air-water gas exchange: Topics by Science.gov

Continuous measurement of air-water gas exchange by underwater eddy covariance

NASA Astrophysics Data System (ADS)

Berg, Peter; Pace, Michael L.

2017-12-01

Exchange of gases, such as O2, CO2, and CH4, over the air-water interface is an important component in aquatic ecosystem studies, but exchange rates are typically measured or estimated with substantial uncertainties. This diminishes the precision of common ecosystem assessments associated with gas exchanges such as primary production, respiration, and greenhouse gas emission. Here, we used the aquatic eddy covariance technique - originally developed for benthic O2 flux measurements - right below the air-water interface (˜ 4 cm) to determine gas exchange rates and coefficients. Using an acoustic Doppler velocimeter and a fast-responding dual O2-temperature sensor mounted on a floating platform the 3-D water velocity, O2 concentration, and temperature were measured at high-speed (64 Hz). By combining these data, concurrent vertical fluxes of O2 and heat across the air-water interface were derived, and gas exchange coefficients were calculated from the former. Proof-of-concept deployments at different river sites gave standard gas exchange coefficients (k600) in the range of published values. A 40 h long deployment revealed a distinct diurnal pattern in air-water exchange of O2 that was controlled largely by physical processes (e.g., diurnal variations in air temperature and associated air-water heat fluxes) and not by biological activity (primary production and respiration). This physical control of gas exchange can be prevalent in lotic systems and adds uncertainty to assessments of biological activity that are based on measured water column O2 concentration changes. For example, in the 40 h deployment, there was near-constant river flow and insignificant winds - two main drivers of lotic gas exchange - but we found gas exchange coefficients that varied by several fold. This was presumably caused by the formation and erosion of vertical temperature-density gradients in the surface water driven by the heat flux into or out of the river that affected the turbulent
On factors influencing air-water gas exchange in emergent wetlands

USGS Publications Warehouse

Ho, David T.; Engel, Victor C.; Ferron, Sara; Hickman, Benjamin; Choi, Jay; Harvey, Judson W.

2018-01-01

Knowledge of gas exchange in wetlands is important in order to determine fluxes of climatically and biogeochemically important trace gases and to conduct mass balances for metabolism studies. Very few studies have been conducted to quantify gas transfer velocities in wetlands, and many wind speed/gas exchange parameterizations used in oceanographic or limnological settings are inappropriate under conditions found in wetlands. Here six measurements of gas transfer velocities are made with SF6 tracer release experiments in three different years in the Everglades, a subtropical peatland with surface water flowing through emergent vegetation. The experiments were conducted under different flow conditions and with different amounts of emergent vegetation to determine the influence of wind, rain, water flow, waterside thermal convection, and vegetation on air-water gas exchange in wetlands. Measured gas transfer velocities under the different conditions ranged from 1.1 cm h−1 during baseline conditions to 3.2 cm h−1 when rain and water flow rates were high. Commonly used wind speed/gas exchange relationships would overestimate the gas transfer velocity by a factor of 1.2 to 6.8. Gas exchange due to thermal convection was relatively constant and accounted for 14 to 51% of the total measured gas exchange. Differences in rain and water flow among the different years were responsible for the variability in gas exchange, with flow accounting for 37 to 77% of the gas exchange, and rain responsible for up to 40%.
Turbulence and wave breaking effects on air-water gas exchange

PubMed

Boettcher; Fineberg; Lathrop

2000-08-28

We present an experimental characterization of the effects of turbulence and breaking gravity waves on air-water gas exchange in standing waves. We identify two regimes that govern aeration rates: turbulent transport when no wave breaking occurs and bubble dominated transport when wave breaking occurs. In both regimes, we correlate the qualitative changes in the aeration rate with corresponding changes in the wave dynamics. In the latter regime, the strongly enhanced aeration rate is correlated with measured acoustic emissions, indicating that bubble creation and dynamics dominate air-water exchange.
Gas exchange rates across the sediment-water and air-water interfaces in south San Francisco Bay

USGS Publications Warehouse

Hartman, Blayne; Hammond, Douglas E.

1984-01-01

Radon 222 concentrations in the water and sedimentary columns and radon exchange rates across the sediment-water and air-water interfaces have been measured in a section of south San Francisco Bay. Two independent methods have been used to determine sediment-water exchange rates, and the annual averages of these methods agree within the uncertainty of the determinations, about 20%. The annual average of benthic fluxes from shoal areas is nearly a factor of 2 greater than fluxes from the channel areas. Fluxes from the shoal and channel areas exceed those expected from simple molecular diffusion by factors of 4 and 2, respectively, apparently due to macrofaunal irrigation. Values of the gas transfer coefficient for radon exchange across the air-water interface were determined by constructing a radon mass balance for the water column and by direct measurement using floating chambers. The chamber method appears to yield results which are too high. Transfer coefficients computed using the mass balance method range from 0.4 m/day to 1.8 m/day, with a 6-year average of 1.0 m/day. Gas exchange is linearly dependent upon wind speed over a wind speed range of 3.2–6.4 m/s, but shows no dependence upon current velocity. Gas transfer coefficients predicted from an empirical relationship between gas exchange rates and wind speed observed in lakes and the oceans are within 30% of the coefficients determined from the radon mass balance and are considerably more accurate than coefficients predicted from theoretical gas exchange models.
Air-water gas exchange and CO2 flux in a mangrove-dominated estuary

USGS Publications Warehouse

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

2014-01-01

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.
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...
Wind driven vertical transport in a vegetated, wetland water column with air-water gas exchange

NASA Astrophysics Data System (ADS)

Poindexter, C.; Variano, E. A.

2010-12-01

Flow around arrays of cylinders at low and intermediate Reynolds numbers has been studied numerically, analytically and experimentally. Early results demonstrated that at flow around randomly oriented cylinders exhibits reduced turbulent length scales and reduced diffusivity when compared to similarly forced, unimpeded flows (Nepf 1999). While horizontal dispersion in flows through cylinder arrays has received considerable research attention, the case of vertical dispersion of reactive constituents has not. This case is relevant to the vertical transfer of dissolved gases in wetlands with emergent vegetation. We present results showing that the presence of vegetation can significantly enhance vertical transport, including gas transfer across the air-water interface. Specifically, we study a wind-sheared air-water interface in which randomly arrayed cylinders represent emergent vegetation. Wind is one of several processes that may govern physical dispersion of dissolved gases in wetlands. Wind represents the dominant force for gas transfer across the air-water interface in the ocean. Empirical relationships between wind and the gas transfer coefficient, k, have been used to estimate spatial variability of CO2 exchange across the worlds’ oceans. Because wetlands with emergent vegetation are different from oceans, different model of wind effects is needed. We investigated the vertical transport of dissolved oxygen in a scaled wetland model built inside a laboratory tank equipped with an open-ended wind tunnel. Plastic tubing immersed in water to a depth of approximately 40 cm represented emergent vegetation of cylindrical form such as hard-stem bulrush (Schoenoplectus acutus). After partially removing the oxygen from the tank water via reaction with sodium sulfite, we used an optical probe to measure dissolved oxygen at mid-depth as the tank water re-equilibrated with the air above. We used dissolved oxygen time-series for a range of mean wind speeds to estimate the
Aqueous turbulence structure immediately adjacent to the air - water interface and interfacial gas exchange

NASA Astrophysics Data System (ADS)

Wang, Binbin

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
The Effect of Rain on Air-Water Gas Exchange

NASA Technical Reports Server (NTRS)

Ho, David T.; Bliven, Larry F.; Wanninkhof, Rik; Schlosser, Peter

1997-01-01

The relationship between gas transfer velocity and rain rate was investigated at NASA's Rain-Sea Interaction Facility (RSIF) using several SF, evasion experiments. During each experiment, a water tank below the rain simulator was supersaturated with SF6, a synthetic gas, and the gas transfer velocities were calculated from the measured decrease in SF6 concentration with time. The results from experiments with IS different rain rates (7 to 10 mm/h) and 1 of 2 drop sizes (2.8 or 4.2 mm diameter) confirm a significant and systematic enhancement of air-water gas exchange by rainfall. The gas transfer velocities derived from our experiment were related to the kinetic energy flux calculated from the rain rate and drop size. The relationship obtained for mono-dropsize rain at the RSIF was extrapolated to natural rain using the kinetic energy flux of natural rain calculated from the Marshall-Palmer raindrop size distribution. Results of laboratory experiments at RSIF were compared to field observations made during a tropical rainstorm in Miami, Florida and show good agreement between laboratory and field data.
Reprint of: A numerical modelling of gas exchange mechanisms between air and turbulent water with an aquarium chemical reaction

NASA Astrophysics Data System (ADS)

Nagaosa, Ryuichi S.

2014-08-01

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

NASA Astrophysics Data System (ADS)

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

2014-05-01

Air-sea gas exchange is important to the global partitioning of CO2.Exchange fluxes are products of an air-sea gas concentration difference, ΔC, 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
Influence of current velocity and wind speed on air-water gas exchange in a mangrove estuary

NASA Astrophysics Data System (ADS)

Ho, David T.; Coffineau, Nathalie; Hickman, Benjamin; Chow, Nicholas; Koffman, Tobias; Schlosser, Peter

2016-04-01

Knowledge of air-water gas transfer velocities and water residence times is necessary to study the fate of mangrove derived carbon exported into surrounding estuaries and ultimately to determine carbon balances in mangrove ecosystems. For the first time, the 3He/SF6 dual tracer technique, which has been proven to be a powerful tool to determine gas transfer velocities in the ocean, is applied to Shark River, an estuary situated in the largest contiguous mangrove forest in North America. The mean gas transfer velocity was 3.3 ± 0.2 cm h-1 during the experiment, with a water residence time of 16.5 ± 2.0 days. We propose a gas exchange parameterization that takes into account the major sources of turbulence in the estuary (i.e., bottom generated shear and wind stress).
On the parameters influencing air-water gas exchange

NASA Astrophysics Data System (ADS)

JäHne, Bernd; Münnich, Karl Otto; BöSinger, Rainer; Dutzi, Alfred; Huber, Werner; Libner, Peter

1987-02-01

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-⅔ to k ∝ Sc-½indicating a change in the boundary conditions at the surface. Moreover, energy put into the wave field by wind is transferred to near-surface turbulence enhancing gas transfer. The data show that the mean square slope of the waves is the best parameter to characterize the free wavy surface with respect to water-side transfer processes.
Air-water gas exchange of chlorinated pesticides in four lakes spanning a 1,205 meter elevation range in the Canadian Rocky Mountains.

PubMed

Wilkinson, Andrew C; Kimpe, Lynda E; Blais, Jules M

2005-01-01

Concentrations of selected persistent organic pollutants (POPs) in air and water were measured from four lakes that transect the Canadian Rocky Mountains. These data were used in combination with wind velocity and temperature-adjusted Henry's law constants to estimate the direction and magnitude of chemical exchange across the air-water interface of these lakes. Bow Lake (1,975 m above sea level [masl]) was studied during the summers of 1998 through 2000; Donald (770 masl) was studied during the summer of 1999; Dixon Dam Lake (946 masl) and Kananaskis Lake (1,667 masl) were studied during the summer of 2000. Hexachlorobenzene (HCB) and dieldrin volatilized from Bow Lake in spring and summer of 1998 to 2000 at a rate of 0.92 +/-1.1 and 0.55+/-0.37 ng m(-2) d(-1), respectively. The alpha-endosulfan deposited to Bow Lake at a rate of 3.4+/-2.2 ng m(-2) d(-1). Direction of gas exchange for gamma-hexachlorocyclohexane (gamma-HCH) changed from net deposition in 1998 to net volatilization in 1999, partly because of a surge in y-HCH concentrations in the water at Bow Lake in 1999. Average gamma-HCH concentrations in air declined steadily over the three-year period, from 0.021 ng m(-3) in 1998, to 0.0023 ng m(-3) in 2000, and to volatilization in 1999 and 2000. Neither the concentrations of organochlorine compounds (OCs) in air and water, nor the direction and rate of air-water gas exchange correlate with temperature or elevation. In general, losses of pesticides by outflow were greater than the amount exchanged across the air-water interface in these lakes.
Spume Drops: Their Potential Role in Air-Sea Gas Exchange

NASA Astrophysics Data System (ADS)

