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1

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

PubMed Central

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

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

1997-01-01

2

Gas exchange and electrical activity of the skeletal musculature of animals in a helium and oxygen medium  

NASA Technical Reports Server (NTRS)

The gas exchange electrical activity of the skeletal musculature (EAM) -- the heat regulating tonus, and the rectal temperature for rats which were kept for one hour in the air, in a helium-oxygen mixture and again in air, were studied. Animals kept in the helium-oxygen atmosphere at room temperature showed a definite increase in the level of gas exchange, an increase of the EAM, and a drop in rectal temperature. Transition to air respiration brought about normalization of almost all the functions. Increasing the temperature by 5 deg (25-27 deg) in comparison with that of air (20-22 deg) led to a small decrease of EAM indices, gas exchange, and body temperature.

Troshikhin, G. V.

1973-01-01

3

Pulmonary gas exchange is not impaired 24 h after extravehicular activity.  

PubMed

Extravehicular activity (EVA) during spaceflight involves a significant decompression stress. Previous studies have shown an increase in the inhomogeneity of ventilation-perfusion ratio (VA/Q) after some underwater dives, presumably through the embolic effects of venous gas microemboli in the lung. Ground-based chamber studies simulating EVA have shown that venous gas microemboli occur in a large percentage of the subjects undergoing decompression, despite the use of prebreathe protocols to reduce dissolved N(2) in the tissues. We studied eight crewmembers (7 male, 1 female) of the International Space Station who performed 15 EVAs (initial cabin pressure 748 mmHg, final suit pressure either approximately 295 or approximately 220 mmHg depending on the suit used) and who followed the denitrogenation procedures approved for EVA from the International Space Station. The intrabreath VA/Q slope was calculated from the alveolar Po(2) and Pco(2) in a prolonged exhalation maneuver on the day after EVA and compared with measurements made in microgravity on days well separated from the EVA. There were no significant changes in intrabreath VA/Q slope as a result of EVA, although there was a slight increase in metabolic rate and ventilation (approximately 9%) on the day after EVA. Vital capacity and other measures of pulmonary function were largely unaltered by EVA. Because measurements could only be performed on the day after EVA because of logistical constraints, we were unable to determine an acute effect of EVA on VA/Q inequality. The results suggest that current denitrogenation protocols do not result in any major lasting alteration to gas exchange in the lung. PMID:16123205

Prisk, G Kim; Fine, Janelle M; Cooper, Trevor K; West, John B

2005-12-01

4

Gas Exchange, Partial Pressure Gradients,  

E-print Network

Gas Exchange, Partial Pressure Gradients, and the Oxygen Window Johnny E. Brian, Jr., M affect the precise gas exchange occurring in individual areas of the lungs and body tissues. To make of circulatory and gas transport physiology, and the best place to start is with normobaric physiology. LIFE

Riba Sagarra, Jaume

5

BOREAS TE-12 Leaf Gas Exchange Data  

NASA Technical Reports Server (NTRS)

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).

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

2000-01-01

6

Active microchannel heat exchanger  

DOEpatents

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.

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

7

BOREAS TE-5 Leaf Gas Exchange Data  

NASA Technical Reports Server (NTRS)

The BOREAS TE-5 team collected measurements in the NSA and SSA on gas exchange, gas composition, and tree growth. The leaf photosynthetic gas exchange data were collected in the BOREAS NSA and the SSA from 06-Jun- 1994 to 13-Sep- 1994 using a LI-COR 6200 portable photosynthesis system. The data were collected to compare the photosynthetic capacity, stomata] conductance, and leaf intercellular CO, concentrations among the major tree species at the BOREAS sites. The data are average values from diurnal measurements on the upper canopy foliage (sun leaves). The data are available 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 Activity Archive Center (DAAC).

Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Ehleriinger, Jim; Brooks, J. Renee; Flanagan, Larry

2000-01-01

8

A high throughput gas exchange screen for determining rates of photorespiration or regulation of C4 activity  

PubMed Central

Large-scale research programmes seeking to characterize the C4 pathway have a requirement for a simple, high throughput screen that quantifies photorespiratory activity in C3 and C4 model systems. At present, approaches rely on model-fitting to assimilatory responses (A/C i curves, PSII quantum yield) or real-time carbon isotope discrimination, which are complicated and time-consuming. Here we present a method, and the associated theory, to determine the effectiveness of the C4 carboxylation, carbon concentration mechanism (CCM) by assessing the responsiveness of V O/V C, the ratio of RuBisCO oxygenase to carboxylase activity, upon transfer to low O2. This determination compares concurrent gas exchange and pulse-modulated chlorophyll fluorescence under ambient and low O2, using widely available equipment. Run time for the procedure can take as little as 6 minutes if plants are pre-adapted. The responsiveness of V O/V C is derived for typical C3 (tobacco, rice, wheat) and C4 (maize, Miscanthus, cleome) plants, and compared with full C3 and C4 model systems. We also undertake sensitivity analyses to determine the impact of R LIGHT (respiration in the light) and the effectiveness of the light saturating pulse used by fluorescence systems. The results show that the method can readily resolve variations in photorespiratory activity between C3 and C4 plants and could be used to rapidly screen large numbers of mutants or transformants in high throughput studies. PMID:25006037

Bellasio, Chandra; Burgess, Steven J; Griffiths, Howard

2014-01-01

9

BOREAS TE-10 Leaf Gas Exchange Data  

NASA Technical Reports Server (NTRS)

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).

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

2000-01-01

10

BOREAS TE-11 Leaf Gas Exchange Measurements  

NASA Technical Reports Server (NTRS)

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).

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

2000-01-01

11

Where is air-sea gas exchange happening? Carbon isotope  

E-print Network

Where is air-sea gas exchange happening? Carbon isotope evidence Nir Krakauer California Institute: An application of generalized cross validation · The regional distribution of air-sea gas exchange · Seasonality;Gas exchange in perspective Applications of gas exchange rates · To infer the space and time

Krakauer, Nir Y.

12

Anesthesia and gas exchange in tracheal surgery.  

PubMed

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

Wiedemann, Klaus; Mnnle, Clemens

2014-02-01

13

Air-Water Gas Exchange  

Microsoft Academic Search

The exchange of inert and sparingly soluble gases -- including carbon dioxide, methane, and oxygen -- between the atmosphere and oceans is controlled by a thin 20- to 200-m-thick boundary layer at the top of the ocean. The hydrodynamics in this layer are significantly different from boundary layers at rigid walls, since the orbital motion of the waves is of

B. Jhne; H. Hauecker

1998-01-01

14

Greenhouse gas exchange over grazed systems  

NASA Astrophysics Data System (ADS)

Grasslands act as sinks and sources of greenhouse gases (GHG) and are, in conjunction with livestock production systems, responsible for a large share of GHG emissions. Whereas ecosystem scale flux measurements (eddy covariance) are commonly used to investigate CO2 exchange (and is becoming state-of-the-art for other GHGs, too), GHG emissions from agricultural animals are usually investigated on the scale of individual animals. Therefore eddy covariance technique has to be tested for combined systems (i.e. grazed systems). Our project investigates the ability of field scale flux measurements to reliably quantify the contribution of grazing dairy cows to the net exchange of CO2 and CH4. To quantify the contribution of the animals to the net flux the position, movement, and grazing/rumination activity of each cow are recorded. In combination with a detailed footprint analysis of the eddy covariance fluxes, the animal related CO2 and CH4 emissions are derived and compared to standard emission values derived from respiration chambers. The aim of the project is to test the assumption whether field scale CO2 flux measurements adequately include the respiration of grazing cows and to identify potential errors in ecosystem Greenhouse gas budgets.

Felber, R.; Ammann, C.; Neftel, A.

2012-04-01

15

Forced convection modulates gas exchange in cnidarians  

PubMed Central

Boundary layer thickness is a potentially important component of the diffusive pathway for gas exchange in aquatic organisms. The soft coral Alcyonium siderium (Octocorallia) and sea anemone Metridium senile (Actiniaria) exhibit significant increases in respiration with water flow over a range of Reynolds numbers encountered subtidally. A nondimensional mass transfer analysis of the effect of forced convection demonstrates the importance of the state of the organism's boundary layer in regulating metabolism in these invertebrates. Flow-modulated gas exchange may limit secondary productivity in subtidal environments. PMID:16594087

Patterson, Mark R.; Sebens, Kenneth P.

1989-01-01

16

ANALYSIS AND MODELING OF GAS EXCHANGE PROCESSES IN SCAEVOLA AEMULA  

Technology Transfer Automated Retrieval System (TEKTRAN)

Scaevola aemula is a popular ornamental crop cultivated as a bedding plant or for hanging baskets. We characterized gas exchange properties of S.aemula 'New Wonder' in response to photo synthetically active radiation (PAR), carbon dioxide concentration, and leaf temperature. Net CO2 assimilation ra...

17

Gas and solid particulate material heat exchanger  

SciTech Connect

This patent describes an apparatus for carrying out heat exchange between a gas and solid particulate material comprising a casing having an upper inlet for particulate material and a lower outlet for particulate material and a lower grate mounted in the casing extending from the upper inlet to the lower outlet for supporting a bed of particulate material for movement from the inlet to the outlet along the lower grate. A means defines an upper grate mounted in the casing and is spaced from the lower grate including generally vertically oriented slats, each spaced from and positioned below a preceding slat in the direction from the inlet toward the outlet for defining the top of the bed of material while permitting the bed of material to expand. The casing includes an inlet for gas on one side of the casing and an outlet for gas on the other side of the casing whereby gas flows from the inlet through the lower grate, the bed of material and through the upper grate to the outlet for gas for carrying out heat exchange between the gas and the solid particulate material. Each of the slats is perforated to permit gas and fine material to pass therethrough while retaining the bed of material on the lower grate.

Kreisberg, A.J.; Warshawsky, J.

1986-12-16

18

Diffusion in gas exchange of insects.  

PubMed

The air-filled tracheal system constitutes the organ for gas exchange in terrestrial insects-its finest branches, the tracheoles, contacting individual cells. In the pupal stage, in which the animal lacks significant ventilatory movement, diffusion in the gas phase of the tracheal system constitutes the only mechanism for gas transfer between the environment and the tissues, transport in the hemolymph being insignificant. We have attempted to identify the main sites of diffusional resistance in the tracheal gas system by measuring the evolution of inert gases of low solubility from the pupa of the giant silkworm moth (Hyalophora cecropia). The results are compatible wih a single model in which the resistance to diffusional gas transfer in the tracheal system is concentrated at its opening at the body surface (spiracle). PMID:6281073

Scheid, P; Hook, C; Bridges, C R

1982-04-01

19

Original article Variation in forest gas exchange at landscape  

E-print Network

Original article Variation in forest gas exchange at landscape to continental scales John D the first network for monitoring and comparing gas exchange of forest ecosystems via eddy covariance tech and biogeochemistry at landscape, regional and continental scales. ( Inra/Elsevier, Paris.) forest gas exchange

Paris-Sud XI, Université de

20

Experimental setup for the investigation of bubble mediated gas exchange  

E-print Network

Experimental setup for the investigation of bubble mediated gas exchange Wolfgang Mischler1.Mischler@iup.uni-heidelberg.de Abstract. An experimental setup for the measurement of the contribution of air bubbles to gas exchange spectroscopy. The effect of the tracer solubility on the bubble- mediated gas exchange is demonstrated. Key

Jaehne, Bernd

21

Original article Effects of water supply on gas exchange  

E-print Network

Original article Effects of water supply on gas exchange in Pinus pinaster Ait. provenances during, 28040, Madrid, Spain (Received 26 March 1999; accepted 16 July 1999) Abstract ­ Gas exchange parameters. maritime pine / early selection / gas exchange parameters Résumé ­ Effets de l'alimentation en eau sur les

Paris-Sud XI, Université de

22

COLLISON-ACTIVATED CLEAVAGE OF A PEPTIDE/ANTIOBIOTIC LINKAGE: EVIDENCE FOR GAS-PHASE INTRAMOLECULAR DISULFIDE EXCHANGE  

Technology Transfer Automated Retrieval System (TEKTRAN)

Ceftiofur is a third generation beta-lactam antibiotic widely used in livestock for treatment of infections. Upon administration, ceftiofur is rapidly metabolized to desfuroylceftiofur, an antimicrobially active metabolite that has a free thiol functional group. Previous experiments using electron...

23

Nitrogen gas exchange in the human knee  

SciTech Connect

Human decompression sickness is presumed to result from excess inert gas in the body when ambient pressure is reduced. Although the most common symptom is pain in the skeletal joints, no direct study of nitrogen exchange in this region has been undertaken. For this study, nitrogen tagged with radioactive 13N was prepared in a linear accelerator. Nine human subjects rebreathed this gas from a closed circuit for 30 min, then completed a 40- to 100-min washout period breathing room air. The isotope 13N was monitored continuously in the subject's knee during the entire period using positron detectors. After correction for isotope decay (half-life = 9.96 min), the concentration in most knees continued to rise for at least 30 min into the washout period. Various causes of this unexpected result are discussed, the most likely of which is an extensive redistribution of gas within avascular knee tissues.

Weathersby, P.K.; Meyer, P.; Flynn, E.T.; Homer, L.D.; Survanshi, S.

1986-10-01

24

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

E-print Network

Improved helium exchange gas cryostat and sample tube designs for automated gas sampling of atmospheric gases from polar ice cores, two units of a redesigned top load helium exchange gas cryostat were changeover system. Components: 6641 words, 9 figures, 2 tables. Keywords: helium exchange gas refrigerator

Severinghaus, Jeffrey P.

25

Educational software for illustrating gas-exchange processes in plants  

SciTech Connect

Simulation models are increasingly being used to describe physiological processes in the plant sciences. These models, while useful for research purposes, also offer tremendous potential for demonstrating a wide array of scientific topics to students. The authors have developed an educational software package, based on currently accepted principles, that illustrates the environmental and biochemical control of plant gas-exchange. Graphic and tabular presentations, coupled with on-screen requests for student input, serve to effectively convey the basic fundamentals of photosynthesis and transpiration, as well as the diurnal patterns of plant gas-exchange in response to fluctuating environmental conditions. More advanced topics focus on the biochemical limitations to photosynthesis imposed by Rubisco activity, electron transport capacity, and the regeneration of inorganic phosphorus. Also included is an exercise that challenges students to call upon the lessons learned in order to optimize carbon assimilation, while minimizing water losses, over a 72-h simulation period.

Wullschleger, S.D.; Hanson, P.J. (Oak Ridge National Lab., TN (United States)); Sage, R.F. (Univ. of Georgia, Athens (United States))

1991-05-01

26

BOREAS TF-11 SSA-Fen Leaf Gas Exchange Data  

NASA Technical Reports Server (NTRS)

The BOREAS TF-11 team gathered a variety of data to complement its tower flux measurements collected at the SSA-Fen site. This data set contains single-leaf gas exchange data from the SSA-Fen site during 1994 and 1995. These leaf gas exchange properties were measured for the dominant vascular plants using portable gas exchange systems. The data are stored in tabular ASCII files.

Arkebauer, Timothy J.; Hall, Forrest G. (Editor); Knapp, David E. (Editor)

2000-01-01

27

Eccentric exercise-induced muscle damage dissociates the lactate and gas exchange thresholds  

Microsoft Academic Search

We tested the hypothesis that exercise-induced muscle damage would increase the ventilatory ([Vdot]E) response to incremental\\/ramp cycle exercise (lower the gas exchange threshold) without altering the blood lactate profile, thereby dissociating the gas exchange and lactate thresholds. Ten physically active men completed maximal incremental cycle tests before (pre) and 48h after (post) performing eccentric exercise comprising 100 squats. Pulmonary gas

Rosemary C. Davies; Ann V. Rowlands; David C. Poole; Andrew M. Jones; Roger G. Eston

2011-01-01

28

Trace Gas Exchange of Biofuel Crops  

NASA Astrophysics Data System (ADS)

In 2010 leaf level gas exchange and VOC fluxes from switchgrass and corn grown at the CSU horticultural farm in Ft Collins (CO) were measured using a PTR-MS coupled to a modified Li6400 cuvette system. Both species are C4 plants with corn currently being the dominant biofuel crop in the USA whilst switchgrass being a promising candidate for cellulosic fuel ethanol production. Amongst the strongest VOC emissions from both plants were methanol, acetic acid, acetaldehyde, acetone and toluene. The switchgrass VOC emissions compare reasonably well with the only published data measured from potted plants in a whole plant enclosure (Eller et al. 2011). VOC emission studies on corn are almost as scarce as those of switchgrass. Considering the acreage of corn grown in the USA every year, VOC flux measurements of this plant species are largely under-represented in the literature. The emission rates that do exist in the literature do not compare well with the numbers found in this study (e.g. Das et al. 2003; 35?g methanol per hour per gram biomass). To investigate the biosphere atmosphere exchange of corn fields in more detail the field campaign BioCORN 2011 was initiated. In summer 2011 an eddy covariance system was set up in a corn field at ARDEC (CSU, Ft Collins, CO) to investigate the energy flux and the trace gas exchange of the US' dominant biofuel crop. Besides energy flux, evapotranspiration and CO2 flux a comprehensive suite of volatile organic compounds and inorganic species (O3, NO, NO2, CO) are measured for virtual disjunct eddy covariance (vDEC) analysis and true eddy covariance (EC) fluxes, respectively. VOCs are monitored by PTR-MS and, for the first time, fluxes of formic acid are measured utilizing NI-CIMS data for vDEC analysis. Besides the EC approach leaf level flux measurements and soil flux measurements are performed using a GC-MS system (TACOH) coupled to a modified Li6400 system and to soil chambers, respectively. Ethanol and methanol are amongst the compounds with the largest emissions from corn leaves and surprisingly, DMS is amongst the species found to be emitted by the soil. To our knowledge this is the first experiment to take a comprehensive look at and focus on VOC fluxes from one of the most abundant plant species in the USA and these results will help us better understand the potential influence of agricultural crops on regional air chemistry.

Graus, M.; Warneke, C.; Williams, E. J.; Lerner, B. M.; Gilman, J. B.; Li, R.; Eller, A. S.; Gray, C.; Fierer, N.; Fall, R.; Harley, P. C.; Roberts, J. M.; Yuan, B.; Qian, Y.; Westra, P.; Fryrear, C.; Collins, M.; Whitman, K.; De Gouw, J. A.

2011-12-01

29

[CO2-gas exchange of mosses following water vapour uptake].  

PubMed

The CO2-gas exchange of dry mosses which were exposed to air of high water vapour content has been followed. Some moss species behave as do lichens and aerophilic green algae: they are able to take up enough water vapour to make a rather high photosynthetic activity possible. Other species lack this ability. They need liquid water for reactivation of photosynthesis, as do poikilohydric ferns and phanerogams. In this respect too the mosses are located between the real thallophytes and the cormophytes. From this point of view they are useful objects for studying the relationships between water vapour reactivation, morphological organisation and ecological capability. PMID:24504355

Lange, O L

1969-03-01

30

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

E-print Network

Uncertainties in gas exchange parameterization during the SAGE dual-tracer experiment Murray J Ocean. Wind speed/ gas exchange parameterization is characterised by significant variability and we estimates, the comparison between gas exchange parameterizations from diverse experiments should clearly

Ho, David

31

GAS COOLED, MOLTEN SALT HEAT EXCHANGER--DESIGN STUDY  

Microsoft Academic Search

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

MacPherson

1958-01-01

32

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

NASA Astrophysics Data System (ADS)

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.

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

2014-02-01

33

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

NASA Astrophysics Data System (ADS)

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.

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

2014-07-01

34

Teaching Pulmonary Gas Exchange Physiology Using Computer Modeling  

ERIC Educational Resources Information Center

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

Kapitan, Kent S.

2008-01-01

35

Gas exchange in terrestrial environments comes at the cost of evaporative water loss from respiratory surfaces.  

E-print Network

3477 Gas exchange in terrestrial environments comes at the cost of evaporative water loss from of gas exchange, both within and among species (Lighton, 1998; Shelton and Appel, 2001; Chown, 2002). The classical pattern is that of discontinuous gas exchange, or discontinuous gas-exchange cycles (DGC; Lighton

Franz, Nico M.

36

Gas exchange and ventilation-perfusion relationships in the lung.  

PubMed

This review provides an overview of the relationship between ventilation/perfusion ratios and gas exchange in the lung, emphasising basic concepts and relating them to clinical scenarios. For each gas exchanging unit, the alveolar and effluent blood partial pressures of oxygen and carbon dioxide (PO2 and PCO2) are determined by the ratio of alveolar ventilation to blood flow (V'A/Q') for each unit. Shunt and low V'A/Q' regions are two examples of V'A/Q' mismatch and are the most frequent causes of hypoxaemia. Diffusion limitation, hypoventilation and low inspired PO2 cause hypoxaemia, even in the absence of V'A/Q' mismatch. In contrast to other causes, hypoxaemia due to shunt responds poorly to supplemental oxygen. Gas exchanging units with little or no blood flow (high V'A/Q' regions) result in alveolar dead space and increased wasted ventilation, i.e. less efficient carbon dioxide removal. Because of the respiratory drive to maintain a normal arterial PCO2, the most frequent result of wasted ventilation is increased minute ventilation and work of breathing, not hypercapnia. Calculations of alveolar-arterial oxygen tension difference, venous admixture and wasted ventilation provide quantitative estimates of the effect of V'A/Q' mismatch on gas exchange. The types of V'A/Q' mismatch causing impaired gas exchange vary characteristically with different lung diseases. PMID:25063240

Petersson, Johan; Glenny, Robb W

2014-10-01

37

A Biochemical Ocean State Estimate in the Southern1 Ocean Gas Exchange Experiment2  

E-print Network

1 A Biochemical Ocean State Estimate in the Southern1 Ocean Gas Exchange Experiment2 S. Dwivedi1-evolving distribution of mixed-layer colored dissolved organic matter13 (CDOM) during the Southern Ocean Gas Exchange during the Southern Ocean Gas Exchange38 Experiment (SO GasEx). Figure 1 shows the SO GasEx area

Haine, Thomas W. N.

38

Analytical simulation of rich hydrogen gas - Air Proton Exchange Membrane Fuel Cell system fueled by natural gas  

Microsoft Academic Search

A low temperature Proton Exchange Membrane Fuel Cell (PEMFC) system, fueled by natural gas is proposed and its performance is investigated by establishing a thermodynamic model of integral approach using energy and species mass conservation in addition to chemical and thermal equilibrium and electrochemical principals. Adiabatic cell reactions with temperature changes are assumed. Activation, ohmic and concentration potential losses are

H. A. Khater; O. E. Abdelsalam; M. Hanafy; Y. A. Abdelraouf

2008-01-01

39

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

E-print Network

AIR-WATER GAS EXCHANGE: MECHANISMS GOVERNING THE COMBINED EFFECTS OF WIND AND RAIN ON THE GAS, rain and iv #12;their effects on air-water gas and momentum exchanges. Funding for the Everglades, and for their continued support for the past two and a half decades. v #12;ABSTRACT Air-water gas exchange is an important

Luther, Douglas S.

40

Impacts of winter storms on air-sea gas exchange  

NASA Astrophysics Data System (ADS)

The objective of this study is to investigate air-sea gas exchange during winter storms, using field measurements from Ocean Station Papa in the Northeast Pacific (50N, 145W). We show that increasing gas transfer rates are coincident with increasing winds and deepening depth of bubble penetration, and that this process depends on sea state. Wave-breaking is shown to be an important factor in the gas transfer velocity during the peaks of the storms, increasing the flux rates by up to 20%. Gas transfer rates and concentrations can exhibit asymmetry, reflecting a sudden increase with the onset of a storm, and gradual recovery stages.

Zhang, Weiqing; Perrie, Will; Vagle, Svein

2006-07-01

41

Automated measurement of respiratory gas exchange by an inert gas dilution technique  

NASA Technical Reports Server (NTRS)

A respiratory gas analyzer (RGA) has been developed wherein a mass spectrometer is the sole transducer required for measurement of respiratory gas exchange. The mass spectrometer maintains all signals in absolute phase relationships, precluding the need to synchronize flow and gas composition as required in other systems. The RGA system was evaluated by comparison with the Douglas bag technique. The RGA system established the feasibility of the inert gas dilution method for measuring breath-by-breath respiratory gas exchange. This breath-by-breath analytical capability permits detailed study of transient respiratory responses to exercise.

Sawin, C. F.; Rummel, J. A.; Michel, E. L.

1974-01-01

42

Sunlight supply and gas exchange systems in microalgal bioreactor  

NASA Technical Reports Server (NTRS)

The bioreactor with sunlight supply system and gas exchange systems presented has proved feasible in ground tests and shows much promise for space use as a closed ecological life support system device. The chief conclusions concerning the specification of total system needed for a life support system for a man in a space station are the following: (1) Sunlight supply system - compactness and low electrical consumption; (2) Bioreactor system - high density and growth rate of chlorella; and (3) Gas exchange system - enough for O2 production and CO2 assimilation.

Mori, K.; Ohya, H.; Matsumoto, K.; Furune, H.

1987-01-01

43

Radiative Net Exchange Formulation Within One Dimensional Gas Enclosures With Reflective Surfaces  

E-print Network

Radiative Net Exchange Formulation Within One Dimensional Gas Enclosures With Reflective Surfaces exchanges within gas enclosures. This formulation has some common principles with the exchange factor, France October 6, 1997 1. Introduction The Net Exchange Formulation (NEF) and the Exchange Monte Carlo

Dufresne, Jean-Louis

44

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

E-print Network

The SOLAS air­sea gas exchange experiment (SAGE) 2004 Mike J. Harvey a,n , Cliff S. Law a , Murray­sea gas exchange Iron fertilisation Ocean biogeochemistry SOLAS a b s t r a c t The SOLAS air­sea gas exchange experiment (SAGE) was a multiple-objective study investigating gas- transfer processes

Ho, David

45

SURFACE ENERGY BALANCE AFFECTS GAS EXCHANGE OF THREE SHRUB SPECIES  

Microsoft Academic Search

We investigated the energy balance of vegetative and nonvegetative surfaces and gas exchange for 3 shrub species growing over each surface. During a 1 -week period, incoming short-wave radiation, surface and soil tempera- ture, and soil heat flux for turf and pine-bark mulch surfaces were gathered. Air temperature and relative humidity at 2 heights over each surface were also measured.

Thayne Montague; Roger Kjelgren; Larry Rupp

46

Gas exchange between humans and multibiological life support system  

Microsoft Academic Search

To establish a Bioregenerative Life Support System (BLSS) in lunar or Mars bases in the future, manned stimulation experiments including several kinds of creatures are needed to be conducted first. Gas exchange relation, element transfer and transformation principles, etc. between humans and the multibiological system composed of plants, animals, microalgae and so on must be investigated in order to place

Ling Tong; Dawei Hu; Hong Liu; Ming Li; Yuming Fu; Boyang Jia; Fangzhou Du; Enzhu Hu

2011-01-01

47

ORIGINAL PAPER Impacts of ocean acidification on respiratory gas exchange  

E-print Network

ORIGINAL PAPER Impacts of ocean acidification on respiratory gas exchange and acid­base balance that ocean acidification has on the CaCO3 saturation state. Shell Communicated by I.D. Hume. A. J. Esbaugh; Orr et al. 2005). Consequently, the effects of ocean acidification on these organisms have been

Grosell, Martin

48

[External respiration, pulmonary gas exchange and energy expenditure in weightlessness].  

PubMed

This paper summarizes the data on external respiration and energy expenditures of men exposed to zero-g for 185 days and to 1/6 g on the lunar surface reported by Soviet and foreign authors. The paper also discusses factors that may be responsible for a higher level of gas exchange processes at reduced g. PMID:6392736

Kas'ian, I I; Makarov, G F

1984-01-01

49

The functional ontogeny of the teleost gill: which comes first, gas or ion exchange?  

PubMed

For most of the last century, the need to obtain sufficient oxygen to meet the respiratory requirements of the tissues was viewed as the primary selective pressure driving gill development in teleost fish. Recently, however, it has been suggested that ionoregulatory pressures may actually be more important. This manuscript reviews the theoretical and empirical evidence dealing with the functional ontogeny of the gill in the context of the oxygen and ionoregulatory hypotheses. Gas and ion exchange are subject to similar geometric constraints in developing fish. Both initially are exclusively cutaneous but shift to the gill with tissue growth because of declining surface-to-volume ratios. Based on the appearance of mitochondria-rich cells (MRCs), ionoregulatory activity shifts to the gill in advance of gas exchange. In every species examined to date, MRCs appear on the developing gill in advance of secondary lamellae, the definitive gas exchange structure of the adult gill. Biochemical and histochemical studies indicate that these early branchial MRCs are actively involved in ion exchange. In some cases, the specific activity is many times greater than in the adult gill. In contrast, O2 microelectrode and hemoglobin ablation experiments suggest that the early gill contributes little O2 to the general systemic circulation. Any oxygen taken up appears to be consumed locally. Functional ablation experiments with zebrafish indicated that the larval gill became essential for ion balance well before it was needed for O2 uptake. Similar experiments with rainbow trout, however, found that the gill became essential in terms of gas and ion exchange at about the same time. On balance, the evidence appears to favour the ionoregulatory hypothesis but the oxygen hypothesis cannot be absolutely rejected without more information. Some of the major deficiencies in our knowledge regarding the transition from cutaneous to branchial gas and ion exchange are highlighted and potential implications of the ionoregulatory hypothesis are discussed. PMID:17451987

Rombough, Peter

2007-12-01

50

BIODEGRADATION AND GAS-EXCHANGE OF GASEOUS ALKANES IN MODEL ESTUARINE ECOSYSTEMS  

EPA Science Inventory

Gas exchange-biodegradation experiments conducted in model estuarine ecosystems indicate that the ease of degradation of gaseious normal alkanes increases with chain length. The behavior of gaseous perhalogenated alkanes can be explained by gas exchange alone with no degradation....

51

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

E-print Network

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

Paris-Sud XI, Université de

52

BOREAS TE-4 Gas Exchange Data from Boreal Tree Species  

NASA Technical Reports Server (NTRS)

The BOREAS TE-4 team collected steady-state gas exchange and reflectance data from several species in the BOREAS SSA during 1994 and in the NSA during 1996. Measurements of light, CO2, temperature, and humidity response curves were made by the BOREAS TE-4 team during the summers of 1994 and 1996 using intact attached leaves of boreal forest species located in the BOREAS SSA and NSA. These measurements were conducted to calibrate models used to predict photosynthesis, stomatal conductance, and leaf respiration. The 1994 and 1996 data can be used to construct plots of response functions or for parameterizing models. Parameter values are suitable for application in SiB2 (Sellers et al., 1996) or the leaf model of Collatz et al. (1991), and programs can be obtained from the investigators. 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).

Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Collatz, G. James; Berry, Joseph A.; Gamon, John; Fredeen, Art; Fu, Wei

2000-01-01

53

Using noble gases to constrain gas exchange and biological productivity  

NASA Astrophysics Data System (ADS)

The five noble gases (He, Ne, Ar, Kr, and Xe) are biologically and chemically inert, making them useful oceanographic tracers. Moreover, the noble gases have a wide range of solubilities and diffusivities, and thus respond differently to physical forcing. We present here a one year time-series of the five noble gases and the isotope 3He, measured in the upper 400 m of the Sargasso Sea with monthly resolution at the Bermuda Atlantic Time-series Site (BATS). Two profiles of the noble gases in the entire water column down to 4200 m are presented as well. We combine the upper ocean noble gas time-series data, nutrient, oxygen, and hydrographic data from BATS, and a one-dimensional vertical mixed layer model (a modified Price-Weller-Pinkel model) in order to quantify air-sea gas exchange processes. We use inverse modeling to quantify the magnitude of both diffusive gas exchange and air injection processes. The estimates obtained constrain the seasonal time-scale gas exchange rate to a precision of 6% and the bubble injection fluxes to 15%, valid for wind speeds up to 15 m/sec. The overall results suggest that the Wanninkhof quadratic formulation needs to be adjusted downward by approximately 20%. Additionally, 3He is used as a tracer of upwelling nutrients in order to constrain new production. Nutrients in the upper thermocline are well correlated with 3He, and thus 3He and nitrate measurements, combined with estimates of gas exchange, are used to quantify the input of new nutrients into the mixed layer. 3He measurement are also used in conjunction with tritium and oxygen data in order to calculate apparent oxygen utilization rates (AOUR) and thus to estimate export production.

Stanley, R.; Jenkins, W. J.; Lott, D. E.; Doney, S. C.

2007-12-01

54

Respiratory gas exchange using a triaxial alveolar gas diagram.  

PubMed Central

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

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

1993-01-01

55

An active heat and moisture exchanger.  

PubMed

We have carried out a laboratory evaluation of an active heat and moisture exchanging filter (aHMEF). The device consists of a conventional heat and moisture exchanging filter (HMEF) with an additional heating element and water supply. It was compared with a standard HMEF using a model lung. The aHMEF with the heating element alone, reduced 2-hourly water loss compared with the HMEF (P < 0.001); with both the heating element and additional water, this was reduced further (P < 0.001). The mean catheter mount temperature with the HMEF and heater was 32.7 (SD 1.8) degrees C and with the complete aHMEF was 34.6 (1.6) degrees C. The maximum temperature with the heating element in use was 37.7 degrees C. We conclude that the aHMEF provided effective, controllable and convenient humidification of inspired gases. PMID:1467111

Kapadia, F; Shelly, M P; Anthony, J M; Park, G R

1992-12-01

56

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

E-print Network

Evaluation of Fiber Bundle Rotation for Enhancing Gas Exchange in a Respiratory Assist Catheter and enhanced gas exchange in intravenous respiratory assist catheters. Using a simple test apparatus of a rotating densely packed bundle of hollow fiber membranes, water and blood gas exchange levels were

Federspiel, William J.

57

On Factors Controlling AirWater Gas Exchange in a Large Tidal River  

E-print Network

On Factors Controlling Air­Water Gas Exchange in a Large Tidal River David T. Ho & Peter Schlosser and Estuarine Research Federation 2011 Abstract Air­water gas exchange is an important process in aquatic for determining gas exchange over a range of temporal and spatial scales in the ocean and these measurements have

Ho, David

58

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

E-print Network

On morphometric measurement of oxygen diffusing capacity in middle ear gas exchange Stephen Chad.00203.2004.--An accurate mathematical model of trans- mucosal gas exchange is prerequisite constants for all extant conditions as input parame- ters. However, studies on pulmonary gas exchange have

Federspiel, William J.

59

PHOTOSYNTHETICA 41 (2): 221-226, 2003 Diurnal gas exchange and superior resources use efficiency  

E-print Network

PHOTOSYNTHETICA 41 (2): 221-226, 2003 221 Diurnal gas exchange and superior resources use of L. chinensis were depressed at noon and had two peaks in their diurnal courses. Gas exchange traits. The diurnal changes of gas exchange of C3 and C4 species has also been intro- duced (Read et al. 1997, Matos

60

Plant Gas Exchange in Urban Landscapes L. Brooke McDowell and Chris A. Martin  

E-print Network

Plant Gas Exchange in Urban Landscapes L. Brooke McDowell and Chris A. Martin Department of Plant-term monitoring of gas exchange, irrigation practices, and microclimate in urban landscape plants was initiated on preliminary seasonal measurements of diel gas exchange patterns (McDowell and Martin, 1998). Measurements were

Hall, Sharon J.

61

Seasonal gas exchange characteristics of Schinus terebinthifolius in a native and disturbed upland community in  

E-print Network

Seasonal gas exchange characteristics of Schinus terebinthifolius in a native and disturbed upland of the community. The purpose of this study was to determine if gas exchange patterns of Schinus were significantly gas exchange, leaf nitrogen and carbon stable isotope contents were contrasted with four native

Ling, Sharon Ewe Mei

62

Original article Effect of fungal infection on leaf gas-exchange  

E-print Network

Original article Effect of fungal infection on leaf gas-exchange and chlorophyll fluorescence after excision of the shoot. Leaf gas-exchange and chlorophyll a fluorescence were recorded on plants in resprouts, which showed higher gas- exchange rates. Quercus ilex / Cryphonectria parasitica /Phomopsis spp

Boyer, Edmond

63

Discontinuous gas exchange cycles (DGCs) are widespread in terrestrial arthropods. First described in lepidopteran pupae,  

E-print Network

Discontinuous gas exchange cycles (DGCs) are widespread in terrestrial arthropods. First described are closed and gas exchange is negligible during the closed (C) phase. During this time, O2 is removed from of changing metabolic rates is a relatively little-studied aspect of the discontinuous gas exchange cycles

Saltzman, Wendy

64

PHOTOSYNTHETICA 42 (1): 1-6, 2004 Gas exchange and chlorophyll fluorescence response to simulated rainfall  

E-print Network

PHOTOSYNTHETICA 42 (1): 1-6, 2004 Gas exchange and chlorophyll fluorescence response to simulated of Sciences, 20 Nanxincun, 100093, Beijing, P.R. China Abstract The response of gas exchange and chlorophyll/Ci appeared 3 d after watering while gs and leaf were recovered 1 d after treatment. Gas exchange characters

65

Environmental turbulent mixing controls on air-water gas exchange in marine and aquatic systems  

E-print Network

Environmental turbulent mixing controls on air-water gas exchange in marine and aquatic systems is not well known. Widely used models of gas exchange rates are based on empirical relationships linked turbulence that predicts gas exchange for a range of aquatic and marine processes. Findings indicate

Ho, David

66

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

E-print Network

Universal model for water costs of gas exchange by animals and plants H. Arthur Woods1 and Jennifer 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

67

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

E-print Network

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. INTRODUCTION The gas-exchange system is a primary factor in the performance of a combustion engine. Designing

Marsland, Stephen

68

H/D Exchange Levels of Shape-Resolved Cytochrome c Conformers in the Gas Phase  

E-print Network

H/D Exchange Levels of Shape-Resolved Cytochrome c Conformers in the Gas Phase Stephen J. Valentine) in the gas phase are examined by simultaneous ion-mobility and hydrogen-deuterium exchange measurements with the idea that compact structures protect some hydrogens in the gas phase. Many sites that rapidly exchange

Clemmer, David E.

69

Effects of stomatal delays on the economics of leaf gas exchange under intermittent light regimes  

E-print Network

Effects of stomatal delays on the economics of leaf gas exchange under intermittent light regimes to highly intermittent light availability and their leaf gas exchanges are mediated by delayed responses fluctuations was assembled. To interpret these experimental observations, a leaf gas exchange model

Katul, Gabriel

70

Reactive oxygen species production and discontinuous gas exchange in insects  

PubMed Central

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

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

2012-01-01

71

Gas exchange on Mono Lake and Crowley Lake, California  

NASA Technical Reports Server (NTRS)

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.

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

1987-01-01

72

A Continuum Model for Metabolic Gas Exchange in Pear Fruit  

PubMed Central

Exchange of O2 and CO2 of plants with their environment is essential for metabolic processes such as photosynthesis and respiration. In some fruits such as pears, which are typically stored under a controlled atmosphere with reduced O2 and increased CO2 levels to extend their commercial storage life, anoxia may occur, eventually leading to physiological disorders. In this manuscript we have developed a mathematical model to predict the internal gas concentrations, including permeation, diffusion, and respiration and fermentation kinetics. Pear fruit has been selected as a case study. The model has been used to perform in silico experiments to evaluate the effect of, for example, fruit size or ambient gas concentration on internal O2 and CO2 levels. The model incorporates the actual shape of the fruit and was solved using fluid dynamics software. Environmental conditions such as temperature and gas composition have a large effect on the internal distribution of oxygen and carbon dioxide in fruit. Also, the fruit size has a considerable effect on local metabolic gas concentrations; hence, depending on the size, local anaerobic conditions may result, which eventually may lead to physiological disorders. The model developed in this manuscript is to our knowledge the most comprehensive model to date to simulate gas exchange in plant tissue. It can be used to evaluate the effect of environmental stresses on fruit via in silico experiments and may lead to commercial applications involving long-term storage of fruit under controlled atmospheres. PMID:18369422

Ho, Q. Tri; Verboven, Pieter; Verlinden, Bert E.; Lammertyn, Jeroen; Vandewalle, Stefan; Nicola, Bart M.

