Isotopic exchange between CO2 and H2O and labelling kinetics of photosynthetic oxygen

International Nuclear Information System (INIS)

Gerster, Richard

1971-01-01

The reaction of carbon dioxide with water has been studied by measuring the rate of oxygen exchange between C 18 O 2 and H 2 16 O. The mathematical treatment of the kinetics allows to determine with accuracy the diffusion flow between the gas and the liquid phase, in the same way as the CO 2 hydration rate. The velocity constant of this last process, whose value gives the in situ enzymatic activity of carbonic anhydrase, has been established in the case of chloroplast and Euglena suspensions and of aerial leaves. The study of the isotopic exchange between C 18 O 2 and a vegetable submitted to alternations of dark and light has allowed to calculate the isotopic abundance of the metabolized CO 2 whose value has been compared to that of the intracellular water and that of photosynthetic oxygen. In addition, a new method using 13 C 18 O 2 gives the means to measure with accuracy eventual isotopic effects. The labelling kinetics of the oxygen evolved by Euglena suspensions whose water has been enriched with 18 O have been established at different temperatures. (author) [fr

Ion Exchange Kinetics of CO2+ Ions In the Particles of Some Organic and Inorganic Sorbents

International Nuclear Information System (INIS)

El-Naggar, I.M.; Abou-Messalam, M.M; Shady, S.A.

2000-01-01

The rate of exchange and diffusion mechanism of Co 2+ and Zn 2+ on the hydrogen form of cerium (IV) antimonate Ce/Sb and polyacrylamide acrylic acid resin impregnated with zirconium phosphate p(A M-A A) Zr-P was determined at different reaction temperatures 25,45 and 60 degree. The exchange rate was controlled by a particle diffusion mechanism and a limited batch technique. The effective diffusion coefficients of exchange reactions, values of activation energies, entropy of activation have been calculated and were confirmed by the B t versus t plots

[Effect of air temperature and rainfall on wetland ecosystem CO2 exchange in China].

Science.gov (United States)

Chu, Xiao-jing; Han, Guang-xuan

2015-10-01

Wetland can be a potential efficient sink to reduce global warming due to its higher primary productivity and lower carbon decomposition rate. While there has been a series progress on the influence mechanism of ecosystem CO2 exchange over China' s wetlands, a systematic metaanalysis of data still needs to be improved. We compiled data of ecosystem CO2 exchange of 21 typical wetland vegetation types in China from 29 papers and carried out an integrated analysis of air temperature and precipitation effects on net ecosystem CO2 exchange (NEE), ecosystem respiration (Reco), gross primary productivity (GPP), the response of NEE to PAR, and the response of Reco to temperature. The results showed that there were significant responses (P0.05). Across different Chinese wetlands, both precipitation and temperature had no significant effect on apparent quantum yield (α) or ecosystem respiration in the daytime (Reco,day, P>0.05). The maximum photosynthesis rate (Amax) was remarkably correlated with precipitation (P 0.05). Precipitation was negatively correlated with temperature sensitivity of Reco (Q10, P<0.05). Furthermore, temperature accounted for 35% and 46% of the variations in temperature sensitivity of Reco (Q10) and basal respiration (Rref P<0.05), respectively.

Studying biosphere-atmosphere exchange of CO2 through Carbon-13 stable isotopes

NARCIS (Netherlands)

Velde, van der I.R.

2015-01-01

Summary Thesis ‘Studying biosphere-atmosphere exchange of CO2 through

carbon-13 stable isotopes’

Ivar van der Velde

Making predictions of future climate is difficult, mainly due to large uncertainties in the carbon cycle. The rate at which carbon is stored in the oceans and

Enrichment of 13C by chemical exchange between CO2 and amine carbamate in nonaqueous solvent

International Nuclear Information System (INIS)

Raica, Paula; Axente, D.

2009-01-01

Full text: Enrichment of 13 C by chemical exchange between CO 2 and amine carbamate in nonaqueous solvent has been mathematically modelled in two ways. The height equivalent to a theoretical plate and steady-state separation, based on the two models, have been obtained. If only the isotopic exchange between CO 2 gas and amine carbamate is considered, the model can estimate the process performance for pressures close to the atmospheric one and room temperature. For process analysis at pressures higher than atmospheric one and lower temperatures, a two-step model has been developed. Using the two models the effects of pressure increasing have been studied. At atmospheric pressure and 2M DNBA - methanol solution the isotope transfer rate is lower at 5 deg. C than at 25 deg. C. The isotope transfer is supported by pressure increasing according the increase of the CO 2 concentration in the amine solution. A lower temperature determines also an increase in the concentration of dissolved CO 2 and, for this reason, at 5 deg.C and higher pressures the isotope exchange reaction rate is higher than at 25 deg. C, HETP being lower with more than 100% at 5 deg. C than at 25 deg. C. (authors)

Modeling canopy CO2 exchange in the European Russian Arctic

DEFF Research Database (Denmark)

Kiepe, Isabell; Friborg, Thomas; Herbst, Mathias

2013-01-01

In this study, we use the coupled photosynthesis-stomatal conductance model of Collatz et al. (1991) to simulate the current canopy carbon dioxide exchange of a heterogeneous tundra ecosystem in European Russia. For the parameterization, we used data obtained from in situ leaf level measurements...... in combination with meteorological data from 2008. The modeled CO2 fluxes were compared with net ecosystem exchange (NEE), measured by the eddy covariance technique during the snow-free period in 2008. The findings from this study indicated that the main state parameters of the exchange processes were leaf area...... index (LAI) and Rubisco capacity (v(cmax)). Furthermore, this ecosystem was found to be functioning close to its optimum temperature regarding carbon accumulation rates. During the modeling period from May to October, the net assimilation was greater than the respiration, leading to a net accumulation...

On-line interconversion of [15O]O2 and [15O]CO2 via metal oxide by isotopic exchange

International Nuclear Information System (INIS)

Iwata, Ren; Ido, Tatsuo; Fujisawa, Yoshiki; Yamazaki, Shigeki

1988-01-01

A novel method has been developed for the on-line production of 15 O-labelled gases. The 15 O exchange reactions between O 2 and CO 2 assisted by a metal oxide catalyst were successfully applied to on-line interconversion of [ 15 O]O 2 and [ 15 O]CO 2 with Hopcalite II(CuO 40% and MnO 2 60%). The conversion reactions were optimized as to the reaction temperature, the amount of the catalyst, and the flow rate of a gas added for oxygen exchange. [ 15 O]O 2 was converted to [ 15 O]CO 2 in a 80% yield with 0.7 g of Hopcalite II and 100 mL/min of CO 2 at 500 0 C, and [ 15 O]CO 2 to [ 15 O]O 2 in 70% with 100 mL/min of O 2 at 650 0 C. The radiochemical purities of the 15 O-labelled gases converted under the optimal conditions were high enough for clinical studies using the standard dilution and inhalation procedures. (author)

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

Science.gov (United States)

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.

Atmosphere-soil-vegetation model including CO2 exchange processes: SOLVEG2

International Nuclear Information System (INIS)

Nagai, Haruyasu

2004-11-01

A new atmosphere-soil-vegetation model named SOLVEG2 (SOLVEG version 2) was developed to study the heat, water, and CO 2 exchanges between the atmosphere and land-surface. The model consists of one-dimensional multilayer sub-models for the atmosphere, soil, and vegetation. It also includes sophisticated processes for solar and long-wave radiation transmission in vegetation canopy and CO 2 exchanges among the atmosphere, soil, and vegetation. Although the model usually simulates only vertical variation of variables in the surface-layer atmosphere, soil, and vegetation canopy by using meteorological data as top boundary conditions, it can be used by coupling with a three-dimensional atmosphere model. In this paper, details of SOLVEG2, which includes the function of coupling with atmosphere model MM5, are described. (author)

The determinants of exchange rate in Croatia

Directory of Open Access Journals (Sweden)

Manuel BENAZIC

2016-06-01

Full Text Available The dilemma for every country with an independent monetary policy is which kind of exchange rate arrangement should be applied. Through the exchange rate policy, countries can influence their economies, i.e. price stability and export competiveness. Croatia is a new EU member state, it has its own monetary policy and currency but it is on the way to euro introduction. Regarding the experiences from the beginning of the 1990s when Croatia was faced with serious monetary instabilities and hyperinflation, the goal of Croatian National Bank (CNB is to ensure price stability and one way to do so is through exchange rate policy. Croatia, as a small and open economy, has applied a managed floating exchange rate regime. The exchange rate is determined primarily by the foreign exchange supply and demand on the foreign exchange market, with occasional market interventions by the CNB. Therefore, in order to maintain exchange rate stability, policymakers must be able to recognize how changes in these factors affect changes in the exchange rate. This research aims to find a relationship among the main sources of foreign currency inflow and outflow and the level of exchange rate in Croatia. The analysis is carried out by using the bounds testing (ARDL approach for co-integration. The results indicate the existence of a stable co-integration relationship between the observed variables, whereby an increase in the majority of variables leads to an exchange rate appreciation.

Monitoring Exchange of CO2 - A KISS Workshop Report 2009

Science.gov (United States)

Miller, Charles; Wennberg, Paul

2009-01-01

The problem and context: Can top-down estimates of carbon dioxide (CO2) fluxes resolve the anthropogenic emissions of China, India, the United States, and the European Union with an accuracy of +/-10% or better?The workshop "Monitoring Exchange of Carbon Dioxide" was convened at the Keck Institute for Space Studies in Pasadena, California in February 2010 to address this question. The Workshop brought together an international, interdisciplinary group of 24 experts in carbon cycle science, remote sensing, emissions inventory estimation, and inverse modeling. The participants reviewed the potential of space-based and sub-orbital observational and modeling approaches to monitor anthropogenic CO2 emissions in the presence of much larger natural fluxes from the exchange of CO2 between the land, atmosphere, and ocean. This particular challenge was motivated in part by the NRC Report "Verifying Greenhouse Gas Emissions" [Pacala et al., 2010]. This workshop report includes several recommendations for improvements to observing strategies and modeling frameworks for optimal and cost-effective monitoring of carbon exchange

Experimental Investigation of Gaseous Reaction Products from Na-CO{sub 2} Reaction in Na/CO{sub 2} Heat Exchanger leakage scenario

Energy Technology Data Exchange (ETDEWEB)

Go, A-Reum; Jung, Hwa-Young; Kim, Min Seok; Lee, Jeong Ik [KAIST, Daejeon (Korea, Republic of); Min, Jaehong; Wi, Myung-Hwan [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2015-10-15

The SFRs have operated with the steam Rankine cycle as a power conversion system. However, the potential sodium-water reaction (SWR) whose chemical reactivity is vigorous and instantaneous has been one of the major issues concerning the safety and integrity of the SFRs. In order to avoid SWR, supercritical CO{sub 2}(S-CO{sub 2}) Brayton cycles have been investigated recently. Compared to conventional steam Rankine cycles, S-CO{sub 2} Brayton cycle features higher thermal efficiency and potential compactness of its required equipment. In spite of the superiority of S-CO{sub 2} Brayton cycle, there is a potential reactive process between sodium and CO{sub 2} if the pressure boundary fails in the sodium-CO{sub 2} heat exchanger. The leakage scenario which could lead to mechanical and thermal problems should be evaluated. Previous studies have reported the following major reaction formulas. Each reaction occurs competitively. In this paper, the experimental setup to observe the pressure variation and CO concentration in Na-CO{sub 2} heat exchanger during the CO{sub 2} leak is explained. Before the experiment is carried out, water-CO{sub 2} mock-up test will be performed. In order to evaluate the leakage scenario in Na-CO{sub 2} heat exchanger more accurately, this study will be important for guaranteeing the system of SFR coupled with S-CO{sub 2} cycle.

Net ecosystem CO2 exchange over a larch forest in Hokkaido, Japan

International Nuclear Information System (INIS)

Huimin Wang; Saigusa, Nobuko; Yamamoto, Susumu; Kondo, Hiroaki; Hirano, Takashi; Toriyama, Atsushi; Fujinuma, Yasumi

2004-01-01

Larch forests are distributed extensively in the east Eurasian continent and are expected to play a significant role in the terrestrial ecosystem carbon cycling process. In view of the fact that studies on carbon exchange for this important biome have been very limited, we have initiated a long-term flux observation in a larch forest ecosystem in Hokkaido in northern Japan since 2000. The net ecosystem CO 2 exchange (NEE) showed large seasonal and diurnal variation. Generally, the larch forest ecosystem released CO 2 in nighttime and assimilated CO 2 in daytime during the growing season from May to October. The ecosystem started to become a net carbon sink in May, reaching a maximum carbon uptake as high as 186 g C m -2 month -1 in June. With the yellowing, senescing and leaf fall, the ecosystem turned into a carbon source in November. During the non-growing season, the larch forest ecosystem became a net source of CO 2 , releasing an average of 16.7 g C m -2 month -1 . Overall, the ecosystem sequestered 141-240 g C m -2 yr -1 in 2001. The NEE was significantly influenced by environmental factors. Respiration of the ecosystem, for example, was exponentially dependent on air temperature, while photosynthesis was related to the incident PAR in a manner consistent with the Michaelis-Menten model. Although the vapor pressure deficit (VPD) was scarcely higher than 15 hPa, the CO 2 uptake rate was also depressed when VPD surpassed 10 hPa (Author)

Facilitated transport in hydroxide-exchange membranes for post-combustion CO2 separation.

Science.gov (United States)

Xiong, Laj; Gu, Shuang; Jensen, Kurt O; Yan, Yushan S

2014-01-01

Hydroxide-exchange membranes are developed for facilitated transport CO2 in post-combustion flue-gas feed. First, a correlation between the basicity of fixed-site functional groups and CO2 -separation performance is discovered. This relationship is used to identify phosphonium as a promising candidate to achieve high CO2 -separation performance. Consequently, quaternary phosphonium-based hydroxide-exchange membranes are demonstrated to have a separation performance that is above the Robeson upper bound. Specifically, a CO2 permeability as high as 1090 Barrer and a CO2 /N2 selectivity as high as 275 is achieved. The high performance observed in the membranes can be attributed to the quaternary phosphonium moiety. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Compact interior heat exchangers for CO{sub 2} mobile heat pumping systems

Energy Technology Data Exchange (ETDEWEB)

Hafner, Armin

2003-07-01

The natural refrigerant carbon dioxide (CO{sub 2}) offers new possibilities for design of flexible, efficient and environmentally safe mobile heat pumping systems. As high-efficient car engines with less waste heat are developed, extra heating of the passenger compartment is needed in the cold season. A reversible transcritical CO{sub 2} system with gliding temperature heat rejection can give high air delivery temperature which results in rapid heating of the passenger compartment and rapid defogging or defrosting of windows. When operated in cooling mode, the efficiency of transcritical CO{sub 2} systems is higher compared to common (HFC) air conditioning systems, at most dominant operating conditions. Several issues were identified for the design of compact interior heat exchangers for automotive reversible CO{sub 2} heat pumping systems. Among theses issues are: (1) Refrigerant flow distribution, (2) Heat exchanger fluid flow circuiting, (3) Air temperature uniformity downstream of the heat exchanger, (4) Minimization of temperature approach, (5) Windshield flash fogging due to retained water inside the heat exchanger, (6) Internal beat conduction in heating mode operation, and (7) Refrigerant side pressure drop In order to provide a basis for understanding these issues, the author developed a calculation model and set up a test facility and investigated different prototype heat exchangers experimentally.

Formation of Aqueous MgUO2(CO3)32- Complex and Uranium Anion Exchange Mechanism onto an Exchange Resin

International Nuclear Information System (INIS)

Dong, Wenming; Brooks, Scott C

2008-01-01

The formation of and stability constants for aqueous Mg-UO2-CO3 complexes were determined using an anion exchange method. Magnesium concentration was varied (up to 20 mmol/L) at constant ionic strength (I = 0.101, 0.202, 0.304, 0.406, and 0.509 mol/kg NaNO3), pH = 8.1, total [U(VI)] = 10.4 mol/L under equilibrium with atmospheric CO2. The results indicate that only the MgUO2(CO3)32- complex is formed. The cumulative formation constant extrapolated to zero ionic strength is similar regardless of the activity correction convention used: log = 25.8 b 0.5 using Davies equation and = 25.02 b 0.08 using specific ion interaction theory (SIT). Uranium sorption onto the exchange resin decreased in the presence of Mg putatively due to the formation of MgUO2(CO3)32- that had a lower affinity for the resin than UO2(CO3)34-. Uranium sorption results are consistent with an equivalent anion exchange reaction between NO3- and UO2(CO3)34- species to retain charge neutrality regardless of Mg concentration. No Mg was associated with the anion exchange resin indicating that the MgUO2(CO3)32- complex did not sorb

Net ecosystem CO2 exchange of a primary tropical peat swamp forest in Sarawak, Malaysia

Science.gov (United States)

Tang Che Ing, A.; Stoy, P. C.; Melling, L.

2014-12-01

Tropical peat swamp forests are widely recognized as one of the world's most efficient ecosystems for the sequestration and storage of carbon through both their aboveground biomass and underlying thick deposits of peat. As the peat characteristics exhibit high spatial and temporal variability as well as the structural and functional complexity of forests, tropical peat ecosystems can act naturally as both carbon sinks and sources over their life cycles. Nonetheless, few reports of studies on the ecosystem-scale CO2 exchange of tropical peat swamp forests are available to-date and their present roles in the global carbon cycle remain uncertain. To quantify CO2 exchange and unravel the prevailing factors and potential underlying mechanism regulating net CO2 fluxes, an eddy covariance tower was erected in a tropical peat swamp forest in Sarawak, Malaysia. We observed that the diurnal and seasonal patterns of net ecosystem CO2 exchange (NEE) and its components (gross primary productivity (GPP) and ecosystem respiration (RE)) varied between seasons and years. Rates of NEE declined in the wet season relative to the dry season. Conversely, both the gross primary productivity (GPP) and ecosystem respiration (RE) were found to be higher during the wet season than the dry season, in which GPP was strongly negatively correlated with NEE. The average annual NEE was 385 ± 74 g C m-2 yr-1, indicating the primary peat swamp forest functioned as net source of CO2 to the atmosphere over the observation period.

Influence of soil erosion on CO2 exchange within the CarboZALF manipulation experiment

Science.gov (United States)

Hoffmann, Mathias; Augustin, Jürgen; Sommer, Michael

2014-05-01

Agriculture in the hummocky ground moraine landscape of NE-Germany is characterized by an increase in energy crop cultivation, like maize or sorghum. Both enhance lateral C fluxes by erosion and induce feedbacks on C dynamics of agroecosystems as a result of the time limited land cover and the vigorous crop growth. However, the actual impact of these phenomena on the CO2-sink/-source function of agricultural landscapes, is still not clear. Therefore we established the interdisciplinary project 'CarboZALF' in 2009. In our field experiment CarboZALF-D we are monitoring CO2 fluxes for soil-plant systems, which cover all landscape relevant soil states in respect to erosion and deposition, like Albic Cutanic Luvisol, Calcic Cutanic Luvisol, Calcaric Regosol and Endogleyic Colluvic Regosol. Furthermore, we induced erosion / deposition in a manipulation experiment. Automated chamber systems (2.5 m, basal area 1 m2, transparent) are placed at the manipulated sites as well as at one site neither influenced by erosion, nor by deposition. CO2 flux modelling of high temporal resolution includes ecosystem respiration (Reco), gross primary productivity (GPP) and net ecosystem exchange (NEE) based on parallel and continuous measurements of the CO2 exchange, soil and air temperatures as well as photosynthetic active radiation (PAR). Modelling includes gap filling which is needed in case of chamber malfunctions and abrupt disturbances by farming practice. In our presentation we would like to show results of the CO2 exchange measurements for one year. Differences are most pronounced between the non-eroded and the colluvial soil: The Endogleyic Colluvic Regosol showed higher flux rates for Reco and NEE compared to the Albic Cutanic Luvisol. The eroded soil (Calcic Cutanic Luvisol) demonstrated CO2fluxes intermediate between the non-affected and depositional site. Site-specific consequences for the soil C stocks will be also discussed in the presentation.

Development of novel exchange spring magnet by employing nanocomposites of CoFe_2O_4 and CoFe_2

International Nuclear Information System (INIS)

Safi, Rohollah; Ghasemi, Ali; Shoja-Razavi, Reza; Tavoosi, Majid

2016-01-01

CoFe_2O_4−CoFe2 hard–soft nanocomposites were prepared via reduction of the cobalt ferrite CoFe_2O_4 in hydrogen atmosphere at different temperature. The structure and the room temperature magnetization of the samples were characterized by X-ray diffraction, field emission scanning electron microscope (FESEM) and vibrating sample magnetometer (VSM). It was found that the saturation magnetization of the nanocomposite powders increases by reduction temperature while their coercivity decreases. The highest M_r/M_s ratio of 0.52 was obtained for sample reduced at 550 °C. Single smooth hysteresis loops of nanocomposites show that these nanocomposites behave as the single-phase materials. This result indicates the presence of exchange coupling between two different hard and soft phases. - Highlights: • CoFe_2O_4–CoFe_2 was successfully synthesized by reduction diffusion process. • Two phases are effectively exchange coupled in nanocomposite. • Single smooth hysteresis loop was developed in nanocomposites.

Complex ion kinetics. Reaction rates on ion-exchange resins compared to those in water

International Nuclear Information System (INIS)

Liss, I.B.; Murmann, R.K.

1975-01-01

A comparison has been made between the rates in water and on an ion-exchange resin for the aquation of [(NH 3 ) 5 CoOReO 3 ] 2+ and [(H 2 O) 5 CrCl] 2+ and for the 18 O isotopic exchange of water with [(NH 3 ) 5 Co(OH 2 )] 3+ and ReO 4 - . The rate of water exchange on [(NH 3 ) 5 Co(OH 2 )] 3+ was not changed by association with Dowex 50W resins. Aquation of [(NH 3 ) 5 CoOReO 3 ] 2+ and water exchange on ReO 4 - had modified pH dependencies when associated with a resin. With the cobalt complex the rates were faster on the resin in the acidic region and slower on the resin in the basic region. A new term in the rate equation was observed when ReO 4 - was on the resin, first order in H + , while the other terms appear to be unchanged. Aquation of [(H 2 O) 5 CrCl] 2+ was much slower when it was absorbed on the resin. This was related to the known ionic strength effect of the reaction. (auth)

Biophysical remote sensing and terrestrial CO2 exchange at Cape Bounty, Melville Island

Science.gov (United States)

Gregory, Fiona Marianne

Cape Bounty, Melville Island is a partially vegetated High Arctic landscape with three main plant communities: polar semi-desert (47% of the study area), mesic tundra (31%) , and wet sedge meadows (7%). The objective of this research was to relate biophysical measurements of soil, vegetation, and CO2 exchange rates in each vegetation type to high resolution satellite data from IKONOS-2, extending plot level measurements to a landscape scale. Field data was collected through six weeks of the 2008 growing season. Two IKONOS images were acquired, one on July 4th and the other on August 2nd. Two products were generated from the satellite data: a land-cover classification and the Normalized Difference Vegetation Index (NDVI). The three vegetation types were found to have distinct soil and vegetation characteristics. Only the wet sedge meadows were a net sink for CO2; soil respiration tended to exceed photosynthesis in the sparsely vegetated mesic tundra and polar semi-desert. Scaling up the plot measurements by vegetation type area suggested that Cape Bounty was a small net carbon source (0.34 +/- 0.47 g C m-2 day-1) in the summer of 2008. NDVI was strongly correlated with percent vegetation cover, vegetation volume, soil moisture, and moderately with soil nitrogen, biomass, and leaf area index (LAI). Photosynthesis and respiration of CO2 both positively correlated with NDVI, most strongly when averaged over the season. NDVI increased over time in every vegetation type, but this change was not reflected in any significant measured changes in vegetation or CO2 flux rates. A simple spatial model was developed to estimate Net Ecosystem Exchange (NEE) at every pixel on the satellite images based on NDVI, temperature and incoming solar radiation. It was found that the rate of photosynthesis per unit NDVI was higher early in the growing season. The model estimated a mean flux to the atmosphere of 0.21 g C m-2 day-1 at the time of image acquisition on July 4th, and -0.07 g C m

Automated exchange transfusion and exchange rate.

Science.gov (United States)

Funato, M; Shimada, S; Tamai, H; Taki, H; Yoshioka, Y

1989-10-01

An automated blood exchange transfusion (BET) with a two-site technique has been devised by Goldmann et al and by us, using an infusion pump. With this method, we successfully performed exchange transfusions 189 times in the past four years on 110 infants with birth weights ranging from 530 g to 4,000 g. The exchange rate by the automated method was compared with the rate by Diamond's method. Serum bilirubin (SB) levels before and after BET and the maximal SB rebound within 24 hours after BET were: 21.6 +/- 2.4, 11.5 +/- 2.2, and 15.0 +/- 1.5 mg/dl in the automated method, and 22.0 +/- 2.9, 11.2 +/- 2.5, and 17.7 +/- 3.2 mg/dl in Diamond's method, respectively. The result showed that the maximal rebound of the SB level within 24 hours after BET was significantly lower in the automated method than in Diamond's method (p less than 0.01), though SB levels before and after BET were not significantly different between the two methods. The exchange rate was also measured by means of staining the fetal red cells (F cells) both in the automated method and in Diamond's method, and comparing them. The exchange rate of F cells in Diamond's method went down along the theoretical exchange curve proposed by Diamond, while the rate in the automated method was significantly better than in Diamond's, especially in the early stage of BET (p less than 0.01). We believe that the use of this automated method may give better results than Diamond's method in the rate of exchange, because this method is performed with a two-site technique using a peripheral artery and vein.

Net CO2 exchange rates in three different successional stages of the 'Dark Taiga' of central Siberia

International Nuclear Information System (INIS)

Roeser, C.; Schulze, E.D.; Montagnani, L.

2002-01-01

The net ecosystem exchange (NEE) of successional stages of the Abies-dominated dark taiga was measured in central Siberia (61 deg N, 90 deg E) during the growing season of the year 2000 using the eddy covariance technique. Measurements started before snow melt and canopy activity in spring on day of year (DOY) 99 and lasted until a permanent snow cover had developed and respiration had ceased in autumn DOY 299. Three stands growing in close vicinity were investigated: 50 yr-old Betula pubescens ('Betula stand', an early successional stage after fire), 250 yr-old mixed boreal forest, representing the transition from Betula-dominated to Abies-dominated canopies, and 200-yr-old Abies sibirica ('Abies stand', representing a late successional stage following the mixed boreal forest). The mixed boreal forest had a multi-layered canopy with dense under story and trees of variable height and age below the main canopy, which was dominated by Abies sibirica, Picea obovata and few old Betula pubescens and Populus tremula trees. The Abies stand had a uniform canopy dominated by Abies sibirica. This stand appears to have established not after fire but after wind break or insect damage in a later successional stage. The stands differed with respect to the number of days with net CO 2 uptake (Betula stand 89 days, mixed boreal forest 109 days, and Abies stand 135 days), maximum measured LAI (Betula 2.6 m 2 /m 2 , mixed boreal forest 3.5 m 2 /m 2 and Abies stand 4.1 m 2 /m 2 ) and basal area (Betula stand 30.2 m 2 /ha, mixed boreal forest 35.7 m 2 /ha, and Abies stand 46.5 m 2 /ha). In the mixed boreal forest, many days with net daytime CO 2 release were observed in summer. Both other sites were almost permanent sinks in summer. Mean daytime CO 2 exchange rates in July were 8.45 mol/m 2 /s in the Betula stand, 4.65 mol/m 2 /s in the mixed boreal forest and 6.31 mol/m 2 /s in the Abies stand. Measured uptake for the growing season was 247.2 g C/m 2 in the Betula stand, 99.7 g C/m 2

Photodissociation dynamics of gaseous CpCo(CO)2 and ligand exchange reactions of CpCoH2 with C3H4, C3H6, and NH3.

Science.gov (United States)

Oana, Melania; Nakatsuka, Yumiko; Albert, Daniel R; Davis, H Floyd

2012-05-31

The photodissociation dynamics of CpCo(CO)(2) was studied in a molecular beam using photofragment translational energy spectroscopy with 157 nm photoionization detection of the metallic products. At 532 and 355 nm excitation, the dominant one-photon channel involved loss of a single CO ligand producing CpCoCO. The product angular distributions were isotropic, and a large fraction of excess energy appeared as product vibrational excitation. Production of CpCO + 2CO resulted from two-photon absorption processes. The two-photon dissociation of mixtures containing CpCo(CO)(2) and H(2) at the orifice of a pulsed nozzle was used to produce a novel 16-electron unsaturated species, CpCoH(2). Transition metal ligand exchange reactions, CpCoH(2) + L → CpCoL + H(2) (L = propyne, propene, or ammonia), were studied under single-collision conditions for the first time. In all cases, ligand exchange occurred via 18-electron association complexes with lifetimes comparable to their rotational periods. Although ligand exchange reactions were not detected from CpCoH(2) collisions with methane or propane (L = CH(4) or C(3)H(8)), a molecular beam containing CpCoCH(4) was produced by photolysis of mixtures containing CpCo(CO)(2) and CH(4).

Exchange-coupled Fe3O4/CoFe2O4 nanoparticles for advanced magnetic hyperthermia

Science.gov (United States)

Glassell, M.; Robles, J.; Das, R.; Phan, M. H.; Srikanth, H.

Iron oxide nanoparticles especially Fe3O4, γ-Fe2O3 have been extensively studied for magnetic hyperthermia because of their tunable magnetic properties and stable suspension in superparamagnetic regime. However, their relatively low heating capacity hindered practical application. Recently, a large improvement in heating efficiency has been reported in exchange-coupled nanoparticles with exchange coupling between soft and hard magnetic phases. Here, we systematically studied the effect of core and shell size on the heating efficiency of the Fe3O4/CoFe2O4 core/shell nanoparticles. The nanoparticles were synthesized using thermal decomposition of organometallic precursors. Transmission electron microscopy (TEM) showed formation of spherical shaped Fe3O4 and Fe3O-/CoFe2O4 nanoparticles. Magnetic measurements showed high magnetization (≅70 emu/g) and superparamagnetic behavior for the nanoparticles at room temperature. Magnetic hyperthermia results showed a large increase in specific absorption rate (SAR) for 8nm Fe3O4/CoFe2O4 compared to Fe3O4 nanoparticles of the same size. The heating efficiency of the Fe3O4/CoFe2O4 with 1 nm CoFe2O4 (shell) increased from 207 to 220 W/g (for 800 Oe) with increase in core size from 6 to 8 nm. The heating efficiency of the Fe3O4/CoFe2O4 with 2 nm CoFe2O4 (shell) and core size of 8 nm increased from 220 to 460 W/g (for 800 Oe). These exchange-coupled Fe3O4/CoFe2O4 core/shell nanoparticles can be a good candidate for advanced hyperthermia application.

Fe atom exchange between aqueous Fe2+ and magnetite.

Science.gov (United States)

Gorski, Christopher A; Handler, Robert M; Beard, Brian L; Pasakarnis, Timothy; Johnson, Clark M; Scherer, Michelle M

2012-11-20

The reaction between magnetite and aqueous Fe(2+) has been extensively studied due to its role in contaminant reduction, trace-metal sequestration, and microbial respiration. Previous work has demonstrated that the reaction of Fe(2+) with magnetite (Fe(3)O(4)) results in the structural incorporation of Fe(2+) and an increase in the bulk Fe(2+) content of magnetite. It is unclear, however, whether significant Fe atom exchange occurs between magnetite and aqueous Fe(2+), as has been observed for other Fe oxides. Here, we measured the extent of Fe atom exchange between aqueous Fe(2+) and magnetite by reacting isotopically "normal" magnetite with (57)Fe-enriched aqueous Fe(2+). The extent of Fe atom exchange between magnetite and aqueous Fe(2+) was significant (54-71%), and went well beyond the amount of Fe atoms found at the near surface. Mössbauer spectroscopy of magnetite reacted with (56)Fe(2+) indicate that no preferential exchange of octahedral or tetrahedral sites occurred. Exchange experiments conducted with Co-ferrite (Co(2+)Fe(2)(3+)O(4)) showed little impact of Co substitution on the rate or extent of atom exchange. Bulk electron conduction, as previously invoked to explain Fe atom exchange in goethite, is a possible mechanism, but if it is occurring, conduction does not appear to be the rate-limiting step. The lack of significant impact of Co substitution on the kinetics of Fe atom exchange, and the relatively high diffusion coefficients reported for magnetite suggest that for magnetite, unlike goethite, Fe atom diffusion is a plausible mechanism to explain the rapid rates of Fe atom exchange in magnetite.

Atmospheric and Surface-Condition Effects on CO2 Exchange in the Liaohe Delta Wetland, China

Directory of Open Access Journals (Sweden)

Qingyu Jia

2017-10-01

Full Text Available The eddy covariance method was used to study the CO2 budget of the Liaohe Delta reed wetland in northern China during 2012–2015. The changes in environmental factors (including meteorology, vegetation, hydrology, and soil were analyzed simultaneously. The change in the trend of the CO2 concentration in the reed wetland was similar to global changes over the four years. The average annual CO2 accumulation was 2.037 kg·CO2·m−2, ranging from 1.472 to 2.297 kg·CO2·m−2. The seasonal characteristics of the CO2 exchange included high CO2 absorption in June and July, and high emissions in April and from September to October, with the highest emissions in July 2015. The average temperatures from 2013 to 2015 were higher than the 50-year average, largely due to increased temperatures in winter. Precipitation was below the 50-year average, mainly because of low precipitation in summer. The average wind speed was less than the 50-year average, and sunshine duration decreased each year. The CO2 exchange and environmental factors had a degree of correlation or consistency. The contribution of meteorology, vegetation, hydrology, and soil to the CO2 budget was analyzed using the partial least squares method. Water and soil temperature had a greater effect on the CO2 exchange variability. The regression equation of the CO2 budget was calculated using the significant contributing factors, including temperature, precipitation, relative humidity, water-table level, salinity, and biomass. The model fit explained more than 70% of the CO2 exchange, and the simulation results were robust.

Dynamic adsorption of CO2/N2 on cation-exchanged chabazite SSZ-13: A breakthrough analysis

Energy Technology Data Exchange (ETDEWEB)

Bower, Jamey K.; Barpaga, Dushyant; Prodinger, Sebastian; Krishna, Rajamani; Schaef, Herbert T.; McGrail, Bernard P.; Derewinski, Miroslaw A.; Motkuri, Radha K.

