Sample records for activity gas exchange

  1. Enhanced pulmonary and active skeletal muscle gas exchange during intense exercise after sprint training in men.

    PubMed Central

    McKenna, M J; Heigenhauser, G J; McKelvie, R S; Obminski, G; MacDougall, J D; Jones, N L

    1997-01-01

    1. This study investigated the effects of 7 weeks of sprint training on gas exchange across the lungs and active skeletal muscle during and following maximal cycling exercise in eight healthy males. 2. Pulmonary oxygen uptake (VO2) and carbon dioxide output (VCO2) were measured before and after training during incremental exercise (n = 8) and during and in recovery from a maximal 30 s sprint exercise bout by breath-by-breath analysis (n = 6). To determine gas exchange by the exercising leg muscles, brachial arterial and femoral venous blood O2 and CO2 contents and lactate concentration were measured at rest, during the final 10 s of exercise and during 10 min of recovery. 3. Training increased (P < 0.05) the maximal incremental exercise values of ventilation (VE, by 15.7 +/- 7.1%), VCO2 (by 9.3 +/- 2.1%) and VO2 (by 15.0 +/- 4.2%). Sprint exercise peak power (3.9 +/- 1.0% increase) and cumulative 30 s work (11.7 +/- 2.8% increase) were increased and fatigue index was reduced (by -9.2 +/- 1.5%) after training (P < 0.05). The highest VE, VCO2 and VO2 values attained during sprint exercise were not significantly changed after training, but a significant (P < 0.05) training effect indicated increased VE (by 19.2 +/- 7.9%), VCO2 (by 9.3 +/- 2.1%) and VO2 (by 12.7 +/- 6.5%), primarily reflecting elevated post-exercise values after training. 4. Arterial O2 and CO2 contents were lower after training, by respective mean differences of 3.4 and 21.9 ml l-1 (P < 0.05), whereas the arteriovenous O2 and CO2 content differences and the respiratory exchange ratio across the leg were unchanged by training. 5. Arterial whole blood lactate concentration and the net lactate release by exercising muscle were unchanged by training. 6. The greater peak pulmonary VO2 and VCO2 with sprint exercise, the increased maximal incremental values, unchanged arterial blood lactate concentration and greater sprint performance all point strongly towards enhanced gas exchange across the lungs and in active muscles after sprint training. Enhanced aerobic metabolism after sprint training may contribute to reduced fatigability during maximal exercise, whilst greater pulmonary CO2 output may improve acid-base control after training. PMID:9218229

  2. Activities Exchange

    NSDL National Science Digital Library

    Texas Instruments

    2008-01-31

    The site provides a free, colaborative forum where educators share activities that employ TI technology. This page links to hundreds of math and science activities for K-12, authored by teachers as well as Texas Instruments professionals. Social studies and language arts are also well represented in the list of subjects. Activities can be searched as well by curriculum standard or by textbook connection.

  3. Gas Exchange of Algae

    PubMed Central

    Ammann, Elizabeth C. B.; Lynch, Victoria H.

    1966-01-01

    Changes in the oxygen partial pressure of air over the range of 8 to 258 mm of Hg did not adversely affect the photosynthetic capacity of Chlorella pyrenoidosa. Gas exchange and growth measurements remained constant for 3-week periods and were similar to air controls (oxygen pressure of 160 mm of Hg). Oxygen partial pressures of 532 and 745 mm of Hg had an adverse effect on algal metabolism. Carbon dioxide consumption was 24% lower in the gas mixture containing oxygen at a pressure 532 mm of Hg than in the air control, and the growth rate was slightly reduced. Oxygen at a partial pressure of 745 mm of Hg decreased the photosynthetic rate 39% and the growth rate 37% over the corresponding rates in air. The lowered metabolic rates remained constant during 14 days of measurements, and the effect was reversible after this time. Substitution of helium or argon for the nitrogen in air had no effect on oxygen production, carbon dioxide consumption, or growth rate for 3-week periods. All measurements were made at a total pressure of 760 mm of Hg, and all gas mixtures were enriched with 2% carbon dioxide. Thus, the physiological functioning and reliability of a photosynthetic gas exchanger should not be adversely affected by: (i) oxygen partial pressures ranging from 8 to 258 mm of Hg; (ii) the use of pure oxygen at reduced total pressure (155 to 258 mm of Hg) unless pressure per se affects photosynthesis, or (iii) the inclusion of helium or argon in the gas environment (up to a partial pressure of 595 mm of Hg). PMID:5927028

  4. Insect gas exchange patterns: a phylogenetic perspective.

    PubMed

    Marais, Elrike; Klok, C Jaco; Terblanche, John S; Chown, Steven L

    2005-12-01

    Most investigations of insect gas exchange patterns and the hypotheses proposed to account for their evolution have been based either on small-scale, manipulative experiments, or comparisons of a few closely related species. Despite their potential utility, no explicit, phylogeny-based, broad-scale comparative studies of the evolution of gas exchange in insects have been undertaken. This may be due partly to the preponderance of information for the endopterygotes, and its scarcity for the apterygotes and exopterygotes. Here we undertake such a broad-scale study. Information on gas exchange patterns for the large majority of insects examined to date (eight orders, 99 species) is compiled, and new information on 19 exemplar species from a further ten orders, not previously represented in the literature (Archaeognatha, Zygentoma, Ephemeroptera, Odonata, Mantodea, Mantophasmatodea, Phasmatodea, Dermaptera, Neuroptera, Trichoptera), is provided. These data are then used in a formal, phylogeny-based parsimony analysis of the evolution of gas exchange patterns at the order level. Cyclic gas exchange is likely to be the ancestral gas exchange pattern at rest (recognizing that active individuals typically show continuous gas exchange), and discontinuous gas exchange probably originated independently a minimum of five times in the Insecta. PMID:16339869

  5. BOREAS TE-12 Leaf Gas Exchange Data

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Arkebauer, Timothy J.; Yang, Litao

    2000-01-01

    The BOREAS TE-12 team collected several data sets in support of its efforts to characterize and interpret information on the reflectance, transmittance, and gas exchange of boreal vegetation. This data set contains measurements of leaf gas exchange conducted in the SSA during the growing seasons of 1994 and 1995 using a portable gas exchange system. The data are stored in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Center (DAAC).

  6. Active microchannel heat exchanger

    DOEpatents

    Tonkovich, Anna Lee Y. (Pasco, WA) [Pasco, WA; Roberts, Gary L. (West Richland, WA) [West Richland, WA; Call, Charles J. (Pasco, WA) [Pasco, WA; Wegeng, Robert S. (Richland, WA) [Richland, WA; Wang, Yong (Richland, WA) [Richland, WA

    2001-01-01

    The present invention is an active microchannel heat exchanger with an active heat source and with microchannel architecture. The microchannel heat exchanger has (a) an exothermic reaction chamber; (b) an exhaust chamber; and (c) a heat exchanger chamber in thermal contact with the exhaust chamber, wherein (d) heat from the exothermic reaction chamber is convected by an exothermic reaction exhaust through the exhaust chamber and by conduction through a containment wall to the working fluid in the heat exchanger chamber thereby raising a temperature of the working fluid. The invention is particularly useful as a liquid fuel vaporizer and/or a steam generator for fuel cell power systems, and as a heat source for sustaining endothermic chemical reactions and initiating exothermic reactions.

  7. Electron gas exchange for atoms

    Microsoft Academic Search

    José Luis Gázquez; Jaime Keller

    1977-01-01

    Current use of electron gas theory for exchange allows calculations of Hartree-Fock (HF) energies through the use of local potentials. A recent proposal of Gopinathan, Whitehead, and Bogdanovic to use a realistic pair correlation function f??(1, 2) that incorporates the boundary conditions of Kutzelnigg, Del Re, and Berthier, which consider the finite number of electrons of a given spin, showed

  8. Pulmonary gas exchange in diving.

    PubMed

    Moon, R E; Cherry, A D; Stolp, B W; Camporesi, E M

    2009-02-01

    Diving-related pulmonary effects are due mostly to increased gas density, immersion-related increase in pulmonary blood volume, and (usually) a higher inspired Po(2). Higher gas density produces an increase in airways resistance and work of breathing, and a reduced maximum breathing capacity. An additional mechanical load is due to immersion, which can impose a static transrespiratory pressure load as well as a decrease in pulmonary compliance. The combination of resistive and elastic loads is largely responsible for the reduction in ventilation during underwater exercise. Additionally, there is a density-related increase in dead space/tidal volume ratio (Vd/Vt), possibly due to impairment of intrapulmonary gas phase diffusion and distribution of ventilation. The net result of relative hypoventilation and increased Vd/Vt is hypercapnia. The effect of high inspired Po(2) and inert gas narcosis on respiratory drive appear to be minimal. Exchange of oxygen by the lung is not impaired, at least up to a gas density of 25 g/l. There are few effects of pressure per se, other than a reduction in the P50 of hemoglobin, probably due to either a conformational change or an effect of inert gas binding. PMID:19008484

  9. BOREAS TE-10 Leaf Gas Exchange Data

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Papagno, Andrea (Editor); Middleton, Elizabeth; Sullivan, Joseph

    2000-01-01

    The Boreal Ecosystem-Atmospheric Study (BOREAS) TE-10 (Terrestrial Ecology) team collected several data sets in support of its efforts to characterize and interpret information on the reflectance, transmittance, gas exchange, chlorophyll content, carbon content, hydrogen content, and nitrogen content of boreal vegetation. This data set contains measurements of assimilation, stomatal conductance, transpiration, internal CO2 concentration, and water use efficiency conducted in the Southern Study Area (SSA) during the growing seasons of 1994 and 1996 using a portable gas exchange system. The data are stored in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

  10. History of respiratory gas exchange.

    PubMed

    West, John B

    2011-07-01

    As early as the 6th century B.C. the Greeks speculated on a substance pneuma that meant breath or soul, and they argued that this was essential for life. An important figure in the 2nd century A.D. was Galen whose school developed an elaborate cardiopulmonary system that influenced scientific thinking for 1400 years. A key concept was that blood was mixed with pneuma from the lung in the left ventricle thus forming vital spirit. It was also believed that blood flowed from the right to the left ventricle of the heart through pores in the interventricular septum but this view was challenged first by the Arab physician Ibn al-Nafis in the 13th century and later by Michael Servetus in the 16th century. The 17th century saw an enormous burgeoning of knowledge about the respiratory gases. First Torricelli explained the origin of atmospheric pressure, and then a group of physiologists in Oxford clarified the properties of inspired gas that were necessary for life. This culminated in the work of Lavoisier who first clearly elucidated the nature of the respiratory gases, oxygen, carbon dioxide and nitrogen. At that time it was thought that oxygen was consumed in the lung itself, and the fact that the actual metabolism took place in peripheral tissues proved to be a very elusive concept. It was not until the late 19th century that the issue was finally settled by Pflüger. In the early 20th century there was a colorful controversy about whether oxygen was secreted by the lung. During and shortly after World War II, momentous strides were made on the understanding of pulmonary gas exchange, particularly the role of ventilation-perfusion inequality. A critical development in the 1960s was the introduction of blood gas electrodes, and these have transformed the management of patients with severe lung disease. PMID:23733651

  11. BOREAS TE-11 Leaf Gas Exchange Measurements

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Papagno, Andrea (Editor); Saugier, Bernard; Pontailler, J. Y.

    2000-01-01

    The Boreal Ecosystem-Atmospheric Study (BOREAS) TE-11 (Terrestrial Ecology) team collected several data sets in support of its efforts to characterize and interpret information on the sap flow, gas exchange, and lichen photosynthesis of boreal vegetation and meteorological data of the area studied. This data set contains measurements of assimilation and transpiration conducted at the Old Jack Pine (OJP) site during the growing seasons of 1993 and 1994. The data are stored in ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

  12. How does lung structure affect gas exchange?

    PubMed

    Weibel, E R

    1983-04-01

    The lung is characterized morphologically by establishing a very large surface and an exceedingly thin barrier between air and blood. A model for relating these structural features to the lung's gas exchange function is first developed. It is then shown that DO2 estimated by morphometry is about two times larger than that estimated by physiology; there are possible reasons for this. Comparing animals of high activity (dog, horse) with corresponding species of lower activity (man, cow) reveals that DO2 is proportional to O2 needs. The mechanical properties of the lung are discussed which allow such a large surface with such a thin barrier to be maintained lifelong. Surfactant properties of the lining layer are important factors in stabilizing the alveolar surface. Repair processes are also essential and require metabolic activities of the cells lining the barrier. The case of adult respiratory distress syndrome is used to illustrate the consequences of severe damage to the cell linings of alveoli: the barrier is thickened, and a good part of the alveolar surface is flooded by edema fluid, so that gas exchange is severely impaired. PMID:6687569

  13. Reversible brain inactivation induces discontinuous gas exchange in cockroaches.

    PubMed

    Matthews, Philip G D; White, Craig R

    2013-06-01

    Many insects at rest breathe discontinuously, alternating between brief bouts of gas exchange and extended periods of breath-holding. The association between discontinuous gas exchange cycles (DGCs) and inactivity has long been recognised, leading to speculation that DGCs lie at one end of a continuum of gas exchange patterns, from continuous to discontinuous, linked to metabolic rate (MR). However, the neural hypothesis posits that it is the downregulation of brain activity and a change in the neural control of gas exchange, rather than low MR per se, which is responsible for the emergence of DGCs during inactivity. To test this, Nauphoeta cinerea cockroaches had their brains inactivated by applying a Peltier-chilled cold probe to the head. Once brain temperature fell to 8°C, cockroaches switched from a continuous to a discontinuous breathing pattern. Re-warming the brain abolished the DGC and re-established a continuous breathing pattern. Chilling the brain did not significantly reduce the cockroaches' MR and there was no association between the gas exchange pattern displayed by the insect and its MR. This demonstrates that DGCs can arise due to a decrease in brain activity and a change in the underlying regulation of gas exchange, and are not necessarily a simple consequence of low respiratory demand. PMID:23430991

  14. Plant physiology Stomatal movements and gas exchanges

    E-print Network

    Paris-Sud XI, Université de

    was avoided by stomatal closure in rye and Triticum df, whereas in T300 the stomata stayed open and gas exchange were lower than in control plants. stomata / water-use efficiency / osmotic stress / triticale

  15. Anesthesia and gas exchange in tracheal surgery.

    PubMed

    Wiedemann, Klaus; Männle, Clemens

    2014-02-01

    Tracheobronchial surgery constitutes a challenge to the anesthetist because it involves the anatomic structures dedicated to bulk gas transport. Common approaches to airway management and gas exchange for extrathoracic and intrathoracic airway surgery are reviewed, with due regard to less common methods thought crucial for specific procedures. Tracheal surgery, beyond sharing the airways, requires sharing with the surgeon ideas on preoperative assessment, on the impact on gas exchange of induction across compromised airways, and of emergence from anesthesia with airways altered by surgical repair. Mutual understanding is essential to prevent, rapidly identify, and correct imminent loss of airway viability. PMID:24295656

  16. Relationship between cardioventilatory coupling and pulmonary gas exchange.

    PubMed

    Sin, P Y W; Webber, M R; Galletly, D C; Tzeng, Y C

    2012-11-01

    Cardioventilatory coupling (CVC) is a temporal alignment between the heartbeat and inspiratory activity caused by pulsatile baroreceptor afferent activity. However, although first described over a century ago, the functional significance of CVC has yet to be established. One hypothesis is that baroreceptor triggering of inspiration positions heartbeats into phases of the respiratory cycle that may optimize pulmonary gas exchange efficiency. To test this hypothesis, we recruited ten patients with permanently implanted fixed-rate cardiac pacemakers and instructed them to pace breathe at heart rate-to-respiratory rate (HR/f) ratios of 3·8, 4·0 and 4·2. This breathing protocol enabled us to simulate heartbeat distributions similar to those seen in the presence (4·0) and complete absence (3·8, 4·2) of CVC. Results showed that heart rate, mean arterial pressure, end-tidal carbon dioxide and tidal volume remained unchanged across the three conditions (P> 0·05). Pulmonary gas exchange efficiency, as determined by the ventilatory equivalents of carbon dioxide (V·E/V·CO2) and oxygen (V·E/V·O2) did not differ significantly by HR/f ratio (P = 0·29 and P = 0·70, respectively). These data suggest that CVC does not play a significant role in optimizing pulmonary gas exchange efficiency in humans. PMID:23031069

  17. Original article Gas exchange in young Scots pine following

    E-print Network

    Boyer, Edmond

    Original article Gas exchange in young Scots pine following pruning of current shoots E Troeng B; A pine shoot beetle attack was simulated by cutting all current shoots in the upper crown of 2 20-yr-old Scots pines (Pinus sylvestris L) while gas exchange was followed continuously before and after the shoot

  18. Circadian rhythms constrain leaf and canopy gas exchange in an Amazonian forest

    NASA Astrophysics Data System (ADS)

    Doughty, Christopher E.; Goulden, Michael L.; Miller, Scott D.; da Rocha, Humberto R.

    2006-08-01

    We used a controlled-environment leaf gas-exchange system and the micrometeorological technique eddy covariance to determine whether circadian rhythms constrain the rates of leaf and canopy gas exchange in an Amazonian forest over a day. When exposed to continuous and constant light for 20 to 48 hours leaves of eleven of seventeen species reduced their photosynthetic rates and closed their stomata during the normally dark period and resumed active gas exchange during the normally light period. Similarly, the rate of whole-forest CO2 uptake at a predetermined irradiance declined during the late afternoon and early morning and increased during the middle of the day. We attribute these cycles to circadian rhythms that are analogous to ones that have been reported for herbaceous plants in the laboratory. The importance of endogenous gas exchange rhythms presents a previously unrecognized challenge for efforts to both interpret and model land-atmosphere energy and mass exchange.

  19. Bacterioneuston control of air-water methane exchange determined with a laboratory gas exchange tank

    NASA Astrophysics Data System (ADS)

    Upstill-Goddard, Robert C.; Frost, Thomas; Henry, Gordon R.; Franklin, Mark; Murrell, J. Colin; Owens, Nicholas J. P.

    2003-12-01

    The apparent transfer velocities (kw) of CH4, N2O, and SF6 were determined for gas invasion and evasion in a closed laboratory exchange tank. Tank water (pure Milli-RO® water or artificial seawater prepared in Milli-RO®) and/or tank air gas compositions were adjusted, with monitoring of subsequent gas transfer by gas chromatography. Derived kw was converted to "apparent k600," the value for CO2 in freshwater at 20°C. For CH4, analytical constraints precluded estimating apparent k600 based on tank air measurements. In some experiments we added strains of live methanotrophs. In others we added chemically deactivated methanotrophs, non-CH4 oxidizers (Vibrio), or bacterially associated surfactants, as controls. For all individual controls, apparent k600 estimated from CH4, N2O, or SF6 was indistinguishable. However, invasive estimates always exceeded evasive estimates, implying some control of gas invasion by bubbles. Estimates of apparent k600 differed significantly between methanotroph strains, possibly reflecting species-specific surfactant release. For individual strains during gas invasion, apparent k600 estimated from CH4, N2O, or SF6 was indistinguishable, whereas during gas evasion, k600-CH4 was significantly higher than either k600-N2O or k600-SF6, which were identical. Hence evasive k600-CH4/k600-SF6 was always significantly above unity, whereas invasive k600-CH4/k600-SF6 was not significantly different from unity. Similarly, k600-CH4/k600-SF6 for the controls and k600-N2O/k600-SF6 for all experiments did not differ significantly from unity. Our results are consistent with active metabolic control of CH4 exchange by added methanotrophs in the tank microlayer, giving enhancements of ˜12 ± 10% for k600-CH4. Hence reactive trace gas fluxes determined by conventional tracer methods at sea may be in error, prompting a need for detailed study of the role of the sea surface microlayer in gas exchange.

  20. Experimental Investigation on Heat Transfer Characteristics of a Gas-to-Gas Counterflow Microchannel Heat Exchanger

    Microsoft Academic Search

    K. Koyama; Y. Asako

    2010-01-01

    Heat transfer characteristics of a gas-to-gas counterflow microchannel heat exchanger have been experimentally investigated. Temperatures and pressures at inlets and outlets of the heat exchanger have been measured to obtain heat transfer rates and pressure drops. The heat transfer and the pressure drop characteristics are discussed. Since the partition wall of the heat exchanger is thick compared with the microchannel

  1. GAS COOLED, MOLTEN SALT HEAT EXCHANGER--DESIGN STUDY

    Microsoft Academic Search

    MacPherson

    1958-01-01

    BS> One of the major problems in the economic evaluation of the ; application of forced circulation, gas cooling to high temperature, molten salt ; power reactor systems is the definition of the required heat transfer equipment, ; its size and operating cost. A design study of the saltto-gas heat exchangers ; for such a gas-cooled system has recently been

  2. Improved helium exchange gas cryostat and sample tube designs for automated gas sampling and cryopumping

    E-print Network

    Severinghaus, Jeffrey P.

    Improved helium exchange gas cryostat and sample tube designs for automated gas sampling, California 92093-0244, USA [1] In order to eliminate the use of liquid helium for the extraction of atmospheric gases from polar ice cores, two units of a redesigned top load helium exchange gas cryostat were

  3. An automated gas exchange tank for determining gas transfer velocities in natural seawater samples

    NASA Astrophysics Data System (ADS)

    Schneider-Zapp, K.; Salter, M. E.; Upstill-Goddard, R. C.

    2014-07-01

    In order to advance understanding of the role of seawater surfactants in the air-sea exchange of climatically active trace gases via suppression of the gas transfer velocity (kw), we constructed a fully automated, closed air-water gas exchange tank and coupled analytical system. The system allows water-side turbulence in the tank to be precisely controlled with an electronically operated baffle. Two coupled gas chromatographs and an integral equilibrator, connected to the tank in a continuous gas-tight system, allow temporal changes in the partial pressures of SF6, CH4 and N2O to be measured simultaneously in the tank water and headspace at multiple turbulence settings, during a typical experimental run of 3.25 h. PC software developed by the authors controls all operations and data acquisition, enabling the optimisation of experimental conditions with high reproducibility. The use of three gases allows three independent estimates of kw for each turbulence setting; these values are subsequently normalised to a constant Schmidt number for direct comparison. The normalised kw estimates show close agreement. Repeated experiments with Milli-Q water demonstrate a typical measurement accuracy of 4% for kw. Experiments with natural seawater show that the system clearly resolves the effects on kw of spatial and temporal trends in natural surfactant activity. The system is an effective tool with which to probe the relationships between kw, surfactant activity and biogeochemical indices of primary productivity, and should assist in providing valuable new insights into the air-sea gas exchange process.

  4. An automated gas exchange tank for determining gas transfer velocities in natural seawater samples

    NASA Astrophysics Data System (ADS)

    Schneider-Zapp, K.; Salter, M. E.; Upstill-Goddard, R. C.

    2014-02-01

    In order to advance understanding of the role of seawater surfactants in the air-sea exchange of climatically active trace gases via suppression of the gas transfer velocity (kw), we constructed a fully automated, closed air-water gas exchange tank and coupled analytical system. The system allows water-side turbulence in the tank to be precisely controlled with an electronically operated baffle. Two coupled gas chromatographs and an integral equilibrator, connected to the tank in a continuous gas-tight system, allow temporal changes in the partial pressures of SF6, CH4 and N2O to be measured simultaneously in the tank water and headspace at multiple turbulence settings, during a typical experimental run of 3.25 h. PC software developed by the authors controls all operations and data acquisition, enabling the optimisation of experimental conditions with high reproducibility. The use of three gases allows three independent estimates of kw for each turbulence setting; these values are subsequently normalised to a constant Schmidt number for direct comparison. The normalised kw estimates show close agreement. Repeated experiments with MilliQ water demonstrate a typical measurement accuracy of 4% for kw. Experiments with natural seawater show that the system clearly resolves the effects on kw of spatial and temporal trends in natural surfactant activity. The system is an effective tool with which to probe the relationships between kw, surfactant activity and biogeochemical indices of primary productivity, and should assist in providing valuable new insights into the air-sea gas exchange process.

  5. Discontinuous gas exchange in dung beetles: patterns and ecological implications

    Microsoft Academic Search

    Frances D. Duncan; Marcus J. Byrne

    2000-01-01

    This study correlates a distinctive pattern of external gas exchange, referred to as the discontinuous gas exchange cycle\\u000a (DGC), observed in the laboratory, with habitat associations of five species of telecoprid dung beetles. The beetles were\\u000a chosen from a variety of habitats that would be expected to present different amounts of water stress. All five species exhibited\\u000a DGC. Sisyphus fasciculatus

  6. Teaching Pulmonary Gas Exchange Physiology Using Computer Modeling

    ERIC Educational Resources Information Center

    Kapitan, Kent S.

    2008-01-01

    Students often have difficulty understanding the relationship of O[subscript 2] consumption, CO[subscript 2] production, cardiac output, and distribution of ventilation-perfusion ratios in the lung to the final arterial blood gas composition. To overcome this difficulty, I have developed an interactive computer simulation of pulmonary gas exchange…

  7. Thermal activation in exchange biased bilayers

    Microsoft Academic Search

    T. Hughes; K. O’Grady; H. Laidler; R. W. Chantrell

    2001-01-01

    Magnetisation reversal in an exchange biased ferromagnetic\\/antiferromagnetic bilayer is extremely complex due to the coupling between the spins at the interface. Particular importance should be paid to the issue of thermally activated and hence time dependent reversal of the antiferromagnet during the reversal of the adjacent ferromagnet. This reversal of the antiferromagnet is one mechanism that can lead to an

  8. Relationship between wind speed and gas exchange over the ocean

    NASA Technical Reports Server (NTRS)

    Wanninkhof, Rik

    1992-01-01

    A quadratic dependence of gas exchange on wind speed is employed to analyze the relationship between gas transfer and wind speed with particular emphasizing variable and/or low wind speeds. The quadratic dependence is fit through gas-transfer velocities over the ocean determined by methods based on the natural C-14 disequilibrium and the bomb C-14 inventory. The variation in the CO2 levels is related to these mechanisms, but the results show that other causes play significant roles. A weaker dependence of gas transfer on wind is suggested for steady winds, and long-term averaged winds demonstrate a stronger dependence in the present model. The chemical enhancement of CO2 exchange is also shown to play a role by increasing CO2 fluxes at low wind speeds.

  9. Gas turbine power plant having a heat exchanger

    SciTech Connect

    Huller, J.; Krockow, W.

    1981-12-29

    A gas turbine power plant, such as a gas turbine engine for a motor vehicle, having a gas turbine, a combustor for producing hot gas to drive the turbine, and an air compressor for furnishing compressed air to the combustor are described. A heat exchanger, such as a rotary regenerator or a cross-flow recuperator, is located between the air compressor and the combustor for heating air by exhaust gas from the turbine before the air enters the combustor. The air leaving the exit of the heat exchanger decreases in temperature in a direction from one end of the exit to the other. A plurality of separate ducts conduct air from successive areas along the length of the heat exchanger exit to corresponding successive regions along the length of the combustor, the air temperature being lower in each succeeding duct. The lowest temperature air is conducted to the region containing a forward portion, e.g., the head, of the combustor, and air of progressively higher temperature being ducted to successive regions closer to the exhaust end of the combustor.

  10. Leaf gas exchange and carbohydrate concentrations in Pinus pinaster plants subjected to elevated CO2

    E-print Network

    Paris-Sud XI, Université de

    Note Leaf gas exchange and carbohydrate concentrations in Pinus pinaster plants subjected, whereas no significant CO2 effect was observed on the soluble carbohydrate concentration. These compounds. (© Inra/Elsevier, Paris.) elevated [CO2] / drought / leaf gas exchange / carbohydrate / Pinus

  11. Greenhouse Gas Exchange in Small Arctic Thaw Ponds

    NASA Astrophysics Data System (ADS)

    Laurion, I.; Bégin, P. N.; Bouchard, F.; Preskienis, V.

    2014-12-01

    Arctic lakes and ponds can represent up to one quarter of the land surface in permafrost landscapes, particularly in lowland tundra landscapes characterized by ice wedge organic polygons. Thaw ponds can be defined as the aquatic ecosystems associated to thawing of organic soils, either resulting from active layer processes and located above low-center peat polygons (hereafter low-center polygonal or LCP ponds), or resulting from thermokarst slumping above melting ice wedges linked to the accelerated degradation of permafrost (hereafter ice-wedge trough or IWT ponds). These ponds can merge together forming larger water bodies, but with relatively stable shores (hereafter merged polygonal or MPG ponds), and with limnological characteristics similar to LCP ponds. These aquatic systems are very small and shallow, and present a different physical structure than the larger thermokarst lakes, generated after years of development and land subsidence. In a glacier valley on Bylot Island, Nunavut, Canada, thermokarst and kettle lakes together represent 29% of the aquatic area, with a thermal profile resembling those of more standard arctic lakes (mixed epilimnion). The IWT ponds (44% of the area) are stratified for a large fraction of the summer despite their shallowness, while LCP and MPG ponds (27% of the area) show a more homogeneous water column. This will affect gas exchange in these diverse aquatic systems, in addition to their unique microbiota and organic carbon lability that control the production and consumption rates of greenhouse gases. The stratification in IWT ponds generates hypoxic conditions at the bottom, and together with the larger availability of organic carbon, stimulates methanogenesis and limits the mitigating action of methanotrophs. Overall, thaw ponds are largely supersaturated in methane, with IWT ponds dominating the emissions in this landscape (92% of total aquatic emissions estimated for the same valley), and they present large variations in emission rates. Conventional wind-based models seem inappropriate to simulate GHG exchanges, as seen when comparing with floating chamber estimations. Surface renewal models that consider heat exchanges are used to estimate flux more accurately, and ebullition flux are measured with submerged funnels to compare with diffusive flux estimations.

  12. Modeled natural and excess radiocarbon: Sensitivities to the gas exchange formulation and ocean

    E-print Network

    Fischlin, Andreas

    Modeled natural and excess radiocarbon: Sensitivities to the gas exchange formulation and ocean. Stocker (2008), Modeled natural and excess radiocarbon: Sensitivities to the gas exchange formulation descriptions of the air-sea gas exchange the models produce similar column inventories for excess 14 C among

  13. Respiratory gas exchange using a triaxial alveolar gas diagram.

    PubMed Central

    Fuster, J. F.; Pages, T.; Palacios, L.

    1993-01-01

    A triaxial alveolar gas diagram to depict fractional concentration of oxygen, carbon dioxide and nitrogen is described, in which the R = 1 line is always implicit. Although it is not claimed that this representation leads to new insights into respiratory physiology, a method of plotting on a triaxial coordinate system has been found to be well suited to many applications when a direct display of fractional nitrogen concentration is required. PMID:8303637

  14. Different characteristic of gas exchange between leaf and canopy scale

    NASA Astrophysics Data System (ADS)

    Zhang, Q.; Lei, H.; Yang, D.

    2012-12-01

    The eddy covariance system is a powerful tool for research on carbon and water exchange between the atmosphere and the terrestrial ecosystem on canopy scale, meanwhile gas exchange measurement on leaf scale fosters understanding towards stomata behavior on controlling carbon and water. In this research, coupling relationship of water and carbon were compared on canopy and leaf scale. Canopy scale transpiration was derived from LE (latent heat flux) observed by eddy covariance and simulated soil evaporation by Penman equation validated through bare soil evaporation measurements using micro-lysimeter, canopy scale carbon assimilation was acquired through partitioning NEE (Net Ecosystem Exchange) into GPP (Gross Primary Productivity) and ER (Ecosystem Respiration). And leaf level gas exchange measurements were conducted in order to get transpiration and net carbon assimilation. Results showed that net carbon assimilation rate correlated well with transpiration in a linear manner on canopy scale, similar relationship also exists on leaf scale, however, regression coefficients differ. So carbon and water coupling relationship on canopy scale does not perform the same as that on leaf scale. What's more, when the Ball-Berry model was applied to estimate stomatal conductance for leaf scale and canopy conductance for canopy scale, the prime coefficients of m and b also showed different magnitude, that means Ball-Berry model calibrated on leaf scale was not necessarily applicable on canopy scale. While it is important to get the knowledge filling the gap between the two different scale, especially for upscaling gas exchange measurements from leaf scale to canopy scale. Transpiration and carbon assimilation relationship on leaf and canopy scale Ball-Berry model on leaf and canopy scale

  15. Reactive oxygen species production and discontinuous gas exchange in insects.

    PubMed

    Boardman, Leigh; Terblanche, John S; Hetz, Stefan K; Marais, Elrike; Chown, Steven L

    2012-03-01

    While biochemical mechanisms are typically used by animals to reduce oxidative damage, insects are suspected to employ a higher organizational level, discontinuous gas exchange mechanism to do so. Using a combination of real-time, flow-through respirometry and live-cell fluorescence microscopy, we show that spiracular control associated with the discontinuous gas exchange cycle (DGC) in Samia cynthia pupae is related to reactive oxygen species (ROS). Hyperoxia fails to increase mean ROS production, although minima are elevated above normoxic levels. Furthermore, a negative relationship between mean and mean ROS production indicates that higher ROS production is generally associated with lower . Our results, therefore, suggest a possible signalling role for ROS in DGC, rather than supporting the idea that DGC acts to reduce oxidative damage by regulating ROS production. PMID:21865257

  16. Gas exchange on Mono Lake and Crowley Lake, California

    NASA Technical Reports Server (NTRS)

    Wanninkhof, Rik; Ledwell, James R.; Broecker, Wallace S.

    1987-01-01

    Gas exchange coefficients (k) have been determined for freshwater Crowley Lake and saline Mono Lake through the use of a man-made purposefully injected gas, SF6. The concentration decreased from an initial value of 40 to 4 pmol/L for Mono Lake and from 20 to 1 pmol/L for Crowley lake over a period of 6 wks. Wind-speed (u) records from anemometers on the shore of each lake made it possible to determine the relationship between k and u. The average u and k values for the experiment were identical for the two lakes, despite the large chemical differences. It is estimated that, for the u values observed over Mono Lake from July to December 1984, the exchange of CO2 occurred 2.5 times faster than without chemical enhancement. This is a factor of 4 lower than needed to explain the high invasion rate of C-14 produced by nuclear bomb tests.

  17. Gas exchange strategy in the Nile crocodile: a morphometric study

    Microsoft Academic Search

    S. F. Perry

    1990-01-01

    The respiratory surface area (SAR) per kilogram body mass (MB), the harmonic mean thickness of the air-blood barrier (thtR) in the gas exchange tissue, and the anatomical diffusion factor (ADF=SAR\\/thtR per MB) were calculated for four juvenile Nile crocodiles. The ADF of three small specimens (mean MB=3.59 kg) was 625 cm2·µm-1·kg-1. The values varied considerably among individuals and were similar

  18. The use of stable isotopes to study ecosystem gas exchange

    Microsoft Academic Search

    D. Yakir; L. da S. L. Sternberg

    2000-01-01

    Stable isotopes are a powerful research tool in environmental sciences and their use in ecosystem research is increasing.\\u000a In this review we introduce and discuss the relevant details underlying the use of carbon and oxygen isotopic compositions\\u000a in ecosystem gas exchange research. The current use and potential developments of stable isotope measurements together with\\u000a concentration and flux measurements of CO2

  19. Hydraulic and thermal design of a gas microchannel heat exchanger

    NASA Astrophysics Data System (ADS)

    Yang, Yahui; Brandner, Juergen J.; Morini, Gian Luca

    2012-05-01

    In this paper investigations on the design of a gas flow microchannel heat exchanger are described in terms of hydrodynamic and thermal aspects. The optimal choice for thermal conductivity of the solid material is discussed by analysis of its influences on the thermal performance of a micro heat exchanger. Two numerical models are built by means of a commercial CFD code (Fluent). The simulation results provide the distribution of mass flow rate, inlet pressure and pressure loss, outlet pressure and pressure loss, subjected to various feeding pressure values. Based on the thermal and hydrodynamic analysis, a micro heat exchanger made of polymer (PEEK) is designed and manufactured for flow and heat transfer measurements in air flows. Sensors are integrated into the micro heat exchanger in order to measure the local pressure and temperature in an accurate way. Finally, combined with numerical simulation, an operating range is suggested for the present micro heat exchanger in order to guarantee uniform flow distribution and best thermal and hydraulic performances.

  20. Gas-exchange activity, carbohydrate status, and protein turnover in root nodule subpopulations of field pea ( Pisum sativum L. cv. Century)

    Microsoft Academic Search

    Per-Åke Vikman; J. Kevin Vessey

    1993-01-01

    Root nodule ontogeny was followed in different parts of the root system of field peas (Pisum sativum L. cv. Century) to investigate the contribution to total nitrogen fixation by different nodule subpopulations. Seed-inoculated\\u000a plants were grown to maturity in controlled-environment growth chambers. In a flow-through system nitrogenase activity (H2-evolution in air) and nodulated-root respiration (net CO2-evolution) were measured weekly or

  1. Test results from a helium gas-cooled porous metal heat exchanger

    Microsoft Academic Search

    Mark T. North; John H. Rosenfeld; Dennis L. Youchison

    1996-01-01

    A helium-cooled porous metal heat exchanger was built and tested, which successfully absorbed heat fluxes exceeding all previously tested gas-cooled designs. Helium-cooled plasma-facing components are being evaluated for fusion applications. Helium is a favorable coolant for fusion devices because it is not a plasma contaminant, it is not easily activated, and it is easily removed from the device in the

  2. Transition Metal Exchanged Zeolite Layers for Selectivity Enhancement of Metal-Oxide Semiconductor Gas Sensors

    Microsoft Academic Search

    Dominic P. Mann; Keith F. E. Pratt; Themis Paraskeva; Ivan P. Parkin; David E. Williams

    2007-01-01

    A novel method of improving the selectivity of metal oxide gas sensors has been developed by using catalytically active molecular sieve materials. They have been successfully introduced into a proprietary sensor array. The cracking patterns of linear alkanes over transition metal exchanged zeolite Y have been measured using a zeolite bed\\/GC\\/MS experimental set-up within a temperature range of 300degC to

  3. A systematic method for validation of gas exchange measurements.

    PubMed

    Damask, M C; Weissman, C; Askanazi, J; Hyman, A I; Rosenbaum, S H; Kinney, J M

    1982-09-01

    The measurement of gas exchange is useful, but thus far, has not been practical during the mechanical ventilation of critically ill patients. To validate two new commercial instruments, (Siemens-Elema Servo Ventilator 900B, Beckman Metabolic Cart), the authors constructed a lung model into which they delivered CO2 and N2 at precise rates to simulate Co2 production (Vco2) and O2 consumption (Vos). The model consists of 13.5-1 gas jar with an attached one liter anesthesia bag. The lung model was ventilated at present tidal volumes and frequencies. The authors also compared the measured respiratory quotient (RQ) with the known RQ of burning methanol (RQ = 0.67) in the jar. When the model was ventilated with levels of tidal volume and gas exchange applicable to adults, both instruments measured V02 within 5 to 13% of predicted values. Varying the FI02 did not significantly affect this accuracy. At tidal volumes below 350 ml, the difference increased between predicted VCO2 and measured VCO2. The difference between measured vs. the actual RQ of methanol was 5 and 1.5% in the Siemens-Elema and Beckman Systems, respectively. PMID:6810731

  4. PREDICTION OF TOTAL DISSOLVED GAS EXCHANGE AT HYDROPOWER DAMS

    SciTech Connect

    Hadjerioua, Boualem [ORNL; Pasha, MD Fayzul K [ORNL; Stewart, Kevin M [ORNL; Bender, Merlynn [Bureau of Reclamation; Schneider, Michael L. [U.S. Army Corps of Engineers

    2012-07-01

    Total dissolved gas (TDG) supersaturation in waters released at hydropower dams can cause gas bubble trauma in fisheries resulting in physical injuries and eyeball protrusion that can lead to mortality. Elevated TDG pressures in hydropower releases are generally caused by the entrainment of air in spillway releases and the subsequent exchange of atmospheric gasses into solution during passage through the stilling basin. The network of dams throughout the Columbia River Basin (CRB) are managed for irrigation, hydropower production, flood control, navigation, and fish passage that frequently result in both voluntary and involuntary spillway releases. These dam operations are constrained by state and federal water quality standards for TDG saturation which balance the benefits of spillway operations designed for Endangered Species Act (ESA)-listed fisheries versus the degradation to water quality as defined by TDG saturation. In the 1970s, the United States Environmental Protection Agency (USEPA), under the federal Clean Water Act (Section 303(d)), established a criterion not to exceed the TDG saturation level of 110% in order to protect freshwater and marine aquatic life. The states of Washington and Oregon have adopted special water quality standards for TDG saturation in the tailrace and forebays of hydropower facilities on the Columbia and Snake Rivers where spillway operations support fish passage objectives. The physical processes that affect TDG exchange at hydropower facilities have been studied throughout the CRB in site-specific studies and routine water quality monitoring programs. These data have been used to quantify the relationship between project operations, structural properties, and TDG exchange. These data have also been used to develop predictive models of TDG exchange to support real-time TDG management decisions. These empirically based predictive models have been developed for specific projects and account for both the fate of spillway and powerhouse flows in the tailrace channel and resultant exchange in route to the next downstream dam. Currently, there exists a need to summarize the general finding from operational and structural TDG abatement programs conducted throughout the CRB and for the development of a generalized prediction model that pools data collected at multiple projects with similar structural attributes. A generalized TDG exchange model can be tuned to specific projects and coupled with water regulation models to allow the formulation of optimal daily water regulation schedules subject to water quality constraints for TDG supersaturation. A generalized TDG exchange model can also be applied to other hydropower dams that affect TDG pressures in tailraces and can be used to develop alternative operational and structural measures to minimize TDG generation. It is proposed to develop a methodology for predicting TDG levels downstream of hydropower facilities with similar structural properties as a function of a set of variables that affect TDG exchange; such as tailwater depth, spill discharge and pattern, project head, and entrainment of powerhouse releases. TDG data from hydropower facilities located throughout the northwest region of the United States will be used to identify relationships between TDG exchange and relevant dependent variables. Data analysis and regression techniques will be used to develop predictive TDG exchange expressions for various structural categories.

  5. Gas exchange in litchi under controlled and field conditions

    Microsoft Academic Search

    Jer-Chia Chang; Tzong-Shyan Lin

    2007-01-01

    Gas exchange of 3-year-old potted ‘73-S-20’ litchi (Litchi chinensis Sonn.) plants were measured under controlled conditions. At 28.8±0.3°C, dark respiration (Rd) was estimated at 0.6 CO2?molm?2s?1, quantum yield (?) was 0.024mol CO2 mol?1, and light compensation point (PPFDcomp) was 24?molm?2s?1 photosynthetic photo flux density (PPFD). Maximum net CO2 assimilation (ACO2) (6.5–8?molm?2s?1), stomatal conductance (gs) (0.07–0.09molm?2s?1) and transpiration (E) (0.7mmolm?2s?1) were

  6. Gas developments lead Canadian activity

    SciTech Connect

    Riahi, M.L.; Perdue, J.M.; Kunkel, B.

    1998-05-01

    Canada has an immense supply of natural gas. The Western Sedimentary Basin of Canada is North America`s largest gas-bearing geologic province and extends from British Columbia on Canada`s west coast, eastward through the provinces of Alberta, Saskatchewan and Manitoba and includes portions of the Northwest Territories and the Yukon. The basin supplies most of Canada`s natural gas with nearly 85% of it coming from Alberta. The production of natural gas supplies from conventional fields continues to increase. Major gas discoveries, made in the frontier and offshore regions, are going to be developed as well over time, as the economics and the markets dictate. Furthermore, Canada`s relatively unexplored Arctic and offshore basins, which promise excellent geological potential, will be developed at some point in the future. The paper discusses gas exploration and drilling activities, market access, the future of Canadian natural gas, how price challenges development of heavy oil and tar sands, and extending life of oil fields.

  7. Teaching pulmonary gas exchange physiology using computer modeling

    NSDL National Science Digital Library

    Kent S Kapitan (Southern Ilinois University Pulmonary Medicine)

    2007-11-19

    Students often have difficulty understanding the relationship of O2 consumption, CO2 production, cardiac output, and distribution of ventilation-perfusion ratios in the lung to the final arterial blood gas composition. To overcome this difficulty, I have developed an interactive computer simulation of pulmonary gas exchange that is web based and allows the student to vary multiple factors simultaneously and observe the final effect on the arterial blood gas composition (available at www.siumed.edu/medicine/pulm/vqmodeling.htm). In this article, the underlying mathematics of the computer model is presented, as is the teaching strategy. The simulation is applied to a typical clinical case drawn from the intensive care unit to demonstrate the interdependence of the above factors as well as the less-appreciated importance of the Bohr and Haldane effects in clinical pulmonary medicine. The use of a computer to vary the many interacting factors involved in the arterial blood gas composition appeals to today's students and demonstrates the importance of basic physiology to the actual practice of medicine.

  8. Sulfur gas exchange in Sphagnum-dominated wetlands

    NASA Technical Reports Server (NTRS)

    Hines, Mark E.; Demello, William Zamboni; Porter, Carolyn A.

    1992-01-01

    Sulfur gases are important components of the global cycle of S. They contribute to the acidity of precipitation and they influence global radiation balance and climate. The role of terrestrial sources of biogenic S and their effect on atmospheric chemistry remain as major unanswered questions in our understanding of the natural S cycle. The role of northern wetlands as sources and sinks of gaseous S was investigated by measuring rates of S gas exchange as a function of season, hydrologic conditions, and gradients in trophic status. The effects of inorganic S input on the production and emission of gaseous S were also investigated. Experiments were conducted in wetlands in New Hampshire, particularly a poor fen, fens within the Experimental Lakes Area (ELA) in Ontario, Canada and in freshwater and marine tundra. Emissions were determined using Teflon enclosures, gas cryotrapping methods, and gas chromatography (GC) with flame photometric detection. Dynamic (sweep flow) and static enclosures were employed. Dissolved gases were determined by gas stripping followed by GC.

  9. [Modification of gas exchange and metabolism by various hemodialysis procedures].

    PubMed

    Grosser, S; Kreymann, G; Meierling, S; Daerr, W; Raedler, A; Greten, H

    1990-08-17

    We compared the effects of various dialysate composition on pulmonary and transdialyzer gas exchange in patients during hemodialysis. Under acetate hemodialysis there was a permanent loss of CO2 (45-68 ml/min) into the dialysate resulting in a significant decrease of arterial pO2, which can be explained by a reduced alveolar ventilation. The pulmonary oxygen uptake increased up to +20% during treatment, reflecting rising energy metabolism and possibly increased cardiopulmonary instability. Using different concentrates for bicarbonatehemodialysis we saw a moderate to clinical relevant uptake of CO2 (40-60 ml/min) from the dialysate into the blood of the patients, cause the pCO2 in the dialysate varied between 45 and 115 mmHg. Bicarbonate hemodialysis with high pCO2-levels in the dialysate led to hyperventilation and markedly increased oxygen consumption. In critically ill hemodialysis patients the pathophysiologic effects on pulmonary gas exchange of either acetatehemodialysis and bicarbonatehemodialysis with high pCO2 can explain the higher incidence of severe complications. PMID:2120511

  10. 32 CFR 643.112 - Army exchange activities.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...2010-07-01 2010-07-01 true Army exchange activities. 643.112 Section...Defense (Continued) DEPARTMENT OF THE ARMY (CONTINUED) REAL PROPERTY REAL ESTATE...Authority of Commanders § 643.112 Army exchange activities. Use of space...

  11. 32 CFR 643.112 - Army exchange activities.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...2011-07-01 2011-07-01 false Army exchange activities. 643.112 Section...Defense (Continued) DEPARTMENT OF THE ARMY (CONTINUED) REAL PROPERTY REAL ESTATE...Authority of Commanders § 643.112 Army exchange activities. Use of space...

  12. 32 CFR 643.112 - Army exchange activities.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...2014-07-01 2013-07-01 true Army exchange activities. 643.112 Section...Defense (Continued) DEPARTMENT OF THE ARMY (CONTINUED) REAL PROPERTY REAL ESTATE...Authority of Commanders § 643.112 Army exchange activities. Use of space...

  13. 32 CFR 643.112 - Army exchange activities.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...2013-07-01 2013-07-01 false Army exchange activities. 643.112 Section...Defense (Continued) DEPARTMENT OF THE ARMY (CONTINUED) REAL PROPERTY REAL ESTATE...Authority of Commanders § 643.112 Army exchange activities. Use of space...

  14. 32 CFR 643.112 - Army exchange activities.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...2012-07-01 2011-07-01 true Army exchange activities. 643.112 Section...Defense (Continued) DEPARTMENT OF THE ARMY (CONTINUED) REAL PROPERTY REAL ESTATE...Authority of Commanders § 643.112 Army exchange activities. Use of space...

  15. BOREAS TE-9 In Situ Diurnal Gas Exchange of NAS Boreal Forest Stands

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Margolis, Hank; Coyea, Marie; Dang, Qinglai

    2000-01-01

    The BOREAS TE-9 team collected several data sets related to chemical and photosynthetic properties of leaves in boreal forest tree species. The purpose of the BOREAS TE-09 study was threefold: 1) to provide in situ gas exchange data that will be used to validate models of photosynthetic responses to light, temperature, and carbon dioxide (CO2); 2) to compare the photosynthetic responses of different tree crown levels (upper and lower); and 3) to characterize the diurnal water potential curves for these sites to get an indication of the extent to which soil moisture supply to leaves might be limiting photosynthesis. The gas exchange data of the BOREAS NSA were collected to characterize diurnal gas exchange and water potential of two canopy levels of five boreal canopy cover types: young jack pine, old jack pine, old aspen, lowland old black spruce, and upland black spruce. These data were collected between 27-May-1994 and 17-Sep-1994. The data are provided in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

  16. Leaf water relations and maintenance of gas exchange in coffee cultivars grown in drying soil.

    PubMed

    Meinzer, F C; Grantz, D A; Goldstein, G; Saliendra, N Z

    1990-12-01

    Plant water status, leaf tissue pressure-volume relationships, and photosynthetic gas exchange were monitored in five coffee (Coffea arabica L.) cultivars growing in drying soil in the field. There were large differences among cultivars in the rates at which leaf water potential (Psi(L)) and gas exchange activity declined when irrigation was discontinued. Pressure-volume curve analysis indicated that increased leaf water deficits in droughted plants led to reductions in bulk leaf elasticity, osmotic potential, and in the Psi(L) at which turgor loss occurred. Adjustments in Psi(L) at zero turgor were not sufficient to prevent loss or near loss of turgor in three of five cultivars at the lowest values of midday Psi(L) attained. Maintenance of protoplasmic volume was more pronounced than maintenance of turgor as soil drying progressed. Changes in assimilation and stomatal conductance were largely independent of changes in bulk leaf turgor, but were associated with changes in relative symplast volume. It is suggested that osmotic and elastic adjustment contributed to maintenance of gas exchange in droughted coffee leaves probably through their effects on symplast volume rather than turgor. PMID:16667916

  17. Surviving submerged--Setal tracheal gills for gas exchange in adult rheophilic diving beetles.

    PubMed

    Kehl, Siegfried; Dettner, Konrad

    2009-11-01

    The gas exchange in adult diving beetles (Coleoptera: Dytiscidae) relies on a subelytral air store, which has to be renewed in regular intervals at the water surface. The dive duration varies from a few minutes to 24 h depending on the species, activity, and temperature. However, some species remain submerged for several weeks. Stygobiont species do not ascend to the surface and gas exchange of these species remains unclear, but it is assumed that they require air filled voids for respiration or they use cutaneous respiration. In this study, we investigate the gas exchange in the running water diving beetle Deronectes aubei, which survive submerged for over 6 weeks. The diffusion distance through the cuticle is too great for cutaneous respiration. Therefore, the dissolved oxygen uptake of submerged beetles was determined and an oxygen uptake via the rich tracheated elytra was observed. Fine structure analyses (SEM and TEM) of the beetles showed tracheated setae mainly on the elytral surface, which acts as tracheal gills. Prevention of the air bubble formation at the tip of the abdomen, which normally act as physical gill in Dytiscidae, resulted in no effect in oxygen uptake in D. aubei, but this was the sole way for a submerged Hydroporus palustris to get oxygen. The setal gas exchange technique explains the restriction of D. aubei to rivers and brooks with high oxygen concentration and it may also be used by subterran living diving beetles, which lack access to atmospheric oxygen. The existence of setal tracheal gills in species in running water which are often found in the hyporheic zone and in stygobiont species supports the known evolution of stygobiont Dytiscidae from species of the hyporheic zone. For species in running water, setal tracheal gills could be seen as an adaptation to avoid drifting downstream by the current. PMID:19480011

  18. Waste heat recovery using heat pipe heat exchanger for heating automobile using exhaust gas

    Microsoft Academic Search

    Feng Yang; Xiugan Yuan; Guiping Lin

    2003-01-01

    The feasibility of using heat pipe heat exchangers for heating applying automotive exhaust gas is studied and the calculation method is developed. Practical heat pipe heat exchanger is set up for heating HS663, a large bus. Simple experiments are carried out to examine the performance of the heat exchanger. It is shown that the experimental results, which indicate the benefit

  19. Respiratory gas exchange of high altitude adapted chick embryos

    NASA Technical Reports Server (NTRS)

    Wangensteen, O. D.; Rahn, H.; Burton, R. R.; Smith, A. H.

    1974-01-01

    Study of gas exchange by embryos from chickens acclimatized to an altitude of 3800 m. The oxygen partial pressure and carbon dioxide partial pressure differences across the egg shell were measured and found to be less than the values previously reported for sea-level eggs by about a factor of two. Further measurements of embryonic oxygen consumption and shell conductivity to oxygen indicated that, compared to eggs at sea level, oxygen consumption was reduced by a factor of 0.58 while conductivity to oxygen was increased only by a factor of 1.07 in the high-altitude eggs. These independent measurements predict the change in oxygen partial pressure across the egg shell of the high-altitude eggs to be only 0.54 times that of sea-level eggs; the directly measured factor was 0.53. The authors conclude that at high altitude, a major adaptation of the chick embryo is a reduced metabolism which decreases the change in oxygen partial pressure across the egg shell since its gas conductivity remains essentially unchanged.

  20. Gas exchange characteristics of Pinus canariensis needles in a forest stand on Tenerife, Canary Islands

    Microsoft Academic Search

    Juliane Peters; Domingo Morales; M. Soledad Jiménez

    2003-01-01

    Gas exchange characteristics and chlorophyll fluorescence of the Canarian endemic pine ( Pinus canariensis) were measured during the day for a year in a field stand on Tenerife, Canary Islands, Spain. Diurnal tendencies of gas exchange were variable depending on ambient conditions. In general they paralleled photosynthetic photon flux density with only one peak at midday, except on summer days

  1. The SOLAS airsea gas exchange experiment (SAGE) 2004 Mike J. Harvey a,n

    E-print Network

    Ho, David

    The SOLAS air­sea gas exchange experiment (SAGE) 2004 Mike J. Harvey a,n , Cliff S. Law a , Murray exchange experiment (SAGE) was a multiple-objective study investigating gas- transfer processes-March and mid-April 2004. In common with other mesoscale iron addition experiments (FeAX's), SAGE was designed

  2. Discontinuous Gas Exchange in Insects: A Clarification of Hypotheses and Approaches*

    E-print Network

    Ahmad, Sajjad

    333 Discontinuous Gas Exchange in Insects: A Clarification of Hypotheses and Approaches* Steven L Accepted 4/25/2005; Electronically Published 2/2/2006 ABSTRACT Many adult and diapausing pupal insects. Introduction Discontinuous gas exchange is often regarded as the quintes- sential characteristic of insect

  3. Optimisation of the Gas-Exchange System of Combustion Engines by Genetic Algorithm

    E-print Network

    Marsland, Stephen

    Optimisation of the Gas-Exchange System of Combustion Engines by Genetic Algorithm C. D. Rose, S. R of combustion engine gas-exchange systems still predominantly use trial and error. This paper proposes a new. Keywords - genetic algorithm; variable-length input encoding; combustion engine; optimisation I

  4. New designs of heat exchangers for natural gas liquefying and separating plants

    Microsoft Academic Search

    O. K. Krasnikova; O. M. Popov; V. N. Udut

    2006-01-01

    The special operational features of heat exchangers of natural gas liquefying and separating plants are shown. A new design\\u000a of coil heat exchanger having tubes finned with round wire with a statically uniform structure is described. The technical\\u000a specifications of heat exchangers finned with wire having annular intensifiers and of conventional coil flat-tube heat exchanger\\u000a are compared.

  5. Understanding Fraudulent Activities in Online Ad Exchanges

    E-print Network

    California at Santa Barbara, University of

    revenue that is exchanged in transactions that it oversees. Thus, in the network model of advertising. There is currently a multi-billion dollar market for online advertising, which generates the primary revenue for some Science Foundation for Research and Technology, Hellas zarras@ics.forth.gr ABSTRACT Online advertisements

  6. Universal model for water costs of gas exchange by animals and plants

    PubMed Central

    Woods, H. Arthur; Smith, Jennifer N.

    2010-01-01

    For terrestrial animals and plants, a fundamental cost of living is water vapor lost to the atmosphere during exchange of metabolic gases. Here, by bringing together previously developed models for specific taxa, we integrate properties common to all terrestrial gas exchangers into a universal model of water loss. The model predicts that water loss scales to gas exchange with an exponent of 1 and that the amount of water lost per unit of gas exchanged depends on several factors: the surface temperature of the respiratory system near the outside of the organism, the gas consumed (oxygen or carbon dioxide), the steepness of the gradients for gas and vapor, and the transport mode (convective or diffusive). Model predictions were largely confirmed by data on 202 species in five taxa—insects, birds, bird eggs, mammals, and plants—spanning nine orders of magnitude in rate of gas exchange. Discrepancies between model predictions and data seemed to arise from biologically interesting violations of model assumptions, which emphasizes how poorly we understand gas exchange in some taxa. The universal model provides a unified conceptual framework for analyzing exchange-associated water losses across taxa with radically different metabolic and exchange systems. PMID:20404161

  7. Bunchgrass architecture, light interception, and water-use efficiency: assessment by fiber optic point quadrats and gas exchange

    Microsoft Academic Search

    M. M. Caldwell; T. J. Dean; R. S. Nowak; R. S. Dzurec; J. H. Richards

    1983-01-01

    The bunchgrass growth form, which is very prominent in water-limited environments, can result in considerable self-shading of photosynthetically active foliage. The consequences of this growth form for light interception and water-use efficiency (photosynthesis\\/transpiration, P\\/T) were investigated for two Agropyron species which differ in tussock density and degree of self-shading. During the period of most active gas exchange, the tussocks were

  8. Compact Ceramic Heat Exchangers for Corrosive Waste Gas Applications

    E-print Network

    Laws, W. R.; Reed, G. R.

    1982-01-01

    The development of large ceramic heat exchangers is described and performance data given for units installed on steel industry soaking pits in the U.K. Operational experience since 1973 confirms that ceramic heat exchangers capable of operating...

  9. Gas-Substrate Heat Exchange During Cold-Gas Dynamic Spraying

    NASA Astrophysics Data System (ADS)

    McDonald, A. G.; Ryabinin, A. N.; Irissou, E.; Legoux, J.-G.

    2013-03-01

    In this study, the temperature distribution of the surfaces of several substrates under an impinging gas jet from a cold spray nozzle was determined. A low-pressure cold-gas dynamic spraying unit was used to generate a jet of hot compressed nitrogen that impinged upon flat substrates. Computer codes based on a finite differences method were used to solve a simplified 2D temperature distribution equation for the substrate to produce nondimensional relationships between the surface temperature and the radius of the impinging fluid jet, the axial velocity of the cold spray nozzle, the substrate thickness, and the heating time. It was found that a single profile of the transient nondimensional maximum surface temperature could be used to estimate the dimensional maximum surface temperature, regardless of the value of the compressed gas temperature. It was found further that, as the thermal conductance of the substrate increased, the maximum surface temperature of the substrate beneath the gas jet decreased. Heat exchange between the substrate and the compressed gas jet during motion of the nozzle to produce heat conduction within the substrate was characterized by the nondimensional Peclét number. It was found that lower Peclét numbers produced higher temperatures within the substrate. The close agreement of the numerical results with the experimental results suggests that the nondimensionalized results may be applied to a wide range of conditions and materials.

  10. Gas exchange characteristics of Pinus edulis and Juniperus monosperma

    SciTech Connect

    Barnes, F.J.

    1987-07-01

    A shift in the relative dominance of Pinus edulis and Juniperus monosperma is associated with a complex elevational gradient in northern new Mexico. The ecophysiological parameters contributing to this dominance pattern were studied by determining the gas exchange characteristics of the two species in response to temperature, light and water stress under controlled conditions. P. edulis has a higher photosynthetic capacity than J. monosperma, and has a tendency to form ecotypes with individuals from mesic sites having higher rates of carbon gain than xeric site individuals. J. monosperma is more drought-tolerant than P. edulis. As soil moisture decreases, zero carbon gain in J. monosperma occurs at a lower predawn leaf water potential (-4.6 MPa) than in P. edulis (-2.2 MPa). There is no significant difference between species in the temperature of peak carbon gain. J. monosperma has a significantly wider temperature optimum than P. edulis with the additional range being at high temperatures. The observed lower elevational limit of P. edulis coincides with its physiological tolerance of water stress as estimated by seasonal leaf carbon gain. Environmental limitations to the distribution of J. monosperma were not found at higher elevations where P. edulis is dominant.

  11. Ethylene directly inhibits foliar gas exchange in Glycine max

    SciTech Connect

    Gunderson, C.A.; Taylor, G.E. Jr. (Oak Ridge National Lab., TN (United States))

    1991-01-01

    Gas exchange of individual attached leaves of soybean, Glycine max (L,) Merr cv Davis, was monitored during exposure to exogenous ethylene (C{sub 2}H{sub 4}) to test the hypothesis that the effects of C{sub 2}H{sub 4} on net photosynthesis (P{sub n}) and stomatal conductance to H{sub 2}O{sub 4} vapor (g{sub s}) are direct and not mediated by changes in leaf orientation to light. Leaflets were held perpendicular to incident light in a temperature-controlled cuvette throughout a 5.5 hour exposure to 10 microliters per liter C{sub 2}H{sub 4}. Declines in both P{sub N} and g{sub s} were evident within 2 hours and became more pronounced throughout the exposure period. In C{sub 2}H{sub 4} treated plants, P{sub N} and g{sub s} decreased to 80 and 62%, respectively, of the rates in control plants. Because epinastic movement of the leaflets was prohibited by the cuvette, the observed declines in P{sub N} and g{sub s} were a direct effect of C{sub 2}H{sub 4} rather than the result of reduced light interception caused by changing leaf angle.

  12. The effect of wind and currents on gas exchange in an estuarine system

    NASA Technical Reports Server (NTRS)

    Broecker, W. S.; Ledwell, J. R.; Bopp, R.

    1987-01-01

    The objectives were to develop a non-volatile tracer to use in gas exchange experiments in laterally unconfined systems and to study applications of deliberate tracers in limnology and oceanography. Progress was made on both fronts but work on the development of the non-volatile tracer proved to be more difficult and labor intensive that anticipated so no field experiments using non-volatile tracers was performed as yet. In the search for a suitable non-volatile tracer for an ocean scale gas exchange experiment a tracer was discovered which does not have the required sensitivity for a large scale experiment, but is very easy to analyze and will be well suited for smaller experiments such as gas exchange determinations on rivers and streams. Sulfur hexafluoride, SF6, was used successfully as a volatile tracer along with tritium as a non-volatile tracer to study gas exchange rates from a primary stream. This is the first gas exchange experiment in which gas exchange rates were determined on a head water stream where significant groundwater input occurs along the reach. In conjunction with SF6, Radon-222 measurements were performed on the groundwater and in the stream. The feasibility of using a combination of SF6 and radon is being studied to determine groundwater inputs and gas exchange of rates in streams with significant groundwater input without using a non-volatile tracer.

  13. Gas exchange-wind speed relation measured with sulfur hexafluoride on a lake

    NASA Technical Reports Server (NTRS)

    Wanninkhof, R.; Broecker, W. S.; Ledwell, J. R.

    1985-01-01

    Gas-exchange processes control the uptake and release of various gases in natural systems such as oceans, rivers, and lakes. Not much is known about the effect of wind speed on gas exchange in such systems. In the experiment described here, sulfur hexafluoride was dissolved in lake water, and the rate of escape of the gas with wind speed (at wind speeds up to 6 meters per second) was determined over a 1-month period. A sharp change in the wind speed dependence of the gas-exchange coefficient was found at wind speeds of about 2.4 meters per second, in agreement with the results of wind-tunnel studies. However the gas-exchange coefficients at wind speeds above 3 meters per second were smaller than those observed in wind tunnels and are in agreement with earlier lake and ocean results.

  14. Gas exchange-wind speed relation measured with sulfur hexafluoride on a lake.

    PubMed

    Wanninkhof, R; Ledwell, J R; Broecker, W S

    1985-03-01

    Gas-exchange processes control the uptake and release of various gases in natural systems such as oceans, rivers, and lakes. Not much is known about the effect of wind speed on gas exchange in such systems. In the experiment described here, sulfur hexafluoride was dissolved in lake water, and the rate of escape of the gas with wind speed (at wind speeds up to 6 meters per second) was determined over a 1-month period. A sharp change in the wind speed dependence of the gas-exchange coefficient was found at wind speeds of about 2.4 meters per second, in agreement with the results of wind-tunnel studies. However, the gas-exchange coefficients at wind speeds above 3 meters per second were smaller than those observed in wind tunnels and are in agreement with earlier lake and ocean results. PMID:17757865

  15. Evaluation of Fiber Bundle Rotation for Enhancing Gas Exchange in a Respiratory Assist Catheter

    E-print Network

    Federspiel, William J.

    of a rotating densely packed bundle of hollow fiber membranes, water and blood gas exchange levels were sweep gas flow. Oxygen diffuses out of the gas permeable HFMs into the blood stream while carbon dioxide*§ Supplemental oxygenation and carbon dioxide removal through an intravenous respiratory assist catheter can

  16. Long-term gas exchange characteristics as markers of deterioration in patients with cystic fibrosis

    Microsoft Academic Search

    Richard Kraemer; Philipp Latzin; Isabelle Pramana; Pietro Ballinari; Sabina Gallati; Urs Frey

    2009-01-01

    BACKGROUND AND AIM: In patients with cystic fibrosis (CF) the architecture of the developing lungs and the ventilation of lung units are progressively affected, influencing intrapulmonary gas mixing and gas exchange. We examined the long-term course of blood gas measurements in relation to characteristics of lung function and the influence of different CFTR genotype upon this process. METHODS: Serial annual

  17. Regulation of gas exchange and haemolymph pH in the cockroach Nauphoeta cinerea.

    PubMed

    Matthews, Philip G D; White, Craig R

    2011-09-15

    Ventilatory control of internal CO(2) plays an important role in regulating extracellular acid-base balance in terrestrial animals. While this phenomenon is well understood among vertebrates, the role that respiration plays in the acid-base balance of insects is in need of much further study. To measure changes in insect haemolymph pH, we implanted micro pH optodes into the haemocoel of cockroaches (Nauphoeta cinerea). They were then exposed to normoxic, hypoxic, hyperoxic and hypercapnic atmospheres while their haemolymph pH, VCO(2) and abdominal ventilation frequency were measured simultaneously. Intratracheal O(2) levels were also measured in separate experiments. It was found that cockroaches breathing continuously control their ventilation to defend a haemolymph pH of 7.3, except under conditions where hypoxia (<10% O(2)) induces hyperventilation, or where ambient hypercapnia is in excess of haemolymph (>1% CO(2)). In contrast, intratracheal O(2) levels fluctuated widely, but on average remained above 15% in normoxic (21% O(2)) atmospheres. Decapitation caused the cockroaches to display discontinuous gas exchange cycles (DGCs). The alternating periods of ventilation and apnoea during DGCs caused haemolymph pH to fluctuate by 0.11 units. Exposure to hypoxia caused haemolymph pH to increase and initiated brief bouts of spiracular opening prior to the active ventilation phase. The spontaneous occurrence of DGCs in decapitated cockroaches indicates that central pattern generators in the thoracic and abdominal ganglia generate the periodic gas exchange pattern in the absence of control from the cephalic ganglion. This pattern continues to maintain gas exchange, but with less precision. PMID:21865519

  18. Linking Employee Development Activity, Social Exchange and Organizational Citizenship Behavior

    ERIC Educational Resources Information Center

    Pierce, Heather R.; Maurer, Todd J.