2008-01-01

73

On the parameters influencing air-water gas exchange  

Microsoft Academic Search

Detailed gas exchange measurements from two circular and one linear wind\\/wave tunnels are presented. Heat, He, CH4, CO2, Kr, and Xe have been used as tracers. The experiments show the central importance of waves for the water-side transfer process. With the onset of waves the Schmidt number dependence of the transfer velocity k changes from k ~ Sc-2\\/3 to k

Bernd Jhne; Karl Otto Mnnich; Rainer Bsinger Alfred Dutzi; Werner Huber; Peter Libner

1987-01-01

74

Carbon dioxide absorption and gas exchange during pelvic laparoscopy  

Microsoft Academic Search

Twelve ASA physical status I-II patients undergoing pelvic laparoscopy for infertility were enrolled in a study to quantify\\u000a the effects of CO2 insufflation and the Trendelenburg position on CO2 elimination and pulmonary gas exchange, and to determine the minute ventilation required to maintain normocapnia during CO2 insufflation. Measurements of O2 uptake (VO2), CO2 elimination (VCO2), minute ventilation (Ve), FlO2, and

P. L. Tan; T. L. Lee; W. A. Tweed

1992-01-01

75

The use of stable isotopes to study ecosystem gas exchange  

Microsoft Academic Search

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

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

2000-01-01

76

A stability dependent theory for air-sea gas exchange  

Microsoft Academic Search

The author expands on a recently presented local-scale model for air-sea gas exchange which includes an explicit treatment of oceanic whitecaps. The author introduces thermal stability of the air-sea interface as a function of temperature and humidity gradients. This model is then extended to a global scale, and compared with other models by introducing it into a global climate model

David J. Erickson

1993-01-01

77

Gas Diodes for Thermoacoustic Self-circulating Heat Exchangers  

NASA Astrophysics Data System (ADS)

An asymmetrical constriction in a pipe functions as an imperfect gas diode for acoustic oscillations in the gas in the pipe. One or more gas diodes in a resonant loop of pipe create substantial steady flow, which can carry substantial heat between a remote heat exchanger and a thermoacoustic or Stirling engine or refrigerator; the flow is driven directly by the oscillations in the engine or refrigerator itself. This invention gives Stirling and thermoacoustic devices unprecedented flexibility, and may lead to Stirling engines of unprecedented power. We have built two of these resonant self-circulating heat exchangers, one as a fundamental test bed and the other as a demonstration of practical levels of heat transfer. Measurements of flow and heat transfer are in factor-of-two agreement with either of two simple calculation methods. One calculation method treats the oscillating and steady flows as independent and simply superimposed, except in the gas diodes. The other method accounts for the interaction between the oscillating and steady flow with the quasi-steady approximation. The mutual influence of superimposed turbulent oscillating and steady flows is a theoretical challenge.

Swift, Greg; Backhaus, Scott

2006-05-01

78

Impact of an artificial surfactant release on airsea gas fluxes during Deep Ocean Gas Exchange Experiment II  

E-print Network

Impact of an artificial surfactant release on airsea gas fluxes during Deep Ocean Gas Exchange released surfactant (oleyl alcohol) on gas transfer velocities (kw) in the open ocean. Exchange rates were to be influenced by the surfactant. These exhibited suppression from 5% to 55% at intermediate wind speeds (U10

Ho, David

79

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

Microsoft Academic Search

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

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

2007-01-01

80

RMP Colloquia Spin-exchange optical pumping of noble-gas nuclei  

E-print Network

RMP Colloquia Spin-exchange optical pumping of noble-gas nuclei Thad G. Walker Department He gas that was polar- ized by spin-exchange optical pumping, is shown in Fig. 1. Laser technology, Princeton University, Princeton, New Jersey 08544 Spin-exchange optical pumping of mixtures of alkali

Walker, Thad G.

81

PREDICTION OF TOTAL DISSOLVED GAS EXCHANGE AT HYDROPOWER DAMS  

SciTech Connect

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.

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

82

Determination of Gas Exchange Rate Constants for a Small Stream on Walker Branch Watershed, Tennessee  

Microsoft Academic Search

The steady state tracer gas method was used to determine gas exchange rate constants (k) for a small stream (annual average flow <=1 m3\\/min) draining the West Fork of Walker Branch watershed in eastern Tennessee. Chloride was used as a conservative tracer to account for dilution by lateral inflow, and propane and ethane were used as volatile tracers. Gas exchange

David P. Genereux; Harold F. Hemond

1992-01-01

83

Determination of gas exchange rate constants for a small stream on Walker Branch Watershed, Tennessee  

Microsoft Academic Search

The steady state tracer gas method was used to determine gas exchange rate constants (k) for a small stream (annual average flow ?1 m3\\/min) draining the West Fork of Walker Branch watershed in eastern Tennessee. Chloride was used as a conservative tracer to account for dilution by lateral inflow, and propane and ethane were used as volatile tracers. Gas exchange

David P. Genereux; Harold F. Hemond

1992-01-01

84

Teaching pulmonary gas exchange physiology using computer modeling  

NSDL National Science Digital Library

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.

Kent S Kapitan (Southern Ilinois University Pulmonary Medicine)

2007-11-19

85

The effects of temperature on the gas exchange cycle in Agathemera crassa.  

PubMed

Insects exhibit three patterns of gas exchange: continuous (CoGE), cyclic (CGE) and discontinuous (DGE). In this work, we present the first record of a DGE in Phasmatodea and its transition to CGE and to CoGE through a thermal gradient. The rate of CO2 production (VCO2) at 10, 20 and 30C was examined in adults of Agathemera crassa, a high-Andean phasmid of central Chile. Carbon dioxide release was recorded during 24h with L:D cycle of 12:12h in order to record both rest and activity periods. At rest, A. crassa showed three patterns of gas exchange, highlighting the use of DGE preferably at 10C. As the temperature increased, the CoGE pattern was more frequent being the only pattern observed in all individuals at 30C. During activity, patterns changed to CoGE with a significant increase in VCO2. Our results support the idea that gas exchange patterns in insects are not distinct but correspond to a continuum of responses addressed by metabolic demand and where DGE can be expressed only under an absolute state of rest. Our results support the idea that the presence of the DGE may be underestimated in other insect taxa because they may have been measured under conditions where this pattern not necessarily can be expressed. PMID:25624164

Thienel, Mariana; Canals, Mauricio; Bozinovic, Francisco; Veloso, Claudio

2015-05-01

86

Determination of low activities released by a decommissioned fuel fabrication plant through natural air exchange  

SciTech Connect

In this paper a method to determine the release of low activities through natural air exchange from a decommissioned fuel fabrication plant is described. The method has been applied to the buildings of the NUKEM-A plant and was important in obtaining governmental authorization for the plant decommissioning. The air exchange rate in the NUKEM-A plant was measured by using a tracer gas method. For that purpose, N{sub 2}O as inert gas was injected into representative rooms, and the decrease of concentration caused by exfiltration processes was measured by an infrared gas analyzer as a function of time. The knowledge of this decay curve allows the calculation of low activities, which may be released into the environment by the natural air exchange.

Sohnius, B.; Anton, R.; Wehner, E. (Nukem GmbH, Hanau (Germany)); Heidt, F.D.; Rabenstein, R. (Siegen Univ. (Gesamthochschule) (Germany))

1992-08-01

87

Gas-Surface Energy Exchange in Collisions of Helium Atoms with Aligned Single-Walled Carbon  

E-print Network

1 Gas-Surface Energy Exchange in Collisions of Helium Atoms with Aligned Single-Walled Carbon #12;2 ABSTRACT Since gas flows in micro/nano devices are dominated by the interaction of gas molecules accommodation of gas molecules on surfaces. The scattering of gas molecules on quartz surfaces covered with VA

Maruyama, Shigeo

88

Observations of O2:CO2 exchange ratios during ecosystem gas W. A. Brand, M. Heimann, and J. Lloyd2  

E-print Network

Observations of O2:CO2 exchange ratios during ecosystem gas exchange U. Seibt,1 W. A. Brand, M. Wingate (2004), Observations of O2:CO2 exchange ratios during ecosystem gas exchange, Global Biogeochem September 2004; accepted 21 September 2004; published 2 December 2004. [1] We determined O2:CO2 exchange

89

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

NASA Technical Reports Server (NTRS)

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).

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

2000-01-01

90

Leaf Water Relations and Maintenance of Gas Exchange in Coffee Cultivars Grown in Drying Soil 1  

PubMed Central

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 (?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 ?L at which turgor loss occurred. Adjustments in ?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 ?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

Meinzer, Frederick C.; Grantz, David A.; Goldstein, Guillermo; Saliendra, Nicanor Z.

1990-01-01

91

Gas exchange pattern transitions in the workers of the harvester termite.  

PubMed

The evolutionary genesis and the current adaptive significance of the use of the discontinuous gas exchange cycle (DGC) for respiration by insects is the subject of intense debate. Years of research have resulted in several leading hypotheses, one of which is the emergent-property hypothesis. This hypothesis states that DGC is an emergent property or consequence of interactions between the O2 and CO2 set points that regulate spiracular function, i.e. opening and closing. Workers of the harvester termite, Hodotermes mossambicus were selected as a model to test this hypothesis. The respiratory patterns of major workers, investigated using flow-through respirometry, were obtained at 100% relative humidity (RH) under varying temperature to evaluate the assumptions of the emergent-property hypothesis. Metabolic rate, measured as VCO2 increased significantly after 15C. As VCO2 increased in response to increasing temperature and activity, the gas exchange pattern displayed by workers transitioned to a continuous gas exchange. A true DGC, defined as showing all three phases and a coefficient of variation value close to 2, was not expressed under the experimental conditions. The conclusion drawn from this study of termite workers is that changes in respiratory patterns are most likely an emergent property of the insects' nervous and respiratory system. PMID:25770978

Inder, Isabelle M; Duncan, Frances D

2015-04-01

92

Factors controlling sulfur gas exchange in Sphagnum-dominated wetlands  

NASA Technical Reports Server (NTRS)

Atmosphere-peatland exchange of reduced sulfur gases was determined seasonally in fen in NH, and in an artificially-acidified fen at the Experimental Lakes Area (ELA) in Canada. Dimethyl sulfide (DMS) dominated gas fluxes at rates as high as 400 nmol/m(sup -2)hr(sup -1). DMS fluxes measured using enclosures were much higher than those calculated using a stagnant-film model, suggesting that Sphagnum regulated efflux. Temperature controlled diel and seasonal variability in DMS emissions. Use of differing enclosure techniques indicated that vegetated peatlands consume atmospheric carbonyl sulfide. Sulfate amendments caused DMS and methane thiol concentrations in near-surface pore waters to increase rapidly, but fluxes of these gases to the atmosphere were not affected. However, emission data from sites experiencing large differences in rates of sulfate deposition from the atmosphere suggested that chronic elevated sulfate inputs enhance DMS emissions from northern wetlands.

Demello, William Zamboni; Hines, Mark E.; Bayley, Suzanne E.

1992-01-01

93

The relationship between near-surface turbulence and gas transfer velocity in freshwater systems and its implications for floating chamber measurements of gas exchange  

E-print Network

and its implications for floating chamber measurements of gas exchange Dominic Vachon,a,* Yves T. Prairie performed a series of gas exchange measurements in 12 diverse aquatic systems to develop the direct of the associated gas transfer velocity even at short temporal and spatial scales. Gas exchange at the air

Berkowitz, Alan R.

94

Analysis and modeling of gas exchange processes in Scaevola aemula Soo-Hyung Kim a,*, Paul R. Fisher b  

E-print Network

Analysis and modeling of gas exchange processes in Scaevola aemula Soo-Hyung Kim a,*, Paul R crop cultivated as a bedding plant or for hanging baskets. We characterized gas exchange properties but significantly reduced at 15 8C. These gas exchange results were used to test the extendibility of a coupled gas

Lieth, J. Heinrich

95

Human Regional Pulmonary Gas Exchange with Xenon Polarization Transfer (XTC)  

NASA Astrophysics Data System (ADS)

Xenon Transfer Contrast (XTC) is an existing imaging method (Ruppert et al, Magn Reson Med, 51:676-687, 2004) that measures the fraction F of ^129Xe magnetization that diffuses from alveolar gas spaces to septal parenchymal tissue in lungs in a specified exchange time. As previously implemented, XTC is a 2-breath method and has been demonstrated in anesthetized animals. To use XTC in humans and to avoid issues associated with obtaining identical gas volumes on subsequent breath-hold experiments as well as precise image registration in post-processing, a single breath XTC method was developed that acquires three consecutive gradient echo images in an 8s acquisition. We report here initial measurements of the mean and variance of F for 5 normal healthy subjects as well as 7 asymptomatic smokers. The experiments were performed at two lung volumes (45 and 65% of TLC). We found that both the mean and variance of F increased with smoking history. In comparison, standard pulmonary function tests such as DLCO FEV1 showed no correlation with smoking history.

Muradian, Iga; Butler, James; Hrovat, Mirko; Topulos, George; Hersman, Elizabeth; Ruset, Iulian; Covrig, Silviu; Frederick, Eric; Ketel, Stephen; Hersman, F. W.; Patz, Samuel

2007-03-01

96

Respiratory gas exchange of high altitude adapted chick embryos  

NASA Technical Reports Server (NTRS)

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.

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

1974-01-01

97

Pulmonary and Cutaneous O[subscript 2] Gas Exchange: A Student Laboratory Exercise in the Frog  

ERIC Educational Resources Information Center

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 O[subscript 2] uptake and CO[subscript 2] excretion between respiratory organs with different efficiencies. For example, due to

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

2013-01-01

98

Air-water Gas Exchange Rates on a Large Impounded River Measured Using Floating Domes (Poster)  

EPA Science Inventory

Mass balance models of dissolved gases in rivers typically serve as the basis for whole-system estimates of greenhouse gas emission rates. An important component of these models is the exchange of dissolved gases between air and water. Controls on gas exchange rates (K) have be...

99

The combined effect of rain and wind on airwater gas exchange: A feasibility study  

E-print Network

The combined effect of rain and wind on air­water gas exchange: A feasibility study David T. Ho a to examine the combined effects of rain and wind on air­water 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

Ho, David

100

In situ evaluation of air-sea gas exchange parameterizations using novel conservative and volatile tracers  

Microsoft Academic Search

Measurements of air-sea gas exchange rates are reported from two deliberate tracer experiments in the southern North Sea during February 1992 and 1993. A conservative tracer, spores of the bacterium Bacillus globigii var. Niger, was used for the first time in an in situ air-sea gas exchange experiment. This nonvolatile tracer is used to correct for dispersive dilution of the

Philip D. Nightingale; Gill Malin; Cliff S. Law; Andrew J. Watson; Peter S. Liss; Malcolm I. Liddicoat; Jacqueline Boutin; Robert C. Upstill-Goddard

2000-01-01

101

Exchange-driven instability and spin polarization of the two-dimensional electron gas  

E-print Network

Exchange-driven instability and spin polarization of the two-dimensional electron gas P Giudici gas formed in a GaAs single quantum well undergoes a first-order phase transition, as the first-functional calculations with exact exchange potential for a 2D electron system reveal that this transition is driven

Nabben, Reinhard

102

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

E-print Network

Circadian rhythms constrain leaf and canopy gas exchange in an Amazonian forest Christopher E circadian rhythms constrain the rates of leaf and canopy gas exchange in an Amazonian forest over a day of the day. We attribute these cycles to circadian rhythms that are analogous to ones that have been reported

Goulden, Michael L.

103

JOINT ACTION OF O3 AND SO2 IN MODIFYING PLANT GAS EXCHANGE  

EPA Science Inventory

The joint action of O3 and SO2 stress on plants was investigated. Gas exchange measurements of O3, SO2, and H2O vapor were made for garden pea. Plants were grown under controlled environments; O3, SO2, H2O vapor fluxes were evaluated with a whole-plant gas exchange chamber using ...

104

Active galaxies and cluster gas.  

PubMed

Two lines of evidence indicate that active galaxies, principally radio galaxies, have heated the diffuse hot gas in clusters. The first is the general need for additional heating to explain the steepness of the X-ray luminosity-temperature relation in clusters, the second is to solve the cooling-flow problem in cluster cores. The inner core of many clusters is radiating energy as X-rays on a time-scale much shorter than its likely age. Although the temperature in this region drops by a factor of about three from that of the surrounding gas, little evidence is found for gas much cooler than that. Some form of heating appears to be taking place, probably by energy transported outward from the central accreting black hole or radio source. How that energy heats the gas depends on poorly understood transport properties (conductivity and viscosity) of the intracluster medium. Viscous heating is discussed as a possibility. Such heating processes have consequences for the truncation of the luminosity function of massive galaxies. PMID:15681290

Fabian, A C

2005-03-15

105

Market Power, Innovative Activity and Exchange Rate Pass-Through  

Microsoft Academic Search

This paper considers an international oligopoly where firms simultaneously choose both the amount of output produced and the proportion of R&D investment to output. The model captures the links between the exchange rate, market power, innovative activity and price, which are important for the determination of the optimal degree of exchange rate pass-through. It is found that in the long

Sophocles N. Brissimis; Theodora S. Kosma

2005-01-01

106

Tritium labelled nucleotides: Heterogeneous metal catalyzed exchange labelling of ATP with tritium gas  

SciTech Connect

Adenosine 5{prime} triphosphate (ATP) in aqueous solution has been labeled by exchange with tritium gas in the presence of palladium oxide catalyst. Comparison with our experiments using Pd/BaSO{sub 4} as the catalyst shows that we have obtained product with higher specific activity and improved chemical purity. {sup 3}H NMR spectroscopy of the tritiated ATP shows labelling in both the C-8 and C-2 positions, and the integral ratio of these positions was found to vary from 3:1 to 1:1 under different reaction conditions. 5 refs., 1 fig., 2 tabs.

Jaiswal, D.K. (Defence Research and Development Establishment, Gwalior (India)); Morimoto, H.; Williams, P.G.; Wemmer, D.E. (Lawrence Berkeley Lab., CA (United States))

1991-09-01

107

Risk factors for transient dysfunction of gas exchange after cardiac surgery  

PubMed Central

Objective A retrospective cohort study was preformed aiming to verify the presence of transient dysfunction of gas exchange in the postoperative period of cardiac surgery and determine if this disorder is linked to cardiorespiratory events. Methods We included 942 consecutive patients undergoing cardiac surgery and cardiac procedures who were referred to the Intensive Care Unit between June 2007 and November 2011. Results Fifteen patients had acute respiratory distress syndrome (2%), 199 (27.75%) had mild transient dysfunction of gas exchange, 402 (56.1%) had moderate transient dysfunction of gas exchange, and 39 (5.4%) had severe transient dysfunction of gas exchange. Hypertension and cardiogenic shock were associated with the emergence of moderate transient dysfunction of gas exchange postoperatively (P=0.02 and P=0.019, respectively) and were risk factors for this dysfunction (P=0.0023 and P=0.0017, respectively). Diabetes mellitus was also a risk factor for transient dysfunction of gas exchange (P=0.03). Pneumonia was present in 8.9% of cases and correlated with the presence of moderate transient dysfunction of gas exchange (P=0.001). Severe transient dysfunction of gas exchange was associated with patients who had renal replacement therapy (P=0.0005), hemotherapy (P=0.0001), enteral nutrition (P=0.0012), or cardiac arrhythmia (P=0.0451). Conclusion Preoperative hypertension and cardiogenic shock were associated with the occurrence of postoperative transient dysfunction of gas exchange. The preoperative risk factors included hypertension, cardiogenic shock, and diabetes. Postoperatively, pneumonia, ventilator-associated pneumonia, renal replacement therapy, hemotherapy, and cardiac arrhythmia were associated with the appearance of some degree of transient dysfunction of gas exchange, which was a risk factor for reintubation, pneumonia, ventilator-associated pneumonia, and renal replacement therapy in the postoperative period of cardiac surgery and cardiac procedures. PMID:25859864

Rodrigues, Cristiane Delgado Alves; Moreira, Marcos Mello; Lima, Nbia Maria Freire Vieira; de Figueirdo, Luciana Castilho; Falco, Antnio Luis Eiras; Petrucci, Orlando; Dragosavac, Desanka

2015-01-01

108

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

PubMed Central

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 taxainsects, birds, bird eggs, mammals, and plantsspanning 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

Woods, H. Arthur; Smith, Jennifer N.

2010-01-01

109

Surfactant control of air-sea gas exchange across contrasting biogeochemical regimes  

NASA Astrophysics Data System (ADS)

Air-sea gas exchange is important to the global partitioning of CO2.Exchange fluxes are products of an air-sea gas concentration difference, ?C, and a gas transfer velocity, kw. The latter is controlled by the rate of turbulent diffusion at the air-sea interface but it cannot be directly measured and has a high uncertainty that is now considered one of the greatest challenges to quantifying net global air-sea CO2 exchange ...(Takahashi et al., 2009). One important control on kw is exerted by sea surface surfactants that arise both naturally from biological processes and through anthropogenic activity. They influence gas exchange in two fundamental ways: as a monolayer physical barrier and through modifying sea surface hydrodynamics and hence turbulent energy transfer. These effects have been demonstrated in the laboratory with artificial surfactants ...(Bock et al., 1999; Goldman et al., 1988) and through purposeful surfactant releases in coastal waters .(.).........().(Brockmann et al., 1982) and in the open ocean (Salter et al., 2011). Suppression of kwin these field experiments was ~5-55%. While changes in both total surfactant concentration and the composition of the natural surfactant pool might be expected to impact kw, the required in-situ studies are lacking. New data collected from the coastal North Sea in 2012-2013 shows significant spatio-temporal variability in the surfactant activity of organic matter within the sea surface microlayer that ranges from 0.07-0.94 mg/L T-X-100 (AC voltammetry). The surfactant activities show a strong winter/summer seasonal bias and general decrease in concentration with increasing distance from the coastline possibly associated with changing terrestrial vs. phytoplankton sources. Gas exchange experiments of this seawater using a novel laboratory tank and gas tracers (CH4 and SF6) demonstrate a 12-45% reduction in kw compared to surfactant-free water. Seasonally there is higher gas exchange suppression in the summer months likely from primary production and spatially there is less suppression of air-sea gas exchange with increasing distance from the shoreline, which is likely due to riverine inputs. REFERENCES Bock, E. J., Hara, T., Frew, N. M., and McGillis, W. R., 1999. Relationship between air-sea gas transfer and short wind waves. Journal of Geophysical Research-Oceans 104, 25821-25831. Brockmann, U. H., Huhnerfuss, H., Kattner, G., Broecker, H. C., and Hentzschel, G., 1982. Artificial surface-films in the sea area near sylt. Limnology and Oceanography 27, 1050-1058. Goldman, J. C., Dennett, M. R., and Frew, N. M., 1988. Surfactant effects on air sea gas-exchange under turbulent conditions. Deep-Sea Research Part a-Oceanographic Research Papers 35, 1953-1970. McKenna, S. P. and McGillis, W. R., 2004. The role of free-surface turbulence and surfactants in air-water gas transfer. International Journal of Heat and Mass Transfer 47, 539-553. Salter, M. E., R. C. Upstill-Goddard, P. D. Nightingale, S. D. Archer, B. Blomquist, D. T. Ho, B. Huebert, P. Schlosser, and M. Yang (2011), Impact of an artificial surfactant release on air-sea gas fluxes during Deep Ocean Gas Exchange Experiment II, J. Geophys. Res., 116, C11016, doi:10.1029/2011JC00702 Takahashi, T., Sutherland, S. C., Wanninkhof, R., Sweeney, C., Feely, R. A., Chipman, D. W., Hales, B., Friederich, G., Chavez, F., Sabine, C., Watson, A., Bakker, D. C. E., Schuster, U., Metzl, N., Yoshikawa-Inoue, H., Ishii, M., Midorikawa, T., Nojiri, Y., Krtzinger, A., Steinhoff, T., Hoppema, M., Olafsson, J., Arnarson, T. S., Tilbrook, B., Johannessen, T., Olsen, A., Bellerby, R., Wong, C. S., Delille, B., Bates, N. R., and de Baar, H. J. W., 2009. Climatological mean and decadal change in surface ocean pCO 2, and net sea-air CO 2 flux over the global oceans. Deep-Sea Research Part II: Topical Studies in Oceanography 56, 554-577.

Pereira, Ryan; Schneider-Zapp, Klaus; Upstill-Goddard, Robert

2014-05-01

110

INTERNATIONAL INFORMATION EXCHANGE ACTIVITIES ON DIOXINS  

EPA Science Inventory

A project promoting the exchange of information on polychlorinated dibenzo-p-dioxins and related chemicals has been initiated on an international basis. The project is being conducted under the auspices of the Committee on the Challenges of Modern Society of the North Atlantic Tr...

111

Allosteric Activation of Sodium-Calcium Exchange Activity by Calcium: Persistence at Low Calcium Concentrations  

Microsoft Academic Search

The activity of the cardiac Na ? \\/Ca 2 ? exchanger is stimulated allosterically by Ca 2 ? , but estimates of the half-maximal activating concentration have varied over a wide range. In Chinese hamster ovary cells express- ing the cardiac Na ? \\/Ca 2 ? exchanger, the time course of exchange-mediated Ca 2 ? influx showed a pronounced lag

John P. Reeves; Madalina Condrescu

2003-01-01

112

POSTING: Technician 5 Heat and Greenhouse gas Exchange The Centre for Earth Observation Science (CEOS) within the Faculty of Environment,  

E-print Network

POSTING: Technician 5 ­ Heat and Greenhouse gas Exchange technician in support of multidisciplinary research on heat and greenhouse gas exchange within marine and estuarine environments of the Arctic and sub

113

Gas exchange characteristics of Pinus edulis and Juniperus monosperma  

SciTech Connect

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.

Barnes, F.J.

1987-07-01

114

Effects of Ozone on Gas Exchange in Invasive Forest Plants.  

NASA Astrophysics Data System (ADS)

Evaluations of invasive plant biology have failed to investigate the relationship between leaf structure and effects of ozone among closely related native and non-native plants. When exposed to toxic pollutants plants with lower stomatal density and lower stomatal conductance might experience reduced exposure and consequently be more competitive. To test for systematic differences between invasive and native species, experiments assessed the stomatal density and stomatal conductance of nine non-native invasive species and thirteen native species. Field sites, used for forest surveys, centered on three urban areas including sites with differing ozone levels (low 0-60 ppb, medium 80-99 ppb, high 111-125+ ppb). Three sites were selected within each of the three urban areas, and surveys were taken at each of the nine sites determining the native and non-native plant composition. The low level sites had greater densities of native plants than the high ozone level sites. Leaf impressions revealed a significantly higher (t = 14.13, p < 0.0001) stomatal density for the natives, and a LI-COR 1600 showed significantly higher (Fndf,ddf = 12.88, p = 0.0004) stomatal conductance for native plants. Dissimilar gas-exchange capacities are likely to be linked to the observed differences in plant composition among study sites. The importance of addressing air and biotic pollution grows every year as human health, agriculture, and ecosystem function are negatively affected in new areas.

Elton, E. E.

2006-12-01

115

Selection of the air heat exchanger operating in a gas turbine air bottoming cycle  

NASA Astrophysics Data System (ADS)

A gas turbine air bottoming cycle consists of a gas turbine unit and the air turbine part. The air part includes a compressor, air expander and air heat exchanger. The air heat exchanger couples the gas turbine to the air cycle. Due to the low specific heat of air and of the gas turbine exhaust gases, the air heat exchanger features a considerable size. The bigger the air heat exchanger, the higher its effectiveness, which results in the improvement of the efficiency of the gas turbine air bottoming cycle. On the other hand, a device with large dimensions weighs more, which may limit its use in specific locations, such as oil platforms. The thermodynamic calculations of the air heat exchanger and a preliminary selection of the device are presented. The installation used in the calculation process is a plate heat exchanger, which is characterized by a smaller size and lower values of the pressure drop compared to the shell and tube heat exchanger. Structurally, this type of the heat exchanger is quite similar to the gas turbine regenerator. The method on which the calculation procedure may be based for real installations is also presented, which have to satisfy the economic criteria of financial profitability and cost-effectiveness apart from the thermodynamic criteria.

Chmielniak, Tadeusz; Czaja, Daniel; Lepszy, Sebastian

2013-12-01

116

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

Microsoft Academic Search

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

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

1983-01-01

117

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

NASA Technical Reports Server (NTRS)

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.

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

1987-01-01

118

Measurements of air-sea gas exchange at high wind speeds in the Southern Ocean: Implications for global parameterizations  

E-print Network

Measurements of air-sea gas exchange at high wind speeds in the Southern Ocean: Implications August 2006. [1] The SOLAS Air-Sea Gas Exchange (SAGE) Experiment was conducted in the western Pacific that factors controlling air-sea gas exchange in this region are similar to those in other parts of the world

Ho, David

119

Simultaneous measurement of acetylene reduction and respiratory gas exchange of attached root nodules.  

PubMed

A method was developed for the simultaneous measurement of acetylene reduction, carbon dioxide evolution and oxygen uptake by individual root nodules of intact nitrogen-fixing plants (Alnus rubra Bong.). The nodules were enclosed in a temperature-controlled leak-tight cuvette. Assay gas mixtures were passed through the cuvette at a constant, known flow rate and gas exchange was measured by the difference between inlet and outlet gas compositions. Gas concentrations were assayed by a combination of an automated gas chromatograph and a programmable electronic integrator. Carbon dioxide and ethylene evolution were determined with a coefficient of variation which was less than 2%, whereas the coefficient of variation for oxygen uptake measurements was less than 5%. Nodules subjected to repeated removal from and reinsertion into the cuvette and to long exposures of 10% v/v acetylene showed no irreversible decline in respiration or acetylene reduction. This system offers long-term stability and freedom from disturbance artifacts plus the ability to monitor continuously, rapidly and specifically the changes in root nodule activity caused by environmental perturbation. PMID:16662496

Winship, L J; Tjepkema, J D

1982-08-01

120

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

NASA Technical Reports Server (NTRS)

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.

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

1985-01-01

121

a Numerical Investigation of Gas Flow and Heat Transfer in Proton Exchange Membrane Fuel Cells  

Microsoft Academic Search

Gas flow and heat transfer in both cathode and anode channels have been modeled and analyzed for proton exchange membrane fuel cells. The simulated channel consists of a porous electrode layer (anode or cathode), gas flow duct, and solid current collector. The characteristics of gas flow and heat transfer in terms of friction factor and Nusselt number were investigated by

Jinliang Yuan; Masoud Rokni; Bengt Sundn

2003-01-01

122

Dynamic Modeling of Combustion and Gas Exchange Processes for Controlled Auto-Ignition Engines  

E-print Network

Dynamic Modeling of Combustion and Gas Exchange Processes for Controlled Auto-Ignition Engines Auto-Ignition. It uses sim- ple thermodynamic concepts, and well-established gas ex- change and heat was found. Con- trolled Auto-Ignition was attained by diluting the mixture with exhaust gas trapped

Cambridge, University of

123

Experimental study of work exchange with a granular gas: the viewpoint of the Fluctuation Theorem.  

E-print Network

epl draft Experimental study of work exchange with a granular gas: the viewpoint of the Fluctuation of the fluctuations of energy flux between a granular gas and a small driven harmonic oscillator. The DC-motor driving forcing, between the motor and the gas are examined from the viewpoint of the Fluctuation Theorem

Boyer, Edmond

124

Prototype Vent Gas Heat Exchanger for Exploration EVA - Performance and Manufacturing Characteristics  

NASA Technical Reports Server (NTRS)

NASA is developing new portable life support system (PLSS) technologies, which it is demonstrating in an unmanned ground based prototype unit called PLSS 2.0. One set of technologies within the PLSS provides suitable ventilation to an astronaut while on an EVA. A new component within the ventilation gas loop is a liquid-to-gas heat exchanger to transfer excess heat from the gas to the thermal control system s liquid coolant loop. A unique bench top prototype heat exchanger was built and tested for use in PLSS 2.0. The heat exchanger was designed as a counter-flow, compact plate fin type using stainless steel. Its design was based on previous compact heat exchangers manufactured by United Technologies Aerospace Systems (UTAS), but was half the size of any previous heat exchanger model and one third the size of previous liquid-to-gas heat exchangers. The prototype heat exchanger was less than 40 cubic inches and weighed 2.57 lb. Performance of the heat exchanger met the requirements and the model predictions. The water side and gas side pressure drops were less 0.8 psid and 0.5 inches of water, respectively, and an effectiveness of 94% was measured at the nominal air side pressure of 4.1 psia.

Quinn, Gregory J.; Strange, Jeremy; Jennings, Mallory

2013-01-01

125

Greenhouse Gas Exchange and Biogeochemistry of Fertilized Canadian Plantation Forests  

NASA Astrophysics Data System (ADS)

Canada's ratification of the Kyoto Protocol in 2002 has raised questions of the role of ecosystem management as a tool to temporarily reduce the net greenhouse gas burden of the forestry industry and potentially generate emission offset credits. We examined growing season methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2) fluxes, soil nutrient chemistry, and microbial biomass and CH4-oxidizing bacterial communities in 20-year-old sub-boreal lodgepole pine and maritime hemlock plantations under control conditions and simulated operational fertilization with N (200kg urea-N per ha, applied twice) and N, P, K, and micronutrients. CH4 uptake was significantly greater in the lodgepole pine site than in the hemlock site (152-221 and 57-81 micrograms CH4 consumed per square meter per hour), and there were no significant differences among treatments at either site. Among sites, treatments, and sampling times, CH4 uptake correlated positively with NH4 concentrations and negatively with extractable organic N:P quotients, indicating that this process may potentially be limited by nutrient availability to the CH4-oxidizing bacteria. N2O efflux was measured sporadically at a few flux collars, but was not significantly different from zero at any site, treatment, or time. Soil respiration (CO2 efflux) rates were faster in the hemlock than lodgepole pine site (243-409 and 100-266 milligrams CO2 per square meter per hour), and significant treatment differences were observed at individual times, though with fertilized plots exhibiting both faster and slower rates than controls. Soil respiration correlated significantly with microbial biomass C and N and NO3. Within each site, soil respiration, but not CH4 uptake, was positively correlated with soil temperature. New experiments examining the short-term effects of fertilization on greenhouse gas exchanges are underway, and both short and long-term effects will be evaluated in relation to changes in C storage in plant biomass, litter, and soil organic matter under the same fertilized and control conditions.

Basiliko, N.; Grayston, S. J.; Roy, R.; Mohn, W. W.; Yolova, V.; Prescott, C.

2005-12-01

126

Mechanistic basis for the gas exchange threshold in Thoroughbred horses.  

PubMed

The exercising Thoroughbred horse (TB) is capable of exceptional cardiopulmonary performance. However, because the ventilatory equivalent for O2 (VE/VO2) does not increase above the gas exchange threshold (Tge), hypercapnia and hypoxemia accompany intense exercise in the TB compared with humans, in whom VE/VO2 increases during supra-Tge work, which both removes the CO2 produced by the HCO buffering of lactic acid and prevents arterial partial pressure of CO2 (PaCO2) from rising. We used breath-by-breath techniques to analyze the relationship between CO2 output (VCO2) and VO2 [V-slope lactate threshold (LT) estimation] during an incremental test to fatigue (7 to approximately 15 m/s; 1 m x s(-1) x min(-1)) in six TB. Peak blood lactate increased to 29.2 +/- 1.9 mM/l. However, as neither VE/VO2 nor VE/VCO2 increased, PaCO2 increased to 56.6 +/- 2.3 Torr at peak VO2 (VO2 max). Despite the presence of a relative hypoventilation (i.e., no increase in VE/VO2 or VE/VCO2), a distinct Tge was evidenced at 62.6 +/- 2.7% VO2 max. Tge occurred at a significantly higher (P < 0.05) percentage of VO2 max than the lactate (45.1 +/- 5.0%) or pH (47.4 +/- 6.6%) but not the bicarbonate (65.3 +/- 6.6%) threshold. In addition, PaCO2 was elevated significantly only at a workload > Tge. Thus, in marked contrast to healthy humans, pronounced V-slope (increase VCO2/VO2) behavior occurs in TB concomitant with elevated PaCO2 and without evidence of a ventilatory threshold. PMID:11896016

McDonough, Paul; Kindig, Casey A; Erickson, Howard H; Poole, David C

2002-04-01

127

Effects of temperature and altitude on ventilation and gas exchange in chukars ( Alectoris chukar )  

Microsoft Academic Search

The effects of ambient temperature (Ta) on ventilation and gas exchange in chukar partridges (Alectoris chukar) were determined after acclimation to low and high altitute (LA and HA; 340 and 3,800 m, respectively).

Mark A. Chappell; Theresa L. Bucher

1987-01-01

128

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

E-print Network

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 ...

Latcham, Jacob G. (Jacob Greco)

2009-01-01

129

Linking Employee Development Activity, Social Exchange and Organizational Citizenship Behavior  

ERIC Educational Resources Information Center

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

Pierce, Heather R.; Maurer, Todd J.

2009-01-01

130

Aust. J. Plant Physiol., 1992, 19, 171-84 Carbon Isotope Discrimination and Gas Exchange  

E-print Network

exchange, and growth were monitored in container-grown coffee (Coffuurubicu L.) plants for 120 days underAust. J. Plant Physiol., 1992, 19, 171-84 Carbon Isotope Discrimination and Gas Exchange in Coffea. CrisostoAB A Hawaiian Sugar Planters' Association, PO Box 1057, Aiea, HI 96701, USA. 9240 So. Riverbend

Crisosto, Carlos H.

131

Impact of leaf physiology on gas exchange in a Japanese evergreen broad-leaved forest  

Microsoft Academic Search

We used a multi-layer model to analyse the impact of leaf physiology on the diurnal, seasonal, and inter-annual fluctuations in gas exchange in a warm-temperate evergreen broad-leaved forest in Japan. The influences of physiological parameters at the single leaf scale on the canopy scale gas exchange were investigated, including normalised dark respiration rate, Rnleaf25, normalised maximum carboxylation rate, Vcmax25, and

Yoshiko Kosugi; Satoru Takanashi; Naoko Matsuo; Katsunori Tanaka; Hiroki Tanaka

2006-01-01

132

Vasomotor tone does not affect perfusion heterogeneity and gas exchange in normal primate lungs during normoxia  

NASA Technical Reports Server (NTRS)

To determine whether vasoregulation is an important cause of pulmonary perfusion heterogeneity, we measured regional blood flow and gas exchange before and after giving prostacyclin (PGI(2)) to baboons. Four animals were anesthetized with ketamine and mechanically ventilated. Fluorescent microspheres were used to mark regional perfusion before and after PGI(2) infusion. The lungs were subsequently excised, dried inflated, and diced into approximately 2-cm(3) pieces (n = 1,208-1,629 per animal) with the spatial coordinates recorded for each piece. Blood flow to each piece was determined for each condition from the fluorescent signals. Blood flow heterogeneity did not change with PGI(2) infusion. Two other measures of spatial blood flow distribution, the fractal dimension and the spatial correlation, did not change with PGI(2) infusion. Alveolar-arterial O(2) differences did not change with PGI(2) infusion. We conclude that, in normal primate lungs during normoxia, vasomotor tone is not a significant cause of perfusion heterogeneity. Despite the heterogeneous distribution of blood flow, active regulation of regional perfusion is not required for efficient gas exchange.

