC and TOC storage from 1985 to 1987 and 2003 to 2006, which were coeval with the water impoundment in the Gezhouba and Three Gorges dams, respectively. The high-resolution records of the carbon storage rates and fluxes in the SYSA and MZB reflect the synchronous responses to human activities and provide an important reference for assessing the carbon sequestration capacity of the marginal seas of China.

Neutron flux measurements in C-9 capsule pressure tube

International Nuclear Information System (INIS)

Barbos, D.; Roth, C. S.; Gugiu, D.; Preda, M.

2001-01-01

C-9 capsule is a fuel testing facility in which the testing consists of a daily cycle ranging between the limits 100% power to 50% power. C-9 in-pile section with sample holder an instrumentation are introduced in G-9 and G-10 experimental channels. The experimental fuel channel has a maximum value when the in-pile section (pressure tube) is in G-9 channel and minimum value in G-10 channel. In this paper the main goals are determination or measurements of: - axial thermal neutron flux distribution in C-9 pressure tube both in G-9 and G-10 channel; - ratio of maximum neutron flux value in G-9 and the same value in G-9 channel and the same value in G-10 channel; - neutron flux-spectrum. On the basis of axial neutron flux distribution measurements, the experimental fuel element in sample holder position in set. Both axial neutron flux distribution of thermal neutrons and neutron flux-spectrum were performed using multi- foil activation technique. Activation rates were obtained by absolute measurements of the induced activity using gamma spectroscopy methods. To determine the axial thermal neutron flux distribution in G-9 and G-10, Cu 100% wire was irradiated at the reactor power of 2 MW. Ratio between the two maximum values, in G-9 and G-10 channels, is 2.55. Multi-foil activation method was used for neutron flux spectrum measurements. The neutron spectra and flux were obtained from reaction rate measurements by means of SAND 2 code. To obtain gamma-ray spectra, a HPGe detector connected to a multichannel analyzer was used. The spectrometer is absolute efficiency calibrated. The foils were irradiated at 2 MW reactor power in previously determined maximum flux position resulted from wire measurements. This reaction rates were normalized for 10 MW reactor power. Neutron self shielding corrections for the activation foils were applied. The self-shielding corrections are computed using Monte Carlo simulation methods. The measured integral flux is 1.1·10 14 n/cm 2 s

Interaction of storage carbohydrates and other cyclic fluxes with central metabolism : A quantitative approach by non-stationary 13C metabolic flux analysis

NARCIS (Netherlands)

Suarez-Mendez, C. A.; Hanemaaijer, M.; ten Pierick, Angela; Wolters, J. C.; Heijnen, J.J.; Wahl, S. A.

2016-01-01

13C labeling experiments in aerobic glucose limited cultures of Saccharomyces cerevisiae at four different growth rates (0.054; 0.101, 0.207, 0.307 h-1) are used for calculating fluxes that include intracellular cycles (e.g., storage carbohydrate cycles, exchange fluxes with amino acids), which are

Comparison of Radiation Dose Rates with the Flux to Dose Conversion Factors Recommended in ICRP-74 and ICRP-116

International Nuclear Information System (INIS)

Jeong, Hae Sun; Kil, A Reum; Lee, Jo Eun; Jeong, Hyo Joon; Kim, Eun Han; Han, Moon Hee; Hwang, Won Tae

2016-01-01

The evaluation of radiation shielding has been performed for the design and maintenance of various facilities using radioactive sources such as nuclear fuel, accelerator, and radionuclide. The conversion of flux to dose mainly used in nuclear and radiation fields has been generally made with the dose coefficients presented in ICRP Publication 74 (ICRP- 74), which are produced based on ICRP Publication 60. On the other hand, ICRP Publication 116 (ICRP-116), which adopts the protection system of ICRP Publication 103, has recently been published and provides the dose conversion coefficients calculated with a variety of Monte Carlo codes. The coefficients have more than an update of those in ICRP-74, including new particle types and a greatly expanded energy range. In this study, a shielding evaluation of a specific container for neutron and gamma sources was performed with the MCNP6 code. The dose rates from neutron and gamma-ray sources were calculated using the MCNP6 codes, and these results were based on the flux to dose conversion factors recommended in ICRP-74 and ICRP-116. As a result, the dose rates evaluated with ICRP-74 were generally shown higher than those with ICRP-116. For neutrons, the difference is mainly occurred by the decrease of radiation weighting factors in a part of energy ranges in the ICRP-116 recommendations. For gamma-rays, the ICRP-74 recommendation applied with the kerma approximation leads to overestimated results than the other assessment

Seasonal variations of 222Rn and SGD fluxes to Ubatuba embayments, Sao Paulo

International Nuclear Information System (INIS)

Oliveira, J.; Costa, P.; Braga, E.S.

2006-01-01

We describe here an application of excess 222 Rn to estimate submarine groundwater discharge in a series of small embayments of Ubatuba, Sao Paulo State, Brazil. Excess 222 Rn inventories obtained in 11 vertical profiles varied from (3.3±1.1) x 10 3 to (19±5) x 10 3 dpm x m -2 . The estimated total fluxes required to support the inventories varied from (0.6±0.2) x 10 3 to (3.4±0.9) x 10 3 dpm x m -2 x d -1 . Considering these results, the submarine groundwater discharge advective rates necessary to balance the sub-pycnocline fluxes calculated in Ubatuba embayments ranged from 0.06 to 1.9 cm x d -1 . During the period of this investigation (from March/03 to May/2004), the highest 222 Rn in excess inventories were observed late in the summer season (March). Taking into account all vertical profiles established, the relative variability was 67%. Although, if we consider only the fluxes determined in both Flamengo and Fortaleza embayments, the relative variation was 21%. (author)

Differentiating transpiration from evaporation in seasonal agricultural wetlands and the link to advective fluxes in the root zone

International Nuclear Information System (INIS)

Bachand, P.A.M.; Bachand, S.; Fleck, J.; Anderson, F.; Windham-Myers, L.

2014-01-01

The current state of science and engineering related to analyzing wetlands overlooks the importance of transpiration and risks data misinterpretation. In response, we developed hydrologic and mass budgets for agricultural wetlands using electrical conductivity (EC) as a natural conservative tracer. We developed simple differential equations that quantify evaporation and transpiration rates using flow rates and tracer concentrations at wetland inflows and outflows. We used two ideal reactor model solutions, a continuous flow stirred tank reactor (CFSTR) and a plug flow reactor (PFR), to bracket real non-ideal systems. From those models, estimated transpiration ranged from 55% (CFSTR) to 74% (PFR) of total evapotranspiration (ET) rates, consistent with published values using standard methods and direct measurements. The PFR model more appropriately represents these non-ideal agricultural wetlands in which check ponds are in series. Using a flux model, we also developed an equation delineating the root zone depth at which diffusive dominated fluxes transition to advective dominated fluxes. This relationship is similar to the Peclet number that identifies the dominance of advective or diffusive fluxes in surface and groundwater transport. Using diffusion coefficients for inorganic mercury (Hg) and methylmercury (MeHg) we calculated that during high ET periods typical of summer, advective fluxes dominate root zone transport except in the top millimeters below the sediment–water interface. The transition depth has diel and seasonal trends, tracking those of ET. Neglecting this pathway has profound implications: misallocating loads along different hydrologic pathways; misinterpreting seasonal and diel water quality trends; confounding Fick's First Law calculations when determining diffusion fluxes using pore water concentration data; and misinterpreting biogeochemical mechanisms affecting dissolved constituent cycling in the root zone. In addition, our understanding of

Determining Near-Bottom Fluxes of Passive Tracers in Aquatic Environments

Science.gov (United States)

Bluteau, Cynthia E.; Ivey, Gregory N.; Donis, Daphne; McGinnis, Daniel F.

2018-03-01

In aquatic systems, the eddy correlation method (ECM) provides vertical flux measurements near the sediment-water interface. The ECM independently measures the turbulent vertical velocities w' and the turbulent tracer concentration c' at a high sampling rate (> 1 Hz) to obtain the vertical flux w'c'¯ from their time-averaged covariance. This method requires identifying and resolving all the flow-dependent time (and length) scales contributing to w'c'¯. With increasingly energetic flows, we demonstrate that the ECM's current technology precludes resolving the smallest flux-contributing scales. To avoid these difficulties, we show that for passive tracers such as dissolved oxygen, w'c'¯ can be measured from estimates of two scalar quantities: the rate of turbulent kinetic energy dissipation ɛ and the rate of tracer variance dissipation χc. Applying this approach to both laboratory and field observations demonstrates that w'c'¯ is well resolved by the new method and can provide flux estimates in more energetic flows where the ECM cannot be used.

Expanded flux variability analysis on metabolic network of Escherichia coli

Institute of Scientific and Technical Information of China (English)

CHEN Tong; XIE ZhengWei; OUYANG Qi

2009-01-01

Flux balance analysis,based on the mass conservation law in a cellular organism,has been extensively employed to study the interplay between structures and functions of cellular metabolic networks.Consequently,the phenotypes of the metabolism can be well elucidated.In this paper,we introduce the Expanded Flux Variability Analysis (EFVA) to characterize the intrinsic nature of metabolic reactions,such as flexibility,modularity and essentiality,by exploring the trend of the range,the maximum and the minimum flux of reactions.We took the metabolic network of Escherichia coli as an example and analyzed the variability of reaction fluxes under different growth rate constraints.The average variability of all reactions decreases dramatically when the growth rate increases.Consider the noise effect on the metabolic system,we thus argue that the microorganism may practically grow under a suboptimal state.Besides,under the EFVA framework,the reactions are easily to be grouped into catabolic and anabolic groups.And the anabolic groups can be further assigned to specific biomass constitute.We also discovered the growth rate dependent essentiality of reactions.

Evaporation of Liquid Droplet in Nano and Micro Scales from Statistical Rate Theory.

Science.gov (United States)

Duan, Fei; He, Bin; Wei, Tao

2015-04-01

The statistical rate theory (SRT) is applied to predict the average evaporation flux of liquid droplet after the approach is validated in the sessile droplet experiments of the water and heavy water. The steady-state experiments show a temperature discontinuity at the evaporating interface. The average evaporation flux is evaluated by individually changing the measurement at a liquid-vapor interface, including the interfacial liquid temperature, the interfacial vapor temperature, the vapor-phase pressure, and the droplet size. The parameter study shows that a higher temperature jump would reduce the average evaporation flux. The average evaporation flux can significantly be influenced by the interfacial liquid temperature and the vapor-phase pressure. The variation can switch the evaporation into condensation. The evaporation flux is found to remain relative constant if the droplet is larger than a micro scale, while the smaller diameters in nano scale can produce a much higher evaporation flux. In addition, a smaller diameter of droplets with the same liquid volume has a larger surface area. It is suggested that the evaporation rate increases dramatically as the droplet shrinks into nano size.

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

Science.gov (United States)

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

2012-12-01

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

A Year in the Life: Annual Patterns of CO2 and CH4 from a Northern Finland Peatland, Including Anaerobic Methane Oxidation and Summer Ebullition Rates

Science.gov (United States)

Miller, K.; Lipson, D.; Biasi, C.; Dorodnikov, M.; Männistö, M.; Lai, C. T.

2014-12-01

The major ecological controls on methane (CH4) and carbon dioxide (CO2) fluxes in northern wetland systems are well known, yet estimates of source/sink magnitudes are often incongruous with measured rates. This mismatch persists because holistic flux datasets are rare, preventing 'whole picture' determinations of flux controls. To combat this, we measured net CO2 and CH4 fluxes from September 2012-2013 within a peatland in northern Lapland, Finland. In addition, we performed in situ manipulations and in vitro soil incubations to quantify anaerobic methane oxidation and methanogenic rates as they related to alternative electron acceptor availability. Average annual fluxes varied substantially between different depressions within the wetland, a pattern that persisted through all seasons. Season was a strong predictor of both CO2 and CH4 flux rates, yet CH4 rates were not related to melt-season 10cm or 30cm soil temperatures, and only poorly predicted with air temperatures. We found evidence for both autumnal and spring thaw CH4 bursts, collectively accounting for 26% of annual CH4 flux, although the autumnal burst was more than 5 fold larger than the spring burst. CH4 ebullition measured throughout the growing season augmented the CH4 source load by a factor of 1.5, and was linked with fine-scale spatial heterogeneity within the wetland. Surprisingly, CH4 flux rates were insensitive to Fe(III) and humic acid soil amendments, both of which amplified CO2 fluxes. Using in vitro incubations, we determined anaerobic methane oxidation and methanogenesis rates. Measured anaerobic oxidation rates showed potential consumption of between 6-39% of the methane produced, contributing approximately 1% of total carbon dioxide flux. Treatments of nitrate, sulfate and ferric iron showed that nitrate suppressed methanogenesis, but were not associated with anaerobic oxidation rates.

Assessing the applicability of the 1D flux theory to full-scale secondary settling tank design with a 2D hydrodynamic model.

Science.gov (United States)

Ekama, G A; Marais, P

2004-02-01

The applicability of the one-dimensional idealized flux theory (1DFT) for the design of secondary settling tanks (SSTs) is evaluated by comparing its predicted maximum surface overflow (SOR) and solids loading (SLR) rates with that calculated with the two-dimensional computational fluid dynamics model SettlerCAD using as a basis 35 full-scale SST stress tests conducted on different SSTs with diameters from 30 to 45m and 2.25-4.1m side water depth (SWD), with and without Stamford baffles. From the simulations, a relatively consistent pattern appeared, i.e. that the 1DFT can be used for design but its predicted maximum SLR needs to be reduced by an appropriate flux rating, the magnitude of which depends mainly on SST depth and hydraulic loading rate (HLR). Simulations of the Watts et al. (Water Res. 30(9)(1996)2112) SST, with doubled SWDs and the Darvill new (4.1m) and old (2.5m) SSTs with interchanged depths, were run to confirm the sensitivity of the flux rating to depth and HLR. Simulations with and without a Stamford baffle were also performed. While the design of the internal features of the SST, such as baffling, has a marked influence on the effluent SS concentration while the SST is underloaded, these features appeared to have only a small influence on the flux rating, i.e. capacity, of the SST. Until more information is obtained, it would appear from the simulations that the flux rating of 0.80 of the 1DFT maximum SLR recommended by Ekama and Marais (Water Pollut. Control 85(1)(1986)101) remains a reasonable value to apply in the design of full-scale SSTs-for deep SSTs (4m SWD) the flux rating could be increased to 0.85 and for shallow SSTs (2.5m SWD) decreased to 0.75. It is recommended that (i) while the apparent interrelationship between SST flux rating and depth suggests some optimization of the volume of the SST, this be avoided and (ii) the depth of the SST be designed independently of the surface area as is usually the practice and once selected, the

Inverse modeling of the terrestrial carbon flux in China with flux covariance among inverted regions

Science.gov (United States)

Wang, H.; Jiang, F.; Chen, J. M.; Ju, W.; Wang, H.

2011-12-01

Quantitative understanding of the role of ocean and terrestrial biosphere in the global carbon cycle, their response and feedback to climate change is required for the future projection of the global climate. China has the largest amount of anthropogenic CO2 emission, diverse terrestrial ecosystems and an unprecedented rate of urbanization. Thus information on spatial and temporal distributions of the terrestrial carbon flux in China is of great importance in understanding the global carbon cycle. We developed a nested inversion with focus in China. Based on Transcom 22 regions for the globe, we divide China and its neighboring countries into 17 regions, making 39 regions in total for the globe. A Bayesian synthesis inversion is made to estimate the terrestrial carbon flux based on GlobalView CO2 data. In the inversion, GEOS-Chem is used as the transport model to develop the transport matrix. A terrestrial ecosystem model named BEPS is used to produce the prior surface flux to constrain the inversion. However, the sparseness of available observation stations in Asia poses a challenge to the inversion for the 17 small regions. To obtain additional constraint on the inversion, a prior flux covariance matrix is constructed using the BEPS model through analyzing the correlation in the net carbon flux among regions under variable climate conditions. The use of the covariance among different regions in the inversion effectively extends the information content of CO2 observations to more regions. The carbon flux over the 39 land and ocean regions are inverted for the period from 2004 to 2009. In order to investigate the impact of introducing the covariance matrix with non-zero off-diagonal values to the inversion, the inverted terrestrial carbon flux over China is evaluated against ChinaFlux eddy-covariance observations after applying an upscaling methodology.

Nitrogen fluxes through unsaturated zones in five agricultural settings across the United States

Science.gov (United States)

Green, C.T.; Fisher, L.H.; Bekins, B.A.

2008-01-01

The main physical and chemical controls on nitrogen (N) fluxes between the root zone and the water table were determined for agricultural sites in California, Indiana, Maryland, Nebraska, and Washington from 2004 to 2005. Sites included irrigated and nonirrigated fields; soil textures ranging from clay to sand; crops including corn, soybeans, almonds, and pasture; and unsaturated zone thicknesses ranging from 1 to 22 m. Chemical analyses of water from lysimeters and shallow wells indicate that advective transport of nitrate is the dominant process affecting the flux of N below the root zone. Vertical profiles of (i) nitrogen species, (ii) stable isotopes of nitrogen and oxygen, and (iii) oxygen, N, and argon in unsaturated zone air and correlations between N and other agricultural chemicals indicate that reactions do not greatly affect N concentrations between the root zone and the capillary fringe. As a result, physical factors, such as N application rate, water inputs, and evapotranspiration, control the differences in concentrations among the sites. Concentrations of N in shallow lysimeters exhibit seasonal variation, whereas concentrations in lysimeters deeper than a few meters are relatively stable. Based on concentration and recharge estimates, fluxes of N through the deep unsaturated zone range from 7 to 99 kg ha-1 yr-1. Vertical fluxes of N in ground water are lower due to spatial and historical changes in N inputs. High N fluxes are associated with coarse sediments and high N application rates. Copyright ?? 2008 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. All rights reserved.

Methane Flux of Amazonian Peatland Ecosystems: Large Ecosystem Fluxes with Substantial Contribution from Palm (maritia Flexuosa) STEM Emissions

Science.gov (United States)

Van Haren, J. L. M.; Cadillo-Quiroz, H.

2015-12-01

Methane (CH4) emissions through plants have long been known in wetlands. However, most measurements have focused on stem tops and leaves. Recently, measurements at the lower parts of stems have shown that stem emissions can exceed soil CH4 emissions in Asian peatlands (Pangala et al. 2013). The addition of stem fluxes to soil fluxes for total ecosystem fluxes has the potential to bridge the discrepancy between modeled to measured and bottom-up to top-down flux estimates. Our measurements in peatlands of Peru show that especially Mauritia flexuosa, a palm species, can emit very large quantities of CH4, although most trees emitted at least some CH4. We used flexible stem chambers to adapt to stems of any size above 5cm in diameter. The chambers were sampled in closed loop with a Gasmet DX4015 for flux measurements, which lasted ~5 minutes after flushing with ambient air. We found that M. flexuosa stem fluxes decrease with height along the stem and were positively correlated with soil fluxes. Most likely CH4 is transported up the stem with the xylem water. Measured M. flexuosa stem fluxes below 1.5m averaged 11.2±1.5 mg-C m-2 h-1 (±95% CI) with a maximum of 123±3.5 mg-C m-2 h-1 (±SE), whereas soil fluxes averaged 6.7±1.7 mg-C m-2 h-1 (±95% CI) with a maximum of 31.6±0.4 mg-C m-2 h-1 (±SE). Significant CH4 fluxes were measured up to 5 m height along the stems. Combined with the high density of ~150 M. flexuosa individuals per hectare in these peatlands and the consistent diameter of ~30cm, the high flux rates add ~20% to the soil flux. With anywhere between 1 and 5 billion M. flexuosa stems across Amazon basin wetlands, stem fluxes from this palm species could represent a major addition to the overall Amazon basin CH4 flux.

EURISOL-DS Multi-MWatt Hg Target: Neutron flux and fission rate calculations for the MAFF configuration

CERN Document Server

Romanets, Y; Vaz, P; Herrera-Martinez, A; Kadi, Y; Kharoua, C; Lettry, J; Lindroos, M

The EURISOL (The EURopean Isotope Separation On-Line Radioactive Ion Beam) project aims at producing high intensity radioactive ion beams produced by neutron induced fission on a fissile target (235U) surrounding a liquid mercury converter. A proton beam of 1 GeV and 4 MW impinges on the Hg converter generating by spallation reactions high neutron fluxes. In this work the state-of-the-art Monte Carlo codes MCNPX and FLUKA were used to assess the neutronics performance of the system which geometry, inspired from the MAFF concept, allows a versatile manipulation of the fission targets. The objective of the study was to optimize the geometry of the system and the materials used in the fuel and reflector elements of the system, in order to achieve the highest possible fission rate.

Increased particle flux to the deep ocean related to monsoons

Digital Repository Service at National Institute of Oceanography (India)

Nair, R.R.; Ittekkot, V.; Manganini, S.J.; Ramaswamy, V.; Haake, B.; Degens, E.T.; Desai, B.N.; Honjo, S.

. To assess the impact of monsoon-driven processes on the downward particle flux variations in the open ocean we deployed three moored arrays consisting of six time-series sediment traps at selected locations in the western, central and eastern parts...

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

Science.gov (United States)

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

2005-03-01

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 μg 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.

Turbulent transport across invariant canonical flux surfaces

International Nuclear Information System (INIS)

Hollenberg, J.B.; Callen, J.D.

1994-07-01

Net transport due to a combination of Coulomb collisions and turbulence effects in a plasma is investigated using a fluid moment description that allows for kinetic and nonlinear effects via closure relations. The model considered allows for ''ideal'' turbulent fluctuations that distort but preserve the topology of species-dependent canonical flux surfaces ψ number-sign,s triple-bond ∫ dF · B number-sign,s triple-bond ∇ x [A + (m s /q s )u s ] in which u s is the flow velocity of the fluid species. Equations for the net transport relative to these surfaces due to ''nonideal'' dissipative processes are found for the total number of particles and total entropy enclosed by a moving canonical flux surface. The corresponding particle transport flux is calculated using a toroidal axisymmetry approximation of the ideal surfaces. The resulting Lagrangian transport flux includes classical, neoclassical-like, and anomalous contributions and shows for the first time how these various contributions should be summed to obtain the total particle transport flux

Salp contributions to vertical carbon flux in the Sargasso Sea

Science.gov (United States)

Stone, Joshua P.; Steinberg, Deborah K.

2016-07-01

We developed a one-dimensional model to estimate salp contributions to vertical carbon flux at the Bermuda Atlantic Time-series Study (BATS) site in the North Atlantic subtropical gyre for a 17-yr period (April 1994 to December 2011). We based the model parameters on published rates of salp physiology and experimentally determined sinking and decomposition rates of salp carcasses. Salp grazing was low during non-bloom conditions, but routinely exceeded 100% of chlorophyll standing stock and primary production during blooms. Fecal pellet production was the largest source of salp carbon flux (78% of total), followed by respiration below 200 m (19%), sinking of carcasses (3%), and DOC excretion below 200 m (salp-mediated carbon flux. Seasonally, salp flux was higher during spring-summer than fall-winter, due to seasonal changes in species composition and abundance. Salp carbon export to 200 m was on average 2.3 mg C m-2 d-1 across the entire time series. This is equivalent to 11% of the mean 200 m POC flux measured by sediment traps in the region. During years with significant salp blooms, however, annually-averaged salp carbon export was the equivalent of up to 60% of trap POC flux at 200 m. Salp carbon flux attenuated slowly, and at 3200 m the average modeled carbon from salps was 109% of the POC flux measured in sediment traps at that depth. Migratory and carcass carbon export pathways should also be considered (alongside fecal pellet flux) as facilitating carbon export to sequestration depths in future studies.

Diffusion piecewise homogenization via flux discontinuity factors

International Nuclear Information System (INIS)

Sanchez, Richard; Zmijarevic, Igor

2011-01-01

We analyze the calculation of flux discontinuity factors (FDFs) for use with piecewise subdomain assembly homogenization. These coefficients depend on the numerical mesh used to compute the diffusion problem. When the mesh has a single degree of freedom on subdomain interfaces the solution is unique and can be computed independently per subdomain. For all other cases we have implemented an iterative calculation for the FDFs. Our numerical results show that there is no solution to this nonlinear problem but that the iterative algorithm converges towards FDFs values that reproduce subdomains reaction rates with a relatively high precision. In our test we have included both the GET and black-box FDFs. (author)

Estimation of core body temperature from skin temperature, heat flux, and heart rate using a Kalman filter.

Science.gov (United States)

Welles, Alexander P; Xu, Xiaojiang; Santee, William R; Looney, David P; Buller, Mark J; Potter, Adam W; Hoyt, Reed W

2018-05-18

Core body temperature (T C ) is a key physiological metric of thermal heat-strain yet it remains difficult to measure non-invasively in the field. This work used combinations of observations of skin temperature (T S ), heat flux (HF), and heart rate (HR) to accurately estimate T C using a Kalman Filter (KF). Data were collected from eight volunteers (age 22 ± 4 yr, height 1.75 ± 0.10 m, body mass 76.4 ± 10.7 kg, and body fat 23.4 ± 5.8%, mean ± standard deviation) while walking at two different metabolic rates (∼350 and ∼550 W) under three conditions (warm: 25 °C, 50% relative humidity (RH); hot-humid: 35 °C, 70% RH; and hot-dry: 40 °C, 20% RH). Skin temperature and HF data were collected from six locations: pectoralis, inner thigh, scapula, sternum, rib cage, and forehead. Kalman filter variables were learned via linear regression and covariance calculations between T C and T S , HF, and HR. Root mean square error (RMSE) and bias were calculated to identify the best performing models. The pectoralis (RMSE 0.18 ± 0.04 °C; bias -0.01 ± 0.09 °C), rib (RMSE 0.18 ± 0.09 °C; bias -0.03 ± 0.09 °C), and sternum (RMSE 0.20 ± 0.10 °C; bias -0.04 ± 0.13 °C) were found to have the lowest error values when using T S , HF, and HR but, using only two of these measures provided similar accuracy. Copyright © 2018. Published by Elsevier Ltd.

Flux dependency of particulate/colloidal fouling in seawater reverse osmosis systems

KAUST Repository

Salinas Rodríguez, S. G.

2012-01-01

Fouling is the main operational problem in seawater reverse osmosis systems (SWRO). Particulate fouling is traditionally measured through the silt density index (SDI) and through the modified fouling index (MFI). In recent years, ultrafiltration membranes were used successfully at constant flux-MFI-UF-to measure particulate/colloidal fouling potential and tested in sea water applications. Furthermore, constant flux operation allows predicting the rate of fouling in RO systems. The objectives of this study are: (1) to measure the flux effect in MFI-UF with different membranes (100, 30 and 10 kDa) for raw seawater and pre-treated water before reverse osmosis in three different locations; (2) to study the particulate and colloidal fouling potential of seawater in reverse osmosis systems; (3) to project the increase in pressure due to cake resistance in reverse osmosis systems. In this research, flat ultrafiltration membranes (100, 50, 30 and 10 kDa) are used in a con- stant flux filtration mode to test and compare real seawaters from various locations (North and Mediterranean Sea) and from various full scale facilities including different pre-treatments (i.e., ultrafiltration and coagulation + dual media filtration). The operated fluxes range from 350 down to values close to real RO operation, 15l(m2h)-1. After each filtration test, the MFI-UF is calculated to assess the particulate fouling potential. The obtained results showed that: (1) the particulate and colloidal fouling potential is directly proportional to the applied flux during filtration. This proportionality is related to the compression of the cake deposit occurring at high flux values; (2) the higher the flux, the higher the required pressure, the less porous the cake and therefore the higher the specific cake resistance; (3) particulate and colloidal fouling potential of seawater is site specific and is influenced by pre-treatment. © 2012 Desalination Publications. All rights reserved.

SCALPLO - a universal program for plotting flux output from SCALE modules and related programs. User`s manual

Energy Technology Data Exchange (ETDEWEB)

Hersman, A; Leege, P F.A. de; Hoogenboom, J E

1992-04-01

The FORTRAN-77 program SCALPLO is being developed to make an easy and quick graphic survey of flux and/or power data calculated with SCALE modules or other core calculation or shielding codes. The basic plot functions it can perform are one- and two-dimensional plots of flux or power distributions and flux energy spectra. More specifically it can produce plots of the flux distribution in a one-dimensional geometry for one or more energy groups in one figure. It can also plot the flux distribution along a cut through a two- or three-dimensional geometry along one of the coordinate axes and it can plot a two-dimensional view of the flux distribution of a two-dimensional geometry or of a plane cut through a three-dimensional geometry. The same can be done for the power distribution in a system. Furthermore SCALPLO can plot the particle flux spectrum as a function of energy, either as group fluxes or as group fluxes per unit energy or per unit lethargy. (orig./HP).

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

International Nuclear Information System (INIS)

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

1985-01-01

Radiotracer techniques were used to measure influx and efflux rates of Ca 2+ in freshwater-adapted Oreochromis mossambicus. The influx rate of Ca 2+ is related to body weight (W) as Fin = 50W0.805 nmol Ca 2+ /h. For a 20-g fish the calculated influx rate was 558 nmol Ca 2+ /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 Ca 2+ /h. The Ca 2+ efflux rate was calculated using the initial rate of appearance of radiotracer in the ambient water and the specific activity of plasma Ca 2+ . 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 Ca 2+ is related to body weight as Fout = 30W0.563 nmol Ca 2+ /h, which means an efflux rate of 162 nmol Ca 2+ /h for a 20-g fish. The net whole-body Ca 2+ 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 Ca 2+

Twofold reduction of phosphofructokinase activity in Lactococcus lactis results in strong decreases in growth rate and in glycolytic flux

DEFF Research Database (Denmark)

Andersen, Heidi Winterberg; Solem, Christian; Hammer, Karin

2001-01-01

reduced. Surprisingly, the mutants still showed homolactic fermentation, which indicated that the limitation was different from standard glucose-limited conditions, One explanation could be that the reduced activity of phosphofructokinase resulted in the accumulation of sugar-phosphates. Indeed, when one...... kinase and lactate dehydrogenase remained closer to the wild-type level. In defined medium supplemented with glucose, the growth rate of the mutants was reduced to 57 to 70% of wild-type levels and the glycolytic flux was reduced to 62 to 76% of wild-type levels. In complex medium growth was even further...... of the mutants was starved for glucose in glucose-limited chemostat, the growth rate could gradually be increased to 195% of the growth fate observed in glucose-saturated batch culture, suggesting that phosphofructokinase does affect the concentration of upstream metabolites. The pools of glucose-6- phosphate...

AmeriFlux Site and Data Exploration System

Science.gov (United States)

Krassovski, M.; Boden, T.; Yang, B.; Jackson, B.

2011-12-01

The AmeriFlux network was established in 1996. The network provides continuous observations of ecosystem-level exchanges of CO2, water, energy and momentum spanning diurnal, synoptic, seasonal, and interannual time scales. The current network, including both active and inactive sites, consists of 141 sites in North, Central, and South America. The Carbon Dioxide Information Analysis Center (CDIAC) at Oak Ridge National Laboratory (ORNL) provides data management support for the AmeriFlux network including long-term data storage and dissemination. AmeriFlux offers a broad suite of value-added data products: Level 1 data products at 30 minute or hourly time intervals provided by the site teams, Level 2 data processed by CDIAC and Level 3 and 4 files created using CarboEurope algorithms. CDIAC has developed a relational database to house the vast array of AmeriFlux data and information and a web-based interface to the database, the AmeriFlux Site and Data Exploration System (http://ameriflux.ornl.gov), to help users worldwide identify, and more recently, download desired AmeriFlux data. AmeriFlux and CDIAC offer numerous value-added AmeriFlux data products (i.e., Level 1-4 data products, biological data) and most of these data products are or will be available through the new data system. Vital site information (e.g., location coordinates, dominant species, land-use history) is also displayed in the new system. The data system provides numerous ways to explore and extract data. Searches can be done by site, location, measurement status, available data products, vegetation types, and by reported measurements just to name a few. Data can be accessed through the links to full data sets reported by a site, organized by types of data products, or by creating customized datasets based on user search criteria. The new AmeriFlux download module contains features intended to ease compliance of the AmeriFlux fair-use data policy, acknowledge the contributions of submitting

Spatial and stress-related variation in benthic microbial gas flux in northeastern Alberta wetlands

International Nuclear Information System (INIS)

Ciborowski, J.; Gardner Costa, J.