2018-04-17

Alkali exchanged SSZ-13 adsorbents were investigated for their applicability in separating N2 from CO2 in flue gas streams using a dynamic breakthrough method. In contrast to IAST calculations based on equilibrium isotherms, K+ exchanged SSZ-13 was found to yield the best N2 productivity under dynamic conditions where diffusion properties play a significant role. This was attributed to the selective, partial blockage of access to the CHA cavities enhancing the separation potential in a 15/85 CO2/N2 binary gas mixture.

Sea ice contribution to the air-sea CO(2) exchange in the Arctic and Southern Oceans

DEFF Research Database (Denmark)

Rysgaard...[], Søren; Bendtsen, Jørgen; Delille, B.

2011-01-01

Although salt rejection from sea ice is a key process in deep-water formation in ice-covered seas, the concurrent rejection of CO(2) and the subsequent effect on air-sea CO(2) exchange have received little attention. We review the mechanisms by which sea ice directly and indirectly controls the air......-sea CO(2) exchange and use recent measurements of inorganic carbon compounds in bulk sea ice to estimate that oceanic CO(2) uptake during the seasonal cycle of sea-ice growth and decay in ice-covered oceanic regions equals almost half of the net atmospheric CO(2) uptake in ice-free polar seas. This sea......-sea CO(2) exchange during winter, and (3) release of CO(2)-depleted melt water with excess total alkalinity during sea-ice decay and (4) biological CO(2) drawdown during primary production in sea ice and surface oceanic waters....

Stem photosynthesis in a desert ephemeral, Eriogonum inflatum : Characterization of leaf and stem CO2 fixation and H2O vapor exchange under controlled conditions.

Science.gov (United States)

Osmond, C B; Smith, S D; Gui-Ying, B; Sharkey, T D

1987-07-01

The gas exchange characteristics of photosynthetic tissues of leaves and stems of Eriogonum inflatum are described. Inflated stems were found to contain extraordinarily high internal CO 2 concentrations (to 14000 μbar), but fixation of this internal CO 2 was 6-10 times slower than fixation of atmospheric CO 2 by these stems. Although the pool of CO 2 is a trivial source of CO 2 for stem photosynthesis, it may result in higher water-use efficiency of stem tissues. Leaf and stem photosynthetic activities were compared by means of CO 2 fixation in CO 2 response curves, light and temperature response curves in IRGA systems, and by means of O 2 exchange at CO 2 saturation in a leaf disc O 2 electrode system. On an area basis leaves contain about twice the chlorophyll and nitrogen as stems, and are capable of up to 4-times the absolute CO 2 and O 2 exchange rates. However, the stem shape is such that lighting of the shaded side leads to a substantial increase in overall stem photosynthesis on a projected area basis, to about half the leaf rate in air. Stem conductance is lower than leaf conductance under most conditions and is less sensitive to high temperature or high VPD. Under most conditions, the ratio C i /C a is lower in stems than in leaves and stems show greater water-use efficiency (higher ratio assimilation/transpiration) as a function of VPD. This potential advantage of stem photosynthesis in a water limited environment may be offset by the higher VPD conditions in the hotter, drier part of the year when stems are active after leaves have senesced. Stem and leaf photosynthesis were similarly affected by decreasing plant water potential.

Variability of annual CO2 exchange from Dutch grasslands

NARCIS (Netherlands)

Jacobs, C.M.J.; Jacobs, A.F.G.; Bosveld, F.C.; Hendriks, D.M.D.; Hensen, A.; Kroon, P.; Moors, E.J.; Nol, L.; Schrier-Uijl, A.P.; Veenendaal, E.M.

2007-01-01

An intercomparison is made of the Net Ecosystem Exchange of CO2, NEE, for eight Dutch grassland sites: four natural grasslands, two production grasslands and two meteorological stations within a rotational grassland region. At all sites the NEE was determined during at least 10 months per site,

Fluidized-Bed Heat Transfer Modeling for the Development of Particle/Supercritical-CO2 Heat Exchanger

Energy Technology Data Exchange (ETDEWEB)

Ma, Zhiwen [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Martinek, Janna G [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

2017-06-03

Concentrating solar power (CSP) technology is moving toward high-temperature and high-performance design. One technology approach is to explore high-temperature heat-transfer fluids and storage, integrated with a high-efficiency power cycle such as the supercritical carbon dioxide (s-CO2) Brayton power cycle. The s-CO2 Brayton power system has great potential to enable the future CSP system to achieve high solar-to-electricity conversion efficiency and to reduce the cost of power generation. Solid particles have been proposed as a possible high-temperature heat-transfer medium that is inexpensive and stable at high temperatures above 1,000 degrees C. The particle/heat exchanger provides a connection between the particles and s-CO2 fluid in the emerging s-CO2 power cycles in order to meet CSP power-cycle performance targets of 50% thermal-to-electric efficiency, and dry cooling at an ambient temperature of 40 degrees C. The development goals for a particle/s-CO2 heat exchanger are to heat s-CO2 to =720 degrees C and to use direct thermal storage with low-cost, stable solid particles. This paper presents heat-transfer modeling to inform the particle/s-CO2 heat-exchanger design and assess design tradeoffs. The heat-transfer process was modeled based on a particle/s-CO2 counterflow configuration. Empirical heat-transfer correlations for the fluidized bed and s-CO2 were used in calculating the heat-transfer area and optimizing the tube layout. A 2-D computational fluid-dynamics simulation was applied for particle distribution and fluidization characterization. The operating conditions were studied from the heat-transfer analysis, and cost was estimated from the sizing of the heat exchanger. The paper shows the path in achieving the cost and performance objectives for a heat-exchanger design.

Water relations and gas exchange in poplar and willow under water stress and elevated atmospheric CO2.

Science.gov (United States)

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.

Sodium citrate-assisted anion exchange strategy for construction of Bi2O2CO3/BiOI photocatalysts

International Nuclear Information System (INIS)

Song, Peng-Yuan; Xu, Ming; Zhang, Wei-De

2015-01-01

Highlights: • Heterostructured Bi 2 O 2 CO 3 /BiOI microspheres were prepared via anion exchange. • Sodium citrate-assisted anion exchange for construction of composite photocatalysts. • Bi 2 O 2 CO 3 /BiOI composites show high visible light photocatalytic activity. - Abstract: Bi 2 O 2 CO 3 /BiOI heterojuncted photocatalysts were constructed through a facile partial anion exchange strategy starting from BiOI microspheres and urea with the assistance of sodium citrate. The content of Bi 2 O 2 CO 3 in the catalysts was regulated by modulating the amount of urea as a precursor, which was decomposed to generate CO 3 2− in the hydrothermal process. Citrate anion plays a key role in controlling the morphology and composition of the products. The Bi 2 O 2 CO 3 /BiOI catalysts display much higher photocatalytic activity than pure BiOI and Bi 2 O 2 CO 3 towards the degradation of rhodamine B (RhB) and bisphenol A (BPA). The enhancement of photocatalytic activity of the heterojuncted catalysts is attributed to the formation of p–n junction between p-BiOI and n-Bi 2 O 2 CO 3 , which is favorable for retarding the recombination of photoinduced electron-hole pairs. Moreover, the holes are demonstrated to be the main active species for the degradation of RhB and BPA

Annual CO2 budget and seasonal CO2 exchange signals at a high Arctic permafrost site on Spitsbergen, Svalbard archipelago

DEFF Research Database (Denmark)

Luërs, J.; Westermann, Signe; Piel, K.

2014-01-01

-lasting snow cover, and several months of darkness. This study presents a complete annual cycle of the CO2 net ecosystem exchange (NEE) dynamics for a high Arctic tundra area at the west coast of Svalbard based on eddy covariance flux measurements. The annual cumulative CO2 budget is close to 0 g C m-2 yr-1...

Exchange Bias in Layered GdBaCo2O5.5 Cobaltite

Science.gov (United States)

Solin, N. I.; Naumov, S. V.; Telegin, S. V.; Korolev, A. V.

2017-12-01

It is established that excess oxygen content δ influences the exchange bias (EB) in layered GdBa-Co2O5 + δ cobaltite. The EB effect arises in p-type (δ > 0.5) cobaltite and disappears in n-type (δ training effect inherent in systems with EB has been studied. The results are explained in terms of exchange interaction between the FM and AFM phases. It is assumed that the EB originates from the coexistence of Co3+ and Co4+ ions that leads to the formation of monodomain FM clusters in the AFM matrix of cobaltite.

Co2+ ion exchange with NaY

International Nuclear Information System (INIS)

Garcia, I.; Solache-Rios, M.; Bulbulian, S.; Bosch, P.

1993-01-01

Co 2+ ion exchange from aqueous cobalt chloride-sodium chloride solutions with NaY zeolite has been investigated. The effect of contact time on the sorption of Co 2+ by dehydrated Y zeolite at 150 degrees C is unusual. A fast sorption uptake is observed in which 1.73 mequiv/g of zeolite of Na + ions is replaced by cobalt ions, followed by a desorption process where the uptake decreases to 1.56 mequiv/g of zeolite. This behavior is explained by the location and coordination of cobalt in Y zeolite sites. It is suggested that the maximum uptake corresponds to cobalt ions being simultaneously in two sites; tetrahedrally coordinated in the sodalite units and octahedrally coordinated in the large cavities. It is also suggested that the desorption process is a consequence of a reaction between Cl - ions and the tetrahedral species. 20 refs., 4 figs

Chartist Trading in Exchange Rate Theory

OpenAIRE

Selander, Carina

2006-01-01

This thesis consists of four papers, of which paper 1 and 4 are co-written with Mikael Bask. Paper [1] implements chartists trading in a sticky-price monetary model for determining the exchange rate. It is demonstrated that chartists cause the exchange rate to "overshoot the overshooting equilibrium" of a sticky-price monetary model. Chartists base their trading on a short-long moving average. The importance of technical trading depends inversely on the time horizon in currency trade. The exc...

Interfaces exchange bias and magnetic properties of ordered CoFe_2O_4/Co_3O_4 nanocomposites

International Nuclear Information System (INIS)

Zhang, B.B.; Xu, J.C.; Wang, P.F.; Han, Y.B.; Hong, B.; Jin, H.X.; Jin, D.F.; Peng, X.L.; Li, J.; Yang, Y.T.; Gong, J.; Ge, H.L.; Wang, X.Q.

2015-01-01

Graphical abstract: - Highlights: • CoFe_2O_4 nanoparticles were well-dispersed anchored in mesopores of Co_3O_4. • The magnetic behavior of nanocomposites changed greatly at low temperature. • CoFe_2O_4 nanoparticles reinforced the interfaces magnetic interaction of nanocomposites. • M increased with the doping of CoFe_2O_4 and the decreasing temperature. • Exchange bias effect was observed at 100 K and increased with the doping of CoFe_2O_4. - Abstract: Cobalt ferrites (CoFe_2O_4) nanoparticles were implanted into the ordered mesoporous cobaltosic oxide (Co_3O_4) nanowires to synthesize magnetic CoFe_2O_4/Co_3O_4 nanocomposites. X-ray diffraction (XRD), N_2 physical absorption–desorption, transmission electron microscope (TEM) and energy disperse spectroscopy (EDS) were used to characterize the microstructure of mesoporous Co_3O_4 and CoFe_2O_4/Co_3O_4 nanocomposites. The percent of pore-volume of mesoporous Co_3O_4 nanowires was calculated to be about 41.99% and CoFe_2O_4 nanoparticles were revealed to exist in the mesopores of Co_3O_4_. The magnetic behavior of both samples were investigated with superconducting quantum interference device (SQUID). Magnetization increased with the doping CoFe_2O_4 and decreasing temperature, while coercivity hardly changed. The exchange bias effect was obviously observed at 100 K and enhanced with the doping CoFe_2O_4. CoFe_2O_4 nanoparticles reinforced the interfaces magnetic interaction between antiferromagnetic Co_3O_4 and ferrimagnetic CoFe_2O_4.

Carbon isotope exchange between gaseous CO2 and thin solution films: Artificial cave experiments and a complete diffusion-reaction model

Science.gov (United States)

Hansen, Maximilian; Scholz, Denis; Froeschmann, Marie-Louise; Schöne, Bernd R.; Spötl, Christoph

2017-08-01

Speleothem stable carbon isotope (δ13C) records provide important paleoclimate and paleo-environmental information. However, the interpretation of these records in terms of past climate or environmental change remains challenging because of various processes affecting the δ13C signals. A process that has only been sparsely discussed so far is carbon isotope exchange between the gaseous CO2 of the cave atmosphere and the dissolved inorganic carbon (DIC) contained in the thin solution film on the speleothem, which may be particularly important for strongly ventilated caves. Here we present a novel, complete reaction diffusion model describing carbon isotope exchange between gaseous CO2 and the DIC in thin solution films. The model considers all parameters affecting carbon isotope exchange, such as diffusion into, out of and within the film, the chemical reactions occurring within the film as well as the dependence of diffusion and the reaction rates on isotopic mass and temperature. To verify the model, we conducted laboratory experiments under completely controlled, cave-analogue conditions at three different temperatures (10, 20, 30 °C). We exposed thin (≈0.1 mm) films of a NaHCO3 solution with four different concentrations (1, 2, 5 and 10 mmol/l, respectively) to a nitrogen atmosphere containing a specific amount of CO2 (1000 and 3000 ppmV). The experimentally observed temporal evolution of the pH and δ13C values of the DIC is in good agreement with the model predictions. The carbon isotope exchange times in our experiments range from ca. 200 to ca. 16,000 s and strongly depend on temperature, film thickness, atmospheric pCO2 and the concentration of DIC. For low pCO2 (between 500 and 1000 ppmV, as for strongly ventilated caves), our time constants are substantially lower than those derived in a previous study, suggesting a potentially stronger influence of carbon isotope exchange on speleothem δ13C values. However, this process should only have an

Preliminary conceptual design of the secondary sodium circuit-eliminated JSFR (Japan Sodium Fast Reactor) adopting a supercritical CO2 turbine system (1). Sodium/CO2 heat exchanger

International Nuclear Information System (INIS)

Kisohara, Naoyuki; Sakamoto, Yoshihiko; Kotake, Shoji

2014-09-01

Research and development of the supercritical CO 2 (S-CO 2 ) cycle turbine system is underway in various countries for further improvement of the safety and economy of sodium-cooled fast reactors. The Component Design and Balance-Of-Plant (CD and BOP) of the Generation IV International Nuclear Forum (Gen-IV) has addressed this study, and their analytical and experimental results have been discussed between the relevant countries. JAEA, who is a member of the CD and BOP, has performed a design study of an S-CO 2 gas turbine system applied to the Japan Sodium-cooled Fast Reactor (JSFR). In this study, the S-CO 2 cycle turbine system was directly connected to the primary sodium system of the JSFR to eliminate the secondary sodium circuit, aiming for further economical improvement. This is because there is no risk of sodium-water reaction in the S-CO 2 cycle turbine system of SFRs. The Na/CO 2 heat exchanger is one of the key components for the secondary sodium system eliminated SFR, and this report describes its structure and the safety in case of CO 2 leak. A Printed Circuit Heat Exchanger (PCHE), which has a greater heat transfer performance, is employed to the heat exchanger. Another advantage of the PCHE is to limit the area affected by a leak of CO 2 because of its partitioned flow path structure. A SiC/SiC ceramic composite material is used for the PCHE to prevent crack growth and to reduce thermal stress. The Na/CO 2 heat exchanger has been designed in such a way that a number of small heat transfer modules are combined in the vessel in consideration of manufacture and repair. The primary sodium pump is installed in the center of the heat exchanger vessel. CO 2 leak events in the heat exchanger have been also evaluated, and it revealed that no significant effect has arisen on the core or the primary sodium boundary. (author)

Measurement and Calculation of Absolute Single- and Multiple-Charge-Exchange Cross Sections for Fe^q+ Ions Impacting CO and CO₂

Energy Technology Data Exchange (ETDEWEB)

Simcic, J. [Jet Propulsion Laboratory/Caltech; Schultz, David Robert [ORNL; Mawhorter, R. J. [Pomona College; Cadez, I. [Jozef Stefan Institute, Slovenia; Greenwood, J. B. [Queen' s University, Belfast; Chutjian, A. [Jet Propulsion Laboratory/Caltech; Lisse, Carey M. [Johns Hopkins University; Smith, S. J. [Indiana Wesleyan University, Marion

2010-01-01

Absolute cross sections are reported for single, double, and triple charge exchange of Feq+ (q=5- 13) ions with CO and CO2. The highly-charged Fe ions are generated in an electron cyclotron resonance ion source. Absolute data are derived from knowledge of the target gas pressure, target path length, and incident and charge-exchanged ion currents. Experimental results are compared with new calculations of these cross sections in the n-electron classical trajectory Monte-Carlo approximation, in which the ensuing radiative and non-radiative cascades are approximated with scaled hydrogenic transition probabilities and scaled Auger rates. The present data are needed in astrophysical applications of solar- and stellar-wind charge-exchange with comets, planetary atmospheres, and circumstellar clouds.

Oxygen exchange between C18O2 and ''acidic'' oxide and zeolite catalysts

International Nuclear Information System (INIS)

Peri, J.B.

1975-01-01

The exchange of oxygen between C 18 O 2 and several high-area oxides, including silica, γ-alumina, silica--alumina, and zeolite catalysts, was studied. Infrared spectra of adsorbed CO 2 and of surface ''carbonates'' were used to follow the rate of oxygen exchange and investigate the nature of unusually exchangeable surface oxide ions, present at low concentrations. Interaction of CO 2 with the surface typically produced initial exchange of one oxygen atom, as expected from interaction with a single oxide ion (CO 2 + O 2- reversible CO 3 2- ), and the number of exchangeable ions increased with increasing temperature. The rate of oxygen exchange did not correlate with chemisorption to form stable surface carbonates or with the extent of strong physical adsorption of CO 2 . With dry silica, exchange was insignificant below 600 0 ; with catalytically active zeolites and dry γ-alumina, it was detectable at 200 0 and fairly rapid at 300--400 0 . Silica--alumina required 100--150 0 higher temperature for exchange than did an active zeolite. Activity for cracking and other hydrocarbon reactions may be related to the ease of exchange of some surface oxide ions with CO 2 . Active zeolites have reactive oxide sites resembling those on dry γ-alumina, but such sites on zeolites are probably less-readily eliminated by chemisorption of H 2 O or other compounds. (U.S.)

The Arctic Ocean marine carbon cycle: evaluation of air-sea CO2 exchanges, ocean acidification impacts and potential feedbacks

Directory of Open Access Journals (Sweden)

N. R. Bates

2009-11-01

Full Text Available At present, although seasonal sea-ice cover mitigates atmosphere-ocean gas exchange, the Arctic Ocean takes up carbon dioxide (CO2 on the order of −66 to −199 Tg C year−1 (1012 g C, contributing 5–14% to the global balance of CO2 sinks and sources. Because of this, the Arctic Ocean has an important influence on the global carbon cycle, with the marine carbon cycle and atmosphere-ocean CO2 exchanges sensitive to Arctic Ocean and global climate change feedbacks. In the near-term, further sea-ice loss and increases in phytoplankton growth rates are expected to increase the uptake of CO2 by Arctic Ocean surface waters, although mitigated somewhat by surface warming in the Arctic. Thus, the capacity of the Arctic Ocean to uptake CO2 is expected to alter in response to environmental changes driven largely by climate. These changes are likely to continue to modify the physics, biogeochemistry, and ecology of the Arctic Ocean in ways that are not yet fully understood. In surface waters, sea-ice melt, river runoff, cooling and uptake of CO2 through air-sea gas exchange combine to decrease the calcium carbonate (CaCO3 mineral saturation states (Ω of seawater while seasonal phytoplankton primary production (PP mitigates this effect. Biological amplification of ocean acidification effects in subsurface waters, due to the remineralization of organic matter, is likely to reduce the ability of many species to produce CaCO3 shells or tests with profound implications for Arctic marine ecosystems

Parametric study of a capillary tube-suction line heat exchanger in a transcritical CO2 heat pump cycle

International Nuclear Information System (INIS)

Agrawal, Neeraj; Bhattacharyya, Souvik

2008-01-01

The capillary tube in a transcritical CO 2 system behaves differently as temperature and pressure are two independent parameters unlike those in a sub-critical cycle. A capillary tube-suction line heat exchanger (CL-SLHX) in a transcritical vapour compression cycle considering homogeneous two-phase flow is modelled in this study based on mass, energy and momentum equations. Effects of gas cooler temperature, evaporator temperature and internal diameter of capillary tube are investigated. Heat transfer rate is observed to be influenced by refrigerant quality, mass flow rate and the prevailing temperature difference. Heat transfer rate variation with gas cooler temperature is unique, recording an initial increase followed by a decrease. Frictional pressure drop influences the heat transfer; consequently, chances of re-condensation of refrigerant vapour are very marginal. Larger diameter of capillary tube leads to increase in refrigerant mass flow rate and increase in heat transfer rate as well. Shorter inlet adiabatic capillary length with larger heat exchanger length is better for heat transfer. This study is an attempt to dispel the scepticism prevailing in transcritical CO 2 system community overemphasising the need for a throttle valve to control the optimum discharge pressure

Isotope exchange of molecular oxygen with oxygen of La0,7Sr0,3CoO3-δ

International Nuclear Information System (INIS)

Vdovin, G.K.; Kuzin, B.L.; Kurumchin, Eh.Kh.

1991-01-01

The exchange rate of the oxygen in La 0,7 Sr 0,3 CoO 3-δ has been measured by an isotopic exchange method at temperatures 620-1250 K and pressures 1.6-10 torr. The activation energy and the dependence of the exchange rate on pressures in gas have been defined. It is suggested that the knees on the temperature dependences of the exchange rate are attributed to the appearance of Co 2+ ions on the surface of the sample at elevated temperature as new centres of the exchange reaction. The activation energies of the adsorption and desorption processes on the La 0,7 Sr 0,3 CoO 3-δ surface have been estimated

CO2/H2O adsorption equilibrium and rates on metal-organic frameworks: HKUST-1 and Ni/DOBDC.

Science.gov (United States)

Liu, Jian; Wang, Yu; Benin, Annabelle I; Jakubczak, Paulina; Willis, Richard R; LeVan, M Douglas

2010-09-07

Metal-organic frameworks (MOFs) have recently attracted intense research interest because of their permanent porous structures, huge surface areas, and potential applications as novel adsorbents and catalysts. In order to provide a basis for consideration of MOFs for removal of carbon dioxide from gases containing water vapor, such as flue gas, we have studied adsorption equilibrium of CO(2), H(2)O vapor, and their mixtures and also rates of CO(2) adsorption in two MOFs: HKUST-1 (CuBTC) and Ni/DOBDC (CPO-27-Ni or Ni/MOF-74). The MOFs were synthesized via solvothermal methods, and the as-synthesized products were solvent exchanged and regenerated before experiments. Pure component adsorption equilibria and CO(2)/H(2)O binary adsorption equilibria were studied using a volumetric system. The effects of H(2)O adsorption on CO(2) adsorption for both MOF samples were determined, and the results for 5A and NaX zeolites were included for comparison. The hydrothermal stabilities for the two MOFs over the course of repetitive measurements of H(2)O and CO(2)/H(2)O mixture equilibria were also studied. CO(2) adsorption rates from helium for the MOF samples were investigated by using a unique concentration-swing frequency response (CSFR) system. Mass transfer into the MOFs is rapid with the controlling resistance found to be macropore diffusion, and rate parameters were established for the mechanism.

Development of novel exchange spring magnet by employing nanocomposites of CoFe{sub 2}O{sub 4} and CoFe{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Safi, Rohollah; Ghasemi, Ali, E-mail: ali13912001@yahoo.com; Shoja-Razavi, Reza; Tavoosi, Majid

2016-12-01

CoFe{sub 2}O{sub 4}−CoFe2 hard–soft nanocomposites were prepared via reduction of the cobalt ferrite CoFe{sub 2}O{sub 4} in hydrogen atmosphere at different temperature. The structure and the room temperature magnetization of the samples were characterized by X-ray diffraction, field emission scanning electron microscope (FESEM) and vibrating sample magnetometer (VSM). It was found that the saturation magnetization of the nanocomposite powders increases by reduction temperature while their coercivity decreases. The highest M{sub r}/M{sub s} ratio of 0.52 was obtained for sample reduced at 550 °C. Single smooth hysteresis loops of nanocomposites show that these nanocomposites behave as the single-phase materials. This result indicates the presence of exchange coupling between two different hard and soft phases. - Highlights: • CoFe{sub 2}O{sub 4}–CoFe{sub 2} was successfully synthesized by reduction diffusion process. • Two phases are effectively exchange coupled in nanocomposite. • Single smooth hysteresis loop was developed in nanocomposites.

Are international fund flows related to exchange rate dynamics?

NARCIS (Netherlands)

Li, Suxiao; de Haan, Jakob; Scholtens, Bert

2018-01-01

Employing monthly data for 53 countries between 1996 and 2015, we investigate the relationship between international fund flows and exchange rate dynamics. We find strong co-movement between funds flows (as measured with the EPFR Global data base) and bilateral real exchange rates vis-à-vis the USD.

Sea ice contribution to the air-sea CO{sub 2} exchange in the Arctic and Southern Oceans

Energy Technology Data Exchange (ETDEWEB)

Rysgaard, Soeren (Greenland Climate Research Centre, Greenland Inst. of Natural Resources, Nuuk, Greenland (Denmark); Centre for Earth Observation Science, CHR Faculty of Environment Earth and Resources, Univ. of Manitoba, Winnipeg (Canada)), e-mail: rysgaard@natur.gl; Bendtsen, Joergen (Greenland Climate Research Centre, Greenland Inst. of Natural Resources, Nuuk, Greenland (Denmark); Centre for Ice and Climate, Niels Bohr Inst., Univ. of Copenhagen, Copenhagen O (Denmark)); Delille, Bruno (Unit' e d' Oceanographie Chimique, Interfacultary Centre for Marine Research, Universite de Liege, Liege (Belgium)); Dieckmann, Gerhard S. (Alfred Wegener Inst. for Polar and Marine Research, Bremerhaven (Germany)); Glud, Ronnie N. (Greenland Climate Research Centre, Greenland Inst. of Natural Resources, Nuuk, Greenland (Denmark); Scottish Association of Marine Sciences, Scotland UK, Southern Danish Univ. and NordCee, Odense M (Denmark)); Kennedy, Hilary; Papadimitriou, Stathys (School of Ocean Sciences, Bangor Univ., Menai Bridge, Anglesey, Wales (United Kingdom)); Mortensen, John (Greenland Climate Research Centre, Greenland Inst. of Natural Resources, Nuuk, Greenland (Denmark)); Thomas, David N. (School of Ocean Sciences, Bangor Univ., Menai Bridge, Anglesey, Wales (United Kingdom); Finnish Environment Inst. (SYKE), Marine Research Centre, Helsinki (Finland)); Tison, Jean-Louis (Glaciology Unit, Dept. of Earth and Environmental Sciences, Universite Libre de Bruxelles, Bruxelles, (Belgium))

2011-11-15

Although salt rejection from sea ice is a key process in deep-water formation in ice-covered seas, the concurrent rejection of CO{sub 2} and the subsequent effect on air-sea CO{sub 2} exchange have received little attention. We review the mechanisms by which sea ice directly and indirectly controls the air-sea CO{sub 2} exchange and use recent measurements of inorganic carbon compounds in bulk sea ice to estimate that oceanic CO{sub 2} uptake during the seasonal cycle of sea-ice growth and decay in ice-covered oceanic regions equals almost half of the net atmospheric CO{sub 2} uptake in ice-free polar seas. This sea-ice driven CO{sub 2} uptake has not been considered so far in estimates of global oceanic CO{sub 2} uptake. Net CO{sub 2} uptake in sea-ice-covered oceans can be driven by; (1) rejection during sea-ice formation and sinking of CO{sub 2}-rich brine into intermediate and abyssal oceanic water masses, (2) blocking of air-sea CO{sub 2} exchange during winter, and (3) release of CO{sub 2}-depleted melt water with excess total alkalinity during sea-ice decay and (4) biological CO{sub 2} drawdown during primary production in sea ice and surface oceanic waters

Exchange rate policy

Directory of Open Access Journals (Sweden)

Plačkov Slađana

2013-01-01

Full Text Available Small oscillations of exchange rate certainly affect the loss of confidence in the currency (Serbian dinar, CSD and because of the shallow market even the smallest change in the supply and demand leads to a shift in exchange rate and brings uncertainty. Some economists suggest that the course should be linked to inflation and thus ensure predictable and stable exchange rates. Real exchange rate or slightly depressed exchange rate will encourage the competitiveness of exporters and perhaps ensure the development of new production lines which, in terms of overvalued exchange rate, had no economic justification. Fixed exchange rate will bring lower interest rates, lower risk and lower business uncertainty (uncertainty avoidance, but Serbia will also reduce foreign exchange reserves by following this trend. On the other hand, a completely free exchange rate, would lead to a (real fall of Serbian currency, which in a certain period would lead to a significant increase in exports, but the consequences for businessmen and citizens with loans pegged to the euro exchange rate, would be disastrous. We will pay special attention to the depreciation of the exchange rate, as it is generally favorable to the export competitiveness of Serbia and, on the other hand, it leads to an increase in debt servicing costs of the government as well as of the private sector. Oscillations of the dinar exchange rate, appreciation and depreciation, sometimes have disastrous consequences on the economy, investors, imports and exports. In subsequent work, we will observe the movement of the dinar exchange rate in Serbia, in the time interval 2009-2012, in order to strike a balance and maintain economic equilibrium. A movement of foreign currencies against the local currency is controlled in the foreign exchange market, so in case economic interests require, The National Bank of Serbia (NBS, on the basis of arbitrary criteria, can intervene in the market.

Is the surface oxygen exchange rate linked to bulk ion diffusivity in mixed conducting Ruddlesden-Popper phases?

Science.gov (United States)

Tomkiewicz, Alex C; Tamimi, Mazin A; Huq, Ashfia; McIntosh, Steven

2015-01-01

The possible link between oxygen surface exchange rate and bulk oxygen anion diffusivity in mixed ionic and electronic conducting oxides is a topic of great interest and debate. While a large body of experimental evidence and theoretical analyses support a link, observed differences between bulk and surface composition of these materials are hard to reconcile with this observation. This is further compounded by potential problems with simultaneous measurement of both parameters. Here we utilize separate techniques, in situ neutron diffraction and pulsed isotopic surface exchange, to examine bulk ion mobility and surface oxygen exchange rates of three Ruddlesden-Popper phases, general form A(n-1)A(2)'B(n)O(3n+1), A(n-1)A(2)'B(n)X(3n+1); LaSrCo(0.5)Fe(0.5)O(4-δ) (n = 1), La(0.3)Sr(2.7)CoFeO(7-δ) (n = 2) and LaSr3Co(1.5)Fe(1.5)O(10-δ) (n = 3). These measurements are complemented by surface composition determination via high sensitivity-low energy ion scattering. We observe a correlation between bulk ion mobility and surface exchange rate between materials. The surface exchange rates vary by more than one order of magnitude with high anion mobility in the bulk of an oxygen vacancy-rich n = 2 Ruddlesden-Popper material correlating with rapid oxygen exchange. This is in contrast with the similar surface exchange rates which we may expect due to similar surface compositions across all three samples. We conclude that experimental limitations lead to inherent convolution of surface and bulk rates, and that surface exchange steps are not likely to be rate limiting in oxygen incorporation.

Exfoliation Propensity of Oxide Scale in Heat Exchangers Used for Supercritical CO2 Power Cycles

Energy Technology Data Exchange (ETDEWEB)

Sabau, Adrian S [ORNL; Shingledecker, John P. [Electric Power Research Institute (EPRI); Kung, Steve [Electric Power Research Institute (EPRI); Wright, Ian G. [WrightHT, Inc.; Nash, Jim [Brayton Energy, LLC, Hampton, NH

2016-01-01

Supercritical CO2 (sCO2) Brayton cycle systems offer the possibility of improved efficiency in future fossil energy power generation plants operating at temperatures of 650 C and above. As there are few data on the oxidation/corrosion behavior of structural alloys in sCO2 at these temperatures, modeling to predict the propensity for oxide exfoliation is not well developed, thus hindering materials selection for these novel cycles. The ultimate goal of this effort is to provide needed data on scale exfoliation behavior in sCO2 for confident alloy selection. To date, a model developed by ORNL and EPRI for the exfoliation of oxide scales formed on boiler tubes in high-temperature, high-pressure steam has proven useful for managing exfoliation in conventional steam plants. A major input provided by the model is the ability to predict the likelihood of scale failure and loss based on understanding of the evolution of the oxide morphologies and the conditions that result in susceptibility to exfoliation. This paper describes initial steps taken to extend the existing model for exfoliation of steam-side oxide scales to sCO2 conditions. The main differences between high-temperature, high-pressure steam and sCO2 that impact the model involve (i) significant geometrical differences in the heat exchangers, ranging from standard pressurized tubes seen typically in steam-producing boilers to designs for sCO2 that employ variously-curved thin walls to create shaped flow paths for extended heat transfer area and small channel cross-sections to promote thermal convection and support pressure loads; (ii) changed operating characteristics with sCO2 due to the differences in physical and thermal properties compared to steam; and (iii) possible modification of the scale morphologies, hence properties that influence exfoliation behavior, due to reaction with carbon species from sCO2. The numerical simulations conducted were based on an assumed sCO2 operating schedule and several

Exchange of CO2 in Arctic tundra: impacts of meteorological variations and biological disturbance

Science.gov (United States)

López-Blanco, Efrén; Lund, Magnus; Williams, Mathew; Tamstorf, Mikkel P.; Westergaard-Nielsen, Andreas; Exbrayat, Jean-François; Hansen, Birger U.; Christensen, Torben R.

2017-10-01

An improvement in our process-based understanding of carbon (C) exchange in the Arctic and its climate sensitivity is critically needed for understanding the response of tundra ecosystems to a changing climate. In this context, we analysed the net ecosystem exchange (NEE) of CO2 in West Greenland tundra (64° N) across eight snow-free periods in 8 consecutive years, and characterized the key processes of net ecosystem exchange and its two main modulating components: gross primary production (GPP) and ecosystem respiration (Reco). Overall, the ecosystem acted as a consistent sink of CO2, accumulating -30 g C m-2 on average (range of -17 to -41 g C m-2) during the years 2008-2015, except 2011 (source of 41 g C m-2), which was associated with a major pest outbreak. The results do not reveal a marked meteorological effect on the net CO2 uptake despite the high interannual variability in the timing of snowmelt and the start and duration of the growing season. The ranges in annual GPP (-182 to -316 g C m-2) and Reco (144 to 279 g C m-2) were > 5 fold larger than the range in NEE. Gross fluxes were also more variable (coefficients of variation are 3.6 and 4.1 % respectively) than for NEE (0.7 %). GPP and Reco were sensitive to insolation and temperature, and there was a tendency towards larger GPP and Reco during warmer and wetter years. The relative lack of sensitivity of NEE to meteorology was a result of the correlated response of GPP and Reco. During the snow-free season of the anomalous year of 2011, a biological disturbance related to a larvae outbreak reduced GPP more strongly than Reco. With continued warming temperatures and longer growing seasons, tundra systems will increase rates of C cycling. However, shifts in sink strength will likely be triggered by factors such as biological disturbances, events that will challenge our forecasting of C states.