Glenny, R. W.; Robertson, H. T.; Hlastala, M. P.

2000-01-01

133

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

PubMed

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

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

2012-11-01

134

Prototype Vent Gas Heat Exchanger for Exploration EVA - Performance and Manufacturing Characteristics  

NASA Technical Reports Server (NTRS)

NASA is developing new portable life support system (PLSS) technologies, which it is demonstrating in an unmanned ground based prototype unit called PLSS 2.0. One set of technologies within the PLSS provides suitable ventilation to an astronaut while on an EVA. A new component within the ventilation gas loop is a liquid-to-gas heat exchanger to transfer excess heat from the gas to the thermal control system's liquid coolant loop. A unique bench top prototype heat exchanger was built and tested for use in PLSS 2.0. The heat exchanger was designed as a counter-flow, compact plate fin type using stainless steel. Its design was based on previous compact heat exchangers manufactured by United Technologies Aerospace Systems, but was half the size of any previous heat exchanger model and one third the size of previous liquid-to-gas heat exchangers. The prototype heat exchanger was less than 40 cubic inches and weighed 2.6 lb. The water side and gas side pressure drops were 0.8 psid and 0.5 inches of water, respectively. Performance of the heat exchanger at the nominal pressure of 4.1 psia was measured at 94%, while a gas inlet pressure of 25 psia resulted in an effectiveness of 84%. These results compared well with the model, which was scaled for the small size. Modeling of certain phenomena that affect performance, such as flow distribution in the headers was particularly difficult due to the small size of the heat exchanger. Data from the tests has confirmed the correction factors that were used in these parts of the model.

Jennings, Mallory; Quinn, Gregory; Strange, Jeremy

2012-01-01

135

Effect of impeller design and spacing on gas exchange in a percutaneous respiratory assist catheter.  

PubMed

Providing partial respiratory assistance by removing carbon dioxide (CO2 ) can improve clinical outcomes in patients suffering from acute exacerbations of chronic obstructive pulmonary disease and acute respiratory distress syndrome. An intravenous respiratory assist device with a small (25 Fr) insertion diameter eliminates the complexity and potential complications associated with external blood circuitry and can be inserted by nonspecialized surgeons. The impeller percutaneous respiratory assist catheter (IPRAC) is a highly efficient CO2 removal device for percutaneous insertion to the vena cava via the right jugular or right femoral vein that utilizes an array of impellers rotating within a hollow-fiber membrane bundle to enhance gas exchange. The objective of this study was to evaluate the effects of new impeller designs and impeller spacing on gas exchange in the IPRAC using computational fluid dynamics (CFD) and in vitro deionized water gas exchange testing. A CFD gas exchange and flow model was developed to guide a progressive impeller design process. Six impeller blade geometries were designed and tested in vitro in an IPRAC device with 2- or 10-mm axial spacing and varying numbers of blades (2-5). The maximum CO2 removal efficiency (exchange per unit surface area) achieved was 573 8 mL/min/m(2) (40.1 mL/min absolute). The gas exchange rate was found to be largely independent of blade design and number of blades for the impellers tested but increased significantly (5-10%) with reduced axial spacing allowing for additional shaft impellers (23 vs. 14). CFD gas exchange predictions were within 2-13% of experimental values and accurately predicted the relative improvement with impellers at 2- versus 10-mm axial spacing. The ability of CFD simulation to accurately forecast the effects of influential design parameters suggests it can be used to identify impeller traits that profoundly affect facilitated gas exchange. PMID:24749994

Jeffries, R Garrett; Frankowski, Brian J; Burgreen, Greg W; Federspiel, William J

2014-12-01

136

Noninvasive detection of gas exchange rate by near infrared spectroscopy  

NASA Astrophysics Data System (ADS)

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.

Xu, Guodong; Mao, Zongzhen; Wang, Bangde

2008-12-01

137

Finite Temperature Dipolar ultra-cold Bose gas with Exchange Interactions  

E-print Network

We develop finite temperature theory for a trapped dipolar Bose gas including thermal exchange interactions. Previous treatments neglected these, difficult to compute, terms. We present a methodology for numerically evaluating the thermal exchange contributions, making use of cylindrical symmetry. We then investigate properties of the dipolar gas, including calculating the excitation spectrum over the full range of trap anisotropy. We evaluate the contributions due to thermal exchange noting that, under some regimes, these effects can be at least as significant as the direct interaction. We therefore provide guidance as to when these cumbersome terms can be neglected and when care should be exercised regarding their omission.

S. C. Cormack; D. A. W. Hutchinson

2012-09-20

138

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

E-print Network

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

Paris-Sud XI, Universit de

139

Conventional versus specific types of heat exchangers in the case of polluted flue gas as the process fluid A review  

Microsoft Academic Search

The present contribution shows certain practical aspects of selection and design of heat exchangers for industrial applications where polluted flue gas (off-gas) represents one process fluid.One of the key factors in designing heat exchangers for these applications is the primary selection of a suitable type. The presently available possibilities and methodologies of efficient heat exchanging device selection and supporting software

Petr Stehlk

2011-01-01

140

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

NASA Technical Reports Server (NTRS)

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 (approximately 100-300 microns in 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 as a vortex chamber.The large heat transfer area presented by the small droplets permits heat exchanger effectiveness of 0.9-0.95 in a compact, lightweight geometry which avoids many of the limitations of conventional plate and fin or tube and shell heat exchangers, such as their tendency toward single point failure. The application of the LDHX in a high temperature Brayton cycle is discussed to illustrate the performance and operational characteristics of this new heat exchanger concept.

Bruckner, A. P.; Mattick, A. T.

1983-01-01

141

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

NASA Technical Reports Server (NTRS)

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 as a vortex chamber. The large heat transfer area presented by the small droplets permits heat exchanger effectiveness of 0.9 to 0.95 in a compact, lightweight geometry which avoids many of the limitations of conventional plate and fin or tube and shell heat exchangers, such as their tendency toward single point failure. The application of the LDHX in a high temperature Bryaton cycle is discussed to illustrate the performance and operational characteristics of this heat exchanger concept.

Bruckner, A. P.; Mattick, A. T.

1983-01-01

142

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

Microsoft Academic Search

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

Dennis D. Baldocchi; Tilden P. Meyers

1991-01-01

143

Hydraulically actuated gas exchange valve assembly and engine using same  

DOEpatents

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.

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

2002-09-03

144

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

PubMed Central

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

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

2012-01-01

145

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

NASA Technical Reports Server (NTRS)

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.

Bowman, William D.

1989-01-01

146

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

Microsoft Academic Search

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

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

1985-01-01

147

Gas sensing in microplates with optodes: influence of oxygen exchange between sample, air, and plate material.  

PubMed

Microplates with integrated optical oxygen sensors are a new tool to study metabolic rates and enzyme activities. Precise measurements are possible only if oxygen exchange between the sample and the environment is known. In this study we quantify gas exchange in plastic microplates. Dissolved oxygen was detected using either an oxygen-sensitive film fixed at the bottom of each well or a needle-type sensor. The diffusion of oxygen into wells sealed with different foils, paraffin oil, and paraffin wax, respectively, was quantified. Although foil covers showed the lowest oxygen permeability, they include an inevitable gas phase between sample and sealing and are difficult to manage. The use of oil was found to be critical due to the extensive shaking caused by movement of the plates during measurements in microplate readers. Thus, paraffin wax was the choice material because it avoids convection of the sample and is easy to handle. Furthermore, without shaking, significant gradients in pO2 levels within a single well of a polystyrene microplate covered with paraffin oil were detected with the needle-type sensor. Higher pO2 levels were obtained near the surface of the sample as well as near the wall of the well. A significant diffusion of oxygen through the plastic plate material was found using plates based on polystyrene. Thus, the location of a sensor element within the well has an effect on the measured pO2 level. Using a sensor film fixed on the bottom of a well or using a dissolved pO2-sensitive indicator results in pO2 offset and in apparently lower respiration rates or enzyme activities. Oxygen diffusion through a polystyrene microplate was simulated for measurements without convection--that is, for samples without oxygen diffusion through the cover and for unshaken measurements using permeable sealings. This mathematical model allows for calculation of the correct kinetic parameters. PMID:15772950

Arain, Sarina; Weiss, Svenja; Heinzle, Elmar; John, Gernot T; Krause, Christian; Klimant, Ingo

2005-05-01

148

Relationship Between Wind Speed and Gas Exchange Over the Ocean  

Microsoft Academic Search

Relationships between wind speed and gas transfer, combined with knowledge of the partial pressure difference of CO2 across the air-sea interface, are frequently used to determine the CO2 flux between the ocean and the atmosphere. Little attention has been paid to the influence of variability in wind speed on the calculated gas transfer velocities and the possibility of chemical enhancement

Rik Wanninkhof

1992-01-01

149

Effect of channel materials and trapezoidal corner angles on emerging droplet behavior in Proton Exchange Membrane Fuel Cell gas channels  

E-print Network

Exchange Membrane Fuel Cell gas channels Preethi Gopalan a , Satish G. Kandlikar a,b,* a Microsystems dynamics in Proton Exchange Membrane Fuel Cell (PEMFC) gas channels with different trapezoid channel open droplet behavior in a trapezoid gas channel. At lower air velocities droplet showed corner filling

Kandlikar, Satish

150

Exchange and Correlation Effects in the 3D Electron Gas in Strong Magnetic Fields and Application to Graphite 3  

E-print Network

Exchange and Correlation Effects in the 3D Electron Gas in Strong Magnetic Fields and Application the exchange and correlation effects in the three­dimensional electron gas in strong magnetic fields. We find. This is the case similar to the two­dimensional (2D) electron gas in which the fractional quantum Hall effect (FQHE

Takada, Yasutami

151

The state of the photosynthetic apparatus in leaves as analyzed by rapid gas exchange and optical methods: the pH of the chloroplast stroma and activation of enzymes in vivo.  

PubMed

The exchange of CO2 and O2 was measured in leaves using specially constructed equipment capable of responding to rapid transients. Optical measurements provided information on cytochrome f and P 700 oxidation in the light. The following results were obtained: i) The solubilization of CO2 was used to calculate the pH of the chloroplast stroma in darkened leaves. Values ranged from pH 7.8 to pH 8.0 in different C3 plants. ii) Illumination of predarkened leaves of Helianthus annuus L. resulted in three distinct phases of O2 evolution that illustrate the complexity of light activation of the photosynthetic apparatus. A first burst of O2 is attributed to the reduction of electron carriers of the electron-transport chain. While plastoquinone was reduced, cytochrome f was oxidized. Appreciable oxidation of P 700 became possible only during the second O2 burst, which indicates the reduction of the phosphoglycerate pool. Extensive oxidation required the opening of an electron gate on the reducing side of photosystem I. The subsequent slow rise in O2 evolution towards a steady state reflects activation of the Calvin cycle and is the result of CO2 assimilation. iii) Light-dependent CO2 uptake by predarkened leaves occurred in four phases, three of them based on pH changes in the chloroplast stroma. Initial CO2 uptake was small and probably caused by protonation of reduced plastoquinone. In the second phase, which coincided with the reduction of the pool of phosphoglycerate, the initial alkalization of the chloroplast stroma was substantially increased. In the third phase, the stroma alkalization decreased, and the fourth phase was dominated by CO2 assimilation. iv) Respiratory CO2 production was partially suppressed in the light during the second phase of O2 evolution while phosphoglycerate was being reduced. PMID:24212428

Laisk, A; Oja, V; Kiirats, O; Raschke, K; Heber, U

1989-03-01

152

Respiratory gas exchange and metabolic responses during exercise in McArdle's disease.  

PubMed

During normal progressive exercise, the gas exchange anaerobic threshold occurs when CO2 production (VCO2) and ventilation (VE) increase so as to depart from a linear relationship to O2 consumption (VO2). This is thought to represent a gas exchange response to metabolic acidosis due to lactate accumulation. Patients with McArdle's disease have previously been reported to exhibit a steepened ventilatory response relative to VCO2, despite an inability to produce lactate. However, the VCO2 response has not been studied. We therefore investigated the VCO2-VO2 and VE-VO2 relationships in seven McArdle's disease patients and seven control subjects during symptom-limited maximal treadmill exercise. Analysis of gas exchange showed that whereas all control subjects had an easily identifiable anaerobic threshold, four of the patients had none and the other three displayed an attenuated threshold. The occurrence of the threshold in one patient was associated with a small rise in lactate and in another patient with an abrupt rise in leg discomfort, suggesting a pain response. Ammonia and the purine metabolite hypoxanthine were elevated during exercise in all patients, suggesting that ammonia may be a product of adenosine monophosphate degradation. Free fatty acid levels were also elevated, and a shift toward utilization of lipid may contribute to abnormal gas exchange responses. It is concluded that lactic acidosis contributes to the gas exchange anaerobic threshold but that other factors, such as discomfort, may be involved in the excess Ve seen during heavy exercise. PMID:8226478

Riley, M; Nicholls, D P; Nugent, A M; Steele, I C; Bell, N; Davies, P M; Stanford, C F; Patterson, V H

1993-08-01

153

Passive and Active Ion-Exchanged Glass Waveguides and Devices  

NASA Astrophysics Data System (ADS)

This thesis studies the fabrication and the characterization of passive and active ion-exchanged glass waveguides and devices that are mainly used for applications in integrated optics area. Potassium and silver double-ion-exchange process is developed to fabricate high performance passive glass waveguides and devices. Three different processes are investigated for the fabrication of rare-earth-doped glass waveguides on active and passive substrates. They are dilute silver ion exchange for rare-earth-doped silicate glass substrates, spin-coated rare-earth-doped phosphate overlays on passive glass waveguides and composite structures employing active cover glass on passive waveguides. The main rare-earth elements employed in the fabrication of active waveguides are neodymium and erbium. Grating assisted glass waveguides, symmetric Y -branches, a novel four-port nonsymmetric Mach-Zehnder interferometer and a new integrated optical ring resonator are developed. They are potentially important for active applications in connection with rare-earth-doped glass waveguides. Finally, a composite erbium-doped glass waveguide amplifier is demonstrated and more than 10 dB net gain has been achieved with a 4.7 mm long sample and less than 30 mW guided pump power in the waveguide.

Wang, Wei-Jian

154

Temperature and water regulation of gas exchange of Opuntia polyacantha  

Microsoft Academic Search

Opuntia polyacantha was collected from the shortgrass prairie in Colorado. Carbon dioxide and water vapor exchange was monitored in plants pretreated and analyzed under cool temperatures (20\\/15C) and warm temperatures (35\\/15C). Well watered plants under a 35\\/15 thermoperiod supported the fixation of atmospheric CO2 during the night, early morning, and late afternoon. Plants under a 20\\/15 thermoperiod exhibited CO2 uptake

B. Clifford Gerwick; George J. Williams

1978-01-01

155

Effect of Vacuum Infiltration on Photosynthetic Gas Exchange in Leaf Tissue  

PubMed Central

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

MacDonald, Ian R.

1975-01-01

156

Recovery of Water from Boiler Flue Gas Using Condensing Heat Exchangers  

SciTech Connect

Most of the water used in a thermoelectric power plant is used for cooling, and DOE has been focusing on possible techniques to reduce the amount of fresh water needed for cooling. DOE has also been placing emphasis on recovery of usable water from sources not generally considered, such as mine water, water produced from oil and gas extraction, and water contained in boiler flue gas. This report deals with development of condensing heat exchanger technology for recovering moisture from flue gas from coal-fired power plants. The report describes: An expanded data base on water and acid condensation characteristics of condensing heat exchangers in coal-fired units. This data base was generated by performing slip stream tests at a power plant with high sulfur bituminous coal and a wet FGD scrubber and at a power plant firing highmoisture, low rank coals. Data on typical concentrations of HCl, HNO{sub 3} and H{sub 2}SO{sub 4} in low temperature condensed flue gas moisture, and mercury capture efficiencies as functions of process conditions in power plant field tests. Theoretical predictions for sulfuric acid concentrations on tube surfaces at temperatures above the water vapor dewpoint temperature and below the sulfuric acid dew point temperature. Data on corrosion rates of candidate heat exchanger tube materials for the different regions of the heat exchanger system as functions of acid concentration and temperature. Data on effectiveness of acid traps in reducing sulfuric acid concentrations in a heat exchanger tube bundle. Condensed flue gas water treatment needs and costs. Condensing heat exchanger designs and installed capital costs for full-scale applications, both for installation immediately downstream of an ESP or baghouse and for installation downstream of a wet SO{sub 2} scrubber. Results of cost-benefit studies of condensing heat exchangers.

Levy, Edward; Bilirgen, Harun; DuPont, John

2011-03-31

157

Recovery of Water from Boiler Flue Gas Using Condensing Heat Exchangers  

SciTech Connect

Most of the water used in a thermoelectric power plant is used for cooling, and DOE has been focusing on possible techniques to reduce the amount of fresh water needed for cooling. DOE has also been placing emphasis on recovery of usable water from sources not generally considered, such as mine water, water produced from oil and gas extraction, and water contained in boiler flue gas. This report deals with development of condensing heat exchanger technology for recovering moisture from flue gas from coal-fired power plants. The report describes: (1) An expanded data base on water and acid condensation characteristics of condensing heat exchangers in coal-fired units. This data base was generated by performing slip stream tests at a power plant with high sulfur bituminous coal and a wet FGD scrubber and at a power plant firing high-moisture, low rank coals. (2) Data on typical concentrations of HCl, HNO{sub 3} and H{sub 2}SO{sub 4} in low temperature condensed flue gas moisture, and mercury capture efficiencies as functions of process conditions in power plant field tests. (3) Theoretical predictions for sulfuric acid concentrations on tube surfaces at temperatures above the water vapor dewpoint temperature and below the sulfuric acid dew point temperature. (4) Data on corrosion rates of candidate heat exchanger tube materials for the different regions of the heat exchanger system as functions of acid concentration and temperature. (5) Data on effectiveness of acid traps in reducing sulfuric acid concentrations in a heat exchanger tube bundle. (6) Condensed flue gas water treatment needs and costs. (7) Condensing heat exchanger designs and installed capital costs for full-scale applications, both for installation immediately downstream of an ESP or baghouse and for installation downstream of a wet SO{sub 2} scrubber. (8) Results of cost-benefit studies of condensing heat exchangers.

Edward Levy; Harun Bilirgen; John DuPoint

2011-03-31

158

Gas exchange in disease: asthma, chronic obstructive pulmonary disease, cystic fibrosis, and interstitial lung disease.  

PubMed

Ventilation-perfusion (VA/Q) inequality is the underlying abnormality determining hypoxemia and hypercapnia in lung diseases. Hypoxemia in asthma is characterized by the presence of low VA/Q units, which persist despite improvement in airway function after an attack. This hypoxemia is generally attenuated by compensatory redistribution of blood flow mediated by hypoxic vasoconstriction and changes in cardiac output, however, mediator release and bronchodilator therapy may cause deterioration. Patients with chronic obstructive pulmonary disease have more complex patterns of VA/Q inequality, which appear more fixed, and changes in blood flow and ventilation have less benefit in improving gas exchange efficiency. The inability of ventilation to match increasing cardiac output limits exercise capacity as the disease progresses. Deteriorating hypoxemia during exacerbations reflects the falling mixed venous oxygen tension from increased respiratory muscle activity, which is not compensated by any redistribution of VA/Q ratios. Shunt is not a feature of any of these diseases. Patients with cystic fibrosis (CF) have no substantial shunt when managed according to modern treatment regimens. Interstitial lung diseases demonstrate impaired oxygen diffusion across the alveolar-capillary barrier, particularly during exercise, although VA/Q inequality still accounts for most of the gas exchange abnormality. Hypoxemia may limit exercise capacity in these diseases and in CF. Persistent hypercapnic respiratory failure is a feature of advancing chronic obstructive pulmonary disease and CF, closely associated with sleep disordered breathing, which is not a prominent feature of the other diseases. Better understanding of the mechanisms of hypercapnic respiratory failure, and of the detailed mechanisms controlling the distribution of ventilation and blood flow in the lung, are high priorities for future research. PMID:23737199

Young, Iven H; Bye, Peter T P

2011-04-01

159

Correlation between CAM-Cycling and Photosynthetic Gas Exchange in Five Species of Talinum (Portulacaceae) 1  

PubMed Central

Photosynthetic gas exchange and malic acid fluctuations were monitored in 69 well-watered plants from five morphologically similar species of Talinum in an investigation of the ecophysiological significance of the Crassulacean acid metabolism (CAM)-cycling mode of photosynthesis. Unlike CAM, atmospheric CO2 uptake in CAM-cycling occurs exclusively during the day; at night, the stomata are closed and respiratory CO2 is recaptured to form malic acid. All species showed similar patterns of day-night gas exchange and overnight malic acid accumulation, confirming the presence of CAM-cycling. Species averages for gas exchange parameters and malic acid fluctuation were significantly different such that the species with the highest daytime gas exchange had the lowest malic acid accumulation and vice versa. Also, daytime CO2 exchange and transpiration were negatively correlated with overnight malic acid fluctuation for all individuals examined together, as well as within one species. This suggests that malic acid may effect reductions in both atmospheric CO2 uptake and transpiration during the day. No significant correlation between malic acid fluctuation and water-use efficiency was found, although a nonsignificant trend of increasing water-use efficiency with increasing malic acid fluctuation was observed among species averages. This study provides evidence that CO2 recycling via malic acid is negatively correlated with daytime transpirational water losses in well-watered plants. Thus, CAM-cycling could be important for survival in the thin, frequently desiccated soils of rock outcrops on which these plants occur. PMID:16668307

Harris, Fred S.; Martin, Craig E.

1991-01-01

160

Correlation between CAM-Cycling and Photosynthetic Gas Exchange in Five Species of Talinum (Portulacaceae).  

PubMed

Photosynthetic gas exchange and malic acid fluctuations were monitored in 69 well-watered plants from five morphologically similar species of Talinum in an investigation of the ecophysiological significance of the Crassulacean acid metabolism (CAM)-cycling mode of photosynthesis. Unlike CAM, atmospheric CO(2) uptake in CAM-cycling occurs exclusively during the day; at night, the stomata are closed and respiratory CO(2) is recaptured to form malic acid. All species showed similar patterns of day-night gas exchange and overnight malic acid accumulation, confirming the presence of CAM-cycling. Species averages for gas exchange parameters and malic acid fluctuation were significantly different such that the species with the highest daytime gas exchange had the lowest malic acid accumulation and vice versa. Also, daytime CO(2) exchange and transpiration were negatively correlated with overnight malic acid fluctuation for all individuals examined together, as well as within one species. This suggests that malic acid may effect reductions in both atmospheric CO(2) uptake and transpiration during the day. No significant correlation between malic acid fluctuation and water-use efficiency was found, although a nonsignificant trend of increasing water-use efficiency with increasing malic acid fluctuation was observed among species averages. This study provides evidence that CO(2) recycling via malic acid is negatively correlated with daytime transpirational water losses in well-watered plants. Thus, CAM-cycling could be important for survival in the thin, frequently desiccated soils of rock outcrops on which these plants occur. PMID:16668307

Harris, F S; Martin, C E

1991-08-01

161

Relationship between gas exchange, wind speed, and radar backscatter in a large wind-wave tank  

NASA Technical Reports Server (NTRS)

The relationships between the gas exchange, wind speed, friction velocity, and radar backscatter from the water surface was investigated using data obtained in a large water tank in the Delft (Netherlands) wind-wave tunnel, filled with water supersaturated with SF6, N2O, and CH4. Results indicate that the gas-transfer velocities of these substances were related to the wind speed with a power law dependence. Microwave backscatter from water surface was found to be related to gas transfer velocities by a relationship in the form k(gas) = a 10 exp (b A0), where k is the gas transfer velocity for the particular gas, the values of a and b are obtained from a least squares fit of the average backscatter cross section and gas transfer at 80 m, and A0 is the directional (azimuthal) averaged return.

Wanninkhof, Richard H.; Bliven, L. F.

1991-01-01

162

Greenhouse gas exchange in tropical mountain ecosystems in Tanzania  

NASA Astrophysics Data System (ADS)

Tropical mountain ecosystems with their mostly immense biodiversity are important regions for natural resources but also for agricultural production. Their supportive ecosystem processes are particularly vulnerable to the combined impacts of global warming and the conversion of natural to human-modified landscapes. Data of impacts of climate and land use change on soil-atmosphere interactions due to GHG (CO2, CH4, and N2O) exchange from these ecosystems are still scarce, in particular for Africa. Tropical forest soils are underestimated as sinks for atmospheric CH4 with regard to worldwide GHG budgets (Werner et al. 2007, J GEOPHYS RES Vol. 112). Even though these soils are an important source for the atmospheric N2O budget, N2O emissions from tropical forest ecosystems are still poorly characterized (Castaldi et al. 2013, Biogeosciences 10). To obtain an insight of GHG balances of selected ecosystems soil-atmosphere exchange of N2O, CH4 and CO2 was investigated along the southern slope of Mt. Kilimanjaro, Tanzania. We will present results for tropical forests in three different altitudes (lower montane, Ocotea, and Podocarpus forest), home garden (extensive agro-forestry), and coffee plantation (intensive agro-forestry). Therefore we used a combined approach consisting of a laboratory parameterization experiment (3 temperature and 2 moisture levels) and in situ static chamber measurements for GHG exchange. Field measurements were conducted during different hygric seasons throughout two years. Seasonal variation of temperature and especially of soil moisture across the different ecosystems resulted in distinct differences in GHG exchange. In addition environmental parameters like soil bulk density and substrate availability varying in space strongly influenced the GHG fluxes within sites. The results from parameterization experiments and in situ measurements show that natural forest ecosystems and extensive land use had higher uptakes of CH4. For the investigated forest ecosystems we found considerable differences in soil sink strength for CH4. N2O emissions were highest in natural forest ecosystems even though N input in the intensively managed system was considerably higher. Highest N2O efflux rates were identified in the region of highest mean annual precipitation. CO2 emissions reduced from managed to natural ecosystems. In general an increase in temperature as well as in soil moisture caused higher GHG fluxes throughout all investigated natural and managed ecosystems. With increasing altitude of the investigated forests GHG emissions reduced overall.

Gerschlauer, Friederike; Kikoti, Imani; Kiese, Ralf

2014-05-01

163

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

NASA Technical Reports Server (NTRS)

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.

Offenhaeuser, F.

1987-01-01

164

Active heat exchange thermal storage unit with pentaerythritol  

Microsoft Academic Search

A latent thermal energy storage unit with pentaerythritol was developed, and in the storage unit an active heat transfer enhancement was performed. The phase change material, pentaerythritol, was mixed with a hydrocarbon heat transfer oil and this two-phase storage medium was stirred in a shell-coil type heat exchanger. Through the preliminary experiments in a glass vessel, a lab-scale storage unit

Y. Abe; M. Kamimoto; K. Kanari; T. Ozawa; R. Sakamoto; Y. Takahashi

1984-01-01

165

Parameterization of Leaf-Level Gas Exchange for Plant Functional Groups From Amazonian Seasonal Tropical Rain Forest  

NASA Astrophysics Data System (ADS)

Plant communities exert strong influence over the magnitude of carbon and water cycling through ecosystems by controlling photosynthetic gas exchange and respiratory processes. Leaf-level gas exchange fluxes result from a combination of physiological properties, such as carboxylation capacity, respiration rates and hydraulic conductivity, interacting with environmental drivers such as water and light availability, leaf-to-air vapor pressure deficit, and temperature. Carbon balance models concerned with ecosystem-scale responses have as a common feature the description of eco-physiological properties of vegetation. Here we focus on the parameterization of ecophysiological gas-exchange properties of plant functional groups from a pristine Amazonian seasonally dry tropical rain forest ecosystem (FLONA-Tapajs, Santarm, PA, Brazil). The parameters were specific leaf weight, leaf nitrogen content, leaf carbon isotope ratio, maximum photosynthetic assimilation rate, photosynthetic carboxylation capacity, dark respiration rates, and stomatal conductance to water vapor. Our plant functional groupings were lianas at the top of the canopy, trees at the top of the canopy, mid-canopy trees and undestory trees. Within the functional groups, we found no evidence that leaves acclimated to seasonal changes in precipitation. However, there were life-form dependent distinctions when a combination of parameters was included. Top-canopy lianas were statistically different from top-canopy trees for leaf carbon isotope ratio, maximum photosynthetic assimilation rate, and stomatal conductance to water vapor, suggesting that lianas are more conservative in the use of water, causing a stomatal limitation on photosynthetic assimilation. Top-canopy, mid canopy and understory groupings were distinct for specific leaf weight, leaf nitrogen content, leaf carbon isotope ratio, maximum photosynthetic assimilation rate, and photosynthetic carboxylation capacity. The recognition that plant functional groups have distinct impacts on ecosystem-scale gas exchange can increase the accuracy of process-based carbon balance models where structure is known and when logging activities are incorporated into production models.

Domingues, T. F.; Berry, J. A.; Ometto, J. P.; Martinelli, L. A.; Ehleringer, J. R.

2004-12-01

166

Gamma radiation effect on gas production in anion exchange resins  

NASA Astrophysics Data System (ADS)

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.

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

2013-10-01

167

The Viking gas exchange experiment results from Chryse and Utopia surface samples  

Microsoft Academic Search

Immediate gas changes occurred when untreated Martian surface samples were humidified and\\/or wet by an aqueous nutrient medium in the Viking lander gas exchange experiment. The evolutions of N2, CO2, and Ar are mainly associated with soil surface desorption caused by water vapor, while O2 evolution is primarily associated with decomposition of superoxides inferred to be present on Mars. On

Vance I. Oyama; B. J. Berdahl

1977-01-01

168

Is there a significant gas exchange through the skin of the shrew Crocidura russula monacha?  

PubMed

Because of its small body mass, the shrew Crocidura russula monacha has a relatively high surface area to volume ratio, thin skin, and high thermal conductance compared with larger mammals. This study was aimed at examining the possibility that such a mammal may exhibit a significant skin gas exchange. Gas composition was measured in subcutaneous gas pockets. CO2 and O2 exchange through skin were measured both in vitro and in vivo. In 7-wk-old gas pockets, the steady-state PO2 and PCO2 values were 50 Torr (where 1 Torr = 133.322 Pa) and 35 Torr, respectively, compared with PO2 and Pco2 values of 73 Torr and 33 Torr, respectively, in 1-wk-old gas pockets. These changes are attributed to an increased capillary density and a decreased skin thickness after 7 wk. There was no significant gas exchange through skin during in vitro measurements. In vivo measurements indicated that O2 uptake was 0.5% and CO2 loss was 0.9% of total body metabolism at 20 degrees C. At 35 degrees C, skin O2 uptake and CO2 loss increased to 1.3% and 2.9%, respectively. These values are only part of the expected skin metabolism; thus, the rest must come from blood. Because gas exchange through the skin of this shrew is within the range of other mammals, the relatively low PCO2 and high PO2 in the gas pockets is better explained by the relative hyperventilation state exhibited by this shrew. PMID:9678501

Mover-Lev, H; Minzberg, H; Ar, A

1998-01-01

169

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

Microsoft Academic Search

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 20 kW. We arranged the components of a primary gas loop

Hong SungDeok; Oh DongSeok; Lee WonJae; Chang JongHwa

2006-01-01

170

Respiratory gas exchange in the assessment of patients with impaired ventricular function  

Microsoft Academic Search

Respiratory gas exchange on exercise was evaluated as a non-invasive method of assessing patients with heart failure. Twenty four men (age 28-72) with symptomatic chronic stable heart failure (New York Heart Association class II-III) and ten controls aged 36-70 were studied. During treadmill exercise oxygen consumption and carbon dioxide production were measured continuously by analysis of mixed expired gas with

D P Lipkin; J Perrins; P A Poole-Wilson

1985-01-01

171

Comparative heat and gas exchange measurements in the Heidelberg Aeolotron, a large annular wind-wave tank  

NASA Astrophysics Data System (ADS)

A comparative study of simultaneous heat and gas exchange measurements was performed in the large annular Heidelberg Air-Sea Interaction Facility, the Aeolotron, under homogeneous water surface conditions. The use of two gas tracers, N2O and C2HF5, resulted not only in gas transfer velocities, but also in the measurement of the Schmidt number exponent n with a precision of 0.025. The original controlled flux or active thermographic technique proposed by Jhne et al. (1989) was applied by heating a large patch at the water surface to measure heat transfer velocities. Heating a large patch, the active thermography technique is laterally homogeneous and problems of lateral transport effects are avoided. Using the measured Schmidt number exponents, the ratio of the scaled heat transfer velocities to the measured gas transfer velocities is 1.046 0.040, a good agreement within the limits of experimental uncertainties. This indicates the possibility to scale heat transfer velocities measured by active thermography to gas transfer velocities, provided the Schmidt number exponent is known and that the heated patch is large enough to reach the thermal equilibrium.

Nagel, L.; Krall, K. E.; Jhne, B.

2014-06-01

172

Comparative heat and gas exchange measurements in the Heidelberg Aeolotron, a large annular wind-wave tank  

NASA Astrophysics Data System (ADS)

A comparative study of simultaneous heat and gas exchange measurements was performed in the large annular Heidelberg Air-Sea Interaction Facility, the Aeolotron, under homogeneous water surface conditions. The use of two gas tracers, N2O and C2HF5, resulted not only in gas transfer velocities, but also in the measurement of the Schmidt number exponent n with a precision of 0.025. The original controlled flux, or active thermographic, technique proposed by Jhne et al. (1989) was applied by heating a large patch at the water surface to measure heat transfer velocities. Heating a large patch, the active thermography technique is laterally homogeneous, and problems of lateral transport effects are avoided. Using the measured Schmidt number exponents, the ratio of the scaled heat transfer velocities to the measured gas transfer velocities is 1.046 0.040, a good agreement within the limits of experimental uncertainties. This indicates the possibility to scale heat transfer velocities measured by active thermography to gas transfer velocities, provided that the Schmidt number exponent is known and that the heated patch is large enough to reach the thermal equilibrium.

Nagel, L.; Krall, K. E.; Jhne, B.

2015-01-01

173

Meteorological controls of gas exchange at a small English lake  

Microsoft Academic Search

The relationships between gas transfer velocity, k600, wind speed, wind direction, rainfall, and relative humidity were examined using measurements of SF6 evasion from Coatenhill Reservoir, a small (0.017 km 2 ), shallow (1.9 6 0.1 m), man-made lake in northeast England characterized by predominantly low to intermediate wind speeds ;1-10 m s 21 . A graphical method was used to

Thomas Frost; Robert C. Upstill-Goddard

2002-01-01

174

DOI: 10.1002/chem.201002135 High Gas Sorption and Metal-Ion Exchange of Microporous MetalOrganic  

E-print Network

DOI: 10.1002/chem.201002135 High Gas Sorption and Metal-Ion Exchange of Microporous Metal of their potential ap- plications in gas storage, gas separation, catalysis, and fabri- cation of nanoparticles.[1 nanoparticles in the MOF.[1,2f,3] Gas sorption properties also depend on pore volume and ligand structures

Paik Suh, Myunghyun

175

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

E-print Network

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

Paris-Sud XI, Universit de

176

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...

177

The Multifunctional Fish Gill: Dominant Site of Gas Exchange, Osmoregulation, Acid-Base Regulation, and  

E-print Network

The Multifunctional Fish Gill: Dominant Site of Gas Exchange, Osmoregulation, Acid-Base Regulation, Maine I. Introduction 98 II. Evolutionary Origin and External Structure 98 A. Gills of protovertebrates and modern fishes 98 B. External structure of fish gills 99 III. Internal Structure: Vascular and Neural 109

Evans, David H.

178

Effect of local disturbance of bronchial patency on the circulation and gas exchange in the lungs  

SciTech Connect

The purpose of this paper was to obtain proof that alveolar hypoxia develops in the presence of local bronchial obstruction and to establish the role of the latter in disturbances of pulmonary circulation and gas exchange. Experiments were conducted on male mongrel dogs. Albumin microspheres labelled with technetium 99m were injected intravenously to trace the distribution and loss of blood flow.

Putov, N.V.; Danilov, D.N.; Lebedeva, E.S.; Chermenskii, Yu.V.

1987-06-01

179

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

E-print Network

reduction in the therapy of respiratory failure. Conclusions: Progress has been made toward developingA respiratory gas exchange catheter: In vitro and in vivo tests in large animals Brack G. Hattler, PhD Brian Frankowski, AD William J. Federspiel, PhD Objectives: Acute respiratory failure

Federspiel, William J.

180

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

E-print Network

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

Boyer, Edmond

181

Indirect effects of insect herbivory on leaf gas exchange in soybean  

Microsoft Academic Search

Herbivory can affect plant carbon gain directly by removing photosynthetic leaf tissue and indirectly by inducing the production of costly defensive compounds or disrupting the movement of water and nutrients. The indirect effects of herbivory on carbon and water fluxes of soybean leaves were investigated using gas exchange, chlorophyll fluores- cence and thermal imaging. Herbivory by Popillia japon- ica and

MIHAI ALDEA; JASON G. HAMILTON; JOSEPH P. RESTI; ARTHUR R. ZANGERL; MAY R. BERENBAUM; EVAN H. D eLUCIA

2005-01-01

182

The Effects of Body Mass on Lung Volumes, Respiratory Mechanics, and Gas Exchange During General Anesthesia  

Microsoft Academic Search

We investigated the effects of body mass index (BMI) on functional residual capacity (FRC), respiratory me- chanics (compliance and resistance), gas exchange, and the inspiratory mechanical work done per liter of venti- lation during general anesthesia. We used the esopha- geal balloon technique, together with rapid airway oc- clusion during constant inspiratory flow, to partition the mechanics of the respiratory

Paolo Pelosi; Massimo Croci; Irene Ravagnan; Stefano Tredici; Alessia Pedoto; Alfredo Lissoni; Luciano Gattinoni

1998-01-01

183

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

Microsoft Academic Search

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

Alan K. Knapp; Joseph B. Yavitt

1995-01-01

184

Inhibition by light of CO 2 evolution from dark respiration: Comparison of two gas exchange methods  

Microsoft Academic Search

Two approaches to determine the fraction (?) of mitochondrial respiration sustained during illumination by measuring CO2 gas exchange are compared. In single leaves, the respiration rate in the light (`day respiration' rate Rd) is determined as the ordinate of the intersection point of Aci curves at various photon flux densities and compared with the CO2 evolution rate in darkness (`night

Martin Peisker; Hannelore Apel

2001-01-01

185

Multicomponent transport in porous electrodes of proton exchange membrane fuel cells using the interdigitated gas distributors  

Microsoft Academic Search

Hydrodynamics of gases in the cathode of a proton exchange membrane fuel cell that is contacted to an interdigitated gas distributor are investigated using a steady-state multicomponent transport model. The model describes the two-dimensional flow patterns and the distributions of the gaseous species in the porous electrode and predicts the current density generated t the electrode and membrane interface as

Jung Seok Yi; T. van Nguyen

1999-01-01

186

The role of discontinuous gas exchange in insects: the chthonic hypothesis does not hold water  

Microsoft Academic Search

Insects breathe through valved openings (spiracles) in their cuticle. Many insects open and close their spiracles in a cyclic pattern (discontinuous gas-exchange cycles, or DGC). These cycles were observed over half a century ago, their hypothesized function being to minimize loss of water from the tracheal system. However, numerous recent studies have found that respiration accounts for a small fraction

Allen G. Gibbs; Robert A. Johnson

2004-01-01

187

ACCENTUATION OF GAS EXCHANGE GRADIENTS IN FLUSHES OF PONDEROSA PINE EXPOSED TO OZONE  

EPA Science Inventory

Patterns of O3 injury have been positively correlated with leaf age in deciduous trees and needle age-classes in conifers. his study was designed to determine the patterns of gas exchange within and between needle flushes and to determine how O3 affects those patterns. esults wil...