2010-01-01

This study investigated the effects of oil sands process material (OSPM) on the sediment microbial respiration in newly constructed wetlands located in northeastern Alberta. The sediment gas flux in 10 wetlands with various sediment characteristics and ages was studied. Analyses of variance (ANOVA) were used to contrast the mean wetland production of methane (CH 4 ) and carbon dioxide (CO 2 ) with season, wetland status, wetland age, and wetland zones. The study showed that CH 4 was significantly higher in reference wetlands than in OSPM-impacted wetlands. A significant relationship between the status and zone of the wetland was observed for CH 4 fluxes in reference wetlands. CH 4 fluxes were higher in the non-vegetated zones of reference wetlands than in the vegetated zones of reference wetlands. CO 2 fluxes were low and not significantly different in any of the studied sites. Results indicated that the wetlands contributed little atmospheric carbon.

Carbon dioxide, water vapour and energy fluxes over a semi ...

Indian Academy of Sciences (India)

42

of energy fluxes showed dominance of latent heat fluxes over sensible heat flux. .... for measurement of air temperature, rainfall, relative humidity, wind speed etc. ... within the radius of 100 m around the tower by using plant canopy analyzer ..... 2001), similar mechanisms might operate in our study resulting in flux deficit.

Landscape-level terrestrial methane flux observed from a very tall tower

Science.gov (United States)

Desai, Ankur R.; Xu, Ke; Tian, Hanqin; Weishampel, Peter; Thom, Jonthan; Baumann, Daniel D.; Andrews, Arlyn E.; Cook, Bruce D.; King, Jennifer Y.; Kolka, Randall

2015-01-01

Simulating the magnitude and variability of terrestrial methane sources and sinks poses a challenge to ecosystem models because the biophysical and biogeochemical processes that lead to methane emissions from terrestrial and freshwater ecosystems are, by their nature, episodic and spatially disjunct. As a consequence, model predictions of regional methane emissions based on field campaigns from short eddy covariance towers or static chambers have large uncertainties, because measurements focused on a particular known source of methane emission will be biased compared to regional estimates with regards to magnitude, spatial scale, or frequency of these emissions. Given the relatively large importance of predicting future terrestrial methane fluxes for constraining future atmospheric methane growth rates, a clear need exists to reduce spatiotemporal uncertainties. In 2010, an Ameriflux tower (US-PFa) near Park Falls, WI, USA, was instrumented with closed-path methane flux measurements at 122 m above ground in a mixed wetland–upland landscape representative of the Great Lakes region. Two years of flux observations revealed an average annual methane (CH4) efflux of 785 ± 75 mg CCH4 m−2 yr−1, compared to a mean CO2 sink of −80 g CCO2 m−2 yr−1, a ratio of 1% in magnitude on a mole basis. Interannual variability in methane flux was 30% of the mean flux and driven by suppression of methane emissions during dry conditions in late summer 2012. Though relatively small, the magnitude of the methane source from the very tall tower measurements was mostly within the range previously measured using static chambers at nearby wetlands, but larger than a simple scaling of those fluxes to the tower footprint. Seasonal patterns in methane fluxes were similar to those simulated in the Dynamic Land Ecosystem Model (DLEM), but magnitude depends on model parameterization and input data, especially regarding wetland extent. The model was unable to simulate short

DAYCENT Simulations to Test the Influence of Fire Regime and Fire Suppression on Trace Gas Fluxes and Nitrogen Biogeochemistry of Colorado Forests

Directory of Open Access Journals (Sweden)

Mark A. Gathany

2012-07-01

Full Text Available Biological activity and the physical environment regulate greenhouse gas fluxes (CH₄, N₂O and NO from upland soils. Wildfires are known to alter these factors such that we collected daily weather records, fire return intervals, or specific fire years, and soil data of four specific sites along the Colorado Front Range. These data were used as primary inputs into DAYCENT. In this paper we test the ability of DAYCENT to simulate four forested sites in this area and to address two objectives: (1 to evaluate the short-term influence of fire on trace gas fluxes from burned landscapes; and (2 to compare trace gas fluxes among locations and between pre-/post- fire suppression. The model simulations indicate that CH₄ oxidation is relatively unaffected by wildfire. In contrast, gross nitrification rates were reduced by 13.5–37.1% during the fire suppression period. At two of the sites, we calculated increases in gross nitrification rates (>100%, and N₂O and NO fluxes during the year of fire relative to the year before a fire. Simulated fire suppression exhibited decreased gross nitrification rates presumably as nitrogen is immobilized. This finding concurs with other studies that highlight the importance of forest fires to maintain soil nitrogen availability.

Relationships between Microbial Activities and Subduction-related Outgassing and Volatile Flux at Aleutian Arc Volcanoes

Science.gov (United States)

Miller, H.; Lopez, T. M.; Fischer, T. P.; Schrenk, M. O.

2016-12-01

Subduction-related processes, including the movement and alteration of carbon compounds, are an important component of global geochemical cycles. Actively degassing volcanoes of the Aleutian Island arc offer interesting opportunities to not only characterize the composition and abundance of volatiles, but also to identify the origin of the discharging gases (e.g. mantle, organic matter, or carbonates). Taking this approach a step further, microbial activities in and around volcanic fumarole areas may impact the composition and flux of reduced volcanic gases, either through their modification or their assimilation into fixed biomass. Microbiological studies of these systems can be used to develop predictive models to complement those based upon geochemical data while providing greater understanding of the causal relationships between microbial populations and their environment, and ultimately refine estimates of volcanic outgassing. Coupled fumarole soil and gas samples were collected from several Aleutian Island volcanoes in 2015 (Gareloi, Kanaga, Kiska, Little Sitkin) and 2016 (Okmok, Resheschnoi). DNA was extracted from the soil and used to describe microbial community composition, while gas samples were analyzed through chromatography and mass spectrometry. Preliminary data suggests a relationship between the abundance of specific groups of prokaryotes known to metabolize reduced gases, such as sulfur-oxidizers and methanotrophs, and the abundances of the degassing volatiles, including sulfur dioxide and methane. Ongoing studies aimed at investigating the relationship between the genomic composition of the fumarolic microbial community and the physical and chemical properties of the soil (i.e. mineralogy, bulk geochemistry, nutrient concentration, gas flux, and environmental measurements) are underway. These data will be used to evaluate the potential for microbial communities to remove volcanic carbon and store it as biomass, or to modify the volatile carbon

Connecting Related Rates and Differential Equations

Science.gov (United States)

Brandt, Keith

2012-01-01

This article points out a simple connection between related rates and differential equations. The connection can be used for in-class examples or homework exercises, and it is accessible to students who are familiar with separation of variables.

Surface radiation fluxes in transient climate simulations

Science.gov (United States)

Garratt, J. R.; O'Brien, D. M.; Dix, M. R.; Murphy, J. M.; Stephens, G. L.; Wild, M.

1999-01-01

Transient CO 2 experiments from five coupled climate models, in which the CO 2 concentration increases at rates of 0.6-1.1% per annum for periods of 75-200 years, are used to document the responses of surface radiation fluxes, and associated atmospheric properties, to the CO 2 increase. In all five models, the responses of global surface temperature and column water vapour are non-linear and fairly tightly constrained. Thus, global warming lies between 1.9 and 2.7 K at doubled, and between 3.1 and 4.1 K at tripled, CO 2, whilst column water vapour increases by between 3.5 and 4.5 mm at doubled, and between 7 and 8 mm at tripled, CO 2. Global cloud fraction tends to decrease by 1-2% out to tripled CO 2, mainly the result of decreases in low cloud. Global increases in column water, and differences in these increases between models, are mainly determined by the warming of the tropical oceans relative to the middle and high latitudes; these links are emphasised in the zonal profiles of warming and column water vapour increase, with strong water vapour maxima in the tropics. In all models the all-sky shortwave flux to the surface S↓ (global, annual average) changes by less than 5 W m -2 out to tripled CO 2, in some cases being essentially invariant in time. In contrast, the longwave flux to the surface L↓ increases significantly, by 25 W m -2 typically at tripled CO 2. The variations of S↓ and L↓ (clear-sky and all-sky fluxes) with increase in CO 2 concentration are generally non-linear, reflecting the effects of ocean thermal inertia, but as functions of global warming are close to linear in all five models. This is best illustrated for the clear-sky downwelling fluxes, and the net radiation. Regionally, as illustrated in zonal profiles and global distributions, greatest changes in both S↓ and L↓ are the result primarily of local maxima in warming and column water vapour increases.

Methane oxidation and methane fluxes in the ocean surface layer and deep anoxic waters

Science.gov (United States)

Ward, B. B.; Kilpatrick, K. A.; Novelli, P. C.; Scranton, M. I.

1987-01-01

Measured biological oxidation rates of methane in near-surface waters of the Cariaco Basin are compared with the diffusional fluxes computed from concentration gradients of methane in the surface layer. Methane fluxes and oxidation rates were investigated in surface waters, at the oxic/anoxic interface, and in deep anoxic waters. It is shown that the surface-waters oxidation of methane is a mechanism which modulates the flux of methane from marine waters to the atmosphere.

Water flux in animals: analysis of potential errors in the tritiated water method

International Nuclear Information System (INIS)

Nagy, K.A.; Costa, D.

1979-03-01

Laboratory studies indicate that tritiated water measurements of water flux are accurate to within -7 to +4% in mammals, but errors are larger in some reptiles. However, under conditions that can occur in field studies, errors may be much greater. Influx of environmental water vapor via lungs and skin can cause errors exceeding +-50% in some circumstances. If water flux rates in an animal vary through time, errors approach +-15% in extreme situations, but are near +-3% in more typical circumstances. Errors due to fractional evaporation of tritiated water may approach -9%. This error probably varies between species. Use of an inappropriate equation for calculating water flux from isotope data can cause errors exceeding +-100%. The following sources of error are either negligible or avoidable: use of isotope dilution space as a measure of body water volume, loss of nonaqueous tritium bound to excreta, binding of tritium with nonaqueous substances in the body, radiation toxicity effects, and small analytical errors in isotope measurements. Water flux rates measured with tritiated water should be within +-10% of actual flux rates in most situations

Water flux in animals: analysis of potential errors in the tritiated water method

Energy Technology Data Exchange (ETDEWEB)

Nagy, K.A.; Costa, D.

1979-03-01

Laboratory studies indicate that tritiated water measurements of water flux are accurate to within -7 to +4% in mammals, but errors are larger in some reptiles. However, under conditions that can occur in field studies, errors may be much greater. Influx of environmental water vapor via lungs and skin can cause errors exceeding +-50% in some circumstances. If water flux rates in an animal vary through time, errors approach +-15% in extreme situations, but are near +-3% in more typical circumstances. Errors due to fractional evaporation of tritiated water may approach -9%. This error probably varies between species. Use of an inappropriate equation for calculating water flux from isotope data can cause errors exceeding +-100%. The following sources of error are either negligible or avoidable: use of isotope dilution space as a measure of body water volume, loss of nonaqueous tritium bound to excreta, binding of tritium with nonaqueous substances in the body, radiation toxicity effects, and small analytical errors in isotope measurements. Water flux rates measured with tritiated water should be within +-10% of actual flux rates in most situations.

Role of plasma enhanced atomic layer deposition reactor wall conditions on radical and ion substrate fluxes

Energy Technology Data Exchange (ETDEWEB)

Sowa, Mark J., E-mail: msowa@ultratech.com [Ultratech/Cambridge NanoTech, 130 Turner Street, Building 2, Waltham, Massachusetts 02453 (United States)

2014-01-15

Chamber wall conditions, such as wall temperature and film deposits, have long been known to influence plasma source performance on thin film processing equipment. Plasma physical characteristics depend on conductive/insulating properties of chamber walls. Radical fluxes depend on plasma characteristics as well as wall recombination rates, which can be wall material and temperature dependent. Variations in substrate delivery of plasma generated species (radicals, ions, etc.) impact the resulting etch or deposition process resulting in process drift. Plasma enhanced atomic layer deposition is known to depend strongly on substrate radical flux, but film properties can be influenced by other plasma generated phenomena, such as ion bombardment. In this paper, the chamber wall conditions on a plasma enhanced atomic layer deposition process are investigated. The downstream oxygen radical and ion fluxes from an inductively coupled plasma source are indirectly monitored in temperature controlled (25–190 °C) stainless steel and quartz reactors over a range of oxygen flow rates. Etch rates of a photoresist coated quartz crystal microbalance are used to study the oxygen radical flux dependence on reactor characteristics. Plasma density estimates from Langmuir probe ion saturation current measurements are used to study the ion flux dependence on reactor characteristics. Reactor temperature was not found to impact radical and ion fluxes substantially. Radical and ion fluxes were higher for quartz walls compared to stainless steel walls over all oxygen flow rates considered. The radical flux to ion flux ratio is likely to be a critical parameter for the deposition of consistent film properties. Reactor wall material, gas flow rate/pressure, and distance from the plasma source all impact the radical to ion flux ratio. These results indicate maintaining chamber wall conditions will be important for delivering consistent results from plasma enhanced atomic layer deposition

Flux control-based design of furfural-resistance strains of Saccharomyces cerevisiae for lignocellulosic biorefinery.

Science.gov (United States)

Unrean, Pornkamol

2017-04-01

We have previously developed a dynamic flux balance analysis of Saccharomyces cerevisiae for elucidation of genome-wide flux response to furfural perturbation (Unrean and Franzen, Biotechnol J 10(8):1248-1258, 2015). Herein, the dynamic flux distributions were analyzed by flux control analysis to identify target overexpressed genes for improved yeast robustness against furfural. The flux control coefficient (FCC) identified overexpressing isocitrate dehydrogenase (IDH1), a rate-controlling flux for ethanol fermentation, and dicarboxylate carrier (DIC1), a limiting flux for cell growth, as keys of furfural-resistance phenotype. Consistent with the model prediction, strain characterization showed 1.2- and 2.0-fold improvement in ethanol synthesis and furfural detoxification rates, respectively, by IDH1 overexpressed mutant compared to the control. DIC1 overexpressed mutant grew at 1.3-fold faster and reduced furfural at 1.4-fold faster than the control under the furfural challenge. This study hence demonstrated the FCC-based approach as an effective tool for guiding the design of robust yeast strains.

DSM-flux: A new technology for reliable Combined Sewer Overflow discharge monitoring with low uncertainties.

Science.gov (United States)

Maté Marín, Ainhoa; Rivière, Nicolas; Lipeme Kouyi, Gislain

2018-06-01

In the past ten years, governments from the European Union have been encouraged to collect volume and quality data for all the effluent overflows from separated stormwater and combined sewer systems that result in a significant environmental impact on receiving water bodies. Methods to monitor and control these flows require improvements, particularly for complex Combined Sewer Overflow (CSO) structures. The DSM-flux (Device for Stormwater and combined sewer flows Monitoring and the control of pollutant fluxes) is a new pre-designed and pre-calibrated channel that provides appropriate hydraulic conditions suitable for measurement of overflow rates and volumes by means of one water level gauge. In this paper, a stage-discharge relation for the DSM-flux is obtained experimentally and validated for multiple inflow hydraulic configurations. Uncertainties in CSO discharges and volumes are estimated within the Guide to the expression of Uncertainty in Measurement (GUM) framework. Whatever the upstream hydraulic conditions are, relative uncertainties are lower than 15% and 2% for the investigated discharges and volumes, respectively. Copyright © 2018 Elsevier Ltd. All rights reserved.

Measurements of the Canonical Helicity Evolution of a Gyrating Kinked Flux Rope

Science.gov (United States)

von der Linden, J.; Sears, J.; Intrator, T.; You, S.

2017-12-01

Magnetic structures in the solar corona and planetary magnetospheres are often modelled as magnetic flux ropes governed by magnetohydrodynamics (MHD); however, inside these structures, as exhibited in reconnection, conversions between magnetic and kinetic energies occur over a wide range of scales. Flux ropes based on the flux of canonical momentum circulation extend the flux rope concept to include effects of finite particle momentum and present the distinct advantage of reconciling all plasma regimes - e.g. kinetic, two-fluid, and MHD - with the topological concept of helicity: twists, writhes, and linkages. This presentation shows the first visualization and analysis of the 3D dynamics of canonical flux ropes and their relative helicity evolution from laboratory measurements. Ion and electron canonical flux ropes are visualized from a dataset of Mach, triple, and Ḃ probe measurements at over 10,000 spatial locations of a gyrating kinked flux rope. The flux ropes co-gyrate with the peak density and electron temperature in and out of a measurement volume. The electron and ion canonical flux ropes twist with opposite handedness and the ion flux ropes writhe around the electron flux ropes. The relative cross helicity between the magnetic and ion flow vorticity flux ropes dominates the relative ion canonical helicity and is anti-correlated with the relative magnetic helicity. The 3D nature of the kink and a reverse eddy current affect the helicity evolution. This work is supported by DOE Grant DE-SC0010340 and the DOE Office of Science Graduate Student Research Program and prepared in part by LLNL under Contract DE-AC52-07NA27344. LLNL-ABS-735426

Uncertainty characterization of HOAPS 3.3 latent heat-flux-related parameters

Science.gov (United States)

Liman, Julian; Schröder, Marc; Fennig, Karsten; Andersson, Axel; Hollmann, Rainer

2018-03-01

Latent heat flux (LHF) is one of the main contributors to the global energy budget. As the density of in situ LHF measurements over the global oceans is generally poor, the potential of remotely sensed LHF for meteorological applications is enormous. However, to date none of the available satellite products have included estimates of systematic, random, and sampling uncertainties, all of which are essential for assessing their quality. Here, the challenge is taken on by matching LHF-related pixel-level data of the Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite (HOAPS) climatology (version 3.3) to in situ measurements originating from a high-quality data archive of buoys and selected ships. Assuming the ground reference to be bias-free, this allows for deriving instantaneous systematic uncertainties as a function of four atmospheric predictor variables. The approach is regionally independent and therefore overcomes the issue of sparse in situ data densities over large oceanic areas. Likewise, random uncertainties are derived, which include not only a retrieval component but also contributions from in situ measurement noise and the collocation procedure. A recently published random uncertainty decomposition approach is applied to isolate the random retrieval uncertainty of all LHF-related HOAPS parameters. It makes use of two combinations of independent data triplets of both satellite and in situ data, which are analysed in terms of their pairwise variances of differences. Instantaneous uncertainties are finally aggregated, allowing for uncertainty characterizations on monthly to multi-annual timescales. Results show that systematic LHF uncertainties range between 15 and 50 W m-2 with a global mean of 25 W m-2. Local maxima are mainly found over the subtropical ocean basins as well as along the western boundary currents. Investigations indicate that contributions from qa (U) to the overall LHF uncertainty are on the order of 60 % (25 %). From an

ORR core re-configuration measurements to increase the fast neutron flux in the Magnetic Fusion Energy (MFE) experiments

International Nuclear Information System (INIS)

Hobbs, R.W.; Stinnett, R.M.; Sims, T.M.

1985-06-01

A study has been made of the relative increases obtainable in the fast neutron flux in the Magnetic Fusion Energy (MFE) experiment positions by reconfiguring the current ORR core. The study was made at the request of the MFE program to examine the percentage increase possible in the current displacement per atom (dpa) rate (assumed proportional to the fast flux). The principle methods investigated to increase the fast flux consisted of reducing the current core size (number of fuel elements) to increase the core average power density and arrangement of the fuel elements in the reduced-size core to tilt the core power distribution towards the MFE positions. The study concluded that fast fluxes in the E-3 core position could be increased by approximately 15 to 20% over current values and in E-5 by approximately 45 to 55%

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

Science.gov (United States)

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

2009-02-01

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

Thermodynamics of the Heat-Flux Avalanches at the First-Order Magnetic Transition in Magnetocaloric Materials

Science.gov (United States)

Piazzi, Marco; Bennati, Cecilia; Basso, Vittorio

2017-10-01

We investigate the kinetics of first-order magnetic phase transitions by measuring and modeling the heat-flux avalanches corresponding to the irreversible motion of the phase-boundary interface separating the coexisting low- and high-temperature stable magnetic phases. By means of out-of-equilibrium thermodynamics, we encompass the damping mechanisms of the boundary motion in a phenomenological parameter αs. By analyzing the time behavior of the heat-flux signals measured on La (Fe -Mn -Si )13-H magnetocaloric compounds through Peltier calorimetry temperature scans performed at low rates, we relate the linear rise of the individual avalanches to the intrinsic-damping parameter αs.

Leaf, branch, stand and landscape scale measurements of volatile organic compound fluxes from U. S. woodlands

Energy Technology Data Exchange (ETDEWEB)

Guenther, A.; Greenberg, J.; Harley, P.; Helmig, D.; Klinger, L.; Vierling, L.; Zimmerman, P. [National Center for Atmospheric Research, Boulder, CO (United States). Atmospheric Chemistry Div.; Geron, C. [Environmental Protection Agency, Research Triangle Park, NC (United States)

1996-01-01

Natural volatile organic compound (VOC) fluxes were measured in three U.S. woodlands. Fluxes from individual leaves and branches were estimated with enclosure techniques and used to initialize and evaluate VOC emission model estimates. Ambient measurements were used to estimate above canopy fluxes for entire stands. A total of 78 VOCs were identified, with hexenol derivatives being the most commonly observed oxygenated compounds. There was also evidence of high rates of isoprene emission and high rates of monoterpenes in some genera of trees. Model predictions of diurnal variations were within + or - 35 per cent of observed flux variations. Fluxes predicted by a recent version of a biogenic emission model were within 10 per cent to 50 per cent of observed fluxes, leading to the conclusion that existing databases can provide isoprene and monoterpene emission rate potentials within acceptable limits for the dominant plant species at these three woodland sites. 21 refs., 5 tabs., 2 figs.

Sediment Equilibrium and Diffusive Fluxes in Relation to Phosphorus Dynamics in the Turbid Minnesota River

National Research Council Canada - National Science Library

James, William F

2009-01-01

...) concentration in large river systems. However, in-stream processes such as equilibrium P flux from suspended sediment and diffusive P flux from deposited sediment stored in river channels may also play a role in soluble P control...

FluxVisualizer, a Software to Visualize Fluxes through Metabolic Networks

Directory of Open Access Journals (Sweden)

Tim Daniel Rose

2018-04-01

Full Text Available FluxVisualizer (Version 1.0, 2017, freely available at https://fluxvisualizer.ibgc.cnrs.fr is a software to visualize fluxes values on a scalable vector graphic (SVG representation of a metabolic network by colouring or increasing the width of reaction arrows of the SVG file. FluxVisualizer does not aim to draw metabolic networks but to use a customer’s SVG file allowing him to exploit his representation standards with a minimum of constraints. FluxVisualizer is especially suitable for small to medium size metabolic networks, where a visual representation of the fluxes makes sense. The flux distribution can either be an elementary flux mode (EFM, a flux balance analysis (FBA result or any other flux distribution. It allows the automatic visualization of a series of pathways of the same network as is needed for a set of EFMs. The software is coded in python3 and provides a graphical user interface (GUI and an application programming interface (API. All functionalities of the program can be used from the API and the GUI and allows advanced users to add their own functionalities. The software is able to work with various formats of flux distributions (Metatool, CellNetAnalyzer, COPASI and FAME export files as well as with Excel files. This simple software can save a lot of time when evaluating fluxes simulations on a metabolic network.

Morphodynamic Modeling of the Lower Yellow River, China: Flux (Equilibrium) Form or Entrainment (Nonequilibrium) Form of Sediment Mass Conservation?

Science.gov (United States)

An, C.; Parker, G.; Ma, H.; Naito, K.; Moodie, A. J.; Fu, X.

2017-12-01

Models of river morphodynamics consist of three elements: (1) a treatment of flow hydraulics, (2) a formulation relating some aspect of sediment transport to flow hydraulics, and (3) a description of sediment conservation. In the case of unidirectional river flow, the Exner equation of sediment conservation is commonly described in terms of a flux-based formulation, in which bed elevation variation is related to the streamwise gradient of sediment transport rate. An alternate formulation of the Exner equation, however, is the entrainment-based formulation in which bed elevation variation is related to the difference between the entrainment rate of bed sediment into suspension and the deposition rate of suspended sediment onto the bed. In the flux-based formulation, sediment transport is regarded to be in a local equilibrium state (i.e., sediment transport rate locally equals sediment transport capacity). However, the entrainment-based formulation does not require this constraint; the sediment transport rate may lag in space and time behind the changing flow conditions. In modeling the fine-grained Lower Yellow River, it is usual to treat sediment conservation in terms of an entrainment-based (nonequilibrium) rather than a flux-based (equilibrium) formulation with the consideration that fine-grained sediment may be entrained at one place but deposited only at some distant location downstream. However, the differences in prediction between the two formulations are still not well known, and the entrainment formulation may not always be necessary for the Lower Yellow River. Here we study this problem by comparing the results of flux-based and entrainment-based morphodynamics under conditions typical of the Yellow River, using sediment transport equations specifically designed for the Lower Yellow River. We find, somewhat unexpectedly, that in a treatment of a 200-km reach using uniform sediment, there is little difference between the two formulations unless the

Measuring Convective Mass Fluxes Over Tropical Oceans

Science.gov (United States)

Raymond, David

2017-04-01

Deep convection forms the upward branches of all large-scale circulations in the tropics. Understanding what controls the form and intensity of vertical convective mass fluxes is thus key to understanding tropical weather and climate. These mass fluxes and the corresponding conditions supporting them have been measured by recent field programs (TPARC/TCS08, PREDICT, HS3) in tropical disturbances considered to be possible tropical storm precursors. In reality, this encompasses most strong convection in the tropics. The measurements were made with arrays of dropsondes deployed from high altitude. In some cases Doppler radar provided additional measurements. The results are in some ways surprising. Three factors were found to control the mass flux profiles, the strength of total surface heat fluxes, the column-integrated relative humidity, and the low to mid-tropospheric moist convective instability. The first two act as expected, with larger heat fluxes and higher humidity producing more precipitation and stronger lower tropospheric mass fluxes. However, unexpectedly, smaller (but still positive) convective instability produces more precipitation as well as more bottom-heavy convective mass flux profiles. Furthermore, the column humidity and the convective instability are anti-correlated, at least in the presence of strong convection. On spatial scales of a few hundred kilometers, the virtual temperature structure appears to be in dynamic balance with the pattern of potential vorticity. Since potential vorticity typically evolves on longer time scales than convection, the potential vorticity pattern plus the surface heat fluxes then become the immediate controlling factors for average convective properties. All measurements so far have taken place in regions with relatively flat sea surface temperature (SST) distributions. We are currently seeking funding for a measurement program in the tropical east Pacific, a region that exhibits strong SST gradients and

Method and system of simulating nuclear power plant count rate for training purposes

International Nuclear Information System (INIS)

Alliston, W.H.; Koenig, R.H.

1975-01-01

A method and system are described for the real-time simulation of the dynamic operation of a nuclear power plant in which nuclear flux rate counters are provided for monitoring the rate of nuclear fission of the reactor. The system utilizes apparatus that includes digital computer means for calculating data relating to the rate of nuclear fission of a simulated reactor model, which rate is controlled in accordance with the operation of control panel devices. A digital number from the computer corresponding to the flux rate controls an oscillator driven counter means to produce a pulse after a predetermined count. This pulse controls an oscillator driven polynomial counter to count a random number that controls a third counter in accordance with pulse from the first counter to produce a random fission count for operating the meters. (U.S.)

Flux-line-cutting losses in type-II superconductors

International Nuclear Information System (INIS)

Clem, J.R.

1982-01-01

Energy dissipation associated with flux-line cutting (intersection and cross-joining of adjacent nonparallel vortices) is considered theoretically. The flux-line-cutting contribution to the dissipation per unit volume, arising from mutual annihilation of transverse magnetic flux, is identified as J/sub parallel/xE/sub parallel/, where J/sub parallel/ and E/sub parallel/ are the components of the current density and the electric field parallel to the magnetic induction. The dynamical behavior of the magnetic structure at the flux-line-cutting threshold is shown to be governed by a special critical-state model similar to that proposed by previous authors. The resulting flux-line-cutting critical-state model, characterized in planar geometry by a parallel critical current density J/sub c/parallel or a critical angle gradient k/sub c/, is used to calculate predicted hysteretic ac flux-line-cutting losses in type-II superconductors in which the flux pinning is weak. The relation of the theory to previous experiments is discussed

Flux creep and penetration in Fe-doped YBa2Cu3O7

International Nuclear Information System (INIS)

Mohamed, M.A.; Jung, J.; Franck, J.P.