Controlling exchange bias in Co-CoOx nanoparticles by oxygen content

International Nuclear Information System (INIS)

Kovylina, Miroslavna; Muro, Montserrat GarcIa del; Konstantinovic, Zorica; Iglesias, Oscar; Labarta, AmIlcar; Batlle, Xavier; Varela, Manuel

2009-01-01

We report on the occurrence of exchange bias on laser-ablated granular thin films composed of Co nanoparticles embedded in an amorphous zirconia matrix. The deposition method allows one to control the degree of oxidation of the Co particles by tuning the oxygen pressure at the vacuum chamber (from 2 x 10 -5 to 10 -1 mbar). The nature of the nanoparticles embedded in the nonmagnetic matrix is monitored from metallic, ferromagnetic (FM) Co to antiferromagnetic (AFM) CoO x , with a FM/AFM intermediate regime for which the percentage of the AFM phase can be increased at the expense of the FM phase, leading to the occurrence of exchange bias in particles of about 2 nm in size. For an oxygen pressure of about 10 -3 mbar the ratio between the FM and AFM phases is optimum with an exchange bias field of about 900 Oe at 1.8 K. The mutual exchange coupling between the AFM and FM is also at the origin of the induced exchange anisotropy on the FM leading to high irreversible hysteresis loops, and the blocking of the AFM clusters due to proximity to the FM phase.

A numerical study of the supercritical CO2 plate heat exchanger subject to U-type, Z-type, and multi-pass arrangements

Science.gov (United States)

Zhu, Chen-Xi; Wang, Chi-Chuan

2018-01-01

This study proposes a numerical model for plate heat exchanger that is capable of handling supercritical CO2 fluid. The plate heat exchangers under investigation include Z-type (1-pass), U-type (1-pass), and 1-2 pass configurations. The plate spacing is 2.9 mm with a plate thickness of 0.8 mm, and the size of the plate is 600 mm wide and 218 mm in height with 60 degrees chevron angle. The proposed model takes into account the influence of gigantic change of CO2 properties. The simulation is first compared with some existing data for water-to-water plate heat exchangers with good agreements. The flow distribution, pressure drop, and heat transfer performance subject to the supercritical CO2 in plate heat exchangers are then investigated. It is found that the flow velocity increases consecutively from the entrance plate toward the last plate for the Z-type arrangement, and this is applicable for either water side or CO2 side. However, the flow distribution of the U-type arrangement in the water side shows opposite trend. Conversely, the flow distribution for U-type arrangement of CO2 depends on the specific flow ratio (C*). A lower C* like 0.1 may reverse the distribution, i.e. the flow velocity increases moderately alongside the plate channel like Z-type while a large C* of 1 would resemble the typical distribution in water channel. The flow distribution of CO2 side at the first and last plate shows a pronounced drop/surge phenomenon while the channels in water side does not reveal this kind of behavior. The performance of 2-pass plate heat exchanger, in terms of heat transfer rate, is better than that of 1-pass design only when C* is comparatively small (C* < 0.5). Multi-pass design is more effective when the dominant thermal resistance falls in the CO2 side.

Conversion of a moderately rewetted fen to a shallow lake - implications for net CO2 exchange

Science.gov (United States)

Koebsch, Franziska; Glatzel, Stephan; Hofmann, Joachim; Forbrich, Inke; Jurasinski, Gerald

2013-04-01

Extensive rewetting projects to re-establish the natural carbon (C) sequestration function of degraded peatlands are currently taking place in Europe and North-America. Year-round flooding provides a robust measure to prevent periods of drought that are associated with ongoing peat mineralization and to initiate the accumulation of new organic matter. Here, we present measurements of net carbon dioxide (CO2) exchange during the gradual conversion of a moderately rewetted fen to a shallow lake. When we started our measurements in 2009, mean growing season water level (MWGL) was 0 cm. In 2010 the site was flooded throughout the year with MWGL of 36 cm. Extraordinary strong rainfalls in July 2011 resulted in a further increase of MWGL to 56 cm. Measurements of net ecosystem exchange (NEE) were conducted during growing seasons (May-October) using the Eddy Covariance method. Information about vegetation vitality was deduced from the enhanced vegetation index (EVI) based on MODIS data. Ecosystem respiration (Reco) and gross ecosystem production (GEP) were high during vegetation period 2009 (1273.4 and -1572.1 g CO2-C m-2), but decreased by 61 and 46% respectively when the fen was flooded throughout 2010. Under water-logged conditions, heterotrophic respiration declines and gas exchange is limited. Moreover, flooding is a severe stress factor for plants and decreases autotrophic respiration and photosynthesis. However, in comparison to 2010, rates of Reco and GEP doubled during the beginning of growing season 2011, indicating plastic response strategies of wetland plants to flooding. Presumably, plants were not able to cope with the further increase of water levels to up to 120 cm in June/July 2011, resulting in another drop of GEP and Reco. The effects of plant vitality on GEP were confirmed by the remote sensed vegetation index. Throughout all three growing seasons, the fen was a distinct net CO2 sink (2009: -333.3±12.3, 2010: -294.1±8.4, -352.4±5.1 g CO2-C m-2

Giant exchange bias in MnPd/Co bilayers

International Nuclear Information System (INIS)

Nguyen Thanh Nam; Nguyen Phu Thuy; Nguyen Anh Tuan; Nguyen Nguyen Phuoc; Suzuki, Takao

2007-01-01

A systematic study of exchange bias in MnPd/Co bilayers has been carried out, where the dependences of exchange bias, unidirectional anisotropy constant and coercivity on the thicknesses of MnPd and Co layers were investigated. A huge unidirectional anisotropy constant, J K =2.5erg/cm 2 was observed, which is in reasonable agreement with the theoretical prediction based on the model by Meiklejohn and Bean. The angular dependences of exchange bias field and coercivity have also been examined showing that both exchange bias and coercivity follow 1/cosα rule

The interaction of soil phototrophs and fungi with pH and their impact on soil CO2, CO18O and OCS exchange.

Science.gov (United States)

Sauze, Joana; Ogée, Jérôme; Maron, Pierre-Alain; Crouzet, Olivier; Nowak, Virginie; Wohl, Steven; Kaisermann, Aurore; Jones, Sam P; Wingate, Lisa

2017-12-01

The stable oxygen isotope composition of atmospheric CO 2 and the mixing ratio of carbonyl sulphide (OCS) are potential tracers of biospheric CO 2 fluxes at large scales. However, the use of these tracers hinges on our ability to understand and better predict the activity of the enzyme carbonic anhydrase (CA) in different soil microbial groups, including phototrophs. Because different classes of the CA family (α, β and γ) may have different affinities to CO 2 and OCS and their expression should also vary between different microbial groups, differences in the community structure could impact the 'community-integrated' CA activity differently for CO 2 and OCS. Four soils of different pH were incubated in the dark or with a diurnal cycle for forty days to vary the abundance of native phototrophs. Fluxes of CO 2 , CO 18 O and OCS were measured to estimate CA activity alongside the abundance of bacteria, fungi and phototrophs. The abundance of soil phototrophs increased most at higher soil pH. In the light, the strength of the soil CO 2 sink and the CA-driven CO 2 -H 2 O isotopic exchange rates correlated with phototrophs abundance. OCS uptake rates were attributed to fungi whose abundance was positively enhanced in alkaline soils but only in the presence of increased phototrophs. Our findings demonstrate that soil-atmosphere CO 2 , OCS and CO 18 O fluxes are strongly regulated by the microbial community structure in response to changes in soil pH and light availability and supports the idea that different members of the microbial community express different classes of CA, with different affinities to CO 2 and OCS.

Soil-atmospheric exchange of CO2, CH4, and N2O in three subtropical forest ecosystems in southern China

Science.gov (United States)

Tang, X.; Liu, S.; Zhou, G.; Zhang, Dongxiao; Zhou, C.

2006-01-01

The magnitude, temporal, and spatial patterns of soil-atmospheric greenhouse gas (hereafter referred to as GHG) exchanges in forests near the Tropic of Cancer are still highly uncertain. To contribute towards an improvement of actual estimates, soil-atmospheric CO2, CH4, and N2O fluxes were measured in three successional subtropical forests at the Dinghushan Nature Reserve (hereafter referred to as DNR) in southern China. Soils in DNR forests behaved as N2O sources and CH4 sinks. Annual mean CO2, N2O, and CH4 fluxes (mean ?? SD) were 7.7 ?? 4.6MgCO2-Cha-1 yr-1, 3.2 ?? 1.2 kg N2ONha-1 yr-1, and 3.4 ?? 0.9 kgCH4-Cha-1 yr-1, respectively. The climate was warm and wet from April through September 2003 (the hot-humid season) and became cool and dry from October 2003 through March 2004 (the cool-dry season). The seasonality of soil CO2 emission coincided with the seasonal climate pattern, with high CO2 emission rates in the hot-humid season and low rates in the cool-dry season. In contrast, seasonal patterns of CH4 and N2O fluxes were not clear, although higher CH4 uptake rates were often observed in the cool-dry season and higher N2O emission rates were often observed in the hot-humid season. GHG fluxes measured at these three sites showed a clear increasing trend with the progressive succession. If this trend is representative at the regional scale, CO2 and N2O emissions and CH4 uptake in southern China may increase in the future in light of the projected change in forest age structure. Removal of surface litter reduced soil CO2 effluxes by 17-44% in the three forests but had no significant effect on CH4 absorption and N2O emission rates. This suggests that microbial CH4 uptake and N2O production was mainly related to the mineral soil rather than in the surface litter layer. ?? 2006 Blackwell Publishing Ltd.

Low impact of dry conditions on the CO2 exchange of a Northern-Norwegian blanket bog

International Nuclear Information System (INIS)

Lund, Magnus; Parmentier, F J W; Bjerke, J W; Tømmervik, H; Drake, B G; Engelsen, O; Hansen, G H; Powell, T L; Silvennoinen, H; Weldon, S; Rasse, D P; Sottocornola, M

2015-01-01

Northern peatlands hold large amounts of organic carbon (C) in their soils and are as such important in a climate change context. Blanket bogs, i.e. nutrient-poor peatlands restricted to maritime climates, may be extra vulnerable to global warming since they require a positive water balance to sustain their moss dominated vegetation and C sink functioning. This study presents a 4.5 year record of land–atmosphere carbon dioxide (CO 2 ) exchange from the Andøya blanket bog in northern Norway. Compared with other peatlands, the Andøya peatland exhibited low flux rates, related to the low productivity of the dominating moss and lichen communities and the maritime settings that attenuated seasonal temperature variations. It was observed that under periods of high vapour pressure deficit, net ecosystem exchange was reduced, which was mainly caused by a decrease in gross primary production. However, no persistent effects of dry conditions on the CO 2 exchange dynamics were observed, indicating that under present conditions and within the range of observed meteorological conditions the Andøya blanket bog retained its C uptake function. Continued monitoring of these ecosystem types is essential in order to detect possible effects of a changing climate. (letter)

The Driving Forces of Guest Substitution in Gas Hydrates—A Laser Raman Study on CH4-CO2 Exchange in the Presence of Impurities

Directory of Open Access Journals (Sweden)

Bettina Beeskow-Strauch

2012-02-01

Full Text Available The recovery of CH4 gas from natural hydrate formations by injection of industrially emitted CO2 is considered to be a promising solution to simultaneously access an unconventional fossil fuel reserve and counteract atmospheric CO2 increase. CO2 obtained from industrial processes may contain traces of impurities such as SO2 or NOx and natural gas hydrates may contain higher hydrocarbons such as C2H6 and C3H8. These additions have an influence on the properties of the resulting hydrate phase and the conversion process of CH4-rich hydrates to CO2-rich hydrates. Here we show results of a microscopic and laser Raman in situ study investigating the effects of SO2-polluted CO2 and mixed CH4-C2H6 hydrate on the exchange process. Our study shows that the key driving force of the exchange processes is the establishment of the chemical equilibrium between hydrate phase and the surrounding phases. The exchange rate is also influenced by the guest-to-cavity ratio as well as the thermodynamic stability in terms of p-T conditions of the original and resulting hydrate phase. The most effective molecule exchange is related to structural changes (sI-sII which indicates that hydrate decomposition and reformation processes are the occurring processes.

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

Science.gov (United States)

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.

Interest Rate Rules, Exchange Market Pressure, and Successful Exchange Rate Management

NARCIS (Netherlands)

Klaassen, F.; Mavromatis, K.

2016-01-01

Central banks with an exchange rate objective set the interest rate in response to what they call ''pressure.'' Instead, existing interest rate rules rely on the exchange rate minus its target. To stay closer to actual policy, we introduce a rule that uses exchange market pressure (EMP), the

Effect of climate warming on the annual terrestrial net ecosystem CO2 exchange globally in the boreal and temperate regions.

Science.gov (United States)

Zhang, Zhiyuan; Zhang, Renduo; Cescatti, Alessandro; Wohlfahrt, Georg; Buchmann, Nina; Zhu, Juan; Chen, Guanhong; Moyano, Fernando; Pumpanen, Jukka; Hirano, Takashi; Takagi, Kentaro; Merbold, Lutz

2017-06-08

The net ecosystem CO 2 exchange is the result of the imbalance between the assimilation process (gross primary production, GPP) and ecosystem respiration (RE). The aim of this study was to investigate temperature sensitivities of these processes and the effect of climate warming on the annual terrestrial net ecosystem CO 2 exchange globally in the boreal and temperate regions. A database of 403 site-years of ecosystem flux data at 101 sites in the world was collected and analyzed. Temperature sensitivities of rates of RE and GPP were quantified with Q 10 , defined as the increase of RE (or GPP) rates with a temperature rise of 10 °C. Results showed that on the annual time scale, the intrinsic temperature sensitivity of GPP (Q 10sG ) was higher than or equivalent to the intrinsic temperature sensitivity of RE (Q 10sR ). Q 10sG was negatively correlated to the mean annual temperature (MAT), whereas Q 10sR was independent of MAT. The analysis of the current temperature sensitivities and net ecosystem production suggested that temperature rise might enhance the CO 2 sink of terrestrial ecosystems both in the boreal and temperate regions. In addition, ecosystems in these regions with different plant functional types should sequester more CO 2 with climate warming.

Estimating CO2 gas exchange in mixed age vegetable plant communities grown on soil-like substrates for life support systems

Science.gov (United States)

Velichko, V. V.; Tikhomirov, A. A.; Ushakova, S. A.

2018-02-01

If soil-like substrate (SLS) is to be used in human life support systems with a high degree of mass closure, the rate of its gas exchange as a compartment for mineralization of plant biomass should be understood. The purpose of this study was to compare variations in CO2 gas exchange of vegetable plant communities grown on the soil-like substrate using a number of plant age groups, which determined the so-called conveyor interval. Two experimental plant communities were grown as plant conveyors with different conveyor intervals. The first plant community consisted of conveyors with intervals of 7 days for carrot and beet and 14 days for chufa sedge. The conveyor intervals in the second plant community were 14 days for carrot and beet and 28 days for chufa sedge. This study showed that increasing the number of age groups in the conveyor and, thus, increasing the frequency of adding plant waste to the SLS, decreased the range of variations in CO2 concentration in the "plant-soil-like substrate" system. However, the resultant CO2 gas exchange was shifted towards CO2 release to the atmosphere of the plant community with short conveyor intervals. The duration of the conveyor interval did not significantly affect productivity and mineral composition of plants grown on the SLS.

The empirical relationship between energy futures prices and exchange rates

International Nuclear Information System (INIS)

Sadorsky, P.

2000-01-01

This paper investigates the interaction between energy futures prices and exchange rates. Results are presented to show that futures prices for crude oil, heating oil and unleaded gasoline are co-integrated with a trade-weighted index of exchange rates. This is important because it means that there exists a long-run equilibrium relationship between these four variables. Granger causality results for both the long- and short-run are presented. Evidence is also presented that suggests exchange rates transmit exogenous shocks to energy futures prices. 22 refs

Air–sea exchanges of CO2 in the world's coastal seas

Directory of Open Access Journals (Sweden)

C.-T. A. Chen

2013-10-01

Full Text Available The air–sea exchanges of CO2 in the world's 165 estuaries and 87 continental shelves are evaluated. Generally and in all seasons, upper estuaries with salinities of less than two are strong sources of CO2 (39 ± 56 mol C m−2 yr−1, positive flux indicates that the water is losing CO2 to the atmosphere; mid-estuaries with salinities of between 2 and 25 are moderate sources (17.5 ± 34 mol C m−2 yr−1 and lower estuaries with salinities of more than 25 are weak sources (8.4 ± 14 mol C m−2 yr−1. With respect to latitude, estuaries between 23.5 and 50° N have the largest flux per unit area (63 ± 101 mmol C m−2 d−1; these are followed by lower-latitude estuaries (23.5–0° S: 44 ± 29 mmol C m−2 d−1; 0–23.5° N: 39 ± 55 mmol C m−2 d−1, and then regions north of 50° N (36 ± 91 mmol C m−2 d−1. Estuaries south of 50° S have the smallest flux per unit area (9.5 ± 12 mmol C m−2 d−1. Mixing with low-pCO2 shelf waters, water temperature, residence time and the complexity of the biogeochemistry are major factors that govern the pCO2 in estuaries, but wind speed, seldom discussed, is critical to controlling the air–water exchanges of CO2. The total annual release of CO2 from the world's estuaries is now estimated to be 0.10 Pg C yr−1, which is much lower than published values mainly because of the contribution of a considerable amount of heretofore unpublished or new data from Asia and the Arctic. The Asian data, although indicating high pCO2, are low in sea-to-air fluxes because of low wind speeds. Previously determined flux values rely heavily on data from Europe and North America, where pCO2 is lower but wind speeds are much higher, such that the CO2 fluxes are higher than in Asia. Newly emerged CO2 flux data in the Arctic reveal that estuaries there mostly absorb rather than release CO2. Most continental shelves, and especially those at high latitude, are undersaturated in terms of CO2 and absorb CO2 from the

Sensitivity of molecular vibrational dynamics to energy exchange rate constants

International Nuclear Information System (INIS)

Billing, G D; Coletti, C; Kurnosov, A K; Napartovich, A P

2003-01-01

The sensitivity of molecular vibrational population dynamics, governing the CO laser operated in fundamental and overtone transitions, to vibration-to-vibration rate constants is investigated. With this aim, three rate constant sets have been used, differing in their completeness (i.e. accounting for single-quantum exchange only, or for multi-quantum exchange with a limited number of rate constants obtained by semiclassical calculations, and, finally, with an exhaustive set of rate constants including asymmetric exchange processes, as well) and in the employed interaction potential. The most complete set among these three is introduced in this paper. An existing earlier kinetic model was updated to include the latter new data. Comparison of data produced by kinetic modelling with the above mentioned sets of rate constants shows that the vibrational distribution function, and, in particular, the CO overtone laser characteristics, are very sensitive to the choice of the model. The most complete model predicts slower evolution of the vibrational distribution, in qualitative agreement with experiments

Experimental and CFD Analysis of Printed Circuit Heat Exchanger for Supercritical CO{sub 2} Power Cycle Application

Energy Technology Data Exchange (ETDEWEB)

Baik, Seungjoon; Kim, Hyeon Tae; Kim, Seong Gu; Lee, Jekyoung; Lee, Jeong Ik [KAIST, Daejeon (Korea, Republic of)

2015-10-15

The supercritical carbon dioxide (S-CO{sub 2}) power cycle has been suggested as an alternative for the SFR power generation system. First of all, relatively mild sodium-CO{sub 2} interaction can reduce the accident probability. Also the S-CO{sub 2} power conversion cycle can achieve high efficiency with SFR core thermal condition. Moreover, the S-CO{sub 2} power cycle can reduce cycle footprint due to high density of the working fluid. Recently, various compact heat exchangers have been studied for developing an optimal heat exchanger. In this paper, the printed circuit heat exchanger was selected for S-CO{sub 2} power cycle applications and was closely investigated experimentally and analytically. Recently, design and performance prediction of PCHE received attention due to its importance in high pressure power systems such as S-CO{sub 2} cycle. To evaluate a PCHE performance with CO{sub 2} to water, KAIST research team designed and tested a lab-scale PCHE. From the experimental data and CFD analysis, pressure drop and heat transfer correlations are obtained. For the CFD analysis, Ansys-CFX commercial code was utilized with RGP table implementation. In near future, the turbulence model sensitivity study will be followed.

Investigating Liquid CO2 as a Coolant for a MTSA Heat Exchanger Design

Science.gov (United States)

Paul, Heather L.; Padilla, Sebastian; Powers, Aaron; Iacomini, Christie

2009-01-01

Metabolic heat regenerated Temperature Swing Adsorption (MTSA) technology is being developed for thermal and carbon dioxide (CO 2) control for a future Portable Life Support System (PLSS), as well as water recycling. CO 2 removal and rejection is accomplished by driving a sorbent through a temperature swing of approximately 210 K to 280 K . The sorbent is cooled to these sub-freezing temperatures by a Sublimating Heat Exchanger (SHX) with liquid coolant expanded to sublimation temperatures. Water is the baseline coolant available on the moon, and if used, provides a competitive solution to the current baseline PLSS schematic. Liquid CO2 (LCO2) is another non-cryogenic coolant readily available from Martian resources which can be produced and stored using relatively low power and minimal infrastructure. LCO 2 expands from high pressure liquid (5800 kPa) to Mars ambient (0.8 kPa) to produce a gas / solid mixture at temperatures as low as 156 K. Analysis and experimental work are presented to investigate factors that drive the design of a heat exchanger to effectively use this sink. Emphasis is given to enabling efficient use of the CO 2 cooling potential and mitigation of heat exchanger clogging due to solid formation. Minimizing mass and size as well as coolant delivery are also considered. The analysis and experimental work is specifically performed in an MTSA-like application to enable higher fidelity modeling for future optimization of a SHX design. In doing so, the work also demonstrates principles and concepts so that the design can be further optimized later in integrated applications (including Lunar application where water might be a choice of coolant).

Perpendicular exchange coupling effects in ferrimagnetic TbFeCo/GdFeCo hard/soft structures

Science.gov (United States)

Wang, Ke; Wang, Yahong; Ling, Fujin; Xu, Zhan

2018-04-01

Bilayers consisting of magnetically hard TbFeCo and soft GdFeCo alloy were fabricated. Exchange-spring and sharp switching in a step-by-step fashion were observed in the TbFeCo/GdFeCo hard/soft bilayers with increasing GdFeCo thickness. A perpendicular exchange bias field of several hundred Oersteds is observed from the shift of minor loops pinned by TbFeCo layer. The perpendicular exchange energy is derived to be in the range of 0.18-0.30 erg/cm2. The exchange energy is shown to increase with the thickness of GdFeCo layer in the bilayers, which can be attributed to the enhanced perpendicular anisotropy of GdFeCo layer in our experimental range.

Decadal trends in the seasonal-cycle amplitude of terrestrial CO2 exchange resulting from the ensemble of terrestrial biosphere models

Directory of Open Access Journals (Sweden)

Akihiko Ito

2016-05-01

Full Text Available The seasonal-cycle amplitude (SCA of the atmosphere–ecosystem carbon dioxide (CO2 exchange rate is a useful metric of the responsiveness of the terrestrial biosphere to environmental variations. It is unclear, however, what underlying mechanisms are responsible for the observed increasing trend of SCA in atmospheric CO2 concentration. Using output data from the Multi-scale Terrestrial Model Intercomparison Project (MsTMIP, we investigated how well the SCA of atmosphere–ecosystem CO2 exchange was simulated with 15 contemporary terrestrial ecosystem models during the period 1901–2010. Also, we made attempt to evaluate the contributions of potential mechanisms such as atmospheric CO2, climate, land-use, and nitrogen deposition, through factorial experiments using different combinations of forcing data. Under contemporary conditions, the simulated global-scale SCA of the cumulative net ecosystem carbon flux of most models was comparable in magnitude with the SCA of atmospheric CO2 concentrations. Results from factorial simulation experiments showed that elevated atmospheric CO2 exerted a strong influence on the seasonality amplification. When the model considered not only climate change but also land-use and atmospheric CO2 changes, the majority of the models showed amplification trends of the SCAs of photosynthesis, respiration, and net ecosystem production (+0.19 % to +0.50 % yr−1. In the case of land-use change, it was difficult to separate the contribution of agricultural management to SCA because of inadequacies in both the data and models. The simulated amplification of SCA was approximately consistent with the observational evidence of the SCA in atmospheric CO2 concentrations. Large inter-model differences remained, however, in the simulated global tendencies and spatial patterns of CO2 exchanges. Further studies are required to identify a consistent explanation for the simulated and observed amplification trends, including their

Virtual lesion extension : a measure to quantify the effects of bacterial blight on rice leaf CO2 exchange

NARCIS (Netherlands)

Elings, A.; Rossing, W.A.H.; Werf, van der W.

1999-01-01

Virtual lesion extension was proposed as a measure to summarize the effects of foliar diseases with single spreading lesions on CO2-exchange parameters at the whole-leaf level. Visible lesion plus virtual lesion extension constitute a virtual lesion, in which CO2 exchange was postulated to be nil.

Running Head: Control and Adjustment of the Rate of Photosynthesis Above Present CO(sub 2) Levels; FINAL

International Nuclear Information System (INIS)

Ball, J. Timothy

1996-01-01

The adjustment of photosynthesis to different environmental conditions and especially to elevated CO(sub 2) is often characterized in terms of changes in the processes that establish (limit) the net CO(sub 2) assimilation rate. At slightly above present ambient pCO(sub 2) light-saturated photosynthetic responses to CO(sub 2) depart limitation by the catalytic capacity of tissue rubisco content. An hypothesis attributing this departure to limited thylakoid reaction/electron transport capacity is widely accepted, although we find no experimental evidence in the literature supporting this proposition.. The results of several tests point to the conclusion that the capacity of the thyiakoid reactions cannot be generally responsible for the deviation from rubisco limitation. This conclusion leaves a significant gap in the interpretation of gas exchange responses to CO(sub 2). Since the inputs to the photosynthetic carbon reduction cycle (CO(sub 2) and photon-capture/electron-transport products) do not limit photosynthesis on the shoulder of the A=f(c(sub i)) curve, the control of photosynthesis can be characterized as: due to feedback. Several characteristics of gas exchange and fluorescence that occur when steady-states in this region are perturbed by changes in CO(sub 2) or O(sub 2) suggest significant regulation by conditions other than directly by substrate RuBP levels. A strong candidate to explain these responses is the triose-phosphate flux/ inorganic phosphate regulatory sequence, although not all of the gas exchange characteristics expected with ''TPU-limitation'' are present (e.g. oxygen-insensitive photosynthesis). Interest in nitrogen allocation between rubisco and light capture/electron transport as the basis for photosynthetic adjustment to elevated CO(sub 2) may need to be reconsidered as a result of these findings. Contributors to the feedback regulation of photosynthesis (which may include sucrose phosphate synthase and fructose bisphosphatase activities

Gross primary production controls the subsequent winter CO2 exchange in a boreal peatland.

Science.gov (United States)

Zhao, Junbin; Peichl, Matthias; Öquist, Mats; Nilsson, Mats B

2016-12-01

In high-latitude regions, carbon dioxide (CO 2 ) emissions during the winter represent an important component of the annual ecosystem carbon budget; however, the mechanisms that control the winter CO 2 emissions are currently not well understood. It has been suggested that substrate availability from soil labile carbon pools is a main driver of winter CO 2 emissions. In ecosystems that are dominated by annual herbaceous plants, much of the biomass produced during the summer is likely to contribute to the soil labile carbon pool through litter fall and root senescence in the autumn. Thus, the summer carbon uptake in the ecosystem may have a significant influence on the subsequent winter CO 2 emissions. To test this hypothesis, we conducted a plot-scale shading experiment in a boreal peatland to reduce the gross primary production (GPP) during the growing season. At the growing season peak, vascular plant biomass in the shaded plots was half that in the control plots. During the subsequent winter, the mean CO 2 emission rates were 21% lower in the shaded plots than in the control plots. In addition, long-term (2001-2012) eddy covariance data from the same site showed a strong correlation between the GPP (particularly the late summer and autumn GPP) and the subsequent winter net ecosystem CO 2 exchange (NEE). In contrast, abiotic factors during the winter could not explain the interannual variation in the cumulative winter NEE. Our study demonstrates the presence of a cross-seasonal link between the growing season biotic processes and winter CO 2 emissions, which has important implications for predicting winter CO 2 emission dynamics in response to future climate change. © 2016 John Wiley & Sons Ltd.

Vibrational deactivation and atom exchange in O(3P)+CO(X 1Σ+) collisions

International Nuclear Information System (INIS)

Kelley, J.D.; Thommarson, R.L.

1977-01-01

A quasiclassical Monte Carlo averaged trajectory study of the ground-state O, CO collision system is presented. An ''effective'' adiabatic potential surface is constructed using pertinent theoretical and experimental data. Vibrational deactivation rates for CO(v=1, 3) and atom exchange rates for CO(v=0, 1, 3) are calculated and compared with experimental data. The high-temperature (400 K< T<2000 K) and low-temperature (270 K< T<400 K) CO deactivation data, and the low-temperature (300 K< T<400 K) atom exchange data are all fit reasonably well by the calculation. However, comparison of the deactivation data to the atom exchange data suggests that at temperatures below 400 K an additional nonadiabatic mechanism may be contributing to the overall deactivation rate

Reconciling top-down and bottom-up estimates of CO2 fluxes to understand increased seasonal exchange in Northern ecosystems

Science.gov (United States)

Bastos, A.; Ciais, P.; Zhu, D.; Maignan, F.; Wang, X.; Chevallier, F.; Ballantyne, A.

2017-12-01

Continuous atmospheric CO2 monitoring data indicate enhanced seasonal exchange in the high-latitudes in the Northern Hemisphere (above 40oN), mainly attributed to terrestrial ecosystems. Whether this enhancement is mostly explained by increased vegetation growth due to CO2 fertilization and warming, or by changes in land-use and land-management practices is still an unsettled question (e.g. Forkel et al. (2016) and Zeng et al. (2013)). Previous studies have shown that models present variable performance in capturing trends in CO2 amplitude at CO2 monitoring sites, and that Earth System Models present large spread in their estimates of such trends. Here we integrate data of atmospheric CO2 exchange in terrestrial ecosystems by a set of atmospheric CO2 inversions and a range of land-surface models to evaluate the ability of models to reproduce changes in CO2 seasonal exchange within the observation uncertainty. We then analyze the factors that explain the model spread to understand if the trend in seasonal CO2 amplitude may indeed be a useful metric to constrain future changes in terrestrial photosynthesis (Wenzel et al., 2016). We then compare model simulations with satellite and other observation-based datasets of vegetation productivity, biomass stocks and land-cover change to test the contribution of natural (CO2 fertilization, climate) and human (land-use change) factors to the increasing trend in seasonal CO2 amplitude. Forkel, Matthias, et al. "Enhanced seasonal CO2 exchange caused by amplified plant productivity in northern ecosystems." Science 351.6274 (2016): 696-699. Wenzel, Sabrina, et al. "Projected land photosynthesis constrained by changes in the seasonal cycle of atmospheric CO2." Nature 538, no. 7626 (2016): 499-501.Zeng, Ning, et al. "Agricultural Green Revolution as a driver of increasing atmospheric CO2 seasonal amplitude." Nature 515.7527 (2014): 394.

Novel approach for evaluation of air change rate in naturally ventilated occupied spaces based on metabolic CO2 time variation

DEFF Research Database (Denmark)

Melikov, Arsen Krikor; Markov, Detelin G.

2014-01-01

IAQ in many residential buildings relies on non-organized natural ventilation. Accurate evaluation of air change rate (ACR) in this situation is difficult due to the nature of the phenomenon - intermittent infiltration-exfiltration periods of mass exchange between the room air and the outdoor air...... at low rate. This paper describes a new approach for ACR evaluation in naturally ventilated occupied spaces. Actual metabolic CO2 time variation record in an interval of time is compared with the computed variation of metabolic CO2 for the same time interval under reference conditions: sleeping occupants...

Carbon Dioxide Impacts in the Deep-Sea: Is Maintaining a Metabolically Required CO2 Efflux Rate Challenging?

Science.gov (United States)

Peltzer, E. T.; Hofmann, A. F.; Brewer, P. G.

2011-12-01

Increasing ocean acidification from fossil fuel CO2 invasion, from temperature driven changes in respiration, and from possible leakage from sub-seabed geologic CO2 disposal has aroused concern over the impacts of elevated CO2 concentrations on marine life. Here we describe the rate problem for animals who must export CO2 at about the same rate at which O2 is consumed. We analyze the basic properties controlling CO2 export within the diffusive boundary of marine animals in a changing ocean in order to compare the challenges posed by O2 uptake under stress with the equivalent problem of CO2 expulsion. The problem is more complex than that for a non-reactive gas since, as with gas exchange of CO2 at the air-sea interface, the influence of the ensemble of reactions within the CO2 - HCO3- - CO3= acid-base system needs to be considered. These reactions appear as an enhancement factor which significantly facilitates CO2 efflux compared to O2 intake at equal temperature, pressure and flow rate under typical oceanic concentrations. Possibly as an adaptation to this chemical advantage marine animals typically can respond to external CO2 stress simply by metabolic adjustment. This is energetically more favorable than having to resort to mechanically increasing flow over their surface to thin the boundary layer as is required to alleviate O2 stress. Regionally as with O2 the combination of T, P, and pH/pCO2 creates a zone of maximum CO2 stress at around 1000 m depth. But the net result is that the combination of an increase in T combined with declining O2 poses a greater respiratory challenge to marine life than does increasing CO2. The relationships developed here allow a more accurate prediction of the impacts on marine life from the combined effects of changing T, O2, and CO2 than can be estimated from single variable studies.

Underwater photosynthesis and respiration in leaves of submerged wetland plants: gas films improve CO2 and O2 exchange

DEFF Research Database (Denmark)

Colmer, Timothy David; Pedersen, Ole

2007-01-01

(N) was enhanced up to sixfold. Gas films on submerged leaves enable continued gas exchange via stomata and thus bypassing of cuticle resistance, enhancing exchange of O(2) and CO(2) with the surrounding water, and therefore underwater P(N) and respiration.......Many wetland plants have gas films on submerged leaf surfaces. We tested the hypotheses that leaf gas films enhance CO(2) uptake for net photosynthesis (P(N)) during light periods, and enhance O(2) uptake for respiration during dark periods. Leaves of four wetland species that form gas films......, and two species that do not, were used. Gas films were also experimentally removed by brushing with 0.05% (v/v) Triton X. Net O(2) production in light, or O(2) consumption in darkness, was measured at various CO(2) and O(2) concentrations. When gas films were removed, O(2) uptake in darkness was already...