    2009-01-01

    The authors examined "perceived beneficiary" of employee development (self, organization) for relationships with employee development activity. Perceived organizational support served as a moderator. The authors conclude that employees may engage in development activities to partly benefit their organization to the extent that a positive exchange…

  19. Ceramic heat exchangers for gas turbines or turbojets

    NASA Astrophysics Data System (ADS)

    Boudigues, S.; Fabri, J.

    The required performance goals and several proposed designs for SiC heat exchangers for aerospace turbines are presented. Ceramic materials are explored as a means for achieving higher operating temperatures while controlling the weight and cost of the heat exchangers. Thermodynamic analyses and model tests by ONERA have demonstrated the efficacy of introducing a recooling cycle and placing the heat exchangers between stages of the turbine. Sample applications are discussed for small general aviation aircraft and subsonic missiles equipped with single-flux exchangers. A double-flux exchanger is considered for an aircraft capable of Mach 0.8 speed and at least 11 km altitude for cruise. Finally, the results of initial attempts to manufacture SiC honeycomb heat exchangers are detailed.

  20. Pulmonary and cutaneous O?gas exchange: a student laboratory exercise in the frog.

    PubMed

    Tattersall, Glenn J; Currie, Suzanne; LeBlanc, Danielle M

    2013-03-01

    Gas exchange in animals is ultimately diffusion based, generally occurring across dedicated respiratory organs. In many aquatic amphibians, however, multiple modes of gas exchange exist, allowing for the partitioning of O2 uptake and CO2 excretion between respiratory organs with different efficiencies. For example, due to the physical properties of O2 being vastly different between air and water phases, the lung and skin play disproportionately important roles in O2 uptake. Many aquatic frogs are renowned for their cutaneous gas exchange capacity, where often the majority of CO2 is excreted across the skin. Furthermore, the roles of these gas exchange organs change with the animal's behavior. Under diving conditions, most of the frog's gas exchange needs must be met by the skin. In this article, we describe an interactive undergraduate laboratory that allows a class of students to share equipment while assessing pulmonary and cutaneous respiration in frogs provided with an air/water choice and under enforced dive conditions. Concepts explored in this laboratory exercise include animal energetics, diving reflex, pulmonary and cutaneous gas exchange processes, diffusion-based gas flux, and O2 debt. PMID:23471257

  1. Stomatal behaviour and gas exchange of Sedges ( Carex spp.) under different soil moisture regimes

    NASA Astrophysics Data System (ADS)

    Busch, J.; Lösch, R.

    Sedges ( Carex spec., Cyperaceae) are important members of different vegetation types in temperate zones nearly all over the world. For this, knowledge of gas exchange and stomata behaviour of sedges is significant for understanding the exchange of water vapour and carbon dioxide between such vegetation types and the atmosphere. The gas exchange of several Carex species was studied in an experimental site of the Botanical Garden Düsseldorf (Germany). Transpiration and netassimilation rates (A), leaf conductances (g) and microclimatic parameters were measured porometrically during two vegetation periods. Patterns of dependence of leaf gas exchange on microclimatic conditions were worked out for different species and culture regimes. The sedges differ in stomatal sensitivity to changing air humidity. Water loss through transpiration is therefore decoupled from evaporation in a species-specific degree. Resulting mathematical models of g and A are presented and the importance of these species-specific differences in modelling and upscaling water vapour, carbon dioxide and trace gas fluxes are pointed out.

  2. Heat exchanger design for thermoelectric electricity generation from low temperature flue gas streams

    E-print Network

    Latcham, Jacob G. (Jacob Greco)

    2009-01-01

    An air-to-oil heat exchanger was modeled and optimized for use in a system utilizing a thermoelectric generator to convert low grade waste heat in flue gas streams to electricity. The NTU-effectiveness method, exergy, and ...

  3. [Prone position: effect on gas exchange and functional capacity for exercise in patients with pulmonary hypertension].

    PubMed

    Bastidas-L, Andrea Carolina; Colina-Chourio, José A; Guevara, Jesnel M; Nunez, Alexis

    2015-03-01

    The objective of this investigation was to evaluate gas exchange and cardiopulmonary functional behavior in patients with pulmonary hypertension (PH) before, during and after the change to a prone position. Thirty patients with PH and alterations in gas exchange were included in the study. Gas exchange measurements were performed in four stages: at the baseline supine position and after 30, 120 and 240 minutes in prone position. Also, the patients were evaluated by the six minutes walking test (6MWT) after 30 days in prone position during night's sleep. After four hours in prone position, all patients showed an increase of PaO2 and arterial saturation of oxygen (SaO2), with a decrease of intrapulmonary shunts, improving the gas exchange and therefore the physiological demand imposed by exercise in patients with PH. PMID:25920183

  4. Gas permeation properties of ion-exchanged ZSM-5 zeolite membranes

    Microsoft Academic Search

    Kanna Aoki; Vu A Tuan; John L Falconer; Richard D Noble

    2000-01-01

    Hydrothermally synthesized, ZSM-5 zeolite membranes (Si\\/Al=25 and 600) were ion exchanged with H+, Na+, K+, Cs+, Ca2+ and Ba2+ cations, and the membranes were stable after exchange. Their gas permeation properties were measured over the temperature range of 323–523 K. Both the Si\\/Al ratio and the exchanged ion size affected the separation performance. For the membrane with a Si\\/Al ratio

  5. Heat transfer in a compact tubular heat exchanger with helium gas at 3.5 MPa

    Microsoft Academic Search

    Douglas A. Olson; Michael P. Glover

    1990-01-01

    A compact heat exchanger was constructed consisting of circular tubes in parallel brazed to a grooved base plate. This tube specimen heat exchanger was tested in an apparatus which radiatively heated the specimen on one side at a heat flux of up to 54 W\\/sq cm, and cooled the specimen with helium gas at 3.5 MPa and Reynolds numbers of

  6. Study of heat exchange during interaction between an electric arc and a longitudinal gas flow

    Microsoft Academic Search

    A. I. Ivliutin; Iu. V. Kurochkin; E. I. Molodykh; A. V. Pustogarov; M. N. Supronenko

    1975-01-01

    An experimental investigation was made of the local heat exchange in a gas flow in a cylindrical electric-arc channel which is insulated from the electrodes. Argon and helium flows were studied, with Reynolds numbers ranging from 50 to 9000. It was found that the nature of the heat exchange in the stabilized arc channel with Re less than 300-500 is

  7. Failure analysis of heat exchanger tubes of four gas coolers

    Microsoft Academic Search

    S. R. Allahkaram; P. Zakersafaee; S. A. M. Haghgoo

    2011-01-01

    A Number of leaks occurred on four heat exchangers used on an off-shore platform in the south of Iran. As a result heat exchanger tubes made of Inconel 625 failed after only two years in operation. The failure was caused by pitting corrosion in two contact regions, tubes and baffles as well as in tube sheet and shell contact regions

  8. Vertical variation in leaf gas exchange parameters for a Southeast Asian tropical rainforest in Peninsular Malaysia.

    PubMed

    Kosugi, Yoshiko; Takanashi, Satoru; Yokoyama, Naoto; Philip, Elizabeth; Kamakura, Mai

    2012-11-01

    Vertical variation in leaf gas exchange characteristics of trees grown in a lowland dipterocarp forest in Peninsular Malaysia was investigated. Maximum net photosynthetic rate, stomatal conductance, and electron transport rate of leaves at the upper canopy, lower canopy, and forest floor were studied in situ with saturated condition photosynthetic photon flux density. The dark respiration rate of leaves at the various heights was also studied. Relationships among gas exchange characteristics, and also with nitrogen content per unit leaf area and leaf dry matter per area were clearly detected, forming general equations representing the vertical profile of several important parameters related to gas exchange. Numerical analysis revealed that the vertical distribution of gas exchange parameters was well determined showing both larger carbon gain for the whole canopy and at the same time positive carbon gain for the leaves of the lowest layer. For correct estimation of gas exchange at both leaf and canopy scales using multi-layer models, it is essential to consider the vertical distribution of gas exchange parameters with proper scaling coefficients. PMID:22644315

  9. Activated carbon for gas separation and storage

    Microsoft Academic Search

    S. Sircar; T. C. Golden; M. B. Rao

    1996-01-01

    Activated carbons offer a large spectrum of pore structures and surface chemistry for adsorption of gases, which are being used to design practical pressure swing and thermal swing adsorption processes for separation and purification of gas mixtures. The activated carbons are often preferred over the zeolitic adsorbents in a gas separation process because of their relatively moderate strengths of adsorption

  10. The effect of prolonged submaximal exercise on gas exchange kinetics and ventilation during heavy exercise in humans

    Microsoft Academic Search

    Stephane Perrey; Robin Candau; Jean-Denis Rouillon; Richard L. Hughson

    2003-01-01

    This study compared ventilation, gas exchange (oxygen uptake, V?O2) and the surface electromyogram (EMG) activity of four major lower limb muscles during heavy exercise before (Pre-Ex) and\\u000a after (Post-Ex) a sustained 90-min cycling exercise at 60% V?O2peak. The 90-min exercise was incorporated under the hypothesis that sustained exercise would alter substrate availability in\\u000a the second exercise bout causing differences in

  11. Energy Recovery By Direct Contact Gas-Liquid Heat Exchange 

    E-print Network

    Fair, J. R.; Bravo, J. L.

    1988-01-01

    Energy from hot gas discharge streams can be recovered by transfer directly to a coolant liquid in one of several available gas-liquid contacting devices. The design of the device is central to the theme of this paper, ...

  12. Noninvasive detection of gas exchange rate by near infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Xu, Guodong; Mao, Zongzhen; Wang, Bangde

    2008-12-01

    In order to study the relationship among the oxygen concentration in skeletal muscle tissues and the heart rate (HR), oxygen uptake (VO2), respiratory exchange ratio (RER) during incremental running exercises on a treadmill, a near-infrared spectroscopy muscle oxygen monitor system is employed to measure the relative change in muscle oxygenation, with the heart rate, oxygen uptake, production of carbon dioxide (VCO2) and respiratory exchange ratio are recorded synchronously. The results indicate parameters mentioned above present regular changes during the incremental exercise. High correlations are discovered between relative change of oxy-hemoglobin concentration and heart rate, oxygen uptake, respiratory exchange ratio at the significance level (P=0.01). This research might introduce a new measurement technology and/or a novel biological monitoring parameter to the evaluation of physical function status, control the training intensity, estimation of the effectiveness of exercise. Keywords: near-infrared spectroscopy; muscle oxygen concentration; heart rate; oxygen uptake; respiratory exchange ratio.

  13. Short-range exchange-correlation energy of a uniform electron gas with modified electron-electron interaction

    E-print Network

    Paris-Sud XI, Université de

    Short-range exchange-correlation energy of a uniform electron gas with modified electron the short-range exchange-correlation energy of the uniform electron gas with two modified electron-electron interactions. While the short-range exchange functionals are calculated analytically, Coupled-Cluster and Fermi

  14. Canopy photosynthesis and transpiration in micro-gravity: Gas exchange measurements aboard Mir

    Microsoft Academic Search

    O. Monje; G. E. Bingham; J. G. Carman; W. F. Campbell; F. B. Salisbury; B. K. Eames; V. Sytchev; M. A. Levinskikh; I. Podolsky

    2000-01-01

    The SVET Greenhouse on-board the Orbital Station Mir was used to measure canopy photosynthesis and transpiration rates for the first time in space. During the Greenhouse IIB experiment on Mir (June – January 1997), carbon and water vapor fluxes from two wheat (cv. Superdwarf) canopies were measured using the US developed Gas Exchange Measurement System (GEMS). Gas analyzers capable of

  15. Air pressure in clamp-on leaf chambers: a neglected issue in gas exchange measurements

    Microsoft Academic Search

    Siegfried Jahnke; Roland Pieruschka

    2006-01-01

    Air pressure in leaf chambers is thought to affect gas exchange measurements through changes in partial pressure of the air components. However, other effects may come into play when homobaric leaves are measured in which internal lateral gas flow may occur. When there was no pressure difference between the leaf chamber and ambient air (DP50), it was found in previous

  16. Trace gas exchange above the floor of a deciduous forest: 1. Evaporation and CO2 efflux

    Microsoft Academic Search

    Dennis D. Baldocchi; Tilden P. Meyers

    1991-01-01

    The eddy correlation method has great potential for directly measuring trace gas fluxes at the floor of a forest canopy, but a thorough validation study has not been yet conducted. Another appeal of the eddy correlation method is its ability to study processes that regulate and modulate gas exchange between the soil\\/litter complex and the atmosphere that cannot be probed

  17. On morphometric measurement of oxygen diffusing capacity in middle ear gas exchange

    E-print Network

    Federspiel, William J.

    On morphometric measurement of oxygen diffusing capacity in middle ear gas exchange Stephen Chad, and William J. Federspiel. On morphometric measurement of oxy- gen diffusing capacity in middle ear gas shown that a morphometric model that incorporates more fundamental physio- chemical and anatomic

  18. Alveolar gas exchange and tissue oxygenation during incremental treadmill exercise, and their associations with blood O2 carrying capacity

    PubMed Central

    Rissanen, Antti-Pekka E.; Tikkanen, Heikki O.; Koponen, Anne S.; Aho, Jyrki M.; Hägglund, Harriet; Lindholm, Harri; Peltonen, Juha E.

    2012-01-01

    The magnitude and timing of oxygenation responses in highly active leg muscle, less active arm muscle, and cerebral tissue, have not been studied with simultaneous alveolar gas exchange measurement during incremental treadmill exercise. Nor is it known, if blood O2 carrying capacity affects the tissue-specific oxygenation responses. Thus, we investigated alveolar gas exchange and tissue (m. vastus lateralis, m. biceps brachii, cerebral cortex) oxygenation during incremental treadmill exercise until volitional fatigue, and their associations with blood O2 carrying capacity in 22 healthy men. Alveolar gas exchange was measured, and near-infrared spectroscopy (NIRS) was used to monitor relative concentration changes in oxy- (?[O2Hb]), deoxy- (?[HHb]) and total hemoglobin (?[tHb]), and tissue saturation index (TSI). NIRS inflection points (NIP), reflecting changes in tissue-specific oxygenation, were determined and their coincidence with ventilatory thresholds [anaerobic threshold (AT), respiratory compensation point (RC); V-slope method] was examined. Blood O2 carrying capacity [total hemoglobin mass (tHb-mass)] was determined with the CO-rebreathing method. In all tissues, NIPs coincided with AT, whereas RC was followed by NIPs. High tHb-mass associated with leg muscle deoxygenation at peak exercise (e.g., ?[HHb] from baseline walking to peak exercise vs. tHb-mass: r = 0.64, p < 0.01), but not with arm muscle- or cerebral deoxygenation. In conclusion, regional tissue oxygenation was characterized by inflection points, and tissue oxygenation in relation to alveolar gas exchange during incremental treadmill exercise resembled previous findings made during incremental cycling. It was also found out, that O2 delivery to less active m. biceps brachii may be limited by an accelerated increase in ventilation at high running intensities. In addition, high capacity for blood O2 carrying was associated with a high level of m. vastus lateralis deoxygenation at peak exercise. PMID:22934021

  19. Effect of acetazolamide on pulmonary and muscle gas exchange during normoxic and hypoxic exercise

    PubMed Central

    Jonk, Amy M; van den Berg, Irene P; Olfert, I Mark; Wray, D Walter; Arai, Tatsuya; Hopkins, Susan R; Wagner, Peter D

    2007-01-01

    Acetazolamide (ACZ) is used to prevent acute mountain sickness at altitude. Because it could affect O2 transport in several different and potentially conflicting ways, we examined its effects on pulmonary and muscle gas exchange and acid–base status during cycle exercise at ?30, 50 and 90% in normoxia (FIO2= 0.2093) and acute hypoxia (FIO2= 0.125). In a double-blind, order-balanced, crossover design, six healthy, trained men (normoxic = 59 ml kg?1 min?1) exercised at both FIO2values after ACZ (3 doses of 250 mg, 8 h apart) and placebo. One week later this protocol was repeated using the other drug (placebo or ACZ). We measured cardiac output , leg blood flow (LBF), and muscle and pulmonary gas exchange, the latter using the multiple inert gas elimination technique. ACZ did not significantly affect , , LBF or muscle gas exchange. As expected, ACZ led to lower arterial and venous blood [HCO3?], pH and lactate levels (P < 0.05), and increased ventilation (P < 0.05). In both normoxia and hypoxia, ACZ resulted in higher arterial PO2 and saturation and a lower alveolar–arterial PO2 difference (AaDO2) due to both less mismatch and less diffusion limitation (P < 0.05). In summary, ACZ improved arterial oxygenation during exercise, due to both greater ventilation and more efficient pulmonary gas exchange. However, muscle gas exchange was unaffected. PMID:17218362

  20. The relationship between leaf water status, gas exchange, and spectral reflectance in cotton leaves

    NASA Technical Reports Server (NTRS)

    Bowman, William D.

    1989-01-01

    Measurements of leaf spectral reflectance, the components of water potential, and leaf gas exchanges as a function of leaf water content were made to evaluate the use of NIR reflectance as an indicator of plant water status. Significant correlations were determined between spectral reflectance at 810 nm, 1665 nm, and 2210 nm and leaf relative water content, total water potential, and turgor pressure. However, the slopes of these relationships were relatively shallow and, when evaluated over the range of leaf water contents in which physiological activity occurs (e.g., photosynthesis), had lower r-squared values, and some relationships were not statistically significant. NIR reflectance varied primarily as a function of leaf water content, and not independently as a function of turgor pressure, which is a sensitive indicator of leaf water status. The limitations of this approach to measuring plant water stress are discussed.

  1. Environmental assessment, p-019, Medical/Dental Clinic; Navy Exchange, Gas Station/Car Wash Facility

    SciTech Connect

    NONE

    1995-12-31

    In accordance with the National Environmental Policy Act (NEPA) of 1969 as amended, and OPNAVINST 5O90.lB, Chapter 2, an Environmental Assessment is to be prepared when a Federal action has the potential to impact the human environment. At Naval Security Group Activity Northwest (hereafter Northwest or the Installation), a new medical/dental clinic is proposed for construction. A Navy Exchange (NEX) and gas station with car wash have also been proposed for construction in the vicinity of the medical/dental clinic. Construction of the projects will not take place during the same timeframe. The first project, the medical/dental clinic, is scheduled for construction in FY96. The projects are sited for the northeastern portion of the Installation. This action, its justification and need, and associated environmental impacts directly or indirectly caused by the action will be assessed.

  2. Hydraulically actuated gas exchange valve assembly and engine using same

    DOEpatents

    Carroll, Thomas S. (Peoria, IL); Taylor, Gregory O. (Hinsdale, IL)

    2002-09-03

    An engine comprises a housing that defines a hollow piston cavity that is separated from a gas passage by a valve seat. The housing further defines a biasing hydraulic cavity and a control hydraulic cavity. A gas valve member is also included in the engine and is movable relative to the valve seat between an open position at which the hollow piston cavity is open to the gas passage and a closed position in which the hollow piston cavity is blocked from the gas passage. The gas valve member includes a ring mounted on a valve piece and a retainer positioned between the ring and the valve piece. A closing hydraulic surface is included on the gas valve member and is exposed to liquid pressure in the biasing hydraulic cavity.

  3. Process using serpentine heat exchange relationship for condensing substantially single component gas streams

    Microsoft Academic Search

    J. M. Geist; M. R. Alvarez; H. C. Rowles; H. L. Vines; D. W. Woodward

    1985-01-01

    A method is disclosed for cooling, condensing and sub-cooling a substantially single component gas stream by passing the gas stream through a heat exchange relationship with a vaporizing multicomponent stream so that carry-up of the condensed liquid phase is maintained without condensed phase backmixing and pot-boiling of the coolant stream is avoided. The single component gas stream is passed through

  4. High effectiveness liquid droplet\\/gas heat exchanger for space power applications

    Microsoft Academic Search

    A. P. Bruckner; A. T. Mattick

    1983-01-01

    A high-effectiveness liquid droplet\\/gas heat exchanger (LDHX) concept for thermal management in space is described. Heat is transferred by direct contact between fine droplets (approx. 100 to 300 micron diameter) of a suitable low vapor pressure liquid and an inert working gas. Complete separation of the droplet and gas media in the zero-g environment is accomplished by configuring the LDHX

  5. Development of residential gas-fired furnaces using heat pipe heat exchangers. Final report, July 1988February 1992

    Microsoft Academic Search

    P. M. Dussinger; J. R. Hartenstine

    1992-01-01

    The principal objective of the heat pipe heat exchanger development program was to design, fabricate, and demonstrate the performance of heat pipe heat exchangers for gas-fired residential furnaces that improved upon the previously marketed heat pipe furnace.

  6. AIR-WATER GAS EXCHANGE: MECHANISMS GOVERNING THE COMBINED EFFECTS OF WIND AND RAIN ON THE GAS TRANSFER

    E-print Network

    Luther, Douglas S.

    A THESIS SUBMITTED TO THE GRADUATE DIVISION OF THE UNIVERSITY OF HAWAI`I IN PARTIAL FULFILLMENT, Thomas Kilpatrick, and Tyson Hilmer, as well as many other colleagues at the University of Hawaii. Sara, and to study local ecosystem dynamics. Although our knowledge of the mechanisms driving gas exchange due

  7. Compact Ceramic Heat Exchangers for Corrosive Waste Gas Applications 

    E-print Network

    Laws, W. R.; Reed, G. R.

    1982-01-01

    of the original silicon carbide tubes. Maintenance costs over the period have been low despite the frequent shut downs which have occurred due to the works' preference for operating blast furnace gas fired pits during periods of reduced production...~ of the re-meltir~ cycle either high grades of ,silicon carbide with special glazir~ are required qr alternatively mullite based materials shou]d be used. 3. Copper Copper anode and reverberatory furnaces pr 'vide severe conditions with waste gas...

  8. The impact of ten years at -20°C on gas exchange in five lichen species

    Microsoft Academic Search

    D. W. Larson

    1989-01-01

    Rates of net CO2 exchange in five sympatric species of Umbilicaria were measured after 10 years at-20°C. During that time, the lichens had been at either a high (saturated) or a low (air-dry) water content. The results showed an immediate, return to normal rates of gas exchange for air-dried then frozen U.vellea. Rates returned to normal for air-dried U. deusta

  9. Effect of Vacuum Infiltration on Photosynthetic Gas Exchange in Leaf Tissue

    PubMed Central

    MacDonald, Ian R.

    1975-01-01

    Using a manometric method, photosynthetic oxygen evolution and 14CO2 fixation have been determined for leaf tissue of Triticum aestivum L., Hordeum vulgare L., Phaseolus vulgaris L., and Lemna minor L. Approximately similar values in the range 0.2 to 0.4 millimoles grams fresh weight?1 hour?1 were obtained for both gases. In tissue subjected to vacuum infiltration, O2 evolution and 14CO2 fixation were barely measurable. It is considered that the elimination of photosynthetic gas exchange results from a decreased supply of CO2 to the chloroplasts. Chopping wheat laminae also leads to a reduction in photosynthetic gas exchange, slices 1 millimeter or less giving only 10 to 20% of the value for whole tissue. Respiration is unaffected by either treatment. Carbonic anhydrase did not improve photosynthetic gas exchange in infiltrated tissue. The use of sliced or vacuum-infiltrated leaf tissue in photosynthetic studies is discussed. PMID:16659238

  10. Gas generation and bubble formation model for crystalline silicotitanate ion exchange columns

    SciTech Connect

    Hang, T.

    2000-07-19

    The authors developed a transient model to describe the process of gas generation due to radiolysis and bubble formation in crystalline silicotitanate (CST) ion exchange (IX) columns using the Aspen Custom Modeler (ACM) software package. The model calculates gas concentrations and onset of bubble formation for large CST IX columns. The calculations include cesium loading as a function of time, gas generation as a function of cesium loading, and bubble formation as a function of gas solubility. This report summarizes the model development and predictions.

  11. Kinetic model for the vibrational energy exchange in flowing molecular gas mixtures. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Offenhaeuser, F.

    1987-01-01

    The present study is concerned with the development of a computational model for the description of the vibrational energy exchange in flowing gas mixtures, taking into account a given number of energy levels for each vibrational degree of freedom. It is possible to select an arbitrary number of energy levels. The presented model uses values in the range from 10 to approximately 40. The distribution of energy with respect to these levels can differ from the equilibrium distribution. The kinetic model developed can be employed for arbitrary gaseous mixtures with an arbitrary number of vibrational degrees of freedom for each type of gas. The application of the model to CO2-H2ON2-O2-He mixtures is discussed. The obtained relations can be utilized in a study of the suitability of radiation-related transitional processes, involving the CO2 molecule, for laser applications. It is found that the computational results provided by the model agree very well with experimental data obtained for a CO2 laser. Possibilities for the activation of a 16-micron and 14-micron laser are considered.

  12. Near and Far Scale Gas Exchange Associated with Natural Marine Hydrocarbon Seeps

    NASA Astrophysics Data System (ADS)

    Clark, J. F.; Mau, S.; Valentine, D. L.; Ohlmann, J. C.; Washburn, L.; Leifer, I.

    2006-12-01

    The Coal Oil Point seep field, Santa Barbara Channel, CA, USA is one of the world's most intense areas of natural marine hydrocarbon seepage. Oil and gas is emitted from seafloor vents, which occur mostly in water depths between 20 and 70 m over an area of about 3 km2. Detailed measurements of bubble composition, dissolved gas concentrations, seepage rates, and plume dynamics have been conducted over the last decade. Within rising bubble plumes, methane, carbon dioxide, and heavier hydrocarbons are lost while nitrogen and oxygen are gained due to bubble-seawater gas exchange. Dissolved methane concentrations are more than 4 orders of magnitude greater than atmospheric equilibrium concentrations in the water, which surrounds and rises with the bubbles. Strong upwelling flows (typically >40cm/s) were observed and bubble rise times are on the order of 1 minute (depending on water depth and upwelling flow), demonstrating the rapid exchange of gases within the bubble plume. Dissolved hydrocarbon plumes were mapped more than 20 km down current of the seep field. Surface mapping of the plume reveal that gas concentrations vary with current velocity (determined with the CODAR network). The influence of the far field air-water gas exchange is being examined in detail with Lagrangian experiments, where the water mass has been followed using surface drifters and dual gas (sulfur hexafluoride-He-3) tracer experiments. Preliminary results suggest gas loss is reduced by the oil slicks, which also drift down current from the seep field.

  13. Neural control of gas exchange patterns in insects: locust density-dependent phases as a test case.

    PubMed

    Berman, Tali S; Ayali, Amir; Gefen, Eran

    2013-01-01

    The adaptive significance of discontinuous gas exchange cycles (DGC) in insects is contentious. Based on observations of DGC occurrence in insects of typically large brain size and often socially-complex life history, and spontaneous DGC in decapitated insects, the neural hypothesis for the evolution of DGC was recently proposed. It posits that DGC is a non-adaptive consequence of adaptive down-regulation of brain activity at rest, reverting ventilatory control to pattern-generating circuits in the thoracic ganglia. In line with the predictions of this new hypothesis, we expected a higher likelihood of DGC in the gregarious phase of the desert locust (Schistocerca gregaria, Orthoptera), which is characterized by a larger brain size and increased sensory sensitivity compared with the solitary phase. Furthermore, surgical severing of the neural connections between head and thoracic ganglia was expected to increase DGC prevalence in both phases, and to eliminate phase-dependent variation in gas exchange patterns. Using flow-through respirometry, we measured metabolic rates and gas exchange patterns in locusts at 30°C. In contrast to the predictions of the neural hypothesis, we found no phase-dependent differences in DGC expression. Likewise, surgically severing the descending regulation of thoracic ventilatory control did not increase DGC prevalence in either phase. Moreover, connective-cut solitary locusts abandoned DGC altogether, and employed a typical continuous gas exchange pattern despite maintaining metabolic rate levels of controls. These results are not consistent with the predictions of the neural hypothesis for the evolution of DGC in insects, and instead suggest neural plasticity of ventilatory control. PMID:23555850

  14. Gas exchange dynamics in modified atmosphere packaging of soft cheese

    Microsoft Academic Search

    Rocio Rodriguez-Aguilera; Jorge C. Oliveira; Julio C. Montanez; Pramod V. Mahajan

    2009-01-01

    Modified Atmosphere Packaging (MAP) is a shelf-life extension technique that has been widely applied to horticultural, meat and dairy products. It relies on the interaction between product, packaging material and environment, which determines the gas composition inside the package at steady state. Therefore, MAP design needs to take into consideration O2 consumption and CO2 production rates of the product and

  15. Gamma radiation effect on gas production in anion exchange resins

    NASA Astrophysics Data System (ADS)

    Traboulsi, A.; Labed, V.; Dauvois, V.; Dupuy, N.; Rebufa, C.

    2013-10-01

    Radiation-induced decomposition of Amberlite IRA400 anion exchange resin in hydroxide form by gamma radiolysis has been studied at various doses in different atmospheres (anaerobic, anaerobic with liquid water, and aerobic). The effect of these parameters on the degradation of ion exchange resins is rarely investigated in the literature. We focused on the radiolysis gases produced by resin degradation. When the resin was irradiated under anaerobic conditions with liquid water, the liquid phase over the resin was also analyzed to identify any possible water-soluble products released by degradation of the resin. The main products released are trimethylamine (TMA), molecular hydrogen (H2g) and carbon dioxide (CO2g). TMA and H2g are produced in all the irradiation atmospheres. However, TMA was in gaseous form under anaerobic and aerobic conditions and in aqueous form in presence of liquid water. In the latter conditions, TMAaq was associated with aqueous dimethylamine (DMAaq), monomethylamine (MMAaq) and ammonia (NH). CO2g is formed in the presence of oxygen due to oxidation of organic compounds present in the system, in particular the degradation products such as TMAg.

  16. High Capacity Na+/H+ Exchange Activity in Mineralizing Osteoblasts

    PubMed Central

    Liu, Li; Schlesinger, Paul H.; Slack, Nicole M.; Friedman, Peter A.; Blair, Harry C.

    2015-01-01

    Osteoblasts synthesize bone in polarized groups of cells sealed by tight junctions. Large amounts of acid are produced as bone mineral is precipitated. We addressed the mechanism by which cells manage this acid load by measuring intracellular pH (pHi) in non-transformed osteoblasts in response to weak acid or bicarbonate loading. Basal pHi in mineralizing osteoblasts was ?7.3 and decreased by ? 1.4 units upon replacing extracellular Na+ with N-methyl-d-glucamine. Loading with 40 mM acetic or propionic acids, in normal extracellular Na+, caused only mild cytosolic acidification. In contrast, in Na+-free solutions, weak acids reduced pHi dramatically. After Na+ reintroduction, pHi recovered rapidly, in keeping with Na+/H+exchanger (NHE) activity. Sodium-dependent pHi recovery from weak acid loading was inhibited by amiloride with the Ki consistent with NHEs. NHE1 and NHE6 were expressed strongly, and expression was upregulated highly, by mineralization, in human osteoblasts. Antibody labeling of mouse bone showed NHE1 on basolateral surfaces of all osteoblasts. NHE6 occurred on basolateral surfaces of osteoblasts mainly in areas of mineralization. Conversely, elevated HCO3- alkalinized osteoblasts, and pH recovered in medium containing CI-, with or without Na+, in keeping with Na+-independent CI-/HCO3- exchange. The exchanger AE2 also occurred on the basolateral surface of osteoblasts, consistent with CI-/HCO3- exchange for elimination of metabolic carbonate. Overexpression of NHE6 or knockdown of NHE1 in MG63 human osteosarcoma cells confirmed roles of NHE1 and NHE6 in maintaining pHi. We conclude that in mineralizing osteoblasts, slightly basic basal pHi is maintained, and external acid load is dissipated, by high-capacity Na+/H+ exchange via NHE1 and NHE6. PMID:21413028

  17. Development and Evaluation of a Coupled Photosynthesis-Based Gas Exchange Evapotranspiration Model (GEM) for Mesoscale Weather Forecasting Applications

    E-print Network

    Niyogi, Dev

    Development and Evaluation of a Coupled Photosynthesis-Based Gas Exchange Evapotranspiration Model with a photosynthesis-based scheme and still achieve dynamically consistent results. To demonstrate this transformative potential, the authors developed and coupled a photosynthesis, gas exchange­based surface evapotranspiration

  18. Effects of Angular Leaf Spot and Rust on Leaf Gas Exchange and Yield of Common Bean ( Phaseolus Vulgaris )

    Microsoft Academic Search

    W. C. Jesus Junior; F. X. R. Vale; C. A. Martinez; R. R. Coelho; L. C. Costa; B. Hau; L. Zambolim

    2001-01-01

    Isolated and interactive effects of angular leaf spot (caused by Phaeoisariopsis griseola) and rust (caused by Uromyces appendiculatus) on leaf gas exchange and yield was studied in common bean (Phaseolus vulgaris L. cv. Carioca) plants. Gas exchange was measured on 37, 44, 51, and 58 d after planting using a portable photosynthesis system. The inoculation of plants with P. griseola

  19. Gas-exchange patterns of Mediterranean fruit fly Pupae (Diptera: Tephritidae): A tool to forecast developmental stage

    Microsoft Academic Search

    D. Nestel; E. Nemny-Lavy; V. Alchanatis

    2007-01-01

    The pattern of gas-exchange (COâ emission) was investigated for developing Mediterranean fruit fly (medfly) Ceratitis capitata (Wiedemann) pupae incubated at different temperatures. This study was undertaken to explore the usefulness of gas-exchange systems in the determination of physiological age in developing pupae that are mass produced for sterile insect technique projects. The rate of COâ emission was measured in a

  20. Hydraulic Properties of Rice and the Response of Gas Exchange to Water Stress1

    E-print Network

    Stiller, Volker

    Hydraulic Properties of Rice and the Response of Gas Exchange to Water Stress1 Volker Stiller*, H.R.L.) We investigated the role of xylem cavitation, plant hydraulic conductance, and root pressure-specific photosynthetic rate, leaf diffusive conductance, and soil-leaf hydraulic conductance that were associated

  1. Cardiovascular Function and Alveolar Gas Exchange during Isovolemic Hemodialysis with Acetate in Healthy Man

    Microsoft Academic Search

    A. Danielsson; U. Freyschuss; J. Bergström

    1987-01-01

    In order to elucidate the hemodynamic responses and alveolar gas exchange during isovolemic hemodialysis (IHD), without the influence of the uremic state and its complications, 7 healthy men underwent IHD. The dialysate contained acetate (40 mmol\\/l) and the sodium concentration was adjusted to the individual’s predetermined plasma sodium concentration. By invasive techniques cardiac index (thermodilution), stroke index, heart rate, brachial

  2. In situ CO 2 gas-exchange in fruits of a tropical tree, Durio zibethinus Murray

    Microsoft Academic Search

    Kazuharu Ogawal; Akio Furukawa; Akio Hagihara; Ahmad Makmom Abdullah; Muhamad Awang

    1995-01-01

    We examined the in situ CO2 gas-exchange of fruits of a tropical tree, Durio zibethinus Murray, growing in an experimental field station of the Universiti Pertanian Malaysia. Day and night dark respiration rates were exponentially related to air temperature. The temperature dependent dark respiration rate showed a clockwise loop as time progressed from morning to night, and the rate was

  3. Gas exchange responses of Chesapeake Bay tidal marsh species under field and laboratory conditions

    Microsoft Academic Search

    T. M. DeJong; B. G. Drake; R. W. Pearcy

    1982-01-01

    Laboratory and field gas exchange measurements were made on C3 (Scirpus olneyi Gray) and C4 (Spartina patens (Ait.) Mahl., Distichlis spicata (L.) Green) species from an irregularly flooded tidal marsh on the Chesapeake Bay. Laboratory measurements were made on plants grown from root stocks that were transplanted to a greenhouse and grown under high light and high nutrient conditions. The

  4. Original article Modelling age-and density-related gas exchange

    E-print Network

    Paris-Sud XI, Université de

    radiation absorption, the net photosynthesis and transpiration of single trees, and gas exchange of tree water availability. For our humid montane stands, these simplifying assumptions appeared to be acceptable. Comparisons of modelled daily tree transpiration with water use estimates from xylem sapflow

  5. Carbon dioxide control in an open system that measures canopy gas exchanges

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Atmospheric carbon dioxide concentration ([CO2]) effects both C3 net assimilation (A) as well as crop water use. Methods for measuring whole canopy gas exchange responses under [CO2] enrichment are needed for breeding programs aiming to develop crop cultivars resistant to stresses like drought in a...

  6. Assessment of saltwater intrusion impact on gas exchange behavior of Louisiana Gulf Coast wetland species

    Microsoft Academic Search

    S. R. Pezeshki; R. D. DeLaune

    1989-01-01

    A review of gas exchange responses of wetland plants to salinity is presented for several species representative of different wetland habitats extending along water level and salinity gradients in the Louisiana Gulf Coast, U.S.A. The information was synthesized from earlier plant physiological response studies. Vegetation examined represent a broad range of sensitivity to salt, including brackish marsh, freshwater marsh, and

  7. Lack of agreement between gas exchange variables measured by two metabolic systems

    Microsoft Academic Search

    Djordje G. Jakovljevic; David Nunan; Gay Donovan; Lynette D. Hodges; Gavin R. H. Sandercock; David A. Brodie

    2008-01-01

    The purpose of this study was to assess the agreement and con- sistency between gas exchange variables measured by two online metabolic systems during an incremental exercise test. After obtaining local ethics approval and informed consent, 15 healthy subjects performed an incremental exercise test to voli- tional fatigue using the Bruce protocol. The Innocor (Innovision, Denmark) and CardiO2 (Medical Graphics,

  8. Gas exchange characteristics of Typha latifolia L. from nine sites across North America

    Microsoft Academic Search

    Alan K. Knapp; Joseph B. Yavitt

    1995-01-01

    Gas exchange characteristics were measured in the field for nine populations of Typha latifolia L. from Florida to Minnesota in North America. These populations spanned a substantial gradient in growing season length and environmental conditions. The purpose of this study was to assess geographic variability in stomatal conductance (gst) in T. latifolia populations, as well as to identify key environmental

  9. Respiratory Physiology & Neurobiology 154 (2006) 1829 Discontinuous gas exchange in insects

    E-print Network

    Ahmad, Sajjad

    2006-01-01

    Respiratory Physiology & Neurobiology 154 (2006) 18­29 Discontinuous gas exchange in insects, University of Nevada, Las Vegas, NV 89154, USA Accepted 7 April 2006 Abstract Insect respiratory physiology has been studied for many years, and interest in this area of insect biology has become revitalized

  10. Effects of elevated carbon dioxide on leaf gas exchange and growth of cork-oak

    E-print Network

    Paris-Sud XI, Université de

    Short note Effects of elevated carbon dioxide on leaf gas exchange and growth of cork-oak (Quercus) and at elevated (700 ?mol mor-1) concentrations of carbon dioxide. In well-watered conditions, daily max- imum. In conditions of moderate drought, net CO2 assimilation was at least twice as great in elevated CO2

  11. Leaf gas exchange and water relation characteristics of field quinoa ( Chenopodium quinoa Willd.) during soil drying

    Microsoft Academic Search

    C. R Jensen; S.-E Jacobsen; M. N Andersen; N Núñez; S. D Andersen; L Rasmussen; V. O Mogensen

    2000-01-01

    The effects of soil drying on leaf water relations and gas exchange were studied in quinoa grown in pots with sandy soil and in lysimeter plots with sandy loam in the field. Midday values of leaf water potential (?l), leaf osmotic potential (??), relative water content (RWC), leaf conductance (gl), light saturated net photosynthesis (Asat), and specific leaf area (SLA)

  12. A respiratory gas exchange catheter: In vitro and in vivo tests in large animals

    E-print Network

    Federspiel, William J.

    and increased mean pressure decreases across the device become significant only with the larger balloon (40-m surrounded by hollow fibers. The pulsating balloon redirects blood toward the fibers, enhances red cell in the venous system as a function of hemodynamics and gas exchange. Results: In vitro performance in water

  13. Gas exchange and water relations of evergreen and deciduous tropical savanna trees

    E-print Network

    Boyer, Edmond

    in the oligotrophic soils which predominate, while the deciduous species form small forest 'islands' located on patches of richer soil (Sarmiento, 1984). The trees in these forest islands are mostly drought deciduousGas exchange and water relations of evergreen and deciduous tropical savanna trees G. Goldstein1 F

  14. Response of shoot growth and gas exchange of Picea abies clones to rain acidity

    E-print Network

    Paris-Sud XI, Université de

    Response of shoot growth and gas exchange of Picea abies clones to rain acidity and the addition, particularly the effect of acidity and the addition of a realistic ionic mixture to simulated acidic.0 with a mixture of sulfuric and nitric acids (S02-/NO-weight ratio = 2.4). Ionic concentrations m mg/1were: 4.50 S

  15. Effects of diffuse radiation on canopy gas exchange processes in a forest ecosystem

    Microsoft Academic Search

    Alexander Knohl; Dennis D. Baldocchi

    2008-01-01

    Forest ecosystems across the globe show an increase in ecosystem carbon uptake efficiency under conditions with high fraction of diffuse radiation. Here, we combine eddy covariance flux measurements at a deciduous temperate forest in central Germany with canopy-scale modeling using the biophysical multilayer model CANVEG to investigate the impact of diffuse radiation on various canopy gas exchange processes and to

  16. Variation in gas exchange and water use efficiency patterns among populations of western redcedar

    Microsoft Academic Search

    Steven C. Grossnickle; Shihe Fan; John H. Russell

    2005-01-01

    Western redcedar ( Thuja plicata Donn) populations were planted out on a reforestation site and measured, during the summer, to define their gas exchange processes in relation to evaporative demand under non-limiting light and edaphic conditions. These populations came from various locations across a longitudinal transect representing various biogeoclimatic subzones, differing in annual and summer precipitation, in British Columbia, Canada.

  17. Airway Gas Exchange and Exhaled Biomarkers Steven C. George*1,2

    E-print Network

    George, Steven C.

    tree is thought largely to provide a conduit for the respiratory gases, oxygen and carbon dioxide the blood when compared to the alveolar region, the airway tree can participate in gas exchange under alveolar membrane. Given the significant structural differences between the airways and the alveolar region

  18. Slag and seed deposition on heat exchanger surfaces from gas-droplet mixtures

    Microsoft Academic Search

    K. H. Im; L. W. Carlson; P. M. Chung

    1978-01-01

    Mechanisms of particulate deposition from turbulent streams to solid surfaces are first discussed. Two problems of current interest in MHD application are then analyzed. One is the collection of slag droplets on the interior wall of vertical tubes from the turbulent droplet-laden gas stream. Such processes take place during the cycle of the regenerative heat exchanger used to preheat combustion

  19. Field Evaluation of Open System Chambers for Measuring Whole Canopy Gas Exchanges

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The ability to monitor whole canopy CO2 and H2O fluxes of crop plants in the field is needed for many research efforts ranging from plant breeding to the study of Climate Change effects on crops. Four portable, transparent, open system chambers for measuring canopy gas exchanges were field tested on...

  20. Field studies of leaf gas exchanges in oil palm tree (Elaeis guineensis Jacq.)

    E-print Network

    Paris-Sud XI, Université de

    Field studies of leaf gas exchanges in oil palm tree (Elaeis guineensis Jacq.) E. Dufrene B. Our purpose was to characterize, under conditions of good water supply, variations in leaf photosyn) or leaf water potential and stomatal conductance (Adjahossou, 1983). Only 2 experiments were conducted

  1. Guest Molecule Exchange Kinetics for the 2012 Ignik Sikumi Gas Hydrate Field Trial

    SciTech Connect

    White, Mark D.; Lee, Won Suk

    2014-05-14

    A commercially viable technology for producing methane from natural gas hydrate reservoirs remains elusive. Short-term depressurization field tests have demonstrated the potential for producing natural gas via dissociation of the clathrate structure, but the long-term performance of the depressurization technology ultimately requires a heat source to sustain the dissociation. A decade of laboratory experiments and theoretical studies have demonstrated the exchange of pure CO2 and N2-CO2 mixtures with CH4 in sI gas hydrates, yielding critical information about molecular mechanisms, recoveries, and exchange kinetics. Findings indicated the potential for producing natural gas with little to no production of water and rapid exchange kinetics, generating sufficient interest in the guest-molecule exchange technology for a field test. In 2012 the U.S. DOE/NETL, ConocoPhillips Company, and Japan Oil, Gas and Metals National Corporation jointly sponsored the first field trial of injecting a mixture of N2-CO2 into a CH4-hydrate bearing formation beneath the permafrost on the Alaska North Slope. Known as the Ignik Sikumi #1 Gas Hydrate Field Trial, this experiment involved three stages: 1) the injection of a N2-CO2 mixture into a targeted hydrate-bearing layer, 2) a 4-day pressurized soaking period, and 3) a sustained depressurization and fluid production period. Data collected during the three stages of the field trial were made available after an extensive quality check. These data included continuous temperature and pressure logs, injected and recovered fluid compositions and volumes. The Ignik Sikumi #1 data set is extensive, but contains no direct evidence of the guest-molecule exchange process. This investigation is directed at using numerical simulation to provide an interpretation of the collected data. A numerical simulator, STOMP-HYDT-KE, was recently completed that solves conservation equations for energy, water, mobile fluid guest molecules, and hydrate guest molecules, for up to three gas hydrate guest molecules: CH4, CO2, and N2. The independent tracking of mobile fluid and hydrate guest molecules allows for the kinetic exchange of guest molecules between the mobile fluids and hydrate. The particular interest of this numerical investigation is to determine whether kinetic exchange parameters, determined from laboratory-scale experiments, are directly applicable to interpreting the Ignik Sikumi #1 data.

  2. Hybrid heat exchange for the compression capture of CO2 from recirculated flue gas

    SciTech Connect

    Oryshchyn, Danylo B.; Ochs, Thomas L.; Summers, Cathy A.

    2004-01-01

    An approach proposed for removal of CO2 from flue gas cools and compresses a portion of a recirculated flue-gas stream, condensing its volatile materials for capture. Recirculating the flue gas concentrates SOx, H2O and CO2 while dramatically reducing N2 and NOx, enabling this approach, which uses readily available industrial components. A hybrid system of indirect and direct-contact heat exchange performs heat and mass transfer for pollutant removal and energy recovery. Computer modeling and experimentation combine to investigate the thermodynamics, heat and mass transfer, chemistry and engineering design of this integrated pollutant removal (IPR) system.

  3. Effects of flow rate and temperature on cyclic gas exchange in tsetse flies (Diptera, Glossinidae).

    PubMed

    Terblanche, John S; Chown, Steven L

    2010-05-01

    Air flow rates may confound the investigation and classification of insect gas exchange patterns. Here we report the effects of flow rates (50, 100, 200, 400 ml min(-1)) on gas exchange patterns in wild-caught Glossina morsitans morsitans from Zambia. At rest, G. m. morsitans generally showed continuous or cyclic gas exchange (CGE) but no evidence of discontinuous gas exchange (DGE). Flow rates had little influence on the ability to detect CGE in tsetse, at least in the present experimental setup and under these laboratory conditions. Importantly, faster flow rates resulted in similar gas exchange patterns to those identified at lower flower rates suggesting that G. m. morsitans did not show DGE which had been incorrectly identified as CGE at lower flow rates. While CGE cycle frequency was significantly different among the four flow rates (p<0.05), the direction of effects was inconsistent. Indeed, inter-individual variation in CGE cycle frequency exceeded flow rate treatment variation. Using a laboratory colony of closely related, similar-sized G. morsitans centralis we subsequently investigated the effects of temperature, gender and feeding status on CGE pattern variation since these factors can influence insect metabolic rates. At 100 ml min(-1) CGE was typical of G. m. centralis at rest, although it was significantly more common in females than in males (57% vs. 43% of 14 individuals tested per gender). In either sex, temperature (20, 24, 28 and 32 degrees C) had little influence on the number of individuals showing CGE. However, increases in metabolic rate with temperature were modulated largely by increases in burst volume and cycle frequency. This is unusual among insects showing CGE or DGE patterns because increases in metabolic rate are usually modulated by increases in frequency, but either no change or a decline in burst volume. PMID:20399350

  4. Seasonal differences in needle gas exchange between mature branches and seedlings of Pinus ponderosa

    SciTech Connect

    Houpis, J.L.J.; Anderson, P.D. (Lawrence Livermore National Lab., CA (United States))

    1991-05-01

    In 1990, an interactive study was initiated to understand the differing physiological and morphological response of mature tissue and seedling tissue to stress. The study was conducted at the Air Pollution and Climate Change Exposure Facility in a Pinus ponderosa seed production orchard at the US Forest Service Tree Improvement Center in Chico, CA. The orchard consists of clonal trees and the authors have planted half-sibling seedlings which correspond to the mature clones which were measured. Both the mature trees and seedlings were regularly irrigated and fertilized. The result is that they have minimized the genetic and environmental differences that might otherwise influence the physiological differences between mature and seedling tissue. One of the physiological parameters which was measured was seasonal and diurnal gas exchange using a LICOR 6200. They measured gas exchange in November 1989, March, July, and October 1990. They found that throughout the year, all gas exchange components (eg. photosynthesis, transpiration, stomatal conductance) were significantly greater for seedling tissue. Photosynthetic differences were greater during early October, with diurnal mean rates of 1.1 {mu}mol m{sup {minus}2}s{sup {minus}1} and 0.5 {mu}mol m{sup {minus}2}s{sup {minus}1} for seedling and mature tissue, respectively. Transpiration differences were greater during early October, with diurnal mean rates of 2.2 mmol m{sup {minus}2}2{sup {minus}1} and 1.2 mmol m{sup {minus}2}s{sup {minus}1} for seedling and mature tissue, respectively. Finally, gas exchange differences between seedling and mature tissue were greater for current needles than one-year old needles. The results of this study demonstrate that gas exchange differences between seedling and mature tissue observed in the field may be the result of inherent physiological differences, and not merely genetic and environmental differences.

  5. Performance analysis of three nanofluids in liquid to gas and liquid to liquid heat exchangers

    NASA Astrophysics Data System (ADS)

    Ray, Dustin R.

    One purpose of this research was to analyze the thermal and fluid dynamic performance of nanofluids in an automotive radiator (liquid to gas). Detailed computations were performed on an automotive radiator using three different nanofluids containing aluminum oxide, copper oxide and silicon dioxide nanoparticles dispersed in the base fluid, 60:40 ethylene glycol and water (EG/W) by mass. The computational scheme adopted was the effectiveness-Number of Transfer Unit (epsilon-NTU) method encoded in Matlab. The computational scheme was validated by comparing the predicted results with that of the base fluid reported by other researchers. Then, the scheme was adapted to compute the performance of nanofluids. Results show that a dilute 1% volumetric concentration of nanoparticles can have substantial savings in the pumping power or surface area of the heat exchanger, while transferring the same amount of heat as the base fluid. The second purpose of this research was to carry out experimental and theoretical studies for a plate heat exchanger (PHE). A benchmark test was performed with the minichannel PHE to validate the test apparatus with water. Next, using a 0.5% aluminum oxide nanoparticle concentration dispersed in EG/W preliminary correlations for the Nusselt number and the friction factor for nanofluid flow in a PHE were derived. Then, a theoretical study was conducted to compare the performance of three nanofluids comprised of aluminum oxide, copper oxide and silicon dioxide nanoparticles in EG/W. This theoretical analysis was conducted using the epsilon-NTU method. The operational parameters were set by the active thermal control system currently under design by NASA. The analysis showed that for a dilute particle volumetric concentration of 1%, all the nanofluids showed improvements in their performance over the base fluid by reducing the pumping power and surface area of the PHE.

  6. Isomeric Differentiation of Green Tea Catechins using Gas-Phase Hydrogen/Deuterium Exchange Reactions

    PubMed Central

    Niemeyer, Emily D.; Brodbelt, Jennifer S.

    2007-01-01

    Hydrogen/deuterium exchange reactions in a quadrupole ion trap mass spectrometer are used to differentiate galloylated catechin stereoisomers (catechin gallate and epicatechin gallate; gallocatechin gallate and epigallocatechin gallate) and the non-galloylated analogs (catechin and epicatechin, gallocatechin and epigallocatechin). Significant differences in the hydrogen/deuterium exchange behavior of the four pairs of deprotonated catechin stereoisomers are observed upon reaction with D2O. Interestingly, the non-galloylated catechins undergo H/D exchange to a much greater extent than the galloylated species, incorporating deuterium at both aromatic/allylic and active phenolic sites. Non-galloylated catechin isomers are virtually indistinguishable by their H/D exchange kinetics over a wide range of reaction times (0.05 to 10 s). Our experimental results are explained using high-level ab initio calculations to elucidate the subtle structural variations in the catechin stereoisomers that lead to their differing H/D exchange kinetics. PMID:17702600

  7. A Three-Dimensional Multiscale Model for Gas Exchange in Fruit1[C][W][OA

    PubMed Central

    Ho, Quang Tri; Verboven, Pieter; Verlinden, Bert E.; Herremans, Els; Wevers, Martine; Carmeliet, Jan; Nicolaï, Bart M.

    2011-01-01

    Respiration of bulky plant organs such as roots, tubers, stems, seeds, and fruit depends very much on oxygen (O2) availability and often follows a Michaelis-Menten-like response. A multiscale model is presented to calculate gas exchange in plants using the microscale geometry of the tissue, or vice versa, local concentrations in the cells from macroscopic gas concentration profiles. This approach provides a computationally feasible and accurate analysis of cell metabolism in any plant organ during hypoxia and anoxia. The predicted O2 and carbon dioxide (CO2) partial pressure profiles compared very well with experimental data, thereby validating the multiscale model. The important microscale geometrical features are the shape, size, and three-dimensional connectivity of cells and air spaces. It was demonstrated that the gas-exchange properties of the cell wall and cell membrane have little effect on the cellular gas exchange of apple (Malus × domestica) parenchyma tissue. The analysis clearly confirmed that cells are an additional route for CO2 transport, while for O2 the intercellular spaces are the main diffusion route. The simulation results also showed that the local gas concentration gradients were steeper in the cells than in the surrounding air spaces. Therefore, to analyze the cellular metabolism under hypoxic and anoxic conditions, the microscale model is required to calculate the correct intracellular concentrations. Understanding the O2 response of plants and plant organs thus not only requires knowledge of external conditions, dimensions, gas-exchange properties of the tissues, and cellular respiration kinetics but also of microstructure. PMID:21224337

  8. Analysis of the effectiveness of gas exchange in a membrane oxygenator with repeated mixing of the blood flow

    Microsoft Academic Search

    V. V. Petrash; A. R. Os'mak

    1987-01-01

    It is known that the effectiveness of the gas-exchange function of membrane oxygenators is determined not only by the gas permeability of the membrane used but also by the character of the blood fl0w in the region of gas exchange, i.e., by the thickness of the blood layer and degree of its mixing during flow [5, 7, 9, 13]. Since

  9. Plant mineral nutrition, gas exchange and photosynthesis in space: A review

    NASA Astrophysics Data System (ADS)

    Wolff, S. A.; Coelho, L. H.; Zabrodina, M.; Brinckmann, E.; Kittang, A.-I.

    2013-02-01

    Successful growth and development of higher plants in space rely on adequate availability and uptake of water and nutrients, and efficient energy distribution through photosynthesis and gas exchange. In the present review, literature has been reviewed to assemble the relevant knowledge within space plant research for future planetary missions. Focus has been on fractional gravity, space radiation, magnetic fields and ultimately a combined effect of these factors on gas exchange, photosynthesis and transport of water and solutes. Reduced gravity prevents buoyancy driven thermal convection in the physical environment around the plant and alters transport and exchange of gases and liquids between the plant and its surroundings. In space experiments, indications of root zone hypoxia have frequently been reported, but studies on the influences of the space environment on plant nutrition and water transport are limited or inconclusive. Some studies indicate that uptake of potassium is elevated when plants are grown under microgravity conditions. Based on the current knowledge, gas exchange, metabolism and photosynthesis seem to work properly in space when plants are provided with a well stirred atmosphere and grown at moderate light levels. Effects of space radiation on plant metabolism, however, have not been studied so far in orbit. Ground experiments indicated that shielding from the Earth's magnetic field alters plant gas exchange and metabolism, though more studies are required to understand the effects of magnetic fields on plant growth. It has been shown that plants can grow and reproduce in the space environment and adapt to space conditions. However, the influences of the space environment may result in a long term effect over multiple generations or have an impact on the plants' role as food and part of a regenerative life support system. Suggestions for future plant biology research in space are discussed.

  10. Cell wall integrity modulates RHO1 activity via the exchange factor ROM2.

    PubMed Central

    Bickle, M; Delley, P A; Schmidt, A; Hall, M N

    1998-01-01

    The essential phosphatidylinositol kinase homologue TOR2 of Saccharomyces cerevisiae controls the actin cytoskeleton by activating a GTPase switch consisting of RHO1 (GTPase), ROM2 (GEF) and SAC7 (GAP). We have identified two mutations, rot1-1 and rot2-1, that suppress the loss of TOR2 and are synthetic-lethal. The wild-type ROT1 and ROT2 genes and a multicopy suppressor, BIG1, were isolated by their ability to rescue the rot1-1 rot2-1 double mutant. ROT2 encodes glucosidase II, and ROT1 and BIG1 encode novel proteins. We present evidence that cell wall defects activate RHO1. First, rot1, rot2, big1, cwh41, gas1 and fks1 mutations all confer cell wall defects and suppress tor2(ts). Second, destabilizing the cell wall by supplementing the growth medium with 0.005% SDS also suppresses a tor2(ts) mutation. Third, disturbing the cell wall with SDS or a rot1, rot2, big1, cwh41, gas1 or fks1 mutation increases GDP/GTP exchange activity toward RHO1. These results suggest that cell wall defects suppress a tor2 mutation by activating RHO1 independently of TOR2, thereby inducing TOR2-independent polarization of the actin cytoskeleton and cell wall synthesis. Activation of RHO1, a subunit of the cell wall synthesis enzyme glucan synthase, by a cell wall alteration would ensure that cell wall synthesis occurs only when and where needed. The mechanism of RHO1 activation by a cell wall alteration is via the exchange factor ROM2 and could be analogous to signalling by integrin receptors in mammalian cells. PMID:9545237

  11. A test of the oxidative damage hypothesis for discontinuous gas exchange in the locust Locusta migratoria.

    PubMed

    Matthews, Philip G D; Snelling, Edward P; Seymour, Roger S; White, Craig R

    2012-08-23

    The discontinuous gas exchange cycle (DGC) is a breathing pattern displayed by many insects, characterized by periodic breath-holding and intermittently low tracheal O(2) levels. It has been hypothesized that the adaptive value of DGCs is to reduce oxidative damage, with low tracheal O(2) partial pressures (PO(2) ? 2-5 kPa) occurring to reduce the production of oxygen free radicals. If this is so, insects displaying DGCs should continue to actively defend a low tracheal PO(2) even when breathing higher than atmospheric levels of oxygen (hyperoxia). This behaviour has been observed in moth pupae exposed to ambient PO(2) up to 50 kPa. To test this observation in adult insects, we implanted fibre-optic oxygen optodes within the tracheal systems of adult migratory locusts Locusta migratoria exposed to normoxia, hypoxia and hyperoxia. In normoxic and hypoxic atmospheres, the minimum tracheal PO(2) that occurred during DGCs varied between 3.4 and 1.2 kPa. In hyperoxia up to 40.5 kPa, the minimum tracheal PO(2) achieved during a DGC exceeded 30 kPa, increasing with ambient levels. These results are consistent with a respiratory control mechanism that functions to satisfy O(2) requirements by maintaining PO(2) above a critical level, not defend against high levels of O(2). PMID:22491761

  12. Gas exchange efficiency of an oxygenator with integrated pulsatile displacement blood pump for neonatal patients.

    PubMed

    Schlanstein, Peter C; Borchardt, Ralf; Mager, Ilona; Schmitz-Rode, Thomas; Steinseifer, Ulrich; Arens, Jutta

    2014-01-01

    Oxygenators have been used in neonatal extracorporeal membrane oxygenation (ECMO) since the 1970s. The need to develop a more effective oxygenator for this patient cohort exists due to their size and blood volume limitations. This study sought to validate the next design iteration of a novel oxygenator for neonatal ECMO with an integrated pulsatile displacement pump, thereby superseding an additional blood pump. Pulsating blood flow within the oxygenator is generated by synchronized active air flow expansion and contraction of integrated silicone pump tubes and hose pinching valves located at the oxygenator inlet and outlet. The current redesign improved upon previous prototypes by optimizing silicone pump tube distribution within the oxygenator fiber bundle; introduction of an oval shaped inner fiber bundle core, and housing; and a higher fiber packing density, all of which in combination reduced the priming volume by about 50% (50 to 27 mL and 41 to 20 mL, respectively). Gas exchange efficiency was tested for two new oxygenators manufactured with different fiber materials: one with coating and one with smaller pore size, both capable of long-term use (OXYPLUS® and CELGARD®). Results demonstrated that the oxygen transfer for both oxygenators was 5.3-24.7 mlO2/min for blood flow ranges of 100-500 mlblood/min. Carbon dioxide transfer for both oxygenators was 3.7-26.3 mlCO2/min for the same blood flow range. These preliminary results validated the oxygenator redesign by demonstrating an increase in packing density and thus in gas transfer, an increase in pumping capacity and a reduction in priming volume. PMID:24634337

  13. Method for determination of pulmonary gas exchange in connection with birth.

    PubMed

    Tunell, R

    1975-01-01

    An apparatus built on the "open" system for determination of pulmonary gas exchange in the newborn infant after birth is described. At four-minute intervals diluted expired air (5-7 1/min) was collected in bags. The oxygen and carbon dioxide fraction in the bags were analysed with a Nyons Diaferometer (working on the principle of thermoconductivity). In calibration experiments using a gas-mixing technique a high degree of linearity was found, both in the determination of the fraction of oxygen and carbon dioxide (r equal to 0.9996). Reproducibility from duplicate readings was also good (for oxygen determination 0.9% and for carbon dioxide determination 0.8%). Duplicate determinations performed on infants with the same degree of motor activity resulted in an estimated error of the method of 5.8% for VO2 and 7.8% for VCO2 respectively. A metabolic chamber was used to control environmental temperature. The air temperature and wall temperature in the chamber were regulated by water from a thermostatically controlled waterbath and were kept equal within 0.5 degrees C. As the method for determination of the fraction of oxygen and carbon dioxide is not specific, other gaseous materials exhaled by the infants influence the measurements and nitrous oxide was found to interfere with the determinations, and made VO2 and VCO2 determinations in these patients impossible. Experience from more than 50 investigations on newborn infants has shown that the method is well suited to this particular type of study. PMID:1114897

  14. Regulation and acclimation of leaf gas exchange in a piñon-juniper woodland exposed to three different precipitation regimes.

    PubMed

    Limousin, Jean-Marc; Bickford, Christopher P; Dickman, Lee T; Pangle, Robert E; Hudson, Patrick J; Boutz, Amanda L; Gehres, Nathan; Osuna, Jessica L; Pockman, William T; McDowell, Nate G

    2013-10-01

    Leaf gas-exchange regulation plays a central role in the ability of trees to survive drought, but forecasting the future response of gas exchange to prolonged drought is hampered by our lack of knowledge regarding potential acclimation. To investigate whether leaf gas-exchange rates and sensitivity to drought acclimate to precipitation regimes, we measured the seasonal variations of leaf gas exchange in a mature piñon-juniper Pinus edulis-Juniperus monosperma woodland after 3 years of precipitation manipulation. We compared trees receiving ambient precipitation with those in an irrigated treatment (+30% of ambient precipitation) and a partial rainfall exclusion (-45%). Treatments significantly affected leaf water potential, stomatal conductance and photosynthesis for both isohydric piñon and anisohydric juniper. Leaf gas exchange acclimated to the precipitation regimes in both species. Maximum gas-exchange rates under well-watered conditions, leaf-specific hydraulic conductance and leaf water potential at zero photosynthetic assimilation all decreased with decreasing precipitation. Despite their distinct drought resistance and stomatal regulation strategies, both species experienced hydraulic limitation on leaf gas exchange when precipitation decreased, leading to an intraspecific trade-off between maximum photosynthetic assimilation and resistance of photosynthesis to drought. This response will be most detrimental to the carbon balance of piñon under predicted increases in aridity in the southwestern USA. PMID:23461476

  15. Laser photoacoustic spectroscopy of biosystems gas exchange with the atmosphere

    NASA Astrophysics Data System (ADS)

    Ageev, B. G.; Ponomarev, Y. N.; Sapozhnikova, V. A.

    1998-10-01

    A response of plants to stress action is characterized by an activation of the respiration process. The CO2 evolution by some plants exposed to elevated concentration of pollutants and pressure decrease is studied using a photoacoustic spectrometer with a CO2 laser. The measurements show a considerable CO2 evolution by all kinds of the test plants. The quantity of CO2 emitted by pea seedlings at 8 kPa, for example, exceeds the control one by about 20 times (24 h after the exposure start). The exposure of pea seedlings to C2H4 and O3 at various concentrations also increases CO2 evolution: the 48-h exposure of test plants to C2H4 (at 0.01 ppm) increases CO2 evolution by approximately 100% with respect to the control plants.

  16. Activation-triggered subunit exchange between CaMKII holoenzymes facilitates the spread of kinase activity

    PubMed Central

    Stratton, Margaret; Lee, Il-Hyung; Bhattacharyya, Moitrayee; Christensen, Sune M; Chao, Luke H; Schulman, Howard; Groves, Jay T; Kuriyan, John

    2014-01-01

    The activation of the dodecameric Ca2+/calmodulin dependent kinase II (CaMKII) holoenzyme is critical for memory formation. We now report that CaMKII has a remarkable property, which is that activation of the holoenzyme triggers the exchange of subunits between holoenzymes, including unactivated ones, enabling the calcium-independent phosphorylation of new subunits. We show, using a single-molecule TIRF microscopy technique, that the exchange process is triggered by the activation of CaMKII, and that exchange is modulated by phosphorylation of two residues in the calmodulin-binding segment, Thr 305 and Thr 306. Based on these results, and on the analysis of molecular dynamics simulations, we suggest that the phosphorylated regulatory segment of CaMKII interacts with the central hub of the holoenzyme and weakens its integrity, thereby promoting exchange. Our results have implications for an earlier idea that subunit exchange in CaMKII may have relevance for information storage resulting from brief coincident stimuli during neuronal signaling. DOI: http://dx.doi.org/10.7554/eLife.01610.001 PMID:24473075

  17. Effects of an SCBA on breathing pattern, gas exchange, and heart rate during exercise.

    PubMed

    Louhevaara, V; Smolander, J; Tuomi, T; Korhonen, O; Jaakkola, J

    1985-03-01

    The effects of a pressure demand-type self-contained breathing apparatus (SCBA) (total weight, 15.5 kg) on breathing pattern, gas exchange, and heart rate were studied in 13 firemen. The subjects performed sequential progressive exercise tests on a treadmill both without and with an SCBA. The use of an SCBA consistently limited tidal volume. During submaximal exercise oxygen consumption and heart rate increased remarkably more with the SCBA than without it. Four subjects reached their maximal heart rate with the SCBA. Their mean ventilation rate was 68% and oxygen consumption was 83% of the maximal values attained without the SCBA. The shoulder harness of the heavy SCBA prevented free motion of the thorax, affecting the regulation of breathing, and thus seriously disturbed ventilation and gas exchange, particularly at heavier exercise levels. PMID:3981278

  18. Leaf gas exchange and ABA accumulation in Phaseolus vulgaris genotypes of contrasting drought tolerance

    SciTech Connect

    Bertrand, A.; Castonguay, Y.; Nadeau, P. (Agriculture Canada, Ste-Foy, Quebec (Canada))

    1991-05-01

    Drought tolerance mechanisms in Phaseolus vulgaris (Pv) are still largely unknown. Gas exchange responses and ABA accumulation were monitored in Pv genotypes differing in their drought adaptation. Higher rates of photosynthesis were observed under well-watered conditions in drought sensitive genotypes. Water stress caused a significant reduction in leaf water potential and photosynthetic rates regardless of drought adaptation. Higher photosynthetic rates were maintained under stress conditions in one drought tolerant genotype. Interestingly water stress caused significant ABA accumulation only in this genotype. Root ABA levels were similar among genotypes and were not modified by water stress. Endogenous levels of free ABA in leaves and roots did not correlated with gas exchange response to water stress. These results differ from previous reports on genotypic variation in ABA accumulation under water stress.