1990-01-01

Measurements of the magnetic-field distribution, flux penetration, and decay of trapped flux were performed for a disc-shaped sample of YBa 2 Cu 2.95 Fe 0.05 O 7-δ at 77 K. Time-dependent magnetic-flux penetration, i.e., a decay of diamagnetic shielding and the Meissner field, was observed for zero-field-cooled (ZFC) and field-cooled (FC) samples. The decays were found to be logarithmic in time. The logarithmic decay rate of diamagnetic shielding depends on an applied magnetic field and reaches its maximum at an applied field of about 30 G. The dependence of a trapped field versus an applied field shows a maximum at an applied field of 100 G for the FC case and 200 G for the ZFC case. The maximum amount of the trapped field is about two times less than that for a pure, undoped YBa 2 Cu 3 O 7-δ sample of similar dimensions. The logarithmic decay rate of the trapped field versus the initial trapped field is described by a linear function with the change of its slope at the trapped field corresponding to an applied field of about 30 G for both the FC and ZFC cases. These results are related to the sample microstructure, i.e., grain size and porosity. Trapped field decays can be explained in terms of the interaction between intergranular vortices and persistent current circulating around normal regions or voids, in the framework of the conventional flux-creep model recently proposed by Hagen, Griessen, and Salomons [Physica 157C, 199 (1989)

A punctual flux estimator and reactions rates optimization in neutral particles transport calculus by the Monte Carlo method; Mise au point d'un estimateur ponctuel du flux et des taux de reactions dans les calculs de transport de particules neutres par la methode de monte carlo

Energy Technology Data Exchange (ETDEWEB)

Authier, N

1998-12-01

One of the questions asked in radiation shielding problems is the estimation of the radiation level in particular to determine accessibility of working persons in controlled area (nuclear power plants, nuclear fuel reprocessing plants) or to study the dose gradients encountered in material (iron nuclear vessel, medical therapy, electronics in satellite). The flux and reaction rate estimators used in Monte Carlo codes give average values in volumes or on surfaces of the geometrical description of the system. But in certain configurations, the knowledge of punctual deposited energy and dose estimates are necessary. The Monte Carlo estimate of the flux at a point of interest is a calculus which presents an unbounded variance. The central limit theorem cannot be applied thus no easy confidencelevel may be calculated. The convergence rate is then very poor. We propose in this study a new solution for the photon flux at a point estimator. The method is based on the 'once more collided flux estimator' developed earlier for neutron calculations. It solves the problem of the unbounded variance and do not add any bias to the estimation. We show however that our new sampling schemes specially developed to treat the anisotropy of the photon coherent scattering is necessary for a good and regular behavior of the estimator. This developments integrated in the TRIPOLI-4 Monte Carlo code add the possibility of an unbiased punctual estimate on media interfaces. (author)

A punctual flux estimator and reactions rates optimization in neutral particles transport calculus by the Monte Carlo method; Mise au point d'un estimateur ponctuel du flux et des taux de reactions dans les calculs de transport de particules neutres par la methode de monte carlo

Energy Technology Data Exchange (ETDEWEB)

Authier, N

1998-12-01

One of the questions asked in radiation shielding problems is the estimation of the radiation level in particular to determine accessibility of working persons in controlled area (nuclear power plants, nuclear fuel reprocessing plants) or to study the dose gradients encountered in material (iron nuclear vessel, medical therapy, electronics in satellite). The flux and reaction rate estimators used in Monte Carlo codes give average values in volumes or on surfaces of the geometrical description of the system. But in certain configurations, the knowledge of punctual deposited energy and dose estimates are necessary. The Monte Carlo estimate of the flux at a point of interest is a calculus which presents an unbounded variance. The central limit theorem cannot be applied thus no easy confidencelevel may be calculated. The convergence rate is then very poor. We propose in this study a new solution for the photon flux at a point estimator. The method is based on the 'once more collided flux estimator' developed earlier for neutron calculations. It solves the problem of the unbounded variance and do not add any bias to the estimation. We show however that our new sampling schemes specially developed to treat the anisotropy of the photon coherent scattering is necessary for a good and regular behavior of the estimator. This developments integrated in the TRIPOLI-4 Monte Carlo code add the possibility of an unbiased punctual estimate on media interfaces. (author)

MAGNETIC FLUX CANCELLATION IN ELLERMAN BOMBS

Energy Technology Data Exchange (ETDEWEB)

Reid, A.; Mathioudakis, M.; Nelson, C. J.; Henriques, V. [Astrophysics Research Centre, School of Mathematics and Physics, Queen’s University Belfast, BT7 1NN, Northern Ireland (United Kingdom); Doyle, J. G. [Armagh Observatory, College Hill, Armagh, BT61 9DG (United Kingdom); Scullion, E. [Trinity College Dublin, College Green, Dublin 2 (Ireland); Ray, T., E-mail: areid29@qub.ac.uk [Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2 (Ireland)

2016-06-01

Ellerman Bombs (EBs) are often found to be co-spatial with bipolar photospheric magnetic fields. We use H α imaging spectroscopy along with Fe i 6302.5 Å spectropolarimetry from the Swedish 1 m Solar Telescope (SST), combined with data from the Solar Dynamic Observatory , to study EBs and the evolution of the local magnetic fields at EB locations. EBs are found via an EB detection and tracking algorithm. Using NICOLE inversions of the spectropolarimetric data, we find that, on average, (3.43 ± 0.49) × 10{sup 24} erg of stored magnetic energy disappears from the bipolar region during EB burning. The inversions also show flux cancellation rates of 10{sup 14}–10{sup 15} Mx s{sup −1} and temperature enhancements of 200 K at the detection footpoints. We investigate the near-simultaneous flaring of EBs due to co-temporal flux emergence from a sunspot, which shows a decrease in transverse velocity when interacting with an existing, stationary area of opposite polarity magnetic flux, resulting in the formation of the EBs. We also show that these EBs can be fueled further by additional, faster moving, negative magnetic flux regions.

Theoretical simulation of the dual-heat-flux method in deep body temperature measurements.

Science.gov (United States)

Huang, Ming; Chen, Wenxi

2010-01-01

Deep body temperature reveals individual physiological states, and is important in patient monitoring and chronobiological studies. An innovative dual-heat-flux method has been shown experimentally to be competitive with the conventional zero-heat-flow method in its performance, in terms of measurement accuracy and step response to changes in the deep temperature. We have utilized a finite element method to model and simulate the dynamic process of a dual-heat-flux probe in deep body temperature measurements to validate the fundamental principles of the dual-heat-flux method theoretically, and to acquire a detailed quantitative description of the thermal profile of the dual-heat-flux probe. The simulation results show that the estimated deep body temperature is influenced by the ambient temperature (linearly, at a maximum rate of 0.03 °C/°C) and the blood perfusion rate. The corresponding depth of the estimated temperature in the skin and subcutaneous tissue layer is consistent when using the dual-heat-flux probe. Insights in improving the performance of the dual-heat-flux method were discussed for further studies of dual-heat-flux probes, taking into account structural and geometric considerations.

VOC flux measurements using a novel Relaxed Eddy Accumulation GC-FID system in urban Houston, Texas

Science.gov (United States)

Park, C.; Schade, G.; Boedeker, I.

2008-12-01

Houston experiences higher ozone production rates than most other major cities in the US, which is related to high anthropogenic VOC emissions from both area/mobile sources (car traffic) and a large number of petrochemical facilities. The EPA forecasts that Houston is likely to still violate the new 8-h NAAQS in 2020. To monitor neighborhood scale pollutant fluxes, we established a tall flux tower installation a few kilometers north of downtown Houston. We measure energy and trace gas fluxes, including VOCs from both anthropogenic and biogenic emission sources in the urban surface layer using eddy covariance and related techniques. Here, we describe a Relaxed Eddy Accumulation (REA) system combined with a dual-channel GC-FID used for VOC flux measurements, including first results. Ambient air is sampled at approximately 15 L min-1 through a 9.5 mm OD PFA line from 60 m above ground next to a sonic anemometer. Subsamples of this air stream are extracted through an ozone scrubber and pushed into two Teflon bag reservoirs, from which they are transferred to the GC pre-concentration units consisting of carbon-based adsorption traps encapsulated in heater blocks for thermal desorption. We discuss the performance of our system and selected measurement results from the 2008 spring and summer seasons in Houston. We present diurnal variations of the fluxes of the traffic tracers benzene, toluene, ethylbenzene, and xylenes (BTEX) during different study periods. Typical BTEX fluxes ranged from -0.36 to 3.10 mg m-2 h-1 for benzene, and -0.47 to 5.04 mg m-2 h-1 for toluene, and exhibited diurnal cycles with two dominant peaks related to rush-hour traffic. A footprint analysis overlaid onto a geographic information system (GIS) will be presented to reveal the dominant emission sources and patterns in the study area.

Quantum depinning of flux lines from columnar defects

International Nuclear Information System (INIS)

Chudnovsky, E.M.; Ferrera, A.; Vilenkin, A.

1995-01-01

The depinning of a flux line from a columnar defect is studied within the path-integral approach. Instantons of the quantum field theory in 1+1 dimensions are computed for the flux line whose dynamics is dominated by the Magnus force. The universal temperature dependence of the decay rate in the proximity of the critical current is obtained. This problem provides an example of macroscopic quantum tunneling, which is accessible to the direct comparison between theory and experiment

Divertor Heat Flux Reduction and Detachment in the National Spherical Torus eXperiment.

Science.gov (United States)

Soukhanovskii, Vsevolod

2007-11-01

Steady-state handling of the heat flux is a critical divertor issue for both the International Thermonuclear Experimental Reactor and spherical torus (ST) devices. Because of an inherently compact divertor, it was thought that ST-based devices might not be able to fully utilize radiative and dissipative divertor techniques based on induced power and momentum loss. However, initial experiments conducted in the National Spherical Torus Experiment in an open geometry horizontal carbon plate divertor using 0.8 MA 2-6 MW NBI-heated lower single null H-mode plasmas at the lower end of elongations κ=1.8-2.4 and triangularities δ=0.45-0.75 demonstrated that high divertor peak heat fluxes, up to 6-10 MW/ m^2, could be reduced by 50-75% using a high-recycling radiative divertor regime with D2 injection. Furthermore, similar reduction was obtained with a partially detached divertor (PDD) at high D2 injection rates, however, it was accompanied by an X-point MARFE that quickly led to confinement degradation. Another approach takes advantage of the ST relation between strong shaping and high performance, and utilizes the poloidal magnetic flux expansion in the divertor region. Up to 60 % reduction in divertor peak heat flux was achieved at similar levels of scrape-off layer power by varying plasma shaping and thereby increasing the outer strike point (OSP) poloidal flux expansion from 4-6 to 18-22. In recent experiments conducted in highly-shaped 1.0-1.2 MA 6 MW NBI heated H-mode plasmas with divertor D2 injection at rates up to 10^22 s-1, a PDD regime with OSP peak heat flux 0.5-1.5 MW/m^2 was obtained without noticeable confinement degradation. Calculations based on a two point scrape-off layer model with parameterized power and momentum losses show that the short parallel connection length at the OSP sets the upper limit on the radiative exhaust channel, and both the impurity radiation and large momentum sink achievable only at high divertor neutral pressures are required

Seasonal and annual variation in planktonic foraminiferal fluxes including warm period related El Niño in the northwestern North Pacific

Science.gov (United States)

Kuroyanagi, A.; Kawahata, H.; Nishi, H.; Honda, M. C.

2007-12-01

Planktonic foraminifera provide a record of the upper ocean environment through their species assemblage and individual tests. To investigate the relationship between foraminifera and oceanographic conditions and the impact of El Niño on foraminifera, we analyzed foraminiferal fluxes and relative abundances by using sediment trap samples collected biweekly at three sites in the northwestern North Pacific: Site 40N (39 °60'N, 165 °00'E), Site KNOT (43 °58'N, 155 °03'E), and Site 50N (50 °01'N, 165 °02'E) from 1998- 2001, a period that included an El Niño effect. Based on foraminiferal production and assemblage composition, we divided the sampling duration into several periods during which certain characteristic oceanographic properties were observed. These sampling periods were classified into five types (I-V) based upon four factors: 1) the predominant foraminiferal group, 2) total foraminiferal fluxes (TFFs), 3) organic matter (OM) fluxes, and 4) hydrographic conditions, which included sea surface temperature (SST) and thermal structure. Our results suggest that seasonal changes in foraminifera were closely related to water mass properties in addition to SST. If species compositions were the same, then water mass properties were the most important factors affecting the seasonal variation of foraminiferal abundance in the northwestern North Pacific. Although one of the major controlling factors for foraminiferal fluxes is food availability, the controlling factors for each type (types I-V) are different because of specific oceanographic situations, such as phytoplankton blooms, which result in an excess food supply for foraminifera. At Site KNOT in 1998, SST was remarkably high because of El Niño, and high surface temperatures and weak winds would have lowered nutrient supply and intensified water column stratification, resulting in the relatively low fluxes of total foraminifera, N. pachyderma, and G. bulloides, and the high fluxes of N. dutertrei that

Sequential cryogen spraying for heat flux control at the skin surface

Science.gov (United States)

Majaron, Boris; Aguilar, Guillermo; Basinger, Brooke; Randeberg, Lise L.; Svaasand, Lars O.; Lavernia, Enrique J.; Nelson, J. Stuart

2001-05-01

Heat transfer rate at the skin-air interface is of critical importance for the benefits of cryogen spray cooling in combination with laser therapy of shallow subsurface skin lesions, such as port-wine stain birthmarks. With some cryogen spray devices, a layer of liquid cryogen builds up on the skin surface during the spurt, which may impair heat transfer across the skin surface due to relatively low thermal conductivity and potentially higher temperature of the liquid cryogen layer as compared to the spray droplets. While the mass flux of cryogen delivery can be adjusted by varying the atomizing nozzle geometry, this may strongly affect other spray properties, such as lateral spread (cone), droplet size, velocity, and temperature distribution. We present here first experiments with sequential cryogen spraying, which may enable accurate mass flux control through variation of spray duty cycle, while minimally affecting other spray characteristics. The observed increase of cooling rate and efficiency at moderate duty cycle levels supports the above described hypothesis of isolating liquid layer, and demonstrates a novel approach to optimization of cryogen spray devices for individual laser dermatological applications.

A conceptual high flux reactor design with scope for use in ADS ...

Indian Academy of Sciences (India)

By design the flux level in the seed fuel has been kept lower than in the high flux trap zones so that the burning rate of the seed is reduced. Another important objective of the design is to maximize the time interval of refueling. As against a typical refueling interval of a few weeks in such high flux reactor cores, it is desired to ...

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

Energy Technology Data Exchange (ETDEWEB)

Mitrica, Bogdan, E-mail: mitrica@nipne.ro [Horia Hulubei National Institute for Physics and Nuclear Engineering, P.O.B. MG-6, 077125 Magurele (Romania); Margineanu, Romul; Stoica, Sabin; Petcu, Mirel; Brancus, Iliana [Horia Hulubei National Institute for Physics and Nuclear Engineering, P.O.B. MG-6, 077125 Magurele (Romania); Jipa, Alexandru; Lazanu, Ionel; Sima, Octavian [Department of Physics, University of Bucharest, P.O.B. MG-11 (Romania); Haungs, Andreas; Rebel, Heinigerd [Institut fur Kernphysik, Karlsruhe Institute of Technology - Campus North, 76021 Karlsruhe (Germany); Petre, Marian; Toma, Gabriel; Saftoiu, Alexandra; Stanca, Denis; Apostu, Ana; Gomoiu, Claudia [Horia Hulubei National Institute for Physics and Nuclear Engineering, P.O.B. MG-6, 077125 Magurele (Romania)

2011-10-21

Muons comprise an important contribution of the natural radiation dose in air (approx. 30 nSv/h of a total dose rate of 65-130 nSv/h), as well as in underground sites even when the flux and relative contribution are significantly reduced. The flux of muons observed underground can be used as an estimator for the depth in mwe (meter water equivalent) of the underground site. The water equivalent depth is important information to devise physics experiments feasible for a specific site. A mobile detector for performing measurements of the muon flux was developed in IFIN-HH, Bucharest. Consisting of two scintillator plates (approx. 0.9 m{sup 2}) which measure in coincidence, the detector is installed on a van which facilitates measurements at different locations at the surface or underground. The detector was used to determine muon fluxes at different sites in Romania. In particular, data were taken and the values of meter water equivalents were assessed for several locations at the salt mine in Slanic-Prahova, Romania. The measurements have been performed in two different galleries of the Slanic mine at different depths. In order to test the stability of the method, also measurements of the muon flux at the surface at different elevations were performed. The results were compared with predictions of Monte-Carlo simulations using the CORSIKA and MUSIC codes.

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

International Nuclear Information System (INIS)

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

2011-01-01

Muons comprise an important contribution of the natural radiation dose in air (approx. 30 nSv/h of a total dose rate of 65-130 nSv/h), as well as in underground sites even when the flux and relative contribution are significantly reduced. The flux of muons observed underground can be used as an estimator for the depth in mwe (meter water equivalent) of the underground site. The water equivalent depth is important information to devise physics experiments feasible for a specific site. A mobile detector for performing measurements of the muon flux was developed in IFIN-HH, Bucharest. Consisting of two scintillator plates (approx. 0.9 m 2 ) which measure in coincidence, the detector is installed on a van which facilitates measurements at different locations at the surface or underground. The detector was used to determine muon fluxes at different sites in Romania. In particular, data were taken and the values of meter water equivalents were assessed for several locations at the salt mine in Slanic-Prahova, Romania. The measurements have been performed in two different galleries of the Slanic mine at different depths. In order to test the stability of the method, also measurements of the muon flux at the surface at different elevations were performed. The results were compared with predictions of Monte-Carlo simulations using the CORSIKA and MUSIC codes.

Role of magnetic flux perturbations in confinement bifurcations in TUMAN-3M

International Nuclear Information System (INIS)

Lebedev, S.V.; Andreiko, M.V.; Askinazi, L.G.

2003-01-01

Poloidal magnetic flux variations in the small tokamak TUMAN-3M allowed observation of transitions between different confinement modes. The possibility of switching on/off the ohmic H-mode by edge poloidal magnetic flux perturbations has been found. The flux perturbations were created by fast current ramp up/down or by magnetic compression/decompression produced by fast increase/decrease in the toroidal magnetic field. It was found that positive flux perturbations (current ramp-up and magnetic compression scenarios) are useful means of H-mode triggering. If a negative flux perturbation (current ramp-down or magnetic decompression) is applied, the H-mode terminated. Various mechanisms involved in the L-H and H-L transition physics in the flux perturbation experiments were analyzed. The experimental observations of the transitions between confinement modes might be understood in terms of the model of a sheared radial electric field generation, which takes into account the electron Ware drift in a perturbed longitudinal electric field. Another scenario of improved confinement was observed in the initial phase of an ohmic discharge, when change in the poloidal flux is associated with current ramp-up. Variation of the rates of current ramp-up and working gas puffing in the beginning of a discharge resulted in a fast increase in the electron temperature near the axis. The increase correlates with low m/n MHD mode growth. The observed core electron confinement improvement is apparently connected with the rate of current ramp. Deviation from the optimal rate results in disappearance of the improvement. The role of magnetic shear profile and rational magnetic surfaces in the core electron confinement improvement in the initial phase of ohmic discharges is discussed. (author)

Reactor core flow rate control system

International Nuclear Information System (INIS)

Sakuma, Hitoshi; Tanikawa, Naoshi; Takahashi, Toshiyuki; Miyakawa, Tetsuya.

1996-01-01

When an internal pump is started by a variable frequency power source device, if magnetic fields of an AC generator are introduced after the rated speed is reached, neutron flux high scram occurs by abrupt increase of a reactor core flow rate. Then, in the present invention, magnetic fields for the AC generator are introduced at a speed previously set at which the fluctuation range of the reactor core flow rate (neutron flux) by the start up of the internal pump is within an allowable value. Since increase of the speed of the internal pump upon its start up is suppressed to determine the change of the reactor core flow rate within an allowable range, increase of neutron fluxes is suppressed to enable stable start up. Then, since transition boiling of fuels caused by abrupt decrease of the reactor core flow rate upon occurrence of abnormality in an external electric power system is prevented, and the magnetic fields for the AC generator are introduced in such a manner to put the speed increase fluctuation range of the internal pump upon start up within an allowable value, neutron flux high scram is not caused to enable stable start-up. (N.H.)

Photon flux determination for a precision measurement of the neutral pion lifetime

Energy Technology Data Exchange (ETDEWEB)

Teymurazyan, Aram [Univ. of Kentucky, Lexington, KY (United States)

2008-01-01

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 performed throughout the run. In these measurements, both the photon energy and flux were determined by the Jefferson Lab Hall B tagger, and the electron-positron pairs were swept by a magnetic field and detected in the new 1728 channel hybrid calorimeter (HyCal). The pair production crosssection was extracted with an uncertainty of ~ 2%, producing an agreement with theoretical calculations at the level of ~ 2%. This measurement provided a unique opportunity to verify the photon flux determination procedure for the PrimEx experiment.

Gradient-driven flux-tube simulations of ion temperature gradient turbulence close to the non-linear threshold

Energy Technology Data Exchange (ETDEWEB)

Peeters, A. G.; Rath, F.; Buchholz, R.; Grosshauser, S. R.; Strintzi, D.; Weikl, A. [Physics Department, University of Bayreuth, Universitätsstrasse 30, Bayreuth (Germany); Camenen, Y. [Aix Marseille Univ, CNRS, PIIM, UMR 7345, Marseille (France); Candy, J. [General Atomics, PO Box 85608, San Diego, California 92186-5608 (United States); Casson, F. J. [CCFE, Culham Science Centre, Abingdon OX14 3DB, Oxon (United Kingdom); Hornsby, W. A. [Max Planck Institut für Plasmaphysik, Boltzmannstrasse 2 85748 Garching (Germany)

2016-08-15

It is shown that Ion Temperature Gradient turbulence close to the threshold exhibits a long time behaviour, with smaller heat fluxes at later times. This reduction is connected with the slow growth of long wave length zonal flows, and consequently, the numerical dissipation on these flows must be sufficiently small. Close to the nonlinear threshold for turbulence generation, a relatively small dissipation can maintain a turbulent state with a sizeable heat flux, through the damping of the zonal flow. Lowering the dissipation causes the turbulence, for temperature gradients close to the threshold, to be subdued. The heat flux then does not go smoothly to zero when the threshold is approached from above. Rather, a finite minimum heat flux is obtained below which no fully developed turbulent state exists. The threshold value of the temperature gradient length at which this finite heat flux is obtained is up to 30% larger compared with the threshold value obtained by extrapolating the heat flux to zero, and the cyclone base case is found to be nonlinearly stable. Transport is subdued when a fully developed staircase structure in the E × B shearing rate forms. Just above the threshold, an incomplete staircase develops, and transport is mediated by avalanche structures which propagate through the marginally stable regions.

Quantifying landscape-level methane fluxes in subarctic Finland using a multiscale approach.

Science.gov (United States)

Hartley, Iain P; Hill, Timothy C; Wade, Thomas J; Clement, Robert J; Moncrieff, John B; Prieto-Blanco, Ana; Disney, Mathias I; Huntley, Brian; Williams, Mathew; Howden, Nicholas J K; Wookey, Philip A; Baxter, Robert

2015-10-01

Quantifying landscape-scale methane (CH4 ) fluxes from boreal and arctic regions, and determining how they are controlled, is critical for predicting the magnitude of any CH4 emission feedback to climate change. Furthermore, there remains uncertainty regarding the relative importance of small areas of strong methanogenic activity, vs. larger areas with net CH4 uptake, in controlling landscape-level fluxes. We measured CH4 fluxes from multiple microtopographical subunits (sedge-dominated lawns, interhummocks and hummocks) within an aapa mire in subarctic Finland, as well as in drier ecosystems present in the wider landscape, lichen heath and mountain birch forest. An intercomparison was carried out between fluxes measured using static chambers, up-scaled using a high-resolution landcover map derived from aerial photography and eddy covariance. Strong agreement was observed between the two methodologies, with emission rates greatest in lawns. CH4 fluxes from lawns were strongly related to seasonal fluctuations in temperature, but their floating nature meant that water-table depth was not a key factor in controlling CH4 release. In contrast, chamber measurements identified net CH4 uptake in birch forest soils. An intercomparison between the aerial photography and satellite remote sensing demonstrated that quantifying the distribution of the key CH4 emitting and consuming plant communities was possible from satellite, allowing fluxes to be scaled up to a 100 km(2) area. For the full growing season (May to October), ~ 1.1-1.4 g CH4  m(-2) was released across the 100 km(2) area. This was based on up-scaled lawn emissions of 1.2-1.5 g CH4  m(-2) , vs. an up-scaled uptake of 0.07-0.15 g CH4  m(-2) by the wider landscape. Given the strong temperature sensitivity of the dominant lawn fluxes, and the fact that lawns are unlikely to dry out, climate warming may substantially increase CH4 emissions in northern Finland, and in aapa mire regions in general. © 2015 The

Gas loop - continuous measurement of thermal and fast neutron fluxes; Boucle a gaz - mesure continue de flux de neutrons thermiques et rapides

Energy Technology Data Exchange (ETDEWEB)

Droulers, Y; Pleyber, G; Sciers, P; Maurin, G [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires

1964-07-01

The measurement method described in this report can be applied both to thermal and fast neutron fluxes. A description is given of two practical applications in each of these two domains. This method is particularly suitable for measurements carried out on 'loop' type equipment. The measurement of the relative flux variations are carried out with an accuracy of 5 per cent. The choice of the shape of the gas circuit leaves a considerable amount of liberty for the adaptation of the measurement circuit to the experimental conditions. (authors) [French] La methode de mesure defrite dans ce rapport s1 applique aussi bien au flux de neutrons thermiques, qu'au flux de neutrons rapides. On donne la description de deux realisations pratiques dans chacun de ces domaines. Cette methode est particulierement adaptee a des mesures effectuees sur des dispositifs du type 'boucle'. La mesure des variations relatives de flux se fait avec une precision de 5 pour cent. Le choix de la configuration du circuit gazeux donne une grande souplesse dans l'adaptation du circuit de mesure aux conditions experimentales. (auteurs)

Flux expulsion and trapping in rotating discs of type II superconductors

International Nuclear Information System (INIS)

Boyer, R.; Leblanc, M.A.R.

1977-01-01

The magnetic flux rotating in step with a type II superconducting disc is measured with orthogonal pick up coils for various previous magnetic histories vs H 0 applied at right angles to the axis of rotation. For some initial magnetic states, flux expulsion, independent of the rate of rotation, occurs during the initial rotation. A simple model where flux lines leave the specimen against the magnetic pressure in the active region accounts for the observations. (author)

Invariability of Central Metabolic Flux Distribution in Shewanella oneidensis MR-1 Under Environmental or Genetic Perturbations

Energy Technology Data Exchange (ETDEWEB)

Tang, Yinjie; Martin, Hector Garcia; Deutschbauer, Adam; Feng, Xueyang; Huang, Rick; Llora, Xavier; Arkin, Adam; Keasling, Jay D.

2009-04-21

An environmentally important bacterium with versatile respiration, Shewanella oneidensis MR-1, displayed significantly different growth rates under three culture conditions: minimal medium (doubling time {approx} 3 hrs), salt stressed minimal medium (doubling time {approx} 6 hrs), and minimal medium with amino acid supplementation (doubling time {approx}1.5 hrs). {sup 13}C-based metabolic flux analysis indicated that fluxes of central metabolic reactions remained relatively constant under the three growth conditions, which is in stark contrast to the reported significant changes in the transcript and metabolite profiles under various growth conditions. Furthermore, ten transposon mutants of S. oneidensis MR-1 were randomly chosen from a transposon library and their flux distributions through central metabolic pathways were revealed to be identical, even though such mutational processes altered the secondary metabolism, for example, glycine and C1 (5,10-Me-THF) metabolism.

The influence of measurement and relaxation time on flux jumps in high temperature superconductors

International Nuclear Information System (INIS)

Yang Xiaobin; Zhou Youhe; Tu Shandong

2010-01-01

The influence of the magnetization and relaxation time on flux jumps in high temperature superconductors (HTSC) under varying magnetic field is studied using the fundamental electromagnetic field equations and the thermal diffusion equation; temperature variety corresponding to flux jump is also discussed. We find that for a low sweep rate of the applied magnetic field, the measurement and relaxation times can reduce flux jump and to constrain the number of flux jumps, even stabilizing the HTSC, since much heat produced by the motion of magnetic flux can transfer into coolant during the measurement and relaxation times. As high temperature superconductors are subjected to a high sweep rate or a strong pulsed magnetic field, magnetization undergoes from stability or oscillation to jump for different pause times. And the period of temperature oscillation is equal to the measurement and relaxation time.

Measurement of erosion rate by absorption spectroscopy in a Hall thruster

International Nuclear Information System (INIS)

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

2005-01-01

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

Self-powered neutron and gamma-ray flux detector

International Nuclear Information System (INIS)

Allan, C.J.; Shields, R.B.; Lynch, G.F.; Cuttler, J.M.

1980-01-01

A new type of self-powered neutron detector was developed which is sensitive to both the neutron and gamma-ray fluxes. The emitter comprises two parts. The central emitter core is made of materials that generate high-energy electrons on exposure to neutrons. The outer layer acts as a gamma-ray/electron converter, and since it has a higher atomic number and higher back-scattering coefficient than the collector, increases the net outflow or emmission of electrons. The collector, which is around the emitter outer layer, is insulated from the outer layer electrically with dielectric insulation formed from compressed metal-oxide powder. The fraction of electrons given off by the emitter that is reflected back by the collector is less than the fraction of electrons emitted by the collector that is reflected back by the emitter. The thickness of the outer layer needed to achieve this result is very small. A detector of this design responds to external reactor gamma-rays as well as to neutron capture gamma-rays from the collector. The emitter core is either nickel, iron or titanium, or alloys based on these metals. The outer layer is made of platinum, tantalum, osmium, molybdenum or cerium. The detector is particularly useful for monitoring neutron and gamma ray flux intensities in nuclear reactor cores in which the neutron and gamma ray flux intensities are closely proportional, are unltimately related to the fission rate, and are used as measurements of nuclear reactor power. (DN)

The luminosity function and formation rate history of GRBs

International Nuclear Information System (INIS)

Firmani, C.; Avila-Reese, V.; Ghisellini, G.; Tutukov, A.V.

2005-01-01

The isotropic luminosity function (LF) and formation rate history (FRH) of long GRBs is by the first time constrained by using jointly both the observed GRB peak-flux and redshift distributions. Our results support an evolving LF and a FRH that keeps increasing after z = 2. We discuss some interesting implications related to these results

Reconnection Fluxes in Eruptive and Confined Flares and Implications for Superflares on the Sun

Science.gov (United States)

Tschernitz, Johannes; Veronig, Astrid M.; Thalmann, Julia K.; Hinterreiter, Jürgen; Pötzi, Werner

2018-01-01

We study the energy release process of a set of 51 flares (32 confined, 19 eruptive) ranging from GOES class B3 to X17. We use Hα filtergrams from Kanzelhöhe Observatory together with Solar Dynamics Observatory HMI and Solar and Heliospheric Observatory MDI magnetograms to derive magnetic reconnection fluxes and rates. The flare reconnection flux is strongly correlated with the peak of the GOES 1–8 Å soft X-ray flux (c = 0.92, in log–log space) for both confined and eruptive flares. Confined flares of a certain GOES class exhibit smaller ribbon areas but larger magnetic flux densities in the flare ribbons (by a factor of 2). In the largest events, up to ≈50% of the magnetic flux of the active region (AR) causing the flare is involved in the flare magnetic reconnection. These findings allow us to extrapolate toward the largest solar flares possible. A complex solar AR hosting a magnetic flux of 2 × 1023 Mx, which is in line with the largest AR fluxes directly measured, is capable of producing an X80 flare, which corresponds to a bolometric energy of about 7 × 1032 erg. Using a magnetic flux estimate of 6 × 1023 Mx for the largest solar AR observed, we find that flares of GOES class ≈X500 could be produced (E bol ≈ 3 × 1033 erg). These estimates suggest that the present day’s Sun is capable of producing flares and related space weather events that may be more than an order of magnitude stronger than have been observed to date.

Relation between gamma-ray emission, radio bursts, and proton fluxes from solar flares

International Nuclear Information System (INIS)

Fomichev, V.V.; Chertok, I.M.

1985-01-01

Data on solar gamma-ray flares, including 24 flares with gamma-ray lines, recorded up to June 1982, are analyzed. It is shown that from the point of view of radio emission the differences between flares with and without gamma-ray lines has a purely quantitative character: the former are accompanied by the most intense microwave bursts. Meter type II bursts are not a distinctive feature of flares with gamma-ray lines. Pulsed flares, regardless of the presence or absence of gamma-ray lines, are not accompanied by significant proton fluxes at the earth. On the whole, contrary to the popular opinion in the literature, flares with gamma-ray lines do not display a deficit of proton flux in interplanetary space in comparison with similar flares without gamma-ray lines. The results of quantitative diagnostics of proton flares based on radio bursts are not at variance with the presence of flares without detectable gamma-ray emission in lines but with a pronounced increase in the proton flux at the earth. 23 references

Implicit flux-split schemes for the Euler equations

Science.gov (United States)

Thomas, J. L.; Walters, R. W.; Van Leer, B.

1985-01-01

Recent progress in the development of implicit algorithms for the Euler equations using the flux-vector splitting method is described. Comparisons of the relative efficiency of relaxation and spatially-split approximately factored methods on a vector processor for two-dimensional flows are made. For transonic flows, the higher convergence rate per iteration of the Gauss-Seidel relaxation algorithms, which are only partially vectorizable, is amply compensated for by the faster computational rate per iteration of the approximately factored algorithm. For supersonic flows, the fully-upwind line-relaxation method is more efficient since the numerical domain of dependence is more closely matched to the physical domain of dependence. A hybrid three-dimensional algorithm using relaxation in one coordinate direction and approximate factorization in the cross-flow plane is developed and applied to a forebody shape at supersonic speeds and a swept, tapered wing at transonic speeds.