188

Quantifying biases in non-steady state chamber measurements of soil-atmosphere gas exchange  

Technology Transfer Automated Retrieval System (TEKTRAN)

Limitations of non-steady state (NSS) chamber methods for determining soil-to-atmosphere trace gas exchange rates have been recognized for several decades. Of these limitations, the so-called chamber effect is one of the most challenging to overcome. The chamber effect can be defined as the inhere...

189

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

E-print Network

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

Stiller, Volker

190

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...

191

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

Technology Transfer Automated Retrieval System (TEKTRAN)

Atmospheric carbon dioxide concentration affects both C3 carbon net assimilation as well as crop water use. Methods for measuring whole canopy gas exchange responses under carbon dioxide enrichment are needed for breeding programs aiming to develop crop cultivars resistant to stresses like drought i...

192

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

E-print Network

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 CO2, but no change in root/shoot ratio was observed. Quercus suber / carbon dioxide / photosynthesis

Paris-Sud XI, Université de

193

Cerebral autoregulation and gas exchange studied using a human cardiopulmonary model  

E-print Network

developed a model of the human cardiopulmonary (CP) system, which included the whole body circulatory system Dynamical Systems Group, Rice University, Houston 77005; 2 Baylor College of Medicine, Houston 77005; 3, lung and peripheral tissue gas exchange, and the central nervous system control of arterial pressure

194

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

E-print Network

Field studies of leaf gas exchanges in oil palm tree (Elaeis guineensis Jacq.) E. Dufrene B This study is part of a larger research pro- gram on climatic and biological factors affecting oil palm yield (A) in oil palm. Most of them have used young plants under laboratory conditions to study effects

Paris-Sud XI, Université de

195

A STAGE-BASED STUDY OF DROUGHT RESPONSE IN CRYPTANTHA FLAVA (BORAGINACEAE): GAS EXCHANGE, WATER USE  

E-print Network

A STAGE-BASED STUDY OF DROUGHT RESPONSE IN CRYPTANTHA FLAVA (BORAGINACEAE): GAS EXCHANGE, WATER USE in the frequency of major droughts, yet we know little about the consequences of drought for the demography (Boraginaceae) to determine how plants of different developmental stages respond to drought through changes

Wait, D. Alexander

196

Gas Exchange in Dry Seeds: Circadian Rhythmicity in the Absence of DNA Replication, Transcription, and Translation  

Microsoft Academic Search

A 24-hour rhythm of gas exchange has been detected in dry onion seeds. The rhythm persists in constant conditions, and its period appears to be independent of temperature. Since DNA replication, transcription, and perhaps translation do not occur in this quiescent state, it is concluded that the basic oscillation that defines circadian rhythmicity does not derive directly from these processes.

Truman R. Bryant

1972-01-01

197

Gas exchange in NASA's biomass production chamber - A preprototype closed human life support system  

NASA Technical Reports Server (NTRS)

The unique capabilities of the NASA biomass production chamber for monitoring and evaluating gas exchange rates are examined. Special emphasis is given to results with wheat and soybeans. The potential of the chamber as a preprototype of a closed human life support system is considered.

Corey, Kenneth A.; Wheeler, Raymond M.

1992-01-01

198

Oxygen-induced plasticity in tracheal morphology and discontinuous gas exchange cycles in cockroaches Nauphoeta cinerea.  

PubMed

The function and mechanism underlying discontinuous gas exchange in terrestrial arthropods continues to be debated. Three adaptive hypotheses have been proposed to explain the evolutionary origin or maintenance of discontinuous gas exchange cycles (DGCs), which may have evolved to reduce respiratory water loss, facilitate gas exchange in high CO2 and low O2 micro-environments, or to ameliorate potential damage as a result of oversupply of O2. None of these hypotheses have unequivocal support, and several non-adaptive hypotheses have also been proposed. In the present study, we reared cockroaches Nauphoeta cinerea in selected levels of O2 throughout development, and examined how this affected growth rate, tracheal morphology and patterns of gas exchange. O2 level in the rearing environment caused significant changes in tracheal morphology and the exhibition of DGCs, but the direction of these effects was inconsistent with all three adaptive hypotheses: water loss was not associated with DGC length, cockroaches grew fastest in hyperoxia, and DGCs exhibited by cockroaches reared in normoxia were shorter than those exhibited by cockroaches reared in hypoxia or hyperoxia. PMID:25378216

Bartrim, Hamish; Matthews, Philip G D; Lemon, Sussan; White, Craig R

2014-12-01

199

Elevated atmospheric CO2 and drought effects leaf gas exchange properties of barley.  

Technology Transfer Automated Retrieval System (TEKTRAN)

Since atmospheric CO2 concentration (Ca) continues to rise, global change seems inevitable. It seems prudent, therefore, to investigate the interactive effects that elevated Ca and drought will impart on the leaf gas exchange properties and subsequent growth response of an important cereal grain cr...

200

Ecosystem Warming Affects Vertical Distribution of Leaf Gas Exchange Properties and Water Relations of Spring Wheat  

Technology Transfer Automated Retrieval System (TEKTRAN)

The vertical distribution of gas exchange and water relations responses to full-season in situ infrared (IR) warming were evaluated for hard red spring wheat (Triticum aestivum L. cv. Yecora Rojo) grown in an open field in a semiarid desert region of the Southwest USA. A Temperature Free-Air Contro...

201

Gas Exchange and Water Relations Responses of Spring Wheat to Full-Season Infrared Warming  

Technology Transfer Automated Retrieval System (TEKTRAN)

Gas exchange and water relations were evaluated under full-season in situ infrared (IR) warming for hard red spring wheat (Triticum aestivum L. cv. Yecora Rojo) grown in an open field in a semiarid desert region of the southwest USA. A temperature free-air controlled enhancement (T-FACE) apparatus u...

202

Gas exchange and water relations responses of spring wheat to full-season infrared warming  

Technology Transfer Automated Retrieval System (TEKTRAN)

Gas exchange and water relations responses to full-season in situ infrared (IR) warming were evaluated for hard red spring wheat (Triticum aestivum L. cv. Yecora Rojo) grown in an open field in a semi-arid desert region of the Southwest USA. A Temperature Free-Air Controlled Enhancement (T-FACE) ap...

203

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

E-print Network

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

Niyogi, Dev

204

Influence of rain on air-sea gas exchange: Lessons from a model ocean David T. Ho,1,2  

E-print Network

Influence of rain on air-sea gas exchange: Lessons from a model ocean David T. Ho,1,2 Christopher J; published 1 July 2004. [1] Rain has been shown to significantly enhance the rate of air-water gas exchange experiments. In the ocean, the effects of rain are complicated by the potential influence of density

Ho, David

205

Gas exchange measurements, what can they tell us about the underlying limitations to photosynthesis? Procedures and sources of error  

Microsoft Academic Search

The principles, equipment and procedures for meas- uring leaf and canopy gas exchange have been described previously as has chlorophyll fluores- cence. Simultaneous measurement of the responses of leaf gas exchange and modulated chlorophyll fluorescence to light and CO2 concentration now pro- vide a means to determine a wide range of key bio- chemical and biophysical limitations on photo- synthesis

S. P. Long; C. J. Bernacchi

2003-01-01

206

Exchange instability of the two-dimensional electron gas in semiconductor quantum wells A. R. Gon~i,1  

E-print Network

Exchange instability of the two-dimensional electron gas in semiconductor quantum wells A. R. Gon-dimensional 2D electron gas formed in a modulation-doped GaAs/AlxGa1 xAs single quantum well undergoes a first- functional theory, which treat the 2D exchange potential exactly, show that this thermodynamical instability

Nabben, Reinhard

207

Effects of the exchange instability on collective spin and charge excitations of the two-dimensional electron gas  

E-print Network

and the compressibility of the electron gas were also found in the low-density regime, where exchange- interaction termsEffects of the exchange instability on collective spin and charge excitations of the two-dimensional electron gas P. Giudici, A. R. Goñi,* and C. Thomsen Institut für Festkörperphysik, Technische Universität

Nabben, Reinhard

208

Mercury gas exchanges over selected bare soil and flooded sites in the bay St. Franois wetlands (Qubec, Canada)  

Microsoft Academic Search

In order to evaluate and understand the mercury gas exchange processes in fluvial wetlands, related researches were initiated in a St. Lawrence River wetland (Bay St. Franois, Qu., Canada). Mercury fluxes were measured using dynamic flux chamber methods, coupled with an automatic mercury vapor analyzer (namely, Tekran, Model 2537A). Mercury airsurface gas exchanges as well as meteorological conditions were measured

Laurier Poissant; Martin Pilote; Philippe Constant; Conrad Beauvais; Hong H Zhang; Xiaohong Xu

2004-01-01

209

The Gas Exchange Experiment for life detection - The Viking Mars Lander.  

NASA Technical Reports Server (NTRS)

The Gas Exchange Experiment of the Viking mission accepts a sample of Martian soil, incubates this soil with nutrient medium, and periodically samples the enclosed atmosphere over this soil for the gases H2, N2, O2, Kr, and CO2. These gases are analyzed by an automated gas chromatograph, and the data are transmitted to earth. The design of the experiment and the qualitative and quantitative changes, if any, of gas composition should allow conclusions to be made on the presence of life on Mars. Data and theory substantiating this approach are presented.

Oyama, V. I.

1972-01-01

210

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

SciTech Connect

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.

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

1991-05-01

211

A three-dimensional multiscale model for gas exchange in fruit.  

PubMed

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 (Malusdomestica) 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

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

2011-03-01

212

EXCHANGE  

SciTech Connect

EXCHANGE is published monthly by the Idaho National Engineering Laboratory (INEL), a multidisciplinary facility operated for the US Department of Energy (DOE). The purpose of EXCHANGE is to inform computer users about about recent changes and innovations in both the mainframe and personal computer environments and how these changes can affect work being performed at DOE facilities.

Boltz, J.C. (ed.)

1992-09-01

213

Predict the temperature distribution in gas-to-gas heat pipe heat exchanger  

NASA Astrophysics Data System (ADS)

A theoretical model has been developed to investigate the thermal performance of a continuous finned circular tubing of an air-to-air thermosyphon-based heat pipe heat exchanger. The model has been used to determine the heat transfer capacity, which expresses the thermal performance of heat pipe heat exchanger. The model predicts the temperature distribution in the flow direction for both evaporator and condenser sections and also the saturation temperature of the heat pipes. The approach used for the present study considers row-by-row heat-transfer in evaporator and condenser sections of the heat pipe heat exchanger.

Azad, E.

2012-07-01

214

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

PubMed Central

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

Niemeyer, Emily D.; Brodbelt, Jennifer S.

2007-01-01

215

Active heat exchange thermal storage unit with pentaerythritol  

SciTech Connect

A latent thermal energy storage unit with pentaerythritol was developed, and in the storage unit an active heat transfer enhancement was performed. The phase change material, pentaerythritol, was mixed with a hydrocarbon heat transfer oil and this two-phase storage medium was stirred in a shell-coil type heat exchanger. Through the preliminary experiments in a glass vessel, a lab-scale storage unit of 1 kWh storage capacity was developed. The storage unit demonstrated the feature of latent thermal energy storage; constant-temperature output in both charge and discharge periods was observed.

Abe, Y.; Kamimoto, M.; Kanari, K.; Ozawa, T.; Sakamoto, R.; Takahashi, Y.

1984-08-01

216

Analysis of effect of the solubility on gas exchange in nonhomogeneous lungs  

NASA Technical Reports Server (NTRS)

A comparison is made of the gas exchange in nonhomogeneous lung models and in homogeneous lung models with the same total blood flow and ventilation. It is shown that the ratio of the rate of gas transfer of the inhomogeneous lung model over the rate of gas transfer of the homogeneous lung model as a function of gas solubility always has the qualitative features for gases with linear dissociation curves. This ratio is 1 for a gas with zero solubility and decreases to a single minimum. It subsequently rises to approach 1 as the solubility tends to infinity. The early portion of the graph of this function is convex, then after a single inflection point it is concave.

Colburn, W. E., Jr.; Evans, J. W.; West, J. B.

1974-01-01

217

Poly-Use Multi-Level Sampling Rod to Measure Soil-Gas Exchange in Glacier Forefield Soils  

NASA Astrophysics Data System (ADS)

The forefields of receding glaciers provide unique opportunities to investigate initial microbial processes in the vadose zone and their role in soil formation. Various studies revealed a surprising diversity of microbes and of their strategies to cope with the extreme conditions in this C- and N-limited environment. In the forefield of receding glaciers as well as in developed soils microorganisms are the driving force for the exchange of greenhouse gases between soil and atmosphere. However, in young and developing soils, little is known about soil-gas exchange and the activities of the involved microorganisms. Knowledge of soil-gas composition and gas diffusion at various depths in a soil profile allows for the precise calculation of gas fluxes among different depths within the vadose zone and at the soil-atmosphere boundary. The acquisition of undisturbed soil-gas samples at a high depth-resolution is difficult, and the estimation of soil-gas diffusion coefficients requires knowledge of volumetric water content at the exact location of gas sampling. By using conventional techniques, e.g. the burial of permanent probes, these tasks are virtually impossible to accomplish in a remote glacier forefield dominated by rocks and boulders. We developed a novel poly-use multi-level sampling rod (PULSAR) primarily consisting of two devices: a newly-designed multi-level sampler (MLS) for soil-gas sampling, and a commercially available profile probe (PR2) for non-invasive multi-level water content measurements. These devices fit into the same access tubes (ATs) of 1.1m length, which need to be pre-installed into the soil with the help of a steel rod. We modified the ATs to feature eight 1mm diameter holes each at 20 sampling depths in intervals of 5cm. Our MLS can be inserted into the ATs and allows for the selective extraction of soil-gas from each sampling depth. The interspaces between the sampling depths are sealed by inflatable rubber membranes for the time of sampling. Once soil-gas has been extracted, soil water content can be measured with the PR2 probe at each sampled depth. After gas concentration analysis, knowledge of water content and soil-gas composition at 20 different depths allows for the quantification of depth-resolved soil-gas fluxes and calculation of microbial production and degradation rates in situ with minimal disturbance. The PULSAR concept was applied to investigate greenhouse gas fluxes in the forefields of two receding glaciers on calcareous and siliceous bedrock in the Swiss Alps. We installed a total of 33 ATs distributed among three soil-age groups of approx. 10, 40 and 70 years. Soil-gas sampling and water content measurements were performed twice during the snow-free season. In between sampling, the ATs were sealed with inflatable rubber tubes featuring iButton temperature loggers. The resulting data will provide valuable insights into the development of gas exchange of these young soils, while illustrating the feasibility of the PULSAR in soils with high skeleton contents.

Nauer, P. A.; Schroth, M. H.; Zeyer, J. A.

2012-12-01

218

Scaling up a water-gas flow model with mass exchange A. Bourgeat1 M. Jurak2  

E-print Network

Scaling up a water-gas flow model with mass exchange A. Bourgeat1 M. Jurak2 1ICJ, UMR 5208-phase compressible flow with mass exchange Upscaling A. Bourgeat, M. Jurak () Water-gas flow CE-MoMaS, Calais Oct Oct 2006 A. Bourgeat, M. Jurak () Water-gas flow CE-MoMaS, Calais Oct 2006 1 / 31 #12;Outline Two

Rogina, Mladen

219

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

NASA Astrophysics Data System (ADS)

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.

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

2013-02-01

220

Submaximal exercise gas exchange is an important prognostic tool to predict adverse outcomes in heart failure  

PubMed Central

Aims Traditionally, VO2peak has been used to determine prognosis in heart failure; however, this measure has limitations. Hence, other exercise and gas exchange parameters measured submaximally, e.g. breathing efficiency (VE/VCO2), end-tidal CO2 (PETCO2), oxygen uptake efficiency slope (OUES), and circulatory power [ systolic blood pressure (SBP)], have been investigated. The aim of this study was to investigate the prognostic relevance of submaximal exercise gas exchange in heart failure patients. Method and results One hundred and thirty-two consecutive heart failure patients (mean age 56 12 years, ejection fraction 29 11%) performed peak treadmill testing. Gas exchange and haemodynamic variables were measured continuously. Gas exchange data obtained from the first 2 min of exercise and at a respiratory exchange ratio (RER) of 0.9 were the measurements of interest. Over a median follow-up period of 62.4 (range 0114) months, there were 44 endpoints (death or transplant). Univariate analysis demonstrated submaximal predictors of survival, which included VE/VCO2 slope and ratio, PETCO2, OUES, and circulatory power (P? 0.01). When these and additional submaximal variables were included together in the multivariable analysis, the strongest submaximal exercise predictive model (C-statistic 0.75) comprised data from the first stage of exercise (VE and circulatory power) and at an RER of 0.9 (VE/VCO2 ratio). The inclusion of VO2peak and demographic data, with submaximal data (VE/VCO2 ratio at an RER = 0.9), increased the predictiveness of the model (C-statistic 0.78). Conclusion Submaximal exercise measures provide useful prognostic information for predicting survival in heart failure. This form of testing is logistically easier, cheaper, and safer for patients compared with maximal exercise. PMID:21036777

Woods, Paul R.; Bailey, Kent R.; Wood, Christina M.; Johnson, Bruce D.

2011-01-01

221

Rapid hydraulic recovery in Eucalyptus pauciflora after drought: linkages between stem hydraulics and leaf gas exchange.  

PubMed

In woody plants, photosynthetic capacity is closely linked to rates at which the plant hydraulic system can supply water to the leaf surface. Drought-induced embolism can cause sharp declines in xylem hydraulic conductivity that coincide with stomatal closure and reduced photosynthesis. Recovery of photosynthetic capacity after drought is dependent on restored xylem function, although few data exist to elucidate this coordination. We examined the dynamics of leaf gas exchange and xylem function in Eucalyptus pauciflora seedlings exposed to a cycle of severe water stress and recovery after re-watering. Stomatal closure and leaf turgor loss occurred at water potentials that delayed the extensive spread of embolism through the stem xylem. Stem hydraulic conductance recovered to control levels within 6?h after re-watering despite a severe drought treatment, suggesting an active mechanism embolism repair. However, stomatal conductance did not recover after 10?d of re-watering, effecting tighter control of transpiration post drought. The dynamics of recovery suggest that a combination of hydraulic and non-hydraulic factors influenced stomatal behaviour post drought. PMID:23937187

Martorell, Sebasti; Diaz-Espejo, Antonio; Medrano, Hiplito; Ball, Marilyn C; Choat, Brendan

2014-03-01

222

Gas Flow Structure in Binary Systems with Mass Exchange Driven by Stellar Wind  

E-print Network

Results of calculations of the flow structure in binary systems with mass exchange driven by stellar wind are presented. 2D simulations have been carried out using the Roe-Oscher scheme. The fine grid we used allowed us to detect the details of the flow structure. In particular, it was found out that solutions with the wind velocity V of the order of the orbital velocity of the system Vs are unstable: in solutions with VVs -- the cone shock forms. Consideration of the minor variations of the wind velocity V around Vs shows that they can influence greatly the flow structure causing transition from disk accretion to the accretion from the flow. During the flow rearrangement period (the accretion disk destruction) the accretion rate increases in dozens times for a short time (~0.1 of the orbital period of the system). This change can result in the drop-off of the gas from the accretor that is usually associated with activity in these systems.

A. A. Boyarchuk; D. V. Bisikalo; E. Yu. Kilpio; O. A. Kuznetsov

2002-12-10

223

[Respiratory gas exchange and glucose uptake by the human spleen in situ (author's transl)].  

PubMed

Blood samples were taken from the splenic artery, vein and pulp of 16 patients suffering from lymphoproliferative diseases, essential thrombocytopenia or hereditary spherocytosis and undergoing early splenectomy. The relevant parameters of the respiratory gas exchange as well as glucose and lactate concentrations were determined in these samples. In no case did the thorough examination of the splenic tissue reveal any histopathologic aspects. Taking into account a mean splenic blood flow of 100 ml/100 g/min during anaesthesia, the mean oxygen consumption of the splenic tissue attains 1.1 ml/100 g/min. The glucose uptake and the lactate release show to be 9 mg/100 g/min and 5.2 mg/100 g/min, respectively. Despite high glucose uptake rates and pronounced glycolytic activities there is no evidence of the existence of low pH values, a glucose depletion or hypoxia in the normal spleen. In the normal spleen, therefore, the intrasplenic sequestration of red blood cells cannot be explained by unfavourable metabolic conditions. PMID:846185

Vaupel, P; Wendling, P; Thom, H; Fischer, T J

1977-03-01

224

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

PubMed

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

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

2014-01-01

225

Gas-exchange properties of developing cotton fruit  

SciTech Connect

Field studies were conducted to document the photosynthetic and respiratory properties of cotton (Gossypium hirsutum L.) fruit during ontogeny. Dark respiration by the developing boll averaged {minus}18.7 {mu}mol per meter squared per second for the first six days after anthesis and gradually declined to less than 16% of this value after 40 days. Diurnal patterns of respiration were age dependent and closely correlated with stomatal conductance of the capsule wall. Stomata of young fruit were highly responsive to diurnal signals but lost this capacity with increasing age. Radio-labeled carbon dioxide injected into the fruit was rapidly assimilated by the outer capsule wall in the light, while fiber and seed fixed significant carbon-14 activity in both the light and dark. These data indicate that cotton fruit are sites of carbon dioxide evolution, but also serve a role in the reassimilation of carbon dioxide and thereby, function as important sources of assimilate for reproductive development.

Wullschleger, S.D.; Oosterhuis, D.M. (Univ. of Arkansas, Fayetteville (USA))

1990-05-01

226

Laser photoacoustic spectroscopy of biosystems gas exchange with the atmosphere  

NASA Astrophysics Data System (ADS)

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.

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

1998-10-01

227

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

PubMed

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 pion-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 pion 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 pion under predicted increases in aridity in the southwestern USA. PMID:23461476

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

228

Reply to comment by X. Zhang on ``Measurements of air-sea gas exchange at high wind speeds in the Southern Ocean: Implications for  

E-print Network

Reply to comment by X. Zhang on ``Measurements of air-sea gas exchange at high wind speeds Exchange (SAGE) experiment [Ho et al., 2006]. Specifically, he assumes that we only analyzed the gas in fact, we were merely assessing existing wind speed/gas exchange relationships. In the following, we

Ho, David

229

Effects of soil temperature on gas exchange and mor-phological structure of shoot and root in 1 yr old Scots  

E-print Network

Effects of soil temperature on gas exchange and mor- phological structure of shoot and root in 1 yr. With regard to gas exchange and growth, soil temperature is often underoptimal in spring and early summer (S6 decreases (Lopushinsky and Kauf- mann, 1977) which leads to decreased gas exchange and growth. The aim

Paris-Sud XI, Université de

230

The Effect of Thermal Convection on Earth-Atmosphere CO2 Gas Exchange in Aggregated Soil  

NASA Astrophysics Data System (ADS)

Gas transport in soils and surface-atmosphere gas exchange are important processes that affect different aspects of soil science such as soil aeration, nutrient bio-availability, sorption kinetics, soil and groundwater pollution and soil remediation. Diffusion and convection are the two main mechanisms that affect gas transport, fate and emissions in the soils and in the upper vadose zone. In this work we studied CO2 soil-atmosphere gas exchange under both day-time and night-time conditions, focusing on the impact of thermal convection (TCV) during the night. Experiments were performed in a climate-controlled laboratory. One meter long columns were packed with matrix of different grain size (sand, gravel and soil aggregates). Air with 2000 ppm CO2 was injected into the bottom of the columns and CO2 concentration within the columns was continuously monitored by an Infra Red Gas Analyzer. Two scenarios were compared for each soil: (1) isothermal conditions, representing day time conditions; and (2) thermal gradient conditions, i.e., atmosphere colder than the soil, representing night time conditions. Our results show that under isothermal conditions, diffusion is the major mechanism for surface-atmosphere gas exchange for all grain sizes; while under night time conditions the prevailing mechanism is dependent on the air permeability of the matrix: for sand and gravel it is diffusion, and for soil aggregates it is TCV. Calculated CO2 flux for the soil aggregates column shows that the TCV flux was three orders of magnitude higher than the diffusive flux.

Ganot, Y.; Weisbrod, N.; Dragila, M. I.

2011-12-01

231

Operation of an experimental algal gas exchanger for use in a CELSS  

NASA Technical Reports Server (NTRS)

Concepts of a CELSS anticipate the use of photosynthetic organisms for air revitalization. The rates of production and uptake of carbon dioxide and oxygen between the crew and the photosynthetic organisms are mismatched. An algal system used for gas exchange only will have the difficulty of an accumulation or depletion of these gases beyond physiologically tolerable limits. The results of a study designed to test the feasibility of using environmental manipulations to maintain physiologically appropriate atmospheres for algae (Chlorella pyrenoidosa) and mice (Mus musculus strain DW/J) in a gas-closed system is reported. Specifically, the atmosphere behavior of this system with Chlorella grown on nitrate or urea and at different light intensities and optical densities is considered. Manipulation of both the photosynthetic rate and the assimilatory quotient of the alga has been found to reduce the mismatch of gas requirements and allow operation of the system in a gas-stable manner.

Smernoff, David T.; Wharton, Robert A., Jr.; Averner, Maurice M.

1987-01-01

232

Oxygen-sulfur exchange and the gas-phase reactivity of cobalt sulfide cluster anions with molecular oxygen.  

PubMed

We present here a study of gas-phase reactivity of cobalt sulfide cluster anions Co(m)S(n)(-) with molecular oxygen. Nascent Co(m)S(n)(-) clusters were prepared via a laser ablation source and reacted with oxygen in a fast flow reactor under thermal collision conditions. We chose (18)O2 in place of (16)O2 to avoid mass degeneration with sulfur, and a time-of-flight (TOF) mass spectrometer was used to detect the cluster distributions in the absence and presence of the reactant. It was found that oxygen-sulfur exchange occurs in the reactions for those with specific compositions (CoS)(n)(-) and (CoS)(n)S(-) (n = 2-5) according to a consistent pathway, "Co(m)S(n)(-) + (18)O2 ? Co(m)S(n-1)(18)O(-) + S(18)O". Typically, for "Co2S2(-) + (18)O2" we have calculated the reaction coordinates by employing the density functional theory (DFT), where both the oxygen-sulfur exchange and SO molecule release are thermodynamically and kinetically favorable. It is noteworthy that the reaction with molecular oxygen (triplet ground state) needs to overcome a spin excitation as well as a large O-O activation energy. This study sheds light on the activation of molecular oxygen by cobalt sulfides on one hand and also provides insight into the regeneration mechanism of cobalt oxides from the counterpart sulfides in the presence of oxygen gas on the other hand. PMID:24588651

Jia, Mei-Ye; Luo, Zhixun; He, Sheng-Gui; Ge, Mao-Fa

2014-09-18

233

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

SciTech Connect

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.

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

1991-05-01

234

Effects of long-term ozone fumigations on growth and gas exchange of Fraser fir seedlings.  

PubMed

Fraser fir seedlings from two seed sources in the Southern Appalachians (Mt Mitchell, North Carolina, a declining population; and Mt Rogers, Virginia, a relatively healthy population) were subjected to long-term (2.5 years) intermittent ozone fumigations (0.025, 0.070, and 0.150 ppm) while being grown through five growth cycles in an accelerated-growing regime. Fumigations took place during bud break, stem elongation and bud set. Following each growing cycle, gas exchange parameters and dry weights were determined. The ozone fumigations did not produce any effect on seedling growth. The ozone fumigation effects on gas exchange parameters were inconsistent, and generally not statistically different, with no differences occurring between seed sources. There was no correlation between photosynthetic rates and seedling growth. These results provide no evidence that ozone may be contributing to the differences in decline noted between the Mt Rogers and Mt Mitchell populations of Fraser fir. PMID:15091656

Seiler, J R; Tyszko, P B; Chevone, B I

1994-01-01

235

Organic iodine removal from simulated dissolver off-gas systems utilizing silver-exchanged mordenite  

SciTech Connect

The removal of methyl iodide by adsorption onto silver mordenite was studied using a simulated off-gas from the fuel dissolution step of a nuclear fuel reprocessing plant. The adsorption of methyl iodide on silver mordenite was examined for the effect of NO/sub x/, humidity, iodine concentration, filter temperature, silver loadings and filter pretreatment. The highest iodine loading achieved in these tests was 142 mg CH/sub 3/I per g of substrate on fully exchanged zeolite, approximately the same as elemental iodine loadings. A filter using fully exchanged silver mordenite operating at 200/sup 0/C obtained higher iodine loadings than a similar filter operating at 150/sup 0/C. Pretreatment of the sorbent bed with hydrogen rather than dry air, at a temperature of 200/sup 0/C, also improved the loading. Variations in the methyl iodide concentration had minimal effects on the overall loading. Filters exposed to moist air streams attained higher loadings than those in contact with dry air. Partially exchanged silver mordenite achieved higher silver utilizations than the fully exchanged material. The partially exchanged mordenite also achieved higher loadings at 200/sup 0/C than at 250/sup 0/C. The iodine loaded onto these beds was not stripped at 500/sup 0/C by either 4.5% hydrogen or 100% hydrogen; however, the iodine could be removed by air at 500/sup 0/C, and the bed could be reloaded. A study of the regeneration characteristics of fully exchanged silver mordenite indicates limited adsorbent capacity after complete removal of the iodine with 4.5% hydrogen in the regeneration gas stream at 500/sup 0/C. The loss of adsorbent capacity is much higher for silver mordenite regenerated in a stainless steel filter housing than in a glass filter housing.

Jubin, R.T.

1981-01-01

236

Air-water gas exchange and CO2 flux in a mangrove-dominated estuary  

USGS Publications Warehouse

Mangrove forests are highly productive ecosystems, but the fate of mangrove-derived carbon remains uncertain. Part of that uncertainty stems from the fact that gas transfer velocities in mangrove-surrounded waters are not well determined, leading to uncertainty in air-water CO2 fluxes. Two SF6 tracer release experiments were conducted to determine gas transfer velocities (k(600)?=?8.3??0.4 and 8.1??0.6?cm?h?1), along with simultaneous measurements of pCO2 to determine the air-water CO2 fluxes from Shark River, Florida (232.11??23.69 and 171.13??20.28?mmol C m?2 d?1), an estuary within the largest contiguous mangrove forest in North America. The gas transfer velocity results are consistent with turbulent kinetic energy dissipation measurements, indicating a higher rate of turbulence and gas exchange than predicted by commonly used wind speed/gas exchange parameterizations. The results have important implications for carbon fluxes in mangrove ecosystems.

Ho, David T.; Ferrn, Sara; Engel, Victor C.; Larsen, Laurel G.; Barr, Jordan G.

2014-01-01

237

Air-water gas exchange and CO2 flux in a mangrove-dominated estuary  

NASA Astrophysics Data System (ADS)

forests are highly productive ecosystems, but the fate of mangrove-derived carbon remains uncertain. Part of that uncertainty stems from the fact that gas transfer velocities in mangrove-surrounded waters are not well determined, leading to uncertainty in air-water CO2 fluxes. Two SF6 tracer release experiments were conducted to determine gas transfer velocities (k(600) = 8.3 0.4 and 8.1 0.6 cm h-1), along with simultaneous measurements of pCO2 to determine the air-water CO2 fluxes from Shark River, Florida (232.11 23.69 and 171.13 20.28 mmol C m-2 d-1), an estuary within the largest contiguous mangrove forest in North America. The gas transfer velocity results are consistent with turbulent kinetic energy dissipation measurements, indicating a higher rate of turbulence and gas exchange than predicted by commonly used wind speed/gas exchange parameterizations. The results have important implications for carbon fluxes in mangrove ecosystems.

Ho, David T.; Ferrn, Sara; Engel, Victor C.; Larsen, Laurel G.; Barr, Jordan G.

2014-01-01

238

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

SciTech Connect

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)

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

2006-07-01

239

Adsorbed natural gas storage with activated carbon  

SciTech Connect

Despite technical advances to reduce air pollution emissions, motor vehicles still account for 30 to 70% emissions of all urban air pollutants. The Clean Air Act Amendments of 1990 require 100 cities in the United States to reduce the amount of their smog within 5 to 15 years. Hence, auto emissions, the major cause of smog, must be reduced 30 to 60% by 1998. Natural gas con be combusted with less pollutant emissions. Adsorbed natural gas (ANG) uses adsorbents and operates with a low storage pressure which results in lower capital costs and maintenance. This paper describes the production of an activated carbon adsorbent produced from an Illinois coal for ANG.

Sun, Jian; Brady, T.A.; Rood, M.J. [Univ. of Illinois, Urbana, IL (United States)] [and others

1996-12-31

240

Growing season ecosystem and leaf-level gas exchange of an exotic and native semiarid bunchgrass  

Microsoft Academic Search

The South African grass, Lehmann lovegrass (Eragrostis lehmanniana), may alter ecosystem processes across extensive semiarid grasslands and savannahs of western North America. We compared\\u000a volumetric soil moisture (?), total and green tissue leaf area index (LAI), ecosystem (i.e. whole-plant and soil), and leaf-level gas exchange of Lehmann\\u000a lovegrass and the native bush muhly (Muhlenbergia porteri) over the 2008 monsoon season

Erik P. Hamerlynck; Russell L. Scott; M. Susan Moran; Timothy O. Keefer; Travis E. Huxman

2010-01-01

241

Gas exchange at extreme altitude: results from the British 40th Anniversary Everest Expedition  

Microsoft Academic Search

Gas exchange at high extreme altitude: results from the British 40th Anniversary Everest Expedition. A.J. Peacock, P.L. Jones. ERS Journals Ltd 1997. ABSTRACT: Since Messner and Habeler climbed to the summit of Mount Everest (8,848 m) without oxygen in 1978, there has been controversy between scientists trying to explain this feat. Field studies have suggested better respiratory perfor- mance than

A. J. Peacock; P. L. Jones

1997-01-01

242

Gas Exchange and Water Use Efficiency of Three Native Tree Species in Hunshandak Sandland of China  

Microsoft Academic Search

Only three tree species, i.e. Ulmus pumila, Malus baccata, and Prunus padus, are distributed in Hunshandak Sandland (HS) in Inner Mongolia, China. Field studies of gas exchange and chlorophyll (Chl)\\u000a fluorescence of these three tree species were conducted in three arid periods of growth season 2002. Net photosynthetic rate\\u000a (P\\u000a N), transpiration rate (E), stomatal conductance (g\\u000a s), and Fv\\/Fm

Y. G. Li; G. M. Jiang; S. L. Niu; M. Z. Liu; Y. Peng; S. L. Yu; L. M. Gao

2003-01-01

243

Growth and gas exchange response to water shortage of a maize crop on different soil types  

Microsoft Academic Search

The effect of water shortage on growth and gas exchange of maize grown on sandy soil (SS) and clay soil was studied. The lower\\u000a soil water content in the SS during vegetative growth stages did not affect plant height, above-ground biomass, and leaf area\\u000a index (LAI). LAI reduction was observed on the SS during the reproductive stage due to early

Luca Vitale; Paul Di Tommasi; Carmen Arena; Michele Riondino; Annachiara Forte; Angelo Verlotta; Angelo Fierro; Amalia Virzo De Santo; Amodio Fuggi; Vincenzo Magliulo

2009-01-01

244

Alterations in gas exchange after aerolized orciprenaline in relation to obstruction and hypoxemia  

Microsoft Academic Search

Summary The effect of orciprenaline inhalation on gas exchange was studied in 27 patients with obstructive lung disease and 9 patients without airway obstructive lung disease and 9 patients without airway obstruction. Significant increases of AaDO2 and VD\\/VT were reccorded in patients with marked obstruction and marked hypoxemia. Decreases of arterial oxygen tension were more pronounced in patients with slight

R. Thoma; G. Siemon; R. Keller

1975-01-01

245

Worsening of pulmonary gas exchange with nitric oxide inhalation in chronic obstructive pulmonary disease  

Microsoft Academic Search

SummaryBackground Inhalation of nitric oxide (NO) causes selective pulmonary vasodilation and improves arterial oxygenation in acute respiratory distress syndrome. But some patients do not respond or gas exchange worsens when inhaling NO. We hypothesised that this detrimental effect might be related to the reversion of hypoxic vasoconstriction in those patients where this mechanism contributes to ventilation-perfusion ( V?A\\/ Q?) matching.Methods

J. A Barber; N Roger; J Roca; R Rodriguez-Roisin; I Rovira; T. W Higenbottam

1996-01-01

246

A gas-exchange study of photosynthesis and isoprene emission in Quercus rubra L  

Microsoft Academic Search

We have investigated the signals which affect the rate of isoprene emission from photosynthesizing leaves of red oak (Quercus rubra L.) using analytical gas-exchange techniques, chlorophyll-fluorescence measurements, and inhibitor feeding. Isoprene emission\\u000a increased with increasing photon flux density at low CO2 but much less so at high CO2 partial pressure. Photosynthetic CO2 assimilation exhibited the opposite behavior. In CO2-free air,

Francesco Loreto; Thomas D. Sharkey

1990-01-01

247

Effects of the Prone Position on Respiratory Mechanics and Gas Exchange during Acute Lung Injury  

Microsoft Academic Search

We studied 16 patients with acute lung injury receiving volume-controlled ventilation to assess the relationships between gas exchange and respiratory mechanics before, during, and after 2 h in the prone position. We measured the end-expiratory lung volume (EELV, helium dilution), the total respi- ratory system (Cst,rs), the lung (Cst,L) and the thoracoabdominal cage (Cst,w) compliances (end- inspiratory occlusion technique and

PAOLO PELOSI; DANIELA TUBIOLO; DANIELE MASCHERONI; PIERLUIGI VICARDI; STEFANIA CROTTI; FRANCO VALENZA; LUCIANO GATTINONI

1998-01-01

248

The gas exchange of hydrogen-adapted algae as followed by mass spectrometry.  

NASA Technical Reports Server (NTRS)

The combination of a mass spectrometer inlet and an oxygen electrode in the same vessel permitted continuous recording of the gas exchange of hydrogenase-containing anaerobically adapted algae. In contrast to conventional manometry, the present method made it possible to discern the simultaneous course of reactions involving O2, CO2, and H2. The experiments strongly support the idea of a balance between the photoproduction and photoutilization of H2.

Stuart, T. S.; Gaffron, H.

1972-01-01

249

Impairment of gas exchange and structure in birch leaves ( Betula pendula ) caused by low ozone concentrations  

Microsoft Academic Search

Injury caused by low O3 concentrations (0, 0.05, 0.075, 0.1 l 1-1) was analyzed in the epidermis and mesophyll of fully developed birch leaves by gas exchange experiments and low-temperature SEM: (I) after leaf formation in O3-free and ozonated air, and (II) after transferring control plants into ozonated air. In control leaves, autumnal senescence also was studied in O3-free air

Rainer Matyssek; Madeleine S. Giinthardt-Goerg; Theodor Keller; Christoph Scheidegger

1991-01-01

250

Leaf gas exchange characteristics of three neotropical mangrove species in response to varying hydroperiod  

USGS Publications Warehouse

We determined how different hydroperiods affected leaf gas exchange characteristics of greenhouse-grown seedlings (2002) and saplings (2003) of the mangrove species Avicennia germinans (L.) Stearn., Laguncularia racemosa (L.) Gaertn. f., and Rhizophora mangle L. Hydroperiod treatments included no flooding (unflooded), intermittent flooding (intermittent), and permanent flooding (flooded). Plants in the intermittent treatment were measured under both flooded and drained states and compared separately. In the greenhouse study, plants of all species maintained different leaf areas in the contrasting hydroperiods during both years. Assimilation-light response curves indicated that the different hydroperiods had little effect on leaf gas exchange characteristics in either seedlings or saplings. However, short-term intermittent flooding for between 6 and 22 days caused a 20% reduction in maximum leaf-level carbon assimilation rate, a 51% lower light requirement to attain 50% of maximum assimilation, and a 38% higher demand from dark respiration. Although interspecific differences were evident for nearly all measured parameters in both years, there was little consistency in ranking of the interspecific responses. Species by hydroperiod interactions were significant only for sapling leaf area. In a field study, R. mangle saplings along the Shark River in the Everglades National Park either demonstrated no significant effect or slight enhancement of carbon assimilation and water-use efficiency while flooded. We obtained little evidence that contrasting hydroperiods affect leaf gas exchange characteristics of mangrove seedlings or saplings over long time intervals; however, intermittent flooding may cause short-term depressions in leaf gas exchange. The resilience of mangrove systems to flooding, as demonstrated in the permanently flooded treatments, will likely promote photosynthetic and morphological adjustment to slight hydroperiod shifts in many settings. ?? 2006 Heron Publishing.