Projecting Soil Feedbacks to Atmospheric CO2 Following Erosion and Deposition on Centennial Timescales in Two Contrasting Forests: A Study of Critical Zone-Atmosphere Exchange

Science.gov (United States)

Billings, S. A.; Richter, D., Jr.; Ziegler, S. E.; Prestegaard, K. L.

2016-12-01

For almost 20 y there has been a growing recognition that erosion and associated lateral movement of SOC does not necessarily result in a net CO2 source from terrestrial sources to the atmosphere. Eroded SOC may undergo mineralization to CO2 at a more rapid pace than it would have in situ, but the eroding ecosystem continues to generate SOC at a potentially modified rate, and the eroding profile may also experience changing SOC mineralization rates. No one knows how these process rates may change upon erosion. Years ago, we introduced a model that computes the influence of erosion on biosphere-atmosphere CO2 exchange for any profile of interest. The model permits the user to test how assumptions of changing SOC production and mineralization can influence the degree to which erosion induces a net CO2 sink or source. Here we present an analogous model depicting how deposition of eroded SOC also can result in altered biosphere-atmosphere CO2 exchange. We employ both models to investigate how erosion and deposition in two contrasting forested regions may influence regional C budgets. Runoff-induced erosion in a boreal forest occurs at low rates, but removes C-rich, organic material; anthropogenically-enhanced erosion in a warm temperate forest removed both O- and mineral-rich A-horizons. Model runs (100 y) suggest that even though the great volume of mineral soil eroded from the temperate forest was relatively low-SOC, high erosion rates prompted greater potential for erosion to serve as a net CO2 sink compared to the boreal forest where C-rich material was lost but erosion rates remained low. The models further suggest that changes in SOC production and mineralization at eroding sites in both forest types are a greater influence on CO2 source or sink strength than analogous changes at depositional sites. The fate of eroded material and the influence of erosion and deposition on SOC dynamics remain knowledge gaps critical for projecting atmospheric CO2.

Flow with vibrational energy exchange, application to CO2 electric laser

International Nuclear Information System (INIS)

Dahan, Claude.

1974-01-01

The performances of a continuous wave (CO 2 , N 2 , He) laser ionized by an electron beam are calculated. Several types of phenomena are considered: energy exchange processes between molecules of laser medium, electron molecular excitation processes, aerodynamic phenomena: the energy exchanges accompanying the laser effect generate important quantities of heat, which have to be evacuated by the flow. After a survey of the fundamental assumptions on molecular phenomena, a computer code was developed for following, along the flow, the evolution of the thermodynamic parameters (pressure, temperature), of the laser gain, and of the electrical properties (electron density and temperature). To provide a finer description of the last ones, a model giving the energy distribution of the electrons in the laser medium was established [fr

Kinetic bottlenecks to chemical exchange rates for deep-sea animals II: Carbon dioxide

Science.gov (United States)

Hofmann, A. F.; Peltzer, E. T.; Brewer, P. G.

2012-11-01

Increased ocean acidification from fossil fuel CO2 invasion, from temperature-driven changes in respiration, and from possible leakage from sub-seabed geologic CO2 disposal has aroused concern over the impacts of elevated CO2 concentrations on marine life. Discussion of these impacts has so far focused only on changes in the oceanic bulk fluid properties (ΔpH, Δ[∑CO2] etc.) as the critical variable and with a major focus on carbonate shell dissolution. Here we describe the rate problem for animals that must export CO2 at about the same rate at which O2 is consumed. We analyze the basic properties controlling CO2 export within the diffusive boundary layer around marine animals in an ocean changing in temperature (T) and CO2 concentration in order to compare the challenges posed by O2 uptake under stress with the equivalent problem of CO2 expulsion. The problem is more complex than that for a non-reactive gas since, as with gas exchange of CO2 at the air-sea interface, the influence of the ensemble of reactions within the CO2-HCO3--CO32- acid-base system needs to be considered. These reactions significantly facilitate CO2 efflux compared to O2 intake at equal temperature, pressure and flow rate under typical oceanic concentrations.The effect of these reactions can be described by an enhancement factor. For organisms, this means mechanically increasing flow over their surface to thin the boundary layer as is required to alleviate O2 stress seems not necessary to facilitate CO2 efflux. Nevertheless the elevated pCO2 cost most likely is non-zero. Regionally as with O2 the combination of T, P, and pH/pCO2 creates a zone of maximum CO2 stress at around 1000 m depth. But the net result is that, for the problem of gas exchange with the bulk ocean, the combination of an increasing T combined with declining O2 poses a greater challenge to marine life than does increasing CO2. The relationships developed here allow a more accurate prediction of the impacts on marine life

Geospatial variability of soil CO2-C exchange in the main terrestrial ecosystems of Keller Peninsula, Maritime Antarctica.

Science.gov (United States)

Thomazini, A; Francelino, M R; Pereira, A B; Schünemann, A L; Mendonça, E S; Almeida, P H A; Schaefer, C E G R

2016-08-15

Soils and vegetation play an important role in the carbon exchange in Maritime Antarctica but little is known on the spatial variability of carbon processes in Antarctic terrestrial environments. The objective of the current study was to investigate (i) the soil development and (ii) spatial variability of ecosystem respiration (ER), net ecosystem CO2 exchange (NEE), gross primary production (GPP), soil temperature (ST) and soil moisture (SM) under four distinct vegetation types and a bare soil in Keller Peninsula, King George Island, Maritime Antarctica, as follows: site 1: moss-turf community; site 2: moss-carpet community; site 3: phanerogamic antarctic community; site 4: moss-carpet community (predominantly colonized by Sanionia uncinata); site 5: bare soil. Soils were sampled at different layers. A regular 40-point (5×8 m) grid, with a minimum separation distance of 1m, was installed at each site to quantify the spatial variability of carbon exchange, soil moisture and temperature. Vegetation characteristics showed closer relation with soil development across the studied sites. ER reached 2.26μmolCO2m(-2)s(-1) in site 3, where ST was higher (7.53°C). A greater sink effect was revealed in site 4 (net uptake of 1.54μmolCO2m(-2)s(-1)) associated with higher SM (0.32m(3)m(-3)). Spherical models were fitted to describe all experimental semivariograms. Results indicate that ST and SM are directly related to the spatial variability of CO2 exchange. Heterogeneous vegetation patches showed smaller range values. Overall, poorly drained terrestrial ecosystems act as CO2 sink. Conversely, where ER is more pronounced, they are associated with intense soil carbon mineralization. The formations of new ice-free areas, depending on the local soil drainage condition, have an important effect on CO2 exchange. With increasing ice/snow melting, and resulting widespread waterlogging, increasing CO2 sink in terrestrial ecosystems is expected for Maritime Antarctica. Copyright �

A comparative study of United States and China exchange rate behavior: A co integration analysis

Directory of Open Access Journals (Sweden)

Khuram Shafi

2015-02-01

Full Text Available Exchange rates always affect the prices of the imports and export of products and services in which countries are trading with other parts of the world. Therefore, exchange rate calculation is one of the essential issues for making appropriate policies. This research investigates the determinants of trade, i.e. import, export, industrial growth, consumption level and oil prices fluctuation, which bring changes in exchange rate and their influence eventually on balance of payments. Data of defined variables was collected on yearly basis for China and USA for thirty one years. By applying cointegration, it is estimated that there existed a long run relationship in both countries. USA and China had significant and correct signs on the short run dynamic and some of the factors did not. Exchange rate did not granger cause balance of payment and balance of payment did not granger cause exchange rate. In conclusion, we found that determinants of balance of trade could affect the exchange rates, also, these rates had considerable effect (positive or negative on balance of payments. In this twofold study, we found relationship of exchange rate with selected determinants of trade, and also examined their bilateral effect, and then made contrast of both countries.

CO2 Capture Rate Sensitivity Versus Purchase of CO2 Quotas. Optimizing Investment Choice for Electricity Sector

Directory of Open Access Journals (Sweden)

Coussy Paula

2014-09-01

Full Text Available Carbon capture technology (and associated storage, applied to power plants, reduces atmospheric CO2 emissions. This article demonstrates that, in the particular case of the deployment phase of CO2 capture technology during which CO2 quota price may be low, capturing less than 90% of total CO2 emissions from power plants can be economically attractive. Indeed, for an electric power company capture technology is interesting, only if the discounted marginal cost of capture is lower than the discounted marginal cost of purchased quotas. When CO2 price is low, it is interesting to have flexibility and reduce the overall capture rate of the site, by stopping the capture system of one of the combustion trains if the site has multiple ones, or by adopting less than 90% CO2 capture rate.

Exchange-coupled hard magnetic Fe-Co/CoPt nanocomposite films fabricated by electro-infiltration

Directory of Open Access Journals (Sweden)

Xiao Wen

2017-05-01

Full Text Available This paper introduces a potentially scalable electro-infiltration process to produce exchange-coupled hard magnetic nanocomposite thin films. Fe-Co/CoPt nanocomposite films are fabricated by deposition of CoFe2O4 nanoparticles onto Si substrate, followed by electroplating of CoPt. Samples are subsequently annealed under H2 to reduce the CoFe2O4 to magnetically soft Fe-Co and also induce L10 ordering in the CoPt. Resultant films exhibit 0.97 T saturation magnetization, 0.70 T remanent magnetization, 127 kA/m coercivity and 21.8 kJ/m3 maximum energy density. First order reversal curve (FORC analysis and δM plot are used to prove the exchange coupling between soft and hard magnetic phases.

A novel pump-driven veno-venous gas exchange system during extracorporeal CO2-removal.

Science.gov (United States)

Hermann, Alexander; Riss, Katharina; Schellongowski, Peter; Bojic, Andja; Wohlfarth, Philipp; Robak, Oliver; Sperr, Wolfgang R; Staudinger, Thomas

2015-10-01

Pump-driven veno-venous extracorporeal CO2-removal (ECCO2-R) increasingly takes root in hypercapnic lung failure to minimize ventilation invasiveness or to avoid intubation. A recently developed device (iLA activve(®), Novalung, Germany) allows effective decarboxylation via a 22 French double lumen cannula. To assess determinants of gas exchange, we prospectively evaluated the performance of ECCO2-R in ten patients receiving iLA activve(®) due to hypercapnic respiratory failure. Sweep gas flow was increased in steps from 1 to 14 L/min at constant blood flow (phase 1). Similarly, blood flow was gradually increased at constant sweep gas flow (phase 2). At each step gas transfer via the membrane as well as arterial blood gas samples were analyzed. During phase 1, we observed a significant increase in CO2 transfer together with a decrease in PaCO2 levels from a median of 66 mmHg (range 46-85) to 49 (31-65) mmHg from 1 to 14 L/min sweep gas flow (p gas flow rates. During phase 2, oxygen transfer significantly increased leading to an increase in PaO2 from 67 (49-87) at 0.5 L/min to 117 (66-305) mmHg at 2.0 L/min (p gas flow results in effective CO2-removal, which can be further reinforced by raising blood flow. The clinically relevant oxygenation effect in this setting could broaden the range of indications of the system and help to set up an individually tailored configuration.

Empirical Studies of Exchange Rates: Price Behavior, Rate Determinationand Market Efficiency

OpenAIRE

Richard M. Levich

1983-01-01

Theoretical and empirical research completed over the last decade has dramatically increased our understanding of exchange rate behavior. The major insight to come from this decade of research is that foreign exchange is a financial asset. In an asset pricing framework, current exchange rates reflect the expected values of future exogenous variables. The purpose of this paper is to survay the empirical evidence on exchange rate behavior, market efficiency and related topics. Section 2 present...

Exchange rate rebounds after foreign exchange market interventions

Science.gov (United States)

Hoshikawa, Takeshi

2017-03-01

This study examined the rebounds in the exchange rate after foreign exchange intervention. When intervention is strongly effective, the exchange rate rebounds at next day. The effect of intervention is reduced slightly by the rebound after the intervention. The exchange rate might have been 67.12-77.47 yen to a US dollar without yen-selling/dollar-purchasing intervention of 74,691,100 million yen implemented by the Japanese government since 1991, in comparison to the actual exchange rate was 103.19 yen to the US dollar at the end of March 2014.

Bretton Woods Fixed Exchange Rate System versus Floating Exchange Rate System

OpenAIRE

Geza, Paula; Giurca Vasilescu, Laura

2011-01-01

One of the most important issues of monetary policy is to find out whether the state should intervene among the exchange rates, taking into account the fact that changes in the exchange rates represent a significant transmission channel of the effects generated by the monetary policy. Taking into consideration the failure of fixed exchange rate regimes and the recent improvement of financial markets, the return in the near future to such a regime – as for example the Bretton Woods system –...

An experimental study of trans-critical CO2 water–water heat pump using compact tube-in-tube heat exchangers

International Nuclear Information System (INIS)

Jiang, Yuntao; Ma, Yitai; Li, Minxia; Fu, Lin

2013-01-01

Highlights: • Thermodynamic analyses of transcritical CO 2 cycle with and without IHX are provided. • A transcritical CO 2 heat pump system adopts compact tube-in-tube heat exchangers. • Experiment results of systems with and without IHX have been analyzed and compared. • IHX can improve the performance of the transcritical CO 2 heat pump system. - Abstract: A transcritical CO 2 water–water heat pump system is introduced in this study, which employs compact tube-in-tube evaporator and gas cooler. Its primary test standards and operating conditions are introduced. Under test conditions, experiments have been carried out with compression cycles with and without internal heat exchanger (IHX). Experiment results have been analyzed and compared, showing that IHX can improve the coefficient of performance of the system. The analyses are done mainly on the variations of outlet CO 2 temperature of the gas cooler, compressor discharge pressure, compressor lubricant temperature, hot water mass flow rate, etc. When the inlet water temperature of the gas cooler is 15 °C, 20 °C, 25 °C respectively, the hot water temperature ranges from 45 °C to 70 °C, the relative COP h (coefficient of performance when heating) change index (RCI COP ) of the heat pump system with IHX is about 3.5–8% higher than that without IHX. The relative capacity change index (RCI Q ) of the heat pump system with IHX is about 5–10% higher than that without IHX. Temperature of CO 2 increases at the outlet of the gas cooler when the outlet water temperature of the gas cooler increases. Lowering the outlet CO 2 temperature of the gas cooler is an important way to improve the performance of the system

The determinants of exchange rates and the movements of EUR/RON exchange rate via non-linear stochastic processes

Directory of Open Access Journals (Sweden)

Petrică Andreea-Cristina

2017-07-01

Full Text Available Modeling exchange rate volatility became an important topic for research debate starting with 1973, when many countries switched to floating exchange rate system. In this paper, we focus on the EUR/RON exchange rate both as an economic measure and present the implied economic links, and also as a financial investment and analyze its movements and fluctuations through two volatility stochastic processes: the Standard Generalized Autoregressive Conditionally Heteroscedastic Model (GARCH and the Exponential Generalized Autoregressive Conditionally Heteroscedastic Model (EGARCH. The objective of the conditional variance processes is to capture dependency in the return series of the EUR/RON exchange rate. On this account, analyzing exchange rates could be seen as the input for economic decisions regarding Romanian macroeconomics - the exchange rates being influenced by many factors such as: interest rates, inflation, trading relationships with other countries (imports and exports, or investments - portfolio optimization, risk management, asset pricing. Therefore, we talk about political stability and economic performance of a country that represents a link between the two types of inputs mentioned above and influences both the macroeconomics and the investments. Based on time-varying volatility, we examine implied volatility of daily returns of EUR/RON exchange rate using the standard GARCH model and the asymmetric EGARCH model, whose parameters are estimated through the maximum likelihood method and the error terms follow two distributions (Normal and Student’s t. The empirical results show EGARCH(2,1 with Asymmetric order 2 and Student’s t error terms distribution performs better than all the estimated standard GARCH models (GARCH(1,1, GARCH(1,2, GARCH(2,1 and GARCH(2,2. This conclusion is supported by the major advantage of the EGARCH model compared to the GARCH model which consists in allowing good and bad news having different impact on the

Rates of volcanic CO2 degassing from airborne determinations of SO2 Emission rates and plume CO2SO2: test study at Pu′u ′O′o Cone, Kilauea Volcano, Hawaii

Science.gov (United States)

Gerlach, Terrence M.; McGee, Kenneth A.; Sutton, A. Jefferson; Elias, Tamar

1998-01-01

We present an airborne method that eliminates or minimizes several disadvantages of the customary plume cross-section sampling method for determining volcanic CO2 emission rates. A LI-COR CO2analyzer system (LICOR), a Fourier transform infrared spectrometer system (FTIR), and a correlation spectrometer (COSPEC) were used to constrain the plume CO2/SO2 and the SO2 emission rate. The method yielded a CO2 emission rate of 300 td−1 (metric tons per day) for Pu′u ′O′o cone, Kilauea volcano, on 19 September 1995. The CO2/SO2 of 0.20 determined from airborne LICOR and FTIR plume measurements agreed with the CO2/SO2 of 204 ground-based samples collected from vents over a 14-year period since the Pu′u ′O′o eruption began in January 1983.

Is a more stable exchange rate associated with reduced exchange rate pass-through?

OpenAIRE

Mark J. Holmes

2007-01-01

Pass-through from the nominal effective exchange rate to import prices is modelled within a regime-switching environment. Evidence suggests that exchange rate pass through can be characterised as regime-specific where the probability of switching between regimes is influenced by the extent of exchange rate volatility.

Absorption of carbon dioxide and isotope exchange rate of carbon in a reaction system between carbon dioxide and carbamic acid

International Nuclear Information System (INIS)

Takeshita, Kenji; Kitamoto, Asashi

1985-01-01

The performance of isotope separation of carbon-13 by chemical exchange between carbon dioxide and carbamic acid was studied. The working fluid used in the study was a solution of DNBA, (C 4 H 9 ) 2 NH and n-octane mixture. Factors related to the isotope exchange rate were measured, such as the absorption rate of carbon dioxide into the solution of DNBA and n-octane, the isotope exchange rate and the separation factor in the reaction between CO 2 and carbamic acid. The absorption of CO 2 into the working fluid was the sum of chemical absorption by DNBA and physical absorption by n-octane. The absorption of carbon dioxide into the working fluid was negligible at temperatures over 90 0 C, but increased gradually at lower temperatures. Carbon dioxide was absorbed into DNBA by chemical absorption, and DNBA was converted to carbamic acid by the reaction. The reaction for synthesis and decomposition of carbamic acid was reversible. The separation factor in equilibrium reached a large value at lower temperatures. The isotope exchange rate between gas and liquid was proportional to the product of the concentration of carbamic acid and the concentration of CO 2 by physical absorption. The isotope separation of carbon by chemical exchange reaction is better operated under the conditions of lower temperature and higher pressure. (author)

Design analysis of a lead–lithium/supercritical CO2 Printed Circuit Heat Exchanger for primary power recovery

International Nuclear Information System (INIS)

Fernández, Iván; Sedano, Luis

2013-01-01

Highlights: • A design for a PbLi/CO 2 (SC) Printed Circuit Heat Exchanger which optimizes the pressure drop performance is proposed. • Numerical analyses have been performed to optimize the airfoil fins shape and arrangement. • SiC is proposed as structural material and tritium permeation barrier for the PCHE. • The integrated flux is larger than expected and allows reducing the CO 2 mass flow in this sector of the power cycle. • A transport model has been developed to evaluate the permeation of tritium from the liquid metal to the secondary CO 2 . -- Abstract: One of the key issues for fusion power plant technology is the efficient, reliable and safe recovery of the power extracted by the primary coolants. An interesting design option for power conversion cycles based on Dual Coolant Breeding Blankets (DCBB) is a Printed Circuit Heat Exchanger, which is supported by the advantages of its compactness, thermal effectiveness, high temperature and pressure capability and corrosion resistance. This work presents a design analysis of a silicon carbide Printed Circuit Heat Exchanger for lead–lithium/supercritical CO 2 at DEMO ranges (4× segmentation)

Seasonal and temporal CO2 dynamics in three tropical mangrove creeks - A revision of global mangrove CO2 emissions

Science.gov (United States)

Rosentreter, Judith A.; Maher, D. T.; Erler, D. V.; Murray, R.; Eyre, B. D.

2018-02-01

Continuous high-resolution surface water pCO2 and δ13C-CO2 and 222Rn (dry season only) were measured over two tidal cycles in the wet and dry season in three tropical tidal mangrove creeks on the north-eastern coast of Queensland, Australia. Mangrove surface water pCO2 followed a clear tidal pattern (ranging from 387 to 13,031 μatm) with higher pCO2-values in the wet season than in the dry season. The δ13C-CO2 in the mangrove waters ranged from -21.7 to -8.8‰ and was rather indicative of a mixed source than a distinct mangrove signature. Surface water CO2 was likely driven by a combination of mangrove and external carbon sources, e.g. exchange with groundwater/pore water enriched in 13C, or terrestrial carbon inputs with a significant contribution of C4-vegetation (sugar cane) source. The kinetic and equilibrium fractionation during the gas exchange at the water-atmosphere interface may have further caused a 13C-enrichment of the CO2 pool in the mangrove surface waters. Average CO2 evasion rates (58.7-277.6 mmol m-2 d-1) were calculated using different empirical gas transfer velocity models. Using our high-resolution time series data and previously published data, the average CO2 flux rate in mangrove ecosystems was estimated to be 56.5 ± 8.9 mmol m-2 d-1, which corresponds to a revised global mangrove CO2 emission of 34.1 ± 5.4 Tg C per year.

Net ecosystem CO2 exchange of a cutover peatland rehabilitated with a transplanted acrotelm

International Nuclear Information System (INIS)

Cagampan, J.P.; Waddington, J.M.

2008-01-01

Peatlands are an important long-term sink for atmospheric carbon dioxide (CO 2 ). The storage function of peatland ecosystems is significantly impacted by drainage and extraction processes, which can result in the release of significant amounts of CO 2 . This paper investigated the net ecosystem CO 2 exchange of a newly developed extraction-restoration technique that preserved the acrotelm and replaced it directly on the cut surface of the peatlands. The technique used a modified block-cut method with a back-hoe to create a drainage ditch. Actrotelm and surface vegetation were removed and placed to one side, and the peat was mechanically removed. The acrotelm was then transplanted over the older and more decomposed catotelm peat to create a trench topography in which the natural peatland was higher than the extracted zone. Air temperatures, water table levels, and volumetric moisture content levels were measured throughout the experiment. Measurements of CO 2 exchange were taken for the duration of a Spring and summer growing season at 12 sampling locations. Results of the experiment showed that the technique was successful in maintaining moisture conditions similar to those observed in the natural peatlands. However, the peatlands where the technique was used were still net emitters of CO 2 . Recommendations for improving the technique included using more care when removing upper peat layers; limiting surface damage; and reducing spaces and gaps between the transplanted acrotelm. 34 refs., 8 figs

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

Science.gov (United States)

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.

Interannual variability in CO2 and CH4 exchange in a brackish tidal marsh in Northern California

Science.gov (United States)

Knox, S. H.; Windham-Myers, L.; Anderson, F. E.; Bergamaschi, B. A.

2017-12-01

Carbon (C) cycling in coastal wetlands is difficult to measure and model due to extremely dynamic atmospheric and hydrologic fluxes, as well as sensitivities to dynamic land- and ocean-based drivers. To date, few studies have begun continuous measurements of net ecosystem CO2 exchange (NEE) in these systems, and as such our understanding of the key drivers of NEE in coastal wetlands remain poorly understood. Recent eddy covariance measurements of NEE in these environments show considerable variability both within and across sites, with daily CO2 uptake and annual net CO2 budgets varying by nearly an order of magnitude between years and across locations. Furthermore, measurements of CH4 fluxes in these systems are even more limited, despite the potential for CH4 emissions from brackish and freshwater coastal wetlands. Here we present 3 years of near-continuous eddy covariance measurements of CO2 and CH4 fluxes from a brackish tidal marsh in Northern California and explore the drivers of interannual variability in CO2 and CH4 exchange. CO2 fluxes showed significant interannual variability; net CO2 uptake was near-zero in 2014 (6 ± 26 g C-CO2 m-2 yr-1), while much greater uptake was observed in 2015 and 2016 (209 ± 27 g C- CO2 m-2 yr-1 and 243 ± 26 g C-CO2 m-2 yr-1, respectively). Conversely, annual CH4 emissions were small and consistent across years, with the wetland emitting on average 1 ± 0.1 g C-CH4 m-2 yr-1. With respect to the net atmospheric GHG budget (assuming a sustained global warming potential (SGWP) of 45, expressed in units of CO2 equivalents), the wetland was near neutral in 2014, but a net GHG sink of 706 ± 105 g CO2 eq m-2 yr-1 and 836 ± 83 g CO2 eq m-2 yr-1 in 2015 and 2016, respectively. The large interannual variability in CO2 exchange was driven by notable year-to-year differences in temperature and precipitation as California experienced a severe drought and record high temperatures from 2012 to 2015. The large interannual variability in

Plant functional types define magnitude of drought response in peatland CO2 exchange

NARCIS (Netherlands)

Kuiper, J.J.; Mooij, W.M.; Bragazza, L.; Robroek, B.J.M.

2014-01-01

Peatlands are important sinks for atmospheric carbon (C), yet the role of plant functional types (PFTs) for C sequestration under climatic perturbations is still unclear. A plant removal experiment was used to study the importance of vascular PFTs for the net ecosystem CO2 exchange (NEE) during

Plant functional types define magnitude of drought response in peatland CO2 exchange

NARCIS (Netherlands)

Kuiper, J.J.; Mooij, W.M.; Bragazza, L.; Robroek, B.J.M.

2014-01-01

Peatlands are important sinks for atmospheric carbon (C), yet the role of plant functional types (PFTs) for C sequestration under climatic perturbations is still unclear. A plant-removal experiment was used to study the importance of vascular PFTs for the net ecosystem CO2 exchange (NEE) during

14 CFR 65.43 - Rating privileges and exchange.

Science.gov (United States)

2010-01-01

... 14 Aeronautics and Space 2 2010-01-01 2010-01-01 false Rating privileges and exchange. 65.43... § 65.43 Rating privileges and exchange. (a) The holder of a senior rating on August 31, 1970, may at any time after that date exchange his rating for a facility rating at the same air traffic control...

Choice of exchange rate regimes for African countries: Fixed or Flexible Exchange rate regimes?

OpenAIRE

Simwaka, Kisu

2010-01-01

The choice of an appropriate exchange rate regime has been a subject of ongoing debate in international economics. The majority of African countries are small open economies and thus where the choice of the exchange rate regime is an important policy issue. Aside from factors such as interest rates and inflation, the exchange rate is one of the most important determinants of a country’s relative level of economic health. For this reason, exchange rates are among the most watched analyzed and ...

Giant exchange bias and its angular dependence in Co/CoO core-shell nanowire assemblies

Energy Technology Data Exchange (ETDEWEB)

Gandha, Kinjal; Chaudhary, Rakesh P.; Mohapatra, Jeotikanta; Koymen, Ali R.; Liu, J. Ping, E-mail: pliu@uta.edu

2017-07-12

The exchange-bias field (H{sub EB}) and its angular dependence are systematically investigated in Co/CoO core-shell nanowire assemblies (∼15 nm in diameter and ∼200 nm in length) consisting of single-crystalline Co core and polycrystalline CoO shell. Giant exchange-bias field (H{sub EB}) up to 2.4 kOe is observed below a blocking temperature (T{sub EB} ∼150 K) in the aligned Co/CoO nanowire assemblies. It is also found that there is an angular dependence between the H{sub EB} and the applied magnetization direction. The H{sub EB} showed a peak at 30° between the applied field and the nanowire aligned direction, which may be attributed to the noncollinear spin orientations at the interface between the ferromagnetic core and the antiferromagnetic shell. This behavior is quantitatively supported by an analytical calculation based on Stoner–Wohlfarth model. This study underlines the importance of the competing magnetic anisotropies at the interface of Co/CoO core-shell nanowires. - Highlights: • Giant exchange bias is observed in oriented Co/CoO core-shell nanowire assemblies. • Study of angular and temperature dependence of the exchange bias effect. • Competing magnetic anisotropies at the interface of Co/CoO core-shell nanowires. • Effect of misaligned spins in FM/AFM interface on angular dependence of exchange bias. • We explain the analytical model that accounts for experimental results.

Giant exchange bias and its angular dependence in Co/CoO core-shell nanowire assemblies

International Nuclear Information System (INIS)

Gandha, Kinjal; Chaudhary, Rakesh P.; Mohapatra, Jeotikanta; Koymen, Ali R.; Liu, J. Ping

2017-01-01

The exchange-bias field (H EB ) and its angular dependence are systematically investigated in Co/CoO core-shell nanowire assemblies (∼15 nm in diameter and ∼200 nm in length) consisting of single-crystalline Co core and polycrystalline CoO shell. Giant exchange-bias field (H EB ) up to 2.4 kOe is observed below a blocking temperature (T EB ∼150 K) in the aligned Co/CoO nanowire assemblies. It is also found that there is an angular dependence between the H EB and the applied magnetization direction. The H EB showed a peak at 30° between the applied field and the nanowire aligned direction, which may be attributed to the noncollinear spin orientations at the interface between the ferromagnetic core and the antiferromagnetic shell. This behavior is quantitatively supported by an analytical calculation based on Stoner–Wohlfarth model. This study underlines the importance of the competing magnetic anisotropies at the interface of Co/CoO core-shell nanowires. - Highlights: • Giant exchange bias is observed in oriented Co/CoO core-shell nanowire assemblies. • Study of angular and temperature dependence of the exchange bias effect. • Competing magnetic anisotropies at the interface of Co/CoO core-shell nanowires. • Effect of misaligned spins in FM/AFM interface on angular dependence of exchange bias. • We explain the analytical model that accounts for experimental results.

Indoor Levels of Formaldehyde and Other Pollutants and Relationship to Air Exchange Rates and Human Activities

Science.gov (United States)

Huangfu, Y.; O'Keeffe, P.; Kirk, M.; Walden, V. P.; Lamb, B. K.; Jobson, B. T.

2017-12-01

This paper reports results on an indoor air quality study conducted on six homes in summer and winter, contrasting indoor and outdoor concentrations of O3, CO, CO2, NOx, PM2.5, and selected volatile organic hydrocarbons measured by PTR-MS. Data were collected as 1 minute averages. Air exchange rates of the homes were determined by CO2 tracer release. Smart home sensors, recording human activity level in various places in the home, and window and doors openings, were utilized to better understand the link between human activity and indoor air pollution. From our study, averaged air exchange rates of the homes ranged from 0.2 to 1.2 hour-1 and were greatly affected by the ventilation system type and window and door openings. In general, a negative correlation between air exchange rate and indoor VOCs levels was observed, with large variation of pollutant levels between the homes. For most of the VOCs measured in the house, including formaldehyde and acetaldehyde, summer levels were much higher than winter levels. In some homes formaldehyde levels displayed a time of day variation that was linked to changes in indoor temperature. During a wildfire period in the summer of 2015, outdoor levels of PM2.5, formaldehyde, and benzene dramatically increased, significantly impacting indoor levels due to infiltration. Human activities, such as cooking, can significantly change the levels of most of the compounds measured in the house and the levels can be significantly elevated for short periods of time, with peak levels can be several orders higher compared with typical levels. The data suggest that an outcome of state energy codes that require new homes to be energy efficient, and as a consequence built with lower air exchange rates, will be unacceptable levels of air toxics, notably formaldehyde.

Estimating marginal CO2 emissions rates for national electricity systems

International Nuclear Information System (INIS)

Hawkes, A.D.

2010-01-01

The carbon dioxide (CO 2 ) emissions reduction afforded by a demand-side intervention in the electricity system is typically assessed by means of an assumed grid emissions rate, which measures the CO 2 intensity of electricity not used as a result of the intervention. This emissions rate is called the 'marginal emissions factor' (MEF). Accurate estimation of MEFs is crucial for performance assessment because their application leads to decisions regarding the relative merits of CO 2 reduction strategies. This article contributes to formulating the principles by which MEFs are estimated, highlighting the strengths and weaknesses in existing approaches, and presenting an alternative based on the observed behaviour of power stations. The case of Great Britain is considered, demonstrating an MEF of 0.69 kgCO 2 /kW h for 2002-2009, with error bars at +/-10%. This value could reduce to 0.6 kgCO 2 /kW h over the next decade under planned changes to the underlying generation mix, and could further reduce to approximately 0.51 kgCO 2 /kW h before 2025 if all power stations commissioned pre-1970 are replaced by their modern counterparts. Given that these rates are higher than commonly applied system-average or assumed 'long term marginal' emissions rates, it is concluded that maintenance of an improved understanding of MEFs is valuable to better inform policy decisions.

Direct and indirect controls of the interannual variability in atmospheric CO₂ exchange of three contrasting ecosystems in Denmark

DEFF Research Database (Denmark)

Jensen, Rasmus; Herbst, Mathias; Friborg, Thomas

2017-01-01

neighboring sites (agriculture, forest, and meadow) subjected to management in variable degree were evaluated to determine typical CO2 budgets and controlling factors of IAV. In terms of average annual net ecosystem exchange (NEE) the agricultural and wet meadow site showed identical rates of −156 (±110...... sources of IAV of CO2 fluxes between direct climatic effects and indirect effects (functional changes). This analysis showed that NEE at the forest (through both GPP and RE) was most prone to interannual functional changes. The wet meadow showed moderate functional changes with respect to RE and thus NEE...

Modeling and sizing of the heat exchangers of a new supercritical CO2 Brayton power cycle for energy conversion for fusion reactors

International Nuclear Information System (INIS)

Serrano, I.P.; Cantizano, A.; Linares, J.I.; Moratilla, B.Y.