Sovereign ratings in the post-crisis world : an analysis of actual, shadow and relative risk ratings

OpenAIRE

Basu, Kaushik; De, Supriyo; Ratha, Dilip; Timmer, Hans

2013-01-01

This paper analyzes the evolution of sovereign credit ratings in the wake of the global financial crisis by studying changes in actual, shadow, and relative ratings between 2008 and 2012. For countries that do not have a rating from the major rating agencies, shadow ratings are estimated as a function of macroeconomic, structural, and governance variables. The shadow rating exercise confir...

Flux of aquatic insect productivity to land: comparison of lentic and lotic ecosystems.

Science.gov (United States)

Gratton, Claudio; Vander Zanden, M Jake

2009-10-01

Recently, food web studies have started exploring how resources from one habitat or ecosystem influence trophic interactions in a recipient ecosystem. Benthic production in lakes and streams can be exported to terrestrial habitats via emerging aquatic insects and can therefore link aquatic and terrestrial ecosystems. In this study, we develop a general conceptual model that highlights zoobenthic production, insect emergence, and ecosystem geometry (driven principally by area-to-edge ratio) as important factors modulating the flux of aquatic production across the ecosystem boundary. Emerging insect flux, defined as total insect production emerging per meter of shoreline (g C x m(-1) x yr(-1)) is then distributed inland using decay functions and is used to estimate insect deposition rate to terrestrial habitats (g C x m(-2) x yr(-1)). Using empirical data from the literature, we simulate insect fluxes across the water-land ecosystem boundary to estimate the distribution of fluxes and insect deposition inland for lakes and streams. In general, zoobenthos in streams are more productive than in lakes (6.67 vs. 1.46 g C x m(-2) x yr(-1)) but have lower insect emergence to aquatic production ratios (0.19 vs. 0.30). However, as stream width is on average smaller than lake radius, this results in flux (F) estimates 2 1/2 times greater for lakes than for streams. Ultimately, insect deposition onto land (within 100 m of shore) adjacent to average-sized lakes (10-ha lakes, 0.021 g C x m(-2) x yr(-1)) is greater than for average-sized streams (4 m width, 0.002 g C x m(-2) x yr(-1)) used in our comparisons. For the average lake (both in size and productivity), insect deposition rate approaches estimates of terrestrial secondary production in low-productivity ecosystems (e.g., deserts and tundra, approximately 0.07 g C x m(-2) x yr(-1)). However, larger lakes (1300 ha) and streams (16 m) can have average insect deposition rates (approximately 0.01-2.4 g C x m(-2) x yr(-1

High Upward Fluxes of Formic Acid from a Boreal Forest Canopy

Science.gov (United States)

Schobesberger, Siegfried; Lopez-Hilifiker, Felipe D.; Taipale, Ditte; Millet, Dylan B.; D'Ambro, Emma L.; Rantala, Pekka; Mammarella, Ivan; Zhou, Putian; Wolfe, Glenn M.; Lee, Ben H.;

Determination of lead 210 atmospheric fluxes in Syria

International Nuclear Information System (INIS)

Al-Masri, M. S.; Shaik Khalil, H.

2001-01-01

Lead 210 atmospheric fluxes were determined by collecting 51 profiles from Syrian soil during 1998. Lead 210 fluxes in Syria calculated from lead 210 inventory in soil ranged from 15 Bq.m -2 .y -1 and 407 Bq.m -2 .y -1 with an average value of 128 Bq.m -2 .y -1 . the highest fluxes were found to be in Hama area due to the Gaab fault, which is considered as a radon source in the area. In addition, fluxes were also high in most sites, which are located in Syria valleys and around the lakes. Moreover, the study has indicated that there is no linear relation between lead 210 flux values and other parameters such as annual rainfall and bulk density of the soil. On the other hand, an effect, of those two factors on lead 210 distribution with depth has been observed. In addition, the results of variable lead 210 fluxes from site to another have proved that it is necessary, in order to obtain a representative mean value of lead 210 flux obtained in this study is within the worldwide range for lead 210 flux. (Author)

Characterization of high flux magnetized helium plasma in SCU-PSI linear device

Science.gov (United States)

Xiaochun, MA; Xiaogang, CAO; Lei, HAN; Zhiyan, ZHANG; Jianjun, WEI; Fujun, GOU

2018-02-01

A high-flux linear plasma device in Sichuan University plasma-surface interaction (SCU-PSI) based on a cascaded arc source has been established to simulate the interactions between helium and hydrogen plasma with the plasma-facing components in fusion reactors. In this paper, the helium plasma has been characterized by a double-pin Langmuir probe. The results show that the stable helium plasma beam with a diameter of 26 mm was constrained very well at a magnetic field strength of 0.3 T. The core density and ion flux of helium plasma have a strong dependence on the applied current, magnetic field strength and gas flow rate. It could reach an electron density of 1.2 × 1019 m-3 and helium ion flux of 3.2 × 1022 m-2 s-1, with a gas flow rate of 4 standard liter per minute, magnetic field strength of 0.2 T and input power of 11 kW. With the addition of -80 V applied to the target to increase the helium ion energy and the exposure time of 2 h, the flat top temperature reached about 530 °C. The different sizes of nanostructured fuzz on irradiated tungsten and molybdenum samples surfaces under the bombardment of helium ions were observed by scanning electron microscopy. These results measured in the SCU-PSI linear device provide a reference for International Thermonuclear Experimental Reactor related PSI research.

Neutron flux enhancement in the NRAD reactor

International Nuclear Information System (INIS)

Weeks, A.A.; Heidel, C.C.; Imel, G.R.

1988-01-01

In 1987 a series of experiments were conducted at the NRAD reactor facility at Argonne National Laboratory - West (ANL-W) to investigate the possibility of increasing the thermal neutron content at the end of the reactor's east beam tube through the use of hydrogenous flux traps. It was desired to increase the thermal flux for a series of experiments to be performed in the east radiography cell, in which the enhanced flux was required in a relatively small volume. Hence, it was feasible to attempt to focus the cross section of the beam to a smaller area. Two flux traps were constructed from unborated polypropylene and tested to determine their effectiveness. Both traps were open to the entire cross-sectional area of the neutron beam (as it emerges from the wall and enters the beam room). The sides then converged such that at the end of the trap the beam would be 'focused' to a greater intensity. The differences in the two flux traps were primarily in length, and hence angle to the beam as the inlet and outlet cross-sectional areas were held constant. The experiments have contributed to the design of a flux trap in which a thermal flux of nearly 10 9 was obtained, with an enhancement of 6.61

Magnitudes and sources of precipitation and dry deposition fluxes of industrial and natural leads to the North Pacific at Enewetak

International Nuclear Information System (INIS)

Settle, D.M.; Patterson, C.C.

1982-01-01

A total atmospheric PB input flux of 7 ng Pb cm - 2 yr - 1 was measured in the North Pacific Easterlies at Enewetak. Parameters used to measure this flux were ratio of dry deposition flux to precipitation flux; Pb/ 210 Pb in precipitation and seawater; 210 Pb flux; washout factor; and Pb concentrations in air, rain, and dry deposition deposits. Relations among these parameters estabilished at Enewetak were used to recompute and comfirm previous estimates of lead fluxes to the oceans (ng Pb cm - 2 yr - 1 ) at the following locations: North Altantic Westerlies, 170; North Pacific Westerlies, 50; and South Pacific Easterlies, 3. Prehistoric lead output fluxes to sediments (ng Pb cm - 2 yr - 1 ) at these locations have been previously measured and were 4 (Enewetak); 30 North Atlantic Westerlies; 3 North Pacific Westerlies; 4 South Pacific Easterlies. These data show that the rates of atmospheric imputs of lead to the oceans vary directly with variations in rates of upwind emission of industrial lead from urban complexes on land. In the North Pacific and North Atlantic, present rates of atmospheric lead inputs are 10-fold greater than prehistoric outputs. In equatorial regions, present inputs and past outputs are more nearly equal. These observations disclose the effects of intense industrial atmospheric emissions of lead in the northern hemisphere westerlies which have overwhelmed prehistoric natural fluxes of lead to the oceans. The average concentration of lead in marine air at Enewetak is 170n pg m - 3 and varies less than a factor of 2 from that mean. One to 15% of this lead comes from seaspray, while the remainder comes from sources on land. About 90% of the seaspray lead is industrial, while 80 to 99% of that originating from land sources is industrial. Concentrations of lead in rain at Enewetak range from 6 to 63 pg/g with a mean value of 28

The role of metabolism in modulating CO2 fluxes in boreal lakes

Science.gov (United States)

Bogard, Matthew J.; del Giorgio, Paul A.

2016-10-01

Lake CO2 emissions are increasingly recognized as an important component of the global CO2 cycle, yet the origin of these emissions is not clear, as specific contributions from metabolism and in-lake cycling, versus external inputs, are not well defined. To assess the coupling of lake metabolism with CO2 concentrations and fluxes, we estimated steady state ratios of gross primary production to respiration (GPP:R) and rates of net ecosystem production (NEP = GPP-R) from surface water O2 dynamics (concentration and stable isotopes) in 187 boreal lakes spanning long environmental gradients. Our findings suggest that internal metabolism plays a dominant role in regulating CO2 fluxes in most lakes, but this pattern only emerges when examined at a resolution that accounts for the vastly differing relationships between lake metabolism and CO2 fluxes. Fluxes of CO2 exceeded those from NEP in over half the lakes, but unexpectedly, these effects were most common and typically largest in a subset ( 30% of total) of net autotrophic lakes that nevertheless emitted CO2. Equally surprising, we found no environmental characteristics that distinguished this category from the more common net heterotrophic, CO2 outgassing lakes. Excess CO2 fluxes relative to NEP were best predicted by catchment structure and hydrologic properties, and we infer from a combination of methods that both catchment inputs and internal anaerobic processes may have contributed this excess CO2. Together, our findings show that the link between lake metabolism and CO2 fluxes is often strong but can vary widely across the boreal biome, having important implications for catchment-wide C budgets.

Multi-flux-tube system in the dual Ginzburg-Landau theory

International Nuclear Information System (INIS)

Ichie, H.; Suganuma, H.; Toki, H.

1996-01-01

We study the multi-flux-tube system in terms of the dual Ginzburg-Landau theory. We consider two periodic cases, where the directions of all the flux tubes are the same in one case and alternating in the other case for neighboring flux tubes. We formulate the multi-flux-tube system by regarding it as the system of two flux tubes penetrating through a two-dimensional spherical surface. We find the multi-flux-tube configuration becomes uniform above some critical flux-tube number density ρ c =1.3 endash 1.7 fm -2 . On the other hand, the inhomogeneity of the color electric distribution appears when the flux-tube density is smaller than ρ c . We study the inhomogeneity on the color electric distribution in relation with the flux-tube number density, and discuss the quark-gluon plasma formation process in ultrarelativistic heavy-ion collisions. copyright 1996 The American Physical Society

Landscape analysis of soil methane flux across complex terrain

Science.gov (United States)

Kaiser, Kendra E.; McGlynn, Brian L.; Dore, John E.

2018-05-01

Relationships between methane (CH4) fluxes and environmental conditions have been extensively explored in saturated soils, while research has been less prevalent in aerated soils because of the relatively small magnitudes of CH4 fluxes that occur in dry soils. Our study builds on previous carbon cycle research at Tenderfoot Creek Experimental Forest, Montana, to identify how environmental conditions reflected by topographic metrics can be leveraged to estimate watershed scale CH4 fluxes from point scale measurements. Here, we measured soil CH4 concentrations and fluxes across a range of landscape positions (7 riparian, 25 upland), utilizing topographic and seasonal (29 May-12 September) gradients to examine the relationships between environmental variables, hydrologic dynamics, and CH4 emission and uptake. Riparian areas emitted small fluxes of CH4 throughout the study (median: 0.186 µg CH4-C m-2 h-1) and uplands increased in sink strength with dry-down of the watershed (median: -22.9 µg CH4-C m-2 h-1). Locations with volumetric water content (VWC) below 38 % were methane sinks, and uptake increased with decreasing VWC. Above 43 % VWC, net CH4 efflux occurred, and at intermediate VWC net fluxes were near zero. Riparian sites had near-neutral cumulative seasonal flux, and cumulative uptake of CH4 in the uplands was significantly related to topographic indices. These relationships were used to model the net seasonal CH4 flux of the upper Stringer Creek watershed (-1.75 kg CH4-C ha-1). This spatially distributed estimate was 111 % larger than that obtained by simply extrapolating the mean CH4 flux to the entire watershed area. Our results highlight the importance of quantifying the space-time variability of net CH4 fluxes as predicted by the frequency distribution of landscape positions when assessing watershed scale greenhouse gas balances.

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

Directory of Open Access Journals (Sweden)

J. D. Whitehead

2010-01-01

Full Text Available 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 (v_d[O₃]=0.302±0.095 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 (v_d[O₃]=1.00±0.10 mm s⁻¹ and daytime (v_d[O₃]=2.05±0.16 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

Relating landfill gas emissions to atmospheric pressure using numerical modeling and state-space analysis

DEFF Research Database (Denmark)

Poulsen, T.G.; Christophersen, Mette; Moldrup, P.

2003-01-01

were applied: (I) State-space analysis was used to identify relations between gas flux and short-term (hourly) variations in atmospheric pressure. (II) A numerical gas transport model was fitted to the data and used to quantify short-term impacts of variations in atmospheric pressure, volumetric soil......-water content, soil gas permeability, soil gas diffusion coefficients, and biological CH4 degradation rate upon landfill gas concentration and fluxes in the soil. Fluxes and concentrations were found to be most sensitive to variations in volumetric soil water content, atmospheric pressure variations and gas...... permeability whereas variations in CH4 oxidation rate and molecular coefficients had less influence. Fluxes appeared to be most sensitive to atmospheric pressure at intermediate distances from the landfill edge. Also overall CH4 fluxes out of the soil over longer periods (years) were largest during periods...

Non-stationary (13)C-metabolic flux ratio analysis.

Science.gov (United States)

Hörl, Manuel; Schnidder, Julian; Sauer, Uwe; Zamboni, Nicola

2013-12-01

(13)C-metabolic flux analysis ((13)C-MFA) has become a key method for metabolic engineering and systems biology. In the most common methodology, fluxes are calculated by global isotopomer balancing and iterative fitting to stationary (13)C-labeling data. This approach requires a closed carbon balance, long-lasting metabolic steady state, and the detection of (13)C-patterns in a large number of metabolites. These restrictions mostly reduced the application of (13)C-MFA to the central carbon metabolism of well-studied model organisms grown in minimal media with a single carbon source. Here we introduce non-stationary (13)C-metabolic flux ratio analysis as a novel method for (13)C-MFA to allow estimating local, relative fluxes from ultra-short (13)C-labeling experiments and without the need for global isotopomer balancing. The approach relies on the acquisition of non-stationary (13)C-labeling data exclusively for metabolites in the proximity of a node of converging fluxes and a local parameter estimation with a system of ordinary differential equations. We developed a generalized workflow that takes into account reaction types and the availability of mass spectrometric data on molecular ions or fragments for data processing, modeling, parameter and error estimation. We demonstrated the approach by analyzing three key nodes of converging fluxes in central metabolism of Bacillus subtilis. We obtained flux estimates that are in agreement with published results obtained from steady state experiments, but reduced the duration of the necessary (13)C-labeling experiment to less than a minute. These results show that our strategy enables to formally estimate relative pathway fluxes on extremely short time scale, neglecting cellular carbon balancing. Hence this approach paves the road to targeted (13)C-MFA in dynamic systems with multiple carbon sources and towards rich media. © 2013 Wiley Periodicals, Inc.

Ozone uptake (flux) as it relates to ozone-induced foliar symptoms of Prunus serotina and Populus maximowizii x trichocarpa

International Nuclear Information System (INIS)

Orendovici-Best, T.; Skelly, J.M.; Davis, D.D.; Ferdinand, J.A.; Savage, J.E.; Stevenson, R.E.

2008-01-01

Field studies were conducted during 2003 and 2004 from early June to the end of August, at 20 sites of lower or higher elevation within north-central Pennsylvania, using seedlings of black cherry (Prunus serotina, Ehrh.) and ramets of hybrid poplar (Populus maximowizii x trichocarpa). A linear model was developed to estimate the influence of local environmental conditions on stomatal conductance. The most significant factors explaining stomatal variance were tree species, air temperature, leaf vapor pressure deficit, elevation, and time of day. Overall, environmental factors explained less than 35% of the variation in stomatal conductance. Ozone did not affect gas exchange rates in either poplar or cherry. Ozone-induced foliar injury was positively correlated with cumulative ozone exposures, expressed as SUM40. Overall, the amount of foliar injury was better correlated to a flux-based approach rather than to an exposure-based approach. More severe foliar injuries were observed on plants growing at higher elevations. - Within heterogeneous environments, ozone flux does not completely explain the variation observed in ozone-induced visible injury

Seasonal and interannual variability in deep ocean particle fluxes at the Oceanic Flux Program (OFP)/Bermuda Atlantic Time Series (BATS) site in the western Sargasso Sea near Bermuda

Science.gov (United States)

Conte, Maureen H.; Ralph, Nate; Ross, Edith H.

consistent with a model of rapid particle turnover and material scavenging from the suspended pool during new particle formation. We suggest that much of the deep mass flux is generated in situ by deep-dwelling zooplankton, and that mass flux, as well as scavenging of suspended materials from the deep water column, varies in proportion to changes in grazer activity. Labile, very rapidly sinking aggregates (e.g., salp fecal material) arriving in the bathypelagic zone within days of their upper ocean production may act to stimulate zooplankton grazing rates and increase large particle production and deep mass flux days to weeks in advance of the arrival of bulk of surface-produced material. This process could reconcile mean particle sinking rate estimates with the phase coherence observed between upper and deep ocean mass fluxes.

a Borehole-Dilution Method for Quantifying Vertical Darcy Fluxes in the Hyporheic Zone

Science.gov (United States)

Augustine, S. D.; Annable, M. D.; Cho, J.

2017-12-01

The borehole dilution method has consistently and successfully been used for estimating local water fluxes, however, this method can be relatively labor intensive and expensive. The focus of this research is aimed at developing a low-cost, borehole dilution method for quantifying vertical water fluxes in the hyporheic zone at the surface-groundwater interface. This would allow for the deployment of multiple units within a targeted surface water body and thus produce high-resolution, spatially distributed data on the infiltration rates over a short period of time with minimal set-up requirements. The device consists of a 2-inch, inner diameter PVC pipe containing short, screened sections in its upper and lower segments. The working unit is driven into the sediment and acts as a continuous flow reactor creating a pathway between the subsurface pore-water and the overlying surface water where the presence of a hydraulic gradient facilitates vertical movement. We developed a simple electrode and tracer-injection system housed within the unit to inject and measure salt tracer concentrations at the desired intervals while monitoring and storing those measurements using open-source Arduino technology. Preliminary lab and field scale trials provided data that was fit to both zero and first order reaction rate functions for analysis. The field test was conducted over approximately one day within a wet retention basin. The initial results estimated a vertical Darcy flux of 113.5 cm/d. Additional testing over a range of expected Darcy fluxes will be presented along with an evaluation considering enhanced water flow due to the high hydraulic conductivity of the device.

Heat transfer for ultrahigh flux reactor

International Nuclear Information System (INIS)

Wadkins, R.P.; Lake, J.A.; Oh, C.H.

1987-01-01

The use of a uniquely designed nuclear reactor to supply neutrons for materials research is the focus of recent reactor design efforts. The biological, materials, and fundamental physics aspects of research require neutron fluxes much higher than present research and testing facilities can produce. The most advanced research using neutrons as probing detectors is being done in the High Flux Reactor at the Institut Laue Langeuin, France. The design of a reactor that can produce neutron fluxes of 1.0 x 10 16 n/cm 2 .s requires a relatively high power (300 MW range) and a small core volume (approximately 30 liters). This combination of power and volume leads to a high power density which places increased demands on thermal hydraulic margins

Historical deposition and fluxes of mercury in Narraguinnep Reservoir, southwestern Colorado, USA

International Nuclear Information System (INIS)

Gray, John E.; Fey, David L.; Holmes, Charles W.; Lasorsa, Brenda K.

2005-01-01

Narraguinnep Reservoir has been identified as containing fish with elevated Hg concentrations and has been posted with an advisory recommending against consumption of fish. There are presently no point sources of significant Hg contamination to this reservoir or its supply waters. To evaluate potential historical Hg sources and deposition of Hg to Narraguinnep Reservoir, the authors measured Hg concentrations in sediment cores collected from this reservoir. The cores were dated by the 137 Cs method and these dates were further refined by relating water supply basin hydrological records with core sedimentology. Rates of historical Hg flux were calculated (ng/cm 2 /a) based on the Hg concentrations in the cores, sediment bulk densities, and sedimentation rates. The flux of Hg found in Narraguinnep Reservoir increased by approximately a factor of 2 after about 1970. The 3 most likely sources of Hg to Narraguinnep Reservoir are surrounding bedrocks, upstream inactive Au-Ag mines, and several coal-fired electric power plants in the Four Corners region. Patterns of Hg flux do not support dominant Hg derivation from surrounding bedrocks or upstream mining sources. There are 14 coal-fired power plants within 320 km of Narraguinnep Reservoir that produce over 80 x 10 6 MWH of power and about 1640 kg-Hg/a are released through stack emissions, contributing significant Hg to the surrounding environment. Two of the largest power plants, located within 80 km of the reservoir, emit about 950 kg-Hg/a. Spatial and temporal patterns of Hg fluxes for sediment cores collected from Narraguinnep Reservoir suggest that the most likely source of Hg to this reservoir is from atmospheric emissions from the coal-fired electric power plants, the largest of which began operation in this region in the late-1960s and early 1970s

Fast neutron flux and intracranial dose distribution at a neutron irradiation facility

International Nuclear Information System (INIS)

Matsumoto, Tetsuo; Aizawa, Otohiko; Nozaki, Tetsuya

1981-01-01

A head phantom filled with water was used to measure the fast neutron flux using 115 In(n, n')sup(115m)In and 103 Rh(n, n')sup(103m)Rh reactions. γ-ray from sup(115m)In and x-ray from sup(103m)Rh were detected by a Ge(Li) and a Na(Tl)I counter, respectively. TLD was used to investigate the γ-dose rate distribution inside the phantom. Flux of fast neutron inside the phantom was about 1 x 10 6 n/cm 2 sec, which was 3 order smaller than that of thermal neutron. The fast neutron flux decreased to 1/10 at 15 cm depth, and γ-dose rate was about 200 R/h at 100 kW inside the phantom. Total dose at the surface was 350 rad/h, to which, fast neutrons contributed more than γ-rays. The rate of fast neutron dose was about 10% of thermal neutron's in Kerma dose unit (rad), however, the rate was highly dependent on RBE value. (Nakanishi, T.)

Neutron flux control systems validation

International Nuclear Information System (INIS)

Hascik, R.

2003-01-01

In nuclear installations main requirement is to obtain corresponding nuclear safety in all operation conditions. From the nuclear safety point of view is commissioning and start-up after reactor refuelling appropriate period for safety systems verification. In this paper, methodology, performance and results of neutron flux measurements systems validation is presented. Standard neutron flux measuring chains incorporated into the reactor protection and control system are used. Standard neutron flux measuring chain contains detector, preamplifier, wiring to data acquisition unit, data acquisition unit, wiring to display at control room and display at control room. During reactor outage only data acquisition unit and wiring and displaying at reactor control room is verified. It is impossible to verify detector, preamplifier and wiring to data acquisition recording unit during reactor refuelling according to low power. Adjustment and accurate functionality of these chains is confirmed by start-up rate (SUR) measurement during start-up tests after refuelling of the reactors. This measurement has direct impact to nuclear safety and increase operational nuclear safety level. Briefly description of each measuring system is given. Results are illustrated on measurements performed at Bohunice NPP during reactor start-up tests. Main failures and their elimination are described (Authors)

Radar meteor rates and solar activity

International Nuclear Information System (INIS)

Prikryl, P.

1983-01-01

The short-term variation of diurnal radar meteor rates with solar activity represented by solar microwave flux Fsub(10.7), and sunspots relative number Rsub(z), is investigated. Applying the superposed-epoch analysis to the observational material of radar meteor rates from Christchurch (1960-61 and 1963-65), a decrease in the recorded radar rates is found during days of enhanced solar activity. No effect of geomagnetic activity similar to the one reported for the Swedish and Canadian radar meteor data was found by the author in the Christchurch data. A possible explanation of the absence of the geomagnetic effect on radar meteor rates from New Zealand due to a lower echo ceiling height of the Christchurch radar is suggested. The variation of the atmospheric parameters as a possible cause of the observed variation in radar meteor rates is also discussed. (author)

Field experiment on 222Rn flux from reclaimed uranium tailings

International Nuclear Information System (INIS)

Hinton, T.G.

1983-01-01

Design and construction techniques are described for a 1.6 ha experimental uranium mill tailings reclamation plot. A passive, activated charcoal device was developed and tested for measurements of radon flux. Experiments on radon flux versus overburden depth showed that tailings covered with 1.5 m of revegetated or 0.3 m of bare overburden had exhalation rates comparable to background. Vegetated subplots exhibited a significantly higher (often an order of magnitude) flux than the bare subplots. Results on the variation of flux over time did not reveal any definitive patterns, possibly due to the high variability among replicates. A positive correlation was demonstrated between precipitation and radon flux. This is discussed in detail and possibly explained by the increase in water content of the micropores within the tailings, which increases the emanation coefficient without adversely effecting the diffusion coefficient of the overburden. 30 references, 7 figures, 3 tables

A platinum in-core flux detector

International Nuclear Information System (INIS)

Shields, R.B.

1976-01-01

The performance is described of a platinum emitter self-powered detector having the following parameters: emitter diameter 0.51 mm, Inconel 600 collector of 1.5 mm outer diameter and 0.25 mm wall thickness, compacted powder MgO insulant, thermal neutron flux 10 14 n.cm -2 .s -1 and gamma radiation dose rate 1.2 x 10 8 rad.h -1 . The advantage of the detector is its sensitivity to both neutrons and gamma radiation. A comparison is made with other types of detectors using Ce, Ta, Os, Rh, V, Co, Zr as emitters, especially in relation to the emitter response time to neutrons or gammas, the output signal amplitude, sensitivity, and the emitter half-life. Extensive tests of the detectors proceeded for two years on the NRU and CANDU-BLW reactors in Gentilly, Canada. (J.B.)

Observation of magnetic flux generated spontaneously during a rapid quench of superconducting films

International Nuclear Information System (INIS)

Maniv, A.; Polturak, E.; Koren, G.

2003-01-01

We report observations of spontaneous formation of magnetic flux lines during a rapid quench of YBa 2 Cu 3 O 7-δ films through T c . This effect is predicted according to the Kibble-Zurek mechanism of creation of topological defects of the order parameter during a symmetry-breaking phase transition. Our previous experiment, at a quench rate of 20 K/s, gave null results. In the present experiment, the quench rate was increased to >10 8 K/s. The amount of spontaneous flux increases weakly with the cooling rate

Enzyme mechanisms for pyruvate-to-lactate flux attenuation: a study of Sherpas, Quechuas, and hummingbirds.

Science.gov (United States)

Hochachka, P W; Stanley, C; McKenzie, D C; Villena, A; Monge, C

1992-10-01

During incremental exercise to fatigue under hypobaric hypoxia, Andean Quechua natives form and accumulate less plasma lactate than do lowlanders under similar conditions. This phenomenon of low lactate accumulation despite hypobaric hypoxia, first discovered some half century ago, is known in Quechuas to be largely unaffected by acute exposure to hypoxia or by acclimatization to sea level conditions. Earlier Nuclear Magnetic Resonance (NMR) spectroscopy and metabolic biochemistry studies suggest that closer coupling of energy demand and energy supply in Quechuas allows given changes in work rate with relatively modest changes in muscle adenylate and phosphagen concentrations, thus tempering the activation of glycolytic flux to pyruvate--a coarse control mechanism operating at the level of overall pathway flux. Later studies of enzyme activities in skeletal muscles of Quechuas and of Sherpas have identified a finely-tuned control mechanism which by adaptive modifications of a few key enzymes apparently serves to specifically attenuate pyruvate flux to lactate.

Design of a flux buffer based on the flux shuttle

International Nuclear Information System (INIS)

Gershenson, M.

1991-01-01

This paper discusses the design considerations for a flux buffer based on the flux-shuttle concept. Particular attention is given to the issues of flux popping, stability of operation and saturation levels for a large input. Modulation techniques used in order to minimize 1/f noise, in addition to offsets are also analyzed. Advantages over conventional approaches using a SQUID for a flux buffer are discussed. Results of computer simulations are presented

PC based system for absolute neutron flux-spectrum measurements. Final report for the period 1 April 1994 - 15 December 1997

International Nuclear Information System (INIS)

Dobrea, D.

1998-01-01

When measuring absolute neutron flux-spectra, thin detector foils are irradiated in a neutron field. The absolute activity of isotopes generated by activation or fission reactions (fission products) is then measured, using an efficiency calibrated high resolution gamma-ray spectroscopy system, and the absolute reaction rates for their production is determined. Finally the flux-spectrum is determined based upon the reaction rate values. A general method to obtain flux-spectra from the reaction rate is the unfolding method. The above process involves computations of photopeak area, reaction rate, flux perturbation corrections and flux-spectrum. The PC's are well suited for the data processing system outlined above. Using available interfaces, the PC's can be involved even in the data acquisition. Graphical facilities allow decision upon the data processing flow

Dryout-type critical heat flux in vertical upward annular flow: effects of entrainment rate, initial entrained fraction and diameter

Science.gov (United States)

Wu, Zan; Wadekar, Vishwas; Wang, Chenglong; Sunden, Bengt

2018-01-01

This study aims to reveal the effects of liquid entrainment, initial entrained fraction and tube diameter on liquid film dryout in vertical upward annular flow for flow boiling. Entrainment and deposition rates of droplets were included in mass conservation equations to estimate the local liquid film mass flux in annular flow, and the critical vapor quality at dryout conditions. Different entrainment rate correlations were evaluated using flow boiling data of water and organic liquids including n-pentane, iso-octane and R134a. Effect of the initial entrained fraction (IEF) at the churn-to-annular flow transition was also investigated. A transitional Boiling number was proposed to separate the IEF-sensitive region at high Boiling numbers and the IEF-insensitive region at low Boiling numbers. Besides, the diameter effect on dryout vapor quality was studied. The dryout vapor quality increases with decreasing tube diameter. It needs to be pointed out that the dryout characteristics of submillimeter channels might be different because of different mechanisms of dryout, i.e., drying of liquid film underneath long vapor slugs and flow boiling instabilities.

Microtopography and methane flux in boreal peatlands, northern Ontario, Canada

International Nuclear Information System (INIS)

Bubier, J.; Costello, A.; Moore, T.R.; Roulet, N.T.; Savage, K.