  19. Carbon dioxide gas exchange of cembran pine (Pinus cembra) at the alpine timberline during winter.

    PubMed

    Wieser, G

    1997-07-01

    Winter CO(2) gas exchange of the last three flushes of cembran pine (Pinus cembra L.) was studied under ambient conditions at the alpine timberline, an ecotone with strong seasonal changes in climate. During the coldest months of the year, December to March, gas exchange was almost completely suppressed and even the highest irradiances and temperatures did not cause a significant increase in net photosynthesis compared to spring and fall. In general, daily CO(2) balance was negative between December and March except during extended warm periods in late winter. However, because twig respiration was also reduced to a minimum during the December-March period, daily carbon losses were minimal. Total measured carbon loss during the winter months was small, equalling the photosynthetic production of one to two warm days in spring or summer when average air temperature was above 6 degrees C. PMID:14759840

  20. A method for temporary complete substitution of gas exchange function of the lung.

    PubMed

    Osipov, V P; Efuny, S; Lurie, G; Knjazeva, G; Saveljev, S; Jushkov, M; Mosolova, L

    1982-08-01

    Total substitution of lung gas exchange function can be achieved by oxygenating all blood in a heart-lung machine and requires thoracotomy. In accordance with calculations based on physical principles, if extracorporeal oxygenation is combined with barometric pressure raised to 3 atm, half of the cardiac output will suffice to maintain normal blood oxygenation. Excessive amounts of oxygen dissolved in blood passed through an oxygenator will suffice for the total oxygenation of the rest of the blood. This assumption was investigated in 15 experiments on dogs and one human patient in a hyperbaric chamber. The bubble oxygenator and pneumatic membrane pumps were used. The results suggest that this method of total substitution of lung gas exchange function is feasible. This technique does not require thoracotomy and can be carried out on a patient in any position on the operating table. This method can be used during bronchoscopy treatment, lung lavage, and trachea surgery. PMID:7181732

  1. Design of a Small Scale High Temperature Gas Loop for Process Heat Exchanger Design Tests

    SciTech Connect

    SungDeok, Hong; DongSeok, Oh; WonJae, Lee; JongHwa, Chang [Korea Atomic Energy Research Institute, Yuseong-Gu, Daejeon, 305-600 (Korea, Republic of)

    2006-07-01

    We designed a small scale gas loop that can simulate reference operating conditions, that is, a temperature up to 950 deg C and a pressure up to 6 MPa. Main objective of the loop is to screen the candidate process-heat-exchanger designs of a very small capacity of 10 {approx} 20 kW. We arranged the components of a primary gas loop and a secondary SO{sub 3} loop. Design requirements are prepared for the safe design of a main heater, a hot-gas-duct and a process heat exchanger that avoid a risk of a failure owing to thermal stresses, a flow-induced vibration or an acoustic vibration in both nitrogen and helium mediums. In the primary and secondary loops, the hot-gas-ducts are internally insulated by a ceramic fiber insulation material to protect the pressure housing from high gas temperatures. We determined a total pressure loss of the primary loop to be 66 kPa and the minimum outer diameter of the loop pressure pipe to be 90 mm at a hot location that will prevent a thermal failure. Very toxic SO{sub 3} secondary loop is needed a scrubber and a SO{sub 3} collector for safety and preventing a contamination of the environment. (authors)

  2. Making Activated Carbon for Storing Gas

    NASA Technical Reports Server (NTRS)

    Wojtowicz, Marek A.; Serio, Michael A.; Suuberg, Eric M.

    2005-01-01

    Solid disks of microporous activated carbon, produced by a method that enables optimization of pore structure, have been investigated as means of storing gas (especially hydrogen for use as a fuel) at relatively low pressure through adsorption on pore surfaces. For hydrogen and other gases of practical interest, a narrow distribution of pore sizes <2 nm is preferable. The present method is a variant of a previously patented method of cyclic chemisorption and desorption in which a piece of carbon is alternately (1) heated to the lower of two elevated temperatures in air or other oxidizing gas, causing the formation of stable carbon/oxygen surface complexes; then (2) heated to the higher of the two elevated temperatures in flowing helium or other inert gas, causing the desorption of the surface complexes in the form of carbon monoxide. In the present method, pore structure is optimized partly by heating to a temperature of 1,100 C during carbonization. Another aspect of the method exploits the finding that for each gas-storage pressure, gas-storage capacity can be maximized by burning off a specific proportion (typically between 10 and 20 weight percent) of the carbon during the cyclic chemisorption/desorption process.

  3. Enhanced gas-phase hydrogen-deuterium exchange of oligonucleotide and protein ions stored in an external multipole ion reservoir.

    PubMed

    Hofstadler, S A; Sannes-Lowery, K A; Griffey, R H

    2000-01-01

    Rapid gas-phase hydrogen-deuterium (H-D) exchange from D(2)O and ND(3) into oligonucleotide and protein ions was achieved during storage in a hexapole ion reservoir. Deuterated gas is introduced through a capillary line that discharges directly into the low-pressure region of the reservoir. Following exchange, the degree of H-D exchange is determined using Fourier transform ion cyclotron resonance mass spectrometry. Gas-phase H-D exchange experiments can be conducted more than 100 times faster than observed using conventional in-cell exchange protocols that require lower gas pressures and additional pump-down periods. The short experimental times facilitate the quantitation of the number of labile hydrogens for less reactive proteins and structured oligonucleotides. For ubiquitin, we observe approximately 65 H-D exchanges after 20 s. Exchange rates of > 250 hydrogens s(-1) are observed for oligonucleotide ions when D(2)O or ND(3) is admitted directly into the external ion reservoir owing to the high local pressure in the hexapole. Partially deuterated oligonucleotide ions have been fragmented in the reservoir using infrared multiphoton dissociation (IRMPD). The resulting fragment ions show that exchange predominates at charged sites on the 5'- and 3'-ends of the oligonucleotide, whereas exchange is slower in the core. This hardware configuration is independent of the mass detector and should be compatible with other mass spectrometric platforms including quadrupole ion trap and time-of-flight mass spectrometers. PMID:10633235

  4. Cryogenic Heat-Exchanger Design for Freeze-out Removal of Carbon Dioxide from Landfill Gas

    Microsoft Academic Search

    Ho-Myung Chang; Myung Jin Chung; Seong Bum Park

    2009-01-01

    A cryogenic heat exchanger to remove carbon dioxide from landfill gas (LFG) is proposed and designed for applications to LNG production in distributed-scale. Since the major components of LFG are methane and carbon dioxide, CO2 removal is a significant pre-process in the liquefaction systems. A new and simple approach is proposed to directly remove carbon dioxide as frost on the

  5. Respiratory gas exchange and physiological demands during a fire fighter evaluation circuit in men and women

    Microsoft Academic Search

    D. G. Harvey; J. L. Kraemer; M. T. Sharratt; R. L. Hughson

    2008-01-01

    We examined the oxygen uptake (VO2) and carbon dioxide output (VCO2) during completion of a circuit developed for testing fire fighters and related performance time to laboratory measures of\\u000a fitness. Twenty-two healthy university students (ten women) were trained in the tasks then performed the circuit as quickly\\u000a as possible. Breath-by-breath gas exchange and heart rate were continuously measured with a

  6. Effects of drought stress on photosynthetic gas exchange, chlorophyll fluorescence and stem diameter of soybean plants

    Microsoft Academic Search

    Y. Ohashi; N. Nakayama; H. Saneoka; K. Fujita

    2006-01-01

    Changes in plant growth, photosynthetic gas exchange, chlorophyll fluorescence and stem diameter of soybean [Glycine max (L.) Merr.] plants under drought stress were studied. Total plant dry mass was reduced by 30 % compared to well-watered control\\u000a plants. Leaf water potential was slightly decreased by water stress. Water stress induced daytime shrinkage and reduced night-time\\u000a expansion of stem. Photosynthetic rate,

  7. Modeled natural and excess radiocarbon: Sensitivities to the gas exchange formulation and ocean transport strength

    Microsoft Academic Search

    S. A. Müller; F. Joos; G.-K. Plattner; N. R. Edwards; T. F. Stocker

    2008-01-01

    Observation-based surface ocean ?14C distributions and regional inventories for excess, bomb-produced radiocarbon are compared with results of two ocean models of intermediate complexity. By applying current descriptions of the air-sea gas exchange the models produce similar column inventories for excess 14C among all basins. This result is robust across a wide range of transport parameter settings, but inconsistent with data-based

  8. Detection of disturbances in pulmonary gas exchanges during exercise from arterialized earlobe PO2.

    PubMed

    Aguilaniu, Bernard; Maitre, Jocelyne; Diab, Samia; Perrault, Hélène; Péronnet, François

    2011-06-30

    Blood sampling from the arterialized earlobe is widely used in clinical exercise testing but Fajac et al. (1998) (Eur. Respir. J. 11, 712-715) have shown that arterialized P(O2) Pc(CO2) is not a valid surrogate for Pa(O2). In the present study, in order to detect disturbances in pulmonary gas exchanges during clinical exercise testing from the alveolar-arterial gradient of P(O2) (P[Ai-a](O2)), a correction factor for Pc(O2) was validated from data on a large cohort (107 patients at one or two levels of exercise: 172 pairs of samples). Pulmonary gas exchanges and pH, P(O2), P(CO2), PA(iO2) and P(Ai-a)(O2) from arterial and arterialized blood were measured or computed. Arterial and arterialized pH and P(CO2) (and thus PA(iO2)) were similar but P(CO2) was lower than arterial P(O2) (Pa(O2)). However, when corrected for the systematic bias between Pa(O2) and Pc(O2), which increased with Pc(O2), Pc(O2) adequately detected disturbances in pulmonary gas exchanges with a very high sensibility and specificity (predictive values of a negative or positive test ?95%). PMID:21397053

  9. Emphysema following vitrectomy with fluid–gas exchange: description of a rare complication

    PubMed Central

    Damasceno, Eduardo F; Damasceno, Nadyr; Horowitz, Soraya; Rodrigues, Marcio Mortera

    2014-01-01

    Purpose To report a case of subcutaneous emphysema involving the orbit, mediastinum, and face after pars plana vitrectomy with fluid–gas exchange. Methods Case report of a 55-year-old man who presented with bilateral eyelid and face edema and dysphagia in the immediate postoperative period after pars plana vitrectomy. Orbital and chest computed tomographies were performed, revealing emphysema of the orbit and soft tissue of the face, extending from the neck to the upper chest. Results The patient with a retinal detachment in the right eye underwent 23-gauge vitrectomy surgery with fluid–gas exchange and an implantation of silicone oil. The patient had a previous history of facial trauma for more than 20 years with an orbital fracture. After surgery, the patient developed emphysema of the orbit, soft tissue of the face and upper chest. Systemic prophylactic antibiotics associated with antibiotics and steroid drops performed a satisfactory evolution. Conclusion The fluid–gas exchange during pars plana vitrectomy in patients with orbital fracture can lead to emphysema of the face, chest, and soft tissue. PMID:24610998

  10. Use of Noninvasive Gas Exchange to Track Pulmonary Vascular Responses to Exercise in Heart Failure

    PubMed Central

    Taylor, Bryan J.; Olson, Thomas P.; Chul-Ho-Kim; MacCarter, Dean; Johnson, Bruce D.

    2013-01-01

    We determined whether a non-invasive gas exchange based estimate of pulmonary vascular (PV) capacitance [PVCAP = stroke volume (SV) × pulmonary arterial pressure (Ppa)] (GXCAP) tracked the PV response to exercise in heart-failure (HF) patients. Pulmonary wedge pressure (Ppw), Ppa, PV resistance (PVR), and gas exchange were measured simultaneously during cycle exercise in 42 HF patients undergoing right-heart catheterization. During exercise, PETCO2 and VE/VCO2 were related to each other (r = ?0.93, P < 0.01) and similarly related to mean Ppa (mPpa) (r = ?0.39 and 0.36; P < 0.05); PETCO2 was subsequently used as a metric of mPpa. Oxygen pulse (O2 pulse) tracked the SV response to exercise (r = 0.91, P < 0.01). Thus, GXCAP was calculated as O2 pulse × PETCO2. During exercise, invasively determined PVCAP and non-invasive GXCAP were related (r = 0.86, P < 0.01), and GXCAP correlated with mPpa and PVR (r = ?0.46 and ?0.54; P < 0.01). In conclusion, noninvasive gas exchange measures may represent a simple way to track the PV response to exercise in HF. PMID:24093002

  11. Kinetics of response of foliar gas exchange to exogenously applied ethylene

    SciTech Connect

    Taylor, G.E. Jr.; Gunderson, C.A.

    1987-04-01

    While the sensitivity of foliar gas exchange to ethylene in some species is documented, the kinetics of response, including reaction rates, effective concentrations, and mode of action, are not well characterized. The responses of carbon dioxide assimilation and stomatal conductance were investigated in Glycine max grown in a controlled environment and exposed to a range of exogenously applied ethylene concentrations. The gas-exchange responses exhibited first-order kinetics at low concentrations (less than 20 ..mu..moles per cubic meter) but zero-order kinetics at all higher concentrations. In the region of first-order kinetics, the rate of inhibition per unit change is ethylene concentration was twice as great for stomatal conductance as for carbon dioxide assimilation. The ethylene concentrations resulting in one-half maximal inhibition of stomatal conductance and carbon dioxide assimilation were 7.4 and 15.6 ..mu..moles per cubic meter, respectively. The ethylene influence on foliar gas exchange exhibited features of capacity-limited or saturation kinetics.

  12. Multidiurnal warm layer and inhibited gas exchange in the Peruvian upwelling regime

    NASA Astrophysics Data System (ADS)

    Fischer, Tim; Kock, Annette; Arévalo-Martínez, Damian L.; Dengler, Marcus; Brandt, Peter; Thomsen, Soeren; Bange, Hermann W.

    2015-04-01

    Upper ocean observations off Peru from December 2012 to February 2013 are used to study the air-sea gas exchange in coastal upwelling regions. Observations include high-resolution profiles of nitrous oxide (N2O) in the topmost 10 meters far from ship's influence, ship based N2O profiles and underway transects, hydrography data from lowered CTD, microstructure probe profiles, and glider transects. We observed distinct vertical N2O gradients in the topmost 10 m of the Peruvian upwelling regime. These gas gradients are associated with periods of persistent stratification in the oceanic top layer of longer than 24 hours up to several days ('multidiurnal warm layer'). The persistent stratification inhibits gas exchange between the ocean boundary layer and deeper layers, resulting in N2O depletion at the surface by outgassing. This can lead to systematic error, when estimating oceanic gas emissions from measured concentrations a few meters below the surface. Surface layer vertical gradients of N2O were found in the high-resolution profiles far from the ship, and were also indicated in the ship based profiles. Stronger vertical N2O gradients were found associated with higher N2O concentrations, and higher N2O concentrations were found associated with stratified surface layers not eroded by night time convection. From 250 days of glider measurements, persistent surface layer stratification was found to be a frequent feature in the Peruvian upwelling regime. The findings have direct implications for air-sea gas exchange estimations in upwelling regions. In the here studied case of ship based N2O concentration measurements at 5 to 10 m depth, emissions will be overestimated and the bias will be strongest at places where the impact on the total emission estimate is largest.

  13. The gas-chromatographic analysis system in the JET active gas handling plant

    Microsoft Academic Search

    R. Lässer; B. Grieveson; J. L. Hemmerich; R. Stagg; T. Dowhyluk; K. Torr; R. Massey; P. Chambers

    1993-01-01

    A gas chromatographic system for the analysis of gas species to be collected from the JET torus and to be processed in the JET active gas handling plant during the active operation phase with deuterium and tritium plasmas was designed and built by CFFTP under contract with JET. The gas-chromatograph consists of a compression\\/injection stage and of two parallel, analytical

  14. Plant Water Use Efficiency over Geological Time – Evolution of Leaf Stomata Configurations Affecting Plant Gas Exchange

    PubMed Central

    Assouline, Shmuel; Or, Dani

    2013-01-01

    Plant gas exchange is a key process shaping global hydrological and carbon cycles and is often characterized by plant water use efficiency (WUE - the ratio of CO2 gain to water vapor loss). Plant fossil record suggests that plant adaptation to changing atmospheric CO2 involved correlated evolution of stomata density (d) and size (s), and related maximal aperture, amax. We interpreted the fossil record of s and d correlated evolution during the Phanerozoic to quantify impacts on gas conductance affecting plant transpiration, E, and CO2 uptake, A, independently, and consequently, on plant WUE. A shift in stomata configuration from large s-low d to small s-high d in response to decreasing atmospheric CO2 resulted in large changes in plant gas exchange characteristics. The relationships between gas conductance, gws, A and E and maximal relative transpiring leaf area, (amax?d), exhibited hysteretic-like behavior. The new WUE trend derived from independent estimates of A and E differs from established WUE-CO2 trends for atmospheric CO2 concentrations exceeding 1,200 ppm. In contrast with a nearly-linear decrease in WUE with decreasing CO2 obtained by standard methods, the newly estimated WUE trend exhibits remarkably stable values for an extended geologic period during which atmospheric CO2 dropped from 3,500 to 1,200 ppm. Pending additional tests, the findings may affect projected impacts of increased atmospheric CO2 on components of the global hydrological cycle. PMID:23844085

  15. The Role of Snow Cover on Surface Trace Gas Exchanges at Toolik Lake, AK

    NASA Astrophysics Data System (ADS)

    Helmig, D.; Obrist, D.; Moore, C.; Van Dam, B.; Jacques, H.; Molnar, T.; Williams, M. W.; Kramer, L. J.; Doskey, P. V.; Fain, X.

    2014-12-01

    Snow has a profound influence on the emission and deposition of atmospheric trace gases in the arctic environment. Processes that play a role in modulating gas exchanges include biological, soil biogeochemical, snow chemical, and snow physical processes. Environmental conditions underneath the snow are relatively stable throughout the winter period. Above the snow surface, variations in temperature, radiation, and wind exert a wide range of influences on snowpack gas chemistry, gas exchanges at the snow-air interface, and chemical interactions between the interstitial snowpack air and vegetation and soil below the snowpack. This presentation will present an overview of experimental approaches for continuous, all winter-long experiments conducted at a permafrost site at the Long-Term Ecological Research (LTER) station at Toolik Lake on the north slope of the Brooks Range, Alaska. These studies include observations of carbon dioxide and the reactive gases ozone, nitrogen oxides, and gaseous elemental mercury. Parameterizations developed from these measurements are used for improving descriptions of trace gas budgets and their feedbacks on climate and associated snow cover changes in the Arctic and seasonally snow-covered midlatitude environments.

  16. An Experimental Investigation of an Exhaust-gas-to-air Heat Exchanger for Use on Jet-stack-equipped Engines

    NASA Technical Reports Server (NTRS)

    Stalder, Jackson R; Spies, Ray J , Jr

    1948-01-01

    Tests were made to determine the loss in exhaust-jet thrust and engine power resulting from the insertion of an exhaust-gas-to-air heat exchanger in a jet-type exhaust stack of an aircraft engine. The thermal performance of the heat exchanger was also determined.

  17. Numerical evaluation of static-chamber measurements of soil-atmosphere gas exchange: Identification of physical processes

    Microsoft Academic Search

    Richard W. Healy; Robert G. Striegl; Thomas F. Russell; Gordon L. Hutchinson; Gerald P. Livingston

    1996-01-01

    The exchange of gases between soil and atmosphere is an important process that affects atmospheric chemistry and therefore climate. The static-chamber method is the most commonly used technique for estimating the rate of that exchange. We examined the method under hypothetical field conditions where diffusion was the only mechanism for gas transport and the atmosphere outside the chamber was maintained

  18. Classical transient receptor potential channel 6 (TRPC6) is essential for hypoxic pulmonary vasoconstriction and alveolar gas exchange

    PubMed Central

    Weissmann, Norbert; Dietrich, Alexander; Fuchs, Beate; Kalwa, Hermann; Ay, Mahmut; Dumitrascu, Rio; Olschewski, Andrea; Storch, Ursula; Mederos y Schnitzler, Michael; Ghofrani, Hossein Ardeschir; Schermuly, Ralph Theo; Pinkenburg, Olaf; Seeger, Werner; Grimminger, Friedrich; Gudermann, Thomas

    2006-01-01

    Regional alveolar hypoxia causes local vasoconstriction in the lung, shifting blood flow from hypoxic to normoxic areas, thereby maintaining gas exchange. This mechanism is known as hypoxic pulmonary vasoconstriction (HPV). Disturbances in HPV can cause life-threatening hypoxemia whereas chronic hypoxia triggers lung vascular remodeling and pulmonary hypertension. The signaling cascade of this vitally important mechanism is still unresolved. Using transient receptor potential channel 6 (TRPC6)-deficient mice, we show that this channel is a key regulator of acute HPV as this regulatory mechanism was absent in TRPC6?/? mice whereas the pulmonary vasoconstrictor response to the thromboxane mimetic U46619 was unchanged. Accordingly, induction of regional hypoventilation resulted in severe arterial hypoxemia in TRPC6?/? but not in WT mice. This effect was mirrored by a lack of hypoxia-induced cation influx and currents in smooth-muscle cells from precapillary pulmonary arteries (PASMC) of TRPC6?/? mice. In both WT and TRPC6?/? PASMC hypoxia caused diacylglycerol (DAG) accumulation. DAG seems to exert its action via TRPC6, as DAG kinase inhibition provoked a cation influx only in WT but not in TRPC6?/? PASMC. Notably, chronic hypoxia-induced pulmonary hypertension was independent of TRPC6 activity. We conclude that TRPC6 plays a unique and indispensable role in acute hypoxic pulmonary vasoconstriction. Manipulation of TRPC6 function may thus offer a therapeutic strategy for the control of pulmonary hemodynamics and gas exchange. PMID:17142322

  19. Seasonal trends in reduced leaf gas exchange and ozone-induced foliar injury in three ozone sensitive woody plant species

    Microsoft Academic Search

    K. Novak; M. Schaub; J. Fuhrer; J. M. Skelly; C. Hug; W. Landolt; P. Bleuler; N. Kräuchi

    2005-01-01

    Seasonal trends in leaf gas exchange and ozone-induced visible foliar injury were investigated for three ozone sensitive woody plant species. Seedlings of Populus nigra L., Viburnum lantana L., and Fraxinus excelsior L. were grown in charcoal-filtered chambers, non-filtered chambers and open plots. Injury assessments and leaf gas exchange measurements were conducted from June to October during 2002. All species developed

  20. The role of body surfaces and ventilation in gas exchange of the abalone, Haliotis iris.

    PubMed

    Taylor, H H; Ragg, N L C

    2005-10-01

    The archaeogastropod Haliotis iris possesses paired bipectinate gills and normally four to six shell holes. In still water, endogenous water flow entered the branchial chamber anteriorly to the left of the head and was exhaled primarily from the three most posterior holes. The first or second anterior aperture was occasionally weakly inhalant. Cardiac interaction superimposed an oscillatory component upon ciliary ventilation but did not augment mean flow. At normal endogenous flow rates 49% of oxygen was extracted from the branchial flow, increasing to 71% at lower flows. In still water, normoxic M(O(2)) was 0.47 micromol g(-1) h(-1). Oxyregulation occurred down to P(O(2)) approximately 80 Torr, with partial oxyregulation down to 45 Torr (P (crit)), and oxyconformity below this. The oxyregulatory plateau was absent in artificially ventilated animals but normoxic M(O(2)) was higher (0.65 micromol g(-1) h(-1)). Endogenous ventilation was unaffected by hypoxia to 15 Torr. Heart rate decreased by approximately 20% at 26 Torr before falling more steeply. Oxygen uptake from the branchial ventilation stream fully accounted for normoxic M(O(2)). In hypoxia (<30 Torr), no uptake occurred from the head or foot despite extensive eversion of the epipodium. Blood oxygen measurements excluded the right mantle as a significant gas exchange organ. Changes in oxygen uptake caused by changes in the velocity of external water currents support the concept of induced ventilation and suggest that in still water aerobic respiration was ventilation-limited. Although ciliary ventilation appears adequate to support resting aerobic metabolism, induced ventilation may provide increased aerobic scope for activity and repayment of oxygen debt. PMID:16075269

  1. Biogenic emissions and CO 2 gas exchange investigated on four Mediterranean shrubs

    NASA Astrophysics Data System (ADS)

    Hansen, U.; van Eijk, J.; Bertin, N.; Staudt, M.; Kotzias, D.; Seufert, G.; Fugit, J.-L.; Torres, L.; Cecinato, A.; Brancaleoni, E.; Ciccioli, P.; Bomboi, T.

    In order to investigate the impact of plant physiology on emissions of biogenic volatile organic compounds monoterpene emission rates from Rosmarinus officinalis (L.) and Pistacia lentiscus (L.) and isoprene emission rates from Erica arborea (L.) and Myrtus communis (L.) were determined. The study, an activity in the framework of BEMA (Biogenic Emissions in the Mediterranean Area), was carried out in May 1994 at Castelporziano near Rome in Italy, using a dynamic enclosure technique combined with recording CO 2 gas exchange, temperature and irradiance data. The monoterpenes dominating the emission pattern were 1,8-cineol, ?-pinene and ?-pinene for rosemary and ?-pinene, linalool and ?-pinene + sabinene for pistachio. Total monoterpene emission rates standardized to 30°C of 1.84 ± 0.24 and 0.35 ± 0.04 ?g Cg -1 dw h -1 were found for rosemary and pistachio, respectively (on a leaf dry weight basis). Myrtle emitted 22.2 ± 4.9 ?g C g -1 dw h -1 at standard conditions (30°C, PAR 1000 ?mol photons m -2 s -1 as isoprene and erica 5.61 ?g C g -1 dw h -1 The carbon loss due to terpenoid emissions per photosynthetically carbon uptake was about 0.01-0.1% for the monoterpene emitters. The isoprene emitting shrubs lost 0-0.9% of the assimilated carbon. The rapid induction of emissions in the sun after temporary shading indicates that isoprene emissions were closely linked to photosynthesis. A higher proportion of the assimilated carbon was lost as isoprene under conditions of high light and temperature compared to the morning and evening hours.

  2. A mathematical model of alveolar gas exchange in partial liquid ventilation.

    PubMed

    Suresh, Vinod; Anderson, Joseph C; Grotberg, James B; Hirschl, Ronald B

    2005-02-01

    In partial liquid ventilation (PLV), perfluorocarbon (PFC) acts as a diffusion barrier to gas transport in the alveolar space since the diffusivities of oxygen and carbon dioxide in this medium are four orders of magnitude lower than in air. Therefore convection in the PFC layer resulting from the oscillatory motions of the alveolar sac during ventilation can significantly affect gas transport. For example, a typical value of the Péclet number in air ventilation is Pe approximately 0.01, whereas in PLV it is Pe approximately 20. To study the importance of convection, a single terminal alveolar sac is modeled as an oscillating spherical shell with gas, PFC, tissue and capillary blood compartments. Differential equations describing mass conservation within each compartment are derived and solved to obtain time periodic partial pressures. Significant partial pressure gradients in the PFC layer and partial pressure differences between the capillary and gas compartments (P(C)-Pg) are found to exist. Because Pe> 1, temporal phase differences are found to exist between P(C)-Pg and the ventilatory cycle that cannot be adequately described by existing non-convective models of gas exchange in PLV The mass transfer rate is nearly constant throughout the breath when Pe>1, but when Pe<1 nearly 100% of the transport occurs during inspiration. A range of respiratory rates (RR), including those relevant to high frequency oscillation (HFO) +PLV, tidal volumes (V(T)) and perfusion rates are studied to determine the effect of heterogeneous distributions of ventilation and perfusion on gas exchange. The largest changes in P(C)O2 and P(C)CO2 occur at normal and low perfusion rates respectively as RR and V(T) are varied. At a given ventilation rate, a low RR-high V(T) combination results in higher P(C)O2, lower P(C)CO2 and lower (P(C)-Pg) than a high RR-low V(T) one. PMID:15868788

  3. Air/sea DMS gas transfer in the North Atlantic: evidence for limited interfacial gas exchange at high wind speed

    NASA Astrophysics Data System (ADS)

    Bell, T. G.; De Bruyn, W.; Miller, S. D.; Ward, B.; Christensen, K.; Saltzman, E. S.

    2013-05-01

    Shipboard measurements of eddy covariance DMS air/sea fluxes and seawater concentration were carried out in the North Atlantic bloom region in June/July 2011. Gas transfer coefficients (k660) show a linear dependence on mean horizontal wind speed at wind speeds up to 11 m s-1. At higher wind speeds the relationship between k660 and wind speed weakens. At high winds, measured DMS fluxes were lower than predicted based on the linear relationship between wind speed and interfacial stress extrapolated from low to intermediate wind speeds. In contrast, the transfer coefficient for sensible heat did not exhibit this effect. The apparent suppression of air/sea gas flux at higher wind speeds appears to be related to sea state, as determined from shipboard wave measurements. These observations are consistent with the idea that long waves suppress near surface water side turbulence, and decrease interfacial gas transfer. This effect may be more easily observed for DMS than for less soluble gases, such as CO2, because the air/sea exchange of DMS is controlled by interfacial rather than bubble-mediated gas transfer under high wind speed conditions.

  4. PLASMODIUM FALCIPARUM Na+/H+ EXCHANGER ACTIVITY AND QUININE RESISTANCE +

    PubMed Central

    Bennett, Tyler N.; Patel, Jigar; Ferdig, Michael T.; Roepe, Paul D.

    2009-01-01

    Mutations in the Plasmodium falciparum pfcrt gene cause resistance to the 4 – amino quinoline chloroquine (CQ) and other antimalarial drugs. Mutations and/or overexpression of a P. falciparum multidrug resistance gene homologue (pfmdr1) may further modify or tailor the degree of quinoline drug resistance. Recently (M.T. Ferdig et al., Molecular Microbiology 52: 985–997 [2004]) QTL analysis further implicated a region of P. falciparum chromosome 13 as a partner (with pfcrt) in conferring resistance to the first quinoline – based antimalarial drug, quinine (QN). Since QN resistance (QNR) and CQR are often (but not always) observed together in parasite strains, since elevated cytosolic pH is frequently (but not always) found in CQR parasites, and since the chr 13 segment linked to QNR prominently harbors a gene encoding what appears to be a P. falciparum Na+/H+ exchanger (PfNHE), we have systematically measured cytosolic pH and PfNHE activity for an extended series of parasite strains used in the QTL analysis. Altered PfNHE activity does not correlate with CQR as previously proposed, but significantly elevated PfNHE activity is found for strains with high levels of QNR, regardless their CQR status. We propose that either an elevated pHcyt or a higher vacuolar pH – to – cytosolic pH gradient contributes to one common route to malarial QNR that is also characterized by recently defined chr 13 – chr 9 pairwise interactions. Based on sequence analysis we propose a model whereby observed polymorphisms in PfNHE may lead to altered Na+/H+ set point regulation in QNR parasites. PMID:17353059

  5. Polarization exchange in colliding photon beams in an atomic gas medium

    NASA Astrophysics Data System (ADS)

    Sawyer, R. F.

    2014-05-01

    Photon-photon interactions mediated by an atomic gas can effect efficient polarization exchanges between two beams, leaving the medium exactly in its initial state. In, e.g., hydrogen, the distance required for macroscopic exchange is of the order of one-tenth the distance in which the ordinary nonlinear index of refraction would induce a phase change of ?. Several examples are worked out that show the variety of behaviors that can result, depending on the initial respective polarizations stated and the angle between the beams. Of particular interest are initial conditions in which there is no exchange at a mean-field level, conventionally believed to apply when the number of photons N is large. Then the full theory leads both to large exchange and to large entanglement between the beams. Our most solid results indicate that one would have to wait a time proportional to log[N] to see this effect, but there are some indications that this behavior can be circumvented.

  6. Estimating gas exchange of CO2 and CH4 between headwater systems and the atmosphere in Southwest Sweden

    NASA Astrophysics Data System (ADS)

    Somlai, Celia; Natchimuthu, Sivakiruthika; Bastviken, David; Lorke, Andreas

    2015-04-01

    Quantifying the role of inland water systems in terms of carbon sinks and sources and their connection to the terrestrial ecosystems and landscapes is fundamental for improving the balance approach of regional and global carbon budgets. Recent research showed that freshwater bodies emit significant amounts of CO2 and CH4 into the atmosphere. The extent of the emissions from small streams and headwaters, however, remains uncertain due to a limited availability of data. Studies have shown that headwater systems receive most of the terrestrial organic carbon, have the highest dissolved CO2 concentration and the highest gas exchange velocities and cover the largest fractional surface area within fluvial networks. The gas exchange between inland waters and the atmosphere is controlled by two factors: the difference between the dissolved gas concentration and its atmospheric equilibrium concentration, and the gas exchange velocity. The direct measurement of the dissolved gas concentration of greenhouse gases can be measured straightforwardly, for example, by gas chromatography from headspace extraction of water sample. In contrast, direct measurement of gas exchange velocity is more complex and time consuming, as simultaneous measurements with a volatile and nonvolatile inert tracer gas are needed. Here we analyze measurements of gas exchange velocities, concentrations and fluxes of dissolved CO2 and CH4, as well as loads of total organic and inorganic carbon in 10 reaches in headwater streams in Southwest Sweden. We compare the gas exchange velocities measured directly through tracer injections with those estimated through various empirical approaches, which are based on modelled and measured current velocity, stream depth and slope. Furthermore, we estimate the resulting uncertainties of the flux estimates. We also present different time series of dissolved CO2, CH4 and O2 concentration, water temperature, barometric pressure, electro conductivity, and pH values measured during the period of tracer injection.

  7. Optical Pumping Spin Exchange {sup 3}He Gas Cells for Magnetic Resonance Imaging

    SciTech Connect

    Kim, W. [Department of Physics, Kyungpook National University Daegu, 702-701 (Korea, Republic of); Korea Basic Science Institute (Korea, Republic of); Stepanyan, S. S.; Kim, A.; Jung, Y.; Woo, S.; Yurov, M.; Jang, J. [Department of Physics, Kyungpook National University Daegu, 702-701 (Korea, Republic of)

    2009-08-04

    We present a device for spin-exchange optical pumping system to produce large quantities of polarized noble gases for Magnetic Resonance Imaging (MRI). A method and design of apparatus for pumping the polarization of noble gases is described. The method and apparatus enable production, storage and usage of hyperpolarized noble gases for different purposes, including Magnetic Resonance Imaging of human and animal subjects. Magnetic imaging agents breathed into lungs can be observed by the radio waves of the MRI scanner and report back physical and functional information about lung's health and desease. The technique known as spin exchange optical pumping is used. Nuclear magnetic resonance is implemented to measure the polarization of hyperpolarized gas. The cells prepared and sealed under high vacuum after handling Alkali metals into the cell and filling with the {sup 3}He-N{sub 2} mixture. The cells could be refilled. The {sup 3}He reaches around 50% polarization in 5-15 hours.

  8. Uncertainties in gas exchange parameterization during the SAGE dual-tracer experiment

    NASA Astrophysics Data System (ADS)

    Smith, Murray J.; Ho, David T.; Law, Cliff S.; McGregor, John; Popinet, Stéphane; Schlosser, Peter

    2011-03-01

    A dual tracer experiment was carried out during the SAGE experiment using the inert tracers SF 6 and 3He, in order to determine the gas transfer velocity, k, at high wind speeds in the Southern Ocean. Wind speed/gas exchange parameterization is characterised by significant variability and we examine the major measurement uncertainties that contribute to that scatter. Correction for the airflow distortion over the research vessel, as determined by computational fluid dynamics (CFD) modelling, had the effect of increasing the calculated value of k by 30%. On the short time scales of such experiments, the spatial variability of the wind field resulted in differences between ship and satellite QuikSCAT winds, which produced significant differences in transfer velocity. With such variability between wind estimates, the comparison between gas exchange parameterizations from diverse experiments should clearly be made on the basis of the same wind product. Uncertainty in mixed layer depth of ˜10% arose from mixed layer deepening at high wind speed and limited resolution of vertical sampling. However the assumption of equal mixing of the two tracers is borne out by the experiment. Two dual tracer releases were carried out during SAGE, and showed no significant difference in transfer velocities using QuikSCAT winds, despite the differences in wind history. In the SAGE experiment, duration limitation on the development of waves was shown to be an important factor for Southern Ocean waves, despite the presence of long fetches.

  9. The combined effect of rain and wind on air water gas exchange: A feasibility study

    NASA Astrophysics Data System (ADS)

    Ho, David T.; Veron, Fabrice; Harrison, Emily; Bliven, Larry F.; Scott, Nicholas; McGillis, Wade R.

    2007-06-01

    A series of experiments were conducted at University of Delaware's Air-Sea Interaction Laboratory to examine the combined effects of rain and wind on air-water gas exchange. During this study, ASIL WRX I, a combination of 3 rain rates and 4 wind speeds were used, for a total of 12 different environmental conditions. The SF 6 evasion method was used to determine the bulk gas transfer velocities, and airside profiles of wind and CO 2 were used to estimate flux-profiles of momentum and carbon dioxide. In addition to measurements of fluxes with and without rain in a wind-wave boundary layer, measurements of wave properties were also obtained. Rain is shown to alter the wind profile in the flume, and dampen surface waves. Also, SF 6 evasion indicates that with the present experimental setup, for most of the experimental conditions, rain and wind combine linearly to influence air-water gas exchange. Flux-profile relationships for marine atmospheric boundary layers, which were performed to scale up to field measurements, were explored by a comparison between SF 6-derived bulk fluxes and airside CO 2 profile measurements.

  10. Gas exchange characteristics, metabolic rate and water loss of the Heelwalker, Karoophasma biedouwensis (Mantophasmatodea: Austrophasmatidae).

    PubMed

    Chown, S L; Marais, E; Picker, M D; Terblanche, J S

    2006-05-01

    This study presents the first physiological information for a member of the wingless Mantophasmatodea, or Heelwalkers. This species shows cyclic gas exchange with no evidence of a Flutter period (more typical of discontinuous gas exchange in insects) and no indication that the spiracles are fully occluded during quiescent metabolism. Standard metabolic rate at 20 degrees C was 21.32+/-2.73 microl CO(2)h(-1) (mean+/-S.E.), with a Q(10) (10-25 degrees C) of 1.7. Increases in V()CO(2) associated with variation in mass and with trial temperature were modulated by an increase in burst period volume and a decline in cycle frequency. Total water loss rate, determined by infrared gas analysis, was 0.876+/-0.08 mg H(2)Oh(-1) (range 0.602-1.577, n=11) whilst cuticular water loss rate, estimated by linear regression of total water loss rate and metabolic rate, was 0.618+/-0.09 mg H(2)Oh(-1) (range 0.341-1.363, n=11). Respiratory water loss rate was therefore no more than 29% of the total rate of water loss. Both total water loss rate and estimated cuticular water loss rate were significantly repeatable, with intraclass correlation coefficients of 0.745 and 0.553, respectively. PMID:16466738

  11. Molecular Dynamics Calculation of the Activation Volume for Water Exchange on Lithium.

    SciTech Connect

    Rustad, James R. [University of California, Davis; Stack, Andrew G [ORNL

    2006-08-01

    The activation volume of water exchange around Li+ (aq) was determined from reactive flux calculations using molecular dynamics simulations with a classical force field. The barrier height for exchange decreases with pressure, giving a negative activation volume, in agreement with the current paradigm for inferring exchange mechanism from activation volume. However, it is also demonstrated that pressure-dependent transmission effects make a significant contribution to the overall activation volume. These calculations indicate that small activation volumes should not be regarded as mechanistically indicative because of the potential contributions from transmission effects.

  12. Gas exchange dependency on diffusion coefficient: direct /sup 222/Rn and /sup 3/He comparisons in a small lake

    SciTech Connect

    Torgersen, T.; Mathieu, G.; Hesslein, R.H.; Broecker, W.S.

    1982-01-20

    A direct field comparison was conducted to determine the dependency of gas exchange coefficient (k/sub x/) on the diffusion coefficient (D/sub x/). The study also sought to confirm the enhanced vertical exchange properties of limnocorrals and similar enclosures. Gas exchange coefficients for /sup 222/Rn and /sup 3/He were determined in a small northern Ontario lake, using a /sup 226/Ra and /sup 3/H spike to gain the necessary precision. The results indicate that the gas exchange coefficient is functionally dependent on the diffusion coefficient raised to the 1.22/sub -35//sup + > 12/ power (k/sub x/ = f(D/sub x//sup 1.22)), clearly supporting the stagnant film model of gas exchange. Limnocorrals were found to have gas exchange rates up to 1.7 times higher than the whole lake in spite of the observation of more calm surface conditions in the corral than in the open lake. 33 references, 6 figures, 8 tables.

  13. Gas to particle conversion-gas exchange technique for direct analysis of metal carbonyl gas by inductively coupled plasma mass spectrometry.

    PubMed

    Nishiguchi, Kohei; Utani, Keisuke; Gunther, Detlef; Ohata, Masaki

    2014-10-21

    A novel gas to particle conversion-gas exchange technique for the direct analysis of metal carbonyl gas by inductively coupled plasma mass spectrometry (ICPMS) was proposed and demonstrated in the present study. The technique is based on a transfer of gas into particle, which can be directly analyzed by ICPMS. Particles from metal carbonyl gases such as Cr(CO)6, Mo(CO)6, and W(CO)6 are formed by reaction with ozone (O3) and ammonium (NH3) gases within a newly developed gas to particle conversion device (GPD). The reaction mechanism of the gas to particle conversion is based on either oxidation of metal carbonyl gas by O3 or agglomeration of metal oxide with ammonium nitrate (NH4NO3) which is generated by the reaction of O3 and NH3. To separate the reaction gases (remaining O3 and NH3) from the formed particles, a previously reported gas exchange device (GED) was used and the in argon stabilized analyte particles were directly introduced and measured by ICPMS. This new technique provided limits of detection (LOD) of 0.15 pL L(-1) (0.32 ng m(-3)), 0.02 pL L(-1) (0.07 ng m(-3)), and 0.01 pL L(-1) (0.07 ng m(-3)) for Cr(CO)6, Mo(CO)6, and W(CO)6, respectively, which were 4-5 orders of magnitude lower than those conventional applied for detecting these gases, e.g., gas chromatography with electron captured detector (GC-ECD) as well as Fourier transform-infrared spectroscopy (FT-IR). The achieved LODs were also similar or slightly better than those for ICPMS coupled to GC. Since the gas to particle conversion technique can achieve the direct measurement of metal carbonyl gases as well as the removal of reaction and ambient gases from metal carbonyl gases, the technique is considered to be well suited to monitor gas quality in semiconductor industry, engine exhaust gases, and or waste incineration products. PMID:25247610

  14. Operation of an ADR Using Helium Exchange Gas as a Substitute for a Failed Heat Switch

    NASA Technical Reports Server (NTRS)

    Shirron, P.; DiPirro, M.; Kimball, M.; Sneiderman, G.; Porter, F. S.; Kilbourne, C.; Kelley, R.; Fujimoto, R.; Yoshida, S.; Takei, Y.; Mitsuda, K.

    2014-01-01

    The Soft X-ray Spectrometer (SXS) is one of four instruments on the Japanese Astro-H mission, which is currently planned for launch in late 2015. The SXS will perform imaging spectroscopy in the soft X-ray band (0.3-12 keV) using a 6 6 pixel array of microcalorimeters cooled to 50 mK. The detectors are cooled by a 3-stage adiabatic demagnetization refrigerator (ADR) that rejects heat to either a superfluid helium tank (at 1.2 K) or to a 4.5 K Joule-Thomson (JT) cryocooler. Four gas-gap heat switches are used in the assembly to manage heat flow between the ADR stages and the heat sinks. The engineering model (EM) ADR was assembled and performance tested at NASA/GSFC in November 2011, and subsequently installed in the EM dewar at Sumitomo Heavy Industries, Japan. During the first cooldown in July 2012, a failure of the heat switch that linked the two colder stages of the ADR to the helium tank was observed. Operation of the ADR requires some mechanism for thermally linking the salt pills to the heat sink, and then thermally isolating them. With the failed heat switch unable to perform this function, an alternate plan was devised which used carefully controlled amounts of exchange gas in the dewar's guard vacuum to facilitate heat exchange. The process was successfully demonstrated in November 2012, allowing the ADR to cool the detectors to 50 mK for hold times in excess of 10 h. This paper describes the exchange-gas-assisted recycling process, and the strategies used to avoid helium contamination of the detectors at low temperature.

  15. Gas exchange and hydraulics in seedlings of Hevea brasiliensis during water stress and recovery.

    PubMed

    Chen, Jun-Wen; Zhang, Qiang; Li, Xiao-Shuang; Cao, Kun-Fang

    2010-07-01

    The response of plants to drought has received significant attention, but far less attention has been given to the dynamic response of plants during recovery from drought. Photosynthetic performance and hydraulic capacity were monitored in seedlings of Hevea brasiliensis under water stress and during recovery following rewatering. Leaf water relation, gas exchange rate and hydraulic conductivity decreased gradually after water stress fell below a threshold, whereas instantaneous water use efficiency and osmolytes increased significantly. After 5 days of rewatering, leaf water relation, maximum stomatal conductance (g(s-max)) and plant hydraulic conductivity had recovered to the control levels except for sapwood area-specific hydraulic conductivity, photosynthetic assimilation rate and osmolytes. During the phase of water stress, stomata were almost completely closed before water transport efficiency decreased substantially, and moreover, the leaf hydraulic pathway was more vulnerable to water stress-induced embolism than the stem hydraulic pathway. Meanwhile, g(s-max) was linearly correlated with hydraulic capacity when water stress exceeded a threshold. In addition, a positive relationship was shown to occur between the recovery of g(s-max) and of hydraulic capacity during the phase of rewatering. Our results suggest (i) that stomatal closure effectively reduces the risk of xylem dysfunction in water-stressed plants at the cost of gas exchange, (ii) that the leaf functions as a safety valve to protect the hydraulic pathway from water stress-induced dysfunction to a larger extent than does the stem and (iii) that the full drought recovery of gas exchange is restricted by not only hydraulic factors but also non-hydraulic factors. PMID:20516484

  16. Low loss liquid helium transfer system, using a high performance centrifugal pump and cold gas exchange

    NASA Astrophysics Data System (ADS)

    Berndt, H.; Doll, R.; Jahn, U.; Wiedemann, W.

    A liquid-He transfer system with overall transfer losses of less than 2 percent is proposed. In comparison with a conventional transfer system, the design achieves energy and running time savings for He-liquefaction of up to 30 percent. The system consists of a reliable completely magnetic suspended centrifugal pump, submerged in the liquid, and a double transfer line allowing cold gas exchange between the transport vessel and the storage tank. The high-reliability maintenance-free operation, high total performance, and pure one-phase liquid flow make the present design suitable for transferring liquid He II in space applications.

  17. [Gas exchange features of Ambrosia artemisiifolia leaves and fruits and their correlations with soil heavy metals].

    PubMed

    Zu, Yuangang; Wang, Wenjie; Chen, Huafeng; Yang, Fengjian; Zhang, Zhonghua

    2006-12-01

    Ambrosia artemisiifolia can survive well in the habitats of heavy human disturbance and partial soil pollution. Weather its photosynthetic features benefit their survival is worthwhile to concern. With a refuse dump in Changchun City (43 degrees 50'N, 125 degrees 23'E) as study site, this paper analyzed the contents of soil Cu, Pb, Zn, Mn, Cr, Co, Ni, Cd, As, Sb and Hg at ten plots, and measured in situ the gas exchange in A. artemisiifolia leaves and young fruits. The results showed that the study site was slightly contaminated by Ni, but the contents of other soil heavy metals were approached to or substantially lower than their threshold values. The net photosynthetic rate of leaves ranged from 1.88 to 9.41 micromol x m(-2) x s(-1), while that of young fruits could be up to 2. 81 micromol x m(-2) s(-1). Averagely, the respiration rate, stomatal conductance, photosynthetic rate, and water utilization efficiency of leaves were 1.81 micromol x m(-2) x s(-1), 75.7 mmol x m(-2) x s(-1), 6.05 micromol x m(-2) x s(-1), and 4.72 micromol CO2 x mmol(-1) H2O, being 5.26, 0.64, 1.31 and 1.69 times as much as those of young fruits, respectively, indicating that the respiratory and photosynthetic capacities and water use efficiency of A. artemisiifolia young fruits were equivalent to or higher than those of its leaves. Many test heavy metals, such as Cu, Pb, Zn, Cd, As, Sb and Hg, had no significant effects on the gas exchange features of leaves and fruits, but there were significant correlations of Ni and Cr with the stomatal conductance and water use efficiency of leaves and young fruits, Cr with the gross photosynthesis of leaves, and As with the stomatal conductance of young fruits, suggesting that a majority of test soil heavy metals had no direct effects on the gas exchange in A. artemisiifolia leaves and fruits, but soil Ni, Cr and As with the contents approached to or substantially lower than the threshold values could affect the gas exchange features of A. artemisiifolia. PMID:17330473

  18. Nesting behaviour influences species-specific gas exchange across avian eggshells

    PubMed Central

    Portugal, Steven J.; Maurer, Golo; Thomas, Gavin H.; Hauber, Mark E.; Grim, Tomáš; Cassey, Phillip

    2014-01-01

    Carefully controlled gas exchange across the eggshell is essential for the development of the avian embryo. Water vapour conductance (GH2O) across the shell, typically measured as mass loss during incubation, has been demonstrated to optimally ensure the healthy development of the embryo while avoiding desiccation. Accordingly, eggs exposed to sub-optimal gas exchange have reduced hatching success. We tested the association between eggshell GH2O and putative life-history correlates of adult birds, ecological nest parameters and physical characteristics of the egg itself to investigate how variation in GH2O has evolved to maintain optimal water loss across a diverse set of nest environments. We measured gas exchange through eggshell fragments in 151 British breeding bird species and fitted phylogenetically controlled, general linear models to test the relationship between GH2O and potential predictor parameters of each species. Of our 17 life-history traits, only two were retained in the final model: wet-incubating parent and nest type. Eggs of species where the parent habitually returned to the nest with wet plumage had significantly higher GH2O than those of parents that returned to the nest with dry plumage. Eggs of species nesting in ground burrows, cliffs and arboreal cups had significantly higher GH2O than those of species nesting on the ground in open nests or cups, in tree cavities and in shallow arboreal nests. Phylogenetic signal (measured as Pagel's ?) was intermediate in magnitude, suggesting that differences observed in the GH2O are dependent upon a combination of shared ancestry and species-specific life history and ecological traits. Although these data are correlational by nature, they are consistent with the hypothesis that parents constrained to return to the nest with wet plumage will increase the humidity of the nest environment, and the eggs of these species have evolved a higher GH2O to overcome this constraint and still achieve optimal water loss during incubation. We also suggest that eggs laid in cup nests and burrows may require a higher GH2O to overcome the increased humidity as a result from the confined nest microclimate lacking air movements through the nest. Taken together, these comparative data imply that species-specific levels of gas exchange across avian eggshells are variable and evolve in response to ecological and physical variation resulting from parental and nesting behaviours. PMID:25232199

  19. Guard cell biochemistry: response to environmental stimuli causing changes in gas exchange. Progress report

    SciTech Connect

    Not Available

    1983-01-01

    A progress report covering several interrelated studies on the biochemistry and metabolism of leaf guard cells is presented. Subjects covered are: (1) abscisic acid and the control of stomatal aperture size; (2) real-time, direct measurements of NAD(P)H in microdroplets; (3) electron transport through the PSII reaction center in guard cells; (4) organic anion/acid fluctuations as a general phenomena; (5) histological compartmentation of metabolic functions; (6) construction of a gas exchange system; and (7) guard cell protoplast isolation. (DT)

  20. Flue gas carbon dioxide sequestration during water softening with ion-exchange fibers

    SciTech Connect

    Greenleaf, J.E.; SenGupta, A.K. [Lafayette College, Easton, PA (United States). Dept. of Civil & Environmental Engineering

    2009-06-15

    This study examines the use of ion-exchange fibers (IX fibers) to permanently sequester carbon dioxide present in flue gas into an aqueous phase as calcium or magnesium alkalinity while concurrently softening hard water. The only process inputs besides carbon dioxide (or flue gas) are snowmelt (or rainwater); no other chemicals are required for the regeneration of the IX fibers. Importantly, the process is not energy intensive and carbon dioxide does not need to be compressed to excessive pressures (>150 psi) for efficient use. Sources of carbon dioxide do not require concentration and, therefore, the use of raw flue gas (similar to 17% CO{sub 2}) is feasible with the rate of sequestration governed only by the partial pressure of carbon dioxide. While valid for flue gas obtained from any combustion process (e.g., coal, oil, natural gas, etc.), emissions from oil or gas combustion may be more appropriate for use in the described process due to the absence of mercury and particulates. It should also be noted that the presence of sulfur dioxide in flue gas would not adversely affect the process and may even enhance regeneration efficiency. The only product of the proposed process is an environmentally benign regenerant stream containing calcium and/or magnesium alkalinity. The unique property of IX fibers that makes the proposed process both environmentally sustainable and economically feasible is amenability to efficient regeneration with carbon dioxide and harvested snowmelt. Low intraparticle diffusional resistance is the underlying reason why IX fibers are amenable to efficient regeneration using snowmelt sparged with carbon dioxide; 95% calcium recovery was attained at a CO{sub 2} partial pressure of 6.8 atm. The energy balance for a typical electric utility shows that up to 1% of carbon dioxide emitted during combustion would be sequestered in the softening process.

  1. Assessing Gibberellins Oxidase Activity by Anion Exchange/Hydrophobic Polymer Monolithic Capillary Liquid Chromatography-Mass Spectrometry

    PubMed Central

    Liu, Jiu-Feng; Wu, Yan; Feng, Yu-Qi; Yuan, Bi-Feng

    2013-01-01

    Bioactive gibberellins (GAs) play a key regulatory role in plant growth and development. In the biosynthesis of GAs, GA3-oxidase catalyzes the final step to produce bioactive GAs. Thus, the evaluation of GA3-oxidase activity is critical for elucidating the regulation mechanism of plant growth controlled by GAs. However, assessing catalytic activity of endogenous GA3-oxidase remains challenging. In the current study, we developed a capillary liquid chromatography – mass spectrometry (cLC-MS) method for the sensitive assay of in-vitro recombinant or endogenous GA3-oxidase by analyzing the catalytic substrates and products of GA3-oxidase (GA1, GA4, GA9, GA20). An anion exchange/hydrophobic poly([2-(methacryloyloxy)ethyl]trimethylammonium-co-divinylbenzene-co-ethylene glycol dimethacrylate)(META-co-DVB-co-EDMA) monolithic column was successfully prepared for the separation of all target GAs. The limits of detection (LODs, Signal/Noise?=?3) of GAs were in the range of 0.62–0.90 fmol. We determined the kinetic parameters (Km) of recombinant GA3-oxidase in Escherichia coli (E. coli) cell lysates, which is consistent with previous reports. Furthermore, by using isotope labeled substrates, we successfully evaluated the activity of endogenous GA3-oxidase that converts GA9 to GA4 in four types of plant samples, which is, to the best of our knowledge, the first report for the quantification of the activity of endogenous GA3-oxidase in plant. Taken together, the method developed here provides a good solution for the evaluation of endogenous GA3-oxidase activity in plant, which may promote the in-depth study of the growth regulation mechanism governed by GAs in plant physiology. PMID:23922762

  2. Assessing gibberellins oxidase activity by anion exchange/hydrophobic polymer monolithic capillary liquid chromatography-mass spectrometry.

    PubMed

    Chen, Ming-Luan; Su, Xin; Xiong, Wei; Liu, Jiu-Feng; Wu, Yan; Feng, Yu-Qi; Yuan, Bi-Feng

    2013-01-01

    Bioactive gibberellins (GAs) play a key regulatory role in plant growth and development. In the biosynthesis of GAs, GA3-oxidase catalyzes the final step to produce bioactive GAs. Thus, the evaluation of GA3-oxidase activity is critical for elucidating the regulation mechanism of plant growth controlled by GAs. However, assessing catalytic activity of endogenous GA3-oxidase remains challenging. In the current study, we developed a capillary liquid chromatography--mass spectrometry (cLC-MS) method for the sensitive assay of in-vitro recombinant or endogenous GA3-oxidase by analyzing the catalytic substrates and products of GA3-oxidase (GA1, GA4, GA9, GA20). An anion exchange/hydrophobic poly([2-(methacryloyloxy)ethyl]trimethylammonium-co-divinylbenzene-co-ethylene glycol dimethacrylate)(META-co-DVB-co-EDMA) monolithic column was successfully prepared for the separation of all target GAs. The limits of detection (LODs, Signal/Noise = 3) of GAs were in the range of 0.62-0.90 fmol. We determined the kinetic parameters (K m) of recombinant GA3-oxidase in Escherichia coli (E. coli) cell lysates, which is consistent with previous reports. Furthermore, by using isotope labeled substrates, we successfully evaluated the activity of endogenous GA3-oxidase that converts GA9 to GA4 in four types of plant samples, which is, to the best of our knowledge, the first report for the quantification of the activity of endogenous GA3-oxidase in plant. Taken together, the method developed here provides a good solution for the evaluation of endogenous GA3-oxidase activity in plant, which may promote the in-depth study of the growth regulation mechanism governed by GAs in plant physiology. PMID:23922762

  3. Whole Plant and Leaf Steady State Gas Exchange during Ethylene Exposure in Xanthium strumarium L. 1

    PubMed Central

    Woodrow, Lorna; Jiao, Jirong; Tsujita, M. James; Grodzinski, Bernard

    1989-01-01

    The effects of ethylene evolved from ethephon on leaf and whole plant photosynthesis in Xanthium strumarium L. were examined. Ethylene-induced epinasty reduced light interception by the leaves of ethephon treated plants by up to 60%. Gas exchange values of individual, attached leaves under identical assay conditions were not inhibited even after 36 hours of ethylene exposure, although treated leaves required a longer induction period to achieve steady state photosynthesis. The speed of translocation of recently fixed 11C-assimilate movement was not seriously impaired following ethephon treatment; however, a greater proportion of the assimilate was partitioned downward toward the roots. Within 24 hours of ethephon treatment, the whole plant net carbon exchange rate expressed on a per plant basis or a leaf area basis had dropped by 35%. The apparent inhibition of net carbon exchange rate was reversed by physically repositioning the leaves with respect to the light source. Ethylene exposure also inhibited expansion of young leaves which was partially reversed when the leaves were repositioned. The data indicated that ethylene indirectly affected net C gain and plant growth through modification of light interception and altered sink demand without directly inhibiting leaf photosynthesis. Images Figure 1 PMID:16666773

  4. Phospholipid base exchange activity in the leukocyte membranes of patients with inflammatory disorders.

    PubMed Central

    Niwa, Y.; Sakane, T.; Ozaki, Y.; Kanoh, T.; Taniguchi, S.

    1987-01-01

    Phospholipid base exchange and cholinephosphotransferase (CPT) and ethanolaminephosphotransferase (EPT) activities were assessed in the membranes of neutrophils or lymphocytes from patients with various inflammatory disorders. Ethanolamine exchange activity was significantly enhanced in both neutrophils and lymphocytes from patients with active Behçet's disease, active systemic lupus erythematosus (SLE), and severe bacterial infections and slightly enhanced in those from patients with active rheumatoid arthritis (RA), compared with healthy controls. No abnormal findings were found in CPT, EPT, or serine or choline base exchange activities in the leukocytes from any of the diseased groups tested or in the ethanolamine exchange activity of patients with severe viral infections and inactive SLE, RA, and Behçet's disease. The authors have recently demonstrated the enhancement of transmethylation and phospholipase A2 activity in human leukocyte membranes at the height of inflammatory disease states, as well as the activation of leukocyte ethanolamine exchange by bioactive stimulants. These data postulate that phosphatidylethanolamine synthesis by the base exchange reaction may be the precursor of transmethylation and its subsequent activation of phospholipase A2, leading to the induction of arachidonic acid cascade. PMID:3034067

  5. Ozone affects gas exchange, growth and reproductive development in Brassica campestris (Wisconsin fast plants).

    PubMed

    Black, V J; Stewart, C A; Roberts, J A; Black, C R

    2007-01-01

    Exposure to ozone (O(3)) may affect vegetative and reproductive development, although the consequences for yield depend on the effectiveness of the compensatory processes induced. This study examined the impact on reproductive development of exposing Brassica campestris (Wisconsin Fast Plants) to ozone during vegetative growth. Plants were exposed to 70 ppb ozone for 2 d during late vegetative growth or 10 d spanning most of the vegetative phase. Effects on gas exchange, vegetative growth, reproductive development and seed yield were determined. Impacts on gas exchange and foliar injury were related to pre-exposure stomatal conductance. Exposure for 2 d had no effect on growth or reproductive characteristics, whereas 10-d exposure reduced vegetative growth and reproductive site number on the terminal raceme. Mature seed number and weight per pod and per plant were unaffected because seed abortion was reduced. The observation that mature seed yield per plant was unaffected by exposure during the vegetative phase, despite adverse effects on physiological, vegetative and reproductive processes, shows that indeterminate species such as B. campestris possess sufficient compensatory flexibility to avoid reductions in seed production. PMID:17803646

  6. Effects of tree height on branch hydraulics, leaf structure and gas exchange in California redwoods.

    PubMed

    Ambrose, Anthony R; Sillett, Stephen C; Dawson, Todd E

    2009-07-01

    We examined changes in branch hydraulic, leaf structure and gas exchange properties in coast redwood (Sequoia sempervirens) and giant sequoia (Sequoiadendron giganteum) trees of different sizes. Leaf-specific hydraulic conductivity (k(L)) increased with height in S. sempervirens but not in S. giganteum, while xylem cavitation resistance increased with height in both species. Despite hydraulic adjustments, leaf mass per unit area (LMA) and leaf carbon isotope ratios (delta(13)C) increased, and maximum mass-based stomatal conductance (g(mass)) and photosynthesis (A(mass)) decreased with height in both species. As a result, both A(mass) and g(mass) were negatively correlated with branch hydraulic properties in S. sempervirens and uncorrelated in S. giganteum. In addition, A(mass) and g(mass) were negatively correlated with LMA in both species, which we attributed to the effects of decreasing leaf internal CO(2) conductance (g(i)). Species-level differences in wood density, LMA and area-based gas exchange capacity constrained other structural and physiological properties, with S. sempervirens exhibiting increased branch water transport efficiency and S. giganteum exhibiting increased leaf-level water-use efficiency with increasing height. Our results reveal different adaptive strategies for the two redwoods that help them compensate for constraints associated with growing taller, and reflect contrasting environmental conditions each species faces in its native habitat. PMID:19210642

  7. Fluorescence Quenching and Gas Exchange in a Water Stressed C3 Plant, Digitalis lanata

    PubMed Central

    Stuhlfauth, Thomas; Sültemeyer, Dieter F.; Weinz, Stefanie; Fock, Heinrich P.

    1988-01-01

    A leaf cuvette has been adapted for use with a pulse-modulation fluorometer and an open gas exchange system. Leaf water potential (?) was decreased by withholding watering from Digitalis lanata EHRH. plants. At different stages of water deficiency the photochemical (qQ) and nonphotochemical (qE) fluorescence quenching was determined during the transition between darkness and light-induced steady state photosynthesis of the attached leaves. In addition, the steady state CO2 and H2O gas exchange was recorded. Following a decrease of leaf water potential with increasing water deficiency, the transition of photochemical quenching was almost unaffected, whereas nonphotochemical quenching increased. This is indicative of an enhanced thylakoid membrane energization during the transition and is interpreted as a partial inhibition of either the ATP generating or the ATP consuming reaction sequences. Complete reversion of the stress induced changes was achieved within 6 hours after rewatering. In contrast to the variations during transition, the final steady state values of qQ and qE remained unchanged over the entire stress range from ?0.7 to ?2.5 megapascals. From these results we conclude that, once established, electron transport via photosystem II and the transmembrane proton gradient remain unaffected by water stress. These data are indicative of a protective mechanism against photoinhibition during stress, when net CO2 uptake is limited. PMID:16665875

  8. Dry deposition and soil-air gas exchange of polychlorinated biphenyls (PCBs) in an industrial area.

    PubMed

    Bozlaker, Ayse; Odabasi, Mustafa; Muezzinoglu, Aysen

    2008-12-01

    Ambient air and dry deposition, and soil samples were collected at the Aliaga industrial site in Izmir, Turkey. Atmospheric total (particle+gas) Sigma(41)-PCB concentrations were higher in summer (3370+/-1617 pg m(-3), average+SD) than in winter (1164+/-618 pg m(-3)), probably due to increased volatilization with temperature. Average particulate Sigma(41)-PCBs dry deposition fluxes were 349+/-183 and 469+/-328 ng m(-2) day(-1) in summer and winter, respectively. Overall average particulate deposition velocity was 5.5+/-3.5 cm s(-1). The spatial distribution of Sigma(41)-PCB soil concentrations (n=48) showed that the iron-steel plants, ship dismantling facilities, refinery and petrochemicals complex are the major sources in the area. Calculated air-soil exchange fluxes indicated that the contaminated soil is a secondary source to the atmosphere for lighter PCBs and as a sink for heavier ones. Comparable magnitude of gas exchange and dry particle deposition fluxes indicated that both mechanisms are equally important for PCB movement between air and soil in Aliaga. PMID:18640753

  9. Do we need exercise tests to detect gas exchange impairment in fibrotic idiopathic interstitial pneumonias?

    PubMed

    Wallaert, Benoit; Wemeau-Stervinou, Lidwine; Salleron, Julia; Tillie-Leblond, Isabelle; Perez, Thierry

    2012-01-01

    In patients with fibrotic idiopathic interstitial pneumonia (f-IIP), the diffusing capacity for carbon monoxide (DLCO) has been used to predict abnormal gas exchange in the lung. However, abnormal values for arterial blood gases during exercise are likely to be the most sensitive manifestations of lung disease. The aim of this study was to compare DLCO, resting PaO(2), P(A-a)O(2) at cardiopulmonary exercise testing peak, and oxygen desaturation during a 6-min walk test (6MWT). Results were obtained in 121 patients with idiopathic pulmonary fibrosis (IPF, n = 88) and fibrotic nonspecific interstitial pneumonias (NSIP, n = 33). All but 3 patients (97.5%) had low DLCO values (35?mmHg) and 100 (83%) demonstrated significant oxygen desaturation during 6MWT (>4%). Interestingly 27 patients had low DLCO and normal P(A-a)O(2), peak and/or no desaturation during the 6MWT. The 3 patients with normal DLCO also had normal PaO(2), normal P(A-a)O(2), peak, and normal oxygen saturation during 6MWT. Our results demonstrate that in fibrotic IIP, DLCO better defines impairment of pulmonary gas exchange than resting PaO(2), exercise P(A-a)O(2), peak, or 6MWT SpO(2). PMID:22900170

  10. Gas turbine engine active clearance control

    NASA Technical Reports Server (NTRS)

    Deveau, Paul J. (Inventor); Greenberg, Paul B. (Inventor); Paolillo, Roger E. (Inventor)

    1985-01-01

    Method for controlling the clearance between rotating and stationary components of a gas turbine engine are disclosed. Techniques for achieving close correspondence between the radial position of rotor blade tips and the circumscribing outer air seals are disclosed. In one embodiment turbine case temperature modifying air is provided in flow rate, pressure and temperature varied as a function of engine operating condition. The modifying air is scheduled from a modulating and mixing valve supplied with dual source compressor air. One source supplies relatively low pressure, low temperature air and the other source supplies relatively high pressure, high temperature air. After the air has been used for the active clearance control (cooling the high pressure turbine case) it is then used for cooling the structure that supports the outer air seal and other high pressure turbine component parts.

  11. Activation of AMP-activated protein kinase revealed by hydrogen/deuterium exchange mass spectrometry.

    PubMed

    Landgraf, Rachelle R; Goswami, Devrishi; Rajamohan, Francis; Harris, Melissa S; Calabrese, Matthew F; Hoth, Lise R; Magyar, Rachelle; Pascal, Bruce D; Chalmers, Michael J; Busby, Scott A; Kurumbail, Ravi G; Griffin, Patrick R

    2013-11-01

    AMP-activated protein kinase (AMPK) monitors cellular energy, regulates genes involved in ATP synthesis and consumption, and is allosterically activated by nucleotides and synthetic ligands. Analysis of the intact enzyme with hydrogen/deuterium exchange mass spectrometry reveals conformational perturbations of AMPK in response to binding of nucleotides, cyclodextrin, and a synthetic small molecule activator, A769662. Results from this analysis clearly show that binding of AMP leads to conformational changes primarily in the ? subunit of AMPK and subtle changes in the ? and ? subunits. In contrast, A769662 causes profound conformational changes in the glycogen binding module of the ? subunit and in the kinase domain of the ? subunit, suggesting that the molecular binding site of the latter resides between the ? and ? subunits. The distinct short- and long-range perturbations induced upon binding of AMP and A769662 suggest fundamentally different molecular mechanisms for activation of AMPK by these two ligands. PMID:24076403

  12. The effects of dobutamine and dopamine on intrapulmonary shunt and gas exchange in healthy humans

    PubMed Central

    Bryan, Tracey L.; van Diepen, Sean; Bhutani, Mohit; Shanks, Miriam; Welsh, Robert C.