Monahan, Edward C.; Staniec, Allison; Vlahos, Penny

2017-12-01

After summarizing the time scales defining the change of the physical properties of spume and other droplets cast up from the sea surface, the time scales governing drop-atmosphere gas exchange are compared. Following a broad review of the spume drop production functions described in the literature, a subset of these functions is selected via objective criteria, to represent typical, upper bound, and lower bound production functions. Three complementary mechanisms driving spume-atmosphere gas exchange are described, and one is then used to estimate the relative importance, over a broad range of wind speeds, of this spume drop mechanism compared to the conventional, diffusional, sea surface mechanism in air-sea gas exchange. While remaining uncertainties in the wind dependence of the spume drop production flux, and in the immediate sea surface gas flux, preclude a definitive conclusion, the findings of this study strongly suggest that, at high wind speeds (>20 m s-1 for dimethyl sulfide and >30 m s-1 for gases such a carbon dioxide), spume drops do make a significant contribution to air-sea gas exchange.Plain Language SummaryThis paper evaluates the existing spume drop generation functions available to date and selects a reasonable upper, lower and mid range function that are reasonable for use in air sea exchange models. Based on these the contribution of spume drops to overall air sea gas exchange at different wind speeds is then evaluated to determine the % contribution of spume. Generally below 20ms-1 spume drops contribute <1% of gas exchange but may account for a significant amount of gas exchange at higher wind speeds. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002EGSGA..27..874S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002EGSGA..27..874S">Observational Studies of Parameters Influencing Air-sea Gas Exchange</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Schimpf, U.; Frew, N. M.; Bock, E. J.; Hara, T.; Garbe, C. S.; Jaehne, B. A physically-based modeling of the air-sea gas transfer that can be used to predict the gas transfer rates with sufficient accuracy as a function of micrometeorological parameters is still lacking. State of the art are still simple gas transfer rate/wind speed relationships. Previous measurements from Coastal Ocean Experiment in the Atlantic revealed positive correlations between mean square slope, near surface turbulent dis- sipation, and wind stress. It also demonstrated a strong negative correlation between mean square slope and the fluorescence of surface-enriched colored dissolved organic matter. Using heat as a proxy tracer for gases the exchange process at the air/water interface and the micro turbulence at the water surface can be investigated. The anal- ysis of infrared image sequences allow the determination of the net heat flux at the ocean surface, the temperature gradient across the air/sea interface and thus the heat transfer velocity and gas transfer velocity respectively. Laboratory studies were carried out in the new Heidelberg wind-wave facility AELOTRON. Direct measurements of the Schmidt number exponent were done in conjunction with classical mass balance methods to estimate the transfer velocity. The laboratory results allowed to validate the basic assumptions of the so called controlled flux technique by applying differ- ent tracers for the gas exchange in a large Schmidt number regime. Thus a modeling of the Schmidt number exponent is able to fill the gap between laboratory and field measurements field. Both, the results from the laboratory and the field measurements should be able to give a further understanding of the mechanisms controlling the trans- port processes across the aqueous boundary layer and to relate the forcing functions to parameters measured by remote sensing. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21141036','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21141036">Advances in quantifying air-sea gas exchange and environmental forcing.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Wanninkhof, Rik; Asher, William E; Ho, David T; Sweeney, Colm; McGillis, Wade R 2009-01-01 The past decade has seen a substantial amount of research on air-sea gas exchange and its environmental controls. These studies have significantly advanced the understanding of processes that control gas transfer, led to higher quality field measurements, and improved estimates of the flux of climate-relevant gases between the ocean and atmosphere. This review discusses the fundamental principles of air-sea gas transfer and recent developments in gas transfer theory, parameterizations, and measurement techniques in the context of the exchange of carbon dioxide. However, much of this discussion is applicable to any sparingly soluble, non-reactive gas. We show how the use of global variables of environmental forcing that have recently become available and gas exchange relationships that incorporate the main forcing factors will lead to improved estimates of global and regional air-sea gas fluxes based on better fundamental physical, chemical, and biological foundations. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22418709','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22418709">Discontinuous gas exchange, water loss, and metabolism in Protaetia cretica (Cetoniinae, Scarabaeidae).</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Matthews, Philip G D; White, Craig R 2012-01-01 Insects are at high risk of desiccation because of their small size, high surface-area-to-volume ratio, and air-filled tracheal system that ramifies throughout their bodies to transport O(2) and CO(2) to and from respiring cells. Although the tracheal system offers a high-conductance pathway for the movement of respiratory gases, it has the unintended consequence of allowing respiratory transpiration to the atmosphere. When resting, many species exchange respiratory gases discontinuously, and an early hypothesis for the origin of these discontinuous gas exchange cycles (DGCs) is that they serve to reduce respiratory water loss. In this study, we test this "hygric" hypothesis by comparing rates of CO(2) exchange and water loss among flower beetles Protaetia cretica (Cetoniinae, Scarabaeidae) breathing either continuously or discontinuously. We show that, consistent with the expectations of the hygric hypothesis, rates of total water loss are higher during continuous gas exchange than during discontinuous gas exchange and that the ratio of respiratory water loss to CO(2) exchange is lower during discontinuous gas exchange. This conclusion is in agreement with other studies of beetles and cockroaches that also support the hygric hypothesis. However, this result does not exclude other adaptive hypotheses supported by work on ants and moth pupae. This ambiguity may arise because there are multiple independent evolutionary origins of DGCs and no single adaptive function underlying their genesis. Alternatively, the observed reduction in water loss during DGCs may be a side effect of a nonadaptive gas exchange pattern that is elicited during periods of inactivity. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/20000740-coupling-phytoplankton-uptake-air-water-exchange-persistent-organic-pollutants','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/20000740-coupling-phytoplankton-uptake-air-water-exchange-persistent-organic-pollutants">Coupling of phytoplankton uptake and air-water exchange of persistent organic pollutants</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Dachs, J.; Eisenreich, S.J.; Baker, J.E. 1999-10-15 A dynamic model that couples air-water exchange and phytoplankton uptake of persistent organic pollutants has been developed and then applied to PCB data from a small experimental lake. A sensitivity analysis of the model, taking into account the influence of physical environmental conditions such as temperature, wind speed, and mixing depth as well as plankton-related parameters such as biomass and growth rate was carried out for a number of PCBs with different physical-chemical properties. The results indicate that air-water exchange dynamics are influenced not only by physical parameters but also by phytoplankton biomass and growth rate. New phytoplankton production resultsmore » in substantially longer times to reach equilibrium. Phytoplankton uptake-induced depletion of the dissolved phase concentration maintains air and water phases out of equilibrium. Furthermore, PCBs in phytoplankton also take longer times to reach equilibrium with the dissolved water phase when the latter is supported by diffusive air-water exchange. However, both model analysis and model application to the Experimental Lakes Area of northwestern Ontario (Canada) suggest that the gas phase supports the concentrations of persistent organic pollutants, such as PCBs, in atmospherically driven aquatic environments.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.B53A0937M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.B53A0937M">Using Riverboat-Mounted Eddy Covariance for Direct Measurements of Air-water Gas Exchange in Amazonia</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Miller, S. D.; Freitas, H.; Read, E.; Goulden, M. L.; Rocha, H. 2007-12-01 Gas evasion from Amazonian rivers and lakes to the atmosphere has been estimated to play an important role in the regional budget of carbon dioxide (Richey et al., 2002) and the global budget of methane (Melack et al., 2004). These flux estimates were calculated by combining remote sensing estimates of inundation area with water-side concentration gradients and gas transfer rates (piston velocities) estimated primarily from floating chamber measurements (footprint ~1 m2). The uncertainty in these fluxes was large, attributed primarily to uncertainty in the gas exchange parameterization. Direct measurements of the gas exchange coefficient are needed to improve the parameterizations in these environments, and therefore reduce the uncertainty in fluxes. The micrometeorological technique of eddy covariance is attractive since it is a direct measurement of gas exchange that samples over a much larger area than floating chambers, and is amenable to use from a moving platform. We present eddy covariance carbon dioxide exchange measurements made using a small riverboat in rivers and lakes in the central Amazon near Santarem, Para, Brazil. Water-side carbon dioxide concentration was measured in situ, and the gas exchange coefficient was calculated. We found the piston velocity at a site on the Amazon River to be similar to existing ocean-based parameterizations, whereas the piston velocity at a site on the Tapajos River was roughly a factor 5 higher. We hypothesize that the enhanced gas exchange at the Tapajos site was due to a shallow upwind fetch. Our results demonstrate the feasibility of boat-based eddy covariance on these rivers, and also the utility of a mobile platform to investigate spatial variability of gas exchange. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li class="active">1</li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_2" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_1");'>1</a></li> <li class="active">2</li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="21"> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26196214','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26196214">20 Years of Air-Water Gas Exchange Observations for Pesticides in the Western Arctic Ocean.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Jantunen, Liisa M; Wong, Fiona; Gawor, Anya; Kylin, Henrik; Helm, Paul A; Stern, Gary A; Strachan, William M J; Burniston, Deborah A; Bidleman, Terry F 2015-12-01 The Arctic has been contaminated by legacy organochlorine pesticides (OCPs) and currently used pesticides (CUPs) through atmospheric transport and oceanic currents. Here we report the time trends and air-water exchange of OCPs and CUPs from research expeditions conducted between 1993 and 2013. Compounds determined in both air and water were trans- and cis-chlordanes (TC, CC), trans- and cis-nonachlors (TN, CN), heptachlor exo-epoxide (HEPX), dieldrin (DIEL), chlorobornanes (ΣCHBs and toxaphene), dacthal (DAC), endosulfans and metabolite endosulfan sulfate (ENDO-I, ENDO-II, and ENDO SUL), chlorothalonil (CHT), chlorpyrifos (CPF), and trifluralin (TFN). Pentachloronitrobenzene (PCNB and quintozene) and its soil metabolite pentachlorothianisole (PCTA) were also found in air. Concentrations of most OCPs declined in surface water, whereas some CUPs increased (ENDO-I, CHT, and TFN) or showed no significant change (CPF and DAC), and most compounds declined in air. Chlordane compound fractions TC/(TC + CC) and TC/(TC + CC + TN) decreased in water and air, while CC/(TC + CC + TN) increased. TN/(TC + CC + TN) also increased in air and slightly, but not significantly, in water. These changes suggest selective removal of more labile TC and/or a shift in chlordane sources. Water-air fugacity ratios indicated net volatilization (FR > 1.0) or near equilibrium (FR not significantly different from 1.0) for most OCPs but net deposition (FR < 1.0) for ΣCHBs. Net deposition was shown for ENDO-I on all expeditions, while the net exchange direction of other CUPs varied. Understanding the processes and current state of air-surface exchange helps to interpret environmental exposure and evaluate the effectiveness of international protocols and provides insights for the environmental fate of new and emerging chemicals. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://lofe.dukejournals.org/content/2/1.abstract','USGSPUBS'); return false;" href="http://lofe.dukejournals.org/content/2/1.abstract">Air-water oxygen exchange in a large whitewater river</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Hall, Robert O.; Kennedy, Theodore A.; Rosi-Marshall, Emma J. 2012-01-01 Air-water gas exchange governs fluxes of gas into and out of aquatic ecosystems. Knowing this flux is necessary to calculate gas budgets (i.e., O2) to estimate whole-ecosystem metabolism and basin-scale carbon budgets. Empirical data on rates of gas exchange for streams, estuaries, and oceans are readily available. However, there are few data from large rivers and no data from whitewater rapids. We measured gas transfer velocity in the Colorado River, Grand Canyon, as decline in O2 saturation deficit, 7 times in a 28-km segment spanning 7 rapids. The O2 saturation deficit exists because of hypolimnetic discharge from Glen Canyon Dam, located 25 km upriver from Lees Ferry. Gas transfer velocity (k600) increased with slope of the immediate reach. k600 was -1 in flat reaches, while k600 for the steepest rapid ranged 3600-7700 cm h-1, an extremely high value of k600. Using the rate of gas exchange per unit length of water surface elevation (Kdrop, m-1), segment-integrated k600 varied between 74 and 101 cm h-1. Using Kdrop we scaled k600 to the remainder of the Colorado River in Grand Canyon. At the scale corresponding to the segment length where 80% of the O2 exchanged with the atmosphere (mean length = 26.1 km), k600 varied 4.5-fold between 56 and 272 cm h-1 with a mean of 113 cm h-1. Gas transfer velocity for the Colorado River was higher than those from other aquatic ecosystems because of large rapids. Our approach of scaling k600 based on Kdrop allows comparing gas transfer velocity across rivers with spatially heterogeneous morphology. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/203613-gaseous-exchange-polycyclic-aromatic-hydrocarbons-across-air-water-interface-lower-chesapeake-bay','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/203613-gaseous-exchange-polycyclic-aromatic-hydrocarbons-across-air-water-interface-lower-chesapeake-bay">Gaseous exchange of polycyclic aromatic hydrocarbons across the air-water interface of lower Chesapeake Bay</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Gustafson, K.E.; Dickhut, R.M. 1995-12-31 The gaseous exchange fluxes of polycyclic aromatic hydrocarbons (PAHs) across the air-water interface of lower Chesapeake Bay were determined using a modified two-film exchange model. Sampling covered the period January 1994 to June 1995 for five sites on lower Chesapeake Bay ranging from rural to urban and highly industrialized. Simultaneous air and water samples were collected and the atmospheric gas phase and water column dissolved phase analyzed via GC/MS for 17 PAHs. The direction and magnitude of flux for each PAH was calculated using Henry`s law constants, hydrological and meteorological parameters, Temperature was observed to be an important environmental factormore » in determining both the direction and magnitude of PAH gas exchange. Nonetheless, wind speed significantly impacts mass transfer coefficients, and therefore was found to control the magnitude of flux. Spatial and temporal variation of PAH gaseous exchange fluxes were examined. Fluxes were determined to be both into and out of Chesapeake Bay. The range of gas exchange fluxes ({minus}560 to 600{micro}g/M{sup 2}*Mo) is of the same order to 10X greater than atmospheric wet and dry depositional fluxes to lower Chesapeake Bay. The results of this study support the hypothesis that gas exchange is a major transport process affecting the net loadings of PAHs in lower Chesapeake Bay.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRD..122.7664L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRD..122.7664L">Atmospheric deposition and air-sea gas exchange fluxes of DDT and HCH in the Yangtze River Estuary, East China Sea</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Li, Zhongxia; Lin, Tian; Li, Yuanyuan; Jiang, Yuqing; Guo, Zhigang 2017-07-01 The Yangtze River Estuary (YRE) is strongly influenced by the Yangtze River and lies on the pathway of the East Asian Monsoon. This study examined atmospheric deposition and air-sea gas exchange fluxes of dichlorodiphenyltrichloroethane (DDT) and hexachlorocyclohexane (HCH) to determine whether the YRE is a sink or source of selected pesticides at the air-water interface under the influences of river input and atmospheric transport. The air-sea gas exchange of DDT was characterized by net volatilization with a marked difference in its fluxes between summer (140 ng/m2/d) and the other three seasons (12 ng/m2/d), possibly due to the high surface seawater temperatures and larger riverine input in summer. However, there was no obvious seasonal variation in the atmospheric HCH deposition, and the air-sea gas exchange reached equilibrium because of low HCH levels in the air and seawater after the long-term banning of HCH and the degradation. The gas exchange flux of HCH was comparable to the dry and wet deposition fluxes at the air-water interface. This suggests that the influences from the Yangtze River input and East Asian continental outflow on the fate of HCH in the YRE were limited. The gas exchange flux of DDT was about fivefold higher than the total dry and wet deposition fluxes. DDT residues in agricultural soil transported by enhanced riverine runoff were responsible for sustaining such a high net volatilization in summer. Moreover, our results indicated that there were fresh sources of DDT from the local environment to sustain net volatilization throughout the year. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1980Tell...32..470H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1980Tell...32..470H">Gas exchange across the air-sea interface</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Hasse, L.; Liss, P. S. 1980-10-01 The physics of gas exchange at the air-sea interface are reviewed. In order to describe the transfer of gases in the liquid near the boundary, a molecular plus eddy diffusivity concept is used, which has been found useful for smooth flow over solid surfaces. From consideration of the boundary conditions, a similar dependence of eddy diffusivity on distance from the interface can be derived for the flow beneath a gas/liquid interface, at least in the absence of waves. The influence of waves is then discussed. It is evident from scale considerations that the effect of gravity waves is small. It is known from wind tunnel work that capillary waves enhance gas transfer considerably. The existing hypotheses are apparently not sufficient to explain the observations. Examination of field data is even more frustrating since the data do not show the expected increase of gas exchange with wind speed. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOS.A24C2606P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOS.A24C2606P">Surfactant control of air-sea gas exchange from North Sea coastal waters and the Atlantic Meridional Transect</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Pereira, R. 2016-02-01 suppression and SA is much weaker (r2 = <0.01, n = 22). While organic matter composition and sources may have variable control on air-sea gas exchange between the provinces, the poor relationship observed between SA and k660 suggests that other environmental factors maybe more influential on air-sea gas exchange in the open ocean compared to North Sea coastal waters. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21917934','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21917934">Air-gas exchange reevaluated: clinically important results of a computer simulation.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Shunmugam, Manoharan; Shunmugam, Sudhakaran; Williamson, Tom H; Laidlaw, D Alistair 2011-10-21 The primary aim of this study was to evaluate the efficiency of air-gas exchange techniques and the factors that influence the final concentration of an intraocular gas tamponade. Parameters were varied to find the optimum method of performing an air-gas exchange in ideal circumstances. A computer model of the eye was designed using 3D software with fluid flow analysis capabilities. Factors such as angular distance between ports, gas infusion gauge, exhaust vent gauge and depth were varied in the model. Flow rate and axial length were also modulated to simulate faster injections and more myopic eyes, respectively. The flush volume of gas required to achieve a 97% intraocular gas fraction concentration were compared. Modulating individual factors did not reveal any clinically significant difference in the angular distance between ports, exhaust vent size, and depth or rate of gas injection. In combination, however, there was a 28% increase in air-gas exchange efficiency comparing the most efficient with the least efficient studied parameters in this model. The gas flush volume required to achieve a 97% gas fill also increased proportionately at a ratio of 5.5 to 6.2 times the volume of the eye. A 35-mL flush is adequate for eyes up to 25 mm in axial length; however, eyes longer than this would require a much greater flush volume, and surgeons should consider using two separate 50-mL gas syringes to ensure optimal gas concentration for eyes greater than 25 mm in axial length. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1570919','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1570919">Structure, function and evolution of the gas exchangers: comparative perspectives</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Maina, JN 2002-01-01 Over the evolutionary continuum, animals have faced similar fundamental challenges of acquiring molecular oxygen for aerobic metabolism. Under limitations and constraints imposed by factors such as phylogeny, behaviour, body size and environment, they have responded differently in founding optimal respiratory structures. A quintessence of the aphorism that ‘necessity is the mother of invention’, gas exchangers have been inaugurated through stiff cost–benefit analyses that have evoked transaction of trade-offs and compromises. Cogent structural–functional correlations occur in constructions of gas exchangers: within and between taxa, morphological complexity and respiratory efficiency increase with metabolic capacities and oxygen needs. Highly active, small endotherms have relatively better-refined gas exchangers compared with large, inactive ectotherms. Respiratory structures have developed from the plain cell membrane of the primeval prokaryotic unicells to complex multifunctional ones ofthe modern Metazoa. Regarding the respiratory medium used to extract oxygen from, animal life has had only two choices – water or air – within the biological range of temperature and pressure the only naturally occurring respirable fluids. In rarer cases, certain animalshave adapted to using both media. Gills (evaginated gas exchangers) are the primordial respiratory organs: they are the archetypal water breathing organs. Lungs (invaginated gas exchangers) are the model air breathing organs. Bimodal (transitional) breathers occupy the water–air interface. Presentation and exposure of external (water/air) and internal (haemolymph/blood) respiratory media, features determined by geometric arrangement of the conduits, are important features for gas exchange efficiency: counter-current, cross-current, uniform pool and infinite pool designs have variably developed. PMID:12430953 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2889562','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2889562">Universal model for water costs of gas exchange by animals and plants</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Woods, H. Arthur; Smith, Jennifer N. 2010-01-01 For terrestrial animals and plants, a fundamental cost of living is water vapor lost to the atmosphere during exchange of metabolic gases. Here, by bringing together previously developed models for specific taxa, we integrate properties common to all terrestrial gas exchangers into a universal model of water loss. The model predicts that water loss scales to gas exchange with an exponent of 1 and that the amount of water lost per unit of gas exchanged depends on several factors: the surface temperature of the respiratory system near the outside of the organism, the gas consumed (oxygen or carbon dioxide), the steepness of the gradients for gas and vapor, and the transport mode (convective or diffusive). Model predictions were largely confirmed by data on 202 species in five taxa—insects, birds, bird eggs, mammals, and plants—spanning nine orders of magnitude in rate of gas exchange. Discrepancies between model predictions and data seemed to arise from biologically interesting violations of model assumptions, which emphasizes how poorly we understand gas exchange in some taxa. The universal model provides a unified conceptual framework for analyzing exchange-associated water losses across taxa with radically different metabolic and exchange systems. PMID:20404161 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20404161','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20404161">Universal model for water costs of gas exchange by animals and plants.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Woods, H Arthur; Smith, Jennifer N 2010-05-04 For terrestrial animals and plants, a fundamental cost of living is water vapor lost to the atmosphere during exchange of metabolic gases. Here, by bringing together previously developed models for specific taxa, we integrate properties common to all terrestrial gas exchangers into a universal model of water loss. The model predicts that water loss scales to gas exchange with an exponent of 1 and that the amount of water lost per unit of gas exchanged depends on several factors: the surface temperature of the respiratory system near the outside of the organism, the gas consumed (oxygen or carbon dioxide), the steepness of the gradients for gas and vapor, and the transport mode (convective or diffusive). Model predictions were largely confirmed by data on 202 species in five taxa--insects, birds, bird eggs, mammals, and plants--spanning nine orders of magnitude in rate of gas exchange. Discrepancies between model predictions and data seemed to arise from biologically interesting violations of model assumptions, which emphasizes how poorly we understand gas exchange in some taxa. The universal model provides a unified conceptual framework for analyzing exchange-associated water losses across taxa with radically different metabolic and exchange systems. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013GeoRL..40.5683H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013GeoRL..40.5683H">Efficient gas exchange between a boreal river and the atmosphere</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Huotari, Jussi; Haapanala, Sami; Pumpanen, Jukka; Vesala, Timo; Ojala, Anne 2013-11-01 largest uncertainties in accurately resolving the role of rivers and streams in carbon cycling stem from difficulties in determining gas exchange between water and the atmosphere. So far, estimates for river-atmosphere gas exchange have lacked direct ecosystem-scale flux measurements not disturbing gas exchange across the air-water interface. We conducted the first direct riverine gas exchange measurements with eddy covariance in tandem with continuous surface water CO2 measurements in a large boreal river for 30 days. Our measured gas transfer velocity was, on average, 20.8 cm h-1, which is clearly higher than the model estimates based on river channel morphology and water velocity, whereas our floating chambers gave comparable values at 17.3 cm h-1. These results demonstrate that present estimates for riverine CO2 emissions are very likely too low. This result is also relevant to any other gases emitted, as their diffusive exchange rates are similarly proportional to gas transfer velocity. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=245933','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=245933">Gas exchange and water relations responses of spring wheat to full-season infrared warming</a> <a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a> 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... </li> <li> <a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=276837','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=276837">Gas Exchange and Water Relations Responses of Spring Wheat to Full-Season Infrared Warming</a> <a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a> 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... </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1084027','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1084027">Recovery of Water from Boiler Flue Gas Using Condensing Heat Exchangers</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Levy, Edward; Bilirgen, Harun; DuPont, John 2011-03-31 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 characteristicsmore » 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.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1037725','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1037725">Recovery of Water from Boiler Flue Gas Using Condensing Heat Exchangers</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Edward Levy; Harun Bilirgen; John DuPoint 2011-03-31 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 characteristicsmore » 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.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/864049','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/servlets/purl/864049">Fluidized bed heat exchanger with water cooled air distributor and dust hopper</a> <a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a> Jukkola, Walfred W.; Leon, Albert M.; Van Dyk, Jr., Garritt C.; McCoy, Daniel E.; Fisher, Barry L.; Saiers, Timothy L.; Karstetter, Marlin E. 1981-11-24 A fluidized bed heat exchanger is provided in which air is passed through a bed of particulate material containing fuel. A steam-water natural circulation system is provided for heat exchange and the housing of the heat exchanger has a water-wall type construction. Vertical in-bed heat exchange tubes are provided and the air distributor is water-cooled. A water-cooled dust hopper is provided in the housing to collect particulates from the combustion gases and separate the combustion zone from a volume within said housing in which convection heat exchange tubes are provided to extract heat from the exiting combustion gases. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006GeoRL..3314803Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006GeoRL..3314803Z">Impacts of winter storms on air-sea gas exchange</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Zhang, Weiqing; Perrie, Will; Vagle, Svein 2006-07-01 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 (50°N, 145°W). 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. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFMOS31B1280P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFMOS31B1280P">Micrometeorological Measurement of Fetch- and Atmospheric Stability-Dependent Air- Water Exchange of Legacy Semivolatile Organic Contaminants in Lake Superior</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Perlinger, J. A.; Tobias, D. E.; Rowe, M. D. 2008-12-01 Coastal waters including the Laurentian Great Lakes are particularly susceptible to local, regional, and long- range transport and deposition of semivolatile organic contaminants (SOCs) as gases and/or associated with particles. Recently-marketed SOCs can be expected to undergo net deposition in surface waters, whereas legacy SOCs such as polychlorinated biphenyls (PCBs) are likely to be at equilibrium with respect to air-water exchange, or, if atmospheric concentrations decrease through, e.g., policy implementation, to undergo net gas emission. SOC air-water exchange flux is usually estimated using the two-film model. This model describes molecular diffusion through the air and water films adjacent to the air-water interface. Air-water exchange flux is estimated as the product of SOC fugacity, typically based on on-shore gaseous concentration measurements, and a transfer coefficient, the latter which is estimated from SOC properties and environmental conditions. The transfer coefficient formulation commonly applied neglects resistance to exchange in the internal boundary layer under atmospherically stable conditions, and the use of on-shore gaseous concentration neglects fetch-dependent equilibration, both of which will tend to cause overestimation of flux magnitude. Thus, for legacy chemicals or in any highly contaminated surface water, the rate at which the water is cleansed through gas emission tends to be over-predicted using this approach. Micrometeorological measurement of air-water exchange rates of legacy SOCs was carried out on ships during four transect experiments during off-shore flow in Lake Superior using novel multicapillary collection devices and thermal extraction technology to measure parts-per-quadrillion SOC levels. Employing sensible heat in the modified Bowen ratio, fluxes at three over-water stations along the transects were measured, along with up-wind, onshore gaseous concentration and aqueous concentration. The atmosphere was unstable for </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012JGRC..117.5035A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012JGRC..117.5035A">Statistics of surface divergence and their relation to air-water gas transfer velocity</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Asher, William E.; Liang, Hanzhuang; Zappa, Christopher J.; Loewen, Mark R.; Mukto, Moniz A.; Litchendorf, Trina M.; Jessup, Andrew T. 2012-05-01 Air-sea gas fluxes are generally defined in terms of the air/water concentration difference of the gas and the gas transfer velocity,kL. Because it is difficult to measure kLin the ocean, it is often parameterized using more easily measured physical properties. Surface divergence theory suggests that infrared (IR) images of the water surface, which contain information concerning the movement of water very near the air-water interface, might be used to estimatekL. Therefore, a series of experiments testing whether IR imagery could provide a convenient means for estimating the surface divergence applicable to air-sea exchange were conducted in a synthetic jet array tank embedded in a wind tunnel. Gas transfer velocities were measured as a function of wind stress and mechanically generated turbulence; laser-induced fluorescence was used to measure the concentration of carbon dioxide in the top 300 μm of the water surface; IR imagery was used to measure the spatial and temporal distribution of the aqueous skin temperature; and particle image velocimetry was used to measure turbulence at a depth of 1 cm below the air-water interface. It is shown that an estimate of the surface divergence for both wind-shear driven turbulence and mechanically generated turbulence can be derived from the surface skin temperature. The estimates derived from the IR images are compared to velocity field divergences measured by the PIV and to independent estimates of the divergence made using the laser-induced fluorescence data. Divergence is shown to scale withkLvalues measured using gaseous tracers as predicted by conceptual models for both wind-driven and mechanically generated turbulence. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17674350','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17674350">Air bells of water spiders are an extended phenotype modified in response to gas composition.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Schütz, Dolores; Taborsky, Michael; Drapela, Thomas 2007-10-01 The water spider Argyroneta aquatica (Clerck) is the only spider that spends its whole life under water. Water spiders keep an air bubble around their body for breathing and build under-water air bells, which they use for shelter and raising offspring, digesting and consuming prey, moulting, depositing eggs and sperm, and copulating. It is unclear whether these bells are an important oxygen reservoir for breathing under water, or whether they serve mainly to create water-free space for feeding and reproduction. In this study, we manipulated the composition of the gas inside the bell of female water spiders to test whether they monitor the quality of this gas, and replenish oxygen if required. We exchanged the entire gas in the bell either with pure O2, pure CO2, or with ambient air as control, and monitored behavioural responses. The test spiders surfaced and replenished air more often in the CO2 treatment than in the O2 treatment, and they increased bell building behaviour. In addition to active oxygen regulation, they monitored and adjusted the bells by adding silk. These results show that water spiders use the air bell as an oxygen reservoir, and that it functions as an external lung, which renders it essential for living under water permanently. A. aquatica is the only animal that collects, transports, and stores air, and monitors its property for breathing, which is an adaptive response of a terrestrial animal to the colonization of an aquatic habitat. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_1");'>1</a></li> <li class="active">2</li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_3" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_1");'>1</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li class="active">3</li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="41"> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26910987','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26910987">[Summer Greenhouse Gases Exchange Flux Across Water-air Interface in Three Water Reservoirs Located in Different Geologic Setting in Guangxi, China].</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Li, Jian-hong; Pu, Jun-bing; Sun, Ping-an; Yuan, Dao-xian; Liu, Wen; Zhang, Tao; Mo, Xue 2015-11-01 Due to special hydrogeochemical characteristics of calcium-rich, alkaline and DIC-rich ( dissolved inorganic carbon) environment controlled by the weathering products from carbonate rock, the exchange characteristics, processes and controlling factors of greenhouse gas (CO2 and CH4) across water-air interface in karst water reservoir show obvious differences from those of non-karst water reservoir. Three water reservoirs (Dalongdong reservoir-karst reservoir, Wulixia reservoir--semi karst reservoir, Si'anjiang reservoir-non-karst reservoir) located in different geologic setting in Guangxi Zhuang Autonomous Region, China were chosen to reveal characteristics and controlling factors of greenhouse gas exchange flux across water-air interface. Two common approaches, floating chamber (FC) and thin boundary layer models (TBL), were employed to research and contrast greenhouse gas exchange flux across water-air interface from three reservoirs. The results showed that: (1) surface-layer water in reservoir area and discharging water under dam in Dalongdong water reservoir were the source of atmospheric CO2 and CH4. Surface-layer water in reservoir area in Wulixia water reservoir was the sink of atmospheric CO2 and the source of atmospheric CH4, while discharging water under dam was the source of atmospheric CO2 and CH4. Surface-layer water in Si'anjiang water reservoir was the sink of atmospheric CO2 and source of atmospheric CH4. (2) CO2 and CH4 effluxes in discharging water under dam were much more than those in surface-layer water in reservoir area regardless of karst reservoir or non karst reservoir. Accordingly, more attention should be paid to the CO2 and CH4 emission from discharging water under dam. (3) In the absence of submerged soil organic matters and plants, the difference of CH4 effluxes between karst groundwater-fed reservoir ( Dalongdong water reservoir) and non-karst area ( Wulixia water reservoir and Si'anjiang water reservoir) was less. However, CO2 </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014OcSci..10..587S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014OcSci..10..587S">An automated gas exchange tank for determining gas transfer velocities in natural seawater samples</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Schneider-Zapp, K.; Salter, M. E.; Upstill-Goddard, R. C. 2014-07-01 In order to advance understanding of the role of seawater surfactants in the air-sea exchange of climatically active trace gases via suppression of the gas transfer velocity (kw), we constructed a fully automated, closed air-water gas exchange tank and coupled analytical system. The system allows water-side turbulence in the tank to be precisely controlled with an electronically operated baffle. Two coupled gas chromatographs and an integral equilibrator, connected to the tank in a continuous gas-tight system, allow temporal changes in the partial pressures of SF6, CH4 and N2O to be measured simultaneously in the tank water and headspace at multiple turbulence settings, during a typical experimental run of 3.25 h. PC software developed by the authors controls all operations and data acquisition, enabling the optimisation of experimental conditions with high reproducibility. The use of three gases allows three independent estimates of kw for each turbulence setting; these values are subsequently normalised to a constant Schmidt number for direct comparison. The normalised kw estimates show close agreement. Repeated experiments with Milli-Q water demonstrate a typical measurement accuracy of 4% for kw. Experiments with natural seawater show that the system clearly resolves the effects on kw of spatial and temporal trends in natural surfactant activity. The system is an effective tool with which to probe the relationships between kw, surfactant activity and biogeochemical indices of primary productivity, and should assist in providing valuable new insights into the air-sea gas exchange process. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014OcScD..11..693S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014OcScD..11..693S">An automated gas exchange tank for determining gas transfer velocities in natural seawater samples</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Schneider-Zapp, K.; Salter, M. E.; Upstill-Goddard, R. C. 2014-02-01 In order to advance understanding of the role of seawater surfactants in the air-sea exchange of climatically active trace gases via suppression of the gas transfer velocity (kw), we constructed a fully automated, closed air-water gas exchange tank and coupled analytical system. The system allows water-side turbulence in the tank to be precisely controlled with an electronically operated baffle. Two coupled gas chromatographs and an integral equilibrator, connected to the tank in a continuous gas-tight system, allow temporal changes in the partial pressures of SF6, CH4 and N2O to be measured simultaneously in the tank water and headspace at multiple turbulence settings, during a typical experimental run of 3.25 h. PC software developed by the authors controls all operations and data acquisition, enabling the optimisation of experimental conditions with high reproducibility. The use of three gases allows three independent estimates of kw for each turbulence setting; these values are subsequently normalised to a constant Schmidt number for direct comparison. The normalised kw estimates show close agreement. Repeated experiments with MilliQ water demonstrate a typical measurement accuracy of 4% for kw. Experiments with natural seawater show that the system clearly resolves the effects on kw of spatial and temporal trends in natural surfactant activity. The system is an effective tool with which to probe the relationships between kw, surfactant activity and biogeochemical indices of primary productivity, and should assist in providing valuable new insights into the air-sea gas exchange process. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013ACPD...1313285B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ACPD...1313285B">Air/sea DMS gas transfer in the North Atlantic: evidence for limited interfacial gas exchange at high wind speed</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Bell, T. G.; De Bruyn, W.; Miller, S. D.; Ward, B.; Christensen, K.; Saltzman, E. S. 2013-05-01 Shipboard measurements of eddy covariance DMS air/sea fluxes and seawater concentration were carried out in the North Atlantic bloom region in June/July 2011. Gas transfer coefficients (k660) show a linear dependence on mean horizontal wind speed at wind speeds up to 11 m s-1. At higher wind speeds the relationship between k660 and wind speed weakens. At high winds, measured DMS fluxes were lower than predicted based on the linear relationship between wind speed and interfacial stress extrapolated from low to intermediate wind speeds. In contrast, the transfer coefficient for sensible heat did not exhibit this effect. The apparent suppression of air/sea gas flux at higher wind speeds appears to be related to sea state, as determined from shipboard wave measurements. These observations are consistent with the idea that long waves suppress near surface water side turbulence, and decrease interfacial gas transfer. This effect may be more easily observed for DMS than for less soluble gases, such as CO2, because the air/sea exchange of DMS is controlled by interfacial rather than bubble-mediated gas transfer under high wind speed conditions. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=260737','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=260737">Ecosystem Warming Affects Vertical Distribution of Leaf Gas Exchange Properties and Water Relations of Spring Wheat</a> <a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a> 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... </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=68872&keyword=water+AND+gas+AND+exchange&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=68872&keyword=water+AND+gas+AND+exchange&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">DIFFUSIVE EXCHANGE OF GASEOUS POLYCYCLIC AROMATIC HYDROCARBONS AND POLYCHLORINATED BIPHENYLS ACROSS THE AIR-WATER INTERFACE OF THE CHESAPEAKE BAY. (R825245)</a> <a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> Dissolved and gas-phase concentrations of nine polycyclic aromatic hydrocarbons and 46 polychlorinated biphenyl congeners were measured at eight sites on the Chesapeake Bay at four different times of the year to estimate net diffusive air-water gas exchange rates. Gaseous PAHs ar... </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27461227','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27461227">Air breathing and aquatic gas exchange during hypoxia in armoured catfish.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Scott, Graham R; Matey, Victoria; Mendoza, Julie-Anne; Gilmour, Kathleen M; Perry, Steve F; Almeida-Val, Vera M F; Val, Adalberto L 2017-01-01 Air breathing in fish is commonly believed to have arisen as an adaptation to aquatic hypoxia. The effectiveness of air breathing for tissue O 2 supply depends on the ability to avoid O 2 loss as oxygenated blood from the air-breathing organ passes through the gills. Here, we evaluated whether the armoured catfish (Hypostomus aff. pyreneusi)-a facultative air breather-can avoid branchial O 2 loss while air breathing in aquatic hypoxia, and we measured various other respiratory and metabolic traits important for O 2 supply and utilization. Fish were instrumented with opercular catheters to measure the O 2 tension (PO 2 ) of expired water, and air breathing and aquatic respiration were measured during progressive stepwise hypoxia in the water. Armoured catfish exhibited relatively low rates of O 2 consumption and gill ventilation, and gill ventilation increased in hypoxia due primarily to increases in ventilatory stroke volume. Armoured catfish began air breathing at a water PO 2 of 2.5 kPa, and both air-breathing frequency and hypoxia tolerance (as reflected by PO 2 at loss of equilibrium, LOE) was greater in individuals with a larger body mass. Branchial O 2 loss, as reflected by higher PO 2 in expired than in inspired water, was observed in a minority (4/11) of individuals as water PO 2 approached that at LOE. Armoured catfish also exhibited a gill morphology characterized by short filaments bearing short fused lamellae, large interlamellar cell masses, low surface area, and a thick epithelium that increased water-to-blood diffusion distance. Armoured catfish had a relatively low blood-O 2 binding affinity when sampled in normoxia (P 50 of 3.1 kPa at pH 7.4), but were able to rapidly increase binding affinity during progressive hypoxia exposure (to a P 50 of 1.8 kPa). Armoured catfish also had low activities of several metabolic enzymes in white muscle, liver, and brain. Therefore, low rates of metabolism and gill ventilation, and a reduction in branchial gas-exchange </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A22A..08Q','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A22A..08Q">The air, carbon, water synergies and trade-offs in China's natural gas industry</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Qin, Y.; Mauzerall, D. L.; Höglund-Isaksson, L.; Wagner, F.; Byers, E. 2017-12-01 Both energy production and consumption can simultaneously affect regional air quality, local water stress, and the global climate. Identifying air, carbon and water impacts of various energy sources and end-uses is important in determining the relative merits of various energy policies. Here, we examine the air-carbon-water interdependencies of China's six major natural gas source choices (domestic conventional natural gas, domestic coal-based synthetic natural gas (SNG), domestic shale gas, imported liquefied natural gas, imported Russian pipeline gas, and imported Central Asian pipeline gas) and three end-use coal-to-gas deployment strategies (with substitution strategies that focus in turn on air quality, carbon, and water) in 2020. On the supply side, we find that gas sources other than SNG offer national air-carbon-water co-benefits. However, we find striking air-carbon/water trade-offs for SNG at the national scale. Moreover, the use of SNG significantly increases water demand and carbon emissions in regions already suffering from the most severe water stress and the highest per capita carbon footprint. On the end-use side, gas substitution for coal can result in enormous variations in air quality, carbon, and water impacts, with notable air-carbon synergies but air-water trade-offs. Our study finds that, except for SNG, end-use choices generally have a much larger influence on air quality, carbon emissions and water use than do gas source choices. Simultaneous consideration of air, carbon, and water impacts is necessary in designing both beneficial energy development and deployment policies. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013ACP....1311073B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ACP....1311073B">Air-sea dimethylsulfide (DMS) gas transfer in the North Atlantic: evidence for limited interfacial gas exchange at high wind speed</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Bell, T. G.; De Bruyn, W.; Miller, S. D.; Ward, B.; Christensen, K.; Saltzman, E. S. 2013-11-01 Shipboard measurements of eddy covariance dimethylsulfide (DMS) air-sea fluxes and seawater concentration were carried out in the North Atlantic bloom region in June/July 2011. Gas transfer coefficients (k660) show a linear dependence on mean horizontal wind speed at wind speeds up to 11 m s-1. At higher wind speeds the relationship between k660 and wind speed weakens. At high winds, measured DMS fluxes were lower than predicted based on the linear relationship between wind speed and interfacial stress extrapolated from low to intermediate wind speeds. In contrast, the transfer coefficient for sensible heat did not exhibit this effect. The apparent suppression of air-sea gas flux at higher wind speeds appears to be related to sea state, as determined from shipboard wave measurements. These observations are consistent with the idea that long waves suppress near-surface water-side turbulence, and decrease interfacial gas transfer. This effect may be more easily observed for DMS than for less soluble gases, such as CO2, because the air-sea exchange of DMS is controlled by interfacial rather than bubble-mediated gas transfer under high wind speed conditions. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17328184','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17328184">Air-water exchange and dry deposition of polybrominated diphenyl ethers at a coastal site in Izmir Bay, Turkey.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Cetin, Banu; Odabasi, Mustafa 2007-02-01 The air-water exchange of polybrominated diphenyl ethers (PBDEs), an emerging class of persistent organic pollutants (POPs), was investigated using paired air-water samples (n = 15) collected in July and December, 2005 from Guzelyali Port in Izmir Bay, Turkey. Total dissolved-phase water concentrations of PBDEs (sigma7PBDEs) were 212 +/- 65 and 87 +/- 57 pg L(-1) (average +/- SD) in summer and winter, respectively. BDE-209 was the most abundant congener in all samples, followed by BDE-99 and -47. Average ambient gas-phase sigma7PBDE concentrations were between 189 +/- 61 (summer) and 76 +/- 65 pg m(-3) (winter). Net air-water exchange fluxes ranged from -0.9 +/- 1.0 (BDE-28) (volatilization) to 11.1 +/- 5.4 (BDE-209) ng m(-2) day(-1) (deposition). The BDE-28 fluxes were mainly volatilization while the other congeners were deposited. Gas- and dissolved-phase concentrations were significantly correlated (P = 0.33-0.55, p < 0.05, except for BDE-209, r = 0.05, p > 0.05) indicating thatthe atmosphere controls the surface water PBDE levels in this coastal environment. Estimated particulate dry deposition fluxes ranged between 2.7 +/- 1.9 (BDE-154) and 116 +/- 84 ng m(-2) day(-1) (BDE-209) indicating that dry deposition is also a significant input to surface waters in the study area. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018HMT....54.1951C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018HMT....54.1951C">Performance of casting aluminum-silicon alloy condensing heating exchanger for gas-fired boiler</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Cao, Weixue; Liu, Fengguo; You, Xue-yi 2018-07-01 Condensing gas boilers are widely used due to their high heat efficiency, which comes from their ability to use the recoverable sensible heat and latent heat in flue gas. The condensed water of the boiler exhaust has strong corrosion effect on the heat exchanger, which restricts the further application of the condensing gas boiler. In recent years, a casting aluminum-silicon alloy (CASA), which boasts good anti-corrosion properties, has been introduced to condensing hot water boilers. In this paper, the heat transfer performance, CO and NOx emission concentrations and CASA corrosion resistance of a heat exchanger are studied by an efficiency bench test of the gas-fired boiler. The experimental results are compared with heat exchangers produced by Honeywell and Beka. The results show that the excess air coefficient has a significant effect on the heat efficiency and CO and NOx emission of the CASA water heater. When the excess air coefficient of the CASA gas boiler is 1.3, the CO and NOx emission concentration of the flue gas satisfies the design requirements, and the heat efficiency of water heater is 90.8%. In addition, with the increase of heat load rate, the heat transfer coefficient of the heat exchanger and the heat efficiency of the water heater are increased. However, when the heat load rate is at 90%, the NOx emission in the exhaust gas is the highest. Furthermore, when the temperature of flue gas is below 57 °C, the condensation of water vapor occurs, and the pH of condensed water is in the 2.5 5.5 range. The study shows that CASA water heater has good corrosion resistance and a high heat efficiency of 88%. Compared with the heat exchangers produced by Honeywell and Beka, there is still much work to do in optimizing and improving the water heater. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018HMT...tmp...25C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018HMT...tmp...25C">Performance of casting aluminum-silicon alloy condensing heating exchanger for gas-fired boiler</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Cao, Weixue; Liu, Fengguo; You, Xue-yi 2018-01-01 Condensing gas boilers are widely used due to their high heat efficiency, which comes from their ability to use the recoverable sensible heat and latent heat in flue gas. The condensed water of the boiler exhaust has strong corrosion effect on the heat exchanger, which restricts the further application of the condensing gas boiler. In recent years, a casting aluminum-silicon alloy (CASA), which boasts good anti-corrosion properties, has been introduced to condensing hot water boilers. In this paper, the heat transfer performance, CO and NOx emission concentrations and CASA corrosion resistance of a heat exchanger are studied by an efficiency bench test of the gas-fired boiler. The experimental results are compared with heat exchangers produced by Honeywell and Beka. The results show that the excess air coefficient has a significant effect on the heat efficiency and CO and NOx emission of the CASA water heater. When the excess air coefficient of the CASA gas boiler is 1.3, the CO and NOx emission concentration of the flue gas satisfies the design requirements, and the heat efficiency of water heater is 90.8%. In addition, with the increase of heat load rate, the heat transfer coefficient of the heat exchanger and the heat efficiency of the water heater are increased. However, when the heat load rate is at 90%, the NOx emission in the exhaust gas is the highest. Furthermore, when the temperature of flue gas is below 57 °C, the condensation of water vapor occurs, and the pH of condensed water is in the 2.5 5.5 range. The study shows that CASA water heater has good corrosion resistance and a high heat efficiency of 88%. Compared with the heat exchangers produced by Honeywell and Beka, there is still much work to do in optimizing and improving the water heater. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26868055','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26868055">A meta-analysis of leaf gas exchange and water status responses to drought.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Yan, Weiming; Zhong, Yangquanwei; Shangguan, Zhouping 2016-02-12 Drought is considered to be one of the most devastating natural hazards, and it is predicted to become increasingly frequent and severe in the future. Understanding the plant gas exchange and water status response to drought is very important with regard to future climate change. We conducted a meta-analysis based on studies of plants worldwide and aimed to determine the changes in gas exchange and water status under different drought intensities (mild, moderate and severe), different photosynthetic pathways (C3 and C4) and growth forms (herbs, shrubs, trees and lianas). Our results were as follows: 1) drought negatively impacted gas exchange and water status, and stomatal conductance (gs) decreased more than other physiological traits and declined to the greatest extent in shrubs and C3 plants. Furthermore, C4 plants had an advantage compared to C3 plants under the same drought conditions. 2) The decrease in gs mainly reduced the transpiration rate (Tr), and gs could explain 55% of the decrease in the photosynthesis (A) and 74% of the decline in Tr. 3). Finally, gas exchange showed a close relationship with the leaf water status. Our study provides comprehensive information about the changes in plant gas exchange and water status under drought. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4751433','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4751433">A meta-analysis of leaf gas exchange and water status responses to drought</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Yan, Weiming; Zhong, Yangquanwei; Shangguan, Zhouping 2016-01-01 Drought is considered to be one of the most devastating natural hazards, and it is predicted to become increasingly frequent and severe in the future. Understanding the plant gas exchange and water status response to drought is very important with regard to future climate change. We conducted a meta-analysis based on studies of plants worldwide and aimed to determine the changes in gas exchange and water status under different drought intensities (mild, moderate and severe), different photosynthetic pathways (C3 and C4) and growth forms (herbs, shrubs, trees and lianas). Our results were as follows: 1) drought negatively impacted gas exchange and water status, and stomatal conductance (gs) decreased more than other physiological traits and declined to the greatest extent in shrubs and C3 plants. Furthermore, C4 plants had an advantage compared to C3 plants under the same drought conditions. 2) The decrease in gs mainly reduced the transpiration rate (Tr), and gs could explain 55% of the decrease in the photosynthesis (A) and 74% of the decline in Tr. 3). Finally, gas exchange showed a close relationship with the leaf water status. Our study provides comprehensive information about the changes in plant gas exchange and water status under drought. PMID:26868055 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19778365','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19778365">Why and how terrestrial plants exchange gases with air.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Cieslik, S; Omasa, K; Paoletti, E 2009-11-01 This work is intended as a review of gas exchange processes between the atmosphere and the terrestrial vegetation, which have been known for more than two centuries since the discovery of photosynthesis. The physical and biological mechanisms of exchange of carbon dioxide, water vapour, volatile organic compounds emitted by plants and air pollutants taken up by them, is critically reviewed. The role of stomatal physiology is emphasised, as it controls most of these processes. The techniques used for measurement of gas exchange fluxes between the atmosphere and vegetation are outlined. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998PhDT........22V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998PhDT........22V">Photochemical influences on the air-water exchange of mercury</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Vette, Alan Frederic The formation of dissolved gaseous mercury (DGM) in natural waters is an important component in the biogeochemical cycle of mercury (Hg). The predominate form of DGM in natural waters, gaseous elemental Hg (Hg0), may be transferred from the water to the atmosphere. Gas exchange may reduce the amount of Hg available for methyl-Hg formation, the most toxic form of Hg that bioaccumulates in the food chain. Determining the mechanisms and rates of DGM formation is essential in understanding the fate and cycling of Hg in aquatic ecosystems. Field and laboratory experiments were conducted to evaluate the effect of light on DGM formation in surface waters containing different levels of dissolved organic carbon (DOC). Water samples collected from the Tahqwamenon River and Whitefish Bay on Lake Superior were amended with divalent Hg (Hg2+) and irradiated under a variety of reaction conditions to determine rates of DGM formation. The water samples were also analyzed for various Hg species (total, filtered, easily reducible and dissolved gaseous Hg), DOC and light attenuation. Additional field studies were conducted on Lake Michigan to measure gaseous Hg in air and water. These data were used to develop a mechanistic model to estimate air-water exchange of gaseous Hg. This research found that photochemical formation of DGM was affected by penetration of UV A radiation (320-400 nm). Formation of DGM was enhanced at higher DOC concentrations, indicating DOC photosensitized the reduction of Hg2+ to Hg0. Wavelength studies determined that formation of DGM was significantly reduced in the absence of UV A. Field studies showed DGM concentrations were highest near the water surface and peaked at mid-day, indicating a photo-induced source of DGM. The conversion of reducible Hg2+ to Hg0 was suppressed in high DOC waters where UV A penetration was limited. The mechanistic model predicted similar DGM concentrations to the observed values and demonstrated that deposition and emission </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15557031','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15557031">The hyperoxic switch: assessing respiratory water loss rates in tracheate arthropods with continuous gas exchange.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Lighton, John R B; Schilman, Pablo E; Holway, David A 2004-12-01 Partitioning the relative contributions of cuticular and respiratory water loss in a tracheate arthropod is relatively easy if it undergoes discontinuous gas exchange cycles or DGCs, leaving its rate of cuticular water loss in primary evidence while its spiracles are closed. Many arthropods are not so obliging and emit CO(2) continuously, making cuticular and respiratory water losses difficult or impossible to partition. We report here that by switching ambient air from 21 to 100% O(2), marked spiracular constriction takes place, causing a transient but substantial - up to 90% - reduction in CO(2) output. A reduction in water loss rate occurs at the same time. Using this approach, we investigated respiratory water loss in Drosophila melanogaster and in two ant species, Forelius mccooki and Pogonomyrmex californicus. Our results - respiratory water loss estimates of 23%, 7.6% and 5.6% of total water loss rates, respectively - are reasonable in light of literature estimates, and suggest that the 'hyperoxic switch' may allow straightforward estimation of respiratory water loss rates in arthropods lacking discontinuous gas exchange. In P. californicus, which we were able to measure with and without a DGC, presence or absence of a DGC did not affect respiratory vs total water loss rates. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26538177','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26538177">Gas exchange and dive characteristics of the free-swimming backswimmer Anisops deanei.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Jones, Karl K; Snelling, Edward P; Watson, Amy P; Seymour, Roger S 2015-11-01 Many aquatic insects utilise air bubbles on the surface of their bodies to supply O2 while they dive. The bubbles can simply store O2, as in the case of an 'air store', or they can act as a physical 'gas gill', extracting O2 from the water. Backswimmers of the genus Anisops augment their air store with O2 from haemoglobin cells located in the abdomen. The O2 release from the haemoglobin helps stabilise bubble volume, enabling backswimmers to remain near neutrally buoyant for a period of the dive. It is generally assumed that the backswimmer air store does not act as a gas gill and that gas exchange with the water is negligible. This study combines measurements of dive characteristics under different exotic gases (N2, He, SF6, CO) with mathematical modelling, to show that the air store of the backswimmer Anisops deanei does exchange gases with the water. Our results indicate that approximately 20% of O2 consumed during a dive is obtained directly from the water. Oxygen from the water complements that released from the haemoglobin, extending the period of near-neutral buoyancy and increasing dive duration. © 2015. Published by The Company of Biologists Ltd. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12578005','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12578005">Effects of air current speed on gas exchange in plant leaves and plant canopies.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Kitaya, Y; Tsuruyama, J; Shibuya, T; Yoshida, M; Kiyota, M 2003-01-01 To obtain basic data on adequate air circulation to enhance plant growth in a closed plant culture system in a controlled ecological life support system (CELSS), an investigation was made of the effects of the air current speed ranging from 0.01 to 1.0 m s-1 on photosynthesis and transpiration in sweetpotato leaves and photosynthesis in tomato seedlings canopies. The gas exchange rates in leaves and canopies were determined by using a chamber method with an infrared gas analyzer. The net photosynthetic rate and the transpiration rate increased significantly as the air current speeds increased from 0.01 to 0.2 m s-1. The transpiration rate increased gradually at air current speeds ranging from 0.2 to 1.0 m s-1 while the net photosynthetic rate was almost constant at air current speeds ranging from 0.5 to 1.0 m s-1. The increase in the net photosynthetic and transpiration rates were strongly dependent on decreased boundary-layer resistances against gas diffusion. The net photosynthetic rate of the plant canopy was doubled by an increased air current speed from 0.1 to 1.0 m s-1 above the plant canopy. The results demonstrate the importance of air movement around plants for enhancing the gas exchange in the leaf, especially in plant canopies in the CELSS. c2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23821716','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23821716">Gas exchange patterns and water loss rates in the Table Mountain cockroach, Aptera fusca (Blattodea: Blaberidae).</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Groenewald, Berlizé; Bazelet, Corinna S; Potter, C Paige; Terblanche, John S 2013-10-15 The importance of metabolic rate and/or spiracle modulation for saving respiratory water is contentious. One major explanation for gas exchange pattern variation in terrestrial insects is to effect a respiratory water loss (RWL) saving. To test this, we measured the rates of CO2 and H2O release ( and , respectively) in a previously unstudied, mesic cockroach, Aptera fusca, and compared gas exchange and water loss parameters among the major gas exchange patterns (continuous, cyclic, discontinuous gas exchange) at a range of temperatures. Mean , and per unit did not differ among the gas exchange patterns at all temperatures (P>0.09). There was no significant association between temperature and gas exchange pattern type (P=0.63). Percentage of RWL (relative to total water loss) was typically low (9.79±1.84%) and did not differ significantly among gas exchange patterns at 15°C (P=0.26). The method of estimation had a large impact on the percentage of RWL, and of the three techniques investigated (traditional, regression and hyperoxic switch), the traditional method generally performed best. In many respects, A. fusca has typical gas exchange for what might be expected from other insects studied to date (e.g. , , RWL and cuticular water loss). However, we found for A. fusca that expressed as a function of metabolic rate was significantly higher than the expected consensus relationship for insects, suggesting it is under considerable pressure to save water. Despite this, we found no consistent evidence supporting the conclusion that transitions in pattern type yield reductions in RWL in this mesic cockroach. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_1");'>1</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li class="active">3</li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_4" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li class="active">4</li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="61"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A43G2558W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A43G2558W">Air-sea exchange and gas-particle partitioning of polycyclic aromatic hydrocarbons over the northwestern Pacific Ocean: Role of East Asian continental outflow</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Wu, Z.; Guo, Z. 2017-12-01 We measured 15 parent polycyclic aromatic hydrocarbons (PAHs) in atmosphere and water during a research cruise from the East China Sea (ECS) to the northwestern Pacific Ocean (NWP) in the spring of 2015 to investigate the occurrence, air-sea gas exchange, and gas-particle partitioning of PAHs with a particular focus on the influence of East Asian continental outflow. The gaseous PAH composition and identification of sources were consistent with PAHs from the upwind area, indicating that the gaseous PAHs (three- to five-ring PAHs) were influenced by upwind land pollution. In addition, air-sea exchange fluxes of gaseous PAHs were estimated to be -54.2 to 107.4 ng m-2 d-1, and was indicative of variations of land-based PAH inputs. The logarithmic gas-particle partition coefficient (logKp) of PAHs regressed linearly against the logarithmic subcooled liquid vapor pressure, with a slope of -0.25. This was significantly larger than the theoretical value (-1), implying disequilibrium between the gaseous and particulate PAHs over the NWP. The non-equilibrium of PAH gas-particle partitioning was shielded from the volatilization of three-ring gaseous PAHs from seawater and lower soot concentrations in particular when the oceanic air masses prevailed. Modeling PAH absorption into organic matter and adsorption onto soot carbon revealed that the status of PAH gas-particle partitioning deviated more from the modeling Kp for oceanic air masses than those for continental air masses, which coincided with higher volatilization of three-ring PAHs and confirmed the influence of air-sea exchange. Meanwhile, significant linear regressions between logKp and logKoa (logKsa) for PAHs were observed for continental air masses, suggesting the dominant effect of East Asian continental outflow on atmospheric PAHs over the NWP during the sampling campaign. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23238597','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23238597">Water-gas exchange of organochlorine pesticides at Lake Chaohu, a large Chinese lake.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Ouyang, Hui-Ling; He, Wei; Qin, Ning; Kong, Xiang-Zhen; Liu, Wen-Xiu; He, Qi-Shuang; Yang, Chen; Jiang, Yu-Jiao; Wang, Qing-Mei; Yang, Bin; Xu, Fu-Liu 2013-04-01 Organochlorine pesticides (OCPs), a potential threat to ecosystems and human health, are still widely residual in the environment. The residual levels of OCPs in the water and gas phase were monitored in Lake Chaohu, a large Chinese lake, from March 2010 to February 2011. Nineteen types of OCPs were detected in the water with a total concentration of 7.27 ± 3.32 ng/l. Aldrin, DDTs and HCHs were the major OCPs in the water, accounting for 38.3%, 28.9% and 23.6% of the total, respectively. The highest mean concentration (12.32 ng/l) in the water was found in September, while the lowest (1.74 ng/l) was found in November. Twenty types of gaseous OCPs were detected in the atmosphere with a total concentration of 542.0 ± 636.5 pg/m(3). Endosulfan, DDTs and chlordane were the major gaseous OCPs in the atmosphere, accounting for 48.9%, 22.5% and 14.4% of the total, respectively. The mean concentration of gaseous OCPs was significantly higher in summer than in winter. o,p'-DDE was the main metabolite of DDT in both the water and gas phase. Of the HCHs, 52.3% existed as β-HCH in the water, while α-HCH (37.9%) and γ-HCH (30.9%) were dominant isomers in the gas phase. The average fluxes were -21.11, -3.30, -152.41, -35.50 and -1314.15 ng/(m(2) day) for α-HCH, γ-HCH, HCB, DDT and DDE, respectively. The water-gas exchanges of the five types of OCPs indicate that water was the main potential source of gaseous OCPs in the atmosphere. A sensitivity analysis indicated that the water-gas flux of α-HCH, γ-HCH and DDT is more vulnerable than that of HCB and DDE to the variation of the parameters. The possible source of the HCHs in the water was from the historical usage of lindane; however, that in the air was mainly from the recent usage of lindane. The technical DDT and dicofol might be the source of DDTs in the water and air. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013BGeo...10.1379C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013BGeo...10.1379C">Technical Note: A simple method for air-sea gas exchange measurements in mesocosms and its application in carbon budgeting</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Czerny, J.; Schulz, K. G.; Ludwig, A.; Riebesell, U. 2013-03-01 Mesocosms as large experimental units provide the opportunity to perform elemental mass balance calculations, e.g. to derive net biological turnover rates. However, the system is in most cases not closed at the water surface and gases exchange with the atmosphere. Previous attempts to budget carbon pools in mesocosms relied on educated guesses concerning the exchange of CO2 with the atmosphere. Here, we present a simple method for precise determination of air-sea gas exchange in mesocosms using N2O as a deliberate tracer. Beside the application for carbon budgeting, transfer velocities can be used to calculate exchange rates of any gas of known concentration, e.g. to calculate aquatic production rates of climate relevant trace gases. Using an arctic KOSMOS (Kiel Off Shore Mesocosms for future Ocean Simulation) experiment as an exemplary dataset, it is shown that the presented method improves accuracy of carbon budget estimates substantially. Methodology of manipulation, measurement, data processing and conversion to CO2 fluxes are explained. A theoretical discussion of prerequisites for precise gas exchange measurements provides a guideline for the applicability of the method under various experimental conditions. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013BGeo...10.5793S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013BGeo...10.5793S">Biology and air-sea gas exchange controls on the distribution of carbon isotope ratios (δ13C) in the ocean</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Schmittner, A.; Gruber, N.; Mix, A. C.; Key, R. M.; Tagliabue, A.; Westberry, T. K. 2013-09-01 Analysis of observations and sensitivity experiments with a new three-dimensional global model of stable carbon isotope cycling elucidate processes that control the distribution of δ13C of dissolved inorganic carbon (DIC) in the contemporary and preindustrial ocean. Biological fractionation and the sinking of isotopically light δ13C organic matter from the surface into the interior ocean leads to low δ13CDIC values at depths and in high latitude surface waters and high values in the upper ocean at low latitudes with maxima in the subtropics. Air-sea gas exchange has two effects. First, it acts to reduce the spatial gradients created by biology. Second, the associated temperature-dependent fractionation tends to increase (decrease) δ13CDIC values of colder (warmer) water, which generates gradients that oppose those arising from biology. Our model results suggest that both effects are similarly important in influencing surface and interior δ13CDIC distributions. However, since air-sea gas exchange is slow in the modern ocean, the biological effect dominates spatial δ13CDIC gradients both in the interior and at the surface, in contrast to conclusions from some previous studies. Calcium carbonate cycling, pH dependency of fractionation during air-sea gas exchange, and kinetic fractionation have minor effects on δ13CDIC. Accumulation of isotopically light carbon from anthropogenic fossil fuel burning has decreased the spatial variability of surface and deep δ13CDIC since the industrial revolution in our model simulations. Analysis of a new synthesis of δ13CDIC measurements from years 1990 to 2005 is used to quantify preformed and remineralized contributions as well as the effects of biology and air-sea gas exchange. The model reproduces major features of the observed large-scale distribution of δ13CDIC as well as the individual contributions and effects. Residual misfits are documented and analyzed. Simulated surface and subsurface δ13CDIC are influenced by </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/13382','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/13382">Water use in forest canopy black cherry trees and its relationship to leaf gas exchange and environment</a> <a target="_blank" href="http://www.fs.usda.gov/treesearch/">Treesearch</a> B. J. Joyce; K. C. Steiner; J. M. Skelly 1996-01-01 Models of canopy gas exchange are needed to connect leaf-level measurement to higher scales. Because of the correspondence between leaf gas exchange and water use, it may be possible to predict variation in leaf gas exchange at the canopy level by monitoring rates of branch water use. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=197971&Lab=NERL&keyword=gas+AND+behaviour&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=197971&Lab=NERL&keyword=gas+AND+behaviour&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">Simulating the Vapour Phase Air/Water Exchange of p,p′-DDE, p,p′-DDT, Lindane, and 2,3,7,8-Tetrachlorodibenzodioxin</a> <a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> Uncertainties in our understanding of gaseous air/water exchange have emerged as major sources of concern in efforts to construct global and regional mass balances of both the green house gas carbon dioxide and semi-volatile persistent, bioaccumulative and toxic chemicals. Hoff e... </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26359720','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26359720">Different Apparent Gas Exchange Coefficients for CO2 and CH4: Comparing a Brown-Water and a Clear-Water Lake in the Boreal Zone during the Whole Growing Season.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Rantakari, Miitta; Heiskanen, Jouni; Mammarella, Ivan; Tulonen, Tiina; Linnaluoma, Jessica; Kankaala, Paula; Ojala, Anne 2015-10-06 The air-water exchange of carbon dioxide (CO2) and methane (CH4) is a central process during attempts to establish carbon budgets for lakes and landscapes containing lakes. Lake-atmosphere diffusive gas exchange is dependent on the concentration gradient between air and surface water and also on the gas transfer velocity, often described with the gas transfer coefficient k. We used the floating-chamber method in connection with surface water gas concentration measurements to estimate the gas transfer velocity of CO2 (kCO2) and CH4 (kCH4) weekly throughout the entire growing season in two contrasting boreal lakes, a humic oligotrophic lake and a clear-water productive lake, in order to investigate the earlier observed differences between kCO2 and kCH4. We found that the seasonally averaged gas transfer velocity of CH4 was the same for both lakes. When the lakes were sources of CO2, the gas transfer velocity of CO2 was also similar between the two study lakes. The gas transfer velocity of CH4 was constantly higher than that of CO2 in both lakes, a result also found in other studies but for reasons not yet fully understood. We found no differences between the lakes, demonstrating that the difference between kCO2 and kCH4 is not dependent on season or the characteristics of the lake. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24484174','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24484174">Oxo-exchange of gas-phase uranyl, neptunyl, and plutonyl with water and methanol.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Lucena, Ana F; Odoh, Samuel O; Zhao, Jing; Marçalo, Joaquim; Schreckenbach, Georg; Gibson, John K 2014-02-17 A challenge in actinide chemistry is activation of the strong bonds in the actinyl ions, AnO2(+) and AnO2(2+), where An = U, Np, or Pu. Actinyl activation in oxo-exchange with water in solution is well established, but the exchange mechanisms are unknown. Gas-phase actinyl oxo-exchange is a means to probe these processes in detail for simple systems, which are amenable to computational modeling. Gas-phase exchange reactions of UO2(+), NpO2(+), PuO2(+), and UO2(2+) with water and methanol were studied by experiment and density functional theory (DFT); reported for the first time are experimental results for UO2(2+) and for methanol exchange, as well as exchange rate constants. Key findings are faster exchange of UO2(2+) versus UO2(+) and faster exchange with methanol versus water; faster exchange of UO2(+) versus PuO2(+) was quantified. Computed potential energy profiles (PEPs) are in accord with the observed kinetics, validating the utility of DFT to model these exchange processes. The seemingly enigmatic result of faster exchange for uranyl, which has the strongest oxo-bonds, may reflect reduced covalency in uranyl as compared with plutonyl. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17936295','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17936295">Breathe softly, beetle: continuous gas exchange, water loss and the role of the subelytral space in the tenebrionid beetle, Eleodes obscura.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Schilman, Pablo E; Kaiser, Alexander; Lighton, John R B 2008-01-01 Flightless, diurnal tenebrionid beetles are commonly found in deserts. They possess a curious morphological adaptation, the subelytral cavity (an air space beneath the fused elytra) the function of which is not completely understood. In the tenebrionid beetle Eleodes obscura, we measured abdominal movements within the subelytral cavity, and the activity of the pygidial cleft (which seals or unseals the subelytral cavity), simultaneously with total CO2 release rate and water loss rate. First, we found that E. obscura has the lowest cuticular permeability measured in flow-through respirometry in an insect (0.90 microg H2O cm(-2) Torr(-1) h(-1)). Second, it does not exhibit a discontinuous gas exchange cycle. Third, we describe the temporal coupling between gas exchange, water loss, subelytral space volume, and the capacity of the subelytral space to exchange gases with its surroundings as indicated by pygidial cleft state. Fourth, we suggest possible mechanisms that may reduce respiratory water loss rates in E. obscura. Finally, we suggest that E. obscura cannot exchange respiratory gases discontinuously because of a morphological constraint (small tracheal or spiracular conductance). This "conductance constraint hypothesis" may help to explain the otherwise puzzling phylogenetic patterns of continuous vs. discontinuous gas exchange observed in tracheate arthropods. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12806145','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12806145">Mercury exchange at the air-water-soil interface: an overview of methods.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Fang, Fengman; Wang, Qichao; Liu, Ruhai 2002-06-12 An attempt is made to assess the present knowledge about the methods of determining mercury (Hg) exchange at the air-water-soil interface during the past 20 years. Methods determining processes of wet and dry removal/deposition of atmospheric Hg to aquatic and terrestrial ecosystems, as well as methods determining Hg emission fluxes to the atmosphere from natural surfaces (soil and water) are discussed. On the basis of the impressive advances that have been made in the areas relating to Hg exchange among air-soil-water interfaces, we analyzed existing problems and shortcomings in our current knowledge. In addition, some important fields worth further research are discussed and proposed. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhDT........15Q','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhDT........15Q">The Air-Carbon-Water Synergies and Trade-Offs in China's Natural Gas Industry</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Qin, Yue China's coal-dominated energy structure is partly responsible for its domestic air pollution, local water stress, and the global climate change. Primarily to tackle the haze issue, China has been actively promoting a nationwide coal to natural gas end-use switch. My dissertation focuses on evaluating the air quality, carbon, and water impacts and their interactions in China's natural gas industry. Chapter 2 assesses the lifecycle climate performance of China's shale gas in comparison to coal based on stage-level energy consumption and methane leakage rates. I find the mean lifecycle carbon footprint of shale gas is about 30-50% lower than that of coal under both 20 year and 100 year global warming potentials (GWP20 and GWP100). However, primarily due to large uncertainties in methane leakage, the lifecycle carbon footprint of shale gas in China could be 15-60% higher than that of coal across sectors under GWP20. Chapter 3 evaluates the air quality, human health, and the climate impacts of China's coal-based synthetic natural gas (SNG) development. Based on earlier 2020 SNG production targets, I conduct an integrated assessment to identify production technologies and end-use applications that will bring as large air quality and health benefits as possible while keeping carbon penalties as small as possible. I find that, due to inefficient and uncontrolled coal combustion in households, allocating currently available SNG to the residential sector proves to be the best SNG allocation option. Chapter 4 compares the air quality, carbon, and water impacts of China's six major gas sources under three end-use substitution scenarios, which are focused on maximizing air pollutant emission reductions, CO 2 emission reductions, and water stress index (WSI)-weighted water consumption reductions, respectively. I find striking national air-carbon/water trade-offs due to SNG, which also significantly increases water demands and carbon emissions in regions already suffering from </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.B34A..02L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.B34A..02L">Air-Water Exchange of Legacy and Emerging Organic Pollutants across the Great Lakes</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Lohmann, R.; Ruge, Z.; Khairy, M.; Muir, D.; Helm, P. 2014-12-01 Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) are transported to great water bodies via long-range atmospheric transport and released from the surface water as air concentrations continue to diminish. As the largest fresh water bodies in North America, the Great Lakes have both the potential to accumulate and serve as a secondary source of persistent bioaccumulative toxins. OCP and PCB concentrations were sampled at 30+ sites across Lake Superior, Ontario and Erie in the summer of 2011. Polyethylene passive samplers (PEs) were simultaneously deployed in surface water and near surface atmosphere to determine air-water gaseous exchange of OCPs and PCBs. In Lake Superior, surface water and atmospheric concentrations were dominated by α-HCH (average 250 pg/L and 4.2 pg/m3, respectively), followed by HCB (average 17 pg/L and 89 pg/m3, respectively). Air-water exchange varied greatly between sites and individual OCPs, however α-endosulfan was consistently deposited into the surface water (average 19 pg/m2/day). PCBs in the air and water were characterized by penta- and hexachlorobiphenyls with distribution along the coast correlated with proximity to developed areas. Air-water exchange gradients generally yielded net volatilization of PCBs out of Lake Superior. Gaseous concentrations of hexachlorobenzene, dieldrin and chlordanes were significantly higher (p < 0.05) at Lake Erie than Lake Ontario. A multiple linear regression that incorporated meteorological, landuse and population data was used to explain variability in the atmospheric concentrations. Results indicated that landuse (urban and/or cropland) greatly explained the variability in the data. Freely dissolved concentrations of OCPs (<LOD-114 pg/L) were lower than previously detected concentrations. Nonetheless, concentrations of p,p'-DDE and chlordanes were higher than water quality guidelines for the protection of human health from the consumption of fish. Spatial distributions of </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20130011141','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20130011141">Prototype Vent Gas Heat Exchanger for Exploration EVA - Performance and Manufacturing Characteristics</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Quinn, Gregory J.; Strange, Jeremy; Jennings, Mallory 2013-01-01 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. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24643387','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24643387">Concentrations, atmospheric partitioning, and air-water/soil surface exchange of polychlorinated dibenzo-p-dioxin and dibenzofuran along the upper reaches of the Haihe River basin, North China.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Nie, Zhiqiang; Die, Qingqi; Yang, Yufei; Tang, Zhenwu; Wang, Qi; Huang, Qifei 2014-01-01 Polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/PCDF) were overall measured and compared in ambient air, water, soils, and sediments along the upper reaches of the Haihe River of North China, so as to evaluate their concentrations, profiles, and to understand the processes of gas-particle partitioning and air-water/soil exchange. The following results were obtained: (1) The average concentrations (toxic equivalents, TEQs) of 2,3,7,8-PCDD/PCDF in air, water, sediment, and soil samples were 4,855 fg/m(3), 9.5 pg/L, 99.2 pg/g dry weight (dw), and 56.4 pg/g (203 fg TEQ/m(3), 0.46 pg TEQ/L, 2.2 pg TEQ/g dw, and 1.3 pg TEQ/g, respectively), respectively. (2) Although OCDF, 1,2,3,4,6,7,8-HpCDF, OCDD, and 1,2,3,4,6,7,8-HpCDD were the dominant congeners among four environmental sinks, obvious discrepancies of these congener and homologue patterns of PCDD/PCDF were observed still. (3) Significant linear correlations for PCDD/PCDF were observed between the gas-particle partition coefficient (K p) and the subcooled liquid vapor pressure (P L (0)) and octanol-air partition coefficient (K oa). (4) Fugacity fraction values of air-water exchange indicated that most of PCDD/PCDF homologues were dominated by net volatilization from water into air. The low-chlorinated PCDD/PCDF (tetra- to hexa-) presented a strong net volatilization from the soil into air, while high-chlorinated PCDD/PCDF (hepta- to octa-) were mainly close to equilibrium for air-soil exchange. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28675854','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28675854">Air-sea exchange and gas-particle partitioning of polycyclic aromatic hydrocarbons over the northwestern Pacific Ocean: Role of East Asian continental outflow.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Wu, Zilan; Lin, Tian; Li, Zhongxia; Jiang, Yuqing; Li, Yuanyuan; Yao, Xiaohong; Gao, Huiwang; Guo, Zhigang 2017-11-01 We measured 15 parent polycyclic aromatic hydrocarbons (PAHs) in atmosphere and water during a research cruise from the East China Sea (ECS) to the northwestern Pacific Ocean (NWP) in the spring of 2015 to investigate the occurrence, air-sea gas exchange, and gas-particle partitioning of PAHs with a particular focus on the influence of East Asian continental outflow. The gaseous PAH composition and identification of sources were consistent with PAHs from the upwind area, indicating that the gaseous PAHs (three-to five-ring PAHs) were influenced by upwind land pollution. In addition, air-sea exchange fluxes of gaseous PAHs were estimated to be -54.2-107.4 ng m -2 d -1 , and was indicative of variations of land-based PAH inputs. The logarithmic gas-particle partition coefficient (logK p ) of PAHs regressed linearly against the logarithmic subcooled liquid vapor pressure (logP L 0 ), with a slope of -0.25. This was significantly larger than the theoretical value (-1), implying disequilibrium between the gaseous and particulate PAHs over the NWP. The non-equilibrium of PAH gas-particle partitioning was shielded from the volatilization of three-ring gaseous PAHs from seawater and lower soot concentrations in particular when the oceanic air masses prevailed. Modeling PAH absorption into organic matter and adsorption onto soot carbon revealed that the status of PAH gas-particle partitioning deviated more from the modeling K p for oceanic air masses than those for continental air masses, which coincided with higher volatilization of three-ring PAHs and confirmed the influence of air-sea exchange. Meanwhile, significant linear regressions between logK p and logK oa (logK sa ) for PAHs were observed for continental air masses, suggesting the dominant effect of East Asian continental outflow on atmospheric PAHs over the NWP during the sampling campaign. Copyright © 2017 Elsevier Ltd. All rights reserved. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23957244','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23957244">Differences in gas exchange contribute to habitat differentiation in Iberian columbines from contrasting light and water environments.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Jaime, R; Serichol, C; Alcántara, J M; Rey, P J 2014-03-01 During photosynthesis, respiration and transpiration, gas exchange occurs via the stomata and so plants face a trade-off between maximising photosynthesis while minimising transpiration (expressed as water use efficiency, WUE). The ability to cope with this trade-off and regulate photosynthetic rate and stomatal conductance may be related to niche differentiation between closely related species. The present study explored this as a possible mechanism for habitat differentiation in Iberian columbines. The roles of irradiance and water stress were assessed to determine niche differentiation among Iberian columbines via distinct gas exchange processes. Photosynthesis-irradiance curves (P-I curves) were obtained for four taxa, and common garden experiments were conducted to examine plant responses to water and irradiance stress, by measuring instantaneous gas exchange and plant performance. Gas exchange was also measured in ten individuals using two to four field populations per taxon. The taxa had different P-I curves and gas exchange in the field. At the species level, water stress and irradiance explained habitat differentiation. Within each species, a combination of irradiance and water stress explained the between-subspecies habitat differentiation. Despite differences in stomatal conductance and CO2 assimilation, taxa did not have different WUE under field conditions, which suggests that the environment equally modifies photosynthesis and transpiration. The P-I curves, gas exchange in the field and plant responses to experimental water and irradiance stresses support the hypothesis that habitat differentiation is associated with differences among taxa in tolerance to abiotic stress mediated by distinct gas exchange responses. © 2013 German Botanical Society and The Royal Botanical Society of the Netherlands. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=104827&keyword=applications+AND+thermodynamic&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=104827&keyword=applications+AND+thermodynamic&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">A CRITICAL ASSESSMENT OF ELEMENTAL MERCURY AIR/WATER EXCHANGE PARTNERS</a> <a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> Although evasion of elemental mercury from aquatic systems can significantly deplete net mercury accumulation resulting from atmospheric deposition, the current ability to model elemental mercury air/water exchange is limited by uncertainties in our understanding of all gaseous a... </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOS.A34C2670V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOS.A34C2670V">Setting an Upper Limit on Gas Exchange Through Sea-Spray</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Vlahos, P.; Monahan, E. C.; Andreas, E. L. 2016-02-01 Air-sea gas exchange parameterization is critical to understanding both climate forcing and feedbacks and is key in biogeochemistry cycles. Models based on wind speed have provided empirical estimates of gas exchange that are useful though it is likely that at high wind speeds of over 10 m/s there are important gas exchange parameters including bubbles and sea spray that have not been well constrained. Here we address the sea-spray component of gas exchange at these high wind speeds to set sn upper boundary condition for the gas exchange of the six model gases including; nobel gases helium, neon and argon, diatomic gases nitrogen and oxygen and finally, the more complex gas carbon dioxide. Estimates are based on the spray generation function of Andreas and Monahan and the gases are tested under three scenarios including 100 percent saturation and complete droplet evaporation, 100 percent saturation and a more realistic scenario in which a fraction of droplets evaporate completely, a fraction evaporate to some degree and a fraction returns to the water side without significant evaporation. Finally the latter scenario is applied to representative under saturated concentrations of the gases. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=59799&keyword=Exchange+AND+gaseous&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=59799&keyword=Exchange+AND+gaseous&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">THE EFFECT OF SALINITY ON RATES OF ELEMENTAL MERCURY AIR/WATER EXCHANGE</a> <a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> The U.S. EPA laboratory in Athens, Georgia i spursuing the goal of developing a model for describing toxicant vapor phase air/water exchange under all relevant environmental conditions. To date, the two-layer exchange model (suitable for low wind speed conditions) has been modif... </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25743409','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25743409">Estimation of air-water gas exchange coefficient in a shallow lagoon based on 222Rn mass balance.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Cockenpot, S; Claude, C; Radakovitch, O 2015-05-01 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 10 m height (wind range from 2 to 12.5 m/s). When compared with those from the literature, these equations fit particularly well with the one of Kremer et al. (2003). Finally, we emphasize that some gas transfer exchange may always occur, even for conditions without wind. Copyright © 2015 Elsevier Ltd. All rights reserved. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_2");'>2</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li class="active">4</li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_5" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li class="active">5</li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="81"> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=546779','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=546779">Gas Exchange of Algae</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Ammann, Elizabeth C. B.; Lynch, Victoria H. 1966-01-01 Changes in the oxygen partial pressure of air over the range of 8 to 258 mm of Hg did not adversely affect the photosynthetic capacity of Chlorella pyrenoidosa. Gas exchange and growth measurements remained constant for 3-week periods and were similar to air controls (oxygen pressure of 160 mm of Hg). Oxygen partial pressures of 532 and 745 mm of Hg had an adverse effect on algal metabolism. Carbon dioxide consumption was 24% lower in the gas mixture containing oxygen at a pressure 532 mm of Hg than in the air control, and the growth rate was slightly reduced. Oxygen at a partial pressure of 745 mm of Hg decreased the photosynthetic rate 39% and the growth rate 37% over the corresponding rates in air. The lowered metabolic rates remained constant during 14 days of measurements, and the effect was reversible after this time. Substitution of helium or argon for the nitrogen in air had no effect on oxygen production, carbon dioxide consumption, or growth rate for 3-week periods. All measurements were made at a total pressure of 760 mm of Hg, and all gas mixtures were enriched with 2% carbon dioxide. Thus, the physiological functioning and reliability of a photosynthetic gas exchanger should not be adversely affected by: (i) oxygen partial pressures ranging from 8 to 258 mm of Hg; (ii) the use of pure oxygen at reduced total pressure (155 to 258 mm of Hg) unless pressure per se affects photosynthesis, or (iii) the inclusion of helium or argon in the gas environment (up to a partial pressure of 595 mm of Hg). PMID:5927028 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11967744','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11967744">[Phylogeny of gas exchange systems].</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Jürgens, K D; Gros, G 2002-04-01 found in the respiration via the skin, which is of significance in some amphibians, but is limited by the thickness of the skin that constitutes a substantial diffusion path for O2 and CO2. The thick skin, on the other hand, provides mechanical protection as well as flexibility for the animals' body and helps avoid massive water loss via the body surface. The gills of fishes, in contrast, exhibit rather short diffusion distances, are located in a mechanically protected space, and the problem of water loss does not exist. The flows of blood and water occur in opposite direction (countercurrent flow) and this situation makes an arterial PO2 approaching the environmental PO2 possible. A major disadvantage is constituted by the environmental medium since water contains little O2 compared to air and, to compensate this, much energy is expended to maintain a high flow rate of water through the gills. In the mammalian lung ("pool system"), the presence of a dead space and the rhythmic ventilation that replaces only a small fraction of the gas volume of the lung per breath, are responsible for an arterial PO2 (2/3 of the atmospheric PO2) that cannot reach the expiratory PO2. However, an advantage of this feature is the constantly high alveolar and arterial PCO2, which provides a highly effective H(+) buffer system in the entire body. The apparent disadvantage of the mammalian lung is avoided by the avian lung, which uses an extended system of airways to establish continuous equilibration of a part of the capillary blood with fresh air (cross current system), during inspiration as well as during expiration. In this system, arterial PO2 can significantly exceed expiratory PO2. A disadvantage here is the enormous amount of space taken up by the avian lung, in animals of 1 kg body weight three times as much as taken up by the mammalian lung. All respiratory exchange systems considered here exhibit high degrees of optimization - yet follow highly diverse construction principles </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28416704','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28416704">Diurnal Variation in Gas Exchange: The Balance between Carbon Fixation and Water Loss.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Matthews, Jack S A; Vialet-Chabrand, Silvere R M; Lawson, Tracy 2017-06-01 Stomatal control of transpiration is critical for maintaining important processes, such as plant water status, leaf temperature, as well as permitting sufficient CO 2 diffusion into the leaf to maintain photosynthetic rates ( A ). Stomatal conductance often closely correlates with A and is thought to control the balance between water loss and carbon gain. It has been suggested that a mesophyll-driven signal coordinates A and stomatal conductance responses to maintain this relationship; however, the signal has yet to be fully elucidated. Despite this correlation under stable environmental conditions, the responses of both parameters vary spatially and temporally and are dependent on species, environment, and plant water status. Most current models neglect these aspects of gas exchange, although it is clear that they play a vital role in the balance of carbon fixation and water loss. Future efforts should consider the dynamic nature of whole-plant gas exchange and how it represents much more than the sum of its individual leaf-level components, and they should take into consideration the long-term effect on gas exchange over time. © 2017 American Society of Plant Biologists. All Rights Reserved. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19850005886&hterms=heat+exchange&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dheat%2Bexchange','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19850005886&hterms=heat+exchange&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dheat%2Bexchange">Air-sea heat exchange, an element of the water cycle</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Chahine, M. T. 1984-01-01 The distribution and variation of water vapor, clouds and precipitation are examined. Principal driving forces for these distributions are energy exchange and evaporation at the air-sea interface, which are also important elements of air-sea interaction studies. The overall aim of air-sea interaction studies is to quantitatively determine mass, momentum and energy fluxes, with the goal of understanding the mechanisms controlling them. The results of general circulation simulations indicate that the atmosphere in mid-latitudes responds to changes in the oceanic surface conditions in the tropics. This correlation reflects the strong interaction between tropical and mid-latitude conditions caused by the transport of heat and momentum from the tropics. Studies of air-sea exchanges involve a large number of physica, chemical and dynamical processes including heat flux, radiation, sea-surface temperature, precipitation, winds and ocean currents. The fluxes of latent heat are studied and the potential use of satellite data in determining them evaluated. Alternative ways of inferring heat fluxes will be considered. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=180684&keyword=global+AND+water+AND+issues&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=180684&keyword=global+AND+water+AND+issues&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">ISSUES IN SIMULATING ELEMENTAL MERCURY AIR/WATER EXCHANGE AND AQUEOUS MONOMETHYLMERCURY SPECIATION</a> <a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> This presentation focuses on two areas relevant to assessing the global fate and bioavailability of mercury: elemental mercury air/water exchange and aqueous environmental monomethylmercury speciation. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18640753','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18640753">Dry deposition and soil-air gas exchange of polychlorinated biphenyls (PCBs) in an industrial area.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Bozlaker, Ayse; Odabasi, Mustafa; Muezzinoglu, Aysen 2008-12-01 Ambient air and dry deposition, and soil samples were collected at the Aliaga industrial site in Izmir, Turkey. Atmospheric total (particle+gas) Sigma(41)-PCB concentrations were higher in summer (3370+/-1617 pg m(-3), average+SD) than in winter (1164+/-618 pg m(-3)), probably due to increased volatilization with temperature. Average particulate Sigma(41)-PCBs dry deposition fluxes were 349+/-183 and 469+/-328 ng m(-2) day(-1) in summer and winter, respectively. Overall average particulate deposition velocity was 5.5+/-3.5 cm s(-1). The spatial distribution of Sigma(41)-PCB soil concentrations (n=48) showed that the iron-steel plants, ship dismantling facilities, refinery and petrochemicals complex are the major sources in the area. Calculated air-soil exchange fluxes indicated that the contaminated soil is a secondary source to the atmosphere for lighter PCBs and as a sink for heavier ones. Comparable magnitude of gas exchange and dry particle deposition fluxes indicated that both mechanisms are equally important for PCB movement between air and soil in Aliaga. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4510840','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4510840">Oxygen-limited thermal tolerance is seen in a plastron-breathing insect and can be induced in a bimodal gas exchanger</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Verberk, Wilco C. E. P.; Bilton, David T. 2015-01-01 ABSTRACT Thermal tolerance has been hypothesized to result from a mismatch between oxygen supply and demand. However, the generality of this hypothesis has been challenged by studies on various animal groups, including air-breathing adult insects. Recently, comparisons across taxa have suggested that differences in gas exchange mechanisms could reconcile the discrepancies found in previous studies. Here, we test this suggestion by comparing the behaviour of related insect taxa with different gas exchange mechanisms, with and without access to air. We demonstrate oxygen-limited thermal tolerance in air-breathing adults of the plastron-exchanging water bug Aphelocheirus aestivalis. Ilyocoris cimicoides, a related, bimodal gas exchanger, did not exhibit such oxygen-limited thermal tolerance and relied increasingly on aerial gas exchange with warming. Intriguingly, however, when denied access to air, oxygen-limited thermal tolerance could also be induced in this species. Patterns in oxygen-limited thermal tolerance were found to be consistent across life-history stages in these insects, with nymphs employing the same gas exchange mechanisms as adults. These results advance our understanding of oxygen limitation at high temperatures; differences in the degree of respiratory control appear to modulate the importance of oxygen in setting tolerance limits. PMID:25964420 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/11366','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/11366">A Controlled Environment System For Measuring Plant-Atmosphere Gas Exchange</a> <a target="_blank" href="http://www.fs.usda.gov/treesearch/">Treesearch</a> James M. Brown 1975-01-01 Describes an inexpensive, efficient system for measuring plant-atmosphere gas exchange. Designed to measure transpiration from potted tree seedlings, it is readily adaptable for measuring other gas exchanges or gas exchange by plant parts. Light level, air and root temperature can be precisely controlled at minimum cost. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19830046452&hterms=water+gas+exchange&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dwater%2Bgas%2Bexchange','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19830046452&hterms=water+gas+exchange&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dwater%2Bgas%2Bexchange">Methane flux across the air-water interface - Air velocity effects</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Sebacher, D. I.; Harriss, R. C.; Bartlett, K. B. 1983-01-01 Methane loss to the atmosphere from flooded wetlands is influenced by the degree of supersaturation and wind stress at the water surface. Measurements in freshwater ponds in the St. Marks Wildlife Refuge, Florida, demonstrated that for the combined variability of CH4 concentrations in surface water and air velocity over the water surface, CH4 flux varied from 0.01 to 1.22 g/sq m/day. The liquid exchange coefficient for a two-layer model of the gas-liquid interface was calculated as 1.7 cm/h for CH4 at air velocity of zero and as 1.1 + 1.2 v to the 1.96th power cm/h for air velocities from 1.4 to 3.5 m/s and water temperatures of 20 C. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21822726','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21822726">Seasonal photosynthetic gas exchange and water-use efficiency in a constitutive CAM plant, the giant saguaro cactus (Carnegiea gigantea).</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Bronson, Dustin R; English, Nathan B; Dettman, David L; Williams, David G 2011-11-01 Crassulacean acid metabolism (CAM) and the capacity to store large quantities of water are thought to confer high water use efficiency (WUE) and survival of succulent plants in warm desert environments. Yet the highly variable precipitation, temperature and humidity conditions in these environments likely have unique impacts on underlying processes regulating photosynthetic gas exchange and WUE, limiting our ability to predict growth and survival responses of desert CAM plants to climate change. We monitored net CO(2) assimilation (A(net)), stomatal conductance (g(s)), and transpiration (E) rates periodically over 2 years in a natural population of the giant columnar cactus Carnegiea gigantea (saguaro) near Tucson, Arizona USA to investigate environmental and physiological controls over carbon gain and water loss in this ecologically important plant. We hypothesized that seasonal changes in daily integrated water use efficiency (WUE(day)) in this constitutive CAM species would be driven largely by stomatal regulation of nighttime transpiration and CO(2) uptake responding to shifts in nighttime air temperature and humidity. The lowest WUE(day) occurred during time periods with extreme high and low air vapor pressure deficit (D(a)). The diurnal with the highest D(a) had low WUE(day) due to minimal net carbon gain across the 24 h period. Low WUE(day) was also observed under conditions of low D(a); however, it was due to significant transpiration losses. Gas exchange measurements on potted saguaro plants exposed to experimental changes in D(a) confirmed the relationship between D(a) and g(s). Our results suggest that climatic changes involving shifts in air temperature and humidity will have large impacts on the water and carbon economy of the giant saguaro and potentially other succulent CAM plants of warm desert environments. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20170009534','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20170009534">Gas Turbine Engine with Air/Fuel Heat Exchanger</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Krautheim, Michael Stephen (Inventor); Chouinard, Donald G. (Inventor); Donovan, Eric Sean (Inventor); Karam, Michael Abraham (Inventor); Vetters, Daniel Kent (Inventor) 2017-01-01 One embodiment of the present invention is a unique aircraft propulsion gas turbine engine. Another embodiment is a unique gas turbine engine. Another embodiment is a unique gas turbine engine. Other embodiments include apparatuses, systems, devices, hardware, methods, and combinations for gas turbine engines with heat exchange systems. Further embodiments, forms, features, aspects, benefits, and advantages of the present application will become apparent from the description and figures provided herewith. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25964420','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25964420">Oxygen-limited thermal tolerance is seen in a plastron-breathing insect and can be induced in a bimodal gas exchanger.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Verberk, Wilco C E P; Bilton, David T 2015-07-01 Thermal tolerance has been hypothesized to result from a mismatch between oxygen supply and demand. However, the generality of this hypothesis has been challenged by studies on various animal groups, including air-breathing adult insects. Recently, comparisons across taxa have suggested that differences in gas exchange mechanisms could reconcile the discrepancies found in previous studies. Here, we test this suggestion by comparing the behaviour of related insect taxa with different gas exchange mechanisms, with and without access to air. We demonstrate oxygen-limited thermal tolerance in air-breathing adults of the plastron-exchanging water bug Aphelocheirus aestivalis. Ilyocoris cimicoides, a related, bimodal gas exchanger, did not exhibit such oxygen-limited thermal tolerance and relied increasingly on aerial gas exchange with warming. Intriguingly, however, when denied access to air, oxygen-limited thermal tolerance could also be induced in this species. Patterns in oxygen-limited thermal tolerance were found to be consistent across life-history stages in these insects, with nymphs employing the same gas exchange mechanisms as adults. These results advance our understanding of oxygen limitation at high temperatures; differences in the degree of respiratory control appear to modulate the importance of oxygen in setting tolerance limits. © 2015. Published by The Company of Biologists Ltd. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18805813','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18805813">Investigating onychophoran gas exchange and water balance as a means to inform current controversies in arthropod physiology.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Clusella-Trullas, Susana; Chown, Steven L 2008-10-01 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. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20516484','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20516484">Gas exchange and hydraulics in seedlings of Hevea brasiliensis during water stress and recovery.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Chen, Jun-Wen; Zhang, Qiang; Li, Xiao-Shuang; Cao, Kun-Fang 2010-07-01 The response of plants to drought has received significant attention, but far less attention has been given to the dynamic response of plants during recovery from drought. Photosynthetic performance and hydraulic capacity were monitored in seedlings of Hevea brasiliensis under water stress and during recovery following rewatering. Leaf water relation, gas exchange rate and hydraulic conductivity decreased gradually after water stress fell below a threshold, whereas instantaneous water use efficiency and osmolytes increased significantly. After 5 days of rewatering, leaf water relation, maximum stomatal conductance (g(s-max)) and plant hydraulic conductivity had recovered to the control levels except for sapwood area-specific hydraulic conductivity, photosynthetic assimilation rate and osmolytes. During the phase of water stress, stomata were almost completely closed before water transport efficiency decreased substantially, and moreover, the leaf hydraulic pathway was more vulnerable to water stress-induced embolism than the stem hydraulic pathway. Meanwhile, g(s-max) was linearly correlated with hydraulic capacity when water stress exceeded a threshold. In addition, a positive relationship was shown to occur between the recovery of g(s-max) and of hydraulic capacity during the phase of rewatering. Our results suggest (i) that stomatal closure effectively reduces the risk of xylem dysfunction in water-stressed plants at the cost of gas exchange, (ii) that the leaf functions as a safety valve to protect the hydraulic pathway from water stress-induced dysfunction to a larger extent than does the stem and (iii) that the full drought recovery of gas exchange is restricted by not only hydraulic factors but also non-hydraulic factors. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28426140','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28426140">Stomatal kinetics and photosynthetic gas exchange along a continuum of isohydric to anisohydric regulation of plant water status.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Meinzer, Frederick C; Smith, Duncan D; Woodruff, David R; Marias, Danielle E; McCulloh, Katherine A; Howard, Ava R; Magedman, Alicia L 2017-08-01 Species' differences in the stringency of stomatal control of plant water potential represent a continuum of isohydric to anisohydric behaviours. However, little is known about how quasi-steady-state stomatal regulation of water potential may relate to dynamic behaviour of stomata and photosynthetic gas exchange in species operating at different positions along this continuum. Here, we evaluated kinetics of light-induced stomatal opening, activation of photosynthesis and features of quasi-steady-state photosynthetic gas exchange in 10 woody species selected to represent different degrees of anisohydry. Based on a previously developed proxy for the degree of anisohydry, species' leaf water potentials at turgor loss, we found consistent trends in photosynthetic gas exchange traits across a spectrum of isohydry to anisohydry. More anisohydric species had faster kinetics of stomatal opening and activation of photosynthesis, and these kinetics were closely coordinated within species. Quasi-steady-state stomatal conductance and measures of photosynthetic capacity and performance were also greater in more anisohydric species. Intrinsic water-use efficiency estimated from leaf gas exchange and stable carbon isotope ratios was lowest in the most anisohydric species. In comparisons between gas exchange traits, species rankings were highly consistent, leading to species-independent scaling relationships over the range of isohydry to anisohydry observed. © 2017 John Wiley & Sons Ltd. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/5388528-conversion-deuterium-gas-heavy-water-catalytic-isotopic-exchange-using-wetproof-catalyst','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/5388528-conversion-deuterium-gas-heavy-water-catalytic-isotopic-exchange-using-wetproof-catalyst">Conversion of deuterium gas to heavy water by catalytic isotopic exchange using wetproof catalyst</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Quaiattini, R.J.; McGauley, M.P.; Burns, D.L. The invention at Chalk River Nuclear Laboratories of a simple method of wetproofing platinum catalysts allows them to retain their activity in liquid water. High performance catalysts for the hydrogen-water isotope exchange reaction that remain active for years can now be routinely produced. The first commercial application using the ordered-bed-type wetproofed isotope exchange catalyst developed and patented by Atomic Energy of Canada Ltd. has been successfully completed. Approximately 9100 m/sup 3/ of deuterium gas stored at Brookhaven National Laboratory was converted to high grade heavy water. Conversion efficiency exceeded 99.8%. The product D/sub 2/O concentration was 6.7 percentage points highermore » than the feed D/sub 2/ gas.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013BGD....10.8415S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013BGD....10.8415S">Biology and air-sea gas exchange controls on the distribution of carbon isotope ratios (δ13C) in the ocean</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Schmittner, A.; Gruber, N.; Mix, A. C.; Key, R. M.; Tagliabue, A.; Westberry, T. K. 2013-05-01 Analysis of observations and sensitivity experiments with a new three-dimensional global model of stable carbon isotope cycling elucidate the processes that control the distribution of δ13C in the contemporary and preindustrial ocean. Biological fractionation dominates the distribution of δ13CDIC of dissolved inorganic carbon (DIC) due to the sinking of isotopically light δ13C organic matter from the surface into the interior ocean. This process leads to low δ13CDIC values at dephs and in high latitude surface waters and high values in the upper ocean at low latitudes with maxima in the subtropics. Air-sea gas exchange provides an important secondary influence due to two effects. First, it acts to reduce the spatial gradients created by biology. Second, the associated temperature dependent fractionation tends to increase (decrease) δ13CDIC values of colder (warmer) water, which generates gradients that oppose those arising from biology. Our model results suggest that both effects are similarly important in influencing surface and interior δ13CDIC distributions. However, air-sea gas exchange is slow, so biological effect dominate spatial δ13CDIC gradients both in the interior and at the surface, in constrast to conclusions from some previous studies. Analysis of a new synthesis of δ13CDIC measurements from years 1990 to 2005 is used to quantify preformed (δ13Cpre) and remineralized (δ13Crem) contributions as well as the effects of biology (Δδ13Cbio) and air-sea gas exchange (δ13C*). The model reproduces major features of the observed large-scale distribution of δ13CDIC, δ13Cpre, δ13Crem, δ13C*, and Δδ13Cbio. Residual misfits are documented and analyzed. Simulated surface and subsurface δ13CDIC are influenced by details of the ecosystem model formulation. For example, inclusion of a simple parameterization of iron limitation of phytoplankton growth rates and temperature-dependent zooplankton grazing rates improves the agreement with δ13CDIC </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.C31D..01L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.C31D..01L">Gas exchange in the ice zone: the role of small waves and big animals</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Loose, B.; Takahashi, A.; Bigdeli, A. 2016-12-01 The balance of air-sea gas exchange and net biological carbon fixation determine the transport and transformation of carbon dioxide and methane in the ocean. Air-sea gas exchange is mostly driven by upper ocean physics, but biology can also play a role. In the open ocean, gas exchange increases proportionate to the square of wind speed. When sea ice is present, this dependence breaks down in part because breaking waves and air bubble entrainment are damped out by interactions between sea ice and the wave field. At the same time, sea ice motions, formation, melt, and even sea ice-associated organisms can act to introduce turbulence and air bubbles into the upper ocean, thereby enhancing air-sea gas exchange. We take advantage of the knowledge advances of upper ocean physics including bubble dynamics to formulate a model for air-sea gas exchange in the sea ice zone. Here, we use the model to examine the role of small-scale waves and diving animals that trap air for insulation, including penguins, seals and polar bears. We compare these processes to existing parameterizations of wave and bubble dynamics in the open ocean, to observe how sea ice both mitigates and locally enhances air-sea gas transfer. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3976162','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3976162">Rapid and long-term effects of water deficit on gas exchange and hydraulic conductance of silver birch trees grown under varying atmospheric humidity</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> 2014-01-01 Background Effects of water deficit on plant water status, gas exchange and hydraulic conductance were investigated in Betula pendula under artificially manipulated air humidity in Eastern Estonia. The study was aimed to broaden an understanding of the ability of trees to acclimate with the increasing atmospheric humidity predicted for northern Europe. Rapidly-induced water deficit was imposed by dehydrating cut branches in open-air conditions; long-term water deficit was generated by seasonal drought. Results The rapid water deficit quantified by leaf (ΨL) and branch water potentials (ΨB) had a significant (P < 0.001) effect on gas exchange parameters, while inclusion of ΨB in models resulted in a considerably better fit than those including ΨL, which supports the idea that stomatal openness is regulated to prevent stem rather than leaf xylem dysfunction. Under moderate water deficit (ΨL≥-1.55 MPa), leaf conductance to water vapour (gL), transpiration rate and leaf hydraulic conductance (KL) were higher (P < 0.05) and leaf temperature lower in trees grown in elevated air humidity (H treatment) than in control trees (C treatment). Under severe water deficit (ΨL<-1.55 MPa), the treatments showed no difference. The humidification manipulation influenced most of the studied characteristics, while the effect was to a great extent realized through changes in soil water availability, i.e. due to higher soil water potential in H treatment. Two functional characteristics (gL, KL) exhibited higher (P < 0.05) sensitivity to water deficit in trees grown under increased air humidity. Conclusions The experiment supported the hypothesis that physiological traits in trees acclimated to higher air humidity exhibit higher sensitivity to rapid water deficit with respect to two characteristics - leaf conductance to water vapour and leaf hydraulic conductance. Disproportionate changes in sensitivity of stomatal versus leaf hydraulic conductance to water deficit </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24655599','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24655599">Rapid and long-term effects of water deficit on gas exchange and hydraulic conductance of silver birch trees grown under varying atmospheric humidity.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Sellin, Arne; Niglas, Aigar; Õunapuu-Pikas, Eele; Kupper, Priit 2014-03-24 Effects of water deficit on plant water status, gas exchange and hydraulic conductance were investigated in Betula pendula under artificially manipulated air humidity in Eastern Estonia. The study was aimed to broaden an understanding of the ability of trees to acclimate with the increasing atmospheric humidity predicted for northern Europe. Rapidly-induced water deficit was imposed by dehydrating cut branches in open-air conditions; long-term water deficit was generated by seasonal drought. The rapid water deficit quantified by leaf (ΨL) and branch water potentials (ΨB) had a significant (P < 0.001) effect on gas exchange parameters, while inclusion of ΨB in models resulted in a considerably better fit than those including ΨL, which supports the idea that stomatal openness is regulated to prevent stem rather than leaf xylem dysfunction. Under moderate water deficit (ΨL≥-1.55 MPa), leaf conductance to water vapour (gL), transpiration rate and leaf hydraulic conductance (KL) were higher (P < 0.05) and leaf temperature lower in trees grown in elevated air humidity (H treatment) than in control trees (C treatment). Under severe water deficit (ΨL<-1.55 MPa), the treatments showed no difference. The humidification manipulation influenced most of the studied characteristics, while the effect was to a great extent realized through changes in soil water availability, i.e. due to higher soil water potential in H treatment. Two functional characteristics (gL, KL) exhibited higher (P < 0.05) sensitivity to water deficit in trees grown under increased air humidity. The experiment supported the hypothesis that physiological traits in trees acclimated to higher air humidity exhibit higher sensitivity to rapid water deficit with respect to two characteristics - leaf conductance to water vapour and leaf hydraulic conductance. Disproportionate changes in sensitivity of stomatal versus leaf hydraulic conductance to water deficit will impose greater risk of desiccation </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_3");'>3</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li class="active">5</li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_6" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active">6</li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="101"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AIPC.1879b0006C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AIPC.1879b0006C">Devise of an exhaust gas heat exchanger for a thermal oil heater in a palm oil refinery plant</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Chucherd, Panom; Kittisupakorn, Paisan 2017-08-01 This paper presents the devise of an exhaust gas heat exchanger for waste heat recovery of the exhausted flue gas of palm oil refinery plant. This waste heat can be recovered by installing an economizer to heat the feed water which can save the fuel consumption of the coal fired steam boiler and the outlet temperature of flue gas will be controlled in order to avoid the acid dew point temperature and protect the filter bag. The decrease of energy used leads to the reduction of CO2 emission. Two designed economizer studied in this paper are gas in tube and water in tube. The gas in tube exchanger refers to the shell and tube heat exchanger which the flue gas flows in tube; this designed exchanger is used in the existing unit. The new designed water in tube refers to the shell and tube heat exchanger which the water flows in the tube; this designed exchanger is proposed for new implementation. New economizer has the overall coefficient of heat transfer of 19.03 W/m2.K and the surface heat transfer area of 122 m2 in the optimized case. Experimental results show that it is feasible to install economizer in the exhaust flue gas system between the air preheater and the bag filter, which has slightly disadvantage effect in the system. The system can raise the feed water temperature from 40 to 104°C and flow rate 3.31 m3/h, the outlet temperature of flue gas is maintained about 130 °C. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016E%26ES...35a2003A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016E%26ES...35a2003A">The potential role of sea spray droplets in facilitating air-sea gas transfer</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Andreas, E. L.; Vlahos, P.; Monahan, E. C. 2016-05-01 For over 30 years, air-sea interaction specialists have been evaluating and parameterizing the role of whitecap bubbles in air-sea gas exchange. To our knowledge, no one, however, has studied the mirror image process of whether sea spray droplets can facilitate air-sea gas exchange. We are therefore using theory, data analysis, and numerical modeling to quantify the role of spray on air-sea gas transfer. In this, our first formal work on this subject, we seek the rate-limiting step in spray-mediated gas transfer by evaluating the three time scales that govern the exchange: τ air , which quantifies the rate of transfer between the atmospheric gas reservoir and the surface of the droplet; τ int , which quantifies the exchange rate across the air-droplet interface; and τ aq , which quantifies gas mixing within the aqueous solution droplet. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=59576&keyword=film+AND+analysis&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=59576&keyword=film+AND+analysis&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">THE ROLE OF AQUEOUS THIN FILM EVAPORATIVE COOLING ON RATES OF ELEMENTAL MERCURY AIR-WATER EXCHANGE UNDER TEMPERATURE DISEQUILIBRIUM CONDITIONS</a> <a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> The technical conununity has only recently addressed the role of atmospheric temperature variations on rates of air-water vapor phase toxicant exchange. The technical literature has documented that: 1) day time rates of elemental mercury vapor phase air-water exchange can exceed ... </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21669328','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21669328">Atmospheric concentrations and air-soil gas exchange of polycyclic aromatic hydrocarbons (PAHs) in remote, rural village and urban areas of Beijing-Tianjin region, North China.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Wang, Wentao; Simonich, Staci; Giri, Basant; Chang, Ying; Zhang, Yuguang; Jia, Yuling; Tao, Shu; Wang, Rong; Wang, Bin; Li, Wei; Cao, Jun; Lu, Xiaoxia 2011-07-01 Forty passive air samplers were deployed to study the occurrence of gas and particulate phase PAHs in remote, rural village and urban areas of Beijing-Tianjin region, North China for four seasons (spring, summer, fall and winter) from 2007 to 2008. The influence of emissions on the spatial distribution pattern of air PAH concentrations was addressed. In addition, the air-soil gas exchange of PAHs was studied using fugacity calculations. The median gaseous and particulate phase PAH concentrations were 222 ng/m³ and 114 ng/m³, respectively, with a median total PAH concentration of 349 ng/m³. Higher PAH concentrations were measured in winter than in other seasons. Air PAH concentrations measured at the rural villages and urban sites in the northern mountain region were significantly lower than those measured at sites in the southern plain during all seasons. However, there was no significant difference in PAH concentrations between the rural villages and urban sites in the northern and southern areas. This urban-rural PAH distribution pattern was related to the location of PAH emission sources and the population distribution. The location of PAH emission sources explained 56%-77% of the spatial variation in ambient air PAH concentrations. The annual median air-soil gas exchange flux of PAHs was 42.2 ng/m²/day from soil to air. Among the 15 PAHs measured, acenaphthylene (ACY) and acenaphthene (ACE) contributed to more than half of the total exchange flux. Furthermore, the air-soil gas exchange fluxes of PAHs at the urban sites were higher than those at the remote and rural sites. In summer, more gaseous PAHs volatilized from soil to air because of higher temperatures and increased rainfall. However, in winter, more gaseous PAHs deposited from air to soil due to higher PAH emissions and lower temperatures. The soil TOC concentration had no significant influence on the air-soil gas exchange of PAHs. Copyright © 2011 Elsevier B.V. All rights reserved. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25399878','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25399878">Estimation of bias with the single-zone assumption in measurement of residential air exchange using the perfluorocarbon tracer gas method.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Van Ryswyk, K; Wallace, L; Fugler, D; MacNeill, M; Héroux, M È; Gibson, M D; Guernsey, J R; Kindzierski, W; Wheeler, A J 2015-12-01 Residential air exchange rates (AERs) are vital in understanding the temporal and spatial drivers of indoor air quality (IAQ). Several methods to quantify AERs have been used in IAQ research, often with the assumption that the home is a single, well-mixed air zone. Since 2005, Health Canada has conducted IAQ studies across Canada in which AERs were measured using the perfluorocarbon tracer (PFT) gas method. Emitters and detectors of a single PFT gas were placed on the main floor to estimate a single-zone AER (AER(1z)). In three of these studies, a second set of emitters and detectors were deployed in the basement or second floor in approximately 10% of homes for a two-zone AER estimate (AER(2z)). In total, 287 daily pairs of AER(2z) and AER(1z) estimates were made from 35 homes across three cities. In 87% of the cases, AER(2z) was higher than AER(1z). Overall, the AER(1z) estimates underestimated AER(2z) by approximately 16% (IQR: 5-32%). This underestimate occurred in all cities and seasons and varied in magnitude seasonally, between homes, and daily, indicating that when measuring residential air exchange using a single PFT gas, the assumption of a single well-mixed air zone very likely results in an under prediction of the AER. The results of this study suggest that the long-standing assumption that a home represents a single well-mixed air zone may result in a substantial negative bias in air exchange estimates. Indoor air quality professionals should take this finding into consideration when developing study designs or making decisions related to the recommendation and installation of residential ventilation systems. © 2014 Her Majesty the Queen in Right of Canada. Indoor Air published by John Wiley & Sons Ltd Reproduced with the permission of the Minister of Health Canada. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28526196','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28526196">Use of a numerical simulation approach to improve the estimation of air-water exchange fluxes of polycyclic aromatic hydrocarbons in a coastal zone.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Lai, I-Chien; Lee, Chon-Lin; Ko, Fung-Chi; Lin, Ju-Chieh; Huang, Hu-Ching; Shiu, Ruei-Feng 2017-07-15 The air-water exchange is important for determining the transport, fate, and chemical loading of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere and in aquatic systems. Investigations of PAH air-water exchange are mostly based on observational data obtained using complicated field sampling processes. This study proposes a new approach to improve the estimation of long-term PAH air-water exchange fluxes by using a multivariate regression model to simulate hourly gaseous PAH concentrations. Model performance analysis and the benefits from this approach indicate its effectiveness at improving the flux estimations and at decreasing the field sampling difficulty. The proposed GIS mapping approach is useful for box model establishment and is tested for visualization of the spatiotemporal variations of air-water exchange fluxes in a coastal zone. The air-water exchange fluxes illustrated by contour maps suggest that the atmospheric PAHs might have greater impacts on offshore sites than on the coastal area in this study. Copyright © 2017 Elsevier Ltd. All rights reserved. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/952467','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/952467">Recovery of Water from Boiler Flue Gas</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Edward Levy; Harun Bilirgen; Kwangkook Jeong 2008-09-30 This project dealt with use of condensing heat exchangers to recover water vapor from flue gas at coal-fired power plants. Pilot-scale heat transfer tests were performed to determine the relationship between flue gas moisture concentration, heat exchanger design and operating conditions, and water vapor condensation rate. The tests also determined the extent to which the condensation processes for water and acid vapors in flue gas can be made to occur separately in different heat transfer sections. The results showed flue gas water vapor condensed in the low temperature region of the heat exchanger system, with water capture efficiencies depending stronglymore » on flue gas moisture content, cooling water inlet temperature, heat exchanger design and flue gas and cooling water flow rates. Sulfuric acid vapor condensed in both the high temperature and low temperature regions of the heat transfer apparatus, while hydrochloric and nitric acid vapors condensed with the water vapor in the low temperature region. Measurements made of flue gas mercury concentrations upstream and downstream of the heat exchangers showed a significant reduction in flue gas mercury concentration within the heat exchangers. A theoretical heat and mass transfer model was developed for predicting rates of heat transfer and water vapor condensation and comparisons were made with pilot scale measurements. Analyses were also carried out to estimate how much flue gas moisture it would be practical to recover from boiler flue gas and the magnitude of the heat rate improvements which could be made by recovering sensible and latent heat from flue gas.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25993893','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25993893">Modelling non-steady-state isotope enrichment of leaf water in a gas-exchange cuvette environment.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Song, Xin; Simonin, Kevin A; Loucos, Karen E; Barbour, Margaret M 2015-12-01 The combined use of a gas-exchange system and laser-based isotope measurement is a tool of growing interest in plant ecophysiological studies, owing to its relevance for assessing isotopic variability in leaf water and/or transpiration under non-steady-state (NSS) conditions. However, the current Farquhar & Cernusak (F&C) NSS leaf water model, originally developed for open-field scenarios, is unsuited for use in a gas-exchange cuvette environment where isotope composition of water vapour (δv ) is intrinsically linked to that of transpiration (δE ). Here, we modified the F&C model to make it directly compatible with the δv -δE dynamic characteristic of a typical cuvette setting. The resultant new model suggests a role of 'net-flux' (rather than 'gross-flux' as suggested by the original F&C model)-based leaf water turnover rate in controlling the time constant (τ) for the approach to steady sate. The validity of the new model was subsequently confirmed in a cuvette experiment involving cotton leaves, for which we demonstrated close agreement between τ values predicted from the model and those measured from NSS variations in isotope enrichment of transpiration. Hence, we recommend that our new model be incorporated into future isotope studies involving a cuvette condition where the transpiration flux directly influences δv . There is an increasing popularity among plant ecophysiologists to use a gas-exchange system coupled to laser-based isotope measurement for investigating non-steady state (NSS) isotopic variability in leaf water (and/or transpiration); however, the current Farquhar & Cernusak (F&C) NSS leaf water model is unsuited for use in a gas-exchange cuvette environment due to its implicit assumption of isotope composition of water vapor (δv ) being constant and independent of that of transpiration (δE ). In the present study, we modified the F&C model to make it compatible with the dynamic relationship between δv and δE as is typically associated </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009HMT....46..175M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009HMT....46..175M">High temperature heat exchanger studies for applications to gas turbines</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Min, June Kee; Jeong, Ji Hwan; Ha, Man Yeong; Kim, Kui Soon 2009-12-01 Growing demand for environmentally friendly aero gas-turbine engines with lower emissions and improved specific fuel consumption can be met by incorporating heat exchangers into gas turbines. Relevant researches in such areas as the design of a heat exchanger matrix, materials selection, manufacturing technology, and optimization by a variety of researchers have been reviewed in this paper. Based on results reported in previous studies, potential heat exchanger designs for an aero gas turbine recuperator, intercooler, and cooling-air cooler are suggested. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26642083','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26642083">Gaseous and Freely-Dissolved PCBs in the Lower Great Lakes Based on Passive Sampling: Spatial Trends and Air-Water Exchange.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Liu, Ying; Wang, Siyao; McDonough, Carrie A; Khairy, Mohammed; Muir, Derek C G; Helm, Paul A; Lohmann, Rainer 2016-05-17 Polyethylene passive sampling was performed to quantify gaseous and freely dissolved polychlorinated biphenyls (PCBs) in the air and water of Lakes Erie and Ontario during 2011-2012. In view of differing physical characteristics and the impacts of historical contamination by PCBs within these lakes, spatial variation of PCB concentrations and air-water exchange across these lakes may be expected. Both lakes displayed statistically similar aqueous and atmospheric PCB concentrations. Total aqueous concentrations of 29 PCBs ranged from 1.5 pg L(-1) in the open lake of Lake Erie (site E02) in 2011 spring to 105 pg L(-1) in Niagara (site On05) in 2012 summer, while total atmospheric concentrations were 7.7-634 pg m(-3) across both lakes. A west-to-east gradient was observed for aqueous PCBs in Lake Erie. River discharge and localized influences (e.g., sediment resuspension and regional alongshore transport) likely dominated spatial trends of aqueous PCBs in both lakes. Air-water exchange fluxes of Σ7PCBs ranged from -2.4 (±1.9) ng m(-2) day(-1) (deposition) in Sheffield (site E03) to 9.0 (±3.1) ng m(-2) day(-1) (volatilization) in Niagara (site On05). Net volatilization of PCBs was the primary trend across most sites and periods. Almost half of variation in air-water exchange fluxes was attributed to the difference in aqueous concentrations of PCBs. Uncertainty analysis in fugacity ratios and mass fluxes in air-water exchange of PCBs indicated that PCBs have reached or approached equilibrium only at the eastern Lake Erie and along the Canadian shore of Lake Ontario sites, where air-water exchange fluxes dominated atmospheric concentrations. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22319207','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22319207">Quantitative variation in water-use efficiency across water regimes and its relationship with circadian, vegetative, reproductive, and leaf gas-exchange traits.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Edwards, Christine E; Ewers, Brent E; McClung, C Robertson; Lou, Ping; Weinig, Cynthia 2012-05-01 Drought limits light harvesting, resulting in lower plant growth and reproduction. One trait important for plant drought response is water-use efficiency (WUE). We investigated (1) how the joint genetic architecture of WUE, reproductive characters, and vegetative traits changed across drought and well-watered conditions, (2) whether traits with distinct developmental bases (e.g. leaf gas exchange versus reproduction) differed in the environmental sensitivity of their genetic architecture, and (3) whether quantitative variation in circadian period was related to drought response in Brassica rapa. Overall, WUE increased in drought, primarily because stomatal conductance, and thus water loss, declined more than carbon fixation. Genotypes with the highest WUE in drought expressed the lowest WUE in well-watered conditions, and had the largest vegetative and floral organs in both treatments. Thus, large changes in WUE enabled some genotypes to approach vegetative and reproductive trait optima across environments. The genetic architecture differed for gas-exchange and vegetative traits across drought and well-watered conditions, but not for floral traits. Correlations between circadian and leaf gas-exchange traits were significant but did not vary across treatments, indicating that circadian period affects physiological function regardless of water availability. These results suggest that WUE is important for drought tolerance in Brassica rapa and that artificial selection for increased WUE in drought will not result in maladaptive expression of other traits that are correlated with WUE. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19203976','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19203976">The hydraulic conductance of Fraxinus ornus leaves is constrained by soil water availability and coordinated with gas exchange rates.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Gortan, Emmanuelle; Nardini, Andrea; Gascó, Antonio; Salleo, Sebastiano 2009-04-01 Leaf hydraulic conductance (Kleaf) is known to be an important determinant of plant gas exchange and photosynthesis. Little is known about the long-term impact of different environmental factors on the hydraulic construction of leaves and its eventual consequences on leaf gas exchange. In this study, we investigate the impact of soil water availability on Kleaf of Fraxinus ornus L. as well as the influence of Kleaf on gas exchange rates and plant water status. With this aim, Kleaf, leaf conductance to water vapour (gL), leaf water potential (Psileaf) and leaf mass per area (LMA) were measured in F. ornus trees, growing in 21 different sites with contrasting water availability. Plants growing in arid sites had lower Kleaf, gL and Psileaf than those growing in sites with higher water availability. On the contrary, LMA was similar in the two groups. The Kleaf values recorded in sites with two different levels of soil water availability were constantly different from each other regardless of the amount of precipitation recorded over 20 days before measurements. Moreover, Kleaf was correlated with gL values. Our data suggest that down-regulation of Kleaf is a component of adaptation of plants to drought-prone habitats. Low Kleaf implies reduced gas exchange which may, in turn, influence the climatic conditions on a local/regional scale. It is concluded that leaf hydraulics and its changes in response to resource availability should receive greater attention in studies aimed at modelling biosphere-atmosphere interactions. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=315495','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=315495">Deficit irrigation: Arriving at the crop water stress index via gas exchange measurements</a> <a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a> Plant gas exchange provides a highly sensitive measure of the degree of drought stress. Canopy temperature (Tc) provides a much easier to acquire indication of crop water deficit that has been used in irrigation scheduling systems, but interpretation of this measurement has proven difficult. Our goa... </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/8143714','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/8143714">Pulmonary gas exchange in acute respiratory failure.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Rodriguez-Roisin, R 1994-01-01 The principal function of the lung is to facilitate the exchange of the respiratory gases, oxygen (O2) and carbon dioxide (CO2). When the lung fails as a gas exchanger respiratory failure ensues. Clinically, it is generally accepted that an arterial oxygen tension (PaO2) of less than 60 mmHg or a PaCO2 of greater than 50 mmHg, or both, whilst breathing room air are values consistent with the concept of respiratory failure. This article will deal, firstly, with some basic aspects of the physiology of pulmonary gas exchange and more specifically on the measurement of ventilation-perfusion (VA/Q) relationships, the most influential factor determining hypoxaemia. The second part highlights the most important findings on pulmonary gas exchange in the adult respiratory distress syndrome (ARDS) and other common acute respiratory failure conditions, such as pneumonia, acute exacerbation of chronic obstructive pulmonary disease (COPD) and status asthmaticus, based on the data obtained by means of the multiple inert gas elimination approach, a technique which gives a detailed picture of VA/Q ratio distributions. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4674977','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4674977">Estimation of bias with the single-zone assumption in measurement of residential air exchange using the perfluorocarbon tracer gas method</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Van Ryswyk, K; Wallace, L; Fugler, D; MacNeill, M; Héroux, M È; Gibson, M D; Guernsey, J R; Kindzierski, W; Wheeler, A J 2015-01-01 Residential air exchange rates (AERs) are vital in understanding the temporal and spatial drivers of indoor air quality (IAQ). Several methods to quantify AERs have been used in IAQ research, often with the assumption that the home is a single, well-mixed air zone. Since 2005, Health Canada has conducted IAQ studies across Canada in which AERs were measured using the perfluorocarbon tracer (PFT) gas method. Emitters and detectors of a single PFT gas were placed on the main floor to estimate a single-zone AER (AER1z). In three of these studies, a second set of emitters and detectors were deployed in the basement or second floor in approximately 10% of homes for a two-zone AER estimate (AER2z). In total, 287 daily pairs of AER2z and AER1z estimates were made from 35 homes across three cities. In 87% of the cases, AER2z was higher than AER1z. Overall, the AER1z estimates underestimated AER2z by approximately 16% (IQR: 5–32%). This underestimate occurred in all cities and seasons and varied in magnitude seasonally, between homes, and daily, indicating that when measuring residential air exchange using a single PFT gas, the assumption of a single well-mixed air zone very likely results in an under prediction of the AER. PMID:25399878 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27209375','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27209375">Gas Exchange Models for a Flexible Insect Tracheal System.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Simelane, S M; Abelman, S; Duncan, F D 2016-06-01 In this paper two models for movement of respiratory gases in the insect trachea are presented. One model considers the tracheal system as a single flexible compartment while the other model considers the trachea as a single flexible compartment with gas exchange. This work represents an extension of Ben-Tal's work on compartmental gas exchange in human lungs and is applied to the insect tracheal system. The purpose of the work is to study nonlinear phenomena seen in the insect respiratory system. It is assumed that the flow inside the trachea is laminar, and that the air inside the chamber behaves as an ideal gas. Further, with the isothermal assumption, the expressions for the tracheal partial pressures of oxygen and carbon dioxide, rate of volume change, and the rates of change of oxygen concentration and carbon dioxide concentration are derived. The effects of some flow parameters such as diffusion capacities, reaction rates and air concentrations on net flow are studied. Numerical simulations of the tracheal flow characteristics are performed. The models developed provide a mathematical framework to further investigate gas exchange in insects. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25761782','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25761782">Protein structural dynamics at the gas/water interface examined by hydrogen exchange mass spectrometry.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Xiao, Yiming; Konermann, Lars 2015-08-01 Gas/water interfaces (such as air bubbles or foam) are detrimental to the stability of proteins, often causing aggregation. This represents a potential problem for industrial processes, for example, the production and handling of protein drugs. Proteins possess surfactant-like properties, resulting in a high affinity for gas/water interfaces. The tendency of previously buried nonpolar residues to maximize contact with the gas phase can cause significant structural distortion. Most earlier studies in this area employed spectroscopic tools that could only provide limited information. Here we use hydrogen/deuterium exchange (HDX) mass spectrometry (MS) for probing the conformational dynamics of the model protein myoglobin (Mb) in the presence of N(2) bubbles. HDX/MS relies on the principle that unfolded and/or highly dynamic regions undergo faster deuteration than tightly folded segments. In bubble-free solution Mb displays EX2 behavior, reflecting the occurrence of short-lived excursions to partially unfolded conformers. A dramatically different behavior is seen in the presence of N(2) bubbles; EX2 dynamics still take place, but in addition the protein shows EX1 behavior. The latter results from interconversion of the native state with conformers that are globally unfolded and long-lived. These unfolded species likely correspond to Mb that is adsorbed to the surface of gas bubbles. N(2) sparging also induces aggregation. To explain the observed behavior we propose a simple model, that is, "semi-unfolded" ↔ "native" ↔ "globally unfolded" → "aggregated". This model quantitatively reproduces the experimentally observed kinetics. To the best of our knowledge, the current study marks the first exploration of surface denaturation phenomena by HDX/MS. © 2015 The Protein Society. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27458653','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27458653">Spatial Distribution and Air-Water Exchange of Organic Flame Retardants in the Lower Great Lakes.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> McDonough, Carrie A; Puggioni, Gavino; Helm, Paul A; Muir, Derek; Lohmann, Rainer 2016-09-06 Organic flame retardants (OFRs) such as polybrominated diphenyl ethers (PBDEs) and novel halogenated flame retardants (NHFRs) are ubiquitous, persistent, and bioaccumulative contaminants that have been used in consumer goods to slow combustion. In this study, polyethylene passive samplers (PEs) were deployed throughout the lower Great Lakes (Lake Erie and Lake Ontario) to measure OFRs in air and water, calculate air-water exchange fluxes, and investigate spatial trends. Dissolved Σ12BDE was greatest in Lake Ontario near Toronto (18 pg/L), whereas gaseous Σ12BDE was greatest on the southern shoreline of Lake Erie (11 pg/m(3)). NHFRs were generally below detection limits. Air-water exchange was dominated by absorption of BDEs 47 and 99, ranging from -964 pg/m(2)/day to -30 pg/m(2)/day. Σ12BDE in air and water was significantly correlated with surrounding population density, suggesting that phased-out PBDEs continued to be emitted from population centers along the Great Lakes shoreline in 2012. Correlation with dissolved Σ12BDE was strongest when considering population within 25 km while correlation with gaseous Σ12BDE was strongest when using population within 3 km to the south of each site. Bayesian kriging was used to predict dissolved Σ12BDE over the lakes, illustrating the utility of relatively highly spatially resolved measurements in identifying potential hot spots for future study. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21692813','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21692813">Responses to water stress of gas exchange and metabolites in Eucalyptus and Acacia spp.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Warren, Charles R; Aranda, Ismael; Cano, F Javier 2011-10-01 Studies of water stress commonly examine either gas exchange or leaf metabolites, and many fail to quantify the concentration of CO₂ in the chloroplasts (C(c)). We redress these limitations by quantifying C(c) from discrimination against ¹³CO₂ 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 (Ψ(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. γ-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. © 2011 Blackwell Publishing Ltd. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUSM.H33C..06B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUSM.H33C..06B">Air Sparging Versus Gas Saturated Water Injection for Remediation of Volatile LNAPL in the Borden Aquifer</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Barker, J.; Nelson, L.; Doughty, C.; Thomson, N.; Lambert, J. 2009-05-01 In the shallow, rather homogeneous, unconfined Borden sand aquifer, field trials of air sparging (Tomlinson et al., 2003) and pulsed air sparging (Lambert et al., 2009) have been conducted, the latter to remediate a residual gasoline source emplaced below the water table. As well, a supersaturated (with CO2) water injection (SWI) technology, using the inVentures inFusion system, has been trialed in two phases: 1. in the uncontaminated sand aquifer to evaluate the radius of influence, extent of lateral gas movement and gas saturation below the water table, and 2. in a sheet pile cell in the Borden aquifer to evaluate the recovery of volatile hydrocarbon components (pentane and hexane) of an LNAPL emplaced below the water table (Nelson et al., 2008). The SWI injects water supersaturated with CO2. The supersaturated injected water moves laterally away from the sparge point, releasing CO2 over a wider area than does gas sparging from a single well screen. This presentation compares these two techniques in terms of their potential for remediating volatile NAPL components occurring below the water table in a rather homogeneous sand aquifer. Air sparging created a significantly greater air saturation in the vicinity of the sparge well than did the CO2 system (60 percent versus 16 percent) in the uncontaminated Borden aquifer. However, SWI pushed water, still supersaturated with CO2, up to about 2.5 m from the injection well. This would seem to provide a considerable advantage over air sparging from a point, in that gas bubbles are generated at a much larger radius from the point of injection with SWI and so should involve additional gas pathways through a residual NAPL. Overall, air sparging created a greater area of influence, defined by measurable air saturation in the aquifer, but air sparging also injected about 12 times more gas than was injected in the SWI trials. The pulsed air sparging at Borden (Lambert et al.) removed about 20 percent (4.6 kg) of gasoline </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_4");'>4</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li class="active">6</li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_7" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active">7</li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="121"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ThEng..65..300O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ThEng..65..300O">Study of Cycling Air-Cooling System with a Cold Accumulator for Micro Gas-Turbine Installations</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ochkov, V. F.; Stepanova, T. A.; Katenev, G. M.; Tumanovskii, V. A.; Borisova, P. N. 2018-05-01 Using the cycling air-cooling systems of the CTIC type (Combustion Turbine Inlet Cooling) with a cold accumulator in a micro gas-turbine installation (micro-GTI) to preserve its capacity under the seasonal temperature rise of outside air is described. Water ice is used as the body-storage in the accumulators, and ice water (water at 0.5-1.0°C) is used as the body that cools air. The ice water circulates between the accumulator and the air-water heat exchanger. The cold accumulator model with renewable ice resources is considered. The model contains the heat-exchanging tube lattice-evaporator covered with ice. The lattice is cross-flowed with water. The criterion heat exchange equation that describes the process in the cold accumulator under consideration is presented. The calculations of duration of its active operation were performed. The dependence of cold accumulator service life on water circulation rate was evaluated. The adequacy of the design model was confirmed experimentally in the mock-up of the cold accumulator with a refrigerating machine periodically creating a 200 kg ice reserve in the reservoir-storage. The design model makes it possible to determine the weight of ice reserve of the discharged cold accumulator for cooling the cycle air in the operation of a C-30 type micro- GTI produced by the Capstone Company or micro-GTIs of other capacities. Recommendations for increasing the working capacity of cold accumulators of CTIC-systems of a micro-GTI were made. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12010472','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12010472">Water relations and gas exchange in poplar and willow under water stress and elevated atmospheric CO2.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Johnson, Jon D; Tognetti, Roberto; Paris, Piero 2002-05-01 Predictions of shifts in rainfall patterns as atmospheric [CO2] increases could impact the growth of fast growing trees such as Populus spp. and Salix spp. and the interaction between elevated CO2 and water stress in these species is unknown. The objectives of this study were to characterize the responses to elevated CO2 and water stress in these two species, and to determine if elevated CO2 mitigated drought stress effects. Gas exchange, water potential components, whole plant transpiration and growth response to soil drying and recovery were assessed in hybrid poplar (clone 53-246) and willow (Salix sagitta) rooted cuttings growing in either ambient (350 &mgr;mol mol-1) or elevated (700 &mgr;mol mol-1) atmospheric CO2 concentration ([CO2]). Predawn water potential decreased with increasing water stress while midday water potentials remained unchanged (isohydric response). Turgor potentials at both predawn and midday increased in elevated [CO2], indicative of osmotic adjustment. Gas exchange was reduced by water stress while elevated [CO2] increased photosynthetic rates, reduced leaf conductance and nearly doubled instantaneous transpiration efficiency in both species. Dark respiration decreased in elevated [CO2] and water stress reduced Rd in the trees growing in ambient [CO2]. Willow had 56% lower whole plant hydraulic conductivity than poplar, and showed a 14% increase in elevated [CO2] while poplar was unresponsive. The physiological responses exhibited by poplar and willow to elevated [CO2] and water stress, singly, suggest that these species respond like other tree species. The interaction of [CO2] and water stress suggests that elevated [CO2] did mitigate the effects of water stress in willow, but not in poplar. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSEC54B1327H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSEC54B1327H">First System-Wide Estimates of Air-Sea Exchange of Carbon Dioxide in the Chesapeake Bay</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Herrmann, M.; Najjar, R.; Menendez, A. 2016-02-01 Estuaries are estimated to play a major role in the global carbon cycle by degassing between 0.25 and 0.4 Pg C y-1, comparable to the uptake of atmospheric CO2 by continental shelf waters and as much as one quarter of the uptake of atmospheric CO2 by the open ocean. However, the global estimates of estuarine CO2 gas exchange are highly uncertain mostly due to limited data availability and extreme heterogeneity of coastal systems. Notably, the air-water CO2 flux for the largest U.S. estuary, the Chesapeake Bay, is yet unknown. Here we provide first system-level CO2 gas exchange estimates for the Chesapeake Bay, using data from the Chesapeake Bay Water Quality Monitoring Program (CBWQMP) and other data sources. We focus on the main stem of the Chesapeake Bay; hence, tributaries, such as the tidal portions of the Potomac and James Rivers, are not included in this first estimation of the flux. The preliminary results show the Bay to be a net source of CO2 to the atmosphere, outgassing on average 0.2 Tg C yr-1 over the study period, between 1985 and 2013. The spatial and temporal variability of the gas exchange will be discussed. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22292498','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22292498">Comparison of leaf gas exchange and stable isotope signature of water-soluble compounds along canopy gradients of co-occurring Douglas-fir and European beech.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Bögelein, Rebekka; Hassdenteufel, Martin; Thomas, Frank M; Werner, Willy 2012-07-01 Combined δ(13) C and δ(18) O analyses of water-soluble leaf and twig phloem material were used to determine intrinsic water-use efficiency (iWUE) and variability of stomatal conductance at different crown positions in adult European beech (Fagus sylvatica) and Douglas-fir (Pseudotsuga menziesii) trees. Simultaneous gas exchange measurements allowed evaluation of the differences in calculating iWUE from leaf or phloem water-soluble compounds, and comparison with a semi-quantitative dual isotope model to infer variability of net photosynthesis (A(n) ) between the investigated crown positions. Estimates of iWUE from δ(13) C of leaf water-soluble organic matter (WSOM) outperformed the estimates from phloem compounds. In the beech crown, δ(13) C of leaf WSOM coincided clearly with gas exchange measurements. The relationship was not as reliable in the Douglas-fir. The differences in δ(18) O between leaf and phloem material were found to correlate with stomatal conductance. The semi-quantitative model approach was applicable for comparisons of daily average A(n) between different crown positions and trees. Intracanopy gradients were more pronounced in the beech than in the Douglas-fir, which reached higher values of iWUE at the respective positions, particularly under dry air conditions. © 2012 Blackwell Publishing Ltd. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20336837','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20336837">Impact of airway gas exchange on the multiple inert gas elimination technique: theory.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Anderson, Joseph C; Hlastala, Michael P 2010-03-01 The multiple inert gas elimination technique (MIGET) provides a method for estimating alveolar gas exchange efficiency. Six soluble inert gases are infused into a peripheral vein. Measurements of these gases in breath, arterial blood, and venous blood are interpreted using a mathematical model of alveolar gas exchange (MIGET model) that neglects airway gas exchange. A mathematical model describing airway and alveolar gas exchange predicts that two of these gases, ether and acetone, exchange primarily within the airways. To determine the effect of airway gas exchange on the MIGET, we selected two additional gases, toluene and m-dichlorobenzene, that have the same blood solubility as ether and acetone and minimize airway gas exchange via their low water solubility. The airway-alveolar gas exchange model simulated the exchange of toluene, m-dichlorobenzene, and the six MIGET gases under multiple conditions of alveolar ventilation-to-perfusion, VA/Q, heterogeneity. We increased the importance of airway gas exchange by changing bronchial blood flow, Qbr. From these simulations, we calculated the excretion and retention of the eight inert gases and divided the results into two groups: (1) the standard MIGET gases which included acetone and ether and (2) the modified MIGET gases which included toluene and m-dichlorobenzene. The MIGET mathematical model predicted distributions of ventilation and perfusion for each grouping of gases and multiple perturbations of VA/Q and Qbr. Using the modified MIGET gases, MIGET predicted a smaller dead space fraction, greater mean VA, greater log(SDVA), and more closely matched the imposed VA distribution than that using the standard MIGET gases. Perfusion distributions were relatively unaffected. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25830350','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25830350">Peach water relations, gas exchange, growth and shoot mortality under water deficit in semi-arid weather conditions.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Rahmati, Mitra; Davarynejad, Gholam Hossein; Génard, Michel; Bannayan, Mohammad; Azizi, Majid; Vercambre, Gilles 2015-01-01 In this study the sensitivity of peach tree (Prunus persica L.) to three water stress levels from mid-pit hardening until harvest was assessed. Seasonal patterns of shoot and fruit growth, gas exchange (leaf photosynthesis, stomatal conductance and transpiration) as well as carbon (C) storage/mobilization were evaluated in relation to plant water status. A simple C balance model was also developed to investigate sink-source relationship in relation to plant water status at the tree level. The C source was estimated through the leaf area dynamics and leaf photosynthesis rate along the season. The C sink was estimated for maintenance respiration and growth of shoots and fruits. Water stress significantly reduced gas exchange, and fruit, and shoot growth, but increased fruit dry matter concentration. Growth was more affected by water deficit than photosynthesis, and shoot growth was more sensitive to water deficit than fruit growth. Reduction of shoot growth was associated with a decrease of shoot elongation, emergence, and high shoot mortality. Water scarcity affected tree C assimilation due to two interacting factors: (i) reduction in leaf photosynthesis (-23% and -50% under moderate (MS) and severe (SS) water stress compared to low (LS) stress during growth season) and (ii) reduction in total leaf area (-57% and -79% under MS and SS compared to LS at harvest). Our field data analysis suggested a Ψstem threshold of -1.5 MPa below which daily net C gain became negative, i.e. C assimilation became lower than C needed for respiration and growth. Negative C balance under MS and SS associated with decline of trunk carbohydrate reserves--may have led to drought-induced vegetative mortality. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4382189','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4382189">Peach Water Relations, Gas Exchange, Growth and Shoot Mortality under Water Deficit in Semi-Arid Weather Conditions</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Rahmati, Mitra; Davarynejad, Gholam Hossein; Génard, Michel; Bannayan, Mohammad; Azizi, Majid; Vercambre, Gilles 2015-01-01 In this study the sensitivity of peach tree (Prunus persica L.) to three water stress levels from mid-pit hardening until harvest was assessed. Seasonal patterns of shoot and fruit growth, gas exchange (leaf photosynthesis, stomatal conductance and transpiration) as well as carbon (C) storage/mobilization were evaluated in relation to plant water status. A simple C balance model was also developed to investigate sink-source relationship in relation to plant water status at the tree level. The C source was estimated through the leaf area dynamics and leaf photosynthesis rate along the season. The C sink was estimated for maintenance respiration and growth of shoots and fruits. Water stress significantly reduced gas exchange, and fruit, and shoot growth, but increased fruit dry matter concentration. Growth was more affected by water deficit than photosynthesis, and shoot growth was more sensitive to water deficit than fruit growth. Reduction of shoot growth was associated with a decrease of shoot elongation, emergence, and high shoot mortality. Water scarcity affected tree C assimilation due to two interacting factors: (i) reduction in leaf photosynthesis (-23% and -50% under moderate (MS) and severe (SS) water stress compared to low (LS) stress during growth season) and (ii) reduction in total leaf area (-57% and -79% under MS and SS compared to LS at harvest). Our field data analysis suggested a Ψstem threshold of -1.5 MPa below which daily net C gain became negative, i.e. C assimilation became lower than C needed for respiration and growth. Negative C balance under MS and SS associated with decline of trunk carbohydrate reserves – may have led to drought-induced vegetative mortality. PMID:25830350 </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ThEng..64..680B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ThEng..64..680B">Investigation and optimization of the depth of flue gas heat recovery in surface heat exchangers</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Bespalov, V. V.; Bespalov, V. I.; Melnikov, D. V. 2017-09-01 Economic issues associated with designing deep flue gas heat recovery units for natural gas-fired boilers are examined. The governing parameter affecting the performance and cost of surface-type condensing heat recovery heat exchangers is the heat transfer surface area. When firing natural gas, the heat recovery depth depends on the flue gas temperature at the condenser outlet and determines the amount of condensed water vapor. The effect of the outlet flue gas temperature in a heat recovery heat exchanger on the additionally recovered heat power is studied. A correlation has been derived enabling one to determine the best heat recovery depth (or the final cooling temperature) maximizing the anticipated reduced annual profit of a power enterprise from implementation of energy-saving measures. Results of optimization are presented for a surface-type condensing gas-air plate heat recovery heat exchanger for the climatic conditions and the economic situation in Tomsk. The predictions demonstrate that it is economically feasible to design similar heat recovery heat exchangers for a flue gas outlet temperature of 10°C. In this case, the payback period for the investment in the heat recovery heat exchanger will be 1.5 years. The effect of various factors on the optimal outlet flue gas temperature was analyzed. Most climatic, economical, or technological factors have a minor effect on the best outlet temperature, which remains between 5 and 20°C when varying the affecting factors. The derived correlation enables us to preliminary estimate the outlet (final) flue gas temperature that should be used in designing the heat transfer surface of a heat recovery heat exchanger for a gas-fired boiler as applied to the specific climatic conditions. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1050299','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1050299">PREDICTION OF TOTAL DISSOLVED GAS EXCHANGE AT HYDROPOWER DAMS</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Hadjerioua, Boualem; Pasha, MD Fayzul K; Stewart, Kevin M 2012-07-01 Total dissolved gas (TDG) supersaturation in waters released at hydropower dams can cause gas bubble trauma in fisheries resulting in physical injuries and eyeball protrusion that can lead to mortality. Elevated TDG pressures in hydropower releases are generally caused by the entrainment of air in spillway releases and the subsequent exchange of atmospheric gasses into solution during passage through the stilling basin. The network of dams throughout the Columbia River Basin (CRB) are managed for irrigation, hydropower production, flood control, navigation, and fish passage that frequently result in both voluntary and involuntary spillway releases. These dam operations are constrained bymore » 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 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/39792','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/39792">Growth, gas exchange, foliar nitrogen content, and water use of subirrigated and overhead irrigated Populus tremuloides Michx. seedlings</a> <a target="_blank" href="http://www.fs.usda.gov/treesearch/">Treesearch</a> Anthony S. Davis; Matthew M. Aghai; Jeremiah R. Pinto; Kent G. Apostal 2011-01-01 Because limitations on water used by container nurseries has become commonplace, nursery growers will have to improve irrigation management. Subirrigation systems may provide an alternative to overhead irrigation systems by mitigating groundwater pollution and excessive water consumption. Seedling growth, gas exchange, leaf nitrogen (N) content, and water use were... </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16246857','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16246857">Water stress-induced modifications of leaf hydraulic architecture in sunflower: co-ordination with gas exchange.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Nardini, Andrea; Salleo, Sebastiano 2005-12-01 The hydraulic architecture, water relationships, and gas exchange of leaves of sunflower plants, grown under different levels of water stress, were measured. Plants were either irrigated with tap water (controls) or with PEG600 solutions with osmotic potential of -0.4 and -0.8 MPa (PEG04 and PEG08 plants, respectively). Mature leaves were measured for hydraulic resistance (R(leaf)) before and after making several cuts across minor veins, thus getting the hydraulic resistance of the venation system (R(venation)). R(leaf) was nearly the same in controls and PEG04 plants but it was reduced by about 30% in PEG08 plants. On the contrary, R(venation) was lowest in controls and increased in PEG04 and PEG08 plants as a likely result of reduction in the diameter of the veins' conduits. As a consequence, the contribution of R(venation) to the overall R(leaf) markedly increased from controls to PEG08 plants. Leaf conductance to water vapour (g(L)) was highest in controls and significantly lower in PEG04 and PEG08 plants. Moreover, g(L) was correlated to R(venation) and to leaf water potential (psi(leaf)) with highly significant linear relationships. It is concluded that water stress has an important effect on the hydraulic construction of leaves. This, in turn, might prove to be a crucial factor in plant-water relationships and gas exchange under water stress conditions. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998EPJAP...3..295B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998EPJAP...3..295B">Optimization of heat and mass transfers in counterflow corrugated-plate liquid-gas exchangers used in a greenhouse dehumidifier</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Bentounes, N.; Jaffrin, A. 1998-09-01 Heat and mass transfers occuring in a counterflow direct contact liquid-gas exchanger determine the performance of a new greenhouse air dehumidifier designed at INRA. This prototype uses triethylene glycol (TEG) as the desiccant fluid which extracts water vapor from the air. The regeneration of the TEG desiccant fluid is then performed by direct contact with combustion gas from a high efficiency boiler equipped with a condensor. The heat and mass transfers between the thin film of diluted TEG and the hot gas were simulated by a model which uses correlation formula from the literature specifically relevant to the present cross-corrugated plates geometry. A simple set of analytical solutions is first derived, which explains why some possible processes can clearly be far from optimal. Then, more exact numerical calculations confirm that some undesirable water recondensations on the upper part of the exchanger were limiting the performance of this prototype. More suitable conditions were defined for the process, which lead to a new design of the apparatus. In this second prototype, a gas-gas exchanger provides dryer and cooler gas to the basis of the regenerators, while a warmer TEG is fed on the top. A whole range of operating conditions was experimented and measured parameters were compared with numerical simulations of this new configuration: recondensation did not occur any more. As a consequence, this second prototype was able to concentrate the desiccant fluid at the desired rate of 20 kg H_{2O}/hour, under temperature and humidity conditions which correspond to the dehumidification of a 1000 m2 greenhouse heated at night during the winter season. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24854169','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24854169">Dynamics of leaf gas exchange, xylem and phloem transport, water potential and carbohydrate concentration in a realistic 3-D model tree crown.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Nikinmaa, Eero; Sievänen, Risto; Hölttä, Teemu 2014-09-01 Tree models simulate productivity using general gas exchange responses and structural relationships, but they rarely check whether leaf gas exchange and resulting water and assimilate transport and driving pressure gradients remain within acceptable physical boundaries. This study presents an implementation of the cohesion-tension theory of xylem transport and the Münch hypothesis of phloem transport in a realistic 3-D tree structure and assesses the gas exchange and transport dynamics. A mechanistic model of xylem and phloem transport was used, together with a tested leaf assimilation and transpiration model in a realistic tree architecture to simulate leaf gas exchange and water and carbohydrate transport within an 8-year-old Scots pine tree. The model solved the dynamics of the amounts of water and sucrose solute in the xylem, cambium and phloem using a fine-grained mesh with a system of coupled ordinary differential equations. The simulations predicted the observed patterns of pressure gradients and sugar concentration. Diurnal variation of environmental conditions influenced tree-level gradients in turgor pressure and sugar concentration, which are important drivers of carbon allocation. The results and between-shoot variation were sensitive to structural and functional parameters such as tree-level scaling of conduit size and phloem unloading. Linking whole-tree-level water and assimilate transport, gas exchange and sink activity opens a new avenue for plant studies, as features that are difficult to measure can be studied dynamically with the model. Tree-level responses to local and external conditions can be tested, thus making the approach described here a good test-bench for studies of whole-tree physiology. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26388365','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26388365">Direct analysis of ultra-trace semiconductor gas by inductively coupled plasma mass spectrometry coupled with gas to particle conversion-gas exchange technique.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Ohata, Masaki; Sakurai, Hiromu; Nishiguchi, Kohei; Utani, Keisuke; Günther, Detlef 2015-09-03 An inductively coupled plasma mass spectrometry (ICPMS) coupled with gas to particle conversion-gas exchange technique was applied to the direct analysis of ultra-trace semiconductor gas in ambient air. The ultra-trace semiconductor gases such as arsine (AsH3) and phosphine (PH3) were converted to particles by reaction with ozone (O3) and ammonia (NH3) gases within a gas to particle conversion device (GPD). The converted particles were directly introduced and measured by ICPMS through a gas exchange device (GED), which could penetrate the particles as well as exchange to Ar from either non-reacted gases such as an air or remaining gases of O3 and NH3. The particle size distribution of converted particles was measured by scanning mobility particle sizer (SMPS) and the results supported the elucidation of particle agglomeration between the particle converted from semiconductor gas and the particle of ammonium nitrate (NH4NO3) which was produced as major particle in GPD. Stable time-resolved signals from AsH3 and PH3 in air were obtained by GPD-GED-ICPMS with continuous gas introduction; however, the slightly larger fluctuation, which could be due to the ionization fluctuation of particles in ICP, was observed compared to that of metal carbonyl gas in Ar introduced directly into ICPMS. The linear regression lines were obtained and the limits of detection (LODs) of 1.5 pL L(-1) and 2.4 nL L(-1) for AsH3 and PH3, respectively, were estimated. Since these LODs revealed sufficiently lower values than the measurement concentrations required from semiconductor industry such as 0.5 nL L(-1) and 30 nL L(-1) for AsH3 and PH3, respectively, the GPD-GED-ICPMS could be useful for direct and high sensitive analysis of ultra-trace semiconductor gas in air. Copyright © 2015 Elsevier B.V. All rights reserved. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ERL....13d5004S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ERL....13d5004S">Gas exchange at whole plant level shows that a less conservative water use is linked to a higher performance in three ecologically distinct pine species</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Salazar-Tortosa, D.; Castro, J.; Rubio de Casas, R.; Viñegla, B.; Sánchez-Cañete, E. P.; Villar-Salvador, P. 2018-04-01 Increasing temperatures and decreasing precipitation in large areas of the planet as a consequence of global warming will affect plant growth and survival. However, the impact of climatic conditions will differ across species depending on their stomatal response to increasing aridity, as this will ultimately affect the balance between carbon assimilation and water loss. In this study, we monitored gas exchange, growth and survival in saplings of three widely distributed European pine species (Pinus halepensis, P. nigra and P. sylvestris) with contrasting distribution and ecological requirements in order to ascertain the relationship between stomatal control and plant performance. The experiment was conducted in a common garden environment resembling rainfall and temperature conditions that two of the three species are expected to encounter in the near future. In addition, gas exchange was monitored both at the leaf and at the whole-plant level using a transient-state closed chamber, which allowed us to model the response of the whole plant to increased air evaporative demand (AED). P. sylvestris was the species with lowest survival and performance. By contrast, P. halepensis showed no mortality, much higher growth (two orders of magnitude), carbon assimilation (ca. 14 fold higher) and stomatal conductance and water transpiration (ca. 4 fold higher) than the other two species. As a consequence, P. halepensis exhibited higher values of water-use efficiency than the rest of the species even at the highest values of AED. Overall, the results strongly support that the weaker stomatal control of P. halepensis, which is linked to lower stem water potential, enabled this species to maximize carbon uptake under drought stress and ultimately outperform the more water conservative P. nigra and P. sylvestris. These results suggest that under a hotter drought scenario P. nigra and P. sylvestris would very likely suffer increased mortality, whereas P. halepensis could maintain </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19900054400&hterms=Cotton&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DCotton','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19900054400&hterms=Cotton&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DCotton">The relationship between leaf water status, gas exchange, and spectral reflectance in cotton leaves</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Bowman, William D. 1989-01-01 Measurements of leaf spectral reflectance, the components of water potential, and leaf gas exchanges as a function of leaf water content were made to evaluate the use of NIR reflectance as an indicator of plant water status. Significant correlations were determined between spectral reflectance at 810 nm, 1665 nm, and 2210 nm and leaf relative water content, total water potential, and turgor pressure. However, the slopes of these relationships were relatively shallow and, when evaluated over the range of leaf water contents in which physiological activity occurs (e.g., photosynthesis), had lower r-squared values, and some relationships were not statistically significant. NIR reflectance varied primarily as a function of leaf water content, and not independently as a function of turgor pressure, which is a sensitive indicator of leaf water status. The limitations of this approach to measuring plant water stress are discussed. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/862648','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/servlets/purl/862648">Process for hydrogen isotope concentration between liquid water and hydrogen gas</a> <a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a> Stevens, William H. 1976-09-21 A process for hydrogen isotope exchange and concentration between liquid water and hydrogen gas, wherein liquid water and hydrogen gas are contacted, in an exchange section, with one another and with at least one catalyst body comprising at least one metal selected from Group VIII of the Periodic Table and preferably a support therefor, the catalyst body has a liquid-water-repellent, gas permeable polymer or organic resin coating, preferably a fluorinated olefin polymer or silicone coating, so that the isotope concentration takes place by two simultaneously occurring steps, namely, ##EQU1## WHILE THE HYDROGEN GAS FED TO THE EXCHANGE SECTION IS DERIVED IN A REACTOR VESSEL FROM LIQUID WATER THAT HAS PASSED THROUGH THE EXCHANGE SECTION. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMED13B0888G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMED13B0888G">The AirWaterGas Teacher Professional Development Program: Lessons Learned by Pairing Scientists and Teachers to Develop Curriculum on Global Climate Change and Regional Unconventional Oil and Gas Development</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Gardiner, L. S.; Hatheway, B.; Rogers, J. D.; Casey, J. G.; Lackey, G.; Birdsell, D.; Brown, K.; Polmear, M.; Capps, S.; Rosenblum, J.; Sitterley, K.; Hafich, K. A.; Hannigan, M.; Knight, D. 2015-12-01 The AirWaterGas Teacher Professional Development Program, run by the UCAR Center for Science Education, brought together scientists and secondary science teachers in a yearlong program culminating in the development of curriculum related to the impacts of unconventional oil and gas development. Graduate students and research scientists taught about their research area and its relationship to oil and gas throughout three online courses during the 2015-16 school year, during which teachers and scientists engaged in active online discussions. Topics covered included climate change, oil and gas infrastructure, air quality, water quality, public health, and practices and policies relating to oil and gas development. Building upon their initial online interactions and a face-to-face meeting in March, teachers were paired with appropriate AirWaterGas team members as science advisors during a month-long residency in Boulder, Colorado. During the residency, graduate student scientists provided resources and feedback as teachers developed curriculum projects in collaboration with each other and UCAR science educators. Additionally, teachers and AirWaterGas researchers shared experiences on an oil and gas well site tour, and a short course on drilling methods with a drilling rig simulator. Here, we share lessons learned from both sides of the aisle, including initial results from program assessment conducted with the participating teachers. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16545998','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16545998">Foliar trichomes, boundary layers, and gas exchange in 12 species of epiphytic Tillandsia (Bromeliaceae).</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Benz, Brett W; Martin, Craig E 2006-04-01 We examined the relationships between H2O and CO2 gas exchange parameters and leaf trichome cover in 12 species of Tillandsia that exhibit a wide range in trichome size and trichome cover. Previous investigations have hypothesized that trichomes function to enhance boundary layers around Tillandsioid leaves thereby buffering the evaporative demand of the atmosphere and retarding transpirational water loss. Data presented herein suggest that trichome-enhanced boundary layers have negligible effects on Tillandsia gas exchange, as indicated by the lack of statistically significant relationships in regression analyses of gas exchange parameters and trichome cover. We calculated trichome and leaf boundary layer components, and their associated effects on H2O and CO2 gas exchange. The results further indicate trichome-enhanced boundary layers do not significantly reduce transpirational water loss. We conclude that although the trichomes undoubtedly increase the thickness of the boundary layer, the increase due to Tillandsioid trichomes is inconsequential in terms of whole leaf boundary layers, and any associated reduction in transpirational water loss is also negligible within the whole plant gas exchange pathway. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018AtmEn.178...31J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018AtmEn.178...31J">Seasonal atmospheric deposition and air-sea gas exchange of polycyclic aromatic hydrocarbons over the Yangtze River Estuary, East China Sea: Implications for source-sink processes</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Jiang, Yuqing; Lin, Tian; Wu, Zilan; Li, Yuanyuan; Li, Zhongxia; Guo, Zhigang; Yao, Xiaohong 2018-04-01 In this work, air samples and surface seawater samples covering four seasons from March 2014 to January 2015 were collected from a background receptor site in the YRE to explore the seasonal fluxes of air-sea gas exchange and dry and wet deposition of 15 polycyclic aromatic hydrocarbons (PAHs) and their source-sink processes at the air-sea interface. The average dry and wet deposition fluxes of 15 PAHs were estimated as 879 ± 1393 ng m-2 d-1 and 755 ± 545 ng m-2 d-1, respectively. Gaseous PAH release from seawater to the atmosphere averaged 3114 ± 1999 ng m-2 d-1 in a year round. The air-sea gas exchange of PAHs was the dominant process at the air-sea interface in the YRE as the magnitude of volatilization flux of PAHs exceeded that of total dry and wet deposition. The gas PAH exchange flux was dominated by three-ring PAHs, with the highest value in summer and lowest in winter, indicating a marked seasonal variation owing to differences in Henry's law constants associated with temperature, as well as wind speed and gaseous-dissolved gradient among seasons. Based on the simplified mass balance estimation, a net 11 tons y-1 of PAHs (mainly three-ring PAHs) were volatilized from seawater to the atmosphere in a ∼20,000 km2 area in the YRE. Other than the year-round Yangtze River input and ocean ship emissions, the selective release of low-molecular-weight PAHs from bottom sediments in winter due to resuspension triggered by the East Asian winter monsoon is another potential source of PAHs. This work suggests that the source-sink processes of PAHs at the air-sea interface in the YRE play a crucial role in regional cycling of PAHs. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_5");'>5</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li class="active">7</li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_8" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active">8</li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="141"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFMOS31B1259A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFMOS31B1259A">The Relationship Between Temperature and Gas Concentration Fluctuation Rates at an Air-Water Interface</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Asher, W. E.; Jessup, A. T.; Liang, H.; Zappa, C. J. 2008-12-01 The air-sea flux, F, of a sparingly soluble nonreactive gas can be expressed as F = kG(CS-CW), where kG is the gas transfer velocity, CS is the concentration of gas that would be expected in the water if the system were in Henry's Gas Law equilibrium, and CW is the gas concentration in the bulk water. An analogous relationship for the net heat flux can also be written using the heat transfer velocity, kH, and the bulk-skin temperature difference in the aqueous phase. Surface divergence theory for the air-water transfer of gas and heat predicts that kG and kH will scale as the square root of the surface divergence rate, r. However, because of the interaction between diffusivity and the scale depth of the surface divergences, the scale factor for heat is likely to be different from the scale factor for gases. Infrared imagery was used to measure the timescales of variations in temperature at a water surface and laser-induced fluorescence (LIF) was used to measure temporal fluctuations in aqueous-phase concentrations of carbon dioxide (CO2) at a water surface. The rate at which these temperature and concentration fluctuations occur is then assumed to be related to r. The divergence rates derived for temperature from the IR images can be compared to the rates for gas derived from the LIF measurements to understand how r estimated from the two measurements differ. The square root of r is compared to concurrently measured kG for helium and sulfur hexafluoride to test the assumption that r1/2 scales with kG. Additionally, we measured kH using the active controlled flux technique, and those heat transfer velocities can also be used to test for a r1/2 dependence. All measurements reported here were made in the APL-UW synthetic jet array facility. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/351688-sensing-flux-volatile-chemicals-through-air-water-interface','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/351688-sensing-flux-volatile-chemicals-through-air-water-interface">Sensing the flux of volatile chemicals through the air-water interface</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Mackay, D.; Schroeder, W.H.; Ooijen, H. von 1997-12-31 There are several situations in which there is a need to assess the direction and magnitude of the flux across the air-water interface. Contaminants may be evaporating or absorbing in wastewater treatment systems in natural lake, river, estuarine and marine systems, and any attempt to compile a mass balance must include this process. In this study the authors review the theory underlying air-water exchange, then describe and discuss a sparging approach by which the direction and magnitude of the flux can be ascertained. The principle of the method is that a known flow rate of air is bubbled through themore » sparger and allowed to equilibrate with the water. The gas exiting the water surface is passed through a sorbent trap and later analyzed. The concentration, and hence the fugacity, of the contaminant in the sparged air can be deduced. In parallel, a similar flow of air from the atmosphere above the water is drawn through another sparger at a similar flow rate for a similar time and the trapped chemical analyzed giving the concentration and fugacity in the air. These data show the direction of air-water exchange (i.e. from high to low fugacity) and with information on the mass transfer coefficients and area, the flux. Successful tests were conducted of the system in a laboratory tank, in Lake Ontario and in Hamilton Harbour. Analyses of the traps showed a large number of peaks on the chromatogram many of which are believed to be of petroleum origin from fuels and vessel exhaust. The system will perform best under conditions where concentrations of specific contaminants are large, as occurs in waste water treatment systems. The approach has the potential to contribute to more accurate assessment of air-water fluxes. It avoids the problems of different analytical methodologies and the effect of sorption in the water column.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017APS..DFD.E4003J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017APS..DFD.E4003J">Respiratory Mechanics and Gas Exchange: The Effect of Surfactants</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Jbaily, Abdulrahman; Szeri, Andrew J. 2017-11-01 The purpose of the lung is to exchange gases, primarily oxygen and carbon dioxide, between the atmosphere and the circulatory system. To enable this exchange, the airways in the lungs terminate in some 300 million alveoli that provide adequate surface area for transport. During breathing, work must be done to stretch various tissues to accommodate a greater volume of gas. Considerable work must also be done to expand the liquid lining (hypophase) that coats the interior surfaces of the alveoli. This is enabled by a surface active lipo-protein complex, known as pulmonary surfactant, that modifies the surface tension at the hypophase-air interface. Surfactants also serve as physical barriers that modify the rate of gas transfer across interfaces. We develop a mathematical model to study the action of pulmonary surfactant and its determinative contributions to breathing. The model is used to explore the influence of surfactants on alveolar mechanics and on gas exchange: it relates the work of respiration at the level of the alveolus to the gas exchange rate through the changing influence of pulmonary surfactant over the breathing cycle. This work is motivated by a need to develop improved surfactant replacement therapies to treat serious medical conditions. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/55311','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/55311">Stomatal kinetics and photosynthetic gas exchange along a continuum of isohydric to anisohydric regulation of plant water status</a> <a target="_blank" href="http://www.fs.usda.gov/treesearch/">Treesearch</a> Frederick C. Meinzer; Duncan D. Smith; David R. Woodruff; Danielle E. Marias; Katherine A. McCulloh; Ava R. Howard; Alicia L. Magedman 2017-01-01 Speciesâ differences in the stringency of stomatal control of plant water potential represent a continuum of isohydric to anisohydric behaviours. However, little is known about how quasi-steady-state stomatal regulation of water potential may relate to dynamic behaviour of stomata and photosynthetic gas exchange in species operating at different positions along this... </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007GBioC..21.2015S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007GBioC..21.2015S">Constraining global air-sea gas exchange for CO2 with recent bomb 14C measurements</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Sweeney, Colm; Gloor, Emanuel; Jacobson, Andrew R.; Key, Robert M.; McKinley, Galen; Sarmiento, Jorge L.; Wanninkhof, Rik 2007-06-01 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 in the global ocean and confirm that there is a 25% decrease from previous estimates using older DI14C data sets. Additionally, we find a 33% lower globally averaged gas transfer velocity for CO2 compared to previous estimates (Wanninkhof, 1992) using the NCEP/NCAR Reanalysis 1 1954-2000 where the global mean winds are 6.9 m s-1. Unlike some earlier ocean radiocarbon studies, the implied gas transfer velocity finally closes the gap between small-scale deliberate tracer studies and global-scale estimates. Additionally, the total inventory of bomb-produced radiocarbon in the ocean is now in agreement with global budgets based on radiocarbon measurements made in the stratosphere and troposphere. Using the implied relationship between wind speed and gas transfer velocity ks = 0.27<u102>(Sc/660)-0.5 and standard partial pressure difference climatology of CO2 we obtain an net air-sea flux estimate of 1.3 ± 0.5 PgCyr-1 for 1995. After accounting for the carbon transferred from rivers to the deep ocean, our estimate of oceanic uptake (1.8 ± 0.5 PgCyr-1) compares well with estimates based on ocean inventories, ocean transport inversions using ocean concentration data, and model simulations. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17664033','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17664033">Carbon source/sink function of a subtropical, eutrophic lake determined from an overall mass balance and a gas exchange and carbon burial balance.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Yang, Hong; Xing, Yangping; Xie, Ping; Ni, Leyi; Rong, Kewen 2008-02-01 Although studies on carbon burial in lake sediments have shown that lakes are disproportionately important carbon sinks, many studies on gaseous carbon exchange across the water-air interface have demonstrated that lakes are supersaturated with CO(2) and CH(4) causing a net release of CO(2) and CH(4) to the atmosphere. In order to more accurately estimate the net carbon source/sink function of lake ecosystems, a more comprehensive carbon budget is needed, especially for gaseous carbon exchange across the water-air interface. Using two methods, overall mass balance and gas exchange and carbon burial balance, we assessed the carbon source/sink function of Lake Donghu, a subtropical, eutrophic lake, from April 2003 to March 2004. With the overall mass balance calculations, total carbon input was 14 905 t, total carbon output was 4950 t, and net carbon budget was +9955 t, suggesting that Lake Donghu was a great carbon sink. For the gas exchange and carbon burial balance, gaseous carbon (CO(2) and CH(4)) emission across the water-air interface totaled 752 t while carbon burial in the lake sediment was 9477 t. The ratio of carbon emission into the atmosphere to carbon burial into the sediment was only 0.08. This low ratio indicates that Lake Donghu is a great carbon sink. Results showed good agreement between the two methods with both showing Lake Donghu to be a great carbon sink. This results from the high primary production of Lake Donghu, substantive allochthonous carbon inputs and intensive anthropogenic activity. Gaseous carbon emission accounted for about 15% of the total carbon output, indicating that the total output would be underestimated without including gaseous carbon exchange. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25813755','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25813755">Water relations and gas exchange of fan bryophytes and their adaptations to microhabitats in an Asian subtropical montane cloud forest.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Song, Liang; Zhang, Yong-Jiang; Chen, Xi; Li, Su; Lu, Hua-Zheng; Wu, Chuan-Sheng; Tan, Zheng-Hong; Liu, Wen-Yao; Shi, Xian-Meng 2015-07-01 Fan life forms are bryophytes with shoots rising from vertical substratum that branch repeatedly in the horizontal plane to form flattened photosynthetic surfaces, which are well suited for intercepting water from moving air. However, detailed water relations, gas exchange characteristics of fan bryophytes and their adaptations to particular microhabitats remain poorly understood. In this study, we measured and analyzed microclimatic data, as well as water release curves, pressure-volume relationships and photosynthetic water and light response curves for three common fan bryophytes in an Asian subtropical montane cloud forest (SMCF). Results demonstrate high relative humidity but low light levels and temperatures in the understory, and a strong effect of fog on water availability for bryophytes in the SMCF. The facts that fan bryophytes in dry air lose most of their free water within 1 h, and a strong dependence of net photosynthesis rates on water content, imply that the transition from a hydrated, photosynthetically active state to a dry, inactive state is rapid. In addition, fan bryophytes developed relatively high cell wall elasticity and the osmoregulatory capacity to tolerate desiccation. These fan bryophytes had low light saturation and compensation point of photosynthesis, indicating shade tolerance. It is likely that fan bryophytes can flourish on tree trunks in the SMCF because of substantial annual precipitation, average relative humidity, and frequent and persistent fog, which can provide continual water sources for them to intercept. Nevertheless, the low water retention capacity and strong dependence of net photosynthesis on water content of fan bryophytes indicate a high risk of unbalanced carbon budget if the frequency and severity of drought increase in the future as predicted. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002GMS...127..141S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002GMS...127..141S">A model of air-sea gas exchange incorporating the physics of the turbulent boundary layer and the properties of the sea surface</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Soloviev, Alexander; Schluessel, Peter The model presented contains interfacial, bubble-mediated, ocean mixed layer, and remote sensing components. The interfacial (direct) gas transfer dominates under conditions of low and—for quite soluble gases like CO2—moderate wind speeds. Due to the similarity between the gas and heat transfer, the temperature difference, ΔT, across the thermal molecular boundary layer (cool skin of the ocean) and the interfacial gas transfer coefficient, Kint are presumably interrelated. A coupled parameterization for ΔT and Kint has been derived in the context of a surface renewal model [Soloviev and Schluessel, 1994]. In addition to the Schmidt, Sc, and Prandtl, Pr, numbers, the important parameters are the surface Richardson number, Rƒ0, and the Keulegan number, Ke. The more readily available cool skin data are used to determine the coefficients that enter into both parameterizations. At high wind speeds, the Ke-number dependence is further verified with the formula for transformation of the surface wind stress to form drag and white capping, which follows from the renewal model. A further extension of the renewal model includes effects of solar radiation and rainfall. The bubble-mediated component incorporates the Merlivat et al. [1993] parameterization with the empirical coefficients estimated by Asher and Wanninkhof [1998]. The oceanic mixed layer component accounts for stratification effects on the air-sea gas exchange. Based on the example of GasEx-98, we demonstrate how the results of parameterization and modeling of the air-sea gas exchange can be extended to the global scale, using remote sensing techniques. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120017344','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120017344">Prototype Vent Gas Heat Exchanger for Exploration EVA - Performance and Manufacturing Characteristics</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Jennings, Mallory; Quinn, Gregory; Strange, Jeremy 2012-01-01 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. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JPhCS1015c2072S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JPhCS1015c2072S">Modeling of Hydrate Formation Mode in Raw Natural Gas Air Coolers</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Scherbinin, S. V.; Prakhova, M. Yu; Krasnov, A. N.; Khoroshavina, E. A. 2018-05-01 Air cooling units (ACU) are used at all the gas fields for cooling natural gas after compressing. When using ACUs on raw (wet) gas in a low temperature condition, there is a danger of hydrate plug formation in the heat exchanging tubes of the ACU. To predict possible hydrate formation, a mathematical model of the air cooler thermal behavior used in the control system shall adequately calculate not only gas temperature at the cooler's outlet, but also a dew point value, a temperature at which condensation, as well as the gas hydrate formation point, onsets. This paper proposes a mathematical model allowing one to determine the pressure in the air cooler which makes hydrate formation for a given gas composition possible. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008OSJ....43...17L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008OSJ....43...17L">Gas exchange rates measured using a dual-tracer (SF6 and3he) method in the coastal waters of Korea</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Lee, Hyun-Woo; Lee, Kitack; Kaown, Duk-In 2008-03-01 Over a period of 5 days between August 12 and 17, 2005, we performed a gas exchange experiment using the dual tracer method in a tidal coastal ocean located off the southern coast of Korea. The gas exchange rate was determined from temporal changes in the ratio of3He to SF6 measured daily in the surface mixed layer. The measured gas exchange rate ( k CO 2), normalized to a Schmidt number of 600 for CO2 in fresh water at 20°C, was approximately 5.0 cm h-1 at a mean wind speed of 3.9 m s-1 during the study period. This value is significantly less than those obtained from floating chamber-based experiments performed previously in estuarine environments, but is similar in magnitude to values obtained using the dual tracer method in river and tidal coastal waters and values predicted on the basis of the relationship between the gas exchange rate and wind speed (Wanninkhof 1992), which is generally applicable to the open ocean. Our result is also consistent with the relationship of Raymond and Cole (2001), which was derived from experiments carried out in estuarine environments using222Rn and chlorofluorocarbons along with measurements undertaken in the Hudson River, Canada, using SF6 and3He. Our results indicate that tidal action in a microtidal region did not discernibly enhance the measured k CO 2 value. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010004231','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010004231">BOREAS TE-10 Leaf Gas Exchange Data</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Hall, Forrest G. (Editor); Papagno, Andrea (Editor); Middleton, Elizabeth; Sullivan, Joseph 2000-01-01 The Boreal Ecosystem-Atmospheric Study (BOREAS) TE-10 (Terrestrial Ecology) team collected several data sets in support of its efforts to characterize and interpret information on the reflectance, transmittance, gas exchange, chlorophyll content, carbon content, hydrogen content, and nitrogen content of boreal vegetation. This data set contains measurements of assimilation, stomatal conductance, transpiration, internal CO2 concentration, and water use efficiency conducted in the Southern Study Area (SSA) during the growing seasons of 1994 and 1996 using a portable gas exchange system. The data are stored in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23844085','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23844085">Plant water use efficiency over geological time--evolution of leaf stomata configurations affecting plant gas exchange.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Assouline, Shmuel; Or, Dani 2013-01-01 Plant gas exchange is a key process shaping global hydrological and carbon cycles and is often characterized by plant water use efficiency (WUE - the ratio of CO2 gain to water vapor loss). Plant fossil record suggests that plant adaptation to changing atmospheric CO2 involved correlated evolution of stomata density (d) and size (s), and related maximal aperture, amax . We interpreted the fossil record of s and d correlated evolution during the Phanerozoic to quantify impacts on gas conductance affecting plant transpiration, E, and CO2 uptake, A, independently, and consequently, on plant WUE. A shift in stomata configuration from large s-low d to small s-high d in response to decreasing atmospheric CO2 resulted in large changes in plant gas exchange characteristics. The relationships between gas conductance, gws , A and E and maximal relative transpiring leaf area, (amax ⋅d), exhibited hysteretic-like behavior. The new WUE trend derived from independent estimates of A and E differs from established WUE-CO2 trends for atmospheric CO2 concentrations exceeding 1,200 ppm. In contrast with a nearly-linear decrease in WUE with decreasing CO2 obtained by standard methods, the newly estimated WUE trend exhibits remarkably stable values for an extended geologic period during which atmospheric CO2 dropped from 3,500 to 1,200 ppm. Pending additional tests, the findings may affect projected impacts of increased atmospheric CO2 on components of the global hydrological cycle. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA282842','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA282842">Oceanic Whitecaps and Associated, Bubble-Mediated, Air-Sea Exchange Processes</a> <a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a> 1992-10-01 experiments performed in laboratory conditions using Air-Sea Exchange Monitoring System (A-SEMS). EXPERIMENTAL SET-UP In a first look, the Air-Sea Exchange...Model 225, equipped with a Model 519 plug-in module. Other complementary information on A-SEMS along with results from first tests and calibration...between 9.50C and 22.40C within the first 24 hours after transferring the water sample into laboratory conditions. The results show an enhancement of </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25232199','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25232199">Nesting behaviour influences species-specific gas exchange across avian eggshells.