Krauss, K.W.; Twilley, R.R.; Doyle, T.W.; Gardiner, E.S.

2006-01-01

251

Differential leaf gas exchange responses to salinity and drought in the mangrove tree Avicecennia germinans (Avicenniaceae)  

Microsoft Academic Search

Leaf gas exchange was assessed in Avicennia germinans L. grown under different NaCl concentra- tions (0-40), after salt-relief, and then during drought. Stomatal conductance (gs) and net photosynthetic rate (Pn) decreased with increasing NaCl concentration, and intrinsic water use efficiency (Pn \\/ gs) increased. Under desalinization Pn \\/ gs declined. Thus, gs did not change in plants grown at low

M. A. Sobrado

2006-01-01

252

Constraining global air-sea gas exchange for CO2 with recent bomb 14C measurements  

Microsoft Academic Search

The 14CO2 released into the stratosphere during bomb testing in the early 1960s provides a global constraint on air-sea gas exchange of soluble atmospheric gases like CO2. Using the most complete database of dissolved inorganic radiocarbon, DI14C, available to date and a suite of ocean general circulation models in an inverse mode we recalculate the ocean inventory of bomb-produced DI14C

Colm Sweeney; Emanuel Gloor; Andrew R. Jacobson; Robert M. Key; Galen McKinley; Jorge L. Sarmiento; Rik Wanninkhof

2007-01-01

253

Gas exchange responses to constant work rate exercise in chronic cardiac failure.  

PubMed Central

OBJECTIVE--To examine the time course of changes in minute oxygen consumption and other gas exchange variables and heart rate during constant work rate exercise in patients with chronic cardiac failure. DESIGN--Treadmill exercise with on line measurement of gas exchange and a target duration of 10 minutes. SUBJECTS--Seven men in New York Heart Association class II, six in class III, and seven controls. MAIN OUTCOME MEASURES--Gas exchange variables and heart rate were averaged for the final two minutes of exercise. Time constants were calculated for the increase in all variables. RESULTS--Consumption of oxygen at the end of exercise (VO2) was similar in class II patients (mean (95% confidence interval (95% CI) 14.9 (13.6 to 16.1) ml kg-1 min-1), class III patients (13.2 (11.2 to 15.1) ml kg-1 min-1), and controls (13.3 (12.5 to 14.2) ml kg-1 min-1). The patients reached this VO2 more slowly with longer exponential time constants of 0.82 (0.59 to 1.04) min in class II and 1.19 (0.86 to 1.51) min in class III, than the 0.49 (0.35 to 0.64) min in the controls. Time constants of other gas exchange variables and heart rate were also longer in patients. By analysis of covariance, peak VO2 accounted for the between group difference in the time constant for VO2, suggesting that circulatory factors may be an important cause of the delayed kinetics. CONCLUSIONS--A delayed rise in VO2 in response to exercise may be responsible for subnormal values of VO2 early in exercise in patients with chronic cardiac failure. PMID:7917688

Riley, M; Prszsz, J; Stanford, C F; Nicholls, D P

1994-01-01

254

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

PubMed

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

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

2000-01-01

255

Carbon Isotope Discrimination, Gas Exchange, and Growth of Sugarcane Cultivars under Salinity.  

PubMed

Physiological features associated with differential resistance to salinity were evaluated in two sugarcane (Saccharum spp. hybrid) cultivars over an 8-week period during which greenhouse-grown plants were drip-irrigated with water or with NaCI solutions of 2, 4, 8, or 12 decisiemens (dS) m-1 electrical conductivity (EC). The CO2 assimilation rate (A), stomatal conductance (g), and shoot growth rate (SGR) began to decline as EC of the irrigation solution increased above 2 dS m-1. A, g, and SGR of a salinity-resistant cultivar (H69-8235) were consistently higher than those of a salinity-susceptible cultivar (H65-7052) at all levels of salinity and declined less sharply with increasing salinity. Carbon isotope discrimination ([delta]) in tissue obtained from the uppermost fully expanded leaf increased with salinity and with time elapsed from the beginning of the experiment, but [delta] was consistently lower in the resistant than in the susceptible cultivar at all levels of salinity. Gas-exchange measurements suggested that variation in [delta] was attributable largely to variation in bundle sheath leakiness to CO2 ([phi]). Salinity-induced increases in [phi] appeared to be caused by a reduction in C3 pathway activity relative to C4 pathway activity rather than by physical changes in the permeability of the bundle sheath to CO2. A strong correlation between [delta] and A, g, and SGR permitted these to be predicted from [delta] regardless of the cultivar and salinity level. [delta] thus provided an integrated measure of several components of physiological performance and response. PMID:12232101

Meinzer, F. C.; Plaut, Z.; Saliendra, N. Z.

1994-02-01

256

Modulating the light environment with the peach asymmetric orchard: effects on gas exchange performances, photoprotection, and photoinhibition  

PubMed Central

The productivity of fruit trees is a linear function of the light intercepted, although the relationship is less tight when greater than 50% of available light is intercepted. This paper investigates the management of light energy in peach using the measurement of whole-tree light interception and gas exchange, along with the absorbed energy partitioning at the leaf level by concurrent measurements of gas exchange and chlorophyll fluorescence. These measurements were performed on trees of a custom-built asymmetric orchard. Whole-tree gas exchange for northsouth, vertical canopies (C) was similar to that for canopies intercepting the highest irradiance in the morning hours (W), but trees receiving the highest irradiance in the afternoon (E) had the highest net photosynthesis and transpiration while maintaining a water use efficiency (WUE) comparable to the other treatments. In the W trees, 29% and 8% more photosystems were damaged than in C and E trees, respectively. The quenching partitioning revealed that the non-photochemical quenching (NPQ) played the most important role in excess energy dissipation, but it was not fully active at low irradiance, possibly due to a sub-optimal trans-thylakoid ?pH. The non-net carboxylative mechanisms (NC) appeared to be the main photoprotective mechanisms at low irradiance levels and, probably, they could facilitate the establishment of a trans-thylakoid ?pH more appropriate for NPQ. These findings support the conclusion that irradiance impinging on leaves may be excessive and can cause photodamage, whose repair requires energy in the form of carbohydrates that are thereby diverted from tree growth and productivity. PMID:20124356

Losciale, Pasquale; Chow, Wah Soon; Corelli Grappadelli, Luca

2010-01-01

257

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

PubMed Central

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

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

2014-01-01

258

Effects of local gas diffusion layer gas permeability variations on spatial proton exchange membrane fuel cells performance  

NASA Astrophysics Data System (ADS)

The effects of local gas diffusion layer (GDL) gas permeability variation and its location on spatial and overall proton exchange membrane fuel cell (PEMFC) performance were studied using a segmented cell approach. Variations in the physical and chemical parameters of the main membrane electrode assembly's (MEA) components (e.g., the membrane, electrode, and GDL) are considered defects and might negatively affect fuel cell performance. An artificial GDL defect was introduced by exchanging a standard (or intact) cathode GDL at one segment (segment 4 or 9) with a defective GDL. The standard and defective cathode GDLs had different through-plane gas permeabilities, while values were similar for in-plane permeability and some other structural parameters. The effects from a defective GDL were observed at a high current. Introducing a highly permeable GDL as a defect increased local performance due to a decrease in mass-transfer overpotential. For a defective GDL with lower permeability than the standard GDL, a local performance decrease was observed because mass-transfer losses increased. Simultaneously, downstream segment performance improved, which might be due to changes in water management. Defect localization at the cell outlet resulted in the detection of the defect at a lower current density compared with localization at the cell inlet. Spatial polarization curves (VI) and electrochemical impedance spectroscopy (EIS) facilitated detection and localization of GDL defects. Thus it was demonstrated that the local GDL anomalies are detectable by the segmented cell system.

Reshetenko, Tatyana V.; St-Pierre, Jean; Rocheleau, Richard

2013-11-01

259

Making Activated Carbon for Storing Gas  

NASA Technical Reports Server (NTRS)

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.

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

2005-01-01

260

Gas exchange  

MedlinePLUS Videos and Cool Tools

... lungs to the bloodstream, and the elimination of carbon dioxide from the bloodstream to the lungs. It occurs ... membrane with the capillaries in which oxygen and carbon dioxide move freely between the respiratory system and the ...

261

Exchange of structurally bound phosphate in muscular activity  

PubMed Central

1. When rectus abdominis and sartorius muscles of the frog are incubated with 32P-orthophosphate and subsequently minced, extracted with carbonate-bicarbonate buffer and water, and converted to acetone powders, considerable radioactivity remains associated with the solid material. 2. Muscles labelled with 32P and subjected to contracture at room temperature with KCl or ACh yield acetone powders which, in comparison with those of uncontracted control muscles, show a significantly decreased radioactivity. There is no evidence for a corresponding decrease in the total phosphate content. 3. Relaxation of a contracted muscle restores the 32P content of its acetone powder at least to the level for a resting, control muscle. 4. When two recti are incubated with 5 10-4 M-DNP after labelling with 32P, subsequent depolarization of one muscle with KCl usually results in an increase in the activity of the bound phosphate fraction, with little or no contracture in addition to that already caused by the DNP. 5. It is concluded that the bound phosphate fraction undergoes exchange during activation, shortening and relaxation of muscle, and may represent a source of energy for muscular activity. PMID:5919564

Cheesman, D. F.; Hilton, Elizabeth

1966-01-01

262

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

Microsoft Academic Search

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

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

1996-01-01

263

Parameterization of Leaf-Level Gas Exchange for Plant Functional Groups From Amazonian Seasonal Tropical Rain Forest  

Microsoft Academic Search

Plant communities exert strong influence over the magnitude of carbon and water cycling through ecosystems by controlling photosynthetic gas exchange and respiratory processes. Leaf-level gas exchange fluxes result from a combination of physiological properties, such as carboxylation capacity, respiration rates and hydraulic conductivity, interacting with environmental drivers such as water and light availability, leaf-to-air vapor pressure deficit, and temperature. Carbon

T. F. Domingues; J. A. Berry; J. P. Ometto; L. A. Martinelli; J. R. Ehleringer

2004-01-01

264

Dynamics of Exchange at Gas-Zeolite Interfaces 1: Pure Component n-Butane and Isobutane  

SciTech Connect

The authors present the results of molecular dynamics simulations of n-butane and isobutane in silicalite. They begin with a comparison of the bulk adsorption and diffusion properties for two different parameterizations of the interaction potential between the hydrocarbon species, both of which have been shown to reproduce experimental gas-liquid coexistence curves. They examine diffusion as a function of the loading of the zeolite, as well as the temperature dependence of the diffusion constant at loading and for infinite dilution. They continue with simulations in which interfaces are formed between single component gases and the zeolite. After reaching equilibrium, they examine the dynamics of exchange between the bulk gas and the zeolite. Finally, they calculate the permeability of the zeolite for n-butane and isobutane as a function of pressure. Their simulations are performed for a number of different gas temperatures and pressures, covering a wide range of state points.

CHANDROSS,MICHAEL E.; WEBB III,EDMUND B.; GREST,GARY S.; MARTIN,MARCUS G.; THOMPSON,AIDAN P.; ROTH,M.W.

2000-07-13

265

The Viking gas exchange experiment results from Chryse and Utopia surface samples  

NASA Technical Reports Server (NTRS)

Immediate gas changes occurred when untreated Martian surface samples were humidified and/or wet by an aqueous nutrient medium in the Viking lander gas exchange experiment. The evolutions of N2, CO2, and Ar are mainly associated with soil surface desorption caused by water vapor, while O2 evolution is primarily associated with decomposition of superoxides inferred to be present on Mars. On recharges with fresh nutrient and test gas, only CO2 was given off, and its rate of evolution decreased with each recharge. This CO2 evolution is thought to come from the oxidation of organics present in the nutrient by gamma Fe2O3 in the surface samples. Atmospheric analyses were also performed at both sites. The mean atmospheric composition from four analyses is N2, 2.3%; O2, not greater than 0.15%; Ar, 1.5% and CO2, 96.2%.

Oyama, V. I.; Berdahl, B. J.

1977-01-01

266

A Multivariable Index for Grading Exercise Gas Exchange Severity in Patients with Pulmonary Arterial Hypertension and Heart Failure  

PubMed Central

Patients with pulmonary arterial hypertension (PAH) and heart failure (HF) display many abnormalities in respiratory gas exchange. These abnormalities are accentuated with exercise and track with disease severity. However, use of gas exchange measures in day-to-day clinical practice is limited by several issues, including the large number of variables available and difficulty in data interpretation. Moreover, maximal exercise testing has limitations in clinical populations due to their complexity, patient anxiety and variability in protocols and cost. Therefore, a multivariable gas exchange index (MVI) that integrates key gas exchange variables obtained during submaximal exercise into a severity score that ranges from normal to severe-very-severe is proposed. To demonstrate the usefulness of this index, we applied this to 2 groups (PAH, n = 42 and HF, n = 47) as well as to age matched healthy controls (n = 25). We demonstrate that this score tracks WHO classification and right ventricular systolic pressure in PAH (r = 0.53 and 0.73, P ? 0.01) and NYHA and cardiac index in HF (r = 0.49 and 0.74, P ? 0.01). This index demonstrates a stronger relationship than any single gas exchange variable alone. In conclusion, MVI obtained from light, submaximal exercise gas exchange is a useful approach to simplify data interpretation in PAH and HF populations. PMID:23346397

Kim, Chul-Ho; Anderson, Steve; MacCarter, Dean; Johnson, Bruce

2012-01-01

267

The impact of lower sea-ice extent on Arctic greenhouse-gas exchange  

USGS Publications Warehouse

In September 2012, Arctic sea-ice extent plummeted to a new record low: two times lower than the 19792000 average. Often, record lows in sea-ice cover are hailed as an example of climate change impacts in the Arctic. Less apparent, however, are the implications of reduced sea-ice cover in the Arctic Ocean for marineatmosphere CO2 exchange. Sea-ice decline has been connected to increasing air temperatures at high latitudes. Temperature is a key controlling factor in the terrestrial exchange of CO2 and methane, and therefore the greenhouse-gas balance of the Arctic. Despite the large potential for feedbacks, many studies do not connect the diminishing sea-ice extent with changes in the interaction of the marine and terrestrial Arctic with the atmosphere. In this Review, we assess how current understanding of the Arctic Ocean and high-latitude ecosystems can be used to predict the impact of a lower sea-ice cover on Arctic greenhouse-gas exchange.

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

2013-01-01

268

Effect of multi-stream heat exchanger on performance of natural gas liquefaction with mixed refrigerant  

NASA Astrophysics Data System (ADS)

A thermodynamic study is carried out to investigate the effect of multi-stream heat exchanger on the performance of natural gas (NG) liquefaction with mixed refrigerant (MR). A cold stream (low-pressure MR) is in thermal contact with opposite flow of two hot streams (high-pressure MR and NG feed) at the same time. In typical process simulation with commercial software (such as Aspen HYSYS), the liquefaction performance is estimated with a method of minimum temperature approach, simply assuming that two hot streams have the same temperature. In this study, local energy balance equations are rigorously solved with temperature-dependent properties of MR and NG feed, and are linked to the thermodynamic cycle analysis. The figure of merit (FOM) is quantitatively examined in terms of UA (the product of overall heat transfer coefficient and heat exchange area) between respective streams. In a single-stage MR process, it is concluded that the temperature profile from HYSYS is difficult to realize in practice, and the FOM value from HYSYS is an over-estimate, but can be closely achieved with a proper heat-exchanger design. It is also demonstrated that there exists a unique optimal ratio in three UA's, and no direct heat exchanger between hot streams is recommended.

Chang, Ho-Myung; Lim, Hye Su; Choe, Kun Hyung

2012-12-01

269

Polarization exchange in colliding photon beams in a medium of an atomic gas  

E-print Network

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 order one tenth the distance in which the ordinary non-linear index of refraction would induce a phase change of pi. 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.

R. F. Sawyer

2014-02-20

270

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

NASA Technical Reports Server (NTRS)

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 3000 to 35,000. The measured friction factor of the tube specimen was lower than that of a circular tube with fully developed turbulent flow, although the uncertainty was high due to entrance and exit losses. 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 circular tubes.

Olson, Douglas A.; Glover, Michael P.

1990-01-01

271

Responses to water stress of gas exchange and metabolites in Eucalyptus and Acacia spp.  

PubMed

Studies of water stress commonly examine either gas exchange or leaf metabolites, and many fail to quantify the concentration of CO? in the chloroplasts (C(c)). We redress these limitations by quantifying C(c) from discrimination against CO? and using gas chromatography-mass spectrometry (GC-MS) for leaf metabolite profiling. Five Eucalyptus and two Acacia species from semi-arid to mesic habitats were subjected to a 2 month water stress treatment (?(pre-dawn) = -1.7 to -2.3 MPa). Carbohydrates dominated the leaf metabolite profiles of species from dry areas, whereas organic acids dominated the metabolite profiles of species from wet areas. Water stress caused large decreases in photosynthesis and C(c), increases in 17-33 metabolites and decreases in 0-9 metabolites. In most species, fructose, glucose and sucrose made major contributions to osmotic adjustment. In Acacia, significant osmotic adjustment was also caused by increases in pinitol, pipecolic acid and trans-4-hydroxypipecolic acid. There were also increases in low-abundance metabolites (e.g. proline and erythritol), and metabolites that are indicative of stress-induced changes in metabolism [e.g. ?-aminobutyric acid (GABA) shunt, photorespiration, phenylpropanoid pathway]. The response of gas exchange to water stress and rewatering is rather consistent among species originating from mesic to semi-arid habitats, and the general response of metabolites to water stress is rather similar, although the specific metabolites involved may vary. PMID:21692813

Warren, Charles R; Aranda, Ismael; Cano, F Javier

2011-10-01

272

High temperature corrosion of advanced ceramic materials for hot gas filters and heat exchangers. Final report  

SciTech Connect

Experimental corrosion studies of hot gas filter materials and heat exchanger materials in oxidizing combustion environments have been initiated. Filter materials from 3M Co. and DuPont Lanxide Composites Inc. are being tested over a range of temperatures, times and gas flows. It has been demonstrated that morphological and phase changes due to corrosive effects occur after exposure of these materials to a simulated coal combustion environment for relatively short periods of time (10-50 hours). Heat exchanger tubes from DuPont Lanxide Composite Inc. were cut and infiltrated with Cr by heating in a Cr{sub 2}O{sub 3} powder bed. This resulted in continuous Cr-rich layers with thicknesses ranging from 20 to 250 {mu}m. The Cr-free and the Cr-infiltrated specimens were reacted with the molten Illinois No. 6 slag for 2 and 20 h at 1260{degrees}C, and the reaction layers examined with SEM and EDX. In the Cr-free specimens, the segregation of Fe and the precipitation of Fe{sub 2}O{sub 3} were detected near the liquid/gas interface, but no evidence of corrosion was present. In the Cr-infiltrate specimens, corrosion was evident, since a rearrangement and segregation of the Cr-rich grains occurred toward the surface of the molten slag. In addition, evidence of the diffusion of major quantities of Fe was observed from the liquid slag into the Cr-rich layer formed by infiltration.

Kupp, E.R.; Trubelja, K.E.; Spear, K.E.; Tressler, R.E. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Materials Science and Engineering

1995-08-01

273

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

NASA Astrophysics Data System (ADS)

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 = 0.8 to 15 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 three) was observed for N2O under a surfactant covered water surface. In contrast, the surfactant affected CH3OH, the high solubility tracer only weakly.

Mesarchaki, E.; Kruter, C.; Krall, K. E.; Bopp, M.; Helleis, F.; Williams, J.; Jhne, B.

2014-06-01

274

Importance of ventricular rate after mode switching during low intensity exercise as assessed by clinical symptoms and ventilatory gas exchange.  

PubMed

Automatic mode switching from DDD(R) to DDI(R) or VVI(R) pacing modes has improved dual chamber pacing in patients at high risk for supraventricular tachyarrhythmias. However, little is known about the effect of ventricular pacing rate adaptation after mode switching. We conducted a single-blinded, crossover study in 15 patients (58 +/- 21 years) with a DDD pacemaker who had AV block and normal sinus node function to investigate the influence of pacing rate adaptation to intrinsic heart rate during low intensity exercise. Patients performed two tests (A/B) of low intensity treadmill exercise (0.5 W/kg) in randomized order. They initially walked for 6 minutes while paced in DDD mode. The pacing mode was then switched to VVI with a pacing rate of either 70 beats/min (test A) or matched to the intrinsic heart rate (95 +/- 11 beats/min test B). Respiratory gas exchange variables were determined and patients classified the effort before and after mode switching on a Borg scale from 6 to 20. Percentage changes of respiratory gas exchange measurements were significantly larger (O2 consumption: -8.2 +/- 5.0% vs. -0.6 +/- 7.2%; ventilatory equivalent of CO2 exhalation: 5.3 +/- 4.9% vs. 1.5 +/- 4.3%; respiratory exchange ratio: 7.0 +/- 2.2% vs. 3.5 +/- 3.0%; end-tidal CO2: -5.7 +/- 2.9% vs. -1.8 +/- 2.7%; all P < 0.01) and the increase in subjective assessment of the effort tended to be higher (mean increase on Borg scale: 1.6 +/- 1.9 vs. 1.1 +/- 1.8, P = 0.07) after heart rate unadjusted than after adjusted mode switching. Mode switching from DDD to VVI pacing is better tolerated and gas exchange measurements are less influenced if ventricular pacing rate is adjusted to the level of physical activity. Thus, pacing rate adjustment should be considered as part of automatic mode switch algorithms. PMID:10666751

Brunner-La Rocca, H P; Rickli, H; Weilenmann, D; Duru, F; Candinas, R

2000-01-01

275

Function of the Nucleotide Exchange Activity of Vav1 in T cell Development and Activation*  

PubMed Central

The guanine nucleotide exchange factor (GEF) Vav1 is essential for transducing T cell antigen receptor (TCR) signals and therefore plays a critical role in the development and activation of T cells. It has been presumed that the GEF activity of Vav1 is important for its function; however, there has been no direct demonstration of this. Here, we generated mice expressing enzymatically inactive, but normally folded, Vav1 protein. Analysis of these mice showed that the GEF activity of Vav1 was necessary for the selection of thymocytes and for the optimal activation of T cells, including signal transduction to Rac1, Akt, and integrins. In contrast, the GEF activity of Vav1 was not required for TCR-induced calcium flux, activation of extracellular signalregulated kinase (ERK) and protein kinase D1 (PKD1), and cell polarization. Thus, in T cells, the GEF activity of Vav1 is essential for some, but not all, of its functions. PMID:20009105

Saveliev, Alexander; Vanes, Lesley; Ksionda, Olga; Rapley, Jonathan; Smerdon, Stephen J.; Rittinger, Katrin; Tybulewicz, Victor L. J.

2012-01-01

276

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

SciTech Connect

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.

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

1982-01-20

277

Operation of an ADR using helium exchange gas as a substitute for a failed heat switch  

NASA Astrophysics Data System (ADS)

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.

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

2014-11-01

278

Leaf Gas Exchange Response of 'Arapaho' Blackberry and Six Red Raspberry Cultivars to Moderate and High Temperatures  

Microsoft Academic Search

Leaf gas exchange of six red raspberry (Rubus idaeus L.) and one blackberry (Rubus L. subgenus Rubus Watson) genotypes growing in 12-L containers was measured at four temperatures (20, 25, 30, and 35 C) once a month for 3 months in growth chambers by infrared gas analysis. Measurements were taken on three successive leaves on the same primocane between the

Eric T. Stafne; John R. Clark; Curt R. Rom

279

Extraction of extracellular polymers from activated sludge using a cation exchange resin  

Microsoft Academic Search

The extraction of water soluble extracellular polymeric substances (EPS) from activated sludge was investigated. The extraction procedure was based upon cation exchange using a cation exchange resin (CER). Activated sludge from two different types of treatment plants responded very similarly to the extraction procedure. The EPS yield was enhanced by increasing the stirring intensity, the amounts of CER added and

Bo Frlund; Rikke Palmgren; Kristian Keiding; Per Halkjr Nielsen

1996-01-01

280

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

PubMed

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

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

2006-12-01

281

Nesting behaviour influences species-specific gas exchange across avian eggshells  

PubMed Central

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

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

2014-01-01

282

Numerical simulation of gas dynamics and heat exchange tasks in fuel assemblies of the nuclear reactors  

NASA Astrophysics Data System (ADS)

This report presents a PC-based program for solution gas dynamics and heat exchange mathematical tasks in fuel assemblies of the fast-neutron nuclear reactors. A fuel assembly consisting of bulk heat-generating elements, which are integrated together by the system of supply and pressure manifolds, is examined. Spherical heat-generating microelements, which contain nuclear fuel, are pulled into the heat-generating elements. Gaseous coolant proceed from supply manifolds to heat-generating elements, where it withdraws the nuclear reaction heat and assembles in pressure manifolds.

Zhuchenko, S. V.

2014-11-01

283

Preliminary findings of the Viking gas exchange experiment and a model for Martian surface chemistry  

NASA Technical Reports Server (NTRS)

Earlier results reported from the Viking Lander-1 experiment are reexamined and interpreted in terms of a model of the Martian soil surface morphology and chemistry. Major events in the gas exchange experiment (GEX) first cycle are tabulated and data are presented on the sample processing and transport environments experienced by the soil samples. Oxygen and CO2 evolved from humidified Martian soil in GEX and slight changes in N2 present are investigated. A soil model involving iron oxide coating on silicate material is entertained to yield a mechanistic explanation of the experimental findings, and invocation of biotic processes is eschewed.

Oyama, V. I.; Berdahl, B. J.; Carle, G. C.

1977-01-01

284

Aqueous turbulence structure immediately adjacent to the air - water interface and interfacial gas exchange  

NASA Astrophysics Data System (ADS)

Air-sea interaction and the interfacial exchange of gas across the air-water interface are of great importance in coupled atmospheric-oceanic environmental systems. Aqueous turbulence structure immediately adjacent to the air-water interface is the combined result of wind, surface waves, currents and other environmental forces and plays a key role in energy budgets, gas fluxes and hence the global climate system. However, the quantification of turbulence structure sufficiently close to the air-water interface is extremely difficult. The physical relationship between interfacial gas exchange and near surface turbulence remains insufficiently investigated. This dissertation aims to measure turbulence in situ in a complex environmental forcing system on Lake Michigan and to reveal the relationship between turbulent statistics and the CO2 flux across the air-water interface. The major objective of this dissertation is to investigate the physical control of the interfacial gas exchange and to provide a universal parameterization of gas transfer velocity from environmental factors, as well as to propose a mechanistic model for the global CO2 flux that can be applied in three dimensional climate-ocean models. Firstly, this dissertation presents an advanced measurement instrument, an in situ free floating Particle Image Velocimetry (FPIV) system, designed and developed to investigate the small scale turbulence structure immediately below the air-water interface. Description of hardware components, design of the system, measurement theory, data analysis procedure and estimation of measurement error were provided. Secondly, with the FPIV system, statistics of small scale turbulence immediately below the air-water interface were investigated under a variety of environmental conditions. One dimensional wave-number spectrum and structure function sufficiently close to the water surface were examined. The vertical profiles of turbulent dissipation rate were intensively studied. Comparison between the turbulence structures measured during the wind wave initiation period and those obtained during the growing period was presented. Significant wave effects on near surface turbulence were found. A universal scaling law was proposed to parameterize turbulent dissipation rate immediately below the air-water interface with friction velocity, significant wave height and wave age. Finally, the gas transfer velocity was measured with a floating chamber (FC) system, along with simultaneously FPIV measurements. Turbulent dissipation rate both at the interface and at a short distance away from the interface (~ 10 cm) were analyzed and used to examine the small scale eddy model. The model coefficient was found to be dependent on the level of turbulence, instead of being a constant. An empirical relationship between the model coefficient and turbulent dissipation rate was provided, which improved the accuracy of the gas transfer velocity estimation by more than 100% for data acquired. Other data from the literature also supported this empirical relation. Furthermore, the relationship between model coefficient and turbulent Reynolds number was also investigated. In addition to physical control of gas exchange, the disturbance on near surface hydrodynamics by the FC was also discussed. Turbulent dissipation rates are enhanced at the short distance away from the interface, while the surface dissipation rates do not change significantly.

Wang, Binbin

285

Technical review of DOE activities in the eastern gas shales  

Microsoft Academic Search

US Department of Energy activities in the eastern gas shales are directed at deetermining the geologic character and magnitude of the Devonian age shale gas resource and toward increasing production of natural gas. Geologic evaluations of the collected formation characterization data are essentially complete to determine basin limits and stratigraphic intervals as potential gas sources. With these developments, large areas

C. A. Komar; A. E. Hunt; A. B. Yost

1980-01-01

286

Gas separation using ion exchange membranes for producing hydrogen from synthesis gas  

SciTech Connect

The main goal of this project is to demonstrate the use of facilitated transport membranes to separate gases resulting from the formation of H{sub 2}, specifically C0{sub 2} and H{sub 2}S from CO and H{sub 2}. As part of this goal a field test is performed at a producing natural gas plant (Carter Creek Chevron Natural Gas Plant, Evanston, WY) to evaluate the performance and long term stability of candidate membranes. Laboratory work at the National Institute of Standard and Technology (NIST) leads and parallels the field tests. Through a series of tests in the WIST laboratory and at the Chevron/Carter Creek test rig, the investigators are establishing the apparent separation and productivity capabilities of polymer membranes imbibed with various solvents and chemical carriers. In some samples the membranes are also subjected to solvent-swelling heat treatment (gel-treatment). The polymer material is polyperfluorosufonic acid (PFSA-Nafion). The chemical carriers, e.g. methyldiethanolamine (EDA) and ethylenediamine (EDA) enhance the transport and selectivity of the membrane. They may be in solution with H{sub 2}0, glycerol, ethylene glycol, and n-methylpyrrolidone (NMP). Nafion 117 (NE117) is a commercial film, 200 microns thick, which is available from DuPont Co. A developmental polymer film, Nafion 111 (NE111) 30--40 microns thick was made available by the DuPont Co.

Pellegrino, J.J.; Giarratano, P.J.

1992-01-01

287

Carbon nano-chain and carbon nano-fibers based gas diffusion layers for proton exchange membrane fuel cells  

Microsoft Academic Search

Gas diffusion layers (GDL) for proton exchange membrane fuel cell have been developed using a partially ordered graphitized nano-carbon chain (Pureblack carbon) and carbon nano-fibers. The GDL samples characteristics such as, surface morphology, surface energy, bubble-point pressure and pore size distribution were characterized using electron microscope, inverse gas chromatograph, gas permeability and mercury porosimetry, respectively. Fuel cell performance of the

Arunachala M. Kannan; Lakshmi Munukutla

2007-01-01

288

Surface Chemical Composition Effect on Internal Gas Flow and Molecular Heat Exchange in a Gas-Solids System  

NASA Astrophysics Data System (ADS)

On the basis of classical knowledge about movement of atoms and lattice theory of F. Goodman and G. Wachman the program modeling helium atom interaction with a three-dimensional crystal tungsten lattice taking into account partial surface covering by chemisorbed oxygen atoms is developed. An efficiency of molecular heat exchange of helium for pure and partially chemisorbed tungsten surface is calculated for different temperatures. Similar model of the surface and procedure of calculations have been applied for description of free-molecular gas flow in long cylindrical channel with clean and fully chemisorbed metal surface. Within the limits of the developed approach the results of calculations for both problems agree well with available experiments with surface contamination control.

Ukhov, Alexander; Borisov, Sergey; Porodnov, Boris

2011-05-01

289

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

PubMed

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 (11)C-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. PMID:16666773

Woodrow, L; Jiao, J; Tsujita, M J; Grodzinski, B

1989-05-01

290

Simple model of the static exchange-correlation kernel of a uniform electron gas with long-range electron-electron interaction  

E-print Network

Simple model of the static exchange-correlation kernel of a uniform electron gas with long is given for the static exchange- correlation kernel of a uniform electron gas interacting with the long, information from the momentum distribution of the uniform electron gas with the same interaction that have

Paris-Sud XI, Université de

291

Operation of an experimental algal gas exchanger for use in a CELSS  

NASA Astrophysics Data System (ADS)

Concepts of a CELSS anticipate the use of photosynthetic organisms (higher plants and algae) for air revitalization. The rates of production and uptake of carbon dioxide and oxygen between the crew and the photosynthetic organisms are mismatched. An aglal system used for gas exchange only will have the difficulty of an accumulation or depletion of these gases beyond physiologically tolerable limits (in a materially closed system the mismatch between assimilatory quotient (AQ) and respiratory quotient (RQ) will be balanced by the operation of the waste processor). We report the results of a study designed to test the feasibility of using environmental manipulations to maintain physiologically appropriate atmospheres for algae (Chlorella pyrenoidosa) and mice (Mus musculus strain DW/J) in a gas-closed system. Specifically, we consider the atmosphere behavior of this system with Chlorella grown on nitrate or urea and at different light intensities and optical densities. Manipulation of both the photosynthetic rate and AQ of the alga has been found to reduce the mismatch of gas requirements and allow operation of the system in a gas-stable manner. Operation of such a system in a CELSS may be useful for reduction of buffer sizes, as a backup system for higher plant air revitalization and to supply extra oxygen to the waste processor or during crew changes. In addition, mass balance for components of the system (mouse, algae and a waste processor) are presented.

Smernoff, David T.; Wharton, Robert A.; Averner, Maurice M.

292

Dissolution without disappearing: multicomponent gas exchange for CO2 bubbles in a microfluidic channel.  

PubMed

We studied the dissolution dynamics of CO2 gas bubbles in a microfluidic channel, both experimentally and theoretically. In the experiments, spherical CO2 bubbles in a flow of a solution of sodium dodecyl sulfate (SDS) first shrink rapidly before attaining an equilibrium size. In the rapid dissolution regime, the time to obtain a new equilibrium is 30 ms regardless of SDS concentration, and the equilibrium radius achieved varies with the SDS concentration. To explain the lack of complete dissolution, we interpret the results by considering the effects of other gases (O2, N2) that are already dissolved in the aqueous phase, and we develop a multicomponent dissolution model that includes the effect of surface tension and the liquid pressure drop along the channel. Solutions of the model for a stationary gas bubble show good agreement with the experimental results, which lead to our conclusion that the equilibrium regime is obtained by gas exchange between the bubbles and liquid phase. Also, our observations from experiments and model calculations suggest that SDS molecules on the gas-liquid interface form a diffusion barrier, which controls the dissolution behaviour and the eventual equilibrium radius of the bubble. PMID:24874437

Shim, Suin; Wan, Jiandi; Hilgenfeldt, Sascha; Panchal, Prathamesh D; Stone, Howard A

2014-07-21

293

Red spruce gas exchange in response to light, temperature, CO sub 2 and water stress  

SciTech Connect

The objective of this research was to examine the gas exchange responses of native red spruce seedlings to light, temperature and CO{sub 2} in combination with water stress to determine how red spruce physiologically responds to water stress. Gas exchange responses were examined under well-watered conditions and at an average leaf water potential of {minus}1.6 MPa. Net photosynthesis (Pnet) and leaf conductance (gl) were on average 35% and 53% lower, respectively, during water stress. The nature of the response of Pnet and gl to temperature and CO{sub 2} was similar to the well-watered response. Pnet was lower with water stress at high irradiances only. Water use efficiency was greater during water stress at 15C but not at 25 and 35C. No change in osmotic potential during water stress was observed. The response of red spruce physiology to varying light, temperature and CO{sub 2} does not appear to be greatly modified by water stress.

Samuelson, L.; Seiler, J. (Virginia Polytechnic Inst., Blacksburg (United States))

1991-05-01

294

Effects of phosphine on the neural regulation of gas exchange in Periplaneta americana.  

PubMed

Phosphine is used for fumigating stored commodities, however an understanding of the physiological response to phosphine in insects is limited. Here we show how the central pattern generator for ventilation in the central nervous system (CNS) responds to phosphine and influences normal resting gas exchange. Using the American cockroach, Periplaneta americana, that perform discontinuous gas exchange (DGE) at rest, we simultaneously measure ventilatory nervous output from the intact CNS, VCO(2) and water loss from live specimens. Exposure to 800 ppm phosphine at 25 degrees C for 2 h (n=13) during recording did not cause any mortality or obvious sub-lethal effects. Within 60 s of introducing phosphine into the air flow, all animals showed a distinct CNS response accompanied by a burst release of CO(2). The initial ventilatory response to phosphine displaced DGE and was typically followed by low, stable and continuous CO(2) output. CNS output was highest and most orderly under normoxic conditions during DGE. Phosphine caused a series of ventilatory CNS spikes preceding almost complete cessation of CNS output. Minimal CNS output was maintained during the 2 h normoxic recovery period and DGE was not reinstated. VCO(2) was slightly reduced and water loss significantly lower during the recovery period compared with those rates prior to phosphine exposure. A phosphine narcosis effect is rejected based on animals remaining alert at all times during exposure. PMID:18158274

Woodman, James D; Haritos, Victoria S; Cooper, Paul D

2008-04-01

295

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

PubMed Central

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

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

1988-01-01

296

Observations of Volatile Organic Compounds (VOC) from the Remote North Atlantic: Preliminary Results from the High-Wind Gas-Exchange Study (HiWinGS)  

NASA Astrophysics Data System (ADS)

Marine biogenic volatile organic compounds (BVOCs) can play a controlling role in setting the oxidative capacity of the marine boundary layer, secondary organic aerosol production rates and the chemistry of the upper ocean. Models suggest a wide range of significance for these reactive trace gases driven largely by local biophysical controls. This variability remains poorly constrained by observations, particularly from open-ocean regions. Here, we report preliminary BVOC mixing ratios and direct flux measurements from the High-Wind Gas Exchange Study (HiWinGS). This research cruise targeted regions of enhanced trace gas exchange, driven by elevated biological activity and strong surface winds in the remote North Atlantic during Fall of 2013. A custom-built chemical-ionization time-of-flight mass spectrometer was deployed to capture full mass spectra at high resolution (10 Hz) with demonstrated sensitivity (>10^2 Hz/pptv) to a wide range of BVOC species such as dimethylsulfide, isoprene, monoterpenes and alkylamines.

Karydis, V.; Capps, S.; Henze, D. K.; Nenes, A.