    2012-01-01

    The development of intrapulmonary shunts with increased cardiac output during exercise in healthy humans has been reported in several recent studies, but mechanisms governing their recruitment remain unclear. Dobutamine and dopamine are inotropes commonly used to augment cardiac output; however, both can increase venous admixture/shunt fraction (Qs/Qt). It is possible that, as with exercise, intrapulmonary shunts are recruited with increased cardiac output during dobutamine and/or dopamine infusion that may contribute to the observed increase in Qs/Qt. The purpose of this study was to examine how dobutamine and dopamine affect intrapulmonary shunt and gas exchange. Nine resting healthy subjects received serial infusions of dobutamine and dopamine at incremental doses under normoxic and hyperoxic (inspired O2 fraction = 1.0) conditions. At each step, alveolar-to-arterial Po2 difference (A-aDo2) and Qs/Qt were calculated from arterial blood gas samples, intrapulmonary shunt was evaluated using contrast echocardiography, and cardiac output was calculated by Doppler echocardiography. Both dobutamine and dopamine increased cardiac output and Qs/Qt. Intrapulmonary shunt developed in most subjects with both drugs and paralleled the increase in Qs/Qt. A-aDo2 was unchanged due to a concurrent rise in mixed venous oxygen content. Hyperoxia consistently eliminated intrapulmonary shunt. These findings contribute to our present understanding of the mechanisms governing recruitment of these intrapulmonary shunts as well as their impact on gas exchange. In addition, given the deleterious effect on Qs/Qt and the risk of neurological complications with intrapulmonary shunts, these findings could have important implications for use of dobutamine and dopamine in the clinical setting. PMID:22700799

  13. A hierarchy of factors influence discontinuous gas exchange in the grasshopper Paracinema tricolor (Orthoptera: Acrididae).

    PubMed

    Groenewald, Berlizé; Chown, Steven L; Terblanche, John S

    2014-10-01

    The evolutionary origin and maintenance of discontinuous gas exchange (DGE) in tracheate arthropods are poorly understood and highly controversial. We investigated prioritization of abiotic factors in the gas exchange control cascade by examining oxygen, water and haemolymph pH regulation in the grasshopper Paracinema tricolor. Using a full-factorial design, grasshoppers were acclimated to hypoxic or hyperoxic (5% O2, 40% O2) gas conditions, or dehydrated or hydrated, whereafter their CO2 release was measured under a range of O2 and relative humidity (RH) conditions (5%, 21%, 40% O2 and 5%, 60%, 90% RH). DGE was significantly less common in grasshoppers acclimated to dehydrating conditions compared with the other acclimations (hypoxia, 98%; hyperoxia, 100%; hydrated, 100%; dehydrated, 67%). Acclimation to dehydrating conditions resulted in a significant decrease in haemolymph pH from 7.0±0.3 to 6.6±0.1 (mean ± s.d., P=0.018) and also significantly increased the open (O)-phase duration under 5% O2 treatment conditions (5% O2, 44.1±29.3 min; 40% O2, 15.8±8.0 min; 5% RH, 17.8±1.3 min; 60% RH, 24.0±9.7 min; 90% RH, 20.6±8.9 min). The observed acidosis could potentially explain the extension of the O-phase under low RH conditions, when it would perhaps seem more useful to reduce the O-phase to lower respiratory water loss. The results confirm that DGE occurrence and modulation are affected by multiple abiotic factors. A hierarchical framework for abiotic factors influencing DGE is proposed in which the following stressors are prioritized in decreasing order of importance: oxygen supply, CO2 excretion and pH modulation, oxidative damage protection and water savings. PMID:25063854

  14. On-line stable isotope gas exchange reveals an inducible but leaky carbon concentrating mechanism in Nannochloropsis salina.

    PubMed

    Hanson, David T; Collins, Aaron M; Jones, Howland D T; Roesgen, John; Lopez-Nieves, Samuel; Timlin, Jerilyn A

    2014-09-01

    Carbon concentrating mechanisms (CCMs) are common among microalgae, but their regulation and even existence in some of the most promising biofuel production strains is poorly understood. This is partly because screening for new strains does not commonly include assessment of CCM function or regulation despite its fundamental role in primary carbon metabolism. In addition, the inducible nature of many microalgal CCMs means that environmental conditions should be considered when assessing CCM function and its potential impact on biofuels. In this study, we address the effect of environmental conditions by combining novel, high frequency, on-line (13)CO2 gas exchange screen with microscope-based lipid characterization to assess CCM function in Nannochloropsis salina and its interaction with lipid production. Regulation of CCM function was explored by changing the concentration of CO2 provided to continuous cultures in airlift bioreactors where cell density was kept constant across conditions by controlling the rate of media supply. Our isotopic gas exchange results were consistent with N. salina having an inducible "pump-leak" style CCM similar to that of Nannochloropsis gaditana. Though cells grew faster at high CO2 and had higher rates of net CO2 uptake, we did not observe significant differences in lipid content between conditions. Since the rate of CO2 supply was much higher for the high CO2 conditions, we calculated that growing cells bubbled with low CO2 is about 40 % more efficient for carbon capture than bubbling with high CO2. We attribute this higher efficiency to the activity of a CCM under low CO2 conditions. PMID:24844569

  15. Seasonal trends in reduced leaf gas exchange and ozone-induced foliar injury in three ozone sensitive woody plant species.

    PubMed

    Novak, K; Schaub, M; Fuhrer, J; Skelly, J M; Hug, C; Landolt, W; Bleuler, P; Kräuchi, N

    2005-07-01

    Seasonal trends in leaf gas exchange and ozone-induced visible foliar injury were investigated for three ozone sensitive woody plant species. Seedlings of Populus nigra L., Viburnum lantana L., and Fraxinus excelsior L. were grown in charcoal-filtered chambers, non-filtered chambers and open plots. Injury assessments and leaf gas exchange measurements were conducted from June to October during 2002. All species developed typical ozone-induced foliar injury. For plants exposed to non-filtered air as compared to the charcoal-filtered air, mean net photosynthesis was reduced by 25%, 21%, and 18% and mean stomatal conductance was reduced by 25%, 16%, and 8% for P. nigra, V. lantana, and F. excelsior, respectively. The timing and severity of the reductions in leaf gas exchange were species specific and corresponded to the onset of visible foliar injury. PMID:15809106

  16. Characterization techniques for gas diffusion layers for proton exchange membrane fuel cells - A review

    NASA Astrophysics Data System (ADS)

    Arvay, A.; Yli-Rantala, E.; Liu, C.-H.; Peng, X.-H.; Koski, P.; Cindrella, L.; Kauranen, P.; Wilde, P. M.; Kannan, A. M.

    2012-09-01

    The gas diffusion layer (GDL) in a proton exchange membrane fuel cell (PEMFC) is one of the functional components that provide a support structure for gas and water transport. The GDL plays a crucial role when the oxidant is air, especially when the fuel cell operates in the higher current density region. There has been an exponential growth in research and development because the PEMFC has the potential to become the future energy source for automotive applications. In order to serve in this capacity, the GDL requires due innovative analysis and characterization toward performance and durability. It is possible to achieve the optimum fuel cell performance only by understanding the characteristics of GDLs such as structure, pore size, porosity, gas permeability, wettability, thermal and electrical conductivities, surface morphology and water management. This review attempts to bring together the characterization techniques for the essential properties of the GDLs as handy tools for R&D institutions. Topics are categorized based on the ex-situ and in-situ characterization techniques of GDLs along with related modeling and simulation. Recently reported techniques used for accelerated durability evaluation of the GDLs are also consolidated within the ex-situ and in-situ methods.

  17. Leaf Gas Exchange in Relict Spruce-Fir Cloud Forests of the Southern Appalachian Mountains, USA.

    NASA Astrophysics Data System (ADS)

    Reinhardt, K.; Smith, W. K.

    2007-12-01

    The relict spruce-fir (Picea rubens Sarg. - Abies fraseri (Pursh) Poir.) forests of the southern Appalachian mountains are found only on high altitude mountain tops that receive copious precipitation (>2000 mm annually) and experience frequent cloud immersion (~65% of the total growth season days). Cloud deposition accounts for up to 50% of the annual water budget for these high-elevation forests. Two sites in North Carolina were established to investigate the influences of cloudiness and cloud immersion on leaf gas exchange and water relations of Fraser fir: Mt. Mitchell (2028 m elevation) and Roan Mtn., NC (1890 m elevation). It was hypothesized that the cool, moist, and cloudy conditions at these sites would exert a strong influence on leaf carbon and water fluxes. Water status was high throughout all hours on measurement days, with xylem water potential always >-1.75 MPa and soil water content always >0.1 m3 m-3. Leaves were wet frequently (>60% of all hours) due to cloud immersion and nightly dewfall, which did not appear to limit photosynthesis, but may influence stomatal response and transpiration. Maximum photosynthesis (Amax) was about 15 umol CO2 m-2 s-1, and saturated at sunlight levels between 400-500 umol m-2 s-1. Maximum leaf conductance (gmax) and transpiration (Emax) were 0.31 mol m-2 s-1 and 3.9 mmol m-2 s-1, respectively, and were strongly associated with LAVD. At both sites, conductance and transpiration decreased exponentially as LAVD increased, with 50-75% reduction between 0-0.5 kPa. Mean instantaneous water use efficiency on clear days was 3.5 umol CO2 m-2 s-1/mmol H2O m-2 s-1 across all transpiration fluxes, but increased on cloudy and cloud-immersed days (range of 2.3 - 6.0 umol CO2 m-2 s-1/mmol H2O m-2 s-1) as transpiration increased. Leaf gas exchange appeared tightly coupled to the response of conductance to LAVD which maintained high water status, even at the relatively low LAVD of these cloud forests. Thus, the cloudy, humid environment of these refugial forests appears to exert a strong influence on leaf gas exchange and water relations of these montane species. Because global climate change is predicted to increase regional cloud ceiling levels, more research on cloud impacts on carbon gain and water relations is needed to predict the future survival of these relic forests.

  18. Alterations in Gas Exchange and Oxidative Metabolism in Rice Leaves Infected by Pyricularia oryzae are Attenuated by Silicon.

    PubMed

    Domiciano, Gisele Pereira; Cacique, Isaías Severino; Chagas Freitas, Cecília; Filippi, Marta Cristina Corsi; DaMatta, Fábio Murilo; do Vale, Francisco Xavier Ribeiro; Rodrigues, Fabrício Ávila

    2015-06-01

    Rice blast, caused by Pyricularia oryzae, is the most important disease in rice worldwide. This study investigated the effects of silicon (Si) on the photosynthetic gas exchange parameters (net CO2 assimilation rate [A], stomatal conductance to water vapor [gs], internal-to-ambient CO2 concentration ratio [Ci/Ca], and transpiration rate [E]); chlorophyll fluorescence a (Chla) parameters (maximum photochemical efficiency of photosystem II [Fv/Fm], photochemical [qP] and nonphotochemical [NPQ] quenching coefficients, and electron transport rate [ETR]); concentrations of pigments, malondialdehyde (MDA), and hydrogen peroxide (H2O2); and activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR), and lypoxigenase (LOX) in rice leaves. Rice plants were grown in a nutrient solution containing 0 or 2 mM Si (-Si or +Si, respectively) with and without P. oryzae inoculation. Blast severity decreased with higher foliar Si concentration. The values of A, gs and E were generally higher for the +Si plants in comparison with the -Si plants upon P. oryzae infection. The Fv/Fm, qp, NPQ, and ETR were greater for the +Si plants relative to the -Si plants at 108 and 132 h after inoculation (hai). The values for qp and ETR were significantly higher for the -Si plants in comparison with the +Si plants at 36 hai, and the NPQ was significantly higher for the -Si plants in comparison with the +Si plants at 0 and 36 hai. The concentrations of Chla, Chlb, Chla+b, and carotenoids were significantly greater in the +Si plants relative to the -Si plants. For the -Si plants, the MDA and H2O2 concentrations were significantly higher than those in the +Si plants. The LOX activity was significantly higher in the +Si plants than in the -Si plants. The SOD and GR activities were significantly higher for the -Si plants than in the +Si plants. The CAT and APX activities were significantly higher in the +Si plants than in the -Si plants. The supply of Si contributed to a decrease in blast severity, improved the gas exchange performance, and caused less dysfunction at the photochemical level. PMID:25607719

  19. Structured Exchanges and Childhood Learning: Hyperaggressive Children. Program Activity 12.

    ERIC Educational Resources Information Center

    Hamblin, Robert L.; Buckholdt, David

    Recognizing that punishment for aggression often is noneffective or inadvertently reinforces the aggressive act, the authors discuss an alternative approach and provide an explanation of the exchange theory of aggression. Three classroom experiments, operated with children chosen as the most severe behavior problems in a local school system, are…

  20. Comparison of activated carbon and ion-exchange resins in recovering copper from cyanide leach solutions

    Microsoft Academic Search

    X. Dai; P. L. Breuer; M. I. Jeffrey

    2010-01-01

    The use of activated carbon and ion-exchange resins for recovering copper cyanide from gold leach solutions is compared in detail. When using activated carbon, the overall cyanide-to-copper ratio should be reduced to ?2 to achieve the most effective adsorption. This can be accomplished by dissolving metallic copper into the leach solution. However when using ion-exchange resins to recover the copper,

  1. Activation of catalysts for synthesizing methanol from synthesis gas

    DOEpatents

    Blum, David B. (108 Tall Oaks Dr., Wayne, NJ 07470); Gelbein, Abraham P. (45 Headley Rd., Morristown, NJ 07960)

    1985-01-01

    A method for activating a methanol synthesis catalyst is disclosed. In this method, the catalyst is slurried in an inert liquid and is activated by a reducing gas stream. The activation step occurs in-situ. That is, it is conducted in the same reactor as is the subsequent step of synthesizing methanol from a methanol gas stream catalyzed by the activated catalyst still dispersed in a slurry.

  2. Gas exchange: large surface and thin barrier determine pulmonary diffusing capacity.

    PubMed

    Weibel, E R

    1999-06-01

    The lung is characterized by its diffusing capacity for oxygen, DLO2, which is estimated from morphometric information as a theoretical capacity. It is determined by the large gas exchange surface, the thin tissue barrier, and the amount of capillary blood. The question is asked whether DLO2 could be a limiting factor for O2 uptake in heavy exercise, particularly in athletes with their 50% higher O2 demand. This is answered by studying the relation between DLO2 and maximal O2 consumption in different sedentary and athletic mammals, comparing horse and cow, dog and goat, and, finally, the most athletic mammal, the pronghorn antelope of the Rocky Mountains. It is concluded that in athletic species the lung is just sufficient to satisfy the O2 needs and can therefore be a limiting factor for aerobic work. PMID:10394805

  3. A simple method for air/sea gas exchange measurement in mesocosms and its application in carbon budgeting

    NASA Astrophysics Data System (ADS)

    Czerny, J.; Schulz, K. G.; Ludwig, A.; Riebesell, U.

    2012-09-01

    Mesocosms as large experimental vessels principally provide the opportunity of performing elemental budget calculations e.g. to derive net biological turnover rates. However, the system is in most cases not closed at the water surface and gases can exchange with the atmosphere. Previous attempts to budget carbon pools in mesocosms relied on educated guesses concerning the exchange of CO2 with the atmosphere. Nevertheless, net primary production rates derived from these budget calculations were, despite large uncertainties in air/sea gas exchange, often more reasonable than cumulative extrapolations of bioassays. While bioassays have limitations representing the full spectrum of trophic levels and abiotic conditions inside the mesocosms, calculating dissolved inorganic carbon uptake inside the mesocosms has the potential to deliver net community production rates representative of the enclosed system. Here, we present a simple method for precise determination of air/sea gas exchange velocities in mesocosms using N2O as a deliberate tracer. Beside the application for carbon budgeting, exchange velocities can be used to calculate exchange rates of any gas of known concentration, e.g. to calculate aquatic production rates of climate relevant trace gases. Using an arctic (Kiel Off Shore Mesocosms for future Ocean Simulation) mesocosm experiment as an exemplary dataset, it is shown that application of the presented method largely improves accuracy of carbon budget estimates. Methodology of manipulation, measurement, data processing and conversion to CO2 fluxes are explained. A theoretical discussion of prerequisites for precise gas exchange measurements provides a guideline for the applicability of the method under various experimental conditions.

  4. Gas exchange and intrapulmonary distribution of ventilation during continuous-flow ventilation

    SciTech Connect

    Vettermann, J.; Brusasco, V.; Rehder, K.

    1988-05-01

    In 12 anesthetized paralyzed dogs, pulmonary gas exchange and intrapulmonary inspired gas distribution were compared between continuous-flow ventilation (CFV) and conventional mechanical ventilation (CMV). Nine dogs were studied while they were lying supine, and three dogs were studied while they were lying prone. A single-lumen catheter for tracheal insufflation and a double-lumen catheter for bilateral endobronchial insufflation (inspired O2 fraction = 0.4; inspired minute ventilation = 1.7 +/- 0.3 (SD) 1.kg-1.min-1) were evaluated. Intrapulmonary gas distribution was assessed from regional 133Xe clearances. In dogs lying supine, CO2 elimination was more efficient with endobronchial insufflation than with tracheal insufflation, but the alveolar-arterial O2 partial pressure difference was larger during CFV than during CMV, regardless of the type of insufflation. By contrast, endobronchial insufflation maintained both arterial PCO2 and alveolar-arterial O2 partial pressure difference at significantly lower levels in dogs lying prone than in dogs lying supine. In dogs lying supine, the dependent lung was preferentially ventilated during CMV but not during CFV. In dogs lying prone, gas distribution was uniform with both modes of ventilation. The alveolar-arterial O2 partial pressure difference during CFV in dogs lying supine was negatively correlated with the reduced ventilation of the dependent lung, which suggests that increased ventilation-perfusion mismatching was responsible for the increase in alveolar-arterial O2 partial pressure difference. The more efficient oxygenation during CFV in dogs lying prone suggests a more efficient matching of ventilation to perfusion, presumably because the distribution of blood flow is also nearly uniform.

  5. Dense gas in normal and active galaxies

    NASA Astrophysics Data System (ADS)

    Kohno, Kotaro; Nakanishi, Koichiro; Tosaki, Tomoka; Muraoka, Kazuyuki; Miura, Rie; Ezawa, Hajime; Kawabe, Ryohei

    2008-01-01

    Dense molecular medium plays essential roles in galaxies. As demonstrated by the tight and linear correlation between HCN(1 0) and FIR luminosities among star-forming galaxies, from very nearby to high-z ones, the observation of a dense molecular component is indispensable to understand the star formation laws in galaxies. In order to obtain a general picture of the global distributions of dense molecular medium in normal star-forming galaxies, we have conducted an extragalactic CO(3 2) imaging survey of nearby spiral galaxies using the Atacama Submillimeter Telescope Experiment (ASTE). From the survey (ADIoS; ASTE Dense gas Imaging of Star-forming galaxies), CO(3 2) images of M 83 and NGC 986 are presented. Emphasis is placed on the correlation between the CO(3 2)/CO(1 0) ratio and the star formation efficiency in galaxies. In the central regions of some active galaxies, on the other hand, we often find enhanced or overluminous HCN(1 0) emission. The HCN(1 0)/CO(1 0) and HCN(1 0)/HCO+(1 0) intensities are often enhanced up to ˜0.2 0.3 and ˜2 3, respectively. Such elevated ratios have never been observed in the nuclear starburst regions. One possible explanation for these high HCN(1 0)/CO(1 0) and HCN(1 0)/HCO+(1 0) ratios is X-ray induced chemistry in X-ray dominated regions (XDRs), i.e., the overabundance of the HCN molecule in the X-ray irradiated dense molecular tori. If this view is true, the known tight correlation between HCN(1 0) and the star-formation rate breaks in the vicinity of active nuclei. Although the interpretation of these ratios is still an open question, these ratios have a great potential for a new diagnostic tool for the energy sources of dusty galaxies in the ALMA era because these molecular lines are free from dust extinction.

  6. Whole-Plant Gas Exchange and Reductive Biosynthesis in White Lupin1

    PubMed Central

    Cen, Yan-Ping; Turpin, David H.; Layzell, David B.

    2001-01-01

    Simultaneous measurements of CO2 (CER) and O2 (OER) exchange in roots and shoots of vegetative white lupin (Lupinus albus) were used to calculate the flow of reducing power to the synthesis of biomass that was more reduced per unit of carbon than carbohydrate. On a whole-plant basis, the diverted reductant utilization rate (DRUR which is: 4 × [CER + OER]) of shoot tissue was consistently higher than that of roots, and values obtained in the light were greater than those in the dark. An analysis of the biomass being synthesized over a 24-h period provided an estimate of whole-plant DRUR (3.5 mmol e? plant?1 d?1), which was similar to that measured by gas exchange (3.2 mmol e? plant?1 d?1). Given that nitrate reduction to ammonia makes up about 74% of whole-plant DRUR, root nitrate reduction in white lupin was estimated to account for less than 43% of whole-plant nitrate reduction. The approach developed here should offer a powerful tool for the noninvasive study of metabolic regulation in intact plants or plant organs. PMID:11500554

  7. Carbon gas exchange at a southern Rocky Mountain wetland, 1996-1998

    USGS Publications Warehouse

    Wickland, K.P.; Striegl, R.G.; Mast, M.A.; Clow, D.W.

    2001-01-01

    Carbon dioxide (CO2) and methane (CH4) exchange between the atmosphere and a subalpine wetland located in Rocky Mountain National Park, Colorado, at 3200 m elevation were measured during 1996-1998. Respiration, net CO2 flux, and CH4 flux were measured using the closed chamber method during snow-free periods and using gas diffusion calculations during snow-covered periods. The ranges of measured flux were 1.2-526 mmol CO2 m-2 d-1 (respiration), -1056-100 mmol CO2 m-2 d-1 (net CO2 exchange), and 0.1-36.8 mmol CH4 m-2 d-1 (a positive value represents efflux to the atmosphere). Respiration and CH4 emission were significantly correlated with 5 cm soil temperature. Annual respiration and CH4 emission were modeled by applying the flux-temperature relationships to a continuous soil temperature record during 1996-1998. Gross photosynthesis was modeled using a hyperbolic equation relating gross photosynthesis, photon flux density, and soil temperature. Modeled annual flux estimates indicate that the wetland was a net source of carbon gas to the atmosphere each of the three years: 8.9 mol C m-2 yr-1 in 1996, 9.5 mol C m-2 yr-1 in 1997, and 9.6 mol C m-2 yr-1 in 1998. This contrasts with the long-term carbon accumulation of ???0.7 mol m-2 yr-1 determined from 14C analyses of a peat core collected from the wetland.

  8. How Accurately Can One Measure Air-Sea Gas Exchange Velocities Using Eddy Covariance?

    NASA Astrophysics Data System (ADS)

    Huebert, B. J.; Blomquist, B. W.

    2005-12-01

    The eddy covariance (EC) method for measuring air-sea gas fluxes offers a tremendous potential for improving our understanding of the controls on all air-sea gas fluxes. Observation intervals of less than an hour make it possible to see - on the same day, with the same winds, weather, and sun - how much the flux changes when a research ship encounters a surface slick, or when the wave slope or bubble spectrum changes significantly. This sub-hour time response enables very nicely constrained studies of the factors controlling fluxes. We have demonstrated the ability to make DMS flux measurements in times less than an hour, enabling DMS to be used as a model for the fluxes of other carbon-containing gases. Under some conditions (e.g., INTEX), DMS itself dominates the air-sea exchange of carbon. The flux-related quantity most easily generalized to other gases (CO2, CH4, CO, etc.) and conditions is the exchange velocity, k, which is the measured flux divided by the measured sea-air concentration difference. The uncertainty in the kDMS we derive is thus controlled in part by the frequency and uncertainty of the sea water DMS concentrations measured in parallel with our DMS fluxes. EC measurements from ships involve many potential sources of error: the response speed of chemical sensors, flow distortion by the ship, ship-motion contamination of wind measurements, covariance uncertainties, calibration errors, and the sea water DMS uncertainty. Based on estimates of each of these errors for DMS, we argue that a k uncertainty of a few tens of percent is achievable for hourly values.

  9. Anaerobic metabolism, gas exchange, and acid-base balance during hypoxic exposure in the channel catfish,Ictalurus punctatus

    Microsoft Academic Search

    Warren W. Burggren; James N. Cameron

    1980-01-01

    Gill ventilation, blood gas and acid-base values, Mo,, Mc.02 and the gas exchange ratio have been measured before, during, and after exposure to hypoxia in the channel catfish, Zctalurus punctatus. Z.punctatus maintains M,,, at control levels to a PI,, as low as 60 mm Hg, through a profound branchial hyperventilation. Concomitantly, however, a lactic acidosis usually develops, indicating a significant

  10. Probing the regional distribution of pulmonary gas exchange through single-breath gas- and dissolved-phase 129Xe MR imaging

    PubMed Central

    Kaushik, S. Sivaram; Freeman, Matthew S.; Cleveland, Zackary I.; Davies, John; Stiles, Jane; Virgincar, Rohan S.; Robertson, Scott H.; He, Mu; Kelly, Kevin T.; Foster, W. Michael; McAdams, H. Page

    2013-01-01

    Although some central aspects of pulmonary function (ventilation and perfusion) are known to be heterogeneous, the distribution of diffusive gas exchange remains poorly characterized. A solution is offered by hyperpolarized 129Xe magnetic resonance (MR) imaging, because this gas can be separately detected in the lung's air spaces and dissolved in its tissues. Early dissolved-phase 129Xe images exhibited intensity gradients that favored the dependent lung. To quantitatively corroborate this finding, we developed an interleaved, three-dimensional radial sequence to image the gaseous and dissolved 129Xe distributions in the same breath. These images were normalized and divided to calculate “129Xe gas-transfer” maps. We hypothesized that, for healthy volunteers, 129Xe gas-transfer maps would retain the previously observed posture-dependent gradients. This was tested in nine subjects: when the subjects were supine, 129Xe gas transfer exhibited a posterior-anterior gradient of ?2.00 ± 0.74%/cm; when the subjects were prone, the gradient reversed to 1.94 ± 1.14%/cm (P < 0.001). The 129Xe gas-transfer maps also exhibited significant heterogeneity, as measured by the coefficient of variation, that correlated with subject total lung capacity (r = 0.77, P = 0.015). Gas-transfer intensity varied nonmonotonically with slice position and increased in slices proximal to the main pulmonary arteries. Despite substantial heterogeneity, the mean gas transfer for all subjects was 1.00 ± 0.01 while supine and 1.01 ± 0.01 while prone (P = 0.25), indicating good “matching” between gas- and dissolved-phase distributions. This study demonstrates that single-breath gas- and dissolved-phase 129Xe MR imaging yields 129Xe gas-transfer maps that are sensitive to altered gas exchange caused by differences in lung inflation and posture. PMID:23845983

  11. Technical Note: A simple method for air-sea gas exchange measurements in mesocosms and its application in carbon budgeting

    NASA Astrophysics Data System (ADS)

    Czerny, J.; Schulz, K. G.; Ludwig, A.; Riebesell, U.

    2013-03-01

    Mesocosms as large experimental units provide the opportunity to perform elemental mass balance calculations, e.g. to derive net biological turnover rates. However, the system is in most cases not closed at the water surface and gases exchange with the atmosphere. Previous attempts to budget carbon pools in mesocosms relied on educated guesses concerning the exchange of CO2 with the atmosphere. Here, we present a simple method for precise determination of air-sea gas exchange in mesocosms using N2O as a deliberate tracer. Beside the application for carbon budgeting, transfer velocities can be used to calculate exchange rates of any gas of known concentration, e.g. to calculate aquatic production rates of climate relevant trace gases. Using an arctic KOSMOS (Kiel Off Shore Mesocosms for future Ocean Simulation) experiment as an exemplary dataset, it is shown that the presented method improves accuracy of carbon budget estimates substantially. Methodology of manipulation, measurement, data processing and conversion to CO2 fluxes are explained. A theoretical discussion of prerequisites for precise gas exchange measurements provides a guideline for the applicability of the method under various experimental conditions.

  12. Air-water gas exchange of organochlorine compounds in Lake Baikal, Russia

    SciTech Connect

    McConnell, L.L. [USDA, Beltsville, MD (United States)] [USDA, Beltsville, MD (United States); Kucklick, J.R. [National Marine Fisheries Service, Charleston, SC (United States)] [National Marine Fisheries Service, Charleston, SC (United States); Bidleman, T.F. [Univ. of South Carolina, Columbia, SC (United States)] [Univ. of South Carolina, Columbia, SC (United States); Ivanov, G.P. [Limnological Inst., Irkutsk (Russian Federation)] [Limnological Inst., Irkutsk (Russian Federation); Chernyak, S.M. [Inst. of Fisheries, Moscow (Russian Federation)] [Inst. of Fisheries, Moscow (Russian Federation)

    1996-10-01

    Air and surface water samples were collected at Lake Baikal, Russia, during June 1991 to determine concentrations of organochlorine pesticides and polychlorinated biphenyl (PCB) congeners. These data were combined with Henry`s law constants to estimate the gas flux rate across the air-water interface of each compound class. Air samples were collected at Lake Baikal and from nearby Irkutsk. Water samples were collected from three mid-lake stations and at the mouth of two major tributaries. Average air concentrations of chlorinated bornanes (14 pg m{sup -3}), chlordanes (4.9 pg m{sup -3}), and hexachlorobenzene (HCB) (194 pg m{sup -3}) were similar to global backgound of Arctic levels. However, air concentrations of hexachlorocyclohexanes (HCHs), DDTs, and PCBs were closer to those observed in the Great Lakes region. Significantly higher levels of these three compound classes in air over Irkutsk suggests that regional atmospheric transport and deposition may be an important source of these persistent compounds to Lake Baikal. Air-water gas exchange calculations resulted in net depositional flux values for {alpha}-HCH, {gamma}-HCH, DDTs, and chlorinated bornanes at 112, 23, 3.6, and 2.4 ng m{sup -2} d{sup -1}, respectively. The total net flux of 22 PCB congeners, chlordanes, and HCB was from water to air (volatilization) at 47, 1.8, and 32 ng m{sup -2} d{sup -1}, respectively. 50 refs., 7 figs., 5 tabs.

  13. DOGEE-SOLAS: The Role of Surfactants in Air-Sea Gas Exchange

    NASA Astrophysics Data System (ADS)

    Salter, M. E.; Upstill-Goddard, R. C.; Nightingale, P.

    2008-12-01

    One of the major aims of DOGEE-SOLAS was to improve our understanding of the role of surfactants in air- sea gas exchange. With this in mind we carried out a number of artificial surfactant releases on a research cruise in the North Atlantic (D320), during June-July of 2007. We used oleyl alcohol, a surrogate for natural surfactants which is relatively cheap and easy to obtain (it is used in the manufacture of cosmetics). The main release overlaid a dual tracer "patch" of SF6 and 3He; our aim was to directly compare values of the gas transfer velocity, kw, estimated within the surfactant covered patch with those estimated quasi- simultaneously in a second, surfactant-free patch about 20km away. A second release in conjunction with colleagues from the University of Hawaii had the aim of measuring DMS fluxes by eddy correlation both inside and outside a surfactant slick, and a third was undertaken in the path of one of two 14m ASIS (Air-Sea Interaction Spar) buoys operated by the University of Miami for direct comparison of surfactant effects on the fluxes of CO2, H2O, heat and momentum (eddy correlation) etc. We present here some preliminary findings from the work.

  14. Leaf gas exchange characteristics and water- and nitrogen-use efficiencies of dominant grass and tree species in a West African savanna

    Microsoft Academic Search

    Guillaume Simioni; Xavier Le Roux; Jacques Gignoux; Adrian S. Walcroft

    2004-01-01

    Whereas leaf gas exchange properties are important to assess carbon and water fluxes in ecosystems worldwide, information of this type is scarce for savanna species. In this study, gas exchange characteristics of 2 C4 grass species (Andropogon canaliculatus and Hyparrhenia diplandra) and 2 C3 tree species (Crossopteryx febrifuga and Cussonia arborea) from the West-African savanna of Lamto (Ivory Coast) were

  15. Quantifying the measurement errors in a LI-6400 gas exchange system and their effects on the parameterization of Farquhar et al. model for C3 leaves

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The LI-6400 gas exchange system (Li-Cor, Inc, Lincoln, NE, USA) has been widely used for the measurement of net gas exchanges and calibration/parameterization of leaf models. Measurement errors due to diffusive leakages of water vapor and carbon dioxide between inside and outside of the leaf chamber...

  16. Independent effects of the environment on the leaf gas exchange of three banana ( Musa sp.) cultivars of different genomic constitution

    Microsoft Academic Search

    D. S. Thomas; D. W. Turner; D. Eamus

    1998-01-01

    Circumstantial evidence suggests that the Musa balbisiana (B) genome confers greater drought tolerance to bananas and plantains than the Musa acuminata (A) genome. Hence the genetic makeup of bananas and plantains may affect the response of leaf gas exchange to the environment. Field data cannot be readily used to study the independent effects of environment but laboratory studies allow independent

  17. Leaf Surface Characteristics and Gas Exchange in Artemisia tridentata subspecies wyomingensis and tridentata J. L. Downs R. A. Black

    Microsoft Academic Search

    J. L. Downs

    1999-01-01

    Leaf surface and gas exchange characteristics were examined in 3-year old plants of two subspecies of big sagebrush (Artemisia tridentata) growing in a common garden in southeastern Washington. Scanning electron microscopy (SEM) and subsequent image analysis revealed larger cell size in the tetraploid Wyoming big sagebrush (subspecies wyomingensis) resulting in larger sto- mata. In the diploid basin big sagebrush (subspecies

  18. WATER STRESS AND NITROGEN MANAGEMENT EFFECTS ON GAS EXCHANGE, WATER RELATIONS, AND WATER USE EFFICIENCY IN WHEAT

    Microsoft Academic Search

    Ejaz Ahmad Waraich; R. Ahmad; Saifullah; A. Ahmad

    2011-01-01

    A field experiment was conducted over two years to evaluate the gas exchange, water relations, and water use efficiency (WUE) of wheat under different water stress and nitrogen management practices at Crop Physiology Research Area, University of Agriculture, Faisalabad, Pakistan. Four irrigation regimes and four nitrogen levels, i.e., 0, 50, 100, and 150 kg N ha were applied in this

  19. A comparative study of the gas exchange potential between three wetland species using sulfur hexafluoride as a tracer

    Microsoft Academic Search

    N Salhani; E Stengel

    2001-01-01

    The gas-exchange potential of three wetland species (helophytes) was examined in an aquatic model vegetation facility (AMOVA) using sulfur hexafluoride (SF6) as a tracer. Three beds containing gravel and vegetated with Phragmitesaustralis, Typhalatifolia and Schoenoplectuslacustris were compared to an unvegetated gravel bed as a reference. A mass balance of SF6 emissions revealed a different seasonal emission pattern for the three

  20. Leaf Abscisic Acid Accumulation in Response To Substrate Water Content: Linking Leaf Gas Exchange Regulation with Leaf Abscisic Acid Concentration

    Microsoft Academic Search

    William L. Bauerle; William W. Inman; Jerry B. Dudley

    2006-01-01

    ADDITIONAL INDEX WORDS. stomatal conductance, drought tolerance, genotype variation ABSTRACT. Quantitative differences in leaf abscisic acid (ABAL) among four cultivars of red maple (Acer rubrum L.) and one freeman maple (Acer ×freemanii E. Murray) cultivar were investigated. This study tested the hypothesis that ABAL concentration can be used to compare the effects of water stress on the gas exchange response

  1. Canopy gas exchange and water use efficiency of 'Empire' apple in response to particle film, irrigation, and microclimatic factors

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study examined the interaction between a reflective particle film and water use efficiency (WUE) response of irrigated and non-irrigated apple trees over a wide range of environmental conditions. The objectives were to measure the specific gas exchange and WUE response of 'Empire' apple treate...

  2. Comparison of the acute effects on gas exchange of nasal ventilation and doxapram in exacerbations of chronic obstructive pulmonary disease

    Microsoft Academic Search

    R. M. Angus; A. A. Ahmed; L. J. Fenwick; A. J. Peacock

    1996-01-01

    BACKGROUND: Nasal intermittent positive pressure ventilation (NIPPV) is useful in exacerbations of chronic obstructive pulmonary disease (COPD) complicated by ventilatory failure. The effects of NIPPV were compared with those of the respiratory stimulant doxapram on gas exchange in patients with COPD and acute ventilatory failure. METHODS: Patients admitted with acute exacerbations of COPD and type 2 respiratory failure (Pao2 6.7

  3. Gas exchange of four arctic and alpine tundra plant species in relation to atmospheric and soil moisture stress

    Microsoft Academic Search

    Douglas A. Johnson; Martyn M. Caldwell

    1975-01-01

    Gas exchange measurements of two arctic tundra plants, Dupontia fischeri and Carex aquatilis, and two alpine tundra species, Deschampsia caespitosa and Geum rossii, were conducted under a range of atmospheric and soil moisture stress conditions to determine if photosynthetic adaptations to water stress may play a role in the local distributions of these species. Under low soil moisture stress, the

  4. Effect of nitrogen supply on growth, allocation and gas exchange characteristics of two perennial grasses from inland dunes

    Microsoft Academic Search

    René G. A. Boot; Koen C. Dubbelden

    1990-01-01

    We studied the effects of nitrogen supply on growth, allocation, and gas exchange characteristics of two perennial grasses of dry, nutrient-poor inland dunes: Corynephorus canescens (L.) Beauv. and Agrostis vinealis Schreber. C. canescens invests more biomass in leaves and less in roots, but has less leaf area and more root length per unit plant weight than A. vinealis. A. vinealis

  5. Responses of hardwood regeneration to fire in mesic forest openings. II. Leaf gas exchange, nitrogen concentration, and water status

    Microsoft Academic Search

    Eric L. Kruger; Peter B. Reich

    1997-01-01

    The physiological responses of tree regeneration to fire were studied in openings in a mesic hardwood forest. Gas exchange, nitrogen concentration, and water potential were monitored on foliage of burned and nonburned regeneration of northern red oak (Quercus rubra L.), white ash (Fraxinus americana L.), and sugar maple (Acer saccharum Marsh.) following spring fires in 1989 and 1990. Fire led

  6. Asymmetrical effects of mesophyll conductance on fundamental photosynthetic parameters and their relationships estimated from leaf gas exchange measurements

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Most previous analyses of leaf gas exchange measurements assumed an infinite value of mesophyll conductance (gm) and thus equaled CO2 partial pressures in the substomatal cavity and chloroplast. Yet an increasing number of studies have recognized that gm is finite and there is a drawdown of CO2 part...

  7. Reduced thrombocyte adhesion to endothelialized poly 4-methyl-1-pentene gas exchange membranes—a first step toward bioartificial lung development.

    PubMed

    Hess, Christian; Wiegmann, Bettina; Maurer, Andreas N; Fischer, Philipp; Möller, Lena; Martin, Ulrich; Hilfiker, Andres; Haverich, Axel; Fischer, Stefan

    2010-10-01

    Polymeric materials used in biomedical devices, bioartificial organs, or for the fabrication of tissue engineering scaffolds should completely prevent the activation of the coagulation system and subsequent clot formation. Surface endothelialization is considered an important tool to optimize the blood compatibility of synthetic materials, as a functional endothelial cell layer on an artificial material may help control hemostasis and, therefore, provide a solution to improve the biocompatibility of these materials. Here we report on the endothelialization of poly 4-methyl-1-pentene (PMP) gas exchange membranes using human cord blood-derived late outgrowth endothelial colony forming cells. We achieved complete endothelialization of PMP membranes; and when seeded and cultivated on the membrane, cord blood-derived late outgrowth endothelial colony forming cells maintained both endothelial characteristics and functionality. Endothelialization resulted in significantly lower platelet adhesion and activation compared with unseeded membranes. Of importance, the endothelial layer had no major impact on gas permeability of PMP membranes. This study is a first promising step toward the development of a biofunctionalized surface for the use in gas exchange devices with blood contacting surfaces and a straightforward approach toward a long-term bio-hybrid lung replacement system. PMID:20486793

  8. Toxicodynamics of rigid polystyrene microparticles on pulmonary gas exchange in mice: Implications for microemboli-based drug delivery systems

    SciTech Connect

    Kutscher, H.L. [Department of Pharmaceutics, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, NJ 08854 (United States)] [Department of Pharmaceutics, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, NJ 08854 (United States); Gao, D.; Li, S. [Department of Pharmaceutics, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, NJ 08854 (United States) [Department of Pharmaceutics, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, NJ 08854 (United States); UMDNJ-Rutgers CounterACT Research Center of Excellence, Rutgers, The State University of New Jersey, Piscataway, NJ 08854 (United States); Massa, C.B.; Cervelli, J. [Department of Pharmacology and Toxicology, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, NJ 08854 (United States)] [Department of Pharmacology and Toxicology, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, NJ 08854 (United States); Deshmukh, M. [Department of Pharmaceutics, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, NJ 08854 (United States) [Department of Pharmaceutics, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, NJ 08854 (United States); UMDNJ-Rutgers CounterACT Research Center of Excellence, Rutgers, The State University of New Jersey, Piscataway, NJ 08854 (United States); Joseph, L.B.; Laskin, D.L. [UMDNJ-Rutgers CounterACT Research Center of Excellence, Rutgers, The State University of New Jersey, Piscataway, NJ 08854 (United States) [UMDNJ-Rutgers CounterACT Research Center of Excellence, Rutgers, The State University of New Jersey, Piscataway, NJ 08854 (United States); Department of Pharmacology and Toxicology, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, NJ 08854 (United States); Sinko, P.J., E-mail: sinko@rci.rutgers.edu [Department of Pharmaceutics, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, Piscataway, NJ 08854 (United States); UMDNJ-Rutgers CounterACT Research Center of Excellence, Rutgers, The State University of New Jersey, Piscataway, NJ 08854 (United States)

    2013-01-15

    The toxicodynamic relationship between the number and size of pulmonary microemboli resulting from uniformly sized, rigid polystyrene microparticles (MPs) administered intravenously and their potential effects on pulmonary gas exchange were investigated. CD-1 male mice (6–8 weeks) were intravenously administered 10, 25 and 45 ?m diameter MPs. Oxygen hemoglobin saturation in the blood (SpO{sub 2}) was measured non-invasively using a pulse oximeter while varying inhaled oxygen concentration (F{sub I}O{sub 2}). The resulting data were fit to a physiologically based non-linear mathematical model that estimates 2 parameters: ventilation–perfusion ratio (V{sub A}/Q) and shunt (percentage of deoxygenated blood returning to systemic circulation). The number of MPs administered prior to a statistically significant reduction in normalized V{sub A}/Q was dependent on particle size. MP doses that resulted in a significant reduction in normalized V{sub A}/Q one day post-treatment were 4000, 40,000 and 550,000 MPs/g for 45, 25 and 10 ?m MPs, respectively. The model estimated V{sub A}/Q and shunt returned to baseline levels 7 days post-treatment. Measuring SpO{sub 2} alone was not sufficient to observe changes in gas exchange; however, when combined with model-derived V{sub A}/Q and shunt early reversible toxicity from pulmonary microemboli was detected suggesting that the model and physical measurements are both required for assessing toxicity. Moreover, it appears that the MP load required to alter gas exchange in a mouse prior to lethality is significantly higher than the anticipated required MP dose for effective drug delivery. Overall, the current results indicate that the microemboli-based approach for targeted pulmonary drug delivery is potentially safe and should be further explored. -- Highlights: ? Murine pulmonary gas exchange after microembolization was non-invasively studied. ? A physiologically based model quantified impairment of pulmonary gas exchange. ? Number and size of microemboli determine severity of impaired gas exchange. ? Pulmonary gas exchange returns to baseline within 7 days.

  9. Fouling reduction characteristics of a no-distributor-fluidized-bed heat exchanger for flue gas heat recovery

    SciTech Connect

    Jun, Y.D.; Lee, K.B.; Islam, S.Z.; Ko, S.B. [Kongju National University, Kong Ju (Republic of Korea). Dept. for Mechanical Engineering

    2008-07-01

    In conventional flue gas heat recovery systems, the fouling by fly ashes and the related problems such as corrosion and cleaning are known to be major drawbacks. To overcome these problems, a single-riser no-distributor-fluidized-bed heat exchanger is devised and studied. Fouling and cleaning tests are performed for a uniquely designed fluidized bed-type heat exchanger to demonstrate the effect of particles on the fouling reduction and heat transfer enhancement. The tested heat exchanger model (1 m high and 54 mm internal diameter) is a gas-to-water type and composed of a main vertical tube and four auxiliary tubes through which particles circulate and transfer heat. Through the present study, the fouling on the heat transfer surface could successfully be simulated by controlling air-to-fuel ratios rather than introducing particles through an external feeder, which produced soft deposit layers with 1 to 1.5 mm thickness on the inside pipe wall. Flue gas temperature at the inlet of heat exchanger was maintained at 450{sup o}C at the gas volume rate of 0.738 to 0.768 CMM (0.0123 to 0.0128 m{sup 3}/sec). From the analyses of the measured data, heat transfer performances of the heat exchanger before and after fouling and with and without particles were evaluated. Results showed that soft deposits were easily removed by introducing glass bead particles, and also heat transfer performance increased two times by the particle circulation. In addition, it was found that this type of heat exchanger had high potential to recover heat of waste gases from furnaces, boilers, and incinerators effectively and to reduce fouling related problems.

  10. Carbon source/sink function of a subtropical, eutrophic lake determined from an overall mass balance and a gas exchange and carbon burial balance.

    PubMed

    Yang, Hong; Xing, Yangping; Xie, Ping; Ni, Leyi; Rong, Kewen

    2008-02-01

    Although studies on carbon burial in lake sediments have shown that lakes are disproportionately important carbon sinks, many studies on gaseous carbon exchange across the water-air interface have demonstrated that lakes are supersaturated with CO(2) and CH(4) causing a net release of CO(2) and CH(4) to the atmosphere. In order to more accurately estimate the net carbon source/sink function of lake ecosystems, a more comprehensive carbon budget is needed, especially for gaseous carbon exchange across the water-air interface. Using two methods, overall mass balance and gas exchange and carbon burial balance, we assessed the carbon source/sink function of Lake Donghu, a subtropical, eutrophic lake, from April 2003 to March 2004. With the overall mass balance calculations, total carbon input was 14 905 t, total carbon output was 4950 t, and net carbon budget was +9955 t, suggesting that Lake Donghu was a great carbon sink. For the gas exchange and carbon burial balance, gaseous carbon (CO(2) and CH(4)) emission across the water-air interface totaled 752 t while carbon burial in the lake sediment was 9477 t. The ratio of carbon emission into the atmosphere to carbon burial into the sediment was only 0.08. This low ratio indicates that Lake Donghu is a great carbon sink. Results showed good agreement between the two methods with both showing Lake Donghu to be a great carbon sink. This results from the high primary production of Lake Donghu, substantive allochthonous carbon inputs and intensive anthropogenic activity. Gaseous carbon emission accounted for about 15% of the total carbon output, indicating that the total output would be underestimated without including gaseous carbon exchange. PMID:17664033

  11. FORMALDEHYDE AND TRACER GAS TRANSFER BETWEEN AIRSTREAMS IN ENTHALPY-TYPE AIR-TO-AIR HEAT EXCHANGERS

    SciTech Connect

    Fisk, W. J.; Pedersen, B. S.; Hekmat, D.; Chant, R. E.; Kaboli, H.

    1984-07-01

    Enthalpy exchangers are frequently employed to transfer heat and water between the supply and exhaust airstreams of mechanical ventilation systems. Concern has been expressed that some indoor-generated air pollutants, especially formaldehyde, may be transferred between airstreams by this type of heat exchanger and, thus, returned to the indoor space. This paper describes an experimental study in which the formaldehyde, tracer gas, and water vapor transfer rates in two enthalpy exchangers were measured. The first exchanger uses a crossflow core fabricated from a treated paper. The core of the second heat exchanger is a rotating heat wheel coated with lithium chloride. To reduce the transfer of gases by air leakage each core was installed in a specially fabricated case. Only 5% to 8% of the two tracer gases and 7% to 15% of the formaldehyde injected into the exhaust airstream was transferred to the supply airstream. Therefore, formaldehyde transfer between airstreams by processes other than air leakage does not seriously compromise the performance of these enthalpy exchangers. Theoretical calculations indicate, however, that the transfer of water vapor between airstreams in enthalpy exchangers can significantly diminish their ability to lower indoor formaldehyde concentrations because of the positive coupling between indoor humidity and the emission rates of formaldehyde from building materials.

  12. On active disturbance rejection in temperature regulation of the proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Li, Dazi; Li, Chong; Gao, Zhiqiang; Jin, Qibing

    2015-06-01

    Operating a Proton Exchange Membrane fuel cell (PEMFC) system to maintain the stack temperature stable is one of the key issues in PEMFC's normal electrochemical reaction process. Its temperature characteristic is easily affected by inlet gas humidity, external disturbances, and electrical load changes and so on. Because of the complexity and nonlinearity of the reaction process, it is hard to build a model totally consistent with the real characteristic of the process. If model uncertainty, external disturbances, parameters changes can be regarded as "total disturbance", which is then estimated and compensated, the accurate model is no longer required and the control design can be greatly simplified to meet the practical needs. Based on this idea, an active disturbance rejection control (ADRC) with a switching law is proposed for the problem of precise temperature regulation in PEMFC. Results of the work show that the proposed control system allows the PEMFC to operate successfully at the temperature of 343 K point in the presence of two different disturbances.

  13. In vitro and in vivo evaluation of a new active heat moisture exchanger

    Microsoft Academic Search

    Davide Chiumello; Paolo Pelosi; Gilbert Park; Andrea Candiani; Nicola Bottino; Ezio Storelli; Paolo Severgnini; Dunia D'Onofrio; Luciano Gattinoni; Massimo Chiaranda

    2004-01-01

    INTRODUCTION: In order to improve the efficiency of heat moisture exchangers (HMEs), new hybrid humidifiers (active HMEs) that add water and heat to HMEs have been developed. In this study we evaluated the efficiency, both in vitro and in vivo, of a new active HME (the Performer; StarMed, Mirandola, Italy) as compared with that of existing HMEs (Hygroster and Hygrobac;

  14. Trace gas exchange and the validity of similarity theory in the roughness sublayer above forests

    NASA Astrophysics Data System (ADS)

    Simpson, Isobel Jane

    1997-11-01

    This thesis is an investigation of (1) methane (CH4) and nitrous oxide (N2O) exchange above a boreal aspen (Populus tremuloides) stand near Prince Albert, Saskatchewan, and (2) the similarity theory upon which the flux measurements were based. Although CH4 and N2O play significant roles in the atmosphere, estimates of their global source and sink strengths are only poorly constrained. Boreal ecosystems are a priority trace gas research area, and the CH4 and N2O exchanges were measured as part of the Boreal Ecosystem-Atmosphere Study (BOREAS). The fluxes were determined micrometeorologically using laser-based Trace Gas Analysis Systems (TGAS). Between April and September, 1994, a mean net CH4 emission of 15.7 ± 2.8 ng m-2 s-1 was measured from a tower above the aspen stand. The CH4 emissions peaked in late summer, and the CH4 flux and soil temperature correlated with r2 = 0.70. In contrast, CH4 uptake was recorded near the tower base. Overall, it appears that CH4 emissions from anoxic patches located throughout the above-canopy footprint overwhelmed uptake from drier areas to yield a net emission of CH4. The mean N2O emission of 1.4 ± 0.7 ng m-2 s-1 was attributable to low soil nitrate (NO3/sp-) and ammonium (NH4+) availability. The small CH4 and N2O fluxes required that they be determined using a flux-gradient approach based upon similarity theory. However, similarity theory has been reported to severely underestimate scalar fluxes in the roughness sublayer above forests. Accordingly, the validity of similarity theory was investigated above a mixed deciduous forest at Camp Borden, Ontario, between July and October 1995. The TGAS used in the research enabled a higher resolution measurement than has been previously possible in similarity theory investigations. Between 1.9 and 2.2 canopy heights (hc), the mean enhancement factor (the ratio of independent fluxes to similarity theory values) was 1.15 ± 0.07. Closer to the canopy (1.2 to 1.4 hc), mean enhancement factors of 1.61 ± 0.10 and 1.82 ± 0.11 were measured, before and after leaf senescence, respectively. Overall, it appears that similarity theory can be used within the roughness sublayer of forests with a greater confidence than previously has been believed.

  15. Greenhouse-gas exchange of croplands worldwide: a process-based model simulation

    NASA Astrophysics Data System (ADS)

    Inatomi, M.; Ito, A.

    2009-12-01

    Croplands cover about 15% of the land surface, and play unique roles in global biogeochemical cycles. Especially, greenhouse gas budget of croplands is important for climate projection in the future and for mitigation toward climate stabilization. Sustainable cropland is carbon-neutral (i.e., neither a sink nor a source of CO2 for a long time), but those in developed countries consume fossil fuels for agricultural operations and releases CO2 as revealed by LCAs. Paddy field is one of the substantial sources of CH4, and cropland may be the largest anthropogenic source of N2O. However, these features have not been evaluated and discussed using a spatial-explicit comprehensive framework at the global scale. This study applies a process-based terrestrial ecosystem model (VISIT) to worldwide croplands. Exchange of CO2 is simulated as a difference between photosynthesis and respiration, each of which is calculated in a biogeochemical carbon cycle scheme. Net carbon budget accounts for carbon flows by planting, compost input, and harvest. Exchange of CH4 is simulated as a difference between oxidation by aerobic soils and production by anaerobic soils, each of which is calculated using mechanistic schemes. Emission of N2O from nitrification and denitrification is simulated with a semi-mechanistic scheme on the basis of leaky-pipe concept. We are also validating the model through comparison with chamber and tower flux measurements. Global simulations were conducted during a period from 1901 to 2100 on the basis of historical and projected climate and land-use conditions, at a spatial resolution of 0.5 x 0.5 degree. Cropland type and distribution was derived from SAGE-HYDE dataset and country-base fertilizer input was obtained from FAOSTAT. Our preliminary simulation for the 1990s estimated that croplands are a net sink of CO2 by 1.1 Gt C/yr; this sink is offset by emission by food consumption. Paddy fields are estimated to release CH4 by 46 Tg CH4/yr, and croplands worldwide release N2O by 5.9 Tg N2O/yr. Because of high Global Warming Potential of CH4 (25 for 100-yr) and N2O (298), these results imply that agriculture is a net source of radiative forcing for the atmosphere. Additionally, recent studies show that N2O is the most important substance for stratospheric ozone depletion. Therefore, further studies are needed to improve quantification of greenhouse gas budget in croplands and to design mitigation strategy.

  16. Molecular gas in nearby active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Baker, Andrew Jordan

    2000-06-01

    This thesis describes the distributions, physical conditions, and kinematics of the molecular gas in eight nearby galaxies whose Seyfert and LINER nuclei display broad H? emission. We have mapped these systems at a linear resolution of ~100 pc in the CO(2-1) rotational transition, as well as at lower resolution in the CO(1-0) line, using the Owens Valley Radio Observatory millimeter array. Subsequent kinematical modelling allows us to improve on this angular resolution by exploiting our high effective velocity resolution; we simultaneously determine the radial emissivity profile of each line and the velocity field which the gas traces. Analysis of the molecular emission from individual objects reveals (1)massive concentrations of molecular gas at small galactocentric radii; (2)a pattern of high excitation at small radius, implied by variation in the ratio of CO(2-1) to CO(1-0) integrated intensities, which we attribute in part to the external heating of molecular clouds by energetic photons; (3)a high occurrence of nonaxisymmetric structures within 500 pc of the nucleus, including four gas bars; (4)evidence for episodic mass inflow along stellar bars outside 500 pc; and (5)apparent redirection of radio jets and ionizing photons from the nucleus by the molecular gas which they encounter. Our most striking discoveries are a dynamically decoupled secondary bar in the nucleus of NGC 7479, a mean integrated intensity ratio >1.85 in the nucleus of NGC 2681, and a warped molecular disk in the nucleus of NGC 1068.

  17. The Impact of a Lower Sea Ice Extent on Arctic Greenhouse Gas Exchange

    NASA Astrophysics Data System (ADS)

    Parmentier, Frans-Jan W.; Christensen, Torben R.; Lotte Sørensen, Lise; Rysgaard, Søren; McGuire, A. David; Miller, Paul A.; Walker, Donald A.

    2013-04-01

    Arctic sea ice extent hit a new record low in September 2012, when it fell to a level about two times lower than the 1979-2000 average. Record low sea ice extents such as these are often hailed as an obvious example of the impact of climate change on the Arctic. Less obvious, however, are the further implications of a lower sea ice extent on Arctic greenhouse gas exchange. For example, a reduction in sea ice, in consort with a lower snow cover, has been connected to higher surface temperatures in the terrestrial part of the Arctic (Screen et al., 2012). These higher temperatures and longer growing seasons have the potential to alter the CO2 balance of Arctic tundra through enhanced photosynthesis and respiration, as well as the magnitude of methane emissions. In fact, large changes are already observed in terrestrial ecosystems (Post et al., 2009), and concerns have been raised of large releases of carbon through permafrost thaw (Schuur et al., 2011). While these changes in the greenhouse gas balance of the terrestrial Arctic are described in numerous studies, a connection with a decline in sea ice extent is nonetheless seldom made. In addition to these changes on land, a lower sea ice extent also has a direct effect on the exchange of greenhouse gases between the ocean and the atmosphere. For example, due to sea ice retreat, more ocean surface remains in contact with the atmosphere, and this has been suggested to increase the oceanic uptake of CO2 (Bates et al., 2006). However, the sustainability of this increased uptake is uncertain (Cai et al., 2010), and carbon fluxes related directly to the sea ice itself add much uncertainty to the oceanic uptake of CO2 (Nomura et al., 2006; Rysgaard et al., 2007). Furthermore, significant emissions of methane from the Arctic Ocean have been observed (Kort et al., 2012; Shakhova et al., 2010), but the consequence of a lower sea ice extent thereon is still unclear. Overall, the decline in sea ice that has been seen in recent years has the potential to influence greenhouse gas exchange across terrestrial ecosystems and the Arctic Ocean, but the overall impact remains unclear. In this study, we therefore try to reduce this uncertainty by addressing the influence of the decline in sea ice extent on all affected greenhouse gas fluxes in the high latitudes. Also, we will address the need for more research, on the ocean and on the land, to understand the impact of a lower sea ice extent on Arctic greenhouse gas exchange. References: Bates, N. R., Moran, S. B., Hansell, D. A. and Mathis, J. T.: An increasing CO2 sink in the Arctic Ocean due to sea-ice loss, Geophys. Res. Lett., 33, L23609, doi:10.1029/2006GL027028, 2006. Cai, W.-J., Chen, L., Chen, B., Gao, Z., Lee, S. H., Chen, J., Pierrot, D., Sullivan, K., Wang, Y., Hu, X., Huang, W.-J., et al.: Decrease in the CO2 Uptake Capacity in an Ice-Free Arctic Ocean Basin, Science, 329(5991), 556-559, doi:10.1126/science.1189338, 2010. Kort, E. A., Wofsy, S. C., Daube, B. C., Diao, M., Elkins, J. W., Gao, R. S., Hintsa, E. J., Hurst, D. F., Jimenez, R., Moore, F. L., Spackman, J. R., et al.: Atmospheric observations of Arctic Ocean methane emissions up to 82 degrees north, Nature Geosci., 5(5), 318-321, doi:10.1038/NGEO1452, 2012. Nomura, D., Yoshikawa-Inoue, H. and Toyota, T.: The effect of sea-ice growth on air-sea CO2 flux in a tank experiment, vol. 58, pp. 418-426. 2006. Post, E., Forchhammer, M. C., Bret-Harte, M. S., Callaghan, T. V., Christensen, T. R., Elberling, B., Fox, A. D., Gilg, O., Hik, D. S., Høye, T. T., Ims, R. A., et al.: Ecological Dynamics Across the Arctic Associated with Recent Climate Change, Science, 325(5946), 1355-1358, doi:10.1126/science.1173113, 2009. Rysgaard, S., Glud, R. N., Sejr, M. K., Bendtsen, J. and Christensen, P. B.: Inorganic carbon transport during sea ice growth and decay: A carbon pump in polar seas, J. Geophys. Res., 112, C03016, doi:10.1029/2006JC003572, 2007. Schuur, E. A. G., Abbott, B. and Network, P. C.: High risk of permafrost thaw, Nature, 480(7375), 32-33, 2011. Screen, J. A., Deser, C. and

  18. Microbial activities in soil near natural gas leaks

    Microsoft Academic Search

    A. D. Adamse; J. Hoeks; J. A. M. Bont; J. F. Kessel

    1972-01-01

    From the present experiments it may be concluded that in the surroundings of natural gas leaks, methane, ethane and possibly some other components of the natural gas are oxidized by microbial activities as long as oxygen is available. This is demonstrated by an increased oxygen consumption and carbon dioxide production, as well as by increased numbers of different types of

  19. Adsorption of natural gas and biogas components on activated carbon

    Microsoft Academic Search

    Isabel A. A. C. Esteves; Marta S. S. Lopes; Pedro M. C. Nunes; José P. B. Mota

    2008-01-01

    Experimental results are presented for the adsorption equilibria of methane, ethane, propane, butane, carbon dioxide, and nitrogen, as well as natural gas odorants tert-butyl mercaptan and tetrahydrothiophene, on an activated carbon with the desirable characteristics for use in a guard bed for adsorbed natural gas storage, but that can also be applied for separation of biogas components, such as carbon

  20. Scaling of stomatal size and density optimizes allocation of leaf epidermal space for gas exchange in angiosperms

    NASA Astrophysics Data System (ADS)

    de Boer, Hugo Jan; Price, Charles A.; Wagner-Cremer, Friederike; Dekker, Stefan C.; Franks, Peter J.; Veneklaas, Erik J.

    2015-04-01

    Stomata on plant leaves are key traits in the regulation of terrestrial fluxes of water and carbon. The basic morphology of stomata consists of a diffusion pore and two guard cells that regulate the exchange of CO2 and water vapour between the leaf interior and the atmosphere. This morphology is common to nearly all land plants, yet stomatal size (defined as the area of the guard cell pair) and stomatal density (the number of stomata per unit area) range over three orders of magnitude across species. Evolution of stomatal sizes and densities is driven by selection pressure on the anatomical maximum stomatal conductance (gsmax), which determines the operational range of leaf gas exchange. Despite the importance of stomata traits for regulating leaf gas exchange, a quantitative understanding of the relation between adaptation of gsmax and the underlying co-evolution of stomatal sizes and densities is still lacking. Here we develop a theoretical framework for a scaling relationship between stomatal sizes and densities within the constraints set by the allocation of epidermal space and stomatal gas exchange. Our theory predicts an optimal scaling relationship that maximizes gsmax and minimizes epidermal space allocation to stomata. We test whether stomatal sizes and densities reflect this optimal scaling with a global compilation of stomatal trait data on 923 species reflecting most major clades. Our results show optimal scaling between stomatal sizes and densities across all species in the compiled data set. Our results also show optimal stomatal scaling across angiosperm species, but not across gymnosperm and fern species. We propose that the evolutionary flexibility of angiosperms to adjust stomatal sizes underlies their optimal allocation of leaf epidermal space to gas exchange.

  1. Responses of sap flow, leaf gas exchange and growth of hybrid aspen to elevated atmospheric humidity under field conditions.

    PubMed

    Niglas, Aigar; Kupper, Priit; Tullus, Arvo; Sellin, Arne

    2014-01-01

    An increase in average air temperature and frequency of rain events is predicted for higher latitudes by the end of the 21st century, accompanied by a probable rise in air humidity. We currently lack knowledge on how forest trees acclimate to rising air humidity in temperate climates. We analysed the leaf gas exchange, sap flow and growth characteristics of hybrid aspen (Populus tremula × P. tremuloides) trees growing at ambient and artificially elevated air humidity in an experimental forest plantation situated in the hemiboreal vegetation zone. Humidification manipulation did not affect the photosynthetic capacity of plants, but did affect stomatal responses: trees growing at elevated air humidity had higher stomatal conductance at saturating photosynthetically active radiation (gs sat) and lower intrinsic water-use efficiency (IWUE). Reduced stomatal limitation of photosynthesis in trees grown at elevated air humidity allowed slightly higher net photosynthesis and relative current-year height increments than in trees at ambient air humidity. Tree responses suggest a mitigating effect of higher air humidity on trees under mild water stress. At the same time, trees at higher air humidity demonstrated a reduced sensitivity of IWUE to factors inducing stomatal closure and a steeper decline in canopy conductance in response to water deficit, implying higher dehydration risk. Despite the mitigating impact of increased air humidity under moderate drought, a future rise in atmospheric humidity at high latitudes may be disadvantageous for trees during weather extremes and represents a potential threat in hemiboreal forest ecosystems. PMID:24887000

  2. Responses of sap flow, leaf gas exchange and growth of hybrid aspen to elevated atmospheric humidity under field conditions

    PubMed Central

    Niglas, Aigar; Kupper, Priit; Tullus, Arvo; Sellin, Arne

    2014-01-01

    An increase in average air temperature and frequency of rain events is predicted for higher latitudes by the end of the 21st century, accompanied by a probable rise in air humidity. We currently lack knowledge on how forest trees acclimate to rising air humidity in temperate climates. We analysed the leaf gas exchange, sap flow and growth characteristics of hybrid aspen (Populus tremula × P. tremuloides) trees growing at ambient and artificially elevated air humidity in an experimental forest plantation situated in the hemiboreal vegetation zone. Humidification manipulation did not affect the photosynthetic capacity of plants, but did affect stomatal responses: trees growing at elevated air humidity had higher stomatal conductance at saturating photosynthetically active radiation (gs sat) and lower intrinsic water-use efficiency (IWUE). Reduced stomatal limitation of photosynthesis in trees grown at elevated air humidity allowed slightly higher net photosynthesis and relative current-year height increments than in trees at ambient air humidity. Tree responses suggest a mitigating effect of higher air humidity on trees under mild water stress. At the same time, trees at higher air humidity demonstrated a reduced sensitivity of IWUE to factors inducing stomatal closure and a steeper decline in canopy conductance in response to water deficit, implying higher dehydration risk. Despite the mitigating impact of increased air humidity under moderate drought, a future rise in atmospheric humidity at high latitudes may be disadvantageous for trees during weather extremes and represents a potential threat in hemiboreal forest ecosystems. PMID:24887000

  3. Lagrangian evolution of DMS during the Southern Ocean gas exchange experiment: The effects of vertical mixing and biological community shift

    NASA Astrophysics Data System (ADS)

    Yang, M.; Archer, S. D.; Blomquist, B. W.; Ho, D. T.; Lance, V. P.; Torres, R. J.

    2013-12-01

    Concentrations of dimethylsulfide (DMS) and its precursor dimethylsulfoniopropionate (DMSP) are highly variable in time and space. What is driving the variability in DMS(P), and can those variability be explained by physical processes and changes in the biological community? During the Southern Ocean Gas Exchange Experiment (SO GasEx) in the austral fall of 2008, two 3He/SF6 labeled patches were created in the surface water. SF6 and DMS were surveyed continuously in a Lagrangian framework, while direct measurements of air-sea exchange further constrained the gas budgets. Turbulent diffusivity at the base of the mixed layer was estimated from SF6 profiles and used to calculate the vertical fluxes of DMS and nutrients. Increasing mixed layer nutrient concentrations due to mixing were associated with a shift in the phytoplankton community structure, which in turned likely affected the sulfur dynamics on timescales of days. DMS concentration as well as air-sea DMS flux appeared to be decoupled from the DMSP concentration, possibly due to grazing and bacterial DMS production. Contrary to expectations, in an environment with high winds and modest productivity, physical processes (air-sea exchange, photochemistry, vertical mixing) only accounted for a small fraction of DMS loss from the surface water. Among the DMS sinks, inferred biological consumption most likely dominated during SO GasEx.

  4. Innovative, counterflow gas/fine solids, direct contact heat exchanger: Final report

    SciTech Connect

    Mah, C.S.

    1987-10-01

    The Aerojet Energy Conversion Company has completed the first phase of study for development of a heat exchanger. The heat exchanger, a highly efficient, low cost concept, is a candidate for application in process manufacturing industries such as cement, lime, or glass. The analytical effort was to establish the heat exchanger performance via computer modeling and analysis; the experimental effort was to demonstrate the heat exchanger performance.