1993-01-01

Peatlands act as a major sink of carbon dioxide and a source of methane. Fluxes of methane were measured by a static chamber technique at hummock, hollow, and lawn microtopographic locations in 12 peatland sites near Cochrane, northern Ontario, from May to October 1991. Average fluxes (mg/m 2 /d) were 2.3 at hummocks, 44.4 at hollows, and 15.6 at lawns. Methane flux was negatively correlated with average water table position based on the 36 locations, with hummocks having a smaller flux than hollows or lawns, where the water table depth was <25 cm. Peat samples from a bog hummock and hollow failed to produce methane during anaerobic incubations in the laboratory; samples from a poor fen hollow produced <1.4 μg/g/d. The production decreased with depth but was greater than the rates observed during incubation of samples from an adjacent hummock. Rates of methane consumption during aerobic incubations ranged from 1 to 55 μg/g/d and were greatest in the surface layers and decreased with depth. Differences in methane emissions between hummocks and hollows appear to be controlled primarily by greater methane production rates in hollows compared with hummocks. Of secondary importance are the capacity of the peat profiles to consume methane during its transport to the peat surface and warmer temperatures at the water table beneath hollows compared with hummocks. 29 refs., 4 figs., 2 tabs

Polycrystalline semiconductor probes for monitoring the density distribution of an intense thermal neutron flux in nuclear reactors

International Nuclear Information System (INIS)

Graul, J.; Mueller, R.G.; Wagner, E.

1975-05-01

The applicability of semiconductor detectors for high thermal neutron flux densities is theoretically estimated and experimentally examined. For good thermal stability and low radiation capture rate silicon carbide is used as semiconductor material, produced in polycristalline layers to achieve high radiation resistance. The relations between crystallinity, photoelectric sensitivity and radiation resistance are shown. The radiation resistance of polycrystalline SiC-probes is approximately 100 times greater than that of conventional single crystal radiation detectors. For thermal neutron measurement they can be used in the flux range of approx. 10 10 13 (cm -2 sec -1 ) with operation times of 1.6 a >= tsub(b,max) >= 30 d, resp. (orig.) [de

Solar neutrino flux at keV energies

Science.gov (United States)

Vitagliano, Edoardo; Redondo, Javier; Raffelt, Georg

2017-12-01

We calculate the solar neutrino and antineutrino flux in the keV energy range. The dominant thermal source processes are photo production (γ e→ e νbar nu), bremsstrahlung (e+Ze→ Ze+e+νbar nu), plasmon decay (γ→νbar nu), and νbar nu emission in free-bound and bound-bound transitions of partially ionized elements heavier than hydrogen and helium. These latter processes dominate in the energy range of a few keV and thus carry information about the solar metallicity. To calculate their rate we use libraries of monochromatic photon radiative opacities in analogy to a previous calculation of solar axion emission. Our overall flux spectrum and many details differ significantly from previous works. While this low-energy flux is not measurable with present-day technology, it could become a significant background for future direct searches for keV-mass sterile neutrino dark matter.

Comparison of surface energy fluxes with satellite-derived surface energy flux estimates from a shrub-steppe

International Nuclear Information System (INIS)

Kirkham, R.R.

1993-12-01

This thesis relates the components of the surface energy balance (i.e., net radiation, sensible and latent heat flux densities, soil heat flow) to remotely sensed data for native vegetation in a semi-arid environment. Thematic mapper data from Landsat 4 and 5 were used to estimate net radiation, sensible heat flux (H), and vegetation amount. Several sources of ground truth were employed. They included soil water balance using the neutron thermalization method and weighing lysimeters, and the measurement of energy fluxes with the Bowen ratio energy balance (BREB) technique. Sensible and latent heat flux were measured at four sites on the U.S. Department of Energy's Hanford Site using a weighing lysimeter and/or BREB stations. The objective was to calibrate an aerodynamic transport equation that related H to radiant surface temperature. The transport equation was then used with Landsat thermal data to generate estimates of H and compare these estimates against H values obtained with BREB/lysimeters at the time of overflight. Landsat and surface meteorologic data were used to estimate the radiation budget terms at the surface. Landsat estimates of short-wave radiation reflected from the surface correlate well with reflected radiation measured using inverted Eppley pyranometers. Correlation of net radiation estimates determined from satellite data, pyranometer, air temperature, and vapor pressure compared to net radiometer values obtained at time of overflight were excellent for a single image, but decrease for multiple images. Soil heat flux, G T , is a major component of the energy balance in arid systems and G T generally decreases as vegetation cover increases. Normalized difference vegetation index (NDVI) values generated from Landsat thermatic mapper data were representative of field observations of the presence of green vegetation, but it was not possible to determine a single relationship between NDVI and G T for all sites

Assessing environmental impacts on stream water quality: the use of cumulative flux and cumulative flux difference approaches to deforestation of the Hafren Forest, mid-Wales

Directory of Open Access Journals (Sweden)

C. Neal

2002-01-01

Full Text Available A method for examining the impacts of disturbance on stream water quality based on paired catchment “controlâ€? and “responseâ€? water quality time series is described in relation to diagrams of cumulative flux and cumulative flux difference. The paper describes the equations used and illustrates the patterns expected for idealised flux changes followed by an application to stream water quality data for a spruce forested catchment, the Hore, subjected to clear fell. The water quality determinands examined are sodium, chloride, nitrate, calcium and acid neutralisation capacity. The anticipated effects of felling are shown in relation to reduction in mist capture and nitrate release with felling as well as to the influence of weathering and cation exchange mechanisms, but in a much clearer way than observed previously using other approaches. Keywords: Plynlimon, stream, Hore, acid neutralisation capacity, calcium, chloride, nitrate, sodium, cumulative flux, flux

Changed Relation between Solar 10.7-cm Radio Flux and some ...

Indian Academy of Sciences (India)

The time series of monthly average values of sunspot numbers SSN, 10.7 cm flux ... This radio emission comes from the higher part of the chromosphere and .... work elements on the solar surface on one hand and spots on the other hand ... size, their magnetic fields were less composite and characterized by the greater life-.

Partitioning sediment flux by provenance and tracing erosion patterns in Taiwan

Science.gov (United States)

Resentini, Alberto; Goren, Liran; Castelltort, Sébastien; Garzanti, Eduardo

2017-07-01

We critically evaluate the potential and limitations of an alternative way to calculate erosion rates based on petrographic and mineralogical fingerprints of fluvial sediments coupled with gauged sediment fluxes. Our approach allows us to apportion sediment loads to different lithological units, and consequently to discriminate erosion rates in different tectonic domains within each catchment. Our provenance data on modern Taiwanese sands indicate focused erosion in the Backbone Range and Tananao Complex of the retrowedge. Lower rates are inferred for the northern part of the island characterized by tectonic extension and for the western foothills in the prowedge. The principal factor of uncertainty affecting our estimates is the inevitably inaccurate evaluation of total sediment load, because only the suspended flux was measured. Another is the assumption that suspended load and bed load are derived from the same sources in fixed proportions. Additional errors are caused by the insufficiently precise definition of lithologically similar compositional end-members and by the temporal variability of sediment composition at the outlet of each catchment related to the spatial variability of erosional processes and triggering agents such as earthquakes, typhoons, and landslides. To evaluate the robustness of our findings, we applied a morphometric technique based on the stream-power model. The results obtained are broadly consistent, with local discrepancies ascribed to poorly constrained assumptions and choices of scaling parameters. Our local erosion estimates are consistent with GPS uplift rates measured on a decadal timescale and generally higher than basin-wide results inferred from cosmogenic-nuclide and thermochronology data.

Magnetic-flux pump

Science.gov (United States)

Hildebrandt, A. F.; Elleman, D. D.; Whitmore, F. C. (Inventor)

1966-01-01

A magnetic flux pump is described for increasing the intensity of a magnetic field by transferring flux from one location to the magnetic field. The device includes a pair of communicating cavities formed in a block of superconducting material, and a piston for displacing the trapped magnetic flux into the secondary cavity producing a field having an intense flux density.

Crystallization kinetics of Ga metallic nano-droplets under As flux

International Nuclear Information System (INIS)

Bietti, S; Somaschini, C; Sanguinetti, S

2013-01-01

We present an experimental investigation of the crystallization dynamics of Ga nano-droplets under As flux. The transformation of the metallic Ga contained in the droplets into a GaAs nano-island proceeds by increasing the size of a tiny ring of GaAs which is formed just after the Ga deposition at the rim of a droplet. The GaAs crystallization rate depends linearly on the liquid–solid interface area. The maximum growth rate is set by the As flux impinging on the droplet, thus showing an efficient As incorporation and transport despite the predicted low solubility of the As in metallic Ga at the crystallization temperatures. (paper)

Small-scale experimental study of vaporization flux of liquid nitrogen released on water.

Science.gov (United States)

Gopalaswami, Nirupama; Olewski, Tomasz; Véchot, Luc N; Mannan, M Sam

2015-10-30

A small-scale experimental study was conducted using liquid nitrogen to investigate the convective heat transfer behavior of cryogenic liquids released on water. The experiment was performed by spilling five different amounts of liquid nitrogen at different release rates and initial water temperatures. The vaporization mass fluxes of liquid nitrogen were determined directly from the mass loss measured during the experiment. A variation of initial vaporization fluxes and a subsequent shift in heat transfer mechanism were observed with changes in initial water temperature. The initial vaporization fluxes were directly dependent on the liquid nitrogen spill rate. The heat flux from water to liquid nitrogen determined from experimental data was validated with two theoretical correlations for convective boiling. It was also observed from validation with correlations that liquid nitrogen was found to be predominantly in the film boiling regime. The substantial results provide a suitable procedure for predicting the heat flux from water to cryogenic liquids that is required for source term modeling. Copyright © 2015 Elsevier B.V. All rights reserved.

Related Rates and the Speed of Light.

Science.gov (United States)

Althoen, S. C.; Weidner, J. F.

1985-01-01

Standard calculus textbooks often include a related rates problem involving light cast onto a straight line by a revolving light source. Mathematical aspects to these problems (both in the solution and in the method by which that solution is obtained) are examined. (JN)

Reduced TCA Flux in Diabetic Myotubes

DEFF Research Database (Denmark)

Gaster, Michael

2012-01-01

The diabetic phenotype is complex, requiring elucidation of key initiating defects. Diabetic myotubes express a primary reduced tricarboxylic acid (TCA) cycle flux but at present it is unclear in which part of the TCA cycle the defect is localised. In order to localise the defect we studied ATP p...... production of investigated substrate combinations was significantly reduced in mitochondria isolated from type 2 diabetic subjects compared to lean. However, when ATP synthesis rates at different substrate combinations were normalized to the corresponding individual pyruvate-malate rate...

Diffusion piecewise homogenization via flux discontinuity ratios

International Nuclear Information System (INIS)

Sanchez, Richard; Dante, Giorgio; Zmijarevic, Igor

2013-01-01

We analyze piecewise homogenization with flux-weighted cross sections and preservation of averaged currents at the boundary of the homogenized domain. Introduction of a set of flux discontinuity ratios (FDR) that preserve reference interface currents leads to preservation of averaged region reaction rates and fluxes. We consider the class of numerical discretizations with one degree of freedom per volume and per surface and prove that when the homogenization and computing meshes are equal there is a unique solution for the FDRs which exactly preserve interface currents. For diffusion sub-meshing we introduce a Jacobian-Free Newton-Krylov method and for all cases considered obtain an 'exact' numerical solution (eight digits for the interface currents). The homogenization is completed by extending the familiar full assembly homogenization via flux discontinuity factors to the sides of regions laying on the boundary of the piecewise homogenized domain. Finally, for the familiar nodal discretization we numerically find that the FDRs obtained with no sub-mesh (nearly at no cost) can be effectively used for whole-core diffusion calculations with sub-mesh. This is not the case, however, for cell-centered finite differences. (authors)

The Role of Energy Flux in Weight Management

Directory of Open Access Journals (Sweden)

Clemens Drenowatz

2017-12-01

Full Text Available Excess body weight has been identified as one of the leading threats to public health. In addition to health concerns at the individual level, the increased medical costs put a significant burden on the health care system. Even though an imbalance between energy intake and energy expenditure is ultimately responsible for changes in body weight and body composition such a simple opposition does not reflect the complex interaction of various contributors to energy balance. The limited understanding of the regulation of energy balance is also reflected by rising obesity levels, despite considerable efforts. In addition to energy balance, energy flux, which represents the rate of energy intake and energy expenditure, has been suggested to play an important role in the regulation of energy balance. Particularly a higher energy flux has been associated with a better matching of energy intake and energy expenditure resulting in stable body weight. While a high energy flux has been traditionally attributed to increased levels of physical activity it should be considered that increased body weight also affects energy expenditure and accordingly energy flux. In fact, total daily energy expenditure, and accordingly energy flux, does not differ between people in industrialized countries, living a predominantly sedentary lifestyle and people following a traditional lifestyle, characterized by high physical activity even though there are significant differences in body weight and body composition. It can, therefore, be argued that energy flux, rather than energy balance is a physiologically regulated entity. In this situation body weight and physical activity levels work in opposition to maintain a constant energy flux and weight gain would be a means to maintain a high energy flux with a sedentary lifestyle.

Inverse Flux versus Pressure of Muons from Cosmic Rays

Science.gov (United States)

Buitrago, D.; Armendariz, R.

2017-12-01

When an incoming cosmic ray proton or atom collides with particles in earth's atmosphere a shower of secondary muons is created. Cosmic ray muon flux was measured at the Queensborough Community College using a QuarkNet detector consisting of three stacked scintillator muon counters and a three-fold coincidence trigger. Data was recorded during a three-day period during a severe weather storm that occurred from March 13-17, 2017. A computer program was created in Python to read the muon flux rate and atmospheric pressure sensor readings from the detector's data acquisition board. The program converts the data from hexadecimal to decimal, re-bins the data in a more suitable format, creates and overlays plots of muon flux with atmospheric pressure. Results thus far show a strong correlation between muon flux and atmospheric pressure. More data analysis will be done to verify the above conclusion.

Neutron flux and annealing effects on irradiation hardening of RPV materials

Science.gov (United States)

Chaouadi, R.; Gérard, R.

2011-11-01

This paper aims to examine an eventual effect of neutron flux, sometimes referred to as dose rate effect, on irradiation hardening of a typical A533B reactor pressure vessel steel. Tensile tests on both low flux (reactor surveillance data) and high flux (BR2 reactor) were performed in a large fluence range. The obtained results indicate two features. First, the surveillance data exhibit a constant (˜90 MPa) higher yield strength than the high flux data. However, this difference cannot be explained from a flux effect but most probably from differences in the initial tensile properties. The hardening kinetic of both low and high flux is the same. Annealing at low temperature, 345 °C/40 h, to eventually reveal unstable matrix damage did not affect both BR2 and surveillance specimens. This is confirmed by other annealing experimental data including both tensile and hardness measurements and tensile data on A508 forging and weld. It is suggested that the absence of flux effect on the tensile properties while different radiation-induced microstructures can be attributed to thermal ageing effects.

The relation between reconnected flux, the parallel electric field, and the reconnection rate in a three-dimensional kinetic simulation of magnetic reconnection

International Nuclear Information System (INIS)

Wendel, D. E.; Olson, D. K.; Hesse, M.; Kuznetsova, M.; Adrian, M. L.; Aunai, N.; Karimabadi, H.; Daughton, W.

2013-01-01

We investigate the distribution of parallel electric fields and their relationship to the location and rate of magnetic reconnection in a large particle-in-cell simulation of 3D turbulent magnetic reconnection with open boundary conditions. The simulation's guide field geometry inhibits the formation of simple topological features such as null points. Therefore, we derive the location of potential changes in magnetic connectivity by finding the field lines that experience a large relative change between their endpoints, i.e., the quasi-separatrix layer. We find a good correspondence between the locus of changes in magnetic connectivity or the quasi-separatrix layer and the map of large gradients in the integrated parallel electric field (or quasi-potential). Furthermore, we investigate the distribution of the parallel electric field along the reconnecting field lines. We find the reconnection rate is controlled by only the low-amplitude, zeroth and first–order trends in the parallel electric field while the contribution from fluctuations of the parallel electric field, such as electron holes, is negligible. The results impact the determination of reconnection sites and reconnection rates in models and in situ spacecraft observations of 3D turbulent reconnection. It is difficult through direct observation to isolate the loci of the reconnection parallel electric field amidst the large amplitude fluctuations. However, we demonstrate that a positive slope of the running sum of the parallel electric field along the field line as a function of field line length indicates where reconnection is occurring along the field line

The Maximum Flux of Star-Forming Galaxies

Science.gov (United States)

Crocker, Roland M.; Krumholz, Mark R.; Thompson, Todd A.; Clutterbuck, Julie

2018-04-01

The importance of radiation pressure feedback in galaxy formation has been extensively debated over the last decade. The regime of greatest uncertainty is in the most actively star-forming galaxies, where large dust columns can potentially produce a dust-reprocessed infrared radiation field with enough pressure to drive turbulence or eject material. Here we derive the conditions under which a self-gravitating, mixed gas-star disc can remain hydrostatic despite trapped radiation pressure. Consistently taking into account the self-gravity of the medium, the star- and dust-to-gas ratios, and the effects of turbulent motions not driven by radiation, we show that galaxies can achieve a maximum Eddington-limited star formation rate per unit area \\dot{Σ }_*,crit ˜ 10^3 M_{⊙} pc-2 Myr-1, corresponding to a critical flux of F*, crit ˜ 1013L⊙ kpc-2 similar to previous estimates; higher fluxes eject mass in bulk, halting further star formation. Conversely, we show that in galaxies below this limit, our one-dimensional models imply simple vertical hydrostatic equilibrium and that radiation pressure is ineffective at driving turbulence or ejecting matter. Because the vast majority of star-forming galaxies lie below the maximum limit for typical dust-to-gas ratios, we conclude that infrared radiation pressure is likely unimportant for all but the most extreme systems on galaxy-wide scales. Thus, while radiation pressure does not explain the Kennicutt-Schmidt relation, it does impose an upper truncation on it. Our predicted truncation is in good agreement with the highest observed gas and star formation rate surface densities found both locally and at high redshift.

Modelling radiocesium fluxes in forest ecosystems

International Nuclear Information System (INIS)

Shaw, G.; Kliashtorin, A.; Mamikhin, S.; Shcheglov, A.; Rafferty, B.; Dvornik, A.; Zhuchenko, T.; Kuchma, N.

1996-01-01

Monitoring of radiocesium inventories and fluxes has been carried out in forest ecosystems in Ukraine, Belarus and Ireland to determine distributions and rates of migration. This information has been used to construct and calibrate mathematical models which are being used to predict the likely longevity of contamination of forests and forest products such as timber following the Chernobyl accident

OpenFLUX: efficient modelling software for 13C-based metabolic flux analysis

Directory of Open Access Journals (Sweden)

Nielsen Lars K

2009-05-01

Full Text Available Abstract Background The quantitative analysis of metabolic fluxes, i.e., in vivo activities of intracellular enzymes and pathways, provides key information on biological systems in systems biology and metabolic engineering. It is based on a comprehensive approach combining (i tracer cultivation on 13C substrates, (ii 13C labelling analysis by mass spectrometry and (iii mathematical modelling for experimental design, data processing, flux calculation and statistics. Whereas the cultivation and the analytical part is fairly advanced, a lack of appropriate modelling software solutions for all modelling aspects in flux studies is limiting the application of metabolic flux analysis. Results We have developed OpenFLUX as a user friendly, yet flexible software application for small and large scale 13C metabolic flux analysis. The application is based on the new Elementary Metabolite Unit (EMU framework, significantly enhancing computation speed for flux calculation. From simple notation of metabolic reaction networks defined in a spreadsheet, the OpenFLUX parser automatically generates MATLAB-readable metabolite and isotopomer balances, thus strongly facilitating model creation. The model can be used to perform experimental design, parameter estimation and sensitivity analysis either using the built-in gradient-based search or Monte Carlo algorithms or in user-defined algorithms. Exemplified for a microbial flux study with 71 reactions, 8 free flux parameters and mass isotopomer distribution of 10 metabolites, OpenFLUX allowed to automatically compile the EMU-based model from an Excel file containing metabolic reactions and carbon transfer mechanisms, showing it's user-friendliness. It reliably reproduced the published data and optimum flux distributions for the network under study were found quickly ( Conclusion We have developed a fast, accurate application to perform steady-state 13C metabolic flux analysis. OpenFLUX will strongly facilitate and

Communication: On the calculation of time-dependent electron flux within the Born-Oppenheimer approximation: A flux-flux reflection principle

Science.gov (United States)

Albert, Julian; Hader, Kilian; Engel, Volker

2017-12-01

It is commonly assumed that the time-dependent electron flux calculated within the Born-Oppenheimer (BO) approximation vanishes. This is not necessarily true if the flux is directly determined from the continuity equation obeyed by the electron density. This finding is illustrated for a one-dimensional model of coupled electronic-nuclear dynamics. There, the BO flux is in perfect agreement with the one calculated from a solution of the time-dependent Schrödinger equation for the coupled motion. A reflection principle is derived where the nuclear BO flux is mapped onto the electronic flux.

The independence of irradiation creep in austenitic alloys of displacement rate and helium to dpa ratio

Energy Technology Data Exchange (ETDEWEB)

Garner, F.A.; Toloczko, M.B. [Pacific Northwest National Lab., Richland, WA (United States); Grossbeck, M.L. [Oak Ridge National Lab., TN (United States)

1997-04-01

The majority of high fluence data on the void swelling and irradiation creep of austenitic steels were generated at relatively high displacement rates and relatively low helium/dpa levels that are not characteristic of the conditions anticipated in ITER and other anticipated fusion environments. After reanalyzing the available data, this paper shows that irradiation creep is not directly sensitive to either the helium/dpa ratio or the displacement rate, other than through their possible influence on void swelling, since one component of the irradiation creep rate varies with no correlation to the instantaneous swelling rate. Until recently, however, the non-swelling-related creep component was also thought to exhibit its own strong dependence on displacement rate, increasing at lower fluxes. This perception originally arose from the work of Lewthwaite and Mosedale at temperatures in the 270-350{degrees}C range. More recently this perception was thought to extend to higher irradiation temperatures. It now appears, however, that this interpretation is incorrect, and in fact the steady-state value of the non-swelling component of irradiation creep is actually insensitive to displacement rate. The perceived flux dependence appears to arise from a failure to properly interpret the impact of the transient regime of irradiation creep.

Existence of a time-dependent heat flux-related ponderomotive effect

International Nuclear Information System (INIS)

Schamel, H.; Sack, C.

1980-01-01

The existence of a new ponderomotive effect associated with high-frequency waves is pointed out. It originates when time-dependency, mean velocities, or divergent heat fluxes are involved and it supplements the two effects known previously, namely, the ponderomotive force and fake heating. Two proofs are presented; the first is obtained by establishing the momentum equations generalized by including radiation effects and the second by solving the quasi-linear-type diffusion equation explicitly. For a time-dependent wave packet the solution exhibits a new contribution in terms of an integral over previous states. Owing to this term, the plasma has a memory which leads to a breaking of the time symmetry of the plasma response. The range, influenced by the localized wave packet, expands during the course of time due to streamers emanating from the wave active region. Perturbations, among which is the heat flux, are carried to remote positions and, consequently, the region accessible to wave heating is increased. The density dip appears to be less pronounced at the center, and its generation and decay are delayed. The analysis includes a self-consistent action of high-frequency waves as well as the case of traveling wave packets. In order to establish the existence of this new effect, the analytical results are compared with recent microwave experiments. The possibility of generating fast particles by this new ponderomotive effect is emphasized

Neutron flux response to regulating rod random vibrations

International Nuclear Information System (INIS)

Dach, K.; Nemec, J.; Pecinka, L.

The relation is presented for the mean square value of the deflection of the rod for the n-th vibration shape on an arbitrary site. The relation may serve the obtaining of a variable which may be used both in a mechanical, i.e., stress analysis and in the determination of neutron flux fluctuations. It is demonstrated that the vibration frequency introduced in the reactor by the regulating rod has the same response in the neutron flux. This effect was used in the localization of an enormously vibrating regulating rod. (J.P.)

Kinetically limited weathering at low denudation rates in semiarid climatic conditions

Science.gov (United States)

Schoonejans, Jérôme; Vanacker, Veerle; Opfergelt, Sophie; Ameijeiras-Mariño, Yolanda; Christl, Marcus

2016-02-01

Biogeochemical cycling within the Critical Zone depends on the interactions between minerals and fluids controlling chemical weathering and physical erosion rates. In this study, we explore the role of water availability in controlling soil chemical weathering in semiarid climatic conditions. Weathering rates and intensities were evaluated for nine soil profiles located on convex ridge crests of three mountain ranges in the Spanish Betic Cordillera. We combine a geochemical mass balance with 10Be cosmogenic nuclides to constrain chemical weathering intensities and long-term denudation rates. As such, this study presents new data on chemical weathering and 10Be-derived denudation for understudied semiarid climate systems. In the Betic Cordillera, chemical weathering intensities are relatively low (~5 to 30% of the total denudation of the soil) and negatively correlated with the magnitude of the water deficit in soils. Chemical mass losses are inversely related to denudation rates (14-109 mm/kyr) and positively to soil thickness (14-58 cm); these results are consistent with kinetic limitation of chemical weathering rates. A worldwide compilation of chemical weathering data suggests that soil water balance may regulate the coupling between chemical weathering and physical erosion by modulating soil solute fluxes. Therefore, future landscape evolution models that seek to link chemical weathering and physical erosion should include soil water flux as an essential driver of weathering.

Regulation of flux through metabolic cycles

International Nuclear Information System (INIS)

Walsh, K.

1984-01-01

The branchpoint of the tricarboxylic acid and glyoxylate shunt was characterized in the intact organism by a multidimensional approach. Theory and methodology were developed to determine velocities for the net flow of carbon through the major steps of acetate metabolism in E. coli. Rates were assigned based on the 13 C-NMR spectrum of intracellular glutamate, measured rates of substrate incorporation into end products, the constituent composition of E. coli and a series of conservation equations which described the system at steady state. The in vivo fluxes through the branchpoint of the tricarboxylic acid and glyoxylate cycles were compared to rates calculated from the kinetic constants of the branchpoint enzymes and the intracellular concentrations of their substrates. These studies elucidated the role of isocitrate dehydrogenase phosphorylation in the Krebs cycle and led to the development of a generalized mathematical description of the sensitivity of branchpoints to regulatory control. This theoretical analysis was termed the branchpoint effect and it describes conditions which result in large changes in the flux through an enzyme even though that enzyme is not subject to direct regulatory control. The theoretical and experimental characterization of this system provided a framework to study the effects of enzyme overproduction and underproduction on metabolic processes in the cell. An in vivo method was developed to determine the extent to which an enzyme catalyzes a rate-controlling reaction. The enzyme chosen for this study was citrate synthase

Evaluation on transmutation performance of minor actinides with high-flux BWR

International Nuclear Information System (INIS)

Setiawan, M.B.; Kitamoto, A.; Taniguchi, A.

2001-01-01

The performance of high-flux BWR (HFBWR) for burning and/or transmutation (B/T) treatment of minor actinides (MA) and long-lived fission products (LLFP) was discussed herein for estimating an advanced waste disposal with partitioning and transmutation (P and T). The concept of high-flux B/T reactor was based on a current 33 GWt-BWR, to transmute the mass of long-lived transuranium (TRU) to short-lived fission products (SLFP). The nuclide selected for B/T treatment was MA (Np-237, Am-241, and Am-243) included in the discharged fuel of LWR. The performance of B/T treatment of MA was evaluated by a new function, i.e. [F/T ratio], defined by the ratio of the fission rate to the transmutation rate in the core, at an arbitrary burn-up, due to all MA nuclides. According to the results, HFBWR could burn and/or transmute MA nuclides with higher fission rate than BWR, but the fission rate did not increase proportionally to the flux increment, due to the higher rate of neutron adsorption. The higher B/T fraction of MA would result in the higher B/T capacity, and will reduce the units of HFBWR needed for the treatment of a constant mass of MA. In addition, HFBWR had a merit of higher mass transmutation compared to the reference BWR, under the same mass loading of MA

GEM-CEDAR Challenge: Poynting Flux at DMSP and Modeled Joule Heat

Science.gov (United States)

Rastaetter, Lutz; Shim, Ja Soon; Kuznetsova, Maria M.; Kilcommons, Liam M.; Knipp, Delores J.; Codrescu, Mihail; Fuller-Rowell, Tim; Emery, Barbara; Weimer, Daniel R.; Cosgrove, Russell;

Experimental Study on Hot Metal Desulfurization Using Sintered Red Mud-Based Flux

Science.gov (United States)

Li, Fengshan; Zhang, Yanling; Guo, Zhancheng

2017-09-01

This research presents the results of laboratory and pilot-scale tests conducted on the use of sintered red mud (RM)-based flux in the hot metal desulfurization (HMD) process. Al2O3/Na2O in RM can decrease the melting point of lime-based slag and can work as a flux in the HMD process. Good slag fluidity was observed throughout the process, and high desulfurization rates ( 80%) with a low final S content (pilot-scale test results indicated that a desulfurization rate as high as 91% and a S content <0.0099% could be acquired when RM:lime = 1:1, verifying the feasibility of using sintered RM-based flux in HMD. The data obtained provide important information for promoting the large-scale application of sintered RM in steelmaking.

Multidimensional flux-limited advection schemes

International Nuclear Information System (INIS)

Thuburn, J.

1996-01-01

A general method for building multidimensional shape preserving advection schemes using flux limiters is presented. The method works for advected passive scalars in either compressible or incompressible flow and on arbitrary grids. With a minor modification it can be applied to the equation for fluid density. Schemes using the simplest form of the flux limiter can cause distortion of the advected profile, particularly sideways spreading, depending on the orientation of the flow relative to the grid. This is partly because the simple limiter is too restrictive. However, some straightforward refinements lead to a shape-preserving scheme that gives satisfactory results, with negligible grid-flow angle-dependent distortion

A simple model of the distant Jovian tail with magnetic flux loss

International Nuclear Information System (INIS)

Grzedzielski, S.; Macek, W.; Oberc, P.

1982-01-01

The influence of a small rate of magnetic flux loss on a simple hydromagnetic model of the distant Jovian tail was estimated. The loss of flux leads to a 10-15% decrease of the tail radius at Saturn's distance. Possible encounter of the tail with Uranus in 1983 is also briefly discussed. (author)

Boosted Fast Flux Loop Alternative Cooling Assessment

Energy Technology Data Exchange (ETDEWEB)

Glen R. Longhurst; Donna Post Guillen; James R. Parry; Douglas L. Porter; Bruce W. Wallace

2007-08-01

The Gas Test Loop (GTL) Project was instituted to develop the means for conducting fast neutron irradiation tests in a domestic radiation facility. It made use of booster fuel to achieve the high neutron flux, a hafnium thermal neutron absorber to attain the high fast-to-thermal flux ratio, a mixed gas temperature control system for maintaining experiment temperatures, and a compressed gas cooling system to remove heat from the experiment capsules and the hafnium thermal neutron absorber. This GTL system was determined to provide a fast (E > 0.1 MeV) flux greater than 1.0E+15 n/cm2-s with a fast-to-thermal flux ratio in the vicinity of 40. However, the estimated system acquisition cost from earlier studies was deemed to be high. That cost was strongly influenced by the compressed gas cooling system for experiment heat removal. Designers were challenged to find a less expensive way to achieve the required cooling. This report documents the results of the investigation leading to an alternatively cooled configuration, referred to now as the Boosted Fast Flux Loop (BFFL). This configuration relies on a composite material comprised of hafnium aluminide (Al3Hf) in an aluminum matrix to transfer heat from the experiment to pressurized water cooling channels while at the same time providing absorption of thermal neutrons. Investigations into the performance this configuration might achieve showed that it should perform at least as well as its gas-cooled predecessor. Physics calculations indicated that the fast neutron flux averaged over the central 40 cm (16 inches) relative to ATR core mid-plane in irradiation spaces would be about 1.04E+15 n/cm2-s. The fast-to-thermal flux ratio would be in excess of 40. Further, the particular configuration of cooling channels was relatively unimportant compared with the total amount of water in the apparatus in determining performance. Thermal analyses conducted on a candidate configuration showed the design of the water coolant and

Cosmic muon flux measurements at the Kimballton Underground Research Facility

International Nuclear Information System (INIS)

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

2014-01-01

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

Determination of the atmospheric neutrino fluxes from atmospheric neutrino data

International Nuclear Information System (INIS)

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

2006-06-01

The 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 data analysis, these fluxes are theoretical inputs obtained from sophisticated numerical calculations based on the convolution of the primary cosmic ray spectrum with the expected yield of neutrinos per incident cosmic ray. In this work 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 for faithful error estimation. (author)

Determination of the atmospheric neutrino fluxes from atmospheric neutrino data

International Nuclear Information System (INIS)

Gonzalez-Garcia, Concepcion; Maltoni, Michele; Rojo, Joan

2006-01-01

The 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 data analysis, these fluxes are theoretical inputs obtained from sophisticated numerical calculations based on the convolution of the primary cosmic ray spectrum with the expected yield of neutrinos per incident cosmic ray. In this work 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 for faithful error estimation

Comparison of sap flux, moisture flux tower and MODIS enhanced vegetation index methods for estimating riparian evapotranspiration

Science.gov (United States)

Nagler, Pamela L.; Glenn, Edward P.; Morino, Kiyomi; Neale, Christopher M.U; Cosh, Michael H.