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Portugal, Steven J; Maurer, Golo; Thomas, Gavin H; Hauber, Mark E; Grim, Tomáš; Cassey, Phillip 2014-09-15 achieve optimal water loss during incubation. We also suggest that eggs laid in cup nests and burrows may require a higher G(H2O) 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. © 2014. Published by The Company of Biologists Ltd. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=286462','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=286462">Effects of permethrin and amitraz on gas exchange and water loss in unfed adult females of Amblyomma americanum (Acari: Ixodidae)</a> <a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a> 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... </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17938120','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17938120">Leaf gas exchange of understory spruce-fir saplings in relict cloud forests, southern Appalachian Mountains, USA.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Reinhardt, Keith; Smith, William K 2008-01-01 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 </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AtmEn.147..200O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AtmEn.147..200O">Determination of temperature dependent Henry's law constants of polychlorinated naphthalenes: Application to air-sea exchange in Izmir Bay, Turkey</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Odabasi, Mustafa; Adali, Mutlu 2016-12-01 The Henry's law constant (H) is a crucial variable to investigate the air-water exchange of persistent organic pollutants. H values for 32 polychlorinated naphthalene (PCN) congeners were measured using an inert gas-stripping technique at five temperatures ranging between 5 and 35 °C. H values in deionized water (at 25 °C) varied between 0.28 ± 0.08 Pa m3 mol-1 (PCN-73) and 18.01 ± 0.69 Pa m3 mol-1 (PCN-42). The agreement between the measured and estimated H values from the octanol-water and octanol-air partition coefficients was good (measured/estimated ratio = 1.00 ± 0.41, average ± SD). The calculated phase change enthalpies (ΔHH) were within the interval previously determined for other several semivolatile organic compounds (42.0-106.4 kJ mol-1). Measured H values, paired atmospheric and aqueous concentrations and meteorological variables were also used to reveal the level and direction of air-sea exchange fluxes of PCNs at the coast of Izmir Bay, Turkey. The net PCN air-sea exchange flux varied from -0.55 (volatilization, PCN-24/14) to 2.05 (deposition, PCN-23) ng m-2 day-1. PCN-19, PCN-24/14, PCN-42, and PCN-33/34/37 were mainly volatilized from seawater while the remaining congeners were mainly deposited. The overall number of the cases showing deposition was higher (67.9%) compared to volatilization (21.4%) and near equilibrium (10.7%). </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?direntryid=315010&keyword=climate%20change&subject=climate%20change%20research&showcriteria=2&fed_org_id=111&datebeginpublishedpresented=03/10/2012&dateendpublishedpresented=03/10/2017&sortby=pubdateyear','PESTICIDES'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?direntryid=315010&keyword=climate%20change&subject=climate%20change%20research&showcriteria=2&fed_org_id=111&datebeginpublishedpresented=03/10/2012&dateendpublishedpresented=03/10/2017&sortby=pubdateyear">A dynamic leaf gas-exchange strategy is conserved in woody ...</a> <a target="_blank" href="http://www.epa.gov/pesticides/search.htm">EPA Pesticide Factsheets</a> Rising atmospheric [CO2], ca, is expected to affect stomatal regulation of leaf gas-exchange of woody plants, thus influencing energy fluxes as well as carbon (C), water and nutrient cycling of forests. Researchers have reported that stomata regulate leaf gas-exchange around “set points” that include a constant leaf internal [CO2], ci, a constant drawdown in CO2 (ca - ci), and a constant ci/ca. Because these set points can result in drastically different consequences for leaf gas-exchange, it will be essential for the accuracy of Earth systems models that generalizable patterns in leaf gas-exchange responses to ca be identified if any do exist. We hypothesized that the concept of optimal stomatal behavior, exemplified by woody plants shifting along a continuum of these set point strategies, would provide a unifying framework for understanding leaf gas-exchange responses to ca. We analyzed studies reporting C stable isotope ratio (δ13C) or photosynthetic discrimination (∆13C) from woody plant taxa that grew across ca spanning at least 100 ppm for each species investigated. From these data we calculated ci, and in combination with known or estimated ca, leaf gas-exchange regulation strategies were assessed. Overall, our analyses does not support the hypothesis that trees are canalized towards any of the proposed set points, particularly so for a constant ci. Rather, the results are consistent with the hypothesis that stomatal optimization regulates leaf gas </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/7785756','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/7785756">[Heat and moisture exchangers for conditioning of inspired air of intubated patients in intensive care. The humidification properties of passive air exchangers under clinical conditions].</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Rathgeber, J; Züchner, K; Kietzmann, D; Weyland, W 1995-04-01 Heat and moisture exchangers (HME) are used as artificial noses for intubated patients to prevent tracheo-bronchial or pulmonary damage resulting from dry and cold inspired gases. HME are mounted directly on the tracheal tube, where they collect a large fraction of the heat and moisture of the expired air, adding this to the subsequent inspired breath. The effective performance depends on the water-retention capacity of the HME: the amount of water added to the inspired gas cannot exceed the stored water uptake of the previous breath. This study evaluates the efficiency of four different HME under laboratory and clinical conditions using a new moisture-measuring device. METHODS. In a first step, the absolute efficiency of four different HME (DAR Hygrobac, Gibeck Humid-Vent 2P, Pall BB 22-15 T, and Pall BB 100) was evaluated using a lung model simulating physiological heat and humidity conditions of the upper airways. The model was ventilated with tidal volumes of 500, 1,000, and 1,500 ml and different flow rates. The water content of the ventilated air was determined between tracheal tube and HME using a new high-resolution humidity meter and compared with the absolute water loss of the exhaled air at the gas outlet of a Siemens Servo C ventilator measured with a dew-point hygrometer. Secondly, the moisturizing efficiency was evaluated under clinical conditions in an intensive care unit with 25 intubated patients. Maintaining the ventilatory conditions for each patient, the HME were randomly changed. The humidity data were determined as described above and compared with the laboratory findings. RESULTS AND DISCUSSION. The water content at the respirator outlet is inversely equivalent to the humidity of the inspired gases and represents the water loss from the respiratory tract if the patient is ventilated with dry gases. Moisture retention and heating capacity decreased with higher volumes and higher flow rates. These data are simple to obtain without affecting the </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_6");'>6</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li class="active">8</li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_9" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active">9</li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="161"> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19850045092&hterms=water+gas+exchange&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dwater%2Bgas%2Bexchange','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19850045092&hterms=water+gas+exchange&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dwater%2Bgas%2Bexchange">Gas exchange-wind speed relation measured with sulfur hexafluoride on a lake</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Wanninkhof, R.; Broecker, W. S.; Ledwell, J. R. 1985-01-01 Gas-exchange processes control the uptake and release of various gases in natural systems such as oceans, rivers, and lakes. Not much is known about the effect of wind speed on gas exchange in such systems. In the experiment described here, sulfur hexafluoride was dissolved in lake water, and the rate of escape of the gas with wind speed (at wind speeds up to 6 meters per second) was determined over a 1-month period. A sharp change in the wind speed dependence of the gas-exchange coefficient was found at wind speeds of about 2.4 meters per second, in agreement with the results of wind-tunnel studies. However the gas-exchange coefficients at wind speeds above 3 meters per second were smaller than those observed in wind tunnels and are in agreement with earlier lake and ocean results. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ACP....17.9019B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ACP....17.9019B">Estimation of bubble-mediated air-sea gas exchange from concurrent DMS and CO2 transfer velocities at intermediate-high wind speeds</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Bell, Thomas G.; Landwehr, Sebastian; Miller, Scott D.; de Bruyn, Warren J.; Callaghan, Adrian H.; Scanlon, Brian; Ward, Brian; Yang, Mingxi; Saltzman, Eric S. 2017-07-01 Simultaneous air-sea fluxes and concentration differences of dimethylsulfide (DMS) and carbon dioxide (CO2) were measured during a summertime North Atlantic cruise in 2011. This data set reveals significant differences between the gas transfer velocities of these two gases (Δkw) over a range of wind speeds up to 21 m s-1. These differences occur at and above the approximate wind speed threshold when waves begin breaking. Whitecap fraction (a proxy for bubbles) was also measured and has a positive relationship with Δkw, consistent with enhanced bubble-mediated transfer of the less soluble CO2 relative to that of the more soluble DMS. However, the correlation of Δkw with whitecap fraction is no stronger than with wind speed. Models used to estimate bubble-mediated transfer from in situ whitecap fraction underpredict the observations, particularly at intermediate wind speeds. Examining the differences between gas transfer velocities of gases with different solubilities is a useful way to detect the impact of bubble-mediated exchange. More simultaneous gas transfer measurements of different solubility gases across a wide range of oceanic conditions are needed to understand the factors controlling the magnitude and scaling of bubble-mediated gas exchange. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1998WRR....34.3245B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1998WRR....34.3245B">Air sparging: Air-water mass transfer coefficients</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Braida, Washington J.; Ong, Say Kee 1998-12-01 Experiments investigating the mass transfer of several dissolved volatile organic compounds (VOCs) across the air-water interface were conducted using a single-air- channel air-sparging system. Three different porous media were used in the study. Air velocities ranged from 0.2 cm s-1 to 2.5 cm s-1. The tortuosity factor for each porous medium and the air-water mass transfer coefficients were estimated by fitting experimental data to a one-dimensional diffusion model. The estimated mass transfer coefficients KG ranged from 1.79 × 10-3 cm min-1 to 3.85 × 10-2 cm min-1. The estimated lumped gas phase mass transfer coefficients KGa were found to be directly related to the air diffusivity of the VOC, air velocity, and particle size, and inversely related to the Henry's law constant of the VOCs. Of the four parameters investigated, the parameter that controlled or had a dominant effect on the lumped gas phase mass transfer coefficient was the air diffusivity of the VOC. Two empirical models were developed by correlating the Damkohler and the modified air phase Sherwood numbers with the air phase Peclet number, Henry's law constant, and the reduced mean particle size of porous media. The correlation developed in this study may be used to obtain better predictions of mass transfer fluxes for field conditions. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..DFDH36008C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..DFDH36008C">Surface nanobubble nucleation dynamics during water-ethanol exchange</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Chan, Chon U.; Ohl, Claus-Dieter 2015-11-01 Water-ethanol exchange has been a promising nucleation method for surface attached nanobubbles since their discovery. In this process, water and ethanol displace each other sequentially on a substrate. As the gas solubility is 36 times higher in ethanol than water, it was suggested that the exchange process leads to transient supersaturation and is responsible for the nanobubble nucleation. In this work, we visualize the nucleation dynamics by controllably mixing water and ethanol. It depicts the temporal evolution of the conventional exchange in a single field of view, detailing the conditions for surface nanobubble nucleation and the flow field that influences their spatial organization. This technique can also pattern surface nanobubbles with variable size distribution. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.1015G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.1015G">Evaluation of the swell effect on the air-sea gas transfer in the coastal zone</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Gutiérrez-Loza, Lucía; Ocampo-Torres, Francisco J. 2016-04-01 Air-sea gas transfer processes are one of the most important factors regarding global climate and long-term global climate changes. Despite its importance, there is still a huge uncertainty on how to better parametrize these processes in order to include them on the global climate models. This uncertainty exposes the need to increase our knowledge on gas transfer controlling mechanisms. In the coastal regions, breaking waves become a key factor to take into account when estimating gas fluxes, however, there is still a lack of information and the influence of the ocean surface waves on the air-sea interaction and gas flux behavior must be validated. In this study, as part of the "Sea Surface Roughness as Air-Sea Interaction Control" project, we evaluate the effect of the ocean surface waves on the gas exchange in the coastal zone. Direct estimates of the flux of CO2 (FCO2) and water vapor (FH2O) through eddy covariance, were carried out from May 2014 to April 2015 in a coastal station located at the Northwest of Todos Santos Bay, Baja California, México. For the same period, ocean surface waves are recorded using an Acoustic Doppler Current Profiler (Workhorse Sentinel, Teledyne RD Instruments) with a sampling rate of 2 Hz and located at 10 m depth about 350 m away from the tower. We found the study area to be a weak sink of CO2 under moderate wind and wave conditions with a mean flux of -1.32 μmol/m2s. The correlation between the wind speed and FCO2 was found to be weak, suggesting that other physical processes besides wind may be important factors for the gas exchange modulation at coastal waters. The results of the quantile regression analysis computed between FCO2 and (1) wind speed, (2) significant wave height, (3) wave steepness and (4) water temperature, show that the significant wave height is the most correlated parameter with FCO2; Nevertheless, the behavior of their relation varies along the probability distribution of FCO2, with the linear regression </li> <li> <a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70004693','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70004693">Exchange of Groundwater and Surface-Water Mediated by Permafrost Response to Seasonal and Long Term Air Temperature Variation</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Ge, Shemin; McKenzie, Jeffrey; Voss, Clifford; Wu, Qingbai 2011-01-01 Permafrost dynamics impact hydrologic cycle processes by promoting or impeding groundwater and surface water exchange. Under seasonal and decadal air temperature variations, permafrost temperature changes control the exchanges between groundwater and surface water. A coupled heat transport and groundwater flow model, SUTRA, was modified to simulate groundwater flow and heat transport in the subsurface containing permafrost. The northern central Tibet Plateau was used as an example of model application. Modeling results show that in a yearly cycle, groundwater flow occurs in the active layer from May to October. Maximum groundwater discharge to the surface lags the maximum subsurface temperature by two months. Under an increasing air temperature scenario of 3?C per 100 years, over the initial 40-year period, the active layer thickness can increase by three-fold. Annual groundwater discharge to the surface can experience a similar three-fold increase in the same period. An implication of these modeling results is that with increased warming there will be more groundwater flow in the active layer and therefore increased groundwater discharge to rivers. However, this finding only holds if sufficient upgradient water is available to replenish the increased discharge. Otherwise, there will be an overall lowering of the water table in the recharge portion of the catchment. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70035273','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70035273">Exchange of groundwater and surface-water mediated by permafrost response to seasonal and long term air temperature variation</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Ge, S.; McKenzie, J.; Voss, C.; Wu, Q. 2011-01-01 Permafrost dynamics impact hydrologic cycle processes by promoting or impeding groundwater and surface water exchange. Under seasonal and decadal air temperature variations, permafrost temperature changes control the exchanges between groundwater and surface water. A coupled heat transport and groundwater flow model, SUTRA, was modified to simulate groundwater flow and heat transport in the subsurface containing permafrost. The northern central Tibet Plateau was used as an example of model application. Modeling results show that in a yearly cycle, groundwater flow occurs in the active layer from May to October. Maximum groundwater discharge to the surface lags the maximum subsurface temperature by two months. Under an increasing air temperature scenario of 3C per 100 years, over the initial 40-year period, the active layer thickness can increase by three-fold. Annual groundwater discharge to the surface can experience a similar three-fold increase in the same period. An implication of these modeling results is that with increased warming there will be more groundwater flow in the active layer and therefore increased groundwater discharge to rivers. However, this finding only holds if sufficient upgradient water is available to replenish the increased discharge. Otherwise, there will be an overall lowering of the water table in the recharge portion of the catchment. Copyright 2011 by the American Geophysical Union. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22766042','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22766042">Drought effect on growth, gas exchange and yield, in two strains of local barley Ardhaoui, under water deficit conditions in southern Tunisia.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Thameur, Afwa; Lachiheb, Belgacem; Ferchichi, Ali 2012-12-30 Two local barley strains cv. Ardhaoui originated from Tlalit and Switir, sourthern Tunisia were grown in pots in a glasshouse assay, under well-watered conditions for a month. Plants were then either subjected to water deficit (treatment) or continually well-watered (control). Control pots were irrigated several times each week to maintain soil moisture near field capacity (FC), while stress pots experienced soil drying by withholding irrigation until they reached 50% of FC. Variation in relative water content, leaf area, leaf appearance rate and leaf gas exchange (i.e. net CO(2) assimilation rate (A), transpiration (E), and stomatal conductance (gs)) in response to water deficit was investigated. High leaf relative water content (RWC) was maintained in Tlalit by stomatal closure and a reduction of leaf area. Reduction in leaf area was due to decline in leaf gas exchange during water deficit. Tlalit was found to be drought tolerant and able to maintain higher leaf RWC under drought conditions. Water deficit treatment reduced stomatal conductance by 43% at anthesis. High net CO(2) assimilation rate under water deficit was associated with high RWC (r = 0.998; P < 0.01). Decline in net CO(2) assimilation rate was due mainly to stomatal closure. Significant differences between studied strains in leaf gas exchange parameters were found, which can give some indications on the degree of drought tolerance. Thus, the ability of the low leaf area plants to maintain higher RWC could explain the differences in drought tolerance in studied barley strains. Results showed that Tlalit showed to be more efficient and more productive than Switir. Copyright © 2012 Elsevier Ltd. All rights reserved. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.B32C..01H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.B32C..01H">Small ponds play big role in greenhouse gas emissions from inland waters</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Holgerson, M.; Raymond, P. A. 2017-12-01 Inland waters are an important part of the global carbon cycle, but there is uncertainty in estimating their greenhouse gas emissions. Uncertainty stems from different models and variable estimates of surface water gas concentrations, gas exchange rates, and the global size distribution of water bodies. Emissions from small water bodies are especially difficult to estimate because they are not globally mapped and few studies have assessed their greenhouse gas concentrations and gas exchange rates. To overcome these limitations, we studied greenhouse gases and gas exchange rates in small ponds in temperate forests of the northeastern United States. We then compiled our data with direct measurements of CO2 and CH4 concentrations from 427 ponds and lakes worldwide, and upscaled to estimate greenhouse gas emissions using estimates of gas exchange rates and the size distribution of lakes. We found that small ponds play a disproportionately large role in greenhouse gas emissions. While small ponds only account for about 9% of global lakes and ponds by area, they contribute 15% of CO2 and 41% of diffusive CH4 emissions from inland freshwaters. Secondly, we measured gas exchange velocities (k) in small ponds and compiled direct measurements of k from 67 global water bodies. We found that k is low but highly variable in small ponds, and increases and becomes even more variable with lake size, a finding that is not currently included in global carbon models. In a third study, we found that gas exchange in small ponds is highly sensitive to overnight cooling, which can lead to short bursts of increased k at night, with implications for greenhouse gas emissions. Overall, these studies show that small ponds are a critical part of the global carbon cycle, and also highlight many knowledge gaps. Therefore, understanding small pond carbon cycling is an important research priority. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://files.eric.ed.gov/fulltext/ED259926.pdf','ERIC'); return false;" href="http://files.eric.ed.gov/fulltext/ED259926.pdf">Heat Recovery Ventilation for Housing: Air-to-Air Heat Exchangers.</a> <a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a> Corbett, Robert J.; Miller, Barbara The air-to-air heat exchanger (a fan powered ventilation device that recovers heat from stale outgoing air) is explained in this six-part publication. Topic areas addressed are: (1) the nature of air-to-air heat exchangers and how they work; (2) choosing and sizing the system; (3) installation, control, and maintenance of the system; (4) heat… </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26020102','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26020102">Gas Transfer in Cellularized Collagen-Membrane Gas Exchange Devices.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Lo, Justin H; Bassett, Erik K; Penson, Elliot J N; Hoganson, David M; Vacanti, Joseph P 2015-08-01 Chronic lower respiratory disease is highly prevalent in the United States, and there remains a need for alternatives to lung transplant for patients who progress to end-stage lung disease. Portable or implantable gas oxygenators based on microfluidic technologies can address this need, provided they operate both efficiently and biocompatibly. Incorporating biomimetic materials into such devices can help replicate native gas exchange function and additionally support cellular components. In this work, we have developed microfluidic devices that enable blood gas exchange across ultra-thin collagen membranes (as thin as 2 μm). Endothelial, stromal, and parenchymal cells readily adhere to these membranes, and long-term culture with cellular components results in remodeling, reflected by reduced membrane thickness. Functionally, acellular collagen-membrane lung devices can mediate effective gas exchange up to ∼288 mL/min/m(2) of oxygen and ∼685 mL/min/m(2) of carbon dioxide, approaching the gas exchange efficiency noted in the native lung. Testing several configurations of lung devices to explore various physical parameters of the device design, we concluded that thinner membranes and longer gas exchange distances result in improved hemoglobin saturation and increases in pO2. However, in the design space tested, these effects are relatively small compared to the improvement in overall oxygen and carbon dioxide transfer by increasing the blood flow rate. Finally, devices cultured with endothelial and parenchymal cells achieved similar gas exchange rates compared with acellular devices. Biomimetic blood oxygenator design opens the possibility of creating portable or implantable microfluidic devices that achieve efficient gas transfer while also maintaining physiologic conditions. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AIPC.1738K0008N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AIPC.1738K0008N">The predictive protective control of the heat exchanger</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Nevriva, Pavel; Filipova, Blanka; Vilimec, Ladislav 2016-06-01 The paper deals with the predictive control applied to flexible cogeneration energy system FES. FES was designed and developed by the VITKOVICE POWER ENGINEERING joint-stock company and represents a new solution of decentralized cogeneration energy sources. In FES, the heating medium is flue gas generated by combustion of a solid fuel. The heated medium is power gas, which is a gas mixture of air and water steam. Power gas is superheated in the main heat exchanger and led to gas turbines. To protect the main heat exchanger against damage by overheating, the novel predictive protective control based on the mathematical model of exchanger was developed. The paper describes the principle, the design and the simulation of the predictive protective method applied to main heat exchanger of FES. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/511713','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/511713">Incorporating the gas analyzer response time in gas exchange computations.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Mitchell, R R 1979-11-01 A simple method for including the gas analyzer response time in the breath-by-breath computation of gas exchange rates is described. The method uses a difference equation form of a model for the gas analyzer in the computation of oxygen uptake and carbon dioxide production and avoids a numerical differentiation required to correct the gas fraction wave forms. The effect of not accounting for analyzer response time is shown to be a 20% underestimation in gas exchange rate. The present method accurately measures gas exchange rate, is relatively insensitive to measurement errors in the analyzer time constant, and does not significantly increase the computation time. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24970854','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24970854">Pulmonary gas exchange efficiency during exercise breathing normoxic and hypoxic gas in adults born very preterm with low diffusion capacity.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Duke, Joseph W; Elliott, Jonathan E; Laurie, Steven S; Beasley, Kara M; Mangum, Tyler S; Hawn, Jerold A; Gladstone, Igor M; Lovering, Andrew T 2014-09-01 Adults with a history of very preterm birth (<32 wk gestational age; PRET) have reduced lung function and significantly lower lung diffusion capacity for carbon monoxide (DLCO) relative to individuals born at term (CONT). Low DLCO may predispose PRET to diffusion limitation during exercise, particularly while breathing hypoxic gas because of a reduced O2 driving gradient and pulmonary capillary transit time. We hypothesized that PRET would have significantly worse pulmonary gas exchange efficiency [i.e., increased alveolar-to-arterial Po2 difference (AaDO2)] during exercise breathing room air or hypoxic gas (FiO2 = 0.12) compared with CONT. To test this hypothesis, we compared the AaDO2 in PRET (n = 13) with a clinically mild reduction in DLCO (72 ± 7% of predicted) and CONT (n = 14) with normal DLCO (105 ± 10% of predicted) pre- and during exercise breathing room air and hypoxic gas. Measurements of temperature-corrected arterial blood gases, and direct measure of O2 saturation (SaO2), were made prior to and during exercise at 25, 50, and 75% of peak oxygen consumption (V̇o2peak) while breathing room air and hypoxic gas. In addition to DLCO, pulmonary function and exercise capacity were significantly less in PRET. Despite PRET having low DLCO, no differences were observed in the AaDO2 or SaO2 pre- or during exercise breathing room air or hypoxic gas compared with CONT. Although our findings were unexpected, we conclude that reduced pulmonary function and low DLCO resulting from very preterm birth does not cause a measureable reduction in pulmonary gas exchange efficiency. Copyright © 2014 the American Physiological Society. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20709922','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20709922">Phenotypic plasticity of gas exchange pattern and water loss in Scarabaeus spretus (Coleoptera: Scarabaeidae): deconstructing the basis for metabolic rate variation.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Terblanche, John S; Clusella-Trullas, Susana; Chown, Steven L 2010-09-01 Investigation of gas exchange patterns and modulation of metabolism provide insight into metabolic control systems and evolution in diverse terrestrial environments. Variation in metabolic rate in response to environmental conditions has been explained largely in the context of two contrasting hypotheses, namely metabolic depression in response to stressful or resource-(e.g. water) limited conditions, or elevation of metabolism at low temperatures to sustain life in extreme conditions. To deconstruct the basis for metabolic rate changes in response to temperature variation, here we undertake a full factorial study investigating the longer- and short-term effects of temperature exposure on gas exchange patterns. We examined responses of traits of gas exchange [standard metabolic rate (SMR); discontinuous gas exchange (DGE) cycle frequency; cuticular, respiratory and total water loss rate (WLR)] to elucidate the magnitude and form of plastic responses in the dung beetle, Scarabaeus spretus. Results showed that short- and longer-term temperature variation generally have significant effects on SMR and WLR. Overall, acclimation to increased temperature led to a decline in SMR (from 0.071+/-0.004 ml CO(2) h(-1) in 15 degrees C-acclimated beetles to 0.039+/-0.004 ml CO(2) h(-1) in 25 degrees C-acclimated beetles measured at 20 degrees C) modulated by reduced DGE frequency (15 degrees C acclimation: 0.554+/-0.027 mHz, 20 degrees C acclimation: 0.257+/-0.030 mHz, 25 degrees C acclimation: 0.208+/-0.027 mHz recorded at 20 degrees C), reduced cuticular WLRs (from 1.058+/-0.537 mg h(-1) in 15 degrees C-acclimated beetles to 0.900+/-0.400 mg h(-1) in 25 degrees C-acclimated beetles measured at 20 degrees C) and reduced total WLR (from 4.2+/-0.5 mg h(-1) in 15 degrees C-acclimated beetles to 3.1+/-0.5 mg h(-1) in 25 degrees C-acclimated beetles measured at 25 degrees C). Respiratory WLR was reduced from 2.25+/-0.40 mg h(-1) in 15 degrees C-acclimated beetles to 1.60+/-0.40 mg h </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3046576','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3046576">A Three-Dimensional Multiscale Model for Gas Exchange in Fruit1[C][W][OA</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Ho, Quang Tri; Verboven, Pieter; Verlinden, Bert E.; Herremans, Els; Wevers, Martine; Carmeliet, Jan; Nicolaï, Bart M. 2011-01-01 Respiration of bulky plant organs such as roots, tubers, stems, seeds, and fruit depends very much on oxygen (O2) availability and often follows a Michaelis-Menten-like response. A multiscale model is presented to calculate gas exchange in plants using the microscale geometry of the tissue, or vice versa, local concentrations in the cells from macroscopic gas concentration profiles. This approach provides a computationally feasible and accurate analysis of cell metabolism in any plant organ during hypoxia and anoxia. The predicted O2 and carbon dioxide (CO2) partial pressure profiles compared very well with experimental data, thereby validating the multiscale model. The important microscale geometrical features are the shape, size, and three-dimensional connectivity of cells and air spaces. It was demonstrated that the gas-exchange properties of the cell wall and cell membrane have little effect on the cellular gas exchange of apple (Malus × domestica) parenchyma tissue. The analysis clearly confirmed that cells are an additional route for CO2 transport, while for O2 the intercellular spaces are the main diffusion route. The simulation results also showed that the local gas concentration gradients were steeper in the cells than in the surrounding air spaces. Therefore, to analyze the cellular metabolism under hypoxic and anoxic conditions, the microscale model is required to calculate the correct intracellular concentrations. Understanding the O2 response of plants and plant organs thus not only requires knowledge of external conditions, dimensions, gas-exchange properties of the tissues, and cellular respiration kinetics but also of microstructure. PMID:21224337 </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRC..122.3696L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRC..122.3696L">How well does wind speed predict air-sea gas transfer in the sea ice zone? A synthesis of radon deficit profiles in the upper water column of the Arctic Ocean</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Loose, B.; Kelly, R. P.; Bigdeli, A.; Williams, W.; Krishfield, R.; Rutgers van der Loeff, M.; Moran, S. B. 2017-05-01 We present 34 profiles of radon-deficit from the ice-ocean boundary layer of the Beaufort Sea. Including these 34, there are presently 58 published radon-deficit estimates of air-sea gas transfer velocity (k) in the Arctic Ocean; 52 of these estimates were derived from water covered by 10% sea ice or more. The average value of k collected since 2011 is 4.0 ± 1.2 m d-1. This exceeds the quadratic wind speed prediction of weighted kws = 2.85 m d-1 with mean-weighted wind speed of 6.4 m s-1. We show how ice cover changes the mixed-layer radon budget, and yields an "effective gas transfer velocity." We use these 58 estimates to statistically evaluate the suitability of a wind speed parameterization for k, when the ocean surface is ice covered. Whereas the six profiles taken from the open ocean indicate a statistically good fit to wind speed parameterizations, the same parameterizations could not reproduce k from the sea ice zone. We conclude that techniques for estimating k in the open ocean cannot be similarly applied to determine k in the presence of sea ice. The magnitude of k through gaps in the ice may reach high values as ice cover increases, possibly as a result of focused turbulence dissipation at openings in the free surface. These 58 profiles are presently the most complete set of estimates of k across seasons and variable ice cover; as dissolved tracer budgets they reflect air-sea gas exchange with no impact from air-ice gas exchange. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18245633','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18245633">The hygric hypothesis does not hold water: abolition of discontinuous gas exchange cycles does not affect water loss in the ant Camponotus vicinus.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Lighton, John R B; Turner, Robbin J 2008-02-01 The discontinuous gas exchange cycle (DGC) of insects and other tracheate arthropods temporally decouples oxygen uptake and carbon dioxide emission and generates powerful concentration gradients for both gas species between the outside world and the tracheal system. Although the DGC is considered an adaptation to reduce respiratory water loss (RWL) - the "hygric hypothesis" - it is absent from many taxa, including xeric ones. The "chthonic hypothesis" states that the DGC originated as an adaptation to gas exchange in hypoxic and hypercapnic, i.e. underground, environments. If that is the case then the DGC is not the ancestral condition, and its expression is not necessarily a requirement for reducing RWL. Here we report a study of water loss rate in the ant Camponotus vicinus, measured while its DGC was slowly eliminated by gradual hypoxia (hypoxic ramp de-DGCing). Metabolic rate remained constant. The DGC ceased at a mean P(O2) of 8.4 kPa. RWL in the absence of DGCs was not affected until P(O2) declined below 3.9 kPa. Below that value, non-DGC spiracular regulation failed, accompanied by a large increase in RWL. Thus, the spiracular control strategy of the DGC is not required for low RWL, even in animals that normally express the DGC. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23069190','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23069190">Estimating oxygen diffusive conductances of gas-exchange systems: A stereological approach illustrated with the human placenta.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Mayhew, Terry M 2014-01-01 For many organisms, respiratory gas exchange is a vital activity and different types of gas-exchange apparatus have evolved to meet individual needs. They include not only skin, gills, tracheal systems and lungs but also transient structures such as the chorioallantois of avian eggs and the placenta of eutherian mammals. The ability of these structures to allow passage of oxygen by passive diffusion can be expressed as a diffusive conductance (units: cm(3) O2 min(-1) kPa(-1)). Occasionally, the ability to estimate diffusive conductance by physiological techniques is compromised by the difficulty of obtaining O2 partial pressures on opposite sides of the tissue interface between the delivery medium (air, water, blood) and uptake medium (usually blood). An alternative strategy is to estimate a morphometric diffusive conductance by combining stereological estimates of key structural quantities (volumes, surface areas, membrane thicknesses) with complementary physicochemical data (O2-haemoglobin chemical reaction rates and Krogh's permeability coefficients). This approach has proved valuable in a variety of comparative studies on respiratory organs from diverse species. The underlying principles were formulated in pioneering studies on the pulmonary lung but are illustrated here by taking the human placenta as the gas exchanger. Copyright © 2012 Elsevier GmbH. All rights reserved. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1084201','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/servlets/purl/1084201">Method for controlling exhaust gas heat recovery systems in vehicles</a> <a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a> Spohn, Brian L.; Claypole, George M.; Starr, Richard D 2013-06-11 A method of operating a vehicle including an engine, a transmission, an exhaust gas heat recovery (EGHR) heat exchanger, and an oil-to-water heat exchanger providing selective heat-exchange communication between the engine and transmission. The method includes controlling a two-way valve, which is configured to be set to one of an engine position and a transmission position. The engine position allows heat-exchange communication between the EGHR heat exchanger and the engine, but does not allow heat-exchange communication between the EGHR heat exchanger and the oil-to-water heat exchanger. The transmission position allows heat-exchange communication between the EGHR heat exchanger, the oil-to-water heat exchanger, and the engine. The method also includes monitoring an ambient air temperature and comparing the monitored ambient air temperature to a predetermined cold ambient temperature. If the monitored ambient air temperature is greater than the predetermined cold ambient temperature, the two-way valve is set to the transmission position. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_7");'>7</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li class="active">9</li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_10" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active">10</li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="181"> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=307735&keyword=environmental+AND+assessment+AND+natural+AND+environment&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=307735&keyword=environmental+AND+assessment+AND+natural+AND+environment&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">Review of Air Exchange Rate Models for Air Pollution Exposure Assessments</a> <a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> A critical aspect of air pollution exposure assessments is estimation of the air exchange rate (AER) for various buildings, where people spend their time. The AER, which is rate the exchange of indoor air with outdoor air, is an important determinant for entry of outdoor air pol... </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15852967','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15852967">[Effects of soil water status on gas exchange of peanut and early rice leaves].</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Chen, Jiazhou; Lü, Guoan; He, Yuanqiu 2005-01-01 The gas exchange characteristics of peanut and early rice leaves were investigated in experimental plots under different soil water conditions over a long growth period. The results showed that at the branching stage of peanut, the stomatal conductance (Gs) and transpiration rate (Tr) decreased slightly under mild and moderate soil water stress, while the net photosynthetic rate (Pn) and leaf water use efficiency (WUE) increased. The Gs/Tr ratio also increased under mild water stress, but decreased under moderate water stress. At podding stage, the Gs, Tr, Gs/Tr ratio and Pn decreased, while WUE increased significantly under mild and moderate water stress. The peanut was suffered from water stress at its pod setting stage. At the grain filling stage of early rice, the Gs, Tr and Gs/Tr ratio fluctuated insignificantly under mild and moderate water stress, while Pn and WUE increased significantly, with an increase in grain yield under mild water stress. It's suggested that the combination of Gs and Gs/Tr ratio could be a reference index for crop water stress, namely, crops could be hazarded by water stress when Gs and Gs/Tr decreased synchronously. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5512930','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5512930">Effect of Water Vapor and Surface Morphology on the Low Temperature Response of Metal Oxide Semiconductor Gas Sensors</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Maier, Konrad; Helwig, Andreas; Müller, Gerhard; Hille, Pascal; Eickhoff, Martin 2015-01-01 In this work the low temperature response of metal oxide semiconductor gas sensors is analyzed. Important characteristics of this low-temperature response are a pronounced selectivity to acid- and base-forming gases and a large disparity of response and recovery time constants which often leads to an integrator-type of gas response. We show that this kind of sensor performance is related to the trend of semiconductor gas sensors to adsorb water vapor in multi-layer form and that this ability is sensitively influenced by the surface morphology. In particular we show that surface roughness in the nanometer range enhances desorption of water from multi-layer adsorbates, enabling them to respond more swiftly to changes in the ambient humidity. Further experiments reveal that reactive gases, such as NO2 and NH3, which are easily absorbed in the water adsorbate layers, are more easily exchanged across the liquid/air interface when the humidity in the ambient air is high. PMID:28793583 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/10998035','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/10998035">Contamination of piped medical gas supply with water.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Hay, H 2000-08-01 The failure of anaesthetic equipment as a result of maintenance is extremely rare. The ingress of water into the flowmeters of an anaesthetic machine from the piped medical air supply is reported and is possibly unique. The piped medical air supply was open to the atmosphere during maintenance. Water condensed in the gas pipeline and this was not noticed during subsequent testing. Water was seen leaking from the orthopaedic air tools used for surgery but was assumed to be from the autoclaving process. Later the same day, when medical air from the piped source was used as part of the gas mixture for a general anaesthetic, water was seen filling the barrel of the flowmeter air control valve. This could have had far-reaching and dangerous consequences for the patient, which were fortunately averted. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=65360&keyword=day+AND+night&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=65360&keyword=day+AND+night&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">MONITORING CYCLICAL AIR-WATER ELEMENTAL MERCURY EXCHANGE</a> <a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> Previous experimental work has demonstrated that elemental mercury evasion from natural water displays a diel cycle; evasion rates during the day can be two to three times evasion rates observed at night. A study with polychlorinated biphenyls (PCBS) found that diurnal PCB air/wa... </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5026132','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5026132">Lung Structure and the Intrinsic Challenges of Gas Exchange</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Hsia, Connie C.W.; Hyde, Dallas M.; Weibel, Ewald R. 2016-01-01 Structural and functional complexities of the mammalian lung evolved to meet a unique set of challenges, namely, the provision of efficient delivery of inspired air to all lung units within a confined thoracic space, to build a large gas exchange surface associated with minimal barrier thickness and a microvascular network to accommodate the entire right ventricular cardiac output while withstanding cyclic mechanical stresses that increase several folds from rest to exercise. Intricate regulatory mechanisms at every level ensure that the dynamic capacities of ventilation, perfusion, diffusion, and chemical binding to hemoglobin are commensurate with usual metabolic demands and periodic extreme needs for activity and survival. This article reviews the structural design of mammalian and human lung, its functional challenges, limitations, and potential for adaptation. We discuss (i) the evolutionary origin of alveolar lungs and its advantages and compromises, (ii) structural determinants of alveolar gas exchange, including architecture of conducting bronchovascular trees that converge in gas exchange units, (iii) the challenges of matching ventilation, perfusion, and diffusion and tissue-erythrocyte and thoracopulmonary interactions. The notion of erythrocytes as an integral component of the gas exchanger is emphasized. We further discuss the signals, sources, and limits of structural plasticity of the lung in alveolar hypoxia and following a loss of lung units, and the promise and caveats of interventions aimed at augmenting endogenous adaptive responses. Our objective is to understand how individual components are matched at multiple levels to optimize organ function in the face of physiological demands or pathological constraints. PMID:27065169 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27065169','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27065169">Lung Structure and the Intrinsic Challenges of Gas Exchange.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Hsia, Connie C W; Hyde, Dallas M; Weibel, Ewald R 2016-03-15 Structural and functional complexities of the mammalian lung evolved to meet a unique set of challenges, namely, the provision of efficient delivery of inspired air to all lung units within a confined thoracic space, to build a large gas exchange surface associated with minimal barrier thickness and a microvascular network to accommodate the entire right ventricular cardiac output while withstanding cyclic mechanical stresses that increase several folds from rest to exercise. Intricate regulatory mechanisms at every level ensure that the dynamic capacities of ventilation, perfusion, diffusion, and chemical binding to hemoglobin are commensurate with usual metabolic demands and periodic extreme needs for activity and survival. This article reviews the structural design of mammalian and human lung, its functional challenges, limitations, and potential for adaptation. We discuss (i) the evolutionary origin of alveolar lungs and its advantages and compromises, (ii) structural determinants of alveolar gas exchange, including architecture of conducting bronchovascular trees that converge in gas exchange units, (iii) the challenges of matching ventilation, perfusion, and diffusion and tissue-erythrocyte and thoracopulmonary interactions. The notion of erythrocytes as an integral component of the gas exchanger is emphasized. We further discuss the signals, sources, and limits of structural plasticity of the lung in alveolar hypoxia and following a loss of lung units, and the promise and caveats of interventions aimed at augmenting endogenous adaptive responses. Our objective is to understand how individual components are matched at multiple levels to optimize organ function in the face of physiological demands or pathological constraints. Copyright © 2016 John Wiley & Sons, Inc. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AdSpR..51..465W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AdSpR..51..465W">Plant mineral nutrition, gas exchange and photosynthesis in space: A review</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Wolff, S. A.; Coelho, L. H.; Zabrodina, M.; Brinckmann, E.; Kittang, A.-I. 2013-02-01 Successful growth and development of higher plants in space rely on adequate availability and uptake of water and nutrients, and efficient energy distribution through photosynthesis and gas exchange. In the present review, literature has been reviewed to assemble the relevant knowledge within space plant research for future planetary missions. Focus has been on fractional gravity, space radiation, magnetic fields and ultimately a combined effect of these factors on gas exchange, photosynthesis and transport of water and solutes. Reduced gravity prevents buoyancy driven thermal convection in the physical environment around the plant and alters transport and exchange of gases and liquids between the plant and its surroundings. In space experiments, indications of root zone hypoxia have frequently been reported, but studies on the influences of the space environment on plant nutrition and water transport are limited or inconclusive. Some studies indicate that uptake of potassium is elevated when plants are grown under microgravity conditions. Based on the current knowledge, gas exchange, metabolism and photosynthesis seem to work properly in space when plants are provided with a well stirred atmosphere and grown at moderate light levels. Effects of space radiation on plant metabolism, however, have not been studied so far in orbit. Ground experiments indicated that shielding from the Earth's magnetic field alters plant gas exchange and metabolism, though more studies are required to understand the effects of magnetic fields on plant growth. It has been shown that plants can grow and reproduce in the space environment and adapt to space conditions. However, the influences of the space environment may result in a long term effect over multiple generations or have an impact on the plants' role as food and part of a regenerative life support system. Suggestions for future plant biology research in space are discussed. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23720333','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23720333">Evolution of air breathing: oxygen homeostasis and the transitions from water to land and sky.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Hsia, Connie C W; Schmitz, Anke; Lambertz, Markus; Perry, Steven F; Maina, John N 2013-04-01 Life originated in anoxia, but many organisms came to depend upon oxygen for survival, independently evolving diverse respiratory systems for acquiring oxygen from the environment. Ambient oxygen tension (PO2) fluctuated through the ages in correlation with biodiversity and body size, enabling organisms to migrate from water to land and air and sometimes in the opposite direction. Habitat expansion compels the use of different gas exchangers, for example, skin, gills, tracheae, lungs, and their intermediate stages, that may coexist within the same species; coexistence may be temporally disjunct (e.g., larval gills vs. adult lungs) or simultaneous (e.g., skin, gills, and lungs in some salamanders). Disparate systems exhibit similar directions of adaptation: toward larger diffusion interfaces, thinner barriers, finer dynamic regulation, and reduced cost of breathing. Efficient respiratory gas exchange, coupled to downstream convective and diffusive resistances, comprise the "oxygen cascade"-step-down of PO2 that balances supply against toxicity. Here, we review the origin of oxygen homeostasis, a primal selection factor for all respiratory systems, which in turn function as gatekeepers of the cascade. Within an organism's lifespan, the respiratory apparatus adapts in various ways to upregulate oxygen uptake in hypoxia and restrict uptake in hyperoxia. In an evolutionary context, certain species also become adapted to environmental conditions or habitual organismic demands. We, therefore, survey the comparative anatomy and physiology of respiratory systems from invertebrates to vertebrates, water to air breathers, and terrestrial to aerial inhabitants. Through the evolutionary directions and variety of gas exchangers, their shared features and individual compromises may be appreciated. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3926130','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3926130">Evolution of Air Breathing: Oxygen Homeostasis and the Transitions from Water to Land and Sky</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Hsia, Connie C. W.; Schmitz, Anke; Lambertz, Markus; Perry, Steven F.; Maina, John N. 2014-01-01 Life originated in anoxia, but many organisms came to depend upon oxygen for survival, independently evolving diverse respiratory systems for acquiring oxygen from the environment. Ambient oxygen tension (PO2) fluctuated through the ages in correlation with biodiversity and body size, enabling organisms to migrate from water to land and air and sometimes in the opposite direction. Habitat expansion compels the use of different gas exchangers, for example, skin, gills, tracheae, lungs, and their intermediate stages, that may coexist within the same species; coexistence may be temporally disjunct (e.g., larval gills vs. adult lungs) or simultaneous (e.g., skin, gills, and lungs in some salamanders). Disparate systems exhibit similar directions of adaptation: toward larger diffusion interfaces, thinner barriers, finer dynamic regulation, and reduced cost of breathing. Efficient respiratory gas exchange, coupled to downstream convective and diffusive resistances, comprise the “oxygen cascade”—step-down of PO2 that balances supply against toxicity. Here, we review the origin of oxygen homeostasis, a primal selection factor for all respiratory systems, which in turn function as gatekeepers of the cascade. Within an organism's lifespan, the respiratory apparatus adapts in various ways to upregulate oxygen uptake in hypoxia and restrict uptake in hyperoxia. In an evolutionary context, certain species also become adapted to environmental conditions or habitual organismic demands. We, therefore, survey the comparative anatomy and physiology of respiratory systems from invertebrates to vertebrates, water to air breathers, and terrestrial to aerial inhabitants. Through the evolutionary directions and variety of gas exchangers, their shared features and individual compromises may be appreciated. PMID:23720333 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/21073780-fouling-reduction-characteristics-distributor-fluidized-bed-heat-exchanger-flue-gas-heat-recovery','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/21073780-fouling-reduction-characteristics-distributor-fluidized-bed-heat-exchanger-flue-gas-heat-recovery">Fouling reduction characteristics of a no-distributor-fluidized-bed heat exchanger for flue gas heat recovery</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Jun, Y.D.; Lee, K.B.; Islam, S.Z. 2008-07-01 In conventional flue gas heat recovery systems, the fouling by fly ashes and the related problems such as corrosion and cleaning are known to be major drawbacks. To overcome these problems, a single-riser no-distributor-fluidized-bed heat exchanger is devised and studied. Fouling and cleaning tests are performed for a uniquely designed fluidized bed-type heat exchanger to demonstrate the effect of particles on the fouling reduction and heat transfer enhancement. The tested heat exchanger model (1 m high and 54 mm internal diameter) is a gas-to-water type and composed of a main vertical tube and four auxiliary tubes through which particles circulatemore » 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.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28282689','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28282689">Water exchange for screening colonoscopy increases adenoma detection rate: a multicenter, double-blinded, randomized controlled trial.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Cadoni, Sergio; Falt, Přemysl; Rondonotti, Emanuele; Radaelli, Franco; Fojtik, Petr; Gallittu, Paolo; Liggi, Mauro; Amato, Arnaldo; Paggi, Silvia; Smajstrla, Vit; Urban, Ondřej; Erriu, Matteo; Koo, Malcolm; Leung, Felix W 2017-05-01 Background and study aims Single-center studies, which were retrospective and/or involved unblinded colonoscopists, have suggested that water exchange, but not water immersion, compared with air insufflation significantly increases the adenoma detection rate (ADR), particularly in the proximal and right colon. Head-to-head comparison of the three techniques with ADR as primary outcome and blinded colonoscopists has not been reported to date. In a randomized controlled trial with blinded colonoscopists, we aimed to evaluate the impact of the three insertion techniques on ADR. Patients and methods A total of 1224 patients aged 50 - 70 years (672 males) and undergoing screening colonoscopy were randomized 1:1:1 to water exchange, water immersion, or air insufflation. Split-dose bowel preparation was adopted to optimize colon cleansing. After the cecum had been reached, a second colonoscopist who was blinded to the insertion technique performed the withdrawal. The primary outcome was overall ADR according to the three insertion techniques (water exchange, water immersion, and air insufflation). Secondary outcomes were other pertinent overall and right colon procedure-related measures. Results Baseline characteristics of the three groups were comparable. Compared with air insufflation, water exchange achieved a significantly higher overall ADR (49.3 %, 95 % confidence interval [CI] 44.3 % - 54.2 % vs. 40.4 % 95 %CI 35.6 % - 45.3 %; P = 0.03); water exchange showed comparable overall ADR vs. water immersion (43.4 %, 95 %CI 38.5 % - 48.3 %; P = 0.28). In the right colon, water exchange achieved a higher ADR than air insufflation (24.0 %, 95 %CI 20.0 % - 28.5 % vs. 16.9 %, 95 %CI 13.4 % - 20.9 %; P = 0.04) and a higher advanced ADR (6.1 %, 95 %CI 4.0 % - 9.0 % vs. 2.5 %, 95 %CI 1.2 % - 4.6 %; P = 0.03). Compared with air insufflation, the mean number of </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?direntryid=20677','PESTICIDES'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?direntryid=20677">VOLATILIZATION RATES FROM WATER TO INDOOR AIR ...</a> <a target="_blank" href="http://www.epa.gov/pesticides/search.htm">EPA Pesticide Factsheets</a> Contaminated water can lead to volatilization of chemicals to residential indoor air. Previous research has focused on only one source (shower stalls) and has been limited to chemicals in which gas-phase resistance to mass transfer is of marginal significance. As a result, attempts to extrapolate chemical emissions from high-volatility chemicals to lower volatility chemicals, or to sources other than showers, have been difficult or impossible. This study involved the development of two-phase, dynamic mass balance models for estimating chemical emissions from washing machines, dishwashers, and bathtubs. An existing model was adopted for showers only. Each model required the use of source- and chemical-specific mass transfer coefficients. Air exchange (ventilation) rates were required for dishwashers and washing machines as well. These parameters were estimated based on a series of 113 experiments involving 5 tracer chemicals (acetone, ethyl acetate, toluene, ethylbenzene, and cyclohexane) and 4 sources (showers, bathtubs, washing machines, and dishwashers). Each set of experiments led to the determination of chemical stripping efficiencies and mass transfer coefficients (overall, liquid-phase, gas-phase), and to an assessment of the importance of gas- phase resistance to mass transfer. Stripping efficiencies ranged from 6.3% to 80% for showers, 2.6% to 69% for bathtubs, 18% to 100% for dishwashers, and 3.8% to 100% for washing machines. Acetone and cyclohexane al </li> <li> <a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=332572','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=332572">Scaling leaf measurements to estimate cotton canopy gas exchange</a> <a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a> Diurnal leaf and canopy gas exchange of well watered field grown cotton were measured. Leaf measurements were made with a portable photosynthesis system and canopy measurements with open Canopy Evapo-Transpiration and Assimilation (CETA) systems. Leaf level measurements were arithmetically scaled to... </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PrOce.138...18D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PrOce.138...18D">Nitrous oxide and methane in Atlantic and Mediterranean waters in the Strait of Gibraltar: Air-sea fluxes and inter-basin exchange</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> de la Paz, M.; Huertas, I. E.; Flecha, S.; Ríos, A. F.; Pérez, F. F. 2015-11-01 The global ocean plays an important role in the overall budget of nitrous oxide (N2O) and methane (CH4), as both gases are produced within the ocean and released to the atmosphere. However, for large parts of the open and coastal oceans there is little or no spatial data coverage for N2O and CH4. Hence, a better assessment of marine emissions estimates is necessary. As a contribution to remedying the scarcity of data on marine regions, N2O and CH4 concentrations have been determined in the Strait of Gibraltar at the ocean Fixed Time series (GIFT). During six cruises performed between July 2011 and November 2014 samples were collected at the surface and various depths in the water column, and subsequently measured using gas chromatography. From this we were able to quantify the temporal variability of the gas air-sea exchange in the area and examine the vertical distribution of N2O and CH4 in Atlantic and Mediterranean waters. Results show that surface Atlantic waters are nearly in equilibrium with the atmosphere whereas deeper Mediterranean waters are oversaturated in N2O, and a gradient that gradually increases with depth was detected in the water column. Temperature was found to be the main factor responsible for the seasonal variability of N2O in the surface layer. Furthermore, although CH4 levels did not reveal any feature clearly associated with the circulation of water masses, vertical distributions showed that higher concentrations are generally observed in the Atlantic layer, and that the deeper Mediterranean waters are considerably undersaturated (by up to 50%). Even though surface waters act as a source of atmospheric N2O during certain periods, on an annual basis the net N2O flux in the Strait of Gibraltar is only 0.35 ± 0.27 μmol m-2 d-1, meaning that these waters are almost in a neutral status with respect to the atmosphere. Seasonally, the region behaves as a slight sink for atmospheric CH4 in winter and as a source in spring and fall. Approximating </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28667337','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28667337">Contrasting dynamics of leaf potential and gas exchange during progressive drought cycles and recovery in Amorpha fruticosa and Robinia pseudoacacia.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Yan, Weiming; Zheng, Shuxia; Zhong, Yangquanwei; Shangguan, Zhouping 2017-06-30 Leaf gas exchange is closely associated with water relations; however, less attention has been given to this relationship over successive drought events. Dynamic changes in gas exchange and water potential in the seedlings of two woody species, Amorpha fruticosa and Robinia pseudoacacia, were monitored during recurrent drought. The pre-dawn leaf water potential declined in parallel with gas exchange in both species, and sharp declines in gas exchange occurred with decreasing water potential. A significant correlation between pre-dawn water potential and gas exchange was observed in both species and showed a right shift in R. pseudoacacia in the second drought. The results suggested that stomatal closure in early drought was mediated mainly by elevated foliar abscisic acid (ABA) in R. pseudoacacia, while a shift from ABA-regulated to leaf-water-potential-driven stomatal closure was observed in A. fruticosa. After re-watering, the pre-dawn water potential recovered quickly, whereas stomatal conductance did not fully recover from drought in R. pseudoacacia, which affected the ability to tightly control transpiration post-drought. The dynamics of recovery from drought suggest that stomatal behavior post-drought may be restricted mainly by hydraulic factors, but non-hydraulic factors may also be involved in R. pseudoacacia. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19880001086','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19880001086">The effect of wind and currents on gas exchange in an estuarine system</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Broecker, W. S.; Ledwell, J. R.; Bopp, R. 1987-01-01 The objectives were to develop a non-volatile tracer to use in gas exchange experiments in laterally unconfined systems and to study applications of deliberate tracers in limnology and oceanography. Progress was made on both fronts but work on the development of the non-volatile tracer proved to be more difficult and labor intensive that anticipated so no field experiments using non-volatile tracers was performed as yet. In the search for a suitable non-volatile tracer for an ocean scale gas exchange experiment a tracer was discovered which does not have the required sensitivity for a large scale experiment, but is very easy to analyze and will be well suited for smaller experiments such as gas exchange determinations on rivers and streams. Sulfur hexafluoride, SF6, was used successfully as a volatile tracer along with tritium as a non-volatile tracer to study gas exchange rates from a primary stream. This is the first gas exchange experiment in which gas exchange rates were determined on a head water stream where significant groundwater input occurs along the reach. In conjunction with SF6, Radon-222 measurements were performed on the groundwater and in the stream. The feasibility of using a combination of SF6 and radon is being studied to determine groundwater inputs and gas exchange of rates in streams with significant groundwater input without using a non-volatile tracer. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23305981','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23305981">Airway exchange of highly soluble gases.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Hlastala, Michael P; Powell, Frank L; Anderson, Joseph C 2013-03-01 Highly blood soluble gases exchange with the bronchial circulation in the airways. On inhalation, air absorbs highly soluble gases from the airway mucosa and equilibrates with the blood before reaching the alveoli. Highly soluble gas partial pressure is identical throughout all alveoli. At the end of exhalation the partial pressure of a highly soluble gas decreases from the alveolar level in the terminal bronchioles to the end-exhaled partial pressure at the mouth. A mathematical model simulated the airway exchange of four gases (methyl isobutyl ketone, acetone, ethanol, and propylene glycol monomethyl ether) that have high water and blood solubility. The impact of solubility on the relative distribution of airway exchange was studied. We conclude that an increase in water solubility shifts the distribution of gas exchange toward the mouth. Of the four gases studied, ethanol had the greatest decrease in partial pressure from the alveolus to the mouth at end exhalation. Single exhalation breath tests are inappropriate for estimating alveolar levels of highly soluble gases, particularly for ethanol. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4888954','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4888954">Airway exchange of highly soluble gases</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Powell, Frank L.; Anderson, Joseph C. 2013-01-01 Highly blood soluble gases exchange with the bronchial circulation in the airways. On inhalation, air absorbs highly soluble gases from the airway mucosa and equilibrates with the blood before reaching the alveoli. Highly soluble gas partial pressure is identical throughout all alveoli. At the end of exhalation the partial pressure of a highly soluble gas decreases from the alveolar level in the terminal bronchioles to the end-exhaled partial pressure at the mouth. A mathematical model simulated the airway exchange of four gases (methyl isobutyl ketone, acetone, ethanol, and propylene glycol monomethyl ether) that have high water and blood solubility. The impact of solubility on the relative distribution of airway exchange was studied. We conclude that an increase in water solubility shifts the distribution of gas exchange toward the mouth. Of the four gases studied, ethanol had the greatest decrease in partial pressure from the alveolus to the mouth at end exhalation. Single exhalation breath tests are inappropriate for estimating alveolar levels of highly soluble gases, particularly for ethanol. PMID:23305981 </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhFl...29d5107S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhFl...29d5107S">Surface velocity divergence model of air/water interfacial gas transfer in open-channel flows</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Sanjou, M.; Nezu, I.; Okamoto, T. 2017-04-01 Air/water interfacial gas transfer through a free surface plays a significant role in preserving and restoring water quality in creeks and rivers. However, direct measurements of the gas transfer velocity and reaeration coefficient are still difficult, and therefore a reliable prediction model needs to be developed. Varying systematically the bulk-mean velocity and water depth, laboratory flume experiments were conducted and we measured surface velocities and dissolved oxygen (DO) concentrations in open-channel flows to reveal the relationship between DO transfer velocity and surface divergence (SD). Horizontal particle image velocimetry measurements provide the time-variations of surface velocity divergence. Positive and negative regions of surface velocity divergence are transferred downstream in time, as occurs in boil phenomenon on natural river free-surfaces. The result implies that interfacial gas transfer is related to bottom-situated turbulence motion and vertical mass transfer. The original SD model focuses mainly on small-scale viscous motion, and this model strongly depends on the water depth. Therefore, we modify the SD model theoretically to accommodate the effects of the water depth on gas transfer, introducing a non-dimensional parameter that includes contributions of depth-scale large-vortex motion, such as secondary currents, to surface renewal events related to DO transport. The modified SD model proved effective and reasonable without any dependence on the bulk mean velocity and water depth, and has a larger coefficient of determination than the original SD model. Furthermore, modeling of friction velocity with the Reynolds number improves the practicality of a new formula that is expected to be used in studies of natural rivers. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_8");'>8</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li class="active">10</li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_11" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active">11</li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="201"> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1411972','SCIGOV-DOEDE'); return false;" href="https://www.osti.gov/servlets/purl/1411972">Diurnal leaf gas exchange survey, Feb2016-May2016, PA-SLZ, PA-PNM: Panama</a> <a target="_blank" href="http://www.osti.gov/dataexplorer">DOE Data Explorer</a> Rogers, Alistair [Brookhaven National Lab; Serbin, Shawn [Brookhaven National Lab; Ely, Kim [Brookhaven National Lab; Wu, Jin [BNL; Wolfe, Brett [Smithsonian; Dickman, Turin [Los Alamos National Lab; Collins, Adam [Los Alamos National Lab; Detto, Matteo [Princeton; Grossiord, Charlotte [Los Alamos National Lab; McDowell, Nate [Los Alamos National Lab; Michaletz, Sean 2017-01-01 Diurnal leaf gas exchange survey measured on sunlit canopy trees on a monthly basis from Feb to May 2016 at SLZ and PNM. This data was collected as part of the 2016 ENSO campaign. See related datasets (existing and future) for further sample details, leaf water potential, LMA, leaf spectra, other gas exchange and leaf chemistry. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1917686R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1917686R">Uncertainty of the global oceanic CO2 exchange at the air-water interface induced by the choice of the gas exchange velocity formulation and the wind product: quantification and spatial analysis</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Roobaert, Alizee; Laruelle, Goulven; Landschützer, Peter; Regnier, Pierre 2017-04-01 In lakes, rivers, estuaries and the ocean, the quantification of air-water CO2 exchange (FCO2) is still characterized by large uncertainties partly due to the lack of agreement over the parameterization of the gas exchange velocity (k). Although the ocean is generally regarded as the best constrained system because k is only controlled by the wind speed, numerous formulations are still currently used, leading to potentially large differences in FCO2. Here, a quantitative global spatial analysis of FCO2 is presented using several k-wind speed formulations in order to compare the effect of the choice of parameterization of k on FCO2. This analysis is performed at a 1 degree resolution using a sea surface pCO2 product generated using a two-step artificial neuronal network by Landschützer et al. (2015) over the 1991-2011 period. Four different global wind speed datasets (CCMP, ERA, NCEP 1 and NCEP 2) are also used to assess the effect of the choice of one wind speed product over the other when calculating the global and regional oceanic FCO2. Results indicate that this choice of wind speed product only leads to small discrepancies globally (6 %) except with NCEP 2 which produces a more intense global FCO2 compared to the other wind products. Regionally, theses differences are even more pronounced. For a given wind speed product, the choice of parametrization of k yields global FCO2 differences ranging from 7 % to 16 % depending on the wind product used. We also provide latitudinal profiles of FCO2 and its uncertainty calculated combining all combinations between the different k-relationships and the four wind speed products. Wind speeds >14 m s-1, which only account for 7 % of all observations, contributes disproportionately to the global oceanic FCO2 and, for this range of wind speeds, the uncertainty induced by the choice of formulation for k is maximum ( 50 %). </li> <li> <a target="_blank" onclick="trackOutboundLink('http://www.agu.org/journals/jc/v096/iC04/90JC02642/','USGSPUBS'); return false;" href="http://www.agu.org/journals/jc/v096/iC04/90JC02642/">Atmospheric organochlorine pollutants and air-sea exchange of hexachlorocyclohexane in the Bering and Chukchi Seas</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Hinckley, D.A.; Bidleman, T.F.; Rice, C.P. 1991-01-01 Organochlorine pesticides have been found in Arctic fish, marine mammals, birds, and plankton for some time. The lack of local sources and remoteness of the region imply long-range transport and deposition of contaminants into the Arctic from sources to the south. While on the third Soviet-American Joint Ecological Expedition to the Bering and Chukchi Seas (August 1988), high-volume air samples were taken and analyzed for organochlorine pesticides. Hexachlorocyclohexane (HCH), hexachlorobenzene, polychlorinated camphenes, and chlordane (listed in order of abundance, highest to lowest) were quantified. The air-sea gas exchange of HCH was estimated at 18 stations during the cruise. Average alpha-HCH concentrations in concurrent atmosphere and surface water samples were 250 pg m-3 and 2.4 ng L-1, respectively, and average gamma-HCH concentrations were 68 pg m-3 in the atmosphere and 0.6 ng L-1 in surface water. Calculations based on experimentally derived Henry's law constants showed that the surface water was undersaturated with respect to the atmosphere at most stations (alpha-HCH, average 79% saturation; gamma-HCH, average 28% saturation). The flux for alpha-HCH ranged from -47 ng m-2 day-1 (sea to air) to 122 ng m-2 d-1 (air to sea) and averaged 25 ng m-2 d-1 air to sea. All fluxes of gamma-HCH were from air to sea, ranged from 17 to 54 ng m-2 d-1, and averaged 31 ng m-2 d-1. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=oxygen&pg=3&id=EJ940769','ERIC'); return false;" href="https://eric.ed.gov/?q=oxygen&pg=3&id=EJ940769">Gas Property Demonstrations Using Plastic Water Bottles</a> <a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a> Campbell, Dean J.; Bannon, Stephen J.; Gunter, Molly M. 2011-01-01 Plastic water bottles are convenient containers for demonstrations of gas properties illustrating Boyle's law, Charles's law, and Avogadro's law. The contents of iron-based disposable hand warmer packets can be used to remove oxygen gas from the air within an unfilled plastic water bottle. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1711535S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1711535S">Estimating gas exchange of CO2 and CH4 between headwater systems and the atmosphere in Southwest Sweden</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Somlai, Celia; Natchimuthu, Sivakiruthika; Bastviken, David; Lorke, Andreas 2015-04-01 Quantifying the role of inland water systems in terms of carbon sinks and sources and their connection to the terrestrial ecosystems and landscapes is fundamental for improving the balance approach of regional and global carbon budgets. Recent research showed that freshwater bodies emit significant amounts of CO2 and CH4 into the atmosphere. The extent of the emissions from small streams and headwaters, however, remains uncertain due to a limited availability of data. Studies have shown that headwater systems receive most of the terrestrial organic carbon, have the highest dissolved CO2 concentration and the highest gas exchange velocities and cover the largest fractional surface area within fluvial networks. The gas exchange between inland waters and the atmosphere is controlled by two factors: the difference between the dissolved gas concentration and its atmospheric equilibrium concentration, and the gas exchange velocity. The direct measurement of the dissolved gas concentration of greenhouse gases can be measured straightforwardly, for example, by gas chromatography from headspace extraction of water sample. In contrast, direct measurement of gas exchange velocity is more complex and time consuming, as simultaneous measurements with a volatile and nonvolatile inert tracer gas are needed. Here we analyze measurements of gas exchange velocities, concentrations and fluxes of dissolved CO2 and CH4, as well as loads of total organic and inorganic carbon in 10 reaches in headwater streams in Southwest Sweden. We compare the gas exchange velocities measured directly through tracer injections with those estimated through various empirical approaches, which are based on modelled and measured current velocity, stream depth and slope. Furthermore, we estimate the resulting uncertainties of the flux estimates. We also present different time series of dissolved CO2, CH4 and O2 concentration, water temperature, barometric pressure, electro conductivity, and pH values </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2954549','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2954549">Modified Perfluorocarbon Tracer Method for Measuring Effective Multizone Air Exchange Rates</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Shinohara, Naohide; Kataoka, Toshiyuki; Takamine, Koichi; Butsugan, Michio; Nishijima, Hirokazu; Gamo, Masashi 2010-01-01 A modified procedure was developed for the measurement of the effective air exchange rate, which represents the relationship between the pollutants emitted from indoor sources and the residents’ level of exposure, by placing the dosers of tracer gas at locations that resemble indoor emission sources. To measure the 24-h-average effective air exchange rates in future surveys based on this procedure, a low-cost, easy-to-use perfluorocarbon tracer (PFT) doser with a stable dosing rate was developed by using double glass vials, a needle, a polyethylene-sintered filter, and a diffusion tube. Carbon molecular sieve cartridges and carbon disulfide (CS2) were used for passive sampling and extraction of the tracer gas, respectively. Recovery efficiencies, sampling rates, and lower detection limits for 24-h sampling of hexafluorobenzene, octafluorotoluene, and perfluoroallylbenzene were 40% ± 3%, 72% ± 5%, and 84% ± 6%; 10.5 ± 1.1, 14.4 ± 1.4, and 12.2 ± 0.49 mL min−1; and 0.20, 0.17, and 0.26 μg m−3, respectively. PMID:20948928 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20948928','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20948928">Modified perfluorocarbon tracer method for measuring effective multizone air exchange rates.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Shinohara, Naohide; Kataoka, Toshiyuki; Takamine, Koichi; Butsugan, Michio; Nishijima, Hirokazu; Gamo, Masashi 2010-09-01 A modified procedure was developed for the measurement of the effective air exchange rate, which represents the relationship between the pollutants emitted from indoor sources and the residents' level of exposure, by placing the dosers of tracer gas at locations that resemble indoor emission sources. To measure the 24-h-average effective air exchange rates in future surveys based on this procedure, a low-cost, easy-to-use perfluorocarbon tracer (PFT) doser with a stable dosing rate was developed by using double glass vials, a needle, a polyethylene-sintered filter, and a diffusion tube. Carbon molecular sieve cartridges and carbon disulfide (CS₂) were used for passive sampling and extraction of the tracer gas, respectively. Recovery efficiencies, sampling rates, and lower detection limits for 24-h sampling of hexafluorobenzene, octafluorotoluene, and perfluoroallylbenzene were 40% ± 3%, 72% ± 5%, and 84% ± 6%; 10.5 ± 1.1, 14.4 ± 1.4, and 12.2 ± 0.49 mL min⁻¹; and 0.20, 0.17, and 0.26 μg m⁻³, respectively. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28313925','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28313925">Effects of plant size and water relations on gas exchange and growth of the desert shrub Larrea tridentata.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Franco, A C; de Soyza, A G; Virginia, R A; Reynolds, J F; Whitford, W G 1994-03-01 Larrea tridentata is a xerophytic evergreen shrub, dominant in the arid regions of the southwestern United States. We examined relationships between gasexchange characteristics, plant and soil water relations, and growth responses of large versus small shrubs of L. tridentata over the course of a summer growing season in the Chihuahuan Desert of southern New Mexico, USA. The soil wetting front did not reach 0.6 m, and soils at depths of 0.6 and 0.9 m remained dry throughout the summer, suggesting that L. tridentata extracts water largely from soil near the surface. Surface soil layers (<0.3 m) were drier under large plants, but predawn xylem water potentials were similar for both plant sizes suggesting some access to deeper soil moisture reserves by large plants. Stem elongation rates were about 40% less in large, reproductively active shrubs than in small, reproductively inactive shrubs. Maximal net photosynthetic rates (P max ) occurred in early summer (21.3 μ mol m -2 s -1 ), when pre-dawn xylem water potential (XWP) reached ca. -1 MPa. Although both shrub sizes exhibited similar responses to environmental factors, small shrubs recovered faster from short-term drought, when pre-dawn XWP reached about -4.5 MPa and P max decreased to only ca. 20% of unstressed levels. Gas exchange measurements yielded a strong relationship between stomatal conductance and photosynthesis, and the relationship between leaf-to-air vapor pressure deficit and stomatal conductance was found to be influenced by pre-dawn XWP. Our results indicate that stomatal responses to water stress and vapor pressure deficit are important in determining rates of carbon gain and water loss in L. tridentata. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28653741','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28653741">Gas exchanges and water use efficiency in the selection of tomato genotypes tolerant to water stress.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Borba, M E A; Maciel, G M; Fraga Júnior, E F; Machado Júnior, C S; Marquez, G R; Silva, I G; Almeida, R S 2017-06-20 Water stress can affect the yield in tomato crops and, despite this, there are few types of research aiming to select tomato genotypes resistant to the water stress using physiological parameters. This experiment aimed to study the variables that are related to the gas exchanges and the efficiency in water use, in the selection of tomato genotypes tolerant to water stress. It was done in a greenhouse, measuring 7 x 21 m, in a randomized complete block design, with four replications (blocks), being five genotypes in the F 2 BC 1 generation, which were previously obtained from an interspecific cross between Solanum pennellii versus S. lycopersicum and three check treatments, two susceptible [UFU-22 (pre-commercial line) and cultivar Santa Clara] and one resistant (S. pennellii). At the beginning of flowering, the plants were submitted to a water stress condition, through irrigation suspension. After that CO 2 assimilation, internal CO 2 , stomatal conductance, transpiration, leaf temperature, instantaneous water use efficiency, intrinsic efficiency of water use, instantaneous carboxylation efficiency, chlorophyll a and b, and the potential leaf water (Ψf) were observed. Almost all variables that were analyzed, except CO 2 assimilation and instantaneous carboxylation efficiency, demonstrated the superiority of the wild accession, S. pennellii, concerning the susceptible check treatments. The high photosynthetic rate and the low stomatal conductance and transpiration, presented by the UFU22/F 2 BC 1 #2 population, allowed a better water use efficiency. Because of that, these physiological characteristics are promising in the selection of tomato genotypes tolerant to water stress. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21827644','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21827644">Performance evaluation on an air-cooled heat exchanger for alumina nanofluid under laminar flow.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Teng, Tun-Ping; Hung, Yi-Hsuan; Teng, Tun-Chien; Chen, Jyun-Hong 2011-08-09 This study analyzes the characteristics of alumina (Al2O3)/water nanofluid to determine the feasibility of its application in an air-cooled heat exchanger for heat dissipation for PEMFC or electronic chip cooling. The experimental sample was Al2O3/water nanofluid produced by the direct synthesis method at three different concentrations (0.5, 1.0, and 1.5 wt.%). The experiments in this study measured the thermal conductivity and viscosity of nanofluid with weight fractions and sample temperatures (20-60°C), and then used the nanofluid in an actual air-cooled heat exchanger to assess its heat exchange capacity and pressure drop under laminar flow. Experimental results show that the nanofluid has a higher heat exchange capacity than water, and a higher concentration of nanoparticles provides an even better ratio of the heat exchange. The maximum enhanced ratio of heat exchange and pressure drop for all the experimental parameters in this study was about 39% and 5.6%, respectively. In addition to nanoparticle concentration, the temperature and mass flow rates of the working fluid can affect the enhanced ratio of heat exchange and pressure drop of nanofluid. The cross-section aspect ratio of tube in the heat exchanger is another important factor to be taken into consideration. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3212002','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3212002">Performance evaluation on an air-cooled heat exchanger for alumina nanofluid under laminar flow</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> 2011-01-01 This study analyzes the characteristics of alumina (Al2O3)/water nanofluid to determine the feasibility of its application in an air-cooled heat exchanger for heat dissipation for PEMFC or electronic chip cooling. The experimental sample was Al2O3/water nanofluid produced by the direct synthesis method at three different concentrations (0.5, 1.0, and 1.5 wt.%). The experiments in this study measured the thermal conductivity and viscosity of nanofluid with weight fractions and sample temperatures (20-60°C), and then used the nanofluid in an actual air-cooled heat exchanger to assess its heat exchange capacity and pressure drop under laminar flow. Experimental results show that the nanofluid has a higher heat exchange capacity than water, and a higher concentration of nanoparticles provides an even better ratio of the heat exchange. The maximum enhanced ratio of heat exchange and pressure drop for all the experimental parameters in this study was about 39% and 5.6%, respectively. In addition to nanoparticle concentration, the temperature and mass flow rates of the working fluid can affect the enhanced ratio of heat exchange and pressure drop of nanofluid. The cross-section aspect ratio of tube in the heat exchanger is another important factor to be taken into consideration. PMID:21827644 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15859112','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15859112">Measurement of the oxygen mass transfer through the air-water interface.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Mölder, Erik; Mashirin, Alelxei; Tenno, Toomas 2005-01-01 Gas mass transfer through the liquid-gas interface has enormous importance in various natural and industrial processes. Surfactants or insoluble compounds adsorbed onto an interface will inhibit the gas mass transfer through the liquid-gas surface. This study presents a technique for measuring the oxygen mass transfer through the air-water interface. Experimental data obtained with the measuring device were incorporated into a novel mathematical model, which allowed one to calculate diffusion conduction of liquid surface layer and oxygen mass transfer coefficient in the liquid surface layer. A special measurement cell was constructed. The most important part of the measurement cell is a chamber containing the electrochemical oxygen sensor inside it. Gas exchange between the volume of the chamber and the external environment takes place only through the investigated surface layer. Investigated liquid was deoxygenated, which triggers the oxygen mass transfer from the chamber through the liquid-air interface into the liquid phase. The decrease of oxygen concentration in the cell during time was measured. By using this data it is possible to calculate diffusional parameters of the water surface layer. Diffusion conduction of oxygen through the air-water surface layer of selected wastewaters was measured. The diffusion conduction of different wastewaters was about 3 to 6 times less than in the unpolluted water surface. It was observed that the dilution of wastewater does not have a significant impact on the oxygen diffusion conduction through the wastewater surface layer. This fact can be explained with the presence of the compounds with high surface activity in the wastewater. Surfactants achieved a maximum adsorption and, accordingly, the maximum decrease of oxygen permeability already at a very low concentration of surfactants in the solution. Oxygen mass transfer coefficient of the surface layer of the water is found to be Ds/ls = 0.13 x 10(-3) x cm/s. A simple </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ECSS..176....1M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ECSS..176....1M">Temporal variability of air-sea CO2 exchange in a low-emission estuary</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Mørk, Eva Thorborg; Sejr, Mikael Kristian; Stæhr, Peter Anton; Sørensen, Lise Lotte 2016-07-01 There is the need for further study of whether global estimates of air-sea CO2 exchange in estuarine systems capture the relevant temporal variability and, as such, the temporal variability of bulk parameterized and directly measured CO2 fluxes was investigated in the Danish estuary, Roskilde Fjord. The air-sea CO2 fluxes showed large temporal variability across seasons and between days and that more than 30% of the net CO2 emission in 2013 was a result of two large fall and winter storms. The diurnal variability of ΔpCO2 was up to 400 during summer changing the estuary from a source to a sink of CO2 within the day. Across seasons the system was suggested to change from a sink of atmospheric CO2 during spring to near neutral during summer and later to a source of atmospheric CO2 during fall. Results indicated that Roskilde Fjord was an annual low-emission estuary, with an estimated bulk parameterized release of 3.9 ± 8.7 mol CO2 m-2 y-1 during 2012-2013. It was suggested that the production-respiration balance leading to the low annual emission in Roskilde Fjord, was caused by the shallow depth, long residence time and high water quality in the estuary. In the data analysis the eddy covariance CO2 flux samples were filtered according to the H2Osbnd CO2 cross-sensitivity assessment suggested by Landwehr et al. (2014). This filtering reduced episodes of contradicting directions between measured and bulk parameterized air-sea CO2 exchanges and changed the net air-sea CO2 exchange from an uptake to a release. The CO2 gas transfer velocity was calculated from directly measured CO2 fluxes and ΔpCO2 and agreed to previous observations and parameterizations. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.B11K..06A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.B11K..06A">Limitations on gas exchange recovery following natural drought in Californian oak woodlands.</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ackerly, D.; Skelton, R. P.; Dawson, T.; Thompson, S.; Feng, X.; Weitz, A.; McLaughlin, B. 2017-12-01 Abstract Background/Question/Methods Drought can cause major damage to plant communities, but species damage thresholds and post-drought recovery of forest productivity are not yet predictable. We asked the question how should forest net primary productivity recover following exposure to severe drought? We used a natural drought period to investigate whether drought responses and post-drought recovery of canopy health could be predicted by properties of the water transport system. We aimed to test the hypothesis that recovery of gas exchange and canopy health would be most severely limited by xylem embolism in stems. To do this we monitored leaf level gas exchange and water status for multiple individuals of two deciduous and two evergreen species for four years spanning a severe drought event and following subsequent rehydration. Results/Discussion Severe drought caused major declines in leaf water potential, reduced stomatal conductance and assimilation rates and increased canopy bareness in our four canopy species. Water potential surpassed levels associated with incipient embolism in leaves of most trees. In contrast, due to hydraulic segmentation, water potential only rarely surpassed critical thresholds in the stems of the study trees. Individuals that surpassed critical thresholds of embolism in the stem displayed significant canopy dieback and mortality. Thus, recovery of plant gas exchange and canopy health was predicted by xylem safety margin in stems, but not leaves, providing strong support for stem cavitation vulnerability as an index of damage under natural drought conditions. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28250584','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28250584">Brassinosteroids improve photosystem II efficiency, gas exchange, antioxidant enzymes and growth of cowpea plants exposed to water deficit.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Lima, J V; Lobato, A K S 2017-01-01 Water deficit is considered the main abiotic stress that limits agricultural production worldwide. Brassinosteroids (BRs) are natural substances that play roles in plant tolerance against abiotic stresses, including water deficit. This research aims to determine whether BRs can mitigate the negative effects caused by water deficiency, revealing how BRs act and their possible contribution to increased tolerance of cowpea plants to water deficit. The experiment was a factorial design with the factors completely randomised, with two water conditions (control and water deficit) and three levels of brassinosteroids (0, 50 and 100 nM 24-epibrassinolide; EBR is an active BRs). Plants sprayed with 100 nM EBR under the water deficit presented significant increases in Φ PSII , q P and ETR compared with plants subjected to the water deficit without EBR. With respect to gas exchange, P N , E and g s exhibited significant reductions after water deficit, but application of 100 nM EBR caused increases in these variables of 96, 24 and 33%, respectively, compared to the water deficit + 0 nM EBR treatment. To antioxidant enzymes, EBR resulted in increases in SOD, CAT, APX and POX, indicating that EBR acts on the antioxidant system, reducing cell damage. The water deficit caused significant reductions in Chl a , Chl b and total Chl, while plants sprayed with 100 nM EBR showed significant increases of 26, 58 and 33% in Chl a , Chl b and total Chl, respectively. This study revealed that EBR improves photosystem II efficiency, inducing increases in Φ PSII , q P and ETR. This substance also mitigated the negative effects on gas exchange and growth induced by the water deficit. Increases in SOD, CAT, APX and POX of plants treated with EBR indicate that this steroid clearly increased the tolerance to the water deficit, reducing reactive oxygen species, cell damage, and maintaining the photosynthetic pigments. Additionally, 100 nM EBR resulted in a better dose-response of cowpea </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3234696','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3234696">Removal of infused water predominantly during insertion (water exchange) is consistently associated with an increase in adenoma detection rate - review of data in randomized controlled trials (RCTs) of water-related methods</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Harker, JO; Leung, JW; Siao-Salera, RM; Mann, SK; Ramirez, FC; Friedland, S; Amato, A; Radaelli, F; Paggi, S; Terruzzi, V; Hsieh, YH 2011-01-01 Introduction Variation in outcomes in RcTs comparing water-related methods and air insufflation raises challenging questions regarding the new approach. This report reviews impact of water exchange - simultaneous infusion and removal of infused water during insertion on adenoma detection rate (ADR) defined as proportion of patients with a least one adenoma of any size. Methods Medline (2008–2011) searches, abstract of 2011 Digestive Disease Week (DDW) meeting and personal communications were considered to identify RcTs that compared water-related methods and air insufflation to aid insertion of colonoscope. Results Since 2008, eleven reports of RcTs (6 published, 1 submitted and 4 abstracts, n=1728) described ADR in patients randomized to be examined by air and water-related methods. The water-related methods differed in timing of removal of the infused water -predominantly during insertion (water exchange) (n=825) or predominantly during withdrawal (water immersion) (n=903). Water immersion was associated with both increases and decreases in ADR compared to respective air method patients and the net overall change (-7%) was significant. On the other hand water exchange was associated with increases in ADR consistently and the net changes (overall, 8%; proximal overall, 11%; and proximal <10 mm, 12%) were all significant. Conclusion Comparative data generated the hypothesis that significantly larger increases in overall and proximal colon ADRs were associated with water exchange than water immersion or air insufflation during insertion. The hypothesis should be evaluated by RCTs to elucidate the mechanism of water exchange on adenoma detection. PMID:22163082 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23461476','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23461476">Regulation and acclimation of leaf gas exchange in a piñon-juniper woodland exposed to three different precipitation regimes.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Limousin, Jean-Marc; Bickford, Christopher P; Dickman, Lee T; Pangle, Robert E; Hudson, Patrick J; Boutz, Amanda L; Gehres, Nathan; Osuna, Jessica L; Pockman, William T; McDowell, Nate G 2013-10-01 Leaf gas-exchange regulation plays a central role in the ability of trees to survive drought, but forecasting the future response of gas exchange to prolonged drought is hampered by our lack of knowledge regarding potential acclimation. To investigate whether leaf gas-exchange rates and sensitivity to drought acclimate to precipitation regimes, we measured the seasonal variations of leaf gas exchange in a mature piñon-juniper Pinus edulis-Juniperus monosperma woodland after 3 years of precipitation manipulation. We compared trees receiving ambient precipitation with those in an irrigated treatment (+30% of ambient precipitation) and a partial rainfall exclusion (-45%). Treatments significantly affected leaf water potential, stomatal conductance and photosynthesis for both isohydric piñon and anisohydric juniper. Leaf gas exchange acclimated to the precipitation regimes in both species. Maximum gas-exchange rates under well-watered conditions, leaf-specific hydraulic conductance and leaf water potential at zero photosynthetic assimilation all decreased with decreasing precipitation. Despite their distinct drought resistance and stomatal regulation strategies, both species experienced hydraulic limitation on leaf gas exchange when precipitation decreased, leading to an intraspecific trade-off between maximum photosynthetic assimilation and resistance of photosynthesis to drought. This response will be most detrimental to the carbon balance of piñon under predicted increases in aridity in the southwestern USA. © 2013 John Wiley & Sons Ltd. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12857848','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12857848">Hydraulic properties of rice and the response of gas exchange to water stress.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Stiller, Volker; Lafitte, H Renee; Sperry, John S 2003-07-01 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 (P(50)) 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. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26710629','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26710629">[Effects of different water potentials on leaf gas exchange and chlorophyll fluorescence parameters of cucumber during post-flowering growth stage].</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Lin, Lu; Tang, Yun; Zhang, Ji-tao; Yan, Wan-li; Xiao, Jian-hong; Ding, Chao; Dong, Chuan; Ji, Zeng-shun 2015-07-01 Impacts of different substrate water potentials (SWP) on leaf gas exchange and chlorophyll fluorescence parameters of greenhouse cucumber during its post-flowering growth stage were analyzed in this study. The results demonstrated that -10 and -30 kPa were the critical values for initiating stomatal and non-stomatal limitation of drought stress, respectively. During the stage of no drought stress (-10 kPa < SWP ≤ 0 kPa), gas exchange parameters and chlorophyll fluorescence parameters were not different significantly among treatments. During the stage of stomatal limitation of drought stress (-30 kPa<SWP ≤ -10 kPa), with the decrease of SWP, the stomatal conductance (gs), intercellular carbon dioxide concentration (Ci), net photosynthetic rate (Pn) , apparent quantum efficiency (ε), transpiration rate (Tr), carboxylation efficiency (CE), maximum Rubisco-limited rate of carboxylation (Vc max), maximum rate of electron transport (Jmax), rate of triosephosphate utilization (VTPU), maximum and actual quantum efficiency of PSII (ΦPSII, and Fv/Fm) and photochemical quenching (qP) decreased, but the light compensation point (LCP), dark respiration rate (Rd), carbon dioxide compensation point (CCP), stomatal limitation value (LS), instantaneous water use efficiency (WUEi) and non-photochemical quenching (qN) increased. In this stage, gas exchange parameters changed faster than chlorophyll fluorescence parameters and differed significantly among treatments. During the stage of non-stomatal limitation of drought stress (-45 kPa≤SWP ≤ -30 kPa), with the decrease of SWP, light saturation point (LSP), Rd, CE, Vcmax, VTPU, LS, WUEi, ΦpPSII, Fv/Fm and qp decreased, while CCP, Ci and qN increased. In this stage, chlorophyll fluorescence parameters changed faster than gas exchange parameters and differed significantly among treatments. In production of greenhouse cucumber, -10 and -5 kPa should be the lower and upper limit value of irrigation, respectively. The stomatal </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=546951','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=546951">Gas Exchange of Algae</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Ammann, Elizabeth C. B.; Lynch, Victoria H. 1967-01-01 The oxygen production of a photosynthetic gas exchanger containing Chlorella pyrenoidosa (1% packed cell volume) was measured when various concentrations of carbon dioxide were present within the culture unit. The internal carbon dioxide concentrations were obtained by manipulating the entrance gas concentration and the flow rate. Carbon dioxide percentages were monitored by means of electrodes placed directly in the nutrient medium. The concentration of carbon dioxide in the nutrient medium which produced maximal photosynthesis was in the range of 1.5 to 2.5% by volume. Results were unaffected by either the level of carbon dioxide in the entrance gas or the rate of gas flow. Entrance gases containing 2% carbon dioxide flowing at 320 ml/min, 3% carbon dioxide at 135 ml/min, and 4% carbon dioxide at 55 ml/min yielded optimal carbon dioxide concentrations in the particular unit studied. By using carbon dioxide electrodes implanted directly in the gas exchanger to optimize the carbon dioxide concentration throughout the culture medium, it should be possible to design more efficient large-scale units. PMID:4382391 </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_9");'>9</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li class="active">11</li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_12" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active">12</li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="221"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013JPS...243..946K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013JPS...243..946K">Numerical investigation of interfacial transport resistance due to water droplets in proton exchange membrane fuel cell air channels</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Koz, Mustafa; Kandlikar, Satish G. 2013-12-01 Oxygen transport resistance at the air flow channel and gas diffusion layer (GDL) interface is needed in modelling the performance of a proton exchange membrane fuel cell (PEMFC). This resistance is expressed through the non-dimensional Sherwood number (Sh). The effect of the presence of a droplet on Sh is studied numerically in an isolated air flow channel using a commercially available package, COMSOL Multiphysics®. A droplet is represented as a solid obstruction placed on the GDL-channel interface and centred along the channel width. The effect of a single droplet is first studied for a range of superficial mean air velocities and droplet sizes. Secondly, the effect of droplet spacing on Sh is studied through simulations of two consecutive droplets. Lastly, multiple droplets in a row are studied as a more representative case of a PEMFC air flow channel. The results show that the droplets significantly increase Sh above the fully developed value in the wake region. This enhancement increases with the number of droplets, droplet size, and superficial mean air velocity. Moreover, the analogy between mass and heat transfer is investigated by comparing Sh to the equivalent Nusselt number. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25311102','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25311102">Nondestructive natural gas hydrate recovery driven by air and carbon dioxide.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Kang, Hyery; Koh, Dong-Yeun; Lee, Huen 2014-10-14 Current technologies for production of natural gas hydrates (NGH), which include thermal stimulation, depressurization and inhibitor injection, have raised concerns over unintended consequences. The possibility of catastrophic slope failure and marine ecosystem damage remain serious challenges to safe NGH production. As a potential approach, this paper presents air-driven NGH recovery from permeable marine sediments induced by simultaneous mechanisms for methane liberation (NGH decomposition) and CH₄-air or CH₄-CO₂/air replacement. Air is diffused into and penetrates NGH and, on its surface, forms a boundary between the gas and solid phases. Then spontaneous melting proceeds until the chemical potentials become equal in both phases as NGH depletion continues and self-regulated CH4-air replacement occurs over an arbitrary point. We observed the existence of critical methane concentration forming the boundary between decomposition and replacement mechanisms in the NGH reservoirs. Furthermore, when CO₂ was added, we observed a very strong, stable, self-regulating process of exchange (CH₄ replaced by CO₂/air; hereafter CH₄-CO₂/air) occurring in the NGH. The proposed process will work well for most global gas hydrate reservoirs, regardless of the injection conditions or geothermal gradient. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JaJAP..57a02BCI','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JaJAP..57a02BCI">Simultaneous generation of acidic and alkaline water using atmospheric air plasma formed in water</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Imai, Shin-ichi; Sakaguchi, Yoshihiro; Shirafuji, Tatsuru 2018-01-01 Plasmas on water surfaces and in water can be generated at atmosphere pressure using several kinds of gases, including helium, argon, oxygen, and air. Nitrates are generated in water through the interaction between water and atmospheric plasma that uses ambient air. Water that has been made acidic by the generation of nitric acid and the acidic water can be used for the sterilization of medical instruments, toilet bowls, and washing machines. Dishwashers are another potential application, as alkaline water is needed to remove grease from tableware. To investigate the production of alkaline water and its mechanism, gas component analysis was performed using an atmospheric quadrupole mass spectrometer. It was found that hydrogen gas evolves from the water surrounding both the positive and negative electrodes. The gas and water analyses carried out in this study revealed that acidic water of pH 2.5 and alkaline water of pH 10 can be simultaneously generated by our ambient air plasma device, which has been altered from our original model. The alterative plasma device has a partition wall, which is made of conductive resin, between the positive and negative electrodes. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24222707','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24222707">Ex vivo assessment and validation of water exchange performance of 23 heat and moisture exchangers for laryngectomized patients.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> van den Boer, Cindy; Muller, Sara H; Vincent, Andrew D; van den Brekel, Michiel W M; Hilgers, Frans J M 2014-08-01 Breathing through a tracheostoma results in insufficient warming and humidification of the inspired air. This loss of air conditioning, especially humidification, can be partially restored with the application of a heat and moisture exchanger (HME) over the tracheostoma. For medical professionals, it is not easy to judge differences in water exchange performance of various HMEs owing to the lack of universal outcome measures. This study has three aims: assessment of the water exchange performance of commercially available HMEs for laryngectomized patients, validation of these results with absolute humidity outcomes, and assessment of the role of hygroscopic salt present in some of the tested HMEs. Measurements of weight and absolute humidity at end inspiration and end expiration at different breathing volumes of a healthy volunteer were performed using a microbalance and humidity sensor. Twenty-three HMEs from 6 different manufacturers were tested. Associations were determined between core weight, weight change, breathing volume, and absolute humidity, using both linear and nonlinear mixed effects models. Water exchange of the 23 HMEs at a breathing volume of 0.5 L varies between 0.5 and 3.6 mg. Both water exchange and wet core weight correlate strongly with the end-inspiratory absolute humidity values (r2 =0.89/0.87). Hygroscopic salt increases core weight. The 23 tested HMEs for laryngectomized patients show wide variation in water exchange performance. Water exchange correlates well with the end-inspiratory absolute humidity outcome, which validates the ex vivo weight change method. Wet core weight is a predictor of HME performance. Hygroscopic salt increases the weight of the core material. The results of this study can help medical professionals to obtain a more founded opinion about the performance of available HMEs for pulmonary rehabilitation in laryngectomized patients, and allow them to make an informed decision about which HME type to use. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.B43D2148B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.B43D2148B">Assessing Near-surface Heat, Water Vapor and Carbon Dioxide Exchange Over a Coastal Salt-marsh</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Bogoev, I.; O'Halloran, T. L.; LeMoine, J. 2017-12-01 Coastal ecosystems play an important role in mitigating the effects of climate change by storing significant quantities of carbon. A growing number of studies suggest that vegetated estuarine habitats, specifically salt marshes, have high long-term rates of carbon sequestration, perhaps even higher than mature tropical and temperate forests. Large amounts of carbon, accumulated over thousands of years, are stored in the plant materials and sediment. Improved understanding of the factors that control energy and carbon exchange is needed to better guide restoration and conservation management practices. To that end, we recently established an observation system to study marsh-atmosphere interactions within the North Inlet-Winyah Bay National Estuarine Research Reserve. Near-surface fluxes of heat, water vapor (H2O) and carbon dioxide (CO2) were measured by an eddy-covariance system consisting of an aerodynamic open-path H2O / CO2 gas analyzer with a spatially integrated 3D sonic anemometer/thermometer (IRGASON). The IRGASON instrument provides co-located and highly synchronized, fast response H2O, CO2 and air- temperature measurements, which eliminates the need for spectral corrections associated with the separation between the sonic anemometer and the gas analyzer. This facilitates calculating the instantaneous CO2 molar mixing ratio relative to dry air. Fluxes computed from CO2 and H2O mixing ratios, which are conserved quantities, do not require post-processing corrections for air-density changes associated with temperature and water vapor fluctuations. These corrections are particularly important for CO2, because they could be even larger than the measured flux. Here we present the normalized frequency spectra of air temperature, water vapor and CO2, as well as their co-spectra with the co-located vertical wind. We also show mean daily cycles of sensible, latent and CO2 fluxes and analyze correlations with air/water temperature, wind speed and light availability. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/874299','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/servlets/purl/874299">Method and apparatus for extracting water from air</a> <a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a> Spletzer, Barry L.; Callow, Diane Schafer; Marron, Lisa C.; Salton, Jonathan R. 2002-01-01 The present invention provides a method and apparatus for extracting liquid water from moist air using minimal energy input. The method comprises compressing moist air under conditions that foster the condensation of liquid water. The air can be decompressed under conditions that do not foster the vaporization of the condensate. The decompressed, dried air can be exchanged for a fresh charge of moist air and the process repeated. The liquid condensate can be removed for use. The apparatus can comprise a compression chamber having a variable internal volume. An intake port allows moist air into the compression chamber. An exhaust port allows dried air out of the compression chamber. A condensation device fosters condensation at the desired conditions. A condensate removal port allows liquid water to be removed. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/21350390-two-phase-gas-liquid-flow-characteristics-inside-plate-heat-exchanger','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/21350390-two-phase-gas-liquid-flow-characteristics-inside-plate-heat-exchanger">Two-phase gas-liquid flow characteristics inside a plate heat exchanger</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Nilpueng, Kitti; Wongwises, Somchai In the present study, the air-water two-phase flow characteristics including flow pattern and pressure drop inside a plate heat exchanger are experimentally investigated. A plate heat exchanger with single pass under the condition of counter flow is operated for the experiment. Three stainless steel commercial plates with a corrugated sinusoidal shape of unsymmetrical chevron angles of 55 and 10 are utilized for the pressure drop measurement. A transparent plate having the same configuration as the stainless steel plates is cast and used as a cover plate in order to observe the flow pattern inside the plate heat exchanger. The air-watermore » mixture flow which is used as a cold stream is tested in vertical downward and upward flow. The results from the present experiment show that the annular-liquid bridge flow pattern appeared in both upward and downward flows. However, the bubbly flow pattern and the slug flow pattern are only found in upward flow and downward flow, respectively. The variation of the water and air velocity has a significant effect on the two-phase pressure drop. Based on the present data, a two-phase multiplier correlation is proposed for practical application. (author)« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17874769','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17874769">Air-sea exchange fluxes of synthetic polycyclic musks in the North Sea and the Arctic.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Xie, Zhiyong; Ebinghaus, Ralf; Temme, Christian; Heemken, Olaf; Ruck, Wolfgang 2007-08-15 Synthetic polycyclic musk fragrances Galaxolide (HHCB) and Tonalide (AHTN) were measured simultaneously in air and seawater in the Arctic and the North Sea and in the rural air of northern Germany. Median concentrations of gas-phase HHCB and AHTN were 4 and 18 pg m(-3) in the Arctic, 28 and 18 pg m(-3) in the North Sea, and 71 and 21 pg m(-3) in northern Germany, respectively. Various ratios of HHCB/AHTN implied that HHCB is quickly removed by atmospheric degradation, while AHTN is relatively persistent in the atmosphere. Dissolved concentrations ranged from 12 to 2030 pg L(-1) for HHCB and from below the method detection limit (3 pg L(-1)) to 965 pg L(-1) for AHTN with median values of 59 and 23 pg L(-1), respectively. The medians of volatilization fluxes for HHCB and AHTN were 27.2 and 14.2 ng m(-2) day(-1) and the depositional fluxes were 5.9 and 3.3 ng m(-2) day(-1), respectively, indicating water-to-air volatilization is a significant process to eliminate HHCB and AHTN from the North Sea. In the Arctic, deposition fluxes dominated the air-sea gas exchange of HHCB and AHTN, suggesting atmospheric input controls the levels of HHCB and AHTN in the polar region. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JGRC..123.2293B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JGRC..123.2293B">Wave Attenuation and Gas Exchange Velocity in Marginal Sea Ice Zone</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Bigdeli, A.; Hara, T.; Loose, B.; Nguyen, A. T. 2018-03-01 The gas transfer velocity in marginal sea ice zones exerts a strong control on the input of anthropogenic gases into the ocean interior. In this study, a sea state-dependent gas exchange parametric model is developed based on the turbulent kinetic energy dissipation rate. The model is tuned to match the conventional gas exchange parametrization in fetch-unlimited, fully developed seas. Next, fetch limitation is introduced in the model and results are compared to fetch limited experiments in lakes, showing that the model captures the effects of finite fetch on gas exchange with good fidelity. Having validated the results in fetch limited waters such as lakes, the model is next applied in sea ice zones using an empirical relation between the sea ice cover and the effective fetch, while accounting for the sea ice motion effect that is unique to sea ice zones. The model results compare favorably with the available field measurements. Applying this parametric model to a regional Arctic numerical model, it is shown that, under the present conditions, gas flux into the Arctic Ocean may be overestimated by 10% if a conventional parameterization is used. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15959823','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15959823">Environmental sensitivity of gas exchange in different-sized trees.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> McDowell, Nate G; Licata, Julian; Bond, Barbara J 2005-08-01 The carbon isotope signature (delta13C) of foliar cellulose from sunlit tops of trees typically becomes enriched as trees of the same species in similar environments grow taller, indicative of size-related changes in leaf gas exchange. However, direct measurements of gas exchange in common environmental conditions do not always reveal size-related differences, even when there is a distinct size-related trend in delta13C of the very foliage used for the gas exchange measurements. Since delta13C of foliage predominately reflects gas exchange during spring when carbon is incorporated into leaf cellulose, this implies that gas exchange differences in different-sized trees are most likely to occur in favorable environmental conditions during spring. If gas exchange differs with tree size during wet but not dry conditions, then this further implies that environmental sensitivity of leaf gas exchange varies as a function of tree size. These implications are consistent with theoretical relationships among height, hydraulic conductance and gas exchange. We investigated the environmental sensitivity of gas exchange in different-sized Douglas-fir (Pseudotsuga menziesii) via a detailed process model that specifically incorporates size-related hydraulic conductance [soil-plant-atmosphere (SPA)], and empirical measurements from both wet and dry periods. SPA predicted, and the empirical measurements verified, that differences in gas exchange associated with tree size are greatest in wet and mild environmental conditions and minimal during drought. The results support the hypothesis that annual net carbon assimilation and transpiration of trees are limited by hydraulic capacity as tree size increases, even though at particular points in time there may be no difference in gas exchange between different-sized trees. Maximum net ecosystem exchange occurs in spring in Pacific Northwest forests; therefore, the presence of hydraulic limitations during this period may play a large role </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRG..122.1011H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRG..122.1011H">Gas transfer velocities in small forested ponds</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Holgerson, Meredith A.; Farr, Emily R.; Raymond, Peter A. 2017-05-01 Inland waters actively exchange gases with the atmosphere, and the gas exchange rate informs system biogeochemistry, ecology, and global carbon budgets. Gas exchange in medium- to large-sized lakes is largely regulated by wind; yet less is known about processes regulating gas transfer in small ponds where wind speeds are low. In this study, we determined the gas transfer velocity, k600, in four small (<250 m2) ponds by using a propane (C3H8) gas injection. When estimated across 12 h periods, the average k600 ranged from 0.19 to 0.72 m d-1 across the ponds. We also estimated k600 at 2 to 3 h intervals during the day and evaluated the relationship with environmental conditions. The average daytime k600 ranged from 0.33 to 1.83 m d-1 across the ponds and was best predicted by wind speed and air or air-water temperature; however, the explanatory power was weak (R2 < 0.27) with high variability within and among ponds. To compare our results to larger water bodies, we compiled direct measurements of k600 from 67 ponds and lakes worldwide. Our k600 estimates were within the range of estimates for other small ponds, and variability in k600 increased with lake size. However, the majority of studies were conducted on medium-sized lakes (0.01 to 1 km2), leaving small ponds and large lakes understudied. Overall, this study adds four small ponds to the existing body of research on gas transfer velocities from inland waters and highlights uncertainty in k600, with implications for calculating metabolism and carbon emissions in inland waters. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4052457','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4052457">Responses of sap flow, leaf gas exchange and growth of hybrid aspen to elevated atmospheric humidity under field conditions</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Niglas, Aigar; Kupper, Priit; Tullus, Arvo; Sellin, Arne 2014-01-01 An increase in average air temperature and frequency of rain events is predicted for higher latitudes by the end of the 21st century, accompanied by a probable rise in air humidity. We currently lack knowledge on how forest trees acclimate to rising air humidity in temperate climates. We analysed the leaf gas exchange, sap flow and growth characteristics of hybrid aspen (Populus tremula × P. tremuloides) trees growing at ambient and artificially elevated air humidity in an experimental forest plantation situated in the hemiboreal vegetation zone. Humidification manipulation did not affect the photosynthetic capacity of plants, but did affect stomatal responses: trees growing at elevated air humidity had higher stomatal conductance at saturating photosynthetically active radiation (gs sat) and lower intrinsic water-use efficiency (IWUE). Reduced stomatal limitation of photosynthesis in trees grown at elevated air humidity allowed slightly higher net photosynthesis and relative current-year height increments than in trees at ambient air humidity. Tree responses suggest a mitigating effect of higher air humidity on trees under mild water stress. At the same time, trees at higher air humidity demonstrated a reduced sensitivity of IWUE to factors inducing stomatal closure and a steeper decline in canopy conductance in response to water deficit, implying higher dehydration risk. Despite the mitigating impact of increased air humidity under moderate drought, a future rise in atmospheric humidity at high latitudes may be disadvantageous for trees during weather extremes and represents a potential threat in hemiboreal forest ecosystems. PMID:24887000 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/7836191','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/7836191">Analysis of factors affecting gas exchange in intravascular blood gas exchanger.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Niranjan, S C; Clark, J W; San, K Y; Zwischenberger, J B; Bidani, A 1994-10-01 A mathematical model of an intravascular hollow-fiber gas-exchange device, called IVOX, has been developed using a Krogh cylinder-like approach with a repeating unit structure comprised of a single fiber with gas flowing through its lumen surrounded by a coaxial cylinder of blood flowing in the opposite direction. Species mass balances on O2 and CO2 result in a nonlinear coupled set of convective-diffusion parabolic partial differential equations that are solved numerically using an alternating-direction implicit finite-difference method. Computed results indicated the presence of a large resistance to gas transport on the external (blood) side of the hollow-fiber exchanger. Increasing gas flow through the device favored CO2 removal from but not O2 addition to blood. Increasing blood flow over the device favored both CO2 removal as well as O2 addition. The rate of CO2 removal increased linearly with the transmural PCO2 gradient imposed across the device. The effect of fiber crimping on blood phase mass transfer resistance was evaluated indirectly by varying species blood diffusivity. Computed results indicated that CO2 excretion by IVOX can be significantly enhanced with improved bulk mixing of vena caval blood around the IVOX fibers. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=240307&keyword=water+AND+gas+AND+exchange&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=240307&keyword=water+AND+gas+AND+exchange&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">Controls on gas transfer velocities in a large river</a> <a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> The emission of biogenic gases from large rivers can be an important component of regional greenhouse gas budgets. However, emission rate estimates are often poorly constrained due to uncertainties in the air-water gas exchange rate. We used the floating chamber method to estim... </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.H53A1376G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.H53A1376G">The Effect of Thermal Convection on Earth-Atmosphere CO2 Gas Exchange in Aggregated Soil</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ganot, Y.; Weisbrod, N.; Dragila, M. I. 2011-12-01 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. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19285150','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19285150">Gas exchange in avian embryos and hatchlings.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Mortola, Jacopo P 2009-08-01 The avian egg has been proven to be an excellent model for the study of the physical principles and the physiological characteristics of embryonic gas exchange. In recent years, it has become a model for the studies of the prenatal development of pulmonary ventilation, its chemical control and its interaction with extra-pulmonary gas exchange. Differently from mammals, in birds the initiation of pulmonary ventilation and the transition from diffusive to convective gas exchange are gradual and slow-occurring events amenable to detailed investigations. The absence of the placenta and of the mother permits the study of the mechanisms of embryonic adaptation to prenatal perturbations in a way that would be impossible with mammalian preparations. First, this review summarises the general aspects of the natural history of the avian egg that are pertinent to embryonic metabolism, growth and gas exchange and the characteristics of the structures participating in gas exchange. Then, the review focuses on the embryonic development of pulmonary ventilation, its regulation in relation to the embryo's environment and metabolic state, the effects that acute or sustained changes in embryonic temperature or oxygenation can have on growth, metabolism and ventilatory control. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27609764','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27609764">The opening-closing rhythms of the subelytral cavity associated with gas exchange patterns in diapausing Colorado potato beetle, Leptinotarsa decemlineata.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Kuusik, Aare; Jõgar, Katrin; Metspalu, Luule; Ploomi, Angela; Merivee, Enno; Must, Anne; Williams, Ingrid H; Hiiesaar, Külli; Sibul, Ivar; Mänd, Marika 2016-11-01 The opening-closing rhythms of the subelytral cavity and associated gas exchange patterns were monitored in diapausing Leptinotarsa decemlineata beetles. Measurements were made by means of a flow-through CO 2 analyser and a coulometric respirometer. Under the elytra of these beetles there is a more or less tightly enclosed space, the subelytral cavity (SEC). When the cavity was tightly closed, air pressure inside was sub-atmospheric, as a result of oxygen uptake into the tracheae by the beetle. In about half of the beetles, regular opening-closing rhythms of the SEC were observed visually and also recorded; these beetles displayed a discontinuous gas exchange pattern. The SEC opened at the start of the CO 2 burst and was immediately closed. On opening, a rapid passive suction inflow of atmospheric air into the SEC occurred, recorded coulometrically as a sharp upward peak. As the CO 2 burst lasted beyond the closure of the SEC, we suggest that most of the CO 2 was expelled through the mesothoracic spiracles. In the remaining beetles, the SEC was continually semi-open, and cyclic gas exchange was exhibited. The locking mechanisms and structures between the elytra and between the elytra and the body were examined under a stereomicroscope and by means of microphotography. We conclude that at least some of the L. decemlineata diapausing beetles were able to close their subelytral cavity tightly, and that the cavity then served as a water-saving device. © 2016. Published by The Company of Biologists Ltd. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=62405&keyword=FAN&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=62405&keyword=FAN&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">FACTORS AFFECTING AIR EXCHANGE IN TWO HOUSES</a> <a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> Air exchange rate is critical to determining the relationship between indoor and outdoor concentrations of hazardous pollutants. Approximately 150 air exchange experiments were completed in two residences: a two-story detached house located in Redwood City, CA and a three-story... </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/21355','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/21355">Radiation-use efficiency and gas exchange responses to water and nutrient availability in irrigated and fertilized stands of sweetgum and sycamore</a> <a target="_blank" href="http://www.fs.usda.gov/treesearch/">Treesearch</a> Christopher B. Allen; Rodney E. Will; Robert C. McGravey; David R. Coyle; Mark D. Coleman 2005-01-01 We investigated how water and nutrient availability affect radiation-use effeciency (e) and assessed leaf gas exchange as a possible mechanism for shifts in e. We measured aboveground net primary production (ANPP) and annual photosynthetically active radiation (PAR) capture to calculate e as well as leaf-level physiological variables (light-saturated net photosynthesis... </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010005246','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010005246">BOREAS TE-12 Leaf Gas Exchange Data</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Arkebauer, Timothy J.; Yang, Litao 2000-01-01 The BOREAS TE-12 team collected several data sets in support of its efforts to characterize and interpret information on the reflectance, transmittance, and gas exchange of boreal vegetation. This data set contains measurements of leaf gas exchange conducted in the SSA during the growing seasons of 1994 and 1995 using a portable gas exchange system. The data are stored in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Center (DAAC). </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_10");'>10</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li class="active">12</li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_13" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active">13</li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="241"> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/873724','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/servlets/purl/873724">Method and apparatus for extracting water from air</a> <a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a> Spletzer, Barry L. 2001-01-01 The present invention provides a method and apparatus for extracting liquid water from moist air using minimal energy input. The method comprises compressing moist air under conditions that foster the condensation of liquid water (ideally isothermal to a humidity of 1.0, then adiabatic thereafter). The air can be decompressed under conditions that do not foster the vaporization of the condensate. The decompressed, dried air can be exchanged for a fresh charge of moist air and the process repeated. The liquid condensate can be removed for use. The apparatus can comprise a compression chamber having a variable internal volume. An intake port allows moist air into the compression chamber. An exhaust port allows dried air out of the compression chamber. A condensation device fosters condensation at the desired conditions. A condensate removal port allows liquid water to be removed. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16271812','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16271812">Atmospheric concentrations and air-sea exchanges of nonylphenol, tertiary octylphenol and nonylphenol monoethoxylate in the North Sea.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Xie, Zhiyong; Lakaschus, Soenke; Ebinghaus, Ralf; Caba, Armando; Ruck, Wolfgang 2006-07-01 Concentrations of nonylphenol isomers (NP), tertiary octylphenol (t-OP) and nonylphenol monoethoxylate isomers (NP1EO) have been simultaneously determined in the sea water and atmosphere of the North Sea. A decreasing concentration profile appeared following the distance increasing from the coast to the central part of the North Sea. Air-sea exchanges of t-OP and NP were estimated using the two-film resistance model based upon relative air-water concentrations and experimentally derived Henry's law constant. The average of air-sea exchange fluxes was -12+/-6 ng m(-2)day(-1) for t-OP and -39+/-19 ng m(-2)day(-1) for NP, which indicates a net deposition is occurring. These results suggest that the air-sea vapour exchange is an important process that intervenes in the mass balance of alkylphenols in the North Sea. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25944919','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25944919">Interruption to cutaneous gas exchange is not a likely mechanism of WNS-associated death in bats.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Carey, Charleve S; Boyles, Justin G 2015-07-01 Pseudogymnoascus destructans is the causative fungal agent of white-nose syndrome (WNS), an emerging fungal-borne epizootic. WNS is responsible for a catastrophic decline of hibernating bats in North America, yet we have limited understanding of the physiological interactions between pathogen and host. Pseudogymnoascus destructans severely damages wings and tail membranes, by causing dryness that leads to whole sections crumbling off. Four possible mechanisms have been proposed by which infection could lead to dehydration; in this study, we tested one: P. destructans infection could cause disruption to passive gas-exchange pathways across the wing membranes, thereby causing a compensatory increase in water-intensive pulmonary respiration. We hypothesized that total evaporative water loss would be greater when passive gas exchange was inhibited. We found that bats did not lose more water when passive pathways were blocked. This study provides evidence against the proposed proximal mechanism that disruption to passive gas exchange causes dehydration and death to WNS-infected bats. © 2015. Published by The Company of Biologists Ltd. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70040729','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70040729">The impact of lower sea-ice extent on Arctic greenhouse-gas exchange</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Parmentier, Frans-Jan W.; Christensen, Torben R.; Sørensen, Lise Lotte; Rysgaard, Søren; McGuire, A. David; Miller, Paul A.; Walker, Donald A. 2013-01-01 In September 2012, Arctic sea-ice extent plummeted to a new record low: two times lower than the 1979–2000 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 marine–atmosphere 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. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29267801','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29267801">Gas exchange and antioxidant activity in seedlings of C opaifera langsdorffii Desf. under different water conditions.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Rosa, Derek B C J; Scalon, Silvana P Q; Cremon, Thais; Ceccon, Felipe; Dresch, Daiane M 2017-01-01 The aim of this study was to evaluate gas exchange, efficiency of the photosynthetic apparatus, and antioxidant activity in Copaifera langsdorffii Desf. The seedlings were cultivated under different conditions of water availability, in order to improve the utilization efficiency of available water resources. The seedlings were cultivated in four different water retention capacities (WRC- 25%, 50%, 75%, and 100%), and evaluated at four different time (T- 30, 60, 90, and 120 days). During the experimental period, seedlings presented the highest values for carboxylation efficiency of Rubisco (A/Ci), intrinsic water use efficiency (IWUE = A/gs), chlorophyll index, and stomatal opening, when grown in the substrate with 75% WRC, but the stomatal index (SI) was less the 25% WRC. The efficiency of photosystem II was not significantly altered by the treatments. Comparison between the extreme treatments in terms of water availability, represented by 25% and 100% WRC, represent stress conditions for the species. Water availability causes a high activity of antioxidant enzymes (superoxide dismutase, peroxidase, and catalase) in the plant. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.H23D1302T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.H23D1302T">Direct measurements of wind-water momentum coupling in a marsh with emergent vegetation and implications for gas transfer estimates</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Tse, I.; Poindexter, C.; Variano, E. A. 2013-12-01 Among the numerous ecological benefits of restoring wetlands is carbon sequestration. As emergent vegetation thrive, atmospheric CO2 is removed and converted into biomass that gradually become additional soil. Forecasts and management for these systems rely on accurate knowledge of gas exchange between the atmosphere and the wetland surface waters. Our previous work showed that the rate of gas transfer across the air-water interface is affected by the amount of water column mixing caused by winds penetrating through the plant canopy. Here, we present the first direct measurements of wind-water momentum coupling made within a tule marsh. This work in Twitchell Island in the California Delta shows how momentum is imparted into the water from wind stress and that this wind stress interacts with the surface waters in an interesting way. By correlating three-component velocity signals from a sonic anemometer placed within the plant canopy with data from a novel Volumetric Particle Imager (VoPI) placed in the water, we measure the flux of kinetic energy through the plant canopy and the time-scale of the response. We also use this unique dataset to estimate the air-water drag coefficient using an adjoint method. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4196106','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4196106">Nondestructive natural gas hydrate recovery driven by air and carbon dioxide</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Kang, Hyery; Koh, Dong-Yeun; Lee, Huen 2014-01-01 Current technologies for production of natural gas hydrates (NGH), which include thermal stimulation, depressurization and inhibitor injection, have raised concerns over unintended consequences. The possibility of catastrophic slope failure and marine ecosystem damage remain serious challenges to safe NGH production. As a potential approach, this paper presents air-driven NGH recovery from permeable marine sediments induced by simultaneous mechanisms for methane liberation (NGH decomposition) and CH4-air or CH4-CO2/air replacement. Air is diffused into and penetrates NGH and, on its surface, forms a boundary between the gas and solid phases. Then spontaneous melting proceeds until the chemical potentials become equal in both phases as NGH depletion continues and self-regulated CH4-air replacement occurs over an arbitrary point. We observed the existence of critical methane concentration forming the boundary between decomposition and replacement mechanisms in the NGH reservoirs. Furthermore, when CO2 was added, we observed a very strong, stable, self-regulating process of exchange (CH4 replaced by CO2/air; hereafter CH4-CO2/air) occurring in the NGH. The proposed process will work well for most global gas hydrate reservoirs, regardless of the injection conditions or geothermal gradient. PMID:25311102 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25827140','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25827140">Air-Seawater Exchange of Organochlorine Pesticides along the Sediment Plume of a Large Contaminated River.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Lin, Tian; Guo, Zhigang; Li, Yuanyuan; Nizzetto, Luca; Ma, Chuanliang; Chen, Yingjun 2015-05-05 Gaseous exchange fluxes of organochlorine pesticides (OCPs) across the air-water interface of the coastal East China Sea were determined in order to assess whether the contaminated plume of the Yangtze River could be an important regional source of OCPs to the atmosphere. Hexachlorocyclohexanes (HCHs), chlordane compounds (CHLs), and dichlorodiphenyltrichloroethanes (DDTs) were the most frequently detected OCPs in air and water. Air-water exchange was mainly characterized by net volatilization for all measured OCPs. The net gaseous exchange flux ranged 10-240 ng/(m2·day) for γ-HCH, 60-370 ng/(m2·day) for trans-CHL, 97-410 ng/(m2·day) for cis-CHL, and ∼0 (e.g., equilibrium) to 490 ng/(m2·day) for p,p'-DDE. We found that the plume of the large contaminated river can serve as a significant regional secondary atmospheric source of legacy contaminants released in the catchment. In particular, the sediment plume represented the relevant source of DDT compounds (especially p,p'-DDE) sustaining net degassing when clean air masses from the open ocean reached the plume area. In contrast, a mass balance showed that, for HCHs, contaminated river discharge (water and sediment) plumes were capable of sustaining volatilization throughout the year. These results demonstrate the inconsistencies in the fate of HCHs and DDTs in this large estuarine system with declining primary sources. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhDT.........9G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhDT.........9G">Investigation of water droplet dynamics in PEM fuel cell gas channels</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Gopalan, Preethi Water management in Proton Exchange Membrane Fuel Cell (PEMFC) has remained one of the most important issues that need to be addressed before its commercialization in automotive applications. Accumulation of water on the gas diffusion layer (GDL) surface in a PEMFC introduces a barrier for transport of reactant gases through the GDL to the catalyst layer. Despite the fact that the channel geometry is one of the key design parameters of a fluidic system, very limited research is available to study the effect of microchannel geometry on the two-phase flow structure. In this study, the droplet-wall dynamics and two-phase pressure drop across the water droplet present in a typical PEMFC channel, were examined in auto-competitive gas channel designs (0.4 x 0.7 mm channel cross section). The liquid water flow pattern inside the gas channel was analyzed for different air velocities. Experimental data was analyzed using the Concus-Finn condition to determine the wettability characteristics in the corner region. It was confirmed that the channel angle along with the air velocity and the channel material influences the water distribution and holdup within the channel. Dynamic contact angle emerged as an important parameter in controlling the droplet-wall interaction. Experiments were also performed to understand how the inlet location of the liquid droplet on the GDL surface affects the droplet dynamic behavior in the system. It was found that droplets emerging near the channel wall or under the land lead to corner filling of the channel. Improvements in the channel design has been proposed based on the artificial channel roughness created to act as capillary grooves to transport the liquid water away from the land area. For droplets emerging near the center of the channel, beside the filling and no-filling behavior reported in the literature, a new droplet jumping behavior was observed. As droplets grew and touched the sidewalls, they jumped off to the sidewall leaving the </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.H51L..04B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.H51L..04B">Noble Gas signatures of Enhanced Oil Recovery</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Barry, P. H.; Kulongoski, J. T.; Tyne, R. L.; Hillegonds, D.; Byrne, D. J.; Landon, M. K.; Ballentine, C. J. 2017-12-01 Noble gases are powerful tracers of fluids from various oil and gas production activities in hydrocarbon reservoirs and nearby groundwater. Non-radiogenic noble gases are introduced into undisturbed oil and natural gas reservoirs through exchange with formation waters [1-3]. Reservoirs with extensive hydraulic fracturing, injection for enhanced oil recovery (EOR), and/or waste disposal also show evidence for a component of noble gases introduced from air [4]. Isotopic and elemental ratios of noble gases can be used to 1) assess the migration history of the injected and formation fluids, and 2) determine the extent of exchange between multiphase fluids in different reservoirs. We present noble gas isotope and abundance data from casing, separator and injectate gases of the Lost Hills and Fruitvale oil fields in the San Joaquin basin, California. Samples were collected as part of the California State Water Resource Control Board's Oil and Gas Regional Groundwater Monitoring Program. Lost Hills (n=7) and Fruitvale (n=2) gases are geochemically distinct and duplicate samples are highly reproducible. Lost Hills casing gas samples were collected from areas where EOR and hydraulic fracturing has occurred in the past several years, and from areas where EOR is absent. The Fruitvale samples were collected from a re-injection port. All samples are radiogenic in their He isotopes, typical of a crustal environment, and show enrichments in heavy noble gases, resulting from preferential adsorption on sediments. Fruitvale samples reflect air-like surface conditions, with higher air-derived noble gas concentrations. Lost Hills gases show a gradation from pristine crustal signatures - indicative of closed-system exchange with formation fluids - to strongly air-contaminated signatures in the EOR region. Pristine samples can be used to determine the extent of hydrocarbon exchange with fluids, whereas samples with excess air can be used to quantify the extent of EOR. Determining noble </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26214174','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26214174">Effect of Sediment Gas Voids and Ebullition on Benthic Solute Exchange.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Flury, Sabine; Glud, Ronnie N; Premke, Katrin; McGinnis, Daniel F 2015-09-01 The presence of free gas in sediments and ebullition events can enhance the pore water transport and solute exchange across the sediment-water interface. However, we experimentally and theoretically document that the presence of free gas in sediments can counteract this enhancement effect. The apparent diffusivities (Da) of Rhodamine WT and bromide in sediments containing 8-18% gas (Da,YE) were suppressed by 7-39% compared to the control (no gas) sediments (Da,C). The measured ratios of Da,YE:Da,C were well within the range of ratios predicted by a theoretical soil model for gas-bearing soils. Whereas gas voids in sediments reduce the Da for soluble species, they represent a shortcut for low-soluble species such as methane and oxygen. Therefore, the presence of even minor amounts of gas can increase the fluxes of low-soluble species (i.e., gases) by several factors, while simultaneously suppressing fluxes of dissolved species. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA615405','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA615405">Forecasting Foreign Currency Exchange Rates for Air Force Budgeting</a> <a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a> 2015-03-26 FORECASTING FOREIGN CURRENCY EXCHANGE RATES FOR AIR FORCE BUDGETING THESIS MARCH 2015...States. AFIT-ENV-MS-15-M-178 FORECASTING FOREIGN CURRENCY EXCHANGE RATES FOR AIR FORCE BUDGETING THESIS Presented to the Faculty...FORECASTING FOREIGN CURRENCY EXCHANGE RATES FOR AIR FORCE BUDGETING Nicholas R. Gardner, BS Captain, USAF Committee Membership: Lt Col Jonathan </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017APS..DFDL20011S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017APS..DFDL20011S">Boundary layers at a dynamic interface: air-sea exchange of heat and mass</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Szeri, Andrew 2017-11-01 Exchange of mass or heat across a turbulent liquid-gas interface is a problem of critical interest, especially in air-sea transfer of natural and man-made gases involved in climate change. The goal in this research area is to determine the gas flux from air to sea or vice versa. For sparingly soluble non-reactive gases, this is controlled by liquid phase turbulent velocity fluctuations that act on the thin species concentration boundary layer on the liquid side of the interface. If the fluctuations in surface-normal velocity and gas concentration differences are known, then it is possible to determine the turbulent contribution to the gas flux. However, there is no suitable fundamental direct approach in the general case where neither of these quantities can be easily measured. A new approach is presented to deduce key aspects about the near-surface turbulent motions from remote measurements, which allows one to determine the gas transfer velocity, or gas flux per unit area if overall concentration differences are known. The approach is illustrated with conceptual examples. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040090386&hterms=water+gas+exchange&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dwater%2Bgas%2Bexchange','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040090386&hterms=water+gas+exchange&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dwater%2Bgas%2Bexchange">Steady-state canopy gas exchange: system design and operation</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Bugbee, B. 1992-01-01 This paper describes the use of a commercial growth chamber for canopy photosynthesis, respiration, and transpiration measurements. The system was designed to measure transpiration via water vapor fluxes, and the importance of this measurement is discussed. Procedures for continuous measurement of root-zone respiration are described, and new data is presented to dispel myths about sources of water vapor interference in photosynthesis and in the measurement of CO2 by infrared gas analysis. Mitchell (1992) has described the fundamentals of various approaches to measuring photosynthesis. Because our system evolved from experience with other types of single-leaf and canopy gas-exchange systems, it is useful to review advantages and disadvantages of different systems as they apply to various research objectives. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19800000519&hterms=Water+turbine&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DWater%2Bturbine','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19800000519&hterms=Water+turbine&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DWater%2Bturbine">Thermodynamic and transport properties of air/water mixtures</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Fessler, T. E. 1981-01-01 Subroutine WETAIR calculates properties at nearly 1,500 K and 4,500 atmospheres. Necessary inputs are assigned values of combinations of density, pressure, temperature, and entropy. Interpolation of property tables obtains dry air and water (steam) properties, and simple mixing laws calculate properties of air/water mixture. WETAIR is used to test gas turbine engines and components operating in relatively humid air. Program is written in SFTRAN and FORTRAN. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28577386','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28577386">Hydraulics and gas exchange recover more rapidly from severe drought stress in small pot-grown grapevines than in field-grown plants.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Romero, Pascual; Botía, Pablo; Keller, Markus 2017-09-01 Modifications of plant hydraulics and shoot resistances (R shoot ) induced by water withholding followed by rewatering, and their relationships with plant water status, leaf gas exchange and water use efficiency at the leaf level, were investigated in pot-grown and field-grown, own-rooted Syrah grapevines in an arid climate. Water stress induced anisohydric behavior, gradually reducing stomatal conductance (g s ) and leaf photosynthesis (A) in response to decreasing midday stem water potential (Ψ s ). Water stress also rapidly increased intrinsic water-use efficiency (A/g s ); this effect persisted for many days after rewatering. Whole-plant (K plant ), canopy (K canopy ), shoot (K shoot ) and leaf (K leaf ) hydraulic conductances decreased during water stress, in tune with the gradual decrease in Ψ s , leaf gas exchange and whole plant water use. Water-stressed vines also had a lower Ψ gradient between stem and leaf (ΔΨ l ), which was correlated with lower leaf transpiration rate (E). E and ΔΨ l increased with increasing vapour pressure deficit (VPD) in non-stressed control vines but not in stressed vines. Perfusion of xylem-mobile dye showed that water flow to petioles and leaves was substantially reduced or even stopped under moderate and severe drought stress. Leaf blade hydraulic resistance accounted for most of the total shoot resistance. However, hydraulic conductance of the whole root system (K root ) was not significantly reduced until water stress became very severe in pot-grown vines. Significant correlations between K plant , K canopy and Ψ s , K canopy and leaf gas exchange, K leaf and Ψ s , and K leaf and A support a link between water supply, leaf water status and gas exchange. Upon re-watering, Ψ s recovered faster than gas exchange and leaf-shoot hydraulics. A gradual recovery of hydraulic functionality of plant organs was also observed, the leaves being the last to recover after rewatering. In pot-grown vines, K canopy recovered rather </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/868548','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/servlets/purl/868548">Water augmented indirectly-fired gas turbine systems and method</a> <a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a> Bechtel, Thomas F.; Parsons, Jr., Edward J. 1992-01-01 An indirectly-fired gas turbine system utilizing water augmentation for increasing the net efficiency and power output of the system is described. Water injected into the compressor discharge stream evaporatively cools the air to provide a higher driving temperature difference across a high temperature air heater which is used to indirectly heat the water-containing air to a turbine inlet temperature of greater than about 1,000.degree. C. By providing a lower air heater hot side outlet temperature, heat rejection in the air heater is reduced to increase the heat recovery in the air heater and thereby increase the overall cycle efficiency. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22103582','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22103582">Distribution and air-sea exchange of current-use pesticides (CUPs) from East Asia to the high Arctic Ocean.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Zhong, Guangcai; Xie, Zhiyong; Cai, Minghong; Möller, Axel; Sturm, Renate; Tang, Jianhui; Zhang, Gan; He, Jianfeng; Ebinghaus, Ralf 2012-01-03 Surface seawater and marine boundary layer air samples were collected on the ice-breaker R/V Xuelong (Snow Dragon) from the East China Sea to the high Arctic (33.23-84.5° N) in July to September 2010 and have been analyzed for six current-use pesticides (CUPs): trifluralin, endosulfan, chlorothalonil, chlorpyrifos, dacthal, and dicofol. In all oceanic air samples, the six CUPs were detected, showing highest level (>100 pg/m(3)) in the Sea of Japan. Gaseous CUPs basically decreased from East Asia (between 36.6 and 45.1° N) toward Bering and Chukchi Seas. The dissolved CUPs in ocean water ranged widely from <MDL to 111 pg/L. Latitudinal trends of α-endosulfan, chlorpyrifos, and dicofol in seawater were roughly consistent with their latitudinal trends in air. Trifluralin in seawater was relatively high in the Sea of Japan (35.2° N) and evenly distributed between 36.9 and 72.5° N, but it remained below the detection limit at the highest northern latitudes in Chukchi Sea. In contrast with other CUPs, concentrations of chlorothalonil and dacthal were more abundant in Chukchi Sea and in East Asia. The air-sea gas exchange of CUPs was generally dominated by net deposition. Latitudinal trends of fugacity ratios of α-endosulfan, chlorothalonil, and dacthal showed stronger deposition of these compounds in East Asia than in Chukchi Sea, while trifluralin showed stronger deposition in Chukchi Sea (-455 ± 245 pg/m(2)/day) than in the North Pacific (-241 ± 158 pg/m(2)/day). Air-sea gas exchange of chlorpyrifos varied from net volatilizaiton in East Asia (<40° N) to equilibrium or net deposition in the North Pacific and the Arctic. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1178521-guest-molecule-exchange-kinetics-ignik-sikumi-gas-hydrate-field-trial','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1178521-guest-molecule-exchange-kinetics-ignik-sikumi-gas-hydrate-field-trial">Guest Molecule Exchange Kinetics for the 2012 Ignik Sikumi Gas Hydrate Field Trial</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> White, Mark D.; Lee, Won Suk A commercially viable technology for producing methane from natural gas hydrate reservoirs remains elusive. Short-term depressurization field tests have demonstrated the potential for producing natural gas via dissociation of the clathrate structure, but the long-term performance of the depressurization technology ultimately requires a heat source to sustain the dissociation. A decade of laboratory experiments and theoretical studies have demonstrated the exchange of pure CO2 and N2-CO2 mixtures with CH4 in sI gas hydrates, yielding critical information about molecular mechanisms, recoveries, and exchange kinetics. Findings indicated the potential for producing natural gas with little to no production of water and rapidmore » exchange kinetics, generating sufficient interest in the guest-molecule exchange technology for a field test. In 2012 the U.S. DOE/NETL, ConocoPhillips Company, and Japan Oil, Gas and Metals National Corporation jointly sponsored the first field trial of injecting a mixture of N2-CO2 into a CH4-hydrate bearing formation beneath the permafrost on the Alaska North Slope. Known as the Ignik Sikumi #1 Gas Hydrate Field Trial, this experiment involved three stages: 1) the injection of a N2-CO2 mixture into a targeted hydrate-bearing layer, 2) a 4-day pressurized soaking period, and 3) a sustained depressurization and fluid production period. Data collected during the three stages of the field trial were made available after an extensive quality check. These data included continuous temperature and pressure logs, injected and recovered fluid compositions and volumes. The Ignik Sikumi #1 data set is extensive, but contains no direct evidence of the guest-molecule exchange process. This investigation is directed at using numerical simulation to provide an interpretation of the collected data. A numerical simulator, STOMP-HYDT-KE, was recently completed that solves conservation equations for energy, water, mobile fluid guest molecules, and hydrate </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24438580','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24438580">Argon used as dry suit insulation gas for cold-water diving.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Vrijdag, Xavier Ce; van Ooij, Pieter-Jan Am; van Hulst, Robert A 2013-06-03 Cold-water diving requires good thermal insulation because hypothermia is a serious risk. Water conducts heat more efficiently compared to air. To stay warm during a dive, the choice of thermal protection should be based on physical activity, the temperature of the water, and the duration of exposure. A dry suit, a diving suit filled with gas, is the most common diving suit in cold water. Air is the traditional dry suit inflation gas, whereas the thermal conductivity of argon is approximately 32% lower compared to that of air. This study evaluates the benefits of argon, compared to air, as a thermal insulation gas for a dry suit during a 1-h cold-water dive by divers of the Royal Netherlands Navy. Seven male Special Forces divers made (in total) 19 dives in a diving basin with water at 13 degrees C at a depth of 3 m for 1 h in upright position. A rubber dry suit and woollen undergarment were used with either argon (n = 13) or air (n = 6) (blinded to the divers) as suit inflation gas. Core temperature was measured with a radio pill during the dive. Before, halfway, and after the dive, subjective thermal comfort was recorded using a thermal comfort score. No diver had to abort the test due to cold. No differences in core temperature and thermal comfort score were found between the two groups. Core temperature remained unchanged during the dives. Thermal comfort score showed a significant decrease in both groups after a 60-min dive compared to baseline. In these tests the combination of the dry suit and undergarment was sufficient to maintain core temperature and thermal comfort for a dive of 1h in water at 13 degrees C. The use of argon as a suit inflation gas had no added value for thermal insulation compared to air for these dives. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_11");'>11</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li class="active">13</li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_14" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active">14</li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="261"> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010004659','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010004659">BOREAS TE-9 In Situ Diurnal Gas Exchange of NAS Boreal Forest Stands</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Margolis, Hank; Coyea, Marie; Dang, Qinglai 2000-01-01 The BOREAS TE-9 team collected several data sets related to chemical and photosynthetic properties of leaves in boreal forest tree species. The purpose of the BOREAS TE-09 study was threefold: 1) to provide in situ gas exchange data that will be used to validate models of photosynthetic responses to light, temperature, and carbon dioxide (CO2); 2) to compare the photosynthetic responses of different tree crown levels (upper and lower); and 3) to characterize the diurnal water potential curves for these sites to get an indication of the extent to which soil moisture supply to leaves might be limiting photosynthesis. The gas exchange data of the BOREAS NSA were collected to characterize diurnal gas exchange and water potential of two canopy levels of five boreal canopy cover types: young jack pine, old jack pine, old aspen, lowland old black spruce, and upland black spruce. These data were collected between 27-May-1994 and 17-Sep-1994. The data are provided in tabular ASCII files. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1060285','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1060285">Development and Validation of a Gas-Fired Residential Heat Pump Water Heater - Final Report</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Michael Garrabrant; Roger Stout; Paul Glanville 2013-01-21 For gas-fired residential water heating, the U.S. and Canada is predominantly supplied by minimum efficiency storage water heaters with Energy Factors (EF) in the range of 0.59 to 0.62. Higher efficiency and higher cost ($700 - $2,000) options serve about 15% of the market, but still have EFs below 1.0, ranging from 0.65 to 0.95. To develop a new class of water heating products that exceeds the traditional limit of thermal efficiency, the project team designed and demonstrated a packaged water heater driven by a gas-fired ammonia-water absorption heat pump. This gas-fired heat pump water heater can achieve EFs ofmore » 1.3 or higher, at a consumer cost of $2,000 or less. Led by Stone Mountain Technologies Inc. (SMTI), with support from A.O. Smith, the Gas Technology Institute (GTI), and Georgia Tech, the cross-functional team completed research and development tasks including cycle modeling, breadboard evaluation of two cycles and two heat exchanger classes, heat pump/storage tank integration, compact solution pump development, combustion system specification, and evaluation of packaged prototype GHPWHs. The heat pump system extracts low grade heat from the ambient air and produces high grade heat suitable for heating water in a storage tank for domestic use. Product features that include conventional installation practices, standard footprint and reasonable economic payback, position the technology to gain significant market penetration, resulting in a large reduction of energy use and greenhouse gas emissions from domestic hot water production.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.B52B..02D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.B52B..02D">High Resolution CH4 Emissions and Dissolved CH4 Measurements Elucidate Surface Gas Exchange Processes in Toolik Lake, Arctic Alaska</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Del Sontro, T.; Sollberger, S.; Kling, G. W.; Shaver, G. R.; Eugster, W. 2013-12-01 Approximately 14% of the Alaskan North Slope is covered in lakes of various sizes and depths. Diffusive carbon emissions (CH4 and CO2) from these lakes offset the tundra sink by ~20 %, but the offset would substantially increase if ebullitive CH4 emissions were also considered. Ultimately, arctic lake CH4 emissions are not insignificant in the global CH4 budget and their contribution is bound to increase due to impacts from climate change. Here we present high resolution CH4 emission data as measured via eddy covariance and a Los Gatos gas analyzer during the ice free period from Toolik Lake, a deep (20 m) Arctic lake located on the Alaskan North Slope, over the last few summers. Emissions are relatively low (< 25 mg CH4 m-2 d-1) with little variation over the summer. Diurnal variations regularly occur, however, with up to 3 times higher fluxes at night. Gas exchange is a relatively difficult process to estimate, but is normally done so as the product of the CH4 gradient across the air-water interface and the gas transfer velocity, k. Typically, k is determined based on the turbulence on the water side of the interface, which is most commonly approximated by wind speed; however, it has become increasingly apparent that this assumption does not remain valid across all water bodies. Dissolved CH4 profiles in Toolik revealed a subsurface peak in CH4 at the thermocline of up to 3 times as much CH4 as in the surface water. We hypothesize that convective mixing at night due to cooling surface waters brings the subsurface CH4 to the surface and causes the higher night fluxes. In addition to high resolution flux emission estimates, we also acquired high resolution data for dissolved CH4 in surface waters of Toolik Lake during the last two summers using a CH4 equilibrator system connected to a Los Gatos gas analyzer. Thus, having both the flux and the CH4 gradient across the air-water interface measured directly, we can calculate k and investigate the processes influencing </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19750027247&hterms=respiratory&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Drespiratory','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19750027247&hterms=respiratory&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Drespiratory">Automated measurement of respiratory gas exchange by an inert gas dilution technique</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Sawin, C. F.; Rummel, J. A.; Michel, E. L. 1974-01-01 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. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15562064','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15562064">Conductive heat exchange with a gel-coated circulating water mattress.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Bräuer, Anselm; Pacholik, Larissa; Perl, Thorsten; English, Michael John Murray; Weyland, Wolfgang; Braun, Ulrich 2004-12-01 The use of forced-air warming is associated with costs for the disposable blankets. As an alternative method, we studied heat transfer with a reusable gel-coated circulating water mattress placed under the back in eight healthy volunteers. Heat flux was measured with six calibrated heat flux transducers. Additionally, mattress temperature, skin temperature, and core temperature were measured. Water temperature was set to 25 degrees C, 30 degrees C, 35 degrees C, and 41 degrees C. Heat transfer was calculated by multiplying heat flux by contact area. Mattress temperature, skin temperature, and heat flux were used to determine the heat exchange coefficient for conduction. Heat flux and water temperature were related by the following equation: heat flux = 10.3 x water temperature - 374 (r(2) = 0.98). The heat exchange coefficient for conduction was 121 W . m(-2) . degrees C(-1). The maximal heat transfer with the gel-coated circulating water mattress was 18.4 +/- 3.3 W. Because of the small effect on the heat balance of the body, a gel-coated circulating water mattress placed only on the back cannot replace a forced-air warming system. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19910041723&hterms=water+gas+exchange&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dwater%2Bgas%2Bexchange','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19910041723&hterms=water+gas+exchange&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dwater%2Bgas%2Bexchange">Relationship between gas exchange, wind speed, and radar backscatter in a large wind-wave tank</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Wanninkhof, Richard H.; Bliven, L. F. 1991-01-01 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. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12095811','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12095811">Effects of humidified and dry air on corneal endothelial cells during vitreal fluid-air exchange.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Cekiç, Osman; Ohji, Masahito; Hayashi, Atsushi; Fang, Xiao Y; Kusaka, Shunji; Tano, Yasuo 2002-07-01 To report the immediate anatomic and functional alterations in corneal endothelial cells following use of humidified air and dry air during vitreal fluid-air exchange in rabbits. Experimental study. Rabbits undergoing pars plana vitrectomy and lensectomy were perfused with either dry or humidified air during fluid-air exchange for designated durations. Three different experiments were performed. First, control and experimental corneas were examined by scanning electron microscopy (SEM). Second, corneas were stained with Phalloidin-FITC and examined by fluorescein microscopy. Finally, third, transendothelial permeability for carboxyfluorescein was determined using a diffusion chamber. While different from the corneal endothelial cells, those cells exposed to humidified air were less stressed than cells exposed to dry air by SEM. Actin cytoskeleton was found highly disorganized with dry air exposure. Humidified air maintained the normal actin cytoskeleton throughout the 20 minutes of fluid-air exchange. Paracellular carboxyfluorescein leakage was significantly higher in dry air insufflated eyes compared with that of the humidified air after 5, 10, and 20 minutes of fluid-air exchange (P =.002, P =.004, and P =.002, respectively). Dry air stress during fluid-air exchange causes significant immediate alterations in monolayer appearance, actin cytoskeleton, and barrier function of corneal endothelium in aphakic rabbit eyes. Use of humidified air largely prevents the alterations in monolayer appearance, actin cytoskeleton, and barrier function of corneal endothelial cells. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3718390','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3718390">Atmospheric concentrations and air–soil gas exchange of polycyclic aromatic hydrocarbons (PAHs) in remote, rural village and urban areas of Beijing–Tianjin region, North China</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Wang, Wentao; Simonich, Staci; Giri, Basant; Chang, Ying; Zhang, Yuguang; Jia, Yuling; Tao, Shu; Wang, Rong; Wang, Bin; Li, Wei; Cao, Jun; Lu, Xiaoxia 2013-01-01 Forty passive air samplers were deployed to study the occurrence of gas and particulate phase PAHs in remote, rural village and urban areas of Beijing–Tianjin region, North China for four seasons (spring, summer, fall and winter) from 2007 to 2008. The influence of emissions on the spatial distribution pattern of air PAH concentrations was addressed. In addition, the air–soil gas exchange of PAHs was studied using fugacity calculations. The median gaseous and particulate phase PAH concentrations were 222 ng/m3 and 114 ng/m3, respectively, with a median total PAH concentration of 349 ng/m3. Higher PAH concentrations were measured in winter than in other seasons. Air PAH concentrations measured at the rural villages and urban sites in the northern mountain region were significantly lower than those measured at sites in the southern plain during all seasons. However, there was no significant difference in PAH concentrations between the rural villages and urban sites in the northern and southern areas. This urban–rural PAH distribution pattern was related to the location of PAH emission sources and the population distribution. The location of PAH emission sources explained 56%–77% of the spatial variation in ambient air PAH concentrations. The annual median air–soil gas exchange flux of PAHs was 42.2 ng/m2/day from soil to air. Among the 15 PAHs measured, acenaphthylene (ACY) and acenaphthene (ACE) contributed to more than half of the total exchange flux. Furthermore, the air–soil gas exchange fluxes of PAHs at the urban sites were higher than those at the remote and rural sites. In summer, more gaseous PAHs volatilized from soil to air because of higher temperatures and increased rainfall. However, in winter, more gaseous PAHs deposited from air to soil due to higher PAH emissions and lower temperatures. The soil TOC concentration had no significant influence on the air–soil gas exchange of PAHs. PMID:21669328 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/8625637','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/8625637">Perfluorocarbon-associated gas exchange in normal and acid-injured large sheep.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Hernan, L J; Fuhrman, B P; Kaiser, R E; Penfil, S; Foley, C; Papo, M C; Leach, C L 1996-03-01 We hypothesized that a) perfluorocarbon-associated gas exchange could be accomplished in normal large sheep; b) the determinants of gas exchange would be similar during perfluorocarbon-associated gas exchange and conventional gas ventilation; c)in large animals with lung injury, perfluorocarbon-associated gas exchange could be used to enhance gas exchange without adverse effects on hemodynamics; and d) the large animal with lung injury could be supported with an FIO2 of <1.0 during perfluorocarbon-associated gas exchange. Prospective, observational animal study and prospective randomized, controlled animal study. An animal laboratory in a university setting. Thirty adult ewes. Five normal ewes (61.0 +/- 4.0 kg) underwent perfluorocarbon-associated gas exchange to ascertain the effects of tidal volume, end-inspiratory pressure, and positive end-expiratory pressure (PEEP) on oxygenation. Respiratory rate, tidal volume, and minute ventilation were studied to determine their effects on CO2 clearance. Sheep, weighing 58.9 +/- 8.3 kg, had lung injury induced by instilling 2 mL/kg of 0.05 Normal hydrochloric acid into the trachea. Five minutes after injury, PEEP was increased to 10 cm H2O. Ten minutes after injury, sheep with Pao2 values of <100 torr (<13.3 kPa) were randomized to continue gas ventilation (control, n=9) or to institute perfluorocarbon-associated gas exchange (n=9) by instilling 1.6 L of unoxygenated perflubron into the trachea and resuming gas ventilation. Blood gas and hemodynamic measurements were obtained throughout the 4-hr study. Both tidal volume and end-inspiratory pressure influenced oxygenation in normal sheep during perfluorocarbon-associated gas exchange. Minute ventilation determined CO2 clearance during perfluorocarbon-associated gas exchange in normal sheep. After acid aspiration lung injury, perfluorocarbon-associated gas exchange increased PaO2 and reduced intrapulmonary shunt fraction. Hypoxia and intrapulmonary shunting were unabated </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17575285','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17575285">Leaf water relations and net gas exchange responses of salinized Carrizo citrange seedlings during drought stress and recovery.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Pérez-Pérez, J G; Syvertsen, J P; Botía, P; García-Sánchez, F 2007-08-01 Since salinity and drought stress can occur together, an assessment was made of their interacting effects on leaf water relations, osmotic adjustment and net gas exchange in seedlings of the relatively chloride-sensitive Carrizo citrange, Citrus sinensis x Poncirus trifoliata. Plants were fertilized with nutrient solution with or without additional 100 mm NaCl (salt and no-salt treatments). After 7 d, half of the plants were drought stressed by withholding irrigation water for 10 d. Thus, there were four treatments: salinized and non-salinized plants under drought-stress or well-watered conditions. After the drought period, plants from all stressed treatments were re-watered with nutrient solution without salt for 8 d to study recovery. Leaf water relations, gas exchange parameters, chlorophyll fluorescence, proline, quaternary ammonium compounds and leaf and root concentrations of Cl(-) and Na(+) were measured. Salinity increased leaf Cl(-) and Na(+) concentrations and decreased osmotic potential (Psi(pi)) such that leaf relative water content (RWC) was maintained during drought stress. However, in non-salinized drought-stressed plants, osmotic adjustment did not occur and RWC decreased. The salinity-induced osmotic adjustment was not related to any accumulation of proline, quaternary ammonium compounds or soluble sugars. Net CO(2) assimilation rate (A(CO2)) was reduced in leaves from all stressed treatments but the mechanisms were different. In non-salinized drought-stressed plants, lower A(CO2) was related to low RWC, whereas in salinized plants decreased A(CO2) was related to high levels of leaf Cl(-) and Na(+). A(CO2) recovered after irrigation in all the treatments except in previously salinized drought-stressed leaves which had lower RWC and less chlorophyll but maintained high levels of Cl(-), Na(+) and quaternary ammonium compounds after recovery. High leaf levels of Cl(-) and Na(+) after recovery apparently came from the roots. Plants preconditioned by </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010022736','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010022736">BOREAS TF-11 SSA-Fen Leaf Gas Exchange Data</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Arkebauer, Timothy J.; Hall, Forrest G. (Editor); Knapp, David E. (Editor) 2000-01-01 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. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19443613','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19443613">Leaf gas exchange, carbon isotope discrimination, and grain yield in contrasting rice genotypes subjected to water deficits during the reproductive stage.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Centritto, Mauro; Lauteri, Marco; Monteverdi, Maria Cristina; Serraj, Rachid 2009-01-01 Genotypic variations in leaf gas exchange and yield were analysed in five upland-adapted and three lowland rice cultivars subjected to a differential soil moisture gradient, varying from well-watered to severely water-stressed conditions. A reduction in the amount of water applied resulted in a significant decrease in leaf gas exchange and, subsequently, in above-ground dry mass and grain yield, that varied among genotypes and distance from the line source. The comparison between the variable J and the Delta values in recently synthesized sugars methods, yielded congruent estimations of mesophyll conductance (g(m)), confirming the reliability of these two techniques. Our data demonstrate that g(m) is a major determinant of photosynthesis (A), because rice genotypes with inherently higher g(m) were capable of keeping higher A in stressed conditions. Furthermore, A, g(s), and g(m) of water-stressed genotypes rapidly recovered to the well-watered values upon the relief of water stress, indicating that drought did not cause any lasting metabolic limitation to photosynthesis. The comparisons between the A/C(i) and corresponding A/C(c) curves, measured in the genotypes that showed intrinsically higher and lower instantaneous A, confirmed this finding. Moreover, the effect of drought stress on grain yield was correlated with the effects on both A and total diffusional limitations to photosynthesis. Overall, these data indicate that genotypes which showed higher photosynthesis and conductances were also generally more productive across the entire soil moisture gradient. The analysis of Delta revealed a substantial variation of water use efficiency among the genotypes, both on the long-term (leaf pellet analysis) and short-term scale (leaf soluble sugars analysis). </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018BGeo...15.3085H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018BGeo...15.3085H">Use of argon to measure gas exchange in turbulent mountain streams</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Hall, Robert O., Jr.; Madinger, Hilary L. 2018-05-01 Gas exchange is a parameter needed in stream metabolism and trace gas emissions models. One way to estimate gas exchange is via measuring the decline of added tracer gases such as sulfur hexafluoride (SF6). Estimates of oxygen (O2) gas exchange derived from SF6 additions require scaling via Schmidt number (Sc) ratio, but this scaling is uncertain under conditions of high gas exchange via bubbles because scaling depends on gas solubility as well as Sc. Because argon (Ar) and O2 have nearly identical Schmidt numbers and solubility, Ar may be a useful tracer gas for estimating stream O2 exchange. Here we compared rates of gas exchange measured via Ar and SF6 for turbulent mountain streams in Wyoming, USA. We measured Ar as the ratio of Ar : N2 using a membrane inlet mass spectrometer (MIMS). Normalizing to N2 confers higher precision than simply measuring [Ar] alone. We consistently enriched streams with Ar from 1 to 18 % of ambient Ar concentration and could estimate gas exchange rate using an exponential decline model. The mean ratio of gas exchange of Ar relative to SF6 was 1.8 (credible interval 1.1 to 2.5) compared to the theoretical estimate 1.35, showing that using SF6 would have underestimated exchange of Ar. Steep streams (slopes 11-12 %) had high rates of gas exchange velocity normalized to Sc = 600 (k600, 57-210 m d-1), and slope strongly predicted variation in k600 among all streams. We suggest that Ar is a useful tracer because it is easily measured, requires no scaling assumptions to estimate rates of O2 exchange, and is not an intense greenhouse gas as is SF6. We caution that scaling from rates of either Ar or SF6 gas exchange to CO2 is uncertain due to solubility effects in conditions of bubble-mediated gas transfer. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GBioC..31.1579S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GBioC..31.1579S">Oceanic Uptake of Oxygen During Deep Convection Events Through Diffusive and Bubble-Mediated Gas Exchange</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Sun, Daoxun; Ito, Takamitsu; Bracco, Annalisa 2017-10-01 The concentration of dissolved oxygen (O2) plays fundamental roles in diverse chemical and biological processes throughout the oceans. The balance between the physical supply and the biological consumption controls the O2 level of the interior ocean, and the O2 supply to the deep waters can only occur through deep convection in the polar oceans. We develop a theoretical framework describing the oceanic O2 uptake during open-ocean deep convection events and test it against a suite of numerical sensitivity experiments. Our framework allows for two predictions, confirmed by the numerical simulations. First, both the duration and the intensity of the wintertime cooling contribute to the total O2 uptake for a given buoyancy loss. Stronger cooling leads to deeper convection and the oxygenation can reach down to deeper depths. Longer duration of the cooling period increases the total amount of O2 uptake over the convective season. Second, the bubble-mediated influx of O2 tends to weaken the diffusive influx by shifting the air-sea disequilibrium of O2 toward supersaturation. The degree of compensation between the diffusive and bubble-mediated gas exchange depends on the dimensionless number measuring the relative strength of oceanic vertical mixing and the gas transfer velocity. Strong convective mixing, which may occur under strong cooling, reduces the degree of compensation so that the two components of gas exchange together drive exceptionally strong oceanic O2 uptake. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1358252','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1358252">Miniaturized Air-to-Refrigerant Heat Exchangers</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Radermacher, Reinhard; Bacellar, Daniel; Aute, Vikrant Air-to-refrigerant Heat eXchangers (HX) are an essential component of Heating, Ventilation, Air-Conditioning, and Refrigeration (HVAC&R) systems, serving as the main heat transfer component. The major limiting factor to HX performance is the large airside thermal resistance. Recent literature aims at improving heat transfer performance by utilizing enhancement methods such as fins and small tube diameters; this has lead to almost exhaustive research on the microchannel HX (MCHX). The objective of this project is to develop a miniaturized air-to-refrigerant HX with at least 20% reduction in volume, material volume, and approach temperature compared to current state-of-the-art multiport flat tube designs andmore » also be capable of production within five years. Moreover, the proposed HX’s are expected to have good water drainage and should succeed in both evaporator and condenser applications. The project leveraged Parallel-Parametrized Computational Fluid Dynamics (PPCFD) and Approximation-Assisted Optimization (AAO) techniques to perform multi-scale analysis and shape optimization with the intent of developing novel HX designs whose thermal-hydraulic performance exceeds that of state-of-the-art MCHX. Nine heat exchanger geometries were initially chosen for detailed analysis, selected from 35+ geometries which were identified in previous work at the University of Maryland, College Park. The newly developed optimization framework was exercised for three design optimization problems: (DP I) 1.0kW radiator, (DP II) 10kW radiator and (DP III) 10kW two-phase HX. DP I consisted of the design and optimization of 1.0kW air-to-water HX’s which exceeded the project requirements of 20% volume/material reduction and 20% better performance. Two prototypes for the 1.0kW HX were prototyped, tested and validated using newly-designed airside and refrigerant side test facilities. DP II, a scaled version DP I for 10kW air-to-water HX applications, also yielded optimized HX </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/FR-2013-08-14/pdf/2013-19756.pdf','FEDREG'); return false;" href="https://www.gpo.gov/fdsys/pkg/FR-2013-08-14/pdf/2013-19756.pdf">78 FR 49484 - Exchange of Air Force Real Property for Non-Air Force Real Property</a> <a target="_blank" href="http://www.gpo.gov/fdsys/browse/collection.action?collectionCode=FR">Federal Register 2010, 2011, 2012, 2013, 2014</a> 2013-08-14 ... DEPARTMENT OF DEFENSE Department of Air Force Exchange of Air Force Real Property for Non-Air Force Real Property SUMMARY: Notice identifies excess Federal real property under administrative jurisdiction of the United States Air Force it intends to exchange for real property not currently owned by the... </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28620915','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28620915">Gas exchange recovery following natural drought is rapid unless limited by loss of leaf hydraulic conductance: evidence from an evergreen woodland.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Skelton, Robert P; Brodribb, Timothy J; McAdam, Scott A M; Mitchell, Patrick J 2017-09-01 Drought can cause major damage to plant communities, but species damage thresholds and postdrought recovery of forest productivity are not yet predictable. We used an El Niño drought event as a natural experiment to test whether postdrought recovery of gas exchange could be predicted by properties of the water transport system, or if metabolism, primarily high abscisic acid concentration, might delay recovery. We monitored detailed physiological responses, including shoot sapflow, leaf gas exchange, leaf water potential and foliar abscisic acid (ABA), during drought and through the subsequent rehydration period for a sample of eight canopy and understory species. Severe drought caused major declines in leaf water potential, elevated foliar ABA concentrations and reduced stomatal conductance and assimilation rates in our eight sample species. Leaf water potential surpassed levels associated with incipient loss of leaf hydraulic conductance in four species. Following heavy rainfall gas exchange in all species, except those trees predicted to have suffered hydraulic impairment, recovered to prestressed rates within 1 d. Recovery of plant gas exchange was rapid and could be predicted by the hydraulic safety margin, providing strong support for leaf vulnerability to water deficit as an index of damage under natural drought conditions. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/10369593','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/10369593">Effect of humidity on posterior lens opacification during fluid-air exchange.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Harlan, J B; Lee, E T; Jensen, P S; de Juan, E 1999-06-01 To study the relationship of humidity and the rate of lens opacity formation during fluid-air exchange using an animal model. Vitrectomy and fluid-air exchange was carried out using 16 eyes of 8 pigmented rabbits. One eye of each rabbit was exposed to dry air and the fellow eye received humidified air using an intraocular air humidifier. In each case, the percent humidity of the intraocular air was measured using an in-line hygrometer. Elapsed time from initial air entry to lens feathering was recorded for each eye, with the surgeon-observer unaware of the percent humidity of the air infusion. In each rabbit, use of humidified air resulted in a delay in lens feathering (P<.02), with an overall increase in time to feathering of 80% for humidified air vs room air. Use of a humidifier during fluid-air exchange prolongs intraoperative lens clarity in the rabbit model, suggesting that humidified air should prolong lens clarity during phakic fluid-air exchange in patients. Use of humidified air during vitrectomy and fluid-air exchange may retard the intraoperative loss of lens clarity, promoting better visualization of the posterior segment and enhancing surgical performance. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930038655&hterms=Water+turbine&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DWater%2Bturbine','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930038655&hterms=Water+turbine&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DWater%2Bturbine">Two and three-dimensional prediffuser combustor studies with air-water mixture</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Laing, Peter; Ehresman, C. M.; Murthy, S. N. B. 1993-01-01 Two- and three-dimensional gas turbine prediffuser-combustor sectors were experimentally studied under a number of mixture and flow conditions in a tunnel operating with a two-phase, air-liquid film-droplet mixture. It is concluded that water vaporization in the combustor causes changes in both local gas temperature and state of vitiation and reduces reaction rates. Substantial accumulation of water and water vapor takes place in pocket over the combustor volume, even when the air-water mixture is steady in time. The accuracy of determining combustor performance changes increases with a better knowledge of the state of the air-water mixture in the primary zone. To establish flame-out conditions it is considered to be necessary to combine the prediction of detailed flowfield and chemical activity with that of flame stability and motion characteristics. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFM.B11B0442B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFM.B11B0442B">Regulation of leaf-gas exchange strategies of woody plants under elevated CO2</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Belmecheri, S.; Guerrieri, R.; Voelker, S. 2016-12-01 Estimates of vegetation water use efficiency (WUE) have increasingly been assessed using both eddy covariance and plant stable isotope techniques but these data have often lead to differing conclusions. Eddy covariance can provide forest ecosystem-level responses of coupled carbon and water exchanges to recent global change phenomena. These direct observations, however, are generally less than one or two decades, thus documenting ecosystem-level responses at elevated [CO2] concentrations (350-400 ppm). Therefore, eddy covariance data cannot directly address plant physiological mechanisms and adaptation to climate variability and anthropogenic factors, e.g., increasing atmospheric [CO2]. By contrast, tree based carbon isotope approaches can retrospectively assess intrinsic WUE over long periods and have documented physiological responses to ambient atmospheric [CO2] (ca), which have often been contextualized within generalized strategies for stomatal regulation of leaf gas-exchange. These include maintenance of a constant leaf internal [CO2] (ci), a constant drawdown in [CO2] (ca - ci), and a constant ci/ca . Tree carbon isotope studies, however, cannot account for changes in leaf area of individual trees or canopies, which makes scaling up a difficult task. The limitations of these different approaches to understanding how forest water use efficiency has been impacted by rising [CO2] has contributed to the uncertainty in global terrestrial carbon cycling and the "missing" terrestrial carbon sink. We examined stable C isotope ratios (d13C) from woody plants over a wide range of [CO2] (200-400 ppm) to test for patterns of ci-regulation in response to rising ca. The analyses are not consistent with any of the leaf gas-exchange regulation strategies noted above. The data suggest that ca - ci is still recently increasing in most species but that the rate of increase is less than expected from paleo trees which grew at much lower [CO2]. This evidence demonstrates that a </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active">14</li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active">15</li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA603185','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA603185">Elimination of Acid Cleaning of High Temperature Salt Water Heat Exchangers: Redesigned Pre-Production Full-Scale Heat Pipe Bleed Air Cooler for Shipboard Evaluation</a> <a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a> 2011-11-01 Cleaning of High Temperature Salt Water Heat Exchangers ESTCP WP-200302 Subtitle: Redesigned Pre-production Full-Scale Heat Pipe Bleed Air Cooler For...FINAL 3. DATES COVERED (From - To) 1-Jan-2003 – 1-Oct-2009 4. TITLE AND SUBTITLE Elimination of Acid Cleaning of High Temperature Salt Water Heat...6-5 Figure 6- 6 HP-BAC Tube Sheet Being Immersed in Ultrasonic Cleaning Tank ..................................... 6-6 Figure 6- 7 Heat Pipe </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28634999','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28634999">Plasticity in gas-exchange physiology of mature Scots pine and European larch drive short- and long-term adjustments to changes in water availability.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Feichtinger, Linda M; Siegwolf, Rolf T W; Gessler, Arthur; Buchmann, Nina; Lévesque, Mathieu; Rigling, Andreas 2017-09-01 Adjustment mechanisms of trees to changes in soil-water availability over long periods are poorly understood, but crucial to improve estimates of forest development in a changing climate. We compared mature trees of Scots pine (Pinus sylvestris) and European larch (Larix decidua) growing along water-permeable channels (irrigated) and under natural conditions (control) at three sites in inner-Alpine dry valleys. At two sites, the irrigation had been stopped in the 1980s. We combined measurements of basal area increment (BAI), tree height and gas-exchange physiology (Δ 13 C) for the period 1970-2009. At one site, the Δ 13 C of irrigated pine trees was higher than that of the control in all years, while at the other sites, it differed in pine and larch only in years with dry climatic conditions. During the first decade after the sudden change in water availability, the BAI and Δ 13 C of originally irrigated pine and larch trees decreased instantly, but subsequently reached higher levels than those of the control by 2009 (15 years afterwards). We found a high plasticity in the gas-exchange physiology of pine and larch and site-specific responses to changes in water availability. Our study highlights the ability of trees to adjust to new conditions, thus showing high resilience. © 2017 John Wiley & Sons Ltd. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3234695','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3234695">Removal of infused water predominantly during insertion (water exchange) is consistently associated with a greater reduction of pain score - review of randomized controlled trials (RCTs) of water method colonoscopy</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Harker, JO; Leung, JW; Siao-Salera, RM; Mann, SK; Ramirez, FC; Friedland, S; Amato, A; Radaelli, F; Paggi, S; Terruzzi, V; Hsieh, YH 2011-01-01 Introduction Variation in the outcomes in RcTs comparing water-related methods and air insufflation during the insertion phase of colonoscopy raises challenging questions regarding the approach. This report reviews the impact of water exchange on the variation in attenuation of pain during colonoscopy by water-related methods. Methods Medline (2008 to 2011) searches, abstracts of the 2011 Digestive Disease Week (DDW) and personal communications were considered to identify RcTs that compared water-related methods and air insufflation to aid insertion of the colonoscope. Results: Since 2008 nine published and one submitted RcTs and five abstracts of RcTs presented at the 2011 DDW have been identified. Thirteen RcTs (nine published, one submitted and one abstract, n=1850) described reduction of pain score during or after colonoscopy (eleven reported statistical significance); the remaining reports described lower doses of medication used, or lower proportion of patients experiencing severe pain in colonoscopy performed with water-related methods compared with air insufflation (Tables 1 and 2). The water-related methods notably differ in the timing of removal of the infused water - predominantly during insertion (water exchange) versus predominantly during withdrawal (water immersion). Use of water exchange was consistently associated with a greater attenuation of pain score in patients who did not receive full sedation (Table 3). Conclusion The comparative data reveal that a greater attenuation of pain was associated with water exchange than water immersion during insertion. The intriguing results should be subjected to further evaluation by additional RcTs to elucidate the mechanism of the pain-alleviating impact of the water method. PMID:22163081 </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19740006538','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19740006538">Effect of water injection on nitric oxide emissions of a gas turbine combustor burning natural gas fuel</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Marchionna, N. R.; Diehl, L. A.; Trout, A. M. 1973-01-01 The effect of direct water injection on the exhaust gas emissions of a turbojet combustor burning natural gas fuel was investigated. The results are compared with the results from similar tests using ASTM Jet-A fuel. Increasing water injection decreased the emissions of oxides of nitrogen (NOX) and increased the emissions of carbon monoxide and unburned hydrocarbons. The greatest percentage decrease in NOX with increasing water injection was at the lowest inlet-air temperature tested. The effect of increasing inlet-air temperature was to decrease the effect of the water injection. The reduction in NOX due to water injection was almost identical to the results obtained with Jet-A fuel. However, the emission indices of unburned hydrocarbons, carbon monoxide, and percentage nitric oxide in NOX were not. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22675191','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22675191">Respiratory dynamics of discontinuous gas exchange in the tracheal system of the desert locust, Schistocerca gregaria.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Groenewald, Berlizé; Hetz, Stefan K; Chown, Steven L; Terblanche, John S 2012-07-01 Gas exchange dynamics in insects is of fundamental importance to understanding evolved variation in breathing patterns, such as discontinuous gas exchange cycles (DGCs). Most insects do not rely solely on diffusion for the exchange of respiratory gases but may also make use of respiratory movements (active ventilation) to supplement gas exchange at rest. However, their temporal dynamics have not been widely investigated. Here, intratracheal pressure, V(CO2) and body movements of the desert locust Schistocerca gregaria were measured simultaneously during the DGC and revealed several important aspects of gas exchange dynamics. First, S. gregaria employs two different ventilatory strategies, one involving dorso-ventral contractions and the other longitudinal telescoping movements. Second, although a true spiracular closed (C)-phase of the DGC could be identified by means of subatmospheric intratracheal pressure recordings, some CO(2) continued to be released. Third, strong pumping actions do not necessarily lead to CO(2) release and could be used to ensure mixing of gases in the closed tracheal system, or enhance water vapour reabsorption into the haemolymph from fluid-filled tracheole tips by increasing the hydrostatic pressure or forcing fluid into the haemocoel. Finally, this work showed that the C-phase of the DGC can occur at any pressure. These results provide further insights into the mechanistic basis of insect gas exchange. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930057487&hterms=water&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DTitle%26N%3D0%26No%3D70%26Ntt%3Dwater','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930057487&hterms=water&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DTitle%26N%3D0%26No%3D70%26Ntt%3Dwater">A novel membrane device for the removal of water vapor and water droplets from air</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Ray, Rod; Newbold, David D.; Mccray, Scott B.; Friesen, Dwayne T.; Kliss, Mark 1992-01-01 One of the key challenges facing NASA engineers is the development of systems for separating liquids and gases in microgravity environments. In this paper, a novel membrane-based phase separator is described. This device, known as a water recovery heat exchanger (WRHEX), overcomes the inherent deficiencies of current phase-separation technology. Specifically, the WRHEX cools and removes water vapor or water droplets from feed-air streams without the use of a vacuum or centrifugal force. As is shown in this paper, only a low-power air blower and a small stream of recirculated cool water is required for WRHEX operation. This paper presents the results of tests using this novel membrane device over a wide range of operating conditions. The data show that the WRHEX produces a dry air stream containing no entrained or liquid water - even when the feed air contains water droplets or mist. An analysis of the operation of the WRHEX is presented. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017Th%26Ae..24..483K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017Th%26Ae..24..483K">Estimate for interstage water injection in air compressor incorporated into gas-turbine cycles and combined power plants cycles</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Kler, A. M.; Zakharov, Yu. B.; Potanina, Yu. M. 2017-05-01 The objects of study are the gas turbine (GT) plant and combined cycle power plant (CCPP) with opportunity for injection between the stages of air compressor. The objective of this paper is technical and economy optimization calculations for these classes of plants with water interstage injection. The integrated development environment "System of machine building program" was a tool for creating the mathematic models for these classes of power plants. Optimization calculations with the criterion of minimum for specific capital investment as a function of the unit efficiency have been carried out. For a gas-turbine plant, the economic gain from water injection exists for entire range of power efficiency. For the combined cycle plant, the economic benefit was observed only for a certain range of plant's power efficiency. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/5592373-quality-site-seasonal-report-army-air-force-exchange-service-headquarters-building-sfbp-august-through-may','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/5592373-quality-site-seasonal-report-army-air-force-exchange-service-headquarters-building-sfbp-august-through-may">Quality site seasonal report: Army Air Force Exchange Service Headquarters Building, SFBP 1343, August 1984 through May 1985</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Pollock, E.O. Jr. 1987-10-15 The active solar Domestic Hot Water (DHW) system at the HQ Army-Air Force Exchange Service (AAFES) Building was designed and constructed as part of the Solar in Federal Buildings Programs (SFBP). This retrofitted system is one of eight of the systems in the SFBP selected for quality monitoring. The purpose of this monitoring effort is to document the performance of quality state-of-the-art solar systems in large federal building applications. The six-story HQ AAFES Building houses a cafeteria, officer's mess and club and office space for 2400 employees. The siphon-return drainback system uses 1147 ft/sup 2/ of Aircraftsman flat-plate collectors tomore » collect solar energy which is used to preheat domestic hot water. Solar energy is stored in a 1329-gallon tank and transferred to the hot water load through a heat exchanger located in the 356-gallon DHW preheat tank. Auxiliary energy is supplied by two gas fired boilers which boost the temperature to 130/sup 0/F before it is distributed to the load. Highlights of the performance of the HQ AAFES Building solar system during the monitoring period from August 1984 through May 1985 are presented in this report.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1225372','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1225372">External reflection FTIR of peptide monolayer films in situ at the air/water interface: experimental design, spectra-structure correlations, and effects of hydrogen-deuterium exchange.</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Flach, C R; Brauner, J W; Taylor, J W; Baldwin, R C; Mendelsohn, R 1994-01-01 A Fourier transform infrared spectrometer has been interfaced with a surface balance and a new external reflection infrared sampling accessory, which permits the acquisition of spectra from protein monolayers in situ at the air/water interface. The accessory, a sample shuttle that permits the collection of spectra in alternating fashion from sample and background troughs, reduces interference from water vapor rotation-vibration bands in the amide I and amide II regions of protein spectra (1520-1690 cm-1) by nearly an order of magnitude. Residual interference from water vapor absorbance ranges from 50 to 200 microabsorbance units. The performance of the device is demonstrated through spectra of synthetic peptides designed to adopt alpha-helical, antiparallel beta-sheet, mixed beta-sheet/beta-turn, and unordered conformations at the air/water interface. The extent of exchange on the surface can be monitored from the relative intensities of the amide II and amide I modes. Hydrogen-deuterium exchange may lower the amide I frequency by as much as 11-12 cm-1 for helical secondary structures. This shifts the vibrational mode into a region normally associated with unordered structures and leads to uncertainties in the application of algorithms commonly used for determination of secondary structure from amide I contours of proteins in D2O solution. PMID:7919013 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24749994','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24749994">Effect of impeller design and spacing on gas exchange in a percutaneous respiratory assist catheter.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Jeffries, R Garrett; Frankowski, Brian J; Burgreen, Greg W; Federspiel, William J 2014-12-01 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. Copyright © 2014 International Center for </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1232686','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1232686">Low Cost Polymer heat Exchangers for Condensing Boilers</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Butcher, Thomas; Trojanowski, Rebecca; Wei, George 2015-09-30 Work in this project sought to develop a suitable design for a low cost, corrosion resistant heat exchanger as part of a high efficiency condensing boiler. Based upon the design parameters and cost analysis several geometries and material options were explored. The project also quantified and demonstrated the durability of the selected polymer/filler composite under expected operating conditions. The core material idea included a polymer matrix with fillers for thermal conductivity improvement. While the work focused on conventional heating oil, this concept could also be applicable to natural gas, low sulfur heating oil, and biodiesel- although these are considered tomore » be less challenging environments. An extruded polymer composite heat exchanger was designed, built, and tested during this project, demonstrating technical feasibility of this corrosion-resistant material approach. In such flue gas-to-air heat exchangers, the controlling resistance to heat transfer is in the gas-side convective layer and not in the tube material. For this reason, the lower thermal conductivity polymer composite heat exchanger can achieve overall heat transfer performance comparable to a metal heat exchanger. However, with the polymer composite, the surface temperature on the gas side will be higher, leading to a lower water vapor condensation rate.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.B51F0483P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.B51F0483P">Automatable Measurement of Gas Exchange Rate in Streams: Oxygen-Carbon Method</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Pennington, R.; Haggerty, R.; Argerich, A.; Wondzell, S. M. 2015-12-01 Gas exchange rates between streams and the atmosphere are critically important to measurement of in-stream ecologic processes, as well as fate and transport of hazardous pollutants such as mercury and PCBs. Methods to estimate gas exchange rates include empirical relations to hydraulics, and direct injection of a tracer gas such as propane or SF6. Empirical relations are inconsistent and inaccurate, particularly for lower order, high-roughness streams. Gas injections are labor-intensive, and measured gas exchange rates are difficult to extrapolate in time since they change with discharge and stream geometry. We propose a novel method for calculation of gas exchange rates utilizing O2, pCO2, pH, and temperature data. Measurements, which can be automated using data loggers and probes, are made on the upstream and downstream end of the study reach. Gas exchange rates are then calculated from a solution to the transport equations for oxygen and dissolved inorganic carbon. Field tests in steep, low order, high roughness streams of the HJ Andrews Experimental Forest indicate the method to be viable along stream reaches with high downstream gas concentration gradients and high rates of gas transfer velocity. Automated and continuous collection of oxygen and carbonate chemistry data is increasingly common, thus the method may be used to estimate gas exchange rates through time, and is well suited for interactivity with databases. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeCoA.194..291B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeCoA.194..291B">Noble gases solubility models of hydrocarbon charge mechanism in the Sleipner Vest gas field</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Barry, P. H.; Lawson, M.; Meurer, W. P.; Warr, O.; Mabry, J. C.; Byrne, D. J.; Ballentine, C. J. 2016-12-01 Noble gases are chemically inert and variably soluble in crustal fluids. They are primarily introduced into hydrocarbon reservoirs through exchange with formation waters, and can be used to assess migration pathways and mechanisms, as well as reservoir storage conditions. Of particular interest is the role groundwater plays in hydrocarbon transport, which is reflected in hydrocarbon-water volume ratios. Here, we present compositional, stable isotope and noble gas isotope and abundance data from the Sleipner Vest field, in the Norwegian North Sea. Sleipner Vest gases are generated from primary cracking of kerogen and the thermal cracking of oil. Gas was emplaced into the Sleipner Vest from the south and subsequently migrated to the east, filling and spilling into the Sleipner Ost fields. Gases principally consist of hydrocarbons (83-93%), CO2 (5.4-15.3%) and N2 (0.6-0.9%), as well as trace concentrations of noble gases. Helium isotopes (3He/4He) are predominantly radiogenic and range from 0.065 to 0.116 RA; reported relative to air (RA = 1.4 × 10-6; Clarke et al., 1976; Sano et al., 1988), showing predominantly (>98%) crustal contributions, consistent with Ne (20Ne/22Ne from 9.70 to 9.91; 21Ne/22Ne from 0.0290 to 0.0344) and Ar isotopes (40Ar/36Ar from 315 to 489). Air-derived noble gas isotopes (20Ne, 36Ar, 84Kr, 132Xe) are introduced into the hydrocarbon system by direct exchange with air-saturated water (ASW). The distribution of air-derived noble gas species are controlled by phase partitioning processes; in that they preferentially partition into the gas (i.e., methane) phase, due to their low solubilities in fluids. Therefore, the extent of exchange between hydrocarbon phases and formation waters - that have previously equilibrated with the atmosphere - can be determined by investigating air-derived noble gas species. We utilize both elemental ratios to address process (i.e., open vs. closed system) and concentrations to quantify the extent of hydrocarbon-water </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.H23C0898R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.H23C0898R">Rapid, Real-time Methane Detection in Ground Water Using a New Gas-Water Equilibrator Design</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ruybal, C. J.; DiGiulio, D. C.; Wilkin, R. T.; Hargrove, K. D.; McCray, J. E. 2014-12-01 Recent increases in unconventional gas development have been accompanied by public concern for methane contamination in drinking water wells near production areas. Although not a regulated pollutant, methane may be a marker contaminant for others that are less mobile in groundwater and thus may be detected later, or at a location closer to the source. In addition, methane poses an explosion hazard if exsolved concentrations reach 5 - 15% volume in air. Methods for determining dissolved gases, such as methane, have evolved over 60 years. However, the response time of these methods is insufficient to monitor trends in methane concentration in real-time. To enable rapid, real-time monitoring of aqueous methane concentrations during ground water purging, a new gas-water equilibrator (GWE) was designed that increases gas-water mass exchange rates of methane for measurement. Monitoring of concentration trends allows a comparison of temporal trends between sampling events and comparison of baseline conditions with potential post-impact conditions. These trends may be a result of removal of stored casing water, pre-purge ambient borehole flow, formation physical and chemical heterogeneity, or flow outside of well casing due to inadequate seals. Real-time information in the field can help focus an investigation, aid in determining when to collect a sample, save money by limiting costs (e.g. analytical, sample transport and storage), and provide an immediate assessment of local methane concentrations. Four domestic water wells, one municipal water well, and one agricultural water well were sampled for traditional laboratory analysis and compared to the field GWE results. Aqueous concentrations measured on the GWE ranged from non-detect to 1,470 μg/L methane. Some trends in aqueous methane concentrations measured on the GWE were observed during purging. Applying a paired t-test comparing the new GWE method and traditional laboratory analysis yielded a p-value 0 </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010APS..DFD.MX008H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010APS..DFD.MX008H">Coaxial twin-fluid atomization with pattern air gas streams</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Hei Ng, Chin; Aliseda, Alberto 2010-11-01 Coaxial twin-fluid atomization has numerous industrial applications, most notably fuel injection and spray coating. In the coating process of pharmaceutical tablets, the coaxial atomizing air stream is accompanied by two diametrically opposed side jets that impinge on the liquid/gas coaxial jets at an angle to produce an elliptical shape of the spray's cross section. Our study focuses on the influence of these side jets on the break up process and on the droplet velocity and diameter distribution along the cross section. The ultimate goal is to predict the size distribution and volume flux per unit area in the spray. With this predictive model, an optimal atomizing air/pattern air ratio can be found to achieve the desired coating result. This model is also crucial in scaling up the laboratory setup to production level. We have performed experiments with different atomized liquids, such as water and glycerine-water mixtures, that allow us to establish the effect of liquid viscosity, through the Ohnesorge number, in the spray characteristics. The gas Reynolds number of our experiments ranges from 9000 to 18000 and the Weber number ranges from 400 to 1600. We will present the effect of pattern air in terms of the resulting droplets size, droplet number density and velocity at various distances downstream of the nozzle where the effect of pattern air is significant. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1411867','SCIGOV-DOEDE'); return false;" href="https://www.osti.gov/servlets/purl/1411867">CO2 response (ACi) gas exchange, calculated Vcmax & Jmax parameters, Feb2016-May2016, PA-SLZ, PA-PNM: Panama</a> <a target="_blank" href="http://www.osti.gov/dataexplorer">DOE Data Explorer</a> Rogers, Alistair [Brookhaven National Lab; Serbin, Shawn [Brookhaven National Lab; Ely, Kim [Brookhaven National Lab; Wu, Jin [BNL; Wolfe, Brett [Smithsonian; Dickman, Turin [Los Alamos National Lab; Collins, Adam [Los Alamos National Lab; Detto, Matteo [Princeton; Grossiord, Charlotte [Los Alamos National Lab; McDowell, Nate [Los Alamos National Lab; Michaletz, Sean 2017-01-01 CO2 response (ACi) gas exchange measured on leaves collected from sunlit canopy trees on a monthly basis from Feb to May 2016 at SLZ and PNM. Dataset includes calculated Vcmax and Jmax parameters. This data was collected as part of the 2016 ENSO campaign. See related datasets (existing and future) for further sample details, leaf water potential, LMA, leaf spectra, other gas exchange and leaf chemistry. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110000601','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110000601">Air Circulation and Heat Exchange Under Reduced Pressures</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Rygalov, V.; Wheeler, R.; Dixon, M.; Fowler, P.; Hillhouse, L. 2010-01-01 Heat exchange rates decrease non-linearly with reductions in atmospheric pressure. This decrease creates risk of thermal stress (elevated leaf temperatures) for plants under reduced pressures. Forced convection (fans) significantly increases heat exchange rate under almost all pressures except below 10 kPa. Plant cultivation techniques under reduced pressures will require forced convection. The cooling curve technique is a reliable means of assessing the influence of environmental variables like pressure and gravity on gas exchange of plant. These results represent the extremes of gas exchange conditions for simple systems under variable pressures. In reality, dense plant canopies will exhibit responses in between these extremes. More research is needed to understand the dependence of forced convection on atmospheric pressure. The overall thermal balance model should include latent and radiative exchange components. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24395505','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24395505">Fungal oxygen exchange between denitrification intermediates and water.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Rohe, Lena; Anderson, Traute-Heidi; Braker, Gesche; Flessa, Heinz; Giesemann, Anette; Wrage-Mönnig, Nicole; Well, Reinhard 2014-02-28 Fungi can contribute greatly to N2O production from denitrification. Therefore, it is important to quantify the isotopic signature of fungal N2O. The isotopic composition of N2O can be used to identify and analyze the processes of N2O production and N2O reduction. In contrast to bacteria, information about the oxygen exchange between denitrification intermediates and water during fungal denitrification is lacking, impeding the explanatory power of stable isotope methods. Six fungal species were anaerobically incubated with the electron acceptors nitrate or nitrite and (18)O-labeled water to determine the oxygen exchange between denitrification intermediates and water. After seven days of incubation, gas samples were analyzed for N2O isotopologues by isotope ratio mass spectrometry. All the fungal species produced N2O. N2O production was greater when nitrite was the sole electron acceptor (129 to 6558 nmol N2O g dw(-1) h(-1)) than when nitrate was the electron acceptor (6 to 47 nmol N2O g dw(-1) h(-1)). Oxygen exchange was complete with nitrate as electron acceptor in one of five fungi and with nitrite in two of six fungi. Oxygen exchange of the other fungi varied (41 to 89% with nitrite and 11 to 61% with nitrate). This is the first report on oxygen exchange with water during fungal denitrification. The exchange appears to be within the range previously reported for bacterial denitrification. This adds to the difficulty of differentiating N2O producing processes based on the origin of N2O-O. However, the large oxygen exchange repeatedly observed for bacteria and now also fungi could lead to less variability in the δ(18)O values of N2O from soils, which could facilitate the assessment of the extent of N2O reduction. Copyright © 2013 John Wiley & Sons, Ltd. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ACP....1611125W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ACP....1611125W">Emission-dominated gas exchange of elemental mercury vapor over natural surfaces in China</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Wang, Xun; Lin, Che-Jen; Yuan, Wei; Sommar, Jonas; Zhu, Wei; Feng, Xinbin 2016-09-01 Mercury (Hg) emission from natural surfaces plays an important role in global Hg cycling. The present estimate of global natural emission has large uncertainty and remains unverified against field data, particularly for terrestrial surfaces. In this study, a mechanistic model is developed for estimating the emission of elemental mercury vapor (Hg0) from natural surfaces in China. The development implements recent advancements in the understanding of air-soil and air-foliage exchange of Hg0 and redox chemistry in soil and on surfaces, incorporates the effects of soil characteristics and land use changes by agricultural activities, and is examined through a systematic set of sensitivity simulations. Using the model, the net exchange of Hg0 between the atmosphere and natural surfaces of mainland China is estimated to be 465.1 Mg yr-1, including 565.5 Mg yr-1 from soil surfaces, 9.0 Mg yr-1 from water bodies, and -100.4 Mg yr-1 from vegetation. The air-surface exchange is strongly dependent on the land use and meteorology, with 9 % of net emission from forest ecosystems; 50 % from shrubland, savanna, and grassland; 33 % from cropland; and 8 % from other land uses. Given the large agricultural land area in China, farming activities play an important role on the air-surface exchange over farmland. Particularly, rice field shift from a net sink (3.3 Mg uptake) during April-October (rice planting) to a net source when the farmland is not flooded (November-March). Summing up the emission from each land use, more than half of the total emission occurs in summer (51 %), followed by spring (28 %), autumn (13 %), and winter (8 %). Model verification is accomplished using observational data of air-soil/air-water fluxes and Hg deposition through litterfall for forest ecosystems in China and Monte Carlo simulations. In contrast to the earlier estimate by Shetty et al. (2008) that reported large emission from vegetative surfaces using an evapotranspiration approach, the estimate in </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19880002873','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19880002873">Operation of an experimental algal gas exchanger for use in a CELSS</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Smernoff, David T.; Wharton, Robert A., Jr.; Averner, Maurice M. 1987-01-01 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. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active">15</li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active">16</li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26436513','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26436513">Concentrations, Trends, and Air-Water Exchange of PAHs and PBDEs Derived from Passive Samplers in Lake Superior in 2011.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Ruge, Zoe; Muir, Derek; Helm, Paul; Lohmann, Rainer 2015-12-01 Polycyclic aromatic hydrocarbons (PAHs) and polybrominated diphenylethers (PBDEs) are both currently released into the environment from anthropogenic activity. Both are hence primarily associated with populated or industrial areas, although wildfires can be an important source of PAHs, as well. Polyethylene passive samplers (PEs) were simultaneously deployed in surface water and near surface atmosphere to determine spatial trends and air-water gaseous exchange of 21 PAHs and 11 PBDEs at 19 sites across Lake Superior in 2011. Surface water and atmospheric PAH concentrations were greatest at urban sites (up to 65 ng L(-1) and 140 ng m(-3), respectively, averaged from June to October). Near populated regions, PAHs displayed net air-to-water deposition, but were near equilibrium off-shore. Retene, probably depositing following major wildfires in the region, dominated dissolved PAH concentrations at most Lake Superior sites. Atmospheric and dissolved PBDEs were greatest near urban and populated sites (up to 6.8 pg L(-1) and 15 pg m(-3), respectively, averaged from June to October), dominated by BDE-47. At most coastal sites, there was net gaseous deposition of BDE-47, with less brominated congeners contributing to Sault Ste. Marie and eastern open lake fluxes. Conversely, the central open lake and Eagle Harbor sites generally displayed volatilization of PBDEs into the atmosphere, mainly BDE-47. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22923680','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22923680">The grapevine root-specific aquaporin VvPIP2;4N controls root hydraulic conductance and leaf gas exchange under well-watered conditions but not under water stress.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Perrone, Irene; Gambino, Giorgio; Chitarra, Walter; Vitali, Marco; Pagliarani, Chiara; Riccomagno, Nadia; Balestrini, Raffaella; Kaldenhoff, Ralf; Uehlein, Norbert; Gribaudo, Ivana; Schubert, Andrea; Lovisolo, Claudio 2012-10-01 We functionally characterized the grape (Vitis vinifera) VvPIP2;4N (for Plasma membrane Intrinsic Protein) aquaporin gene. Expression of VvPIP2;4N in Xenopus laevis oocytes increased their swelling rate 54-fold. Northern blot and quantitative reverse transcription-polymerase chain reaction analyses showed that VvPIP2;4N is the most expressed PIP2 gene in root. In situ hybridization confirmed root localization in the cortical parenchyma and close to the endodermis. We then constitutively overexpressed VvPIP2;4N in grape 'Brachetto', and in the resulting transgenic plants we analyzed (1) the expression of endogenous and transgenic VvPIP2;4N and of four other aquaporins, (2) whole-plant, root, and leaf ecophysiological parameters, and (3) leaf abscisic acid content. Expression of transgenic VvPIP2;4N inhibited neither the expression of the endogenous gene nor that of other PIP aquaporins in both root and leaf. Under well-watered conditions, transgenic plants showed higher stomatal conductance, gas exchange, and shoot growth. The expression level of VvPIP2;4N (endogenous + transgene) was inversely correlated to root hydraulic resistance. The leaf component of total plant hydraulic resistance was low and unaffected by overexpression of VvPIP2;4N. Upon water stress, the overexpression of VvPIP2;4N induced a surge in leaf abscisic acid content and a decrease in stomatal conductance and leaf gas exchange. Our results show that aquaporin-mediated modifications of root hydraulics play a substantial role in the regulation of water flow in well-watered grapevine plants, while they have a minor role upon drought, probably because other signals, such as abscisic acid, take over the control of water flow. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23845983','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23845983">Probing the regional distribution of pulmonary gas exchange through single-breath gas- and dissolved-phase 129Xe MR imaging.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Kaushik, S Sivaram; Freeman, Matthew S; Cleveland, Zackary I; Davies, John; Stiles, Jane; Virgincar, Rohan S; Robertson, Scott H; He, Mu; Kelly, Kevin T; Foster, W Michael; McAdams, H Page; Driehuys, Bastiaan 2013-09-01 Although some central aspects of pulmonary function (ventilation and perfusion) are known to be heterogeneous, the distribution of diffusive gas exchange remains poorly characterized. A solution is offered by hyperpolarized 129Xe magnetic resonance (MR) imaging, because this gas can be separately detected in the lung's air spaces and dissolved in its tissues. Early dissolved-phase 129Xe images exhibited intensity gradients that favored the dependent lung. To quantitatively corroborate this finding, we developed an interleaved, three-dimensional radial sequence to image the gaseous and dissolved 129Xe distributions in the same breath. These images were normalized and divided to calculate "129Xe gas-transfer" maps. We hypothesized that, for healthy volunteers, 129Xe gas-transfer maps would retain the previously observed posture-dependent gradients. This was tested in nine subjects: when the subjects were supine, 129Xe gas transfer exhibited a posterior-anterior gradient of -2.00 ± 0.74%/cm; when the subjects were prone, the gradient reversed to 1.94 ± 1.14%/cm (P < 0.001). The 129Xe gas-transfer maps also exhibited significant heterogeneity, as measured by the coefficient of variation, that correlated with subject total lung capacity (r = 0.77, P = 0.015). Gas-transfer intensity varied nonmonotonically with slice position and increased in slices proximal to the main pulmonary arteries. Despite substantial heterogeneity, the mean gas transfer for all subjects was 1.00 ± 0.01 while supine and 1.01 ± 0.01 while prone (P = 0.25), indicating good "matching" between gas- and dissolved-phase distributions. This study demonstrates that single-breath gas- and dissolved-phase 129Xe MR imaging yields 129Xe gas-transfer maps that are sensitive to altered gas exchange caused by differences in lung inflation and posture. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017WRR....53.9519L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017WRR....53.9519L">The Gas-Absorption/Chemical-Reaction Method for Measuring Air-Water Interfacial Area in Natural Porous Media</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Lyu, Ying; Brusseau, Mark L.; El Ouni, Asma; Araujo, Juliana B.; Su, Xiaosi 2017-11-01 The gas-absorption/chemical-reaction (GACR) method used in chemical engineering to quantify gas-liquid interfacial area in reactor systems is adapted for the first time to measure the effective air-water interfacial area of natural porous media. Experiments were conducted with the GACR method, and two standard methods (X-ray microtomographic imaging and interfacial partitioning tracer tests) for comparison, using model glass beads and a natural sand. The results of a series of experiments conducted under identical conditions demonstrated that the GACR method exhibited excellent repeatability for measurement of interfacial area (Aia). Coefficients of variation for Aia were 3.5% for the glass beads and 11% for the sand. Extrapolated maximum interfacial areas (Am) obtained with the GACR method were statistically identical to independent measures of the specific solid surface areas of the media. For example, the Am for the glass beads is 29 (±1) cm-1, compared to 32 (±3), 30 (±2), and 31 (±2) cm-1 determined from geometric calculation, N2/BET measurement, and microtomographic measurement, respectively. This indicates that the method produced accurate measures of interfacial area. Interfacial areas determined with the GACR method were similar to those obtained with the standard methods. For example, Aias of 47 and 44 cm-1 were measured with the GACR and XMT methods, respectively, for the sand at a water saturation of 0.57. The results of the study indicate that the GACR method is a viable alternative for measuring air-water interfacial areas. The method is relatively quick, inexpensive, and requires no specialized instrumentation compared to the standard methods. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22268690','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22268690">Sorption-induced effects of humic substances on mass transfer of organic pollutants through aqueous diffusion boundary layers: the example of water/air exchange.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Ramus, Ksenia; Kopinke, Frank-Dieter; Georgi, Anett 2012-02-21 This study examines the effect of dissolved humic substances (DHS) on the rate of water-gas exchange of organic compounds under conditions where diffusion through the aqueous boundary layer is rate-determining. A synthetic surfactant was applied for comparison. Mass-transfer coefficients were determined from the rate of depletion of the model compounds by means of an apparatus containing a stirred aqueous solution with continuous purging of the headspace above the solution. In addition, experiments with continuous passive dosing of analytes into the water phase were conducted to simulate a system where thermodynamic activity of the chemical in the aqueous phase is identical in the presence and absence of DHS. The experimental results show that DHS and surfactants can affect water-gas exchange rates by the superposition of two mechanisms: (1) hydrodynamic effects due to surface film formation ("surface smoothing"), and (2) sorption-induced effects. Whether sorption accelerates or retards mass transfer depends on its effect on the thermodynamic activity of the pollutant in the aqueous phase. Mass transfer will be retarded if the activity (or freely dissolved concentration) of the pollutant is decreased due to sorption. If it remains unchanged (e.g., due to fast equilibration with a sediment acting as a large source phase), then DHS and surfactant micelles can act as an additional shuttle for the pollutants, enhancing the flux through the boundary layer. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28965822','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28965822">A new method for noninvasive measurement of pulmonary gas exchange using expired gas.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> West, John B; Prisk, G Kim 2018-01-01 Measurement of the gas exchange efficiency of the lung is often required in the practice of pulmonary medicine and in other settings. The traditional standard is the values of the PO2, PCO2, and pH of arterial blood. However arterial puncture requires technical expertise, is invasive, uncomfortable for the patient, and expensive. Here we describe how the composition of expired gas can be used in conjunction with pulse oximetry to obtain useful measures of gas exchange efficiency. The new procedure is noninvasive, well tolerated by the patient, and takes only a few minutes. It could be particularly useful when repeated measurements of pulmonary gas exchange are required. One product of the procedure is the difference between the PO2 of end-tidal alveolar gas and the calculated PO2 of arterial blood. This measurement is related to the classical alveolar-arterial PO2 difference based on ideal alveolar gas. However that traditional index is heavily influenced by lung units with low ventilation-perfusion ratios, whereas the new index has a broader physiological basis because it includes contributions from the whole lung. Copyright © 2017 Elsevier B.V. All rights reserved. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19246596','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19246596">Water and nitrogen conditions affect the relationships of Delta13C and Delta18O to gas exchange and growth in durum wheat.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Cabrera-Bosquet, Llorenç; Molero, Gemma; Nogués, Salvador; Araus, José Luis 2009-01-01 Whereas the effects of water and nitrogen (N) on plant Delta(13)C have been reported previously, these factors have scarcely been studied for Delta(18)O. Here the combined effect of different water and N regimes on Delta(13)C, Delta(18)O, gas exchange, water-use efficiency (WUE), and growth of four genotypes of durum wheat [Triticum turgidum L. ssp. durum (Desf.) Husn.] cultured in pots was studied. Water and N supply significantly increased plant growth. However, a reduction in water supply did not lead to a significant decrease in gas exchange parameters, and consequently Delta(13)C was only slightly modified by water input. Conversely, N fertilizer significantly decreased Delta(13)C. On the other hand, water supply decreased Delta(18)O values, whereas N did not affect this parameter. Delta(18)O variation was mainly determined by the amount of transpired water throughout plant growth (T(cum)), whereas Delta(13)C variation was explained in part by a combination of leaf N and stomatal conductance (g(s)). Even though the four genotypes showed significant differences in cumulative transpiration rates and biomass, this was not translated into significant differences in Delta(18)O(s). However, genotypic differences in Delta(13)C were observed. Moreover, approximately 80% of the variation in biomass across growing conditions and genotypes was explained by a combination of both isotopes, with Delta(18)O alone accounting for approximately 50%. This illustrates the usefulness of combining Delta(18)O and Delta(13)C in order to assess differences in plant growth and total transpiration, and also to provide a time-integrated record of the photosynthetic and evaporative performance of the plant during the course of crop growth. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23715084','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23715084">A review of air exchange rate models for air pollution exposure assessments.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Breen, Michael S; Schultz, Bradley D; Sohn, Michael D; Long, Thomas; Langstaff, John; Williams, Ronald; Isaacs, Kristin; Meng, Qing Yu; Stallings, Casson; Smith, Luther 2014-11-01 A critical aspect of air pollution exposure assessments is estimation of the air exchange rate (AER) for various buildings where people spend their time. The AER, which is the rate of exchange of indoor air with outdoor air, is an important determinant for entry of outdoor air pollutants and for removal of indoor-emitted air pollutants. This paper presents an overview and critical analysis of the scientific literature on empirical and physically based AER models for residential and commercial buildings; the models highlighted here are feasible for exposure assessments as extensive inputs are not required. Models are included for the three types of airflows that can occur across building envelopes: leakage, natural ventilation, and mechanical ventilation. Guidance is provided to select the preferable AER model based on available data, desired temporal resolution, types of airflows, and types of buildings included in the exposure assessment. For exposure assessments with some limited building leakage or AER measurements, strategies are described to reduce AER model uncertainty. This review will facilitate the selection of AER models in support of air pollution exposure assessments. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19880029838&hterms=Chlorella&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DChlorella','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19880029838&hterms=Chlorella&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DChlorella">Operation of an experimental algal gas exchanger for use in a CELSS</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Smernoff, David T.; Wharton, Robert A., Jr.; Averner, Maurice M. 1987-01-01 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. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19825869','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19825869">Xylem anatomy correlates with gas exchange, water-use efficiency and growth performance under contrasting water regimes: evidence from Populus deltoides x Populus nigra hybrids.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Fichot, Régis; Laurans, Françoise; Monclus, Romain; Moreau, Alain; Pilate, Gilles; Brignolas, Franck 2009-12-01 Six Populus deltoides Bartr. ex Marsh. x P. nigra L. genotypes were selected to investigate whether stem xylem anatomy correlated with gas exchange rates, water-use efficiency (WUE) and growth performance. Clonal copies of the genotypes were grown in a two-plot common garden test under contrasting water regimes, with one plot maintained irrigated and the other one subjected to moderate summer water deficit. The six genotypes displayed a large range of xylem anatomy, mean vessel and fibre diameter varying from about 40 to 60 microm and from 7.5 to 10.5 microm, respectively. Decreased water availability resulted in a reduced cell size and an important rise in vessel density, but the extent of xylem plasticity was both genotype and trait dependent. Vessel diameter and theoretical xylem-specific hydraulic conductivity correlated positively with stomatal conductance, carbon isotope discrimination and growth performance-related traits and negatively with intrinsic WUE, especially under water deficit conditions. Vessel diameter and vessel density measured under water deficit conditions correlated with the relative losses in biomass production in response to water deprivation; this resulted from the fact that a more plastic xylem structure was generally accompanied by a larger loss in biomass production. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22209165','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22209165">The effect of strobilurins on leaf gas exchange, water use efficiency and ABA content in grapevine under field conditions.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Diaz-Espejo, Antonio; Cuevas, María Victoria; Ribas-Carbo, Miquel; Flexas, Jaume; Martorell, Sebastian; Fernández, José Enrique 2012-03-01 Strobilurins are one of the most important classes of agricultural fungicides. In addition to their anti-fungal effect, strobilurins have been reported to produce simultaneous effects in plant physiology. This study investigated whether the use of strobilurin fungicide improved water use efficiency in leaves of grapevines grown under field conditions in a Mediterranean climate in southern Spain. Fungicide was applied three times in the vineyard and measurements of leaf gas exchange, plant water status, abscisic acid concentration in sap ([ABA]), and carbon isotope composition in leaves were performed before and after applications. No clear effect on stomatal conductance, leaf water potential and intrinsic water use efficiency was found after three fungicide applications. ABA concentration was observed to increase after fungicide application on the first day, vanishing three days later. Despite this transient effect, evolution of [ABA] matched well with the evolution of leaf carbon isotope ratio, which can be used as a surrogate for plant water use efficiency. Morning stomatal conductance was negatively correlated to [ABA]. Yield was enhanced in strobilurin treated plants, whereas fruit quality remained unaltered. Published by Elsevier GmbH. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010005746','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010005746">BOREAS TE-5 Leaf Gas Exchange Data</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Hall, Forrest G. (Editor); Curd, Shelaine (Editor); Ehleriinger, Jim; Brooks, J. Renee; Flanagan, Larry 2000-01-01 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). </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1714022B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1714022B">Atmospheric exchange of carbon dioxide and methane of a small water body and a floating mat in the Luther Marsh peatland, Ontario, Canada</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Burger, Magdalena; Berger, Sina; Blodau, Christian 2015-04-01 Recent investigations have suggested that small water bodies cover larger areas in northern peatlands than previously assumed. Their role in the carbon cycle and gas exchange rates are poorly constrained so far. To address this issue we measured CO2 and CH4 fluxes on a small water body (ca. 700 m2) and the surrounding floating mat in the Luther Marsh peatland in Ontario, Canada from July to September 2014. To this end we used closed chambers combined with a portable Los Gatos high-resolution trace gas analyzer at different water depths and distances from the shore on the pond and with different dominating plant types on the floating mat surrounding the pond. In addition, CO2 concentrations were recorded in high temporal resolution using an infrared sensor system during selected periods. Air and water temperature, humidity and temperature of the floating mat, wind speed and direction, photosynthetically active radiation, air pressure and relative humidity were also recorded as auxiliary data at the study site. The results show that pond and floating mat were sources of methane throughout the whole measuring period. Methane emissions via the ebullition pathway occurred predominantly near the shore and on the floating mat. During the daytime measurements the floating mat acted as a net sink and the pond as a net source of CO2. The dynamics of CO2 exchange was also strongly time dependent, as CO2 emissions from the pond strongly increased after mid-August. This suggests that photosynthesis was more affected by seasonal decline than respiration process in the pond and that the allochthonous component of the CO2 flux increased in relative importance towards fall. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19077169','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19077169">Surviving floods: leaf gas films improve O₂ and CO₂ exchange, root aeration, and growth of completely submerged rice.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Pedersen, Ole; Rich, Sarah Meghan; Colmer, Timothy David 2009-04-01 When completely submerged, the leaves of some species retain a surface gas film. Leaf gas films on submerged plants have recently been termed 'plant plastrons', analogous with the plastrons of aquatic insects. In aquatic insects, surface gas layers (i.e. plastrons) enlarge the gas-water interface to promote O₂ uptake when under water; however, the function of leaf gas films has rarely been considered. The present study demonstrates that gas films on leaves of completely submerged rice facilitate entry of O₂ from floodwaters when in darkness and CO₂ entry when in light. O₂ microprofiles showed that the improved gas exchange was not caused by differences in diffusive boundary layers adjacent to submerged leaves with or without gas films; instead, reduced resistance to gas exchange was probably due to the enlarged water-gas interface (cf. aquatic insects). When gas films were removed artificially, underwater net photosynthesis declined to only 20% of the rate with gas films present, such that, after 7 days of complete submergence, tissue sugar levels declined, and both shoot and root growth were reduced. Internal aeration of roots in anoxic medium, when shoots were in aerobic floodwater in darkness or when in light, was improved considerably when leaf gas films were present. Thus, leaf gas films contribute to the submergence tolerance of rice, in addition to those traits already recognized, such as the shoot-elongation response, aerenchyma and metabolic adjustments to O₂ deficiency and oxidative stress. © 2009 The Authors. Journal compilation © 2009 Blackwell Publishing Ltd. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23480170','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23480170">Degradation and rearrangement of a lung surfactant lipid at the air-water interface during exposure to the pollutant gas ozone.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Thompson, Katherine C; Jones, Stephanie H; Rennie, Adrian R; King, Martin D; Ward, Andrew D; Hughes, Brian R; Lucas, Claire O M; Campbell, Richard A; Hughes, Arwel V 2013-04-09 The presence of unsaturated lipids in lung surfactant is important for proper respiratory function. In this work, we have used neutron reflection and surface pressure measurements to study the reaction of the ubiquitous pollutant gas-phase ozone, O3, with pure and mixed phospholipid monolayers at the air-water interface. The results reveal that the reaction of the unsaturated lipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, POPC, with ozone leads to the rapid loss of the terminal C9 portion of the oleoyl strand of POPC from the air-water interface. The loss of the C9 portion from the interface is accompanied by an increase in the surface pressure (decrease in surface tension) of the film at the air-water interface. The results suggest that the portion of the oxidized oleoyl strand that is still attached to the lipid headgroup rapidly reverses its orientation and penetrates the air-water interface alongside the original headgroup, thus increasing the surface pressure. The reaction of POPC with ozone also leads to a loss of material from the palmitoyl strand, but the loss of palmitoyl material occurs after the loss of the terminal C9 portion from the oleoyl strand of the molecule, suggesting that the palmitoyl material is lost in a secondary reaction step. Further experiments studying the reaction of mixed monolayers composed of unsaturated lipid POPC and saturated lipid dipalmitoyl-sn-glycero-3-phosphocholine, DPPC, revealed that no loss of DPPC from the air-water interface occurs, eliminating the possibility that a reactive species such as an OH radical is formed and is able to attack nearby lipid chains. The reaction of ozone with the mixed films does cause a significant change in the surface pressure of the air-water interface. Thus, the reaction of unsaturated lipids in lung surfactant changes and impairs the physical properties of the film at the air-water interface. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26614785','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26614785">Leaf gas exchange performance and the lethal water potential of five European species during drought.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Li, Shan; Feifel, Marion; Karimi, Zohreh; Schuldt, Bernhard; Choat, Brendan; Jansen, Steven 2016-02-01 Establishing physiological thresholds to drought-induced mortality in a range of plant species is crucial in understanding how plants respond to severe drought. Here, five common European tree species were selected (Acer campestre L., Acer pseudoplatanus L., Carpinus betulus L., Corylus avellana L. and Fraxinus excelsior L.) to study their hydraulic thresholds to mortality. Photosynthetic parameters during desiccation and the recovery of leaf gas exchange after rewatering were measured. Stem vulnerability curves and leaf pressure-volume curves were investigated to understand the hydraulic coordination of stem and leaf tissue traits. Stem and root samples from well-watered and severely drought-stressed plants of two species were observed using transmission electron microscopy to visualize mortality of cambial cells. The lethal water potential (ψlethal) correlated with stem P99 (i.e., the xylem water potential at 99% loss of hydraulic conductivity, PLC). However, several plants that were stressed beyond the water potential at 100% PLC showed complete recovery during the next spring, which suggests that the ψlethal values were underestimated. Moreover, we observed a 1 : 1 relationship between the xylem water potential at the onset of embolism and stomatal closure, confirming hydraulic coordination between leaf and stem tissues. Finally, ultrastructural changes in the cytoplasm of cambium tissue and mortality of cambial cells are proposed to provide an alternative approach to investigate the point of no return associated with plant death. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29375728','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29375728">Steel reinforced composite silicone membranes and its integration to microfluidic oxygenators for high performance gas exchange.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Matharoo, Harpreet; Dabaghi, Mohammadhossein; Rochow, Niels; Fusch, Gerhard; Saraei, Neda; Tauhiduzzaman, Mohammed; Veldhuis, Stephen; Brash, John; Fusch, Christoph; Selvaganapathy, P Ravi 2018-01-01 Respiratory distress syndrome (RDS) is one of the main causes of fatality in newborn infants, particularly in neonates with low birth-weight. Commercial extracorporeal oxygenators have been used for low-birth-weight neonates in neonatal intensive care units. However, these oxygenators require high blood volumes to prime. In the last decade, microfluidics oxygenators using enriched oxygen have been developed for this purpose. Some of these oxygenators use thin polydimethylsiloxane (PDMS) membranes to facilitate gas exchange between the blood flowing in the microchannels and the ambient air outside. However, PDMS is elastic and the thin membranes exhibit significant deformation and delamination under pressure which alters the architecture of the devices causing poor oxygenation or device failure. Therefore, an alternate membrane with high stability, low deformation under pressure, and high gas exchange was desired. In this paper, we present a novel composite membrane consisting of an ultra-thin stainless-steel mesh embedded in PDMS, designed specifically for a microfluidic single oxygenator unit (SOU). In comparison to homogeneous PDMS membranes, this composite membrane demonstrated high stability, low deformation under pressure, and high gas exchange. In addition, a new design for oxygenator with sloping profile and tapered inlet configuration has been introduced to achieve the same gas exchange at lower pressure drops. SOUs were tested by bovine blood to evaluate gas exchange properties. Among all tested SOUs, the flat design SOU with composite membrane has the highest oxygen exchange of 40.32 ml/min m 2 . The superior performance of the new device with composite membrane was demonstrated by constructing a lung assist device (LAD) with a low priming volume of 10 ml. The LAD was achieved by the oxygen uptake of 0.48-0.90 ml/min and the CO 2 release of 1.05-2.27 ml/min at blood flow rates ranging between 8 and 48 ml/min. This LAD was shown to increase the </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2012-title40-vol34/pdf/CFR-2012-title40-vol34-sec1065-645.pdf','CFR2012'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2012-title40-vol34/pdf/CFR-2012-title40-vol34-sec1065-645.pdf">40 CFR 1065.645 - Amount of water in an ideal gas.</a> <a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2012&page.go=Go">Code of Federal Regulations, 2012 CFR</a> 2012-07-01 ... 40 Protection of Environment 34 2012-07-01 2012-07-01 false Amount of water in an ideal gas. 1065.645 Section 1065.645 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Calculations and Data Requirements § 1065.645 Amount of water in an ideal gas. This section describes how to... </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2013-title40-vol34/pdf/CFR-2013-title40-vol34-sec1065-645.pdf','CFR2013'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2013-title40-vol34/pdf/CFR-2013-title40-vol34-sec1065-645.pdf">40 CFR 1065.645 - Amount of water in an ideal gas.</a> <a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2013&page.go=Go">Code of Federal Regulations, 2013 CFR</a> 2013-07-01 ... 40 Protection of Environment 34 2013-07-01 2013-07-01 false Amount of water in an ideal gas. 1065.645 Section 1065.645 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Calculations and Data Requirements § 1065.645 Amount of water in an ideal gas. This section describes how to... </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2011-title40-vol33/pdf/CFR-2011-title40-vol33-sec1065-645.pdf','CFR2011'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2011-title40-vol33/pdf/CFR-2011-title40-vol33-sec1065-645.pdf">40 CFR 1065.645 - Amount of water in an ideal gas.</a> <a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2011&page.go=Go">Code of Federal Regulations, 2011 CFR</a> 2011-07-01 ... 40 Protection of Environment 33 2011-07-01 2011-07-01 false Amount of water in an ideal gas. 1065.645 Section 1065.645 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Calculations and Data Requirements § 1065.645 Amount of water in an ideal gas. This section describes how to... </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active">16</li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active">17</li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23791347','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23791347">Atmospheric partitioning and the air-water exchange of polycyclic aromatic hydrocarbons in a large shallow Chinese lake (Lake Chaohu).</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Qin, Ning; He, Wei; Kong, Xiang-Zhen; Liu, Wen-Xiu; He, Qi-Shuang; Yang, Bin; Ouyang, Hui-Ling; Wang, Qing-Mei; Xu, Fu-Liu 2013-11-01 The residual levels of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere and in dissolved phase from Lake Chaohu were measured by (GC-MS). The composition and seasonal variation were investigated. The diffusive air-water exchange flux was estimated by a two-film model, and the uncertainty in the flux calculations and the sensitivity of the parameters were evaluated. The following results were obtained: (1) the average residual levels of all PAHs (PAH16) in the atmosphere from Lake Chaohu were 60.85±46.17 ng m(-3) in the gaseous phase and 14.32±23.82 ng m(-3) in the particulate phase. The dissolved PAH16 level was 173.46±132.89 ng L(-1). (2) The seasonal variation of average PAH16 contents ranged from 43.09±33.20 ng m(-3) (summer) to 137.47±41.69 ng m(-3) (winter) in gaseous phase, from 6.62±2.72 ng m(-3) (summer) to 56.13±22.99 ng m(-3) (winter) in particulate phase, and 142.68±74.68 ng L(-1) (winter) to 360.00±176.60 ng L(-1) (summer) in water samples. Obvious seasonal trends of PAH16 concentrations were found in the atmosphere and water. The values of PAH16 for both the atmosphere and the water were significantly correlated with temperature. (3) The monthly diffusive air-water exchange flux of total PAH16 ranged from -1.77×10(4) ng m(-2) d(-1) to 1.11×10(5) ng m(-2) d(-1), with an average value of 3.45×10(4) ng m(-2) d(-1). (4) The results of a Monte Carlo simulation showed that the monthly average PAH fluxes ranged from -3.4×10(3) ng m(-2) d(-1) to 1.6×10(4) ng m(-2) d(-1) throughout the year, and the uncertainties for individual PAHs were compared. (5) According to the sensitivity analysis, the concentrations of dissolved and gaseous phase PAHs were the two most important factors affecting the results of the flux calculations. Copyright © 2013 Elsevier Ltd. All rights reserved. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29593081','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29593081">Cuticular gas exchange by Antarctic sea spiders.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Lane, Steven J; Moran, Amy L; Shishido, Caitlin M; Tobalske, Bret W; Woods, H Arthur 2018-04-25 Many marine organisms and life stages lack specialized respiratory structures, like gills, and rely instead on cutaneous respiration, which they facilitate by having thin integuments. This respiratory mode may limit body size, especially if the integument also functions in support or locomotion. Pycnogonids, or sea spiders, are marine arthropods that lack gills and rely on cutaneous respiration but still grow to large sizes. Their cuticle contains pores, which may play a role in gas exchange. Here, we examined alternative paths of gas exchange in sea spiders: (1) oxygen diffuses across pores in the cuticle, a common mechanism in terrestrial eggshells, (2) oxygen diffuses directly across the cuticle, a common mechanism in small aquatic insects, or (3) oxygen diffuses across both pores and cuticle. We examined these possibilities by modeling diffusive oxygen fluxes across all pores in the body of sea spiders and asking whether those fluxes differed from measured metabolic rates. We estimated fluxes across pores using Fick's law parameterized with measurements of pore morphology and oxygen gradients. Modeled oxygen fluxes through pores closely matched oxygen consumption across a range of body sizes, which means the pores facilitate oxygen diffusion. Furthermore, pore volume scaled hypermetrically with body size, which helps larger species facilitate greater diffusive oxygen fluxes across their cuticle. This likely presents a functional trade-off between gas exchange and structural support, in which the cuticle must be thick enough to prevent buckling due to external forces but porous enough to allow sufficient gas exchange. © 2018. Published by The Company of Biologists Ltd. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21619278','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21619278">An analytical method for trifluoroacetic Acid in water and air samples using headspace gas chromatographic determination of the methyl ester.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Zehavi, D; Seiber, J N 1996-10-01 An analytical method has been developed for the determination of trace levels of trifluoroacetic acid (TFA), an atmospheric breakdown product of several of the hydrofluorocarbon (HFC) and hydrochlorofluorocarbon (HCFC) replacements for the chlorofluorocarbon (CFC) refrigerants, in water and air. TFA is derivatized to the volatile methyl trifluoroacetate (MTFA) and determined by automated headspace gas chromatography (HSGC) with electron-capture detection or manual HSGC using GC/MS in the selected ion monitoring (SIM) mode. The method is based on the reaction of an aqueous sample containing TFA with dimethyl sulfate (DMS) in concentrated sulfuric acid in a sealed headspace vial under conditions favoring distribution of MTFA to the vapor phase. Water samples are prepared by evaporative concentration, during which TFA is retained as the anion, followed by extraction with diethyl ether of the acidified sample and then back-extraction of TFA (as the anion) in aqueous bicarbonate solution. The extraction step is required for samples with a relatively high background of other salts and organic materials. Air samples are collected in sodium bicarbonate-glycerin-coated glass denuder tubes and prepared by rinsing the denuder contents with water to form an aqueous sample for derivatization and analysis. Recoveries of TFA from spiked water, with and without evaporative concentration, and from spiked air were quantitative, with estimated detection limits of 10 ng/mL (unconcentrated) and 25 pg/mL (concentrated 250 mL:1 mL) for water and 1 ng/m(3) (72 h at 5 L/min) for air. Several environmental air, fogwater, rainwater, and surface water samples were successfully analyzed; many showed the presence of TFA. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24097404','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24097404">A membrane inlet mass spectrometry system for noble gases at natural abundances in gas and water samples.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Visser, Ate; Singleton, Michael J; Hillegonds, Darren J; Velsko, Carol A; Moran, Jean E; Esser, Bradley K 2013-11-15 Noble gases dissolved in groundwater can reveal paleotemperatures, recharge conditions, and precise travel times. The collection and analysis of noble gas samples are cumbersome, involving noble gas purification, cryogenic separation and static mass spectrometry. A quicker and more efficient sample analysis method is required for introduced tracer studies and laboratory experiments. A Noble Gas Membrane Inlet Mass Spectrometry (NG-MIMS) system was developed to measure noble gases at natural abundances in gas and water samples. The NG-MIMS system consists of a membrane inlet, a dry-ice water trap, a carbon-dioxide trap, two getters, a gate valve, a turbomolecular pump and a quadrupole mass spectrometer equipped with an electron multiplier. Noble gases isotopes (4)He, (22)Ne, (38)Ar, (84)Kr and (132)Xe are measured every 10 s. The NG-MIMS system can reproduce measurements made on a traditional noble gas mass spectrometer system with precisions of 2%, 8%, 1%, 1% and 3% for He, Ne, Ar, Kr and Xe, respectively. Noble gas concentrations measured in an artificial recharge pond were used to monitor an introduced xenon tracer and to reconstruct temperature variations to within 2 °C. Additional experiments demonstrated the capability to measure noble gases in gas and in water samples, in real time. The NG-MIMS system is capable of providing analyses sufficiently accurate and precise for introduced noble gas tracers at managed aquifer recharge facilities, groundwater fingerprinting based on excess air and noble gas recharge temperature, and field and laboratory studies investigating ebullition and diffusive exchange. Copyright © 2013 John Wiley & Sons, Ltd. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1024521','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1024521">Kitchen Appliance Upgrades Improve Water Efficiency at DOD Exchange Facilities: Best Management Practice Case Study #11: Commercial Kitchen Equipment (Brochure)</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Not Available 2011-09-01 The Exchange, formerly the Army and Air Force Exchange Service (AAFES), is a joint military activity and the U.S. Department of Defense?s (DOD) oldest and largest retailer. The Exchange is taking a leadership role in water efficiency improvements in their commercial kitchens by integrating water efficiency concepts into the organization?s overall sustainability plan and objectives. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017GBioC..31..961W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017GBioC..31..961W">The impact of changing wind speeds on gas transfer and its effect on global air-sea CO2 fluxes</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Wanninkhof, R.; Triñanes, J. 2017-06-01 An increase in global wind speeds over time is affecting the global uptake of CO2 by the ocean. We determine the impact of changing winds on gas transfer and CO2 uptake by using the recently updated, global high-resolution, cross-calibrated multiplatform wind product (CCMP-V2) and a fixed monthly pCO2 climatology. In particular, we assess global changes in the context of regional wind speed changes that are attributed to large-scale climate reorganizations. The impact of wind on global CO2 gas fluxes as determined by the bulk formula is dependent on several factors, including the functionality of the gas exchange-wind speed relationship and the regional and seasonal differences in the air-water partial pressure of CO2 gradient (ΔpCO2). The latter also controls the direction of the flux. Fluxes out of the ocean are influenced more by changes in the low-to-intermediate wind speed range, while ingassing is impacted more by changes in higher winds because of the regional correlations between wind and ΔpCO2. Gas exchange-wind speed parameterizations with a quadratic and third-order polynomial dependency on wind, each of which meets global constraints, are compared. The changes in air-sea CO2 fluxes resulting from wind speed trends are greatest in the equatorial Pacific and cause a 0.03-0.04 Pg C decade-1 increase in outgassing over the 27 year time span. This leads to a small overall decrease of 0.00 to 0.02 Pg C decade-1 in global net CO2 uptake, contrary to expectations that increasing winds increase net CO2 uptake.<abstract type="synopsis"><title type="main">Plain Language SummaryThe effects of changing winds are isolated from the total change in trends in global air-sea CO2 fluxes over the last 27 years. The overall effect of increasing winds over time has a smaller impact than expected as the impact in regions of outgassing is greater than for the regions acting as a CO2 sink. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/5818131-how-gas-cools-apples-can-fall-up','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/5818131-how-gas-cools-apples-can-fall-up">How gas cools (or, apples can fall up)</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Not Available 1987-01-01 This primer on gas cooling systems explains the basics of heat exchange within a refrigeration system, the principle of reverse-cycle refrigeration, and how a gas-engine-driven heat pump can provide cooling, additional winter heating capacity, and hot water year-round. Gas cooling equipment available or under development include natural gas chillers, engine-driven chillers, and absorption chillers. In cogeneration systems, heat recovered from an engine's exhaust and coolant may be used in an absorption chiller to provide air-conditioning. Gas desiccant cooling systems may be used in buildings and businesses that are sensitive to high humidity levels. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1611486M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1611486M">Wind variability and sheltering effects on measurements and modeling of air-water exchange for a small lake</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Markfort, Corey D.; Resseger, Emily; Porté-Agel, Fernando; Stefan, Heinz 2014-05-01 Lakes with a surface area of less than 10 km2 account for over 50% of the global cumulative lake surface water area, and make up more than 99% of the total number of global lakes, ponds, and wetlands. Within the boreal regions as well as some temperate and tropical areas, a significant proportion of land cover is characterized by lakes or wetlands, which can have a dramatic effect on land-atmosphere fluxes as well as the local and regional energy budget. Many of these small water bodies are surrounded by complex terrain and forest, which cause the wind blowing over a small lake or wetland to be highly variable. Wind mixing of the lake surface layer affects thermal stratification, surface temperature and air-water gas transfer, e.g. O2, CO2, and CH4. As the wind blows from the land to the lake, wake turbulence behind trees and other shoreline obstacles leads to a recirculation zone and enhanced turbulence. This wake flow results in the delay of the development of wind shear stress on the lake surface, and the fetch required for surface shear stress to fully develop may be ~O(1 km). Interpretation of wind measurements made on the lake is hampered by the unknown effect of wake turbulence. We present field measurements designed to quantify wind variability over a sheltered lake. The wind data and water column temperature profiles are used to evaluate a new method to quantify wind sheltering of lakes that takes into account lake size, shape and the surrounding landscape features. The model is validated against field data for 36 Minnesota lakes. Effects of non-uniform sheltering and lake shape are also demonstrated. The effects of wind sheltering must be included in lake models to determine the effect of wind-derived energy inputs on lake stratification, surface gas transfer, lake water quality, and fish habitat. These effects are also important for correctly modeling momentum, heat, moisture and trace gas flux to the atmosphere. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/6242231-water-splitting-titanium-exchanged-zeolite-technical-report','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/6242231-water-splitting-titanium-exchanged-zeolite-technical-report">'water splitting' by titanium exchanged zeolite A. Technical report</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Kuznicki, S.M.; Eyring, E.M. 1978-09-01 Visually detectable and chromatographically and mass spectrally identified hydrogen gas evolves from titanium (III) exchanged zeolite A immersed in water and illuminated with visible light. Titanium(III) exchanged zeolite X and zeolite Y do not produce this reaction. A photochemically produced, oxygenated titanium free radical (detected by electron spin resonance) not previously described is the species in the zeolite that reduces protons to molecular hydrogen. The other product of this reduction step is a nonradical, oxygenated titanium species of probable empirical formula TiO4. Heating the spent oxygenated titanium containing zeolite A under vacuum at 375 C restores over fifty percent ofmore » the free radical. Unlike previously reported systems, heating does not restore the original aquotitanium(III) species in the zeolite. Thus a means other than heating must be found to achieve a closed photochemical cycle that harnesses visible solar energy in the production of molecular hydrogen. The titanium exchanged zeolite A does, however, lend itself to a thermolysis of water previously described by Kasai and Bishop. (Author)« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/7203850-enhance-gas-processing-reflux-heat-exchangers','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/7203850-enhance-gas-processing-reflux-heat-exchangers">Enhance gas processing with reflux heat-exchangers</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Finn, A.J. 1994-05-01 Despite recent successes of membrane-based separations in low-throughput applications, cryogenic processing remains the best route for separating and purifying gas mixtures, especially when high recoveries are required. Now conventional units are being modified to yield even higher recoveries at lower costs. Throughout the chemical process industries (CPI), this is being accomplished with reflux or plate-fin exchangers, especially for processing of natural gas, and offgases from refineries and petrochemical facilities. The concept of utilizing a heat exchanger as a multi stage rectification device is not new. However, only in the last fifteen years or so has accurate design of reflux exchangersmore » become feasible. Also helpful have been the availability of prediction techniques for high-quality thermodynamic data, and process simulators that can rapidly solve the complex material, equilibrium and enthalpy relationships involved in simulating the performance of reflux exchangers. Four projects that show the value and effectiveness of reflux exchangers are discussed below in more detail. The first example considers hydrogen recovery from demethanizer overheads; the second highlights a low energy process for NGL and LPG recovery from natural gas. The third is a simple process for recovery of ethylene from fluid-catalytic cracker (FCC) offgas; and the fourth is a similar process for olefin recovery from dehydrogenation-reactor offgas.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=65336&keyword=Austria&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=65336&keyword=Austria&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">CO2 AND O3 ALTER PHOTOSYNTHESIS AND WATER VAPOR EXCHANGE FOR PINUS PONDEROSA NEEDLES</a> <a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> 1. Effects of CO2 and O3 were determined for a key component of ecosystem carbon and water cycling: needle gas exchange (photosynthesis, conductance, transpiration and water use efficiency). The measurements were made on Pinus ponderosa seedlings grown in outdoor, sunlit, mesoc... </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20000119049&hterms=water+purification&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dwater%2Bpurification','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20000119049&hterms=water+purification&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dwater%2Bpurification">Regenerable Air Purification System for Gas-Phase Contaminant Control</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Constantinescu, Ileana C.; Finn, John E.; LeVan, M. Douglas; Lung, Bernadette (Technical Monitor) 2000-01-01 Tests of a pre-prototype regenerable air purification system (RAPS) that uses water vapor to displace adsorbed contaminants from an adsorbent column have been performed at NASA Ames Research Center. A unit based on this design can be used for removing trace gas-phase contaminants from spacecraft cabin air or from polluted process streams including incinerator exhaust. During the normal operation mode, contaminants are removed from the air on the column. Regeneration of the column is performed on-line. During regeneration, contaminants are displaced and destroyed inside the closed oxidation loop. In this presentation we discuss initial experimental results for the performance of RAPS in the removal and treatment of several important spacecraft contaminant species from air. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16731054','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16731054">Ammonia as a respiratory gas in water and air-breathing fishes.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Randall, David J; Ip, Yuen K 2006-11-01 Ammonia is produced in the liver and excreted as NH(3) by diffusion across the gills. Elevated ammonia results in an increase in gill ventilation, perhaps via stimulation of gill oxygen chemo-receptors. Acidification of the water around the fish by carbon dioxide and acid excretion enhances ammonia excretion and constitutes "environmental ammonia detoxification". Fish have difficulties in excreting ammonia in alkaline water or high concentrations of environmental ammonia, or when out of water. The mudskipper, Periphthalmodon schlosseri, is capable of active NH(4)(+) transport, maintaining low internal levels of ammonia. To prevent a back flux of NH(3), these air-breathing fish can increase gill acid excretion and reduce the membrane NH(3) permeability by modifying the phospholipid and cholesterol compositions of their skin. Several air-breathing fish species can excrete ammonia into air through NH(3) volatilization. Some fish detoxify ammonia to glutamine or urea. The brains of some fish can tolerate much higher levels of ammonia than other animals. Studies of these fish may offer insights into the nature of ammonia toxicity in general. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/20018864-economic-analysis-condensers-water-recovery-steam-injected-gas-turbines','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/20018864-economic-analysis-condensers-water-recovery-steam-injected-gas-turbines">Economic analysis of condensers for water recovery in steam injected gas turbines</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> De Paepe, M.; Huvenne, P.; Dick, E. 1998-07-01 Steam injection cycles are interesting for small power ranges because of the high efficiency and the relatively low investment costs. A big disadvantage is the consumption of water by the cycle. Water recovery is seldom realized in industrial practice. In this paper an analysis of the technical and economical possibilities of water recovery by condensation of water out of the exhaust gases is made. Three gas turbines are considered : the Kawasaki M1A-13CC (2.3 MWe), the Allison 501KH (6.8 MWe) and the General Electric LM1600 (17 MWe). For every gas turbine two types of condensers are designed. In the watermore » cooled condenser finned tubes are used to cool the exhaust gases, flowing at the outside of the tubes. The water itself flows at the inside of the tubes and is cooled by a water to air cooler. In the air cooled condenser the exhaust gases flow at the inside of the tubes and the cooling air at the outside. The investment costs of the condensers is compared to the costs of the total installation. The investment costs are relatively smaller if the produced power goes up. The water cooled condenser with water to air cooler is cheaper than the air cooled condenser. Using a condenser results in higher exploitation costs due to the fans and pumps. It is shown that the air cooled condenser has lower exploitation costs than the water cooled one. Pay back time of the total installation does not significantly vary compared to the installation without recovery. Water prices are determined for which water recovery is profitable. For the water cooled condenser the turning point lies at 2.2 Euro/m; for the air cooled condenser this is 0.6 Euro/m.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1611838B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1611838B">The influence of water vapor on atmospheric exchange measurements with an ICOS* based Laser absorption analyzer</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Bunk, Rüdiger; Quan, Zhi; Wandel, Matthias; Yi, Zhigang; Bozem, Heiko; Kesselmeier, Jürgen 2014-05-01 Carbonyl sulfide and carbon monoxide are both atmospheric trace gases of high interest. Recent advances in the field of spectroscopy have enabled instruments that measure the concentration of the above and other trace gases very fast and with good precision. Increasing the effective path length by reflecting the light between two mirrors in a cavity, these instruments reach impressive sensitivities. Often it is possible to measure the concentration of more than one trace gas at the same time. The OCS/CO2 Analyzer by LGR (Los Gatos Research, Inc.) measures the concentration of water vapor [H2O], carbonyl sulfide [COS], carbon dioxide [CO2] and carbon monoxide [CO] simultaneously. For that the cavity is saturated with light, than the attenuation of light is measured as in standard absorption spectroscopy. The instrument proved to be very fast with good precision and to be able to detect even very low concentrations, especially for COS (as low as 30ppt in the case of COS). However, we observed a rather strong cross sensitivity to water vapor. Altering the water vapor content of the sampled air with two different methods led to a change in the perceived concentration of COS, CO and CO2. This proved especially problematic for enclosure (cuvette) measurements, where the concentrations of one of the above species in an empty cuvette are compared to the concentration of another cuvette containing a plant whose exchange of trace gases with the atmosphere is of interest. There, the plants transpiration leads to a large difference in water vapor content between the cuvettes and that in turn produces artifacts in the concentration differences between the cuvettes for the other above mentioned trace gases. For CO, simultaneous measurement with a UV-Emission Analyzer (AL 5002, Aerolaser) and the COS/CO Analyzer showed good agreement of perceived concentrations as long as the sample gas was dry and an increasing difference in perceived concentration when the sample gas was </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28819793','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28819793">The mechanisms underlying the production of discontinuous gas exchange cycles in insects.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Matthews, Philip G D 2018-03-01 This review examines the control of gas exchange in insects, specifically examining what mechanisms could explain the emergence of discontinuous gas exchange cycles (DGCs). DGCs are gas exchange patterns consisting of alternating breath-hold periods and bouts of gas exchange. While all insects are capable of displaying a continuous pattern of gas exchange, this episodic pattern is known to occur within only some groups of insects and then only sporadically or during certain phases of their life cycle. Investigations into DGCs have tended to emphasise the role of chemosensory thresholds in triggering spiracle opening as critical for producing these gas exchange patterns. However, a chemosensory basis for episodic breathing also requires an as-of-yet unidentified hysteresis between internal respiratory stimuli, chemoreceptors, and the spiracles. What has been less appreciated is the role that the insect's central nervous system (CNS) might play in generating episodic patterns of ventilation. The active ventilation displayed by many insects during DGCs suggests that this pattern could be the product of directed control by the CNS rather than arising passively as a result of self-sustaining oscillations in internal oxygen and carbon dioxide levels. This paper attempts to summarise what is currently known about insect gas exchange regulation, examining the location and control of ventilatory pattern generators in the CNS, the influence of chemoreceptor feedback in the form of O 2 and CO 2 /pH fluctuations in the haemolymph, and the role of state-dependent changes in CNS activity on ventilatory control. This information is placed in the context of what is currently known regarding the production of discontinuous gas exchange patterns. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ACP....17.8177K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ACP....17.8177K">The boundary condition for vertical velocity and its interdependence with surface gas exchange</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Kowalski, Andrew S. 2017-07-01 The law of conservation of linear momentum is applied to surface gas exchanges, employing scale analysis to diagnose the vertical velocity (w) in the boundary layer. Net upward momentum in the surface layer is forced by evaporation (E) and defines non-zero vertical motion, with a magnitude defined by the ratio of E to the air density, as w = <mstyle displaystyle="false">E/ρ</mstyle>. This is true even right down at the surface where the boundary condition is w|0 = <mstyle displaystyle="false"><mfrac style="text">E/ρ|0</mfrac></mstyle> (where w|0 and ρ|0 represent the vertical velocity and density of air at the surface). This Stefan flow velocity implies upward transport of a non-diffusive nature that is a general feature of the troposphere but is of particular importance at the surface, where it assists molecular diffusion with upward gas migration (of H2O, for example) but opposes that of downward-diffusing species like CO2 during daytime. The definition of flux-gradient relationships (eddy diffusivities) requires rectification to exclude non-diffusive transport, which does not depend on scalar gradients. At the microscopic scale, the role of non-diffusive transport in the process of evaporation from inside a narrow tube - with vapour transport into an overlying, horizontal airstream - was described long ago in classical mechanics and is routinely accounted for by chemical engineers, but has been neglected by scientists studying stomatal conductance. Correctly accounting for non-diffusive transport through stomata, which can appreciably reduce net CO2 transport and marginally boost that of water vapour, should improve characterisations of ecosystem and plant functioning. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5388163','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5388163">Exchange Bias Optimization by Controlled Oxidation of Cobalt Nanoparticle Films Prepared by Sputter Gas Aggregation</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Antón, Ricardo López; González, Juan A.; Andrés, Juan P.; Normile, Peter S.; Canales-Vázquez, Jesús; Muñiz, Pablo; Riveiro, José M.; De Toro, José A. 2017-01-01 Porous films of cobalt nanoparticles have been obtained by sputter gas aggregation and controllably oxidized by air annealing at 100 °C for progressively longer times (up to more than 1400 h). The magnetic properties of the samples were monitored during the process, with a focus on the exchange bias field. Air annealing proves to be a convenient way to control the Co/CoO ratio in the samples, allowing the optimization of the exchange bias field to a value above 6 kOe at 5 K. The occurrence of the maximum in the exchange bias field is understood in terms of the density of CoO uncompensated spins and their degree of pinning, with the former reducing and the latter increasing upon the growth of a progressively thicker CoO shell. Vertical shifts exhibited in the magnetization loops are found to correlate qualitatively with the peak in the exchange bias field, while an increase in vertical shift observed for longer oxidation times may be explained by a growing fraction of almost completely oxidized particles. The presence of a hummingbird-like form in magnetization loops can be understood in terms of a combination of hard (biased) and soft (unbiased) components; however, the precise origin of the soft phase is as yet unresolved. PMID:28336895 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28336895','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28336895">Exchange Bias Optimization by Controlled Oxidation of Cobalt Nanoparticle Films Prepared by Sputter Gas Aggregation.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Antón, Ricardo López; González, Juan A; Andrés, Juan P; Normile, Peter S; Canales-Vázquez, Jesús; Muñiz, Pablo; Riveiro, José M; De Toro, José A 2017-03-11 Porous films of cobalt nanoparticles have been obtained by sputter gas aggregation and controllably oxidized by air annealing at 100 °C for progressively longer times (up to more than 1400 h). The magnetic properties of the samples were monitored during the process, with a focus on the exchange bias field. Air annealing proves to be a convenient way to control the Co/CoO ratio in the samples, allowing the optimization of the exchange bias field to a value above 6 kOe at 5 K. The occurrence of the maximum in the exchange bias field is understood in terms of the density of CoO uncompensated spins and their degree of pinning, with the former reducing and the latter increasing upon the growth of a progressively thicker CoO shell. Vertical shifts exhibited in the magnetization loops are found to correlate qualitatively with the peak in the exchange bias field, while an increase in vertical shift observed for longer oxidation times may be explained by a growing fraction of almost completely oxidized particles. The presence of a hummingbird-like form in magnetization loops can be understood in terms of a combination of hard (biased) and soft (unbiased) components; however, the precise origin of the soft phase is as yet unresolved. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/6039646-process-gas-hear-recovery','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/6039646-process-gas-hear-recovery">Process gas hear recovery</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Anderson, W.M.; Thurner, R.P. 1977-01-01 In considering the use of regenerative and recuperative heat exchangers for process-gas heat recovery general information regarding heat-exchanger effectiveness versus initial capital investment and operating costs is discussed. Specific examples for preheating combustion air for process furnaces and for using primary and secondary heat exchangers in conjunction with an air-pollution-control system for drying and curing ovens cover basic heat-exchanger design and application considerations as well as investment-payback factors. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active">17</li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active">18</li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1175556','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/servlets/purl/1175556">Co-flow anode/cathode supply heat exchanger for a solid-oxide fuel cell assembly</a> <a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a> Haltiner, Jr., Karl J.; Kelly, Sean M. 2005-11-22 In a solid-oxide fuel cell assembly, a co-flow heat exchanger is provided in the flow paths of the reformate gas and the cathode air ahead of the fuel cell stack, the reformate gas being on one side of the exchanger and the cathode air being on the other. The reformate gas is at a substantially higher temperature than is desired in the stack, and the cathode gas is substantially cooler than desired. In the co-flow heat exchanger, the temperatures of the reformate and cathode streams converge to nearly the same temperature at the outlet of the exchanger. Preferably, the heat exchanger is formed within an integrated component manifold (ICM) for a solid-oxide fuel cell assembly. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009JGRG..114.0C08W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009JGRG..114.0C08W">Diminished mercury emission from waters with duckweed cover</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Wollenberg, Jennifer L.; Peters, Stephen C. 2009-06-01 Duckweeds (Lemnaceae) are a widely distributed type of floating vegetation in freshwater systems. Under suitable conditions, duckweeds form a dense vegetative mat on the water surface, which reduces light penetration into the water column and limits gas exchange at the water-air interface by decreasing the area of open water surface. Experiments were conducted to determine whether duckweed decreases mercury emission by limiting gas diffusion across the water-air interface and attenuating light, or, conversely, enhances emission via transpiration of mercury vapor. Microcosm flux chamber experiments indicate that duckweed decreases mercury emission from the water surface compared to open water controls. Fluxes under duckweed were 17-67% lower than in controls, with lower fluxes occurring at higher percent cover. The decrease in mercury emission suggests that duckweed may limit emission through one of several mechanisms, including limited gas transport across the air-water interface, decreased photoreactions due to light attenuation, and plant-mercury interactions. The results of this experiment were applied to a model lake system to illustrate the magnitude of potential effects on mercury cycling. The mercury retained in the lake as a result of hindered emission may increase bioaccumulation potential in lakes with duckweed cover. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29351442','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29351442">Measurements of pulmonary gas exchange efficiency using expired gas and oximetry: results in normal subjects.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> West, John B; Wang, Daniel L; Prisk, G Kim 2018-04-01 We are developing a novel, noninvasive method for measuring the efficiency of pulmonary gas exchange in patients with lung disease. The patient wears an oximeter, and we measure the partial pressures of oxygen and carbon dioxide in inspired and expired gas using miniature analyzers. The arterial Po 2 is then calculated from the oximeter reading and the oxygen dissociation curve, using the end-tidal Pco 2 to allow for the Bohr effect. This calculation is only accurate when the oxygen saturation is <94%, and therefore, these normal subjects breathed 12.5% oxygen. When the procedure is used in patients with hypoxemia, they breathe air. The Po 2 difference between the end-tidal and arterial values is called the "oxygen deficit." Preliminary data show that this index increases substantially in patients with lung disease. Here we report measurements of the oxygen deficit in 20 young normal subjects (age 19 to 31 yr) and 11 older normal subjects (47 to 88 yr). The mean value of the oxygen deficit in the young subjects was 2.02 ± 3.56 mmHg (means ± SD). This mean is remarkably small. The corresponding value in the older group was 7.53 ± 5.16 mmHg (means ± SD). The results are consistent with the age-related trend of the traditional alveolar-arterial difference, which is calculated from the calculated ideal alveolar Po 2 minus the measured arterial Po 2 . That measurement requires an arterial blood sample. The present study suggests that this noninvasive procedure will be valuable in assessing the degree of impaired gas exchange in patients with lung disease. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17706251','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17706251">Air--sea gaseous exchange of PCB at the Venice lagoon (Italy).</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Manodori, L; Gambaro, A; Moret, I; Capodaglio, G; Cescon, P 2007-10-01 Water bodies are important storage media for persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCBs) and this function is increased in coastal regions because their inputs are higher than those to the open sea. The air-water interface is extensively involved with the global cycling of PCBs because it is the place where they accumulate due to depositional processes and where they may be emitted by gaseous exchange. In this work the parallel collection of air, microlayer and sub-superficial water samples was performed in July 2005 at a site in the Venice lagoon to evaluate the summer gaseous flux of PCBs. The total concentration of PCBs (sum of 118 congeners) in air varies from 87 to 273 pg m(-3), whereas in the operationally defined dissolved phase of microlayer and sub-superficial water samples it varies from 159 to 391 pg L(-1). No significant enrichment of dissolved PCB into the microlayer has been observed, although a preferential accumulation of most hydrophobic congeners occurs. Due to this behaviour, we believe that the modified two-layer model was the most suitable approach for the evaluation of the flux at the air-sea interface, because it takes into account the influence of the microlayer. From its application it appears that PCB volatilize from the lagoon waters with a net flux varying from 58 to 195 ng m(-2)d(-1) (uncertainty: +/-50-64%) due to the strong influence of wind speed. This flux is greater than those reported in the literature for the atmospheric deposition and rivers input and reveals that PCB are actively emitted from the Venice lagoon in summer months. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18849091','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18849091">Juvenile Rhus glabra leaves have higher temperatures and lower gas exchange rates than mature leaves when compared in the field during periods of high irradiance.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Snider, John L; Choinski, John S; Wise, Robert R 2009-05-01 We sought to test the hypothesis that stomatal development determines the timing of gas exchange competency, which then influences leaf temperature through transpirationally driven leaf cooling. To test this idea, daily patterns of gas exchange and leaflet temperature were obtained from leaves of two distinctively different developmental stages of smooth sumac (Rhus glabra) grown in its native habitat. Juvenile and mature leaves were also sampled for ultrastructural studies of stomatal development. When plants were sampled in May-June, the hypothesis was supported: juvenile leaflets were (for part of the day) from 1.4 to 6.0 degrees C warmer than mature leaflets and as much as 2.0 degrees C above ambient air temperature with lower stomatal conductance and photosynthetic rates than mature leaflets. When measurements were taken from July to October, no significant differences were observed, although mature leaflet gas exchange rates declined to the levels of the juvenile leaves. The gas exchange data were supported by the observations that juvenile leaves had approximately half the number of functional stomata on a leaf surface area basis as did mature leaves. It was concluded that leaf temperature and stage of leaf development in sumac are strongly linked with the higher surface temperatures observed in juvenile leaflets in the early spring possibly being involved in promoting photosynthesis and leaf expansion when air temperatures are cooler. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28372820','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28372820">Air-water exchange of PAHs and OPAHs at a superfund mega-site.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Tidwell, Lane G; Blair Paulik, L; Anderson, Kim A 2017-12-15 Chemical fate is a concern at environmentally contaminated sites, but characterizing that fate can be difficult. Identifying and quantifying the movement of chemicals at the air-water interface are important steps in characterizing chemical fate. Superfund sites are often suspected sources of air pollution due to legacy sediment and water contamination. A quantitative assessment of polycyclic aromatic hydrocarbons (PAHs) and oxygenated PAH (OPAHs) diffusive flux in a river system that contains a Superfund Mega-site, and passes through residential, urban and agricultural land, has not been reported before. Here, passive sampling devices (PSDs) were used to measure 60 polycyclic aromatic hydrocarbons (PAHs) and 22 oxygenated PAH (OPAHs) in air and water. From these concentrations the magnitude and direction of contaminant flux between these two compartments was calculated. The magnitude of PAH flux was greater at sites near or within the Superfund Mega-site than outside of the Superfund Mega-site. The largest net individual PAH deposition at a single site was naphthalene at a rate of -14,200 (±5780) (ng/m 2 )/day. The estimated one-year total flux of phenanthrene was -7.9×10 5 (ng/m 2 )/year. Human health risk associated with inhalation of vapor phase PAHs and dermal exposure to PAHs in water were assessed by calculating benzo[a]pyrene equivalent concentrations. Excess lifetime cancer risk estimates show potential increased risk associated with exposure to PAHs at sites within and in close proximity to the Superfund Mega-site. Specifically, estimated excess lifetime cancer risk associated with dermal exposure and inhalation of PAHs was above 1 in 1 million within the Superfund Mega-site. The predominant depositional flux profile observed in this study suggests that the river water in this Superfund site is largely a sink for airborne PAHs, rather than a source. Copyright © 2017 Elsevier B.V. All rights reserved. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/14466','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/14466">Water vapor mass balance method for determining air infiltration rates in houses</a> <a target="_blank" href="http://www.fs.usda.gov/treesearch/">Treesearch</a> David R. DeWalle; Gordon M. Heisler 1980-01-01 A water vapor mass balance technique that includes the use of common humidity-control equipment can be used to determine average air infiltration rates in buildings. Only measurements of the humidity inside and outside the home, the mass of vapor exchanged by a humidifier/dehumidifier, and the volume of interior air space are needed. This method gives results that... </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1985htcg.agarS....N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1985htcg.agarS....N">Heat exchangers in regenerative gas turbine cycles</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Nina, M. N. R.; Aguas, M. P. N. 1985-09-01 Advances in compact heat exchanger design and fabrication together with fuel cost rises continuously improve the attractability of regenerative gas turbine helicopter engines. In this study cycle parameters aiming at reduced specific fuel consumption and increased payload or mission range, have been optimized together with heat exchanger type and size. The discussion is based on a typical mission for an attack helicopter in the 900 kw power class. A range of heat exchangers is studied to define the most favorable geometry in terms of lower fuel consumption and minimum engine plus fuel weight. Heat exchanger volume, frontal area ratio and pressure drop effect on cycle efficiency are considered. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28873626','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28873626">Effectiveness of water-air and octanol-air partition coefficients to predict lipophilic flavor release behavior from O/W emulsions.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Tamaru, Shunji; Igura, Noriyuki; Shimoda, Mitsuya 2018-01-15 Flavor release from food matrices depends on the partition of volatile flavor compounds between the food matrix and the vapor phase. Thus, we herein investigated the relationship between released flavor concentrations and three different partition coefficients, namely octanol-water, octanol-air, and water-air, which represented the oil, water, and air phases present in emulsions. Limonene, 2-methylpyrazine, nonanal, benzaldehyde, ethyl benzoate, α-terpineol, benzyl alcohol, and octanoic acid were employed. The released concentrations of these flavor compounds from oil-in-water (O/W) emulsions were measured under equilibrium using static headspace gas chromatography. The results indicated that water-air and octanol-air partition coefficients correlated with the logarithms of the released concentrations in the headspace for highly lipophilic flavor compounds. Moreover, the same tendency was observed over various oil volume ratios in the emulsions. Our findings therefore suggest that octanol-air and water-air partition coefficients can be used to predict the released concentration of lipophilic flavor compounds from O/W emulsions. Copyright © 2017 Elsevier Ltd. All rights reserved. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.C11A0352L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.C11A0352L">Radon and radium in the ice-covered Arctic Ocean, and what they reveal about gas exchange in the sea ice zone.</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Loose, B.; Kelly, R. P.; Bigdeli, A.; Moran, S. B. 2014-12-01 The polar sea ice zones are regions of high primary productivity and interior water mass formation. Consequently, the seasonal sea ice cycle appears important to both the solubility and biological carbon pumps. To estimate net CO2 transfer in the sea ice zone, we require accurate estimates of the air-sea gas transfer velocity. In the open ocean, the gas transfer velocity is driven by wind, waves and bubbles - all of which are strongly altered by the presence of sea ice, making it difficult to translate open ocean estimates of gas transfer to the ice zone. In this study, we present profiles of 222Rn and 226Ra throughout the mixed-layer and euphotic zone. Profiles were collected spanning a range of sea ice cover conditions from 40 to 100%. The profiles of Rn/Ra can be used to estimate the gas transfer velocity, but the 3.8 day half-life of 222Rn implies that mixed layer radon will have a memory of the past ~20 days of gas exchange forcing, which may include a range of sea ice cover conditions. Here, we compare individual estimates of the gas transfer velocity to the turbulent forcing conditions constrained from shipboard and regional reanalysis data to more appropriately capture the time history upper ocean Rn/Ra. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRC..122.2781S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRC..122.2781S">Boundary layers at a dynamic interface: Air-sea exchange of heat and mass</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Szeri, Andrew J. 2017-04-01 Exchange of mass or heat across a turbulent liquid-gas interface is a problem of critical interest, especially in air-sea transfer of natural and anthropogenic gases involved in the study of climate. The goal in this research area is to determine the gas flux from air to sea or vice versa. For sparingly soluble nonreactive gases, this is controlled by liquid phase turbulent velocity fluctuations that act on the thin species concentration boundary layer on the liquid side of the interface. If the fluctuations in surface-normal velocity w' and gas concentration c' are known, then it is possible to determine the turbulent contribution to the gas flux. However, there is no suitable fundamental direct approach in the general case where neither w' nor c' can be easily measured. A new approach is presented to deduce key aspects about the near-surface turbulent motions from measurements that can be taken by an infrared (IR) camera. An equation is derived with inputs being the surface temperature and heat flux, and a solution method developed for the surface-normal strain experienced over time by boundary layers at the interface. Because the thermal and concentration boundary layers experience the same near-surface fluid motions, the solution for the surface-normal strain determines the gas flux or gas transfer velocity. Examples illustrate the approach in the cases of complete surface renewal, partial surface renewal, and insolation. The prospects for use of the approach in flows characterized by sheared interfaces or rapid boundary layer straining are explored. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18465177','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18465177">Preoperative gender differences in pulmonary gas exchange in morbidly obese subjects.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Zavorsky, Gerald S; Christou, Nicolas V; Kim, Do Jun; Carli, Franco; Mayo, Nancy E 2008-12-01 Morbidly obese men may have poorer pulmonary gas exchange compared to morbidly obese women (see Zavorsky et al., Chest 131:362-367, 2007). The purpose was to compare pulmonary gas exchange in morbidly obese men and women at rest and throughout exercise. Twenty-five women (age=38+/-10 years, 164+/-7 cm, body mass index or BMI = 51+/-7 kg/m(2), peak oxygen consumption or VO(2peak)=2.0+/-0.4 l/min) and 17 men (age=43+/-9 years, 178+/-7 cm, BMI=50+/-10 kg/m(2), VO(2peak)=2.6+/-0.8 l/min) were recruited to perform a graded exercise test on a cycle ergometer with temperature-corrected arterial blood-gas samples taken at rest and every minute of exercise, including peak exercise. At rest, women were 98% predicted for pulmonary diffusion compared to 88% predicted in men. At rest, women had better pulmonary gas exchange compared to the men which was related to women having a lower waist-to-hip ratio (WHR; p<0.01). Only 20% of the subjects had an excessive alveolar-to-arterial oxygen partial pressure difference (>or=25 mmHg) at peak exercise, but 75% of the subjects showed inadequate compensatory hyperventilation at peak exercise (arterial carbon dioxide pressure >35 mmHg), and both were not different between genders. At rest, morbidly obese men have poorer pulmonary gas exchange and pulmonary diffusion compared to morbidly obese women. The better gas exchange in women is related to the lower WHR in the women. During exercise, few subjects showed disturbances in pulmonary gas exchange despite demonstrating poor compensatory hyperventilation at peak exercise. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16615688','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16615688">Testing of heat exchangers in membrane oxygenators using air pressure.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Hamilton, Carole; Stein, Jutta; Seidler, Rainer; Kind, Robert; Beck, Karin; Tosok, Jürgen; Upterfofel, Jörg 2006-03-01 All heat exchangers (HE) in membrane oxygenators are tested by the manufacturer for water leaks during the production phase. However, for safety reasons, it is highly recommended that HEs be tested again before clinical use. The most common method is to attach the heater-cooler to the HE and allow the water to recirculate for at least 10 min, during which time a water leak should be evident. To improve the detection of water leaks, a test was devised using a pressure manometer with an integrated bulb used to pressurize the HE with air. The cardiopulmonary bypass system is set up as per protocol. A pressure manometer adapted to a 1/2" tubing is connected to the water inlet side of the oxygenator. The water outlet side is blocked with a short piece of 1/2" deadend tubing. The HE is pressurized with 250 mmHg for at least 30 sec and observed for any drop. Over the last 2 years, only one oxygenator has been detected with a water leak in which the air-method leaktest was performed. This unit was sent back to the manufacturer who confirmed the failure. Even though the incidence of water leaks is very low, it does occur and it is, therefore, important that all HEs are tested before they are used clinically. This method of using a pressure manometer offers many advantages, as the HE can be tested outside of the operating room (OR), allowing earlier testing of the oxygenator, no water contact is necessary, and it is simple, easy and quick to perform. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5735977','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5735977">Assessing the Effects of Water Deficit on Photosynthesis Using Parameters Derived from Measurements of Leaf Gas Exchange and of Chlorophyll a Fluorescence</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Urban, Laurent; Aarrouf, Jawad; Bidel, Luc P. R. 2017-01-01 Water deficit (WD) is expected to increase in intensity, frequency and duration in many parts of the world as a consequence of global change, with potential negative effects on plant gas exchange and growth. We review here the parameters that can be derived from measurements made on leaves, in the field, and that can be used to assess the effects of WD on the components of plant photosynthetic rate, including stomatal conductance, mesophyll conductance, photosynthetic capacity, light absorbance, and efficiency of absorbed light conversion into photosynthetic electron transport. We also review some of the parameters related to dissipation of excess energy and to rerouting of electron fluxes. Our focus is mainly on the techniques of gas exchange measurements and of measurements of chlorophyll a fluorescence (ChlF), either alone or combined. But we put also emphasis on some of the parameters derived from analysis of the induction phase of maximal ChlF, notably because they could be used to assess damage to photosystem II. Eventually we briefly present the non-destructive methods based on the ChlF excitation ratio method which can be used to evaluate non-destructively leaf contents in anthocyanins and flavonols. PMID:29312367 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29312367','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29312367">Assessing the Effects of Water Deficit on Photosynthesis Using Parameters Derived from Measurements of Leaf Gas Exchange and of Chlorophyll a Fluorescence.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Urban, Laurent; Aarrouf, Jawad; Bidel, Luc P R 2017-01-01 Water deficit (WD) is expected to increase in intensity, frequency and duration in many parts of the world as a consequence of global change, with potential negative effects on plant gas exchange and growth. We review here the parameters that can be derived from measurements made on leaves, in the field, and that can be used to assess the effects of WD on the components of plant photosynthetic rate, including stomatal conductance, mesophyll conductance, photosynthetic capacity, light absorbance, and efficiency of absorbed light conversion into photosynthetic electron transport. We also review some of the parameters related to dissipation of excess energy and to rerouting of electron fluxes. Our focus is mainly on the techniques of gas exchange measurements and of measurements of chlorophyll a fluorescence (ChlF), either alone or combined. But we put also emphasis on some of the parameters derived from analysis of the induction phase of maximal ChlF, notably because they could be used to assess damage to photosystem II. Eventually we briefly present the non-destructive methods based on the ChlF excitation ratio method which can be used to evaluate non-destructively leaf contents in anthocyanins and flavonols. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16667848','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16667848">Influence of vesicular arbuscular mycorrhizae and leaf age on net gas exchange of citrus leaves.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Syvertsen, J P; Graham, J H 1990-11-01 The purpose of this study was to test the hypothesis that vesicular arbuscular mycorrhizal (VAM) fungi affect net assimilation of CO(2) (A) of different-aged citrus leaves independent of mineral nutrition effects of mycorrhizae. Citrus aurantium L., sour orange plants were grown for 6 months in a sandy soil low in phosphorus that was either infested with the VAM fungus, Glomus intraradices Schenck & Smith, or fertilized with additional phosphorus and left nonmycorrhizal (NM). Net CO(2) assimilation, stomatal conductance, water use efficiency, and mineral nutrient status for expanding, recently expanded, and mature leaves were evaluated as well as plant size and relative growth rate of leaves. Nutrient status and net gas exchange varied with leaf age. G. intraradices-inoculated plants had well-established colonization (79% of root length) and were comparable in relative growth rate and size at final harvest with NM plants. Leaf mineral concentrations were generally the same for VAM and NM plants except for nitrogen. Although leaf nitrogen was apparently sufficient for high rates of A, VAM plants did have higher nitrogen concentrations than NM at the time of gas exchange measurements. G. intraradices had no effect on A, stomatal conductance, or water use efficiency, irrespective of leaf age. These results show that well-established VAM colonization does not affect net gas exchange of citrus plants that are comparable in size, growth rate, and nutritional status with NM plants. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29238999','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29238999">Physiological gas exchange mapping of hyperpolarized 129 Xe using spiral-IDEAL and MOXE in a model of regional radiation-induced lung injury.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Zanette, Brandon; Stirrat, Elaine; Jelveh, Salomeh; Hope, Andrew; Santyr, Giles 2018-02-01 To map physiological gas exchange parameters using dissolved hyperpolarized (HP) 129 Xe in a rat model of regional radiation-induced lung injury (RILI) with spiral-IDEAL and the model of xenon exchange (MOXE). Results are compared to quantitative histology of pulmonary tissue and red blood cell (RBC) distribution. Two cohorts (n = 6 each) of age-matched rats were used. One was irradiated in the right-medial lung, producing regional injury. Gas exchange was mapped 4 weeks postirradiation by imaging dissolved-phase HP 129 Xe using spiral-IDEAL at five gas exchange timepoints using a clinical 1.5 T scanner. Physiological lung parameters were extracted regionally on a voxel-wise basis using MOXE. Mean gas exchange parameters, specifically air-capillary barrier thickness (δ) and hematocrit (HCT) in the right-medial lung were compared to the contralateral lung as well as nonirradiated control animals. Whole-lung spectroscopic analysis of gas exchange was also performed. δ was significantly increased (1.43 ± 0.12 μm from 1.07 ± 0.09 μm) and HCT was significantly decreased (17.2 ± 1.2% from 23.6 ± 1.9%) in the right-medial lung (i.e., irradiated region) compared to the contralateral lung of the irradiated rats. These changes were not observed in healthy controls. δ and HCT correlated with histologically measured increases in pulmonary tissue heterogeneity (r = 0.77) and decreases in RBC distribution (r = 0.91), respectively. No changes were observed using whole-lung analysis. This work demonstrates the feasibility of mapping gas exchange using HP 129 Xe in an animal model of RILI 4 weeks postirradiation. Spatially resolved gas exchange mapping is sensitive to regional injury between cohorts that was undetected with whole-lung gas exchange analysis, in agreement with histology. Gas exchange mapping holds promise for assessing regional lung function in RILI and other pulmonary diseases. © 2017 The Authors. Medical Physics published by Wiley </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhDT........23V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhDT........23V">Development and Characterization of Gas Diffusion Layer Using Carbon Slurry Dispersed by Ammonium Lauryl Sulfate for Proton Exchange Member Fuel Cells</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Villacorta, Rashida Gas diffusion layers (GDLs) are a critical and essential part of proton exchange membrane fuel cells (PEMFCs). They carry out various important functions such as transportation of reactants to and from the reaction sites. The material properties and structural characteristics of the substrate and the microporous layer strongly influence fuel cell performance. The microporous layer of the GDLs was fabricated with the carbon slurry dispersed in water containing ammonium lauryl sulfate (ALS) using the wire rod coating method. GDLs were fabricated with different materials to compose the microporous layer and evaluated the effects on PEMFC power output performance. The consistency of the carbon slurry was achieved by adding 25 wt. % of PTFE, a binding agent with a 75:25 ratio of carbon (Pureblack and vapor grown carbon fiber). The GDLs were investigated in PEMFC under various relative humidity (RH) conditions using H2/O2 and H2/Air. GDLs were also fabricated with the carbon slurry dispersed in water containing sodium dodecyl sulfate (SDS) and multiwalled carbon nanotubes (MWCNTs) with isopropyl alcohol (IPA) based for fuel cell performance comparison. MWCNTs and SDS exhibits the highest performance at 60% and 70% RH with a peak power density of 1100 mW.cm-2 and 850 mW.cm-2 using air and oxygen as an oxidant. This means that the gas diffusion characteristics of these two samples were optimum at 60 and 70 % RH with high limiting current density range. It was also found that the composition of the carbon slurry, specifically ALS concentration has the highest peak power density of 1300 and 500mW.cm-2 for both H2/O 2 and H2/Air at 100% RH. However, SDS and MWCNTs demonstrates the lowest power density using air and oxygen as an oxidants at 100% RH. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/875007','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/servlets/purl/875007">Method and apparatus for extracting water from air using a desiccant</a> <a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a> Spletzer, Barry L.; Callow, Diane Schafer 2003-01-01 The present invention provides a method and apparatus for extracting liquid water from moist air using minimal energy input. The method can be considered as four phases: (1) adsorbing water from air into a desiccant, (2) isolating the water-laden desiccant from the air source, (3) desorbing water as vapor from the desiccant into a chamber, and (4) isolating the desiccant from the chamber, and compressing the vapor in the chamber to form liquid condensate. The liquid condensate can be removed for use. Careful design of the dead volumes and pressure balances can minimize the energy required. The dried air can be exchanged for fresh moist air and the process repeated. An apparatus comprises a first chamber in fluid communication with a desiccant, and having ports to intake moist air and exhaust dried air. The apparatus also comprises a second chamber in fluid communication with the desiccant. The second chamber allows variable internal pressure, and has a port for removal of liquid condensate. Each chamber can be configured to be isolated or in communication with the desiccant. The first chamber can be configured to be isolated or in communication with a course of moist air. Various arrangements of valves, pistons, and chambers are described. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/7300088-operating-experiences-rotary-air-air-heat-exchangers-hospitals-schools-nursing-homes-swimming-pools','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/7300088-operating-experiences-rotary-air-air-heat-exchangers-hospitals-schools-nursing-homes-swimming-pools">Operating experiences with rotary air-to-air heat exchangers: hospitals, schools, nursing homes, swimming pools</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Pearson, R.J. 1976-01-01 Systems utilizing rotary air-to-air heat exchangers are discussed. Basic considerations of use (fresh air requirements, system configurations, cost considerations), typical system layout/design considerations, and operating observations by engineers, staff and maintenance personnel are described. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active">18</li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active">19</li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/14753695','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/14753695">Study of the influence of surfactants on the transfer of gases into liquids by inverse gas chromatography.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Atta, Khan Rashid; Gavril, Dimitrios; Loukopoulos, Vassilios; Karaiskakis, George 2004-01-16 The experimental technique of the reversed-flow version of inverse gas chromatography was applied for the study of effects of surfactants in reducing air-water exchange rates. The vinyl chloride (VC)-water system was used as a model, which is of great importance in environmental chemistry. Using suitable mathematical analysis, various physicochemical quantities were calculated, among which the most significant are: Partition coefficients of the VC gas between the surfactant interface and the carrier gas nitrogen, as well as between the bulk of the water + surfactant solution and the carrier gas nitrogen, overall mass transfer coefficients of VC in the liquid (water + surfactant) and the gas (nitrogen) phases, water and surfactant film transfer coefficients, nitrogen, water and surfactant phase resistances for the transfer of VC into the water solution, relative resistance of surfactant in the transfer of VC into the bulk of solution, exchange velocity of VC between nitrogen and the liquid solution, and finally the thickness of the surfactant stagnant film in the liquid phase, according to the three phase resistance model. From the variation of the above parameters with the surfactant's concentration, important conclusions concerning the effects of surfactants on the transfer of a gas at the air-liquid interface, as well as to the bulk of the liquid were extracted. An interesting finding of this work was also that by successive addition of surfactant, the critical micelle concentration of surfactant was obtained, after which follows a steady-state for the transfer of the gas into the water body, which could be attributed to the transition from mono- to multi-layer state. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28003523','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28003523">An experimental evolution study confirms that discontinuous gas exchange does not contribute to body water conservation in locusts.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Talal, Stav; Ayali, Amir; Gefen, Eran 2016-12-01 The adaptive nature of discontinuous gas exchange (DGE) in insects is contentious. The classic 'hygric hypothesis', which posits that DGE serves to reduce respiratory water loss (RWL), is still the best supported. We thus focused on the hygric hypothesis in this first-ever experimental evolution study of any of the competing adaptive hypotheses. We compared populations of the migratory locust (Locusta migratoria) that underwent 10 consecutive generations of selection for desiccation resistance with control populations. Selected locusts survived 36% longer under desiccation stress but DGE prevalence did not differ between these and control populations (approx. 