2011-12-01

297

Observations of Volatile Organic Compounds (VOC) from the Remote North Atlantic: Preliminary Results from the High-Wind Gas-Exchange Study (HiWinGS)  

NASA Astrophysics Data System (ADS)

Marine biogenic volatile organic compounds (BVOCs) can play a controlling role in setting the oxidative capacity of the marine boundary layer, secondary organic aerosol production rates and the chemistry of the upper ocean. Models suggest a wide range of significance for these reactive trace gases driven largely by local biophysical controls. This variability remains poorly constrained by observations, particularly from open-ocean regions. Here, we report preliminary BVOC mixing ratios and direct flux measurements from the High-Wind Gas Exchange Study (HiWinGS). This research cruise targeted regions of enhanced trace gas exchange, driven by elevated biological activity and strong surface winds in the remote North Atlantic during Fall of 2013. A custom-built chemical-ionization time-of-flight mass spectrometer was deployed to capture full mass spectra at high resolution (10 Hz) with demonstrated sensitivity (>10^2 Hz/pptv) to a wide range of BVOC species such as dimethylsulfide, isoprene, monoterpenes and alkylamines.

Kim, M.; Bertram, T. H.

2013-12-01

298

Identification and Validation of Modulators of Exchange Protein Activated by cAMP (Epac) Activity  

PubMed Central

The signaling molecule cAMP primarily mediates its effects by activating PKA and/or exchange protein activated by cAMP (Epac). Epac has been implicated in many responses in cells, but its precise roles have been difficult to define in the absence of Epac inhibitors. Epac, a guanine nucleotide exchange factor for the low molecular weight G protein Rap, is directly activated by cAMP. Using a bioluminescence resonance energy transfer-based assay (CAMYEL) to examine modulators of Epac activity, we took advantage of its intramolecular movement that occurs upon cAMP binding to assess Epac activation. We found that the use of CAMYEL can detect the binding of cAMP analogs to Epac and their modulation of its activity and can distinguish between agonists (cAMP), partial agonists (8-chlorophenylthio-cAMP), and super agonists (8-chlorophenylthio-2?-O-Me-cAMP). The CAMYEL assay can also identify competitive and uncompetitive Epac inhibitors, e.g. (Rp)-cAMPS and CE3F4, respectively. To confirm the results with the CAMYEL assay, we used Swiss 3T3 cells and assessed the ability of cyclic nucleotide analogs to modulate the activity of Epac or PKA, determined by Rap1 activity or VASP phosphorylation, respectively. We used computational molecular modeling to analyze the interaction of analogs with Epac1. The results reveal a rapid means to identify modulators (potentially including allosteric inhibitors) of Epac activity that also provides insight into the mechanisms of Epac activation and inhibition. PMID:24497631

Brown, Loren M.; Rogers, Kathleen E.; McCammon, J. Andrew; Insel, Paul A.

2014-01-01

299

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

PubMed Central

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 0.620.90 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

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

2013-01-01

300

Alveolar ventilation to perfusion heterogeneity and diffusion impairment in a mathematical model of gas exchange  

NASA Technical Reports Server (NTRS)

This study describes a two-compartment model of pulmonary gas exchange in which alveolar ventilation to perfusion (VA/Q) heterogeneity and impairment of pulmonary diffusing capacity (D) are simultaneously taken into account. The mathematical model uses as input data measurements usually obtained in the lung function laboratory. It consists of two compartments and an anatomical shunt. Each compartment receives fractions of alveolar ventilation and blood flow. Mass balance equations and integration of Fick's law of diffusion are used to compute alveolar and blood O2 and CO2 values compatible with input O2 uptake and CO2 elimination. Two applications are presented. The first is a method to partition O2 and CO2 alveolar-arterial gradients into VA/Q and D components. The technique is evaluated in data of patients with chronic obstructive pulmonary disease (COPD). The second is a theoretical analysis of the effects of blood flow variation in alveolar and blood O2 partial pressures. The results show the importance of simultaneous consideration of D to estimate VA/Q heterogeneity in patients with diffusion impairment. This factor plays an increasing role in gas alveolar-arterial gradients as severity of COPD increases. Association of VA/Q heterogeneity and D may produce an increase of O2 arterial pressure with decreasing QT which would not be observed if only D were considered. We conclude that the presented computer model is a useful tool for description and interpretation of data from COPD patients and for performing theoretical analysis of variables involved in the gas exchange process.

Vidal Melo, M. F.; Loeppky, J. A.; Caprihan, A.; Luft, U. C.

1993-01-01

301

The structural design of the bat wing web and its possible role in gas exchange  

PubMed Central

The structure of the skin in the epauletted fruit bat (Epomophorus wahlbergi) wing and body trunk was studied with a view to understanding possible adaptations for gas metabolism and thermoregulation. In addition, gas exchange measurements were performed using a respirometer designed for the purpose. The body skin had an epidermis, a dermis with hair follicles and sweat glands and a fat-laden hypodermis. In contrast, the wing web skin was made up of a thin bilayered epidermis separated by a connective tissue core with collagen and elastic fibres and was devoid of hair follicles and sweat glands. The wings spanned 1824 cm each, with about 753 cm2 of surface exposed to air. The body skin epidermis was thick (61 3 m, SEM), the stratum corneum alone taking a third of it (21 3 m). In contrast, the wing web skin epidermis was thinner at 9.8 0.7 m, with a stratum corneum measuring 4.1 0.3 m (41%). The wing capillaries in the wing web skin ran in the middle of the connective tissue core, with a resultant surface-capillary diffusion distance of 26.8 3.2 m. The rate of oxygen consumption (V?O2) of the wings alone and of the whole animal measured under light anaesthesia at ambient temperatures of 24 C and 33 C, averaged 6% and 10% of the total, respectively. Rate of carbon dioxide production had similar values. The membrane diffusing capacity for the wing web was estimated to be 0.019 ml O2 min?1 mmHg?1. We conclude that in Epomophorus wahlbergi, the wing web has structural modifications that permit a substantial contribution to the total gas exchange. PMID:17971117

Makanya, Andrew N; Mortola, Jacopo P

2007-01-01

302

Activation of AMP-activated protein kinase revealed by hydrogen/deuterium exchange Mass Spectrometry  

PubMed Central

Summary 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 by 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 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

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

2013-01-01

303

Influence of dexamethasone on na+/h+ exchanger activity in dendritic cells.  

PubMed

Glucocorticoids regulate the function of dendritic cells (DCs), antigen-presenting cells linking innate and adaptive immunity. Glucocorticoids influence the function of other cell types by modulating the activity of the Na(+)/H(+)exchanger (NHE), a carrier involved in the regulation of cytosolic pH and cell volume. The present study explored whether dexamethasone influences Na(+)/H(+) exchanger activity in DCs. The DCs were isolated from mouse bone marrow, cell volume was estimated from forward scatter in FACS analysis, cytosolic pH (pH(i)) utilizing BCECF fluorescence and Na(+)/H(+) exchanger activity from the Na(+) dependent realkalinization after an ammonium pulse. Treatment with the glucocorticoid dexamethasone (100 nM; 1, 4, 16 and 24h) significantly decreased pH(i) (?4 h) and gradually increased Na(+)/H(+) exchanger activity (=16 h). The stimulation of Na(+)/H(+) exchanger activity by dexamethasone was virtually abrogated by glucocorticoid receptor blocker mefiprestone (1 ?M) and NHE3 inhibitor dimethyl amiloride (5 ?M), but not prevented by NHE1 inhibitor cariporide (10 ?M). Dexamethasone treatment significantly increased SGK1 mRNA levels. Stimulation of Na(+)/H(+) exchanger activity by dexamethasone was blunted in DCs lacking SGK1. Dexamethasone treatment did not significantly alter ROS formation but significantly decreased the forward scatter. Exposure of DCs to lipopolysacharide (LPS, 1 ?g/ml) led to a transient increase followed by a decline of Na(+)/H(+) exchanger activity and to enhanced forward scatter as well as ROS formation, all effects significantly blunted in the presence of dexamethasone (100 nM). In conclusion, glucocorticoid treatment decreased pH(i) and cell volume, effects paralleled by upregulation of Na(+)/H(+) exchanger activity in DCs. Moreover, glucocorticoids blunted the stimulation of Na(+)/H(+) exchanger activity, cell swelling and ROS formation following LPS treatment. PMID:21865738

Rotte, Anand; Pasham, Venkanna; Eichenmller, Melanie; Yang, Wenting; Bhandaru, Madhuri; Lang, Florian

2011-01-01

304

Gas Exchange in the Filamentous Cyanobacterium Nostoc punctiforme Strain ATCC 29133 and Its Hydrogenase-Deficient Mutant Strain NHM5  

Microsoft Academic Search

Nostoc punctiforme ATCC 29133 is a nitrogen-fixing, heterocystous cyanobacterium of symbiotic origin. During nitrogen fixation, it produces molecular hydrogen (H2), which is recaptured by an uptake hydrogenase. Gas exchange in cultures of N. punctiforme ATCC 29133 and its hydrogenase-free mutant strain NHM5 was studied. Exchange of O2 ,C O 2 ,N 2, and H2 was followed simultaneously with a mass

Pia Lindberg; Peter Lindblad; Laurent Cournac

2004-01-01

305

Recuperated gas turbine aeroengines, part I: early development activities  

Microsoft Academic Search

Purpose Interest is currently being expressed in heat exchanged propulsion gas turbines for a variety of aeroengine applications, and in support of this, the aim of this paper is to evaluate the relevance of experience gained from development testing of several recuperated aeroengines in the USA in the late 1960s. Design\\/methodology\\/approach Technology status, including engine design features, performance,

Colin F. McDonald; Aristide F. Massardo; Colin Rodgers; Aubrey Stone

2008-01-01

306

Determination of low activities released by a decommissioned fuel fabrication plant through natural air exchange  

Microsoft Academic Search

In this paper a method to determine the release of low activities through natural air exchange from a decommissioned fuel fabrication plant is described. The method has been applied to the buildings of the NUKEM-A plant and was important in obtaining governmental authorization for the plant decommissioning. The air exchange rate in the NUKEM-A plant was measured by using a

B. Sohnius; R. Anton; E. Wehner; F. D. Heidt; R. Rabenstein

1992-01-01

307

Operation of an experimental algal gas exchanger for use in a CELSS  

NASA Technical Reports Server (NTRS)

Concepts of a Closed Ecological Life Support System (CELSS) anticipate the use of photosynthetic organisms (higher plants and algae) for air revitalization. The rates of production and uptake of carbon dioxide and oxygen between the crew and the photosynthetic organisms are mismatched. An algal system used for gas exchange only will have the difficulty of an accumulation or depletion of these gases beyond physiologically tolerable limits (in a closed system the mismatch between assimilatory quotient (AQ) and respiratory quotient (RQ) is balanced by the operation of the waste processor). The results are given of a study designed to test the feasibility of using environmental manipulations to maintain physiologically appropriate atmospheres for algae and mice in a gas closed system. Specifically, the atmosphere behavior of this system is considered with algae grown on nitrate or urea and at different light intensities and optical densities. Manipulation of both allow operation of the system in a gas stable manner. Operation of such a system in a CELSS may be useful for reduction of buffer sizes, as a backup system for higher plant air revitalization and to supply extra oxygen to the waste processor or during crew changes.

Smernoff, David T.; Wharton, Robert A., Jr.; Averner, Maurice M.

1987-01-01

308

A numerical modelling of gas exchange mechanisms between air and turbulent water with an aquarium chemical reaction  

NASA Astrophysics Data System (ADS)

This paper proposes a new numerical modelling to examine environmental chemodynamics of a gaseous material exchanged between the air and turbulent water phases across a gas-liquid interface, followed by an aquarium chemical reaction. This study uses an extended concept of a two-compartment model, and assumes two physicochemical substeps to approximate the gas exchange processes. The first substep is the gas-liquid equilibrium between the air and water phases, A(g)?A(aq), with Henry's law constant H. The second is a first-order irreversible chemical reaction in turbulent water, A(aq)+H2O?B(aq)+H+ with a chemical reaction rate ?A. A direct numerical simulation (DNS) technique has been employed to obtain details of the gas exchange mechanisms and the chemical reaction in the water compartment, while zero velocity and uniform concentration of A is considered in the air compartment. The study uses the different Schmidt numbers between 1 and 8, and six nondimensional chemical reaction rates between 10(?0) to 101 at a fixed Reynolds number. It focuses on the effects of the Schmidt number and the chemical reaction rate on fundamental mechanisms of the gas exchange processes across the interface.

Nagaosa, Ryuichi S.

2014-01-01

309

Reprint of: A numerical modelling of gas exchange mechanisms between air and turbulent water with an aquarium chemical reaction  

NASA Astrophysics Data System (ADS)

This paper proposes a new numerical modelling to examine environmental chemodynamics of a gaseous material exchanged between the air and turbulent water phases across a gas-liquid interface, followed by an aquarium chemical reaction. This study uses an extended concept of a two-compartment model, and assumes two physicochemical substeps to approximate the gas exchange processes. The first substep is the gas-liquid equilibrium between the air and water phases, A(g)?A(aq), with Henry's law constant H. The second is a first-order irreversible chemical reaction in turbulent water, A(aq)+H2O?B(aq)+H+ with a chemical reaction rate ?A. A direct numerical simulation (DNS) technique has been employed to obtain details of the gas exchange mechanisms and the chemical reaction in the water compartment, while zero velocity and uniform concentration of A is considered in the air compartment. The study uses the different Schmidt numbers between 1 and 8, and six nondimensional chemical reaction rates between 10(?0) to 101 at a fixed Reynolds number. It focuses on the effects of the Schmidt number and the chemical reaction rate on fundamental mechanisms of the gas exchange processes across the interface.

Nagaosa, Ryuichi S.

2014-08-01

310

Phospholipase Cepsilon guanine nucleotide exchange factor activity and activation of Rap1.  

PubMed

Phospholipase C (PLC) epsilon is directly regulated by Ras and Rap1 small GTPases: Ras and Rap1, in their GTP-bound form, interact with the Ras/Rap1-associationg (RA) domain of PLCepsilon, thereby translocating PLCepsilon to the plasma membrane and the Golgi apparatus, respectively. In the plasma membrane and the Golgi apparatus, PLCepsilon acts as a phosphoinositide-specific PLC, regulating various downstream signaling pathways. PLCepsilon also contains a CDC25 homology domain, which enhances guanine nucleotide exchange on Rap1. Here, we describe biochemical characterization of the CDC25 homology domain of PLCepsilon and provide insights into its physiological role in the regulation of PLCepsilon activity. PMID:16757332

Satoh, Takaya; Edamatsu, Hironori; Kataoka, Tohru

2006-01-01

311

Pt loaded carbon aerogel catalyst for catalytic exchange reactions between water and hydrogen gas  

NASA Astrophysics Data System (ADS)

We report development and characterization of platinum doped carbon aerogel catalyst for catalytic exchange reactions between water and hydrogen gas. The carbon aerogel with uniformly dispersed platinum nanoparticles was prepared by adding platinum precursor during the sol-gel process. Thereafter colloidal PTFE was mixed with the platinum doped carbon aerogel powder and coated on Dixon rings to obtain hydrophobic catalyst with required mechanical strength. Detailed studies have been carried out to observe the effect of physical characteristics of the catalyst powder (surface area and pore size of aerogels, Pt cluster size and its valence state etc) and the different coating parameters (PTFE to Pt-CA ratio and Pt loading on Dixon ring) on volume transfer rate (Ky.a) for H/D reaction. Ky.a values of 0.8 m3 (STP).s-1. m-3 were obtained for Pt loading of 7% and Pt cluster size of 3 nm at atmospheric pressure.

Singh, Rashmi; Singh, Ashish; Kohli, D. K.; Singh, M. K.; Gupta, P. K.

2013-06-01

312

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

PubMed

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

Weibel, E R

1999-06-01

313

Injection of dust into the Martian atmosphere - Evidence from the Viking Gas Exchange experiment  

NASA Technical Reports Server (NTRS)

The hypothesis that predawn midlatitude storms are triggered by a soil humidification process is examined. A freeze/thaw model of the process is evaluated in the Viking Gas Exchange experiments conducted on Mars. The humidification-driven desorption and desiccation state of Martian soil samples are analyzed. The periodic humidification of equatorial regolith soil is studied in terms of pore space pressure during desorption events and soil diffusivity; the thermal properties of the regolith surface layer are modeled using the program of Clifford (1984). Consideration is given to the diurnal and seasonal cycles of the humidification process, the permanent, low-albedo features in the midlatitudes, and the production of H2SO4 and HCl aerosols.

Huguenin, R. L.; Harris, S. L.; Carter, R.

1986-01-01

314

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

SciTech Connect

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.

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

1988-05-01

315

Whole-Plant Gas Exchange and Reductive Biosynthesis in White Lupin1  

PubMed Central

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

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

2001-01-01

316

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

USGS Publications Warehouse

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.

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

2001-01-01

317

A computational study of an HCCI engine with direct injection during gas exchange  

SciTech Connect

We present a new probability density function (PDF)-based computational model to simulate a homogeneous charge compression ignition (HCCI) engine with direct injection (DI) during gas exchange. This stochastic reactor model (SRM) accounts for the engine breathing process in addition to the closed-volume HCCI engine operation. A weighted-particle Monte Carlo method is used to solve the resulting PDF transport equation. While simulating the gas exchange, it is necessary to add a large number of stochastic particles to the ensemble due to the intake air and EGR streams as well as fuel injection, resulting in increased computational expense. Therefore, in this work we apply a down-sampling technique to reduce the number of stochastic particles, while conserving the statistical properties of the ensemble. In this method some of the most important statistical moments (e.g., concentration of the main chemical species and enthalpy) are conserved exactly, while other moments are conserved in a statistical sense. Detailed analysis demonstrates that the statistical error associated with the down-sampling algorithm is more sensitive to the number of particles than to the number of conserved species for the given operating conditions. For a full-cycle simulation this down-sampling procedure was observed to reduce the computational time by a factor of 8 as compared to the simulation without this strategy, while still maintaining the error within an acceptable limit. Following the detailed numerical investigation, the model, intended for volatile fuels only, is applied to simulate a two-stroke, naturally aspirated HCCI engine fueled with isooctane. The in-cylinder pressure and CO emissions predicted by the model agree reasonably well with the measured profiles. In addition, the new model is applied to estimate the influence of engine operating parameters such as the relative air-fuel ratio and early direct injection timing on HCCI combustion and emissions. The qualitative trends observed in the parametric variation study match well with experimental data in literature. (author)

Su, Haiyun; Vikhansky, Alexander; Mosbach, Sebastian; Kraft, Markus [Department of Chemical Engineering, University of Cambridge, Cambridge CB2 3RA (United Kingdom); Bhave, Amit [Reaction Engineering Solutions Ltd., 61 Canterbury Street, Cambridge CB4 3QG (United Kingdom); Kim, Kyoung-Oh; Kobayashi, Tatsuo [Higashifuji Technical Center, Toyota Motor Corporation, Mishuku 1200, Susono, Shizuoka 480-1193 (Japan); Mauss, Fabian [Division of Combustion Physics, Lund Institute of Technology, Box 118, S-22100 Lund (Sweden)

2006-10-15

318

Air-sea exchange and gas-particle partitioning of polycyclic aromatic hydrocarbons in the Mediterranean  

NASA Astrophysics Data System (ADS)

Polycyclic aromatic hydrocarbon (PAH) concentration in air of the central and eastern Mediterranean in summer 2010 was 1.45 (0.30-3.25) ng m-3 (sum of 25 PAHs), with 8 (1-17)% in the particulate phase, almost exclusively associated with particles < 0.25 ?m. The total deposition flux of particulate PAHs was 0.3-0.5 ? g m-2 yr-1. The diffusive air-sea exchange fluxes of fluoranthene and pyrene were mostly found net-depositional or close to phase equilibrium, while retene was net-volatilisational in a large sea region. Regional fire activity records in combination with box model simulations suggest that seasonal depositional input of retene from biomass burning into the surface waters during summer is followed by an annual reversal of air-sea exchange, while interannual variability is dominated by the variability of the fire season. One-third of primary retene sources to the sea region in the period 2005-2010 returned to the atmosphere as secondary emissions from surface seawaters. It is concluded that future negative emission trends or interannual variability of regional sources may trigger the sea to become a secondary PAH source through reversal of diffusive air-sea exchange. Capsule: In late summer the seawater surface in the Mediterranean has turned into a temporary secondary source of PAH, obviously related to biomass burning in the region.

Mulder, M. D.; Heil, A.; Kuku?ka, P.; Klnov, J.; Kuta, J.; Proke, R.; Sprovieri, F.; Lammel, G.

2014-09-01

319

In Vivo Gas Exchange Measurement of the Site and Dynamics of Nitrate Reduction in Soybean1  

PubMed Central

A gas analysis system was built to study the relationship between the reductant cost of NO3? assimilation and the measured rate of CO2 and O2 exchange in roots, leaves, and stems+ petioles of soybean (Glycine max L. Merr. cv Maple glen) plants. The measurements were used to calculate the diverted reductant utilization rate (DRUR = 4*[measured rate of CO2 + measured rate of O2], in moles of high-energy electron [e?] per gram per hour) in plants in the presence (N+) and absence (N?) of NO3?. The differences in DRUR between the N+ and N? treatments provided a measure of the NO3?-coupled DRUR of 25-d-old plants, whereas a 15NO3?-enriched nutrient solution was used to obtain an independent measure of the rate of NO3? assimilation. The measured reductant cost for the whole plant was 9.6 e? per N assimilated, a value within the theoretical range of four to 10 e? per N assimilated. The results predicted that shoots accounted for about 55% of the whole-plant NO3? assimilation over the entire day, with shoots dominating in the light, and roots in the dark. The gas analysis approach described here holds promise as a powerful, noninvasive tool to study the regulation of NO3? assimilation in plant tissue. PMID:12644665

Cen, Yan-Ping; Layzell, David B.

2003-01-01

320

Effect of stratified inequality of blood flow on gas exchange in liquid-filled lungs.  

NASA Technical Reports Server (NTRS)

This investigation set out to answer two questions: (1) are the distal alveoli in the terminal lung units less well perfused than the proximal alveoli, i.e., is there stratification of blood flow; and (2) if so, does this enhance gas exchange in the presence of stratified inequality of ventilation. Excised dog lungs were ventilated with saline and perfused with blood. Following single inspirations of xenon 133 in saline and various periods of breath holding, the expired xenon concentration against volume was measured and it confirmed marked stratified inequality of ventilation under these conditions. By measuring the rate of depletion of xenon from alveoli during a period of blood flow, we showed that the alveoli which emptied at the end of expiration had 16% less blood flow than those exhaling earlier. However, by measuring the xenon concentration in pulmonary venous blood, we found that about 10% less tracer was transferred from the alveoli into the blood when the inspired xenon was stratified within the respiratory zone. Thus while stratification of blood flow was confirmed, it was shown to impair rather than enhance the efficiency of gas transfer.

West, J. B.; Maloney, J. E.; Castle, B. L.

1972-01-01

321

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

SciTech Connect

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.

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

322

Gas exchange measurements within a magnetic environment: validation of a new system.  

PubMed

Although simultaneous measurements of pulmonary oxygen uptake (VO2) and Phosphorus-31 magnetic resonance spectroscopy ((31)P MRS) is attractive to investigate muscular metabolism during exercise, the superconducting magnet requires the design of specific gas exchange analyser (GEA). Thus, this study aimed to assess the validity of a commercial GEA system (ZAN600) compatible with (31)P MRS measurements. Using nonmagnetic pneumotachograph and prolonged sampling line (from 2m, control condition, to 6.5m) did not alter the proper synchronisation between flow and gas concentration signals. Also, end-expiratory fraction of O2 (FETO2) and CO(2) (FETCO2), and finally the values of steady-state ventilation (V(E)), carbon dioxide production (VCO2) and VO2 kinetics during moderate knee-extension exercise were not significantly different between 2m and 6.5m conditions and between 6.5m condition inside and outside the magnet. These results showed that a prolonged sampling line used inside the superconducting magnet did not affect the accuracy of VO2 measurements of a commercial GEA system; the latter appears suitable for simultaneous measurements of VO2 and (31)P MRS. PMID:22366154

Bringard, Aurlien; Layec, Gwenael; Micallef, Jean-Paul; Bendahan, David; Perrey, Stphane

2012-06-15

323

Trace gas exchanges and convective transports over the Amazonian rain forest  

NASA Technical Reports Server (NTRS)

The NASA Amazon Boundary Layer Experiment (ABLE 2A) based in Manaus, Brazil, in July and August 1985, is used to examine meteorological processes responsible for the vertical and horizontal transport of biogenic and anthropogenic trace gases generated over the Amazon basin. Direct sampling of the surrounding environment of deep convective clouds shows marked changes in the vertical distribution of the lower and midtroposphere concentration of O3 and such surface-derived species as CO, CO2, and NO. Thermodynamic observations, together with two-dimensional cloud model simulations, confirm vertical transports within the convection and provide a basis for an estimation of the magnitude and efficiency of cloud upward and downward exchanges. A distinction is drawn between local changes due to convective updrafts and downdrafts and convective overturning as a net result of the storm processes. Marked variability is seen in trace gas concentrations along horizontal flight paths in the vicinity of the convection. Interpretation of simultaneously measured thermodynamic quantities and trace gas concentrations provide the information to infer the presence and direction of atmospheric transports and/or the presence of anthropogenic influences.

Garstang, Michael; Harriss, Robert; Beck, Sherwin; Browell, Edward; Sachse, Glen; Gregory, Gerald; Hill, Gerald; Simpson, Joanne; Tao, Wei-Kuo; Torres, Arnold

1988-01-01

324

Activation of catalysts for synthesizing methanol from synthesis gas  

DOEpatents

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.

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

1985-01-01

325

Growth, gas exchange, and root respiration of Quercus rubra seedlings exposed to low root zone temperatures in solution culture  

Microsoft Academic Search

Spring planting is standard operational practice in the Central Hardwood Region, though little is known about potential impacts of low root temperature (RT) common during spring on establishment success of temperate deciduous forest tree species. The effects of low RT on growth, gas exchange, and root respiration following winter dormancy were studied in 1-year-old northern red oak (Quercus rubra L.)

Kent G. Apostol; Douglass F. Jacobs; Barrett C. Wilson; K. Francis Salifu; R. Kasten Dumroese

2007-01-01

326

Effects of permethrin and amitraz on gas exchange and water loss in unfed adult females of Amblyomma americanum (Acari: Ixodidae)  

Technology Transfer Automated Retrieval System (TEKTRAN)

Effects of permethrin and amitraz on metabolism of the lone star tick, Amblyomma americanum, were examined using a flow-through carbon dioxide (CO2) and water vapor analyzer. Untreated adult female ticks exhibited a distinct discontinuous gas exchange pattern (DGEP) with no measurable water loss. Si...

327

Transpiration efficiency over an annual cycle, leaf gas exchange and wood carbon isotope ratio of three tropical tree species  

E-print Network

Transpiration efficiency over an annual cycle, leaf gas exchange and wood carbon isotope ratio; published online August 6, 2009 Summary Variation in transpiration efficiency (TE) and its relationship. Cumulative transpiration was determined by repeatedly weighing the pots with a pallet truck scale. Dry matter

Bermingham, Eldredge

328

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...

329

Gas exchange and photosynthetic acclimation over subambient to elevated CO2 in a C3-C4 grassland  

Microsoft Academic Search

Atmospheric CO2 (Ca) has risen dramatically since preglacial times and is pro- jected to double in the next century. As part of a 4-year study, we examined leaf gas exchange and photosynthetic acclimation in C3 and C4 plants using unique chambers that maintained a continuous Ca gradient from 200 to 550 mmol mol -1 in a natural grassland. Our goals

LAUREL J. A NDERSON; H AFIZ M AHERALI

2001-01-01

330

High Frequency Nasal Ventilation for 21 Days Maintains Gas Exchange with Lower Respiratory Pressures and Promotes Alveolarization in Preterm Lambs  

PubMed Central

Background Short-term high-frequency nasal ventilation (HFNV) of preterm neonates provides acceptable gas exchange compared to endotracheal intubation and intermittent mandatory ventilation (IMV). Whether long-term HFNV will provide acceptable gas exchange is unknown. We hypothesized that HFNV for up to 21d would lead to acceptable gas exchange at lower inspired oxygen (O2) levels and airway pressures compared to intubation and IMV. Methods Preterm lambs were exposed to antenatal steroids, and treated with perinatal surfactant and postnatal caffeine. Lambs were intubated and resuscitated by IMV. At ~3h of age, half of the lambs were switched to non-invasive HFNV. Support was for 3d or 21d. By design, PaO2 and PaCO2 were not different between groups. Results At 3d (n=5) and 21d (n=4) of HFNV, fractional inspired O2 (FiO2), peak inspiratory pressure, mean airway, intra-tracheal, and positive end-expiratory pressures, oxygenation index, and Alveolar-arterial gradient were significantly lower than matched periods of intubation and IMV. PaO2/FiO2 ratio was significantly higher at 3d and 21d of HFNV compared to matched intubation and IMV. HFNV led to better alveolarization at 3d and 21d. Conclusion Long-term HFNV provides acceptable gas exchange at lower inspired O2 levels and respiratory pressures compared to intubation and IMV. PMID:24378898

Null, Donald M.; Alvord, Jeremy; Leavitt, Wendy; Wint, Albert; Dahl, Mar Janna; Presson, Angela P.; Lane, Robert H.; DiGeronimo, Robert J.; Yoder, Bradley A.; Albertine, Kurt H.

2014-01-01

331

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

Microsoft Academic Search

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

Douglas A. Johnson; Martyn M. Caldwell

1975-01-01

332

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...

333

Growth, nutrient, water relations, and gas exchange in a holm oak plantation in response to irrigation and fertilization  

Microsoft Academic Search

Eighty 6-years-old Quercus ilex L. subsp. ballota seedlings planted on a former agricultural land were subjected during two growing seasons to one of four treatments: fertilization and irrigation, irrigation, fertilization, and control. Seasonal and between-treatment variations on water relations, gas exchange parameters, growth and nutrient status were analyzed. Water potential (?) was related to climatic conditions. Thus, the frequent rain

Marta Pardos; Antonio Royo; Jos A. Pardos

2005-01-01

334

Design of Plant Gas Exchange Experiments in a Variable Pressure Growth Chamber  

NASA Technical Reports Server (NTRS)

Sustainable human presence in extreme environments such as lunar and martian bases will require bioregenerative components to human life support systems where plants are used for generation of oxygen, food, and water. Reduced atmospheric pressures will be used to minimize mass and engineering requirements. Few studies have assessed the metabolic and developmental responses of plants to reduced pressure and varied oxygen atmospheres. The first tests of hypobaric pressures on plant gas exchange and biomass production at the Johnson Space Center will be initiated in January 1996 in the Variable Pressure Growth Chamber (VPGC), a large, closed plant growth chamber rated for 10.2 psi. Experiments were designed and protocols detailed for two complete growouts each of lettuce and wheat to generate a general database for human life support requirements and to answer questions about plant growth processes in reduced pressure and varied oxygen environments. The central objective of crop growth studies in the VPGC is to determine the influence of reduced pressure and reduced oxygen on the rates of photosynthesis, dark respiration, evapotranspiration and biomass production of lettuce and wheat. Due to the constraint of one experimental unit, internal controls, called pressure transients, will be used to evaluate rates of CO2 uptake, O2 evolution, and H2O generation. Pressure transients will give interpretive power to the results of repeated growouts at both reduced and ambient pressures. Other experiments involve the generation of response functions to partial pressures of O2 and CO2 and to light intensity. Protocol for determining and calculating rates of gas exchange have been detailed. In order to build these databases and implement the necessary treatment combinations in short time periods, specific requirements for gas injections and removals have been defined. A set of system capability checks will include determination of leakage rates conducted prior to the actual crop growouts. Schedules of experimental events for lettuce and wheat are outlined and include replications in time of diurnal routines, pressure transients, variable pO2, pO2/pCO2 ratio, and light intensity responses.

Corey, Kenneth A.

1996-01-01

335

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...

336

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

SciTech Connect

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.

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

337

Investigating onychophoran gas exchange and water balance as a means to inform current controversies in arthropod physiology.  

PubMed

Several controversies currently dominate the fields of arthropod metabolic rate, gas exchange and water balance, including the extent to which modulation of gas exchange reduces water loss, the origins of discontinuous gas exchange, the relationship between metabolic rate and life-history strategies, and the causes of Palaeozoic gigantism. In all of these areas, repeated calls have been made for the investigation of groups that might most inform the debates, especially of taxa in key phylogenetic positions. Here we respond to this call by investigating metabolic rate, respiratory water loss and critical oxygen partial pressure (Pc) in the onychophoran Peripatopsis capensis, a member of a group basal to the arthropods, and by synthesizing the available data on the Onychophora. The rate of carbon dioxide release (VCO2) at 20 degrees C in P. capensis is 0.043 ml CO2 h(-1), in keeping with other onychophoran species; suggesting that low metabolic rates in some arthropod groups are derived. Continuous gas exchange suggests that more complex gas exchange patterns are also derived. Total water loss in P. capensis is 57 mg H2O h(-1) at 20 degrees C, similar to modern estimates for another onychophoran species. High relative respiratory water loss rates ( approximately 34%; estimated using a regression technique) suggest that the basal condition in arthropods may be a high respiratory water loss rate. Relatively high Pc values (5-10% O2) suggest that substantial safety margins in insects are also a derived condition. Curling behaviour in P. capensis appears to be a strategy to lower energetic costs when resting, and the concomitant depression of water loss is a proximate consequence of this behaviour. PMID:18805813

Clusella-Trullas, Susana; Chown, Steven L

2008-10-01

338

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

SciTech Connect

The pattern of gas-exchange (CO{sub 2} 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 CO{sub 2} emission was measured in a closed flow-through system connected to commercial infrared gas analysis equipment. Metabolic activity (rate of CO{sub 2} emission) was related to pupal eye-color, which is the current technique used to determine physiological age. Eye-color was characterized digitally with 3 variables (Hue, Saturation and Intensity), and color separated by discriminant analysis. The rate of CO{sub 2} emission throughout pupal development followed a U-shape, with high levels of emission during pupariation, pupal transformation and final pharate adult stages. Temperature affected the development time of pupae, but not the basic CO{sub 2} emission patterns during development. In all temperatures, rates of CO{sub 2} emission 1 and 2 d before adult emergence were very similar. After mid larval-adult transition (e.g., phanerocephalic pupa), digital eye-color was significantly correlated with CO{sub 2} emission. Results support the suggestion that gas-exchange should be explored further as a system to determine pupal physiological age in mass production of fruit flies. (author) [Spanish] En el presente estudio se investigaron los patrones de intercambio gaseoso (emision de CO{sub 2}) en pupas de la mosca de las frutas del Mediterraneo (Ceratitis capitata Wiedemann) incubadas a diferentes temperaturas. El estudio fue realizado con la finalidad de explorar la utilizacion de sistemas de intercambio gaseoso en la determinacion de la edad fisiologica de pupas durante su produccion masiva en proyectos de mosca esteril. La proporcion de emision de CO{sub 2} fue medido en un sistema cerrado de 'flujo a traves del sistema' conectado a un detector infrarrojo de gases. La actividad metabolica de la pupa (emision de CO{sub 2}) fue contrastado al color del ojo de la pupa en desarrollo, que constituye la actual tecnica de determinacion de la edad fisiologica. El color de ojos en pupa fue determinado digitalmente, usando tres variables (Tendencia, Saturacion e Intensidad). Los colores fueron separados utilizando el analisis discriminatorio. Los patrones de emision de CO{sub 2} durante el desarrollo de la pupa sugieren una tendencia de U: una alta actividad metabolica durante la fase inicial de pupacion y transformacion y durante la fase final del adulto. La temperatura de incubacion afecto el tiempo de desarrollo pero no el patron basico de actividad metabolica. La proporcion de emision de CO{sub 2} uno y dos dias antes de la emergencia del adulto fue muy similar para pupas mantenidas en las diversas temperaturas. El color digital del ojo de la pupa se correlaciono significativamente con los patrones de emision de CO{sub 2} detectados a partir de la fase media de la transformacion de larva a adulto. Los resultados soportan la utilizacion de sistemas de intercambio gaseoso como un sistema auxiliar para la determinacion de la edad fisiologica en cria masiva de moscas de la fruta. (author)

Nestel, D.; Nemny-Lavy, E. [Department of Entomology, Institute of Plant Protection, Agricultural Research Organization, Volcani Center, P.O. Box 6, 50250 Beit-Dagan (Israel); Alchanatis, V. [Department of Sensing, Information and Mechanization, Institute of Agricultural Engineering, Agricultural Research Organization, Volcani Center, P.O. Box 6, 50250 Beit-Dagan (Israel)

2007-03-15

339

Growing season ecosystem and leaf-level gas exchange of an exotic and native semiarid bunchgrass.  

PubMed

The South African grass, Lehmann lovegrass (Eragrostis lehmanniana), may alter ecosystem processes across extensive semiarid grasslands and savannahs of western North America. We compared volumetric soil moisture (theta), total and green tissue leaf area index (LAI), ecosystem (i.e. whole-plant and soil), and leaf-level gas exchange of Lehmann lovegrass and the native bush muhly (Muhlenbergia porteri) over the 2008 monsoon season in a semiarid savanna in southern Arizona, USA, to see if these were consistent with high productivity associated with lovegrass invasive success. theta across 0-5 and 0-25 cm was higher while evapotranspiration (ET) was similar between lovegrass and bush muhly plots, except shortly after rainfall, when ET was 32-81% higher in lovegrass plots. Lehmann lovegrass had lower, quickly developing LAI with greater leaf proportions than bush muhly. When early season theta was high, net ecosystem CO(2) exchange (NEE) was similar, but as storm frequency and theta declined, NEE was more negative in lovegrass (-0.69 to -3.00 micromol m(-2) s(-1)) than bush muhly (+1.75 to -1.55 micromol m(-2) s(-1)). Ecosystem respiration (R (eco)) responded quickly to monsoon onset and late-season rains, and was lower in lovegrass (2.44-3.74 micromol m(-2) s(-1)) than bush muhly (3.60-5.3 micromol m(-2) s(-1)) across the season. Gross ecosystem photosynthesis (GEP) was greater in Lehmann lovegrass, concurrent with higher leaf-level photosynthesis and stomatal conductance. We conclude that canopy structure facilitates higher theta under Lehmann lovegrass, reducing phenological constraints and stomatal limitations to whole-plant carbon uptake through the short summer monsoon growing season. PMID:20063168

Hamerlynck, Erik P; Scott, Russell L; Moran, M Susan; Keefer, Timothy O; Huxman, Travis E

2010-07-01

340

Structural basis for Rab GTPase activation by VPS9 domain exchange factors  

PubMed Central

RABEX-5 and other exchange factors with VPS9 domains regulate endocytic trafficking through activation of the Rab family GTPases RAB5, RAB21 and RAB22. Here we report the crystal structure of the RABEX-5 catalytic core in complex with nucleotide-free RAB21, a key intermediate in the exchange reaction pathway. The structure reveals how VPS9 domain exchange factors recognize Rab GTPase substrates, accelerate GDP release and stabilize the nucleotide-free conformation. We further identify an autoinhibitory element in a predicted amphipathic helix located near the C terminus of the VPS9 domain. The autoinhibitory element overlaps with the binding site for the multivalent effector RABAPTIN-5 and potently suppresses the exchange activity of RABEX-5. Autoinhibition can be partially reversed by mutation of conserved residues on the nonpolar face of the predicted amphipathic helix or by assembly of the complex with RABAPTIN-5. PMID:17450153

Delprato, Anna; Lambright, David G

2008-01-01

341

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

NASA Astrophysics Data System (ADS)

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., Hye, 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

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

2013-04-01

342

Design of compact intermediate heat exchangers for gas cooled fast reactors  

E-print Network

Two aspects of an intermediate heat exchanger (IHX) for GFR service have been investigated: (1) the intrinsic characteristics of the proposed compact printed circuit heat exchanger (PCHE); and (2) a specific design optimizing ...

Gezelius, Knut, 1978-

2004-01-01

343

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

Microsoft Academic Search

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;

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

2004-01-01

344

CO2/H2O gas exchange parameters of one- and two-year-old needles of spruce and fir.  