  5. Balloons and Bottles: Activities on Air-Sea Heat Exchange.

    ERIC Educational Resources Information Center

    Murphree, Tom

    1998-01-01

    Presents an activity designed to demonstrate how heating and cooling an air mass affects its temperature, volume, density, and pressure. Illustrates how thermal energy can cause atmospheric motion such as expansion, contraction, and winds. (Author/WRM)

  6. Heat transfer in a compact heat exchanger containing rectangular channels and using helium gas

    NASA Technical Reports Server (NTRS)

    Olson, D. A.

    1991-01-01

    Development of a National Aerospace Plane (NASP), which will fly at hypersonic speeds, require novel cooling techniques to manage the anticipated high heat fluxes on various components. A compact heat exchanger was constructed consisting of 12 parallel, rectangular channels in a flat piece of commercially pure nickel. The channel specimen was radiatively heated on the top side at heat fluxes of up to 77 W/sq cm, insulated on the back side, and cooled with helium gas flowing in the channels at 3.5 to 7.0 MPa and Reynolds numbers of 1400 to 28,000. The measured friction factor was lower than that of the accepted correlation for fully developed turbulent flow, although the uncertainty was high due to uncertainty in the channel height and a high ratio of dynamic pressure to pressure drop. The measured Nusselt number, when modified to account for differences in fluid properties between the wall and the cooling fluid, agreed with past correlations for fully developed turbulent flow in channels. Flow nonuniformity from channel-to-channel was as high as 12 pct above and 19 pct below the mean flow.

  7. Plant size, not age, regulates growth and gas exchange in grafted Scots pine trees.

    PubMed

    Vanderklein, D; Martínez-Vilalta, J; Lee, S; Mencuccini, M

    2007-01-01

    We studied the effect of scion donor-tree age on the physiology and growth of 6- to 7-year-old grafted Scots pine (Pinus sylvestris L.) trees (4 and 5 years after grafting). Physiological measurements included photosynthethetic rate, stomatal conductance, transpiration, whole plant hydraulic conductance, needle nitrogen concentration and carbon isotope composition. Growth measurements included total and component biomasses, relative growth rates and growth efficiency. Scion donor trees ranged in age from 36 to 269 years at the time of grafting. Hydraulic conductance was measured gravimetrically, applying the Ohm's law analogy, and directly, with a high-pressure flow meter. We found no effect of scion donor-tree age on any of the variables measured. There was, however, great variation within scion donor-tree age groups, which was related to the size of the grafted trees. Differences in size may have been caused by variable initial grafting success, but there was no indication that grafting success and age were related. At the stem level, hydraulic conductance scaled with total leaf area so that total conductance per unit leaf area did not vary with crown size. However, leaf specific hydraulic conductance (gravimetric), transpiration, photosynthesis and stomatal conductance declined with increasing total tree leaf area and needle width. We hypothesize that needle width is inversely related to mesophyll conductance. We conclude that canopy and needle size and not scion donor-tree age determined gas exchange in our grafted trees. PMID:17169908

  8. Leaf Gas Exchange and Chlorophyll a Fluorescence Imaging of Rice Leaves Infected with Monographella albescens.

    PubMed

    Tatagiba, Sandro Dan; DaMatta, Fábio Murilo; Rodrigues, Fabrício Ávila

    2015-02-01

    This study was intended to analyze the photosynthetic performance of rice leaf blades infected with Monographella albescens by combining chlorophyll (Chl) a fluorescence images with gas exchange and photosynthetic pigment pools. The net CO2 assimilation rate, stomatal conductance, transpiration rate, total Chl and carotenoid pools, and Chl a/b ratio all decreased but the internal CO2 concentration increased in the inoculated plants compared with their noninoculated counterparts. The first detectable changes in the images of Chl a fluorescence from the leaves of inoculated plants were already evident at 24 h after inoculation (hai) and increased dramatically as the leaf scald lesions expanded. However, these changes were negligible for the photosystem II photochemical efficiency (Fv/Fm) at 24 hai, in contrast to other Chl fluorescence traits such as the photochemical quenching coefficient, yield of photochemistry, and yield for dissipation by downregulation; which, therefore, were much more sensitive than the Fv/Fm ratio in assessing the early stages of fungal infection. It was also demonstrated that M. albescens was able to impair the photosynthetic process in both symptomatic and asymptomatic leaf areas. Overall, it was proven that Chl a fluorescence imaging is an excellent tool to describe the loss of functionality of the photosynthetic apparatus occurring in rice leaves upon infection by M. albescens. PMID:25163009

  9. Gas Exchange Characteristics of the Sorghum-Striga Host-Parasite Association

    PubMed Central

    Press, Malcolm C.; Tuohy, Janet M.; Stewart, George R.

    1987-01-01

    Gas exchange characteristics are reported for both members of the sorghum-Striga host-parasite association. Both Striga hermonthica (Del.) Benth and Striga asiatica (L.) Kuntze had transpiration rates considerably in excess of those of sorghum (Sorghum bicolor (L.) Moench, cv CSH1). Stomatal conductance in both Striga spp. showed little response to periods of darkness and moderate water stress. Low rates of net CO2 fixation and high rates of dark respiration led to no net daily (24 hours) C gain, and Striga would appear to be reliant on its host for photosynthate. Infection of sorghum plants with either S. hermonthica or S. asiatica reduced host photosynthetic capacity. Infected sorghum plants were also more prone to water stress, but reduced rates of CO2 fixation could not be accounted for in terms of lower stomatal conductance. Lower stomatal conductances were associated with an increase in water use efficiency (WUE) in uninfected sorghum; however, Striga-infected sorghum plants had lower WUE than those of uninfected plants. We suggest that Striga exerts a specific effect on processes affecting C acquisition in sorghum leaves. The water relations of S. hermonthica and S. asiatica are not characteristic of plants growing in semiarid environments and are more likely to reflect the nature of the parasitic life-style. Despite transfer of water and solutes from host to parasite, the reduction in C fixation observed in infected sorghum plants appears to be the major determinant of growth reductions observed in sorghum supporting Striga. PMID:16665527

  10. Effect of wind and currents on gas exchange in an estuarine system. Final technical report, 1 August 1986-31 July 1987

    SciTech Connect

    Broecker, W.S.; Ledwell, J.R.; Bopp, R.

    1987-11-01

    The objectives were to develop a non-volatile tracer to use in gas exchange experiments in laterally unconfined systems and to study applications of deliberate tracers in limnology and oceanography. Progress was made on both fronts but work on the development of the non-volatile tracer proved to be more difficult and labor intensive that anticipated so no field experiments using non-volatile tracers was performed as yet. In the search for a suitable non-volatile tracer for an ocean scale gas exchange experiment a tracer was discovered which does not have the required sensitivity for a large scale experiment, but is very easy to analyze and will be well suited for smaller experiments such as gas exchange determinations on rivers and streams. Sulfur hexafluoride, SF/sub 6/, was used successfully as a volatile tracer along with tritium as a non-volatile tracer to study gas exchange rates from a primary stream. This is the first gas exchange experiment in which gas exchange rates were determined on a head water stream where significant groundwater input occurs along the reach. In conjunction with SF/sub 6/, Radon-222 measurements were performed on the groundwater and in the stream. The feasibility of using a combination of SF/sub 6/ and radon is being studied to determine groundwater inputs and gas exchange of rates in streams with significant groundwater input without using a non-volatile tracer.

  11. Extremely low flow tracheal gas insufflation of helium-oxygen mixture improves gas exchange in a rabbit model of piston-type high-frequency oscillatory ventilation

    PubMed Central

    2013-01-01

    Objective The purpose of this study was to show the effects of the tracheal gas insufflation (TGI) technique on gas exchange using helium-oxygen mixtures during high-frequency oscillatory ventilation (HFOV). We hypothesized that a helium-oxygen mixture delivered into the trachea using the TGI technique (0.3 L/min) would enhance gas exchange during HFOV. Methods Three rabbits were prepared and ventilated by HFOV with carrier 70% helium/oxygen or 70% nitrogen/oxygen gas mixture with TGI in a crossover study. Changing the gas mixture from nitrogen70% to helium70% and back was performed three times per animal with constant ventilation parameters. Results Compared with the nitrogen-oxygen mixture, the helium-oxygen mixture of TGI reduced PaCO2 by 7.6 mmHg (p?

  12. Active heat exchange system development for latent heat thermal energy storage

    NASA Technical Reports Server (NTRS)

    Lefrois, R. T.; Mathur, A. K.

    1980-01-01

    Five tasks to select, design, fabricate, test and evaluate candidate active heat exchanger modules for future applications to solar and conventional utility power plants were discussed. Alternative mechanizations of active heat exchange concepts were analyzed for use with heat of fusion phase change materials (PCMs) in the temperature range of 250 to 350 C. Twenty-six heat exchange concepts were reviewed, and eight were selected for detailed assessment. Two candidates were selected for small-scale experimentation: a coated tube and shell heat exchanger and a direct contact reflux boiler. A dilute eutectic mixture of sodium nitrate and sodium hydroxide was selected as the PCM from over 50 candidate inorganic salt mixtures. Based on a salt screening process, eight major component salts were selected initially for further evaluation. The most attractive major components in the temperature range of 250 to 350 C appeared to be NaNO3, NaNO2, and NaOH. Sketches of the two active heat exchange concepts selected for test are given.

  13. Feed line-ultrasonic activated gas injection

    SciTech Connect

    Salter, J.A.; DeWitz, T.S.; Dirkse, J.W.

    1989-07-04

    This patent describes an apparatus for minimizing mass flow rate fluctuations of a particulate solids and gas mixture in the frequency range of about 0.1 to 100 Hertz transported to at least one means for injecting the mixture into a reactor. The apparatus comprises: means for receiving the mixture; means for controlling a discharge flow rate of the mixture exiting the means for receiving the mixture; means for pneumatically transporting the mixture from the means for receiving the mixture to the reactor; means for maintaining a differential pressure between the means for receiving the mixture and the reactor; and means for selectively controlling the mass flow rate of the mixture being transported from the means for receiving the mixture to the reactor including means for injecting a gas at a selected amplitude and ultrasonic frequency into a lower end of the means for receiving the mixture to form an aerated portion.

  14. Natural gas storage with activated carbon from a bituminous coal

    Microsoft Academic Search

    Jian Sun; Mark J. Rood; Massoud Rostam-Abadi; Anthony A. Lizzio

    1996-01-01

    Granular activated carbons (?20 + 100 mesh; 0.149?0.84 mm) were produced by physical activation and chemical activation with KOH from an Illinois bituminous coal (IBC-106) for natural gas storage. The products were characterized by BET surface area, micropore volume, bulk density, and methane adsorption capacities. Volumetric methane adsorption capacities (VmVs) of some of the granular carbons produced by physical activation

  15. Dynamics of Gas Exchange through the Fractal Architecture of the Human Lung, Modeled as an Exactly Solvable Hierarchical Tree

    NASA Astrophysics Data System (ADS)

    Mayo, Michael; Pfeifer, Peter; Gheorghiu, Stefan

    2008-03-01

    The acinar airways lie at the periphery of the human lung and are responsible for the transfer of oxygen from air to the blood during respiration. This transfer occurs by the diffusion-reaction of oxygen over the irregular surface of the alveolar membranes lining the acinar airways. We present an exactly solvable diffusion-reaction model on a hierarchically branched tree, allowing a quantitative prediction of the oxygen current over the entire system of acinar airways responsible for the gas exchange. We discuss the effect of diffusional screening, which is strongly coupled to oxygen transport in the human lung. We show that the oxygen current is insensitive to a loss of permeability of the alveolar membranes over a wide range of permeabilities, similar to a ``constant-current source'' in an electric network. Such fault tolerance has been observed in other treatments of the gas exchange in the lung and is obtained here as a fully analytical result.

  16. Direct-contact heat exchanger for swirling countercurrent flow of hot gas and finely divided solids: A parametric study

    NASA Astrophysics Data System (ADS)

    Bell, K. J.; Arman, B.

    1991-06-01

    A vertically oriented solid-to-gas direct-contact heat exchanger (DCHX) has been proposed for heat recovery in high temperature plants that process finely divided solids. The flows are countercurrent, with the inlet gas flow entering on the centerline and swirling strongly. Swirling enhances heat transfer and centrifuges the solid particles from the center to the wall in order to minimize entrainment and permit gravity separation. A computer program was written to calculate particle trajectories and heat transfer rates (and, therefore, temperature profiles) for gas and solid phases. The flow model considers interactions between the particles and the flow field of the gas. The results of the computer program showed that the introduction of swirl significantly reduced the vertical distance required to achieve a given thermal efficiency. The countercurrent flow arrangement achieves high thermal efficiency in one contacting stage, unlike existing cocurrent suspension preheater systems, which require four or five stages. The practical application of this design to the cement industry appears unlikely, because very low gas velocities and correspondingly large areas of cross-sectional flow are required to prevent elutriation of the 74 micron particles required for the chemical reactions. The computer program can be modified for spray-dryer applications by the addition of mass transfer terms and a spray-formation model. In addition, the concept of a swirling flow heat exchanger may be applicable to other processes in which larger and heavier particles are used.

  17. Lifetime test of a partial model of a high-temperature gas-cooled reactor helium-helium heat exchanger

    Microsoft Academic Search

    M. Kitagawa; J. Hamanaka; H. Hattori; A. Ohtomo; T. Teramae; H. Ukikusa

    1984-01-01

    A design guide for high-temperature gas-cooled reactor components is proposed and applied to the design and construction of the 1.5-MW (thermal) helium heat exchanger test loop for nuclear steelmaking. To assure that the design method covers all conceivable failure modes and has a large enough safety margin, a series of lifetime tests of partial model may be needed. For this

  18. Mass-spectrometric determination of O 2 and CO 2 gas exchange in illuminated higher-plant cells

    Microsoft Academic Search

    Marie-Hélène Avelange; Jean M. Thiéry; Frédéric Sarrey; Pierre Gans; Fabrice Rébeillé

    1991-01-01

    In order to estimate photosynthetic and respiratory rates in illuminated photoautotrophic cells of carnation (Dianthus caryophyllus L.), simultaneous measurements of CO2 and O2 gas exchange were performed using 18O2, 13CO2 and a mass-spectrometry technique. This method allowed the determination, and thus the comparison, of unidirectional fluxes of O2 and CO2. In optimum photosynthetic conditions (i.e. in the presence of high

  19. The architecture of termite mounds: a result of a trade-off between thermoregulation and gas exchange?

    Microsoft Academic Search

    Judith Korb; Karl Eduard Linsenmair

    1999-01-01

    We examined the influence of gas exchange on the architecture of termite mounds. In ComoeNational Park (Cote d'Ivoire), Macrotermes bellicosus builds, as an adaptation to ambient temperature conditions, differently shaped mounds in the shrub savanna and the gallery forest. Previous studies suggested that there might be a constraint that limits the degree of thermal insulation of the interior (i.e., nest)

  20. Leaf Water Relations and Net Gas Exchange Responses of Salinized Carrizo Citrange Seedlings during Drought Stress and Recovery

    Microsoft Academic Search

    J. G. P EREZ-PEREZ; J. P. S YV; E RT S E N; P. B OTIA; F. GA RC IA-SANCHEZ

    2007-01-01

    † Background and Aims Since salinity and drought stress can occur together, an assessment was made of their interacting effects on leaf water relations, osmotic adjustment and net gas exchange in seedlings of the relatively chloride-sensitive Carrizo citrange, Citrus sinensisPoncirus trifoliata. † Methods Plants were fertilized with nutrient solution with or without additional 100 mM NaCl (salt and no-salt treatments).

  1. Seasonal photosynthetic gas exchange and water-use efficiency in a constitutive CAM plant, the giant saguaro cactus ( Carnegiea gigantea )

    Microsoft Academic Search

    Dustin R. Bronson; Nathan B. English; David L. Dettman; David G. Williams

    Crassulacean acid metabolism (CAM) and the capacity to store large quantities of water are thought to confer high water use\\u000a efficiency (WUE) and survival of succulent plants in warm desert environments. Yet the highly variable precipitation, temperature\\u000a and humidity conditions in these environments likely have unique impacts on underlying processes regulating photosynthetic\\u000a gas exchange and WUE, limiting our ability to

  2. Variation of gas exchange within native plant species of Switzerland and relationships with ozone injury: an open-top experiment

    Microsoft Academic Search

    J Zhang; J. A Ferdinand; D. J Vanderheyden; J. M Skelly; J. L Innes

    2001-01-01

    Gas exchange and ozone-induced foliar injury were intensively measured during a 6-day period in mid-August 1998 on leaves of Acer pseudoplatanus, Betula pendula, Corylus avellana, Fagus sylvatica, Fraxinus excelsior, Morus nigra, Prunus avium, Prunus serotina, Rhamnus cathartica, and Viburnum lantana at a forest nursery site in Canton Ticino, Switzerland. Plants were grown in four open plots (AA), four open-top chambers

  3. Dose-dependent effects of almitrine on hemodynamics and gas exchange in an animal model of acute lung injury

    Microsoft Academic Search

    A. Sommerer; U. Kaisers; R. Dembinski; H. P. Bubser; K. J. Falke; R. Rossaint

    2000-01-01

    Objective: To determine the dose-response relationship of almitrine (Alm) on pulmonary gas exchange and hemodynamics in an animal model\\u000a of acute lung injury (ALI).?Design: Prospective, randomized, controlled study.?Methods: Twenty anesthetized, tracheotomized and mechanically ventilated (FIO2 1.0) pigs underwent induction of ALI by repeated saline washout of surfactant. Animals were randomly assigned to either receive\\u000a cumulating doses of Alm intravenously (0.5,

  4. Comparison of Gas Exchange and Bioassay Determinations of the Ammonia Compensation Point in Luzula sylvatica (Huds.) Gaud.1

    PubMed Central

    Hill, Paul W.; Raven, John A.; Loubet, Benjamin; Fowler, David; Sutton, Mark A.

    2001-01-01

    Determinations of the NH3 compensation point for the understory plant of semi-natural woodlands Luzula sylvatica (Huds.) Gaud. were carried out by measurements of gas exchange and by calculation from the NH4+ concentration and pH of extracts of the foliar apoplast. Compensation points determined by gas exchange measurements were among the lowest yet reported (0.51–1.10 ?g NH3 m?3) and those calculated from apoplast extracts were lower than any yet reported (0.017–0.54 ?g NH3 m?3). Those determined by gas exchange were consistently found to be between 2 and 30 times higher than those determined from apoplast extracts. Consideration of possible causes of this discrepancy, which is not confined to this investigation, showed that all likely errors would result in an increase in the discrepancy, or were insufficient to account for observed differences. It is suggested that spatial variability of pH and NH4+ concentration within the foliar apoplast represents the most promising line for further investigation. It is also shown that the foliar apoplast of L. sylvatica is sufficiently buffered to eliminate the need for correction of H+ concentration for dilution during extraction, but that it is necessary to correct the NH4+ concentration of apoplast extracts for dilution. PMID:11154355

  5. Stomatal encryption by epicuticular waxes as a plastic trait modifying gas exchange in a Mediterranean evergreen species (Quercus coccifera L.).

    PubMed

    Roth-Nebelsick, Anita; Fernández, Victoria; Peguero-Pina, José Javier; Sancho-Knapik, Domingo; Gil-Pelegrín, Eustaquio

    2013-03-01

    The adaptive benefit of stomatal crypts remains a matter of controversy. This work studies the effect on gas exchange of cuticular rims that overarch the stomatal pore in the Mediterranean species Quercus coccifera L. growing under Mediterranean (lower relative humidities and high summer temperatures) or oceanic conditions (higher daily relative humidities and mild temperatures). After microscopic assessment of the leaf surfaces and stomatal architecture, the impact of the cuticular 'cup' on gas exchange was evaluated by employing three-dimensional finite element models. Here, we provide evidence for a high plasticity of the Q.?coccifera cuticular cup, with much larger vents under oceanic conditions compared to small vents under Mediterranean conditions. This structure adds a substantial fixed resistance thereby strongly decreasing gas exchange under Mediterranean conditions. The cuticular cup, which also increases leaf internal humidity, might buffer the rapid changes in vapour pressure deficit (VPD) often observed under Mediterranean conditions. Since water loss of guard and adjacent epidermal cells regulates stomatal aperture, we suggest that this structure allows an efficient regulation of stomatal conductance and optimum use of resources under high VPD. This study provides evidence that plasticity of stomatal architecture can be an important structural component of hydraulic adaptation to different climate conditions. PMID:22897384

  6. Interruption to cutaneous gas exchange is not a likely mechanism of WNS-associated death in bats.

    PubMed

    Carey, Charleve S; Boyles, Justin G

    2015-07-01

    Pseudogymnoascus destructans is the causative fungal agent of white-nose syndrome (WNS), an emerging fungal-borne epizootic. WNS is responsible for a catastrophic decline of hibernating bats in North America, yet we have limited understanding of the physiological interactions between pathogen and host. Pseudogymnoascus destructans severely damages wings and tail membranes, by causing dryness that leads to whole sections crumbling off. Four possible mechanisms have been proposed by which infection could lead to dehydration; in this study, we tested one: P. destructans infection could cause disruption to passive gas-exchange pathways across the wing membranes, thereby causing a compensatory increase in water-intensive pulmonary respiration. We hypothesized that total evaporative water loss would be greater when passive gas exchange was inhibited. We found that bats did not lose more water when passive pathways were blocked. This study provides evidence against the proposed proximal mechanism that disruption to passive gas exchange causes dehydration and death to WNS-infected bats. PMID:25944919

  7. Effect of Adding a Regenerator to Kornhauser's MIT "Two-Space" (Gas-Spring+Heat Exchanger) Test Rig

    NASA Technical Reports Server (NTRS)

    Ebiana, Asuquo B.; Gidugu, Praveen

    2008-01-01

    This study employed entropy-based second law post-processing analysis to characterize the various thermodynamic losses inside a 3-space solution domain (gas spring+heat exchanger+regenerator) operating under conditions of oscillating pressure and oscillating flow. The 3- space solution domain is adapted from the 2-space solution domain (gas spring+heat exchanger) in Kornhauser's MIT test rig by modifying the heat exchanger space to include a porous regenerator system. A thermal nonequilibrium model which assumes that the regenerator porous matrix and gas average temperatures can differ by several degrees at a given axial location and time during the cycle is employed. An important and primary objective of this study is the development and application of a thermodynamic loss post-processor to characterize the major thermodynamic losses inside the 3-space model. It is anticipated that the experience gained from thermodynamic loss analysis of the simple 3-space model can be extrapolated to more complex systems like the Stirling engine. It is hoped that successful development of loss post-processors will facilitate the improvement of the optimization capability of Stirling engine analysis codes through better understanding of the heat transfer and power losses. It is also anticipated that the incorporation of a successful thermal nonequilibrium model of the regenerator in Stirling engine CFD analysis codes, will improve our ability to accurately model Stirling regenerators relative to current multidimensional thermal-equilibrium porous media models.

  8. Effects of boron deficiency on major metabolites, key enzymes and gas exchange in leaves and roots of Citrus sinensis seedlings.

    PubMed

    Lu, Yi-Bin; Yang, Lin-Tong; Li, Yan; Xu, Jing; Liao, Tian-Tai; Chen, Yan-Bin; Chen, Li-Song

    2014-06-01

    Boron (B) deficiency is a widespread problem in many crops, including Citrus. The effects of B-deficiency on gas exchange, carbohydrates, organic acids, amino acids, total soluble proteins and phenolics, and the activities of key enzymes involved in organic acid and amino acid metabolism in 'Xuegan' [Citrus sinensis (L.) Osbeck] leaves and roots were investigated. Boron-deficient leaves displayed excessive accumulation of nonstructural carbohydrates and much lower CO2 assimilation, demonstrating feedback inhibition of photosynthesis. Dark respiration, concentrations of most organic acids [i.e., malate, citrate, oxaloacetate (OAA), pyruvate and phosphoenolpyruvate] and activities of enzymes [i.e., phosphoenolpyruvate carboxylase (PEPC), NAD-malate dehydrogenase, NAD-malic enzyme (NAD-ME), NADP-ME, pyruvate kinase (PK), phosphoenolpyruvate phosphatase (PEPP), citrate synthase (CS), aconitase (ACO), NADP-isocitrate dehydrogenase (NADP-IDH) and hexokinase] involved in glycolysis, the tricarboxylic acid (TCA) cycle and the anapleurotic reaction were higher in B-deficient leaves than in controls. Also, total free amino acid (TFAA) concentration and related enzyme [i.e., NADH-dependent glutamate 2-oxoglutarate aminotransferase (NADH-GOGAT) and glutamate OAA transaminase (GOT)] activities were enhanced in B-deficient leaves. By contrast, respiration, concentrations of nonstructural carbohydrates and three organic acids (malate, citrate and pyruvate), and activities of most enzymes [i.e., PEPC, NADP-ME, PK, PEPP, CS, ACO, NAD-isocitrate dehydrogenase, NADP-IDH and hexokinase] involved in glycolysis, the TCA cycle and the anapleurotic reaction, as well as concentration of TFAA and activities of related enzymes (i.e., nitrate reductase, NADH-GOGAT, glutamate pyruvate transaminase and glutamine synthetase) were lower in B-deficient roots than in controls. Interestingly, leaf and root concentration of total phenolics increased, whereas that of total soluble protein decreased, in response to B-deficiency. In conclusion, respiration, organic acid (i.e., glycolysis and the TCA cycle) metabolism, the anapleurotic pathway and amino acid biosynthesis were upregulated in B-deficient leaves with excessive accumulation of carbohydrates to 'consume' the excessive carbon available, but downregulated in B-deficient roots with less accumulation of carbohydrates to maintain the net carbon balance. PMID:24957048

  9. The Effect of Experimentally Induced Root Mortality on Trace Gas Exchange

    NASA Astrophysics Data System (ADS)

    Varner, R. K.; Keller, M.; Robertson, J. R.; Dias, J. D.; Silva, H.; Crill, P. M.; McGroddy, M.; Silver, W. L.

    2002-12-01

    Soil-atmosphere exchange of carbon dioxide (CO2), nitric oxide (NO), nitrous oxide (N2O) and methane (CH4) was measured following a root exclusion experiment in the Tapajos National Forest near Santarem, Para, Brazil. The sampling period (June 4 - August 14, 2000) coincided with the beginning of the dry season. The experiment was set up as a randomized complete block design with 5 pairs of 2.5 x 2.5 m plots in both sand and clay soils. Trenches were dug around one plot in each pair for screen installation. Trace gas fluxes were measured weekly for ten weeks following the trenching. Duplicate flux measurements were made for each of the trenched and non-trenched plots. Enclosures made of 0.25 m diameter PVC pipe were placed on a base imbedded in the soil. Dynamic measurements using a portable backpack system equipped with an NO2 chemiluminescent detector for NO and an infrared gas analyzer for CO2 were completed in the field. CH4 and N2O fluxes were measured through a static enclosure method. Syringe samples of the enclosure headspace were analyzed by GC-FID (CH4) and ECD (N2O) the following day. Daily average fluxes ranged between -0.01 and 60.3 ng-N cm-2 hr-1 for N2O. NO fluxes ranged between 0.58 and 8.74 ng-N cm-2 hr-1. CH4 fluxes varied between net consumption and production from -1.73 to 0.912 mg m-2 d-1. Soil respiration ranged from 1.34 to 5.12 umoles CO2 m-2 s-1. Significant differences were seen between trenched and non-trenched plots in both clay and sand soils for N2O emissions only. Hourly field standardization of the NO2 chemiluminescent analyzer resulted in lower variability than the traditional method of standardization which is completed at the beginning and end of the measurement day. Frequent field standardization of the analyzer is necessary to reduce measurement error due to intra-day variability.

  10. An Activity Theory Exegesis on Conflict and Contradictions in Networked Discussions and Feedback Exchanges

    ERIC Educational Resources Information Center

    Hadjistassou, Stella K.

    2012-01-01

    The goal of this study was to investigate the culturally afforded contradictions that ten advanced English as a Second Language (ESL) learner encountered when they posted their paper topics and exchanged feedback strategies online and contextualized some of these strategies to draft their papers. Using Cultural-Historical Activity Theory (CHAT),…

  11. ARSENIC REMOVAL BY FULL SCALE ION EXCHANGE AND ACTIVATED ALUMINA TREATMENT

    EPA Science Inventory

    This presentation discusses the results of a one year performance evaluation study of two ion exchange plants and two activated alumina plants that were designed and operated for the removal of arsenic from well water. All the plants were shown to be capable of reducing arsenic l...

  12. ARSENIC REMOVAL FROM DRINKING WATER BY ACTIVATED ALUMINA AND ANION EXCHANGE TREATMENT

    EPA Science Inventory

    This paper discusses the results of a one year performance evaluation study of two full scale ion exchange plants and two full scale activated alumina plant that were designed and operated for the removal of arsenic from well water. All the plants were shown to be capable of red...

  13. Active heat exchange system development for latent heat thermal energy storage

    NASA Technical Reports Server (NTRS)

    Lefrois, R. T.; Knowles, G. R.; Mathur, A. K.; Budimir, J.

    1979-01-01

    Active heat exchange concepts for use with thermal energy storage systems in the temperature range of 250 C to 350 C, using the heat of fusion of molten salts for storing thermal energy are described. Salt mixtures that freeze and melt in appropriate ranges are identified and are evaluated for physico-chemical, economic, corrosive and safety characteristics. Eight active heat exchange concepts for heat transfer during solidification are conceived and conceptually designed for use with selected storage media. The concepts are analyzed for their scalability, maintenance, safety, technological development and costs. A model for estimating and scaling storage system costs is developed and is used for economic evaluation of salt mixtures and heat exchange concepts for a large scale application. The importance of comparing salts and heat exchange concepts on a total system cost basis, rather than the component cost basis alone, is pointed out. The heat exchange concepts were sized and compared for 6.5 MPa/281 C steam conditions and a 1000 MW(t) heat rate for six hours. A cost sensitivity analysis for other design conditions is also carried out.

  14. Combined low temperature-high light effects on gas exchange properties of jojoba leaves.

    PubMed

    Loreto, F; Bongi, G

    1989-12-01

    Jojoba (Simmondsia chinensis [Link] Schneider) is an important crop in desert climates. A relatively high frequency of periods of chilling and high photon flux density (PFD) in this environment makes photoinhibition likely, resulting in a reduction of assimilation capacity in overwintering leaves. This could explain the low net photosynthesis found in shoots from the field (4-6 micromoles per square meter per second) when compared to greenhouse grown plants (12-15 micromoles per square meter per second). The responses of photosynthesis and stomatal conductance to changes in absorbed PFD and in substomatal partial pressure of CO(2) were measured on jojoba leaves recovering from chilling temperature (4 degrees C) in high or low PFD. No measurable gas exchange was found immediately after chilling in either high or low PFD. For leaves chilled in low PFD, the original quantum yield was restored after 24 hours. The time course of recovery from chilling in high PFD was much longer. Quantum yield recovered to 60% of its original value in 72 hours but failed to recover fully after 1 week. Measurements of PSII chlorophyll fluorescence at 77 K showed that the reduced quantum yield was caused by photoinhibition. The ratio of variable to maximal fluorescence fell from a control level of 0.82 to 0.41 after the photoinhibitory treatment and recovery was slow. We also found a large increase in net assimilation rate and little closure of stomata as CO(2) was increased from ambient partial pressure of 35 to 85 pascals. For plants grown in full light, the increase in net assimilation rate was 100%. The photosynthetic response at high CO(2) concentration may constitute an ecological advantage of jojoba as a crop in the future. PMID:16667220

  15. Influence of exercise modality on agreement between gas exchange and heart rate variability thresholds

    PubMed Central

    Cunha, F.A.; Montenegro, R.A.; Midgley, A.W.; Vasconcellos, F.; Soares, P.P.; Farinatti, P.

    2014-01-01

    The main purpose of this study was to investigate the level of agreement between the gas exchange threshold (GET) and heart rate variability threshold (HRVT) during maximal cardiopulmonary exercise testing (CPET) using three different exercise modalities. A further aim was to establish whether there was a 1:1 relationship between the percentage heart rate reserve (%HRR) and percentage oxygen uptake reserve (%V?O2?R) at intensities corresponding to GET and HRVT. Sixteen apparently healthy men 17 to 28 years of age performed three maximal CPETs (cycling, walking, and running). Mean heart rate and V?O2 at GET and HRVT were 16 bpm (P<0.001) and 5.2 mL·kg-1·min-1 (P=0.001) higher in running than cycling, but no significant differences were observed between running and walking, or cycling and walking (P>0.05). There was a strong relationship between GET and HRVT, with R2 ranging from 0.69 to 0.90. A 1:1 relationship between %HRR and %V?O2?R was not observed at GET and HRVT. The %HRR was higher during cycling (GET mean difference=7%; HRVT mean difference=11%; both P<0.001), walking (GET mean difference=13%; HRVT mean difference=13%; both P<0.001), or running (GET mean difference=11%; HRVT mean difference=10%; both P<0.001). Therefore, using HRVT to prescribe aerobic exercise intensity appears to be valid. However, to assume a 1:1 relationship between %HRR and %V?O2?R at HRVT would probably result in overestimation of the energy expenditure during the bout of exercise. PMID:25003546

  16. Effects of long-term low atmospheric pressure on gas exchange and growth of lettuce

    NASA Astrophysics Data System (ADS)

    Tang, Yongkang; Guo, Shuangsheng; Dong, Wenping; Qin, Lifeng; Ai, Weidang; Lin, Shan

    2010-09-01

    The objectives of this research were to determine photosynthesis, evapotranspiration and growth of lettuce at long-term low atmospheric pressure. Lettuce ( Lactuca sativa L . cv. Youmaicai) plants were grown at 40 kPa total pressure (8.4 kPa p) or 101 kPa total pressure (20.9 kPa p) from seed to harvest for 35 days. Germination rate of lettuce seeds decreased by 7.6% at low pressure, although this was not significant. There was no significant difference in crop photosynthetic rate between hypobaria and ambient pressure during the 35-day study. The crop evapotranspiration rate was significantly lower at low pressure than that at ambient pressure from 20 to 30 days after planting (DAP), but it had no significant difference before 20 DAP or after 30 DAP. The growth cycle of lettuce plants at low pressure was delayed. At low pressure, lettuce leaves were curly at the seedling stage and this disappeared gradually as the plants grew. Ambient lettuce plants were yellow and had an epinastic growth at harvest. The shoot height, leaf number, leaf length and shoot/root ratio were lower at low pressure than those at ambient pressure, while leaf area and root growth increased. Total biomass of lettuce plants grown at two pressures had no significant difference. Ethylene production at low pressure decreased significantly by 38.8% compared with ambient pressure. There was no significant difference in microelements, nutritional phytochemicals and nitrate concentrations at the two treatments. This research shows that lettuce can be grown at long-term low pressure (40 kPa) without significant adverse effects on seed germination, gas exchange and plant growth. Furthermore, ethylene release was reduced in hypobaria.

  17. Association between tree-ring and needle delta13C and leaf gas exchange in Pinus halepensis under semi-arid conditions.

    PubMed

    Klein, Tamir; Hemming, Deborah; Lin, Tongbao; Grünzweig, José M; Maseyk, Kadmiel; Rotenberg, Eyal; Yakir, Dan

    2005-06-01

    Associations between delta13C values and leaf gas exchanges and tree-ring or needle growth, used in ecophysiological compositions, can be complex depending on the relative timing of CO2 uptake and subsequent redistribution and allocation of carbon to needle and stem components. For palaeoenvironmental and dendroecological studies it is often interpreted in terms of a simple model of delta13C fractionation in C3 plants. However, in spite of potential complicating factors, few studies have actually examined these relationships in mature trees over inter- and intra-annual time-scales. Here, we present results from a 4 years study that investigated the links between variations in leaf gas-exchange properties, growth, and dated delta13C values along the needles and across tree rings of Aleppo pine trees growing in a semi-arid region under natural conditions or with supplemental summer irrigation. Sub-sections of tissue across annual rings and along needles, for which time of formation was resolved from growth rate analyses, showed rapid growth and delta13C responses to changing environmental conditions. Seasonal cycles of growth and delta13C (up to approximately 4 per thousand) significantly correlated (P < 0.01) with photosynthetically active radiation, vapour pressure deficit, air temperature, and soil water content. The irrigation significantly increased leaf net assimilation, stomatal conductance and needle and tree-ring growth rate, and markedly decreased needle and tree-ring delta13C values and its sensitivity to environmental parameters. The delta13C estimates derived from gas-exchange parameters, and weighted by assimilation, compared closely with seasonal and inter-annual delta13C values of needle- and tree-ring tissue. Higher stomatal conductances of the irrigated trees (0.22 vs. 0.08 mol m(-2) s(-1) on average) corresponded with approximately 2.0 per thousand lower average delta13C values, both measured and derived. Derived and measured delta13C values also indicated that needle growth, which occurs throughout the stressful summer was supported by carbon from concurrent, low rate assimilation. For Aleppo pine under semi-arid and irrigated conditions, the delta13C of tree-ring and needle material proved, in general, to be a reasonable indicator of integrated leaf gas-exchange properties. PMID:15868163

  18. Feasibility study on the applicability of a diffusion-welded compact intermediate heat exchanger to next-generation high temperature gas-cooled reactor

    Microsoft Academic Search

    Takeshi Takeda; Kazuhiko Kunitomi; Tetsuji Horie; Katsuo Iwata

    1997-01-01

    The development of an intermediate heat exchanger (IHX) transferring high temperature heat to a process heat application is of prime importance for a next-generation high temperature gas-cooled reactor (HTGR). The IHX needs high structural integrity and reliability over 900°C for a long duration. A plate fin type compact heat exchanger (PFCHX) has a large heat transfer area per heat exchanger

  19. The impact of oil prices, real effective exchange rate and inflation on economic activity: Novel evidence for Vietnam

    Microsoft Academic Search

    Le Viet Trung; Nguyen Thi Thuy Vinh

    2011-01-01

    The goal of this paper is to examine the impact of oil prices on Vietnam's economic activity using vector autoregressive (VAR) modeling and cointegration techniques. We use monthly data for the period 1995-2009 and include inflation and the real effective exchange rate as additional determinants of economic activity. We find evidence of a long-run relationship between oil prices, inflation, exchange

  20. Effects of atenolol, slow-release nifedipine, and their combination on respiratory gas exchange and exercise tolerance in stable effort angina

    Microsoft Academic Search

    S. Wieshammer; M. Hetzel; U. Barnikel; M. Höher; H. Seibold; M. Kochs; V. Hombach

    1991-01-01

    Summary The effects of atenolol, nifedipine, and their combination on gas exchange and exercise tolerance were studied in 27 patients with effort angina and normal global ventricular function in an open-label and randomized cross-over trial. Symptom-limited semi-supine exercise tests using a ramp protocol (20 W\\/min) with simultaneous breath-by-breath analysis of gas exchange were carried out after a 4-day wash-out period

  1. Calcium Activities During Different Ion Exchange Separation Procedures

    NASA Astrophysics Data System (ADS)

    Zhang, Z.; Zhu, H.; Liu, Y.; Liu, F.; Zhang, C.; Sun, W.

    2014-12-01

    Calcium is a major element and participates in many geological processes. Investigations on stable calcium isotopic compositions of natural geological samples provide a great powerful tool to understand all kinds of those geological processes from a view of the field of isotope geochemistry. With the development of modern instruments and chemical separation techniques, calcium isotopic compositions could be determined even more precisely if the column chemistry brings no deviation. Usually, Calcium is separated from matrix elements using cation resin columns and the related chemical separation techniques seem to be robust. However, more detailed work still need to be done on matrix effects and calcium isotopic fractionations on column chemistry or during elution processes. If calcium is run on TIMS instruments, the interference effect could be lower and easier controlled, thus, the requirement to the chemistry is relatively not critic, but calcium fractionation on filaments could be much difficult to monitor. If calcium is run on MC-ICP-MS instruments, the interference effect could be huge and is really difficult to be recognized and subtracted, the requirement to the chemistry is much more critical in order to get a real result of the sample, but the instrument fractionation could be easier to monitor. Here we investigate calcium activities on several kinds of cation resins under different column/acid conditions. We seek to find a good balance between recovery and interference effect on column chemistry and are intend to set up a better chemical separation procedure to satisfy the instrument requirements for calcium. In addition, Calcium isotopic fractionation on column will also be discussed further here based on our previous and ongoing results.

  2. Visualization and void fraction measurement of gas-liquid two-phase flow in plate heat exchanger.

    PubMed

    Asano, H; Takenaka, N; Fujii, T; Maeda, N

    2004-10-01

    Adiabatic and boiling gas-liquid two-phase flows in a simulated plate heat exchanger with a single-ribbed channel were visualized by a thermal neutron radiography method. In the experiments under adiabatic condition, the air-water two-phase flows in an aluminum test section were visualized. In the boiling two-phase flow experiments, chlorofluorocarbon R141b was used as the working fluid. Two-dimensional distributions of void fraction were measured from visualized images via some image processing techniques. As a result, it was shown that both the phases tended to flow straight in the ribbed channel, and mixing of gas and liquid phases was weak. Moreover, when working fluids flew into the test section as a gas-liquid mixture, the phase distributions were strongly affected by a liquid pool at the test section inlet. PMID:15246421

  3. Water relations and gas exchange of fan bryophytes and their adaptations to microhabitats in an Asian subtropical montane cloud forest.

    PubMed

    Song, Liang; Zhang, Yong-Jiang; Chen, Xi; Li, Su; Lu, Hua-Zheng; Wu, Chuan-Sheng; Tan, Zheng-Hong; Liu, Wen-Yao; Shi, Xian-Meng

    2015-07-01

    Fan life forms are bryophytes with shoots rising from vertical substratum that branch repeatedly in the horizontal plane to form flattened photosynthetic surfaces, which are well suited for intercepting water from moving air. However, detailed water relations, gas exchange characteristics of fan bryophytes and their adaptations to particular microhabitats remain poorly understood. In this study, we measured and analyzed microclimatic data, as well as water release curves, pressure-volume relationships and photosynthetic water and light response curves for three common fan bryophytes in an Asian subtropical montane cloud forest (SMCF). Results demonstrate high relative humidity but low light levels and temperatures in the understory, and a strong effect of fog on water availability for bryophytes in the SMCF. The facts that fan bryophytes in dry air lose most of their free water within 1 h, and a strong dependence of net photosynthesis rates on water content, imply that the transition from a hydrated, photosynthetically active state to a dry, inactive state is rapid. In addition, fan bryophytes developed relatively high cell wall elasticity and the osmoregulatory capacity to tolerate desiccation. These fan bryophytes had low light saturation and compensation point of photosynthesis, indicating shade tolerance. It is likely that fan bryophytes can flourish on tree trunks in the SMCF because of substantial annual precipitation, average relative humidity, and frequent and persistent fog, which can provide continual water sources for them to intercept. Nevertheless, the low water retention capacity and strong dependence of net photosynthesis on water content of fan bryophytes indicate a high risk of unbalanced carbon budget if the frequency and severity of drought increase in the future as predicted. PMID:25813755

  4. Dynamic C and N stocks - key factors controlling the C gas exchange of maize in a heterogenous peatland

    NASA Astrophysics Data System (ADS)

    Pohl, M.; Hoffmann, M.; Hagemann, U.; Giebels, M.; Albiac Borraz, E.; Sommer, M.; Augustin, J.

    2014-11-01

    Drainage and cultivation of fen peatlands creates complex small-scale mosaics of soils with extremely variable soil organic carbon (SOC) stocks and groundwater-level (GWL). To date, it remains unclear if such sites are sources or sinks for greenhouse gases like CO2 and CH4, especially if used for cropland. As individual control factors like GWL fail to account for this complexity, holistic approaches combining gas fluxes with the underlying processes are required to understand the carbon (C) gas exchange of drained fens. It can be assumed that the stocks of SOC and N located above the variable GWL - defined as dynamic C and N stocks - play a key role in the regulation of plant- and microbially mediated C gas fluxes of these soils. To test this assumption, the present study analysed the C gas exchange (gross primary production - GPP, ecosystem respiration - Reco, net ecosystem exchange - NEE, CH4) of maize using manual chambers for four years. The study sites were located near Paulinenaue, Germany. Here we selected three soils, which represent the full gradient in pedogenesis, GWL and SOC stocks (0-1 m) of the fen peatland: (a) Haplic Arenosol (AR; 8 kg C m-2); (b) Mollic Gleysol (GL; 38 kg C m-2); and (c) Hemic Histosol (HS; 87 kg C m-2). Daily GWL data was used to calculate dynamic SOC (SOCdyn) and N (Ndyn) stocks. Average annual NEE differed considerably among sites, ranging from 47 ± 30 g C m-2 a-1 at AR to -305 ± 123 g C m-2 a-1 at GL and -127 ± 212 g C m-2 a-1 at HS. While static SOC and N stocks showed no significant effect on C fluxes, SOCdyn and Ndyn and their interaction with GWL strongly influenced the C gas exchange, particularly NEE and the GPP:Reco ratio. Moreover, based on nonlinear regression analysis, 86% of NEE variability was explained by GWL and SOCdyn. The observed high relevance of dynamic SOC and N stocks in the aerobic zone for plant and soil gas exchange likely originates from the effects of GWL-dependent N availability on C formation and transformation processes in the plant-soil system, which promote CO2 input via GPP more than CO2 emission via Reco. The process-oriented approach of dynamic C and N stocks is a promising, potentially generalizable method for system-oriented investigations of the C gas exchange of groundwater-influenced soils and could be expanded to other nutrients and soil characteristics. However, in order to assess the climate impact of arable sites on drained peatlands, it is always necessary to consider the entire range of groundwater-influenced mineral and organic soils and their respective areal extent within the soil landscape.

  5. Sustainable production of acrylic acid: alkali-ion exchanged beta zeolite for gas-phase dehydration of lactic acid.

    PubMed

    Yan, Bo; Tao, Li-Zhi; Liang, Yu; Xu, Bo-Qing

    2014-06-01

    Gas-phase dehydration of lactic acid (LA) to acrylic acid (AA) was investigated over alkali-exchanged ? zeolite (M(x)Na(1-x)?, M=Li(+), K(+), Rb(+), or Cs(+)) of different exchange degrees (x). The reaction was conducted under varying conditions to understand the catalyst selectivity for AA production and trends of byproduct formation. The nature and exchange degree of M(+) were found to be critical for the acid-base properties and catalytic performance of the exchanged zeolite. K(x)Na(1-x)? of x=0.94 appeared to be the best performing catalyst whereas Li(x)Na(1-x)? and Na? were the poorest in terms of AA selectivity and yield. The AA yield as high as 61?mol?% (selectivity: 64?mol?%) could be obtained under optimized reaction conditions for up to 8?h over the best performing K0.94Na0.06?. The acid and base properties of the catalysts were probed, respectively by temperature-programmed desorption (TPD) of adsorbed NH3 and CO2, and were related to the electrostatic potentials of the alkali ions in the zeolite, which provided a basis for the discussion of the acid-base catalysis for sustainable AA formation from LA. PMID:24903259

  6. Hyperpolarized Xenon-129 Gas-Exchange Imaging of Lung Microstructure: First Case Studies in Subjects with Obstructive Lung Disease

    PubMed Central

    Dregely, Isabel; Mugler, John P.; Ruset, Iulian C.; Altes, Talissa A.; Mata, Jaime F.; Miller, G. Wilson; Ketel, Jeffrey; Ketel, Steve; Distelbrink, Jan; Hersman, F.W.; Ruppert, Kai

    2011-01-01

    Purpose To develop and test a method to non-invasively assess the functional lung microstructure. Materials and Methods The Multiple exchange time Xenon polarization Transfer Contrast technique (MXTC) encodes xenon gas-exchange contrast at multiple delay times permitting two lung-function parameters to be derived: 1) MXTC-F, the long exchange-time depolarization value, which is proportional to the tissue to alveolar-volume ratio and 2) MXTC-S, the square root of the xenon exchange-time constant, which characterizes thickness and composition of alveolar septa. Three healthy volunteers, one asthmatic and two COPD (GOLD stage I and II) subjects were imaged with MXTC MRI. In a subset of subjects, hyperpolarized xenon-129 ADC MRI and CT imaging were also performed. Results The MXTC-S parameter was found to be elevated in subjects with lung disease (p-value = 0.018). In the MXTC-F parameter map it was feasible to identify regional loss of functional tissue in a COPD patient. Further, the MXTC-F map showed excellent regional correlation with CT and ADC (? ? 0.90) in one COPD subject. Conclusion The functional tissue-density parameter MXTC-F showed regional agreement with other imaging techniques. The newly developed parameter MXTC-S, which characterizes the functional thickness of alveolar septa, has potential as a novel biomarker for regional parenchymal inflammation or thickening. PMID:21509861

  7. Gas exchange characteristics of Populus trichocarpa, Populus deltoides and Populus trichocarpa x P. deltoides clones.

    PubMed

    Bassman, J H; Zwier, J C

    1991-03-01

    Responses of net photosynthesis, dark respiration, photorespiration, transpiration, and stomatal conductance to irradiance, temperature, leaf-to-air vapor density difference (VDD), and plant water stress were examined in two Populus trichocarpa clones (one from a moist, coastal climate in western Washington and one from a dry, continental climate in eastern Washington), one P. deltoides clone, and two P. trichocarpa x P. deltoides clones. Light saturation of photosynthesis in greenhouse-grown trees occurred at about 800 micromol m(-2) s(-1) for P. deltoides, P. trichocarpa x P. deltoides, and the eastern Washington ecotype of P. trichocarpa, but at about 600 micromol m(-2) s(-1) for the western Washington ecotype of P. trichocarpa. Average net photosynthesis (at saturating irradiance and the optimum temperature of 25 degrees C) was 20.7, 18.8, 18.2 and 13.4 micromol CO(2) m(-2) s(-1) for P. deltoides, P. trichocarpa x P. deltoides, and the eastern and western Washington clones of P. trichocarpa, respectively. In all clones, net photosynthesis decreased about 14% as VDD increased from 3 to 18 g H(2)O m(-3). Stomatal conductance decreased sharply with decreasing xylem pressure potential (XPP) in all clones except the western Washington clone of P. trichocarpa. Stomata in this clone were insensitive to changes in XPP and did not control water loss. Complete stomatal closure (stomatal conductance < 0.05 cm s(-1)) occurred at about -2.0 MPa in the eastern Washington clone of P. trichocarpa and around -1.25 MPa in the P. deltoides and P. trichocarpa x P. deltoides clones. Transpiration rates were highest in the P. trichocarpa x P. deltoides clone and lowest in the western Washington clone of P. trichocarpa. The P. deltoides clone and eastern Washington clone of P. trichocarpa had the highest water use efficiency (WUE) and the western Washington clone of P. trichocarpa had the lowest WUE. The hybrids were intermediate. It was concluded that: (1) gas exchange characteristics of eastern and western Washington clones of P. trichocarpa reflected adaptation to their native environment; (2) crossing the western Washington clone of P. trichocarpa with the more drought resistant P. deltoides clone produced plants better adapted to the interior Pacific Northwest climate, although the stomatal response to soil water deficits in the hybrid was conservative compared with that of the eastern Washington clone of P. trichocarpa; and (3) introducing eastern Washington clones of black cottonwood into breeding programs is likely to yield lines with favorable growth characteristics combined with enhanced WUE and adaptation to soil water deficits. PMID:14972886

  8. Investigation of the effect of intra-molecular interactions on the gas-phase conformation of peptides as probed by ion mobility-mass spectrometry, gas-phase hydrogen/deuterium exchange, and molecular mechanics 

    E-print Network

    Sawyer, Holly Ann

    2006-04-12

    Ion mobility-mass spectrometry (IM-MS), gas-phase hydrogen/deuterium (H/D) exchange ion molecule reactions and molecular modeling provide complimentary information and are used here for the characterization of peptide ion structure, including fine...

  9. Soil-atmosphere trace gas exchange from tropical oil palm plantations on peat

    NASA Astrophysics Data System (ADS)

    Arn Teh, Yit; Manning, Frances; Zin Zawawi, Norliyana; Hill, Timothy; Chocholek, Melanie; Khoon Kho, Lip

    2015-04-01

    Oil palm is the largest agricultural crop in the tropics, accounting for 13 % of all tropical land cover. Due to its large areal extent, oil palm cultivation may have important implications not only for terrestrial stores of C and N, but may also impact regional and global exchanges of material and energy, including fluxes of trace gases and water vapor. In particular, recent expansion of oil palm into tropical peatlands has raised concerns over enhanced soil C emissions from degradation of peat, and elevated N-gas fluxes linked to N fertilizer application. Here we report our preliminary findings on soil carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) fluxes from a long-term, multi-scale project investigating the C, N and greenhouse gas (GHG) dynamics of oil palm ecosystems established on peat soils in Sarawak, Malaysian Borneo. Flux chamber measurements indicate that soil CO2, CH4 and N2O fluxes averaged 20.0 ± 16.0 Mg CO2-C ha-1 yr-1, 37.4 ± 29.9 kg CH4-C ha-1 yr-1 and 4.7 ± 4.2 g N2O-N ha-1 yr-1, respectively. Soil CO2 fluxes were on par with other drained tropical peatlands; whereas CH4 fluxes exceeded observations from similar study sites elsewhere. Nitrous oxide fluxes were in a similar range to fluxes from other drained tropical peatlands, but lower than emissions from mineral-soil plantations by up to three orders of magnitude. Fluxes of soil CO2 and N2O were spatially stratified, and contingent upon the distribution of plants, deposited harvest residues, and soil moisture. Soil CO2 fluxes were most heavily influenced by the distribution of palms and their roots. On average, autotrophic (root) respiration accounted for approximately 78 % of total soil CO2 flux, and total soil respiration declined steeply away from palms; e.g. soil CO2 fluxes in the immediate 1 m radius around palms were up to 6 times greater than fluxes in inter-palm spaces due to higher densities of roots. Placement of harvest residues played an important - but secondary - role in modulating soil CO2 fluxes; soil respiration rates doubled in areas where harvest residues were deposited, reflecting an enhanced input of labile organic matter for decomposition. In contrast, N2O fluxes were best-predicted by the distribution of harvest residues, and were only weakly related to plant distributions or soil moisture. For example, N2O fluxes from harvest residue piles were up to twice of the overall plot-average. In contrast, N2O fluxes showed no clear pattern around palms or in inter-palm spaces; this finding is surprising because N fertilizers are applied within the 1 m radius around palms, and we expected to observe enhanced N2O fluxes in areas of greater fertilizer input. This suggests that palms may be a strong competitor for N in these ecosystems, and that fertilizer application may more closely match overall plant demand than in mineral-soil plantations. Overall, the spatial patterning of soil CO2 and N2O fluxes implies that soil biogeochemical processes are predictably distributed in space, potentially making it easier to model and constrain fluxes of these soil-derived GHGs.

  10. Electron self-exchange activation parameters of diethyl sulfide and tetrahydrothiophene

    PubMed Central

    Vogtherr, Martin

    2013-01-01

    Summary Electron transfer between the title compounds and their radical cations, which were generated by photoinduced electron transfer from the sulfides to excited 2,4,6-triphenylpyrylium cations, was investigated by time-resolved measurements of chemically induced dynamic nuclear polarization (CIDNP) in acetonitrile. The strongly negative activation entropies provide evidence for an associative–dissociative electron exchange involving dimeric radical cations. Despite this mechanistic complication, the free energies of activation were found to be well reproduced by the Marcus theory of electron transfer, with the activation barrier still dominated by solvent reorganization. PMID:23946842

  11. Measuring air-sea gas-exchange velocities in a large-scale annular wind-wave tank

    NASA Astrophysics Data System (ADS)

    Mesarchaki, E.; Kräuter, C.; Krall, K. E.; Bopp, M.; Helleis, F.; Williams, J.; Jähne, B.

    2015-01-01

    In this study we present gas-exchange measurements conducted in a large-scale wind-wave tank. Fourteen chemical species spanning a wide range of solubility (dimensionless solubility, ? = 0.4 to 5470) and diffusivity (Schmidt number in water, Scw = 594 to 1194) were examined under various turbulent (u10 = 0.73 to 13.2 m s-1) conditions. Additional experiments were performed under different surfactant modulated (two different concentration levels of Triton X-100) surface states. This paper details the complete methodology, experimental procedure and instrumentation used to derive the total transfer velocity for all examined tracers. The results presented here demonstrate the efficacy of the proposed method, and the derived gas-exchange velocities are shown to be comparable to previous investigations. The gas transfer behaviour is exemplified by contrasting two species at the two solubility extremes, namely nitrous oxide (N2O) and methanol (CH3OH). Interestingly, a strong transfer velocity reduction (up to a factor of 3) was observed for the relatively insoluble N2O under a surfactant covered water surface. In contrast, the surfactant effect for CH3OH, the high solubility tracer, was significantly weaker.

  12. You can use a mobile device to access your Exchange account. On this page you will find the settings ActiveSync/Exchange to set up your Apple mobile devices.

    E-print Network

    Qiu, Weigang

    the settings ActiveSync/Exchange to set up your Apple mobile devices. If you set up an Exchange/ActiveSync account on your Apple device, the information you sync includes e-mail messages, calendars, contacts and task data! Use these settings to access your Exchange e-mail on an Apple mobile device: Username

  13. Trace gas exchange above the floor of a deciduous forest. 1. Evaporation and CO sub 2 efflux

    SciTech Connect

    Baldocchi, D.D.; Meyers, T.P. (NOAA Atmospheric Turbulence and Diffusion Division, Oak Ridge, TN (USA))

    1991-04-20

    The eddy correlation method has great potential for directly measuring trace gas fluxes at the floor of a forest canopy, but a thorough validation study has not been yet conducted. Another appeal of the eddy correlation method is its ability to study processes that regulate and modulate gas exchange between the soil/litter complex and the atmosphere that cannot be probed with chambers. In this paper, the authors report on eddy correlation measurements of water vapor, sensible heat, and carbon dioxide exchange that were made at the floor of a deciduous forest. The validity of the eddy correlation method to measure the emission of water vapor and CO{sub 2} from a deciduous forest floor is demonstrated by the ability to close the surface energy budget during periods that meet the requirements of the technique. Water vapor fluxes from a dry forest floor are strongly influenced by large-scale turbulent events that penetrate deep into the canopy. The frequency of these turbulent events prevents equilibrium evaporation rates from being achieved because the dynamic time constant for water vapor exchange is longer. Consequently, maximal evaporation rates are capped to rates defined by the product of the driving potential of the atmosphere and the surface conductance. On the other hand, evaporation from a wet forest floor proceeds at rates reaching or exceeding equilibrium evaporation and are highly correlated with static pressure fluctuations. CO{sub 2} efflux rates are governed by litter and soil temperature, as expected. But the authors also find a significant correlation between static pressure fluctuations and soil/litter CO{sub 2} exchange rates.

  14. Kinetic approach to evaluate the energy and entropy of activation for the exchange of alkaline earth metal ions on tin(IV) tungstate cation exchanger

    SciTech Connect

    Varshney, K.G.; Khan, A.A.; Varshney, K.; Agrawal, S.

    1984-01-01

    A new approach based on the Nernst-Planck equations has been applied to study the reaction kinetics on the surface of tin(IV) tungstate for the Mg(II)-H(I), Ca(II)-H(I), Sr(II)-H(I) and Ba(II)-H(I) exchanges under the conditions favouring a particle diffusion phenomenon. On the basis of these studies the various physical parameters such as the effective diffusion coefficients, activation energies and entropies of activation have been evaluated which give some informations regarding the mechanism of ion-exchange on the surface of inorganic materials. 25 references, 3 figures, 3 tables.

  15. Oxygen-limited thermal tolerance is seen in a plastron-breathing insect and can be induced in a bimodal gas exchanger.

    PubMed

    Verberk, Wilco C E P; Bilton, David T

    2015-07-01

    Thermal tolerance has been hypothesized to result from a mismatch between oxygen supply and demand. However, the generality of this hypothesis has been challenged by studies on various animal groups, including air-breathing adult insects. Recently, comparisons across taxa have suggested that differences in gas exchange mechanisms could reconcile the discrepancies found in previous studies. Here, we test this suggestion by comparing the behaviour of related insect taxa with different gas exchange mechanisms, with and without access to air. We demonstrate oxygen-limited thermal tolerance in air-breathing adults of the plastron-exchanging water bug Aphelocheirus aestivalis. Ilyocoris cimicoides, a related, bimodal gas exchanger, did not exhibit such oxygen-limited thermal tolerance and relied increasingly on aerial gas exchange with warming. Intriguingly, however, when denied access to air, oxygen-limited thermal tolerance could also be induced in this species. Patterns in oxygen-limited thermal tolerance were found to be consistent across life-history stages in these insects, with nymphs employing the same gas exchange mechanisms as adults. These results advance our understanding of oxygen limitation at high temperatures; differences in the degree of respiratory control appear to modulate the importance of oxygen in setting tolerance limits. PMID:25964420

  16. Dynamics of natural gas adsorption storage systems employing activated carbon

    Microsoft Academic Search

    J. P. Barbosa Mota; A. E. Rodrigues; E. Saatdjian; D. Tondeur

    1997-01-01

    Various aspects of the dynamics of natural gas adsorption storage systems employing activated carbon are studied theoretically. The fast charge of the storage system is the first subject addressed. Emphasis is given to thermal effects and hydrodynamics of flow through the carbon bed. In order to study the influence of diffusional resistances on charge dynamics, an intraparticle transport equation governed

  17. Amide hydrogen/deuterium exchange & MALDI-TOF mass spectrometry analysis of Pak2 activation.

    PubMed

    Hsu, Yuan-Hao; Traugh, Jolinda A

    2011-01-01

    Amide hydrogen/deuterium exchange (H/D exchange) coupled with mass spectrometry has been widely used to analyze the interface of protein-protein interactions, protein conformational changes, protein dynamics and protein-ligand interactions. H/D exchange on the backbone amide positions has been utilized to measure the deuteration rates of the micro-regions in a protein by mass spectrometry(1,2,3). The resolution of this method depends on pepsin digestion of the deuterated protein of interest into peptides that normally range from 3-20 residues. Although the resolution of H/D exchange measured by mass spectrometry is lower than the single residue resolution measured by the Heteronuclear Single Quantum Coherence (HSQC) method of NMR, the mass spectrometry measurement in H/D exchange is not restricted by the size of the protein(4). H/D exchange is carried out in an aqueous solution which maintains protein conformation. We provide a method that utilizes the MALDI-TOF for detection(2), instead of a HPLC/ESI (electrospray ionization)-MS system(5,6). The MALDI-TOF provides accurate mass intensity data for the peptides of the digested protein, in this case protein kinase Pak2 (also called ?-Pak). Proteolysis of Pak 2 is carried out in an offline pepsin digestion. This alternative method, when the user does not have access to a HPLC and pepsin column connected to mass spectrometry, or when the pepsin column on HPLC does not result in an optimal digestion map, for example, the heavily disulfide-bonded secreted Phospholipase A(2;) (sPLA(2;)). Utilizing this method, we successfully monitored changes in the deuteration level during activation of Pak2 by caspase 3 cleavage and autophosphorylation(7,8,9). PMID:22143461

  18. Membrane androgen receptor sensitive Na+/H+ exchanger activity in prostate cancer cells.

    PubMed

    Chatterjee, Soumya; Schmidt, Sebastian; Pouli, Stella; Honisch, Sabina; Alkahtani, Saad; Stournaras, Christos; Lang, Florian

    2014-05-01

    Membrane androgen receptors (mAR) are expressed in several tumors. mAR activation by testosterone albumin conjugates (TAC) suppresses tumor growth and migration. mAR signaling involves phosphoinositide-3-kinase (PI3K) and Rho-associated protein kinase (ROCK). PI3K stimulates serum- and glucocorticoid-inducible kinase SGK1, which in turn activates Na(+)/H(+)-exchangers (NHE). In prostate cancer cells cytosolic pH (pHi) was determined utilizing 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein-fluorescence and NHE-activity utilizing Na(+)-dependent cytosolic realkalinization following an ammonium pulse. TAC (100 nM) significantly increased pHi and NHE-activity, effects abrogated by NHE1-inhibitor cariporide (10 ?M), SGK1-inhibitors EMD638683 (50 ?M) and GSK650349 (10 ?M) and ROCK-inhibitors Y-27632 (10 ?M) and fasudil (100 ?M). TAC treatment rapidly and significantly increased cell volume and actin polymerization, effects abolished in the presence of cariporide. Thus, mAR-activation activates cariporide-sensitive Na(+)/H(+)-exchangers, an effect requiring SGK1 and ROCK activity. PMID:24607544

  19. Variation of gas exchange within native plant species of Switzerland and relationships with ozone injury: an open-top experiment.

    PubMed

    Zhang, J; Ferdinand, J A; Vanderheyden, D J; Skelly, J M; Innes, J L

    2001-01-01

    Gas exchange and ozone-induced foliar injury were intensively measured during a 6-day period in mid-August 1998 on leaves of Acer pseudoplatanus, Betula pendula, Corylus avellana, Fagus sylvatica, Fraxinus excelsior, Morus nigra, Prunus avium, Prunus serotina, Rhamnus cathartica, and Viburnum lantana at a forest nursery site in Canton Ticino, Switzerland. Plants were grown in four open plots (AA), four open-top chambers receiving carbon-filtered (CF) air, and four receiving non-filtered (NF) air. Significant variation in gas exchange (F > 12.7, P < 0.001) was detected among species with average net photosynthesis and average stomatal conductance differing by a factor of two. Species also varied significantly in foliar injury for those leaves for which we measured gas exchange (F = 39.6, P < 0.001). Fraxinus excelsior, M. nigra, P. avium, P. serotina, R. cathartica, and V. lantana showed more injury than A. pseudoplatanus, B. pendula, C. avellana, and Fagus sylvatica. Plants grown in CF chambers had significantly higher net photosynthesis (A) and stomatal conductance to water vapor (gwv), and lower foliar injury than plants grown in NF chambers and AA plots; interactions between species and ozone treatments were significant for all variables (F > or = 2.2, P < 0.05) except gwv (F = 0.7, P > 0.1). Although A and gwv decreased and foliar injury increased with leaf age, the magnitude of these changes was lower for plants grown in CF chambers than for plants grown in NF chambers and AA plots. Neither ozone uptake threshold (r = 0.26, P > 0.20) nor whole-plant injury (r = -0.15, P > 0.41) was significantly correlated with stomatal conductance across these species. It appears that the relationships between stomatal conductance and foliar injury are species-specific and interactions between physiology and environments and leaf biochemical processes must be considered in determining species sensitivity to ambient ozone exposures. PMID:11383335

  20. Gas exchange and photosynthetic water use efficiency in response to light, CO2 concentration and temperature in Vicia faba.

    PubMed

    Avola, Giovanni; Cavallaro, Valeria; Patanè, Cristina; Riggi, Ezio

    2008-05-26

    Light and temperature-response curves and their resulting coefficients, obtained within ecophysiological characterization of gas exchanges at the leaf level, may represent useful criteria for breeding and cultivar selection and required tools for simulation models aimed at the prediction of potential plant behaviour in response to environmental conditions. Leaf-scale gas exchanges, by means of an IRGA open-flow system, were measured in response to light intensity (8 levels from 0 up to 2000 micromol m(-2) s(-1)), CO(2) concentrations (ambient-350 micromol mol(-1) and short-term enriched-700 micromol mol(-1)) and air temperature (from 7 up to 35 degrees C) on three Vicia faba L. genotypes, each representing one of the three cultivated groups: major, equina and minor. The net assimilation rate response to light intensity was well described by an exponential rise to max function. The short-term CO(2) enrichment markedly increased the values of light response curve parameters such as maximum photosynthetic rate (+80%), light saturation point (+40%) and quantum yield (+30%), while less homogenous behaviour was reported for dark respiration and light compensation point. For each light intensity level, the major and minor genotypes studied showed assimilation rates at least a 30% higher than equina. The positive effects of short-term CO(2) enrichment on photosynthetic water use efficiency (WUE) indicate a relevant advantage in doubling CO(2) concentration. In the major and minor genotypes studied, similar assimilation rates, but different WUE were observed. The optimum leaf temperature for assimilation process, calculated through a polynomial function, was 26-27 degrees C and no relevant limitations were observed in the range between 21 and 32 degrees C. Analysis at the single leaf level provided both rapid information on the variations in gas exchange in response to environmental factors and selection criteria for the screening of genotypes. PMID:18155805

  1. Toward the Active Control of Heat Transfer in the Hot Gas Path of Gas Turbines

    NASA Technical Reports Server (NTRS)

    Oertling, Jeremiah E.