2014-01-01

Highlights: •We propose a procedure to model the heat exchangers of a S-CO2 Brayton power cycle. •Discretization in sub-heat exchangers is performed due to complex behavior of CO 2 . •Different correlations have been tested, verifying them with CFD when necessary. •Obtained sizes are agree with usual values of printed circuit heat exchangers. -- Abstract: TECNO F US is a research program financed by the Spanish Government to develop technologies related to a dual-coolant (He/Pb–Li) breeding blanket design concept including the auxiliary systems for a future power reactor (DEMO). One of the main issues of this program is the optimization of heat recovery from the reactor and its conversion into electrical power. This paper is focused on the methodology employed for the design and sizing of all the heat exchangers of the supercritical CO 2 Brayton power cycle (S-CO2) proposed by the authors. Due to the large pressure difference between the fluids, and also to their compactness, Printed Circuit Heat Exchangers (PCHE) are suggested in literature for these type of cycles. Because of the complex behavior of CO 2 , their design is performed by a numerical discretization into sub-heat exchangers, thus a higher precision is reached when the thermal properties of the fluids vary along the heat exchanger. Different empirical correlations for the pressure drop and the Nusselt number have been coupled and assessed. The design of the precooler (PC) and the low temperature recuperator (LTR) is also verified by simulations using CFD because of the near-critical behavior of CO 2 . The size of all of the heat exchangers of the cycle have been assessed

Testing the Monetary Model for Exchange Rate Determination in South Africa: Evidence from 101 Years of Data

Directory of Open Access Journals (Sweden)

Riané de Bruyn

2013-03-01

Full Text Available Evidence in favor of the monetary model of exchange rate determination for the South African Rand is, at best, mixed. A co-integrating relationship between the nominal exchange rate and monetary fundamentals forms the basis of the monetary model. With the econometric literature suggesting that the span of the data, not the frequency, determines the power of the co-integration tests and the studies on South Africa primarily using short-span data from the post-Bretton Woods era, we decided to test the long-run monetary model of exchange rate determination for the South African Rand relative to the US Dollar using annual data from 1910 – 2010. The results provide some support for the monetary model in that long-run co-integration is found between the nominal exchange rate and the output and money supply deviations. However, the theoretical restrictions required by the monetary model are rejected. A vector error-correction model identifies both the nominal exchange rate and the monetary fundamentals as the channel for the adjustment process of deviations from the long-run equilibrium exchange rate. A subsequent comparison of nominal exchange rate forecasts based on the monetary model with those of the random walk model suggests that the forecasting performance of the monetary model is superior.

Effect of low 60Co dose rates on sister chromatid exchange incidence in the benthic worm. Neanthes arenaceodentata

International Nuclear Information System (INIS)

Harrison, F.L.; Rice, D.W. Jr.

1981-01-01

The usefulness of sister chromatid exchange (SCE) induction as a measure of low-level radiation effect was examined in a benthic marine worm, Neanthes arenaceodentata. Larvae were exposed to 60 Co radiation for 12 to 24 h at total doses ranging from 0.5 to 309 R and at dose rates from 0.04 to 13 R/h. Animals exposed at intermediate dose rates (0.5, 0.6, 1.25, 2.0, and 2.5 R/h) had SCE frequencies per chromosome about twice that of those receiving no radiation (controls), whereas those exposed at the higher dose rates (7.0 and 13 R/h) had SCE frequencies lower than the controls. Animals exposed at the lower dose rates (0.04 and 0.1 R/h) had lower SCE frequencies than those exposed at intermediate dose rates (and higher SCE frequencies than controls). The length of chromosome pair number one differed among metaphase spreads and was used as an index of chromosome condensation in a given metaphase. Because there is a possibility that chromosome morphology may affect the ability to resolve SCEs, morphology will be monitored in future studies. A preliminary experiment was performed to assess the effects of 2.2 and 11.5 R/h for 24 h on growth and development. Larvae observed at 6 and 17 d after irradiation did not have significantly different numbers of abnormal larvae or survival rates

Possibility of high CO{sub 2} fixation rate by coral reef ecosystems

Energy Technology Data Exchange (ETDEWEB)

K. Yamada; Y. Suzuki; B.E. Casareto; H. Komiyama [Shinshu University, Tokida (Japan). Dept. of Fine Materials Engineering

2003-07-01

Previous net rates of CO{sub 2} fixation by coral reef ecosystems have been said to be nearly zero due to a balance between CO{sub 2} fixed by organic carbon production and CO{sub 2} released by both organic carbon decomposition and inorganic carbon formation. But this study, conducted in Bora Bay, Miyako Island, Japan showed net rates of about 7 gC m{sup -2} d{sup -1} inside a coral reef and on a coral reef. It was found by experiment that the photosynthetic rate of coral increased with the increase of the flow rate of seawater. The authors tried to calculate net primary production (= net rates of CO{sub 2} fixation) outside a coral reef with flow rate. A flow rate on the coral reef of the open seaside is much higher than that in a lagoon. As an example, the CO{sub 2} fixation rates at the flow rates of 6 and 30 cm/s are compared. When it is assumed that the length of the whole coral reef facing the ocean is 50,000 km and its width is 100 m, and the flow rate is 30cm/s, the CO{sub 2} fixation rate is calculated to be 6.3 x 10{sup 6} t-C/y (3.5g-C/m{sup 2}d). This value is 2.2 times higher than that at the flow rate of 6 cm/s. This fixation rate is only by the coral itself. It means that the CO{sub 2} fixation rate by coral reef ecosystems can be much higher and the magnitude for worldwide ecosystems can be in the order of 10{sup 6}-10{sup 7} t-C/y. 14 refs., 5 tabs.

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

Science.gov (United States)

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...

ENERGY BALANCE AND CO2 EXCHANGE BEHAVIOUR IN SUB-TROPICAL YOUNG PINE (Pinus roxburghii PLANTATION

Directory of Open Access Journals (Sweden)

B. K. Bhattacharya

2012-08-01

Full Text Available A study was conducted to understand the seasonal and annual energy balance behaviour of young and growing sub-tropical chir pine (Pinus roxburghii plantation of eight years age in the Doon valley, India and its coupling with CO2 exchange. The seasonal cycle of dekadal daytime latent heat fluxes mostly followed net radiation cycle with two minima and range between 50–200 Wm-2 but differed from the latter during the period when soil wetness and cloudiness were not coupled. Dekadal evaporative fraction closely followed the seasonal dryness-wetness cycle thus minimizing the effect of wind on energy partitioning as compared to diurnal variation. Daytime latent heat fluxes were found to have linear relationship with canopy net assimilation rate (Y = 0.023X + 0.171, R2 = 0.80 though nonlinearity exists between canopy latent heat flux and hourly net CO2 assimilation rate . Night-time plant respiration was found to have linear relationship (Y = 0.088 + 1.736, R2 = 0.72 with night-time average vapour pressure deficit (VPD. Daily average soil respiration was found to be non-linearly correlated to average soil temperatures (Y = -0.034X2 + 1.676X – 5.382, R2 = 0.63 The coupled use of empirical models, seasonal energy fluxes and associated parameters would be useful to annual water and carbon accounting in subtropical pine ecosystem of India in the absence high-response eddy covariance tower.

An Empirical Investigation into Exchange Rate Regime Choice and Exchange Rate Volatility

OpenAIRE

Helge Berger; Jan-Egbert Sturm; Jakob de Haan

2000-01-01

We test a simple model of exchange rate regime choice with data for 65 non-OECD countries covering the period 1980-94. We find that the variance of output at home and in potential target c ountries as well as the correlation between home and foreign real activity are powerful and robust predictors of exchange rate regime choice. Surprisingly, a more volatile foreign economy can be an argument in favor of a fixed exchange rate regime once similarities in the business cycle are taken into accou...

The rate constant for the CO + H2O2 reaction

DEFF Research Database (Denmark)

Glarborg, Peter; Marshall, Paul

2009-01-01

The rate constant for the reaction CO + H2O2 -> HOCO + OH (R1) at 713 K is determined based on the batch reactor experiments of Baldwin et al. [ R. R. Baldwin, R. W. Walker, S. J. Webster, Combust. Flame 15 (1970) 167] on decomposition of H2O2 sensitized by CO. The value, k(1) (713 K) = 8.1 x 10...

Controlling exchange bias in Co-CoOx nanoparticles by oxygen content

OpenAIRE

Kovylina, Miroslavna; del Muro, Montserrat Garcia; Konstantinovic, Zorica; Varela, Manuel; Iglesias, Oscar; Labarta, Amilcar; Batlle, Xavier

2009-01-01

We report on the occurrence of exchange bias on laser-ablated granular thin films composed of Co nanoparticles embedded in amorphous zirconia matrix. The deposition method allows controlling the degree of oxidation of the Co particles by tuning the oxygen pressure at the vacuum chamber (from 2x10^{-5} to 10^{-1} mbar). The nature of the nanoparticles embedded in the nonmagnetic matrix is monitored from metallic, ferromagnetic (FM) Co to antiferromagnetic (AFM) CoOx, with a FM/AFM intermediate...

A Data Base of Nutrient Use, Water Use, CO2 Exchange, and Ethylene Production by Soybeans in a Controlled Environment

Science.gov (United States)

Wheeler, R. M.; Mackowiak, C. L.; Peterson, B. V.; Sager, J. C.; Knott, W. M.; Berry, W. L.; Sharifi, M. R.

1998-01-01

A data set is given describing daily nutrient and water uptake, carbon dioxide (CO2) exchange, ethylene production, and carbon and nutrient partitioning from a 20 sq m stand of soybeans (Glycine max (L.) Merr. cv. McCall] for use in bioregenerative life support systems. Stand CO2 exchange rates were determined from nocturnal increases in CO2 (respiration) and morning drawdowns (net photosynthesis) to a set point of 1000 micromol/ mol each day (i.e., a closed system approach). Atmospheric samples were analyzed throughout growth for ethylene using gas chromatography with photoionization detection (GC/PH)). Water use was monitored by condensate production from the humidity control system, as well as water uptake from the nutrient solution reservoirs each day. Nutrient uptake data were determined from daily additions of stock solution and acid to maintain an EC of 0.12 S/m and pH of 5.8. Dry mass yields of seeds, pods (without seeds), leaves, stems, and roots are provided, as well as elemental and proximate nutritional compositions of the tissues. A methods section is included to qualify any assumptions that might be required for the use of the data in plant growth models, along with a daily event calendar documenting set point adjustments and the occasional equipment or sensor failure.

Rates of CO2 Mineralization in Geological Carbon Storage.

Science.gov (United States)

Zhang, Shuo; DePaolo, Donald J

2017-09-19

Geologic carbon storage (GCS) involves capture and purification of CO 2 at industrial emission sources, compression into a supercritical state, and subsequent injection into geologic formations. This process reverses the flow of carbon to the atmosphere with the intention of returning the carbon to long-term geologic storage. Models suggest that most of the injected CO 2 will be "trapped" in the subsurface by physical means, but the most risk-free and permanent form of carbon storage is as carbonate minerals (Ca,Mg,Fe)CO 3 . The transformation of CO 2 to carbonate minerals requires supply of the necessary divalent cations by dissolution of silicate minerals. Available data suggest that rates of transformation are highly uncertain and difficult to predict by standard approaches. Here we show that the chemical kinetic observations and experimental results, when they can be reduced to a single cation-release time scale that describes the fractional rate at which cations are released to solution by mineral dissolution, show sufficiently systematic behavior as a function of pH, fluid flow rate, and time that the rates of mineralization can be estimated with reasonable certainty. The rate of mineralization depends on both the abundance (determined by the reservoir rock mineralogy) and the rate at which cations are released from silicate minerals by dissolution into pore fluid that has been acidified with dissolved CO 2 . Laboratory-measured rates and field observations give values spanning 8 to 10 orders of magnitude, but when they are evaluated in the context of a reservoir-scale reactive transport simulation, this range becomes much smaller. The reservoir scale simulations provide limits on the applicable conditions under which silicate mineral dissolution and subsequent carbonate mineral precipitation are likely to occur (pH 4.5 to 6, fluid flow velocity less than 5 m/year, and 50-100 years or more after the start of injection). These constraints lead to estimates of

Rate of radiocarbon retention onto calcite by isotope exchange

Energy Technology Data Exchange (ETDEWEB)

Lempinen, Janne; Lehto, Jukka [Helsinki Univ. (Finland). Lab. of Radiochemistry

2016-11-01

Radiocarbon ({sup 14}C) is a top priority class radionuclide associated with the long-term safety of spent nuclear fuel disposal. Dissolved inorganic radiocarbon can be retained in bedrock via isotope exchange with calcite (CaCO{sub 3}) at solubility equilibrium with groundwater. In the present study, the rate of the isotope exchange process was investigated on synthetic calcite using batch experiments. Experiments were performed in solutions with a calcium concentration of 0.0002-0.1 M, including two synthetic reference groundwaters. The radiocarbon activity in the solutions decreased exponentially as a function of time, thus following first-order kinetics. The rate of isotope exchange was quantified from an exponential fit to the activity data over time. The rate of radiocarbon retention increased as a function of the calcium activity. The isotope exchange half-life was only 4.3 days at calcium ion activities over 0.01. This half-life is very much shorter than the half-life of {sup 14}C or the time scale of groundwater movements; consequently calcite can effectively retain radiocarbon from brackish and saline groundwaters.

Rate of radiocarbon retention onto calcite by isotope exchange

International Nuclear Information System (INIS)

Lempinen, Janne; Lehto, Jukka

2016-01-01

Radiocarbon ( 14 C) is a top priority class radionuclide associated with the long-term safety of spent nuclear fuel disposal. Dissolved inorganic radiocarbon can be retained in bedrock via isotope exchange with calcite (CaCO 3 ) at solubility equilibrium with groundwater. In the present study, the rate of the isotope exchange process was investigated on synthetic calcite using batch experiments. Experiments were performed in solutions with a calcium concentration of 0.0002-0.1 M, including two synthetic reference groundwaters. The radiocarbon activity in the solutions decreased exponentially as a function of time, thus following first-order kinetics. The rate of isotope exchange was quantified from an exponential fit to the activity data over time. The rate of radiocarbon retention increased as a function of the calcium activity. The isotope exchange half-life was only 4.3 days at calcium ion activities over 0.01. This half-life is very much shorter than the half-life of 14 C or the time scale of groundwater movements; consequently calcite can effectively retain radiocarbon from brackish and saline groundwaters.

Photosynthetic pigments and gas exchange in castor bean under conditions of above the optimal temperature and high CO2

Directory of Open Access Journals (Sweden)

Fabiola França Silva

2015-08-01

Full Text Available The castor bean plant, a Euphorbiaceae oil seed C3-metabolism rustic and drought-resistant plant, is cultivated in a wide range of environments due to its good adaptive capacity. However, given the current environmental changes, many biochemical and physiological impacts may affect the productivity of important crops, such as castor bean. This work aimed to evaluate the impacts of the castor bean gas exchange in response to high temperature and increased CO2concentration.Our experiment was conducted in a phytotron located at Embrapa Algodão in 2010. We adopted a completely randomized design, with four treatments in a factorial combination of two temperatures (30/20 and 37/30°C and two CO2 levels (400 and 800 mmol L-1; four replications were performed, obtained in five surveys over the growth cycle, for a total of 80 sample units. An infrared gas analyzer (IRGA - Infra Red Gas Analyzer was used for the quantification of the photosynthetic rate, stomatal conductance and transpiration. An increase in the atmospheric CO2 concentration and temperature negatively affected the physiology of the castor bean plants, decreasing the net rate of photosynthesis, transpiration and stomatal conductance.

Dynamics of oil price, precious metal prices, and exchange rate

International Nuclear Information System (INIS)

Sari, Ramazan; Soytas, Ugur; Hammoudeh, Shawkat

2010-01-01

This study examines the co-movements and information transmission among the spot prices of four precious metals (gold, silver, platinum, and palladium), oil price, and the US dollar/euro exchange rate. We find evidence of a weak long-run equilibrium relationship but strong feedbacks in the short run. The spot precious metal markets respond significantly (but temporarily) to a shock in any of the prices of the other metal prices and the exchange rate. Furthermore, we discover some evidence of market overreactions in the palladium and platinum cases as well as in the exchange rate market. In conclusion, whether there are overreactions and re-adjustments or not, investors may diversify at least a portion of the risk away by investing in precious metals, oil, and the euro. Policy implications are provided. (author)

The evolutionary synchronization of the exchange rate system in ASEAN+6

Science.gov (United States)

Feng, Xiaobing; Hu, Haibo; Wang, Xiaofan

2010-12-01

Although there are extensive researches on the behavior of the world currency network, the complexity of the Asian regional currency system is not well understood regardless of its importance. Using daily exchange rates this paper examines exchange rate co-movements in the region before and after the China exchange rate reform. It was found that the correlation between Asian currencies and the US Dollar, the previous regional key currency has become weaker and intra-Asia interactions have increased. Cross sample entropy and cross entropy approaches are also applied to examine the synchrony behavior among the Asian currencies. The study also shows that the Asian exchange rate markets featured are neither stochastic nor efficient. These findings may shed some light on the in-depth understanding of collective behaviors in a regional currency network; they will also lay a theoretical foundation for further policy formulation in Asian currency integration.

The tail index of exchange rate returns

NARCIS (Netherlands)

C.G. Koedijk (Kees); M. Schafgans (Marcia); C.G. de Vries (Casper)

1990-01-01

textabstractIn the literature on the empirical distribution of foreign exchange rates there is now consensus that exchange rate yields are fat-tailed. Three problems, however, persist: (1) Which class of distribution functions is most appropriate? (2) Are the parameters of the distribution invariant

Exchange rate regulation, the behavior of exchange rates, and macroeconomic stability in Brazil

Directory of Open Access Journals (Sweden)

Francisco Eduardo Pires de Souza

2011-12-01

Full Text Available In the last two decades an entirely new set of rules governing the foreign exchange transactions was established in Brazil, substituting for the framework inherited from the 1930s. Foreign exchange controls were dismantled and a floating exchange rate regime replaced different forms of peg. In this paper we argue that although successful by comparison to previous experiences, the current arrangement has important flaws that should be addressed. We discuss how it first led to high volatility and extremely high interest rates, which, when overcome, gave way to a long lasting appreciation of the real exchange rate with adverse consequences to industry.

Assessing filtering of mountaintop CO2 mole fractions for application to inverse models of biosphere-atmosphere carbon exchange

Directory of Open Access Journals (Sweden)

S. L. Heck

2012-02-01

Full Text Available There is a widely recognized need to improve our understanding of biosphere-atmosphere carbon exchanges in areas of complex terrain including the United States Mountain West. CO2 fluxes over mountainous terrain are often difficult to measure due to unusual and complicated influences associated with atmospheric transport. Consequently, deriving regional fluxes in mountain regions with carbon cycle inversion of atmospheric CO2 mole fraction is sensitive to filtering of observations to those that can be represented at the transport model resolution. Using five years of CO2 mole fraction observations from the Regional Atmospheric Continuous CO2 Network in the Rocky Mountains (Rocky RACCOON, five statistical filters are used to investigate a range of approaches for identifying regionally representative CO2 mole fractions. Test results from three filters indicate that subsets based on short-term variance and local CO2 gradients across tower inlet heights retain nine-tenths of the total observations and are able to define representative diel variability and seasonal cycles even for difficult-to-model sites where the influence of local fluxes is much larger than regional mole fraction variations. Test results from two other filters that consider measurements from previous and following days using spline fitting or sliding windows are overly selective. Case study examples showed that these windowing-filters rejected measurements representing synoptic changes in CO2, which suggests that they are not well suited to filtering continental CO2 measurements. We present a novel CO2 lapse rate filter that uses CO2 differences between levels in the model atmosphere to select subsets of site measurements that are representative on model scales. Our new filtering techniques provide guidance for novel approaches to assimilating mountain-top CO2 mole fractions in carbon cycle inverse models.

Effective Exchange Rate Classifications and Growth

OpenAIRE

Justin M. Dubas; Byung-Joo Lee; Nelson C. Mark

2005-01-01

We propose an econometric procedure for obtaining de facto exchange rate regime classifications which we apply to study the relationship between exchange rate regimes and economic growth. Our classification method models the de jure regimes as outcomes of a multinomial logit choice problem conditional on the volatility of a country's effective exchange rate, a bilateral exchange rate and international reserves. An `effective' de facto exchange rate regime classification is then obtained by as...

The Effect of RMB Exchange Rate Volatility on Import and Export Trade in China

OpenAIRE

Wanhui Jiang

2014-01-01

The exchange rate volatility always plays a key role in import and export trade. This paper investigates the effect of nominal RMB exchange rate volatility on economic growth in China from 1981 to 2012. Through the ADF stationary test, the co-integration test, and the associated econometric model and the empirical analysis, the paper concludes that in the long run, exchange rate change has a positive impact on import and export trade. Therefore, it is necessary to take relevant policies and m...

Generation rate of carbon monoxide from CO2 arc welding.

Science.gov (United States)

Ojima, Jun

2013-01-01

CO poisoning has been a serious industrial hazard in Japanese workplaces. Although incomplete combustion is the major cause of CO generation, there is a risk of CO poisoning during some welding operations. The aim of the present study was to evaluate the generation rate of CO from CO2 arc welding under controlled laboratory conditions and estimate the ventilation requirements for the prevention of CO poisoning. Bead on plate welding was carried out with an automatic welding robot on a rolled steel base metal under several conditions. The concentration of emitted CO from the welding was measured by a real-time CO monitor in a well-ventilated laboratory that was free from ambient CO contamination. The generation rate of CO was obtained from the three measurements-the flow rate of the welding exhaust gas, CO concentration in the exhaust gas and the arcing time. Then the ventilation requirement to prevent CO poisoning was calculated. The generation rate of CO was found to be 386-883 ml/min with a solid wire and 331-1,293 ml/min with a flux cored wire respectively. It was found that the CO concentration in a room would be maintained theoretically below the OSHA PEL (50 ppm) providing the ventilation rate in the room was 6.6-25.9 m3/min. The actual ventilation requirement was then estimated to be 6.6-259 m3/min considering incomplete mixing. In order to prevent CO poisoning, some countermeasures against gaseous emission as well as welding fumes should be taken eagerly.

Exchange rate smoothing in Hungary

OpenAIRE

Karádi, Péter

2005-01-01

The paper proposes a structural empirical model capable of examining exchange rate smoothing in the small, open economy of Hungary. The framework assumes the existence of an unobserved and changing implicit exchange rate target. The central bank is assumed to use interest rate policy to obtain this preferred rate in the medium term, while market participants are assumed to form rational expectations about this target and influence exchange rates accordingly. The paper applies unobserved varia...

Modeling and sizing of the heat exchangers of a new supercritical CO{sub 2} Brayton power cycle for energy conversion for fusion reactors

Energy Technology Data Exchange (ETDEWEB)

Serrano, I.P.; Cantizano, A.; Linares, J.I., E-mail: linares@upcomillas.es; Moratilla, B.Y.

2014-10-15

Highlights: •We propose a procedure to model the heat exchangers of a S-CO2 Brayton power cycle. •Discretization in sub-heat exchangers is performed due to complex behavior of CO{sub 2}. •Different correlations have been tested, verifying them with CFD when necessary. •Obtained sizes are agree with usual values of printed circuit heat exchangers. -- Abstract: TECNO{sub F}US is a research program financed by the Spanish Government to develop technologies related to a dual-coolant (He/Pb–Li) breeding blanket design concept including the auxiliary systems for a future power reactor (DEMO). One of the main issues of this program is the optimization of heat recovery from the reactor and its conversion into electrical power. This paper is focused on the methodology employed for the design and sizing of all the heat exchangers of the supercritical CO{sub 2} Brayton power cycle (S-CO2) proposed by the authors. Due to the large pressure difference between the fluids, and also to their compactness, Printed Circuit Heat Exchangers (PCHE) are suggested in literature for these type of cycles. Because of the complex behavior of CO{sub 2}, their design is performed by a numerical discretization into sub-heat exchangers, thus a higher precision is reached when the thermal properties of the fluids vary along the heat exchanger. Different empirical correlations for the pressure drop and the Nusselt number have been coupled and assessed. The design of the precooler (PC) and the low temperature recuperator (LTR) is also verified by simulations using CFD because of the near-critical behavior of CO{sub 2}. The size of all of the heat exchangers of the cycle have been assessed.

On the accuracy of instantaneous gas exchange rates, energy expenditure and respiratory quotient calculations obtained from indirect whole room calorimetry

International Nuclear Information System (INIS)

Gribok, Andrei; Rumpler, William; Hoyt, Reed; Buller, Mark

2013-01-01

This paper analyzes the accuracy of metabolic rate calculations performed in the whole room indirect calorimeter using the molar balance equations. The equations are treated from the point of view of cause–effect relationship where the gaseous exchange rates representing the unknown causes need to be inferred from a known, noisy effect—gaseous concentrations. Two methods of such inference are analyzed. The first method is based on the previously published regularized deconvolution of the molar balance equation and the second one, proposed in this paper, relies on regularized differentiation of gaseous concentrations. It is found that both methods produce similar results for the absolute values of metabolic variables and their accuracy. The uncertainty for O 2 consumption rate is found to be 7% and for CO 2 production-–3.2%. The uncertainties in gaseous exchange rates do not depend on the absolute values of O 2 consumption and CO 2 production. In contrast, the absolute uncertainty in respiratory quotient is a function of the gaseous exchange rates and varies from 9.4% during the night to 2.3% during moderate exercise. The uncertainty in energy expenditure was found to be 5.9% and independent of the level of gaseous exchange. For both methods, closed form analytical formulas for confidence intervals are provided allowing quantification of uncertainty for four major metabolic variables in real world studies. (paper)

On the accuracy of instantaneous gas exchange rates, energy expenditure and respiratory quotient calculations obtained from indirect whole room calorimetry.

Science.gov (United States)

Gribok, Andrei; Hoyt, Reed; Buller, Mark; Rumpler, William

2013-06-01

This paper analyzes the accuracy of metabolic rate calculations performed in the whole room indirect calorimeter using the molar balance equations. The equations are treated from the point of view of cause-effect relationship where the gaseous exchange rates representing the unknown causes need to be inferred from a known, noisy effect-gaseous concentrations. Two methods of such inference are analyzed. The first method is based on the previously published regularized deconvolution of the molar balance equation and the second one, proposed in this paper, relies on regularized differentiation of gaseous concentrations. It is found that both methods produce similar results for the absolute values of metabolic variables and their accuracy. The uncertainty for O2 consumption rate is found to be 7% and for CO2 production--3.2%. The uncertainties in gaseous exchange rates do not depend on the absolute values of O2 consumption and CO2 production. In contrast, the absolute uncertainty in respiratory quotient is a function of the gaseous exchange rates and varies from 9.4% during the night to 2.3% during moderate exercise. The uncertainty in energy expenditure was found to be 5.9% and independent of the level of gaseous exchange. For both methods, closed form analytical formulas for confidence intervals are provided allowing quantification of uncertainty for four major metabolic variables in real world studies.

Research on economics and CO2 emission of magnetic and inertial fusion reactors

International Nuclear Information System (INIS)

Mori, Kenjiro; Yamazaki, Kozo; Oishi, Tetsutarou; Arimoto, Hideki; Shoji, Tatsuo

2011-01-01

An economical and environment-friendly fusion reactor system is needed for the realization of attractive power plants. Comparative system studies have been done for magnetic fusion energy (MFE) reactors, and been extended to include inertial fusion energy (IFE) reactors by Physics Engineering Cost (PEC) system code. In this study, we have evaluated both tokamak reactor (TR) and IFE reactor (IR). We clarify new scaling formulas for cost of electricity (COE) and CO 2 emission rate with respect to key design parameters. By the scaling formulas, it is clarified that the plant availability and operation year dependences are especially dominant for COE. On the other hand, the parameter dependences of CO 2 emission rate is rather weak than that of COE. This is because CO 2 emission percentage from manufacturing the fusion island is lower than COE percentage from that. Furthermore, the parameters dependences for IR are rather weak than those for TR. Because the CO 2 emission rate from manufacturing the laser system to be exchanged is very large in comparison with CO 2 emission rate from TR blanket exchanges. (author)

Exchange Rate Policy in Philippine Development

OpenAIRE

Bautista, Romeo M.

2003-01-01

This paper examines the conduct of exchange rate policy in the Philippines since the early 1980s, paying particular attention to the influence of exchange rate adjustments on relative production incentives. While primary interest is in the exchange rate regime and its incentive effects, the role of trade policy has to be simultaneously analyzed in view of its influence on the conduct of exchange rate policy as well as its direct effect on the real exchange rate. Moreover, there are analytical...

Water availability drives gas exchange and growth of trees in northeastern US, not elevated CO2 and reduced acid deposition.

Science.gov (United States)

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.

Kinetic bottlenecks to chemical exchange rates for deep-sea animals - Part 2: Carbon Dioxide

Science.gov (United States)

Hofmann, A. F.; Peltzer, E. T.; Brewer, P. G.

2013-04-01

Increased ocean acidification from fossil fuel CO2 invasion, from temperature-driven changes in respiration, and from possible leakage from sub-seabed geologic CO2 disposal has aroused concern over the impacts of elevated CO2 concentrations on marine life. Discussion of these impacts has so far focused only on changes in the oceanic bulk fluid properties (ΔpH, Δ[∑ CO2], etc.) as the critical variable and with a major focus on carbonate shell formation. Here we describe the rate problem for animals that must export CO2 at about the same rate at which O2 is consumed. We analyse the basic properties controlling CO2 export within the diffusive boundary layer around marine animals in an ocean changing in temperature (T) and CO2 concentration in order to compare the challenges posed by O2 uptake under stress with the equivalent problem of CO2 expulsion. The problem is more complex than that for a non-reactive gas, since with CO2 the influence of the seawater carbonate acid-base system needs to be considered. These reactions significantly facilitate CO2 efflux compared to O2 intake at equal temperature, pressure and fluid flow rate under typical oceanic concentrations. The effect of these reactions can be described by an enhancement factor, similar to that widely used for CO2 invasion at the sea surface. While organisms do need to actively regulate flow over their surface to thin the boundary layer to take up enough O2, this seems to be not necessary to facilitate CO2 efflux. Instead, the main impacts of rising oceanic CO2 will most likely be those associated with classical ocean acidification science. Regionally, as with O2, the combination of T, P and pH/pCO2 creates a zone of maximum CO2 stress at around 1000 m depth.

The effect of light level, CO2 flow rate, and anesthesia on the stress response of mice during CO2 euthanasia.

Science.gov (United States)

Powell, Karin; Ethun, Kelly; Taylor, Douglas K

2016-09-21

Euthanasia protocols are designed to mitigate the stress experienced by animals, and an environment that induces minimal stress helps achieve that goal. A protocol that is efficient and practical in a typical animal research facility is also important. Light intensity, isoflurane, and CO2 flow rate were studied for their impact on the stress response of mice during CO2 euthanasia. Behavior was observed and scored during euthanasia and serum corticosterone was measured immediately after death. Unsurprisingly, animals euthanized with a high-flow rate of CO2 became unconscious in the least amount of time, while animals euthanized with a low-flow rate required the most time to reach unconsciousness. There was a significant increase in anxious behaviors in animals in the isoflurane group (F1,12 = 6.67, P = 0.024), the high-flow rate CO2 group (F1,12 = 10.24, P = 0.007), and bright chamber group (F1,12 = 7.27, P = 0.019). Serum corticosterone was highest in the isoflurane group (124.72 ± 83.98 ng/ml), however there was no significant difference in corticosterone levels observed for the other study variables of light and flow-rate. A darkened chamber and low CO2 flow rates help to decrease stress experienced during CO2 euthanasia, while the use of isoflurane was observed to increase the stress response during euthanasia.

Exchange Rate Reform Policies and Trade Balances in Nigeria ...

African Journals Online (AJOL)

This paper investigates the effect of the exchange rate on the trade balance in Nigeria between 1970 and 2012. Annual data were collected from the Central Bank of Nigeria's Statistical Bulletin, and World Development Indicator of the World Bank. Co-integrating and Error Correcting Method were used for this estimation.

Inferring CO2 Fluxes from OCO-2 for Assimilation into Land Surface Models to Calculate Net Ecosystem Exchange

Science.gov (United States)

Prouty, R.; Radov, A.; Halem, M.; Nearing, G. S.

2016-12-01

Investigations of mid to high latitude atmospheric CO2 show a growing seasonal amplitude. Land surface models poorly predict net ecosystem exchange (NEE) and are unable to substantiate these sporadic observations. An investigation of how the biosphere has reacted to changes in atmospheric CO2 is essential to our understanding of potential climate-vegetation feedbacks. A global, seasonal investigation of CO2-flux is then necessary in order to assimilate into land surface models for improving the prediction of annual NEE. The Atmospheric Radiation Measurement program (ARM) of DOE collects CO2-flux measurements (in addition to CO2 concentration and various other meteorological quantities) at several towers located around the globe at half hour temporal frequencies. CO2-fluxes are calculated via the eddy covariance technique, which utilizes CO2-densities and wind velocities to calculate CO2-fluxes. The global coverage of CO2 concentrations as provided by the Orbiting Carbon Observatory (OCO-2) provide satellite-derived CO2 concentrations all over the globe. A framework relating the satellite-inferred CO2 concentrations collocated with the ground-based ARM as well as Ameriflux stations would enable calculations of CO2-fluxes far from the station sites around the entire globe. Regression techniques utilizing deep-learning neural networks may provide such a framework. Additionally, meteorological reanalysis allows for the replacement of the ARM multivariable meteorological variables needed to infer the CO2-fluxes. We present the results of inferring CO2-fluxes from OCO-2 CO2 concentrations for a two year period, Sept. 2014- Sept. 2016 at the ARM station located near Oklahoma City. A feed-forward neural network (FFNN) is used to infer relationships between the following data sets: F([ARM CO2-density], [ARM Meteorological Data]) = [ARM CO2-Flux] F([OCO-2 CO2-density],[ARM Meteorological Data]) = [ARM CO2-Flux] F([ARM CO2-density],[Meteorological Reanalysis]) = [ARM CO2-Flux

CO2 AND O3 ALTER PHOTOSYNTHESIS AND WATER VAPOR EXCHANGE FOR PINUS PONDEROSA NEEDLES

Science.gov (United States)

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...

CO 2 adsorption in mono-, di- and trivalent cation-exchanged metal-organic frameworks: A molecular simulation study

KAUST Repository

Chen, Yifei

2012-02-28

A molecular simulation study is reported for CO 2 adsorption in rho zeolite-like metal-organic framework (rho-ZMOF) exchanged with a series of cations (Na +, K +, Rb +, Cs +, Mg 2+, Ca 2+, and Al 3+). The isosteric heat and Henry\\'s constant at infinite dilution increase monotonically with increasing charge-to-diameter ratio of cation (Cs + < Rb + < K + < Na + < Ca 2+ < Mg 2+ < Al 3+). At low pressures, cations act as preferential adsorption sites for CO 2 and the capacity follows the charge-to-diameter ratio. However, the free volume of framework becomes predominant with increasing pressure and Mg-rho-ZMOF appears to possess the highest saturation capacity. The equilibrium locations of cations are observed to shift slightly upon CO 2 adsorption. Furthermore, the adsorption selectivity of CO 2/H 2 mixture increases as Cs + < Rb + < K + < Na + < Ca 2+ < Mg 2+ ≈ Al 3+. At ambient conditions, the selectivity is in the range of 800-3000 and significantly higher than in other nanoporous materials. In the presence of 0.1% H 2O, the selectivity decreases drastically because of the competitive adsorption between H 2O and CO 2, and shows a similar value in all of the cation-exchanged rho-ZMOFs. This simulation study provides microscopic insight into the important role of cations in governing gas adsorption and separation, and suggests that the performance of ionic rho-ZMOF can be tailored by cations. © 2012 American Chemical Society.