2010-01-01

Riparian evapotranspiration (ET) was measured on a salt cedar (Tamarix spp.) dominated river terrace on the Lower Colorado River from 2007 to 2009 using tissue-heat-balance sap flux sensors at six sites representing very dense, medium dense, and sparse stands of plants. Salt cedar ET varied markedly across sites, and sap flux sensors showed that plants were subject to various degrees of stress, detected as mid-day depression of transpiration and stomatal conductance. Sap flux results were scaled from the leaf level of measurement to the stand level by measuring plant-specific leaf area index and fractional ground cover at each site. Results were compared to Bowen ratio moisture tower data available for three of the sites. Sap flux sensors and flux tower results ranked the sites the same and had similar estimates of ET. A regression equation, relating measured ET of salt cedar and other riparian plants and crops on the Lower Colorado River to the Enhanced Vegetation Index from the MODIS sensor on the Terra satellite and reference crop ET measured at meteorological stations, was able to predict actual ET with an accuracy or uncertainty of about 20%, despite between-site differences for salt cedar. Peak summer salt cedar ET averaged about 6 mm d-1 across sites and methods of measurement.

Magnetic flux creep in HTSC and Anderson-Kim theory

International Nuclear Information System (INIS)

Lykov, A.N.

2014-01-01

The theoretical and experimental data on flux creep in high-temperature superconductors (HTSC) were analyzed in the review paper. On the one hand, the main attention is paid to the most striking experimental results which have had a significant influence on the investigations of flux creep in HTSC. On the other hand, the analysis of theoretical studies is concentrated on the works, which explain the features of flux creep on the basis of the Anderson-Kim (AK) theory modifications, and received previously unsufficient attention. However, it turned out that the modified AK theory could explain a lot of features of flux creep in HTSC: the scaling behaviour of current-voltage curves of HTSC, the finite rate of flux creep at ultra low temperatures, the logarithmic dependence of effective pinning potential as a function of transport current and its decrease with temperature. The harmonic potential field which is used in this approach makes it possible to solve accurately the both problems: viscous vortex motion and flux creep in this field. Moreover the distribution of pinning potential and the interaction of vortices with each other are taken into account in the approach. Thus, the modification of the AK theory consists, essentially, in its detailed elaboration and approaching to real situations in superconductors

Burnout heat flux in natural flow boiling

International Nuclear Information System (INIS)

Helal, M.M.; Darwish, M.A.; Mahmoud, S.I.

1978-01-01

Twenty runs of experiments were conducted to determine the critical heat flux for natural flow boiling with water flowing upwards through annuli of centrally heated stainless steel tube. The test section has concentric heated tube of 14mm diameter and heated lengthes of 15 and 25 cm. The outside surface of the annulus was formed by various glass tubes of 17.25, 20 and 25.9mm diameter. System pressure is atmospheric. Inlet subcooling varied from 18 to 5 0 C. Obtained critical heat flux varied from 24.46 to 62.9 watts/cm 2 . A number of parameters having dominant influence on the critical heat flux and hydrodynamic instability (flow and pressure oscillations) preceeding the burnout have been studied. These parameters are mass flow rate, mass velocity, throttling, channel geometry (diameters ratio, length to diameter ratio, and test section length), and inlet subcooling. Flow regimes before and at the moments of burnout were observed, discussed, and compared with the existing physical model of burnout

On the increase and decay of the electron fluxes at GEO

Science.gov (United States)

Boynton, R.; Balikhin, M. A.; Alipudin, R.; Chiu, C.; Aryan, H.

2013-12-01

The population of electrons in the Earth's outer radiation belt increases when the magnetosphere is exposed to high speed streams of solar wind. After this increase, the number of electrons decays back to approximately the initial population. This study statistically analyses the increase and decay of the electron fluxes at GEO. For the increase in electrons, the IMF and velocity of the corotating interaction regions is compared to the rate and magnitude of the increase, to determine how the IMF influences the electron population at GEO. The decay rate of the electron fluxes are calculated for 14 energies ranging from 24 keV to 3.5 MeV to identify a relationship between the decay rate and energy of the electrons.

The Effect of the Heat Flux on the Self-Ignition of Oriented Strand Board

Science.gov (United States)

Hirle, Siegfried; Balog, Karol

2017-06-01

This article deals with the initiation phase of flaming and smouldering burning of oriented strand board. The influence of heat flux on thermal degradation of OSB boards, time to ignition, heat release rate and mass loss rate using thermal analysis and vertical electrical radiation panel methods were studied. Significant information on the influence of the heat flux density and the thickness of the material on time to ignition was obtained.

IAEA coordinated research project (CRP). The use of selected safety indicators (concentrations, fluxes) in the assessment of radioactive waste disposal. Report 5: Chemical weathering rates on the Baltic Shield of Finland for use as indicators of nuclear waste repository safety

International Nuclear Information System (INIS)

Tarvainen, T.; Backman, B.; Hatakka, T.; Savolainen, H.; Hellmuth, K.-H.

2003-01-01

In this report the available information from the literature on chemical erosion and weathering rates in Finland and northern Sweden is reviewed and experimental data from recent followup studies in defined catchments is discussed. In glaciated terrain as in Finland the best estimates of chemical erosion rates are obtained when geochemical data of glacial till is used. Elemental fluxes in free-flowing rivers and river-lake systems have been studied in greater detail only in a few case studies. The Kalix river drainage basin investigations gave evidence that the mobilization of rare earth elements (REE) is determined by weathering processes in the upper till layers and that the C-horizon below about 0.75 m depth or generally below the groundwater table is practically unaffected by weathering. Also the removal of U from the watershed was found to happen mostly by groundwater flow through predominantly shallow aquifers. Another type of case study is constrained to regions where certain phenomena cause enhanced trace metal mobilization, as in a region stretched along the western coast of Finland where land-uplift exposes clay sediments rich in sulphides above the groundwater level, with the consequence of increased mobilization of a number of heavy metals. Very little quantitative information on elemental flux balances is available from river-lake systems. Some modelling has been attempted on one great lake system the lake Paeijaenne by use of fall-out nuclides. From the same lake a detailed record of sedimentation rates covering the whole period from the end of the latest glaciation to present is available and erosion rate variations since the end of the latest glaciation can be assessed. The main part of this study focusses on investigations of well-defined small catchments over a longer time period, where groundwater is discharging in springs. Geochemical fluxes worth mentioning seem to be constrained to the surficial geological layers which include overburden and

Comparison of WindTrax and flux-gradient technique in determining PM10 emission rates from a beef cattle feedlot

Science.gov (United States)

Several emission estimation methods can be used to determine emission fluxes from ground-level area sources, including open-lot beef cattle feedlots. This research determined PM10 emission fluxes from a commercial cattle feedlot in Kansas using WindTrax, a backward Lagrangian stochastic-based atmosp...

Fluxes in F-theory compactifications on genus-one fibrations

Energy Technology Data Exchange (ETDEWEB)

Lin, Ling [Institut für Theoretische Physik, Ruprecht-Karls-Universität,Philosophenweg 19, 69120 Heidelberg (Germany); Mayrhofer, Christoph [Arnold-Sommerfeld-Center, Ludwig-Maximilians-Universität,Theresienstraße 37, 80333 München (Germany); Till, Oskar; Weigand, Timo [Institut für Theoretische Physik, Ruprecht-Karls-Universität,Philosophenweg 19, 69120 Heidelberg (Germany)

2016-01-18

We initiate the construction of gauge fluxes in F-theory compactifications on genus-one fibrations which only have a multi-section as opposed to a section. F-theory on such spaces gives rise to discrete gauge symmetries in the effective action. We generalize the transversality conditions on gauge fluxes known for elliptic fibrations by taking into account the properties of the available multi-section. We test these general conditions by constructing all vertical gauge fluxes in a bisection model with gauge group SU(5)×ℤ{sub 2}. The non-abelian anomalies are shown to vanish. These flux solutions are dynamically related to fluxes on a fibration with gauge group SU(5)×U(1) by a conifold transition. Considerations of flux quantization reveal an arithmetic constraint on certain intersection numbers on the base which must necessarily be satisfied in a smooth geometry. Combined with the proposed transversality conditions on the fluxes these conditions are shown to imply cancellation of the discrete ℤ{sub 2} gauge anomalies as required by general consistency considerations.

Fluxes in F-theory compactifications on genus-one fibrations

International Nuclear Information System (INIS)

Lin, Ling; Mayrhofer, Christoph; Till, Oskar; Weigand, Timo

2016-01-01

We initiate the construction of gauge fluxes in F-theory compactifications on genus-one fibrations which only have a multi-section as opposed to a section. F-theory on such spaces gives rise to discrete gauge symmetries in the effective action. We generalize the transversality conditions on gauge fluxes known for elliptic fibrations by taking into account the properties of the available multi-section. We test these general conditions by constructing all vertical gauge fluxes in a bisection model with gauge group SU(5)×ℤ_2. The non-abelian anomalies are shown to vanish. These flux solutions are dynamically related to fluxes on a fibration with gauge group SU(5)×U(1) by a conifold transition. Considerations of flux quantization reveal an arithmetic constraint on certain intersection numbers on the base which must necessarily be satisfied in a smooth geometry. Combined with the proposed transversality conditions on the fluxes these conditions are shown to imply cancellation of the discrete ℤ_2 gauge anomalies as required by general consistency considerations.

Variations of the core luminosity and solar neutrino fluxes

Science.gov (United States)

Grandpierre, Attila

that errors add up linearly. This conservative error estimation gives δ u/u = 1.7 %, δ ρ/ρ = 7 % at r=0.06× Rsolar, and so the δ T/T = 9 %, since δ T/T ~ δ ρ/ρ + δ P/P. At r=0.04× Rsolar, δ u/u=2.2 %, δ ρ/ρ=10 %, δ T/T=13 %. At r=0, δ u/u=3.5 %, therefore δ ρ/ρ=16 % and so δ T/T=20 %. So even with the usual, not conservative error estimation, roughly dividing these conservative errors by 4, with δ u/u=0.4 %, we still get an allowed range cca. 2 % temperature change at r=0.06× Rsolar and higher in the more central regions. In solar core varying cyclically on a decade timescale, the longer timescale nuclear reactions cannot build up equilibrium. In such a short timescale the variations of the local temperature regulates the proton-proton chain instead of the global luminosity constraint that is applicable only on evolutionary timescales. Therefore, the temperature dependences of the pp cycle neutrinos will be different from the ones determined by solar model calculations with the luminosity constraint: instead of the usual pp ~ T-1/2, Be ~ T8, B~ T18. we determined by the nuclear reaction rates formulas pp ~ T4.2, Be ~ T-1/2, B~ T13.5, for τ effects are included besides the neutrino oscillations. Therefore a combined, DSM+MSW model is suggested to calculate the observed solar neutrino fluxes. At present we have three types of neutrino detectors, and they offer us the data as the total rates (3 measurements), zenith angle dependences, energy spectra and day-night variations, all together 6 kind of data. The highest statistical significance is found in the total rates data. The evaluation of these 6 data sets is not straightforward. For example, the combined fits to the rates+spectra+D/N changes give a bad fit to the total rates, indicating the need to include the astrophysical factors besides the MSW effect. The DSM suggest that the core dynamics is induced by intermittent events of dissipation of rotational energy in the solar core, in relation

Dryout heat flux in a debris bed with forced coolant flow from below

International Nuclear Information System (INIS)

Bang, Kwang-Hyun; Kim, Jong-Myung

2004-01-01

The objective of the present study is to experimentally investigate the enhancement of dryout heat flux in debris beds with coolant flow from below. The experimental facility consists mainly of an induction heater (40 kW, 35 kHz), a double-wall quartz-tube test section containing steel-particle bed and coolant injection and recovery condensing loop. A fairly uniform heating of particle bed was achieved by induction heating. This paper reports the experimental data for 5 mm particle bed and 300 mm bed height. The dryout heat rate data were obtained of both top-flooding case and forced coolant injection from below with the injection mass flux up to 1.5 kg/m 2 s. For the top-flooded case, the volumetric dryout heat rate was about 4 MW/m 3 and it increased as the rate of coolant injection from below was increased. At the coolant injection mass flux of 1.5 kg/m 2 s, the volumetric dryout heat rate was about 10 MW/m 3 , the enhancement factor was more than two. (author)

Modular rate laws for enzymatic reactions: thermodynamics, elasticities and implementation.

Science.gov (United States)

Liebermeister, Wolfram; Uhlendorf, Jannis; Klipp, Edda

2010-06-15

Standard rate laws are a key requisite for systematically turning metabolic networks into kinetic models. They should provide simple, general and biochemically plausible formulae for reaction velocities and reaction elasticities. At the same time, they need to respect thermodynamic relations between the kinetic constants and the metabolic fluxes and concentrations. We present a family of reversible rate laws for reactions with arbitrary stoichiometries and various types of regulation, including mass-action, Michaelis-Menten and uni-uni reversible Hill kinetics as special cases. With a thermodynamically safe parameterization of these rate laws, parameter sets obtained by model fitting, sampling or optimization are guaranteed to lead to consistent chemical equilibrium states. A reformulation using saturation values yields simple formulae for rates and elasticities, which can be easily adjusted to the given stationary flux distributions. Furthermore, this formulation highlights the role of chemical potential differences as thermodynamic driving forces. We compare the modular rate laws to the thermodynamic-kinetic modelling formalism and discuss a simplified rate law in which the reaction rate directly depends on the reaction affinity. For automatic handling of modular rate laws, we propose a standard syntax and semantic annotations for the Systems Biology Markup Language. An online tool for inserting the rate laws into SBML models is freely available at www.semanticsbml.org. Supplementary data are available at Bioinformatics online.

Age-Related Racial Disparity in Suicide Rates Among U.S. Youth

Science.gov (United States)

... May 30, 2018 Age-Related Racial Disparity in Youth Suicide Rates May 21, 2018 News by Year 2018 ... May 30, 2018 Age-Related Racial Disparity in Youth Suicide Rates May 21, 2018 News by Year 2018 ...

Boosted Fast Flux Loop Final Report

Energy Technology Data Exchange (ETDEWEB)

Boosted Fast Flux Loop Project Staff

2009-09-01

The Boosted Fast Flux Loop (BFFL) project was initiated to determine basic feasibility of designing, constructing, and installing in a host irradiation facility, an experimental vehicle that can replicate with reasonable fidelity the fast-flux test environment needed for fuels and materials irradiation testing for advanced reactor concepts. Originally called the Gas Test Loop (GTL) project, the activity included (1) determination of requirements that must be met for the GTL to be responsive to potential users, (2) a survey of nuclear facilities that may successfully host the GTL, (3) conceptualizing designs for hardware that can support the needed environments for neutron flux intensity and energy spectrum, atmosphere, flow, etc. needed by the experimenters, and (4) examining other aspects of such a system, such as waste generation and disposal, environmental concerns, needs for additional infrastructure, and requirements for interfacing with the host facility. A revised project plan included requesting an interim decision, termed CD-1A, that had objectives of' establishing the site for the project at the Advanced Test Reactor (ATR) at the Idaho National Laboratory (INL), deferring the CD 1 application, and authorizing a research program that would resolve the most pressing technical questions regarding GTL feasibility, including issues relating to the use of booster fuel in the ATR. Major research tasks were (1) hydraulic testing to establish flow conditions through the booster fuel, (2) mini-plate irradiation tests and post-irradiation examination to alleviate concerns over corrosion at the high heat fluxes planned, (3) development and demonstration of booster fuel fabrication techniques, and (4) a review of the impact of the GTL on the ATR safety basis. A revised cooling concept for the apparatus was conceptualized, which resulted in renaming the project to the BFFL. Before the subsequent CD-1 approval request could be made, a decision was made in April

Convective boundary layer flow and heat transfer in a nanofluid in the presence of second order slip, constant heat flux and zero nanoparticles flux

Energy Technology Data Exchange (ETDEWEB)

Rahman, M.M., E-mail: mansurdu@yahoo.com [Department of Mathematics and Statistics, College of Science, Sultan Qaboos University, PO Box 36, PC 123 Al-Khod, Muscat (Oman); Al-Rashdi, Maryam H. [Department of Mathematics and Statistics, College of Science, Sultan Qaboos University, PO Box 36, PC 123 Al-Khod, Muscat (Oman); Pop, I. [Department of Mathematics, Faculty of Mathematics and Computer Science, Babeş-Bolyai University, Cluj-Napoca 400084 (Romania)

2016-02-15

Highlights: • Convective boundary layer flow and heat transfer in a nanofluid is investigated. • Second order slip increases the rate of shear stress and decreases the rate of heat transfer in a nanofluid. • In nanofluid flow zero normal flux of the nanoparticles at the surface is realistic to apply. • Multiple solutions are identified for certain values of the parameter space. • The upper branch solution is found to be stable, hence physically realizable. - Abstract: In this work, the effects of the second order slip, constant heat flux, and zero normal flux of the nanoparticles due to thermophoresis on the convective boundary layer flow and heat transfer characteristics in a nanofluid using Buongiorno's model over a permeable shrinking sheet is studied theoretically. The nonlinear coupled similarity equations are solved using the function bvp4c using Matlab. Similarity solutions of the flow, heat transfer and nanoparticles volume fraction are presented graphically for several values of the model parameters. The results show that the application of second order slip at the interface is found to be increased the rate of shear stress and decreased the rate of heat transfer in a nanofluid, so need to be taken into account in nanofluid modeling. The results further indicate that multiple solutions exist for certain values of the parameter space. The stability analysis provides guarantee that the lower branch solution is unstable, while the upper branch solution is stable and physically realizable.

Local particle flux reversal under strongly sheared flow

International Nuclear Information System (INIS)

Terry, P.W.; Newman, D.E.; Ware, A.S.

2003-01-01

The advection of electron density by turbulent ExB flow with linearly varying mean yields a particle flux that can reverse sign at certain locations along the direction of magnetic shear. The effect, calculated for strong flow shear, resides in the density-potential cross phase. It is produced by the interplay between the inhomogeneities of magnetic shear and flow shear, but subject to a variety of conditions and constraints. The regions of reversed flux tend to wash out if the turbulence consists of closely spaced modes of different helicities, but survive if modes of a single helicity are relatively isolated. The reversed flux becomes negligible if the electron density response is governed by electron scales while the eigenmode is governed by ion scales. The relationship of these results to experimentally observe flux reversals is discussed

Variable Eddington factors and flux-limiting diffusion coefficients

International Nuclear Information System (INIS)

Whalen, P.P.

1982-01-01

Variable Eddington factors and flux limiting diffusion coefficients arise in two common techniques of closing the moment equations of transport. The first two moment equations of the full transport equation are still frequently used to solve many problems of radiative or particle transport. An approximate analysis, developed by Levermore, exhibits the relation between the coefficients of the two different techniques. This analysis is described and then used to test the validity of several commonly used flux limiters and Eddington factors. All of the ad-hoc flux limiters have limited validity. All of the variable Eddington factors derived from some underlying description of the angular distribution function are generally valid. The use of coefficients from Minerbo's elegant maximum entropy Eddington factor analysis is suggested for use in either flux limited diffusion or variable Eddington factor equations

Four-flux and warped heterotic M-theory compactifications

International Nuclear Information System (INIS)

Curio, Gottfried; Krause, Axel

2001-01-01

In the framework of heterotic M-theory compactified on a Calabi-Yau threefold 'times' an interval, the relation between geometry and four-flux is derived beyond first order. Besides the case with general flux which cannot be described by a warped geometry one is naturally led to consider two special types of four-flux in detail. One choice shows how the M-theory relation between warped geometry and flux reproduces the analogous one of the weakly coupled heterotic string with torsion. The other one leads to a quadratic dependence of the Calabi-Yau volume with respect to the orbifold direction which avoids the problem with negative volume of the first order approximation. As in the first order analysis we still find that Newton's constant is bounded from below at just the phenomenologically relevant value. However, the bound does not require an ad hoc truncation of the orbifold-size any longer. Finally we demonstrate explicitly that to leading order in κ 2/3 no Cosmological constant is induced in the four-dimensional low-energy action. This is in accord with what one can expect from supersymmetry

Experimental study of the surface thermal signature of gravity currents: application to the assessment of lava flow effusion rate

Science.gov (United States)

Garel, F.; Kaminski, E.; Tait, S.; Limare, A.

2011-12-01

transient evolution of the radiated heat flux closely related to the variations of the flow area. The study of experiments with time-variable effusion rates finally gives first leads on the inertia of the thermal surface structure. This is to be related to the time-period over which the thermal proxy averages the actual effusion rate, hence to the acquisition frequency appropriate for a thermal monitoring of effusive volcanic eruptions.

Using cosmogenic isotopes to measure basin-scale rates of erosion

International Nuclear Information System (INIS)

Bierman, P.R.; Steig, E.

1992-01-01

The authors present a new and different approach to interpreting the abundance of in situ-produced cosmogenic nuclides such as 36 Cl, 26 Al, and 10 Be. Unlike most existing models, which are appropriate for evaluating isotope concentrations on bedrock surfaces, this model can be used to interpret isotope concentration in fluvial sediment. Because sediment is a mixture of material derived from the entire drainage basin, measured isotope abundances can be used to estimate spatially-averaged rates of erosion and sediment transport. Their approach has the potential to provide geomorphologists with a relatively simple but powerful means by which to constrain rates of landscape evolution. The model considers the flux of cosmogenic isotopes into and out of various reservoirs. Implicit in model development are the assumptions that a geomorphic steady-state has been reached and that sampled sediment is spatially and temporally representative of all sediment leaving the basin. Each year, the impinging cosmic-ray flux produces a certain quantity of cosmogenic isotopes in the rock and soil of a drainage basin. For a basin in steady state, the outgoing isotope flux is also constant. They solve for the rate of mass loss as a function of isotope abundance in the sediment, the cosmic ray attenuation length, the isotope half life, and the effective isotope production rate. There are only a few published measurements of cosmogenic isotope abundance in sediment. They calculated model denudation rates for sediment samples from Zaire and central Texas. The denudation rates they calculated appear reasonable and are similar to those they have measured directly on granite landforms in Georgia and southeastern California and those calculated for the Appalachian Piedmont

Relative linkages of peatland methane and carbon dioxide fluxes with climatic, environmental and ecological parameters and their inter-comparison

Science.gov (United States)

Banerjee, Tirtha; Hommeltenberg, Janina; Roy, Avipsa; De Roo, Frederik; Mauder, Matthias

2016-04-01

Although methane (CH4) is the second most important greenhouse gas (GHG) after CO2, about 80% of its global production is biogenic (wetlands, enteric fermentation and water disposal from animals) contrary to major anthropogenic sources of most other GHGs. Although on a shorter time scale, global emissions of methane are greater (10 year time frame) or about 80% (20 year time frame) of those of carbon dioxide in terms of their influence on global warming, methane emissions have been studied much less than CO2 emissions. Lakes, reservoirs and wetlands are estimated to contribute about 15-40% to the global methane source budget, which is higher than total oceanic CH4 emission. Half of the world's wetlands are represented by peatlands which cover 3% of the global total land area. Peatlands have a thick water-logged organic soil layer (peat) made up of dead and decaying plant material. Moreover, they are carbon rich, containing twice as much stock as the entire forest biomass of the world (550 Gt carbon). When disturbed, they can become significant sources of greenhouse gas emissions. The organic carbon exposed to air due to various mechanisms can release CH4 or CO2 in the atmosphere. Thus the nature of vegetation cover, radiation environment, wind turbulence, soil characteristics, water table depth etc. are expected to be important forcings that influence the emission of CH4 or CO2 in the shorter time scale. However, long term climate change can also influence these governing factors themselves over a larger time scale, which in turn can influence the wetland GHG emissions. Thus developing a predictive framework and long term source appropriation for wetland CH4 or CO2 warrants an identification of the major environmental forcings on the CH4 or CO2 flux. In the present work, we use a simple and systematic data-analytics approach to determine the relative linkages of different climate and environmental variables with the canopy level half-hourly CH4 or CO2 fluxes over a

Fractional flux quanta in Josephson junctions

Energy Technology Data Exchange (ETDEWEB)

Goldobin, E.; Buckenmaier, K.; Gaber, T.; Kemmler, M.; Pfeiffer, J.; Koelle, D.; Kleiner, R. [Physikalisches Inst. - Experimentalphysik II, Univ. Tuebingen (Germany); Weides, M.; Kohlstedt, H. [Center of Nanoelectronic Systems for Information Technology (CNI), Research Centre Juelich (Germany); Siegel, M. [Inst. fuer Mikro- und Nanoelektronische Systeme, Univ. Karlsruhe (Germany)

2007-07-01

Fractional Josephson vortices may appear in the so-called 0-{kappa} Josephson junctions ({kappa} is an arbitrary number) and carry magnetic flux {phi}, which is a fraction of the magnetic flux quantum {phi}{sub 0}{approx}2.07 x 10{sup -15} Wb. Their properties are very different from the usual integer fluxons: they are pinned, and often represent the ground state of the system with spontaneous circulating supercurrent. They behave as well controlled macroscopic spins and can be used to construct bits, qubits, tunable photonic crystals and to study the (quantum) physics of spin systems. In this talk we discuss recent advances in 0-{pi} junction technology and present recent experimental results: evidence of the spontaneous flux in the ground state, spectroscopy of the fractional vortex eigenfrequencies and observation of dynamics effects related to the flipping of the fractional vortices. (orig.)

Evaluation of HFIR [High Flux Isotope Reactor] pressure-vessel integrity considering radiation embrittlement

International Nuclear Information System (INIS)

Cheverton, R.D.; Merkle, J.G.; Nanstad, R.K.

1988-04-01

The High Flux Isotope Reactor (HFIR) pressure vessel has been in service for 20 years, and during this time, radiation damage was monitored with a vessel-material surveillance program. In mid-November 1986, data from this program indicated that the radiation-induced reduction in fracture toughness was greater than expected. As a result, a reevaluation of vessel integrity was undertaken. Updated methods of fracture-mechanics analysis were applied, and an accelerated irradiations program was conducted using the Oak Ridge Research Reactor. Results of these efforts indicate that (1) the vessel life can be extended 10 years if the reactor power level is reduced 15% and if the vessel is subjected to a hydrostatic proof test each year; (2) during the 10-year life extension, significant radiation damage will be limited to a rather small area around the beam tubes; and (3) the greater-than-expected damage rate is the result of the very low neutron flux in the HFIR vessel relative to that in samples of material irradiated in materials-testing reactors (a factor of ∼10 4 less), that is, a rate effect

The glycolytic flux in Escherichia coli is controlled by the demand for ATP

DEFF Research Database (Denmark)

Købmann, Brian Jensen; Westerhoff, H.V.; Snoep, J.L.

2002-01-01

additional ATP hydrolysis, we increased the flux through glycolysis to 1.7 times that of the wild-type flux. The results demonstrate why attempts in the past to increase the glycolytic flux through overexpression of glycolytic enzymes have been unsuccessful: the majority of flux control (> 75%) resides...... not inside but outside the pathway, i.e., with the enzymes that hydrolyze ATP. These data further allowed us to answer the question of whether catabolic or anabolic reactions control the growth of E. coli. We show that the majority of the control of growth rate resides in the anabolic reactions, i...

Aerosol fluxes and particle growth above managed grassland

Directory of Open Access Journals (Sweden)

E. Nemitz

2009-08-01

Full Text Available Particle deposition velocities (11–3000 nm diameter measured above grassland by eddy covariance during the EU GRAMINAE experiment in June 2000 averaged 0.24 and 0.03 mm s⁻¹ to long (0.75 m and short (0.07 m grass, respectively. After fertilisation with 108 kg N ha⁻¹ as calcium ammonium nitrate, sustained apparent upward fluxes of particles were observed. Analysis of concentrations and fluxes of potential precursor gases, including NH₃, HNO₃, HCl and selected VOCs, shows that condensation of HNO₃ and NH₃ on the surface of existing particles is responsible for this effect. A novel approach is developed to derive particle growth rates at the field scale, from a combination of measurements of vertical fluxes and particle size-distributions. For the first 9 days after fertilization, growth rates of 11 nm particles of 7.04 nm hr⁻¹ and 1.68 nm hr⁻¹ were derived for day and night-time conditions, respectively. This implies total NH₄NO₃ production rates of 1.11 and 0.44 μg m⁻³ h⁻¹, respectively. The effect translates into a small error in measured ammonia fluxes (0.06% day, 0.56% night and a large error in NH₄⁺ and NO₃⁻ aerosol fluxes of 3.6% and 10%, respectively. By converting rapidly exchanged NH₃ and HNO₃ into slowly depositing NH₄NO₃, the reaction modifies the total N budget, though this effect is small (<1% for the 10 days following fertilization, as NH₃ emission dominates the net flux. It is estimated that 3.8% of the fertilizer N was volatilised as NH₃, of which 0.05% re-condensed to form NH₄NO₃ particles within the lowest 2 m of the surface layer. This surface induced process would at least scale up to a global NH₄NO₃ formation of ca. 0.21 kt N yr

Application of a drift-flux model to flashing in straight pipes

International Nuclear Information System (INIS)

Hirt, C.W.; Romero, N.C.

1975-06-01

A new computer program, SOLA-OF, has been written to solve the unsteady, two-dimensional equations of motion for a two-phase mixture. The equations solved are based on the drift-flux approximation and include a phase transition model and a general drift velocity calculation. The SOLA-DF code is used for a study of the blowdown of straight pipes initially filled with water at high temperature and pressure. Computed results are presented that show the relative importance of phase transition rates, pipe friction, drift velocity magnitude, and other model variations. The computed results are also compared with experimental data. 7 references. (auth)

Measuring oxidation processes: Atomic oxygen flux monitor

International Nuclear Information System (INIS)

Anon.