    2003-01-01

    The work at NASA this summer has focused on assisting the Professor's project, namely "Toward the Active Control of Heat Transfer in the Hot Gas Path of Gas Turbines." The mode of controlling the Heat Transfer that the project focuses on is film cooling. Film cooling is used in high temperature regions of a gas turbine and extends the life of the components exposed to these extreme temperatures. A "cool" jet of air is injected along the surface of the blade and this layer of cool air shields the blade from the high temperatures. Cool is a relative term. The hot gas path temperatures reach on the order of 1500 to 2000 K. The "coo" air is on the order of 700 to 1000 K. This cooler air is bled off of an appropriate compressor stage. The next parameter of interest is the jet s position and orientation in the flow-field.

  2. Eucalyptus hydrolysate detoxification with activated charcoal adsorption or ion-exchange resins for xylitol production

    Microsoft Academic Search

    Larissa Canilha; João Batista de Almeida e Silva; Ana Irene Nápoles Solenzal

    2004-01-01

    Eucalyptus hemicellulosic hydrolysate used for xylitol production by Candida guilliermondii FTI20037 was previously treated either with ion-exchange resins or with activated charcoal adsorption combined with pH adjustment, in order that acetic acid, furfural and hydroxymethylfurfural could be removed. The best results for xylitol yield factor (0.76g\\/g) and volumetric productivity (0.68g\\/(lh) were attained when a three-fold concentrated hydrolysate was treated with

  3. Sensitivity of simulated deep ocean natural radiocarbon to gas exchange velocity and historical atmospheric ?14C variations

    NASA Astrophysics Data System (ADS)

    Wagner, Hannes; Koeve, Wolfgang; Kriest, Iris; Oschlies, Andreas

    2015-04-01

    Simulated deep ocean natural radiocarbon is frequently used to assess model performance of deep ocean ventilation in Ocean General Circulation Models (OGCMs). It has been shown to be sensitive to a variety of model parameters, such as the mixing parameterization, convection scheme and vertical resolution. Here we use three different ocean models (MIT2.8, ECCO, UVic) to evaluate the sensitivity of simulated deep ocean natural radiocarbon to two other factors, while keeping the model physics constant: (1) the gas exchange velocity and (2) historic variations in atmospheric ?^1^4C boundary conditions. We find that simulated natural ?^1^4C decreases by 14-20 ‰ throughout the deep ocean and consistently in all three models, if the gas exchange velocity is lowered by 30 % with respect to the OCMIP-2 protocol, to become more consistent with newer estimates of the oceans uptake of bomb derived ^1^4C. Simulated deep ocean natural ?^1^4C furthermore decreases by 3-9 ‰ throughout the deep Pacific, Indian and Southern Oceans and consistently in all three models, if the models are forced with the observed atmospheric ?^1^4C history, instead of an often made pragmatic assumption of a constant atmospheric ?^1^4C value of zero. Applying both improvements (gas exchange reduction, as well as atmospheric ?^1^4C history implementation) concomitantly and accounting for the present uncertainty in gas exchange velocity estimates (between 10 and 40 % reduction with respect to the OCMIP-2 protocol) simulated deep ocean ?^1^4C decreases by 10-30 ‰ throughout the deep Pacific, Indian and Southern Ocean. This translates to a ^1^4C-age increase of 100-300 years and indicates, that models, which in former assessments (based on the OCMIP-2 protocol) had been identified to have an accurate deep ocean ventilation, should now be regarded as rather having a bit too sluggish a ventilation. Models, which on the other hand had been identified to have a bit too fast a deep ocean ventilation, should now be regarded as rather having a more accurate ventilation.

  4. Calculation of the cross section for N IV-H charge-exchange: Significance for the intercloud gas

    Microsoft Academic Search

    R. B. Christensen; W. D. Watson; R. J. Blint

    1977-01-01

    Calculations are performed to determine the cross section for the charge-exchange collision N\\/sup +3\\/+H..-->..N\\/sup +2\\/+H\\/sup +\\/ at energies near 1 eV. A reaction rate approx.3 x 10⁻⁹ cm³ s⁻¹ is obtained for temperatures near 10⁴ K. Highly ionized atoms have been employed as probes of the hot (10⁴ K), dilute interstellar gas. The calculations here indicate that

  5. Grain-based activated carbons for natural gas storage.

    PubMed

    Zhang, Tengyan; Walawender, Walter P; Fan, L T

    2010-03-01

    Natural gas has emerged as a potential alternative to gasoline due to the increase in global energy demand and environmental concerns. An investigation was undertaken to explore the technical feasibility of implementing the adsorbed natural gas (ANG) storage in the fuel tanks of motor vehicles with activated carbons from biomass, e.g., sorghum and wheat. The grain-based activated carbons were prepared by chemical activation; the experimental parameters were varied to identify the optimum conditions. The porosity of the resultant activated carbons was evaluated through nitrogen adsorption; and the storage capacity, through methane adsorption. A comparative study was also carried out with commercial activated carbons from charcoal. The highest storage factor attained was 89 for compacted grain-based activated carbons from grain sorghum with a bulk density of 0.65 g/cm(3), and the highest storage factor attained is 106 for compacted commercial activated carbons (Calgon) with a bulk density of 0.70 g/cm(3). The storage factor was found to increase approximately linearly with increasing bulk density and to be independent of the extent of compaction. This implies that the grain-based activated carbons are the ideal candidates for the ANG storage. PMID:19945864

  6. Experimental Research on Gas-Solid Flow in an External Heat Exchanger with Double Outlets

    NASA Astrophysics Data System (ADS)

    Liu, H. Z.; Lu, X. F.

    A new type scaling-up scheme of CFB boiler that takes separator as center and furnaces are laid around was put forward in this paper. In the recycle system, a new type heat exchanger device with double outlets was designed for this disposal scheme. As we know, the external heat exchanger is very important for the CFB, which be able no only to adjust the steam temperature, but also to adjust the bed temperature. In this paper, through the adjustment of air speed in different room of the heat exchanger, the adjusting performance of the new type heat exchanger was analyzed. Moreover, the test of the pressure in the whole recycle system was analyzed. The pressure balance system of the circulating circuit with this new arrangement scheme was realized. Through this test research, the main conclusions were got as follows: The external heat exchanger, which has two recycled solid outlets, could run flexibly and stably and could successfully discharge the materials from the standpipe into either of the furnaces. This test device has a good pressure and material balance system.

  7. Performance study of the TFTR diagnostic neutral beam for active charge exchange measurements

    SciTech Connect

    Medley, S.S.; Goldston, R.J.; Towner, H.H.

    1980-06-01

    A neutral beam source will be incorporated in the Tokamak Fusion Test Reactor (TFTR) charge exchange diagnostic to provide a time modulated, spatially localized enhancement of the charge exchange efflux. Two autonomous Charge Exchange Neutral Analyzer (CENA) systems are being designed for the TFTR. One system measures the plasma ion temperature along twelve vertical line-of-sight chords spaced approximately equidistantly across the torus minor diameter. The other system is dedicated primarily to measurement of ion phenomena associated with neutral beam injection heating and has a fan-like field of view along eight sight-lines in the equitorial plane. The neutral beam is steerable in order to access the viewing field of both CENA systems, though in general not simultaneously. The performance of the diagnostic neutral beam is evaluated to determine the optimal beam specifications for active charge exchange measurements. Using the optimal beam design parameters, the efficacy of the neutral doping is examined for both CENA systems over the envisioned range of the TFTR plasma density and temperature.

  8. Chamber measurement of surface-atmosphere trace gas exchange: Numerical evaluation of dependence on soil, interfacial layer, and source/sink properties

    NASA Astrophysics Data System (ADS)

    Hutchinson, G. L.; Livingston, G. P.; Healy, R. W.; Striegl, R. G.

    2000-04-01

    We employed a three-dimensional finite difference gas diffusion model to simulate the performance of chambers used to measure surface-atmosphere trace gas exchange. We found that systematic errors often result from conventional chamber design and deployment protocols, as well as key assumptions behind the estimation of trace gas exchange rates from observed concentration data. Specifically, our simulations showed that (1) when a chamber significantly alters atmospheric mixing processes operating near the soil surface, it also nearly instantaneously enhances or suppresses the postdeployment gas exchange rate, (2) any change resulting in greater soil gas diffusivity, or greater partitioning of the diffusing gas to solid or liquid soil fractions, increases the potential for chamber-induced measurement error, and (3) all such errors are independent of the magnitude, kinetics, and/or distribution of trace gas sources, but greater for trace gas sinks with the same initial absolute flux. Finally, and most importantly, we found that our results apply to steady state as well as non-steady-state chambers, because the slow rate of gas diffusion in soil inhibits recovery of the former from their initial non-steady-state condition. Over a range of representative conditions, the error in steady state chamber estimates of the trace gas flux varied from -30 to +32%, while estimates computed by linear regression from non-steady-state chamber concentrations were 2 to 31% too small. Although such errors are relatively small in comparison to the temporal and spatial variability characteristic of trace gas exchange, they bias the summary statistics for each experiment as well as larger scale trace gas flux estimates based on them.

  9. [Methanogenic activity and methanogen diversity in marine gas field sediments].

    PubMed

    Tian, Qi; Wang, Jia; Fan, Xiao-Lei; Luo, Sheng-Jun; Guo, Rong-Bo; Qiu, Yan-Ling

    2014-06-01

    Methanogens play an important role in marine sediments, which are related to methane production and methane hydrate deposits. Methanogenic activity of marine gas field sediments was investigated using substrates that methanogens usually used as carbon sources. H2/CO2, methanol, methylamines and trimethylamines could support the growth and methane production of gas field sediments. 16S rRNA gene sequence analysis indicated that the predominant methanogens in the enrichment cultures were related to known cultured methanogens in the family Methanosarcinaceae of the order Methanosarcinales and the family Methanomicrobiales of the order Methanomicrobiales, with genera Methanococcoides, Methanogenium and Methanosarcina as major methanogens. PMID:25158513

  10. Monitoring radioactive xenon gas in room air using activated charcoal

    SciTech Connect

    Langford, J.; Thompson, G. (Princess Margaret Hospital for Children, Perth (Australia) Sir Charles Gairdner Hospital, Perth (Australia))

    1990-03-01

    A method for monitoring room air for radioactive xenon gas is described. It uses activated charcoal vials, a vacuum source and a well-type scintillation counter. The method may be adapted for detection and identification of any radioactive gas excluding those with ultra-short half-lives. Sampling room air during xenon-133 ({sup 133}Xe) ventilation lung studies was performed using this technique. The results show that low concentrations of {sup 133}Xe in room air can be reliably detected and that staff exposure to {sup 133}Xe at this institution was within ICRP recommendations.

  11. Air-sea dimethylsulfide (DMS) gas transfer in the North Atlantic: evidence for limited interfacial gas exchange at high wind speed

    NASA Astrophysics Data System (ADS)

    Bell, T. G.; De Bruyn, W.; Miller, S. D.; Ward, B.; Christensen, K.; Saltzman, E. S.

    2013-11-01

    Shipboard measurements of eddy covariance dimethylsulfide (DMS) air-sea fluxes and seawater concentration were carried out in the North Atlantic bloom region in June/July 2011. Gas transfer coefficients (k660) show a linear dependence on mean horizontal wind speed at wind speeds up to 11 m s-1. At higher wind speeds the relationship between k660 and wind speed weakens. At high winds, measured DMS fluxes were lower than predicted based on the linear relationship between wind speed and interfacial stress extrapolated from low to intermediate wind speeds. In contrast, the transfer coefficient for sensible heat did not exhibit this effect. The apparent suppression of air-sea gas flux at higher wind speeds appears to be related to sea state, as determined from shipboard wave measurements. These observations are consistent with the idea that long waves suppress near-surface water-side turbulence, and decrease interfacial gas transfer. This effect may be more easily observed for DMS than for less soluble gases, such as CO2, because the air-sea exchange of DMS is controlled by interfacial rather than bubble-mediated gas transfer under high wind speed conditions.

  12. Ccpg1, a Novel Scaffold Protein That Regulates the Activity of the Rho Guanine Nucleotide Exchange Factor Dbs?

    PubMed Central

    Kostenko, Elena V.; Olabisi, Oyenike O.; Sahay, Sutapa; Rodriguez, Pedro L.; Whitehead, Ian P.

    2006-01-01

    Dbs is a Rho-specific guanine nucleotide exchange factor (RhoGEF) with in vitro exchange activity specific for RhoA and Cdc42. Like many RhoGEF family members, the in vivo exchange activity of Dbs is restricted in a cell-specific manner. Here we report the characterization of a novel scaffold protein (designated cell cycle progression protein 1 [Ccpg1]) that interacts with Dbs and modulates its in vivo exchange specificity. When coexpressed in mammalian cells, Ccpg1 binds to the Dbl homology/pleckstrin homology domain tandem motif of Dbs and inhibits its exchange activity toward RhoA, but not Cdc42. Expression of Ccpg1 correlates with the ability of Dbs to activate endogenous RhoA in cultured cells, and suppression of endogenous Ccpg1 expression potentiates Dbs exchange activity toward RhoA. The isolated Dbs binding domain of Ccpg1 is not sufficient to suppress Dbs exchange activity on RhoA, thus suggesting a regulatory interaction. Ccpg1 mediates recruitment of endogenous Src kinase into Dbs-containing complexes and interacts with the Rho family member Cdc42. Collectively, our studies suggest that Ccpg1 represents a new class of regulatory scaffold protein that can function as both an assembly platform for Rho protein signaling complexes and a regulatory protein which can restrict the substrate utilization of a promiscuous RhoGEF family member. PMID:17000758

  13. In Vivo MR Imaging of Pulmonary Perfusion and Gas Exchange in Rats via Continuous Extracorporeal Infusion of Hyperpolarized 129Xe

    PubMed Central

    Cleveland, Zackary I.; Möller, Harald E.; Hedlund, Laurence W.; Nouls, John C.; Freeman, Matthew S.; Qi, Yi; Driehuys, Bastiaan

    2012-01-01

    Background Hyperpolarized (HP) 129Xe magnetic resonance imaging (MRI) permits high resolution, regional visualization of pulmonary ventilation. Additionally, its reasonably high solubility (>10%) and large chemical shift range (>200 ppm) in tissues allow HP 129Xe to serve as a regional probe of pulmonary perfusion and gas transport, when introduced directly into the vasculature. In earlier work, vascular delivery was accomplished in rats by first dissolving HP 129Xe in a biologically compatible carrier solution, injecting the solution into the vasculature, and then detecting HP 129Xe as it emerged into the alveolar airspaces. Although easily implemented, this approach was constrained by the tolerable injection volume and the duration of the HP 129Xe signal. Methods and Principal Findings Here, we overcome the volume and temporal constraints imposed by injection, by using hydrophobic, microporous, gas-exchange membranes to directly and continuously infuse 129Xe into the arterial blood of live rats with an extracorporeal (EC) circuit. The resulting gas-phase 129Xe signal is sufficient to generate diffusive gas exchange- and pulmonary perfusion-dependent, 3D MR images with a nominal resolution of 2×2×2 mm3. We also show that the 129Xe signal dynamics during EC infusion are well described by an analytical model that incorporates both mass transport into the blood and longitudinal relaxation. Conclusions Extracorporeal infusion of HP 129Xe enables rapid, 3D MR imaging of rat lungs and, when combined with ventilation imaging, will permit spatially resolved studies of the ventilation-perfusion ratio in small animals. Moreover, EC infusion should allow 129Xe to be delivered elsewhere in the body and make possible functional and molecular imaging approaches that are currently not feasible using inhaled HP 129Xe. PMID:22363613

  14. Soil-atmosphere greenhouse-gas exchange in a bioretention system

    NASA Astrophysics Data System (ADS)

    Daly, E.; Chan, H.; Beringer, J.; Livesley, S. J.

    2011-12-01

    Bioretention systems are a popular green-technology for the management of urban stormwater runoff in many countries. They typically consist of a trench filled with a highly permeable soil medium that supports vegetation; runoff is diverted to bioretention systems and, by percolating through the filter medium, is subjected to a number of treatment processes. Nitrogen (N) is one of the key pollutants targeted by bioretention systems, which are able to reduce N concentrations considerably from inflow to outflow. To increase N removal, a saturated zone at the bottom of the filter medium is often artificially generated, to both enhance the denitrification process and increase the water available to the vegetation between inflow events. Although studies on the N-removal performance of bioretention systems are widely available in the literature, less is known about the exchange of greenhouse gases (GHG), especially nitrous oxide (N2O), between the bioretention systems and the atmosphere. Here, we present an experimental pilot study to measure N2O and CO2 soil emissions in a bioretention system installed on the Clayton Campus of Monash University in Melbourne, Australia. The bioretention system is divided into three cells, each 15 m2; the system as a whole receives water run-off from 4500 m2 of impervious car park. We monitored two cells with mostly sandy-loam vegetated with native sedges (mainly Carex Appressa and Lomandra Longifolia), one with and one without a saturated zone. Three manual flux chambers were installed in both cells. Gas flux samples were taken twice a week at about 11 am between the 2nd of March and the 18th of May 2011 (late summer and fall). Since October 2010, air-phase soil CO2 concentration profiles were measured continuously using solid-state infrared CO2 transmitters (GMT-221 model, Vaisala, Finland), along with soil moisture and soil temperature. Preliminary analysis of the chamber data (March only) showed that N2O fluxes were in general below 50 ?g N/ (m2 h) with occasional pulse emissions > 150 ?g N /(m2 h) after recent inflow events. Fluxes from the cell with the saturated zone were consistently higher than those from the cell without a saturated zone. CO2 fluxes were comparable between the two cells, and usually between 50 and 200 mg C/(m2 h) whilst temperatures ranged between 12 and 26 degrees Celsius through this late summer/autumn period. Results from the entire data-set (March-May) will be presented along with an investigation of the relationship between these fluxes and other environmental and soil variables, such as soil nitrate and ammonium content and soil redox potential. Seasonal fluctuations and the effect of random inflow pulses will be also assessed and discussed. The results from this pilot study are useful to provide direct quantification of the GHG emissions associated with urban bioretention systems, which are one of the most used green infrastructures to manage stormwater runoff.

  15. Acetylation of human mitochondrial citrate carrier modulates mitochondrial citrate/malate exchange activity to sustain NADPH production during macrophage activation.

    PubMed

    Palmieri, Erika M; Spera, Iolanda; Menga, Alessio; Infantino, Vittoria; Porcelli, Vito; Iacobazzi, Vito; Pierri, Ciro L; Hooper, Douglas C; Palmieri, Ferdinando; Castegna, Alessandra

    2015-08-01

    The mitochondrial citrate-malate exchanger (CIC), a known target of acetylation, is up-regulated in activated immune cells and plays a key role in the production of inflammatory mediators. However, the role of acetylation in CIC activity is elusive. We show that CIC is acetylated in activated primary human macrophages and U937 cells and the level of acetylation is higher in glucose-deprived compared to normal glucose medium. Acetylation enhances CIC transport activity, leading to a higher citrate efflux from mitochondria in exchange with malate. Cytosolic citrate levels do not increase upon activation of cells grown in deprived compared to normal glucose media, indicating that citrate, transported from mitochondria at higher rates from acetylated CIC, is consumed at higher rates. Malate levels in the cytosol are lower in activated cells grown in glucose-deprived compared to normal glucose medium, indicating that this TCA intermediate is rapidly recycled back into the cytosol where it is used by the malic enzyme. Additionally, in activated cells CIC inhibition increases the NADP(+)/NADPH ratio in glucose-deprived cells; this ratio is unchanged in glucose-rich grown cells due to the activity of the pentose phosphate pathway. Consistently, the NADPH-producing isocitrate dehydrogenase level is higher in activated glucose-deprived as compared to glucose rich cells. These results demonstrate that, in the absence of glucose, activated macrophages increase CIC acetylation to enhance citrate efflux from mitochondria not only to produce inflammatory mediators but also to meet the NADPH demand through the actions of isocitrate dehydrogenase and malic enzyme. PMID:25917893

  16. Ideas Exchange: "How Important Is Activity in Young Children (Preschool) to a Lifetime of Physical Activity?"

    ERIC Educational Resources Information Center

    Hushman, GLenn; Morrison, Jaime; Mally, Kristi; McCall, Renee; Corso, Marjorie; Kamla, Jim; Magnotta, John; Chase, Melissa A.; Garrahy, Deborah A.; Lorenzi, David G.; Barnd, Sue

    2009-01-01

    This article presents the opinions of several professionals who were asked: "How important is activity in young children (preschool) to a lifetime of physical activity?" These professionals point out the importance of physical activity to young children.

  17. 78 FR 34703 - Pipeline Safety: Information Collection Activities, Revision to Gas Distribution Annual Report

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-10

    ...Collection Activities, Revision to Gas Distribution Annual Report AGENCY: Pipeline and...Register of its intent to revise the gas distribution annual report (PHMSA F7100.1- 1...titled: ``Annual Report for Gas Distribution Pipeline Operators.'' Summary...

  18. 78 FR 10261 - Pipeline Safety: Information Collection Activities, Revision to Gas Distribution Annual Report

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-13

    ...Collection Activities, Revision to Gas Distribution Annual Report AGENCY: Pipeline and...approval for the revision of the gas distribution annual report currently approved under...submitting to OMB for approval. B. Gas Distribution Annual Report PHMSA intends to...

  19. 76 FR 67201 - Information Collection Activities: Oil and Gas Production Safety Systems; Submitted for Office of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-31

    ...Activities: Oil and Gas Production Safety Systems; Submitted for Office of...Subpart H, ``Oil and Gas Production Safety Systems.'' This notice also provides...Subpart H, Oil and Gas Production Safety Systems. Abstract: The...

  20. Gas-Phase Hydrogen-Deuterium Exchange Labeling of Select Peptide Ion Conformer Types: a Per-Residue Kinetics Analysis.

    PubMed

    Khakinejad, Mahdiar; Kondalaji, Samaneh Ghassabi; Tafreshian, Amirmahdi; Valentine, Stephen J

    2015-07-01

    The per-residue, gas-phase hydrogen deuterium exchange (HDX) kinetics for individual amino acid residues on selected ion conformer types of the model peptide KKDDDDDIIKIIK have been examined using ion mobility spectrometry (IMS) and HDX-tandem mass spectrometry (MS/MS) techniques. The [M + 4H](4+) ions exhibit two major conformer types with collision cross sections of 418 Å(2) and 446 Å(2); the [M + 3H](3+) ions also yield two different conformer types having collision cross sections of 340 Å(2) and 367 Å(2). Kinetics plots of HDX for individual amino acid residues reveal fast- and slow-exchanging hydrogens. The contributions of each amino acid residue to the overall conformer type rate constant have been estimated. For this peptide, N- and C-terminal K residues exhibit the greatest contributions for all ion conformer types. Interior D and I residues show decreased contributions. Several charge state trends are observed. On average, the D residues of the [M + 3H](3+) ions show faster HDX rate contributions compared with [M + 4H](4+) ions. In contrast the interior I8 and I9 residues show increased accessibility to exchange for the more elongated [M + 4H](4+) ion conformer type. The contribution of each residue to the overall uptake rate showed a good correlation with a residue hydrogen accessibility score model calculated using a distance from charge site and initial incorporation site for nominal structures obtained from molecular dynamic simulations (MDS). Graphical Abstract ?. PMID:25895891

  1. Near and Far Scale Gas Exchange Associated with Natural Marine Hydrocarbon Seeps

    Microsoft Academic Search

    J. F. Clark; S. Mau; D. L. Valentine; J. C. Ohlmann; L. Washburn; I. Leifer

    2006-01-01

    The Coal Oil Point seep field, Santa Barbara Channel, CA, USA is one of the world's most intense areas of natural marine hydrocarbon seepage. Oil and gas is emitted from seafloor vents, which occur mostly in water depths between 20 and 70 m over an area of about 3 km2. Detailed measurements of bubble composition, dissolved gas concentrations, seepage rates,

  2. Implementation of a membrane gas-exchange technique based on perfluorodecalin

    Microsoft Academic Search

    B. I. Skorik; D. D. Cherkas; V. V. Shilov; S. P. Kazakov; Yu. V. Goncharov

    1993-01-01

    1. Injection of perfluorodecalin dispersed with oxygen into a gas-containing compartment of porous membrane (e.g., made of teflon) oxygenators modifies the membrane oxygenators, allowing practical application of liquid blood oxygenators safeguarded against penetration of gas-carrying liquid into blood.

  3. Simulation of the heat exchange between the supersonic flow and the stationary body in a gas centrifuge

    NASA Astrophysics Data System (ADS)

    Zvonarev, K. V.; Seleznev, V. D.; Tokmantsev, V. I.; Abramov, Yu. V.

    2012-11-01

    We have made comparative calculations of the heat exchange in the subpersonic flow of gaseous UF6 around the stationary cylindrical body inside the rotating rotor of the gas centrifuge. It has been revealed that the integral heat flux from the gas to the body calculated with the use of the ANSYS-CFX program complex from the viewpoint of the continuum model is much smaller than the heat flow calculated by the Monte Carlo method of direct statistical simulation. Estimates show that under the conditions being considered the boundary layer on the surface of the body has no time to be formed and has a thickness of the order of the mean free path of the gas molecules and, therefore, the use of the methods of continuum mechanics in this region is incorrect. On the contrary, the method of direct statistical simulation permits taking into account the interaction of gas molecules directly with the surface of the streamline body and obtaining more correct results.

  4. [Effect of guided ventilation on gas exchange in kypho-scoliotic patients in post-intensive care].

    PubMed

    Breant, J; Fleury, M F; Delque, G; Vascaut, L

    1989-01-01

    Post-intensive care stabilized kyphoscoliotic patients are characterized by a limited circulation which reduces VCO in relation to VCO2 (specific VCO, Sp VCO) by diminution of the "contact time". This might help in explaining the hypoxaemia observed in these patients concurrently with alveolar hypoventilation and altered ventilation/perfusion ratio. Bradypnoea (Bp) may reduce the last two factors but not the vascular field amputation. In 10 kyphoscoliotic patients examined in spontaneous ventilation (SV), then in Bp, gas exchanges were evaluated under their 2 aspects: gas flow rates and ventilatory efficiency (ERCO2, VA/V). The results obtained in 16 examinations concerning 10 patients were analysed. There were great differences in the amplitude of ventilatory response, a significant increase of VA improving PaCO2 more constantly than PaO2, a slight increase of Sp VCO and a decrease of VCO/VA. In the discussion, ERCO2 and VA/V are compared, the high VA/V and VD/VT values are justified, the uncertain effect of Bp on PaO2 is confirmed, and the relationship of Sp VCO with DuCO and PaO2 is determined. The evaluation of exchanges in SV and Bp provides information on the degree of deterioration of blood perfusion, the physiopathology of each individual subject and the advisability of kinesitherapy with Bp. PMID:2626636

  5. Influence of stratification in near-surface water layer on intensity of gas exchange between atmosphere and water

    NASA Astrophysics Data System (ADS)

    Brekhovskikh, V. F.; Bratkov, V. I.

    1986-07-01

    Little is known concerning the influence of the temperature field in the near-water layer on gas exchange between the atmosphere and water. During periods of calm the transfer of oxygen from the air to water is sometimes impeded and large numbers of fish may die. A laboratory experiment was carried out in glass thermostated containers, in each of which the temperature was maintained with great accuracy. One was heated to 39 to 40 C; another was cooled to 12 to 13 C; a third was kept at ambient temperature. In each case the aeration coefficient and rate of mass transfer were computed. Air and water temperatures were varied to determine temperature gradients in the near-water and near-surface layers. A copper constantan thermocouple was used in measuring temperatures above and below the interface. The influence of petroleum films on the rate of mass transfer was also determined. The rate of evaporation at different temperatures was ascertained. The greatest influence was observed in experiments with cooled air. It was found that temperature stratification in the near-surface water layer exerts a considerable influence on water-air gas exchange. In certain cases a petroleum film increases the temperature gradient and causes an even greater decrease in mass transfer rate.

  6. Theoretical studies of tunneling processes in three-body exchange reactions of van der Waals rare gas dimers

    SciTech Connect

    Turner, R.A.; Raff, L.M.; Thompson, D.L.

    1984-04-01

    Rare gas atom--diatom collisions of Ar+Ar/sub 2/, Xe+Ar/sub 2/, Kr+Xe/sub 2/, Kr+Ne/sub 2/, and Kr+NeAr have been investigated to determine the importance of tunneling processes in exchange and dissociation reactions involving van der Waals molecules. Reaction cross sections, angular distributions, and product-energy distributions have been computed using Monte Carlo quasiclassical trajectories. The effect of tunneling through the rotational barrier upon these quantities has been computed using WKB methods. The results show that metastable diatomic products with energies above the classical dissociation limit, but below the rotational barrier, play a significant role in the dynamics of both exchange and dissociation reactions. Lifetime distributions of such metastable dimers illustrate their importance in crossed molecular beam studies of rare gas systems. The WKB calculations indicate that a significant, and possibly measurable, number of the metastables dissociate by tunneling before they would reach the detector in a molecular beam experiment. Close agreement has been found between these calculations and statistical state-counting calculations of metastable product dimer lifetimes. Experiments are suggested that might permit the direct observation of tunneling in these systems.

  7. Effects of cold storage and water stress on water relations and gas exchange of white spruce (Picea glauca) seedlings.

    PubMed

    Jiang, Y; MacDonald, S E; Zwiazek, J J

    1995-04-01

    To determine the effects of lifting time and storage on water-stress resistance of nursery-grown white spruce (Picea glauca (Moench) Voss) seedlings, we compared gas exchange, water relations and mortality of 3-year-old seedlings lifted in October 1991 and stored at -2 degrees C for 3 months with seedlings lifted in January 1992. The seedlings were placed in nutrient solution and subjected to -1.1 or -2.7 MPa water stress induced by polyethylene glycol 3350 for 9 days. Water stress, but not lifting time, had a significant effect on seedling net assimilation, symplastic volume and turgor loss point. In a second experiment, seedlings lifted in October 1991 were stored at -2 degrees C for 7 months and compared with seedlings lifted in May 1992. The seedlings were planted in pots, and their gas exchange and water relation parameters measured in response to gradual water stress. The results suggest that prolonged cold storage retards photosynthetic recovery of seedlings after planting. Higher rates of net assimilation in seedlings lifted in May were not directly related to their water status. Nonstomatal limitations were the primary factor influencing photosynthetic rate. We conclude that the inferior ability of cold-stored seedlings to tolerate water stress was due to poor osmotic adjustment and a lag in recovery of photosynthesis. PMID:14965967

  8. Development of the gas puff charge exchange recombination spectroscopy (GP-CXRS) technique for ion measurements in the plasma edge

    SciTech Connect

    Churchill, R. M.; Theiler, C.; Lipschultz, B. [MIT Plasma Science and Fusion Center, Cambridge, Massachusetts 02139 (United States)] [MIT Plasma Science and Fusion Center, Cambridge, Massachusetts 02139 (United States); Dux, R.; Pütterich, T.; Viezzer, E. [Max-Planck-Institut für Plasmaphysik, EURATOM Association, Boltzmannstrasse 2, D-85748 Garching (Germany)] [Max-Planck-Institut für Plasmaphysik, EURATOM Association, Boltzmannstrasse 2, D-85748 Garching (Germany); Collaboration: Alcator C-Mod Team; ASDEX Upgrade Team

    2013-09-15

    A novel charge-exchange recombination spectroscopy (CXRS) diagnostic method is presented, which uses a simple thermal gas puff for its donor neutral source, instead of the typical high-energy neutral beam. This diagnostic, named gas puff CXRS (GP-CXRS), is used to measure ion density, velocity, and temperature in the tokamak edge/pedestal region with excellent signal-background ratios, and has a number of advantages to conventional beam-based CXRS systems. Here we develop the physics basis for GP-CXRS, including the neutral transport, the charge-exchange process at low energies, and effects of energy-dependent rate coefficients on the measurements. The GP-CXRS hardware setup is described on two separate tokamaks, Alcator C-Mod and ASDEX Upgrade. Measured spectra and profiles are also presented. Profile comparisons of GP-CXRS and a beam based CXRS system show good agreement. Emphasis is given throughout to describing guiding principles for users interested in applying the GP-CXRS diagnostic technique.

  9. Role of Subunit Exchange and Electrostatic Interactions on the Chaperone Activity of Mycobacterium leprae HSP18

    PubMed Central

    Nandi, Sandip Kumar; Panda, Alok Kumar; Chakraborty, Ayon; Ray, Sougata Sinha; Biswas, Ashis

    2015-01-01

    Mycobacterium leprae HSP18, a major immunodominant antigen of M. leprae pathogen, is a small heat shock protein. Previously, we reported that HSP18 is a molecular chaperone that prevents aggregation of different chemically and thermally stressed client proteins and assists refolding of denatured enzyme at normal temperature. We also demonstrated that it can efficiently prevent the thermal killing of E. coli at higher temperature. However, molecular mechanism behind the chaperone function of HSP18 is still unclear. Therefore, we studied the structure and chaperone function of HSP18 at normal temperature (25°C) as well as at higher temperatures (31–43°C). Our study revealed that the chaperone function of HSP18 is enhanced significantly with increasing temperature. Far- and near-UV CD experiments suggested that its secondary and tertiary structure remain intact in this temperature range (25–43°C). Besides, temperature has no effect on the static oligomeric size of this protein. Subunit exchange study demonstrated that subunits of HSP18 exchange at 25°C with a rate constant of 0.018 min-1. Both rate of subunit exchange and chaperone activity of HSP18 is found to increase with rise in temperature. However, the surface hydrophobicity of HSP18 decreases markedly upon heating and has no correlation with its chaperone function in this temperature range. Furthermore, we observed that HSP18 exhibits diminished chaperone function in the presence of NaCl at 25°C. At elevated temperatures, weakening of interactions between HSP18 and stressed client proteins in the presence of NaCl results in greater reduction of its chaperone function. The oligomeric size, rate of subunit exchange and structural stability of HSP18 were also found to decrease when electrostatic interactions were weakened. These results clearly indicated that subunit exchange and electrostatic interactions play a major role in the chaperone function of HSP18. PMID:26098662

  10. Thyroid hormones increase Na+-H+ exchange activity in renal brush border membranes.

    PubMed Central

    Kinsella, J; Sacktor, B

    1985-01-01

    Na+-H+ exchange activity, i.e., amiloride-sensitive Na+ and H+ flux, in renal proximal tubule brush border (luminal) membrane vesicles was increased in the hyperthyroid rat and decreased in the hypothyroid rat, relative to the euthyroid animal. A positive correlation was found between Na+-H+ exchange activity and serum concentrations of thyroxine (T4) and triiodothyronine (T3). The thyroid status of the animal did not alter amiloride-insensitive Na+ uptake. The rate of passive pH gradient dissipation was higher in membrane vesicles from hyperthyroid rats compared to the rate in vesicles from hypothyroid animals, a result which would tend to limit the increase in Na+ uptake in vesicles from hyperthyroid animals. Na+-dependent phosphate uptake was increased in membrane vesicles from hyperthyroid rats; Na+-dependent D-glucose and L-proline uptakes were not changed by the thyroid status of the animal. The effect of thyroid hormones in increasing the uptake of Na+ in the brush border membrane vesicle is consistent with the action of the hormones in enhancing renal Na+ reabsorption. Further, the regulation of transtubular Na+ flux has now been shown to be concomitant with modulation of the entry of Na+ into the tubular cell across its luminal membrane, mediated by the exchange reaction, and with the previously reported control of the pumping of Na+ out of the cell across its basolateral membrane, mediated by the Na+,K+-ATPase. PMID:2987936

  11. The mechanics of motorised momentum exchange tethers when applied to active debris removal from LEO

    NASA Astrophysics Data System (ADS)

    Caldecott, Ralph; Kamarulzaman, Dayangku N. S.; Kirrane, James P.; Cartmell, Matthew P.; Ganilova, Olga A.

    2014-12-01

    The concept of momentum exchange when applied to space tethers for propulsion is well established, and a considerable body of literature now exists on the on-orbit modelling, the dynamics, and also the control of a large range of tether system applications. The authors consider here a new application for the Motorised Momentum Exchange Tether by highlighting three key stages of development leading to a conceptualisation that can subsequently be developed into a technology for Active Debris Removal. The paper starts with a study of the on-orbit mechanics of a full sized motorised tether in which it is shown that a laden and therefore highly massasymmetrical tether can still be forced to spin, and certainly to librate, thereby confirming its possible usefulness for active debris removal (ADR). The second part of the paper concentrates on the modelling of the centripetal deployment of a symmetrical MMET in order to get it initialized for debris removal operations, and the third and final part of the paper provides an entry into scale modelling for low cost mission design and testing. It is shown that the motorised momentum exchange tether offers a potential solution to the removal of large pieces of orbital debris, and that dynamic methodologies can be implemented to in order to optimise the emergent design.

  12. Gas and Water Vapor Exchanges in Rainfed Corn-Soybean Systems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Corn and soybean production in the Midwestern United States represents one of the most intensive and extensive cropping systems in the world. It is critical to understand the dynamics of CO2 (carbon dioxide) and H2O (water) vapor exchanges above corn and soybean canopies in rainfed environments in o...

  13. Water loss and gas exchange by eggs of Manduca sexta: Trading off costs and benefits

    Microsoft Academic Search

    H. Arthur Woods

    2010-01-01

    Like all terrestrial organisms, insect eggs face a tradeoff between exchanging metabolic gases (O2 and CO2) and conserving water. Here I summarize the physiology underlying this tradeoff and the ecological contexts in which it may be important. The ideas are illustrated primarily by work from my laboratory on eggs of the sphingid moth Manduca sexta. In particular, I discuss: (1)

  14. HIGH CONDUCTIVITY FINS FOR GAS COOLED LIQUID-METAL HEAT EXCHANGERS

    Microsoft Academic Search

    W. F. Brown; R. W. Fisher; H. M. Black

    1963-01-01

    Nickel-plated Cu fina are brazed to the Inconel tubes of an air-cooled ; liquid Na heat exchanger for use to 600 deg C. Methods of plating annular fins ; for tubes are discussed and test results are presented. Brazing techniques for ; fin-to-tube joints are explored, and a resistance brazing process is developed. ; From the results of tests, it

  15. Modeling bronchial circulation with application to soluble gas exchange: description and sensitivity analysis

    E-print Network

    George, Steven C.

    of ethanol ( blood 1,756 at 37°C) in the airways depends on the blood flow rate from the bronchial (0.01­350) of blood solubilities ( blood; ml·ml 1 ·atm 1). Hence, we hypothesize that the exchange circulation. To test this hypothesis, the dynamics of the bronchial circulation were incorporated

  16. Low energy of activation for amide hydrogen exchange reactions in proteins supports a local unfolding model.

    PubMed

    Thomsen, N K; Poulsen, F M

    1993-11-01

    Hydrogen exchange reactions of amides in hen egg white lysozyme that are pH dependent and have a low energy of activation have been shown to be in accordance with a reaction mechanism in two steps, an equilibrium step and an exchange step. These results are not in agreement with the model, proposed by C.K. Woodward & B.D. Hilton, known as the penetration model. Therefore our results suggest that this model should be revised. The amide hydrogen/deuterium exchange rates in hen egg white lysozyme were measured at 4 degrees C, 10 degrees C, 15 degrees C and 25 degrees C at pH 7.0 by 1H nuclear magnetic resonance spectroscopy. Activation energies of the exchange reactions in the range from 20 kJ mol-1 to 333 kJ mol-1 were obtained for 32 of the 129 residues in the protein. The amides of lysozyme studied here could be divided into two groups, one group of amides are characterized by an observed amide exchange rate (ko) in the range 10(-4) to 10(-6) s-1, an equilibrium constant k1/k2 close to 10(-5), a low energy of activation (20 to 50 kJ mol-1) and a distance less than 6 A from solvent. The other group of amides are characterized by a ko less than 10(-6) s-1, a k1/k2 close to 10(-7), higher energies of activation (40 to 330 kJ mol-1) and a distance more than 4 A from solvent. In terms of structure the amides of the last group are from the core of the protein. They are typically involved in a hydrogen bond and form part of the secondary structure either as interior alpha-helices or central strands of beta-sheets. The first group consists of amides that are in the shell of the protein between the core and the surface. These amides are typically hydrogen bonded and involved in secondary structure such as external alpha-helices or outer strands of beta-sheets and turns. PMID:8230202

  17. Active Combustion Control for Aircraft Gas Turbine Engines

    NASA Technical Reports Server (NTRS)

    DeLaat, John C.; Breisacher, Kevin J.; Saus, Joseph R.; Paxson, Daniel E.

    2000-01-01

    Lean-burning combustors are susceptible to combustion instabilities. Additionally, due to non-uniformities in the fuel-air mixing and in the combustion process, there typically exist hot areas in the combustor exit plane. These hot areas limit the operating temperature at the turbine inlet and thus constrain performance and efficiency. Finally, it is necessary to optimize the fuel-air ratio and flame temperature throughout the combustor to minimize the production of pollutants. In recent years, there has been considerable activity addressing Active Combustion Control. NASA Glenn Research Center's Active Combustion Control Technology effort aims to demonstrate active control in a realistic environment relevant to aircraft engines. Analysis and experiments are tied to aircraft gas turbine combustors. Considerable progress has been shown in demonstrating technologies for Combustion Instability Control, Pattern Factor Control, and Emissions Minimizing Control. Future plans are to advance the maturity of active combustion control technology to eventual demonstration in an engine environment.

  18. The guanine nucleotide exchange factor CNrasGEF activates Ras in response to cAMP and cGMP

    Microsoft Academic Search

    N. Pham; I. Cheglakov; C. A. Koch; C. L. de Hoog; M. F. Moran; D. Rotin

    2000-01-01

    Small GTPase proteins such as Ras are key regulators of cellular proliferation and are activated by guanine nucleotide exchange\\/releasing factors (GEFs\\/GRFs). Three classes of Ras GRFs have been identified to date, represented by Sos1\\/2, Ras-GRF1\\/2 and Ras-GRP. Here, we describe a novel candidate Ras activator, cyclic nucleotide rasGEF (CNrasGEF), which contains CDC25, Ras exchange motif (REM), Ras-association (RA), PDZ and

  19. Primary productivity, new productivity, and their relation to carbon flux during two Southern Ocean Gas Exchange tracer experiments

    NASA Astrophysics Data System (ADS)

    Lance, Veronica P.; Strutton, Peter G.; Vaillancourt, Robert D.; Hargreaves, Bruce R.; Zhang, Jia-Zhong; Marra, John

    2012-04-01

    Biological uptake rates of inorganic carbon and nitrate were measured during two sequential tracer release gas exchange experiments, together known as the Southern Ocean Gas Exchange Experiment (SO GasEx) in the southwest Atlantic sector of the Southern Ocean Antarctic Zone (51°N, 38°W). Primary productivity estimated from 14C incubations ranged from 26.7 to 47.2 mmol C m-2 d-1 in the first experiment (Patch 1) and 13.7 to 39.4 mmol C m-2 d-1 in the second experiment (Patch 2). Nitrate-based productivity estimated from 15NO3 incubations ranged from 5.8 to 13.1 mmol C m-2 d-1 in Patch 1 and 1.9 to 7.1 mmol C m-2 d-1 in Patch 2. The average ratio of nitrate-based productivity to primary productivity (approximating the f ratio) was 0.24 in Patch 1 and 0.15 in Patch 2. Chlorophyll concentrations for both patches were less than 1 mg m-3. Photochemical efficiency (Fv/Fm) was low (˜0.3) in Patch 1 and moderate (˜0.45) in Patch 2. Si(OH)4 concentrations were potentially limiting (<1 mmol m-3 for Patch 1 and ˜3 mmol m-3 for Patch 2), while NH4+ concentrations were elevated (˜1 mmol m-3 for Patch 1 and ˜2.2 mmol m-3 for Patch 2) compared with typical open ocean Antarctic Zone water. We hypothesize that Patch 1 productivity was regulated by the availability of Si(OH)4, while Patch 2 productivity was regulated by grazers. Primary production and nitrate-based production (as a proxy for C export) determined here provide components for a mixed layer carbon budget from which the air-sea flux of CO2 will be quantified.

  20. You can use a mobile device to access your Exchange account. On this page you will find the settings ActiveSync/Exchange to set up your Windows mobile devices.

    E-print Network

    Qiu, Weigang

    the settings ActiveSync/Exchange to set up your Windows mobile devices. If you set up an Exchange and task data! Use these settings to access your Exchange e-mail on a Windows mobile device: Username: (incoming and outgoing) mail.hunter.cuny.edu Windows Mobile Device: Here are the full steps for Windows

  1. Heat exchange with direct-flow and counterflow gas streams in a combined-heating oven

    Microsoft Academic Search

    A. S. Kukarkin; V. F. Mysik; B. I. Kitaev; B. I. Babanin; V. F. Parkhetov

    1977-01-01

    This article presents the results of theoretical studies of the temperature-field distribution in a moving gas-blown layer of coal pellets in a continuous-carbonization oven (for both direct-flow and counterflow movement of the coal-pellet and gas streams). It was shown that it is possible to obtain the best temperature-field distribution in the charge, in order to increase the throughput of continuous-carbonization

  2. The production of activated silica with carbon dioxide gas

    E-print Network

    Hayes, William Bell

    1956-01-01

    Silicate Feed System. Page III. Main Orifice Mixer and Phase Separator. . . . 22 IV. Exploded View of Main Mixing Orifice. . . , . 26 V. Phase Separator Construction VI. Gel Time of Activated Silica Sols. VII. Sulfur Dioxide Content of Flue Gas versus...- tion of an acldf. c material or other activant. It is usually wrf. t ten as $102 2. Sol, This I. s a general term applied to colloi- dal disperslons as distinguished from true solutions. S. Gel, A silf. ca gel ls a heavf. ly hvdrated, in- terlaced...

  3. Within-canopy and ozone fumigation effects on delta13C and Delta18O in adult beech (Fagus sylvatica) trees: relation to meteorological and gas exchange parameters.

    PubMed

    Gessler, Arthur; Löw, Markus; Heerdt, Christian; de Beeck, Maarten Op; Schumacher, Johannes; Grams, Thorsten E E; Bahnweg, Günther; Ceulemans, Reinhart; Werner, Herbert; Matyssek, Rainer; Rennenberg, Heinz; Haberer, Kristine

    2009-11-01

    In this study, the effects of different light intensities either in direct sunlight or in the shade crown of adult beech (Fagus sylvatica L.) trees on delta13C and Delta18O were determined under ambient (1 x O3) and twice-ambient (2 x O3) atmospheric ozone concentrations during two consecutive years (2003 and 2004). We analysed the isotopic composition in leaf bulk, leaf cellulose, phloem and xylem material and related the results to (a) meteorological data (air temperature, T and relative humidity, RH), (b) leaf gas exchange measurements (stomatal conductance, g(s); transpiration rate, E; and maximum photosynthetic activity, A(max)) and (c) the outcome of a steady-state evaporative enrichment model. Delta13C was significantly lower in the shade than in the sun crown in all plant materials, whilst Delta18O was increased significantly in the shade than in the sun crown in bulk material and cellulose. Elevated ozone had no effect on delta13C, although Delta18O was influenced by ozone to varied degrees during single months. We observed significant seasonal changes for both parameters, especially in 2004, and also significant differences between the study years. Relating the findings to meteorological data and gas exchange parameters, we conclude that the differences in Delta18O between the sun and the shade crown were predominantly caused by the Péclet effect. This assumption was supported by the modelled Delta18O values for leaf cellulose. It was demonstrated that independent of RH, light-dependent reduction of stomatal conductance (and thus transpiration) and of A(max) can drive the pattern of Delta18O increase with the concomitant decrease of delta13C in the shade crown. The effect of doubling ozone levels on time-integrated stomatal conductance and transpiration as indicated by the combined analysis of Delta18O and delta13C was much lower than the influence caused by the light exposure. PMID:19734546

  4. Element exchange in a water-and gas-closed biological life support system

    NASA Astrophysics Data System (ADS)

    Gribovskaya, I. V.; Kudenko, Yu. A.; Gitelson, J. I.

    1997-01-01

    Liquid human wastes and household water used for nutrition of wheat made possible to realize 24% closure for the mineral exchange in an experiment with a 2-component version of ``Bios-3'' life support system (LSS) Input-output balances of revealed, that elements (primarily trace elements) within the system. The structural materials (steel, titanium), expanded clay aggregate, and catalytic furnace catalysts. By the end of experiment, the permanent nutrient solution, plants, and the human diet gradually built up Ni, Cr, Al, Fe, V, Zn, Cu, and Mo. Thorough selection and pretreatment of materials can substantially reduce this accumulation. To enhance closure of the mineral exchange involves processing of human- metabolic wastes and inedible biomes inside LSS. An efficient method to oxidize wastes by hydrogen peroxide in a quartz reactor at the temperature of 80 degC controlled electromagnetic field is proposed.

  5. Element exchange in a water-and gas-closed biological life support system

    NASA Astrophysics Data System (ADS)

    1997-01-01

    Liquid human wastes and household water used for nutrition of wheat made possible to realize 24% closure for the mineral exchange in an experiment with a 2-component version of ``Bios-3'' life support system (LSS) Input-output balances of revealed, that elements (primarily trace elements) within the system. The structural materials (steel, titanium), expanded clay aggregate, and catalytic furnace catalysts. By the end of experiment, the permanent nutrient solution, plants, and the human diet gradually built up Ni, Cr, Al, Fe, V, Zn, Cu, and Mo. Thorough selection and pretreatment of materials can substantially reduce this accumulation. To enhance closure of the mineral exchange involves processing of human- metabolic wastes and inedible biomes inside LSS. An efficient method to oxidize wastes by hydrogen peroxide in a quartz reactor at the temperature of 80°C controlled electromagnetic field is proposed.

  6. Feasibility study for an advanced coal fired heat exchanger/gas turbine topping cycle for a high efficiency power plant. Technical report, April 1, 1993--June 30, 1993

    SciTech Connect

    Solomon, P.R.; Zhao, Y.; Buggeln, R.C.; Shamroth, S.J.

    1993-08-01

    Significant improvements in efficiency for the conversion of coal into electricity can be achieved by cycles which employ a high temperature recuperative gas turbine topping cycle. The objective of this project is the development of a new and proprietary concept for an externally fired gas turbine system. The chief advantage of this route is that the potential problems caused by the coal`s inorganic constituents are diverted from the high temperature rotating parts of the gas turbine to the high temperature stationary parts of a heat exchanger. The key technology issue is, then, the development of methods to fire a high temperature heat exchanger with coal in such a way that the potential damage from the inorganic constituents is minimized. The solution offered in this project is the design of a High Temperature Advanced Furnace (HITAF) with a Radiatively Enhanced, Aerodynamically Cleaned Heat-Exchanger (REACH-Exchanger). The REACH-Exchanger is fired by radiative and convective heat transfer from a moderately clean fuel stream and radiative heat transfer from the flame of a much larger uncleaned fuel stream. The approach is to utilize the best ceramic technology available for high temperature parts of the REACH-Exchanger and to shield the high temperature surfaces from interaction with coal minerals by employing clean combustion gases that sweep the tube surface exposed to the coal flame. In the proposed system, 80% of the energy to the REACH-Exchanger is supplied by radiation. The clean stream can be natural gas (base cycle) or volatile products of pyrolysis, low BTU gas from coal carbonization, or products of coal gasification (evolutionary cycle). The uncleaned stream can be coal or char.

  7. Studying heat exchange of dispersion-drop gas-liquid flow in granular layer

    Microsoft Academic Search

    N. A. Kuzin; V. A. Kuz'min; A. V. Kulikov; A. B. Shigarov

    1994-01-01

    Conclusions  Experimental procedure has been developed for physical modeling of monopropellant decomposition in a catalytic packet upon\\u000a limiting stage of the process, i.e., during evaporation of a liquid in drop conditions. Heat exchange of liquid drops in a\\u000a catalyst layer heated to high temperatures has been analyzed. Experimental dependence of a volume heat transfer coefficient\\u000a on grain diameter, liquid flow rate

  8. Hydraulic Performance and Gas Behavior of a Tall Crystalline Silicotitanate Ion-Exchange Column

    Microsoft Academic Search

    T. D. Welch; K. K. Anderson; D. A. Bostick; T. A. Dillow; R. D. Hunt; R. Lenarduzzi; A. J. Mattus; P. A. Taylor; W. R. Wilmarth

    2000-01-01

    Crystalline silicotitanate (CST) sorbent is one of several technologies being evaluated by the Savannah River Site (SRS) for removing cesium from high-level tank-waste supernatant. As currently envisioned, three large 5-ft-diam, 20-ft-high ion-exchange columns will be operated in series at a superficial velocity of 4.1 cm\\/min. The CST will be subjected to a high radiation field from the sorbed cesium. The

  9. A symbiotic gas exchange between bioreactors enhances microalgal biomass and lipid productivities: taking advantage of complementary nutritional modes.

    PubMed

    Santos, C A; Ferreira, M E; da Silva, T Lopes; Gouveia, L; Novais, J M; Reis, A

    2011-08-01

    This paper describes the association of two bioreactors: one photoautotrophic and the other heterotrophic, connected by the gas phase and allowing an exchange of O(2) and CO(2) gases between them, benefiting from a symbiotic effect. The association of two bioreactors was proposed with the aim of improving the microalgae oil productivity for biodiesel production. The outlet gas flow from the autotrophic (O(2) enriched) bioreactor was used as the inlet gas flow for the heterotrophic bioreactor. In parallel, the outlet gas flow from another heterotrophic (CO(2) enriched) bioreactor was used as the inlet gas flow for the autotrophic bioreactor. Aside from using the air supplied from the auto- and hetero-trophic bioreactors as controls, one mixotrophic bioreactor was also studied and used as a model, for its claimed advantage of CO(2) and organic carbon being simultaneously assimilated. The microalga Chlorella protothecoides was chosen as a model due to its ability to grow under different nutritional modes (auto, hetero, and mixotrophic), and its ability to attain a high biomass productivity and lipid content, suitable for biodiesel production. The comparison between heterotrophic, autotrophic, and mixotrophic Chlorella protothecoides growth for lipid production revealed that heterotrophic growth achieved the highest biomass productivity and lipid content (>22%), and furthermore showed that these lipids had the most suitable fatty acid profile in order to produce high quality biodiesel. Both associations showed a higher biomass productivity (10-20%), when comparing the two separately operated bioreactors (controls) which occurred on the fourth day. A more remarkable result would have been seen if in actuality the two bioreactors had been inter-connected in a closed loop. The biomass productivity gain would have been 30% and the lipid productivity gain would have been 100%, as seen by comparing the productivities of the symbiotic assemblage with the sum of the two bioreactors operating separately (controls). These results show an advantage of the symbiotic bioreactors association towards a cost-effective microalgal biodiesel production. PMID:20824486

  10. Solution and gas-phase H/D exchange of protein-small-molecule complexes: Cex and its inhibitors.

    PubMed

    Kang, Yang; Terrier, Peran; Ding, Chuanfan; Douglas, D J

    2012-01-01

    The properties of noncovalent complexes of the enzyme exo-1,4-?-D-glycanase ("Cex") with three aza-sugar inhibitors, deoxynojirimycin (X(2)DNJ), isofagomine lactam (X(2)IL), and isofagomine (X(2)IF), have been studied with solution and gas-phase hydrogen deuterium exchange (H/Dx) and measurements of collision cross sections of gas-phase ions. In solution, complexes have lower H/Dx levels than free Cex because binding the inhibitors blocks some sites from H/Dx and reduces fluctuations of the protein. In mass spectra of complexes, abundant Cex ions are seen, which mostly are formed by dissociation of complexes in the ion sampling interface. Both complex ions and Cex ions formed from a solution containing complexes have lower cross sections than Cex ions from a solution of Cex alone. This suggests the Cex ions formed by dissociation "remember" their solution conformations. For a given charge, ions of the complexes have greater gas-phase H/Dx levels than ions of Cex. Unlike cross sections, H/Dx levels of the complexes do not correlate with the relative gas-phase binding strengths measured by MS/MS. Cex ions from solutions with or without inhibitors, which have different cross sections, show the same H/Dx level after 15 s, indicating the ions may fold or unfold on the seconds time scale of the H/Dx experiment. Thus, cross sections show that complexes have more compact conformations than free protein ions on the time scale of ca. 1 ms. The gas-phase H/Dx measurements show that at least some complexes retain different conformations from the Cex ions on a time scale of seconds. PMID:22006406

  11. Arctic Carbon Storage and Gas Exchange Within and Between a Complex of Terrestrial, Freshwater and Marine Ecosystems and Their Interactions with the Atmosphere

    NASA Astrophysics Data System (ADS)

    Christensen, T. R.

    2012-12-01

    The primary goal of this presentation is to provide a measurement-based analysis of the complex relationships relating to the exchange of radiative active trace gases, carbon dioxide and methane, between different arctic landscape components and between the integrated result of these and the atmosphere. Focus will be on typical Arctic landscapes in Greenland starting at glacier forefields and downslope terrestrial permafrost environments to the limnic ecosystems and ultimately the near coastal environment. The terrestrial ecosystems become gradually more productive towards the coast and the transport of organic material towards the riverine and lake ecosystems gets to be more intensive and also increasingly sensitive to permafrost dynamics. A part of this organic material will be stored in sediments but a part of it will continue out to the coastal systems (Figure 1). A fundamental question is how much of this organic carbon is produced and where along this sequence of linked ecosystem processes the most important interactions with the atmosphere takes place. The answer will vary in time and the temporal aspects of the atmospheric exchanges are an important feature needed for a coherent understanding of arctic ecosystem interactions with climate. Hence, it puts pressure on the time-resolution and continuity of measurements in this complex set of different ecosystems and the degree of challenge this represents also vary between systems. With their upstream catchments Greenlandic terrestrial catchment-fjord ecosystems may form good micro- or mesocosm systems to study as model areas that are relevant for large scale understanding also. Some systems in Greenland such as the Nuuk and Zackenberg areas are at the same time some of the areas in the circumpolar North where the most elaborate relevant data are already being gathered on a continues basis as part of the Greenland Ecosystem Monitoring (GEM) activities. Here we provide a mass-balance approach to the storage, transport and atmospheric exchanges of carbon in sub- and high-arctic Greenlandic fjord ecosystem areas respectively. We review the availability of data to provide such mass balances and also the sensitivity of the individual components to changing climatic conditions.igure 1. Budgeting of the integrated storage and transport of organic carbon and the associated greenhouse gas exchange is essentially about quantifying the pools and arrows in this schematic figure. The objective of this presentation is to assess the spatial dynamics in two Greenlandic fjord systems mainly with the use of monitoring data obtained by GEM (see text).

  12. Note on the CO 2 air-sea gas exchange at high temperatures

    NASA Astrophysics Data System (ADS)

    Gröger, Matthias; Mikolajewicz, Uwe

    The temperature dependency of ocean-atmosphere gas transfer velocities is commonly estimated in terms of Schmidt numbers, i.e. the ratio of kinematic viscosity to diffusivity. In numerical models least square regressions are used to fit the limited number of experimentally derived Schmidt numbers to a function of temperature. For CO 2 a well established fit can be found in the literature. This fit constitutes an integral part in standardized carbon cycle simulation projects (e.g. C4MIP, OC4MIP, Friedlingstein et al., 2006). However, the fit is valid only in the range where diffusivity measurements exist, i.e., from 0 to about 30 °C. In many climate warming simulations like e.g. the MPI contribution to the fourth Intergovernmental Panel on Climate Change Assessment Report (IPCC AR 4), sea surface temperatures largely exceed the validated range and approach or even reach the range, where the standard fits leave the physically meaningful range. Thus, this paper underlines the demand for new measurements of seawater diffusivities for CO 2 and other trace gases especially for the temperature range >30 °C. In this paper we provide improved fits for the temperature dependence of the Schmidt number. For carbon dioxide our fit is compared to the established fit under identical climate change simulations carried out with the 3D-carbon cycle model HAMOCC. We find that in many tropical and subtropical high temperature regions the established fit leads to unrealistically short adaption times of the surface water pCO 2 to altered atmospheric pCO 2. In regions where the local oceanic pCO 2 is not primarily controlled by the atmospheric boundary pCO 2 but by other processes such as biological activity, the atmosphere ocean pCO 2 gradient is clearly underestimated when using the established fit. The effect on global oceanic carbon uptake in a greenhouse world is rather small and the potential climate feedback introduced by this bias seems to be negligible. However, the bias will clearly gain in significance the more regions warm up to over 30 °C. On a regional scale, especially in coastal regions at low latitudes, the effect is not negligible and a different steady state is approached.

  13. High Resolution CH4 Emissions and Dissolved CH4 Measurements Elucidate Surface Gas Exchange Processes in Toolik Lake, Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Del Sontro, T.; Sollberger, S.; Kling, G. W.; Shaver, G. R.; Eugster, W.

    2013-12-01

    Approximately 14% of the Alaskan North Slope is covered in lakes of various sizes and depths. Diffusive carbon emissions (CH4 and CO2) from these lakes offset the tundra sink by ~20 %, but the offset would substantially increase if ebullitive CH4 emissions were also considered. Ultimately, arctic lake CH4 emissions are not insignificant in the global CH4 budget and their contribution is bound to increase due to impacts from climate change. Here we present high resolution CH4 emission data as measured via eddy covariance and a Los Gatos gas analyzer during the ice free period from Toolik Lake, a deep (20 m) Arctic lake located on the Alaskan North Slope, over the last few summers. Emissions are relatively low (< 25 mg CH4 m-2 d-1) with little variation over the summer. Diurnal variations regularly occur, however, with up to 3 times higher fluxes at night. Gas exchange is a relatively difficult process to estimate, but is normally done so as the product of the CH4 gradient across the air-water interface and the gas transfer velocity, k. Typically, k is determined based on the turbulence on the water side of the interface, which is most commonly approximated by wind speed; however, it has become increasingly apparent that this assumption does not remain valid across all water bodies. Dissolved CH4 profiles in Toolik revealed a subsurface peak in CH4 at the thermocline of up to 3 times as much CH4 as in the surface water. We hypothesize that convective mixing at night due to cooling surface waters brings the subsurface CH4 to the surface and causes the higher night fluxes. In addition to high resolution flux emission estimates, we also acquired high resolution data for dissolved CH4 in surface waters of Toolik Lake during the last two summers using a CH4 equilibrator system connected to a Los Gatos gas analyzer. Thus, having both the flux and the CH4 gradient across the air-water interface measured directly, we can calculate k and investigate the processes influencing CH4 gas exchange in this lake. Preliminary results indicate that there are two regimes in wind speed that impact k - one at low wind speeds up to ~5 m s-1 and another at higher wind speeds (max ~10 m s-1). The differential wind speeds during night and day may compound the effect of convective mixing and cause the diurnal variation in observed fluxes.

  14. A Novel Human Mutation in the SLC9A1 Gene Results in Abolition of Na+/H+ Exchanger Activity

    PubMed Central

    Li, Xiuju; Fliegel, Larry

    2015-01-01

    The SLC9A1 gene, the Na+/H+ exchanger isoform 1 is the principal plasma membrane Na+/H+ exchanger of mammalian cells and functions by exchanging one intracellular proton for one extracellular sodium. The human protein is 815 amino acids in length. Five hundred N-terminal amino acids make up the transport domain of the protein and are believed to form 12 transmembrane segments. Recently, a genetic mutation of the Na+/H+ exchanger isoform 1, N266H, was discovered in a human patient through exome sequencing. We examined the effect of this mutation on expression, targeting and activity of the Na+/H+ exchanger. Mutant N266H protein was expressed in AP-1 cells, which lack their endogenous Na+/H+ exchanger protein. Targeting of the mutant protein to the cell surface was normal and expression levels were only slightly reduced relative to the wild type protein. However, the N266H mutant protein had no detectable Na+/H+ exchanger activity. A histidine residue at this location may disrupt the cation binding site or the pore of the Na+/H+ exchanger protein. PMID:25760855

  15. Structural basis for membrane recruitment and allosteric activation of cytohesin family Arf GTPase exchange factors

    PubMed Central

    Malaby, Andrew W.; van den Berg, Bert; Lambright, David G.

    2013-01-01

    Membrane recruitment of cytohesin family Arf guanine nucleotide exchange factors depends on interactions with phosphoinositides and active Arf GTPases that, in turn, relieve autoinhibition of the catalytic Sec7 domain through an unknown structural mechanism. Here, we show that Arf6-GTP relieves autoinhibition by binding to an allosteric site that includes the autoinhibitory elements in addition to the PH domain. The crystal structure of a cytohesin-3 construct encompassing the allosteric site in complex with the head group of phosphatidyl inositol 3,4,5-trisphosphate and N-terminally truncated Arf6-GTP reveals a large conformational rearrangement, whereby autoinhibition can be relieved by competitive sequestration of the autoinhibitory elements in grooves at the Arf6/PH domain interface. Disposition of the known membrane targeting determinants on a common surface is compatible with multivalent membrane docking and subsequent activation of Arf substrates, suggesting a plausible model through which membrane recruitment and allosteric activation could be structurally integrated. PMID:23940353

  16. The effect of aqueous transport of CO(2) in xylem sap on gas exchange in woody plants.

    PubMed

    Levy, P. E.; Meir, P.; Allen, S. J.; Jarvis, P. G.

    1999-01-01

    The influence of CO(2) transported in the transpiration stream on measurements of leaf photosynthesis and stem respiration was investigated. Measurements were made on trees in a temperate forest in Scotland and in a tropical rain forest in Cameroon, and on shrubs in the Sahelian zone in Niger. A chamber was designed to measure the CO(2) partial pressure in the gas phase within the woody stems of trees. High CO(2) partial pressures were found, ranging from 3000 to 9200 Pa. Henry's Law was used to estimate the CO(2) concentration of xylem sap, assuming that it was in equilibrium with the measured gas phase partial pressures. The transport of CO(2) in the xylem sap was calculated by multiplying sap CO(2) concentration by transpiration rate. The magnitude of aqueous transport in the studied species ranged from 0.03 to 0.35 &mgr;mol CO(2) m(-2) s(-1), representing 0.5 to 7.1% of typical leaf photosynthetic rates. These values strongly depend on sap pH. To examine the influence of aqueous transport of CO(2) on stem gas exchange, we made simultaneous measurements of stem CO(2) efflux and sap flow on the same stem. After removing the effect of temperature, stem CO(2) efflux was positively related to sap flow. The apparent effect on measurements of stem respiration was up to 0.7 &mgr;mol m(-2) s(-1), representing ~12% of peak stem respiration rates. PMID:12651332

  17. Active exchange of water and nutrients between seawater and shallow pore water in intertidal sandflats

    NASA Astrophysics Data System (ADS)

    Hwang, Dong-Woon; Kim, Guebuem; Yang, Han Soeb

    2008-12-01

    In order to determine the temporal and spatial variations of nutrient profiles in the shallow pore water columns (upper 30 cm depth) of intertidal sandflats, we measured the salinity and nutrient concentrations in pore water and seawater at various coastal environments along the southern coast of Korea. In the intertidal zone, salinity and nutrient concentrations in pore water showed marked vertical changes with depth, owing to the active exchange between the pore water and overlying seawater, while they are temporally more stable and vertically constant in the sublittoral zone. In some cases, the advective flow of fresh groundwater caused strong vertical gradients of salinity and nutrients in the upper 10 cm depth of surface sediments, indicating the active mixing of the fresher groundwater with overlying seawater. Such upper pore water column profiles clearly signified the temporal fluctuation of lower-salinity and higher-Si seawater intrusion into pore water in an intertidal sandflat near the mouth of an estuary. We also observed a semimonthly fluctuation of pore water nutrients due to spring-neap tide associated recirculation of seawater through the upper sediments. Our study shows that the exchange of water and nutrients between shallow pore water and overlying seawater is most active in the upper 20 cm layer of intertidal sandflats, due to physical forces such as tides, wave set-up, and density-thermal gradient.

  18. A Non-malleable Group Key Exchange Protocol Robust Against Active Insiders

    Microsoft Academic Search

    Yvo Desmedt; Josef Pieprzyk; Ron Steinfeld; Huaxiong Wang

    2006-01-01

    In this paper we make progress towards solving an open problem posed by Katz and Yung at CRYPTO 2003. We propose the first\\u000a protocol for key exchange among n ?2k+1 parties which simultaneously achieves all of the following properties:\\u000a \\u000a 1. Key Privacy (including forward security) against active attacks by group outsiders,\\u000a \\u000a \\u000a \\u000a 2. Non-malleability — meaning in particular that no subset

  19. In vitro adsorption removal of paraquat by activated carbon and cation exchange resin

    SciTech Connect

    Kitakouji, M.; Miyoshi, T.; Tanada, M.S.; Nakamura, T. (Univ. of Tokushima (Japan))

    1989-06-01

    With the modernization of agriculture, environmental pollution and accidental poisoning by agricultural chemicals have become a great social problem. With the remarkable increase in the amount of paraquat used, the number of deaths by swallowing of paraquat has also increased in recent years. Presently, an effective antidote and treatment for paraquat poisoning is not available. For primary treatment, administration of an adsorbent is done at the same time as gastrointestinal lavage. As an adsorbent for paraquat poisoning, the efficacy of activated carbon, Fuller's Earth, bentonite, and a cation exchange resin have been reported. In this work, the authors discuss the adsorption characteristics of paraquat in artificial gastric juice and normal saline solution.