Efficiencies of subcritical and transcritical CO2 inverse cycles with and without an internal heat exchanger

International Nuclear Information System (INIS)

Zhang, F.Z.; Jiang, P.X.; Lin, Y.S.; Zhang, Y.W.

2011-01-01

An internal heat exchanger (IHX) is often used to improve the coefficient of performance (COP) of CO 2 inverse cycles. This paper presents a detailed analysis of the IHX's effect in CO 2 inverse cycles and finds suitable operating conditions for the IHX from a thermodynamic performance point of view. The results indicate that the COP is slightly reduced by an IHX in a CO 2 subcritical inverse cycle, so an IHX is not justified. However, for transcritical CO 2 inverse cycles, the compressor discharge pressures and CO 2 gas cooler outlet temperatures both have significant impacts on system performance. The analysis results for transcritical CO 2 inverse cycles show that a transition discharge pressure and a transition CO 2 gas cooler outlet temperature are objective existence above which the IHX improves the cycle performance. - Research highlights: → Find suitable operating conditions for the IHX. → Above transition CO2 gas cooler outlet temperature IHX improves cycle performance. → The IHX is not very useful for optimized space heating and refrigerating cycles.

Modeling inflation rates and exchange rates in Ghana: application of multivariate GARCH models.

Science.gov (United States)

Nortey, Ezekiel Nn; Ngoh, Delali D; Doku-Amponsah, Kwabena; Ofori-Boateng, Kenneth

2015-01-01

This paper was aimed at investigating the volatility and conditional relationship among inflation rates, exchange rates and interest rates as well as to construct a model using multivariate GARCH DCC and BEKK models using Ghana data from January 1990 to December 2013. The study revealed that the cumulative depreciation of the cedi to the US dollar from 1990 to 2013 is 7,010.2% and the yearly weighted depreciation of the cedi to the US dollar for the period is 20.4%. There was evidence that, the fact that inflation rate was stable, does not mean that exchange rates and interest rates are expected to be stable. Rather, when the cedi performs well on the forex, inflation rates and interest rates react positively and become stable in the long run. The BEKK model is robust to modelling and forecasting volatility of inflation rates, exchange rates and interest rates. The DCC model is robust to model the conditional and unconditional correlation among inflation rates, exchange rates and interest rates. The BEKK model, which forecasted high exchange rate volatility for the year 2014, is very robust for modelling the exchange rates in Ghana. The mean equation of the DCC model is also robust to forecast inflation rates in Ghana.

Mathematical Modelling of Arctic Polygonal Tundra with Ecosys: 2. Microtopography Determines How CO2 and CH4 Exchange Responds to Changes in Temperature and Precipitation

Science.gov (United States)

Grant, R. F.; Mekonnen, Z. A.; Riley, W. J.; Arora, B.; Torn, M. S.

2017-12-01

Differences of surface elevation in arctic polygonal landforms cause spatial variation in soil water contents (θ), active layer depths (ALD), and thereby in CO2 and CH4 exchange. Here we test hypotheses in ecosys for topographic controls on CO2 and CH4 exchange in trough, rim, and center features of low- and flat-centered polygons (LCP and FCP) against chamber and eddy covariance (EC) measurements during 2013 at Barrow, Alaska. Larger CO2 influxes and CH4 effluxes were measured with chambers and modeled with ecosys in LCPs than in FCPs and in lower features (troughs) than in higher (rims) within LCPs and FCPs. Spatially aggregated CO2 and CH4 fluxes from ecosys were significantly correlated with EC flux measurements. Lower features were modeled as C sinks (52-56 g C m-2 yr-1) and CH4 sources (4-6 g C m-2 yr-1), and higher features as near C neutral (-2-15 g C m-2 yr-1) and CH4 neutral (0.0-0.1 g C m-2 yr-1). Much of the spatial and temporal variations in CO2 and CH4 fluxes were modeled from topographic effects on water and snow movement and thereby on θ, ALD, and soil O2 concentrations. Model results forced with meteorological data from 1981 to 2015 indicated increasing net primary productivity in higher features and CH4 emissions in some lower and higher features since 2008, attributed mostly to recent rises in precipitation. Small-scale variation in surface elevation causes large spatial variation of greenhouse gas (GHG) exchanges and therefore should be considered in estimates of GHG exchange in polygonal landscapes.

Structural assessment of intermediate printed circuit heat exchanger for sodium-cooled fast reactor with supercritical CO2 cycle

International Nuclear Information System (INIS)

Lee, Youho; Lee, Jeong Ik

2014-01-01

Highlights: • We numerically model PCHE stress arising from pressure, and thermal loadings. • Stress levels are the highest around S-CO 2 channels, due to high pressure of S-CO 2 . • The conventional analytic models for PCHE underestimate actual stress levels. • Plasticity sufficiently lowers stress levels at channel tips. • PCHE for SFR-SCO 2 is anticipated to assure compliance with ASME design standards. - Abstract: Structural integrity of intermediate Printed Circuit Heat Exchanger (PCHE) for Sodium-cooled Fast Reactor (SFR) attached to Supercritical CO 2 (S-CO 2 ) is investigated. ANSYS-Mechanical was used to simulate stress fields of representative PCHE channels, with temperature fields imported from FLUENT simulation. Mechanical stress induced by pressure loading is found to be the primary source of stress. As plasticity sufficiently lowers local stress concentration at PCHE channel tips, PCHE type intermediate heat exchangers made of SS316 are anticipated to reliably assure compliance with design standards prescribed in the ASME standards, thanks to the structure temperature that is below the effective creep inducing point. The actual life time of PCHE for SFR-SCO 2 is likely to be affected by mechanical behavior change of SS316 with reactions with S-CO 2 and fatigue

CO2 sensing and CO2 regulation of stomatal conductance: advances and open questions

Science.gov (United States)

Engineer, Cawas; Hashimoto-Sugimoto, Mimi; Negi, Juntaro; Israelsson-Nordstrom, Maria; Azoulay-Shemer, Tamar; Rappel, Wouter-Jan; Iba, Koh; Schroeder, Julian

2015-01-01

Guard cells form epidermal stomatal gas exchange valves in plants and regulate the aperture of stomatal pores in response to changes in the carbon dioxide (CO2) concentration in leaves. Moreover, the development of stomata is repressed by elevated CO2 in diverse plant species. Evidence suggests that plants can sense CO2 concentration changes via guard cells and via mesophyll tissues in mediating stomatal movements. We review new discoveries and open questions on mechanisms mediating CO2-regulated stomatal movements and CO2 modulation of stomatal development, which together function in CO2-regulation of stomatal conductance and gas exchange in plants. Research in this area is timely in light of the necessity of selecting and developing crop cultivars which perform better in a shifting climate. PMID:26482956

Measurement of the Exchange Rate of Waters of Hydration in Elastin by 2D T(2)-T(2) Correlation Nuclear Magnetic Resonance Spectroscopy.

Science.gov (United States)

Sun, Cheng; Boutis, Gregory S

2011-02-28

We report on the direct measurement of the exchange rate of waters of hydration in elastin by T(2)-T(2) exchange spectroscopy. The exchange rates in bovine nuchal ligament elastin and aortic elastin at temperatures near, below and at the physiological temperature are reported. Using an Inverse Laplace Transform (ILT) algorithm, we are able to identify four components in the relaxation times. While three of the components are in good agreement with previous measurements that used multi-exponential fitting, the ILT algorithm distinguishes a fourth component having relaxation times close to that of free water and is identified as water between fibers. With the aid of scanning electron microscopy, a model is proposed allowing for the application of a two-site exchange analysis between any two components for the determination of exchange rates between reservoirs. The results of the measurements support a model (described elsewhere [1]) wherein the net entropy of bulk waters of hydration should increase upon increasing temperature in the inverse temperature transition.

Detection Test for Leakage of CO2 into Sodium Loop

International Nuclear Information System (INIS)

Park, Sun Hee; Wi, Myung-Hwan; Min, Jae Hong

2015-01-01

This report is about the facility for the detection test for leakage of CO 2 into sodium loop. The facility for the detection test for leakage of CO 2 into sodium loop was introduced. The test will be carried out. Our experimental results are going to be expected to be used for approach methods to detect CO 2 leaking into sodium in heat exchangers. A sodium-and-carbon dioxide (Na-CO 2 ) heat exchanger is one of the key components for the supercritical CO 2 Brayton cycle power conversion system of sodium-cooled fast reactors (SFRs). A printed circuit heat exchanger (PCHE) is considered for the Na-CO 2 heat exchanger, which is known to have potential for reducing the volume occupied by the exchangers compared to traditional shell-and-tube heat exchangers. Among various issues about the Na- CO 2 exchanger, detection of CO 2 leaking into sodium in the heat exchanger is most important thing for its safe operation. It is known that reaction products from sodium and CO 2 such as sodium carbonate (Na 2 CO 3 ) and amorphous carbon are hardly soluble in sodium, which cause plug sodium channels. Detection technique for Na 2 CO 3 in sodium loop has not been developed yet. Therefore, detection of CO 2 and CO from reaction of sodium and CO 2 are proper to detect CO 2 leakage into sodium loop

Exchange Rate Fluctuation and the Nigeria Economic Growth

Directory of Open Access Journals (Sweden)

Lawal Adedoyin Isola

2016-11-01

Full Text Available The aim of this study is to investigate the impact of exchange rate fluctuation on economic growth in Nigeria within the context of four profound theories: purchasing power parity; monetary model of exchange rates; the portfolio balance approach; and the optimal currency area theory. Data was collected from the CBN statistical bulletin in Nigeria from 2003– 2013and the Autoregressive Distributed Lag (ARDL model was employed to estimate the model. In the model, real GDP (RGDP was used as the proxy for economic growth while Inflation rate (IF, Exchange rate (EXC, Interest rate (INT and Money Supply(M2 as proxies for other macroeconomic variables. The empirical results show that exchange rate fluctuation has no effect on economic growth in the long run though a short run relationship exist between the two. Based on these findings, this paper recommends that the Central bank for policy purposes should ensure that stern foreign exchange control policies are put in place in order to help in appropriate determination of the value of the exchange rate. This will in the long run help to strengthen the value of the Naira.

Adsorption Isotherms of Cs+, Co2+, Zn2+ and Eu3+ on Zirconium Vanadate Ion-Exchanger

International Nuclear Information System (INIS)

Shady, S.A.; El-Ashery, S.M.; El-Naggar, I.M.

2009-01-01

Zirconium vanadate had been prepared by the dropwise addition of 0.1 M sodium vanadate and 0.1 M zirconyl chloride by molar ratio of zirconium/vanadium 2. Exchange isotherms for Cs + /H + , Co 2+ /H + ,Zn 2+ /H + and Eu 3+ /H + have been determined at 25, 40 and 60 degree C. Besides, it was proved that cesium, cobalt, zinc and europium are chemically adsorbed. Moreover, the heat of adsorption of these ions on zirconium vanadate had been calculated and indicated that zirconium vanadate is of endothermic behavior towards these ions

CO 2 adsorption in mono-, di- and trivalent cation-exchanged metal-organic frameworks: A molecular simulation study

KAUST Repository

Chen, Yifei; Nalaparaju, Anjaiah; Eddaoudi, Mohamed; JIANG, Jianwen

2012-01-01

A molecular simulation study is reported for CO 2 adsorption in rho zeolite-like metal-organic framework (rho-ZMOF) exchanged with a series of cations (Na +, K +, Rb +, Cs +, Mg 2+, Ca 2+, and Al 3+). The isosteric heat and Henry's constant

Adsorption behaviour and kinetics of exchange of Zn2+ and Eu3+ ions on a composite ion exchanger

International Nuclear Information System (INIS)

Morcos, T.N.

2007-01-01

Equilibria and kinetics of exchange of both Zn2+ and Eu3+ ions on a composite ion-exchanger, cobalt hexacyanocobaltate (III) (CoHCC) incorporated in polyacrylonitrile (PAN), has been studied. The apparent capacity of CoHCC-PAN for Zn2+ and Eu3+ was determined and found to be 0.353 and 0.69 meq/g, respectively. The higher capacity for Eu3+ ions than that for Zn2+ ions is due to the higher electrostatic interaction strength of the higher charge ion with the surface. Freundlich and Langmiur adsorption isotherms were used to investigate solute (Zn2+ or Eu3+) exchange phenomenon at the liquid/solid interface. The results indicated that both Langmuir and Freundlich isotherms fit well for both Zn2+ and Eu3+. Sorption data have been also treated with the Dubinin-Radushkevich equation. The kinetics of Zn2+ or Eu3+ sorption on the composite seems to show that the reaction was proceed via two steps. The first one was fast and probably due to adsorption followed by a slow exchange reaction. In view of the data obtained on the effect of particle size and metal ion concentrations on the rate of exchange reaction, it is concluded that the mechanism for both ions was chemical control. Generally, it seems that there are two exchange sites chemically equivalent but present in pores of different sizes which lead to different degrees of dehydration of the ions sorbed on the two sites

Specific radioactivity of glycolate and photorespiration during 14CO2 assimilation at four different CO2 concentrations by sunflower and bean leaves

International Nuclear Information System (INIS)

Fock, H.; Klug, K.; Krampitz, M.J.

1979-01-01

Using an open gas-exchange system, the rates of apparent CO 2 uptake (APS), true CO 2 uptake (TIPS), CO 2 evolution in light (PR), and the relative specific radioactivity of photorespiration (RSA) by sunflower and bean leaves were measured at four different CO 2 concentrations. At the end of the 14 CO 2 assimilation period the leaves were killed and extract for the analysis of glycolic acid. The rate of PR was CO 2 independent at low and normal CO 2 concentrations but inreased at CO 2 concentrations above normal. The ratio of PR/TPS which declined with an increase in CO 2 was compatible with the ratio of vo/2vo of the RuBP-Carboxylase/Oxygenase reaction. At low and normal concentrations of CO 2 the concentration as well as the specific radioactivity of glycolic acid increased with an increase in CO 2 and the relative specific activity (RSA) of glycolic acid resembled the RSA of photorespiration. It was concluded that these results support the concept of RuBP-carboxylase/oxygenase regulating the fluxes of carbon via the photosynthetic carbon reduction and the glycolate pathway. (orig.) [de

Experimental study on CO2 frosting and clogging in a brazed plate heat exchanger for natural gas liquefaction process

Science.gov (United States)

Wu, Jitan; He, Tianbiao; Ju, Yonglin

2018-04-01

The plate-fin heat exchanger (PFHE), which has been widely used in natural gas liquefaction (LNG) industry at present, has some disadvantages such as being sensitive to the impurities in the feed gas, such as water, CO2 and H2S. Compared with the PFHE, the brazed plate heat exchanger (BPHE), which has been applied in some boil off gas (BOG) recycling LNG plants of small to middle size, has simpler inherent structure and higher impurity tolerance. In this study the BPHE is suggested to replace the PFHE to simplify or even omit the massive CO2 purification equipment for the LNG process. A set of experimental apparatus is designed and constructed to investigate the influence of the CO2 concentration of the natural gas on solid precipitation inside a typical BPHE meanly by considering the flow resistance throughout the LNG process. The results show that the maximum allowable CO2 concentration of the natural gas liquefied in the BPHE is two orders of magnitude higher than that in the PFHE under the same condition. In addition, the solid-liquid separation for the CO2 impurity is studied and the reasonable separating temperature is obtained. The solid CO2 should be separated below 135 K under the pressure of 3 MPa.

Can Exchange Rates Be Predicted?

OpenAIRE

Siriwutiset, Trin

2007-01-01

Foreign exchange rates produce significant impacts on both the macroeconomic and microeconomic scale. Countries� government and multinational companies have been seeking ways to stabilize the exchange rates for a few decades. However, there is no perfect consensus on methods to control and stabilize the exchange rates. In fact, there are several occasions in history where turbulence movements caused crisis in the economies. There are several factors that are identified by economis...

Leaching of 60 Co and 137 Cs from spent ion exchange resins in ...

Indian Academy of Sciences (India)

Cement; radioactive waste; composite; waste management. Abstract. The leaching rate of 60Co and 137Cs from the spent cation exchange resins in cement–bentonite matrix has been studied. The solidification matrix was a standard Portland cement mixed with 290–350 (kg/m3) spent cation exchange resins, with or ...

Characteristics of Atmosphere-Ocean CO2 Exchange due to Typhoon Activities over the East Asian Region

Science.gov (United States)

Lee, G.; Cho, C. H.; Lim, D. H.; Sun, M.; Lee, J.; Byun, Y. H.; Lee, J.

2014-12-01

Although the oceans are generally known as a net carbon sink in global sense, it is expected that CO₂release from oceans can occur locally depending on specific weather. This study addresses investigation of change in CO2 exchange between atmosphere and ocean due to typhoon activities, using "Carbon Tracker-Asia (CTA)". The CTA has constructed and managed at National Institute of Meteorological Research(NIMR) based on Carbon Tracker developed by NOAA. In order to examine effect of typhoon on change in air-sea CO2 exchange, we selected several cases which typhoon approached to Korean peninsula in the summertime and their tracks are similar to each other. Also, we analyzed difference between CO2 flux along typhoon tracks and other adjacent region not to be directly affected by typhoon in these cases. There is a difference in ocean fluxes around 15 gC/m²yr over strong typhoon areas compared to other areas. This difference varied with the wind speeds, the correlation coefficient between the ocean and the wind flux was found 0.7. Changes in carbon flux to affect the concentration of CO₂ in the atmosphere near surface instantly.

Exchange Rate Determinants in Russia; 1992-1993

OpenAIRE

Vincent Koen; Eric Meyermans

1994-01-01

This paper examines the evolution of the exchange rate of the ruble vis-à-vis the U.S. dollar from exchange rate unification, in July 1992, to the end of 1993. The expected and actual paths of the exchange rate are related to the exchange and trade regime and to the stance of financial and exchange rate policies. An econometric analysis based on weekly data is offered, which suggests that monetary factors have a significant impact on the short run behavior of the exchange rate.

North America's net terrestrial CO2 exchange with the atmosphere 1990-2009

Science.gov (United States)

King, A. W.; Andres, R. J.; Davis, K. J.; Hafer, M.; Hayes, D. J.; Huntzinger, D. N.; de Jong, B.; Kurz, W. A.; McGuire, A. D.; Vargas, R.; Wei, Y.; West, T. O.; Woodall, C. W.

2015-01-01

Scientific understanding of the global carbon cycle is required for developing national and international policy to mitigate fossil fuel CO2 emissions by managing terrestrial carbon uptake. Toward that understanding and as a contribution to the REgional Carbon Cycle Assessment and Processes (RECCAP) project, this paper provides a synthesis of net land-atmosphere CO2 exchange for North America (Canada, United States, and Mexico) over the period 1990-2009. Only CO2 is considered, not methane or other greenhouse gases. This synthesis is based on results from three different methods: atmospheric inversion, inventory-based methods and terrestrial biosphere modeling. All methods indicate that the North American land surface was a sink for atmospheric CO2, with a net transfer from atmosphere to land. Estimates ranged from -890 to -280 Tg C yr-1, where the mean of atmospheric inversion estimates forms the lower bound of that range (a larger land sink) and the inventory-based estimate using the production approach the upper (a smaller land sink). This relatively large range is due in part to differences in how the approaches represent trade, fire and other disturbances and which ecosystems they include. Integrating across estimates, "best" estimates (i.e., measures of central tendency) are -472 ± 281 Tg C yr-1 based on the mean and standard deviation of the distribution and -360 Tg C yr-1 (with an interquartile range of -496 to -337) based on the median. Considering both the fossil fuel emissions source and the land sink, our analysis shows that North America was, however, a net contributor to the growth of CO2 in the atmosphere in the late 20th and early 21st century. With North America's mean annual fossil fuel CO2 emissions for the period 1990-2009 equal to 1720 Tg C yr-1 and assuming the estimate of -472 Tg C yr-1 as an approximation of the true terrestrial CO2 sink, the continent's source : sink ratio for this time period was 1720:472, or nearly 4:1.

Exchange Rate Pass-Through in Turkey

OpenAIRE

Marco Rossi; Daniel Leigh

2002-01-01

In light of the strong correlation between exchange rate movements and domestic prices in Turkey, it is important to assess the impact of the exchange rate on domestic prices, in particular as Turkey moves to an inflation targeting regime. This paper uses a recursive vector autoregression model to investigate the impact of exchange rate movements on prices in Turkey. We find that (i) the impact of the exchange rate on prices is over after about a year, but is mostly felt in the first four mon...

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

Science.gov (United States)

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

2000-01-01

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

[Different NaCl-dependence of the circadian CO2-gas-exchange of some halophil growing coastal plants].

Science.gov (United States)

Treichel, Siegfried; Bauer, Peter

1974-03-01

CO 2 -exchange, diurnal changes in malate- and ion concentrations of the halophytes Carpobrotus edulis, Crithmum maritimum, Mesembryanthemum nodiflorum, Salicornia fruticosa, Suaeda maritima, and Trifolium fragiferum were investigated after culture at different NaCl concentrations. In Carp. edulis and Mes. nodiflorum the diurnal rhythm of CO 2 -exchange is in accordance with that of crassulacean acid metabolism (CAM), in Sal. fruticosa, Crithm. maritimum, Suaeda maritima, and Trif. fragiferum with that of Benson-Calvin metabolism (C 3 ). Malate concentration and CO 2 uptake in the sap latter group are not influenced. On the other hand, Carp. edulis and Mes. nodiflorum show an accumulation of malate during the night, which can be interpreted as a further indication of CAM.The two species most resistant to NaCl, Carp. edulis and Sal. fruticosa, greatly differ very much in their NaCl content. NaCl concentration in Salicornia is four times higher than in Carpobrotus.The different metabolic properties studied might be of ecological importance for the plants in their natural habitats. The effect of NaCl on metabolic processes is discussed.

Assessment of model estimates of land-atmosphere CO2 exchange across northern Eurasia

Science.gov (United States)

Rawlins, M.A.; McGuire, A.D.; Kimball, J.S.; Dass, P.; Lawrence, D.; Burke, E.; Chen, X.; Delire, C.; Koven, C.; MacDougall, A.; Peng, S.; Rinke, A.; Saito, K.; Zhang, W.; Alkama, R.; Bohn, T. J.; Ciais, P.; Decharme, B.; Gouttevin, I.; Hajima, T.; Ji, D.; Krinner, G.; Lettenmaier, D.P.; Miller, P.; Moore, J.C.; Smith, B.; Sueyoshi, T.

2015-01-01

A warming climate is altering land-atmosphere exchanges of carbon, with a potential for increased vegetation productivity as well as the mobilization of permafrost soil carbon stores. Here we investigate land-atmosphere carbon dioxide (CO2) cycling through analysis of net ecosystem productivity (NEP) and its component fluxes of gross primary productivity (GPP) and ecosystem respiration (ER) and soil carbon residence time, simulated by a set of land surface models (LSMs) over a region spanning the drainage basin of Northern Eurasia. The retrospective simulations cover the period 1960–2009 at 0.5° resolution, which is a scale common among many global carbon and climate model simulations. Model performance benchmarks were drawn from comparisons against both observed CO2 fluxes derived from site-based eddy covariance measurements as well as regional-scale GPP estimates based on satellite remote-sensing data. The site-based comparisons depict a tendency for overestimates in GPP and ER for several of the models, particularly at the two sites to the south. For several models the spatial pattern in GPP explains less than half the variance in the MODIS MOD17 GPP product. Across the models NEP increases by as little as 0.01 to as much as 0.79 g C m−2 yr−2, equivalent to 3 to 340 % of the respective model means, over the analysis period. For the multimodel average the increase is 135 % of the mean from the first to last 10 years of record (1960–1969 vs. 2000–2009), with a weakening CO2 sink over the latter decades. Vegetation net primary productivity increased by 8 to 30 % from the first to last 10 years, contributing to soil carbon storage gains. The range in regional mean NEP among the group is twice the multimodel mean, indicative of the uncertainty in CO2 sink strength. The models simulate that inputs to the soil carbon pool exceeded losses, resulting in a net soil carbon gain amid a decrease in residence time. Our analysis points to improvements in model

The foreign exchange rate rate exposure of nations

OpenAIRE

Entorf, Horst; Moebert, Jochen; Sonderhof, Katja

2007-01-01

Following the well-known approach by Adler and Dumas (1984) we evaluate the foreign exchange rate exposure of nations. Results based on data from 27 countries show that national foreign exchange rate exposures are significantly related to the current trade balance variables of corresponding economies.

EFECT OF FOREIGN EXCHANGE RATE FLUCTUATIONS ON NIGERIAN ECONOMY

Directory of Open Access Journals (Sweden)

Lawrence Olisaemeka UFOEZE

2018-03-01

Full Text Available This study investigated the effect of exchange rate fluctuations on Nigerian economy. The fixed and floating exchange eras were compared to know the exchange rate system in which the economy has fairly better. The time period covered was 1970 to 2012. The study employed the ordinary least square (OLS multiple regression technique for the analysis. The coefficient of determination (R2, F-test, t-test, beta and Durbin-Watson were used in the interpretation of the results. The resulted revealed that about 85% of the changes in macroeconomic indicators are explained in the fixed exchange era. In the floating exchange era, 99% was explained while the whole periods has 73% explanatory power, hence the floating exchange era (1986 to date is more effective in explaining economic trend in Nigeria. Also, exchange rate has significant positive effect on GDP during the fixed exchange rate era and negative effect the eras floating and all-time; inflation has insignificant negative effect on GDP during the fixed exchange era; significant effect in floating era and significant negative effect in the all-time period; money supply has insignificant negative effect GDP in fixed exchange era; and significant positive effect during the floating and all-time period; and oil revenue has significant positive effect on the GDP in all the exchange rate regimes (floating, fixed and all-time in Nigeria.  The study thus conclude that exchange rate movement is a good indicator for monitoring Nigerian economic growth. So far exchange rate has always been a key economic indicator for Nigeria. The floating exchange period has outperformed the fixed exchange rate in terms of contribution inflation, money supply and oil revenue to economic growth. This indicate that the floating exchange rate has been a better economic regime for sustainable economic growth in Nigeria. From the findings, it is evident that oil revenue has positive effect in Nigeria and has remained the mainstay

Gas exchange rates measured using a dual-tracer (SF6 and3he) method in the coastal waters of Korea

Science.gov (United States)

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.

Measurement of the exchange rate of waters of hydration in elastin by 2D T2-T2 correlation nuclear magnetic resonance spectroscopy

International Nuclear Information System (INIS)

Sun Cheng; Boutis, Gregory S

2011-01-01

We report on a direct measurement of the exchange rate of waters of hydration in elastin by T 2 -T 2 exchange spectroscopy. The exchange rates in bovine nuchal ligament elastin and aortic elastin at temperatures near, below and at the physiological temperature are reported here. Using an inverse Laplace transform (ILT) algorithm, we are able to identify four components in the relaxation times. While three of the components are in good agreement with previous measurements that used multi-exponential fitting, the ILT algorithm distinguishes a fourth component having relaxation times close to that of free water and is identified as water between fibers. With the aid of scanning electron microscopy, a model is proposed that allows for the application of a two-site exchange analysis between any two components for the determination of exchange rates between reservoirs. The results of the measurements support a model (described by Urry and Parker 2002 J. Muscle Res. Cell Motil. 23 543-59) wherein the net entropy of waters of hydration should increase with increasing temperature in the inverse temperature transition.

Real exchange rate misalignments

OpenAIRE

Terra, Maria Cristina T.; Valladares, Frederico Estrella Carneiro

2003-01-01

This paper characterizes episodes of real appreciations and depreciations for a sample of 85 countries, approximately from 1960 to 1998. First, the equilibrium real exchange rate series are constructed for each country using Goldfajn and Valdes (1999) methodology (cointegration with fundamentals). Then, departures from equilibrium real exchange rate (misalignments) are obtained, and a Markov Switching Model is used to characterize the misalignments series as stochastic autor...

The effect of carbonic anhydrase on the kinetics and equilibrium of the oxygen isotope exchange in the CO2-H2O system: Implications for δ18O vital effects in biogenic carbonates

Science.gov (United States)

Uchikawa, Joji; Zeebe, Richard E.

2012-10-01

Interpretations of the primary paleoceanographic information recorded in stable oxygen isotope values (δ18O) of biogenic CaCO3 can be obscured by disequilibrium effects. CaCO3 is often depleted in 18O relative to the δ18O values expected for precipitation in thermodynamic equilibrium with ambient seawater as a result of vital effects. Vital effects in δ18O have been explained in terms of the influence of fluid pH on the overall δ18O of the sum of dissolved inorganic carbon (DIC) species (often referred to as "pH model") and in terms of 18O depletion as a result of the kinetic effects associated with CO2 hydration (CO2 + H2O ↔ H2CO3 ↔ HCO3- + H+) and CO2 hydroxylation (CO2 + OH- ↔ HCO3-) in the calcification sites (so-called "kinetic model"). This study addresses the potential role of an enzyme, carbonic anhydrase (CA), that catalyzes inter-conversion of CO2 and HCO3- in relation to the underlying mechanism of vital effects. We performed quantitative inorganic carbonate precipitation experiments in order to examine the changes in 18O equilibration rate as a function of CA concentration. Experiments were performed at pH 8.3 and 8.9. These pH values are comparable to the average surface ocean pH and elevated pH levels observed in the calcification sites of some coral and foraminiferal species, respectively. The rate of uncatalyzed 18O exchange in the CO2-H2O system is governed by the pH-dependent DIC speciation and the kinetic rate constant for CO2 hydration and hydroxylation, which can be summarized by a simple mathematical expression. The results from control experiments (no CA addition) are in agreement with this expression. The results from control experiments also suggest that the most recently published kinetic rate constant for CO2 hydroxylation has been overestimated. When CA is present, the 18O equilibration process is greatly enhanced at both pH levels due to the catalysis of CO2 hydration by the enzyme. For example, the time required for 18O

The CarbonTracker Data Assimilation System for CO2 and δ13C (CTDAS-C13 v1.0): retrieving information on land-atmosphere exchange processes

Science.gov (United States)

van der Velde, Ivar R.; Miller, John B.; van der Molen, Michiel K.; Tans, Pieter P.; Vaughn, Bruce H.; White, James W. C.; Schaefer, Kevin; Peters, Wouter

2018-01-01

To improve our understanding of the global carbon balance and its representation in terrestrial biosphere models, we present here a first dual-species application of the CarbonTracker Data Assimilation System (CTDAS). The system's modular design allows for assimilating multiple atmospheric trace gases simultaneously to infer exchange fluxes at the Earth surface. In the prototype discussed here, we interpret signals recorded in observed carbon dioxide (CO2) along with observed ratios of its stable isotopologues 13CO2/12CO2 (δ13C). The latter is in particular a valuable tracer to untangle CO2 exchange from land and oceans. Potentially, it can also be used as a proxy for continent-wide drought stress in plants, largely because the ratio of 13CO2 and 12CO2 molecules removed from the atmosphere by plants is dependent on moisture conditions.The dual-species CTDAS system varies the net exchange fluxes of both 13CO2 and CO2 in ocean and terrestrial biosphere models to create an ensemble of 13CO2 and CO2 fluxes that propagates through an atmospheric transport model. Based on differences between observed and simulated 13CO2 and CO2 mole fractions (and thus δ13C) our Bayesian minimization approach solves for weekly adjustments to both net fluxes and isotopic terrestrial discrimination that minimizes the difference between observed and estimated mole fractions.With this system, we are able to estimate changes in terrestrial δ13C exchange on seasonal and continental scales in the Northern Hemisphere where the observational network is most dense. Our results indicate a decrease in stomatal conductance on a continent-wide scale during a severe drought. These changes could only be detected after applying combined atmospheric CO2 and δ13C constraints as done in this work. The additional constraints on surface CO2 exchange from δ13C observations neither affected the estimated carbon fluxes nor compromised our ability to match observed CO2 variations. The prototype presented

Exchange-rate forecasts and asymmetric loss: empirical evidence for the yen/dollar exchange rate

DEFF Research Database (Denmark)

Stadtmann, Georg; Pierdzioch; Rülke

2012-01-01

We used the yen/dollar exchange-rate forecasts of the Wall Street Journal (WSJ) poll to analyse whether exchange-rate forecasters have an asymmetric loss function. To this end, we applied an approach recently developed by Elliott et al. (2005). We found that only few forecasters seem to form...

NMR magnetization exchange dynamics for three spin-1/2 systems

International Nuclear Information System (INIS)

Demco, D.E.; Filip, X.; Filip, C.

1997-01-01

The magnetization exchange dynamics in one-dimensional NMR exchange experiments performed with static samples is analyzed for the relevant case of three spin systems. The magnetization decays recorded in the experiments performed with different chemical shift filters for the short mixing times are derived analytically. In this regime the decay rates depend on the dipolar coupling between the spins belonging to different functional groups. The predictions of the theoretical model are compared with the magnetization exchange data obtained for cross-linked poly(styrene-co-butadiene) samples. The residual dipolar coupling between the functional CH- and CH2-groups of butadiene are measured from the magnetization exchange experiments in the short mixing time regime. (authors)

Experimental investigation of CO{sub 2} condensation process using cryogen

Energy Technology Data Exchange (ETDEWEB)

Lee, Cheonkyu; Yoo, Junghyun; Lee, Jisung; Park, Hana; Jeong, Sangkwon [Korea Advanced Institute of Science and Technology, Daejeon 305-701 (Korea, Republic of)

2014-01-29

Carbon dioxide (CO{sub 2}) is one of the dominant gas molecules that causes greenhouse effect, i.e. global warming. Numerous studies have been carried out to regulate the emission of CO{sub 2} to reduce greenhouse gas. The liquid CO{sub 2} is a convenient form of transportation compared to high-pressurized gaseous CO{sub 2}. Therefore, the direct liquefaction mechanism of CO{sub 2} at low temperature draws technical attention recently. In particular, cold thermal energy of Liquefied Natural Gas (LNG) could be a candidate to condense gaseous CO{sub 2}, especially in the LNG powered ship. In this paper, the detailed direct condensation process of CO{sub 2} using LN{sub 2} with intermittent solidification is investigated. Pressurized CO{sub 2} at 600 kPa is directly liquefied in a vessel by liquid nitrogen which is supplied into the coiled tube heat exchanger inside the CO{sub 2} vessel. The heat exchanger temperature is controlled from 130 K to 205 K to regulate the solidification and sublimation of CO{sub 2} by duty control with cryogenic solenoid valve. The characteristics of CO{sub 2} condensation process with cryogen are analyzed from the measurement results. The results show that the solidification causes the significant degradation of CO{sub 2} condensation heat transfer. Finally, the condensation rate with and without solidification is compared.