1991-01-01

Of the existing 95 high-energy accelerators in the world, the Stanford Linear Collider (SLC) at the Stanford Linear Accelerator Center (SLAC) is the only one of the linear-collider type, where electrons and positrons are smashed together at energies of 50 GeV using linear beams instead of beam rings for achieving interactions. Use of a collider eliminates energy losses in the form of x-rays due to the curved trajectory of the rings, a phenomena known as bremsstrauhlung. Because these losses are eliminated, higher interaction energies are reached. Consequently the SLC produced the first Z particle in quantities large enough to allow measurement of its physical properties with some accuracy. SLAC intends to probe still deeper into the structure of matter by next polarizing the electrons in the beam. The surface of the source for these polarized particles, typically gallium arsenide, must be kept clean of contaminants. One method for accomplishing this task requires the oxidation of the surface, from which the oxidized contaminants are later boiled off. The technique requires careful measurement of the oxidation process. SLAC researchers have developed a technique for measuring the atomic oxygen flux in this process. The method uses a silver film on a quartz-crystal, deposition-rate monitor. Measuring the initial oxidation rate of the silver, which is proportional to the atomic oxygen flux, determines a lower limit on that flux in the range of 10 13 to 10 17 atoms per square centimeter per second. Furthermore, the deposition is reversible by exposing the sensor to atomic hydrogen. This technique has wider applications to processes in solid-state and surface physics as well as surface chemistry. In semiconductor manufacturing where a precise thickness of oxide must be deposited, this technique could be used to monitor the critical flux of atomic oxygen in the process

Stabilization of flux during dead-end ultra-low pressure ultrafiltration.

Science.gov (United States)

Peter-Varbanets, Maryna; Hammes, Frederik; Vital, Marius; Pronk, Wouter

2010-06-01

Gravity driven ultrafiltration was operated in dead-end mode without any flushing or cleaning. In contrary to general expectations, the flux value stabilized after about one week of operation and remained constant during an extended period of time (several months). Different surface water types and diluted wastewater were used as feed water and, depending on the feed water composition, stable flux values were in the range of 4-10 L h(-1) m(-2). When sodium azide was added to the feed water to diminish the biological activity, no stabilization of flux occurred, indicating that biological processes play an important role in the flux stabilization process. Confocal laser scanning microscopy revealed the presence of a biofouling layer, of which the structure changed over time, leading to relatively heterogeneous structures. It is assumed that the stabilization of flux is related to the development of heterogeneous structures in the fouling layer, due to biological processes in the layer. The phenomenon of flux stabilization opens interesting possibilities for application, for instance in simple and low-cost ultrafiltration systems for decentralized drinking water treatment in developing and transition countries, independent of energy supply, chemicals, or complex process control. 2010 Elsevier Ltd. All rights reserved.

Sensible Heat Flux Related to Variations in Atmospheric Turbulence Kinetic Energy on a Sandy Beach

Science.gov (United States)

2017-06-01

production, turbulent transport by pressure fluctuations, dissipation and flux divergence . The TKE budget as explained by Srivastava and Sarthi (2002...generation of turbulence. Term 3 is flux divergence , which describes the differential transport of TKE by turbulent eddies. Term 4, dissipation, is a sink...the time series data to align all signals to the same time base. Winds were rotated into a shore-normal frame of reference. All data outside of T

The Effect of the Heat Flux on the Self-Ignition of Oriented Strand Board

Directory of Open Access Journals (Sweden)

Hirle Siegfried

2017-06-01

Full Text Available This article deals with the initiation phase of flaming and smouldering burning of oriented strand board. The influence of heat flux on thermal degradation of OSB boards, time to ignition, heat release rate and mass loss rate using thermal analysis and vertical electrical radiation panel methods were studied. Significant information on the influence of the heat flux density and the thickness of the material on time to ignition was obtained.

Radiation budget, soil heat flux and latent heat flux at the forest floor in warm, temperate mixed forest

International Nuclear Information System (INIS)

Tamai, K.; Abe, T.; Araki, M.; Ito, H.

1998-01-01

Seasonal changes in the radiation budget and soil heat flux of a forest floor were measured in a mixed forest located in Kyoto, Japan. The basal area at breast height in the survey forest was about 15·82 m 2 ha −1 , for evergreen trees, and 12·46 m 2 ha −1 , for deciduous trees. The sky view factor was 16 and 22% at the survey site in the foliate and defoliate seasons, respectively. The small difference between the sky view factor in the two seasons was reflected in the seasonal change in the radiation budget of the forest floor. Namely, the net long-wave radiation changed rapidly in leafing and falling days, and the rate of net short-wave radiation was highest in April. The distinctive characteristic of the radiation budget was that the rates of available radiation in the daytime and at night were almost equal in September and October. Latent heat flux at the forest floor was estimated to be around 94 MJ m −2 annually, from our measurement with the simulation model. (author)

The Protein Cost of Metabolic Fluxes: Prediction from Enzymatic Rate Laws and Cost Minimization.

Directory of Open Access Journals (Sweden)

Elad Noor

2016-11-01

Full Text Available Bacterial growth depends crucially on metabolic fluxes, which are limited by the cell's capacity to maintain metabolic enzymes. The necessary enzyme amount per unit flux is a major determinant of metabolic strategies both in evolution and bioengineering. It depends on enzyme parameters (such as kcat and KM constants, but also on metabolite concentrations. Moreover, similar amounts of different enzymes might incur different costs for the cell, depending on enzyme-specific properties such as protein size and half-life. Here, we developed enzyme cost minimization (ECM, a scalable method for computing enzyme amounts that support a given metabolic flux at a minimal protein cost. The complex interplay of enzyme and metabolite concentrations, e.g. through thermodynamic driving forces and enzyme saturation, would make it hard to solve this optimization problem directly. By treating enzyme cost as a function of metabolite levels, we formulated ECM as a numerically tractable, convex optimization problem. Its tiered approach allows for building models at different levels of detail, depending on the amount of available data. Validating our method with measured metabolite and protein levels in E. coli central metabolism, we found typical prediction fold errors of 4.1 and 2.6, respectively, for the two kinds of data. This result from the cost-optimized metabolic state is significantly better than randomly sampled metabolite profiles, supporting the hypothesis that enzyme cost is important for the fitness of E. coli. ECM can be used to predict enzyme levels and protein cost in natural and engineered pathways, and could be a valuable computational tool to assist metabolic engineering projects. Furthermore, it establishes a direct connection between protein cost and thermodynamics, and provides a physically plausible and computationally tractable way to include enzyme kinetics into constraint-based metabolic models, where kinetics have usually been ignored or

Eddy covariance fluxes of acyl peroxy nitrates (PAN, PPN and MPAN above a Ponderosa pine forest

Directory of Open Access Journals (Sweden)

G. M. Wolfe

2009-01-01

Full Text Available During the Biosphere Effects on AeRosols and Photochemistry EXperiment 2007 (BEARPEX-2007, we observed eddy covariance (EC fluxes of speciated acyl peroxy nitrates (APNs, including peroxyacetyl nitrate (PAN, peroxypropionyl nitrate (PPN and peroxymethacryloyl nitrate (MPAN, above a Ponderosa pine forest in the western Sierra Nevada. All APN fluxes are net downward during the day, with a median midday PAN exchange velocity of −0.3 cm s⁻¹; nighttime storage-corrected APN EC fluxes are smaller than daytime fluxes but still downward. Analysis with a standard resistance model shows that loss of PAN to the canopy is not controlled by turbulent or molecular diffusion. Stomatal uptake can account for 25 to 50% of the observed downward PAN flux. Vertical gradients in the PAN thermal decomposition (TD rate explain a similar fraction of the flux, suggesting that a significant portion of the PAN flux into the forest results from chemical processes in the canopy. The remaining "unidentified" portion of the net PAN flux (~15% is ascribed to deposition or reactive uptake on non-stomatal surfaces (e.g. leaf cuticles or soil. Shifts in temperature, moisture and ecosystem activity during the summer – fall transition alter the relative contribution of stomatal uptake, non-stomatal uptake and thermochemical gradients to the net PAN flux. Daytime PAN and MPAN exchange velocities are a factor of 3 smaller than those of PPN during the first two weeks of the measurement period, consistent with strong intra-canopy chemical production of PAN and MPAN during this period. Depositional loss of APNs can be 3–21% of the gross gas-phase TD loss depending on temperature. As a source of nitrogen to the biosphere, PAN deposition represents approximately 4–19% of that due to dry deposition of nitric acid at this site.

Seismologically determined bedload flux during the typhoon season.

Science.gov (United States)

Chao, Wei-An; Wu, Yih-Min; Zhao, Li; Tsai, Victor C; Chen, Chi-Hsuan

2015-02-05

Continuous seismic records near river channels can be used to quantify the energy induced by river sediment transport. During the 2011 typhoon season, we deployed a seismic array along the Chishan River in the mountain area of southern Taiwan, where there is strong variability in water discharge and high sedimentation rates. We observe hysteresis in the high-frequency (5-15 Hz) seismic noise level relative to the associated hydrological parameters. In addition, our seismic noise analysis reveals an asymmetry and a high coherence in noise cross-correlation functions for several station pairs during the typhoon passage, which corresponds to sediment particles and turbulent flows impacting along the riverbed where the river bends sharply. Based on spectral characteristics of the seismic records, we also detected 20 landslide/debris flow events, which we use to estimate the sediment supply. Comparison of sediment flux between seismologically determined bedload and derived suspended load indicates temporal changes in the sediment flux ratio, which imply a complex transition process from the bedload regime to the suspension regime between typhoon passage and off-typhoon periods. Our study demonstrates the possibility of seismologically monitoring river bedload transport, thus providing valuable additional information for studying fluvial bedrock erosion and mountain landscape evolution.

Fire increases carbon fluxes from inland waters of the Yukon-Kuskokwim delta, Alaska.

Science.gov (United States)

Mann, P. J.; Bristol, E. M.; Dabrowski, J. S.; Jimmie, J. A.; Melton, S.; Navarro-Perez, E.; Peter, D. L.; Sae-lim, N.; Holmes, R. M.; Natali, S.; Schade, J. D.

2017-12-01

Climate change across high-latitude regions is expected to alter the hydrology and biogeochemistry of arctic environments, significantly impacting ecosystem C cycling and landscape scale C budgets. Fire represents one manifestation of arctic climate change with the number, extent and intensity of fires projected to increase over upcoming decades. The Yukon-Kuskokwim River Delta (YKD), Alaska, experienced unprecedented tundra fires in 2015 when more than 250 km2 underwent burn. In this study, we examined the effects of the 2015 YKD fire upon aquatic and terrestrial C fluxes, and investigated potential mechanisms causing changes to C-cycling. Field work was conducted during summer months (July-Sept) over two years, complimented with aerobic and anaerobic laboratory incubations. Burning of the terrestrial organic layer caused dramatic changes to soil moisture, the proportion of organic versus mineral soils near the land surface, and average active layer depth. Fire caused increased C fluxes (particularly CH4) from re-wet soils relative to unburnt soils, suggesting an interaction exists between fire history and soil moisture. Higher C fluxes from saturated ponds and fens across the landscape provided additional support for this theory. Pore-water chemistry in burnt catchments contained higher inorganic nutrient concentrations, specifically nitrogen, potentially driven by changing soil sorption processes and/ or infiltration rates. Organic matter delivery to inland waters within burns contained DOC of lower apparent molecular weight and aromaticity relative to unburnt waters (inferred from optical measures), and waters typically had higher temperatures, pH and dissolved mineral content. Lake and low-lying pond CO2 and CH4 emissions were consistently higher in burn catchment regions, with three to four-fold higher C emission rates. Our study indicates that fire may promote aquatic and terrestrial pathways for C loss and that these enhanced emissions may persist for years

Fast neutron fluxes distribution in Egyptian ilmenite concrete

International Nuclear Information System (INIS)

Megahed, R.M.; Abou El-Nasr, T.Z.; Bashter, I.I.

1978-01-01

This work is concerned with the study of the distribution of fast neutron fluxes in a new type of heavy concrete made from Egyptian ilmenite ores. The neutron source used was a collimated beam of reactor neutrons emitted from one of the horizontal channels of the ET-RR-1 reactor. Measurements were carried-out using phosphorous activation detectors. Iso-flux curves were represented which give directly the shape and thickness required to attenuate the emitted fast neutron flux to a certain value. The relaxation lengths were also evaluated from the measured data for both disc monodirectional source and infinite plane monodirectional source. The obtained values were compared with that calculated using the derived values of relative number densities and microscopic removal cross-sections of the different constituents. The obtained data show that ilmenite concrete attenuates fast neutron flux more strongly than ordinary concrete. A semiemperical formula was derived to calculate the fast neutron flux at different thicknesses along the beam axis. Another semiemperical formula was also derived to calculate the fast neutron flux in ordinary concrete along the beam axis using the corresponding value in ilmenite concrete

Modeling Anthropogenic Impact on Sediment Balance and Relative Sea-Level Rise in Contemporary and Future Deltas

Science.gov (United States)

Tessler, Z. D.; Vorosmarty, C. J.; Overeem, I.; Syvitski, J. P.

2017-12-01

Modern deltas are dependent on human-mediated freshwater and sediment fluxes. Changes to these fluxes impact delta biogeophysical functioning, and affect the long-term sustainability of these landscapes for both human and natural systems. Here we present contemporary estimates of long-term mean sediment balance and relative sea-level rise across 46 global deltas. We model ongoing development and scenarios of future water resource management and hydropower infrastructure in upstream river basins to explore how changing sediment fluxes impact relative sea-level in coastal delta systems. Model results show that contemporary sediment fluxes, anthropogenic drivers of land subsidence, and sea-level rise result in relative sea-level rise rates in deltas that average 6.8 mm/year. Currently planned or under-construction dams can be expected to increase rates of relative sea-level rise on the order of 1 mm/year. Some deltas systems, including the Magdalena, Orinoco, and Indus, are highly sensitive to future impoundment of river basins, with RSLR rates increasing up to 4 mm/year in a high-hydropower-utilization scenario. Sediment fluxes may be reduced by up to 60% in the Danube and 21% in the Ganges-Brahmaputra-Megnha if all currently planned dams are constructed. Reduced sediment retention on deltas due to increased river channelization and local flood controls increases RSLR on average by nearly 2 mm/year. Long-term delta sustainability requires a more complete understanding of how geophysical and anthropogenic change impact delta geomorphology. Strategies for sustainable delta management that focus on local and regional drivers of change, especially groundwater and hydrocarbon extraction and upstream dam construction, can be highly impactful even in the context of global climate-induced sea-level rise.

Analysis of the behavior of an experimental absorption heat transformer for water purification for different mass flux rates in the generator

International Nuclear Information System (INIS)

Huicochea, Armando; Rivera, Wilfrido; Martínez, Hiram; Siqueiros, Javier; Cadenas, Erasmo

2013-01-01

In the present study, first and second laws of thermodynamics have been used to analyse the performance of an experimental absorption heat transformer for water purification. Irreversibilities, coefficients of performance (COP) and exergy coefficients of performance (ECOP) were determined as function of the mass flow of hot water supplied to the generator and as function of the overall thermal specific energy consumption (OSTEC) parameter defined in this paper. The results showed that the system irreversibilities increase meanwhile the coefficients of performance and the exergy coefficient of performance decrease with an increment of the mass flow of hot water supplied to the generator. Also it was shown that the system performance is better when the production of purified water increases due to the increment of the heat recycled to the generator and evaporator. -- Highlights: ► Exergetic performance of an absorption heat transformer for purifying water to different mass flux rates in the generator. ► The irreversibilities are increasing when the mass flow rate in the generator is major. ► The mass flow rates in the generator plays a decisive role in the whole system efficiency

Three-Dimensional Evolution of Flux-Rope CMEs and Its Relation to the Local Orientation of the Heliospheric Current Sheet

Science.gov (United States)

Isavnin, A.; Vourlidas, A.; Kilpua, E. K. J.

2014-06-01

Flux ropes ejected from the Sun may change their geometrical orientation during their evolution, which directly affects their geoeffectiveness. Therefore, it is crucial to understand how solar flux ropes evolve in the heliosphere to improve our space-weather forecasting tools. We present a follow-up study of the concepts described by Isavnin, Vourlidas, and Kilpua ( Solar Phys. 284, 203, 2013). We analyze 14 coronal mass ejections (CMEs), with clear flux-rope signatures, observed during the decay of Solar Cycle 23 and rise of Solar Cycle 24. First, we estimate initial orientations of the flux ropes at the origin using extreme-ultraviolet observations of post-eruption arcades and/or eruptive prominences. Then we reconstruct multi-viewpoint coronagraph observations of the CMEs from ≈ 2 to 30 R⊙ with a three-dimensional geometric representation of a flux rope to determine their geometrical parameters. Finally, we propagate the flux ropes from ≈ 30 R⊙ to 1 AU through MHD-simulated background solar wind while using in-situ measurements at 1 AU of the associated magnetic cloud as a constraint for the propagation technique. This methodology allows us to estimate the flux-rope orientation all the way from the Sun to 1 AU. We find that while the flux-ropes' deflection occurs predominantly below 30 R⊙, a significant amount of deflection and rotation happens between 30 R⊙ and 1 AU. We compare the flux-rope orientation to the local orientation of the heliospheric current sheet (HCS). We find that slow flux ropes tend to align with the streams of slow solar wind in the inner heliosphere. During the solar-cycle minimum the slow solar-wind channel as well as the HCS usually occupy the area in the vicinity of the solar equatorial plane, which in the past led researchers to the hypothesis that flux ropes align with the HCS. Our results show that exceptions from this rule are explained by interaction with the Parker-spiraled background magnetic field, which dominates

Notes on neutron flux measurement; Notas sobre medida de flujos neutronicos

Energy Technology Data Exchange (ETDEWEB)

Alcala Ruiz, F

1984-07-01

The main purpose of this work is to get an useful guide to carry out topical neutron flux measurements. Although the foil activation technique is used in the majority of the cases, other techniques, such as those based on fission chambers and self-powered neutron detectors, are also shown. Special interest is given to the description and application of corrections on the measurement of relative and absolute induced activities by several types of detectors (scintillators, G-M and gas proportional counters). The thermal arid epithermal neutron fluxes, as determined in this work, are conventional or effective (West cots fluxes), which are extensively used by the reactor experimentalists; however, we also give some expressions where they are related to the integrated neutron fluxes, which are used in neutron calculations. (Author) 16 refs.

Differentiating transpiration from evaporation in seasonal agricultural wetlands and the link to advective fluxes in the root zone

Science.gov (United States)

Bachand, P.A.M.; S. Bachand,; Fleck, Jacob A.; Anderson, Frank E.; Windham-Myers, Lisamarie

2014-01-01

The current state of science and engineering related to analyzing wetlands overlooks the importance of transpiration and risks data misinterpretation. In response, we developed hydrologic and mass budgets for agricultural wetlands using electrical conductivity (EC) as a natural conservative tracer. We developed simple differential equations that quantify evaporation and transpiration rates using flowrates and tracer concentrations atwetland inflows and outflows. We used two ideal reactormodel solutions, a continuous flowstirred tank reactor (CFSTR) and a plug flow reactor (PFR), to bracket real non-ideal systems. From those models, estimated transpiration ranged from 55% (CFSTR) to 74% (PFR) of total evapotranspiration (ET) rates, consistent with published values using standard methods and direct measurements. The PFR model more appropriately represents these nonideal agricultural wetlands in which check ponds are in series. Using a fluxmodel, we also developed an equation delineating the root zone depth at which diffusive dominated fluxes transition to advective dominated fluxes. This relationship is similar to the Peclet number that identifies the dominance of advective or diffusive fluxes in surface and groundwater transport. Using diffusion coefficients for inorganic mercury (Hg) and methylmercury (MeHg) we calculated that during high ET periods typical of summer, advective fluxes dominate root zone transport except in the top millimeters below the sediment–water interface. The transition depth has diel and seasonal trends, tracking those of ET. Neglecting this pathway has profound implications: misallocating loads along different hydrologic pathways; misinterpreting seasonal and diel water quality trends; confounding Fick's First Law calculations when determining diffusion fluxes using pore water concentration data; and misinterpreting biogeochemicalmechanisms affecting dissolved constituent cycling in the root zone. In addition,our understanding of internal

Relations between fluxes and concentrations of Na in cell suspensions of Acer pseudoplatanus

International Nuclear Information System (INIS)

Pennarun, A.-M.

1978-01-01

Taking in account the data provided by preliminary compartmental analysis, the net influxes of 24 Na measured in Acer cells after a short loading period (45 minutes) followed by a short wash (1 minute) represent the influx across the plasmalemma (phi sub(0c)) and, after a long loading period (4 hours) followed by a long wash (2 hours) represent the quasi-steady influx from the external solution to the vacuole (phi sub(0v). At flux equilibrium and when the external Na concentration is high enough, the other unidirectional fluxes - phi sub(c0), phi sub(cv) and phi sub(vc) - can be determined from these measurements. This method was used to study the variation of Na flux in terms of the external concentrations and the resulting internal concentrations. The kinetics obtained confirm the active nature of the efflux phi sub(vc) across the tonoplast according to the conclusions given by the application of the USSING-TEORELL criterion to the results of compartmental analysis. On the contrary, they suggest a passive character for the efflux phi sub(c0) accross the plasmalemma which could be considered as active according to the USSING-TEORELL criterion. The contradiction could be eliminated by taking into consideration the important underestimation of the Na activity coefficient in the cytoplasm, due to the neglecting of water binding [fr

Modeling rainfall infiltration on hillslopes using Flux-concentration relation and time compression approximation

Science.gov (United States)

Wang, Jie; Chen, Li; Yu, Zhongbo

2018-02-01

Rainfall infiltration on hillslopes is an important issue in hydrology, which is related to many environmental problems, such as flood, soil erosion, and nutrient and contaminant transport. This study aimed to improve the quantification of infiltration on hillslopes under both steady and unsteady rainfalls. Starting from Darcy's law, an analytical integral infiltrability equation was derived for hillslope infiltration by use of the flux-concentration relation. Based on this equation, a simple scaling relation linking the infiltration times on hillslopes and horizontal planes was obtained which is applicable for both small and large times and can be used to simplify the solution procedure of hillslope infiltration. The infiltrability equation also improved the estimation of ponding time for infiltration under rainfall conditions. For infiltration after ponding, the time compression approximation (TCA) was applied together with the infiltrability equation. To improve the computational efficiency, the analytical integral infiltrability equation was approximated with a two-term power-like function by nonlinear regression. Procedures of applying this approach to both steady and unsteady rainfall conditions were proposed. To evaluate the performance of the new approach, it was compared with the Green-Ampt model for sloping surfaces by Chen and Young (2006) and Richards' equation. The proposed model outperformed the sloping Green-Ampt, and both ponding time and infiltration predictions agreed well with the solutions of Richards' equation for various soil textures, slope angles, initial water contents, and rainfall intensities for both steady and unsteady rainfalls.

Criticality experiments to provide benchmark data on neutron flux traps

International Nuclear Information System (INIS)

Bierman, S.R.

1988-06-01

The experimental measurements covered by this report were designed to provide benchmark type data on water moderated LWR type fuel arrays containing neutron flux traps. The experiments were performed at the US Department of Energy Hanford Critical Mass Laboratory, operated by Pacific Northwest Laboratory. The experimental assemblies consisted of 2 /times/ 2 arrays of 4.31 wt % 235 U enriched UO 2 fuel rods, uniformly arranged in water on a 1.891 cm square center-to-center spacing. Neutron flux traps were created between the fuel units using metal plates containing varying amounts of boron. Measurements were made to determine the effect that boron loading and distance between the fuel and flux trap had on the amount of fuel required for criticality. Also, measurements were made, using the pulse neutron source technique, to determine the effect of boron loading on the effective neutron multiplications constant. On two assemblies, reaction rate measurements were made using solid state track recorders to determine absolute fission rates in 235 U and 238 U. 14 refs., 12 figs., 7 tabs

Higher order Cambell techniques for neutron flux measurement. Pt. 1

International Nuclear Information System (INIS)

Lux, I.; Baranyai, A.

1982-01-01

An exact mathematical description of arbitrary high order Campbell techniques for measuring particle fluxes is given. The nth order Campbell technique assumes the measurement of the moments of the outcoming voltage up to the nth one. A simple relation is derived among the various moments of the total measured voltage and of the detector signal caused by one incident particle. It is proven that in the monoparticle case combination of the measured moments up to the order n provides an expression proportional to the particle flux and to the nth moment of the detector signal. Generalization to several different particles is given and it is shown that if the flux of the particle causing the largest detector signal is measured with a relative error epsilon in the dc method and the error is due to the signals of other particles, then in the nth order campbelling the error will be of order epsilonsup(n). The effect of a random background on the measured voltage is also investigated and it is established that the nth order campbelling supresses the noise according to the nth power of the relative amplitude of the noise to the signal. The results concerning constant fluxes are generalized to time dependent particle fluxes and a method assuming a Fourier transform of the measured quantities is proposed for their determination. (orig.)

Incidence and progression rates of age-related maculopathy: the Rotterdam Study

NARCIS (Netherlands)

J.J.M. Willemse-Assink (Jacqueline); R. van Leeuwen (Redmer); R.C.W. Wolfs (Roger); J.R. Vingerling (Hans); Th. Stijnen (Theo); P.T.V.M. de Jong (Paulus); C.C.W. Klaver (Caroline); A. Hofman (Albert)

2001-01-01

textabstractPURPOSE: To describe the incidence rate of age-related macular degeneration (AMD) and the progression rates of early stages of age-related maculopathy (ARM), and to study the hierarchy of fundus features that determine progression. METHODS: A group of 4953 subjects

FLUX SENSOR EVALUATIONS AT THE ATR CRITICAL FACILITY

International Nuclear Information System (INIS)

Unruh, Troy; Rempe, Joy; Nigg, David; Imel, George; Harris, Jason; Bonebrake, Eric

2010-01-01

The Advanced Test Reactor (ATR) and the ATR Critical (ATRC) facilities lack real-time methods for detecting thermal neutron flux and fission reaction rates for irradiation capsules. Direct measurements of the actual power deposited into a test are now possible without resorting to complicated correction factors. In addition, it is possible to directly measure minor actinide fission reaction rates and to provide time-dependent monitoring of the fission reaction rate or fast/thermal flux during transient testing. A joint Idaho State University/Idaho National Laboratory ATR National Scientific User Facility (ATR NSUF) project was recently initiated to evaluate new real-time state-of-the-art in-pile flux detection sensors. Initially, the project is comparing the accuracy, response time, and long duration performance of French Atomic Energy Commission (CEA)-developed miniature fission chambers, specialized self-powered neutron detectors (SPNDs) by the Argentinean National Energy Commission (CNEA), specially developed commercial SPNDs, and back-to-back fission (BTB) chambers developed by Argonne National Laboratory (ANL). As discussed in this paper, specialized fixturing and software was developed by INL to facilitate these joint ISU/INL evaluations. Calculations were performed by ISU to assess the performance of and reduce uncertainties in flux detection sensors and compare data obtained from these sensors with existing integral methods employed at the ATRC. Ultimately, project results will be used to select the detector that can provide the best online regional ATRC power measurement. It is anticipated that project results may offer the potential to increase the ATRC's current power limit and its ability to perform low-level irradiation experiments. In addition, results from this effort will provide insights about the viability of using these detectors in the ATR. Hence, this effort complements current activities to improve ATR software tools, computational protocols

On the relative magnitudes of photosynthesis, respiration, growth and carbon storage in vegetation.

Science.gov (United States)

Van Oijen, Marcel; Schapendonk, Ad; Höglind, Mats

2010-05-01

The carbon balance of vegetation is dominated by the two large fluxes of photosynthesis (P) and respiration (R). Mechanistic models have attempted to simulate the two fluxes separately, each with their own set of internal and external controls. This has led to model predictions where environmental change causes R to exceed P, with consequent dieback of vegetation. However, empirical evidence suggests that the R : P ratio is constrained to a narrow range of about 0.4-0.5. Physiological explanations for the narrow range are not conclusive. The aim of this work is to introduce a novel perspective by theoretical study of the quantitative relationship between the four carbon fluxes of P, R, growth and storage (or its inverse, remobilization). Starting from the law of conservation of mass - in this case carbon - equations are derived for the relative magnitudes of all carbon fluxes, which depend on only two parameters: the R : P ratio and the relative rate of storage of carbon in remobilizable reserves. The equations are used to explain observed flux ratios and to analyse incomplete data sets of carbon fluxes. The storage rate is shown to be a freely varying parameter, whereas R : P is narrowly constrained. This explains the constancy of the ratio reported in the literature. With the information thus gained, a data set of R and P in grassland was analysed, and flux estimates could be derived for the periods after cuts in which plant growth is dominated by remobilization before photosynthesis takes over. It is concluded that the relative magnitudes of photosynthesis, respiration, growth and substrate storage are indeed tightly constrained, but because of mass conservation rather than for physiological reasons. This facilitates analysis of incomplete data sets. Mechanistic models, as the embodiment of physiological mechanisms, need to show consistency with the constraints.

Liquid jet impingement cooling with diamond substrates for extremely high heat flux applications

International Nuclear Information System (INIS)

Lienhard V, J.H.

1993-01-01

The combination of impinging jets and diamond substrates may provide an effective solution to a class of extremely high heat flux problems in which very localized heat loads must be removed. Some potential applications include the cooling of high-heat-load components in synchrotron x-ray, fusion, and semiconductor laser systems. Impinging liquid jets are a very effective vehicle for removing high heat fluxes. The liquid supply arrangement is relatively simple, and low thermal resistances can be routinely achieved. A jet's cooling ability is a strong function of the size of the cooled area relative to the jet diameter. For relatively large area targets, the critical heat fluxes can approach 20 W/mm 2 . In this situation, burnout usually originates at the outer edge of the cooled region as increasing heat flux inhibits the liquid supply. Limitations from liquid supply are minimized when heating is restricted to the jet stagnation zone. The high stagnation pressure and high velocity gradients appear to suppress critical flux phenomena, and fluxes of up to 400 W/mm 2 have been reached without evidence of burnout. Instead, the restrictions on heat flux are closely related to properties of the cooled target. Target properties become an issue owing to the large temperatures and large temperature gradients that accompany heat fluxes over 100 W/mm 2 . These conditions necessitate a target with both high thermal conductivity to prevent excessive temperatures and good mechanical properties to prevent mechanical failures. Recent developments in synthetic diamond technology present a possible solution to some of the solid-side constraints on heat flux. Polycrystalline diamond foils can now be produced by chemical vapor deposition in reasonable quantity and at reasonable cost. Synthetic single crystal diamonds as large as 1 cm 2 are also available

Decoherence of Flux Qubits Coupled to Electronic Circuits

NARCIS (Netherlands)

Wilhelm, F.K.; Storcz, M.J.; van der Wal, C.H.; Harmans, C.J.P.M.; Mooij, J.E.

2003-01-01

On the way to solid-state quantum computing, overcoming decoherence is the central issue. In this contribution, we discuss the modeling of decoherence of a superonducting flux qubit coupled to dissipative electronic circuitry. We discuss its impact on single qubit decoherence rates and on the

Fast modeling of flux trapping cascaded explosively driven magnetic flux compression generators.

Science.gov (United States)

Wang, Yuwei; Zhang, Jiande; Chen, Dongqun; Cao, Shengguang; Li, Da; Liu, Chebo

2013-01-01

To predict the performance of flux trapping cascaded flux compression generators, a calculation model based on an equivalent circuit is investigated. The system circuit is analyzed according to its operation characteristics in different steps. Flux conservation coefficients are added to the driving terms of circuit differential equations to account for intrinsic flux losses. To calculate the currents in the circuit by solving the circuit equations, a simple zero-dimensional model is used to calculate the time-varying inductance and dc resistance of the generator. Then a fast computer code is programmed based on this calculation model. As an example, a two-staged flux trapping generator is simulated by using this computer code. Good agreements are achieved by comparing the simulation results with the measurements. Furthermore, it is obvious that this fast calculation model can be easily applied to predict performances of other flux trapping cascaded flux compression generators with complex structures such as conical stator or conical armature sections and so on for design purpose.