  20. Local Area Water Removal Analysis of a Proton Exchange Membrane Fuel Cell under Gas Purge Conditions

    PubMed Central

    Lee, Chi-Yuan; Lee, Yu-Ming; Lee, Shuo-Jen

    2012-01-01

    In this study, local area water content distribution under various gas purging conditions are experimentally analyzed for the first time. The local high frequency resistance (HFR) is measured using novel micro sensors. The results reveal that the liquid water removal rate in a membrane electrode assembly (MEA) is non-uniform. In the under-the-channel area, the removal of liquid water is governed by both convective and diffusive flux of the through-plane drying. Thus, almost all of the liquid water is removed within 30 s of purging with gas. However, liquid water that is stored in the under-the-rib area is not easy to remove during 1 min of gas purging. Therefore, the re-hydration of the membrane by internal diffusive flux is faster than that in the under-the-channel area. Consequently, local fuel starvation and membrane degradation can degrade the performance of a fuel cell that is started from cold. PMID:22368495

  1. Thyroid hormone stimulates the renal Na/H exchanger NHE3 by transcriptional activation

    PubMed Central

    CANO, ADRIANA; BAUM, MICHEL; MOE, ORSON W.

    2014-01-01

    Thyroid hormone stimulates renal proximal tubule NaCl and NaHCO3 absorption in part by activating the apical membrane Na/H exchanger NHE3. We used a renal epithelial cell line, the opossum kidney (OK) cell, to define the mechanism by which 3,5,3?-triiodothyronine (T3) increases NHE3 activity. T3 stimulated NHE3 activity, an effect that was blocked by inhibition of cellular transcription or translation. The increase in activity was associated with increases in steady-state cell surface and total cellular NHE3 protein and NHE3 transcript abundance. T3 stimulated transcription of the NHE3 gene and had no effect on NHE3 transcript stability. The transcriptional activity of the 5?-flanking region of the rat NHE3 gene was stimulated by T3 when expressed in OK cells. When heterologously expressed rat NHE3 transcript levels were clamped constant with a constitutive promoter in OK cells, T3 has no effect on rat NHE3 protein abundance, suggesting the absence of regulation of NHE3 protein stability or translation. These studies demonstrate that T3 stimulates NHE3 activity by activating NHE3 gene transcription and increasing NHE3 transcript and protein abundance. PMID:9886925

  2. Activation of the guanine nucleotide exchange factor Dbl following ACK1-dependent tyrosine phosphorylation.

    PubMed

    Kato, J; Kaziro, Y; Satoh, T

    2000-02-01

    Signals triggered by diverse receptors modulate the activity of Rho family proteins, although the regulatory mechanism remains largely unknown. On the basis of their biochemical activity as guanine nucleotide exchange factors (GEFs), Dbl family proteins are believed to be implicated in the regulation of Rho family GTP-binding proteins in response to a variety of extracellular stimuli. Here we show that GEF activity of full-length proto-Dbl is enhanced upon tyrosine phosphorylation. When transiently coexpressed with the activated form of the non-receptor tyrosine kinase ACK1, a downstream target of Cdc42, Dbl became tyrosine-phosphorylated. In vitro GEF activity of Dbl toward Rho and Cdc42 was augmented following tyrosine phosphorylation. Moreover, accumulation of the GTP-bound form of Rho and Rac within the cell paralleled ACK-1-dependent tyrosine phosphorylation of Dbl. Consistently, activation of c-Jun N-terminal kinase downstream of Rho family GTP-binding proteins was also enhanced when Dbl was tyrosine-phosphorylated. Collectively, these findings suggest that the tyrosine kinase ACK1 may act as a regulator of Dbl, which in turn activates Rho family proteins. PMID:10652228

  3. 77 FR 40354 - Permitting Guidance for Oil and Gas Hydraulic Fracturing Activities Using Diesel Fuels-Draft

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-09

    ...Permitting Guidance for Oil and Gas Hydraulic Fracturing Activities Using Diesel Fuels...Permitting Guidance for Oil and Gas Hydraulic Fracturing Activities Using Diesel Fuels...Permitting Guidance for Oil and Gas Hydraulic Fracturing Activities Using Diesel...

  4. In-situ NMR studies of isobutane activation and exchange in zeolite beta.

    PubMed

    Truitt, Matthew J; White, Jeffery L

    2009-04-01

    (1)H solid-state NMR techniques have been used to simultaneously detect the reactivity of both catalyst and alkane reactant protons in an in-situ experimental design. Specifically, the activation of isobutane C-H bonds by the solid acid zeolite H-Beta is directly observed while the reaction is in progress, and the rate of proton transfer between the solid catalyst surface and gaseous isobutane is quantitatively measured using isotopic (1)H/(2)H exchange methods. Arrhenius analysis of isothermal kinetic runs revealed an apparent activation barrier of 70kJ/mole for the exchange process between isobutane and the 12-membered ring H-Beta, which exceeds our previously determined value of 57kJ/mole for isobutane in the 10-membered ring H-ZSM-5 (JACS 2006, v. 128, p. 1848). Estimation of true activation energies using heat of adsorption data from the literature combined with the experimentally measured apparent E(a) suggests that the true activation barrier differs by only 6-7kJ/mole in the two catalysts. We discuss the possibility that subtle shape selectivity, or inverse shape selectivity, and lattice solvation differences between the two catalysts account for the enhanced solvation of the isobutane transition state in HZSM-5 compared to the larger channel H-Beta. In all experiments, the isobutane reagent was treated to eliminate any unsaturated impurities that might serve as initiators for carbenium-ion mechanisms, and the active catalyst was free of any organic contaminants that might serve as a source of unsaturated initiators. PMID:19185469

  5. Seasonal and diurnal gas exchange differences in ozone-sensitive common milkweed (Asclepias syriaca L.) in relation to ozone uptake.

    PubMed

    Bergweiler, Chris; Manning, William J; Chevone, Boris I

    2008-03-01

    Stomatal conductance and net photosynthesis of common milkweed (Asclepias syriaca L.) plants in two different soil moisture regimes were directly quantified and subsequently modeled over an entire growing season. Direct measurements captured the dynamic response of stomatal conductance to changing environmental conditions throughout the day, as well as declining gas exchange and carbon assimilation throughout the growth period beyond an early summer maximum. This phenomenon was observed in plants grown both with and without supplemental soil moisture, the latter of which should theoretically mitigate against harmful physiological effects caused by exposure to ozone. Seasonally declining rates of stomatal conductance were found to be substantial and incorporated into models, making them less susceptible to the overestimations of effective exposure that are an inherent source of error in ozone exposure indices. The species-specific evidence presented here supports the integration of dynamic physiological processes into flux-based modeling approaches for the prediction of ozone injury in vegetation. PMID:17655989

  6. [Gas exchange determinations of Sphagnum Magellanicum : A contribution to the problem of membrane pigments in sphagna (III)].

    PubMed

    Rudolph, H

    1968-03-01

    Sphagnum magellanicum shows a remarkable variation in colour after the repeated application of cold shocks; mainly red wall pigments are synthesized. An attempt was made to find out in which way the gas exchange of Sphagnum magellanicum under defined conditions is altered after the application of cold shocks.The light-intensity curve of Sphagnum magellanicum cultivated under defined conditions shows no saturation at 8000 lx (0.03 Vol.-% CO2); the compensation point was found to be 400 lx and the optimal temperature 18°C.The O2-uptake of Sphagnum magellanicum drops at 3°C to 10% of the 20°C value.Whereas the oxygen-uptake by Sphagnum magellanicum is not altered by repeated cold shocks during the dark periods the photosynthetic rate is significantly depressed. PMID:24522820

  7. Environmental and canopy control of leaf level gas exchange of two evergreen tree species in a semiarid rangeland.

    NASA Astrophysics Data System (ADS)

    Bendevis, M. A.; Owens, M.; Heilman, J.; McInnes, K.

    2006-05-01

    Ashe juniper (Juniperus asheii) and plateau live oak (Quercus virginiana var fusiformis) have encroached into the historical grasslands of the Edwards Plateau of central Texas. The increased tree density may impact local water budgets because the area is the recharge zone for the Edwards Aquifer, the drinking water source for large municipalities like Austin and San Antonio. On the other hand, the trees have the capability of sequestering a greater amount of carbon than the historic grasslands. This study is a part of a larger NIGEC project examining the energy fluxes of the Oak-Juniper ecosystem. Four trees of each species were permanently marked and sampled with a leaf-level gas exchange system every 5 to 6 weeks throughout an entire year. Each tree was sampled on the northwest and southeast sides of the canopy, and at each location both sun-lit and shaded leaves were sampled. Averaged (± SE) over the entire year, live oak had significantly greater carbon assimilation rates than Ashe juniper (13.12 ± 0.6 vs. 6.47 ± 0.4 µmol CO2/m2/s, respectively). Oak trees exhibited a greater seasonal flux in carbon assimilation than juniper. Carbon assimilation was least in October 2005 for both species (2.47 and 6.46 µmol CO2/m2/s for juniper and oak, respectively) and greatest in November 2004 for juniper (13.02 µmol CO2/m2/s) and in April 2005 for oak (21.64 µmol CO2/m2/s). Sun-lit leaves also had a consistently greater assimilation rate (P<0.01) Transpirational water loss followed the same pattern with seasonal differences (P<0.0001) and canopy level (P<0.01) as critical factors. Xylem water potentials varied significantly by tree species and the month of observation. Juniper trees were initially less water stressed than the oak trees, but when precipitation was low near the end of the observation period the juniper trees showed a much larger increase in water stress. This was reflected in the higher transpiration and photosynthetic rates observed for oak trees. Juniper on the Edwards plateau maintains a lower and steadier rate of water use and carbon uptake throughout the year compared to the oak trees. The eco-hydrologic implications of this study are: 1) the consistent, low rates of gas exchange exhibited by juniper suggests a limitation of either hydraulic conductivity or photosynthetic capacity; 2) the consistently high rates exhibited by oak trees, even during dry periods, suggests a deeper rooting pattern or access to alternative sources of water in the fractured limestone substrate; and 3) gas exchange within this closed woodland was dissimilar from results in a more open woodland in an earlier study. Accurate descriptions of leaf area distribution are being collected to scale this information to the tree level for comparisons with sap flux data, and to relate gas exchange to the stand level data collected in the larger project.

  8. Effect of drought stress on gas exchange in channel millet (Echinochloa turneriana) and pearl millet (Pennisetum americanum)

    SciTech Connect

    Conover, D.G.; Sovonick-Dunford, S. (Univ. of Cincinnati, OH (USA))

    1990-05-01

    Gas exchange measurements were made on well-watered and droughted plants of the drought resistant pearl millet and of channel millet, a potential new crop for semi-arid regions. Photosynthesis and water use efficiency were similar for controls of both species at atmospheric CO{sub 2} levels and were reduced similarly by drought in both species. The CO{sub 2} saturated rate and the carboxylation efficiency were lowered by drought in both species, while stomatal limitation was increased by drought. Autoradiograms indicated that photosynthesis occurs evenly over the surface of well-watered control leaves of both species, but not in leaves of droughted plants. This could result in an overestimate of the effect of nonstomatal inhibition of photosynthesis by drought.

  9. Low loss liquid helium transfer system, using a high performance centrifugal pump and cold gas exchange

    Microsoft Academic Search

    H. Berndt; R. Doll; U. Jahn; W. Wiedemann

    1988-01-01

    A liquid-He transfer system with overall transfer losses of less than 2 percent is proposed. In comparison with a conventional transfer system, the design achieves energy and running time savings for He-liquefaction of up to 30 percent. The system consists of a reliable completely magnetic suspended centrifugal pump, submerged in the liquid, and a double transfer line allowing cold gas

  10. Fluid-thermoacoustic vibration of a gas turbine recuperator tubular heat exchanger system

    SciTech Connect

    Eisinger, F.L. (Foster Wheeler Energy Corp., Clinton, NJ (United States))

    1994-07-01

    Low-frequency acoustic vibration of a vertical gas turbine recuperator during cold start-up is described. The vibration was identified as fluid-thermoacoustic instability driven by a modified Sondhauss tube-like thermoacoustic phenomenon. The problem and its underlying theoretical basis are described. A design guideline for prevention of instability and alternative solutions for the elimination of the vibration are given.

  11. Experimental study of work exchange with a granular gas: the viewpoint of the Fluctuation Theorem.

    E-print Network

    Boyer, Edmond

    Theorem. Antoine Naert. Laboratoire de Physique de l'´Ecole Normale Sup´erieure de Lyon, Universit´e de forcing, between the motor and the gas are examined from the viewpoint of the Fluctuation Theorem the state of the system under scrutiny. Together with the Fluctuation Theorem (FT), this principle is used

  12. Air-water gas exchange of organochlorine compounds in Lake Baikal, Russia

    Microsoft Academic Search

    Laura L. McConnell; John R. Kucklick; Terry F. Bidleman; Genadi P. Ivanov; Sergey M. Chernyak

    1996-01-01

    Air and surface water samples were collected at Lake Baikal, Russia, during June 1991 to determine concentrations of organochlorine pesticides and polychlorinated biphenyl (PCB) congeners. These data were combined with Henry`s law constants to estimate the gas flux rate across the air-water interface of each compound class. Air samples were collected at Lake Baikal and from nearby Irkutsk. Water samples

  13. Experimental study of work exchange with a granular gas: the viewpoint of the Fluctuation Theorem.

    E-print Network

    . Thanks to an out-of-equilibrium extension of the Fluctuation-Dissipation Theorem, they defined an effec forcing, between the motor and the gas are examined from the viewpoint of the Fluctuation Theorem the state of the system under scrutiny. To- gether with the Fluctuation Theorem (FT), this principle is used

  14. On Factors Controlling AirWater Gas Exchange in a Large Tidal River

    E-print Network

    Ho, David

    systems, including tidal rivers and estuaries. While there are now reliable and routine methods and estuaries. Here, we present gas transfer velocities measured in the tidal Hudson River with a method widely that by transferring methodology used in oceanic studies to rivers and estuaries, robust data can be obtained

  15. Light emitting diode-based algal photobioreactor with external gas exchange

    Microsoft Academic Search

    Choul-Gyun Lee; Bernhard Ø. Palsson

    1995-01-01

    Regeneration of atmosphere is an essential component in a long-term manned mission in space. A compact and reliable photobioreactor (PBR) system with an efficient gas transfer module is required for this purpose. Light emitting diodes (LEDs) provide an ideal light source for a small and maintenance-free PBR. Lack of gravity in space prevents the use of sparging, one of the

  16. Plant Gas Exchange in Urban Landscapes L. Brooke McDowell and Chris A. Martin

    E-print Network

    Hall, Sharon J.

    and landscape design affect primary productivity and water use in various urban landscape patch types. Long in 1998 to research this question. Methods Effects of landscape design and land use history on plant gas and xeric or mesic residential landscape designs within the Phoenix metropolitan area. Remnant Sonoran

  17. Peach Water Relations, Gas Exchange, Growth and Shoot Mortality under Water Deficit in Semi-Arid Weather Conditions

    PubMed Central

    Rahmati, Mitra; Davarynejad, Gholam Hossein; Génard, Michel; Bannayan, Mohammad; Azizi, Majid; Vercambre, Gilles

    2015-01-01

    In this study the sensitivity of peach tree (Prunus persica L.) to three water stress levels from mid-pit hardening until harvest was assessed. Seasonal patterns of shoot and fruit growth, gas exchange (leaf photosynthesis, stomatal conductance and transpiration) as well as carbon (C) storage/mobilization were evaluated in relation to plant water status. A simple C balance model was also developed to investigate sink-source relationship in relation to plant water status at the tree level. The C source was estimated through the leaf area dynamics and leaf photosynthesis rate along the season. The C sink was estimated for maintenance respiration and growth of shoots and fruits. Water stress significantly reduced gas exchange, and fruit, and shoot growth, but increased fruit dry matter concentration. Growth was more affected by water deficit than photosynthesis, and shoot growth was more sensitive to water deficit than fruit growth. Reduction of shoot growth was associated with a decrease of shoot elongation, emergence, and high shoot mortality. Water scarcity affected tree C assimilation due to two interacting factors: (i) reduction in leaf photosynthesis (-23% and -50% under moderate (MS) and severe (SS) water stress compared to low (LS) stress during growth season) and (ii) reduction in total leaf area (-57% and -79% under MS and SS compared to LS at harvest). Our field data analysis suggested a ?stem threshold of -1.5 MPa below which daily net C gain became negative, i.e. C assimilation became lower than C needed for respiration and growth. Negative C balance under MS and SS associated with decline of trunk carbohydrate reserves – may have led to drought-induced vegetative mortality. PMID:25830350

  18. Seasonal photosynthetic gas exchange and water-use efficiency in a constitutive CAM plant, the giant saguaro cactus (Carnegiea gigantea).

    PubMed

    Bronson, Dustin R; English, Nathan B; Dettman, David L; Williams, David G

    2011-11-01

    Crassulacean acid metabolism (CAM) and the capacity to store large quantities of water are thought to confer high water use efficiency (WUE) and survival of succulent plants in warm desert environments. Yet the highly variable precipitation, temperature and humidity conditions in these environments likely have unique impacts on underlying processes regulating photosynthetic gas exchange and WUE, limiting our ability to predict growth and survival responses of desert CAM plants to climate change. We monitored net CO(2) assimilation (A(net)), stomatal conductance (g(s)), and transpiration (E) rates periodically over 2 years in a natural population of the giant columnar cactus Carnegiea gigantea (saguaro) near Tucson, Arizona USA to investigate environmental and physiological controls over carbon gain and water loss in this ecologically important plant. We hypothesized that seasonal changes in daily integrated water use efficiency (WUE(day)) in this constitutive CAM species would be driven largely by stomatal regulation of nighttime transpiration and CO(2) uptake responding to shifts in nighttime air temperature and humidity. The lowest WUE(day) occurred during time periods with extreme high and low air vapor pressure deficit (D(a)). The diurnal with the highest D(a) had low WUE(day) due to minimal net carbon gain across the 24 h period. Low WUE(day) was also observed under conditions of low D(a); however, it was due to significant transpiration losses. Gas exchange measurements on potted saguaro plants exposed to experimental changes in D(a) confirmed the relationship between D(a) and g(s). Our results suggest that climatic changes involving shifts in air temperature and humidity will have large impacts on the water and carbon economy of the giant saguaro and potentially other succulent CAM plants of warm desert environments. PMID:21822726

  19. [Differential diagnostic significance of complex values of gas exchange during submaximal physical effort in patients with emphysema and pulmonary fibrosis].

    PubMed

    Kullmer, T; Winkelmann, B; Siekmeier, R; Morbitzer, D; Falkenbach, A; Meier-Sydow, J

    1995-02-01

    The aim of this study was to clarify a) whether the behaviour of functional dead space ratio (VD/VE), alveolo-arterial difference of oxygen tensions (AaDO2) and the venous admixture ratio (QVA/Qt) differed at rest and during submaximal exercise, between patients with pulmonary emphysema and interstitial pulmonary fibrosis as well as from the respective findings in healthy controls, and b) whether a differentiation between these two diseases could be achieved by investigations of complex pulmonary gas exchange. Eleven patients with pulmonary fibrosis (F), which had been diagnosed by pulmonary biopsies, 11 patients with pulmonary emphysema (E) and 11 healthy controls (C) were subjected to conventional pulmonary function tests (PFTs: spirometry, bodyplethysmography, DCO) immediately followed by examinations of pulmonary gas exchange conducted at rest and during an incremental submaximal cycle spiroergometry (ERGO). With normal PFTs for C, vital capacity was diminished in F and the 1" timed vital capacity (FEV1) as well as Tiffeneau's index were reduced in E, while air way resistance and functional residual capacity were augmented in the latter group. In all patients the CO-diffusing capacity was lower compared to C, however, without differences between F and E. In both E and F, the arterial O2 tension were lower at rest as well as during ERGO when compared to C, whereas VD/VE, QVA/Qt and AaDO2 as well as the specific ventilation for O2 were higher, respectively. Alveolar ventilation was similar in all groups.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7724505

  20. Nocturnal transpiration in riparian Tamarix thickets authenticated by sap flux, eddy covariance and leaf gas exchange measurements.

    PubMed

    Moore, Georgianne W; Cleverly, James R; Owens, M Keith

    2008-04-01

    Tamarix chinensis Lour., which is common throughout the southwestern USA, is a phreatophytic riparian tree capable of high water use. We investigated temporal congruence between daily total evapotranspiration (E) estimated from stem sap flux (J(s)) measurements (E(sf)) and eddy covariance (E(cv)), both seasonally and immediately following rain events, and used measurements of leaf-level gas exchange, stem water content and diurnal changes in leaf water potential to track drivers of transpiration. In one study, conducted near the end of the growing season in a pure T. chinensis stand adjacent to the Rio Grande River in central New Mexico, nighttime E(sf) as a proportion of daily E(sf) increased with water availability to a peak of 36.6%. High nighttime E(sf) was associated with underestimates of nighttime E(cv). A second study, conducted in west Texas, beside the Pecos River, investigated the relationships between nighttime J(s) and stem tissue rehydration, on the one hand, and nighttime E, on the other hand. Leaf gas exchange measurements and stomatal impressions suggested that nighttime J(s) was primarily attributed to concurrent transpiration, although there were small overnight changes in stem water content. Both vapor pressure deficit and soil water availability were positively related to nighttime J(s), especially following rainfall events. Thus, both studies indicate that T. chinensis can transpire large amounts at night, a fact that must be considered when attempting to quantify E either by eddy covariance or sap flux methods. PMID:18244939

  1. Gas exchange and low temperature resistance in two tropical high mountain tree species from the Venezuelan Andes

    NASA Astrophysics Data System (ADS)

    Cavieres, Lohengrin A.; Rada, Fermín; Azócar, Aura; García-Núñez, Carlos; Cabrera, Hernán M.

    2000-05-01

    Temperature may determine altitudinal tree distribution in different ways: affecting survival through freezing temperatures or by a negative carbon balance produced by lower photosynthetic rates. We studied gas exchange and supercooling capacity in a timberline and a treeline species ( Podocarpus oleifolius and Espeletia neriifolia, respectively) in order to determine if their altitudinal limits are related to carbon balance, freezing temperature damage, or both. Leaf gas exchange, leaf temperature-net photosynthesis curves and leaf temperature at which ice formation occurred were measured at two sites along an altitudinal gradient. Mean CO 2 assimilation rates for E. neriifolia were 3.4 and 1.3 ?mol·m -2·s -1, at 2?400 and 3?200 m, respectively. Mean night respiration was 2.2 and 0.9 ?mol·m -2·s -1 for this species at 2?400 and 3?200 m, respectively. Mean assimilation rates for P. oleifolius were 3.8 and 2.2 ?mol·m -2·s -1 at 2?550 and 3?200 m, respectively. Night respiration was 0.8 ?mol·m -2·s -1 for both altitudes. E. neriifolia showed similar optimum temperatures for photosynthesis at both altitudes, while a decrease was observed in P. oleifolius.E. neriifolia and P. oleifolius presented supercooling capacities of -6.5 and -3.0 °C, respectively. For E. neriifolia, freezing resistance mechanisms are sufficient to reach higher altitudes; however, other environmental factors such as cloudiness may be affecting its carbon balance. P. oleifolius does not reach higher elevations because it does not have the freezing resistance mechanisms.

  2. Joint action of O/sub 3/ and SO/sub 2/ in modifying plant gas exchange

    SciTech Connect

    Olszyk, D.M.; Tingey, D.T.

    1986-01-01

    The joint action of O/sub 3/ and SO/sub 2/ stress on plants was investigated. Gas exchange measurements of O/sub 3/, SO/sub 2/, and H/sub 2/O vapor were made for garden pea. Plants were grown under controlled environments; O/sub 3/, SO/sub 2/, H/sub 2/O vapor fluxes were evaluated with a whole-plant gas exchange chamber using the mass-balance approach. Maximum O/sub 3/ and SO/sub 2/ fluxes per unit area into leaves averaged 8 nanomoles per square meter per second with exposure to either O/sub 3/ or SO/sub 2/ at 0.1 microliters per liter. Internal fluxes of either O/sub 3/ or SO/sub 2/ were reduced by up to 50% during exposure to combined versus individual pollutants; the greatest reduction occurred with simultaneous versus sequential combinations of the pollutants. Stomatal conductance to H/sub 2/O was substantially altered by the pollutant exposures, with O/sub 3/ molecules twice as effective as SO/sub 2/ molecules in inducing stomatal closure. Stomatal conductance was related to the integrated dose of pollutants. When O/sub 3/ was present at the start of the exposure, then stomatal response resembled that for O/sub 3/ more than the response for SO/sub 2/. The study indicated that stomatal responses with combinations of O/sub 3/ and SO/sub 2/ are not dependent solely on the integrated dose of pollutants, but suggests that a metabolic synergistic effect exists.

  3. Tyrosine Kinase-Stimulated Guanine Nucleotide Exchange Activity of Vav in T Cell Activation

    Microsoft Academic Search

    Erich Gulbins; K. Mark Coggeshall; Gottfried Baier; Shulamit Katzav; Paul Burn; Amnon Altman

    1993-01-01

    The hematopoietically expressed product of the vav proto-oncogene, Vav, shares homology with guanine nucleotide releasing factors (GRFs) [also called guanosine diphosphate-dissociation stimulators (GDSs)] that activate Ras-related small guanosine triphosphate (GTP)-binding proteins. Human T cell lysates or Vav immunoprecipitates possessed GRF activity that increased after T cell antigen receptor (TCR)-CD3 triggering; an in vitro-translated Vav fragment that contained the putative GRF

  4. Food production and gas exchange system using blue-green alga (spirulina) for CELSS

    NASA Technical Reports Server (NTRS)

    Oguchi, Mitsuo; Otsubo, Koji; Nitta, Keiji; Hatayama, Shigeki

    1987-01-01

    In order to reduce the cultivation area required for the growth of higher plants in space adoption of algae, which have a higher photosynthetic ability, seems very suitable for obtaining oxygen and food as a useful source of high quality protein. The preliminary cultivation experiment for determining optimum cultivation conditions and for obtaining the critical design parameters of the cultivator itself was conducted. Spirulina was cultivated in the 6 liter medium containing a sodium hydrogen carbonate solution and a cultivation temperature controlled using a thermostat. Generated oxygen gas was separated using a polypropyrene porous hollow fiber membrane module. Through this experiment, oxygen gas (at a concentration of more than 46 percent) at a rate of 100 to approx. 150 ml per minute could be obtained.

  5. Food production and gas exchange system using blue-green alga (Spirulina) for CELSS

    NASA Astrophysics Data System (ADS)

    Oguchi, Mitsuo; Otsubo, Koji; Nitta, Keiji; Hatayama, Shigeki

    In order to reduce the cultivation area required for the growth of higher plants in space adoption of algae, which have a higher photosynthetic ability, seems very suitable for obtaining oxygen and food as a useful source of high quality protein. The preliminary cultivation experiment for determining optimum cultivation conditions and for obtaining the critical design parameters of the cultivator itself has been conducted. Spirulina was cultivated in the 6-liter medium containing a sodium hydrogen carbonate solution and a cultivation temperature controlled using a thermostat. Generated oxygen gas was separated using a polypropyrene porous hollow fiber membrane module. Through this experiment, oxygen gas (at a concentration of more than 46%) at a rate of 100 ~ 150 ml per minute could be obtained.

  6. Carbon isotope fractionation during gas-water exchange and dissolution of CO 2

    Microsoft Academic Search

    J. Zhang; P. D. Quay; D. O. Wilbur

    1995-01-01

    The kinetic and equilibrium fractionation effects for 13C during CO2 gas transfer (?k and ?ag?g) have been measured in acidified distilled water. The equilibrium fractionation effects between bicarbonate and carbonate and gaseous C02 (?HCO3?g and ?CO3?g) have been measured in NaHC03 and NaHC03 + Na2C03 solutions, respectively, from 5° to 25°C. The measured fractionations, except ?CO3?g, agreed with earlier work

  7. Active Pattern Factor Control for Gas Turbine Engines

    NASA Technical Reports Server (NTRS)

    May, James E.

    1998-01-01

    Small variations in fuel/air mixture ratios within gas turbine combustors can result in measurable, and potentially detrimental, exit thermal gradients. Thermal gradients can increase emissions, as well as shorten the design life of downstream turbomachinery, particularly stator vanes. Uniform temperature profiles are usually sought through careful design and manufacturing of related combustor components. However, small componentto-component variations as well as numerous aging effects degrade system performance. To compensate for degraded thermal performance, researchers are investigating active, closed-loop control schemes.

  8. The production of activated silica with carbon dioxide gas 

    E-print Network

    Hayes, William Bell

    1956-01-01

    . Descri. ption of Equipment Operation of Equi. pment aly t i cal Procedure Discussion of Results, , 18 , 32 . 35 Conclusions, , 51 He fe rences Appendiw . 54 , 56 LIST OF FIGVRES I. Synthetic Flue Gas Feed Svstem II. Water and Sodium... as a conventional coagulant aid. Activated silica is prepared by the total or par- tial neutralization of the sodium oxide of sodium sili- cate. It is a member of a class of chemicals which must be prepared at the point of use, Prior preparation...

  9. Selection and preparation of activated carbon for fuel gas storage

    DOEpatents

    Schwarz, James A. (Fayetteville, NY); Noh, Joong S. (Syracuse, NY); Agarwal, Rajiv K. (Las Vegas, NV)

    1990-10-02

    Increasing the surface acidity of active carbons can lead to an increase in capacity for hydrogen adsorption. Increasing the surface basicity can facilitate methane adsorption. The treatment of carbons is most effective when the carbon source material is selected to have a low ash content i.e., below about 3%, and where the ash consists predominantly of alkali metals alkali earth, with only minimal amounts of transition metals and silicon. The carbon is washed in water or acid and then oxidized, e.g. in a stream of oxygen and an inert gas at an elevated temperature.

  10. Ral-Specific Guanine Nucleotide Exchange Factor Activity Opposes Other Ras Effectors in PC12 Cells by Inhibiting Neurite Outgrowth

    Microsoft Academic Search

    TAKANORI GOI; GABRIEL RUSANESCU; TAKESHI URANO; LARRY A. FEIG

    1999-01-01

    Ras proteins can activate at least three classes of downstream target proteins: Raf kinases, phosphatidyl- inositol-3 phosphate (PI3) kinase, and Ral-specific guanine nucleotide exchange factors (Ral-GEFs). In NIH 3T3 cells, activated Ral-GEFs contribute to Ras-induced cell proliferation and oncogenic transformation by complementing the activities of Raf and PI3 kinases. In PC12 cells, activated Raf and PI3 kinases mediate Ras-induced cell

  11. Irreversible catalyst activation enables hyperpolarization and water solubility for NMR signal amplification by reversible exchange.

    PubMed

    Truong, Milton L; Shi, Fan; He, Ping; Yuan, Bingxin; Plunkett, Kyle N; Coffey, Aaron M; Shchepin, Roman V; Barskiy, Danila A; Kovtunov, Kirill V; Koptyug, Igor V; Waddell, Kevin W; Goodson, Boyd M; Chekmenev, Eduard Y

    2014-12-01

    Activation of a catalyst [IrCl(COD)(IMes)] (IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene; COD = cyclooctadiene)] for signal amplification by reversible exchange (SABRE) was monitored by in situ hyperpolarized proton NMR at 9.4 T. During the catalyst-activation process, the COD moiety undergoes hydrogenation that leads to its complete removal from the Ir complex. A transient hydride intermediate of the catalyst is observed via its hyperpolarized signatures, which could not be detected using conventional nonhyperpolarized solution NMR. SABRE enhancement of the pyridine substrate can be fully rendered only after removal of the COD moiety; failure to properly activate the catalyst in the presence of sufficient substrate can lead to irreversible deactivation consistent with oligomerization of the catalyst molecules. Following catalyst activation, results from selective RF-saturation studies support the hypothesis that substrate polarization at high field arises from nuclear cross-relaxation with hyperpolarized (1)H spins of the hydride/orthohydrogen spin bath. Importantly, the chemical changes that accompanied the catalyst's full activation were also found to endow the catalyst with water solubility, here used to demonstrate SABRE hyperpolarization of nicotinamide in water without the need for any organic cosolvent--paving the way to various biomedical applications of SABRE hyperpolarization methods. PMID:25372972

  12. Ethylene reduces plant gas exchange and growth of lettuce grown from seed to harvest under hypobaric and ambient total pressure.

    PubMed

    He, Chuanjiu; Davies, Fred T

    2012-03-01

    Naturally occurring high levels of ethylene can be a problem in spaceflight and controlled environment agriculture (CEA) leading to sterility and irregular plant growth. There are engineering and safety advantages of growing plants under hypobaria (low pressure) for space habitation. The goals of this research were to successfully grow lettuce (Lactuca sativa cv. Buttercrunch) in a long-term study from seed to harvest under hypobaric conditions, and to investigate how endogenously produced ethylene affects gas exchange and plant growth from seed germination to harvest under hypobaric and ambient total pressure conditions. Lettuce was grown under two levels of total gas pressure [hypobaric or ambient (25 or 101 kPa)] in a long-term, 32-day study. Significant levels of endogenous ethylene occurred by day-15 causing reductions in photosynthesis, dark-period respiration, and a subsequent decrease in plant growth. Hypobaria did not mitigate the adverse ethylene effects on plant growth. Seed germination was not adversely affected by hypobaria, but was reduced by hypoxia (6 kPa pO(2)). Under hypoxia, seed germination was higher under hypobaria than ambient total pressure. This research shows that lettuce can be grown from seed to harvest under hypobaria (?25% of normal earth ambient total pressure). PMID:22118875

  13. VOLUME 85, NUMBER 9 P H Y S I C A L R E V I E W L E T T E R S 28 AUGUST 2000 Turbulence and Wave Breaking Effects on Air-Water Gas Exchange

    E-print Network

    Fineberg, Jay

    -made systems. For instance, in waste water treatment where bioremediation is used in large man-made water Breaking Effects on Air-Water Gas Exchange Evelyn J. Boettcher,1 Jay Fineberg,1,2 and Daniel P. Lathrop1 1 gravity waves on air-water gas exchange in standing waves. We identify two regimes that govern aeration

  14. Induction of CO 2 -gas exchange and electron transport: comparison of dynamic and steady-state responses in Fagus sylvatica leaves

    Microsoft Academic Search

    Michael Schulte; Christian Offer; Ute Hansen

    2003-01-01

    Photosynthetic induction was followed in a juvenile understorey beech (Fagus sylvatica L.) in a shaded habitat which was temporarily exposed to direct sunlight passing through a gap in the canopy. Simultaneous in situ measurements of leaf gas exchange and chlorophyll fluorescence were carried out and a steady-state light response curve of photosynthesis was recorded. The measured dynamic carbon gain was

  15. Different Patterns of Gas Exchange and Photochemical Efficiency in Three Desert Shrub Species Under Two Natural Temperatures and Irradiances in Mu Us Sandy Area of China

    Microsoft Academic Search

    G. M. Jiang; G. J. Zhu

    2001-01-01

    Field studies of gas exchange and chlorophyll fluorescence of three desert shrub species, Hedysarum fruticosum var. mongolicum, Artemisia ordosia, and Salix pasmmophylla, showed different patterns under different leaf temperature (T1) and incident photosynthetic photon flux density (PPFD). H. fruticosum var. mongolicum and A. ordosia exhibited higher PN and gs than S. pasmmophylla, especially under very high T1 (>46 °C) and

  16. Seasonal and inter-annual variations of gas exchange in thirteen woody species along a climatic gradient in the Mediterranean island of Mallorca

    Microsoft Academic Search

    J. Gulías; J. Cifre; S. Jonasson; H. Medrano; J. Flexas

    2009-01-01

    We studied the influence of summer drought and winter temperatures on seasonal and spatial variations of light-saturated net photosynthesis and stomatal conductance in Mediterranean woody species. We measured variations in leaf gas exchange over 3 years in 13 Mediterranean trees and shrubs, located at four different sites along a climate gradient of temperature and precipitation in the island of Mallorca

  17. Juvenile Rhus glabra leaves have higher temperatures and lower gas exchange rates than mature leaves when compared in the field during periods of high irradiance.

    PubMed

    Snider, John L; Choinski, John S; Wise, Robert R

    2009-05-01

    We sought to test the hypothesis that stomatal development determines the timing of gas exchange competency, which then influences leaf temperature through transpirationally driven leaf cooling. To test this idea, daily patterns of gas exchange and leaflet temperature were obtained from leaves of two distinctively different developmental stages of smooth sumac (Rhus glabra) grown in its native habitat. Juvenile and mature leaves were also sampled for ultrastructural studies of stomatal development. When plants were sampled in May-June, the hypothesis was supported: juvenile leaflets were (for part of the day) from 1.4 to 6.0 degrees C warmer than mature leaflets and as much as 2.0 degrees C above ambient air temperature with lower stomatal conductance and photosynthetic rates than mature leaflets. When measurements were taken from July to October, no significant differences were observed, although mature leaflet gas exchange rates declined to the levels of the juvenile leaves. The gas exchange data were supported by the observations that juvenile leaves had approximately half the number of functional stomata on a leaf surface area basis as did mature leaves. It was concluded that leaf temperature and stage of leaf development in sumac are strongly linked with the higher surface temperatures observed in juvenile leaflets in the early spring possibly being involved in promoting photosynthesis and leaf expansion when air temperatures are cooler. PMID:18849091

  18. Drought-induced hydraulic limitations constrain leaf gas exchange recovery after precipitation pulses in the C 3 woody legume, Prosopis velutina

    Microsoft Academic Search

    Víctor Resco; Brent E. Ewers; Wei Sun; Travis E. Huxman; Jake F. Weltzin; David G. Williams

    2009-01-01

    Summary • The hypothesis that drought intensity constrains the recovery of photosynthesis from drought was tested in the C3 woody legume Prosopis velutina, and the mech- anisms underlying this constraint examined.  Hydraulic status and gas exchange were measured the day before a 39 mm precipitation pulse, and up to 7 d afterwards. The experiment was conducted under rainout shelters,

  19. Proceedings of the 22"dAnnual EMBS International Conference, July 23-28,2000, Chicago IL. Interaction of hemodynamics and gas exchange

    E-print Network

    Qiu, Anqi

    systems - respiratory and circulatory systems. It consists of five components: a model of gas transport, exchange and storage in the human, a multi-element nonlinear mathematical model of human circulatory system technologies. Keywords - Hemodynamics, circulatory system, respiratory system, hypoxia, pulmonary hypertension

  20. Lanthanum-exchanged zeolites as active and selective catalysts for the generation of singlet oxygen from hydrogen peroxide.

    PubMed

    Wahlen, Joos; De Vos, Dirk; De Hertogh, Sigrid; Nardello, Veronique; Aubry, Jean-Marie; Alsters, Paul; Jacobs, Pierre

    2005-02-21

    Lanthanum(III)-exchanged zeolites Beta and USY are active and selective catalysts for the generation of singlet oxygen from H2O2 showing superior activity and oxidant efficiency compared to unsupported La-catalysts, e.g. La(OH)3. PMID:15700084

  1. Cobenefit of SO 3 reduction on mercury capture with activated carbon in coal flue gas

    Microsoft Academic Search

    Ye Zhuang; Christopher Martin; John Pavlish; Francois Botha

    2011-01-01

    Parametric experiments were carried out to study the interactions of mercury, SO3, and injected activated carbon (AC) in a coal flue gas stream. The levels of SO3 vapor in flue gas were altered by individually varying flue gas temperature, moisture, or sodium fume injection in the flue gas. Meanwhile, mercury emissions with AC injection (ACI) upstream of an electrostatic precipitator

  2. Gas Exchanges and Dehydration in Different Intensities of Conditioning in Tifton 85 Bermudagrass: Nutritional Value during Hay Storage

    PubMed Central

    Pasqualotto, M.; Neres, M. A.; Guimarães, V. F.; Klein, J.; Inagaki, A. M.; Ducati, C.

    2015-01-01

    The present study aimed at evaluating the intensity of Tifton 85 conditioning using a mower conditioner with free-swinging flail fingers and storage times on dehydration curve, fungi presence, nutritional value and in vitro digestibility of Tifton 85 bermudagrass hay dry matter (DM). The dehydration curve was determined in the whole plant for ten times until the baling. The zero time corresponded to the plant before cutting, which occurred at 11:00 and the other collections were carried out at 8:00, 10:00, 14:00, and 16:00. The experimental design was randomised blocks with two intensities of conditioning (high and low) and ten sampling times, with five replications. The high and low intensities related to adjusting the deflector plate of the free iron fingers (8 and 18 cm). In order to determine gas exchanges during Tifton 85 bermudagrass dehydration, there were evaluations of mature leaves, which were placed in the upper middle third of each branch before the cutting, at every hour for 4 hours. A portable gas analyser was used by an infrared IRGA (6400xt). The analysed variables were photosynthesis (A), stomatal conductance (gs), internal CO2 concentration (Ci), transpiration (T), water use efficiency (WUE), and intrinsic water use efficiency (WUEi). In the second part of this study, the nutritional value of Tifton 85 hay was evaluated, so randomised blocks were designed in a split plot through time, with two treatments placed in the following plots: high and low intensity of cutting and five different time points as subplots: cutting (additional treatment), baling and after 30, 60, and 90 days of storage. Subsequently, fungi that were in green plants as well as hay were determined and samples were collected from the grass at the cutting period, during baling, and after 30, 60, and 90 days of storage. It was observed that Tifton 85 bermudagrass dehydration occurred within 49 hours, so this was considered the best time for drying hay. Gas exchanges were more intense before cutting, although after cutting they decreased until ceasing within 4 hours. The lowest values of acid detergent insoluble nitrogen were obtained with low conditioning intensity after 30 days of storage, 64.8 g/kg DM. The in vitro dry matter of Tifton 85 bermudagrass did not differ among the storage times or the conditioning intensities. There was no fungi present in the samples collected during the storage period up to 90 days after dehydration, with less than 30 colony forming units found on plate counting. The use of mower conditioners in different intensities of injury did not speed up the dehydration time of Tifton 85. PMID:25925058

  3. Trefoil factor 2 requires Na/H exchanger 2 activity to enhance mouse gastric epithelial repair.

    PubMed

    Xue, Lin; Aihara, Eitaro; Wang, Timothy C; Montrose, Marshall H

    2011-11-01

    Trefoil factor (TFF) peptides are pivotal for gastric restitution after surface epithelial damage, but TFF cellular targets that promote cell migration are poorly understood. Conversely, Na/H exchangers (NHE) are often implicated in cellular migration but have a controversial role in gastric restitution. Using intravital microscopy to create microscopic lesions in the mouse gastric surface epithelium and directly measure epithelial restitution, we evaluated whether TFFs and NHE isoforms share a common pathway to promote epithelial repair. Blocking Na/H exchange (luminal 10 ?m 5-(N-ethyl-N-isopropyl) amiloride or 25 ?m HOE694) slows restitution 72-83% in wild-type or NHE1(-/-) mice. In contrast, HOE694 has no effect on the intrinsically defective gastric restitution in NHE2(-/-) mice or TFF2(-/-) mice. In TFF2(-/-) mice, NHE2 protein is reduced 23%, NHE2 remains localized to apical membranes of surface epithelium, and NHE1 protein amount or localization is unchanged. The action of topical rat TFF3 to accelerate restitution in TFF2(-/-) mice was inhibited by AMD3100 (CXCR4 receptor antagonist). Furthermore, rat TFF3 did not rescue restitution when NHE2 was inhibited [TFF2(-/-) mice +HOE694, or NHE2(-/-) mice]. HOE694 had no effect on pH at the juxtamucosal surface before or after damage. We conclude that functional NHE2, but not NHE1, is essential for mouse gastric epithelial restitution and that TFFs activate epithelial repair via NHE2. PMID:21900251

  4. Closed and continuous algae cultivation system for food production and gas exchange in CELSS

    NASA Astrophysics Data System (ADS)

    Oguchi, Mitsuo; Otsubo, Koji; Nitta, Keiji; Shimada, Atsuhiro; Fujii, Shigeo; Koyano, Takashi; Miki, Keizaburo

    In CELSS (Controlled Ecological Life Support System), utilization of photosynthetic algae is an effective means for obtaining food and oxygen at the same time. We have chosen Spirulina, a blue-green alga, and have studied possibilities of algae utilization. We have developed an advanced algae cultivation system, which is able to produce algae continuously in a closed condition. Major features of the new system are as follows. o (1)In order to maintain homogeneous culture conditions, the cultivator was designed so as to cause a swirl on medium circulation. (2)Oxygen gas separation and carbon dioxide supply are conducted by a newly designed membrane module. (3)Algae mass and medium are separated by a specially designed harvester. (4)Cultivation conditions, such as pH, temperature, algae growth rate, light intensity and quanlity of generated oxygen gas are controlled by a computer system and the data are automatically recorded. This equipment is a primary model for ground experiments in order to obtain some design data for space use. A feasibility of algae cultivation in a closed condition is discussed on the basis of data obtained by use of this new system.

  5. Bomb radiocarbon in the Red Sea: A medium-scale gas exchange experiment

    SciTech Connect

    Cember, R.

    1989-02-15

    The history of bomb-produced radiocarbon in the surface waters of the Red Sea and the western Gulf of Aden was reconstructed from annual growth bands of corals. Gulf of Aden surface water entering the Red Sea and flowing to the north at the surface of the Red Sea becomes progressively enriched in bomb /sup 14/C by air-sea exchange of carbon dioxide. With physical oceanographic observations and analysis as the basis of a simple model, this progressive northward enrichment can be used to calculate a mean invasionn flux for CO/sub 2/ across the Red Sea surface. The CO/sub 2/ invasion flux so calculated is 8 mol/m/sup 2//yr with an uncertainty of approximately 2 mol/m/sup 2//yr. When combined with the extensive historical observations of wind speeds in the Red Sea, the calculated CO/sub 2/ invasion flux supports the empirical relationship between CO/sub 2/ invasion and wind speed proposed by other workers. Sea surface pCO/sub 2/ was measured at seven stations along the length of the Red Sea in January 1985. These pCO/sub 2/ data show that in midwinter the net flux of CO/sub 2/ across the Red Sea surface (i.e. the difference between the invasion and evasion fluxes) is approximately zero for the Red Sea as a whole. copyright American Geophysical Union 1989

  6. Educator Exchange Resource Guide.

    ERIC Educational Resources Information Center

    Garza, Cris; Rodriguez, Victor

    This resource guide was developed for teachers and administrators interested in participating in intercultural and international exchange programs or starting an exchange program. An analysis of an exchange program's critical elements discusses exchange activities; orientation sessions; duration of exchange; criteria for participation; travel,…

  7. 77 FR 5778 - Agency Information Collection Activities: Rules Relating to Regulation of Domestic Exchange...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-06

    ...Regulation of Domestic Exchange-Traded Options AGENCY: Commodity Futures Trading Commission...The collection covers rules related to risk disclosure concerning exchange traded commodity options. DATES: Comments must be submitted on...

  8. Cost leveling continues; planned activity drops sharply in US gas pipeline cnstruction

    SciTech Connect

    Morgan, J.M.

    1986-02-01

    Natural gas pipeline construction costs, as measured by the OGJ-Morgan Pipeline cost index for US gas-pipeline construction, barely crept up in the second quarter 1985. Construction activity for lines and compressor stations was down.

  9. 77 FR 58616 - Pipeline Safety: Information Collection Activities, Revision to Gas Transmission and Gathering...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-21

    ...DEPARTMENT OF TRANSPORTATION Pipeline and Hazardous Materials Safety Administration [Docket No. PHMSA-2012-0024] Pipeline Safety: Information Collection Activities...Revision to Gas Transmission and Gathering Pipeline Systems Annual Report, Gas...

  10. 77 FR 22387 - Pipeline Safety: Information Collection Activities, Revision to Gas Transmission and Gathering...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-13

    ...DEPARTMENT OF TRANSPORTATION Pipeline and Hazardous Materials Safety Administration [Docket No. PHMSA-2012-0024] Pipeline Safety: Information Collection Activities...Revision to Gas Transmission and Gathering Pipeline Systems Annual Report, Gas...

  11. Gas Exchange Characteristics of the Submerged Aquatic Crassulacean Acid Metabolism Plant, Isoetes howellii1

    PubMed Central

    Keeley, Jon E.; Bowes, George

    1982-01-01

    The submerged aquatic plant Isoetes howellii Engelmann possesses Crassulacean acid metabolism (CAM) comparable to that known from terrestrial CAM plants. Infrared gas analysis of submerged leaves showed Isoetes was capable of net CO2 uptake in both light and dark. CO2 uptake rates were a function of CO2 levels in the medium. At 2,500 microliters CO2 per liter (gas phase, equivalent to 1.79 milligrams per liter aqueous phase), Isoetes leaves showed continuous uptake in both the light and dark. At this CO2 level, photosynthetic rates were light saturated at about 10% full sunlight and were about 3-fold greater than dark CO2 uptake rates. In the dark, CO2 uptake rates were also a function of length of time in the night period. Measurements of dark CO2 uptake showed that, at both 2,500 and 500 microliters CO2 per liter, rates declined during the night period. At the higher CO2 level, dark CO2 uptake rates at 0600 h were 75% less than at 1800 h. At 500 microliters CO2 per liter, net CO2 uptake in the dark at 1800 h was replaced by net CO2 evolution in the dark at 0600 h. At both CO2 levels, the overnight decline in net CO2 uptake was marked by periodic bursts of accelerated CO2 uptake. CO2 uptake in the light was similar at 1% and 21% O2, and this held for leaves intact as well as leaves split longitudinally. Estimating the contribution of light versus dark CO2 uptake to the total carbon gain is complicated by the diurnal flux in CO2 availability under field conditions. PMID:16662697

  12. Gas Exchange Characteristics of the Submerged Aquatic Crassulacean Acid Metabolism Plant, Isoetes howellii.

    PubMed

    Keeley, J E; Bowes, G

    1982-11-01

    The submerged aquatic plant Isoetes howellii Engelmann possesses Crassulacean acid metabolism (CAM) comparable to that known from terrestrial CAM plants. Infrared gas analysis of submerged leaves showed Isoetes was capable of net CO(2) uptake in both light and dark. CO(2) uptake rates were a function of CO(2) levels in the medium. At 2,500 microliters CO(2) per liter (gas phase, equivalent to 1.79 milligrams per liter aqueous phase), Isoetes leaves showed continuous uptake in both the light and dark. At this CO(2) level, photosynthetic rates were light saturated at about 10% full sunlight and were about 3-fold greater than dark CO(2) uptake rates. In the dark, CO(2) uptake rates were also a function of length of time in the night period. Measurements of dark CO(2) uptake showed that, at both 2,500 and 500 microliters CO(2) per liter, rates declined during the night period. At the higher CO(2) level, dark CO(2) uptake rates at 0600 h were 75% less than at 1800 h. At 500 microliters CO(2) per liter, net CO(2) uptake in the dark at 1800 h was replaced by net CO(2) evolution in the dark at 0600 h. At both CO(2) levels, the overnight decline in net CO(2) uptake was marked by periodic bursts of accelerated CO(2) uptake. CO(2) uptake in the light was similar at 1% and 21% O(2), and this held for leaves intact as well as leaves split longitudinally. Estimating the contribution of light versus dark CO(2) uptake to the total carbon gain is complicated by the diurnal flux in CO(2) availability under field conditions. PMID:16662697

  13. Naphthalene SOA: redox activity and naphthoquinone gas-particle partitioning

    NASA Astrophysics Data System (ADS)

    McWhinney, R. D.; Zhou, S.; Abbatt, J. P. D.

    2013-10-01

    Chamber secondary organic aerosol (SOA) from low-NOx photooxidation of naphthalene by hydroxyl radical was examined with respect to its redox cycling behaviour using the dithiothreitol (DTT) assay. Naphthalene SOA was highly redox-active, consuming DTT at an average rate of 118 ± 14 pmol per minute per ?g of SOA material. Measured particle-phase masses of the major previously identified redox active products, 1,2- and 1,4-naphthoquinone, accounted for only 21 ± 3% of the observed redox cycling activity. The redox-active 5-hydroxy-1,4-naphthoquinone was identified as a new minor product of naphthalene oxidation, and including this species in redox activity predictions increased the predicted DTT reactivity to 30 ± 5% of observations. These results suggest that there are substantial unidentified redox-active SOA constituents beyond the small quinones that may be important toxic components of these particles. A gas-to-SOA particle partitioning coefficient was calculated to be (7.0 ± 2.5) × 10-4 m3 ?g-1 for 1,4-naphthoquinone at 25 °C. This value suggests that under typical warm conditions, 1,4-naphthoquinone is unlikely to contribute strongly to redox behaviour of ambient particles, although further work is needed to determine the potential impact under conditions such as low temperatures where partitioning to the particle is more favourable. Also, higher order oxidation products that likely account for a substantial fraction of the redox cycling capability of the naphthalene SOA are likely to partition much more strongly to the particle phase.

  14. Thermal-Conductivity Characterization of Gas Diffusion Layer in Proton Exchange Membrane Fuel Cells and Electrolyzers Under Mechanical Loading

    NASA Astrophysics Data System (ADS)

    Hamour, M.; Garnier, J. P.; Grandidier, J. C.; Ouibrahim, A.; Martemianov, S.

    2011-05-01

    Accurate information on the temperature field and associated heat transfer rates is particularly important for proton exchange membrane fuel cells (PEMFC) and PEM electrolyzers. An important parameter in fuel cell and electrolyzer performance analysis is the effective thermal conductivity of the gas diffusion layer (GDL) which is a solid porous medium. Usually, this parameter is introduced in modeling and performance analysis without taking into account the dependence of the GDL thermal conductivity ? (in W · m-1 · K-1) on mechanical compression. Nevertheless, mechanical stresses arising in an operating system can change significantly the thermal conductivity and heat exchange. Metrology allowing the characterization of the GDL thermal conductivity as a function of the applied mechanical compression has been developed in this study using the transient hot-wire technique (THW). This method is the best for obtaining standard reference data in fluids, but it is rarely used for thermal-conductivity measurements in solids. The experiments provided with Quintech carbon cloth indicate a strong dependence (up to 300%) of the thermal conductivity ? on the applied mechanical load. The experiments have been provided in the pressure range 0 < p < 8 MPa which corresponds to stresses arising in fuel cells. All obtained experimental results have been fitted by the equation ? = 0.9log(12 p + 17)(1 - 0.4e-50 p ) with 9% uncertainty. The obtained experimental dependence can be used for correct modeling of coupled thermo/electro-mechanical phenomena in fuel cells and electrolyzers. Special attention has been devoted to justification of the main hypotheses of the THW method and for estimation of the possible influence of the contact resistances. For this purpose, measurements with a different number of carbon cloth layers have been provided. The conducted experiments indicate the independence of the measured thermal conductivity on the number of GDL layers and, thus, justify the robustness of the developed method and apparatus for this type of application.

  15. Beta 1-selective and non-selective beta-adrenoceptor blockade, anaerobic threshold and respiratory gas exchange during exercise.

    PubMed Central

    McLeod, A A; Knopes, K D; Shand, D G; Williams, R S

    1985-01-01

    The effect of oral doses of the beta 1-selective adrenoceptor antagonist atenolol (50 mg), the non-selective antagonist propranolol (40 mg) and placebo was investigated during exercise in a crossover comparison in six healthy but untrained subjects. Descriptors of ventilation, respiratory gas exchange, and arterialized blood lactate and glucose were obtained during steady state bicycle ergometric exercise at 20% and 60% of the subjects' previously determined maximal oxygen uptake (VO2 max). At these work intensities, the previously reported increase of respiratory exchange ratio (RER) during non-selective beta-adrenoceptor blockade was found to be trivial (placebo = 0.96 +/- 0.03 s.e. mean; propranolol = 0.97 +/- 0.01; atenolol = 0.97 +/- 0.04; 60% VO2 max, 10 min exercise) and only present during the early minutes of effort. Oxygen uptake and carbon dioxide production did not differ between treatments. Both drugs produced highly significant falls in peak expiratory flow (PEF) rates and tidal volume (VT) which were compensated by an increase in respiratory rate. PEF, 60% VO2 max: placebo = 3.8 +/- 0.3 l/s; propranolol 3.6 +/- 0.3 l/s (P less than 0.03); atenolol 3.1 +/- 0.3 l/s (P less than 0.01). VT, 60% VO2 max: placebo 2.0 +/- 0.1 l; propranolol 1.8 +/- 0.21 (P less than 0.05); atenolol 1.7 +/- 0.1 1 (P less than 0.01). Arterialized lactate was significantly elevated during work at 20% and 60% VO2 max, but rose progressively at the 60% VO2 max load. Ventilation, oxygen uptake and ventilatory equivalent for carbon dioxide also rose progressively at this workload. Ventilatory equivalent for oxygen showed no significant rise.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2858214

  16. Gas-phase carbon exchange between mangrove forests and the atmosphere

    NASA Astrophysics Data System (ADS)

    Rayment, Mark

    2013-04-01

    Mangrove ecosystems are believed to be highly productive, storing carbon at rates as high as or higher than terrestrial tropical rainforests. Their high productivity is reflected in the high levels of organic carbon stored within, and exported from, these ecosystems. This includes so-called blue carbon - carbon of terrestrial origin sequestered in coastal margins. Despite their potential importance, significant knowledge gaps exist both in the magnitudes of the components of mangrove carbon balance, and the factors controlling them. These gaps result from the lack of primary datasets, which is itself a consequence of the complex nature of mangrove ecosystems, and of the difficult working conditions found there. Here, we report on a study designed to elucidate some of the environmental controls on the exchange of CO2 and CH4 to and from intact mangrove ecosystems in East Africa. Gazi Bay (4° 25'S, 39° 30'E), south of Mombasa, Kenya, encompasses around 600 ha of mangrove forest, including partially and severely degraded stands as well as restored areas. The area contains all 10 species of mangrove found in East Africa, including mono-specific areas of the two most common species, Avicennia marina and Rhizophora mucronata, sufficiently extensive for robust eddy covariance (EC) measurements. During 2012, open path EC measurements were made at both Avicennia marina and Rhizophora mucronata sites throughout a spring/neap tidal cycle. Flux data were fitted to a simple model describing the ecosystem level response to environmental variables. Stands of both species exhibited higher maximum net ecosystem uptake, but lower apparent quantum efficiency and lower dark respiration when inundated by high tides. Maximum net ecosystem uptake was higher in Rhizophora (12.8 (dry) - 16.5 (wet) ?mol m-2 s-1) than in Avicennia (5.1 (dry) - 5.9 (wet) ?mol m-2 s-1). Apparent quantum efficiency was twice as high in Rhizophora (0.09 (wet) - 0.12 (dry) mol mol-1) than in Avicennia (0.03 (wet) - 0.06 (dry) mol mol-1). Dark respiration rates were broadly similar when the tide was out (8.3 ?mol m-2 s-1 (Rhizophora), 7.3 ?mol m-2 s-1 (Avicennia)), but high tide reduced respiration much more in Avicennia (0.5 ?mol m-2 s-1) than in Rhizophora (7.5 ?mol m-2 s-1). Methane exchange between the Rhizophora ecosystem and the atmosphere was small and dependant on tidal state, varying between a methane consumption of around 0.2 mg (C) m-2 hr-1 at low and incoming tide to a methane production of around 2.5 mg (C) m-2 hr-1 during outgoing tides. The Avicennia ecosystem was consistently a small consumer of methane (ca. 0.2 mg (C) m-2 hr-1).

  17. Structured Exchange and Childhood Learning: The Severely Retarded Child. Program Activity 12.

    ERIC Educational Resources Information Center

    Hamblin, Robert L.; And Others

    A description of the Social Exchange Laboratory's work with autistic children is presented. The laboratory's philosophy of the exchange theory of autism, seen as a set of habitual response patterns maintained and intensified by exchanges which are inadvertantly structured by others in the child's environment, is set forth with characteristics,…

  18. Ethanolamine requirement of mammary epithelial cells is due to reduced activity of base exchange enzyme

    SciTech Connect

    Kano-Sueoka, T.; King, D.M.

    1987-05-01

    Epithelial cells and some of their transformed derivatives require ethanolamine (Etn) to proliferate normally in defined culture medium. The amount of cellular phosphatidylethanolamine (PtdEtn) is considerably reduced when these cells are cultured without Etn. Using Etn-responsive and -nonresponsive rat mammary carcinoma cell lines, the biochemical mechanism of Etn-responsiveness of investigated. The incorporation of (/sup 3/H)serine into phosphatidylserine (PtdSer) and PtdEtn in Etn-responsive cells was 60 and 37%, respectively, of those in Etn-nonresponsive cells. There was no significant difference between the two cell types in the activities of enzymes involved in PtdEtn synthesis via CDP-Etn. The activity of PtdSer decarboxylase was also very similar in these two cell types. When these cells were cultured in the presence of (/sup 32/P)PtdEtn, the rate of accumulation of (/sup 32/P)-labeled PtdSer from the radioactive PtdEtn was considerably reduced in Etn-responsive cells as compared to Etn-nonresponsive cells. Whereas there was no significant difference in the accumulation of the labeled PtdSer from (/sup 32/P)phosphatidylcholine. These results demonstrate that the Etn-responsiveness is due to a limited ability to synthesize PtdSer resulting from a limited base exchange activity utilizing PtdEtn.

  19. Optical Breath Gas Sensor for Extravehicular Activity Application

    NASA Technical Reports Server (NTRS)

    Wood, William R.; Casias, Miguel E.; Vakhtin, Andrei B.; Pilgrim, Jeffrey S> ; Chullen, Cinda; Falconi, Eric A.

    2012-01-01

    The function of the infrared gas transducer used during extravehicular activity (EVA) in the current space suit is to measure and report the concentration of carbon dioxide (CO2) in the ventilation loop. The next generation Portable Life Support System (PLSS) requires next generation CO2 sensing technology with performance beyond that presently in use on the Shuttle/International Space Station extravehicular mobility unit (EMU). Accommodation within space suits demands that optical sensors meet stringent size, weight, and power requirements. A laser diode (LD) spectrometer based on wavelength modulation spectroscopy (WMS) is being developed for this purpose by Vista Photonics, Inc. Two prototype devices were delivered to NASA Johnson Space Center (JSC) in September 2011. The sensors incorporate a laser diode based CO2 channel that also includes an incidental water vapor (humidity) measurement and a separate oxygen (O2) channel using a vertical cavity surface emitting laser (VCSEL). Both prototypes are controlled digitally with a field-programmable gate array (FPGA)/microcontroller architecture. Based on the results of the initial instrument development, further prototype development and testing of instruments leveraging the lessons learned were desired. The present development extends and upgrades the earlier hardware to the Advanced PLSS 2.0 test article being constructed and tested at JSC. Various improvements to the electronics and gas sampling are being advanced by this project. The combination of low power electronics with the performance of a long wavelength laser spectrometer enables multi-gas sensors with significantly increased performance over that presently offered in the EMU. .

  20. A Helium Gas-Scintillator Active Target for Photoreaction Measurements

    E-print Network

    Jebali, R Al; Adler, J -O; Akkurt, I; Buchanan, E; Brudvik, J; Fissum, K; Gardner, S; Hamilton, D J; Hansen, K; Isaksson, L; Livingston, K; Lundin, M; McGeorge, J C; MacGregor, I J D; MacRae, R; Middleton, D G; Reiter, A J H; Rosner, G; Schröder, B; Sjögren, J; Sokhan, D; Strandberg, B

    2015-01-01

    A multi-cell He gas-scintillator active target, designed for the measurement of photoreaction cross sections, is described. The target has four main chambers, giving an overall thickness of 0.103 $\\mathrm{g/cm^{2}}$ at an operating pressure of 2 MPa. Scintillations are read out by photomultiplier tubes and the addition of small amounts of $\\mathrm{N}_{2}$ to the He, to shift the scintillation emission from UV to visible, is discussed. First results of measurements at the MAX IV Laboratory tagged-photon facility show that the target has good timing resolution and can cope well with a high-flux photon beam. The determination of reaction cross sections from target yields relies on a Monte Carlo simulation, which considers scintillation light transport, photodisintegration processes in $^{4}\\mathrm{He}$, background photon interactions in target windows and interactions of the reaction-product particles in the gas and target container. The predictions of this simulation are compared to the measured target response...

  1. A Helium Gas-Scintillator Active Target for Photoreaction Measurements

    E-print Network

    R. Al Jebali; J. R. M. Annand; J. -O. Adler; I. Akkurt; E. Buchanan; J. Brudvik; K. Fissum; S. Gardner; D. J. Hamilton; K. Hansen; L. Isaksson; K. Livingston; M. Lundin; J. C. McGeorge; I. J. D. MacGregor; R. MacRae; D. G. Middleton; A. J. H. Reiter; G. Rosner; B. Schröder; J. Sjögren; D. Sokhan; B. Strandberg

    2015-03-18

    A multi-cell He gas-scintillator active target, designed for the measurement of photoreaction cross sections, is described. The target has four main chambers, giving an overall thickness of 0.103 $\\mathrm{g/cm^{2}}$ at an operating pressure of 2 MPa. Scintillations are read out by photomultiplier tubes and the addition of small amounts of $\\mathrm{N}_{2}$ to the He, to shift the scintillation emission from UV to visible, is discussed. First results of measurements at the MAX IV Laboratory tagged-photon facility show that the target has good timing resolution and can cope well with a high-flux photon beam. The determination of reaction cross sections from target yields relies on a Monte Carlo simulation, which considers scintillation light transport, photodisintegration processes in $^{4}\\mathrm{He}$, background photon interactions in target windows and interactions of the reaction-product particles in the gas and target container. The predictions of this simulation are compared to the measured target response.

  2. Perfluoropolyether-functionalized gas diffusion layers for proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Gola, Massimo; Sansotera, Maurizio; Navarrini, Walter; Bianchi, Claudia L.; Gallo Stampino, Paola; Latorrata, Saverio; Dotelli, Giovanni

    2014-07-01

    Linear perfluoropolyether (PFPE) peroxide was used to confer superhydrophobic surface properties to gas diffusion layer (GDL) by means of direct functionalization of a GDL based on carbon cloth (CC) material. The thermal decomposition of a linear PFPE peroxide produces linear PFPE radicals that covalently bond the unsaturated moieties on the surface. Perfluorinated radicals are directly and covalently bound to the carbonaceous structure of the CC without any spacer that could decrease both thermal and chemical stability of the GDL. The obtained CC hydrophobicity exceeded the superhydrophobicity threshold and was enduringly stable. The relationship between the linkage of fluorinated chains and the variations of surface chemical-physical properties were studied combining X-ray photoelectron spectroscopy (XPS), resistivity measurements, scanning electron microscopy (SEM) and contact angle measurements. Despite the excellent insulating properties of the PFPE polymer, the functionalized carbonaceous materials substantially retained their conductive properties. The PFPE-modified GDLs were tested in a single fuel cell at the lab scale. The cell tests were run at two temperatures (60 °C and 80 °C) with a relative humidity (RH) of hydrogen and air feeding gases equal to 80/100% and 60/100%, respectively.

  3. Trace gas exchange and gas phase chemistry in a Norway spruce forest: A study with a coupled 1-dimensional canopy atmospheric chemistry emission model

    NASA Astrophysics Data System (ADS)

    Forkel, Renate; Klemm, Otto; Graus, Martin; Rappenglück, Bernhard; Stockwell, William R.; Grabmer, Wolfgang; Held, Andreas; Hansel, Armin; Steinbrecher, Rainer

    Numerical modelling is an efficient tool to investigate the role of chemical degradation of biogenic volatile organic compounds (BVOC) and the effect of dynamical processes on BVOC and product mixing ratios within and above forest canopies. The present study shows an application of the coupled canopy-chemistry model CACHE to a Norway spruce forest at the Waldstein (Fichtelgebirge, Germany). Simulated courses of temperature, trace gas mixing ratios, and fluxes are compared with measurements taken during the BEWA2000 field campaigns. The model permits the interpretation of the observed diurnal course of ozone and VOC by investigating the role of turbulent exchange, chemical formation and degradation, emission, and deposition during the course of the day. The simulation results show that BVOC fluxes into the atmosphere are 10-15% lower than the emission fluxes on branch basis due to chemical BVOC degradation within the canopy. BVOC degradation by the NO 3 radical was found to occur in the lower part of the canopy also during daytime. Furthermore, the simulations strongly indicate that further research is still necessary concerning the emission and deposition of aldehydes and ketones.