Carbon dioxide exchange between atmosphere and ocean and the question of an increase of atmospheric CO/sub 2/ during the past decades

Energy Technology Data Exchange (ETDEWEB)

Revelle, R; Suess, H E

1957-01-01

From a comparison of C/sup 14//C/sup 12/ and C/sup 13//C/sup 12/ ratios in wood and in marine material and from a slight decrease of the C/sup 14/ concentration in terrestrial plants over the past 50 years it can be concluded that the average lifetime of a CO/sub 2/ molecule in the atmosphere before it is dissolved into the sea is of the order of 10 years. This means that most of the CO/sub 2/ released by artificial fuel combustion since the beginning of the industrial revolution must have been absorbed by the oceans. The increase of atmospheric CO/sub 2/ from this cause is at present small but may become significant during future decades of industrial fuel combustion continues to rise exponentially. Present data on the total amount of CO/sub 2/ in the atmosphere, on the rates and mechanisms of exchange, and on possible fluctuations in terrestrial and marine organic carbon, are inadequate for accurate measurement of future changes in atmospheric CO/sub 2/. An opportunity exists during the international geophysical year to obtain much of the necessary information.

Interest Rates and Exchange Rate Relationship in BRIC-T Countries

OpenAIRE

Selim KAYHAN; Tayfur BAYAT; Ahmet UGUR

2013-01-01

This study examines the dynamic relationships between the real exchange rate and the real interest rate in the BRIC-T (Brazil, Russia, India, China and Turkey) countries by employing monthly data from the beginning of flexible exchange rate regime to July 2011. For this aim, non-linear causality test and frequency domain causality test approaches are used. According to frequency domain causality test results, interest rate affects exchange rate in only China and this effect exist only in the ...

Kinetic bottlenecks to chemical exchange rates for deep-sea animals – Part 2: Carbon Dioxide

Directory of Open Access Journals (Sweden)

A. F. Hofmann

2013-04-01

Full Text Available Increased ocean acidification from fossil fuel CO2 invasion, from temperature-driven changes in respiration, and from possible leakage from sub-seabed geologic CO2 disposal has aroused concern over the impacts of elevated CO2 concentrations on marine life. Discussion of these impacts has so far focused only on changes in the oceanic bulk fluid properties (ΔpH, Δ[∑ CO2], etc. as the critical variable and with a major focus on carbonate shell formation. Here we describe the rate problem for animals that must export CO2 at about the same rate at which O2 is consumed. We analyse the basic properties controlling CO2 export within the diffusive boundary layer around marine animals in an ocean changing in temperature (T and CO2 concentration in order to compare the challenges posed by O2 uptake under stress with the equivalent problem of CO2 expulsion. The problem is more complex than that for a non-reactive gas, since with CO2 the influence of the seawater carbonate acid-base system needs to be considered. These reactions significantly facilitate CO2 efflux compared to O2 intake at equal temperature, pressure and fluid flow rate under typical oceanic concentrations. The effect of these reactions can be described by an enhancement factor, similar to that widely used for CO2 invasion at the sea surface. While organisms do need to actively regulate flow over their surface to thin the boundary layer to take up enough O2, this seems to be not necessary to facilitate CO2 efflux. Instead, the main impacts of rising oceanic CO2 will most likely be those associated with classical ocean acidification science. Regionally, as with O2, the combination of T, P and pH/pCO2 creates a zone of maximum CO2 stress at around 1000 m depth.

Aviation and the environment, rating airlines on their co2 efficiency

NARCIS (Netherlands)

Van der Zwan, F.M.; Dorland, N.; Ghijs, S.S.A.; Santema, S.C.; Curran, R.

2009-01-01

The aviation industry contributes about 2% to the total global manmade CO2 emissions, which is seen as the main (manmade) greenhouse gas inducing climate change. This paper focuses on the design of a CO2 rating system which makes it possible to make a fair comparison of the environmental performance

Detection Test for Leakage of CO{sub 2} into Sodium Loop

Energy Technology Data Exchange (ETDEWEB)

Park, Sun Hee; Wi, Myung-Hwan; Min, Jae Hong [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2015-10-15

This report is about the facility for the detection test for leakage of CO{sub 2} into sodium loop. The facility for the detection test for leakage of CO{sub 2} into sodium loop was introduced. The test will be carried out. Our experimental results are going to be expected to be used for approach methods to detect CO{sub 2} leaking into sodium in heat exchangers. A sodium-and-carbon dioxide (Na-CO{sub 2}) heat exchanger is one of the key components for the supercritical CO{sub 2} Brayton cycle power conversion system of sodium-cooled fast reactors (SFRs). A printed circuit heat exchanger (PCHE) is considered for the Na-CO{sub 2} heat exchanger, which is known to have potential for reducing the volume occupied by the exchangers compared to traditional shell-and-tube heat exchangers. Among various issues about the Na- CO{sub 2} exchanger, detection of CO{sub 2} leaking into sodium in the heat exchanger is most important thing for its safe operation. It is known that reaction products from sodium and CO{sub 2} such as sodium carbonate (Na{sub 2}CO{sub 3}) and amorphous carbon are hardly soluble in sodium, which cause plug sodium channels. Detection technique for Na{sub 2}CO{sub 3} in sodium loop has not been developed yet. Therefore, detection of CO{sub 2} and CO from reaction of sodium and CO{sub 2} are proper to detect CO{sub 2} leakage into sodium loop.

Exchange rate regimes and monetary arrangements

Directory of Open Access Journals (Sweden)

Ivan Ribnikar

2005-06-01

Full Text Available There is a close relationship between a country’s exchange rate regime and monetary arrangement and if we are to examine monetary arrangements then exchange rate regimes must first be analysed. Within the conventional and most widely used classification of exchange rate regimes into rigid and flexible or into polar regimes (hard peg and float on one side, and intermediate regimes on the other there, is a much greater variety among intermediate regimes. A more precise and, as will be seen, more useful classification of exchange rate regimes is the first topic of the paper. The second topic is how exchange rate regimes influence or determine monetary arrangements and monetary policy or monetary policy regimes: monetary autonomy versus monetary nonautonomy and discretion in monetary policy versus commitment in monetary policy. Both topics are important for countries on their path to the EU and the euro area

Hydrogen and oxygen isotope exchange reactions over illuminated and nonilluminated TiO2

International Nuclear Information System (INIS)

Sato, S.

1987-01-01

Hydrogen isotope exchange between H 2 , gaseous H 2 O, and the surface hydroxyls of TiO 2 , and oxygen isotope exchange between O 2 , CO 2 , CO, H 2 O vapor, and the hydroxyls over TiO 3 were studied at room temperature in the dark and under illumination. Hydrogen isotope exchange between H 2 O and the hydroxyls occurred rapidly in the dark, but the exchange involving H 2 did not occur at all even under illumination. Oxygen isotope exchange among H 2 O vapor, CO 2 , and the hydroxyls easily took place in the dark, but the exchange involving O 2 required band-gap illumination. Dioxygen isotope equilibration was much faster than the other photoexchange reactions. Although the oxygen exchange between O 2 and illuminated TiO 2 has been considered to involve lattice-oxygen exchange, the present experiments revealed that the hydroxyls of TiO 2 mainly participate in the exchange reaction. The oxygen exchange between O 2 and H 2 O vapor was strongly inhibited by H 2 O vapor itself probably because oxygen adsorption was retarded by adsorbed water. Oxygen in CO was not exchanged with the other substrates under any conditions tested

The CarbonTracker Data Assimilation System for CO2 and δ13C (CTDAS-C13 v1.0: retrieving information on land–atmosphere exchange processes

Directory of Open Access Journals (Sweden)

I. R. van der Velde

2018-01-01

Full Text Available To improve our understanding of the global carbon balance and its representation in terrestrial biosphere models, we present here a first dual-species application of the CarbonTracker Data Assimilation System (CTDAS. The system's modular design allows for assimilating multiple atmospheric trace gases simultaneously to infer exchange fluxes at the Earth surface. In the prototype discussed here, we interpret signals recorded in observed carbon dioxide (CO2 along with observed ratios of its stable isotopologues 13CO2∕12CO2 (δ13C. The latter is in particular a valuable tracer to untangle CO2 exchange from land and oceans. Potentially, it can also be used as a proxy for continent-wide drought stress in plants, largely because the ratio of 13CO2 and 12CO2 molecules removed from the atmosphere by plants is dependent on moisture conditions.The dual-species CTDAS system varies the net exchange fluxes of both 13CO2 and CO2 in ocean and terrestrial biosphere models to create an ensemble of 13CO2 and CO2 fluxes that propagates through an atmospheric transport model. Based on differences between observed and simulated 13CO2 and CO2 mole fractions (and thus δ13C our Bayesian minimization approach solves for weekly adjustments to both net fluxes and isotopic terrestrial discrimination that minimizes the difference between observed and estimated mole fractions.With this system, we are able to estimate changes in terrestrial δ13C exchange on seasonal and continental scales in the Northern Hemisphere where the observational network is most dense. Our results indicate a decrease in stomatal conductance on a continent-wide scale during a severe drought. These changes could only be detected after applying combined atmospheric CO2 and δ13C constraints as done in this work. The additional constraints on surface CO2 exchange from δ13C observations neither affected the estimated carbon fluxes nor compromised our ability to match observed CO2 variations

The effects of real exchange rate misalignment and real exchange volatility on exports

OpenAIRE

Diallo, Ibrahima Amadou

2011-01-01

This paper uses panel data cointegration techniques to study the impacts of real exchange rate misalignment and real exchange rate volatility on total exports for a panel of 42 developing countries from 1975 to 2004. The results show that both real exchange rate misalignment and real exchange rate volatility affect negatively exports. The results also illustrate that real exchange rate volatility is more harmful to exports than misalignment. These outcomes are corroborated by estimations on s...

A Case for Intermediate Exchange-Rate Regimes

OpenAIRE

Agnès Bénassy-Quéré; Véronique Salins

2010-01-01

Despite increasing capital mobility and the subsequent difficulty in controlling exchange rates, intermediate exchange-rate regimes have remained widespread, especially in emerging and developing economies. This piece of evidence hardly fits the "impossible Trinity" theory arguing that it becomes difficult to control the exchange rate without a "hard" device when capital flows are freed. Calvo and Reinhart (2000) have suggested several explanations for such "fear of floating": exchange rate p...

The exchange interaction effects on magnetic properties of the nanostructured CoPt particles

Energy Technology Data Exchange (ETDEWEB)

Komogortsev, S.V., E-mail: komogor@iph.krasn.ru [Kirensky Institute of Physics, SB RAS, 660036 Krasnoyarsk (Russian Federation); Iskhakov, R.S. [Kirensky Institute of Physics, SB RAS, 660036 Krasnoyarsk (Russian Federation); Zimin, A.A. [Siberian Federal University, 660041 Krasnoyarsk (Russian Federation); Filatov, E.Yu.; Korenev, S.V.; Shubin, Yu.V. [Nikolaev Institute of Inorganic Chemistry, SB RAS, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, 630090 Novosibirsk (Russian Federation); Chizhik, N.A. [Siberian Federal University, 660041 Krasnoyarsk (Russian Federation); Yurkin, G.Yu.; Eremin, E.V. [Kirensky Institute of Physics, SB RAS, 660036 Krasnoyarsk (Russian Federation)

2016-03-01

Various manifestations of the exchange interaction effects in magnetization curves of the CoPt nanostructured particles are demonstrated and discussed. The inter-grain exchange constant A in the sponge-like agglomerates of crystallites is estimated as A=(7±1) pJ/m from the approach magnetization to saturation curves that is in good agreement with A=(6.6±0.5) pJ/m obtained from Bloch T {sup 3/2} law. The fractal dimensionality of the exchange coupled crystallite system in the porous media of the disordered CoPt alloy d=(2.60±0.18) was estimated from the approach magnetization to saturation curve. Coercive force decreases with temperature as H{sub c}~T {sup 3/2} which is assumed to be a consequence of the magnetic anisotropy energy reduction due to the thermal spin wave excitations in the investigated CoPt particles. - Highlights: • Nanostructured CoPt particles were synthesized and then annealed in He atmosphere. • The structure of the material and magnetization curves were studied. • The maximum on reduced coercivity vs grain size dependence was observed. • The dimensionality d of exchange coupled crystallite system was estimated. • Exchange stiffness constant A was estimated.

Floating Exchange Rate Regime

OpenAIRE

Quader, Syed Manzur

2004-01-01

In recent years, many developing countries having a history of high inflation, unfavorable balance of payment situation and a high level of foreign currencies denominated debt, have switched or are in the process of switching to a more flexible exchange rate regime. Therefore, the stability of the exchange rate and the dynamics of its volatility are more crucial than before to prevent financial crises and macroeconomic disturbances. This paper is designed to find out the reasons behind Bangla...

Exchange Rate and International Trade: Case From Indonesian Manufacturing Sector

Directory of Open Access Journals (Sweden)

Anung Yoga Anindhita

2017-07-01

Full Text Available Exchange rate fluctuation in Floating Exchange Rate Regime is considered to Exchange rate fluctuation in Floating Exchange Rate Regime is considered to have impacts on the international trade through its adjustment to the price and its volatility to the trade risk. This paper is aimed at estimating those impacts on the international trade of manufacturing sector in Indonesia for period 2007 to 2014. To conduct estimation, it uses multiple regression analysis on two models: First, the import of raw-and-auxiliary materials; Second, the export of manufacturing sector. The results show that the exchange rate impacts both work significantly on the import of raw-and-auxiliary materials. The finding implies that, through the import of raw-and-auxiliary materials, manufacturing sector is very susceptible to the shock caused by exchange rate changes. Meanwhile, the export of manufacturing sector is not able to take advantage of the depreciation of the exchange rate due to the lack of competitiveness.DOI: 10.15408/sjie.v6i2.5210

Rate of oxygen isotope exchange between selenate and water.

Science.gov (United States)

Kaneko, Masanori; Poulson, Simon R

2012-04-17

The rate of oxygen isotope exchange between selenate and water was investigated at conditions of 10 to 80 °C and pH -0.6 to 4.4. Oxygen isotope exchange proceeds as a first-order reaction, and the exchange rate is strongly affected by reaction temperature and pH, with increased rates of isotope exchange at higher temperature and lower pH. Selenate speciation (HSeO(4)(-) vs SeO(4)(2-)) also has a significant effect on the rate of isotope exchange. The half-life for isotope exchange at example natural conditions (25 °C and pH 7) is estimated to be significantly in excess of 10(6) years. The very slow rate of oxygen isotope exchange between selenate and water under most environmental conditions demonstrates that selenate-δ(18)O signatures produced by biogeochemical processes will be preserved and hence that it will be possible to use the value of selenate-δ(18)O to investigate the biogeochemical behavior of selenate, in an analogous fashion to the use of sulfate-δ(18)O to study the biogeochemical behavior of sulfate.

Comparison of circuit patency and exchange rates between 2 different continuous renal replacement therapy machines.

Science.gov (United States)

Razavi, Seyed Amirhossein; Still, Mary D; White, Sharon J; Buchman, Timothy G; Connor, Michael J

2014-04-01

Continuous renal replacement therapy (CRRT) is an important tool in the care of critically ill patients. However, the impact of a specific CRRT machine type on the successful delivery of CRRT is unclear. The purpose of this study was to evaluate the effectiveness of CRRT delivery with an intensive care unit (ICU) bedside nurse delivery model for CRRT while comparing circuit patency and circuit exchange rates in 2 Food and Drug Administration-approved CRRT devices. This article presents the data comparing circuit exchange rates for 2 different CRRT machines. A group of ICU nurses were selected to undergo expanded training in CRRT operation and empowered to deliver all aspects of CRRT. The ICU nurses then provided all aspects of CRRT on 2 Food and Drug Administration-approved CRRT devices for 6 months. Each device was used exclusively in the designated ICU for a 2-week run-in period followed by 3-month data collection period. The primary end point for the study was the differences in average number of filter exchanges per day during each CRRT event. A total of 45 unique patients who underwent 64 separate CRRT treatment periods were included. Four CRRT events were excluded (see text for details). Twenty-eight CRRT events occurred in the NxStage System One arm (NxStage Medical, Lawrence, Mass) and 32 events in the Gambro Prismaflex arm (Gambro Renal Products, Boulder, Colo). Average (SD) filter exchanges per day was 0.443 (0.60) for the NxStage System One machine and 0.553 (0.65) for Gambro Prismaflex machine (P = .09). There was no demonstrable difference in circuit patency as defined by the rate of filter exchanges per day of CRRT therapy. Copyright © 2014 Elsevier Inc. All rights reserved.

Partitioning net ecosystem carbon exchange into net assimilation and respiration using 13CO2 measurements: A cost-effective sampling strategy

Science.gov (United States)

OgéE, J.; Peylin, P.; Ciais, P.; Bariac, T.; Brunet, Y.; Berbigier, P.; Roche, C.; Richard, P.; Bardoux, G.; Bonnefond, J.-M.

2003-06-01

The current emphasis on global climate studies has led the scientific community to set up a number of sites for measuring the long-term biosphere-atmosphere net CO2 exchange (net ecosystem exchange, NEE). Partitioning this flux into its elementary components, net assimilation (FA), and respiration (FR), remains necessary in order to get a better understanding of biosphere functioning and design better surface exchange models. Noting that FR and FA have different isotopic signatures, we evaluate the potential of isotopic 13CO2 measurements in the air (combined with CO2 flux and concentration measurements) to partition NEE into FR and FA on a routine basis. The study is conducted at a temperate coniferous forest where intensive isotopic measurements in air, soil, and biomass were performed in summer 1997. The multilayer soil-vegetation-atmosphere transfer model MuSICA is adapted to compute 13CO2 flux and concentration profiles. Using MuSICA as a "perfect" simulator and taking advantage of the very dense spatiotemporal resolution of the isotopic data set (341 flasks over a 24-hour period) enable us to test each hypothesis and estimate the performance of the method. The partitioning works better in midafternoon when isotopic disequilibrium is strong. With only 15 flasks, i.e., two 13CO2 nighttime profiles (to estimate the isotopic signature of FR) and five daytime measurements (to perform the partitioning) we get mean daily estimates of FR and FA that agree with the model within 15-20%. However, knowledge of the mesophyll conductance seems crucial and may be a limitation to the method.

The Effects of Oil Price Changes And Exchange Rate Volatility On Unemployment: Evidence From Malaysia

Directory of Open Access Journals (Sweden)

Mohd Shahidan Shaari

2016-01-01

Full Text Available The study aims to examine the effects of oil price and exchange rate on unemployment in Malaysia. The empirical analysis commence by analyzing the time series property of data. The Johansen VAR-based co-integration technique was applied to examine the long run relationship between exchange rate, oil price and unemployment and found the long run relationship does exist. The vector error correction model was performed to check the short run dynamics and found that the short run dynamics are influenced by the estimated long run equilibrium. Granger causality was done and found that oil price does not affect unemployment but exchange rate has an influence on unemployment. Therefore, putting the exchange rate under control should be implemented to control unemployment.

A re-examination of the exchange rate overshooting hypothesis

African Journals Online (AJOL)

kirstam

Studies on exchange rate overshooting on the Zambian foreign exchange rate market are .... depreciation between 2008 and 2009 during the great recession. Figure 2 shows ...... manufacturing sector in Nigeria', European Journal of Business and Management, 5(22):. 67–73 .... paper. Washington, DC: IMF Working Paper.

The Abundance of Atmospheric CO{sub 2} in Ocean Exoplanets: a Novel CO{sub 2} Deposition Mechanism

Energy Technology Data Exchange (ETDEWEB)

Levi, A.; Sasselov, D. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Podolak, M., E-mail: amitlevi.planetphys@gmail.com [Dept. of Geosciences, Tel Aviv University, Tel Aviv, 69978 (Israel)

2017-03-20

We consider super-Earth sized planets which have a water mass fraction large enough to form an external mantle composed of high-pressure water-ice polymorphs and also lack a substantial H/He atmosphere. We consider such planets in their habitable zone, so that their outermost condensed mantle is a global, deep, liquid ocean. For these ocean planets, we investigate potential internal reservoirs of CO{sub 2}, the amount of CO{sub 2} dissolved in the ocean for the various saturation conditions encountered, and the ocean-atmosphere exchange flux of CO{sub 2}. We find that, in a steady state, the abundance of CO{sub 2} in the atmosphere has two possible states. When wind-driven circulation is the dominant CO{sub 2} exchange mechanism, an atmosphere of tens of bars of CO{sub 2} results, where the exact value depends on the subtropical ocean surface temperature and the deep ocean temperature. When sea-ice formation, acting on these planets as a CO{sub 2} deposition mechanism, is the dominant exchange mechanism, an atmosphere of a few bars of CO{sub 2} is established. The exact value depends on the subpolar surface temperature. Our results suggest the possibility of a negative feedback mechanism, unique to water planets, where a reduction in the subpolar temperature drives more CO{sub 2} into the atmosphere to increase the greenhouse effect.

Inflation Targeting and Exchange Rate Management in Korea

Directory of Open Access Journals (Sweden)

Won-Am Park

2008-06-01

Full Text Available This paper investigates the experience of inflation targeting in Korea with an emphasis on exchange rate management. The Korean call rate responded to not only expected inflation, but also to output gap and changes in the real effective exchange rate of the Korean won, when we estimated the call rate reaction function over the period of 1999-2007. It was found that the call rate responded to changes in real effective exchange rate more than it did to expected inflation. We also examined whether Korean inflation targeting was actually centered on the exchange rate by estimating the Singaporean style of exchange rate reaction function. It was found that Korean monetary policy was not exchange-rate- centered, since the nominal effective exchange rate of the Korean won responded modestly to inflation and output gap, far less than did the Singaporean dollar.

Interfacial exchange coupling and magnetization reversal in perpendicular [Co/Ni]N/TbCo composite structures.

Science.gov (United States)

Tang, M H; Zhang, Zongzhi; Tian, S Y; Wang, J; Ma, B; Jin, Q Y

2015-06-15

Interfacial exchange coupling and magnetization reversal characteristics in the perpendicular heterostructures consisting of an amorphous ferrimagnetic (FI) TbxCo(100-x) alloy layer exchange-coupled with a ferromagnetic (FM) [Co/Ni]N multilayer have been investigated. As compared with pure TbxCo(100-x) alloy, the magnetization compensation composition of the heterostructures shift to a higher Tb content, implying Co/Ni also serves to compensate the Tb moment in TbCo layer. The net magnetization switching field Hc⊥ and interlayer interfacial coupling field Hex, are not only sensitive to the magnetization and thickness of the switched TbxCo(100-x) or [Co/Ni]N layer, but also to the perpendicular magnetic anisotropy strength of the pinning layer. By tuning the layer structure we achieve simultaneously both large Hc⊥ = 1.31 T and Hex = 2.19 T. These results, in addition to the fundamental interest, are important to understanding of the interfacial coupling interaction in the FM/FI heterostructures, which could offer the guiding of potential applications in heat-assisted magnetic recording or all-optical switching recording technique.

Seasonal soil VOC exchange rates in a Mediterranean holm oak forest and their responses to drought conditions

Science.gov (United States)

Asensio, Dolores; Peñuelas, Josep; Ogaya, Romà; Llusià, Joan

Available information on soil volatile organic compound (VOC) exchange, emissions and uptake, is very scarce. We here describe the amounts and seasonality of soil VOC exchange during a year in a natural Mediterranean holm oak forest growing in Southern Catalonia. We investigated changes in soil VOC dynamics in drought conditions by decreasing the soil moisture to 30% of ambient conditions by artificially excluding rainfall and water runoff, and predicted the response of VOC exchange to the drought forecasted in the Mediterranean region for the next decades by GCM and ecophysiological models. The annual average of the total (detected) soil VOC and total monoterpene exchange rates were 3.2±3.2 and -0.4±0.3 μg m -2 h -1, respectively, in control plots. These values represent 0.003% of the total C emitted by soil at the study site as CO 2 whereas the annual mean of soil monoterpene exchange represents 0.0004% of total C. Total soil VOC exchange rates in control plots showed seasonal variations following changes in soil moisture and phenology. Maximum values were found in spring (17±8 μg m -2 h -1). Although there was no significant global effect of drought treatment on the total soil VOC exchange rates, annual average of total VOC exchange rates in drought plots resulted in an uptake rate (-0.5±1.8 μg m -2 h -1) instead of positive net emission rates. Larger soil VOC and monoterpene exchanges were measured in drought plots than in control plots in summer, which might be mostly attributable to autotrophic (roots) metabolism. The results show that the diversity and magnitude of monoterpene and VOC soil emissions are low compared with plant emissions, that they are driven by soil moisture, that they represent a very small part of the soil-released carbon and that they may be strongly reduced or even reversed into net uptakes by the predicted decreases of soil water availability in the next decades. In all cases, it seems that VOC fluxes in soil might have greater

Measuring the costs of exchange rate volatility

OpenAIRE

Paul R. Bergin

2004-01-01

Many countries go to great lengths to manage their exchange rates. Probably the most prominent recent example is the European Monetary Union, where all the members abandoned their national currencies and adopted the euro. A number of developing countries maintain other kinds of regimes of managed exchange rates, even though they face potent market pressures to let their exchange rates float. One of the main motives for these arrangements stems from the extreme volatility of exchange rates. Th...

Linearity between temperature peak and bio-energy CO2 emission rates

International Nuclear Information System (INIS)

Cherubini, Francesco; Bright, Ryan M.; Stromman, Anders H.; Gasser, Thomas; Ciais, Philippe

2014-01-01

Many future energy and emission scenarios envisage an increase of bio-energy in the global primary energy mix. In most climate impact assessment models and policies, bio-energy systems are assumed to be carbon neutral, thus ignoring the time lag between CO 2 emissions from biomass combustion and CO 2 uptake by vegetation. Here, we show that the temperature peak caused by CO 2 emissions from bio-energy is proportional to the maximum rate at which emissions occur and is almost insensitive to cumulative emissions. Whereas the carbon-climate response (CCR) to fossil fuel emissions is approximately constant, the CCR to bio-energy emissions depends on time, biomass turnover times, and emission scenarios. The linearity between temperature peak and bio-energy CO 2 emission rates resembles the characteristic of the temperature response to short-lived climate forcers. As for the latter, the timing of CO 2 emissions from bio-energy matters. Under the international agreement to limit global warming to 2 C by 2100, early emissions from bio-energy thus have smaller contributions on the targeted temperature than emissions postponed later into the future, especially when bio-energy is sourced from biomass with medium (50-60 years) or long turnover times (100 years). (authors)

CO2 and water vapor exchange of a larch forest in northern Japan

International Nuclear Information System (INIS)

Hirano, Takashi; Hirata, Ryuichi; Harazono, Yoshinobu

2003-01-01

In the northern part of East Asia, forests dominated by larch are extensively distributed and probably play an important role in the global carbon cycle. However, a knowledge of the CO 2 balance of larch forests based on long-term flux measurements is very restricted in East Asia. Thus, a long-term flux measurement has been started in 2000 at a larch plantation on a flat terrain in Hokkaido, Japan to obtain more information on the CO 2 and energy balances of larch forests. From September 2000 to August 2001 the net ecosystem CO 2 exchange (NEE) changed seasonally in accordance with the annual cycles of phenology and climate. NEE was negative for six months of the growing season, May-September; the larch ecosystem was a carbon sink with a peak intensity of -0.38 mol m 2 d1 for this period. In the leafless season from November to April the forest ecosystem was a carbon source with an intensity ranging between 0 and 0.05 mol/m 2 /d. Annual NEE from September 2000 to August 2001 was 24.4 to 32.4 mol m 2 /yr (= 293 to 389 gC/m 2 /yr); this value is compatible with those reported from other temperate forests. Annual evapotranspiration for the same period was 367 mm, which was only 29% of annual precipitation

Preliminary Studies of Two-Phase Reactive Process of Sodium-CO2 in S-CO2 Power Conversion Cycle Coupled to SFR System

International Nuclear Information System (INIS)

Jung, Hwa Young; Ahn, Yoon Han; Lee, You Ho; Lee, Jeong Ik

2013-01-01

As a competing alternative to the steam Rankine cycle, the supercritical CO 2 (S-CO 2 ) Brayton cycle has been highlighted due to its high thermal efficiency, compact turbomachinery and heat exchangers sizes, and the reduced risk of SWRs. While the reduced risk of an SWR is considered as the one of most pronounced benefits of S-CO 2 Brayton cycle, there is still an interaction problem between liquid sodium and CO 2 . Although the chemical interaction between liquid sodium and CO 2 demonstrates less serious potential risks than those of a SWR, the Na/CO 2 interaction should be understood to evaluate safety and reliability of Intermediate Heat eXchanger (IHX). A noticeable characteristic of the reaction environment is that there is a large pressure difference between the liquid sodium and CO 2 side by about 1 and 200 bar, respectively. This would imply that the presence of a micro-crack in a heat exchanger tube will cause a high-pressure leak of CO 2 into liquid sodium side. Although the Na/CO 2 interaction may play an important role in the safety of the SFR reactor system, there has not yet been any research on understanding Na/CO 2 reaction by leakage through IHX. For this problem, the Korea Advanced Institute of Science and Technology (KAIST) research team is studying the mechanism of CO 2 leakage and Na/CO 2 interaction in more details. The KAIST research team developed the MATLAB code, KAIST H XD, which can be used to design and evaluate performance of a heat exchanger of an S-CO 2 cycle. The size of heat exchanger and the amount of CO 2 in the cycle are calculated from the KAIST H XD code to estimate the amount of reaction products in Na/CO 2 interaction as well as liquid sodium

Hydrogen isotope exchange reaction rates in tritium, hydrogen and deuterium mixed gases

International Nuclear Information System (INIS)

Uda, Tatsuhiko

1992-01-01

Hydrogen isotope exchange reaction rates in H 2 +T 2 , D 2 +T 2 and H 2 +D 2 +T 2 mixed gases, as induced by tritium decay and beta radiation, were experimentally measured by laser Raman spectrometry. Initially a glass cell was filled with T 2 gas to a pressure of 30-40 kPa, and an equivalent partial pressure of H 2 and/or D 2 was added. The first-order hydrogen isotope exchange reaction rates were 5.54x10 -2 h -1 for H 2 +T 2 mixed gas and 4.76x10 -2 h -1 for D 2 +T 2 . The actual HT producing rate was nearly equivalent to the rate of DT, but the reverse reaction rate of HT was faster than that of DT. The exchange reaction rates between H, D and T showed the isotope effect, HD>HT>DT. The hydrogen isotope exchange reaction rates observed were about twenty times larger than ion formation rates by beta radiation. This result suggests that a free radical chain reaction in hydrogen isotopes is occurring. (orig.)

Where Would the EUR/CHF Exchange Rate be Without the SNB's Minimum Exchange Rate Policy?

DEFF Research Database (Denmark)

Hanke, Michael; Poulsen, Rolf; Weissensteiner, Alex

2015-01-01

Since its announcement made on September 6, 2011, the Swiss National Bank (SNB) has been pursuing the goal of a minimum EUR/CHF exchange rate of 1.20, promising to intervene on currency markets to prevent the exchange rate from falling below this level.We use a compound option pricing approach...

Air-sea exchange of CO2 in the Gulf of Kutch, northern Arabian Sea based on bomb-carbon in corals and tree rings

International Nuclear Information System (INIS)

Chakraborty, S.; Ramesh, R.; Krishnaswami, S.

1994-01-01

Radiocarbon analyses were carried out in the annual bands of a 40 year old coral collected from the Gulf of Kutch (22.6degN, 70degE) in the northern Arabian Sea and in the annual rings of a teak tree from Thane (19deg14'N, 73deg24'E) near Bombay. These measurements were made in order to obtain the rates of air-sea exchange of CO 2 and the advective mixing of water in the Gulf of Kutch. The Δ 14 C peak in the Thane tree occurs in the year 1964, with a value of ∼630 part per thousand, significantly lower than that of the mean atmospheric Δ 14 C of the northern hemisphere (∼1000 part per thousand). The radiocarbon time series of the coral was modelled considering the supply of carbon and radiocarbon to the gulf through air-sea exchange and advective water transport from the open Arabian Sea. A reasonable fit for the coral data was obtained with an air-sea CO 2 exchange rate of 11-12 mol m -2 yr -1 , and an advective velocity of 28 m yr -1 between the Arabian Sea and the Gulf of Kutch; this was based on a model generated time series for radiocarbon in the Arabian Sea. The deduced velocity (∼ 28 m yr -1 ) of the advective transport of water between the Gulf and the Arabian Sea is much lower than the surface tidal current velocity in this region, but can be understood in terms of net fluxes of carbon and radiocarbon to the gulf to match the observed coral Δ 14 C time series. (author). 30 refs., 7 figs., 2 tabs

Real exchange rate persistence and the excess return puzzle

DEFF Research Database (Denmark)

Juselius, Katarina; Assenmacher, Katrin

2017-01-01

The PPP puzzle refers to the wide swings of nominal exchange rates around their long-run equilibrium values whereas the excess return puzzle represents the persistent deviation of the domestic-foreign interest rate differential from the expected change in the nominal exchange rate. Using the I(2......) cointegrated VAR model, much of the excess return puzzle disappears when an uncertainty premium in the foreign exchange market, proxied by the persistent PPP gap, is introduced. Self-reinforcing feedback mechanisms seem to cause the persistence in the Swiss-US parity conditions. These results support imperfect...

Gas exchange patterns and water loss rates in the Table Mountain cockroach, Aptera fusca (Blattodea: Blaberidae).

Science.gov (United States)

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.

Role of Exchange Rate Volatility in Exchange Rate Pass-Through to Import Prices: Some Evidence from Japan

OpenAIRE

Guneratne Banda Wickremasinghe; Param Silvapulle

2004-01-01

This paper investigates the effect of exchange rate volatility on the degree of exchange rate pass-through in Japan for the period January 1975 to June 1997. Although several studies put forward theoretical arguments for the volatility-domestic import price relationship, only a very few studies produced empirical evidence. The volatility of contractual currency based exchange rate index returns was modelled using GARCH-type processes with skewed student t-distribution, capturing the typical n...

Oxygen isotope exchange rate between dissolved sulfate and water at hydrothermal temperatures

International Nuclear Information System (INIS)

Chiba, H.; Sakai, H.