75%). Evolved changes in DGE properties in the selected locusts included longer cycle and interburst durations. However, in contrast with predictions of the hygric hypothesis, these changes were not associated with reduced RWL rates. Other responses observed in the selected locusts were higher body water content when hydrated and lower total evaporative water loss rates. Hence, our data suggest that DGE cycle properties in selected locusts are a consequence of an evolved increased ability to store water, and thus an improved capacity to buffer accumulated CO 2 , rather than an adaptive response to desiccation. We conclude that DGE is unlikely to be an evolutionary response to dehydration challenge in locusts. © 2016 The Author(s). </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/33600','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/33600">Leaf gas exchange of mature bottomland oak trees</a> <a target="_blank" href="http://www.fs.usda.gov/treesearch/">Treesearch</a> Rico M. Gazal; Mark E. Kubiske; Kristina F. Connor 2009-01-01 We determined how changes in environmental moisture affected leaf gas exchange in Nuttall (Quercus texana Buckley), overcup (Q. lyrata Walt.), and dominant and codominant swamp chestnut (Q. michauxii Nutt.) oak trees in Mississippi and Louisiana. We used canopy access towers to measure leaf level gas... </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016E%26ES...49e2007B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016E%26ES...49e2007B">Dynamic water behaviour due to one trapped air pocket in a laboratory pipeline apparatus</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Bergant, A.; Karadžić, U.; Tijsseling, A. 2016-11-01 Trapped air pockets may cause severe operational problems in hydropower and water supply systems. A locally isolated air pocket creates distinct amplitude, shape and timing of pressure pulses. This paper investigates dynamic behaviour of a single trapped air pocket. The air pocket is incorporated as a boundary condition into the discrete gas cavity model (DGCM). DGCM allows small gas cavities to form at computational sections in the method of characteristics (MOC). The growth of the pocket and gas cavities is described by the water hammer compatibility equation(s), the continuity equation for the cavity volume, and the equation of state of an ideal gas. Isentropic behaviour is assumed for the trapped gas pocket and an isothermal bath for small gas cavities. Experimental investigations have been performed in a laboratory pipeline apparatus. The apparatus consists of an upstream end high-pressure tank, a horizontal steel pipeline (total length 55.37 m, inner diameter 18 mm), four valve units positioned along the pipeline including the end points, and a downstream end tank. A trapped air pocket is captured between two ball valves at the downstream end of the pipeline. The transient event is initiated by rapid opening of the upstream end valve; the downstream end valve stays closed during the event. Predicted and measured results for a few typical cases are compared and discussed. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.loc.gov/pictures/collection/hh/item/id0443.photos.220119p/','SCIGOV-HHH'); return false;" href="https://www.loc.gov/pictures/collection/hh/item/id0443.photos.220119p/">ETR COMPRESSOR BUILDING, TRA643. CAMERA FACES NORTHEAST. WATER HEAT EXCHANGER ...</a> <a target="_blank" href="http://www.loc.gov/pictures/collection/hh/">Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey</a> ETR COMPRESSOR BUILDING, TRA-643. CAMERA FACES NORTHEAST. WATER HEAT EXCHANGER IS IN LEFT FOREGROUND. A PARTIALLY ASSEMBLED PLANT AIR CONDITIONER IS AT CENTER. WORKERS AT RIGHT ASSEMBLE 4000 HORSEPOWER COMPRESSOR DRIVE MOTOR AT RIGHT. INL NEGATIVE NO. 56-3714. R.G. Larsen, Photographer, 11/13/1956 - Idaho National Engineering Laboratory, Test Reactor Area, Materials & Engineering Test Reactors, Scoville, Butte County, ID </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JPS...297..202X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JPS...297..202X">Template-directed fabrication of porous gas diffusion layer for magnesium air batteries</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Xue, Yejian; Miao, He; Sun, Shanshan; Wang, Qin; Li, Shihua; Liu, Zhaoping 2015-11-01 The uniform micropore distribution in the gas diffusion layers (GDLs) of the air-breathing cathode is very important for the metal air batteries. In this work, the super-hydrophobic GDL with the interconnected regular pores is prepared by a facile silica template method, and then the electrochemical properties of the Mg air batteries containing these GDLs are investigated. The results indicate that the interconnected and uniform pore structure, the available water-breakout pressure and the high gas permeability coefficient of the GDL can be obtained by the application of 30% silica template. The maximum power density of the Mg air battery containing the GDL with 30% regular pores reaches 88.9 mW cm-2 which is about 1.2 times that containing the pristine GDL. Furthermore, the GDL with 30% regular pores exhibits the improved the long term hydrophobic stability. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26290590','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26290590">The effect of discontinuous gas exchange on respiratory water loss in grasshoppers (Orthoptera: Acrididae) varies across an aridity gradient.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Huang, Shu-Ping; Talal, Stav; Ayali, Amir; Gefen, Eran 2015-08-01 The significance of discontinuous gas-exchange cycles (DGC) in reducing respiratory water loss (RWL) in insects is contentious. Results from single-species studies are equivocal in their support of the classic 'hygric hypothesis' for the evolution of DGC, whereas comparative analyses generally support a link between DGC and water balance. In this study, we investigated DGC prevalence and characteristics and RWL in three grasshopper species (Acrididae, subfamily Pamphaginae) across an aridity gradient in Israel. In order to determine whether DGC contributes to a reduction in RWL, we compared the DGC characteristics and RWL associated with CO2 release (transpiration ratio, i.e. the molar ratio of RWL to CO2 emission rates) among these species. Transpiration ratios of DGC and continuous breathers were also compared intraspecifically. Our data show that DGC characteristics, DGC prevalence and the transpiration ratios correlate well with habitat aridity. The xeric-adapted Tmethis pulchripennis exhibited a significantly shorter burst period and lower transpiration ratio compared with the other two mesic species, Ocneropsis bethlemita and Ocneropsis lividipes. However, DGC resulted in significant water savings compared with continuous exchange in T. pulchripennis only. These unique DGC characteristics for T. pulchripennis were correlated with its significantly higher mass-specific tracheal volume. Our data suggest that the origin of DGC may not be adaptive, but rather that evolved modulation of cycle characteristics confers a fitness advantage under stressful conditions. This modulation may result from morphological and/or physiological modifications. © 2015. Published by The Company of Biologists Ltd. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AtmEn..75..348P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AtmEn..75..348P">Intensive measurements of gas, water, and energy exchange between vegetation and troposphere during the MONTES campaign in a vegetation gradient from short semi-desertic shrublands to tall wet temperate forests in the NW Mediterranean Basin</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Peñuelas, J.; Guenther, A.; Rapparini, F.; Llusia, J.; Filella, I.; Seco, R.; Estiarte, M.; Mejia-Chang, M.; Ogaya, R.; Ibañez, J.; Sardans, J.; Castaño, L. M.; Turnipseed, A.; Duhl, T.; Harley, P.; Vila, J.; Estavillo, J. M.; Menéndez, S.; Facini, O.; Baraldi, R.; Geron, C.; Mak, J.; Patton, E. G.; Jiang, X.; Greenberg, J. 2013-08-01 MONTES (“Woodlands”) was a multidisciplinary international field campaign aimed at measuring energy, water and especially gas exchange between vegetation and atmosphere in a gradient from short semi-desertic shrublands to tall wet temperate forests in NE Spain in the North Western Mediterranean Basin (WMB). The measurements were performed at a semidesertic area (Monegros), at a coastal Mediterranean shrubland area (Garraf), at a typical Mediterranean holm oak forest area (Prades) and at a wet temperate beech forest (Montseny) during spring (April 2010) under optimal plant physiological conditions in driest-warmest sites and during summer (July 2010) with drought and heat stresses in the driest-warmest sites and optimal conditions in the wettest-coolest site. The objective of this campaign was to study the differences in gas, water and energy exchange occurring at different vegetation coverages and biomasses. Particular attention was devoted to quantitatively understand the exchange of biogenic volatile organic compounds (BVOCs) because of their biological and environmental effects in the WMB. A wide range of instruments (GC-MS, PTR-MS, meteorological sensors, O3 monitors,…) and vertical platforms such as masts, tethered balloons and aircraft were used to characterize the gas, water and energy exchange at increasing footprint areas by measuring vertical profiles. In this paper we provide an overview of the MONTES campaign: the objectives, the characterization of the biomass and gas, water and energy exchange in the 4 sites-areas using satellite data, the estimation of isoprene and monoterpene emissions using MEGAN model, the measurements performed and the first results. The isoprene and monoterpene emission rates estimated with MEGAN and emission factors measured at the foliar level for the dominant species ranged from about 0 to 0.2 mg m-2 h-1 in April. The warmer temperature in July resulted in higher model estimates from about 0 to ca. 1.6 mg m-2 h-1 for </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20130000766','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20130000766">International Space Station Common Cabin Air Assembly Condensing Heat Exchanger Hydrophilic Coating Operation, Recovery, and Lessons Learned</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Balistreri, Steven F.; Steele, John W.; Caron, Mark E.; Laliberte, Yvon J.; Shaw, Laura A. 2013-01-01 The ability to control the temperature and humidity of an environment or habitat is critical for human survival. These factors are important to maintaining human health and comfort, as well as maintaining mechanical and electrical equipment in good working order to support the human and to accomplish mission objectives. The temperature and humidity of the International Space Station (ISS) United States On-orbit Segment (USOS) cabin air is controlled by the Common Cabin Air Assembly (CCAA). The CCAA consists of a fan, a condensing heat exchanger (CHX), an air/water separator, temperature and liquid sensors, and electrical controlling hardware and software. The CHX is the primary component responsible for control of temperature and humidity. The CCAA CHX contains a chemical coating that was developed to be hydrophilic and thus attract water from the humid influent air. This attraction forms the basis for water removal and therefore cabin humidity control. However, there have been several instances of CHX coatings becoming hydrophobic and repelling water. When this behavior is observed in an operational CHX in the ISS segments, the unit s ability to remove moisture from the air is compromised and the result is liquid water carryover into downstream ducting and systems. This water carryover can have detrimental effects on the ISS cabin atmosphere quality and on the health of downstream hardware. If the water carryover is severe and widespread, this behavior can result in an inability to maintain humidity levels in the USOS. This paper will describe the operation of the five CCAAs within the USOS, the potential causes of the hydrophobic condition, and the impacts of the resulting water carryover to downstream systems. It will describe the history of this behavior and the actual observed impacts to the ISS USOS. Information on mitigation steps to protect the health of future CHX hydrophilic coatings as well as remediation and recovery of the full heat exchanger will be </li> <li> <a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=262549','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=262549">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</a> <a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a> 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... </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1361339-european-regional-climate-zone-modeling-commercial-absorption-heat-pump-hot-water-heater','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1361339-european-regional-climate-zone-modeling-commercial-absorption-heat-pump-hot-water-heater">European Regional Climate Zone Modeling of a Commercial Absorption Heat Pump Hot Water Heater</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Sharma, Vishaldeep; Shen, Bo; Keinath, Chris 2017-01-01 High efficiency gas-burning hot water heating takes advantage of a condensing heat exchanger to deliver improved combustion efficiency over a standard non-condensing configuration. The water heating is always lower than the gas heating value. In contrast, Gas Absorption Heat Pump (GAHP) hot water heating combines the efficiency of gas burning with the performance increase from a heat pump to offer significant gas energy savings. An ammonia-water system also has the advantage of zero Ozone Depletion Potential and low Global Warming Potential. In comparison with air source electric heat pumps, the absorption system can maintain higher coefficients of performance in coldermore » climates. In this work, a GAHP commercial water heating system was compared to a condensing gas storage system for a range of locations and climate zones across Europe. The thermodynamic performance map of a single effect ammonia-water absorption system was used in a building energy modeling software that could also incorporate the changing ambient air temperature and water mains temperature for a specific location, as well as a full-service restaurant water draw pattern.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JPhCS.891a2135C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JPhCS.891a2135C">Research on Heat Exchange Process in Aircraft Air Conditioning System</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Chichindaev, A. V. 2017-11-01 Using of heat-exchanger-condenser in the air conditioning system of the airplane Tu-204 (Boeing, Airbus, Superjet 100, MS-21, etc.) for cooling the compressed air by the cold air with negative temperature exiting the turbine results in a number of operational problems. Mainly it’s frosting of the heat exchange surface, which is the cause of live-section channels frosting, resistance increasing and airflow in the system decreasing. The purpose of this work is to analyse the known freeze-up-fighting methods for heat-exchanger-condenser, description of the features of anti-icing protection and offering solutions to this problem. For the problem of optimizing the design of heat exchangers in this work used generalized criterion that describes the ratio of thermal resistances of cold and hot sections, which include: the ratio of the initial values of heat transfer agents flow state; heat exchange surface finning coefficients; factors which describes the ratio of operating parameters and finning area. By controlling the ratio of the thermal resistances can be obtained the desired temperature of the heat exchange surface, which would prevent freezing. The work presents the results of a numerical study of the effect of different combinations of regime and geometrical factors changes on reduction of the heat-exchanger-condenser freezing surface area, including using of variable ratio of thermal resistances. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20160009653&hterms=water&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26Nf%3DPublication-Date%257CBTWN%2B20140101%2B20141231%26N%3D0%26No%3D30%26Ntt%3Dwater','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20160009653&hterms=water&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26Nf%3DPublication-Date%257CBTWN%2B20140101%2B20141231%26N%3D0%26No%3D30%26Ntt%3Dwater">Recent Advances in Water Analysis with Gas Chromatograph Mass Spectrometers</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> MacAskill, John A.; Tsikata, Edem 2014-01-01 We report on progress made in developing a water sampling system for detection and analysis of volatile organic compounds in water with a gas chromatograph mass spectrometer (GCMS). Two approaches are described herein. The first approach uses a custom water pre-concentrator for performing trap and purge of VOCs from water. The second approach uses a custom micro-volume, split-splitless injector that is compatible with air and water. These water sampling systems will enable a single GC-based instrument to analyze air and water samples for VOC content. As reduced mass, volume, and power is crucial for long-duration, manned space-exploration, these water sampling systems will demonstrate the ability of a GCMS to monitor both air and water quality of the astronaut environment, thereby reducing the amount of required instrumentation for long duration habitation. Laboratory prototypes of these water sampling systems have been constructed and tested with a quadrupole ion trap mass spectrometer as well as a thermal conductivity detector. Presented herein are details of these water sampling system with preliminary test results. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28079171','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28079171">Comfortable, high-efficiency heat pump with desiccant-coated, water-sorbing heat exchangers.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Tu, Y D; Wang, R Z; Ge, T S; Zheng, X 2017-01-12 Comfortable, efficient, and affordable heating, ventilation, and air conditioning systems in buildings are highly desirable due to the demands of energy efficiency and environmental friendliness. Traditional vapor-compression air conditioners exhibit a lower coefficient of performance (COP) (typically 2.8-3.8) owing to the cooling-based dehumidification methods that handle both sensible and latent loads together. Temperature- and humidity-independent control or desiccant systems have been proposed to overcome these challenges; however, the COP of current desiccant systems is quite small and additional heat sources are usually needed. Here, we report on a desiccant-enhanced, direct expansion heat pump based on a water-sorbing heat exchanger with a desiccant coating that exhibits an ultrahigh COP value of more than 7 without sacrificing any comfort or compactness. The pump's efficiency is doubled compared to that of pumps currently used in conventional room air conditioners, which is a revolutionary HVAC breakthrough. Our proposed water-sorbing heat exchanger can independently handle sensible and latent loads at the same time. The desiccants adsorb moisture almost isothermally and can be regenerated by condensation heat. This new approach opens up the possibility of achieving ultrahigh efficiency for a broad range of temperature- and humidity-control applications. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5227918','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5227918">Comfortable, high-efficiency heat pump with desiccant-coated, water-sorbing heat exchangers</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Tu, Y. D.; Wang, R. Z.; Ge, T. S.; Zheng, X. 2017-01-01 Comfortable, efficient, and affordable heating, ventilation, and air conditioning systems in buildings are highly desirable due to the demands of energy efficiency and environmental friendliness. Traditional vapor-compression air conditioners exhibit a lower coefficient of performance (COP) (typically 2.8–3.8) owing to the cooling-based dehumidification methods that handle both sensible and latent loads together. Temperature- and humidity-independent control or desiccant systems have been proposed to overcome these challenges; however, the COP of current desiccant systems is quite small and additional heat sources are usually needed. Here, we report on a desiccant-enhanced, direct expansion heat pump based on a water-sorbing heat exchanger with a desiccant coating that exhibits an ultrahigh COP value of more than 7 without sacrificing any comfort or compactness. The pump’s efficiency is doubled compared to that of pumps currently used in conventional room air conditioners, which is a revolutionary HVAC breakthrough. Our proposed water-sorbing heat exchanger can independently handle sensible and latent loads at the same time. The desiccants adsorb moisture almost isothermally and can be regenerated by condensation heat. This new approach opens up the possibility of achieving ultrahigh efficiency for a broad range of temperature- and humidity-control applications. PMID:28079171 </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017NatSR...740437T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017NatSR...740437T">Comfortable, high-efficiency heat pump with desiccant-coated, water-sorbing heat exchangers</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Tu, Y. D.; Wang, R. Z.; Ge, T. S.; Zheng, X. 2017-01-01 Comfortable, efficient, and affordable heating, ventilation, and air conditioning systems in buildings are highly desirable due to the demands of energy efficiency and environmental friendliness. Traditional vapor-compression air conditioners exhibit a lower coefficient of performance (COP) (typically 2.8-3.8) owing to the cooling-based dehumidification methods that handle both sensible and latent loads together. Temperature- and humidity-independent control or desiccant systems have been proposed to overcome these challenges; however, the COP of current desiccant systems is quite small and additional heat sources are usually needed. Here, we report on a desiccant-enhanced, direct expansion heat pump based on a water-sorbing heat exchanger with a desiccant coating that exhibits an ultrahigh COP value of more than 7 without sacrificing any comfort or compactness. The pump’s efficiency is doubled compared to that of pumps currently used in conventional room air conditioners, which is a revolutionary HVAC breakthrough. Our proposed water-sorbing heat exchanger can independently handle sensible and latent loads at the same time. The desiccants adsorb moisture almost isothermally and can be regenerated by condensation heat. This new approach opens up the possibility of achieving ultrahigh efficiency for a broad range of temperature- and humidity-control applications. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16827010','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16827010">Homeostatic maintenance of ponderosa pine gas exchange in response to stand density changes.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> McDowell, Nate G; Adams, Henry D; Bailey, John D; Hess, Marcey; Kolb, Thomas E 2006-06-01 Homeostatic maintenance of gas exchange optimizes carbon gain per water loss. Homeostasis is regulated by short-term physiological and long-term structural mechanisms, both of which may respond to changes in resource availability associated with competition. Therefore, stand density regulation via silvicultural manipulations may facilitate growth and survival through mechanisms operating at both short and long timescales. We investigated the responses of ponderosa pine (Pinus ponderosa) to stand basal area manipulations in Arizona, USA. Stand basal area was manipulated to seven replicated levels in 1962 and was maintained for four decades by decadal thinning. We measured basal area increment (BAI) to assess the response and sustainability of wood growth, carbon isotope discrimination (A) inferred from annual rings to assess the response of crown gas exchange, and ratios of leaf area to sapwood area (A(l):A(s)) to assess longer term structural acclimation. Basal area treatments increased soil water potential (r2 = 0.99) but did not affect photosynthetic capacity. BAI increased within two years of thinning, and the 40-year mean BAI was negatively correlated with stand basal area (r2 = 0.98). delta was negatively correlated with stand basal area for years 5 through 12 after thinning (r2 = 0.90). However, delta was relatively invariant with basal area for the period 13-40 years after initial thinning despite maintenance of treatment basal areas via repeated decadal thinnings. Independent gas exchange measurements verified that the ratio of photosynthesis to stomatal conductance was invariant with basal area, but absolute values of both were elevated at lower basal areas. A(l):A(s) was negatively correlated with basal area (r2 = 0.93). We hypothesize that increased A(l):A(s) is a homeostatic response to increased water availability that maximizes water-use efficiency and whole-tree carbon uptake. Elevated A(l):A(s) of trees at low basal areas was associated with greater </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29341855','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29341855">Probabilistic assessment of the potential indoor air impacts of vent-free gas heating appliances in energy-efficient homes in the United States.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Whitmyre, Gary K; Pandian, Muhilan D 2018-06-01 Use of vent-free gas heating appliances for supplemental heating in U.S. homes is increasing. However, there is currently a lack of information on the potential impact of these appliances on indoor air quality for homes constructed according to energy-efficient and green building standards. A probabilistic analysis was conducted to estimate the impact of vent-free gas heating appliances on indoor air concentrations of carbon monoxide (CO), nitrogen dioxide (NO 2 ), carbon dioxide (CO 2 ), water vapor, and oxygen in "tight" energy-efficient homes in the United States. A total of 20,000 simulations were conducted for each Department of Energy (DOE) heating region to capture a wide range of home sizes, appliance features, and conditions, by varying a number of parameters, e.g., room volume, house volume, outdoor humidity, air exchange rates, appliance input rates (Btu/hr), and house heat loss factors. Predicted airborne levels of CO were below the U.S. Environmental Protection Agency (EPA) standard of 9 ppm for all modeled cases. The airborne concentrations of NO 2 were below the U.S. Consumer Product Safety Commission (CPSC) guideline of 0.3 ppm and the Health Canada benchmark of 0.25 ppm in all cases and were below the World Health Organization (WHO) standard of 0.11 ppm in 99-100% of all cases. Predicted levels of CO 2 were below the Health Canada standard of 3500 ppm for all simulated cases. Oxygen levels in the room of vent-free heating appliance use were not significantly reduced. The great majority of cases in all DOE regions were associated with relative humidity (RH) levels from all indoor water vapor sources that were less than the EPA-recommended 70% RH maximum to avoid active mold and mildew growth. The conclusion of this investigation is that when installed in accordance with the manufacturer's instructions, vent-free gas heating appliances maintain acceptable indoor air quality in tight energy-efficient homes, as defined by the standards referenced in </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25642383','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25642383">Unlocking Chain Exchange in Highly Amphiphilic Block Polymer Micellar Systems: Influence of Agitation.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Murphy, Ryan P; Kelley, Elizabeth G; Rogers, Simon A; Sullivan, Millicent O; Epps, Thomas H 2014-11-18 Chain exchange between block polymer micelles in highly selective solvents, such as water, is well-known to be arrested under quiescent conditions, yet this work demonstrates that simple agitation methods can induce rapid chain exchange in these solvents. Aqueous solutions containing either pure poly(butadiene- b -ethylene oxide) or pure poly(butadiene- b -ethylene oxide- d 4 ) micelles were combined and then subjected to agitation by vortex mixing, concentric cylinder Couette flow, or nitrogen gas sparging. Subsequently, the extent of chain exchange between micelles was quantified using small angle neutron scattering. Rapid vortex mixing induced chain exchange within minutes, as evidenced by a monotonic decrease in scattered intensity, whereas Couette flow and sparging did not lead to measurable chain exchange over the examined time scale of hours. The linear kinetics with respect to agitation time suggested a surface-limited exchange process at the air-water interface. These findings demonstrate the strong influence of processing conditions on block polymer solution assemblies. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28833173','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28833173">Disruption of stomatal lineage signaling or transcriptional regulators has differential effects on mesophyll development, but maintains coordination of gas exchange.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Dow, Graham J; Berry, Joseph A; Bergmann, Dominique C 2017-10-01 Stomata are simultaneously tasked with permitting the uptake of carbon dioxide for photosynthesis while limiting water loss from the plant. This process is mainly regulated by guard cell control of the stomatal aperture, but recent advancements have highlighted the importance of several genes that control stomatal development. Using targeted genetic manipulations of the stomatal lineage and a combination of gas exchange and microscopy techniques, we show that changes in stomatal development of the epidermal layer lead to coupled changes in the underlying mesophyll tissues. This coordinated response tends to match leaf photosynthetic potential (V cmax ) with gas-exchange capacity (g smax ), and hence the uptake of carbon dioxide for water lost. We found that different genetic regulators systematically altered tissue coordination in separate ways: the transcription factor SPEECHLESS (SPCH) primarily affected leaf size and thickness, whereas peptides in the EPIDERMAL PATTERNING FACTOR (EPF) family altered cell density in the mesophyll. It was also determined that interlayer coordination required the cell-surface receptor TOO MANY MOUTHS (TMM). These results demonstrate that stomata-specific regulators can alter mesophyll properties, which provides insight into how molecular pathways can organize leaf tissues to coordinate gas exchange and suggests new strategies for improving plant water-use efficiency. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active">19</li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active">20</li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006GeoRL..3315404D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006GeoRL..3315404D">Circadian rhythms constrain leaf and canopy gas exchange in an Amazonian forest</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Doughty, Christopher E.; Goulden, Michael L.; Miller, Scott D.; da Rocha, Humberto R. 2006-08-01 We used a controlled-environment leaf gas-exchange system and the micrometeorological technique eddy covariance to determine whether circadian rhythms constrain the rates of leaf and canopy gas exchange in an Amazonian forest over a day. When exposed to continuous and constant light for 20 to 48 hours leaves of eleven of seventeen species reduced their photosynthetic rates and closed their stomata during the normally dark period and resumed active gas exchange during the normally light period. Similarly, the rate of whole-forest CO2 uptake at a predetermined irradiance declined during the late afternoon and early morning and increased during the middle of the day. We attribute these cycles to circadian rhythms that are analogous to ones that have been reported for herbaceous plants in the laboratory. The importance of endogenous gas exchange rhythms presents a previously unrecognized challenge for efforts to both interpret and model land-atmosphere energy and mass exchange. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26991124','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26991124">Optimal allocation of leaf epidermal area for gas exchange.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> de Boer, Hugo J; Price, Charles A; Wagner-Cremer, Friederike; Dekker, Stefan C; Franks, Peter J; Veneklaas, Erik J 2016-06-01 A long-standing research focus in phytology has been to understand how plants allocate leaf epidermal space to stomata in order to achieve an economic balance between the plant's carbon needs and water use. Here, we present a quantitative theoretical framework to predict allometric relationships between morphological stomatal traits in relation to leaf gas exchange and the required allocation of epidermal area to stomata. Our theoretical framework was derived from first principles of diffusion and geometry based on the hypothesis that selection for higher anatomical maximum stomatal conductance (gsmax ) involves a trade-off to minimize the fraction of the epidermis that is allocated to stomata. Predicted allometric relationships between stomatal traits were tested with a comprehensive compilation of published and unpublished data on 1057 species from all major clades. In support of our theoretical framework, stomatal traits of this phylogenetically diverse sample reflect spatially optimal allometry that minimizes investment in the allocation of epidermal area when plants evolve towards higher gsmax . Our results specifically highlight that the stomatal morphology of angiosperms evolved along spatially optimal allometric relationships. We propose that the resulting wide range of viable stomatal trait combinations equips angiosperms with developmental and evolutionary flexibility in leaf gas exchange unrivalled by gymnosperms and pteridophytes. © 2016 The Authors New Phytologist © 2016 New Phytologist Trust. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16443233','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16443233">Determination of ethephon residues in water by gas chromatography with cubic mass spectrometry after ion-exchange purification and derivatisation with N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Royer, A; Laporte, F; Bouchonnet, S; Communal, P-Y 2006-03-03 An analytical method has been developed for the determination of residues of ethephon (2-chloroethyl phosphonic acid) in drinking and surface water. The procedure is based on de-ionisation with an anion/cation-exchange resin, solid phase extraction by means of anion-exchange polystyrene-divinylbenzene extraction disks, elution with a mixture of methanol and 10 M hydrochloric acid (98/2, v/v), redisolution into acetonitrile after evaporation and silylation with N-(tert-butyldimethylsilyl)-N-methyltrifluoroacetamide (MTBSTFA). Quantification is performed by gas chromatography with ion-trap cubic mass spectrometric detection in the electron impact mode (GC-EI-MS3). Method validation was conducted using samples of mineral, tap, and river water that were fortified with ethephon at concentration levels ranging from 0.1 to 1.0 microg/L. The mean recovery from all the fortified samples (n = 36) amounted to 88% with a relative standard deviation of 17%. The method, therefore, was shown to allow accurate determination of ethephon residues in drinking and surface water with a limit of quantification of 0.1 microg/L. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20030093589','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20030093589">Membrane-Based Gas Traps for Ammonia, Freon-21, and Water Systems to Simplify Ground Processing</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Ritchie, Stephen M. C. 2003-01-01 Gas traps are critical for the smooth operation of coolant loops because gas bubbles can cause loss of centrifugal pump prime, interference with sensor readings, inhibition of heat transfer, and blockage of passages to remote systems. Coolant loops are ubiquitous in space flight hardware, and thus there is a great need for this technology. Conventional gas traps will not function in micro-gravity due to the absence of buoyancy forces. Therefore, clever designs that make use of adhesion and momentum are required for adequate separation, preferable in a single pass. The gas traps currently used in water coolant loops on the International Space Station are composed of membrane tube sets in a shell. Each tube set is composed of a hydrophilic membrane (used for water transport and capture of bubbles) and a hydrophobic membrane (used for venting of air bubbles). For the hydrophilic membrane, there are two critical pressures, the pressure drop and the bubble pressure. The pressure drop is the decrease in system pressure across the gas trap. The bubble pressure is the pressure required for air bubbles to pass across the water filled membrane. A significant difference between these pressures is needed to ensure complete capture of air bubbles in a single pass. Bubbles trapped by the device adsorb on the hydrophobic membrane in the interior of the hydrophilic membrane tube. After adsorption, the air is vented due to a pressure drop of approximately 1 atmosphere across the membrane. For water systems, the air is vented to the ambient (cabin). Because water vapor can also transport across the hydrophobic membrane, it is critical that a minimum surface area is used to avoid excessive water loss (would like to have a closed loop for the coolant). The currently used gas traps only provide a difference in pressure drop and bubble pressure of 3-4 psid. This makes the gas traps susceptible to failure at high bubble loading and if gas venting is impaired. One mechanism for the latter </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1714679M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1714679M">Carbon speciation at the air-sea interface during rain</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> McGillis, Wade; Hsueh, Diana; Takeshita, Yui; Donham, Emily; Markowitz, Michele; Turk, Daniela; Martz, Todd; Price, Nicole; Langdon, Chris; Najjar, Raymond; Herrmann, Maria; Sutton, Adrienne; Loose, Brice; Paine, Julia; Zappa, Christopher 2015-04-01 This investigation demonstrates the surface ocean dilution during rain events on the ocean and quantifies the lowering of surface pCO2 affecting the air-sea exchange of carbon dioxide. Surface salinity was measured during rain events in Puerto Rico, the Florida Keys, East Coast USA, Panama, and the Palmyra Atoll. End-member analysis is used to determine the subsequent surface ocean carbonate speciation. Surface ocean carbonate chemistry was measured during rain events to verify any approximations made. The physical processes during rain (cold, fresh water intrusion and buoyancy, surface waves and shear, microscale mixing) are described. The role of rain on surface mixing, biogeochemistry, and air-sea gas exchange will be discussed. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15277564','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15277564">Effect of water depth and water velocity upon the surfacing frequency of the bimodally respiring freshwater turtle, Rheodytes leukops.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Gordos, Matthew A; Franklin, Craig E; Limpus, Colin J 2004-08-01 This study examines the effect of increasing water depth and water velocity upon the surfacing behaviour of the bimodally respiring turtle, Rheodytes leukops. Surfacing frequency was recorded for R. leukops at varying water depths (50, 100, 150 cm) and water velocities (5, 15, 30 cm s(-1)) during independent trials to provide an indirect cost-benefit analysis of aquatic versus pulmonary respiration. With increasing water velocity, R. leukops decreased its surfacing frequency twentyfold, thus suggesting a heightened reliance upon aquatic gas exchange. An elevated reliance upon aquatic respiration, which presumably translates into a decreased air-breathing frequency, may be metabolically more efficient for R. leukops compared to the expenditure (i.e. time and energy) associated with air-breathing within fast-flowing riffle zones. Additionally, R. leukops at higher water velocities preferentially selected low-velocity microhabitats, presumably to avoid the metabolic expenditure associated with high water flow. Alternatively, increasing water depth had no effect upon the surfacing frequency of R. leukops, suggesting little to no change in the respiratory partitioning of the species across treatment settings. Routinely long dives (>90 min) recorded for R. leukops indicate a high reliance upon aquatic O2 uptake regardless of water depth. Moreover, metabolic and temporal costs attributed to pulmonary gas exchange within a pool-like environment were likely minimal for R. leukops, irrespective of water depth. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28406724','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28406724">Fifty Years of Research in ARDS. Gas Exchange in Acute Respiratory Distress Syndrome.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Radermacher, Peter; Maggiore, Salvatore Maurizio; Mercat, Alain 2017-10-15 Acute respiratory distress syndrome (ARDS) is characterized by severe impairment of gas exchange. Hypoxemia is mainly due to intrapulmonary shunt, whereas increased alveolar dead space explains the alteration of CO 2 clearance. Assessment of the severity of gas exchange impairment is a requisite for the characterization of the syndrome and the evaluation of its severity. Confounding factors linked to hemodynamic status can greatly influence the relationship between the severity of lung injury and the degree of hypoxemia and/or the effects of ventilator settings on gas exchange. Apart from situations of rescue treatment, targeting optimal gas exchange in ARDS has become less of a priority compared with prevention of injury. A complex question for clinicians is to understand when improvement in oxygenation and alveolar ventilation is related to a lower degree or risk of injury for the lungs. In this regard, a full understanding of gas exchange mechanism in ARDS is imperative for individualized symptomatic support of patients with ARDS. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.B51K..07P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.B51K..07P">The role of hydrodynamic transport in greenhouse gas fluxes at a wetland with emergent vegetation</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Poindexter, C.; Gilson, E.; Knox, S. H.; Matthes, J. H.; Verfaillie, J. G.; Baldocchi, D. D.; Variano, E. A. 2013-12-01 In wetlands with emergent vegetation, the hydrodynamic transport of dissolved gases is often neglected because emergent plants transport gases directly and limit wind-driven air-water gas exchange by sheltering the water surface. Nevertheless, wetland hydrodynamics, and thermally-driven stirring in particular, have the potential to impact gas fluxes in these environments. We are evaluating the importance of hydrodynamic dissolved gas transport at a re-established marsh on Twitchell Island in the Sacramento-San Joaquin Delta (California, USA). At this marsh, the U.S. Geological Survey has previously observed rapid accumulation of organic material (carbon sequestration) as well as very high methane emissions. To assess the role of hydrodynamics in the marsh's greenhouse gas fluxes, we measured dissolved carbon dioxide and methane in the water column on a bi-weekly basis beginning in July 2012. We employed a model for air-water gas fluxes in wetlands with emergent vegetation that predicts gas transfer velocities from meteorological conditions. Modeled air-water gas fluxes were compared with net gas fluxes measured at the marsh via the eddy covariance technique. This comparison revealed that hydrodynamic transport due to thermal convection was responsible for approximately one third of net carbon dioxide and methane fluxes. The cooling at the water surface driving thermal convection occurred each night and was most pronounced during the warmest months of the year. These finding have implications for the prediction and management of greenhouse gas fluxes at re-established marshes in the Sacramento-San Joaquin Delta and other similar wetlands. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=315010&Lab=NHEERL&keyword=smith&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=315010&Lab=NHEERL&keyword=smith&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">A dynamic leaf gas-exchange strategy is conserved in woody plants under changing ambient CO2: evidence from carbon isotope discrimination in paleo and CO2 enrichment studies</a> <a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> Rising atmospheric [CO2], ca, is expected to affect stomatal regulation of leaf gas-exchange of woody plants, thus influencing energy fluxes as well as carbon (C), water and nutrient cycling of forests. Researchers have reported that stomata regulate leaf gas-exchange around “set... </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28337628','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28337628">Study of plasma off-gas treatment from spent ion exchange resin pyrolysis.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Castro, Hernán Ariel; Luca, Vittorio; Bianchi, Hugo Luis 2017-03-23 Polystyrene divinylbenzene-based ion exchange resins are employed extensively within nuclear power plants (NPPs) and research reactors for purification and chemical control of the cooling water system. To maintain the highest possible water quality, the resins are regularly replaced as they become contaminated with a range of isotopes derived from compromised fuel elements as well as corrosion and activation products including 14 C, 60 Co, 90 Sr, 129 I, and 137 Cs. Such spent resins constitute a major proportion (in volume terms) of the solid radioactive waste generated by the nuclear industry. Several treatment and conditioning techniques have been developed with a view toward reducing the spent resin volume and generating a stable waste product suitable for long-term storage and disposal. Between them, pyrolysis emerges as an attractive option. Previous work of our group suggests that the pyrolysis treatment of the resins at low temperatures between 300 and 350 °C resulted in a stable waste product with a significant volume reduction (>50%) and characteristics suitable for long-term storage and/or disposal. However, another important issue to take into account is the complexity of the off-gas generated during the process and the different technical alternatives for its conditioning. Ongoing work addresses the characterization of the ion exchange resin treatment's off-gas. Additionally, the application of plasma technology for the treatment of the off-gas current was studied as an alternative to more conventional processes utilizing oil- or gas-fired post-combustion chambers operating at temperatures in excess of 1000 °C. A laboratory-scale flow reactor, using inductively coupled plasma, operating under sub-atmospheric conditions was developed. Fundamental experiments using model compounds have been performed, demonstrating a high destruction and removal ratio (>99.99%) for different reaction media, at low reactor temperatures and moderate power consumption </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017DSRI..122...17M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017DSRI..122...17M">The air-sea exchange of mercury in the low latitude Pacific and Atlantic Oceans</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Mason, Robert P.; Hammerschmidt, Chad R.; Lamborg, Carl H.; Bowman, Katlin L.; Swarr, Gretchen J.; Shelley, Rachel U. 2017-04-01 Air-sea exchange is an important component of the global mercury (Hg) cycle as it mediates the rate of increase in ocean Hg, and therefore the rate of change in levels of methylmercury (MeHg), the most toxic and bioaccumulative form of Hg in seafood and the driver of human health concerns. Gas evasion of elemental Hg (Hg0) from the ocean is an important sink for ocean Hg with previous studies suggesting that evasion is not uniform across ocean basins. To understand further the factors controlling Hg0 evasion, and its relationship to atmospheric Hg deposition, we made measurements of dissolved Hg0 (DHg0) in surface waters, along with measurements of Hg in precipitation and on aerosols, and Hg0 in marine air, during two GEOTRACES cruises; GP16 in the equatorial South Pacific and GA03 in the North Atlantic. We contrast the concentrations and estimated evasion fluxes of Hg0 during these cruises, and the factors influencing this exchange. Concentrations of DHg0 and fluxes were lower during the GP16 cruise than during the GA03 cruise, and likely reflect the lower atmospheric deposition in the South Pacific. An examination of Hg/Al ratios for aerosols from the cruises suggests that they were anthropogenically-enriched relative to crustal material, although to a lesser degree for the South Pacific than the aerosols over the North Atlantic. Both regions appear to be net sources of Hg0 to the atmosphere (evasion>deposition) and the reasons for this are discussed. Overall, the studies reported here provide further clarification on the factors controlling evasion of Hg0 from the ocean surface, and the role of anthropogenic inputs in influencing ocean Hg concentrations. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997AdSpR..20.2045.','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997AdSpR..20.2045.">Element exchange in a water-and gas-closed biological life support system</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> 1997-01-01 Liquid human wastes and household water used for nutrition of wheat made possible to realize 24% closure for the mineral exchange in an experiment with a 2-component version of ``Bios-3'' life support system (LSS) Input-output balances of revealed, that elements (primarily trace elements) within the system. The structural materials (steel, titanium), expanded clay aggregate, and catalytic furnace catalysts. By the end of experiment, the permanent nutrient solution, plants, and the human diet gradually built up Ni, Cr, Al, Fe, V, Zn, Cu, and Mo. Thorough selection and pretreatment of materials can substantially reduce this accumulation. To enhance closure of the mineral exchange involves processing of human- metabolic wastes and inedible biomes inside LSS. An efficient method to oxidize wastes by hydrogen peroxide in a quartz reactor at the temperature of 80°C controlled electromagnetic field is proposed. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997AdSpR..20.2045G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997AdSpR..20.2045G">Element exchange in a water-and gas-closed biological life support system</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Gribovskaya, I. V.; Kudenko, Yu. A.; Gitelson, J. I. 1997-01-01 Liquid human wastes and household water used for nutrition of wheat made possible to realize 24% closure for the mineral exchange in an experiment with a 2-component version of ``Bios-3'' life support system (LSS) Input-output balances of revealed, that elements (primarily trace elements) within the system. The structural materials (steel, titanium), expanded clay aggregate, and catalytic furnace catalysts. By the end of experiment, the permanent nutrient solution, plants, and the human diet gradually built up Ni, Cr, Al, Fe, V, Zn, Cu, and Mo. Thorough selection and pretreatment of materials can substantially reduce this accumulation. To enhance closure of the mineral exchange involves processing of human- metabolic wastes and inedible biomes inside LSS. An efficient method to oxidize wastes by hydrogen peroxide in a quartz reactor at the temperature of 80 degC controlled electromagnetic field is proposed. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25412353','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25412353">Polycyclic aromatic hydrocarbon (PAH) and oxygenated PAH (OPAH) air-water exchange during the deepwater horizon oil spill.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Tidwell, Lane G; Allan, Sarah E; O'Connell, Steven G; Hobbie, Kevin A; Smith, Brian W; Anderson, Kim A 2015-01-06 Passive sampling devices were used to measure air vapor and water dissolved phase concentrations of 33 polycyclic aromatic hydrocarbons (PAHs) and 22 oxygenated PAHs (OPAHs) at four Gulf of Mexico coastal sites prior to, during, and after shoreline oiling from the Deepwater Horizon oil spill (DWH). Measurements were taken at each site over a 13 month period, and flux across the water-air boundary was determined. This is the first report of vapor phase and flux of both PAHs and OPAHs during the DWH. Vapor phase sum PAH and OPAH concentrations ranged between 1 and 24 ng/m(3) and 0.3 and 27 ng/m(3), respectively. PAH and OPAH concentrations in air exhibited different spatial and temporal trends than in water, and air-water flux of 13 individual PAHs were strongly associated with the DWH incident. The largest PAH volatilizations occurred at the sites in Alabama and Mississippi in the summer, each nominally 10,000 ng/m(2)/day. Acenaphthene was the PAH with the highest observed volatilization rate of 6800 ng/m(2)/day in September 2010. This work represents additional evidence of the DWH incident contributing to air contamination, and provides one of the first quantitative air-water chemical flux determinations with passive sampling technology. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=20677&Lab=NCEA&keyword=gas+AND+liquid&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=20677&Lab=NCEA&keyword=gas+AND+liquid&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">Volatilization Rates from Water to Indoor Air Phase II</a> <a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> Contaminated water can lead to volatilization of chemicals to residential indoor air. Previous research has focused on only one source (shower stalls) and has been limited to chemicals in which gas-phase resistance to mass transfer is of marginal significance. As a result, attemp... </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17330473','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17330473">[Gas exchange features of Ambrosia artemisiifolia leaves and fruits and their correlations with soil heavy metals].</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Zu, Yuangang; Wang, Wenjie; Chen, Huafeng; Yang, Fengjian; Zhang, Zhonghua 2006-12-01 Ambrosia artemisiifolia can survive well in the habitats of heavy human disturbance and partial soil pollution. Weather its photosynthetic features benefit their survival is worthwhile to concern. With a refuse dump in Changchun City (43 degrees 50'N, 125 degrees 23'E) as study site, this paper analyzed the contents of soil Cu, Pb, Zn, Mn, Cr, Co, Ni, Cd, As, Sb and Hg at ten plots, and measured in situ the gas exchange in A. artemisiifolia leaves and young fruits. The results showed that the study site was slightly contaminated by Ni, but the contents of other soil heavy metals were approached to or substantially lower than their threshold values. The net photosynthetic rate of leaves ranged from 1.88 to 9.41 micromol x m(-2) x s(-1), while that of young fruits could be up to 2. 81 micromol x m(-2) s(-1). Averagely, the respiration rate, stomatal conductance, photosynthetic rate, and water utilization efficiency of leaves were 1.81 micromol x m(-2) x s(-1), 75.7 mmol x m(-2) x s(-1), 6.05 micromol x m(-2) x s(-1), and 4.72 micromol CO2 x mmol(-1) H2O, being 5.26, 0.64, 1.31 and 1.69 times as much as those of young fruits, respectively, indicating that the respiratory and photosynthetic capacities and water use efficiency of A. artemisiifolia young fruits were equivalent to or higher than those of its leaves. Many test heavy metals, such as Cu, Pb, Zn, Cd, As, Sb and Hg, had no significant effects on the gas exchange features of leaves and fruits, but there were significant correlations of Ni and Cr with the stomatal conductance and water use efficiency of leaves and young fruits, Cr with the gross photosynthesis of leaves, and As with the stomatal conductance of young fruits, suggesting that a majority of test soil heavy metals had no direct effects on the gas exchange in A. artemisiifolia leaves and fruits, but soil Ni, Cr and As with the contents approached to or substantially lower than the threshold values could affect the gas exchange features of A </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19870051492&hterms=water+cycle&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dwater%2Bcycle','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19870051492&hterms=water+cycle&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dwater%2Bcycle">Air Evaporation closed cycle water recovery technology - Advanced energy saving designs</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Morasko, Gwyndolyn; Putnam, David F.; Bagdigian, Robert 1986-01-01 The Air Evaporation water recovery system is a visible candidate for Space Station application. A four-man Air Evaporation open cycle system has been successfully demonstrated for waste water recovery in manned chamber tests. The design improvements described in this paper greatly enhance the system operation and energy efficiency of the air evaporation process. A state-of-the-art wick feed design which results in reduced logistics requirements is presented. In addition, several design concepts that incorporate regenerative features to minimize the energy input to the system are discussed. These include a recuperative heat exchanger, a heat pump for energy transfer to the air heater, and solar collectors for evaporative heat. The addition of the energy recovery devices will result in an energy reduction of more than 80 percent over the systems used in earlier manned chamber tests. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1212391','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/servlets/purl/1212391">Metal-air cell with ion exchange material</a> <a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a> Friesen, Cody A.; Wolfe, Derek; Johnson, Paul Bryan 2015-08-25 Embodiments of the invention are related to anion exchange membranes used in electrochemical metal-air cells in which the membranes function as the electrolyte material, or are used in conjunction with electrolytes such as ionic liquid electrolytes. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19880002876','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19880002876">Sunlight supply and gas exchange systems in microalgal bioreactor</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Mori, K.; Ohya, H.; Matsumoto, K.; Furune, H. 1987-01-01 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. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015A%26A...584A..98F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015A%26A...584A..98F">Hydrogen isotope exchanges between water and methanol in interstellar ices</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Faure, A.; Faure, M.; Theulé, P.; Quirico, E.; Schmitt, B. 2015-12-01 The deuterium fractionation of gas-phase molecules in hot cores is believed to reflect the composition of interstellar ices. The deuteration of methanol is a major puzzle, however, because the isotopologue ratio [CH2DOH]/[CH3OD], which is predicted to be equal to 3 by standard grain chemistry models, is much larger (~20) in low-mass hot corinos and significantly lower (~1) in high-mass hot cores. This dichotomy in methanol deuteration between low-mass and massive protostars is currently not understood. In this study, we report a simplified rate equation model of the deuterium chemistry occurring in the icy mantles of interstellar grains. We apply this model to the chemistry of hot corinos and hot cores, with IRAS 16293-2422 and the Orion KL Compact Ridge as prototypes, respectively. The chemistry is based on a statistical initial deuteration at low temperature followed by a warm-up phase during which thermal hydrogen/deuterium (H/D) exchanges occur between water and methanol. The exchange kinetics is incorporated using laboratory data. The [CH2DOH]/[CH3OD] ratio is found to scale inversely with the D/H ratio of water, owing to the H/D exchange equilibrium between the hydroxyl (-OH) functional groups of methanol and water. Our model is able to reproduce the observed [CH2DOH]/[CH3OD] ratios provided that the primitive fractionation of water ice [HDO]/[H2O] is ~2% in IRAS 16293-2422 and ~0.6% in Orion KL. We conclude that the molecular D/H ratios measured in hot cores may not be representative of the original mantles because molecules with exchangeable deuterium atoms can equilibrate with water ice during the warm-up phase. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active">20</li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active">21</li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22145748','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22145748">Selective permeation of moisture and VOCs through polymer membranes used in total heat exchangers for indoor air ventilation.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Zhang, L-Z; Zhang, X-R; Miao, Q-Z; Pei, L-X 2012-08-01 Fresh air ventilation is central to indoor environmental control. Total heat exchangers can be key equipment for energy conservation in ventilation. Membranes have been used for total heat exchangers for more than a decade. Much effort has been spent to achieve water vapor permeability of various membranes; however, relatively little attention has been paid to the selectivity of moisture compared with volatile organic compounds (VOCs) through such membranes. In this investigation, the most commonly used membranes, both hydrophilic and hydrophobic ones, are tested for their permeability for moisture and five VOCs (acetic acid, formaldehyde, acetaldehyde, toluene, and ethane). The selectivity of moisture vs. VOCs in these membranes is then evaluated. With a solution-diffusion model, the solubility and diffusivity of moisture and VOCs in these membranes are calculated. The resulting data could provide some reference for future material selection. Total heat exchangers are important equipment for fresh air ventilation with energy conservation. However, their implications for indoor air quality in terms of volatile organic compound permeation have not been known. The data in this article help us to clarify the impacts on indoor VOC levels of membrane-based heat exchangers. Guidelines for material selection can be obtained for future use total heat exchangers for building ventilation. © 2011 John Wiley & Sons A/S. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20150020902','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20150020902">Technology Candidates for Air-to-Air and Air-to-Ground Data Exchange</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Haynes, Brian D. 2015-01-01 Technology Candidates for Air-to-Air and Air-to-Ground Data Exchange is a two-year research effort to visualize the U. S. aviation industry at a point 50 years in the future, and to define potential communication solutions to meet those future data exchange needs. The research team, led by XCELAR, was tasked with identifying future National Airspace System (NAS) scenarios, determining requirements and functions (including gaps), investigating technical and business issues for air, ground, & air-to-ground interactions, and reporting on the results. The project was conducted under technical direction from NASA and in collaboration with XCELAR's partner, National Institute of Aerospace, and NASA technical representatives. Parallel efforts were initiated to define the information exchange functional needs of the future NAS, and specific communication link technologies to potentially serve those needs. Those efforts converged with the mapping of each identified future NAS function to potential enabling communication solutions; those solutions were then compared with, and ranked relative to, each other on a technical basis in a structured analysis process. The technical solutions emerging from that process were then assessed from a business case perspective to determine their viability from a real-world adoption and deployment standpoint. The results of that analysis produced a proposed set of future solutions and most promising candidate technologies. Gap analyses were conducted at two points in the process, the first examining technical factors, and the second as part of the business case analysis. In each case, no gaps or unmet needs were identified in applying the solutions evaluated to the requirements identified. The future communication solutions identified in the research comprise both specific link technologies and two enabling technologies that apply to most or all specific links. As a result, the research resulted in a new analysis approach, viewing the </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19890040446&hterms=quality+life&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dquality%2Blife','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19890040446&hterms=quality+life&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dquality%2Blife">Air and water quality monitor assessment of life support subsystems</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Whitley, Ken; Carrasquillo, Robyn L.; Holder, D.; Humphries, R. 1988-01-01 Preprotype air revitalization and water reclamation subsystems (Mole Sieve, Sabatier, Static Feed Electrolyzer, Trace Contaminant Control, and Thermoelectric Integrated Membrane Evaporative Subsystem) were operated and tested independently and in an integrated arrangement. During each test, water and/or gas samples were taken from each subsystem so that overall subsystem performance could be determined. The overall test design and objectives for both subsystem and integrated subsystem tests were limited, and no effort was made to meet water or gas specifications. The results of chemical analyses for each of the participating subsystems are presented along with other selected samples which were analyzed for physical properties and microbiologicals. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010BGeo....7..121A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010BGeo....7..121A">From biota to chemistry and climate: towards a comprehensive description of trace gas exchange between the biosphere and atmosphere</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Arneth, A.; Sitch, S.; Bondeau, A.; Butterbach-Bahl, K.; Foster, P.; Gedney, N.; de Noblet-Ducoudré, N.; Prentice, I. C.; Sanderson, M.; Thonicke, K.; Wania, R.; Zaehle, S. 2010-01-01 Exchange of non-CO2 trace gases between the land surface and the atmosphere plays an important role in atmospheric chemistry and climate. Recent studies have highlighted its importance for interpretation of glacial-interglacial ice-core records, the simulation of the pre-industrial and present atmosphere, and the potential for large climate-chemistry and climate-aerosol feedbacks in the coming century. However, spatial and temporal variations in trace gas emissions and the magnitude of future feedbacks are a major source of uncertainty in atmospheric chemistry, air quality and climate science. To reduce such uncertainties Dynamic Global Vegetation Models (DGVMs) are currently being expanded to mechanistically represent processes relevant to non-CO2 trace gas exchange between land biota and the atmosphere. In this paper we present a review of important non-CO2 trace gas emissions, the state-of-the-art in DGVM modelling of processes regulating these emissions, identify key uncertainties for global scale model applications, and discuss a methodology for model integration and evaluation. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009BGD.....6.7717A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009BGD.....6.7717A">From biota to chemistry and climate: towards a comprehensive description of trace gas exchange between the biosphere and atmosphere</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Arneth, A.; Sitch, S.; Bondeau, A.; Butterbach-Bahl, K.; Foster, P.; Gedney, N.; de Noblet-Ducoudré, N.; Prentice, I. C.; Sanderson, M.; Thonicke, K.; Wania, R.; Zaehle, S. 2009-07-01 Exchange of non-CO2 trace gases between the land surface and the atmosphere plays an important role in atmospheric chemistry and climate. Recent studies have highlighted its importance for interpretation of glacial-interglacial ice-core records, the simulation of the pre-industrial and present atmosphere, and the potential for large climate-chemistry and climate-aerosol feedbacks in the coming century. However, spatial and temporal variations in trace gas emissions and the magnitude of future feedbacks are a major source of uncertainty in atmospheric chemistry, air quality and climate science. To reduce such uncertainties Dynamic Global Vegetation Models (DGVMs) are currently being expanded to mechanistically represent processes relevant to non-CO2 trace gas exchange between land biota and the atmosphere. In this paper we present a review of important non-CO2 trace gas emissions, the state-of-the-art in DGVM modelling of processes regulating these emissions, identify key uncertainties for global scale model applications, and discuss a methodology for model integration and evaluation. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/19485','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/19485">A two-cell chamber for measuring gas exchange in tree seedlings</a> <a target="_blank" href="http://www.fs.usda.gov/treesearch/">Treesearch</a> Keith F. Jensen; Frederick W. Bender; Roberta G. Masters 1973-01-01 A two-celled chamber for measuring gas exchange in tree seedlings is described. Temperature is controlled within ± 0.5º C by means of a copper coil. The two cells are independent of one another, and one cell can be used as a preconditioning cell while gas exchange measurements are being made in the second cell. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/1208301','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/1208301">[Comparative study of respiratory exchanging surfaces in birds and mammals].</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Jammes, Y 1975-01-01 Anatomical studies of the respiratory apparatus of birds show evidences for a gas exchanging tubular system (parabronchi and air capillaries); these exchanging structures are entirely dissociated from the ventilatory drive acting on the air sacs. A "cross-current" gas exchanging system (perpendicular disposition of air and blood capillaries) allow a good wash-out of carbon dioxide (PaCO2 lower than PECO2). The great efficiency of this lung is allowed by its very large diffusive surface (ASa) and by the high values of lung specific oxygen diffusing capacity (DO2/ASa) and of O2 extraction coefficient in inspired air. The ventilatory pattern of birds is characterized by a greater tidal volume and a smaller respiratory frequency than in mammals of same weight. Respiratory centers of birds receive afferences from lung stretch receptors, CO2-sensitive lung receptors and arterial chemoreceptors. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28393872','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28393872">Water availability drives gas exchange and growth of trees in northeastern US, not elevated CO2 and reduced acid deposition.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Levesque, Mathieu; Andreu-Hayles, Laia; Pederson, Neil 2017-04-10 Dynamic global vegetation models (DGVM) exhibit high uncertainty about how climate change, elevated atmospheric CO 2 (atm. CO 2 ) concentration, and atmospheric pollutants will impact carbon sequestration in forested ecosystems. Although the individual roles of these environmental factors on tree growth are understood, analyses examining their simultaneous effects are lacking. We used tree-ring isotopic data and structural equation modeling to examine the concurrent and interacting effects of water availability, atm. CO 2 concentration, and SO 4 and nitrogen deposition on two broadleaf tree species in a temperate mesic forest in the northeastern US. Water availability was the strongest driver of gas exchange and tree growth. Wetter conditions since the 1980s have enhanced stomatal conductance, photosynthetic assimilation rates and, to a lesser extent, tree radial growth. Increased water availability seemingly overrides responses to reduced acid deposition, CO 2 fertilization, and nitrogen deposition. Our results indicate that water availability as a driver of ecosystem productivity in mesic temperate forests is not adequately represented in DGVMs, while CO 2 fertilization is likely overrepresented. This study emphasizes the importance to simultaneously consider interacting climatic and biogeochemical drivers when assessing forest responses to global environmental changes. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70185308','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70185308">Numerical evaluation of static-chamber measurements of soil-atmospheric gas exchange--Identification of physical processes</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Healy, Richard W.; Striegl, Robert G.; Russell, Thomas F.; Hutchinson, Gordon L.; Livingston, Gerald P. 1996-01-01 The exchange of gases between soil and atmosphere is an important process that affects atmospheric chemistry and therefore climate. The static-chamber method is the most commonly used technique for estimating the rate of that exchange. We examined the method under hypothetical field conditions where diffusion was the only mechanism for gas transport and the atmosphere outside the chamber was maintained at a fixed concentration. Analytical and numerical solutions to the soil gas diffusion equation in one and three dimensions demonstrated that gas flux density to a static chamber deployed on the soil surface was less in magnitude than the ambient exchange rate in the absence of the chamber. This discrepancy, which increased with chamber deployment time and air-filled porosity of soil, is attributed to two physical factors: distortion of the soil gas concentration gradient (the magnitude was decreased in the vertical component and increased in the radial component) and the slow transport rate of diffusion relative to mixing within the chamber. Instantaneous flux density to a chamber decreased continuously with time; steepest decreases occurred so quickly following deployment and in response to such slight changes in mean chamber headspace concentration that they would likely go undetected by most field procedures. Adverse influences of these factors were reduced by mixing the chamber headspace, minimizing deployment time, maximizing the height and radius of the chamber, and pushing the rim of the chamber into the soil. Nonlinear models were superior to a linear regression model for estimating flux densities from mean headspace concentrations, suggesting that linearity of headspace concentration with time was not necessarily a good indicator of measurement accuracy. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22788714','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22788714">Statics and dynamics of free and hydrogen-bonded OH groups at the air/water interface.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Vila Verde, Ana; Bolhuis, Peter G; Campen, R Kramer 2012-08-09 We use classical atomistic molecular dynamics simulations of two water models (SPC/E and TIP4P/2005) to investigate the orientation and reorientation dynamics of two subpopulations of OH groups belonging to water molecules at the air/water interface at 300 K: those OH groups that donate a hydrogen bond (called "bonded") and those that do not (called "free"). Free interfacial OH groups reorient in two distinct regimes: a fast regime from 0 to 1 ps and a slow regime thereafter. Qualitatively similar behavior was reported by others for free OH groups near extended hydrophobic surfaces. In contrast, the net reorientation of bonded OH groups occurs at a rate similar to that of bulk water. This similarity in reorientation rate results from compensation of two effects: decreasing frequency of hydrogen-bond breaking/formation (i.e., hydrogen-bond exchange) and faster rotation of intact hydrogen bonds. Both changes result from the decrease in density at the air/water interface relative to the bulk. Interestingly, because of the presence of capillary waves, the slowdown of hydrogen-bond exchange is significantly smaller than that reported for water near extended hydrophobic surfaces, but it is almost identical to that reported for water near small hydrophobic solutes. In this sense water at the air/water interface has characteristics of water of hydration of both small and extended hydrophobic solutes. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.epa.gov/watersense/cation-exchange-water-softeners','PESTICIDES'); return false;" href="https://www.epa.gov/watersense/cation-exchange-water-softeners">Cation Exchange Water Softeners</a> <a target="_blank" href="http://www.epa.gov/pesticides/search.htm">EPA Pesticide Factsheets</a> WaterSense released a notice of intent to develop a specification for cation exchange water softeners. The program has made the decision not to move forward with a spec at this time, but is making this information available. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26391334','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26391334">A dynamic leaf gas-exchange strategy is conserved in woody plants under changing ambient CO2 : evidence from carbon isotope discrimination in paleo and CO2 enrichment studies.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Voelker, Steven L; Brooks, J Renée; Meinzer, Frederick C; Anderson, Rebecca; Bader, Martin K-F; Battipaglia, Giovanna; Becklin, Katie M; Beerling, David; Bert, Didier; Betancourt, Julio L; Dawson, Todd E; Domec, Jean-Christophe; Guyette, Richard P; Körner, Christian; Leavitt, Steven W; Linder, Sune; Marshall, John D; Mildner, Manuel; Ogée, Jérôme; Panyushkina, Irina; Plumpton, Heather J; Pregitzer, Kurt S; Saurer, Matthias; Smith, Andrew R; Siegwolf, Rolf T W; Stambaugh, Michael C; Talhelm, Alan F; Tardif, Jacques C; Van de Water, Peter K; Ward, Joy K; Wingate, Lisa 2016-02-01 Rising atmospheric [CO2 ], ca , is expected to affect stomatal regulation of leaf gas-exchange of woody plants, thus influencing energy fluxes as well as carbon (C), water, and nutrient cycling of forests. Researchers have proposed various strategies for stomatal regulation of leaf gas-exchange that include maintaining a constant leaf internal [CO2 ], ci , a constant drawdown in CO2 (ca - ci ), and a constant ci /ca . These strategies can result in drastically different consequences for leaf gas-exchange. The accuracy of Earth systems models depends in part on assumptions about generalizable patterns in leaf gas-exchange responses to varying ca . The concept of optimal stomatal behavior, exemplified by woody plants shifting along a continuum of these strategies, provides a unifying framework for understanding leaf gas-exchange responses to ca . To assess leaf gas-exchange regulation strategies, we analyzed patterns in ci inferred from studies reporting C stable isotope ratios (δ(13) C) or photosynthetic discrimination (∆) in woody angiosperms and gymnosperms that grew across a range of ca spanning at least 100 ppm. Our results suggest that much of the ca -induced changes in ci /ca occurred across ca spanning 200 to 400 ppm. These patterns imply that ca - ci will eventually approach a constant level at high ca because assimilation rates will reach a maximum and stomatal conductance of each species should be constrained to some minimum level. These analyses are not consistent with canalization toward any single strategy, particularly maintaining a constant ci . Rather, the results are consistent with the existence of a broadly conserved pattern of stomatal optimization in woody angiosperms and gymnosperms. This results in trees being profligate water users at low ca , when additional water loss is small for each unit of C gain, and increasingly water-conservative at high ca , when photosystems are saturated and water loss is large for each unit C gain. � </li> <li> <a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70178114','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70178114">A dynamic leaf gas-exchange strategy is conserved in woody plants under changing ambient CO2: evidence from carbon isotope discrimination in paleo and CO2 enrichment studies</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Voelker, Steven L.; Brooks, J. Renée; Meinzer, Frederick C.; Anderson, Rebecca D.; Bader, Martin K.-F.; Battipaglia, Giovanna; Becklin, Katie M.; Beerling, David; Bert, Didier; Betancourt, Julio L.; Dawson, Todd E.; Domec, Jean-Christophe; Guyette, Richard P.; Körner, Christian; Leavitt, Steven W.; Linder, Sune; Marshall, John D.; Mildner, Manuel; Ogée, Jérôme; Panyushkina, Irina P.; Plumpton, Heather J.; Pregitzer, Kurt S.; Saurer, Matthias; Smith, Andrew R.; Siegwolf, Rolf T.W.; Stambaugh, Michael C.; Talhelm, Alan F.; Tardif, Jacques C.; Van De Water, Peter K.; Ward, Joy K.; Wingate, Lisa 2016-01-01 Rising atmospheric [CO2], ca, is expected to affect stomatal regulation of leaf gas-exchange of woody plants, thus influencing energy fluxes as well as carbon (C), water, and nutrient cycling of forests. Researchers have proposed various strategies for stomatal regulation of leaf gas-exchange that include maintaining a constant leaf internal [CO2], ci, a constant drawdown in CO2(ca − ci), and a constant ci/ca. These strategies can result in drastically different consequences for leaf gas-exchange. The accuracy of Earth systems models depends in part on assumptions about generalizable patterns in leaf gas-exchange responses to varying ca. The concept of optimal stomatal behavior, exemplified by woody plants shifting along a continuum of these strategies, provides a unifying framework for understanding leaf gas-exchange responses to ca. To assess leaf gas-exchange regulation strategies, we analyzed patterns in ci inferred from studies reporting C stable isotope ratios (δ13C) or photosynthetic discrimination (∆) in woody angiosperms and gymnosperms that grew across a range of ca spanning at least 100 ppm. Our results suggest that much of the ca-induced changes in ci/ca occurred across ca spanning 200 to 400 ppm. These patterns imply that ca − ci will eventually approach a constant level at high ca because assimilation rates will reach a maximum and stomatal conductance of each species should be constrained to some minimum level. These analyses are not consistent with canalization toward any single strategy, particularly maintaining a constant ci. Rather, the results are consistent with the existence of a broadly conserved pattern of stomatal optimization in woody angiosperms and gymnosperms. This results in trees being profligate water users at low ca, when additional water loss is small for each unit of C gain, and increasingly water-conservative at high ca, when photosystems are saturated and water loss is large for each unit C gain. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15266714','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15266714">Variations in water status, gas exchange, and growth in Rosmarinus officinalis plants infected with Glomus deserticola under drought conditions.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Sánchez-Blanco, Ma Jesús; Ferrández, Trinitario; Morales, Ma Angeles; Morte, Asunción; Alarcón, Juan José 2004-06-01 The influence of the arbuscular mycorrhizal fungus Glomus deserticola on the water relations, gas exchange parameters, and vegetative growth of Rosmarinus officinalis plants under water stress was studied. Plants were grown with and without the mycorrhizal fungus under glasshouse conditions and subjected to water stress by withholding irrigation water for 14 days. Along the experimental period, a significant effect of the fungus on the plant growth was observed, and under water stress, mycorrhizal plants showed an increase in aerial and root biomass compared to non-mycorrhizal plants. The decrease in the soil water potential generated a decrease in leaf water potential (psi(l)) and stem water potential (psi(x)) of mycorrhizal and non-mycorrhizal plants, with this decrease being lower in mycorrhizal water-stressed plants. Mycorrhization also had positive effects on the root hydraulic conductivity (Lp) of water stressed plants. Furthermore, mycorrhizal-stressed plants showed a more important decrease in osmotic potential at full turgor (psi(os)) than did non-mycorrhizal-stressed plants, indicating the capacity of osmotic adjustment. Mycorrhizal infection also improved photosynthetic activity (Pn) and stomatal conductance (g(s)) in plants under water stress compared to the non-mycorrhizal-stressed plants. A similar behaviour was observed in the photochemical efficiency of PSII (Fv/Fm) with this parameter being lower in non-mycorrhizal plants than in mycorrhizal plants under water stress conditions. In the same way, under water restriction, mycorrhizal plants showed higher values of chlorophyll content than did non-mycorrhizal plants. Thus, the results obtained indicated that the mycorrhizal symbiosis had a beneficial effect on the water status and growth of Rosmarinus officinalis plants under water-stress conditions. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EPJWC..6702023D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EPJWC..6702023D">Heat exchanger design for hot air ericsson-brayton piston engine</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Ďurčanský, P.; Lenhard, R.; Jandačka, J. 2014-03-01 One of the solutions without negative consequences for the increasing energy consumption in the world may be use of alternative energy sources in micro-cogeneration. Currently it is looking for different solutions and there are many possible ways. Cogeneration is known for long time and is widely used. But the installations are often large and the installed output is more suitable for cities or industry companies. When we will speak about decentralization, the small machines have to be used. The article deals with the principle of hot-air engines, their use in combined heat and electricity production from biomass and with heat exchangers as primary energy transforming element. In the article is hot air engine presented as a heat engine that allows the conversion of heat into mechanical energy while heat supply can be external. In the contribution are compared cycles of hot-air engine. Then are compared suitable heat exchangers for use with hot air Ericsson-Brayton engine. In the final part is proposal of heat exchanger for use in closed Ericsson-Brayton cycle. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21389192','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21389192">The effect of ambient humidity and metabolic rate on the gas-exchange pattern of the semi-aquatic insect Aquarius remigis.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Contreras, Heidy L; Bradley, Timothy J 2011-04-01 We have examined the effects of temperature on metabolic rate and respiratory pattern in the water strider Aquarius remigis. As temperature was increased from 10 to 30°C, the metabolic rate of the insects increased and the respiratory pattern transitioned from discontinuous, to cyclic, to continuous. The discontinuous gas-exchange cycle (DGC) was observed even in insects standing on water when the respirometry chamber was being perfused with humid (>95% relative humidity) air. Comparisons of insects at 20°C in humid and dry air showed no statistically significant differences in metabolic rate or respiratory pattern (P>0.05). The proportion of time that the spiracles were closed was greater at 10°C than at 20°C (P<0.01), and greater at 20°C than at 30°C (P<0.05). These results are compatible with the hypothesis that the respiratory patterns of insects are determined by the relationship between oxygen supply and oxygen demand. There was no evidence in this insect that humidity had any effect on the respiratory pattern. The results are discussed in the context of the ongoing discussion in the literature of the origin, maintenance and adaptive significance of the DGC in insects. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JPS...375..442L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JPS...375..442L">Water permeation through anion exchange membranes</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Luo, Xiaoyan; Wright, Andrew; Weissbach, Thomas; Holdcroft, Steven 2018-01-01 An understanding of water permeation through solid polymer electrolyte (SPE) membranes is crucial to offset the unbalanced water activity within SPE fuel cells. We examine water permeation through an emerging class of anion exchange membranes, hexamethyl-p-terphenyl poly (dimethylbenzimidazolium) (HMT-PMBI), and compare it against series of membrane thickness for a commercial anion exchange membrane (AEM), Fumapem® FAA-3, and a series of proton exchange membranes, Nafion®. The HMT-PMBI membrane is found to possess higher water permeabilities than Fumapem® FAA-3 and comparable permeability than Nafion (H+). By measuring water permeation through membranes of different thicknesses, we are able to decouple, for the first time, internal and interfacial water permeation resistances through anion exchange membranes. Permeation resistances on liquid/membrane interface is found to be negligible compared to that for vapor/membrane for both series of AEMs. Correspondingly, the resistance of liquid water permeation is found to be one order of magnitude smaller compared to that of vapor water permeation. HMT-PMBI possesses larger effective internal water permeation coefficient than both Fumapem® FAA-3 and Nafion® membranes (60 and 18% larger, respectively). In contrast, the effective interfacial permeation coefficient of HMT-PMBI is found to be similar to Fumapem® (±5%) but smaller than Nafion®(H+) (by 14%). </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29251470','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29251470">Effect of saline irrigation water on gas exchange and proline metabolism in ber (Ziziphus).</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Bagdi, D L; Bagri, G K 2016-09-01 An experiment was conducted in pots of 25 kg capacity to study the effect of saline irrigation (EC 0,5,10,15 and 20 dSm-1) prepared by mixing NaCl, NaSO4, CaCl and MgCl2 in 3:1 ratio of chloride and sulphate on gas exchange traits, membrane stability, chlorophyll stability index and osmolytic defense mechanism in Ziziphus rotundifolia and Ziziphus nummularia species of Indian jujube (Z.mauritiana). Result showed that net photosynthetic rate (PN), transpiration (e) and stomatal conductance were comparatively lower in Ziziphus nummularia, which further declined with increasing level of saline irrigation water. Chlorophyll stability and membrane stability also declined significantly in salt stress, with higher magnitude in Ziziphus nummularia. The activity of proline anabolic enzymes; Δ1-Pyrrolline-5-carboxylate reductase, Δ1-Pyrrolline-5-carboxylate synthetase and Ornithine-δ-aminotransferase were recorded higher in Ziziphus rotundifolia with decrease in proline dehydrogenase. The sodium content was observed higher in roots of Ziziphus rotundifolia and leaves of Ziziphus nummularia. Therefore, it is suggested that salt tolerance mechanism was more efficiently operative in Ziziphus rotundifolia owing to better management of physiological attributes, osmolytic defense mechanism and restricted translocation of sodium from root to leaves along with larger accumulation of potassium in its leaves. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1046750','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1046750">Stirling Air Conditioner for Compact Cooling</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> None 2010-09-01 BEETIT Project: Infinia is developing a compact air conditioner that uses an unconventional high efficient Stirling cycle system (vs. conventional vapor compression systems) to produce cool air that is energy efficient and does not rely on polluting refrigerants. The Stirling cycle system is a type of air conditioning system that uses a motor with a piston to remove heat to the outside atmosphere using a gas refrigerant. To date, Stirling systems have been expensive and have not had the right kind of heat exchanger to help cool air efficiently. Infinia is using chip cooling technology from the computer industry tomore » make improvements to the heat exchanger and improve system performance. Infinia’s air conditioner uses helium gas as refrigerant, an environmentally benign gas that does not react with other chemicals and does not burn. Infinia’s improvements to the Stirling cycle system will enable the cost-effective mass production of high-efficiency air conditioners that use no polluting refrigerants.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3279239','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3279239">Local Area Water Removal Analysis of a Proton Exchange Membrane Fuel Cell under Gas Purge Conditions</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Lee, Chi-Yuan; Lee, Yu-Ming; Lee, Shuo-Jen 2012-01-01 In this study, local area water content distribution under various gas purging conditions are experimentally analyzed for the first time. The local high frequency resistance (HFR) is measured using novel micro sensors. The results reveal that the liquid water removal rate in a membrane electrode assembly (MEA) is non-uniform. In the under-the-channel area, the removal of liquid water is governed by both convective and diffusive flux of the through-plane drying. Thus, almost all of the liquid water is removed within 30 s of purging with gas. However, liquid water that is stored in the under-the-rib area is not easy to remove during 1 min of gas purging. Therefore, the re-hydration of the membrane by internal diffusive flux is faster than that in the under-the-channel area. Consequently, local fuel starvation and membrane degradation can degrade the performance of a fuel cell that is started from cold. PMID:22368495 </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active">21</li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active">22</li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22368495','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22368495">Local area water removal analysis of a proton exchange membrane fuel cell under gas purge conditions.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Lee, Chi-Yuan; Lee, Yu-Ming; Lee, Shuo-Jen 2012-01-01 In this study, local area water content distribution under various gas purging conditions are experimentally analyzed for the first time. The local high frequency resistance (HFR) is measured using novel micro sensors. The results reveal that the liquid water removal rate in a membrane electrode assembly (MEA) is non-uniform. In the under-the-channel area, the removal of liquid water is governed by both convective and diffusive flux of the through-plane drying. Thus, almost all of the liquid water is removed within 30 s of purging with gas. However, liquid water that is stored in the under-the-rib area is not easy to remove during 1 min of gas purging. Therefore, the re-hydration of the membrane by internal diffusive flux is faster than that in the under-the-channel area. Consequently, local fuel starvation and membrane degradation can degrade the performance of a fuel cell that is started from cold. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018PlST...20d4011Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018PlST...20d4011Y">Influence of water content on the inactivation of P. digitatum spores using an air-water plasma jet</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Youyi, HU; Weidong, ZHU; Kun, LIU; Leng, HAN; Zhenfeng, ZHENG; Huimin, HU 2018-04-01 In order to investigate whether an air-water plasma jet is beneficial to improve the efficiency of inactivation, a series of experiments were done using a ring-needle plasma jet. The water content in the working gas (air) was accurately measured based on the Karl Fischer method. The effects of water on the production of OH (A2Σ+-X2Πi) and O (3p5P-3s5S) were also studied by optical emission spectroscopy. The results show that the water content is in the range of 2.53-9.58 mg l-1, depending on the gas/water mixture ratio. The production of OH (A2Σ+-X2Πi) rises with the increase of water content, whereas the O (3p5P-3s5S) shows a declining tendency with higher water content. The sterilization experiments indicate that this air-water plasma jet inactivates the P. digitatum spores very effectively and its efficiency rises with the increase of the water content. It is possible that OH (A2Σ+-X2Πi) is a more effective species in inactivation than O (3p5P-3s5S) and the water content benefit the spore germination inhibition through rising the OH (A2Σ+-X2Πi) production. The maximum of the inactivation efficacy is up to 93% when the applied voltage is -6.75 kV and the water content is 9.58 mg l-1. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/6792674','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/6792674">Functional morphology of the gills of the bowfin, Amia calva L., with special reference to their significance during air exposure.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Daxboeck, C; Barnard, D K; Randall, D J 1981-03-01 The bowfin, Amia calva is a facultative air breathing fish restricted to North America and is reported to estivate. The relative and functional gill surface areas of A. calva are not reduced, as in many amphibious fish, but have areas comparable to many completely aquatic species. The secondary lamellae are fused to form a lattice-work of rectangular pores, a gill arrangement unique among fresh-water fishes. This highly modified gill structure imparts considerable rigidity such that these do not collapse upon air exposure. In vivo blood gas measurements from air exposed Amia reveal that these gills must be free of water, since there is both O2 uptake and CO2 excretion across them. The observed ventilatory motions therefore pass air over the secondary lamellae for diffusive gas exchange during air exposure. In the artificial conditions of our experiments, however, air exposure was associated with a marked acidosis and the fish died within 2 hours of being returned to normoxic water. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27063719','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27063719">Temperature Programmed Desorption of Quench-condensed Krypton and Acetone in Air; Selective Concentration of Ultra-trace Gas Components.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Suzuki, Taku T; Sakaguchi, Isao 2016-01-01 Selective concentration of ultra-trace components in air-like gases has an important application in analyzing volatile organic compounds in the gas. In the present study, we examined quench-condensation of the sample gas on a ZnO substrate below 50 K followed by temperature programmed desorption (TPD) (low temperature TPD) as a selective gas concentration technique. We studied two specific gases in the normal air; krypton as an inert gas and acetone as a reactive gas. We evaluated the relationship between the operating condition of low temperature TPD and the lowest detection limit. In the case of krypton, we observed the selective concentration by exposing at 6 K followed by thermal desorption at about 60 K. On the other hand, no selectivity appeared for acetone although trace acetone was successfully concentrated. This is likely due to the solvent effect by a major component in the air, which is suggested to be water. We suggest that pre-condensation to remove the water component may improve the selectivity in the trace acetone analysis by low temperature TPD. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20020083268','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20020083268">Air/Water Purification</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> 1992-01-01 After 18 years of research into air/water pollution at Stennis Space Center, Dr. B. C. Wolverton formed his own company, Wolverton Environmental Services, Inc., to provide technology and consultation in air and water treatment. Common houseplants are used to absorb potentially harmful materials from bathrooms and kitchens. The plants are fertilized, air is purified, and wastewater is converted to clean water. More than 100 U.S. communities have adopted Wolverton's earlier water hyacinth and artificial marsh applications. Catfish farmers are currently evaluating the artificial marsh technology as a purification system. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015JPhCS.655a2035D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015JPhCS.655a2035D">Modelling heat and mass transfer in a membrane-based air-to-air enthalpy exchanger</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Dugaria, S.; Moro, L.; Del, D., Col 2015-11-01 The diffusion of total energy recovery systems could lead to a significant reduction in the energy demand for building air-conditioning. With these devices, sensible heat and humidity can be recovered in winter from the exhaust airstream, while, in summer, the incoming air stream can be cooled and dehumidified by transferring the excess heat and moisture to the exhaust air stream. Membrane based enthalpy exchangers are composed by different channels separated by semi-permeable membranes. The membrane allows moisture transfer under vapour pressure difference, or water concentration difference, between the two sides and, at the same time, it is ideally impermeable to air and other contaminants present in exhaust air. Heat transfer between the airstreams occurs through the membrane due to the temperature gradient. The aim of this work is to develop a detailed model of the coupled heat and mass transfer mechanisms through the membrane between the two airstreams. After a review of the most relevant models published in the scientific literature, the governing equations are presented and some simplifying assumptions are analysed and discussed. As a result, a steady-state, two-dimensional finite difference numerical model is setup. The developed model is able to predict temperature and humidity evolution inside the channels. Sensible and latent heat transfer rate, as well as moisture transfer rate, are determined. A sensitive analysis is conducted in order to determine the more influential parameters on the thermal and vapour transfer. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70028198','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70028198">Leaf gas exchange characteristics of three neotropical mangrove species in response to varying hydroperiod</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Krauss, Ken W.; Twilley, Robert R.; Doyle, Thomas W.; Gardiner, Emile S. 2006-01-01 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.. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27147352','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27147352">Quantification of regional early stage gas exchange changes using hyperpolarized (129)Xe MRI in a rat model of radiation-induced lung injury.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Doganay, Ozkan; Stirrat, Elaine; McKenzie, Charles; Schulte, Rolf F; Santyr, Giles E 2016-05-01 To assess the feasibility of hyperpolarized (HP) (129)Xe MRI for detection of early stage radiation-induced lung injury (RILI) in a rat model involving unilateral irradiation by assessing differences in gas exchange dynamics between irradiated and unirradiated lungs. The dynamics of gas exchange between alveolar air space and pulmonary tissue (PT), PT and red blood cells (RBCs) was measured using single-shot spiral iterative decomposition of water and fat with echo asymmetry and least-squares estimation images of the right and left lungs of two age-matched cohorts of Sprague Dawley rats. The first cohort (n = 5) received 18 Gy irradiation to the right lung using a (60)Co source and the second cohort (n = 5) was not irradiated and served as the healthy control. Both groups were imaged two weeks following irradiation when radiation pneumonitis (RP) was expected to be present. The gas exchange data were fit to a theoretical gas exchange model to extract measurements of pulmonary tissue thickness (LPT) and relative blood volume (VRBC) from each of the right and left lungs of both cohorts. Following imaging, lung specimens were retrieved and percent tissue area (PTA) was assessed histologically to confirm RP and correlate with MRI measurements. Statistically significant differences in LPT and VRBC were observed between the irradiated and non-irradiated cohorts. In particular, LPT of the right and left lungs was increased approximately 8.2% and 5.0% respectively in the irradiated cohort. Additionally, VRBC of the right and left lungs was decreased approximately 36.1% and 11.7% respectively for the irradiated cohort compared to the non-irradiated cohort. PTA measurements in both right and left lungs were increased in the irradiated group compared to the non-irradiated cohort for both the left (P < 0.05) and right lungs (P < 0.01) confirming the presence of RP. PTA measurements also correlated with the MRI measurements for both the non-irradiated (r = 0.79, P < 0.01) and </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20060021945','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20060021945">Conceptual Design of a Condensing Heat Exchanger for Space Systems Using Porous Media</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Hasan, Mohammad M.; Khan, Lutful I.; Nayagam, Vedha; Balasubramaniam, Ramaswamy 2006-01-01 Condensing heat exchangers are used in many space applications in the thermal and humidity control systems. In the International Space Station (ISS), humidity control is achieved by using a water cooled fin surface over which the moist air condenses, followed by "slurper bars" that take in both the condensate and air into a rotary separator and separates the water from air. The use of a cooled porous substrate as the condensing surface provides and attractive alternative that combines both heat removal as well as liquid/gas separation into a single unit. By selecting the pore sizes of the porous substrate a gravity independent operation may also be possible with this concept. Condensation of vapor into and on the porous surface from the flowing air and the removal of condensate from the porous substrate are the critical processes involved in the proposed concept. This paper describes some preliminary results of the proposed condensate withdrawal process and discusses the on-going design and development work of a porous media based condensing heat exchanger at the NASA Glenn Research Center in collaboration with NASA Johnson Space Center. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26163155','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26163155">Ventilatory gas exchange and early response to cardiac resynchronization therapy.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Kim, Chul-Ho; Olson, Lyle J; Shen, Win K; Cha, Yong-Mei; Johnson, Bruce D 2015-11-01 Cardiac resynchronization therapy (CRT) is an accepted intervention for chronic heart failure (HF), although approximately 30% of patients are non-responders. The purpose of this study was to determine whether exercise respiratory gas exchange obtained before CRT implantation predicts early response to CRT. Before CRT implantation, patients were assigned to either a mild-moderate group (Mod G, n = 33, age 67 ± 10 years) or a moderate-severe group (Sev G, n = 31, age 67 ± 10 years), based on abnormalities in exercise gas exchange. Severity of impaired gas exchange was based on a score from the measures of VE/VCO(2) slope, resting PETCO(2) and change of PETCO(2) from resting to peak. All measurements were performed before and 3 to 4 months after CRT implantation. Although Mod G did not have improved gas exchange (p > 0.05), Sev G improved significantly (p < 0.05) post-CRT. In addition, Mod G did not show improved right ventricular systolic pressure (RSVP; pre vs post: 37 ± 14 vs 36 ± 11 mm Hg, p > 0.05), yet Sev G showed significantly improved RVSP, by 23% (50 ± 14 vs 42 ± 12 mm Hg, p < 0.05). Both groups had improved left ventricular ejection fraction (p < 0.05), New York Heart Association class (p < 0.05) and quality of life (p < 0.05), but no significant differences were observed between groups (p > 0.05). No significant changes were observed in brain natriuretic peptide in either group post-CRT. Based on pre-CRT implantation ventilatory gas exchange, subjects with the most impaired values appeared to have more improvement post-CRT, possibly associated with a decrease in RVSP. Copyright © 2015 International Society for Heart and Lung Transplantation. Published by Elsevier Inc. All rights reserved. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70014998','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70014998">Air permeability and trapped-air content in two soils</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Stonestrom, David A.; Rubin, Jacob 1989-01-01 To improve understanding of hysteretic air permeability relations, a need exists for data on the water content dependence of air permeability, matric pressure, and air trapping (especially for wetting-drying cycles). To obtain these data, a special instrument was designed. The instrument is a combination of a gas permeameter (for air permeability determination), a suction plate apparatus (for retentivity curve determination), and an air pycnometer (for trapped-air-volume determination). This design allowed values of air permeability, matric pressure, and air trapping to be codetermined, i.e., determined at the same values of water content using the same sample and the same inflow-outflow boundaries. Such data were obtained for two nonswelling soils. The validity of the air permeability determinations was repeatedly confirmed by rigorous tests of Darcy's law. During initial drying from complete water saturation, supplementary measurements were made to assess the magnitude of gas slip. The extended Darcy equation accurately described the measured flux gradient relations for each condition of absolute gas pressure tested. Air permeability functions exhibited zero-permeability regions at high water contents as well as an abruptly appearing hysteresis at low water contents. Measurements in the zero-permeability regions revealed that the total amount of air in general exceeded the amount of trapped air. This indicates that the medium' s air space is partitioned into three measurable domains: through-flowing air, locally accessible air (i.e., air accessible from only one flow boundary), and trapped air. During repeated wetting and drying, the disappearance and reappearance of air permeability coincided closely with the reappearance and disappearance, respectively, of trapped air. The observed relation between critical features of the air permeability functions and those of the air-trapping functions suggest that water-based blockages play a significant role in the </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23755221','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23755221">Oxygen and air nanobubble water solution promote the growth of plants, fishes, and mice.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Ebina, Kosuke; Shi, Kenrin; Hirao, Makoto; Hashimoto, Jun; Kawato, Yoshitaka; Kaneshiro, Shoichi; Morimoto, Tokimitsu; Koizumi, Kota; Yoshikawa, Hideki 2013-01-01 Nanobubbles (<200 nm in diameter) have several unique properties such as long lifetime in liquid owing to its negatively charged surface, and its high gas solubility into the liquid owing to its high internal pressure. They are used in variety of fields including diagnostic aids and drug delivery, while there are no reports assessing their effects on the growth of lives. Nanobubbles of air or oxygen gas were generated using a nanobubble aerator (BUVITAS; Ligaric Company Limited, Osaka, Japan). Brassica campestris were cultured hydroponically for 4 weeks within air-nanobubble water or within normal water. Sweetfish (for 3 weeks) and rainbow trout (for 6 weeks) were kept either within air-nanobubble water or within normal water. Finally, 5 week-old male DBA1/J mice were bred with normal free-chaw and free-drinking either of oxygen-nanobubble water or of normal water for 12 weeks. Oxygen-nanobubble significantly increased the dissolved oxygen concentration of water as well as concentration/size of nanobubbles which were relatively stable for 70 days. Air-nanobubble water significantly promoted the height (19.1 vs. 16.7 cm; P<0.05), length of leaves (24.4 vs. 22.4 cm; P<0.01), and aerial fresh weight (27.3 vs. 20.3 g; P<0.01) of Brassica campestris compared to normal water. Total weight of sweetfish increased from 3.0 to 6.4 kg in normal water, whereas it increased from 3.0 to 10.2 kg in air-nanobubble water. In addition, total weight of rainbow trout increased from 50.0 to 129.5 kg in normal water, whereas it increased from 50.0 to 148.0 kg in air-nanobubble water. Free oral intake of oxygen-nanobubble water significantly promoted the weight (23.5 vs. 21.8 g; P<0.01) and the length (17.0 vs. 16.1 cm; P<0.001) of mice compared to that of normal water. We have demonstrated for the first time that oxygen and air-nanobubble water may be potentially effective tools for the growth of lives. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/14095','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/14095">Effects of moisture and nitrogen stress on gas exchange and nutrient resorption in Quercus rubra seedlings</a> <a target="_blank" href="http://www.fs.usda.gov/treesearch/">Treesearch</a> K. Francis Salifu; Douglass F. Jacobs 2008-01-01 The effects of simulated soil fertility at three levels (poor, medium, and rich soils) and moisture stress at two levels (well watered versus moisture stressed) on gas exchange and foliar nutrient resorption in 1+0 bareroot northern red oak (Quercus rubra) seedlings were evaluated. Current nitrogen (N) uptake was labeled with the stable isotope </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/2386412','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/2386412">A multiresidue method by high performance liquid chromatography-based fractionation and gas chromatographic determination of trace levels of pesticides in air and water.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Seiber, J N; Glotfelty, D E; Lucas, A D; McChesney, M M; Sagebiel, J C; Wehner, T A 1990-01-01 A multiresidue analytical method is described for pesticides, transformation products, and related toxicants based upon high performance liquid chromatographic (HPLC) fractionation of extracted residue on a Partisil silica gel normal phase column followed by selective-detector gas chromatographic (GC) determination of components in each fraction. The HPLC mobile phase gradient (hexane to methyl t-butyl ether) gave good chromatographic efficiency, resolution, reproducibility and recovery for 61 test compounds, and allowed for collection in four fractions spanning polarities from low polarity organochlorine compounds (fraction 1) to polar N-methylcarbamates and organophosphorus oxons (fraction 4). The multiresidue method was developed for use with air samples collected on XAD-4 and related trapping agents, and water samples extracted with methylene chloride. Detection limits estimated from spiking experiments were generally 0.3-1 ng/m3 for high-volume air samples, and 0.01-0.1 microgram/L for one-liter water samples. Applications were made to determination of pesticides in fogwater and air samples. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1265948-energy-factor-analysis-gas-heat-pump-water-heaters','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1265948-energy-factor-analysis-gas-heat-pump-water-heaters">Energy Factor Analysis for Gas Heat Pump Water Heaters</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Gluesenkamp, Kyle R 2016-01-01 Gas heat pump water heaters (HPWHs) can improve water heating efficiency with zero GWP and zero ODP working fluids. The energy factor (EF) of a gas HPWH is sensitive to several factors. In this work, expressions are derived for EF of gas HPWHs, as a function of heat pump cycle COP, tank heat losses, burner efficiency, electrical draw, and effectiveness of supplemental heat exchangers. The expressions are used to investigate the sensitivity of EF to each parameter. EF is evaluated on a site energy basis (as used by the US DOE for rating water heater EF), and a primary energy-basismore » energy factor (PEF) is also defined and included. Typical ranges of values for the six parameters are given. For gas HPWHs, using typical ranges for component performance, EF will be 59 80% of the heat pump cycle thermal COP (for example, a COP of 1.60 may result in an EF of 0.94 1.28). Most of the reduction in COP is due to burner efficiency and tank heat losses. Gas-fired HPWHs are theoretically be capable of an EF of up to 1.7 (PEF of 1.6); while an EF of 1.1 1.3 (PEF of 1.0 1.1) is expected from an early market entry.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=248583','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=248583">Carbon dioxide and water vapour exchange in a tropical dry forest as influenced by the North American Monsoon System (NAMS)</a> <a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a> To better understand the effects and relationship between precipitation, net ecosystem carbon dioxide (NEE) and water vapor exchange (ET), we report a study conducted in the tropical dry forest (TDF) in the northwest of Mexico. Ecosystem gas exchange was measured using the eddy correlation technique... </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20046684','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20046684">The efficacy of fluid-gas exchange for the treatment of postvitrectomy retinal detachment.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Jang, Ji Hye; Kim, Yu Cheol; Kim, Kwang Soo 2009-12-01 This study was designed to evaluate the efficacy of fluid-gas exchange for the treatment of postvitrectomy retinal detachment. We retrospectively reviewed the records of 33 consecutive patients (35 eyes) who underwent fluid-gas exchange treatment for postvitrectomy retinal detachment using the two-needle pars plana approach technique. The retinal reattachment rate was 80.0% after complete intravitreal gas disappearance following the fluid-gas exchange; the overall success rate was 65.7%. Visual acuity was improved or stable in 80.0% of cases; a two-line or greater vision improvement or a best-corrected visual acuity of 0.4 or better occurred in 62.9% of cases. The success rates for superior retinal detachments and posterior pole retinal detachments were 76.5% and 85.7%, respectively. Fluid-gas exchange represents a simple and cost-effective alternative outpatient procedure for retinal reattachment without reoperation for the treatment of superior and posterior pole retinal detachments. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21292477','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21292477">Experimental study of wood downdraft gasification for an improved producer gas quality through an innovative two-stage air and premixed air/gas supply approach.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Jaojaruek, Kitipong; Jarungthammachote, Sompop; Gratuito, Maria Kathrina B; Wongsuwan, Hataitep; Homhual, Suwan 2011-04-01 This study conducted experiments on three different downdraft gasification approaches: single stage, conventional two-stage, and an innovative two-stage air and premixed air/gas supply approach. The innovative two-stage approach has two nozzle locations, one for air supply at combustion zone and the other located at the pyrolysis zone for supplying the premixed gas (air and producer gas). The producer gas is partially bypassed to mix with air and supplied to burn at the pyrolysis zone. The result shows that producer gas quality generated by the innovative two-stage approach improved as compared to conventional two-stage. The higher heating value (HHV) increased from 5.4 to 6.5 MJ/Nm(3). Tar content in producer gas reduced to less than 45 mg/Nm(3). With this approach, gas can be fed directly to an internal combustion engine. Furthermore, the gasification thermal efficiency also improved by approximately 14%. The approach gave double benefits on gas qualities and energy savings. Copyright © 2010 Elsevier Ltd. All rights reserved. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.5581L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.5581L">Sum-Frequency Generation Spectroscopy for Studying Organic Layers at Water-Air Interfaces: Microlayer Monitoring and Surface Reactivity</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Laß, Kristian; Kleber, Joscha; Bange, Hermann; Friedrichs, Gernot 2015-04-01 The sea surface microlayer, according to commonly accepted terminology, comprises the topmost millimetre of the oceanic water column. It is often enriched with organic matter and is directly influenced by sunlight exposure and gas exchange with the atmosphere, hence making it a place for active biochemistry and photochemistry as well as for heterogeneous reactions. In addition, surface active material either is formed or accumulates directly at the air-water interface and gives rise to very thin layers, sometimes down to monomolecular thickness. This "sea surface nanolayer" determines the viscoelastic properties of the seawater surface and thus may impact the turbulent air-sea gas exchange rates. To this effect, this small scale layer presumably plays an important role for large scale changes of atmospheric trace gas concentrations (e.g., by modulating the ocean carbon sink characteristics) with possible implications for coupled climate models. To date, detailed knowledge about the composition, structure, and reactivity of the sea surface nanolayer is still scarce. Due to its small vertical dimension and the small amount of material, this surfactant layer is very difficult to separate and analyse. A way out is the application of second-order nonlinear optical methods, which make a direct surface-specific and background-free detection of this interfacial layer possible. In recent years, we have introduced the use of vibrational sum frequency generation (VSFG) spectroscopy to gain insight into natural and artificial organic monolayers at the air-water interface. In this contribution, the application of VSFG spectroscopy for the analysis of the sea surface nanolayer will be illustrated. Resulting spectra are interpreted in terms of layer composition and surfactant classes, in particular with respect to carbohydrate-containing molecules such as glycolipids. The partitioning of the detected surfactants into soluble and non-soluble ("wet" and "dry") surfactants will be </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23481438','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23481438">A novel, simplified ex vivo method for measuring water exchange performance of heat and moisture exchangers for tracheostomy application.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> van den Boer, Cindy; Muller, Sara H; Vincent, Andrew D; Züchner, Klaus; van den Brekel, Michiel W M; Hilgers, Frans J M 2013-09-01 Breathing through a tracheostomy results in insufficient warming and humidification of inspired air. This loss of air-conditioning can be partially compensated for with the application of a heat and moisture exchanger (HME) over the tracheostomy. In vitro (International Organization for Standardization [ISO] standard 9360-2:2001) and in vivo measurements of the effects of an HME are complex and technically challenging. The aim of this study was to develop a simple method to measure the ex vivo HME performance comparable with previous in vitro and in vivo results. HMEs were weighed at the end of inspiration and at the end of expiration at different breathing volumes. Four HMEs (Atos Medical, Hörby, Sweden) with known in vivo humidity and in vitro water loss values were tested. The associations between weight change, volume, and absolute humidity were determined using both linear and non-linear mixed effects models. The rating between the 4 HMEs by weighing correlated with previous intra-tracheal measurements (R(2) = 0.98), and the ISO standard (R(2) = 0.77). Assessment of the weight change between end of inhalation and end of exhalation is a valid and simple method of measuring the water exchange performance of an HME. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active">22</li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active">23</li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19780027541&hterms=thought+experiments&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dthought%2Bexperiments','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19780027541&hterms=thought+experiments&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dthought%2Bexperiments">The Viking gas exchange experiment results from Chryse and Utopia surface samples</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Oyama, V. I.; Berdahl, B. J. 1977-01-01 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%. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24699994','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24699994">Air quality concerns of unconventional oil and natural gas production.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Field, R A; Soltis, J; Murphy, S 2014-05-01 Increased use of hydraulic fracturing ("fracking") in unconventional oil and natural gas (O & NG) development from coal, sandstone, and shale deposits in the United States (US) has created environmental concerns over water and air quality impacts. In this perspective we focus on how the production of unconventional O & NG affects air quality. We pay particular attention to shale gas as this type of development has transformed natural gas production in the US and is set to become important in the rest of the world. A variety of potential emission sources can be spread over tens of thousands of acres of a production area and this complicates assessment of local and regional air quality impacts. We outline upstream activities including drilling, completion and production. After contrasting the context for development activities in the US and Europe we explore the use of inventories for determining air emissions. Location and scale of analysis is important, as O & NG production emissions in some US basins account for nearly 100% of the pollution burden, whereas in other basins these activities make up less than 10% of total air emissions. While emission inventories are beneficial to quantifying air emissions from a particular source category, they do have limitations when determining air quality impacts from a large area. Air monitoring is essential, not only to validate inventories, but also to measure impacts. We describe the use of measurements, including ground-based mobile monitoring, network stations, airborne, and satellite platforms for measuring air quality impacts. We identify nitrogen oxides, volatile organic compounds (VOC), ozone, hazardous air pollutants (HAP), and methane as pollutants of concern related to O & NG activities. These pollutants can contribute to air quality concerns and they may be regulated in ambient air, due to human health or climate forcing concerns. Close to well pads, emissions are concentrated and exposure to a wide range of </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930057514&hterms=reverse+osmosis&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dreverse%2Bosmosis','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930057514&hterms=reverse+osmosis&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dreverse%2Bosmosis">Modeling of membrane processes for air revitalization and water recovery</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Lange, Kevin E.; Foerg, Sandra L.; Dall-Bauman, Liese A. 1992-01-01 Gas-separation and reverse-osmosis membrane models are being developed in conjunction with membrane testing at NASA JSC. The completed gas-separation membrane model extracts effective component permeabilities from multicomponent test data, and predicts the effects of flow configuration, operating conditions, and membrane dimensions on module performance. Variable feed- and permeate-side pressures are considered. The model has been applied to test data for hollow-fiber membrane modules with simulated cabin-air feeds. Results are presented for a membrane designed for air drying applications. Extracted permeabilities are used to predict the effect of operating conditions on water enrichment in the permeate. A first-order reverse-osmosis model has been applied to test data for spiral wound membrane modules with a simulated hygiene water feed. The model estimates an effective local component rejection coefficient under pseudosteady-state conditions. Results are used to define requirements for a detailed reverse-osmosis model. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920056264&hterms=gas+natural&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dgas%2Bnatural','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920056264&hterms=gas+natural&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Dgas%2Bnatural">Relationship between wind speed and gas exchange over the ocean</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Wanninkhof, Rik 1992-01-01 A quadratic dependence of gas exchange on wind speed is employed to analyze the relationship between gas transfer and wind speed with particular emphasizing variable and/or low wind speeds. The quadratic dependence is fit through gas-transfer velocities over the ocean determined by methods based on the natural C-14 disequilibrium and the bomb C-14 inventory. The variation in the CO2 levels is related to these mechanisms, but the results show that other causes play significant roles. A weaker dependence of gas transfer on wind is suggested for steady winds, and long-term averaged winds demonstrate a stronger dependence in the present model. The chemical enhancement of CO2 exchange is also shown to play a role by increasing CO2 fluxes at low wind speeds. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/53171','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/53171">A dynamic leaf gas-exchange strategy is conserved in woody plants under changing ambient CO2 : evidence from carbon isotope discrimination in paleo and CO2 enrichment studies</a> <a target="_blank" href="http://www.fs.usda.gov/treesearch/">Treesearch</a> Steven L. Voelker; J. Renee Brooks; Frederick C. Meinzer; Rebecca Anderson; Martin K.-F. Bader; Giovanna Battipaglia; Katie M. Becklin; David Beerling; Didier Bert; Julio L. Betancourt; Todd E. Dawson; Jean-Christophe Domec; Richard P. Guyette; Christian K??rner; Steven W. Leavitt; Sune Linder; John D. Marshall; Manuel Mildner; Jerome Ogee; Irina Panyushkina; Heather J. Plumpton; Kurt S. Pregitzer; Matthias Saurer; Andrew R. Smith; Rolf T. W. Siegwolf; Michael C. Stambaugh; Alan F. Talhelm; Jacques C. Tardif; Peter K. Van de Water; Joy K. Ward; Lisa Wingate 2016-01-01 Rising atmospheric [CO2], ca, is expected to affect stomatal regulation of leaf gas-exchange of woody plants, thus influencing energy fluxes as well as carbon (C), water, and nutrient cycling of forests. Researchers have proposed various strategies for stomatal regulation of leaf gas-exchange that include maintaining a constant leaf internal [CO... </li> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19760022616','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19760022616">Hydrogen rich gas generator</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Houseman, J. (Inventor) 1976-01-01 A process and apparatus is described for producing a hydrogen rich gas by introducing a liquid hydrocarbon fuel in the form of a spray into a partial oxidation region and mixing with a mixture of steam and air that is preheated by indirect heat exchange with the formed hydrogen rich gas, igniting the hydrocarbon fuel spray mixed with the preheated mixture of steam and air within the partial oxidation region to form a hydrogen rich gas. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JASMS..28..971H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JASMS..28..971H">Regio-Selective Intramolecular Hydrogen/Deuterium Exchange in Gas-Phase Electron Transfer Dissociation</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Hamuro, Yoshitomo 2017-05-01 Protein backbone amide hydrogen/deuterium exchange mass spectrometry (HDX-MS) typically utilizes enzymatic digestion after the exchange reaction and before MS analysis to improve data resolution. Gas-phase fragmentation of a peptic fragment prior to MS analysis is a promising technique to further increase the resolution. The biggest technical challenge for this method is elimination of intramolecular hydrogen/deuterium exchange (scrambling) in the gas phase. The scrambling obscures the location of deuterium. Jørgensen's group pioneered a method to minimize the scrambling in gas-phase electron capture/transfer dissociation. Despite active investigation, the mechanism of hydrogen scrambling is not well-understood. The difficulty stems from the fact that the degree of hydrogen scrambling depends on instruments, various parameters of mass analysis, and peptide analyzed. In most hydrogen scrambling investigations, the hydrogen scrambling is measured by the percentage of scrambling in a whole molecule. This paper demonstrates that the degree of intramolecular hydrogen/deuterium exchange depends on the nature of exchangeable hydrogen sites. The deuterium on Tyr amide of neurotensin (9-13), Arg-Pro-Tyr-Ile-Leu, migrated significantly faster than that on Ile or Leu amides, indicating the loss of deuterium from the original sites is not mere randomization of hydrogen and deuterium but more site-specific phenomena. This more precise approach may help understand the mechanism of intramolecular hydrogen exchange and provide higher confidence for the parameter optimization to eliminate intramolecular hydrogen/deuterium exchange during gas-phase fragmentation. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28194737','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28194737">Regio-Selective Intramolecular Hydrogen/Deuterium Exchange in Gas-Phase Electron Transfer Dissociation.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Hamuro, Yoshitomo 2017-05-01 Protein backbone amide hydrogen/deuterium exchange mass spectrometry (HDX-MS) typically utilizes enzymatic digestion after the exchange reaction and before MS analysis to improve data resolution. Gas-phase fragmentation of a peptic fragment prior to MS analysis is a promising technique to further increase the resolution. The biggest technical challenge for this method is elimination of intramolecular hydrogen/deuterium exchange (scrambling) in the gas phase. The scrambling obscures the location of deuterium. Jørgensen's group pioneered a method to minimize the scrambling in gas-phase electron capture/transfer dissociation. Despite active investigation, the mechanism of hydrogen scrambling is not well-understood. The difficulty stems from the fact that the degree of hydrogen scrambling depends on instruments, various parameters of mass analysis, and peptide analyzed. In most hydrogen scrambling investigations, the hydrogen scrambling is measured by the percentage of scrambling in a whole molecule. This paper demonstrates that the degree of intramolecular hydrogen/deuterium exchange depends on the nature of exchangeable hydrogen sites. The deuterium on Tyr amide of neurotensin (9-13), Arg-Pro-Tyr-Ile-Leu, migrated significantly faster than that on Ile or Leu amides, indicating the loss of deuterium from the original sites is not mere randomization of hydrogen and deuterium but more site-specific phenomena. This more precise approach may help understand the mechanism of intramolecular hydrogen exchange and provide higher confidence for the parameter optimization to eliminate intramolecular hydrogen/deuterium exchange during gas-phase fragmentation. Graphical Abstract ᅟ. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5228218','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5228218">Impacts of Changes of Indoor Air Pressure and Air Exchange Rate in Vapor Intrusion Scenarios</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Shen, Rui; Suuberg, Eric M. 2016-01-01 There has, in recent years, been increasing interest in understanding the transport processes of relevance in vapor intrusion of volatile organic compounds (VOCs) into buildings on contaminated sites. These studies have included fate and transport modeling. Most such models have simplified the prediction of indoor air contaminant vapor concentrations by employing a steady state assumption, which often results in difficulties in reconciling these results with field measurements. This paper focuses on two major factors that may be subject to significant transients in vapor intrusion situations, including the indoor air pressure and the air exchange rate in the subject building. A three-dimensional finite element model was employed with consideration of daily and seasonal variations in these factors. From the results, the variations of indoor air pressure and air exchange rate are seen to contribute to significant variations in indoor air contaminant vapor concentrations. Depending upon the assumptions regarding the variations in these parameters, the results are only sometimes consistent with the reports of several orders of magnitude in indoor air concentration variations from field studies. The results point to the need to examine more carefully the interplay of these factors in order to quantitatively understand the variations in potential indoor air exposures. PMID:28090133 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28090133','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28090133">Impacts of Changes of Indoor Air Pressure and Air Exchange Rate in Vapor Intrusion Scenarios.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Shen, Rui; Suuberg, Eric M 2016-02-01 There has, in recent years, been increasing interest in understanding the transport processes of relevance in vapor intrusion of volatile organic compounds (VOCs) into buildings on contaminated sites. These studies have included fate and transport modeling. Most such models have simplified the prediction of indoor air contaminant vapor concentrations by employing a steady state assumption, which often results in difficulties in reconciling these results with field measurements. This paper focuses on two major factors that may be subject to significant transients in vapor intrusion situations, including the indoor air pressure and the air exchange rate in the subject building. A three-dimensional finite element model was employed with consideration of daily and seasonal variations in these factors. From the results, the variations of indoor air pressure and air exchange rate are seen to contribute to significant variations in indoor air contaminant vapor concentrations. Depending upon the assumptions regarding the variations in these parameters, the results are only sometimes consistent with the reports of several orders of magnitude in indoor air concentration variations from field studies. The results point to the need to examine more carefully the interplay of these factors in order to quantitatively understand the variations in potential indoor air exposures. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16665243','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16665243">Photosynthesis Decrease and Stomatal Control of Gas Exchange in Abies alba Mill. in Response to Vapor Pressure Difference.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Guehl, J M; Aussenac, G 1987-02-01 The responses of steady state CO(2) assimilation rate (A), transpiration rate (E), and stomatal conductance (g(s)) to changes in leaf-to-air vapor pressure difference (DeltaW) were examined on different dates in shoots from Abies alba trees growing outside. In Ecouves, a provenance representative of wet oceanic conditions in Northern France, both A and g(s) decreased when DeltaW was increased from 4.6 to 14.5 Pa KPa(-1). In Nebias, which represented the dry end of the natural range of A. alba in southern France, A and g(s) decreased only after reaching peak levels at 9.0 and 7.0 Pa KPa(-1), respectively. The representation of the data in assimilation rate (A) versus intercellular CO(2) partial pressure (C(i)) graphs allowed us to determine how stomata and mesophyll photosynthesis interacted when DeltaW was increased. Changes in A were primarily due to alterations in mesophyll photosynthesis. At high DeltaW, and especially in Ecouves when soil water deficit prevailed, A declined, while C(i) remained approximately constant, which may be interpreted as an adjustment of g(s) to changes in mesophyll photosynthesis. Such a stomatal control of gas exchange appeared as an alternative to the classical feedforward interpretation of E versus DeltaW responses with a peak rate of E. The gas exchange response to DeltaW was also characterized by considerable deviations from the optimization theory of IR Cowan and GD Farquhar (1977 Symp Soc Exp Biol 31: 471-505). </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.B51H1919C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.B51H1919C">Tracking Seasonal and Diurnal Photosynthesis and Plant Water Status in Maize Using SIF, Eddy Covariance Fluxes, PAM Fluorescence and Gas Exchange</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Chang, C.; Melkonian, J.; Riha, S. J.; Gu, L.; Sun, Y. 2017-12-01 Improving the sensitivity of methods for crop monitoring and yield forecasting is crucial as the frequency of extreme weather events increases. Conventional remote monitoring methods rely on greenness-based indices such as NDVI and EVI, which do not directly measure photosynthesis and are not sufficiently sensitive to rapid plant stress response. Solar-induced chlorophyll fluorescence (SIF) is a promising new technology that serves as a direct functional proxy of photosynthesis. We developed the first system utilizing dual QE Pro spectrometers to continuously measure the diurnal and seasonal cycle of SIF, and deployed the system in a corn field in upstate New York in 2017. To complement SIF, canopy-level measurements of carbon and water fluxes were also measured, along with concurrent leaf-level measurements of gas exchange and PAM fluorescence, midday water potential, leaf pigments, phenology, LAI, and soil moisture. We show that SIF is well correlated to GPP during the growing season and show that both are controlled by similar environmental conditions including PAR and water availability. We also describe diurnal changes in photosynthesis and plant water status and demonstrate the sensitivity of SIF to diurnal plant response. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26257361','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26257361">Interactive response of photosynthetic characteristics in Haloxylon ammodendron and Hedysarum scoparium exposed to soil water and air vapor pressure deficits.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Gong, Chunmei; Wang, Jiajia; Hu, Congxia; Wang, Junhui; Ning, Pengbo; Bai, Juan 2015-08-01 C4 plants possess better drought tolerance than C3 plants. However, Hedysarum scoparium, a C3 species, is dominant and widely distributed in the desert areas of northwestern China due to its strong drought tolerance. This study compared it with Haloxylon ammodendron, a C4 species, regarding the interactive effects of drought stress and different leaf-air vapor pressure deficits. Variables of interest included gas exchange, the activity levels of key C4 photosynthetic enzymes, and cellular anatomy. In both species, gas exchange parameters were more sensitive to high vapor pressure deficit than to strong water stress, and the net CO2 assimilation rate (An) was enhanced as vapor pressure deficits increased. A close relationship between An and stomatal conductance (gs) suggested that the species shared a similar response mechanism. In H. ammodendron, the activity levels of key C4 enzymes were higher, including those of phosphoenolpyruvate carboxylase (PEPC) and nicotinamide adenine dinucleotide phosphate-malate enzyme (NADP-ME), whereas in H. scoparium, the activity level of nicotinamide adenine dinucleotide-malate enzyme (NAD-ME) was higher. Meanwhile, H. scoparium utilized adaptive structural features, including a larger relative vessel area and a shorter distance from vein to stomata, which facilitated the movement of water. These findings implied that some C4 biochemical pathways were present in H. scoparium to respond to environmental challenges. Copyright © 2015. Published by Elsevier B.V. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25355625','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25355625">Air concentrations of volatile compounds near oil and gas production: a community-based exploratory study.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Macey, Gregg P; Breech, Ruth; Chernaik, Mark; Cox, Caroline; Larson, Denny; Thomas, Deb; Carpenter, David O 2014-10-30 Horizontal drilling, hydraulic fracturing, and other drilling and well stimulation technologies are now used widely in the United States and increasingly in other countries. They enable increases in oil and gas production, but there has been inadequate attention to human health impacts. Air quality near oil and gas operations is an underexplored human health concern for five reasons: (1) prior focus on threats to water quality; (2) an evolving understanding of contributions of certain oil and gas production processes to air quality; (3) limited state air quality monitoring networks; (4) significant variability in air emissions and concentrations; and (5) air quality research that misses impacts important to residents. Preliminary research suggests that volatile compounds, including hazardous air pollutants, are of potential concern. This study differs from prior research in its use of a community-based process to identify sampling locations. Through this approach, we determine concentrations of volatile compounds in air near operations that reflect community concerns and point to the need for more fine-grained and frequent monitoring at points along the production life cycle. Grab and passive air samples were collected by trained volunteers at locations identified through systematic observation of industrial operations and air impacts over the course of resident daily routines. A total of 75 volatile organics were measured using EPA Method TO-15 or TO-3 by gas chromatography/mass spectrometry. Formaldehyde levels were determined using UMEx 100 Passive Samplers. Levels of eight volatile chemicals exceeded federal guidelines under several operational circumstances. Benzene, formaldehyde, and hydrogen sulfide were the most common compounds to exceed acute and other health-based risk levels. Air concentrations of potentially dangerous compounds and chemical mixtures are frequently present near oil and gas production sites. Community-based research can provide an </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16508435','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16508435">Retinal damage caused by air-fluid exchange during pars plana vitrectomy.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Yang, Sam S; McDonald, H Richard; Everett, A I; Johnson, Robert N; Jumper, J Michael; Fu, Arthur D 2006-03-01 To report two cases of retinal damage associated with air infusion during pars plana vitrectomy. Observational case report. The authors reviewed the course of two patients who had retinal damage during par plana vitrectomy and air-fluid exchange for the treatment of macular hole and optic pit-related macular detachment, respectively. The intraoperative observations, postoperative course, and outcomes were reported. As a result of high air infusion flow during air-fluid exchange, retinal damage was created in the area contralateral to the infusion port. In Case 1, an oval area of whitening was noted on the first postoperative day. This area subsequently developed into a large retinal break associated with retinal detachment. In the second case, retinal whitening was noted intraoperatively. This region of pallor resolved quickly during the early postoperative period but resulted in a corresponding inferotemporal visual field defect. High infusion flow during air-fluid exchange in eyes undergoing vitrectomy surgery may result in significant retinal damage. This pressure-induced trauma initially causes retinal whitening that may be seen intraoperatively or during the early postoperative period. The region of damaged retina may develop a retinal break and detachment or a corresponding visual field defect. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/FR-2012-07-30/pdf/2012-18434.pdf','FEDREG'); return false;" href="https://www.gpo.gov/fdsys/pkg/FR-2012-07-30/pdf/2012-18434.pdf">77 FR 44672 - Notice of Lodging of Consent Decree Under the Clean Water and Clean Air Acts</a> <a target="_blank" href="http://www.gpo.gov/fdsys/browse/collection.action?collectionCode=FR">Federal Register 2010, 2011, 2012, 2013, 2014</a> 2012-07-30 ... DEPARTMENT OF JUSTICE Notice of Lodging of Consent Decree Under the Clean Water and Clean Air Acts... a civil penalty of $1,750,000 to resolve its violations of the Clean Air Act and the Clean Water Act... of coke oven gas. Under the Clean Water Act, Plaintiffs allege that Shenango violated the effluent... </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27835767','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27835767">Improving respiration measurements with gas exchange analyzers.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Montero, R; Ribas-Carbó, M; Del Saz, N F; El Aou-Ouad, H; Berry, J A; Flexas, J; Bota, J 2016-12-01 Dark respiration measurements with open-flow gas exchange analyzers are often questioned for their low accuracy as their low values often reach the precision limit of the instrument. Respiration was measured in five species, two hypostomatous (Vitis Vinifera L. and Acanthus mollis) and three amphistomatous, one with similar amount of stomata in both sides (Eucalyptus citriodora) and two with different stomata density (Brassica oleracea and Vicia faba). CO 2 differential (ΔCO 2 ) increased two-fold with no change in apparent R d , when the two leaves with higher stomatal density faced outside. These results showed a clear effect of the position of stomata on ΔCO 2 . Therefore, it can be concluded that leaf position is important to guarantee the improvement of respiration measurements increasing ΔCO 2 without affecting the respiration results by leaf or mass units. This method will help to increase the accuracy of leaf respiration measurements using gas exchange analyzers. Copyright Â© 2016 Elsevier GmbH. All rights reserved. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25783787','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25783787">Development of gas exchange and ion regulation in two species of air-breathing fish, Betta splendens and Macropodus opercularis.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Huang, Chun-Yen; Lin, Cheng-Huang; Lin, Hui-Chen 2015-07-01 Aquatic air-breathing anabantoids, a group of fish species characterized by the presence of a labyrinth organ and some gills, exhibit morphological variations. This study aimed to examine whether unequal gill growth begins during the early stages and described the sequence of the early gill developmental events in Betta splendens and Macropodus opercularis. To determine when the ion regulatory and gas exchange abilities first appear in the gills, mitochondria-rich cells (MRCs) and neuroepithelial cells (NECs) were examined in young B. splendens. To evaluate the relative importance of the gills and the labyrinth organ under different levels of oxygen uptake stress, the levels of carbonic anhydrase II (CAII) and Na(+)/K(+)-ATPase (NKA) protein expressions in 2 gills and the labyrinth organ were examined in M. opercularis. We found that the first 3 gills developed earlier than the 4th gill in both species, an indication that the morphological variation begins early in life. In B. splendens, the MRCs and NECs clearly appeared in the first 3 gills at 4 dph and were first found in the 4th gill until 11 dph. The oxygen-sensing ability of the gills was concordant with the ionoregulatory function. In M. opercularis, the hypoxic group had a significantly higher air-breathing frequency. CAII protein expression was higher in the labyrinth organ in the hypoxic group. The gills exhibited increased NKA protein expression in the hypoxic and restricted groups, respectively. Functional plasticity in CAII and NKA protein expressions was found between the gills and the labyrinth organ in adult M. opercularis. Copyright © 2015 Elsevier Inc. All rights reserved. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26188268','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26188268">Hypoxia and hypercarbia in endophagous insects: Larval position in the plant gas exchange network is key.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Pincebourde, Sylvain; Casas, Jérôme 2016-01-01 Gas composition is an important component of any micro-environment. Insects, as the vast majority of living organisms, depend on O2 and CO2 concentrations in the air they breathe. Low O2 (hypoxia), and high CO2 (hypercarbia) levels can have a dramatic effect. For phytophagous insects that live within plant tissues (endophagous lifestyle), gas is exchanged between ambient air and the atmosphere within the insect habitat. The insect larva contributes to the modification of this environment by expiring CO2. Yet, knowledge on the gas exchange network in endophagous insects remains sparse. Our study identified mechanisms that modulate gas composition in the habitat of endophagous insects. Our aim was to show that the mere position of the insect larva within plant tissues could be used as a proxy for estimating risk of occurrence of hypoxia and hypercarbia, despite the widely diverse life history traits of these organisms. We developed a conceptual framework for a gas diffusion network determining gas composition in endophagous insect habitats. We applied this framework to mines, galls and insect tunnels (borers) by integrating the numerous obstacles along O2 and CO2 pathways. The nature and the direction of gas transfers depended on the physical structure of the insect habitat, the photosynthesis activity as well as stomatal behavior in plant tissues. We identified the insect larva position within the gas diffusion network as a predictor of risk exposure to hypoxia and hypercarbia. We ranked endophagous insect habitats in terms of risk of exposure to hypoxia and/or hypercarbia, from the more to the less risky as cambium mines>borer tunnels≫galls>bark mines>mines in aquatic plants>upper and lower surface mines. Furthermore, we showed that the photosynthetically active tissues likely assimilate larval CO2 produced. In addition, temperature of the microhabitat and atmospheric CO2 alter gas composition in the insect habitat. We predict that (i) hypoxia indirectly favors </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1084048','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/servlets/purl/1084048">Coaxial fuel and air premixer for a gas turbine combustor</a> <a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a> York, William D; Ziminsky, Willy S; Lacy, Benjamin P 2013-05-21 An air/fuel premixer comprising a peripheral wall defining a mixing chamber, a nozzle disposed at least partially within the peripheral wall comprising an outer annular wall spaced from the peripheral wall so as to define an outer air passage between the peripheral wall and the outer annular wall, an inner annular wall disposed at least partially within and spaced from the outer annular wall, so as to define an inner air passage, and at least one fuel gas annulus between the outer annular wall and the inner annular wall, the at least one fuel gas annulus defining at least one fuel gas passage, at least one air inlet for introducing air through the inner air passage and the outer air passage to the mixing chamber, and at least one fuel inlet for injecting fuel through the fuel gas passage to the mixing chamber to form an air/fuel mixture. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active">23</li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active">24</li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21941230','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21941230">Sildenafil citrate, bronchopulmonary dysplasia and disordered pulmonary gas exchange: any benefits?</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Nyp, M; Sandritter, T; Poppinga, N; Simon, C; Truog, W E 2012-01-01 The objective of this study is to determine the effects that sildenafil citrate has on gas exchange in infants with bronchopulmonary dysplasia (BPD)-associated pulmonary hypertension (PH). A retrospective review was performed from 2005 to 2009. Infants treated with sildenafil citrate for greater than 48 h were included. Standard patient data was collected, including echocardiogram, inspired oxygen and systemic blood pressure, before and during administration of sildenafil citrate. Sildenafil citrate was used in 21 preterm infants with BPD-associated PH. A significant reduction in estimated right ventricular peak systolic pressure was seen after initiation of sildenafil citrate, with the majority of infants showing no improvement in gas exchange at 48 h of treatment. Four infants died during treatment. Sildenafil citrate reduced estimated pulmonary artery pressures, but this reduction was not reflected in improved gas exchange within the first 48 h. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25597683','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25597683">Air-soil exchange of organochlorine pesticides in a sealed chamber.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Yang, Bing; Han, Baolu; Xue, Nandong; Zhou, Lingli; Li, Fasheng 2015-01-01 So far little is known about air-soil exchange under any sealed circumstances (e.g., in plastic and glass sheds), which however has huge implications for the soil-air-plant pathways of persistent organic pollutants including organochlorine pesticides (OCPs). A newly designed passive air sampler was tested in a sealed chamber for measuring the vertical concentration profiles of gaseous phase OCPs (hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs)). Air was sampled at 5, 15, and 30 cm above ground level every 10th day during a 60-day period by deploying polyurethane foam cylinders housed in acrylonitrile butadiene styrene-covered cartridges. Concentrations and compositions of OCPs along the vertical sections indicated a clear relationship with proximity to the mixture of HCHs and DDTs which escapes from the soils. In addition, significant positive correlations were found between air temperatures and concentrations of HCHs and DDTs. These results indicated revolatilization and re-deposition being at or close to dynamic pseudo-equilibrium with the overlying air. The sampler used for addressing air-soil exchange of persistent organic pollutants in any sealed conditions is discussed. Copyright © 2014. Published by Elsevier B.V. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.H11A1162P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.H11A1162P">High-resolution (noble) gas time series for aquatic research</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Popp, A. L.; Brennwald, M. S.; Weber, U.; Kipfer, R. 2017-12-01 We developed a portable mass spectrometer (miniRUEDI) for on-site quantification of gas concentrations (He, Ar, Kr, N2, O2, CO2, CH4, etc.) in terrestrial gases [1,2]. Using the gas-equilibrium membrane-inlet technique (GE-MIMS), the miniRUEDI for the first time also allows accurate on-site and long-term dissolved-gas analysis in water bodies. The miniRUEDI is designed for operation in the field and at remote locations, using battery power and ambient air as a calibration gas. In contrast to conventional sampling and subsequent lab analysis, the miniRUEDI provides real-time and continuous time series of gas concentrations with a time resolution of a few seconds.Such high-resolution time series and immediate data availability open up new opportunities for research in highly dynamic and heterogeneous environmental systems. In addition the combined analysis of inert and reactive gas species provides direct information on the linkages of physical and biogoechemical processes, such as the air/water gas exchange, excess air formation, O2 turnover, or N2 production by denitrification [1,3,4].We present the miniRUEDI instrument and discuss its use for environmental research based on recent applications of tracking gas dynamics related to rapid and short-term processes in aquatic systems. [1] Brennwald, M.S., Schmidt, M., Oser, J., and Kipfer, R. (2016). Environmental Science and Technology, 50(24):13455-13463, doi: 10.1021/acs.est.6b03669[2] Gasometrix GmbH, gasometrix.com[3] Mächler, L., Peter, S., Brennwald, M.S., and Kipfer, R. (2013). Excess air formation as a mechanism for delivering oxygen to groundwater. Water Resources Research, doi:10.1002/wrcr.20547[4] Mächler, L., Brennwald, M.S., and Kipfer, R. (2013). Argon Concentration Time-Series As a Tool to Study Gas Dynamics in the Hyporheic Zone. Environmental Science and Technology, doi: 10.1021/es305309b </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.afdc.energy.gov/case/1','SCIGOVWS'); return false;" href="https://www.afdc.energy.gov/case/1">Alternative Fuels Data Center: Natural Gas Street Sweepers Improve Air</a> <a target="_blank" href="http://www.science.gov/aboutsearch.html">Science.gov Websites</a> Quality in New York</A> Natural Gas Street Sweepers Improve Air Quality in New York to someone by E -mail Share Alternative Fuels Data Center: Natural Gas Street Sweepers Improve Air Quality in New York on Facebook Tweet about Alternative Fuels Data Center: Natural Gas Street Sweepers Improve Air </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22429767-highly-tritiated-water-processing-isotopic-exchange','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22429767-highly-tritiated-water-processing-isotopic-exchange">Highly tritiated water processing by isotopic exchange</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Shu, W.M.; Willms, R.S.; Glugla, M. 2015-03-15 Highly tritiated water (HTW) is produced in fusion machines and one of the promising technologies to process it is isotopic exchange. 3 kinds of Pt-catalyzed zeolite (13X-APG, CBV-100-CY and HiSiv-1000) were tested as candidates for isotopic exchange of highly tritiated water (HTW), and CBV-100-CY (Na-Y type with a SiO{sub 2}/Al{sub 2}O{sub 3} ratio of ∼ 5.0) shows the best performance. Small-scale tritium testing indicates that this method is efficient for reaching an exchange factor (EF) of 100. Full-scale non-tritium testing implies that an EF of 300 can be achieved in 24 hours of operation if a temperature gradient is appliedmore » along the column. For the isotopic exchange, deuterium recycled from the Isotope Separation System (deuterium with 1% T and/or 200 ppm T) should be employed, and the tritiated water regenerated from the Pt-catalyzed zeolite bed after isotopic exchange should be transferred to Water Detritiation System (WDS) for further processing.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AIPC.1851b0077D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AIPC.1851b0077D">Performance evaluation of cross-flow single-phase liquid-to-gas polymer tube heat exchanger</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Dewanjee, Sujan; Hossain, Md. Rakibul; Rahman, Md. Ashiqur 2017-06-01 Reduced core weight and material cost, higher corrosion resistance are some of the major eye catching properties to study polymers over metal in heat exchanger applications in spite of the former's relatively low thermal conductivity and low strength. In the present study, performance of polymer parallel thin tube heat exchanger is numerically evaluated for cross flow liquid to air applications for a wide range of design and operating parameters such as tube diameter, thickness, fluid velocity and temperature, etc. using Computational Fluid Dynamics (CFD). Among a range of available polymeric materials, those with a moderate to high thermal conductivity and strength are selected for this study. A 90 cm × 1 cm single unit of polymer tubes, with appropriate number of tubes such that at least a gap of 5 mm is maintained in between the tubes, is used as a basic unit and multiple combination in the transverse direction of this single unit is simulated to measure the effect. The tube inner diameter is varied from 2 mm to 4 mm and the pressure drop is measured to have a relative idea of pumping cost. For each inner diameter the thickness is varied from .5 mm to 2.5 mm. The water velocity and the air velocity are varied from 0.4 m/s to 2 m/s and 1 m/s to 5 m/s, respectively. The performance of the polymer heat exchanger is compared with that of metal heat exchanger through and an optimum design for polymer heat exchanger is sought out. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18751738','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18751738">Pulvinus activity, leaf movement and leaf water-use efficiency of bush bean (Phaseplus vulgaris L.) in a hot environment.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Raeini-Sarjaz, Mahmoud; Chalavi, Vida 2008-11-01 Pulvinus activity of Phaseolus species in response to environmental stimuli plays an essential role in heliotropic leaf movement. The aims of this study were to monitor the continuous daily pulvinus movement and pulvinus temperature, and to evaluate the effects of leaf movements, on a hot day, on instantaneous leaf water-use efficiency (WUEi), leaf gas exchange, and leaf temperature. Potted plants of Phaseolus vulgaris L. var. Provider were grown in Chicot sandy loam soil under well-watered conditions in a greenhouse. When the second trifoliate leaf was completely extended, one plant was selected to measure pulvinus movement using a beta-ray gauging (BRG) meter with a point source of thallium-204 (204Tl). Leaf gas exchange measurements took place on similar leaflets of three plants at an air temperature interval of 33-42 degrees C by a steady-state LI-6200 photosynthesis system. A copper-constantan thermocouple was used to monitor pulvinus temperature. Pulvinus bending followed the daily diurnal rhythm. Significant correlations were found between the leaf-incident angle and the stomatal conductance (R2 = 0.54; P < 0.01), and photosynthesis rate (R2 = 0.84; P < 0.01). With a reduction in leaf-incidence angle and increase in air temperature, WUEi was reduced. During the measurements, leaf temperature remained below air temperature and was a significant function of air temperature (r = 0.92; P < 0.01). In conclusion, pulvinus bending followed both light intensity and air temperature and influenced leaf gas exchange. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://pubs.er.usgs.gov/publication/70157933','USGSPUBS'); return false;" href="https://pubs.er.usgs.gov/publication/70157933">Natural radium and radon tracers to quantify water exchange and movement in reservoirs</a> <a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a> Smith, Christopher G.; Baskaran, Mark 2011-01-01 Radon and radium isotopes are routinely used to quantify exchange rates between different hydrologic reservoirs. Since their recognition as oceanic tracers in the 1960s, both radon and radium have been used to examine processes such as air-sea exchange, deep oceanic mixing, benthic inputs, and many others. Recently, the application of radon-222 and the radium-quartet (223,224,226,228Ra) as coastal tracers has seen a revelation with the growing interest in coastal groundwater dynamics. The enrichment of these isotopes in benthic fluids including groundwater makes both radium and radon ideal tracers of coastal benthic processes (e.g. submarine groundwater discharge). In this chapter we review traditional and recent advances in the application of radon and radium isotopes to understand mixing and exchange between various hydrologic reservoirs, specifically: (1) atmosphere and ocean, (2) deep and shallow oceanic water masses, (3) coastal groundwater/benthic pore waters and surface ocean, and (4) aquifer-lakes. While the isotopes themselves and their distribution in the environment provide qualitative information about the exchange processes, it is mixing/exchange and transport models for these isotopes that provide specific quantitative information about these processes. Brief introductions of these models and mixing parameters are provided for both historical and more recent studies. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3673973','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3673973">Oxygen and Air Nanobubble Water Solution Promote the Growth of Plants, Fishes, and Mice</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Ebina, Kosuke; Shi, Kenrin; Hirao, Makoto; Hashimoto, Jun; Kawato, Yoshitaka; Kaneshiro, Shoichi; Morimoto, Tokimitsu; Koizumi, Kota; Yoshikawa, Hideki 2013-01-01 Nanobubbles (<200 nm in diameter) have several unique properties such as long lifetime in liquid owing to its negatively charged surface, and its high gas solubility into the liquid owing to its high internal pressure. They are used in variety of fields including diagnostic aids and drug delivery, while there are no reports assessing their effects on the growth of lives. Nanobubbles of air or oxygen gas were generated using a nanobubble aerator (BUVITAS; Ligaric Company Limited, Osaka, Japan). Brassica campestris were cultured hydroponically for 4 weeks within air-nanobubble water or within normal water. Sweetfish (for 3 weeks) and rainbow trout (for 6 weeks) were kept either within air-nanobubble water or within normal water. Finally, 5 week-old male DBA1/J mice were bred with normal free-chaw and free-drinking either of oxygen-nanobubble water or of normal water for 12 weeks. Oxygen-nanobubble significantly increased the dissolved oxygen concentration of water as well as concentration/size of nanobubbles which were relatively stable for 70 days. Air-nanobubble water significantly promoted the height (19.1 vs. 16.7 cm; P<0.05), length of leaves (24.4 vs. 22.4 cm; P<0.01), and aerial fresh weight (27.3 vs. 20.3 g; P<0.01) of Brassica campestris compared to normal water. Total weight of sweetfish increased from 3.0 to 6.4 kg in normal water, whereas it increased from 3.0 to 10.2 kg in air-nanobubble water. In addition, total weight of rainbow trout increased from 50.0 to 129.5 kg in normal water, whereas it increased from 50.0 to 148.0 kg in air-nanobubble water. Free oral intake of oxygen-nanobubble water significantly promoted the weight (23.5 vs. 21.8 g; P<0.01) and the length (17.0 vs. 16.1 cm; P<0.001) of mice compared to that of normal water. We have demonstrated for the first time that oxygen and air-nanobubble water may be potentially effective tools for the growth of lives. PMID:23755221 </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=307512&Lab=NRMRL&keyword=jet+OR+turbine+OR+turbo+OR+turbofan+OR+turbojet+AND+aerofoil+OR+aerofoils+OR+airfoil+OR+airfoils+OR+blade+OR+blades+OR+vane+OR+vanes+AND+aeroengine+OR+aeronautical+OR+aeroturbine+OR+aircraft+OR+aviation+AND+engine&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=307512&Lab=NRMRL&keyword=jet+OR+turbine+OR+turbo+OR+turbofan+OR+turbojet+AND+aerofoil+OR+aerofoils+OR+airfoil+OR+airfoils+OR+blade+OR+blades+OR+vane+OR+vanes+AND+aeroengine+OR+aeronautical+OR+aeroturbine+OR+aircraft+OR+aviation+AND+engine&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">Intensive measurements of gas, water, and energy exchange between vegetation and troposphere during the MONTES Campaign in a vegetation gradient from short semi-desertic shrublands to tall wet temperate forests in the NW Mediterranean basin</a> <a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> MONTES (“Woodlands”) was a multidisciplinary international field campaign aimed at measuring energy, water and especially gas exchange between vegetation and atmosphere in a gradient from short semi-desertic shrublands to tall wet temperate forests in NE Spain in the North Wester... </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/10926641','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/10926641">Response-time enhancement of a clinical gas analyzer facilitates measurement of breath-by-breath gas exchange.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Farmery, A D; Hahn, C E 2000-08-01 Tidal ventilation gas-exchange models in respiratory physiology and medicine not only require solution of mass balance equations breath-by-breath but also may require within-breath measurements, which are instantaneous functions of time. This demands a degree of temporal resolution and fidelity of integration of gas flow and concentration signals that cannot be provided by most clinical gas analyzers because of their slow response times. We have characterized the step responses of the Datex Ultima (Datex Instrumentation, Helsinki, Finland) gas analyzer to oxygen, carbon dioxide, and nitrous oxide in terms of a Gompertz four-parameter sigmoidal function. By inversion of this function, we were able to reduce the rise times for all these gases almost fivefold, and, by its application to real on-line respiratory gas signals, it is possible to achieve a performance comparable to the fastest mass spectrometers. With the use of this technique, measurements required for non-steady-state and tidal gas-exchange models can be made easily and reliably in the clinical setting. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013PhDT........99M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013PhDT........99M">Proton Transfers at the Air-Water Interface</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Mishra, Himanshu Proton transfer reactions at the interface of water with hydrophobic media, such as air or lipids, are ubiquitous on our planet. These reactions orchestrate a host of vital phenomena in the environment including, for example, acidification of clouds, enzymatic catalysis, chemistries of aerosol and atmospheric gases, and bioenergetic transduction. Despite their importance, however, quantitative details underlying these interactions have remained unclear. Deeper insight into these interfacial reactions is also required in addressing challenges in green chemistry, improved water quality, self-assembly of materials, the next generation of micro-nanofluidics, adhesives, coatings, catalysts, and electrodes. This thesis describes experimental and theoretical investigation of proton transfer reactions at the air-water interface as a function of hydration gradients, electrochemical potential, and electrostatics. Since emerging insights hold at the lipid-water interface as well, this work is also expected to aid understanding of complex biological phenomena associated with proton migration across membranes. Based on our current understanding, it is known that the physicochemical properties of the gas-phase water are drastically different from those of bulk water. For example, the gas-phase hydronium ion, H3O +(g), can protonate most (non-alkane) organic species, whereas H 3O+(aq) can neutralize only relatively strong bases. Thus, to be able to understand and engineer water-hydrophobe interfaces, it is imperative to investigate this fluctuating region of molecular thickness wherein the 'function' of chemical species transitions from one phase to another via steep gradients in hydration, dielectric constant, and density. Aqueous interfaces are difficult to approach by current experimental techniques because designing experiments to specifically sample interfacial layers (< 1 nm thick) is an arduous task. While recent advances in surface-specific spectroscopies have provided </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20010082932&hterms=water+purification&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dwater%2Bpurification','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20010082932&hterms=water+purification&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dwater%2Bpurification">Regenerable Air Purification System for Gas-Phase Contaminant Control</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Constantinescu, Ileana C.; Qi, Nan; LeVan, M. Douglas; Finn, Cory K.; Finn, John E.; Luna, Bernadette (Technical Monitor) 2000-01-01 A regenerable air purification system (RAPS) that uses water vapor to displace adsorbed contaminants from an. adsorbent column into a closed oxidation loop is under development through cooperative R&D between Vanderbilt University and NASA Ames Research Center. A unit based on this design can be used for removing trace gas-phase contaminants from spacecraft cabin air or from polluted process streams including incinerator exhaust. Recent work has focused on fabrication and operation of a RAPS breadboard at NASA Ames, and on measurement of adsorption isotherm data for several important organic compounds at Vanderbilt. These activities support the use and validation of RAPS modeling software also under development at Vanderbilt, which will in turn be used to construct a prototype system later in the project. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..1915057L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..1915057L">Cavity Enhanced Spectrometer performance assessment for greenhouse gas dry mole fraction measurement in humid air.</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Laurent, Olivier; Yver Kwok, Camille; Guemri, Ali; Philippon, Carole; Rivier, Leonard; Ramonet, Michel 2017-04-01 Due to the high variability of the water vapor content in the atmosphere, the mole fraction of trace gas such as greenhouse gas (GHG) in the atmosphere is usually presented as mole fraction in dry air. In consequence, the first technology used for GHG measurement, gas chromatography or non-dispersive infra-red spectroscopy, required to dry the air sample prior to analysis at a dew point lower than -50°C. The emergence of new GHG analyzers using infrared Enhanced Cavity Spectroscopy which measure the water vapor content in the air sample, allows providing the dry mole fraction of GHG without any drying system upstream by applying appropriate correction of the water vapor effects (dilution, pressure broadening…). In the framework of ICOS, a European research infrastructure aiming to provide harmonized high precision data for advanced research on carbon cycle and GHG budgets over Europe, the Metrology Lab of the Atmosphere Thematic Centre (ATC), located at LSCE in France, is mainly dedicated to elaborating measurement protocols and evaluating performance of GHG analyzers. Among the different tests conducted to characterize the metrological performance, the Metrology Lab focuses on the water vapor correction to apply on the GHG measurement. Most of the analyzers tested at the Metrology Lab are based on Cavity Enhanced Spectroscopy measuring the ICOS mandatory species, CO2, CH4 and CO. This presentation presents the results of the performance assessment of the manufacturer built-in water vapor correction and the possible improvement. Thanks to the large number of instrument tested, the presentation provides a performance overview of the GHG analyzers deployed in the ICOS atmospheric station network. Finally the performance of the water vapor correction will be discussed in regard of the performance obtained by using a drying system. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27558796','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27558796">Genotypic variation in biomass allocation in response to field drought has a greater affect on yield than gas exchange or phenology.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Edwards, Christine E; Ewers, Brent E; Weinig, Cynthia 2016-08-24 Plant performance in agricultural and natural settings varies with moisture availability, and understanding the range of potential drought responses and the underlying genetic architecture is important for understanding how plants will respond to both natural and artificial selection in various water regimes. Here, we raised genotypes of Brassica rapa under well-watered and drought treatments in the field. Our primary goal was to understand the genetic architecture and yield effects of different drought-escape and dehydration-avoidance strategies. Drought treatments reduced soil moisture by 62 % of field capacity. Drought decreased biomass accumulation and fruit production by as much as 48 %, whereas instantaneous water-use efficiency and root:shoot ratio increased. Genotypes differed in the mean value of all traits and in the sensitivity of biomass accumulation, root:shoot ratio, and fruit production to drought. Bivariate correlations involving gas-exchange and phenology were largely constant across environments, whereas those involving root:shoot varied across treatments. Although root:shoot was typically unrelated to gas-exchange or yield under well-watered conditions, genotypes with low to moderate increases in root:shoot allocation in response to drought survived the growing season, maintained maximum photosynthesis levels, and produced more fruit than genotypes with the greatest root allocation under drought. QTL for gas-exchange and yield components (total biomass or fruit production) had common effects across environments while those for root:shoot were often environment-specific. Increases in root allocation beyond those needed to survive and maintain favorable water relations came at the cost of fruit production. The environment-specific effects of root:shoot ratio on yield and the differential expression of QTL for this trait across water regimes have important implications for efforts to improve crops for drought resistance. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29574258','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29574258">Water relation, leaf gas exchange and chlorophyll a fluorescence imaging of soybean leaves infected with Colletotrichum truncatum.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Dias, Carla Silva; Araujo, Leonardo; Alves Chaves, Joicy Aparecida; DaMatta, Fábio M; Rodrigues, Fabrício A 2018-06-01 Considering the potential of anthracnose to decrease soybean yield and the need to gain more information regarding its effect on soybean physiology, the present study performed an in-depth analysis of the photosynthetic performance of soybean leaflets challenged with Colletotrichum truncatum by combining chlorophyll a fluorescence images with gas-exchange measurements and photosynthetic pigment pools. There were no significant differences between non-inoculated and inoculated plants in leaf water potential, apparent hydraulic conductance, net CO 2 assimilation rate, stomatal conductance to water vapor and transpiration rate. For internal CO 2 concentration, significant difference between non-inoculated and inoculated plants occurred only at 36 h after inoculation. Reductions in the values of the chlorophyll a fluorescence parameters [initial fluorescence (F 0 ), maximal fluorescence (F m ), maximal photosystem II quantum yield (F v /F m ), quantum yield of regulated energy dissipation (Y(NPQ))] and increases in effective PS II quantum yield (Y(II)), quantum yield of non-regulated energy dissipation Y(NO) and photochemical quenching coefficient (q P ) were noticed on the necrotic vein tissue in contrast to the surrounding leaf tissue. It appears that the impact of the infection by C. truncatum on the photosynthetic performance of the leaflets was minimal considering the preference of the fungus to colonize the veins. Copyright © 2018 Elsevier Masson SAS. All rights reserved. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23320654','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23320654">Reduction of molecular gas diffusion through gaskets in leaf gas exchange cuvettes by leaf-mediated pores.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Boesgaard, Kristine S; Mikkelsen, Teis N; Ro-Poulsen, Helge; Ibrom, Andreas 2013-07-01 There is an ongoing debate on how to correct leaf gas exchange measurements for the unavoidable diffusion leakage that occurs when measurements are done in non-ambient CO2 concentrations. In this study, we present a theory on how the CO2 diffusion gradient over the gasket is affected by leaf-mediated pores (LMP) and how LMP reduce diffusive exchange across the gaskets. Recent discussions have so far neglected the processes in the quasi-laminar boundary layer around the gasket. Counter intuitively, LMP reduce the leakage through gaskets, which can be explained by assuming that the boundary layer at the exterior of the cuvette is enriched with air from the inside of the cuvette. The effect can thus be reduced by reducing the boundary layer thickness. The theory clarifies conflicting results from earlier studies. We developed leaf adaptor frames that eliminate LMP during measurements on delicate plant material such as grass leaves with circular cross section, and the effectiveness is shown with respiration measurements on a harp of Deschampsia flexuosa leaves. We conclude that the best solution for measurements with portable photosynthesis systems is to avoid LMP rather than trying to correct for the effects. © 2013 John Wiley & Sons Ltd. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16452079','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16452079">Seasonal patterns of leaf gas exchange and water relations in dry rain forest trees of contrasting leaf phenology.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Choat, Brendan; Ball, Marilyn C; Luly, Jon G; Donnelly, Christine F; Holtum, Joseph A M 2006-05-01 Diurnal and seasonal patterns of leaf gas exchange and water relations were examined in tree species of contrasting leaf phenology growing in a seasonally dry tropical rain forest in north-eastern Australia. Two drought-deciduous species, Brachychiton australis (Schott and Endl.) A. Terracc. and Cochlospermum gillivraei Benth., and two evergreen species, Alphitonia excelsa (Fenzal) Benth. and Austromyrtus bidwillii (Benth.) Burret. were studied. The deciduous species had higher specific leaf areas and maximum photosynthetic rates per leaf dry mass in the wet season than the evergreens. During the transition from wet season to dry season, total canopy area was reduced by 70-90% in the deciduous species and stomatal conductance (g(s)) and assimilation rate (A) were markedly lower in the remaining leaves. Deciduous species maintained daytime leaf water potentials (Psi(L)) at close to or above wet season values by a combination of stomatal regulation and reduction in leaf area. Thus, the timing of leaf drop in deciduous species was not associated with large negative values of daytime Psi(L) (greater than -1.6 MPa) or predawn Psi(L) (greater than -1.0 MPa). The deciduous species appeared sensitive to small perturbations in soil and leaf water status that signalled the onset of drought. The evergreen species were less sensitive to the onset of drought and g(s) values were not significantly lower during the transitional period. In the dry season, the evergreen species maintained their canopies despite increasing water-stress; however, unlike Eucalyptus species from northern Australian savannas, A and g(s) were significantly lower than wet season values. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20100040574&hterms=common+good&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dcommon%2Bgood','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20100040574&hterms=common+good&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dcommon%2Bgood">International Space Station Common Cabin Air Assembly Condensing Heat Exchanger Hydrophilic Coating Failures and Lessons Learned</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Balistreri, Steven F.; Shaw, Laura A.; Laliberte, Yvon 2010-01-01 The ability to control the temperature and humidity of an environment or habitat is critical for human survival. These factors are important to maintaining human health and comfort, as well as maintaining mechanical and electrical equipment in good working order to support the human and to accomplish mission objectives. The temperature and humidity of the International Space Station (ISS) United States On-orbit Segment (USOS) cabin air is controlled by the Common Cabin Air Assembly (CCAA). The CCAA consists of a fan, a condensing heat exchanger (CHX), an air/water separator, temperature and liquid sensors, and electrical controlling hardware and software. The CHX is the primary component responsible for control of temperature and humidity. The CCAA CHX contains a chemical coating that was developed to be hydrophilic and thus attract water from the humid influent air. This attraction forms the basis for water removal and therefore cabin humidity control. However, there have been several instances of CHX coatings becoming hydrophobic and repelling water. When this behavior is observed in an operational CHX, the unit s ability to remove moisture from the air is compromised and the result is liquid water carryover into downstream ducting and systems. This water carryover can have detrimental effects on the cabin atmosphere quality and on the health of downstream hardware. If the water carryover is severe and widespread, this behavior can result in an inability to maintain humidity levels in the USOS. This paper will describe the operation of the five CCAAs within in the USOS, the potential causes of the hydrophobic condition, and the impacts of the resulting water carryover to downstream systems. It will describe the history of this behavior and the actual observed impacts to the ISS USOS. Information on mitigation steps to protect the health of future CHX hydrophilic coatings and potential remediation techniques will also be discussed. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25985421','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25985421">Impact of air and water vapor environments on the hydrophobicity of surfaces.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Weisensee, Patricia B; Neelakantan, Nitin K; Suslick, Kenneth S; Jacobi, Anthony M; King, William P 2015-09-01 Droplet wettability and mobility play an important role in dropwise condensation heat transfer. Heat exchangers and heat pipes operate at liquid-vapor saturation. We hypothesize that the wetting behavior of liquid water on microstructures surrounded by pure water vapor differs from that for water droplets in air. The static and dynamic contact angles and contact angle hysteresis of water droplets were measured in air and pure water vapor environments inside a pressure vessel. Pressures ranged from 60 to 1000 mbar, with corresponding saturation temperatures between 36 and 100°C. The wetting behavior was studied on four hydrophobic surfaces: flat Teflon-coated, micropillars, micro-scale meshes, and nanoparticle-coated with hierarchical micro- and nanoscale roughness. Static advancing contact angles are 9° lower in the water vapor environment than in air on a flat surface. One explanation for this reduction in contact angles is water vapor adsorption to the Teflon. On microstructured surfaces, the vapor environment has little effect on the static contact angles. In all cases, variations in pressure and temperature do not influence the wettability and mobility of the water droplets. In most cases, advancing contact angles increase and contact angle hysteresis decreases when the droplets are sliding or rolling down an inclined surface. Copyright © 2015 Elsevier Inc. All rights reserved. </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active">24</li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active">25</li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19850012858','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19850012858">Combustion gas properties. 2: Natural gas fuel and dry air</a> <a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a> Wear, J. D.; Jones, R. E.; Trout, A. M.; Mcbride, B. J. 1985-01-01 A series of computations has been made to produce the equilibrium temperature and gas composition for natural gas fuel and dry air. The computed tables and figures provide combustion gas property data for pressures from 0.5 to 50 atmospheres and equivalence ratios from 0 to 2.0. Only samples tables and figures are provided in this report. The complete set of tables and figures is provided on four microfiche films supplied with this report. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26406492','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26406492">Cryogenic separation of an oxygen-argon mixture in natural air samples for the determination of isotope and molecular ratios.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Keedakkadan, Habeeb Rahman; Abe, Osamu 2015-04-30 The separation and purification of oxygen-argon mixtures are critical in the high-precision analysis of Δ(17) O and δ(O2 /Ar) for geochemical applications. At present, chromatographic methods are used for the separation and purification of oxygen-argon mixtures or pure oxygen, but these methods require the use of high-purity helium as a carrier gas. Considerable interest has been expressed in the development of a helium-free cryogenic separation of oxygen-argon mixtures in natural air samples. The precise and simplified cryogenic separation of oxygen-argon mixtures from natural air samples presented here was made possible using a single 5A (30/60 mesh) molecular sieve column. The method involves the trapping of eluted gases using molecular sieves at liquid nitrogen temperature, which is associated with isotopic fractionation. We tested the proposed method for the determination of isotopic fractionations during the gas exchange between water and atmospheric air at equilibrium. The dependency of fractionation was studied at different water temperatures and for different methods of equilibration (bubbling and stirring). Isotopic and molecular fractionations during gas desorption from molecular sieves were studied for different amounts and types of molecular sieves. Repeated measurements of atmospheric air yielded a reproducibility (±SD) of 0.021 ‰, 0.044 ‰, 15 per meg and 1.9 ‰ for δ(17) O, δ(18) O, Δ(17) O and δ(O2 /Ar) values, respectively. We applied the method to determine equilibrium isotope fractionation during gas exchange between air and water. Consistent δ(18) O and Δ(17) O results were obtained with the latest two studies, whereas there was a significant difference in δ(18) O values between seawater and deionized water. We have revised a helium-free, cryogenic separation of oxygen-argon mixtures in natural air samples for isotopic and molecular ratio analysis. The use of a single 13X (1/8" pellet) molecular sieve yielded the smallest isotopic </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26286697','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26286697">Deriving C4 photosynthetic parameters from combined gas exchange and chlorophyll fluorescence using an Excel tool: theory and practice.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Bellasio, Chandra; Beerling, David J; Griffiths, Howard 2016-06-01 The higher photosynthetic potential of C4 plants has led to extensive research over the past 50 years, including C4 -dominated natural biomes, crops such as maize, or for evaluating the transfer of C4 traits into C3 lineages. Photosynthetic gas exchange can be measured in air or in a 2% Oxygen mixture using readily available commercial gas exchange and modulated PSII fluorescence systems. Interpretation of these data, however, requires an understanding (or the development) of various modelling approaches, which limit the use by non-specialists. In this paper we present an accessible summary of the theory behind the analysis and derivation of C4 photosynthetic parameters, and provide a freely available Excel Fitting Tool (EFT), making rigorous C4 data analysis accessible to a broader audience. Outputs include those defining C4 photochemical and biochemical efficiency, the rate of photorespiration, bundle sheath conductance to CO2 diffusion and the in vivo biochemical constants for PEP carboxylase. The EFT compares several methodological variants proposed by different investigators, allowing users to choose the level of complexity required to interpret data. We provide a complete analysis of gas exchange data on maize (as a model C4 organism and key global crop) to illustrate the approaches, their analysis and interpretation. © 2015 John Wiley & Sons Ltd. © 2016 John Wiley & Sons Ltd. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMPP31A2205C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMPP31A2205C">Helium Isotopes and Noble Gas Abundances of Cave Dripping Water in Three Caves in East Asia</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Chen, A. T.; Shen, C. C.; Tan, M.; Li, T.; Uemura, R.; Asami, R. 2015-12-01 Paleo-temperature recorded in nature archives is a critical parameter to understand climate change in the past. With advantages of unique inert chemical characteristics and sensitive solubilities with temperature, dissolved noble gases in speleothem inclusion water were recently proposed to retrieve terrestrial temperature history. In order to accurately apply this newly-developed speleothem noble gas temperature (NGT) as a reliable proxy, a fundamental issue about behaviors of noble gases in the karst should be first clarified. In this study, we measured noble gas contents in air and dripping water to evaluate any ratio deviation between noble gases. Cave dripping water samples was collected from three selected caves, Shihua Cave in northern China, Furong Cave in southwestern, and Gyukusen Cave in an island located in the western Pacific. For these caves are characterized by a thorough mixing and long-term storage of waters in a karst aquifer by the absence of seasonal oxygen isotope shifts. Ratios of dripping water noble gases are statistically insignificant from air data. Helium isotopic ratios in the dripping water samples match air value. The results indicate that elemental and isotopic signatures of noble gases from air can be frankly preserved in the epikarst and support the fidelity of NGT techniques. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008APS..MARJ17010M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008APS..MARJ17010M">Dynamics of Gas Exchange through the Fractal Architecture of the Human Lung, Modeled as an Exactly Solvable Hierarchical Tree</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Mayo, Michael; Pfeifer, Peter; Gheorghiu, Stefan 2008-03-01 The acinar airways lie at the periphery of the human lung and are responsible for the transfer of oxygen from air to the blood during respiration. This transfer occurs by the diffusion-reaction of oxygen over the irregular surface of the alveolar membranes lining the acinar airways. We present an exactly solvable diffusion-reaction model on a hierarchically branched tree, allowing a quantitative prediction of the oxygen current over the entire system of acinar airways responsible for the gas exchange. We discuss the effect of diffusional screening, which is strongly coupled to oxygen transport in the human lung. We show that the oxygen current is insensitive to a loss of permeability of the alveolar membranes over a wide range of permeabilities, similar to a ``constant-current source'' in an electric network. Such fault tolerance has been observed in other treatments of the gas exchange in the lung and is obtained here as a fully analytical result. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1993ONERA..75.....A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1993ONERA..75.....A">High temperature heat exchangers for gas turbines and future hypersonic air breathing propulsion</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Avran, Patrick; Bernard, Pierre After surveying the results of ONERA's investigations to date of metallic and ceramic heat exchangers applicable to automotive and aircraft powerplants, which are primarily of finned-tube counterflow configuration, attention is given to the influence of heat-exchanger effectiveness on fuel consumption and exchanger dimensions and weight. Emphasis is placed on the results of studies of cryogenic heat exchangers used by airbreathing hypersonic propulsion systems. The numerical codes developed by ONERA for the modeling of heat exchanger thermodynamics are evaluated. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007AGUFM.P21A0220H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007AGUFM.P21A0220H">Laboratory Measurements of Oxygen Gas Release from Basaltic Minerals Exposed to UV- Radiation: Implications for the Viking Gas Exchange Experiments</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Hurowitz, J. A.; Yen, A. S. 2007-12-01 The biology experiments onboard the Viking Landers determined that the Martian soils at Chryse and Utopia Planitia contain an unknown chemical compound of a highly oxidizing nature. The Gas Exchange Experiments (GEx) demonstrated that the humidification of a 1-cc Martian soil sample resulted in the production of as much as 790 nanomoles of oxygen gas. Yen et al. (2000) have provided experimental evidence that superoxide radicals can be generated on plagioclase feldspar (labradorite) grain surfaces by exposure to ultraviolet (UV) light in the presence of oxygen gas. Adsorbed superoxide radicals are thought to react readily with water vapor, and produce oxygen gas in quantities sufficient to explain the Viking GEx results. Direct evidence for the formation of oxygen gas, however, was not provided in the experiments of Yen et al (2000). Accordingly, the motivation of this study is to determine whether superoxide radicals adsorbed on labradorite surfaces are capable of producing oxygen gas upon exposure to water vapor. We have constructed an experimental apparatus that is capable of monitoring oxygen gas release from basaltic mineral powders that have been exposed to UV-radiation under Martian atmospheric pressure conditions. The apparatus consists of a stainless-steel vacuum chamber with a UV- transparent window where sample radiation exposures are performed. The vacuum chamber has multiple valved ports for injection of gases and water vapor. The vacuum chamber is connected via a precision leak valve to a quadrupole mass spectrometer, which measures changes in the composition of the headspace gases over our mineral samples. We will report on the results of our experiments, which are aimed at detecting and quantifying oxygen gas release from UV-exposed basaltic mineral samples using this new experimental facility. These results will further constrain whether superoxide ions adsorbed on mineral surfaces provide a viable explanation for the Viking GEx results, which have </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRC..121.7369F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRC..121.7369F">Surface shear stress dependence of gas transfer velocity parameterizations using DNS</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Fredriksson, S. T.; Arneborg, L.; Nilsson, H.; Handler, R. A. 2016-10-01 Air-water gas-exchange is studied in direct numerical simulations (DNS) of free-surface flows driven by natural convection and weak winds. The wind is modeled as a constant surface-shear-stress and the gas-transfer is modeled via a passive scalar. The simulations are characterized via a Richardson number Ri=Bν/u*4 where B, ν, and u* are the buoyancy flux, kinematic viscosity, and friction velocity respectively. The simulations comprise 0<Ri<∞ ranging from convection-dominated to shear-dominated cases. The results are used to: (i) evaluate parameterizations of the air-water gas-exchange, (ii) determine, for a given buoyancy flux, the wind speed at which gas transfer becomes primarily shear driven, and (iii) find an expression for the gas-transfer velocity for flows driven by both convection and shear. The evaluated gas transfer-velocity parametrizations are based on either the rate of turbulent kinetic energy dissipation, the surface flow-divergence, the surface heat-flux, or the wind-speed. The parametrizations based on dissipation or divergence show an unfavorable Ri dependence for flows with combined forcing whereas the parametrization based on heat-flux only shows a limited Ri dependence. The two parametrizations based on wind speed give reasonable estimates for the transfer-velocity, depending however on the surface heat-flux. The transition from convection- to shear-dominated gas-transfer-velocity is shown to be at Ri≈0.004. Furthermore, the gas-transfer is shown to be well represented by two different approaches: (i) additive forcing expressed as kg,sum =AShearu*|Ri/Ric+1| 1/4Sc-n where Ric=|AShear/ABuoy|4, and (ii) either buoyancy or shear dominated expressed as, kg=ABuoy|Bν| 1/4Sc-n, Ri>Ric or kg=AShearu*Sc-n, Ri<Ric. Here ABuoy=0.4 and AShear=0.1 are constants, and n is an exponent that depends on the water surface-characteristics. </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010cosp...38.3367R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010cosp...38.3367R">Air Circulation and Heat Exchange under Reduced Pressures</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Rygalov, Vadim; Wheeler, Raymond; Dixon, Mike; Hillhouse, Len; Fowler, Philip Low pressure atmospheres were suggested for Space Greenhouses (SG) design to minimize sys-tem construction and re-supply materials, as well as system manufacturing and deployment costs. But rarified atmospheres modify heat exchange mechanisms what finally leads to alter-ations in thermal control for low pressure closed environments. Under low atmospheric pressures (e.g., lower than 25 kPa compare to 101.3 kPa for normal Earth atmosphere), convection is becoming replaced by diffusion and rate of heat exchange reduces significantly. During a period from 2001 to 2009, a series of hypobaric experiments were conducted at Space Life Sciences Lab (SLSLab) NASA's Kennedy Space Center and the Department of Space Studies, University of North Dakota. Findings from these experiments showed: -air circulation rate decreases non-linearly with lowering of total atmospheric pressure; -heat exchange slows down with pressure decrease creating risk of thermal stress (elevated leaf tem-peratures) for plants in closed environments; -low pressure-induced thermal stress could be reduced by either lowering system temperature set point or increasing forced convection rates (circulation fan power) within certain limits; Air circulation is an important constituent of controlled environments and plays crucial role in material and heat exchange. Theoretical schematics and mathematical models are developed from a series of observations. These models can be used to establish optimal control algorithms for low pressure environments, such as a space greenhouse, as well as assist in fundamental design concept developments for these or similar habitable structures. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/14567951','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/14567951">A simple bubbling system for measuring radon (222Rn) gas concentrations in water samples based on the high solubility of radon in olive oil.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Al-Azmi, D; Snopek, B; Sayed, A M; Domanski, T 2004-01-01 Based on the different levels of solubility of radon gas in organic solvents and water, a bubbling system has been developed to transfer radon gas, dissolving naturally in water samples, to an organic solvent, i.e. olive oil, which is known to be a good solvent of radon gas. The system features the application of a fixed volume of bubbling air by introducing a fixed volume of water into a flask mounted above the system, to displace an identical volume of air from an air cylinder. Thus a gravitational flow of water is provided without the need for pumping. Then, the flushing air (radon-enriched air) is directed through a vial containing olive oil, to achieve deposition of the radon gas by another bubbling process. Following this, the vial (containing olive oil) is measured by direct use of gamma ray spectrometry, without the need of any chemical or physical processing of the samples. Using a standard solution of 226Ra/222Rn, a lowest measurable concentration (LMC) of radon in water samples of 9.4 Bq L(-1) has been achieved (below the maximum contaminant level of 11 Bq L(-1)). </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.8968S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.8968S">Methane gas seepage - Disregard of significant water column filter processes?</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Schneider von Deimling, Jens; Schmale, Oliver 2016-04-01 Marine methane seepage represents a potential contributor for greenhouse gas in the atmosphere and is discussed as a driver for climate change. The ultimate question is how much methane is released from the seafloor on a global scale and what fraction may reach the atmosphere? Dissolved fluxes from methane seepage sites on the seabed were found to be very efficiently reduced by benthic microbial oxidation, whereas transport of free gas bubbles from the seabed is considered to bypass the effective benthic methane filter. Numerical models are available today to predict the fate of such methane gas bubble release to the water column in regard to gas exchange with the ambient water column, respective bubble lifetime and rise height. However, the fate of rising gas bubbles and dissolved methane in the water column is not only governed by dissolution, but is also affected by lateral oceanographic currents and vertical bubble-induced upwelling, microbial oxidation, and physico-chemical processes that remain poorly understood so far. According to this gap of knowledge we present data from two study sites - the anthropogenic North Sea 22/4b Blowout and the natural Coal Oil point seeps - to shed light into two new processes gathered with hydro-acoustic multibeam water column imaging and microbial investigations. The newly discovered processes are hereafter termed Spiral Vortex and Bubble Transport Mechanism. Spiral Vortex describes the evolution of a complex vortical fluid motion of a bubble plume in the wake of an intense gas release site (Blowout, North Sea). It appears very likely that it dramatically changes the dissolution kinetics of the seep gas bubbles. Bubble Transport Mechanism prescribes the transport of sediment-hosted bacteria into the water column via rising gas bubbles. Both processes act as filter mechanisms in regard to vertical transport of seep related methane, but have not been considered before. Spiral Vortex and Bubble Transport Mechanism represent the </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28177581','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28177581">Harvesting Hydrogen Gas from Air Pollutants with an Unbiased Gas Phase Photoelectrochemical Cell.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Verbruggen, Sammy W; Van Hal, Myrthe; Bosserez, Tom; Rongé, Jan; Hauchecorne, Birger; Martens, Johan A; Lenaerts, Silvia 2017-04-10 The concept of an all-gas-phase photoelectrochemical (PEC) cell producing hydrogen gas from volatile organic contaminated gas and light is presented. Without applying any external bias, organic contaminants are degraded and hydrogen gas is produced in separate electrode compartments. The system works most efficiently with organic pollutants in inert carrier gas. In the presence of oxygen, the cell performs less efficiently but still significant photocurrents are generated, showing the cell can be run on organic contaminated air. The purpose of this study is to demonstrate new application opportunities of PEC technology and to encourage further advancement toward PEC remediation of air pollution with the attractive feature of simultaneous energy recovery and pollution abatement. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=47600&Lab=NHEERL&keyword=physiology+AND+stress&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=47600&Lab=NHEERL&keyword=physiology+AND+stress&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">JOINT ACTION OF O3 AND SO2 IN MODIFYING PLANT GAS EXCHANGE</a> <a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> 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 ... </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25562933','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25562933">Impact of emissions from natural gas production facilities on ambient air quality in the Barnett Shale area: a pilot study.</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Zielinska, Barbara; Campbell, Dave; Samburova, Vera 2014-12-01 Rapid and extensive development of shale gas resources in the Barnett Shale region of Texas in recent years has created concerns about potential environmental impacts on water and air quality. The purpose of this study was to provide a better understanding of the potential contributions of emissions from gas production operations to population exposure to air toxics in the Barnett Shale region. This goal was approached using a combination of chemical characterization of the volatile organic compound (VOC) emissions from active wells, saturation monitoring for gaseous and particulate pollutants in a residential community located near active gas/oil extraction and processing facilities, source apportionment of VOCs measured in the community using the Chemical Mass Balance (CMB) receptor model, and direct measurements of the pollutant gradient downwind of a gas well with high VOC emissions. Overall, the study results indicate that air quality impacts due to individual gas wells and compressor stations are not likely to be discernible beyond a distance of approximately 100 m in the downwind direction. However, source apportionment results indicate a significant contribution to regional VOCs from gas production sources, particularly for lower-molecular-weight alkanes (< C6). Although measured ambient VOC concentrations were well below health-based safe exposure levels, the existence of urban-level mean concentrations of benzene and other mobile source air toxics combined with soot to total carbon ratios that were high for an area with little residential or commercial development may be indicative of the impact of increased heavy-duty vehicle traffic related to gas production. Implications: Rapid and extensive development of shale gas resources in recent years has created concerns about potential environmental impacts on water and air quality. This study focused on directly measuring the ambient air pollutant levels occurring at residential properties located near </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/5874683-method-dehydrating-natural-gas','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/5874683-method-dehydrating-natural-gas">Method of dehydrating natural gas</a> <a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a> Wells, R. E. 1985-01-01 A method for dehydration of natural gas is provided wherein well head gas is supplied to a three-phase inlet separator, the vapor mixture of natural gas and water removed from that inlet separator means is supplied to a turboexpander, and the resulting refrigerated mixture of natural gas and condensed water vapor is supplied to a multi-phase outlet separator. The turboexpander may have integral means for subsequent compression of the refrigerated mixture and may be coupled through reduction gears to a means for generating electricity. A portion of the refrigerated mixture may be connected to a heat exchanger for cooling themore » well head natural gas prior to entry into the inlet separator. The flow of refrigerated mixture to this heat exchanger may be controlled by a temperature sensitive valve downstream of the heat exchanger. Methanol may be injected into the vapor mixture prior to entry into the turboexpander. The flow of methanol into the vapor mixture may be controlled by a valve sensitive to the flow rate of the vapor mixture and the water vapor content of the refrigerated mixture. Natural gas vapor from the outlet separator may be recirculated through the turboexpander if the output water vapor content of the natural gas vapor stream is too high.« less </li> <li> <a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.H31G0704O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.H31G0704O">Sensitivity of Photosynthetic Gas Exchange and Growth of Lodgepole Pine to Climate Variability Depends on the Age of Pleistocene Glacial Surfaces</a> <a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a> Osborn, B.; Chapple, W.; Ewers, B. E.; Williams, D. G. 2014-12-01 The interaction between soil conditions and climate variability plays a central role in the ecohydrological functions of montane conifer forests. Although soil moisture availability to trees is largely dependent on climate, the depth and texture of soil exerts a key secondary influence. Multiple Pleistocene glacial events have shaped the landscape of the central Rocky Mountains creating a patchwork of soils differing in age and textural classification. This mosaic of soil conditions impacts hydrological properties, and montane conifer forests potentially respond to climate variability quite differently depending on the age of glacial till and soil development. We hypothesized that the age of glacial till and associated soil textural changes exert strong control on growth and photosynthetic gas exchange of lodgepole pine. We examined physiological and growth responses of lodgepole pine to interannual variation in maximum annual snow water equivalence (SWEmax) of montane snowpack and growing season air temperature (Tair) and vapor pressure deficit (VPD) across a chronosequence of Pleistocene glacial tills ranging in age from 700k to 12k years. Soil textural differences across the glacial tills illustrate the varying degrees of weathering with the most well developed soils with highest clay content on the oldest till surfaces. We show that sensitivity of growth and carbon isotope discrimination, an integrated measure of canopy gas exchange properties, to interannual variation SWEmax , Tair and VPD is greatest on young till surfaces, whereas trees on old glacial tills with well-developed soils are mostly insensitive to these interannual climate fluctuations. Tree-ring widths were most sensitive to changes in SWEmax on young glacial tills (p < 0.01), and less sensitive on the oldest till (p < 0.05). Tair correlates strongly with δ13C values on the oldest and youngest tills sites, but shows no significant relationship on the middle aged glacial till. It is clear that </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/29938338','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/29938338">Calculation algorithms for breath-by-breath alveolar gas exchange: the unknowns!</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Golja, Petra; Cettolo, Valentina; Francescato, Maria Pia 2018-06-25 Several papers (algorithm papers) describe computational algorithms that assess alveolar breath-by-breath gas exchange by accounting for changes in lung gas stores. It is unclear, however, if the effects of the latter are actually considered in literature. We evaluated dissemination of algorithm papers and the relevant provided information. The list of documents investigating exercise transients (in 1998-2017) was extracted from Scopus database. Documents citing the algorithm papers in the same period were analyzed in full text to check consistency of the relevant information provided. Less than 8% (121/1522) of documents dealing with exercise transients cited at least one algorithm paper; the paper of Beaver et al. (J Appl Physiol 51:1662-1675, 1981) was cited most often, with others being cited tenfold less. Among the documents citing the algorithm paper of Beaver et al. (J Appl Physiol 51:1662-1675, 1981) (N = 251), only 176 cited it for the application of their algorithm/s; in turn, 61% (107/176) of them stated the alveolar breath-by-breath gas exchange measurement, but only 1% (1/107) of the latter also reported the assessment of volunteers' functional residual capacity, a crucial parameter for the application of the algorithm. Information related to gas exchange was provided consistently in the methods and in the results in 1 of the 107 documents. Dissemination of algorithm papers in literature investigating exercise transients is by far narrower than expected. The information provided about the actual application of gas exchange algorithms is often inadequate and/or ambiguous. Some guidelines are provided that can help to improve the quality of future publications in the field. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25063854','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25063854">A hierarchy of factors influence discontinuous gas exchange in the grasshopper Paracinema tricolor (Orthoptera: Acrididae).</a> <a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a> Groenewald, Berlizé; Chown, Steven L; Terblanche, John S 2014-10-01 The evolutionary origin and maintenance of discontinuous gas exchange (DGE) in tracheate arthropods are poorly understood and highly controversial. We investigated prioritization of abiotic factors in the gas exchange control cascade by examining oxygen, water and haemolymph pH regulation in the grasshopper Paracinema tricolor. Using a full-factorial design, grasshoppers were acclimated to hypoxic or hyperoxic (5% O2, 40% O2) gas conditions, or dehydrated or hydrated, whereafter their CO2 release was measured under a range of O2 and relative humidity (RH) conditions (5%, 21%, 40% O2 and 5%, 60%, 90% RH). DGE was significantly less common in grasshoppers acclimated to dehydrating conditions compared with the other acclimations (hypoxia, 98%; hyperoxia, 100%; hydrated, 100%; dehydrated, 67%). Acclimation to dehydrating conditions resulted in a significant decrease in haemolymph pH from 7.0±0.3 to 6.6±0.1 (mean ± s.d., P=0.018) and also significantly increased the open (O)-phase duration under 5% O2 treatment conditions (5% O2, 44.1±29.3 min; 40% O2, 15.8±8.0 min; 5% RH, 17.8±1.3 min; 60% RH, 24.0±9.7 min; 90% RH, 20.6±8.9 min). The observed acidosis could potentially explain the extension of the O-phase under low RH conditions, when it would perhaps seem more useful to reduce the O-phase to lower respiratory water loss. The results confirm that DGE occurrence and modulation are affected by multiple abiotic factors. A hierarchical framework for abiotic factors influencing DGE is proposed in which the following stressors are prioritized in decreasing order of importance: oxygen supply, CO2 excretion and pH modulation, oxidative damage protection and water savings. © 2014. Published by The Company of Biologists Ltd. </li> <li> <a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=261773&keyword=Human+AND+interaction&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=261773&keyword=Human+AND+interaction&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50">Spatiotemporally‐Resolved Air Exchange Rate as a Modifier of Acute Air Pollution‐Related Morbidity in AtlantaMorbidity in Atlanta</a> <a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a> Epidemiological studies frequently use central site concentrations as surrogates of exposure to air pollutants. Variability in air pollutant infiltration due to differential air exchange rates (AERs) is potentially a major factor affecting the relationship between central site c... </li> <li> <a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5292819','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5292819">Effect of Leaf Water Potential on Internal Humidity and CO2 Dissolution: Reverse Transpiration and Improved Water Use Efficiency under Negative Pressure</a> <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a> Vesala, Timo; Sevanto, Sanna; Grönholm, Tiia; Salmon, Yann; Nikinmaa, Eero; Hari, Pertti; Hölttä, Teemu 2017-01-01 The pull of water from the soil to the leaves causes water in the transpiration stream to be under negative pressure decreasing the water potential below zero. The osmotic concentration also contributes to the decrease in leaf water potential but with much lesser extent. Thus, the surface tension force is approximately balanced by a force induced by negative water potential resulting in concavely curved water-air interfaces in leaves. The lowered water potential causes a reduction in the equilibrium water vapor pressure in internal (sub-stomatal/intercellular) cavities in relation to that over water with the potential of zero, i.e., over the flat surface. The curved surface causes a reduction also in the equilibrium vapor pressure of dissolved CO2, thus enhancing its physical solubility to water. Although the water vapor reduction is acknowledged by plant physiologists its consequences for water vapor exchange at low water potential values have received very little attention. Consequences of the enhanced CO2 solubility to a leaf water-carbon budget have not been considered at all before this study. We use theoretical calculations and modeling to show how the reduction in the vapor pressures affects transpiration and carbon assimilation rates. Our results indicate that the reduction in vapor pressures of water and CO2 could enhance plant water use efficiency up to about 10% at a leaf water potential of −2 MPa, and much more when water potential decreases further. The low water potential allows for a direct stomatal water vapor uptake from the ambient air even at sub-100% relative humidity values. This alone could explain the observed rates of foliar water uptake by e.g., the coastal redwood in the fog belt region of coastal California provided the stomata are sufficiently open. The omission of the reduction in the water vapor pressure causes a bias in the estimates of the stomatal conductance and leaf internal CO2 concentration based on leaf gas exchange </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active">25</li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> </div> <div class="footer-extlink text-muted" style="margin-bottom:1rem; text-align:center;">Some links on this page may take you to non-federal websites. 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Sample records for air-water gas exchange