  4. Development of AN Active 238UF6 Gas Target

    NASA Astrophysics Data System (ADS)

    Eckardt, C.; Enders, J.; Freudenberger, M.; Göök, A.; von Neumann-Cosel, P.; Oberstedt, A.; Oberstedt, S.

    2014-09-01

    Detailed studies of the fission process, e.g., the search for parity nonconservation (PNC) effects, the energy dependence of fission modes or the population of fission isomers, depend on high quality data, therefore requiring high luminosities. An active gas target containing uranium may overcome the deterioration of energy and angular resolution caused by large solid target thicknesses. A single Frisch-grid ionization chamber has been built to test a mixture of standard counting gases (e.g., argon) with depleted uranium hexafluoride (238UF6), utilizing a triple alpha source to evaluate signal quality and drift velocity. For mass fractions of up to 4 percent of 238U the drift velocity increases with rising UF6 content, while a good signal quality and energy resolution is preserved.

  5. Apparatus and method for gas turbine active combustion control system

    NASA Technical Reports Server (NTRS)

    Umeh, Chukwueloka (Inventor); Kammer, Leonardo C. (Inventor); Shah, Minesh (Inventor); Fortin, Jeffrey B. (Inventor); Knobloch, Aaron (Inventor); Myers, William J. (Inventor); Mancini, Alfred Albert (Inventor)

    2011-01-01

    An Active Combustion Control System and method provides for monitoring combustor pressure and modulating fuel to a gas turbine combustor to prevent combustion dynamics and/or flame extinguishments. The system includes an actuator, wherein the actuator periodically injects pulsed fuel into the combustor. The apparatus also includes a sensor connected to the combustion chamber down stream from an inlet, where the sensor generates a signal detecting the pressure oscillations in the combustor. The apparatus controls the actuator in response to the sensor. The apparatus prompts the actuator to periodically inject pulsed fuel into the combustor at a predetermined sympathetic frequency and magnitude, thereby controlling the amplitude of the pressure oscillations in the combustor by modulating the natural oscillations.

  6. C-terminal motif within Sec7 domain regulates guanine nucleotide exchange activity via tuning protein conformation.

    PubMed

    Qiu, Biao; Zhang, Kai; Wang, Shengliu; Sun, Fei

    2014-03-28

    ADP-ribosylation factors (Arfs) play key roles in controlling membrane traffic and organelle structures. The activation of Arfs from GDP to GTP binding form is triggered by the guanine exchange factors (GEFs). There are six families of Arf-GEFs with a common guanine exchange catalytic domain (Sec7 domain) and various mechanisms of guanine exchange activity regulation. A loop region (loop>J motif) just following the helix J of Sec7 domain was found conserved and important for the catalytic activity regulation of Arf-GEFs. However, the molecular detail of the role the loop>J motif plays has been yet unclear. Here, we studied the catalytic domain of Sec7p, a yeast trans-Golgi network membrane localized Arf-GEFs, and found that the loop>J motif is indispensible for its GEF catalytic activity. Crystallographic, NMR spectrum and mutagenesis studies suggested that the loop>J motif with a key conserved residue Ile1010 modulates the fine conformation of Sec7 domain and thereby regulates its guanine exchange activity. PMID:24613384

  7. A model for control of breathing in mammals: coupling neural dynamics to peripheral gas exchange and transport

    PubMed Central

    Ben-Tal, Alona; Smith, Jeffrey C.

    2008-01-01

    A new model for aspects of the control of respiration in mammals has been developed. The model integrates a reduced representation of the brainstem respiratory neural controller together with peripheral gas exchange and transport mechanisms. The neural controller consists of two components. One component represents the inspiratory oscillator in the pre-Bötzinger complex (pre-BötC) incorporating bio-physical mechanisms for rhythm generation. The other component represents the ventral respiratory group (VRG), which is driven by the pre-BötC for generation of inspiratory (pre)motor output. The neural model was coupled to simplified models of the lungs incorporating oxygen and carbon dioxide transport. The simplified representation of the brainstem neural circuitry has regulation of both frequency and amplitude of respiration and is done in response to partial pressures of oxygen and carbon dioxide in the blood using proportional (P) and proportional plus integral (PI) controllers. We have studied the coupled system under open and closed loop control. We show that two breathing regimes can exist in the model. In one regime an increase in the inspiratory frequency is accompanied by an increase in amplitude. In the second regime an increase in frequency is accompanied by a decrease in amplitude. The dynamic response of the model to changes in the concentration of inspired O2 or inspired CO2 was compared qualitatively with experimental data reported in the physiological literature. We show that the dynamic response with a PI-controller fits the experimental data better but suggests that when high levels of CO2 are inspired the respiratory system cannot reach steady state. Our model also predicts that there could be two possible mechanisms for apnea appearance when 100% O2 is inspired following a period of 5% inspired O2. This paper represents a novel attempt to link neural control and gas transport mechanisms, highlights important issues in amplitude and frequency control and sets the stage for more complete neurophysiological control models. PMID:18262570

  8. Gas-exchange analysis of chloroplastic fructose-1,6-bisphosphatase antisense potatoes at different air humidities and at elevated CO(2).

    PubMed

    Muschak, M; Willmitzer, L; Fisahn, J

    1999-07-01

    Gas-exchange measurements were performed to analyze the leaf conductances and assimilation rates of potato (Solanum tuberosum L. cv. Desireé) plants expressing an antisense construct against chloroplastic fructose-1,6-bisphosphatase (FBPase, EC 3.1.3.11) in response to increasing photon flux densities, different relative air humidities and elevated CO(2) concentrations. Assimilation rates (A) and transpiration rates (E) were observed during a stepwise increase of photon flux density. These experiments were carried out under atmospheric conditions and in air containing 500 micromol mol(-1) CO(2). In both gas atmospheres, two levels of relative air humidity (60-70% and 70-80%) were applied in different sets of measurements. Intercellular CO(2) concentration, leaf conductance, air-to-leaf vapour pressure deficit, and instantaneous water-use efficiency (A/E) were determined. As expected, assimilation rates of the FBPase antisense plants were significantly reduced as compared to the wild type. Saturation of assimilation rates in transgenic plants occurred at a photon flux density of 200 micromol m(-2) s(-1), whereas saturation in wild type plants was observed at 600 micromol m(-2) s(-1). Elevated ambient CO(2) levels did not effect assimilation rates of transgenic plants. At 70-80% relative humidity and atmospheric CO(2) concentration the FBPase antisense plants had significantly higher leaf conductances than wild-type plants while no difference emerged at 60-70%. These differences in leaf conductance vanished at elevated levels of ambient CO(2). Stomatal response to different relative air humidities was not affected by mesophyll photosynthetic activity. It is suggested that the regulation of stomatal opening upon changes in photon flux density is merely mediated by a signal transmitted from mesophyll cells, whereas the intercellular CO(2) concentration plays a minor role in this kind of stomatal response. The results are discussed with respect to stomatal control by environmental parameters and mesophyll photosynthesis. PMID:10467036

  9. Post-synthetic Ti Exchanged UiO-66 Metal-Organic Frameworks that Deliver Exceptional Gas Permeability in Mixed Matrix Membranes

    NASA Astrophysics Data System (ADS)

    Smith, Stefan J. D.; Ladewig, Bradley P.; Hill, Anita J.; Lau, Cher Hon; Hill, Matthew R.

    2015-01-01

    Gas separation membranes are one of the lowest energy technologies available for the separation of carbon dioxide from flue gas. Key to handling the immense scale of this separation is maximised membrane permeability at sufficient selectivity for CO2 over N2. For the first time it is revealed that metals can be post-synthetically exchanged in MOFs to drastically enhance gas transport performance in membranes. Ti-exchanged UiO-66 MOFs have been found to triple the gas permeability without a loss in selectivity due to several effects that include increased affinity for CO2 and stronger interactions between the polymer matrix and the Ti-MOFs. As a result, it is also shown that MOFs optimized in previous works for batch-wise adsorption applications can be applied to membranes, which have lower demands on material quantities. These membranes exhibit exceptional CO2 permeability enhancement of as much as 153% when compared to the non-exchanged UiO-66 mixed-matrix controls, which places them well above the Robeson upper bound at just a 5 wt.% loading. The fact that maximum permeability enhancement occurs at such low loadings, significantly less than the optimum for other MMMs, is a major advantage in large-scale application due to the more attainable quantities of MOF needed.

  10. Leaf age affects the responses of foliar injury and gas exchange to tropospheric ozone in Prunus serotina seedlings.

    PubMed

    Zhang, Jianwei; Schaub, Marcus; Ferdinand, Jonathan A; Skelly, John M; Steiner, Kim C; Savage, James E

    2010-08-01

    We investigated the effect of leaf age on the response of net photosynthesis (A), stomatal conductance (g(wv)), foliar injury, and leaf nitrogen concentration (N(L)) to tropospheric ozone (O(3)) on Prunus serotina seedlings grown in open-plots (AA) and open-top chambers, supplied with either carbon-filtered or non-filtered air. We found significant variation in A, g(wv), foliar injury, and N(L) (P < 0.05) among O(3) treatments. Seedlings in AA showed the highest A and g(wv) due to relatively low vapor pressure deficit (VPD). Older leaves showed significantly lower A, g(wv), N(L), and higher foliar injury (P < 0.001) than younger leaves. Leaf age affected the response of A, g(wv), and foliar injury to O(3). Both VPD and N(L) had a strong influence on leaf gas exchange. Foliar O(3)-induced injury appeared when cumulative O(3) uptake reached 8-12 mmol m(-2), depending on soil water availability. The mechanistic assessment of O(3)-induced injury is a valuable approach for a biologically relevant O(3) risk assessment for forest trees. PMID:20537450

  11. Nitrogen metabolism and gas exchange parameters associated with zinc stress in tobacco expressing an ipt gene for cytokinin synthesis.

    PubMed

    Pavlíková, Daniela; Pavlík, Milan; Procházková, Dagmar; Zemanová, Veronika; Hnili?ka, František; Wilhelmová, Na?a

    2014-04-15

    Increased endogenous plant cytokinin (CK) content through transformation with an isopentyl transferase (ipt) gene has been associated with improved plant stress tolerance. The impact of zinc (tested levels Zn1=250, Zn2=500, Zn3=750mgkg(-1)soil) on gas exchange parameters (net photosynthetic rate, transpiration rate, stomatal conductance, intercellular CO2 concentration) and nitrogen utilization by plants resulted in changes of free amino acid concentrations (glutamic acid, glutamine, asparagine, aspartate, glycine, serine, cystein) and differed for transformed and non-transformed tobacco plants. For pot experiments, tobacco plants (Nicotiana tabacum L., cv. Wisconsin 38) transformed with a construct consisting of SAG12 promoter fused with the ipt gene for cytokinin synthesis (SAG plants) and its wild type (WT plants as a control) were used. Physiological analyses confirmed that SAG plants had improved zinc tolerance compared with the WT plants. The enhanced Zn tolerance of SAG plants was associated with the maintenance of accumulation of amino acids and with lower declines of photosynthetic and transpiration rates. In comparison to WT plants, SAG plants exposed to the highest Zn concentration accumulated lower concentrations of asparagine, which is a major metabolic product during senescence. PMID:24655392

  12. [Effect of surfactant-BL on ventilation and gas exchange function in patients with destructive pulmonary tuberculosis].

    PubMed

    Chernichenko, N V; Shergina, E A; Lovacheva, O V; Erokhin, V V

    2006-01-01

    The fact that the treatment of pulmonary tuberculosis is a topical problem is beyond question. At present, it is well known that there is dissociation between the time of a negative sputum reaction and later cavernous healing, resolution of inflammatory changes. Therefore, search for new possibilities of pathogenetic action on the course of a tuberculous process, healing of destructive changes, and the maximum recovery of functional disorders are one of the ways of enhancing the efficiency of treatment in patients with destructive pulmonary tuberculosis. Over 70 years' history of the discovery and studies of the pulmonary surfactant system has made it possible to formulate a current concept of surfactant as a multicomponent system of cellular and non-cellular elements that ensure the antiatelectatic, antiedematous, protective, and other functions of the lung. The effects of surfactant preparations as an agent of pathogenetic therapy are being investigated at the Central Research Institute of Tuberculosis, Russian Academy of Medical Sciences. The present paper presents the results of changes in external respiratory function and gas exchange before and after surfactant therapy in 64 patients with established drug-resistant infiltrative pulmonary tuberculosis. Along with the performed antituberculous therapy, the natural agent Surfactant-BL made in Russia was used by taking into account individual sensitivity. The agent was inhalationally administered in a daily dose of 25 mg by the schedule for 8 weeks. PMID:16881226

  13. Selective pulmonary vasodilation improves ventriculovascular coupling and gas exchange in a patient with unrepaired single-ventricle physiology

    PubMed Central

    Vanderpool, R.; Jenkins, I.; Dalabih, M.; Colombo, J.; Lax, D.; Seckeler, M.

    2015-01-01

    Abstract We describe a 63-year-old patient with unrepaired tricuspid valve atresia and a hypoplastic right ventricle (single-ventricle physiology) who presented with progressive symptomatic hypoxia. Her anatomy resulted in parallel pulmonary and systemic circulations, pulmonary arterial hypertension, and uncoupling of the ventricle/pulmonary artery. Hemodynamic and coupling data were obtained before and after pulmonary vasoactive treatment, first inhaled nitric oxide and later inhaled treprostinil. The coupling ratio (ratio of ventricular to vascular elastance) shunt fractions and dead space ventilation were calculated before and after treatment. Treatment resulted in improvement of the coupling ratio between the ventricle and the vasculature with optimization of stroke work, equalization of pulmonary and systolic flows, a decrease in dead space ventilation from 75% to 55%, and a significant increase in 6-minute walk distance and improved hypoxia. Inhaled treprostinil significantly increased 6-minute walk distance and improved hypoxia. This is the first report to show that pulmonary vasoactive treatment can be used in a patient with unrepaired single-ventricle anatomy and describes the hemodynamic effects of inhaled therapy on ventriculovascular coupling and gas exchange in the pulmonary circulation in this unique physiology. PMID:26064468

  14. Does Amifostine Reduce Metabolic Rate? Effect of the Drug on Gas Exchange and Acute Ventilatory Hypoxic Response in Humans

    PubMed Central

    Pandit, Jaideep J.; Allen, Caroline; Little, Evelyn; Formenti, Federico; Harris, Adrian L.; Robbins, Peter A.

    2015-01-01

    Amifostine is added to chemoradiation regimens in the treatment of many cancers on the basis that, by reducing the metabolic rate, it protects normal cells from toxic effects of therapy. We tested this hypothesis by measuring the metabolic rate (by gas exchange) over 255 min in 6 healthy subjects, at two doses (500 mg and 1000 mg) of amifostine infused over 15 min at the start of the protocol. We also assessed the ventilatory response to six 1 min exposures to isocapnic hypoxia mid-protocol. There was no change in metabolic rate with amifostine as measured by oxygen uptake (p = 0.113). However in carbon dioxide output and respiratory quotient, we detected a small decline over time in control and drug protocols, consistent with a gradual change from carbohydrate to fat metabolism over the course of the relatively long study protocol. A novel result was that amifostine (1000 mg) increased the mean ± SD acute hypoxic ventilatory response from 12.4 ± 5.1 L/min to 20.3 ± 11.9 L/min (p = 0.045). In conclusion, any cellular protective effects of amifostine are unlikely due to metabolic effects. The stimulatory effect on hypoxic ventilatory responses may be due to increased levels of hypoxia inducible factor, either peripherally in the carotid body, or centrally in the brain. PMID:25894815

  15. Isothermal ice crystallization kinetics in the gas-diffusion layer of a proton-exchange-membrane fuel cell.

    PubMed

    Dursch, T J; Ciontea, M A; Radke, C J; Weber, A Z

    2012-01-17

    Nucleation and growth of ice in the fibrous gas-diffusion layer (GDL) of a proton-exchange membrane fuel cell (PEMFC) are investigated using isothermal differential scanning calorimetry (DSC). Isothermal crystallization rates and pseudo-steady-state nucleation rates are obtained as a function of subcooling from heat-flow and induction-time measurements. Kinetics of ice nucleation and growth are studied at two polytetrafluoroethylene (PTFE) loadings (0 and 10 wt %) in a commercial GDL for temperatures between 240 and 273 K. A nonlinear ice-crystallization rate expression is developed using Johnson-Mehl-Avrami-Kolmogorov (JMAK) theory, in which the heat-transfer-limited growth rate is determined from the moving-boundary Stefan problem. Induction times follow a Poisson distribution and increase upon addition of PTFE, indicating that nucleation occurs more slowly on a hydrophobic fiber than on a hydrophilic fiber. The determined nucleation rates and induction times follow expected trends from classical nucleation theory. A validated rate expression is now available for predicting ice-crystallization kinetics in GDLs. PMID:22133053

  16. [Observation on the air-borne bacteria and ammonia (NS3) gas in laboratory animal facility with rotary heat exchanger].

    PubMed

    Obara, T; Matsuyama, M; Fujita, S; Yamauchi, C

    1979-01-01

    The number of air-borne bacteria in air ducts and barrierred laboratory animal rooms with the so-called econovent rotary heat exchanger, were checked monthly during a year by the pin-hole sumpler method for air ducts and Koch method for animal rooms. Also, concentration of ammonia was checked with the same samples by gas impinger. No significantly difference in number of air-borne bacteria was seen between before and after passing the econovent. Those passing through HEPA filter was not detected. There were more air-borne bacteria in animal rooms, outside locker room and shower room than in the corridor, utensil storage, inside locker room and pass box. No ammonia were detected in the outdoor, but exhaust air duct after passing the econovent contained very small amount of ammonia. On the other hand, high concentration of ammonia were preserved in the supplying air duct, exhaust air duct and mice and rats rooms, about 86% of ammonia in exhaust air duct returned back into the supplying air duct. No influences on reproduction in mice and rats were recognized. PMID:428454

  17. Linking nonstructural carbohydrate dynamics to gas exchange and leaf hydraulic behavior in Pinus edulis and Juniperus monosperma.

    PubMed

    Woodruff, David R; Meinzer, Frederick C; Marias, Danielle E; Sevanto, Sanna; Jenkins, Michael W; McDowell, Nate G

    2015-04-01

    Leaf hydraulics, gas exchange and carbon storage in Pinus edulis and Juniperus monosperma, two tree species on opposite ends of the isohydry-anisohydry spectrum, were analyzed to examine relationships between hydraulic function and carbohydrate dynamics. Leaf hydraulic vulnerability, leaf water potential (?l ), leaf hydraulic conductance (Kleaf ), photosynthesis (A), stomatal conductance (gs) and nonstructural carbohydrate (NSC) content were analyzed throughout the growing season. Leaf hydraulic vulnerability was significantly lower in the relatively anisohydric J. monosperma than in the more isohydric P. edulis. In P. edulis, ?l dropped and stayed below 50% loss of leaf hydraulic conductance (P??) early in the day during May, August and around midday in September, leading to sustained reductions in Kleaf . In J. monosperma, ?l dropped below P?? only during August, resulting in the maintenance of Kleaf during much of the growing season. Mean A and gs during September were significantly lower in P. edulis than in J. monosperma. Foliar total NSC was two to three times greater in J. monosperma than in P. edulis in June, August and September. Consistently lower levels of total NSC in P. edulis suggest that its isohydric strategy pushes it towards the exhaustion of carbon reserves during much of the growing season. PMID:25412472

  18. Effects of UV-B radiation and water stress on gas exchange of soybeans under two different nitrogen levels

    SciTech Connect

    Rosa, L.M.; Forseth, I.N. (Univ. of Maryland, College Park (United States))

    1993-06-01

    Due to anthropogenic destruction of stratospheric ozone, UV-B radiation is projected to increase in the near future. Other potential global climate changes in temperature and precipitation patterns raise the need for research into plant responses to multiple environmental stresses. The objective of this study was to document UV-B and water stress effects on gas exchange of soybean (Glycine max Merr.) under two nitrogen levels. Two soybean cultivars differing in sensitivity to UV-B were tested at fluence rates of 19.1 or 8.5 kJ m[sub [minus]2]day[sub [minus]1] (enhance and natural levels of UV-B, respectively). Measurements of photosaturated CO[sub 2] uptake at ambient CO[sub 2] (A). stomatal conductance. photosaturated O[sub 2] evolution at saturating CO[sub 2] (A[sub max]), long term water use efficiency (using [delta][sup 13]C), and nitrogen fixation (using [sup 15]N) were performed. No significant treatment effects on A could be detected. However A[sub max] was significantly increased, and stomatal conductance reduced (p<0.01) by increased UV-B at all levels of water and nitrogen for both cultivars, suggesting a stronger stomal limitation of photosynthesis under UV-B. Water and nitrogen use efficiency also decreased under increased UV-B in both cultivars (p<0.01).

  19. Tungsten polyoxometalate molecules as active nodes for dynamic carrier exchange in hybrid molecular/semiconductor capacitors

    SciTech Connect

    Balliou, A., E-mail: aballiou@imel.demokritos.gr [Institute of Nanoscience and Nanotechnology, NCSR Demokritos, Aghia Paraskevi, Athens 15310 (Greece); Department of Chemical Engineering, NTUA, Zographou Campus, Athens 15773 (Greece); Douvas, A. M.; Normand, P.; Argitis, P.; Glezos, N. [Institute of Nanoscience and Nanotechnology, NCSR Demokritos, Aghia Paraskevi, Athens 15310 (Greece); Tsikritzis, D.; Kennou, S. [Department of Chemical Engineering, University of Patras, University Campus, Patras 26504 (Greece)

    2014-10-14

    In this work we study the utilization of molecular transition metal oxides known as polyoxometalates (POMs), in particular the Keggin structure anions of the formula PW??O??³?, as active nodes for potential switching and/or fast writing memory applications. The active molecules are being integrated in hybrid Metal-Insulator/POM molecules-Semiconductor capacitors, which serve as prototypes allowing investigation of critical performance characteristics towards the design of more sophisticated devices. The charging ability as well as the electronic structure of the molecular layer is probed by means of electrical characterization, namely, capacitance-voltage and current-voltage measurements, as well as transient capacitance measurements, C (t), under step voltage polarization. It is argued that the transient current peaks observed are manifestations of dynamic carrier exchange between the gate electrode and specific molecular levels, while the transient C (t) curves under conditions of molecular charging can supply information for the rate of change of the charge that is being trapped and de-trapped within the molecular layer. Structural characterization via surface and cross sectional scanning electron microscopy as well as atomic force microscopy, spectroscopic ellipsometry, UV and Fourier-transform IR spectroscopies, UPS, and XPS contribute to the extraction of accurate electronic structure characteristics and open the path for the design of new devices with on-demand tuning of their interfacial properties via the controlled preparation of the POM layer.

  20. Elevated hydrostatic pressure activates sodium/hydrogen exchanger-1 in rat optic nerve head astrocytes

    PubMed Central

    Mandal, Amritlal; Shahidullah, Mohammad; Delamere, Nicholas A.; Terán, Marcos A.

    2009-01-01

    Optic nerve head astrocytes become abnormal in eyes that have elevated intraocular pressure, and cultured astrocytes display altered protein expression after being subjected for ?1 days to elevated hydrostatic pressure. Here we show that 2-h elevated hydrostatic pressure (15 or 30 mmHg) causes phosphorylation of ERK1/2, ribosomal S6 protein kinase (p90RSK), and Na/H exchanger (NHE)1 in cultured rat optic nerve head astrocytes as judged by Western blot analysis. The MEK/ERK inhibitor U0126 abolished phosphorylation of NHE1 and p90RSK as well as ERK1/2. To examine NHE1 activity, cytoplasmic pH (pHi) was measured with BCECF and, in some experiments, cells were acidified by 5-min exposure to 20 mM ammonium chloride. Although baseline pHi was unaltered, the rate of pHi recovery from acidification was fourfold higher in pressure-treated astrocytes. In the presence of either U0126 or dimethylamiloride (DMA), an NHE inhibitor, hydrostatic pressure did not change the rate of pHi recovery. The findings are consistent with NHE1 activation due to phosphorylation of ERK1/2, p90RSK, and NHE1 that occurs in response to hydrostatic pressure. These responses may precede long-term changes of protein expression known to occur in pressure-stressed astrocytes. PMID:19419999

  1. Sediment-water gas exchange in two Swedish lakes measured by Eddy Correlation

    NASA Astrophysics Data System (ADS)

    Kokic, J.; Sahlee, E.; Brand, A.; Sobek, S.

    2014-12-01

    Lake sediments are hotspots for carbon (C) cycling, acting both as sinks and sources through C burial and production of carbon dioxide (CO2) and methane. The fate of this CO2 in the water column is controlled by bottom water turbulence, a factor not accounted for in current estimates of sediment CO2 fluxes. This study is aimed to quantify the turbulent CO2 flux across the sediment-water interface (SWI) by measuring the oxygen (O2) flux with the non-invasive Eddy Correlation (EC) method that combines measurements of 3D velocity (ADV) and O2 fluctuations with a microsensor. Using the metabolic relation (respiratory quotient, RQ) of O2 and CO2 derived from a sediment incubation experiment we present the first estimates of turbulent lake sediment CO2 flux from two boreal lakes in Sweden (Erssjön and Erken, 0.07 km2 and 23.7 km2 respectively). Only ~10 % of the total dataset was extracted for flux calculations due to poor signal-to-noise ratio in the velocity and O2 signals. The sediment in Lake Erssjön was both consuming and producing O2, related to bacterial respiration and photosynthesis. Mean O2 flux was -0.19 and 0.17 ?mol O2 m-2 sec-1, comparing to 0.04 ?mol O2 m-2 sec-1 derived from the sediment incubation experiment. Fluxes for Lake Erken are still to be determined. Experimentally derived RQ of the both lake sediments were close to unity implying that in-situ CO2 fluxes are of similar magnitude as O2 fluxes, varying between -0.15 and 0.18 ?mol C m-2 sec-1. The first measurement of turbulent sediment O2 flux and estimate of turbulent CO2 flux from a small boreal lake show higher and more variable fluxes than previously found in experimental studies. The low amount of data extracted for flux calculations (~10%) point towards the difficulties in EC measurement in low-turbulence environments. On-going work focuses on the turbulence structure in lakes and its influence on the gas fluxes at the SWI.

  2. An innovative treatment concept for future drinking water production: fluidized ion exchange – ultrafiltration – nanofiltration – granular activated carbon filtration

    Microsoft Academic Search

    Sheng Li; S. G. J. Heijman; J. Q. J. C. Verberk; J. C. Van Dijk

    2009-01-01

    A new treatment concept for drinking water production from surface water has been investigated on a pilot scale. The treatment concept consists of fluidized ion exchange (FIEX), ultrafiltration (UF), nanofiltration (NF), and granular activated carbon filtration (GAC). The FIEX process removed calcium and other divalent cations; the UF membrane removed particles and micro-organisms; and the NF membrane and GAC removed

  3. COMBINED USE OF ION EXCHANGE RESINS AND GRANULAR ACTIVATED CARBON FOR THE CONTROL OF ORGANIC MATTER AND DISINFECTION BY PRODUCTS

    EPA Science Inventory

    The use of anion exchange resin as a pretreatment step to granular activated carbon is evaluated. erformance is evaluated by DOC, SAC, TOXFP, and THMFP parameters. hio River water and Palm Beach groundwater are used. he results show that resin pretreatment is significant in exten...

  4. The exchange factor Ras-GRF2 activates Ras-dependent and Rac-dependent mitogen-activated protein kinase pathways

    Microsoft Academic Search

    Wing-Tze Fan; C. Anne Koch; Carmen L. de Hoog; Neil P. Fam; Michael F. Moran

    1998-01-01

    Ras and Rac are membrane-associated GTPases that function as molecular switches activating intracellular mitogen-activated protein kinase (MAPK) cascades and other effector pathways in response to extracellular signals [1]. Activation of Ras and Rac into their GTP-bound conformations is directly controlled by specific guanine-nucleotide exchange factors (GEFs), which catalyze GDP release. Several Ras-specific GEFs that are related to the budding yeast

  5. Na+/H+ and Na+/NH4+ exchange activities of zebrafish NHE3b expressed in Xenopus oocytes

    PubMed Central

    Ito, Yusuke; Kato, Akira; Hirata, Taku; Hirose, Shigehisa

    2014-01-01

    Zebrafish Na+/H+ exchanger 3b (zNHE3b) is highly expressed in the apical membrane of ionocytes where Na+ is absorbed from ion-poor fresh water against a concentration gradient. Much in vivo data indicated that zNHE3b is involved in Na+ absorption but not leakage. However, zNHE3b-mediated Na+ absorption has not been thermodynamically explained, and zNHE3b activity has not been measured. To address this issue, we overexpressed zNHE3b in Xenopus oocytes and characterized its activity by electrophysiology. Exposure of zNHE3b oocytes to Na+-free media resulted in significant decrease in intracellular pH (pHi) and intracellular Na+ activity (aNai). aNai increased significantly when the cytoplasm was acidified by media containing CO2-HCO3? or butyrate. Activity of zNHE3b was inhibited by amiloride or 5-ethylisopropyl amiloride (EIPA). Although the activity was accompanied by a large hyperpolarization of ?50 mV, voltage-clamp experiments showed that Na+/H+ exchange activity of zNHE3b is electroneutral. Exposure of zNHE3b oocytes to medium containing NH3/NH4+ resulted in significant decreases in pHi and aNai and significant increase in intracellular NH4+ activity, indicating that zNHE3b mediates the Na+/NH4+ exchange. In low-Na+ (0.5 mM) media, zNHE3b oocytes maintained aNai of 1.3 mM, and Na+-influx was observed when pHi was decreased by media containing CO2-HCO3? or butyrate. These results provide thermodynamic evidence that zNHE3b mediates Na+ absorption from ion-poor fresh water by its Na+/H+ and Na+/NH4+ exchange activities. PMID:24401990

  6. Active constraint regions for a natural gas liquefaction process Magnus G. Jacobsena

    E-print Network

    Skogestad, Sigurd

    Active constraint regions for a natural gas liquefaction process Magnus G. Jacobsena , Sigurd little attention. this paper addresses optimal operation of a simple natural gas liquefaction process at all times. Keywords: Self-optimizing control, liquefied natural gas, LNG, PRICO, disturbances, optimal

  7. Active NOX Control of Cogen Gas Turbine Exhaust using a Nonlinear Feed Forward with Cascade Architecture

    E-print Network

    Cooper, Doug

    Active NOX Control of Cogen Gas Turbine Exhaust using a Nonlinear Feed Forward with Cascade control, cogeneration, gas turbine, model based control, feed forward, cascade ABSTRACT Presented is a model based strategy for controlling the NOX concentration of natural gas turbine emissions

  8. The effects of exchange gas temperature and pressure on the beta-layering process in solid deuterium-tritium fusion fuel

    SciTech Connect

    Hoffer, J.K.; Foreman, L.R. (Los Alamos National Lab., NM (USA)); Simpson, J.D.; Pattinson, T.R. (KMS Fusion, Inc., Ann Arbor, MI (USA))

    1990-01-01

    It has recently been shown that when solid tritium is confined in an isothermal enclosure, self-heating due to beta decay drives a net sublimation of material from thick, warmer layers to thin, cooler ones, ultimately resulting in layer thickness uniformity. We have observed this process of beta-layering'' in a 50--50 D-T mixture in both cylindrical and spherical enclosures at temperatures from 19.6 K, down to 11.6 K. The measured time constants are found to depend on the {sup 3}He content as suggested by recent theoretical predictions. When using an enclosure having low thermal conductivity, the ultimate layer uniformity is found to be a strong function of the exchange gas pressure. This is due to the presence of thermal convection in the exchange gas and consequent temperature anisotropy at the solid layer surface. 6 refs., 2 figs., 1 tab.

  9. [Effects of fertilization level on diurnal variation of gas exchange of young Eucalyptus grandis leaf].

    PubMed

    Li, Xiao-ping; Wang, Jing-yan; Wang, Dong; Hu, Ting-xing; Chen, Hong-zhi; Gong, Wei

    2010-11-01

    Different levels (0, 90, 180, and 270 g per tree) of compound fertilizer containing 15% N, 15% P2O5, and 15% K2O were applied to young Eucalyptus grandis to study the diurnal variations of its leaf stomatal conductance (Gs), intercellular CO2 concentration (Ci), net photosynthesis rate (Pn), transpiration rate (Tr), water use efficiency (WUE), and vapor pressure deficit on leaf surface (Vpdl) as well as the variation of leaf chlorophyll content, aimed to approach the relationships of E. grandis photosynthesis with fertilization and environmental factors. In all treatments, the diurnal variation of Pn presented a single-peak curve, with the peak at 14:00 and not showing midday depression. The Gs, Tr, and Vpdl showed the similar trend with Pn, while the Ci had a minimum value at 14:00. The WUE demonstrated a double-peak curve, with the first and second peak occurred at 10:00 and 14:00, respectively. Comparing with the control, the mean values of Gs, Pn, Tr, WUE, and chlorophyll a, chlorophyll b, and total chlorophyll contents under fertilization increased by 4.6%-15.9%, 7.8%-21.8%, 4.8%-11.6%, 3.2%-8.8%, 15.5%-62.0%, 14.5%-44.5% and 15.3%-57.1%, respectively, and the increment increased with fertilization level. By contrast, the mean values of Ci and VPdl decreased by 14.5%-44.5% and 15.3%-57.1%, respectively, and the decrement increased with fertilization level. The Gs, Pn, and Tr were significantly correlated with air temperature, relative humidity (RH), and photosynthetic active radiation (PAR), and also, the Gs was significantly correlated with Pn and Tr. It was suggested that fertilization could promote E. grandis growth and enhance its WUE and biological carbon sequestration, and air temperature, RH, PAR, and Gs were the main factors causing the diurnal variations of photosynthesis and transpiration of E. grandis. PMID:21360993

  10. Unexpected nerve gas exposure in the city of Matsumoto: Report of rescue activity in the first sarin gas terrorism

    Microsoft Academic Search

    Hiroshi Okudera; Hiroshi Morita; Tomomi Iwashita; Tatsuhiko Shibata; Tetsutaro Otagiri; Shigeaki Kobayashi; Nobuo Yanagisawa

    1997-01-01

    This report describes the rescue activities and the exposure of rescue and hospital personnel from the first unexpected nerve gas terrorist attack using sarin (isopropyl methylphophonofluoridate) in the city of Matsumoto at midnight on June 27, 1994. The details of the emergency activities in the disaster were studied based on the records from emergency departments of the affiliated hospitals and

  11. Feasibility study for an advanced coal fired heat exchanger/gas turbine topping cycle for a high efficiency power plant. Final report

    SciTech Connect

    Solomon, P.R.; Zhao, Y.; Pines, D.; Buggeln, R.C.; Shamroth, S.J.

    1993-11-01

    Significant improvements in efficiency for the conversion of coal into electricity can be achieved by cycles which employ a high temperature gas turbine topping cycle. The objective of this project is the development of an externally fired gas turbine system. The project computationally tested a new concept for a High Temperature Advanced Furnace (HITAF) and high temperature heat exchanger with a proprietary design to reduce the problems associated with the harsh coal environment. The program addressed two key technology issues: (1) the HITAF/heat exchanger heat transfer through a 2-D computer analysis of the HITAF configuration; (2) 3-D Computational Fluid Dynamics (CFD) model application to simulate the exclusion of particles and corrosive gases from the heat exchanger surface. The basic concept of this new combustor design was verified through the 2D and 3D modeling. It demonstrated that the corrosion and erosion of the exchanger material caused by coal and ash particles can be largely reduced by employing a specially designed firing scheme. It also suggested that a proper combustion geometry design is necessary to maximize the cleaning effect.

  12. Temperature and humidity effects on branchlet gas-exchange in white spruce: an explanation for the increase in transpiration with branchlet temperature

    Microsoft Academic Search

    A. L. Fredeen; R. F. Sage

    1999-01-01

    In situ gas-exchange data, for branchlets of white spruce [Picea glauca (Moench) Voss.] in a mature mixed-wood boreal forest in central Canada (5344N 10514W), were subjected to a multiple regression\\u000a analysis. Vapor pressure deficit (VPD) and branchlet temperature (tleaf) were both significant predictors (Psw) and net photosynthesis (An), together explaining 67 and 64% of the variation in gsw and An,

  13. Pioneer and late stage tropical rainforest tree species (French Guiana) growing under common conditions differ in leaf gas exchange regulation, carbon isotope discrimination and leaf water potential

    Microsoft Academic Search

    R. Huc; A. Ferhi; J. M. Guehl

    1994-01-01

    Leaf gas exchange rates, predawn ?wp and daily minimum ?wm leaf water potentials were measured during a wet-to-dry season transition in pioneer (Jacaranda copaia, Goupia glabra andCarapa guianensis) and late stage rainforest tree species (Dicorynia guianensis andEperua falcata) growing in common conditions in artificial stands in French Guiana. Carbon isotope discrimination (?) was assessed by measuring the stable carbon isotope

  14. Gas exchange and COâ flux in the tropical Atlantic Ocean determined from ²²²Rn and pCOâ measurements

    Microsoft Academic Search

    William M. Smethie; Taro Takahashi; D. W. Chipman; J. R. Ledwell

    1985-01-01

    Measurements of ²²²Rn vertical profiles and pCOâ in the surface water and the atmosphere were made simultaneously in the tropical Atlantic Ocean as part of the TTO\\/TAS program. The gas exchange rate or piston velocity was determined from the ²²²Rn profiles, and the ..delta..pCOâ between the surface ocean and the atmosphere was determined from the pCOâ measurements. The net flux

  15. Gas-exchange analysis of chloroplastic fructose-1,6-bisphosphatase antisense potatoes at different air humidities and at elevated CO 2

    Microsoft Academic Search

    Michael Muschak; Lothar Willmitzer; Joachim Fisahn

    1999-01-01

    .   Gas-exchange measurements were performed to analyze the leaf conductances and assimilation rates of potato (Solanum tuberosum L. cv. Desireé) plants expressing an antisense construct against chloroplastic fructose-1,6-bisphosphatase (FBPase, EC 3.1.3.11)\\u000a in response to increasing photon flux densities, different relative air humidities and elevated CO2 concentrations. Assimilation rates (A) and transpiration rates (E) were observed during a stepwise increase of

  16. Inter and under-canopy soil water, leaf-level and whole-plant gas exchange dynamics of a semi-arid perennial C 4 grass

    Microsoft Academic Search

    Erik P. HamerlynckRussell; Russell L. Scott; M. Susan Moran; Andrea M. Schwander; Erin Connor; Travis E. Huxman

    2011-01-01

    It is not clear if tree canopies in savanna ecosystems exert positive or negative effects on soil moisture, and how these\\u000a might affect understory plant carbon balance. To address this, we quantified rooting-zone volumetric soil moisture (?25 cm), plant size, leaf-level and whole-plant gas exchange of the bunchgrass, bush muhly (Muhlenbergia porteri), growing under and between mesquite (Prosopis velutina) in a

  17. Water and nitrogen conditions affect the relationships of  13C and  18O to gas exchange and growth in durum wheat

    Microsoft Academic Search

    L. Cabrera-Bosquet; G. Molero; S. Nogues; J. L. Araus

    2009-01-01

    Whereas the effects of water and nitrogen (N) on plant D13C have been reported previously, these factors have scarcely been studied for D18O. Here the combined effect of different water and N regimes on D13C, D18O, gas exchange, water-use efficiency (WUE), and growth of four genotypes of durum wheat (Triticum turgidum L. ssp. durum (Desf.) Husn.) cultured in pots was

  18. Gas exchange and chlorophyll fluorescence responses of Pinus radiata D. Don seedlings during and after several storage regimes and their effects on post-planting survival

    Microsoft Academic Search

    A. Mena-Petite; A. Robredo; S. Alcalde; M. Duñabeitia; M. González-Moro; M. Lacuesta; A. Muñoz-Rueda

    2003-01-01

    Post-storage gas exchange parameters like CO2 assimilation, stomatal conductance, transpiration, water use efficiency and intercellular CO2 concentrations, together with several chlorophyll a fluorescence parameters: Fo, Fv, Fv\\/Fm, Fm\\/Fo and Fv\\/Fo were examined in radiata pine (Pinus radiata D. Don) seedlings that were stored for 1, 8 or 15 days at 4° or 10°C with or without soil around the roots.

  19. Sodium/hydrogen exchange activity in type 1 diabetes mellitus: the never-ending story.

    PubMed

    Matteucci, E; Giampietro, O

    2001-08-01

    The amiloride-sensitive Na+/H+ exchanger (NHE) mediates uphill H+ extrusion and thus causes intracellular alkalinization. The NHE plays a major role in pH homeostasis, Na+ absorption, cell volume regulation, and cell proliferation; it is activated by growth factors, mitogens, neurotransmitters, tumor promoters, and others. At intracellular pH (pHi)>7.2-7.4, the system is quiescent; when pHi falls, the rate of H+ - efflux increases in an allosteric manner to reach a maximum around pHi=6.0. The kinetics for external Na+ follows the Michaelis-Menten model with a single, binding site. The effect of intracellular H+ best fits an allosteric model with at least two binding sites. According to the postulate that erythrocyte sodium-lithium countertransport (NLCT) might be one mode of operation of the ubiquitous NHE, and following the trail of previous investigations of NLCT association with hypertension and diabetic nephropathy, several studies have confirmed elevated NHE activity in different cell types in patients with essential hypertension. However, the relation between NHE and either NLCT or hypertension remains unclear and the usefulness of NLCT activity as a risk marker for the development of essential hypertension has been now excluded. On the contrary, few publications have dealt with the physiologic NHE in diabetic nephropathy, and contrasting results have been reported. We have observed an accelerated NHE in essential hypertension and in Type 1 diabetes, however without any relationship with urinary albumin excretion rate. Furthermore, NHE activity increased in non-diabetic first-degree relatives of Type 1 diabetic patients, yet no difference could be observed between relatives of probands with diabetic nephropathy and relatives of probands with normoalbuminuria. Unlike erythrocyte NHE activity, abnormal albumin excretion was a distinctive feature of non-diabetic first-degree relatives of Type 1 diabetic patients with nephropathy. The lack of agreement among Authors, even using both the same cell and the same method, testifies to the difficulty in performing a correct patient selection and uniformly reproducible NHE measurement. We compare individual clinical characteristics among different study populations confirming previous conclusions regarding NLCT in essential hypertension: main determinant for the flux values of NHE seems to be patient selection rather than methodology. A common effort is advisable to collaborate, standardise, compare methodologies, and unify criteria of subject recruitment. PMID:11716294

  20. Trading activity and stock price volatility: evidence from the London Stock Exchange

    Microsoft Academic Search

    Roger D. Huang; Ronald W. Masulis

    2003-01-01

    Analysis of transactions data for the Financial Times Stock Exchange (FTSE-100) stock index on the London Stock Exchange (LSE) shows that trade frequency and average trade size impact price volatility for small trades (i.e. trades of one normal market size (NMS) or less). For large trades, only trade frequency affects price volatility. In further splitting small trades by relative size,

  1. OXIDATIVE STRESS ACTIVATES ANION EXCHANGE PROTEIN 2 AND AP-1 IN AIRWAY EPITHELIAL CELLS

    EPA Science Inventory

    Anion exchange protein 2 (AE2) is a membrane-bound protein that mediates chloride-bicarbonate exchange. In addition to regulating intracellular pH and cell volume, AE2 exports superoxide (O.) to the extracellular matrix in an HCO-dependent process. Given this ability to export O....

  2. Mass, temperature and metabolic effects on discontinuous gas exchange cycles in eucalyptus-boring beetles (Coleoptera: cerambycidae).

    PubMed

    Chappell, M A; Rogowitz, G L

    2000-12-01

    Ventilatory accommodation of changing metabolic rates is a relatively little-studied aspect of the discontinuous gas exchange cycles (DGCs) that occur in a wide variety of terrestrial arthropods. We used correlation analysis of resting metabolic rate (RMR, measured as the rate of CO(2) emission; V(CO2)) and several components of the DGC to examine accommodation to both temperature-induced changes and individual variation in RMR in two wood-boring beetles (Phorocantha recurva and P. semipunctata; Coleoptera: Cerambycidae). At low to moderate ambient temperatures (T(a); 10-20 degrees C), Phorocantha spp. displayed a characteristic DGC with relatively brief but pronounced open (O) phase bursts of CO(2) emission separated by longer periods of low V(CO2), the flutter (F) phase. However, the V(CO2) never fell to zero, and we could not reliably differentiate a typical closed (C) phase from the F phase. Accordingly, we pooled the C and F phases for analysis as the C+F phase. At higher T(a) (30 degrees C), the duration of the combined C+F phase was greatly reduced. There were no differences between the two species or between males and females in either RMR or characteristics of the DGC. We found large variation in the major DGC components (cycle frequency, durations and emission volumes of the O and C+F phases); much of this variation was significantly repeatable. Accommodation of temperature-induced RMR changes was almost entirely due to changes in frequency (primarily in the C+F phase), as has been found in several other discontinuously ventilating arthropods. Frequency changes also contributed to accommodation at constant T(a), but modulation of emission volumes (during both O and C+F phases) played a larger role in this case. The DGC is often viewed as a water conservation mechanism, on the basis that respiratory evaporation is minimal during the C and F phases. This hypothesis assumes that the F phase is primarily convective (because of a reduction in tracheal P(O2) and total intratracheal pressure during the C phase). To test this, we measured the DGC in beetles subjected to varying degrees of hypoxia in addition to normoxia. As predicted for a largely diffusive F phase, we found an increase in the volume of CO(2) emitted during the C+F phase in hypoxic conditions (10.4 % oxygen). This finding, together with a reduced tendency to utilize a DGC at high T(a) (when water stress is greatest) and a natural history in which water availability is probably not limiting for any life stage, suggests that a reduction of respiratory evaporation may not have been critical in the evolution of the DGC of Phorocantha spp. Instead, selection may have favored discontinuous ventilation because it facilitates gas exchange in the hypercapnic and hypoxic environments commonly encountered by animals (such as Phorocantha spp.) that live in confined spaces. PMID:11076743

  3. Impact of bypass flow rate and catheter position in veno-venous extracorporeal membrane oxygenation on gas exchange in vivo.

    PubMed

    Togo, Konomi; Takewa, Yoshiaki; Katagiri, Nobumasa; Fujii, Yutaka; Kishimoto, Satoru; Date, Kazuma; Miyamoto, Yuji; Tatsumi, Eisuke

    2015-06-01

    The clinical use of veno-venous extracorporeal membrane oxygenation (VVECMO) in adult patients with respiratory failure is rapidly increasing. However, recirculation of blood oxygenated by ECMO back into the circuit may occur in VVECMO, resulting in insufficient oxygenation. The cannula position and bypass flow rate are two major factors influencing recirculation, but the relationship and ideal configuration of these factors are not fully understood. In the present study, we attempted to clarify these parameters for effective gas exchange. VVECMO was performed in eight adult goats under general anesthesia. The position of the drainage cannula was fixed in the inferior vena cava (IVC), but the return cannula position was varied between the IVC, right atrium (RA), and superior vena cava (SVC). At each position, the recirculation rates calculated, and the adequacy of oxygen delivery by ECMO in supplying systemic oxygen demand was assessed by measuring the arterial oxygen saturation (SaO2) and pressure (PaO2). Although the recirculation rates increased as the bypass flow rates increased, SaO2 and PaO2 also increased in any position of return cannula. The recirculation rates and PaO2 were 27 ± 2 % and 162 ± 16 mmHg, 36 ± 6 % and 139 ± 11 mmHg, and 63 ± 6 % and 77 ± 9 mmHg in the SVC, RA and IVC position at 4 L/min respectively. In conclusion, the best return cannula position was the SVC, and a high bypass flow rate was advantageous for effective oxygenation. Both the bypass flow rates and cannula position must be considered to achieve effective oxygenation. PMID:25477271

  4. Liming can decrease legume crop yield and leaf gas exchange by enhancing root to shoot ABA signalling

    PubMed Central

    Rothwell, Shane A.; Elphinstone, E. David; Dodd, Ian C.

    2015-01-01

    To meet future requirements for food production, sustainable intensive agricultural systems need to optimize nutrient availability to maximize yield, traditionally achieved by maintaining soil pH within an optimal range (6–6.5) by applying lime (calcium carbonate). However, a field trial that applied recommended liming rates to a sandy loam soil (increasing soil pH from 5.5 to 6.2) decreased pod yield of field bean (Vicia faba L. cv. Fuego) by ~30%. Subsequent pot trials, with liming that raised soil pH to 6.3–6.7, reduced stomatal conductance (g s) by 63, 26, and 59% in V. faba, bean (Phaseolus vulgaris), and pea (Pisum sativum), respectively. Furthermore, liming reduced shoot dry biomass by 16–24% in these species. Ionomic analysis of root xylem sap and leaf tissue revealed a decrease in phosphorus concentration that was correlated with decreased g s: both reductions were partially reversed by adding superphosphate fertilizer. Further analysis of pea suggests that leaf gas exchange was reduced by a systemic increase (roots, xylem sap, and leaves) in the phytohormone abscisic acid (ABA) in response to lime-induced suboptimal plant phosphorus concentrations. Supplying synthetic ABA via the transpiration stream to detached pea leaves, at the same xylem sap concentrations induced by liming, decreased transpiration. Furthermore, the g s of the ABA-deficient mutant pea wilty was unresponsive to liming, apparently confirming that ABA mediates some responses to low phosphorus availability caused by liming. This research provides a detailed mechanistic understanding of the physiological processes by which lime application can limit crop yields, and questions the suitability of current liming recommendations. PMID:25740925

  5. Normal pulmonary gas exchange efficiency and absence of exercise-induced arterial hypoxemia in adults with bronchopulmonary dysplasia.

    PubMed

    Lovering, Andrew T; Laurie, Steven S; Elliott, Jonathan E; Beasley, Kara M; Yang, Ximeng; Gust, Caitlyn E; Mangum, Tyler S; Goodman, Randall D; Hawn, Jerold A; Gladstone, Igor M

    2013-10-01

    Cardiopulmonary function is reduced in adults born very preterm, but it is unknown if this results in reduced pulmonary gas exchange efficiency during exercise and, consequently, leads to reduced aerobic capacity in subjects with and without bronchopulmonary dysplasia (BPD). We hypothesized that an excessively large alveolar to arterial oxygen difference (AaDO2) and resulting exercise-induced arterial hypoxemia (EIAH) would contribute to reduced aerobic fitness in adults born very preterm with and without BPD. Measurements of pulmonary function, lung volumes and diffusion capacity for carbon monoxide (DLco) were made at rest. Measurements of maximal oxygen consumption, peak workload, temperature- and tonometry-corrected arterial blood gases, and direct measure of hemoglobin saturation with oxygen (SaO2) were made preexercise and during cycle ergometer exercise in ex-preterm subjects ?32-wk gestational age, with BPD (n = 12), without BPD (PRE; n = 12), and full term controls (CONT; n = 12) breathing room air. Both BPD and PRE had reduced pulmonary function and reduced DLco compared with CONT. The AaDO2 was not significantly different between groups, and there was no evidence of EIAH (SaO2 < 95% and/or AaDO2 ? 40 Torr) in any subject group preexercise or at any workload. Arterial O2 content was not significantly different between the groups preexercise or during exercise. However, peak power output was decreased in BPD and PRE subjects compared with CONT. We conclude that EIAH in adult subjects born very preterm with and without BPD does not likely contribute to the reduction in aerobic exercise capacity observed in these subjects. PMID:23869070

  6. Gas exchange, leaf structure and nitrogen in contrasting successional tree species growing in open and understory sites during a drought.

    PubMed

    Abrams, M D; Mostoller, S A

    1995-06-01

    Seasonal ecophysiology, leaf structure and nitrogen were measured in saplings of early (Populus grandidentata Michx. and Prunus serotina J.F. Ehrh.), middle (Fraxinus americana L. and Carya tomentosa Nutt.) and late (Acer rubrum L. and Cornus florida L.) successional tree species during severe drought on adjacent open and understory sites in central Pennsylvania, USA. Area-based net photosynthesis (A) and leaf conductance to water vapor diffusion (g(wv)) varied by site and species and were highest in open growing plants and early successional species at both the open and understory sites. In response to the period of maximum drought, both sunfleck and sun leaves of the early successional species exhibited smaller decreases in A than leaves of the other species. Shaded understory leaves of all species were more susceptible to drought than sun leaves and had negative midday A values during the middle and later growing season. Shaded understory leaves also displayed a reduced photosynthetic light response during the peak drought period. Sun leaves were thicker and had a greater mass per area (LMA) and nitrogen (N) content than shaded leaves, and early and middle successional species had higher N contents and concentrations than late successional species. In both sunfleck and sun leaves, seasonal A was positively related to predawn leaf Psi, g(wv), LMA and N, and was negatively related to vapor pressure deficit, midday leaf Psi and internal CO(2). Although a significant amount of plasticity occurred in all species for most gas exchange and leaf structural parameters, middle successional species exhibited the largest degree of phenotypic plasticity between open and understory plants. PMID:14965944

  7. Postsynthetic Metal and Ligand Exchange in MFU-4l: A Screening Approach toward Functional Metal-Organic Frameworks Comprising Single-Site Active Centers.

    PubMed

    Denysenko, Dmytro; Jelic, Jelena; Reuter, Karsten; Volkmer, Dirk

    2015-05-26

    The isomorphous partial substitution of Zn(2+) ions in the secondary building unit (SBU) of MFU-4l leads to frameworks with the general formula [Mx Zn(5-x) Cl4 (BTDD)3 ], in which x?2, M=Mn(II) , Fe(II) , Co(II) , Ni(II) , or Cu(II) , and BTDD=bis(1,2,3-triazolato-[4,5-b],[4',5'-i])dibenzo-[1,4]-dioxin. Subsequent exchange of chloride ligands by nitrite, nitrate, triflate, azide, isocyanate, formate, acetate, or fluoride leads to a variety of MFU-4l derivatives, which have been characterized by using XRPD, EDX, IR, UV/Vis-NIR, TGA, and gas sorption measurements. Several MFU-4l derivatives show high catalytic activity in a liquid-phase oxidation of ethylbenzene to acetophenone with air under mild conditions, among which Co- and Cu derivatives with chloride side-ligands are the most active catalysts. Upon thermal treatment, several side-ligands can be transformed selectively into reactive intermediates without destroying the framework. Thus, at 300?°C, Co(II) -azide units in the SBU of Co-MFU-4l are converted into Co(II) -isocyanate under continuous CO gas flow, involving the formation of a nitrene intermediate. The reaction of Cu(II) -fluoride units with H2 at 240?°C leads to Cu(I) and proceeds through the heterolytic cleavage of the H2 molecule. PMID:25882594

  8. Structural and functional analyses of DNA-sensing and immune activation by human cGAS.

    PubMed

    Kato, Kazuki; Ishii, Ryohei; Goto, Eiji; Ishitani, Ryuichiro; Tokunaga, Fuminori; Nureki, Osamu

    2013-01-01

    The detection of cytosolic DNA, derived from pathogens or host cells, by cytosolic receptors is essential for appropriate host immune responses. Cyclic GMP-AMP synthase (cGAS) is a newly identified cytosolic DNA receptor that produces cyclic GMP-AMP, which activates stimulator of interferon genes (STING), resulting in TBK1-IRF3 pathway activation followed by the production of type I interferons. Here we report the crystal structure of human cGAS. The structure revealed that a cluster of lysine and arginine residues forms the positively charged DNA binding surface of human cGAS, which is important for the STING-dependent immune activation. A structural comparison with other previously determined cGASs and our functional analyses suggested that a conserved zinc finger motif and a leucine residue on the DNA binding surface are crucial for the DNA-specific immune response of human cGAS, consistent with previous work. These structural features properly orient the DNA binding to cGAS, which is critical for DNA-induced cGAS activation and STING-dependent immune activation. Furthermore, we showed that the cGAS-induced activation of STING also involves the activation of the NF-?B and IRF3 pathways. Our results indicated that cGAS is a DNA sensor that efficiently activates the host immune system by inducing two distinct pathways. PMID:24116191

  9. Structural and Functional Analyses of DNA-Sensing and Immune Activation by Human cGAS

    PubMed Central

    Kato, Kazuki; Ishii, Ryohei; Goto, Eiji; Ishitani, Ryuichiro; Tokunaga, Fuminori; Nureki, Osamu

    2013-01-01

    The detection of cytosolic DNA, derived from pathogens or host cells, by cytosolic receptors is essential for appropriate host immune responses. Cyclic GMP-AMP synthase (cGAS) is a newly identified cytosolic DNA receptor that produces cyclic GMP-AMP, which activates stimulator of interferon genes (STING), resulting in TBK1-IRF3 pathway activation followed by the production of type I interferons. Here we report the crystal structure of human cGAS. The structure revealed that a cluster of lysine and arginine residues forms the positively charged DNA binding surface of human cGAS, which is important for the STING-dependent immune activation. A structural comparison with other previously determined cGASs and our functional analyses suggested that a conserved zinc finger motif and a leucine residue on the DNA binding surface are crucial for the DNA-specific immune response of human cGAS, consistent with previous work. These structural features properly orient the DNA binding to cGAS, which is critical for DNA-induced cGAS activation and STING-dependent immune activation. Furthermore, we showed that the cGAS-induced activation of STING also involves the activation of the NF-?B and IRF3 pathways. Our results indicated that cGAS is a DNA sensor that efficiently activates the host immune system by inducing two distinct pathways. PMID:24116191

  10. Activated carbons obtained from sewage sludge by chemical activation: gas-phase environmental applications.

    PubMed

    Boualem, T; Debab, A; Martínez de Yuso, A; Izquierdo, M T

    2014-07-01

    The objective of this study was to evaluate the adsorption capacity for toluene and SO2 of low cost activated carbons prepared from sewage sludge by chemical activation at different impregnation ratios. Samples were characterized by proximate and ultimate analyses, thermogravimetry, infrared spectroscopy and N2 adsorption. Because of the low carbon content of the raw material, the development of porosity in the activated carbons was mainly of a mesoporous nature, with surface areas lower than 300 m(2)/g. The study of gas-phase applications for activated carbons from sewage sludge was carried out using both an organic and an inorganic compound in order to screen for possible applications. Toluene adsorption capacity at saturation was around 280 mg/g, which is a good level of performance given the high ash content of the activated carbons. However, dynamic experiments at low toluene concentration presented diffusion problems resulting from low porosity development. SO2 adsorption capacity is associated with average micropore size, which can be controlled by the impregnation ratio used to prepare the activated carbons. PMID:24747937

  11. Development and implementation of a FT-ICR mass spectrometer for the investigation of ion conformations of peptide sequence isomers containing basic amino acid residues by gas-phase hydrogen/deuterium exchange

    E-print Network

    Marini, Joseph Thomas

    2004-09-30

    The gas-phase hydrogen/deuterium (H/D) exchange of protonated di- and tripeptides containing a basic amino acid residue has been studied with a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. Bimolecular reactions...

  12. Development and implementation of a FT-ICR mass spectrometer for the investigation of ion conformations of peptide sequence isomers containing basic amino acid residues by gas-phase hydrogen/deuterium exchange 

    E-print Network

    Marini, Joseph Thomas

    2004-09-30

    The gas-phase hydrogen/deuterium (H/D) exchange of protonated di- and tripeptides containing a basic amino acid residue has been studied with a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. Bimolecular ...

  13. TILLAGE AND GAS EXCHANGE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In traditional agricultural production, tillage of the soil has been an integral part of the production process. Tillage is the mechanical manipulation of soil and crop residue to prepare a seedbed where crop seeds are planted, sprout, take root and grow into plants to produce grain. Intensive tilla...

  14. Genesis of methane activation sites in Mo-exchanged H–ZSM-5 catalysts

    Microsoft Academic Search

    Young-Ho Kim; Richard W Borry; Enrique Iglesia

    2000-01-01

    Exchanged (Mo2O7)2? dimers form during treatment in air of MoO3\\/H–ZSM-5 (Si\\/Al=14.3) physical mixtures at 773–973K. The amount of water desorbed during exchange and the number of residual protons (measured by D2–OH exchange) showed that each Mo6+ replaces 1.1 (±0.1) protons in H–ZSM-5 (for Mo\\/Al<0.37). 27Al NMR, X-ray absorption, and Raman spectra confirmed the proposed (Mo2O7)2? structure and its location at

  15. Effects of gaseous environments in gas-cooled reactors and solar thermal heat exchangers on the creep and creep-rupture properties of heat-resisting metals and alloys. Final report

    Microsoft Academic Search

    W. D. Nix; K. P. Fuchs

    1977-01-01

    Energy conversion systems employing heat exchangers use closed cycle gas turbines with helium as the working fluid. An important design criterion for heat exchanger and turbine systems is the creep strength of the tubing, blading, and vane materials. The design data for these materials generally has been obtained in air. However, there have been reports of adverse environmental effects of

  16. Investing in International Information Exchange Activities to Improve the Safety, Cost Effectiveness and Schedule of Cleanup - 13281

    SciTech Connect

    Seed, Ian; James, Paula [Cogentus Consulting (United States)] [Cogentus Consulting (United States); Mathieson, John [NDA United Kingdom (United Kingdom)] [NDA United Kingdom (United Kingdom); Judd, Laurie [NuVision Engineering, Inc. (United States)] [NuVision Engineering, Inc. (United States); Elmetti-Ramirez, Rosa; Han, Ana [US DOE (United States)] [US DOE (United States)

    2013-07-01

    With decreasing budgets and increasing pressure on completing cleanup missions as quickly, safely and cost-effectively as possible, there is significant benefit to be gained from collaboration and joint efforts between organizations facing similar issues. With this in mind, the US Department of Energy (DOE) and the UK Nuclear Decommissioning Authority (NDA) have formally agreed to share information on lessons learned on the development and application of new technologies and approaches to improve the safety, cost effectiveness and schedule of the cleanup legacy wastes. To facilitate information exchange a range of tools and methodologies were established. These included tacit knowledge exchange through facilitated meetings, conference calls and Site visits as well as explicit knowledge exchange through document sharing and newsletters. A DOE web-based portal has been established to capture these exchanges and add to them via discussion boards. The information exchange is operating at the Government-to-Government strategic level as well as at the Site Contractor level to address both technical and managerial topic areas. This effort has resulted in opening a dialogue and building working relationships. In some areas joint programs of work have been initiated thus saving resource and enabling the parties to leverage off one another activities. The potential benefits of high quality information exchange are significant, ranging from cost avoidance through identification of an approach to a problem that has been proven elsewhere to cost sharing and joint development of a new technology to address a common problem. The benefits in outcomes significantly outweigh the costs of the process. The applicability of the tools and methods along with the lessons learned regarding some key issues is of use to any organization that wants to improve value for money. In the waste management marketplace, there are a multitude of challenges being addressed by multiple organizations and the effective pooling and exchange of knowledge and experience can only be of benefit to all participants to help complete the cleanup mission more quickly and more cost effectively. This paper examines in detail the tools and processes used to promote information exchange and the progress made to date. It also discusses the challenges and issues involved and proposes recommendations to others who are involved in similar activities. (authors)

  17. Ignition of gas during activities in Hanford waste tanks

    SciTech Connect

    Darby, J.; Unal, C.; Pasamehmetoglu, K. [Los Alamos National Laboratory, NM (United States)

    1996-12-31

    The purpose of this work was to quantity the likelihood of the ignition of flammable gas during core sampling and salt well pumping operations in single-shell waste tanks at the Hanford site. Deflagration of the gas in the tank dome can lead to dome collapse and uncontrolled release of radionuclides and toxic gases from the waste.

  18. Record activity and stability of dealloyed bimetallic catalysts for proton exchange membrane fuel cells

    E-print Network

    Han, Binghong

    We demonstrate the unprecedented proton exchange membrane fuel cell (PEMFC) performance durability of a family of dealloyed Pt–Ni nanoparticle catalysts for the oxygen reduction reaction (ORR), exceeding scientific and ...

  19. Active Geophysical Monitoring in Oil and Gas Industry

    NASA Astrophysics Data System (ADS)

    Bakulin, A.; Calvert, R.

    2005-12-01

    Effective reservoir management is a Holy Grail of the oil and gas industry. Quest for new technologies is never ending but most often they increase effectiveness and decrease the costs. None of the newcomers proved to be a silver bullet in such a key metric of the industry as average oil recovery factor. This factor is still around 30 %, meaning that 70 % of hydrocarbon reserves are left in the ground in places where we already have expensive infrastructure (platforms, wells) to extract them. Main reason for this inefficiency is our inability to address realistic reservoir complexity. Most of the time we fail to properly characterize our reservoirs before production. As a matter of fact, one of the most important parameters -- permeability -- can not be mapped from remote geophysical methods. Therefore we always start production blind even though reservoir state before production is the simplest one. Once first oil is produced, we greatly complicate the things and quickly become unable to estimate the state and condition of the reservoir (fluid, pressures, faults etc) or oilfield hardware (wells, platforms, pumps) to make a sound next decision in the chain of reservoir management. Our modeling capabilities are such that if we know true state of the things - we can make incredibly accurate predictions and make extremely efficient decisions. Thus the bottleneck is our inability to properly describe the state of the reservoirs in real time. Industry is starting to recognize active monitoring as an answer to this critical issue. We will highlight industry strides in active geophysical monitoring from well to reservoir scale. It is worth noting that when one says ``monitoring" production technologists think of measuring pressures at the wellhead or at the pump, reservoir engineers think of measuring extracted volumes and pressures, while geophysicist may think of change in elastic properties. We prefer to think of monitoring as to measuring those parameters of the reservoir or producing equipment (say wells), that are needed to make next most critical (read expensive and risky) reservoir management decision for particular field. Time-lapse seismic monitoring has become a major tool of aerial field monitoring locating bypassed oil. We show examples when 4D seismic can map average distribution of fluids and pressures throughout the reservoir as well as highlight major challenges related to non-repeatability and changes in the overburden. 4D seismic is one of many surveillance tools used by oil and gas industry. Often, it may not be economic to monitor production with 4D seismic in onshore fields with closely spaced wells and a lot of surface infrastructure. Other downhole methods become preferential in those circumstances. Finally, in difficult environments with expensive infrastructure, monitoring of that surface and subsurface infrastructure becomes an important industrial task in itself. For instance, in a deep-water field it may be task of monitoring state of the well itself since loosing such well due to failure or sand production, may be very expensive and one may rather prefer slight changes in production strategies rather than loss of several expensive wells. Another similar tasks include monitoring platforms or subsurface pipelines. It is important to realize that with proper monitoring in place we still require many other technologies that can act upon the information obtained and increase oil recovery. However it is clear that all these technologies are rendered useless without proper real-time knowledge of the reservoir state i.e. without monitoring.

  20. The Investigation of Effects of Blood Exchange Transfusion on Selenium in Newborn Infants by Instrumental Neutron Activation Analysis Method

    PubMed Central

    Khatami, Seyedeh-Fatemeh; Parvaresh, Pouya; Parvaresh, Parviz; Gharib, Morteza

    2013-01-01

    Objective The evidence for the effects of blood exchange transfusion on selenium (Se) in newborn infants is unknown. This study was conducted to determine the possible effects of blood exchange transfusion on Se by comparing the Se blood concentrations before and after exchange transfusion in jaundiced neonates. Methods A total of 30 jaundiced term neonates who underwent blood exchange transfusion (EXT) for first time because of idiopathic unconjugated hyperbilirubinemia, were recruited. The Se level of 30 blood bank donors’ samples used for EXT were measured and 30 pairs of uncontaminated umbilical cord blood samples were investigated for Se before and after exchange transfusion. The samples were analyzed by instrumental neutron activation analysis method. Serum bilirubin concentrations were measured by venous blood samples before EXT. Findings The average of Se concentration before EXT was higher than that after EXT (629.78±283.82 SD ppb versus 454.83±213.75 SD ppb) (P<0.05). There was significant correlation between the blood concentration of Se before and after EXT and also between the blood level of Se before EXT and total serum bilirubin level (P<0.05). There was no significant correlation between the blood concentration of Se before EXT and babies’ gender and weight (P>0.05). The average Se level in samples obtained from transfused blood products was 507.90±223.56 SD ppb. Conclusion Blood exchange transfusion caused a 28% decrease of the blood Se level because the blood donors had lower blood Se levels than the newborns. Furthermore, there was a significant correlation between the blood level of Se before EXT and the total serum bilirubin level. PMID:23724171