PubMed

Gas exchange was characterized in one- and two year-old spruce (Picea abies L. Karst.) and fir seedlings (Abies alba Mill.) which had been exposed to low levels of ozone, sulfur dioxide and simulated rain or a combination of all three variables in open top chambers from 1983 through 1988. The gas exchange measurements were carried out in March 1988 at the end of the five year experiment. The twigs examined did not exhibit any visible sign of injury, specifically no differences were apparent between trees under the treatments of simulated acidic rain at pH 5.0 and pH 4.0. The study of carbon dioxide response curves showed different effects of the pollutants on the tree species. One-Year-old spruce needles treated with O(3) and simulated acidic precipitation pH 4.0 showed noticeable reduction of net photosynthetic rate. Exposure to the combination O(3) and SO(2) at pH 4.0 resulted in a significant depression of photosynthesis in two-year-old needles Transpiration rate was not decreased to a similar extent. No changes either in photosynthesis or transpiration were found in spruce under fumigation with SO(2) alone. These results indicate that ozone is the principal cause of changes in photosynthetic performance of spruce. It alters mesophyll response rather than reducing stomatal conductance. The specific changes that occur in the mesophyll could be diagnosed as inactivation of a carbon fixing enzyme as well as damage of the electron transport system. Fir seem to be more tolerant to ozone. No changes in photosynthesis and transpiration following exposure to O(3) alone were found. However, SO(2) fumigation, alone or in combination with O(3), resulted in a marked decrease of photosynthetic performance. Particularly, carboxylation efficiency and also maximum carboxylation velocity were depressed indicating a reduction in carbon fixing enzyme activity. No differences between single and combined fumigation treatments regarding these variables were determined. However, parameters measured to determine changes in electron transport rate showed a higher depression in the presence of both pollutants. Transpiration also was reduced by SO(2). PMID:15092177

Schweizer, B; Arndt, U

1990-01-01

345

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

PubMed Central

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

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

2014-01-01

346

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

PubMed

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

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

2014-01-01

347

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

NASA Technical Reports Server (NTRS)

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.

Olson, D. A.

1991-01-01

348

Leaf Gas Exchange and Chlorophyll a Fluorescence in Maize Leaves Infected with Stenocarpella macrospora.  

PubMed

ABSTRACT This study investigated the effect of macrospora leaf spot (MLS), caused by Stenocarpella macrospora, on photosynthetic gas exchange parameters and chlorophyll a fluorescence parameters determined in leaves of plants from two maize cultivars ('ECVSCS155' and 'HIB 32R48H') susceptible and highly susceptible, respectively, to S. macrospora. MLS severity was significantly lower in the leaves of plants from ECVSCS155 relative to the leaves of plants from HIB 32R48H. In both cultivars, net CO2 assimilation rate, stomatal conductance, and transpiration rate significantly decreased, while the internal to ambient CO2 concentration ratio increased in inoculated plants relative to noninoculated plants. The initial fluorescence and nonphotochemical quenching significantly increased in inoculated plants of ECVSCS155 and HIB 32R48H, respectively, relative to noninoculated plants. The maximum fluorescence, maximum PSII quantum efficiency, coefficient for photochemical quenching, and electron transport rate significantly decreased in inoculated plants relative to noninoculated plants. For both cultivars, concentrations of total chlorophyll (Chl) (a + b) and carotenoids and the Chl a/b ratio significantly decreased in inoculated plants relative to noninoculated plants. In conclusion, the results from the present study demonstrate, for the first time, that photosynthesis in the leaves of maize plants is dramatically affected during the infection process of S. macrospora, and impacts are primarily associated with limitations of a diffusive and biochemical nature. PMID:25014681

Bermdez-Cardona, Maria Bianney; Filho, Joo Amrico Wordell; Rodrigues, Fabrcio vila

2015-01-01

349

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

PubMed

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

Tatagiba, Sandro Dan; DaMatta, Fbio Murilo; Rodrigues, Fabrcio vila

2015-02-01

350

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

PubMed Central

We investigated the role of xylem cavitation, plant hydraulic conductance, and root pressure in the response of rice (Oryza sativa) gas exchange to water stress. In the field (Philippines), the percentage loss of xylem conductivity (PLC) from cavitation exceeded 60% in leaves even in watered controls. The PLC versus leaf water potential relationship indicated diurnal refilling of cavitated xylem. The leaf water potential causing 50 PLC (P50) was 1.6 MPa and did not differ between upland versus lowland rice varieties. Greenhouse-grown varieties (Utah) were more resistant to cavitation with a 50 PLC of 1.9 MPa but also showed no difference between varieties. Six-day droughts caused concomitant reductions in leaf-specific photosynthetic rate, leaf diffusive conductance, and soil-leaf hydraulic conductance that were associated with cavitation-inducing water potentials and the disappearance of nightly root pressure. The return of root pressure after drought was associated with the complete recovery of leaf diffusive conductance, leaf-specific photosynthetic rate, and soil-leaf hydraulic conductance. Root pressure after the 6-d drought (61.2 8.8 kPa) was stimulated 7-fold compared with well-watered plants before drought (8.5 3.8 kPa). The results indicate: (a) that xylem cavitation plays a major role in the reduction of plant hydraulic conductance during drought, and (b) that rice can readily reverse cavitation, possibly aided by nocturnal root pressure. PMID:12857848

Stiller, Volker; Lafitte, H. Renee; Sperry, John S.

2003-01-01

351

UV-B impairs growth and gas exchange in grapevines grown in high altitude.  

PubMed

We previously demonstrated that solar ultraviolet-B (UV-B) radiation levels in high altitude vineyards improve berry quality in Vitis vinifera cv. Malbec, but also reduce berry size and yield, possibly as a consequence of increased oxidative damage and growth reductions (lower photosynthesis). The defense mechanisms toward UV-B signal and/or evoked damage promote production of antioxidant secondary metabolites instead of primary metabolites. Purportedly, the UV-B effects will depend on tissues developmental stage and interplay with other environmental conditions, especially stressful situations. In this work, grapevines were exposed to high solar UV-B (+UV-B) and reduced (by filtering) UV-B (-UV-B) treatments during three consecutive seasons, and the effects of UV-B, developmental stages and seasons on the physiology were studied, i.e. growth, tissues morphology, photosynthesis, photoprotective pigments, proline content and antioxidant capacity of leaves. The +UV-B reduced photosynthesis and stomatal conductance, mainly through limitation in gas exchange, reducing plant's leaf area, net carbon fixation and growth. The +UV-B augmented leaf thickness, and also the amounts of photoprotective pigments and proline, thereby increasing the antioxidant capacity of leaves. The defense mechanisms triggered by + UV-B reduced lipid peroxidation, but they were insufficient to protect the photosynthetic pigments per leaf dry weight basis. The +UV-B effects depend on tissues developmental stage and interplay with other environmental conditions such as total radiation and air temperatures. PMID:23167433

Berli, Federico J; Alonso, Rodrigo; Bressan-Smith, Ricardo; Bottini, Rubn

2013-09-01

352

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

PubMed

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

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

2007-01-01

353

Comparison of gas exchange, lactate, and lactic acidosis thresholds in patients with chronic obstructive pulmonary disease.  

PubMed

During an incremental exercise test, three consequences of the onset of anaerobic metabolism can be observed: rise in blood lactate (lactate threshold, LT); fall in standard bicarbonate (lactic acidosis threshold, LAT); nonlinear increase in CO2 output (V-slope gas exchange threshold, GET). We compared these thresholds in 31 patients with COPD. We found that the GET and LAT overestimated the LT. A better relationship was found between LAT and GET, even though GET was significantly higher than LAT (by 124 ml/min; p < 0.0001). However, since the bias is appreciably greater at lower LAT values (likely because VCO2 kinetics are slower than VO2 kinetics), we separated the studies into two groups: (A) tests where LAT occurred within the first 2 min of the increasing work rate period, and (B) tests where LAT occurred after 2 min. For Group A, there was a substantial bias between LAT and GET (323 ml/min, p < 0.0001), whereas the bias was much smaller (only 5.4%, though statistically significant) for Group B (57 ml/min, p < 0.01). We conclude that when lactic acidosis occurs after the first 2 min of incremental exercise, the GET closely approximates the point at which blood bicarbonate begins to fall. PMID:8368633

Patessio, A; Casaburi, R; Carone, M; Appendini, L; Donner, C F; Wasserman, K

1993-09-01

354

Contact activation of blood plasma and factor XII by ion-exchange resins.  

PubMed

Sepharose ion-exchange particles bearing strong Lewis acid/base functional groups (sulfopropyl, carboxymethyl, quaternary ammonium, dimethyl aminoethyl, and iminodiacetic acid) exhibiting high plasma protein adsorbent capacities are shown to be more efficient activators of blood factor XII in neat-buffer solution than either hydrophilic clean-glass particles or hydrophobic octyl sepharose particles (FXII (activator)?(surface) FXIIa; a.k.a autoactivation, where FXII is the zymogen and FXIIa is a procoagulant protease). In sharp contrast to the clean-glass standard of comparison, ion-exchange activators are shown to be inefficient activators of blood plasma coagulation. These contrasting activation properties are proposed to be due to the moderating effect of plasma-protein adsorption on plasma coagulation. Efficient adsorption of blood-plasma proteins unrelated to the coagulation cascade impedes FXII contacts with ion-exchange particles immersed in plasma, reducing autoactivation, and causing sluggish plasma coagulation. By contrast, plasma proteins do not adsorb to hydrophilic clean glass and efficient autoactivation leads directly to efficient activation of plasma coagulation. It is also shown that competitive-protein adsorption can displace FXIIa adsorbed to the surface of ion-exchange resins. As a consequence of highly-efficient autoactivation and FXIIa displacement by plasma proteins, ion-exchange particles are slightly more efficient activators of plasma coagulation than hydrophobic octyl sepharose particles that do not bear strong Lewis acid/base surface functionalities but to which plasma proteins adsorb efficiently. Plasma proteins thus play a dual role in moderating contact activation of the plasma coagulation cascade. The principal role is impeding FXII contact with activating surfaces, but this same effect can displace FXIIa from an activating surface into solution where the protease can potentiate subsequent steps of the plasma coagulation cascade. PMID:21982294

Josh Yeh, Chyi-Huey; Dimachkie, Ziad O; Golas, Avantika; Cheng, Alice; Parhi, Purnendu; Vogler, Erwin A

2012-01-01

355

Corrosive resistant heat exchanger  

Microsoft Academic Search

A corrosive and errosive resistant heat exchanger which recovers heat from a contaminated heat stream. The heat exchanger utilizes a boundary layer of innocuous gas, which is continuously replenished, to protect the heat exchanger surface from the hot contaminated gas. The innocuous gas is conveyed through ducts or perforations in the heat exchanger wall. Heat from the heat stream is

Richlen; Scott L

1989-01-01

356

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

SciTech Connect

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.

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

1987-11-01

357

Ohio oil and gas activity, exploration on the upswing  

Microsoft Academic Search

For the first time in several years, there was improvement in almost every area of Ohio oil and gas activity in 1996. Higher oil and gas prices combined with an improved exploratory success rate helped increase drilling. The number of discoveries since 1990 has helped energize operators and change their drilling focus. The Ohio industry in 1996 continued its progression

McCormac

1997-01-01

358

Ion-exchange sorption and preparative chromatography of biologically active materials  

SciTech Connect

This book presents information on the following topics: the problems of fine physico-chemical biotechnology; types of highly permeable network polyelectrolytes; methods for studying the permeability and porosity of network polyelectrolytes; the conformation state and flexibility of the structural elements of network polyelectrolytes; ion-exchange processes without the sorption of physiologically active substances; ion exchange, hydration, and swelling; nucleosides, nucleotides, alkaloids, sulfonamides, and miscellaneous physiologically active subtances; sharp front formation for the exchange of ions with the same valences; standard quasi-equilibrium frontal chromatography on ionites; sorption kinetics in ionites with structural heterogeneity; experimental investigations of the diffusivities of organic and physiologically active ions in ionite beads; and increasing the efficiency of low-pressure chromatography by using surface-layer and bidispersed ionites.

Samsonov, G.V.

1986-01-01

359

Corrosive resistant heat exchanger  

DOEpatents

A corrosive and errosive resistant heat exchanger which recovers heat from a contaminated heat stream. The heat exchanger utilizes a boundary layer of innocuous gas, which is continuously replenished, to protect the heat exchanger surface from the hot contaminated gas. The innocuous gas is conveyed through ducts or perforations in the heat exchanger wall. Heat from the heat stream is transferred by radiation to the heat exchanger wall. Heat is removed from the outer heat exchanger wall by a heat recovery medium.

Richlen, Scott L. (Annandale, VA)

1989-01-01

360

We can combine measurements of the air-sea pCO2 equilibrium in the mid-1990s with various relationships of the air-sea gas exchange rate with wind-  

E-print Network

relationships of the air-sea gas exchange rate with wind- speed (Equation 1) to estimate the net uptake rate Measurements of carbon-14 in the ocean and atmosphere can constrain both the global mean air-sea gas exchange-sea carbon-13 and CO2 fluxes can also be used to test proposed air-sea gas exchange distribu- tions. Based

Krakauer, Nir Y.

361

Contact Activation of Blood Plasma and Factor XII by Ion-exchange Resins  

PubMed Central

Sepharose ion-exchange particles bearing strong Lewis acid/base functional groups (sulfopropyl, carboxymethyl, quarternary ammonium, dimethyl aminoethyl, and iminodiacetic acid) exhibiting high plasma protein adsorbent capacities are shown to be more efficient activators of blood factor XII in neat-buffer solution than either hydrophilic clean-glass particles or hydrophobic octyl sepharose particles ( FXII?surfaceactivatorFXIIa; a.k.a autoactivation, where FXII is the zymogen and FXIIa is a procoagulant protease). In sharp contrast to the clean-glass standard of comparison, ion-exchange activators are shown to be inefficient activators of blood plasma coagulation. These contrasting activation properties are proposed to be due to the moderating effect of plasma-protein adsorption on plasma coagulation. Efficient adsorption of blood plasma proteins unrelated to the coagulation cascade impedes FXII contacts with ion-exchange particles immersed in plasma, reducing autoactivation, and causing sluggish plasma coagulation. By contrast, plasma proteins do not adsorb to hydrophilic clean glass and efficient autoactivation leads directly to efficient activation of plasma coagulation. It is also shown that competitive-protein adsorption can displace FXIIa adsorbed to the surface of ion-exchange resins. As a consequence of highly-efficient autoactivation and FXIIa displacement by plasma proteins, ion-exchange particles are slightly more efficient activators of plasma coagulation than hydrophobic octyl sepharose particles that do not bear strong Lewis acid/base surface functionalities but to which plasma proteins adsorb efficiently. Plasma proteins thus play a dual role in moderating contact activation of the plasma coagulation cascade. The principal role is impeding FXII contact with activating surfaces but this same effect can displace FXIIa from an activating surface into solution where the protease can potentiate subsequent steps of the plasma coagulation cascade. PMID:21982294

Yeh, Chyi-Huey Josh; Dimachkie, Ziad O.; Golas, Avantika; Cheng, Alice; Parhi, Purnendu; Vogler, Erwin A.

2011-01-01

362

Involvement of Plant Growth Substances in the Alteration of Leaf Gas Exchange of Flooded Tomato Plants 1  

PubMed Central

Ethylene, abscisic acid, and cytokinins were tested for their ability to either induce or prevent the changes which occur in gas exchange characteristics of tomato (Lycopersicon esculentum Mill. cv. Rheinlands Ruhm) leaves during short-term soil flooding. Ethylene, which increases in the shoots of flooded plants, had no effect on stomatal conductance or photosynthetic capacity of drained plants. Abscisic acid, which also accumulates in the shoots of flooded plants, could reproduce the stomatal behavior of flooded plants when sprayed on the leaves of drained plants. However, photosynthetic capacity of drained plants was unaffected by abscisic acid sprays. Cytokinin export from the roots to the shoots declines in flooded plants. Spray applications of benzyladenine increased stomatal conductance in both flooded and drained plants. In addition, the decline in photosynthetic capacity during flooding was largely prevented by supplementary cytokinin applications. The possible involvement of these growth substances in modifying leaf gas exchange during flooding is discussed. PMID:16663243

Bradford, Kent J.

1983-01-01

363

The greenhouse gas exchange responses of methane and nitrous oxide to forest change in Europe  

NASA Astrophysics Data System (ADS)

Climate change and air pollution, interact with altering forest management and land-use change to produce short and long-term changes to forest in Europe. The impact of these changes on the forest greenhouse gas (GHG) balance is currently difficult to predict. To improve the mechanistic understanding of the ongoing changes, we studied the response of GHG (N2O, CH4) exchange from forest soils at twelve experimental or natural gradient forest sites, representing anticipated future forest change. The experimental manipulations one or more per site included nitrogen (N) addition (4 sites), changes of climate (temperature, 1 site; precipitation, 2 sites), soil hydrology (3 sites), harvest intensity (1 site), wood ash fertilization (1 site), pH gradient in peat (1 site) and afforestation of cropland (1 site). In most of the investigated treatments N2O emissions increased by 7 3 (range 0-30) ?g N2O-N m-2 h-1 across all treatments on mineral soils, but by up to 10 times the mineral soil maximum on an acidic organic soil. Soil moisture together with mineral soil C/N ratio and pH were found to significantly influence N2O emissions across all treatments. Emissions increased with N availability and decreased with soil C/N ratio, especially in interaction with increased soil moisture. High pH reduced the formation of N2O, even under otherwise favourable soil conditions. Oxidation (uptake) of CH4 was reduced from 16 2 to 4 6 ?g CH4-C m-2 h-1 by the investigated treatments. The CH4 exchange was significantly influenced by soil moisture and soil C/N ratio across all treatments, and CH4 emissions occurred only in wet or water-saturated conditions. For most of the investigated forest manipulations or natural gradients, the response of both N2O and CH4 fluxes was towards reducing the overall GHG forest sink. The most resilient forests were dry Mediterranean forests, as well as forests with high soil C/N ratio or high soil pH. Mitigation strategies may focus on (i) sustainable management of wet forest areas and forested peat lands, (ii) continuous forest cover management, (iii) reducing atmospheric N input and, thus, N availability, and (iv) improving neutralisation capacity of acid soils (e.g. wood ash application).

Gundersen, P.; Christiansen, J. R.; Alberti, G.; Brggemann, N.; Castaldi, S.; Gasche, R.; Kitzler, B.; Klemedtsson, L.; Lobo-do-Vale, R.; Moldan, F.; Rtting, T.; Schleppi, P.; Weslien, P.; Zechmeister-Boltenstern, S.

2012-05-01

364

Dissociative Charge Exchange of Rare-Gas Ions with C2F6 and C3F8  

Microsoft Academic Search

Dissociative charge exchange of rare-gas ions with C2F6 and C3F8 has been studied. The data was obtained with a single-stage Nuclide mass spectrometer by operating the ion source in the CˇermakHerman mode. A charge-transfer mass spectrum was obtained for C2F6 and C3F8 with each rare-gas ion except Xe. The relative ionic abundances were interpreted as portraying the dissociation of C2F6+

Dave Smith; Larry Kevan

1967-01-01

365

Collective nature of two-dimensional electron gas spin excitations revealed by exchange interaction with magnetic ions  

NASA Astrophysics Data System (ADS)

Time-resolved Kerr rotation experiments in CdMnTe quantum wells provide the evidence of mixed spin excitations of the two-dimensional electron gas and magnetic ions. The onset of strong coupling between electron and Mn spin modes reveals the collective (spin-wave) nature of electronic spin excitations probed by this method. We show that resonant exchange coupling between electron-spin waves and magnetic ions spin-flip excitations provide insights in the many-body physics of the two-dimensional electron gas.

Barate, P.; Cronenberger, S.; Vladimirova, M.; Scalbert, D.; Perez, F.; Gmez, J.; Jusserand, B.; Boukari, H.; Ferrand, D.; Mariette, H.; Cibert, J.; Nawrocki, M.

2010-08-01

366

Leaf gas exchange of trees in old-growth and young secondary forest stands in Sulawesi, Indonesia  

Microsoft Academic Search

In the tropics, old-growth forests are converted to other land cover types at a high rate and young secondary forest may gain\\u000a in importance. Information on associated changes in leaf gas exchange and other leaf traits can be valuable for modelling\\u000a biogeochemical fluxes under altered land-use patterns. We studied in situ photosynthetic parameters and stomatal conductance\\u000a for water vapour in

Dirk Hlscher; Christoph Leuschner; Kerstin Bohman; Marc Hagemeier; Jana Juhrbandt; Soekisman Tjitrosemito

2006-01-01

367

The relationship between steady-state gas exchange of bean leaves and the levels of carbon-reduction-cycle intermediates  

Microsoft Academic Search

The relationship between the gas-exchange characteristics of attached leaves of Phaseolus vulgaris L. and the pool sizes of several carbon-reduction-cycle intermediates was examined. After determining the rate of CO2 assimilation at known intercellular CO2 pressure, O2 pressure and light, the leaf was rapidly killed (2, photosynthesis appeared RuBP-saturated at low CO2 pressure and RuBP-limited at high CO2 pressure. In 21

Murray R. Badger; Thomas D. Sharkey; Susanne von Caemmerer

1984-01-01

368

Shoot water relations and gas exchange of western hemlock and western red cedar seedlings during establishment on a reforestation site  

Microsoft Academic Search

Shoot water relations, summer gas exchange response and morphological development of western hemlock [Tsuga heterophylla (Raf.) Sarg.] and western red cedar (Thuja plicata Donn) seedlings were monitored over the first growing season on a coastal reforestation site in British Columbia. In March, osmotic potential (?s) at saturation [?s(sat)] was -1.98 MPa and turgor loss point [?s(tlp)] -2.38 MPa for western

Steven C. Grossnickle

1993-01-01

369

A general model of forest ecosystem processes for regional applications I. Hydrologic balance, canopy gas exchange and primary production processes  

Microsoft Academic Search

Running, S.W. and Coughlan, J.C., 1988. A general model of forest ecosystem processes for regional applications. I. Hydrologic balance, canopy gas exchange and primary production processes. Ecol. Modelling, 42: 125-154. An ecosystem process model is described that calculates the carbon, water and nitrogen cycles through a forest ecosystem. The model, FOREST-BGC, treats canopy interception and evaporation, transpiration, photosynthesis, growth and

STEVEN W. RUNNING; JOSEPH C. COUGHLAN

1988-01-01

370

Leaf gas exchange, chlorophyll fluorescence and growth responses of Melaleuca alternifolia seedlings to flooding and subsequent recovery  

Microsoft Academic Search

Periodic flooding of trees in tropical floodplains and reservoirs where water levels fluctuate is a common phenomenon. The\\u000a effects of flooding and subsequent recovery on gas exchange, chlorophyll fluorescence and growth responses of Melaleuca alternifolia seedlings, a tall shrub species used in floodplain and reservoir forest restoration in southern China, were studied during\\u000a a grow season (from March to December

Y. X. Jing; G. L. Li; B. H. Gu; D. J. Yang; L. Xiao; R. X. Liu; C. L. Peng

2009-01-01

371

Gas exchange across an air-water interface: experimental results and modeling of bubble contribution to transfer  

Microsoft Academic Search

Gas exchange experiments have been performed in a wind-water tunnel filled with fresh water or seawater. Transfer velocities have been measured for nitrous oxide and argon in a range of wind speeds extending from 3 m\\/s to 14 m\\/s. The air-liquid interface was covered either with only normally developed wind waves or with mechanically generated waves in addition. For u<9

Liliane Merlivat; Laurent Memery

1983-01-01

372

Role of gas exchange in the inorganic carbon, oxygen, and ²²²Rn budgets of the Amazon River  

Microsoft Academic Search

Dissolved oxygen, ²²²Rn, pCO, alkalinity, respiration rate, and discharge have been measured at eight mainstem and seven tributary stations during February-March 1984 in a 1700-km stretch of the Amazon River between Vargem Grande and Obidos in Brazil. Air-water gas exchange rates were estimated two ways: measurements of the flux of ²²²Rn int floating domes yielded an average boundary layer thickness

ALLAN H. DEVOL; PAUL D. QUAY; JEFFREY E. RICHEY; LUIZ A. MARTINELLI

1987-01-01

373

Active heat exchange system development for latent heat thermal energy storage  

NASA Technical Reports Server (NTRS)

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.

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

1980-01-01

374

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

PubMed Central

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 (0.511.10 ?g NH3 m?3) and those calculated from apoplast extracts were lower than any yet reported (0.0170.54 ?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

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

2001-01-01

375

Pulmonary hypertension in patients with idiopathic pulmonary fibrosis - the predictive value of exercise capacity and gas exchange efficiency.  

PubMed

Exercise capacity and survival of patients with IPF is potentially impaired by pulmonary hypertension. This study aims to investigate diagnostic and prognostic properties of gas exchange during exercise and lung function in IPF patients with or without pulmonary hypertension. In a multicentre setting, patients with IPF underwent right heart catheterization, cardiopulmonary exercise and lung function testing during their initial evaluation. Mortality follow up was evaluated. Seventy-three of 135 patients [82 males; median age of 64 (56; 72 years)] with IPF had pulmonary hypertension as assessed by right heart catheterization [median mean pulmonary arterial pressure 34 (27; 43) mmHg]. The presence of pulmonary hypertension was best predicted by gas exchange efficiency for carbon dioxide (cut off ?152% predicted; area under the curve 0.94) and peak oxygen uptake (?56% predicted; 0.83), followed by diffusing capacity. Resting lung volumes did not predict pulmonary hypertension. Survival was best predicted by the presence of pulmonary hypertension, followed by peak oxygen uptake [HR 0.96 (0.93; 0.98)]. Pulmonary hypertension in IPF patients is best predicted by gas exchange efficiency during exercise and peak oxygen uptake. In addition to invasively measured pulmonary arterial pressure, oxygen uptake at peak exercise predicts survival in this patient population. PMID:23840349

Glser, Sven; Obst, Anne; Koch, Beate; Henkel, Beate; Grieger, Anita; Felix, Stephan B; Halank, Michael; Bruch, Leonhard; Bollmann, Tom; Warnke, Christian; Schper, Christoph; Ewert, Ralf

2013-01-01

376

Pulmonary Hypertension in Patients with Idiopathic Pulmonary Fibrosis The Predictive Value of Exercise Capacity and Gas Exchange Efficiency  

PubMed Central

Exercise capacity and survival of patients with IPF is potentially impaired by pulmonary hypertension. This study aims to investigate diagnostic and prognostic properties of gas exchange during exercise and lung function in IPF patients with or without pulmonary hypertension. In a multicentre setting, patients with IPF underwent right heart catheterization, cardiopulmonary exercise and lung function testing during their initial evaluation. Mortality follow up was evaluated. Seventy-three of 135 patients [82 males; median age of 64 (56; 72 years)] with IPF had pulmonary hypertension as assessed by right heart catheterization [median mean pulmonary arterial pressure 34 (27; 43) mmHg]. The presence of pulmonary hypertension was best predicted by gas exchange efficiency for carbon dioxide (cut off ?152% predicted; area under the curve 0.94) and peak oxygen uptake (?56% predicted; 0.83), followed by diffusing capacity. Resting lung volumes did not predict pulmonary hypertension. Survival was best predicted by the presence of pulmonary hypertension, followed by peak oxygen uptake [HR 0.96 (0.93; 0.98)]. Pulmonary hypertension in IPF patients is best predicted by gas exchange efficiency during exercise and peak oxygen uptake. In addition to invasively measured pulmonary arterial pressure, oxygen uptake at peak exercise predicts survival in this patient population. PMID:23840349

Glser, Sven; Obst, Anne; Koch, Beate; Henkel, Beate; Grieger, Anita; Felix, Stephan B.; Halank, Michael; Bruch, Leonhard; Bollmann, Tom; Warnke, Christian; Schper, Christoph; Ewert, Ralf

2013-01-01

377

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

NASA Technical Reports Server (NTRS)

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.

Ebiana, Asuquo B.; Gidugu, Praveen

2008-01-01

378

Pulmonary microvascular permeability and gas exchange in patients with syndrome X  

PubMed Central

Aim:This clinical study was planned to assess pulmonary microvascular permeability in patients with Syndrome X (SX) by using a functional imaging tool, technetium-99m-diethyltriaminepentaaceticacid (99mTc-DTPA) lung clearance scintigraphy, and the pulmonary functions test, which includes diffusion capacity of the lung for carbon monoxide (DLCO). Methods:The study population consisted of 22 non-smoker subjects divided into two groups. First group comprised 12 patients (4 male, 8 female, mean age: 484 years, range 36 to 65) with SX. Ten healthy subject (4 men, 6 female, mean age: 453 years, range 34 to 58) were served as control group. Volumetric pulmonary functions, including DLCO were also performed before lung scintigraphy. Alveolar epithelial permeability was assessed by measuring the pulmonary clearance of an inhaled 99mTc-DTPA using a gamma camera. Results: Spirometric data was comparable in both groups. Although volumetric pulmonary measurements were similar, DLCO values of SX patients were lower than those in control (20.91.7 ml/min/mmHg vs. 27.81.3 ml/min/mmHg, p=0.002). The mean clearance rate of 99mTc-DTPA in control subjects was 1066 min, and this value was lower than patients with SX (17919 min; p=0.0001). Conclusion: We conclude that lung is a target organ for SX. The pulmonary gas exchange and microvascular permeability, which is measured by 99mTc-DTPA scintigraphy, are restricted without change of volumetric pulmonary functions in patients with SX. PMID:23935265

Durmus-Altun, G; Vardar, SA; Salihoglu, YS; Aktoz, M; Dirlik, B; Altun, A

2012-01-01

379

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

PubMed Central

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 mLkg-1min-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

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

2014-01-01

380

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

NASA Astrophysics Data System (ADS)

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.

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

2010-09-01

381

Indirect calorimetry: variability of consecutive baseline determinations of carbohydrate and fat utilization from gas exchange measurements.  

PubMed

During the past years, substantial methodological and interpretational limitations of indirect calorimetry, particularly concerning fuel utilisation, have been discussed. The aim of the present study was to evaluate short-time intraindividual variability of two consecutive gas exchange measurement series and of calculated data on total energy expenditure/24 h and carbohydrate and fat utilisation. 24 healthy volunteers (16 f, 8 m, 34.7 +/- 13.1 yrs) were admitted to the study. Trials were performed supine after an 12 h overnight fast. After a resting period of 30-45 min and following equilibration of respiratory values for at least 10 min prior to the test, indirect calorimetry measurements were performed using the Sensor-Medics 2.900 device (canopy). Two measurements series lasting up to 30 min each were performed 15-20 min apart. Total energy production/24 h as well as that obtained from carbohydrate and fat utilisation were calculated in both measurement series. Protein utilisation was derived from estimated urinary 24 h nitrogen excretion. O2-consumption, CO2-production, the respiratory quotient and total energy production/24 h show acceptable mean coefficients of variation of 3.7%, 4.6%, 3.5% and 3.6%, respectively. In contrast, carbohydrate and fat utilisation values demonstrate a coefficient of variation of 21.2% and 17.4%, respectively, suggesting considerable impression of estimates of fuel utilisation by indirect calorimetry. We conclude that for research purposes, particularly over short-time periods, indirect calorimetry provides sufficient accuracy only in estimating total resting energy production, while considerable uncertainty exists in using this method to assess carbohydrate and fat utilisation. PMID:9049647

Gasic, S; Schneider, B; Waldhusl, W

1997-01-01

382

Gas-chromatographic assay for heme oxygenase activity  

SciTech Connect

The authors have developed an improved assay for microsomal heme oxygenase activity, based on the enzymic release of CO from the ..cap alpha..-methene bridge of hemin and the quantitation of CO by gas chromatography. The detection limit for heme oxygenase activity was approximately 1 nmol/h per milligram of microsomal protein. Gas-chromatographic assays of heme oxygenase activities in rat tissues correlated well (r = 0.94) with results by a spectrophotometric assay based on bilirubin production. Heme oxygenase activity was increased 10-fold in kidney microsomes and threefold in liver microsomes from rats killed 17 h after subcutaneous injection of NiCl/sub 2/ (0.5 mmol/kg body wt.). These findings illustrate the efficacy of the gas-chromatographic assay for measuring xenobiotic effects on heme oxygenase activity.

Sunderman, F.W. Jr.; Downs, J.R.; Reid, M.C.; Bibeau, L.M.

1982-01-01

383

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

PubMed

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

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

2014-06-01

384

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

PubMed

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

Klein, Tamir; Hemming, Deborah; Lin, Tongbao; Grnzweig, Jos M; Maseyk, Kadmiel; Rotenberg, Eyal; Yakir, Dan

2005-06-01

385

Active heat exchange system development for latent heat thermal energy storage  

NASA Technical Reports Server (NTRS)

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.

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

1979-01-01

386

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...

387

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...

388

ARSENIC REMOVAL FROM DRINKING WATER BY ION EXCHANGE AND ACTIVATED ALUMINA PLANTS  

EPA Science Inventory

This report documents a long term performance study of two ion exchange (IE) and two activated alumina (AA) treatment plants to remove arsenic from drinking water. Performance information was collected on these systems that are located in the northeast for one full year. The stud...

389

Adsorption and desorption of phenol on anion-exchange resin and activated carbon  

Microsoft Academic Search

Adsorption and desorption of phenol on activated carbon and strong base anion-exchange resin were investigated in a fixed-bed column. Phenol was effectively adsorbed on both adsorbents. Experimental breakthrough curves were compared with values calculated on the assumption of surface diffusion controlling. Two methods of regeneration of adsorbents were carried out, that is, caustic desorption and acid desorption. Regeneration by sodium

Motonobu. Goto; Norio. Hayashi; Shigeo. Goto

1986-01-01

390

Argon-Hydrogen Shielding Gas Mixtures for Activating Flux-Assisted Gas Tungsten Arc Welding  

NASA Astrophysics Data System (ADS)

Using activating flux for gas tungsten arc welding (GTAW) to improve penetration capability is a well-established technique. Argon is an inert gas and the one most widely used as a shielding gas for GTAW. For the most austenitic stainless steels, pure argon does not provide adequate weld penetration. Argon-hydrogen mixtures give a more even heat input to the workpiece, increasing the arc voltage, which tends to increase the volume of molten material in the weld pool as well as the weld depth-to-width ratio. Great interest has been shown in the interaction between activating flux and the hydrogen concentration in an argon-based shielding gas. In this study, the weld morphology, the arc profile, the retained delta ferrite content, the angular distortion, and the microstructures were examined. The application of an activating flux combining argon and hydrogen for GTAW is important in the industry. The results of this study are presented here.

Huang, Her-Yueh

2010-11-01

391

Gas-phase hydrogen/deuterium exchange in a travelling wave ion guide for the examination of protein conformations  

PubMed Central

Accumulating evidence suggests that solution-phase conformations of small globular proteins and large molecular protein assemblies can be preserved for milliseconds after electrospray ionization. Thus, the study of proteins in the gas-phase on this time-scale is highly desirable. Here we demonstrate that a travelling wave ion guide (TWIG) of a Synapt mass spectrometer offers a highly suitable environment for rapid and efficient gas-phase hydrogen/deuterium exchange (HDX). Gaseous ND3 was introduced into either the source TWIG or the TWIG located just after the ion mobility cell, such that ions underwent HDX as they passed through the ND3 on the way to the time-of-flight analyzer. The extent of deuterium labeling could be controlled by varying the quantity of ND3 or the speed of the travelling wave. The gas-phase HDX of model peptides corresponded to labeling of primarily fast exchanging sites due to the short labeling times (ranging from 0.1 to 10 ms). In addition to peptides, gas-phase HDX of ubiquitin, cytochrome c, lysozyme and apomyoglobin were examined. We conclude that HDX of protein ions in a TWIG is highly sensitive to protein conformation, enables the detection of conformers present on sub-milliseconds timescales and can readily be combined with ion mobility spectrometry. PMID:19921790

Rand, Kasper D.; Pringle, Steven D.; Murphy, James P.; Fadgen, Keith E.; Brown, Jeff; Engen, John R.

2009-01-01

392

Program plan for development of hot dirty-gas heat exchangers for coal-gasification systems. [Entrained-flow, moving bed, and fluidized-bed gasifiers  

Microsoft Academic Search

This report deals with the heat exchanger applications, and its scope includes a broad range of gasification systems, such as the generic models for entrained-flow, moving-bed, and fluidized-bed gasifiers. The major application of hot dirty-gas heat exchangers is in the area of heat recovery for improved gasifier efficiency. The inlet temperature requirements for these heat exchangers varies from approx. 650

Churnetski

1983-01-01

393

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

Microsoft Academic Search

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 900C for a long duration. A plate fin type compact heat exchanger (PFCHX) has a large heat transfer area per heat exchanger

Takeshi Takeda; Kazuhiko Kunitomi; Tetsuji Horie; Katsuo Iwata

1997-01-01

394

Comparison of the orders of gas-phase basicities and ammonium ion affinities of polyethers by the kinetic method and ligand exchange technique  

Microsoft Academic Search

The orders of relative gas-phase basicities and ammonium ion affinities of a series of polyethers obtained by application\\u000a of the kinetic method and ligand exchange technique are compared to evaluate the discrepancies of results between the two\\u000a techniques. The order of gas-phase basicities determined by the ligand exchange technique in a quadrupole ion trap agrees\\u000a with the order established previously

H. F. Wu; J. S. Brodbelt

1993-01-01

395

Antisense oligonucleotide suppression of Na +\\/Ca 2+ exchanger activity in primary neurons from rat brain  

Microsoft Academic Search

An antisense (AS) oligodeoxynucleotide based on a conserved sequence in the three isoforms of the Na+\\/Ca2+ exchanger (NCX) was used to decrease expression of this Ca2+ transporter in primary neuronal cultures. Two AS oligo applications decreased NCX activity by ?40% within 1224 h, and neither sense (S) or missense (MS) oligos altered NCX activity. The reduced NCX expression was confirmed

N. S. Ranciat-McComb; K. S. Bland; J. Huschenbett; L. Ramonda; M. Bechtel; A. Zaidi; M. L. Michaelis

2000-01-01

396

17 CFR 229.1206 - (Item 1206) Present activities.  

Code of Federal Regulations, 2010 CFR

...1206 Commodity and Securities Exchanges SECURITIES AND EXCHANGE COMMISSION STANDARD INSTRUCTIONS...SECURITIES ACT OF 1933, SECURITIES EXCHANGE ACT OF 1934 AND ENERGY POLICY...Registrants Engaged in Oil and Gas Producing Activities ...

2010-04-01

397

17 CFR 229.1206 - (Item 1206) Present activities.  

Code of Federal Regulations, 2011 CFR

...1206 Commodity and Securities Exchanges SECURITIES AND EXCHANGE COMMISSION STANDARD INSTRUCTIONS...SECURITIES ACT OF 1933, SECURITIES EXCHANGE ACT OF 1934 AND ENERGY POLICY...Registrants Engaged in Oil and Gas Producing Activities ...

2011-04-01

398

17 CFR 229.1206 - (Item 1206) Present activities.  

Code of Federal Regulations, 2013 CFR

...1206 Commodity and Securities Exchanges SECURITIES AND EXCHANGE COMMISSION STANDARD INSTRUCTIONS...SECURITIES ACT OF 1933, SECURITIES EXCHANGE ACT OF 1934 AND ENERGY POLICY...Registrants Engaged in Oil and Gas Producing Activities ...

2013-04-01

399

17 CFR 229.1206 - (Item 1206) Present activities.  

Code of Federal Regulations, 2012 CFR

...1206 Commodity and Securities Exchanges SECURITIES AND EXCHANGE COMMISSION STANDARD INSTRUCTIONS...SECURITIES ACT OF 1933, SECURITIES EXCHANGE ACT OF 1934 AND ENERGY POLICY...Registrants Engaged in Oil and Gas Producing Activities ...