A simple heat transfer model for a heat flux plate under transient conditions

International Nuclear Information System (INIS)

Ryan, L.; Dale, J.D.

1985-01-01

Heat flux plates are used for measuring rates of heat transfer through surfaces under steady state and transient conditions. Their usual construction is to have a resistive layer bounded by thermopiles and an exterior layer for protection. If properly designed and constructed a linear relationship between the thermopile generated voltage and heat flux results and calibration under steady state conditions is straight forward. Under transient conditions however the voltage output from a heat flux plate cannot instantaneously follow the heat flux because of the thermal capacitance of the plate and the resulting time lag. In order to properly interpret the output of a heat flux plate used under transient conditions a simple heat transfer model was constructed and tested. (author)

Enhancing surface methane fluxes from an oligotrophic lake: exploring the microbubble hypothesis.

Science.gov (United States)

McGinnis, Daniel F; Kirillin, Georgiy; Tang, Kam W; Flury, Sabine; Bodmer, Pascal; Engelhardt, Christof; Casper, Peter; Grossart, Hans-Peter

2015-01-20

Exchange of the greenhouse gases carbon dioxide (CO2) and methane (CH4) across inland water surfaces is an important component of the terrestrial carbon (C) balance. We investigated the fluxes of these two gases across the surface of oligotrophic Lake Stechlin using a floating chamber approach. The normalized gas transfer rate for CH4 (k600,CH4) was on average 2.5 times higher than that for CO2 (k600,CO2) and consequently higher than Fickian transport. Because of its low solubility relative to CO2, the enhanced CH4 flux is possibly explained by the presence of microbubbles in the lake’s surface layer. These microbubbles may originate from atmospheric bubble entrainment or gas supersaturation (i.e., O2) or both. Irrespective of the source, we determined that an average of 145 L m(–2) d(–1) of gas is required to exit the surface layer via microbubbles to produce the observed elevated k600,CH4. As k600 values are used to estimate CH4 pathways in aquatic systems, the presence of microbubbles could alter the resulting CH4 and perhaps C balances. These microbubbles will also affect the surface fluxes of other sparingly soluble gases in inland waters, including O2 and N2.

Analytic flux formulas and tables of shielding functions

International Nuclear Information System (INIS)

Wallace, O.J.

1981-06-01

Hand calculations of radiation flux and dose rates are often useful in evaluating radiation shielding and in determining the scope of a problem. The flux formulas appropriate to such calculations are almost always based on the point kernel and allow for at most the consideration of laminar slab shields. These formulas often require access to tables of values of integral functions for effective use. Flux formulas and function tables appropriate to calculations involving homogeneous source regions with the shapes of lines, disks, slabs, truncated cones, cylinders, and spheres are presented. Slab shields may be included in most of these calculations, and the effect of a cylindrical shield surrounding a cylindrical source may be estimated. Detector points may be located axially, laterally, or interior to a cylindrical source. Line sources may be tilted with respect to a slab shield. All function tables are given for a wide range of arguments

Fast Flux Watch: A mechanism for online detection of fast flux networks

Directory of Open Access Journals (Sweden)

Basheer N. Al-Duwairi

2014-07-01

Full Text Available Fast flux networks represent a special type of botnets that are used to provide highly available web services to a backend server, which usually hosts malicious content. Detection of fast flux networks continues to be a challenging issue because of the similar behavior between these networks and other legitimate infrastructures, such as CDNs and server farms. This paper proposes Fast Flux Watch (FF-Watch, a mechanism for online detection of fast flux agents. FF-Watch is envisioned to exist as a software agent at leaf routers that connect stub networks to the Internet. The core mechanism of FF-Watch is based on the inherent feature of fast flux networks: flux agents within stub networks take the role of relaying client requests to point-of-sale websites of spam campaigns. The main idea of FF-Watch is to correlate incoming TCP connection requests to flux agents within a stub network with outgoing TCP connection requests from the same agents to the point-of-sale website. Theoretical and traffic trace driven analysis shows that the proposed mechanism can be utilized to efficiently detect fast flux agents within a stub network.

Inter-comparison of different direct and indirect methods to determine radon flux from soil

International Nuclear Information System (INIS)

Grossi, C.; Vargas, A.; Camacho, A.; Lopez-Coto, I.; Bolivar, J.P.; Xia Yu; Conen, F.

2011-01-01

The physical and chemical characteristics of radon gas make it a good tracer for use in the application of atmospheric transport models. For this purpose the radon source needs to be known on a global scale and this is difficult to achieve by only direct experimental methods. However, indirect methods can provide radon flux maps on larger scales, but their reliability has to be carefully checked. It is the aim of this work to compare radon flux values obtained by direct and indirect methods in a measurement campaign performed in the summer of 2008. Different systems to directly measure radon flux from the soil surface and to measure the related parameters terrestrial γ dose and 226 Ra activity in soil, for indirect estimation of radon flux, were tested. Four eastern Spanish sites with different geological and soil characteristics were selected: Teruel, Los Pedrones, Quintanar de la Orden and Madrid. The study shows the usefulness of both direct and indirect methods for obtaining radon flux data. Direct radon flux measurements by continuous and integrated monitors showed a coefficient of variation between 10% and 23%. At the same time, indirect methods based on correlations between 222 Rn and terrestrial γ dose rate, or 226 Ra activity in soil, provided results similar to the direct measurements, when these proxies were directly measured at the site. Larger discrepancies were found when proxy values were extracted from existing data bases. The participating members involved in the campaign study were the Institute of Energy Technology (INTE) of the Technical University of Catalonia (UPC), Huelva University (UHU), and Basel University (BASEL).

The coupling of bay hydrodynamics with sediment supply and micro-tidal wetland stability under high rates of relative sea level rise

Science.gov (United States)

Wang, J.; Xu, K.; Restreppo, G. A.; Bentley, S. J.; Meng, X.; Zhang, X.

2017-12-01

Due to global sea level rise, local subsidence and sediment deficit, the Mississippi River (MR) deltaic plain has lost a total of 25% of coastal Louisiana's wetlands during the last century, leading to huge losses of ecological services, economic and social crises. Ecosystem-based restoration strategies which rely on coastal system processes and feedbacks are urgently needed. Understanding linkages between estuarine and coastal systems and the adjacent marshlands will help the designing strategies. To investigate bay hydrodynamics and its impacts on the adjacent micro-tidal wetland stability, hourly measurements of wave, tidal current, and benthic sediment concentration in summer, winter, and spring of 2015-2016 were conducted in Fourleague Bay, Louisiana, USA. The bay-marsh system has been stable for almost 80 years under high relative sea level rising rate, which is 11 km southeast of the Atchafalaya River mouth, with a water depth of 1-3 m. High-temporal resolution data indicate that benthic sediment resuspension is mainly caused by wind-driven waves with a dominant periodicity of 4.8 d. The sediment flux reaches 28 g·m-1·s-1 per unit depth in cm during the events. Net sediment transport is northwestward in summer, and southeastward in winter and spring. Sediment flux available for surrounding marsh varies from 0-500 g·m-1·s-1. An optimal inundation depth of 50 cm is estimated by the equilibrium wetland elevation change model under high relative sea level rising rate of 1.57 cm·yr-1. Seasonal variations of river discharge and wind direction (particularly speeds >3 m·s-1) greatly impact potential sediment contribution from bay to the surrounding wetlands. Three sediment transport regimes are concluded based on the seasonal variations of river discharge and wind direction: the `bypassing' season, the resuspension-accumulation season, and the combined `bypassing' and resuspension-accumulation season. The bay hydrodynamic processes and their impacts on the

Electron heat flux instabilities in the solar wind

International Nuclear Information System (INIS)

Gary, S.P.; Feldman, W.C.; Forslund, D.W.; Montgomery, M.D.

1975-01-01

There are at least three plasma instabilities associated with the electron heat flux in the solar wind. This letter reports the study of the unstable fast magnetosonic, Alfven and whistler modes via a computer code which solves the full electromagnetic, linear, Vlasov dispersion relation. Linear theory demonstrates that both the magnetosonic and Alfven instabilities are candidates for turbulent limitation of the heat flux in the solar wind at 1 A.U

Flow rate-pressure drop relation for deformable shallow microfluidic channels

Science.gov (United States)

Christov, Ivan C.; Cognet, Vincent; Shidhore, Tanmay C.; Stone, Howard A.

2018-04-01

Laminar flow in devices fabricated from soft materials causes deformation of the passage geometry, which affects the flow rate--pressure drop relation. For a given pressure drop, in channels with narrow rectangular cross-section, the flow rate varies as the cube of the channel height, so deformation can produce significant quantitative effects, including nonlinear dependence on the pressure drop [{Gervais, T., El-Ali, J., G\\"unther, A. \\& Jensen, K.\\ F.}\\ 2006 Flow-induced deformation of shallow microfluidic channels.\\ \\textit{Lab Chip} \\textbf{6}, 500--507]. Gervais et. al. proposed a successful model of the deformation-induced change in the flow rate by heuristically coupling a Hookean elastic response with the lubrication approximation for Stokes flow. However, their model contains a fitting parameter that must be found for each channel shape by performing an experiment. We present a perturbation approach for the flow rate--pressure drop relation in a shallow deformable microchannel using the theory of isotropic quasi-static plate bending and the Stokes equations under a lubrication approximation (specifically, the ratio of the channel's height to its width and of the channel's height to its length are both assumed small). Our result contains no free parameters and confirms Gervais et. al.'s observation that the flow rate is a quartic polynomial of the pressure drop. The derived flow rate--pressure drop relation compares favorably with experimental measurements.

FLUX CANCELLATION AND THE EVOLUTION OF THE ERUPTIVE FILAMENT OF 2011 JUNE 7

Energy Technology Data Exchange (ETDEWEB)

Yardley, S. L.; Green, L. M.; Williams, D. R.; Van Driel-Gesztelyi, L.; Valori, G.; Dacie, S., E-mail: stephanie.yardley.13@ucl.ac.uk [Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT (United Kingdom)

2016-08-20

We investigate whether flux cancellation is responsible for the formation of a very massive filament resulting in the spectacular eruption on 2011 June 7. We analyze and quantify the amount of flux cancellation that occurs in NOAA AR 11226 and its two neighboring active regions (ARs 11227 and 11233) using line-of-sight magnetograms from the Heliospheric Magnetic Imager. During a 3.6 day period building up to the eruption of the filament, 1.7 × 10{sup 21} Mx, 21% of AR 11226's maximum magnetic flux, was canceled along the polarity inversion line (PIL) where the filament formed. If the flux cancellation continued at the same rate up until the eruption then up to 2.8 × 10{sup 21} Mx (34% of the AR flux) may have been built into the magnetic configuration that contains the filament plasma. The large flux cancellation rate is due to an unusual motion of the positive-polarity sunspot, which splits, with the largest section moving rapidly toward the PIL. This motion compresses the negative polarity and leads to the formation of an orphan penumbra where one end of the filament is rooted. Dense plasma threads above the orphan penumbra build into the filament, extending its length, and presumably injecting material into it. We conclude that the exceptionally strong flux cancellation in AR 11226 played a significant role in the formation of its unusually massive filament. In addition, the presence and coherent evolution of bald patches in the vector magnetic field along the PIL suggest that the magnetic field configuration supporting the filament material is that of a flux rope.

Neutron flux monitor

International Nuclear Information System (INIS)

Oda, Naotaka.

1993-01-01

The device of the present invention greatly saves an analog processing section such as an analog filter and an analog processing circuit. That is, the device of the present invention comprises (1) a neutron flux detection means for detecting neutron fluxed in the reactor, (2) a digital filter means for dividing signals corresponding to the detected neutron fluxes into predetermined frequency band regions, (3) a calculation processing means for applying a calculation processing corresponding to the frequency band regions to the neutron flux detection signals divided by the digital filter means. With such a constitution, since the neutron detection signals are processed by the digital filter means, the accuracy is improved and the change for the property of the filter is facilitated. Further, when a neutron flux level is obtained, a calculation processing corresponding to the frequency band region can be conducted without the analog processing circuit. Accordingly, maintenance and accuracy are improved by greatly decreasing the number of parts. Further, since problems inherent to the analog circuit are solved, neutron fluxes are monitored at high reliability. (I.S.)

Increase in γ-ray flux at balloon altitude during magnetic disturbances

International Nuclear Information System (INIS)

Martin, I.M; Rai, D.B.; Palmeira, R.A.R.; Trivedi, N.B.; Costa, J.M. da.

1974-01-01

Balloon observations of γ-rays (0.9 - 18 MeV) and charged particle (>=0.7 MeV) flux made at Sao Jose dos campos (23 0 14'S, 45 0 51'W) on quiet and magnetically disturbed days in October 1973 are presented and discussed. The γ-ray flux during the disturbed period shows a considerable increase compared to the quiet day observations. The charged particles count rate also shows an increase but to a much smaller extent. The increase in the γ-ray flux is attributed to the bremsstrahlung of precipitating high energy electrons from the inner radiation belt. A spectral analysis of the count rate of γ-rays shows that the increase in the flux is more pronounced on the low energy end (0.9 - 20 MeV) of the spectrum which lends further support to the bremsstrahlung explanation. Based on the photon spectrum in the range 0.9 - 18 MeV the spectrum of the precipitating electron causing the γ-ray emission is calculated. The photon spectrum is of the form dN/dE α E sup( - 2.2) in the range 0.9 - 2.5 MeV and dN/dE approximately E sup( - 1.1) in the range 7.0 - 18 MeV. Thus it may be concluded that the increase in the γ-ray flux is due to the precipitation of electrons of the inner radiation belt with E > 20 MeV

Nitrous oxide and methane fluxes in six different land use systems in the Peruvian Amazon

Science.gov (United States)

Palm, C. A.; Alegre, J. C.; Arevalo, L.; Mutuo, P. K.; Mosier, A. R.; Coe, R.

2002-12-01

The contribution of different land-use systems in the humid tropics to increasing atmospheric trace gases has focused on forests, pastures, and crops with few measurements from managed, tree-based systems that dominate much of the landscape. This study from the Peruvian Amazon includes monthly nitrous oxide and methane fluxes from two cropping systems, three tree-based systems, and a 23-year secondary forest control. Average N2O fluxes from the cropping systems were two to three times higher than the secondary forest control (9.1 μg N m-2 h-1), while those of the tree-based systems were similar to the secondary forest. Increased fluxes in the cropping systems were attributed to N fertilization, while fluxes from the tree-based systems were related to litterfall N. Average CH4 consumption was reduced by up to half that of the secondary forest (-30.0 μg C m-2 h-1) in the tree-based and low-input cropping systems. There was net CH4 production in the high-input cropping system. This switch to net production was a result of increased bulk density and increased soil respiration resulting in anaerobic conditions. Reduced rates of N2O emissions, similar CH4 consumption, and high C sequestration rates in these tree-based systems compared with mature forests, coupled with the large area of these systems in the humid tropics, may partially offset the past effects of deforestation on increased atmospheric trace gas concentrations. In contrast, cropping systems with higher N2O emissions, substantially reduced CH4 consumption or even net CH4 emissions, and little C sequestration exacerbate those effects.

Feldspar dissolution rates in the Topopah Spring Tuff, Yucca Mountain, Nevada

Science.gov (United States)

Bryan, C.R.; Helean, K.B.; Marshall, B.D.; Brady, P.V.

2009-01-01

Two different field-based methods are used here to calculate feldspar dissolution rates in the Topopah Spring Tuff, the host rock for the proposed nuclear waste repository at Yucca Mountain, Nevada. The center of the tuff is a high silica rhyolite, consisting largely of alkali feldspar (???60 wt%) and quartz polymorphs (???35 wt%) that formed by devitrification of rhyolitic glass as the tuff cooled. First, the abundance of secondary aluminosilicates is used to estimate the cumulative amount of feldspar dissolution over the history of the tuff, and an ambient dissolution rate is calculated by using the estimated thermal history. Second, the feldspar dissolution rate is calculated by using measured Sr isotope compositions for the pore water and rock. Pore waters display systematic changes in Sr isotopic composition with depth that are caused by feldspar dissolution. The range in dissolution rates determined from secondary mineral abundances varies from 10-16 to 10-17 mol s-1 kg tuff-1 with the largest uncertainty being the effect of the early thermal history of the tuff. Dissolution rates based on pore water Sr isotopic data were calculated by treating percolation flux parametrically, and vary from 10-15 to 10-16 mol s-1 kg tuff-1 for percolation fluxes of 15 mm a-1 and 1 mm a-1, respectively. Reconciling the rates from the two methods requires that percolation fluxes at the sampled locations be a few mm a-1 or less. The calculated feldspar dissolution rates are low relative to other measured field-based feldspar dissolution rates, possibly due to the age (12.8 Ma) of the unsaturated system at Yucca Mountain; because oxidizing and organic-poor conditions limit biological activity; and/or because elevated silica concentrations in the pore waters (???50 mg L-1) may inhibit feldspar dissolution. ?? 2009 Elsevier Ltd. All rights reserved.

Temporal fluxomics reveals oscillations in TCA cycle flux throughout the mammalian cell cycle.

Science.gov (United States)

Ahn, Eunyong; Kumar, Praveen; Mukha, Dzmitry; Tzur, Amit; Shlomi, Tomer

2017-11-06

Cellular metabolic demands change throughout the cell cycle. Nevertheless, a characterization of how metabolic fluxes adapt to the changing demands throughout the cell cycle is lacking. Here, we developed a temporal-fluxomics approach to derive a comprehensive and quantitative view of alterations in metabolic fluxes throughout the mammalian cell cycle. This is achieved by combining pulse-chase LC-MS-based isotope tracing in synchronized cell populations with computational deconvolution and metabolic flux modeling. We find that TCA cycle fluxes are rewired as cells progress through the cell cycle with complementary oscillations of glucose versus glutamine-derived fluxes: Oxidation of glucose-derived flux peaks in late G1 phase, while oxidative and reductive glutamine metabolism dominates S phase. These complementary flux oscillations maintain a constant production rate of reducing equivalents and oxidative phosphorylation flux throughout the cell cycle. The shift from glucose to glutamine oxidation in S phase plays an important role in cell cycle progression and cell proliferation. © 2017 The Authors. Published under the terms of the CC BY 4.0 license.

Global diffusive fluxes of methane in marine sediments

Science.gov (United States)

Egger, Matthias; Riedinger, Natascha; Mogollón, José M.; Jørgensen, Bo Barker

2018-06-01

Anaerobic oxidation of methane provides a globally important, yet poorly constrained barrier for the vast amounts of methane produced in the subseafloor. Here we provide a global map and budget of the methane flux and degradation in diffusion-controlled marine sediments in relation to the depth of the methane oxidation barrier. Our new budget suggests that 45-61 Tg of methane are oxidized with sulfate annually, with approximately 80% of this oxidation occurring in continental shelf sediments (methane in steady-state diffusive sediments, we calculate that 3-4% of the global organic carbon flux to the seafloor is converted to methane. We further report a global imbalance of diffusive methane and sulfate fluxes into the sulfate-methane transition with no clear trend with respect to the corresponding depth of the methane oxidation barrier. The observed global mean net flux ratio between sulfate and methane of 1.4:1 indicates that, on average, the methane flux to the sulfate-methane transition accounts for only 70% of the sulfate consumption in the sulfate-methane transition zone of marine sediments.

Type IIB flux vacua from G-theory I

Energy Technology Data Exchange (ETDEWEB)

Candelas, Philip [Mathematical Institute, University of Oxford,Andrew Wiles Building, Radcliffe Observatory Quarter,Woodstock Road, Oxford, OX2 6GG (United Kingdom); Constantin, Andrei [Department of Physics and Astronomy, Uppsala University,SE-751 20, Uppsala (Sweden); Damian, Cesar [Departamento de Fisica, DCI, Campus Leon, Universidad de Guanajuato,C.P. 37150, Leon, Guanajuato (Mexico); Larfors, Magdalena [Department of Physics and Astronomy, Uppsala University,SE-751 20, Uppsala (Sweden); Morales, Jose Francisco [INFN - Sezione di Roma “TorVergata”, Dipartimento di Fisica,Università di Roma “TorVergata”, Via della Ricerca Scientica, 00133 Roma (Italy)

2015-02-27

We construct non-perturbatively exact four-dimensional Minkowski vacua of type IIB string theory with non-trivial fluxes. These solutions are found by gluing together, consistently with U-duality, local solutions of type IIB supergravity on T{sup 4}×ℂ with the metric, dilaton and flux potentials varying along ℂ and the flux potentials oriented along T{sup 4}. We focus on solutions locally related via U-duality to non-compact Ricci-flat geometries. More general solutions and a complete analysis of the supersymmetry equations are presented in the companion paper http://arxiv.org/abs/1411.4786. We build a precise dictionary between fluxes in the global solutions and the geometry of an auxiliary K3 surface fibered over ℂℙ{sup 1}. In the spirit of F-theory, the flux potentials are expressed in terms of locally holomorphic functions that parametrize the complex structure moduli space of the K3 fiber in the auxiliary geometry. The brane content is inferred from the monodromy data around the degeneration points of the fiber.

Type IIB flux vacua from G-theory I

International Nuclear Information System (INIS)

Candelas, Philip; Constantin, Andrei; Damian, Cesar; Larfors, Magdalena; Morales, Jose Francisco

2015-01-01

We construct non-perturbatively exact four-dimensional Minkowski vacua of type IIB string theory with non-trivial fluxes. These solutions are found by gluing together, consistently with U-duality, local solutions of type IIB supergravity on T"4×ℂ with the metric, dilaton and flux potentials varying along ℂ and the flux potentials oriented along T"4. We focus on solutions locally related via U-duality to non-compact Ricci-flat geometries. More general solutions and a complete analysis of the supersymmetry equations are presented in the companion paper http://arxiv.org/abs/1411.4786. We build a precise dictionary between fluxes in the global solutions and the geometry of an auxiliary K3 surface fibered over ℂℙ"1. In the spirit of F-theory, the flux potentials are expressed in terms of locally holomorphic functions that parametrize the complex structure moduli space of the K3 fiber in the auxiliary geometry. The brane content is inferred from the monodromy data around the degeneration points of the fiber.

Aeolian dune sediment flux heterogeneity in Meridiani Planum, Mars.

Science.gov (United States)

Chojnacki, Matthew; Urso, Anna; Fenton, Lori K; Michaels, Timothy I

2017-06-01

It is now known unambiguously that wind-driven bedform activity is occurring on the surface of Mars today, including early detections of active sand dunes in Meridiani Planum's Endeavour crater. Many of these reports are only based on a few sets of observations of relatively isolated bedforms and lack regional context. Here, we investigate aeolian activity across central Meridiani Planum and test the hypothesis that dune sites surrounding Endeavour crater are also active and part of region-wide sediment migration driven by northwesterly winds. All 13 dune fields investigated clearly showed evidence for activity and the majority exhibited dune migration (average rates of 0.6 m/Earth-year). Observations indicate substantial geographic and temporal heterogeneity of dune crest fluxes across the area and per site. Locations with multiple time steps indicate dune sand fluxes can vary by a factor of five, providing evidence for short periods of rapid migration followed by near-stagnation. In contrast, measurements at other sites are nearly identical, indicating that some dunes are in a steady-state as they migrate. The observed sediment transport direction was consistent with a regional northeasterly-to-northwesterly wind regime, revealing more variations than were appreciated from earlier, more localized studies. Craters containing shallow, degraded, flat-floored interiors tended to have dunes with high sediment fluxes/activity, whereas local kilometer-scale topographic obstructions (e.g., central peaks, yardangs) were found to be inversely correlated with dune mobility. Finally, the previous, more limited detections of dune activity in Endeavour crater have been shown to be representative of a broader, region-wide pattern of dune motion.

An assessment of TropFlux and NCEP air-sea fluxes on ROMS simulations over the Bay of Bengal region

Science.gov (United States)

Dey, Dipanjan; Sil, Sourav; Jana, Sudip; Pramanik, Saikat; Pandey, P. C.

2017-12-01

This study presents an assessment of the TropFlux and the National Centers for Environmental Prediction (NCEP) reanalysis air-sea fluxes in simulating the surface and subsurface oceanic parameters over the Bay of Bengal (BoB) region during 2002-2014 using the Regional Ocean Modelling System (ROMS). The assessment has been made by comparing the simulated fields with in-situ and satellite observations. The simulated surface and subsurface temperatures in the TropFlux forced experiment (TropFlux-E) show better agreement with the Research Moored Array for African-Asian-Australian Monsoon Analysis (RAMA) and Argo observations than the NCEP forced experiment (NCEP-E). The BoB domain averaged sea surface temperature (SST) simulated in the NCEP-E is consistently cooler than the satellite SST, with a root mean square error (RMSE) of 0.79 °C. Moreover, NCEP-E shows a limitation in simulating the observed seasonal cycle of the SST due to substantial underestimation of the pre-monsoon SST peak. These limitations are mostly due to the lower values of the NCEP net heat flux. The seasonal and interannual variations of SST in the TropFlux-E are better comparable to the observations with correlations and skills more than 0.80 and 0.90 respectively. However, SST is overestimated during summer monsoon periods mainly due to higher net heat flux. The superiority of TropFlux forcing over the NCEP reanalysis can also be seen when simulating the interannual variabilities of the magnitude and vertical extent of Wyrtki jets at two equatorial RAMA buoy locations. The jet is weaker in the NCEP-E relative to the TropFlux-E and observations. The simulated sea surface height anomalies (SSHA) from both the experiments are able to capture the regions of positive and negative SSHA with respect to satellite-derived altimeter data with better performance in the TropFlux-E. The speed of the westward propagating Rossby wave along 18°N in the TropFlux-E is found to be about 4.7 cm/s, which is close to

Generalized drift-flux correlation

International Nuclear Information System (INIS)

Takeuchi, K.; Young, M.Y.; Hochreiter, L.E.

1991-01-01

A one-dimensional drift-flux model with five conservation equations is frequently employed in major computer codes, such as TRAC-PD2, and in simulator codes. In this method, the relative velocity between liquid and vapor phases, or slip ratio, is given by correlations, rather than by direct solution of the phasic momentum equations, as in the case of the two-fluid model used in TRAC-PF1. The correlations for churn-turbulent bubbly flow and slug flow regimes were given in terms of drift velocities by Zuber and Findlay. For the annular flow regime, the drift velocity correlations were developed by Ishii et al., using interphasic force balances. Another approach is to define the drift velocity so that flooding and liquid hold-up conditions are properly simulated, as reported here. The generalized correlation is used to reanalyze the MB-2 test data for two-phase flow in a large-diameter pipe. The results are applied to the generalized drift flux velocity, whose relationship to the other correlations is discussed. Finally, the generalized drift flux correlation is implemented in TRAC-PD2. Flow reversal from countercurrent to cocurrent flow is computed in small-diameter U-shaped tubes and is compared with the flooding curve

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

Science.gov (United States)

Russell, L. D.

1979-01-01

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

Nares Abyssal Plain Sediment Flux Studies, FY 1985 Annual Report

International Nuclear Information System (INIS)

Dymond, J.; Collier, R.

1987-01-01

The sediment trap NAP-1 was successfully recovered and the materials have been analyzed for a set of bio- and geochemical components. The trap mooring NAP-2 was deployed and recovered but no analyses have been completed. The bulk fluxes are relatively low at this site and are approximately 50% biogenic and 50% terrigenous. The flux of terrigenous material is very high due to primary atmospheric inputs and horizontal transport of resuspended sediments. The buoyant particle fluxes are also extremely low. The accumulation of material in the sediments reflects the crustal nature of the vertical flux and also shows the normal loss of labile biogenic phases

TRANSHEX, 2-D Thermal Neutron Flux Distribution from Epithermal Flux in Hexagonal Geometry

International Nuclear Information System (INIS)

Patrakka, E.

1994-01-01

1 - Description of program or function: TRANSHEX is a multigroup integral transport program that determines the thermal scalar flux distribution arising from a known epithermal flux in two- dimensional hexagonal geometry. 2 - Method of solution: The program solves the isotropic collision probability equations for a region-averaged scalar flux by an iterative method. Either a successive over-relaxation or an inner-outer iteration technique is applied. Flat flux collision probabilities between trigonal space regions with white boundary condition are utilized. The effect of epithermal flux is taken into consideration as a slowing-down source that is calculated for a given spatial distribution and 1/E energy dependence of the epithermal flux

Changing trends of rainfall and sediment fluxes in the Kinta River catchment, Malaysia

Directory of Open Access Journals (Sweden)

W. R. Ismail

2015-03-01

Full Text Available The Kinta River, draining an area of 2566 km2, originates in the Korbu Mountain in Perak, Malaysia, and flows through heterogeneous, mixed land uses ranging from extensive forests to mining, rubber and oil palm plantations, and urban development. A land use change analysis of the Kinta River catchment was carried out together with assessment of the long-term trend in rainfall and sediment fluxes. The Mann-Kendall test was used to examine and assess the long-term trends in rainfall and its relationship with the sediment discharge trend. The land use analysis shows that forests, water bodies and mining land declined whilst built and agricultural land use increased significantly. This has influenced the sediment flux of the catchment. However, most of the rainfall stations and river gauging stations are experiencing an increasing trends, except at Kinta river at Tg. Rambutan. Sediment flux shows a net erosion for the period from 1961 to 1969. The total annual sediment discharge in the Kinta River catchment was low with an average rate of 1,757 t/km2/year. From 1970 to 1985, the annual sediment yield rose to an average rate of 4062 t/km2/year. Afterwards, from 1986 to 1993, the total annual sediment discharge decreased to an average rate of 1,306 t/km2/year and increased back during the period 1994 to 2000 to 2109 t/km2/year. From 2001 to 2006 the average sediment flux rate declined to 865 t/km2/year. The decline was almost 80% from the 1970s. High sediment flux in the early 1970s is partly associated with reduced tin mining activities in the area. This decreasing trend in sediment delivery leaving the Kinta River catchment is expected to continue dropping in the future.

Changing trends of rainfall and sediment fluxes in the Kinta River catchment, Malaysia

Science.gov (United States)

Ismail, W. R.; Hashim, M.

2015-03-01

The Kinta River, draining an area of 2566 km2, originates in the Korbu Mountain in Perak, Malaysia, and flows through heterogeneous, mixed land uses ranging from extensive forests to mining, rubber and oil palm plantations, and urban development. A land use change analysis of the Kinta River catchment was carried out together with assessment of the long-term trend in rainfall and sediment fluxes. The Mann-Kendall test was used to examine and assess the long-term trends in rainfall and its relationship with the sediment discharge trend. The land use analysis shows that forests, water bodies and mining land declined whilst built and agricultural land use increased significantly. This has influenced the sediment flux of the catchment. However, most of the rainfall stations and river gauging stations are experiencing an increasing trends, except at Kinta river at Tg. Rambutan. Sediment flux shows a net erosion for the period from 1961 to 1969. The total annual sediment discharge in the Kinta River catchment was low with an average rate of 1,757 t/km2/year. From 1970 to 1985, the annual sediment yield rose to an average rate of 4062 t/km2/year. Afterwards, from 1986 to 1993, the total annual sediment discharge decreased to an average rate of 1,306 t/km2/year and increased back during the period 1994 to 2000 to 2109 t/km2/year. From 2001 to 2006 the average sediment flux rate declined to 865 t/km2/year. The decline was almost 80% from the 1970s. High sediment flux in the early 1970s is partly associated with reduced tin mining activities in the area. This decreasing trend in sediment delivery leaving the Kinta River catchment is expected to continue dropping in the future.