2012-04-01

400

17 CFR 229.1206 - (Item 1206) Present activities.  

Code of Federal Regulations, 2014 CFR

...1206 Commodity and Securities Exchanges SECURITIES AND EXCHANGE COMMISSION STANDARD INSTRUCTIONS...SECURITIES ACT OF 1933, SECURITIES EXCHANGE ACT OF 1934 AND ENERGY POLICY...Registrants Engaged in Oil and Gas Producing Activities ...

2014-04-01

401

Thermal hydraulic study on a high-temperature gasgas heat exchanger with helically coiled tube bundles  

Microsoft Academic Search

An experimental study was carried out to investigate flow-induced vibration, heat transfer and pressure drop of helically coiled tubes of an intermediate heat exchanger (IHX) for the HTTR, using a full-size partial model and air as the fluid. The test model has 54 helically coiled tubes separated into three layer bundles, surrounding the center pipe. The vibration of the tube

Yoshiyuki Inagaki; Hiroshi Koiso; Hideki Takumi; Ikuo Ioka; Yoshiaki Miyamoto

1998-01-01

402

Evolution of volatile substances from strongly basic anion-exchangers into the gas phase  

SciTech Connect

The purpose of this work was chemical evaluation, from the sanitary standpoint, of strongly basic anion-exchangers and of polyacrylonitrile fibers filled with them, in relation to their use for purification of air intended for human respiration. The carbonate forms of granulated anion-exchange resins AV-17-8 and AV-29-10P and fibers filled with them were investigated. Amines were determined spectrophotometrically. It is determined that the sanitary chemical characteristics of PAN fibers filled with strongly basic anion-exchangers of the polymerization type make them suitable for removing substances which have no destructive effects on the resins from air.

Ryabikina, L.G.; Afanas'eva, E.K.; Vulkih, A.I.; Yakovlev, A.I.

1985-05-10

403

Consistent one-pion exchange currents in electron scattering from a relativistic Fermi gas  

E-print Network

A set of fully relativistic one-pion-exchange electromagnetic operators is developed for use in one-particle emission reactions induced by electrons. To preserve the gauge invariance of the theory additional pionic correlation operators are required beyond the usual meson-exchange current operators. Of these, in the present work emphasis is placed on the self-energy current which is infinite and needs to be renormalized. The renormalized current is expanded to first order to obtain a genuine one-pion-exchange contribution to the inclusive responses.

J. E. Amaro; M. B. Barbaro; J. A. Caballero; T. W. Donnelly; A. Molinari

2001-07-26

404

Gas-Surface Chemical Exchange in the Near-surface Atmosphere of Europa  

NASA Astrophysics Data System (ADS)

The very tenuous O2 atmosphere of Europa is a near-surface (or surface-bounded) atmosphere [1]. It is produced by the radiolysis of Europa's surface due to exposure to solar ultraviolet radiation and energetic magnetospheric plasma ions and electrons. Earlier we developed a collisional Monte Carlo model of Europa's atmosphere [2] accounting for adsorption, thermalization and re-emission of condensed O2, a stable decomposition product of H2O radiolysis. Dissociation and ionization by magnetospheric electron and solar UV-photon impact, and collisional ejection from the atmosphere by the low energy plasma were also taken into account. It was found that to account for the production of oxygen emission observed by HST [3] larger surface fluxes of O2 are required than those assumed in earlier work from measured fluxes of magnetospheric particles [4]. This has since been shown to be due to the fact that radiolysis is occurring in a regolith and not on a laboratory surface [5]. In this report we present the results of an expanded Monte Carlo model of Europa's atmosphere. In this model the sublimation and sputtering sources of H2O molecules and their molecular fragments are also included. Therefore, we account for water and oxygen photochemistry in the near surface atmospheric region and for adsorption-desorption of radiolytic water products onto the satellite surface. This expanded model allowed us to emphasize the important role of chemical exchange in the atmosphere-surface interface of Europa. The numerical modeling of chemical composition in both the near-surface gas-phase boundary region and the satellite surface provides a more complete accounting of the chemical pathways occurring in the icy satellite surface material following decomposition by the solar ultraviolet radiation and the energetic magnetospheric plasma. The model will eventually be expanded to include the effect of the release of trace amounts of SO2 and CO2 that are trapped in the surface ice. [1] Johnson, R.E., 2002, in Atmospheres in the Solar System: Comparative Aeronomy Geophy. Mono. AGU, p. 203. [2] Shematovich and Johnson, 2001, Adv. Space Res., v.27, 1881. [3] Hall et al., 1998, Astrophys. J., v.499, 475. [4] Cooper et al., 2001, Icarus, v.149, 133. [5] Johnson et al., 2003, In Jupiter: Satellites, Atmosphere, Magnetosphere. Ed. by F. Bagenal, Univ. of Arizona Press, 2003.

Shematovich, V. I.; Johnson, R. E.; Cooper, J. F.

2002-12-01

405

Effects of drought on leaf gas exchange in an eastern broadleaf deciduous forest  

NASA Astrophysics Data System (ADS)

Understanding plant physiological adaptations to drought is critical for predicting changes in ecosystem productivity that result from climate variability and future climate change. From 2011-2013, southern Indiana experienced a late growing season drought in 2011, a severe early season drought in 2012, and a wet growing season in 2013 characterized by an absence of water stress with frequent precipitation and milder temperatures. The 2012 drought was unique due to the severity and early onset drought conditions (compared to the more frequent late season drought) and was characterized by a Palmer Drought severity index below -4 and precipitation totals from May - July that were 70% less than the long-term (2000 - 2010) mean. During the 2012 drought, an 11% decline in net ecosystem productivity relative to the long-term mean was observed at the AmeriFlux tower in Morgan Monroe State Forest despite a growing season that started ~25 days earlier. Thus, the objective of this study is to evaluate species-specific contributions to the canopy-scale response to inter-annual variability in water stress. We investigated differences between tree species in their response to climate variability using weekly leaf gas exchange and leaf water potential measurements during the growing seasons of 2011-2013. We used this unique dataset, collected at the top of the canopy with a 25 m boom lift, to evaluate changes in leaf water status and maximum assimilation capacity in the drought versus non-drought years. The leaf-level physiology of oak (Quercus) species appears to be less sensitive to drought than other species (tulip poplar [Liriodendron tulipifera], sassafras [Sassafras albidum] and sugar maple [Acer saccharum]). Preliminary data shows mean canopy leaf water potential for oaks was 30.5% more negative in May-July 2012 versus the same time period in 2013. During these same periods the rate of C assimilation in oaks was reduced by only 3%, whereas other species were reduced by closer to 10-20% in the drought year. We then assess how assimilation capacity and leaf water potential relate to marginal water use efficiency across species and years. Given that this region is predicted to experience more water stress over the coming decades, these results will inform predictions as to how species composition will drive ecosystem responses to climate variability.

Roman, D. T.; Brzostek, E. R.; Dragoni, D.; Rahman, A. F.; Novick, K. A.; Phillips, R.

2013-12-01

406

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

PubMed Central

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

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

407

Gauge and Lorentz invariant one-pion exchange currents in electron scattering from a relativistic Fermi gas  

E-print Network

A consistent analysis of relativistic pionic correlations and meson-exchange currents for electroweak quasielastic electron scattering from nuclei is carried out. Fully-relativistic one-pion-exchange electromagnetic operators are developed for use in one-particle emission electronuclear reactions within the context of the relativistic Fermi gas model. Then the exchange and pionic correlation currents are set up fully respecting the gauge invariance of the theory. Emphasis is placed on the self-energy current which, being infinite, needs to be renormalized. This is achieved starting in the Hartree-Fock framework and then expanding the Hartree-Fock current to first order in the square of the pion coupling constant to obtain a truly, gauge invariant, one-pion-exchange current. The model is applied to the calculation of the parity-conserving (PC) and parity-violating (PV) inclusive responses of nuclei. Interestingly, in the pionic correlations terms exist which arise uniquely from relativity, although their impact on the responses is found to be modest.

J. E. Amaro; M. B. Barbaro; J. A. Caballero; T. W. Donnelly; A. Molinari

2002-04-01

408

Adsorption and desorption of phenol on anion-exchange resin and activated carbon  

SciTech Connect

Adsorption and desorption of phenol on activated carbon and strong base anion-exchange resin were investigated in a fixed-bed column. Phenol was effectively adsorbed on both adsorbents. Experimental breakthrough curves were compared with values calculated on the assumption of surface diffusion controlling. Two methods of regeneration of adsorbents were carried out, that is, caustic desorption and acid desorption. Regeneration by sodium hydroxide or hydrochloric acid was effectively performed for the resin. On the other hand, regeneration of the activated carbon by sodium hydroxide was not performed completely. The adsorption capacity for activated carbon decreased gradually during the repetition process of adsorption and desorption, while the capacity for anion-exchange resin remained constant. 14 references, 9 figures, 1 table.

Goto, M.; Hayashi, N.; Goto, S.

1986-05-01

409

Greenhouse gas exchange in West African savanna ecosystems - how important are emissions from termite mounds?  

NASA Astrophysics Data System (ADS)

Savannas cover large areas of the Earth's surface and play an important role in global carbon and nitrogen cycling. In this study, we present the soil-atmosphere exchange of N2O, CH4, and CO2 during two field campaigns throughout the growing seasons 2005 and 2006 at a natural savanna site that was not subject to human disturbances except for annual burning, and four agricultural sites planted with sorghum (n=2), cotton and peanut in Burkina Faso. The annual N2O emission of the nature reserve site amounted to 0.52 kg N2O-N ha-1 yr-1 in 2005 and to 0.67 kg N2O-N ha-1 yr-1 in 2006, whereas the calculated average annual N2O release of the crop sites was only 0.19 and 0.20 kg N2O-N ha-1 yr-1 in 2005 and 2006, respectively. As a result of a temporal up-scaling approach, a lower bound of annual N2O release could be given for two fertilized sorghum plots, that is, 0.83 kg N2O-N ha-1 yr-1 for a highly fertilized plot and 0.44 kg N2O-N ha-1 yr-1 for a moderately fertilized plot. During the rainy season both CH4 uptake in the range of up to 20 ?g CH4-C m-2 h-1 as well as CH4 emission up to 300 ?g CH4-C m-2 h-1 were observed at the nature reserve site, which was on average a CH4 source of 87.4 and 30.8 ?g CH4-C m-2 h-1 in 2005 and 2006, respectively. All crop sites were on average weak CH4 sinks without significant seasonal variation. Uptake rates ranged between 2.5 and 8.7 ?g CH4-C m-2 h-1. Occasionally very low net CH4 emission was observed after heavy rainfall events. Mean annual CH4 rates could be estimated to 2.48 kg CH4-C ha-1 yr-1 and -0.68 kg CH4-C ha-1 yr-1 for the nature reserve site and the crop sites, respectively. Trace gas emissions from termite (Cubitermes fungifaber) mounds that were almost exclusively found at the nature reserve were one order of magnitude higher for N2O and CO2, and two orders of magnitude higher for CH4 than soil emissions of the respective trace gas. Termite N2O, CH4 and CO2 release at the nature reserve contributed only 3.2%, 8.1% and 0.4% to total soil N2O, CH4 and CO2 emissions, respectively.

Brmmer, C.; Brggemann, N.

2012-04-01

410

MAPLE activities and applications in gas sensors  

NASA Astrophysics Data System (ADS)

During the last decade, many groups have grown thin films of various organic materials by the cryogenic Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique with a wide range of applications. This contribution is focused on the summary of our results with deposition and characterization of thin films of fibrinogen, pullulan derivates, azo-polyurethane, cryoglobulin, polyvinyl alcohol, and bovine serum albumin dissolved in physiological serum, dimethyl sulfoxide, sanguine plasma, phosphate buffer solution, H2O, ethylene glycol, and tert-butanol. MAPLE films were characterized using FTIR, AFM, Raman scattering, and SEM. For deposition, a special hardware was developed including a unique liquid nitrogen cooled target holder. Overview of MAPLE thin film applications is given. We studied SnAcAc, InAcAc, SnO2, porphyrins, and polypyrrole MAPLE fabricated films as small resistive gas sensors. Sensors were tested with ozone, nitrogen dioxide, hydrogen, and water vapor gases. In the last years, our focus was on the study of fibrinogen-based scaffolds for application in tissue engineering, wound healing, and also as a part of layers for medical devices.

Jelnek, Miroslav; Remsa, Jan; Kocourek, Tom; Kubeov, Barbara; Sch?rek, Jakub; Myslk, Vladimr

2011-11-01

411

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

NASA Astrophysics Data System (ADS)

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 stages, one for the detection of helium, hydrogen, oxygen, nitrogen, methane, carbon monoxide, and the six hydrogen molecules by means of a thermal conductivity detector (TCD) and one for the detection of carbon monoxide, methane, carbon dioxide, and higher hydrocarbons by means of a flame ionization detector (FID). A flow proportional counting detector (FPCD) is placed in series to TCD and FID for the specific analysis of tritiated gas compounds. A detailed description of the system and of its performance will be given which was evaluated using several calibrated gas mixtures including test runs with tritiated species at JET. The gas species mentioned above can be detected in the concentration range from ppm levels to 100%. The estimated error is about 20% at very low concentrations and 1% at high concentrations. The required minimum detection limit for the TCD can be achieved by the injection of large samples and the use of large filament currents. In addition, neon or helium can be chosen as carrier gas. The use of Ne increases the sensitivity for hydrogen and allows the detection of He, whereas He carrier gas gives superior TCD results for all other gases. Due to the high sensitivity of the FPCDs ppb levels of tritiated gas species can be detected.

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

1993-09-01

412

Probing the mechanisms and dynamics of gas phase hydrogen-deuterium exchange reactions of sodiated polyglycines.  

PubMed

The rate constants for H-D exchange reactions of sodiated polyglycines (GnNa(+), n = 2-8) and polyalanines (AnNa(+), n = 2, 3 and 5) with ND3 have been measured in the cell of an FT-ICR mass spectrometer. All peptides except G2Na(+) are found to undergo three exchange reactions, all of which are consecutive with no sign of multiple exchanges within a single collision event. This information has been used to construct full mechanistic scenarios with the help of detailed quantum chemical calculations of the possible reaction paths for H-D exchange. The first exchange is always located at the C terminus however with different mechanisms depending upon whether the peptide termini can (larger peptides) or cannot (smaller peptides) interact directly without strong energy penalty. The most favourable mechanisms for the second and third exchanges of the N terminus protons, are found to be different from those for the first for all peptide sizes. The peptide distortions that are necessary in order for some of these reactions to occur are made possible by the energy reservoir provided by the favorable interaction of the peptide ion with ND3. Their occurrence and variety preclude any general relationship between H-D exchange kinetics and the most stable ion structures. There is however a break at G7Na(+) in the kinetics trend, with a first exchange rate which is much smaller than for all other peptide sizes. This break can be directly related to a different structural type in which the C terminus is neither free nor close to the N terminus. PMID:25573245

McMahon, T B; Ohanessian, G

2015-01-28

413

Density-functional study of van der Waals forces on rare-gas diatomics: Hartree-Fock exchange  

NASA Astrophysics Data System (ADS)

A density-functional theory study of van der Waals forces on rare-gas diatomics is carried out. Hartree-Fock-Kohn-Sham formalism is used, that is, the exchange-correlation functional is expressed as the combination of Hartree-Fock exchange plus an approximation to the correlation energy functional. Spectroscopic constants (Re,?e, and De) and potential energy curves for the molecules He2, Ne2, Ar2, HeNe, HeAr, and NeAr are presented. Several approximations to the correlation functional are tested. The best results, in good agreement with reference experimental data, are obtained with the functional proposed by Wilson and Levy [L. C. Wilson and M. Levy, Phys. Rev. B 41, 12930 (1990)].

Prez-Jord, Jos M.; San-Fabin, Emilio; Prez-Jimnez, Angel J.

1999-01-01

414

Effect of N-acetylcysteine on gas exchange after methacholine challenge and isoprenaline inhalation in the dog.  

PubMed

N-acetylcysteine (NAC) has antioxidant and possibly mucolytic properties. To determine whether NAC could be of benefit in acute bronchoconstriction induced by methacholine, 12 of 24 anaesthetized dogs (group 1) received NAC i.v. (loading dose 150 mg.kg-1, then 20 mg.kg-1.hr-1). The other 12 (group 2) received diluent. Nebulized methacholine (1%) was then inhaled until arterial oxygen tension (PaO2) fell to a mean of 5.5 kPa, after which isoprenaline 0.5% was inhaled in six dogs of each group to reverse bronchoconstriction. Over the next 3 h we measured total lung resistance, functional residual capacity (FRC), haemodynamic variables, and pulmonary gas exchange for respiratory and inert gases. After methacholine challenge, lung resistance increased and then fell similarly for both groups, but PaO2 was higher in the NAC group (by 0.6-1.9 kPa) throughout the observation period. The ventilation-perfusion distribution measured by inert gas elimination also showed less abnormality in the NAC treated dogs over this time. Mucus was visible during post-mortem in the large airways in about half of the dogs in both groups, with no significant differences between them. These results show that NAC produces a measurable improvement in gas exchange following methacholine challenge (both with and without subsequent isoprenaline therapy) by mechanisms that remain to be determined. PMID:2659384

Ueno, O; Lee, L N; Wagner, P D

1989-03-01

415

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

NASA Astrophysics Data System (ADS)

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.

Mesarchaki, E.; Kruter, C.; Krall, K. E.; Bopp, M.; Helleis, F.; Williams, J.; Jhne, B.

2015-01-01

416

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

SciTech Connect

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.

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

1991-04-20

417

Association between Carbonyl Sulfide Uptake and 18? during Gas Exchange in C3 and C4 Leaves1[OA  

PubMed Central

Carbonyl sulfide (COS) and C18OO exchange by leaves provide potentially powerful tracers of biosphere-atmosphere CO2 exchange, and both are assumed to depend on carbonic anhydrase (CA) activity and conductance along the diffusive pathway in leaves. We investigated these links using C3 and C4 plants, hypothesizing that the rates of COS and C18OO exchange by leaves respond in parallel to environmental and biological drivers. Using CA-deficient antisense lines of C4 and C3 plants, COS uptake was essentially eliminated and discrimination against C18OO exchange (18?) greatly reduced, demonstrating CAs key role in both processes. 18? showed a positive linear correlation with leaf relative uptake (LRU; ratio of COS to CO2 assimilation rates, As/Ac, normalized to their respective ambient concentrations), which reflected the effects of stomatal conductance on both COS and C18OO exchange. Unexpectedly, a decoupling between As and 18? was observed in comparing C4 and C3 plants, with a large decrease in 18? but no parallel reduction in As in the former. This could be explained by C4 plants having higher COS concentrations at the CA site (maintaining high As with reduced CA) and a high phosphoenolpyruvate carboxylase/CA activity ratio (reducing 18O exchange efficiency between CO2 and water, but not As). Similar As but higher Ac in C4 versus C3 plants resulted in lower LRU values in the former (1.16 0.20 and 1.82 0.18 for C4 and C3, respectively). LRU was, however, relatively constant in both plant types across a wide range of conditions, except low light (<191 ?mol photon m?2 s?1). PMID:21715674

Stimler, Keren; Berry, Joseph A.; Montzka, Steve A.; Yakir, Dan

2011-01-01

418

O2 activation by binuclear Cu sites: Noncoupled versus exchange coupled reaction mechanisms  

NASA Astrophysics Data System (ADS)

Binuclear Cu proteins play vital roles in O2 binding and activation in biology and can be classified into coupled and noncoupled binuclear sites based on the magnetic interaction between the two Cu centers. Coupled binuclear Cu proteins include hemocyanin, tyrosinase, and catechol oxidase. These proteins have two Cu centers strongly magnetically coupled through direct bridging ligands that provide a mechanism for the 2-electron reduction of O2 to a -2:2 side-on peroxide bridged species. This side-on bridged peroxo-CuII2 species is activated for electrophilic attack on the phenolic ring of substrates. Noncoupled binuclear Cu proteins include peptidylglycine -hydroxylating monooxygenase and dopamine -monooxygenase. These proteins have binuclear Cu active sites that are distant, that exhibit no exchange interaction, and that activate O2 at a single Cu center to generate a reactive CuII/O2 species for H-atom abstraction from the C-H bond of substrates. O2 intermediates in the coupled binuclear Cu enzymes can be trapped and studied spectroscopically. Possible intermediates in noncoupled binuclear Cu proteins can be defined through correlation to mononuclear CuII/O2 model complexes. The different intermediates in these two classes of binuclear Cu proteins exhibit different reactivities that correlate with their different electronic structures and exchange coupling interactions between the binuclear Cu centers. These studies provide insight into the role of exchange coupling between the Cu centers in their reaction mechanisms.

Chen, Peng; Solomon, Edward I.

2004-09-01

419

On the correlation between air-sea heat flux and abiotically induced oxygen gas exchange in a circulation model of the North Atlantic  

Microsoft Academic Search

The assumption that abiotic air-sea gas exchange is, via the temperature dependence of the gas' solubility, proportional to the surface heat flux is often used to distinguish between physically and biotically inferred oxygen fluxes across the sea surface. We quantitatively investigate its validity in the context of an eddy-permitting circulation model that contains an abiotic oxygen compartment. In the model,

H. Dietze; A. Oschlies

2005-01-01

420

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

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

Qiu, Weigang

421

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 Android mobile devices.  

E-print Network

the settings ActiveSync/Exchange to set up your Android mobile devices. If you set up an Exchange/ActiveSync account on your Android 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 Android mobile device: Username

Qiu, Weigang

422

Gas exchange and pulmonary hypertension following acute pulmonary thromboembolism: has the emperor got some new clothes yet?  

PubMed Central

Abstract Patients present with a wide range of hypoxemia after acute pulmonary thromboembolism (APTE). Recent studies using fluorescent microspheres demonstrated that the scattering of regional blood flows after APTE, created by the embolic obstruction unique in each patient, significantly worsened regional ventilation/perfusion (V/Q) heterogeneity and explained the variability in gas exchange. Furthermore, earlier investigators suggested the roles of released vasoactive mediators in affecting pulmonary hypertension after APTE, but their quantification remained challenging. The latest study reported that mechanical obstruction by clots accounted for most of the increase in pulmonary vascular resistance, but that endothelin-mediated vasoconstriction also persisted at significant level during the early phase. PMID:25006441

2014-01-01

423

Induction and stability of somaclonal variation in growth, leaf phenotype and gas exchange characteristics of poplar regenerated from callus culture.  

PubMed

Populus trichocarpa Torr. and Grey x P. balsamifera L. TT32 lines were regenerated from calli that had been maintained under differing in vitro conditions for sixteen months. In the final months, calli were maintained with one of six concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D, 0.1, 0.2, 0.3, 0.4, 0.5 or 0.6 mg l(-1))and regenerated with 0.25, 0.50 or 1.0 mg l(-1) benzylaminopurine (BA). Regenerant lines were obtained from 15 of these 18 treatments. The spectrum of variation in several morphological, physiological and leaf gas exchange traits was evaluated in the primary regenerants in 1986, and in their secondary vegetative propagules in the two subsequent years, in relation to differences in the original culture conditions. The results indicate that somoclonal variation was induced largely as a result of prolonged culture in the presence of 2,4-D, but that the terminal maintenance and regeneration phases also induced changes in the regenerants. Qualitative differences among the regenerant lines were detected by the end of 1986. For most traits, these differences were statistically confirmed within the 3-year period. The treatment lines ultimately diverged sufficiently to produce lines showing general performance that was either above or below that of the original TT32 clone. An early visible indicator of this divergence was variation in leaf shape (leaf length/width ratio), which could be related to 2,4-D-BA interactions in the final stages of culture. Graphic illustration of the independent effects of either 2,4-D or BA on stem height and gas exchange parameters suggested an inverse relationship with BA concentration and a complex interaction with 2,4-D. Significant correlations were detected between gas exchange parameters and morphological characteristics representing leaf form and stem development. Overall, the results indicate the presence of somaclonal lines that offer potential for the selective improvement of growth using morphological and gas exchange parameters as screening tools. PMID:14967629

Saieed, N T; Douglas, G C; Fry, D J

1994-01-01

424

Leaf gas exchange of understory spruce-fir saplings in relict cloud forests, southern Appalachian Mountains, USA.  

PubMed

The southern Appalachian spruce-fir (Picea rubens Sarg. and Abies fraseri (Pursh) Poir.) forest is found only on high altitude mountain tops that receive copious precipitation ( > 2000 mm year(-1)) and experience frequent cloud immersion. These high-elevation, temperate rain forests are immersed in clouds on approximately 65% of the total growth season days and for 30-40% of a typical summer day, and cloud deposition accounts for up to 50% of their annual water budget. We investigated environmental influences on understory leaf gas exchange and water relations at two sites: Mt. Mitchell, NC (MM; 35 degrees 45'53'' N, 82 degrees 15'53'' W, 2028 m elevation) and Whitetop Mtn., VA (WT; 36 degrees 38'19'' N, 81 degrees 36'19'' W, 1685 m elevation). We hypothesized that the cool, moist and cloudy conditions at these sites exert a strong influence on leaf gas exchange. Maximum photosynthesis (A(max)) varied between 1.6 and 4.0 micromol CO(2) m(-2) s(-1) for both spruce and fir and saturated at irradiances between approximately 200 and 400 micromol m(-2) s(-1) at both sites. Leaf conductance (g) ranged between 0.05 and 0.25 mol m(-2) s(-1) at MM and between 0.15 and 0.40 mol m(-2) s(-1) at WT and was strongly associated with leaf-to-air vapor pressure difference (LAVD). At both sites, g decreased exponentially as LAVD increased, with an 80-90% reduction in g between 0 and 0.5 kPa. Predawn leaf water potentials remained between -0.25 and -0.5 MPa for the entire summer, whereas late afternoon values declined to between -1.25 and -1.75 MPa by late summer. Thus, leaf gas exchange appeared tightly coupled to the response of g to LAVD, which maintained high water status, even at the relatively low LAVD of these cloud forests. Moreover, the cloudy, humid environment of these refugial forests appears to exert a strong influence on tree leaf gas exchange and water relations. 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 future impacts on these relict forests. PMID:17938120

Reinhardt, Keith; Smith, William K

2008-01-01

425

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

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.

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

1984-01-01

426

Multi-scale Analysis of Methane Gas Hydrate Formation and Dissociation via Point Source Thermal Stimulation and Carbon Dioxide Exchange  

NASA Astrophysics Data System (ADS)

The formation and dissociation of methane gas hydrate was investigated over a range of laboratory scale systems with sample volumes of 1.3 cm 3, 0.059 m3 and 0.141 m3. Three unique hydrate apparatuses were used to study a point source thermal dissociation method in which gas production profiles and cumulative efficiencies were found to be dependent on the initial hydrate saturation and the degree of thermal stimulation. Hydrate growth was observed to develop in a non-homogeneous manner with hydrate distribution displaying strong apparatus specific behavior. Heterogeneous hydrate distribution contributed to the production efficiencies of point source thermal stimulation and is an essential parameter when evaluating a gas hydrate reservoir. Thermal stimulation was applied to sediments with initial pore space hydrate saturations ranging from 10% to 80% producing maximum cumulative thermal production efficiencies ranging from 57% to 90%. Production performance was improved with higher initial hydrate saturation; increasing the initial hydrate saturation from 20% to 35% on the small scale system raised peak cumulative efficiencies from 57-63% to 70-74%. Increasing hydrate saturation from 10% to 30% in the medium scale system increased peak cumulative efficiencies from 83% to 90%. During thermal stimulation experiments in both the medium and large scale reactors a flow recirculation pattern developed within the pore space following an initially conduction dominated heat transfer regime. The outward propagation of the heat front from the heating element resulted in increased permeability and the release of mobile water and gas phases as the hydrate underwent dissociation. This change in flow parameters facilitated convection cells within the reactor causing increased heat transfer away from the heating element while displaying a strong upward bias. The flow development detected within the medium scale system was confirmed via history matching of numerical simulation with experimental data. Increased hydrate saturation and increased heating rate lead to a more intense flow development. Thermal stimulation methane production has been coupled with the simultaneous injection of gaseous carbon dioxide as method of enhancing gas production rates while providing a means for long term storage of carbon dioxide in the hydrate phase. The exchange process was investigated at low and high gas injection rates under conditions of both low and high thermal stimulation applied to a 50% hydrate saturated quartz sand pack. The amount of carbon dioxide stored in the hydrate phased was greatest for the low injection-high heating condition sequestering 69 moles, and lowest for the high injection- low heating condition sequestering 13 moles. The gas exchange is improved with longer contact time between gas phase carbon dioxide and hydrate phase methane, this condition is optimized at low carbon dioxide injection rates. The availability of free water for formation of carbon dioxide is enhanced with the higher heating rates. Thus it is possible to tune the gas production rates and carbon dioxide storage potential by manipulating heating rates and gas injection rates to achieve the desired ratio between methane produced and carbon dioxide sequestered. Understanding the transition period and flow development within the pore fluid mixture should play a large role in determining the optimum placement and geometry of heating and exchange systems on industrial scale hydrate production scenarios. In addition to the optimization of thermal stimulation heating location, the profile and degree of heating rate can be tuned in order to maximize gas collection and minimize excessive heating of unproductive sediment matrix after it has been exhausted of methane hydrate. The production efficiency produced across the three experimental scales averaged between 80 and 90% and appears to be independent of scale. The scale up of this method for industrial scale production should pay close attention to the distribution of heat during thermal stimulation as a result of the

Fitzgerald, Garrett Christopher

427

Activation of protein kinase A acutely inhibits and phosphorylates Na/H exchanger NHE-3.  

PubMed Central

In the mammalian renal proximal tubule, protein kinase A (PKA) plays an important role in mediating hormonal regulation of apical membrane Na/H exchanger activity. This exchanger is likely encoded by NHE-3. The present studies examined regulation of NHE-3 by PKA. NHE-3 was stably expressed in Na/H exchanger-deficient fibroblasts (AP-1/NHE-3 cells). PKA activation (0.1 mM 8-BrcAMP x 20 min) inhibited NHE-3 activity by 39% (P < 0.01) with no change in NHE-3 protein abundance in the plasma membrane. To define the structural requirements for PKA-mediated inhibition, full-length NHE-3 and a cytoplasmic domain-truncated mutant (NHE-3 delta cyto) were expressed in Xenopus laevis oocytes. 8-BrcAMP inhibited NHE-3 activity by 27% (P < 0.05), an effect that was blocked by 10(-7) M PKA inhibitor peptide. NHE-3 delta cyto had baseline activity similar to that of full-length NHE-3 but its activity was not regulated by 8-BrcAMP. The purified recombinant cytoplasmic domain of NHE-3 was phosphorylated in vitro by the catalytic subunit of PKA on serine residues. In AP-1/NHE-3 cells, NHE-3 was immunoprecipitated as a approximately 87-kD phosphoprotein. Addition of 0.1 mM 8-BrcAMP increased the phosphocontent of NHE-3 by threefold. In summary, acute activation of PKA inhibits NHE-3 activity, an effect that is likely mediated by phosphorylation of its cytoplasmic domain. Images PMID:7593604

Moe, O W; Amemiya, M; Yamaji, Y

1995-01-01

428

Key parameters of active layers affecting proton exchange membrane (PEM) fuel cell performance  

Microsoft Academic Search

The 2n full factorial design was applied to identify the key parameters of the active layer affecting the performance of a proton exchange membrane (PEM) fuel cell. Three main selected parameters were considered: carbon-type (Vulcan XC 72R and Black Pearls 2000 conducting furnace blacks, Cabot Corporation Boston, MA), Pt loading (0.1 and 0.5mg\\/cm2), and Nafion sulfonic acid fluoropolymer (Du Pont

Jarupuk Thepkaew; Apichai Therdthianwong; Supaporn Therdthianwong

2008-01-01

429

ENVIRONMENTAL EFFECTS IN GALAXIES: MOLECULAR GAS AND NUCLEAR ACTIVITY  

E-print Network

by open symbols. The HDS is marked by solid symbols. 2.1. OPTICAL SPECTRA ­ NUCLEAR ACTITIVY A total of 47) in these galaxies. Most of the galaxies (38) have spectra showing signs of nuclear star formation. A total of 9ENVIRONMENTAL EFFECTS IN GALAXIES: MOLECULAR GAS AND NUCLEAR ACTIVITY DUILIA DE MELLO and TOMMY

Maia, Marcio Antonio Geimba

430

Activated gas nitriding of 17-4 PH stainless steel  

Microsoft Academic Search

Results of the investigation of nitrided precipitation-hardened steel 17-4 PH surface have been presented. The layers have been created as a result of the gas nitriding process in a partly dissociated ammonia. Hydrogen chloride admixture to ammonia was used as a steel surface activator. The influence of the steel heat treatment before nitriding on the diffusive process has been considered.

P. Kochma?ski; J. Nowacki

2006-01-01

431

Wave slope variance measurements from CALIPSO and applications in estimating airsea gas exchangeand applications in estimating air sea gas exchange  

E-print Network

. After averaging, the wind speed agrees well with AMSR-E wind measurements but the gas transfer velocity is compared with the one derived from AMSR-E wind speedCALIPSO is compared with the one derived from AMSR-E

Kuligowski, Bob

432

Estimation of air-water gas exchange coefficient in a shallow lagoon based on (222)Rn mass balance.  

PubMed

The radon-222 mass balance is now commonly used to quantify water fluxes due to Submarine Groundwater Discharge (SGD) in coastal areas. One of the main loss terms of this mass balance, the radon evasion to the atmosphere, is based on empirical equations. This term is generally estimated using one among the many empirical equations describing the gas transfer velocity as a function of wind speed that have been proposed in the literature. These equations were, however, mainly obtained from areas of deep water and may be less appropriate for shallow areas. Here, we calculate the radon mass balance for a windy shallow coastal lagoon (mean depth of 6m and surface area of 1.55*10(8)m(2)) and use these data to estimate the radon loss to the atmosphere and the corresponding gas transfer velocity. We present new equations, adapted to our shallow water body, to express the gas transfer velocity as a function of wind speed at 10m height (wind range from 2 to 12.5m/s). When compared with those from the literature, these equations fit particularly well with the one of Kremer etal. (2003). Finally, we emphasize that some gas transfer exchange may always occur, even for conditions without wind. PMID:25743409

Cockenpot, S; Claude, C; Radakovitch, O

2015-05-01

433

Effect of Landscape Design and Irrigation on Summertime Gas Exchange of Landscape Trees, Shrubs, and Herbs.  

E-print Network

type by area coverage being residential. The spatial arrangement of residential vegetation is mostly in the Phoenix metropolitan area has displaced native Sonoran Desert vegetation with the dominant urban land use exchange inhibitions of vegetation at the NDV site were apparently related to excessively heat, high VPD

Hall, Sharon J.

434

Modeling bronchial circulation with application to soluble gas exchange: description and sensitivity analysis  

E-print Network

of ethanol ( blood 1,756 at 37C) in the airways depends on the blood flow rate from the bronchial (0.01350) of blood solubilities ( blood; mlml 1 atm 1). Hence, we hypothesize that the exchange of ethanol (R2 0.991) as well as the end-exhalation airstream temperature (34.6C). The model predicts

George, Steven C.

435

Effect of Leaf Rolling on Gas Exchange and Leaf Temperature of Andropogon gerardii and Spartina pectinata  

Microsoft Academic Search

We examined the effect of leaf rolling on CO, and water vapor exchange of two C, prairie grasses with contrasting patterns of leaf rolling. Andropogon gerardii (big bluestem) is a drought-resistant species with predominantly hypostomatal leaves that fold (adaxial surface inward) in response to low leaf water potential, while leaves of Spartina pectinata (prairie cordgrass), a mesic species, are epistomatal

Scott A. Heckathorn; Evan H. DeLucia

1991-01-01

436

Deuterium Exchange in Ethyl Acetoacetate: An Undergraduate GC-MS [Gas Chromatography-Mass Spectroscopy] Experiment  

ERIC Educational Resources Information Center

The role of ethanol O-d in nullifying the deuterolysis may be demonstrated by determining that transesterification of methyl acetoacetate of the ethyl ester occurs as well as deuterium exchange of the five acetoacetate hydrogens. The significant acidity of the methylene protons in the acetoacetate group, the efficacy of base catalysis, the role of

Heinson, C. D.; Williams, J. M.; Tinnerman, W. N.; Malloy, T. B.

2005-01-01

437

Simulation of fixed bed regenerative heat exchangers for flue gas heat recovery  

Microsoft Academic Search

Fixed-bed regenerators are used to provide high temperature process gases in the glass and steel industries, in power plants and in waste heat recovery systems. In all these situations the temperature levels require the regenerator packing to be made from the low thermal conductivity materials such as ceramic. Simulation of the operation of fixed bed heat exchangers must accommodate the

M. T. Zarrinehkafsh; S. M. Sadrameli

2004-01-01

438

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...

439

Water loss and gas exchange by eggs of Manduca sexta: Trading off costs and benefits  

Microsoft Academic Search

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)

H. Arthur Woods

2010-01-01

440

Variation in eggshell characteristics and gas exchange of montane and lowland coot eggs  

Microsoft Academic Search

This study determined how structural features of the eggshells of coots (Fulica americana) laid at 4150 m in the Peruvian Andes differed from those at sea level in Peru and California and how these features affected exchange of water vapor, O2, and CO2. While barometric pressure at 4150 m was reduced to 60% of that at sea level, the conductance

Cynthia Carey; Fabiola Leon-Velarde; Olga Dunin-Borkowski; Theresa L. Bucher; Grimaneza de la Torre; Daniel Espinoza; Carlos Monge

1989-01-01

441

Development of the gas puff charge exchange recombination spectroscopy (GP-CXRS) technique for ion measurements in the plasma edge  

SciTech Connect

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.

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.; Ptterich, T.; Viezzer, E. [Max-Planck-Institut fr Plasmaphysik, EURATOM Association, Boltzmannstrasse 2, D-85748 Garching (Germany)] [Max-Planck-Institut fr Plasmaphysik, EURATOM Association, Boltzmannstrasse 2, D-85748 Garching (Germany); Collaboration: Alcator C-Mod Team; ASDEX Upgrade Team

2013-09-15

442

Development of the gas puff charge exchange recombination spectroscopy (GP-CXRS) technique for ion measurements in the plasma edge  

NASA Astrophysics Data System (ADS)

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.

Churchill, R. M.; Theiler, C.; Lipschultz, B.; Dux, R.; Ptterich, T.; Viezzer, E.; Alcator C-Mod Team; ASDEX Upgrade Team

2013-09-01

443

[Gas-exchange profiles of different algae communities as applied to biological system of human life support].  

PubMed

Previous modeling of the human-chlorella-microorganisms system showed that the absolute balance of atmospheric oxygen and carbon dioxide is unattainable because of inequality of the human respiration factor and chlorella assimilation factor. Analysis of patterns of gas-exchange regulation in a system with open trophic human-algae interrelations revealed that the sine qua non condition for this balance is identity of synthesized algal biomass and digestible part of human ration which is impractical with cultivation of only one algal species. We undertook experimental testing of this supposition with three algae communities: chlorella-chlamydomonas, spirulina-chlamydomonas and spirulina-chlamydomonas-clorella during accumulative cultivation. Investigation of their gas-exchange profiles made it clear that the assimilation factor of such photosynthetic component varies with community structure. The data can be useful in choosing the algae species and specifying their ratio that would permit to keep good balance of oxygen and carbon dioxide in atmosphere of closed systems. PMID:18350824

Nefedova, E L; Levinskikh, M A

2007-01-01