1985-01-01

Oxygen isotope exchange rate between dissolved sulfate and water was experimentally determined at 100, 200 and 300 deg C. The isotope exchange rate is strongly dependent on temperature and pH of the solution. Combining the temperature and pH dependence of the reaction rate, the exchange reaction was estimated to be first-order with respect to sulfate. The logarithm of apparent rate constant of exchange reaction at a given temperature is a function of the pH calculated at the experimental temperatures. From the pH dependence of the apparent rate constant, it was deduced that the isotope exchange reaction between dissolved sulfate and water proceeds through collision between H 2 SO 4 0 and H 2 O at low pH, and between HSO 4 - and H 2 O at intermediate pH. The isotope exchange rate obtained indicates that oxygen isotope geothermometry utilizing the studied isotope exchange is suitable for temperature estimation of geothermal reservoirs. The extrapolated half-life of this reaction to oceanic temperature is about 10 9 years, implying that exchange between oceanic sulfate and water cannot control the oxygen isotope ratio of oceanic sulfates. (author)

Simplified models of rates of CO2 mineralization in Geologic Carbon Storage

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DePaolo, D. J.; Zhang, S.

2017-12-01

Geologic carbon storage (GCS) reverses the flow of carbon to the atmosphere, returning the carbon to long-term geologic storage. Models suggest that most of the injected CO2 will be "trapped" in the subsurface by physical means, but the most risk-free and permanent form of carbon storage is as carbonate minerals (Ca,Mg,Fe)CO3. The transformation of CO2 to carbonate minerals requires supply of divalent cations by dissolution of silicate minerals. Available data suggest that rates of transformation are difficult to predict. We show that the chemical kinetic observations and experimental results, when reduced to a single timescale that describes the fractional rate at which cations are released to solution by mineral dissolution, show sufficiently systematic behavior that the rates of mineralization can be estimated with reasonable certainty. Rate of mineralization depends on both the abundance (determined by the reservoir rock mineralogy) and the rate at which cations are released by dissolution into pore fluid that has been acidified with dissolved CO2. Laboratory-measured rates and field observations give values spanning 8 to 10 orders of magnitude, but when evaluated in the context of reservoir-scale reactive transport simulations, this range becomes much smaller. Reservoir scale simulations indicate that silicate mineral dissolution and subsequent carbonate mineral precipitation occur at pH 4.5 to 6, fluid flow velocity less than 5m/yr, and 50-100 years or more after the start of injection. These constraints lead to estimates of 200 to 2000 years for conversion of 60-90% of injected CO2 when the reservoir rock has a sufficient volume fraction of divalent cation-bearing silicate minerals (ca. 20%), and confirms that when reservoir rock mineralogy is not favorable the fraction of CO2 converted to carbonate minerals is minimal over 104 years. A sufficient amount of reactive minerals represents the condition by which the available cations per volume of rock plus pore

Isotopic versus micrometeorologic ocean CO2 fluxes: A serious conflict

International Nuclear Information System (INIS)

Broecker, W.S.; Ledwell, J.R.; Takahashi, T.; Weiss, R.; Merlivat, L.; Memery, L.; Tsung-Hung Peng; Jahne, B.; Otto Munnich, K.

1986-01-01

Eddy correlation measurements over the ocean give CO 2 fluxes an order of magnitude or more larger than expected from mass balance or more larger than expected from mass balance measurements using radiocarbon and radon 222. In particular, Smith and Jones (1985) reported large upward and downward fluxes in a surf zone at supersaturations of 15% and attributed them to the equilibration of bubbles at elevated pressures. They argue that even on the open ocean such bubble injection may create steady state CO 2 supersaturations and that inferences of fluxes based on air-sea pCO 2 differences and radon exchange velocities must be made with caution. We defend the global average CO 2 exchange rate determined by three independent radioisotopic means: prebomb radiocarbon inventories; global surveys of mixed layer radon deficits; and oceanic uptake of bomb-produced radiocarbon. We argue that laboratory and lake data do not lead one to expect fluxes as large as reported from the eddy correlation technique; that the radon method of determining exchange velocities is indeed useful for estimating CO 2 fluxes; that supersaturations of CO 2 due to bubble injection on the open ocean are negligible; that the hypothesis that Smith and Jones advance cannot account for the fluxes that they report; and that the pCO 2 values reported by Smith and Jones are likely to be systematically much too high. The CO 2 fluxes for the ocean measured to data by the micrometeorological method can be reconciled with neither the observed concentrations of radioisotopes of radon and carbon in the oceans nor the tracer experiments carried out in lakes and in wind/wave tunnels

Effects of elevated CO2 leaf diets on gypsy moth (Lepidoptera: Lymantriidae) respiration rates.

Science.gov (United States)

Foss, Anita R; Mattson, William J; Trier, Terry M

2013-06-01

Elevated levels of CO2 affect plant growth and leaf chemistry, which in turn can alter host plant suitability for insect herbivores. We examined the suitability of foliage from trees grown from seedlings since 1997 at Aspen FACE as diet for the gypsy moth (Lymantria dispar L.) Lepidoptera: Lymantriidae: paper birch (Betula papyrifera Marshall) in 2004-2005, and trembling aspen (Populus tremuloides Michaux) in 2006-2007, and measured consequent effects on larval respiration. Leaves were collected for diet and leaf chemistry (nutritional and secondary compound proxies) from trees grown under ambient (average 380 ppm) and elevated CO2 (average 560 ppm) conditions. Elevated CO2 did not significantly alter birch or aspen leaf chemistry compared with ambient levels with the exception that birch percent carbon in 2004 and aspen moisture content in 2006 were significantly lowered. Respiration rates were significantly higher (15-59%) for larvae reared on birch grown under elevated CO2 compared with ambient conditions, but were not different on two aspen clones, until larvae reached the fifth instar, when those consuming elevated CO2 leaves on clone 271 had lower (26%) respiration rates, and those consuming elevated CO2 leaves on clone 216 had higher (36%) respiration rates. However, elevated CO2 had no apparent effect on the respiration rates of pupae derived from larvae fed either birch or aspen leaves. Higher respiration rates for larvae fed diets grown under ambient or elevated CO2 demonstrates their lower efficiency of converting chemical energy of digested food stuffs extracted from such leaves into their biosynthetic processes.

Exchange bias induced at a Co2FeAl0.5Si0.5/Cr interface

International Nuclear Information System (INIS)

Yu, C N T; Vick, A J; Inami, N; Ono, K; Frost, W; Hirohata, A

2017-01-01

In order to engineer the strength of an exchange bias in a cubic Heusler alloy layer, crystalline strain has been induced at a ferromagnet/antiferromagnet interface by their lattice mismatch in addition to the conventional interfacial exchange coupling between them. Such interfaces have been formed in (Co 2 FeAl 0.5 Si 0.5 (CFAS)/Cr) 3 structures grown by ultrahigh vacuum molecular beam epitaxy. The magnetic and structural properties have been characterised to investigate the exchange interactions at the CFAS/Cr interfaces. Due to the interfacial lattice mismatch of 1.4%, the maximum offset of 18 Oe in a magnetisation curve has been measured for the case of a CFAS (2 nm)/Cr (0.9 nm) interface at 193 K. The half-metallic property of CFAS has been observed to remain unchanged, which agrees with the theoretical prediction by Culbert et al (2008 J. Appl. Phys . 103 07D707). Such a strain-induced exchange bias may provide insight of the interfacial interactions and may offer a wide flexibility in spintronic device design. (paper)

Chemical exchange rotation transfer imaging of intermediate-exchanging amines at 2 ppm.

Science.gov (United States)

Zu, Zhongliang; Louie, Elizabeth A; Lin, Eugene C; Jiang, Xiaoyu; Does, Mark D; Gore, John C; Gochberg, Daniel F

2017-10-01

Chemical exchange saturation transfer (CEST) imaging of amine protons exchanging at intermediate rates and whose chemical shift is around 2 ppm may provide a means of mapping creatine. However, the quantification of this effect may be compromised by the influence of overlapping CEST signals from fast-exchanging amines and hydroxyls. We aimed to investigate the exchange rate filtering effect of a variation of CEST, named chemical exchange rotation transfer (CERT), as a means of isolating creatine contributions at around 2 ppm from other overlapping signals. Simulations were performed to study the filtering effects of CERT for the selection of transfer effects from protons of specific exchange rates. Control samples containing the main metabolites in brain, bovine serum albumin (BSA) and egg white albumen (EWA) at their physiological concentrations and pH were used to study the ability of CERT to isolate molecules with amines at 2 ppm that exchange at intermediate rates, and corresponding methods were used for in vivo rat brain imaging. Simulations showed that exchange rate filtering can be combined with conventional filtering based on chemical shift. Studies on samples showed that signal contributions from creatine can be separated from those of other metabolites using this combined filter, but contributions from protein amines may still be significant. This exchange filtering can also be used for in vivo imaging. CERT provides more specific quantification of amines at 2 ppm that exchange at intermediate rates compared with conventional CEST imaging. Copyright © 2017 John Wiley & Sons, Ltd.

Modelling the diurnal and seasonal dynamics of soil CO2 exchange in a semiarid ecosystem with high plant-interspace heterogeneity

Science.gov (United States)

Gong, Jinnan; Wang, Ben; Jia, Xin; Feng, Wei; Zha, Tianshan; Kellomäki, Seppo; Peltola, Heli

2018-01-01

We used process-based modelling to investigate the roles of carbon-flux (C-flux) components and plant-interspace heterogeneities in regulating soil CO2 exchanges (FS) in a dryland ecosystem with sparse vegetation. To simulate the diurnal and seasonal dynamics of FS, the modelling considered simultaneously the CO2 production, transport and surface exchanges (e.g. biocrust photosynthesis, respiration and photodegradation). The model was parameterized and validated with multivariate data measured during the years 2013-2014 in a semiarid shrubland ecosystem in Yanchi, northwestern China. The model simulation showed that soil rewetting could enhance CO2 dissolution and delay the emission of CO2 produced from rooting zone. In addition, an ineligible fraction of respired CO2 might be removed from soil volumes under respiration chambers by lateral water flows and root uptakes. During rewetting, the lichen-crusted soil could shift temporally from net CO2 source to sink due to the activated photosynthesis of biocrust but the restricted CO2 emissions from subsoil. The presence of plant cover could decrease the root-zone CO2 production and biocrust C sequestration but increase the temperature sensitivities of these fluxes. On the other hand, the sensitivities of root-zone emissions to water content were lower under canopy, which may be due to the advection of water flows from the interspace to canopy. To conclude, the complexity and plant-interspace heterogeneities of soil C processes should be carefully considered to extrapolate findings from chamber to ecosystem scales and to predict the ecosystem responses to climate change and extreme climatic events. Our model can serve as a useful tool to simulate the soil CO2 efflux dynamics in dryland ecosystems.

Search for a new exchange-rate regime.

Science.gov (United States)

Williamson, J

1987-07-31

The regime of unmanaged floating exchange rates was implicitly judged a failure when, with the Plaza Agreement, attempts at cooperative exchange-rate management were reintroduced primarily because of concern at the size of misalignments. Any satisfactory successor regime will need to limit misalignments while retaining the genuine social benefits of exchange-rate flexibility. It is argued that a system of target zones for exchange rates, ideally embedded in a more comprehensive set of guidelines for international economic policy coordination, could best reconcile these needs.

The exchange interaction effects on magnetic properties of the nanostructured CoPt particles

Science.gov (United States)

Komogortsev, S. V.; Iskhakov, R. S.; Zimin, A. A.; Filatov, E. Yu.; Korenev, S. V.; Shubin, Yu. V.; Chizhik, N. A.; Yurkin, G. Yu.; Eremin, E. V.

2016-03-01

Various manifestations of the exchange interaction effects in magnetization curves of the CoPt nanostructured particles are demonstrated and discussed. The inter-grain exchange constant A in the sponge-like agglomerates of crystallites is estimated as A=(7±1) pJ/m from the approach magnetization to saturation curves that is in good agreement with A=(6.6±0.5) pJ/m obtained from Bloch T 3/2 law. The fractal dimensionality of the exchange coupled crystallite system in the porous media of the disordered CoPt alloy d=(2.60±0.18) was estimated from the approach magnetization to saturation curve. Coercive force decreases with temperature as Hc T 3/2 which is assumed to be a consequence of the magnetic anisotropy energy reduction due to the thermal spin wave excitations in the investigated CoPt particles.

On equilibrium real exchange rates in euro area: Special focus on behavioral equilibrium exchange rates in Ireland and Greece

Directory of Open Access Journals (Sweden)

Klára Plecitá

2012-01-01

Full Text Available This paper focuses on the intra-euro-area imbalances. Therefore the first aim of this paper is to identify euro-area countries exhibiting macroeconomic imbalances. The subsequent aim is to estimate equilibrium real exchange rates for these countries and to compute their degrees of real exchange rate misalignment. The intra-area balance is assessed using the Cluster Analysis and the Principle Component Analysis; on this basis Greece and Ireland are selected as the two euro-area countries with largest imbalances in 2010. Further the medium-run equilibrium exchange rates for Greece and Ireland are estimated applying the Behavioral Equilibrium Exchange Rate (BEER approach popularised by Clark and MacDonald (1998. In addition, the long-run equilibrium exchange rates are estimated using the Permanent Equilibrium Exchange Rate (PEER model. Employing the BEER and PEER approaches on quarterly time series of real effective exchange rates (REER from 1997: Q1 to 2010: Q4 we identify an undervaluation of the Greek and Irish REER around their entrance to the euro area. For the rest of the period analysed their REER is broadly in line with estimated BEER and PEER levels.

An Econometric Diffusion Model of Exchange Rate Movements within a Band - Implications for Interest Rate Differential and Credibility of Exchange Rate Policy

OpenAIRE

Rantala, Olavi

1992-01-01

The paper presents a model ofexchange rate movements within a specified exchange rate band enforced by central bank interventions. The model is based on the empirical observation that the exchange rate has usually been strictly inside the band, at least in Finland. In this model the distribution of the exchange rate is truncated lognormal from the edges towards the center of the band and hence quite different from the bimodal distribution of the standard target zone model. The model is estima...

Measurement of the exchange rate of waters of hydration in elastin by 2D T{sub 2}-T{sub 2} correlation nuclear magnetic resonance spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Sun Cheng; Boutis, Gregory S, E-mail: gboutis@brooklyn.cuny.edu [Brooklyn College, Department of Physics, 2900 Bedford Avenue, Brooklyn, NY 11210 (United States)

2011-02-15

We report on a direct measurement of the exchange rate of waters of hydration in elastin by T{sub 2}-T{sub 2} exchange spectroscopy. The exchange rates in bovine nuchal ligament elastin and aortic elastin at temperatures near, below and at the physiological temperature are reported here. Using an inverse Laplace transform (ILT) algorithm, we are able to identify four components in the relaxation times. While three of the components are in good agreement with previous measurements that used multi-exponential fitting, the ILT algorithm distinguishes a fourth component having relaxation times close to that of free water and is identified as water between fibers. With the aid of scanning electron microscopy, a model is proposed that allows for the application of a two-site exchange analysis between any two components for the determination of exchange rates between reservoirs. The results of the measurements support a model (described by Urry and Parker 2002 J. Muscle Res. Cell Motil. 23 543-59) wherein the net entropy of waters of hydration should increase with increasing temperature in the inverse temperature transition.

Response of CO2 exchange in a tussock tundra ecosystem to permafrost thaw and thermokarst development

Science.gov (United States)

Jason Vogel; Edward A.G. Schuur; Christian Trucco; Hanna. Lee

2009-01-01

Climate change in high latitudes can lead to permafrost thaw, which in ice-rich soils can result in ground subsidence, or thermokarst. In interior Alaska, we examined seasonal and annual ecosystem CO2 exchange using static and automatic chamber measurements in three areas of a moist acidic tundra ecosystem undergoing varying degrees of permafrost...

Searching for an Appropriate Exchange Rate Regime

Directory of Open Access Journals (Sweden)

Yunjong Wang

2001-06-01

Full Text Available This paper attempts to survey current debates on the choice of exchange rate regime in emerging market economies. The issue of choosing an appropriate exchange rate regime is being actively discussed since the recent Asian crisis. As a lesson from the recent crises, one widely shared conclusion is that soft peg exchange rate regimes are extremely vulnerable in a world of volatile capital movements. Consequently, new orthodoxy based on the impossible trinity hypothesis favours two corner solutions ― greater flexibility or credible institutional assurance, like a currency board system or dollarization. Nevertheless, questions whether such corner solutions are adequate for developing countries are rising of late. "Fear of floating" is still conspicuous in many developing countries having adopted nominally a free-floating exchange rate regime. Developing countries are sensitive to exchange rate fluctuations because the cost of exchange rate volatility is greater than the benefit when compared to developed countries. Monitoring bands is a compromise solution, but it still needs further enhancement of estimation techniques for fundamental equilibrium exchange rates in order to make those estimation results more workable in practice. Other alternatives include the creation of soft peg of the G-3 currencies. Despite counterarguments, the stability of G-3 currencies could prove to be beneficial to emerging market economies.

Investigation the Impact of Exchange Rate Volatility on the Export of Agricultural Products

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M. Jamalipour

2016-10-01

Full Text Available Introduction: Agricultural commodity export is a main attribute of developing countries and it is the basic force of development, however, developing countries have faced domestic and international instability in their markets and monetary and fiscal policies and these instabilities create a difficult condition for most of producers and exporters. Volatility in exchange market is one of the most important factor and vital concentrate for international trade especially agricultural commodity export. Because of this concern many studies have been conducted in this filed; (Aristotelous, 2001; Chen, 2009 and Sabuhoi and Piri, 2009 .Many of these studies has stated that exchange rate fluctuation has a negative impact on aggregated agricultural export; however, none of them has been focused on the effects of exchange rate fluctuation on exported value of important commodities in long run and short run. In recent years, exchange rate fluctuation has been raised about 6 percent since 2007 to 2010 and it seemed that this phenomenon has a negative impact on agricultural commodity export in Iran. To test this hypothesis exported value of three important commodity (date, orange and grape and exchange rate volatility since 1970 to 2013 have been used. Material and Methods: In order to examine the relation between real exchange rate volatility and export values of date, orange and grapes, first GARCH method has been used to draw out exchange rate volatility; then, Panel unite root test has been used to check the level of integration. Since real exchange rate is not heterogeneous for different cross sections Levi-Lin and Chow unit root test has been used for this variable and IPS test has been applied to export value. Pederoni co-integration test has been used to check the integration between these variables. Finally, FMOLS (Fully Modified Ordinary Least Square and DOLS (Dynamic Ordinary Least Square methods have been used to estimate long run and short run

CO2 and CH4 exchange by Phragmites australis under different climates

Science.gov (United States)

Serrano Ortiz, Penélope; Chojnickic, Bogdan H.; Sánchez-Cañete, Enrique P.; Kowalska, Natalia; López-Ballesteros, Ana; Fernández, Néstor; Urbaniak, Marek; Olejnik, Janusz; Kowalski, Andrew S.

2015-04-01

The key role of wetlands regarding global warming is the resulting balance between net CO2 assimilation, via photosynthesis, and CO2 and CH4 emissions, given the potential to release stored carbon, because of the high temperature sensitivity of heterotrophic soil respiration and anoxic conditions. However, it is still unknown whether wetlands will convert from long-term carbon sinks to sources as a result of climate change and other anthropogenic effects such as land use changes. Phragmites australis is one of the most common species found in wetlands and is considered the most globally widespread and productive plant species in this type of ecosystem. In this context, the main objective of this study is to analyse the GHG exchange (CO2 and CH4) of two wetlands with Phragmites australis as the dominant species under different climates using the eddy covariance (EC) technique. The first site, Padul, is located in southern Spain, with a sub-humid warm climate, characterised by a mean annual temperature of 16°C and annual precipitation of ca. 470 mm, with a very dry summer. The second site, Rzecin is located in Poland with a mean annual temperature of 8°C, and annual precipitation around 600mm with no dry season. The Padul EC station is equipped with two infrared gas analysers to measure CO2 and CH4 fluxes (LI-7200 and LI-7700 respectively) while the Rzecin EC station has the same CH4 sensor as Padul, but also a sensor measuring both GHG fluxes (DLT-100 Fast Methane Analyser, Los Gatos). In this study, we present: i) the results of a CH4 analyser inter-comparison campaign (LI-7700 vs. Los Gatos), ii) a comparative analysis of the functional behaviour of respiration and photosynthesis in both sites testing relationships between CO2 fluxes measured with the EC technique and meteorological variables such as temperature and direct or diffuse radiation and iii) the CH4 dynamicsat both sites by identifying, when possible, annual, seasonal and diurnal patterns.

The Deceptive Resilience of Fixed Exchange Rates

OpenAIRE

Mushin, Jerry

2004-01-01

This paper is an examination of the experience of exchange-rate systems since 1978. Despite the accelerating trend in favour of floating exchange rates, a substantial minority of IMF members have continued to fix the value of their currencies. The recent incidence of each of the principal types of exchange-rate peg is described.

Enhanced exchange bias fields for CoO/Co bilayers: influence of antiferromagnetic grains and mechanisms

Energy Technology Data Exchange (ETDEWEB)

Chang, Cheng-Hsun-Tony; Chang, Shin-Chen [Department of Physics, National Taiwan Normal University, Taipei 116, Taiwan (China); Tsay, Jyh-Shen, E-mail: jstsay@phy.ntnu.edu.tw [Department of Physics, National Taiwan Normal University, Taipei 116, Taiwan (China); Yao, Yeong-Der [Institute of Physics, Academia Sinica, Nankang, Taipei 11529, Taiwan (China)

2017-05-31

Highlights: • An antiferromagnetic grain model on exchange bias phenomena is proposed. • Grain size and grain density are considered. • For smaller grain size, the dependence of t{sub CoO} on T{sub B} showed a less pronounced variation. • An increased grain density is responsible for the enhancement in the exchange bias fields. - Abstract: The emergence and optimization of devices that can be applied to spintronics have attracted considerable interest, and both experimental and theoretical approaches have been used in studies of exchange bias phenomena. A survey of the literature indicates that great efforts have been devoted to improving exchange bias fields, while only limited attempts have been made to control the temperature dependence of exchange bias. In this study, the influence of antiferromagnetic grains on exchange bias phenomena in CoO/Co bilayers on a semiconductor surface was investigated. Based on an antiferromagnetic grain model, a correlation between grain size, grain density, blocking temperature, and the exchange bias field was established. For crystallites with a smaller median diameter, the dependence of the thickness of the CoO layer on blocking temperature showed a less pronounced variation. This is due to the larger thermal agitation of the atomic spin moments in the grain, which causes a weaker exchange coupling between atomic spin moments. The enhanced density of antiferromagnetic/ferromagnetic pinning sites resulting from an increased grain density is responsible for the enhancement in the exchange bias fields. The results reported herein provide insights into our knowledge related to controlling the temperature dependence of exchange bias and related mechanisms.

Net ecosystem exchange of CO2 and H2O fluxes from irrigated grain sorghum and maize in the Texas High Plains

Science.gov (United States)

Net ecosystem exchange (NEE) of carbon dioxide (CO2) and water vapor (H2O) fluxes from irrigated grain sorghum (Sorghum bicolor L. Moench) and maize (Zea mays L.) fields in the Texas High Plains were quantified using the eddy covariance (EC) technique during 2014-2016 growing seasons and examined in...

Empirically constrained estimates of Alaskan regional Net Ecosystem Exchange of CO2, 2012-2014

Science.gov (United States)

Commane, R.; Lindaas, J.; Benmergui, J. S.; Luus, K. A.; Chang, R. Y. W.; Miller, S. M.; Henderson, J.; Karion, A.; Miller, J. B.; Sweeney, C.; Miller, C. E.; Lin, J. C.; Oechel, W. C.; Zona, D.; Euskirchen, E. S.; Iwata, H.; Ueyama, M.; Harazono, Y.; Veraverbeke, S.; Randerson, J. T.; Daube, B. C.; Pittman, J. V.; Wofsy, S. C.

2015-12-01

We present data-driven estimates of the regional net ecosystem exchange of CO2 across Alaska for three years (2012-2014) derived from CARVE (Carbon in the Arctic Reservoirs Vulnerability Experiment) aircraft measurements. Integrating optimized estimates of annual NEE, we find that the Alaskan region was a small sink of CO2 during 2012 and 2014, but a significant source of CO2 in 2013, even before including emissions from the large forest fire season during 2013. We investigate the drivers of this interannual variability, and the larger spring and fall emissions of CO2 in 2013. To determine the optimized fluxes, we couple the Polar Weather Research and Forecasting (PWRF) model with the Stochastic Time-Inverted Lagrangian Transport (STILT) model, to produce footprints of surface influence that we convolve with a remote-sensing driven model of NEE across Alaska, the Polar Vegetation Photosynthesis and Respiration Model (Polar-VPRM). For each month we calculate a spatially explicit additive flux (ΔF) by minimizing the difference between the measured profiles of the aircraft CO2 data and the modeled profiles, using a framework that combines a uniform correction at regional scales and a Bayesian inversion of residuals at smaller scales. A rigorous estimate of total uncertainty (including atmospheric transport, measurement error, etc.) was made with a combination of maximum likelihood estimation and Monte Carlo error propagation. Our optimized fluxes are consistent with other measurements on multiple spatial scales, including CO2 mixing ratios from the CARVE Tower near Fairbanks and eddy covariance flux towers in both boreal and tundra ecosystems across Alaska. For times outside the aircraft observations (Dec-April) we use the un-optimized polar-VPRM, which has shown good agreement with both tall towers and eddy flux data outside the growing season. This approach allows us to robustly estimate the annual CO2 budget for Alaska and investigate the drivers of both the

Effects of Recent Regional Soil Moisture Variability on Global Net Ecosystem CO2 Exchange

Science.gov (United States)

Jones, L. A.; Madani, N.; Kimball, J. S.; Reichle, R. H.; Colliander, A.

2017-12-01

Soil moisture exerts a major regional control on the inter-annual variability of the global land sink for atmospheric CO2. In semi-arid regions, annual biomass production is closely coupled to variability in soil moisture availability, while in cold-season-affected regions, summer drought offsets the effects of advancing spring phenology. Availability of satellite solar-induced fluorescence (SIF) observations and improvements in atmospheric inversions has led to unprecedented ability to monitor atmospheric sink strength. However, discrepancies still exist between such top-down estimates as atmospheric inversion and bottom-up process and satellite driven models, indicating that relative strength, mechanisms, and interaction of driving factors remain poorly understood. We use soil moisture fields informed by Soil Moisture Active Passive Mission (SMAP) observations to compare recent (2015-2017) and historic (2000-2014) variability in net ecosystem land-atmosphere CO2 exchange (NEE). The operational SMAP Level 4 Carbon (L4C) product relates ground-based flux tower measurements to other bottom-up and global top-down estimates to underlying soil moisture and other driving conditions using data-assimilation-based SMAP Level 4 Soil Moisture (L4SM). Droughts in coastal Brazil, South Africa, Eastern Africa, and an anomalous wet period in Eastern Australia were observed by L4C. A seasonal seesaw pattern of below-normal sink strength at high latitudes relative to slightly above-normal sink strength for mid-latitudes was also observed. Whereas SMAP-based soil moisture is relatively informative for short-term temporal variability, soil moisture biases that vary in space and with season constrain the ability of the L4C estimates to accurately resolve NEE. Such biases might be caused by irrigation and plant-accessible ground-water. Nevertheless, SMAP L4C daily NEE estimates connect top-down estimates to variability of effective driving factors for accurate estimates of regional

Management of exchange rate regimes in emerging Asia

Directory of Open Access Journals (Sweden)

Ramkishen S. Rajan

2012-04-01

Full Text Available This paper revisits the issue of exchange rate regimes in emerging Asia over the decade 1999–2009. It finds that while Asia is home to a wide array of exchange rate regimes, there are signs of gradual movement toward somewhat greater exchange rate flexibility in many of the regional countries. There appears to be evidence of an apparent “fear of appreciation” which is manifested in asymmetric exchange rate intervention—i.e., a willingness to allow depreciations but reluctance to allow appreciations. This policy of effective exchange rate undervaluation is rather unorthodox from a neoclassical sense, but is consistent with a development policy centered on suppressing the price of non-tradable goods relative to tradables (i.e., real exchange rate undervaluation.

LMTD Design Methodology Assessment of Spiral Tube Heat Exchanger under the S-CO2 cycle operating condition

International Nuclear Information System (INIS)

Jung, Hwa Young; Lee, Jeong Ik; Ahn, Yoon Han

2013-01-01

The advantages of PCHE are compact high pressure difference endurance high temperature operation. However, PCHE is quite expensive and the resistance to the fast thermal cycling is questionable. In order to overcome this problem, the Korea Advanced Institute of Science and Technology (KAIST) research team is considering an alternative for the PCHE. Currently KAIST research team is using a Spiral Tube Heat Exchanger (STHE) of Sentry Equipment Corp. as a pre cooler in the SCO 2 PE facility. A STHE is relatively cheap but the operating pressure and temperature are acceptable for utilizing it as a pre cooler. A STHE is consisted of spiral shaped tubes (hot side i.e. S-CO 2 ) immersed in a shell (cold side i.e. water). This study is aimed at whether the logarithmic mean temperature difference (LMTD) heat exchanger design methodology is acceptable for designing the S-CO 2 cycle pre cooler. This is because the LMTD method usually assumes a constant specific heat, but the pre cooler in the S-CO 2 cycle operates at the nearest point to the critical point where a dramatic change in properties is expected. Experimentally obtained data are compared to the vendor provided technical specification based on the LMTD method. The detailed specifications provided by the vendor are listed in Table 1

Modelling the diurnal and seasonal dynamics of soil CO2 exchange in a semiarid ecosystem with high plant–interspace heterogeneity

Directory of Open Access Journals (Sweden)

J. Gong

2018-01-01

Full Text Available We used process-based modelling to investigate the roles of carbon-flux (C-flux components and plant–interspace heterogeneities in regulating soil CO2 exchanges (FS in a dryland ecosystem with sparse vegetation. To simulate the diurnal and seasonal dynamics of FS, the modelling considered simultaneously the CO2 production, transport and surface exchanges (e.g. biocrust photosynthesis, respiration and photodegradation. The model was parameterized and validated with multivariate data measured during the years 2013–2014 in a semiarid shrubland ecosystem in Yanchi, northwestern China. The model simulation showed that soil rewetting could enhance CO2 dissolution and delay the emission of CO2 produced from rooting zone. In addition, an ineligible fraction of respired CO2 might be removed from soil volumes under respiration chambers by lateral water flows and root uptakes. During rewetting, the lichen-crusted soil could shift temporally from net CO2 source to sink due to the activated photosynthesis of biocrust but the restricted CO2 emissions from subsoil. The presence of plant cover could decrease the root-zone CO2 production and biocrust C sequestration but increase the temperature sensitivities of these fluxes. On the other hand, the sensitivities of root-zone emissions to water content were lower under canopy, which may be due to the advection of water flows from the interspace to canopy. To conclude, the complexity and plant–interspace heterogeneities of soil C processes should be carefully considered to extrapolate findings from chamber to ecosystem scales and to predict the ecosystem responses to climate change and extreme climatic events. Our model can serve as a useful tool to simulate the soil CO2 efflux dynamics in dryland ecosystems.

Modeling Real Exchange Rate Persistence in Chile

Directory of Open Access Journals (Sweden)

Leonardo Salazar

2017-07-01

Full Text Available The long and persistent swings in the real exchange rate have for a long time puzzled economists. Recent models built on imperfect knowledge economics seem to provide a theoretical explanation for this persistence. Empirical results, based on a cointegrated vector autoregressive (CVAR model, provide evidence of error-increasing behavior in prices and interest rates, which is consistent with the persistence observed in the data. The movements in the real exchange rate are compensated by movements in the interest rate spread, which restores the equilibrium in the product market when the real exchange rate moves away from its long-run benchmark value. Fluctuations in the copper price also explain the deviations of the real exchange rate from its long-run equilibrium value.

Summit CO2 emission rates by the CO2/SO2 ratio method at Kīlauea Volcano, Hawaiʻi, during a period of sustained inflation

Science.gov (United States)

Hager, S.A.; Gerlach, T.M.; Wallace, P.J.

2008-01-01

The emission rate of carbon dioxide escaping from the summit of Kīlauea Volcano, Hawaiʻi, proved highly variable, averaging 4900 ± 2000 metric tons per day (t/d) in June–July 2003 during a period of summit inflation. These results were obtained by combining over 90 measurements of COSPEC-derived SO2emission rates with synchronous CO2/SO2 ratios of the volcanic gas plume along the summit COSPEC traverse. The results are lower than the CO2 emission rate of 8500 ± 300 t/d measured by the same method in 1995–1999 during a period of long-term summit deflation [Gerlach, T.M., McGee, K.A., Elias, T., Sutton, A.J. and Doukas, M.P., 2002. Carbon dioxide emission rate of Kīlauea Volcano: Implications for primary magma and the summit reservoir. Journal of Geophysical Research-Solid Earth, 107(B9): art. no.-2189.]. Analysis of the data indicates that the emission rates of the present study likely reflect changes in the magma supply rate and residence time in the summit reservoir. It is also likely that emission rates during the inflation period were heavily influenced by SO2 pulses emitted adjacent to the COSPEC traverse, which biased CO2/SO2 ratios towards low values that may be unrepresentative of the global summit gas plume. We conclude that the SO2 pulses are consequences of summit re-inflation under way since 2003 and that CO2 emission rates remain comparable to, but more variable than, those measured prior to re-inflation.

Exchange bias in Co nanoparticles embedded in an Mn matrix

International Nuclear Information System (INIS)

Domingo, Neus; Testa, Alberto M.; Fiorani, Dino; Binns, Chris; Baker, Stephen; Tejada, Javier

2007-01-01

Magnetic properties of Co nanoparticles of 1.8 nm diameter embedded in Mn and Ag matrices have been studied as a function of the volume fraction (VFF). While the Co nanoparticles in the Ag matrix show superparamagnetic behavior with T B =9.5 K (1.5% VFF) and T B =18.5 K (8.9% VFF), the Co nanoparticles in the antiferromagnetic Mn matrix show a transition peak at ∼65 K in the ZFC/FC susceptibility measurements, and an increase of the coercive fields at low temperature with respect to the Ag matrix. Exchange bias due to the interface exchange coupling between Co particles and the antiferromagnetic Mn matrix has also been studied. The exchange bias field (H eb ), observed for all Co/Mn samples below 40 K, decreases with decreasing volume fraction and with increasing temperature and depends on the field of cooling (H fc ). Exchange bias is accompanied by an increase of coercivity

Interdependence and Exchange Rate Regimes in East Asia: Intra-regional Transmissions of Exchange Rate Policies after the Crisis (in Japanese)

OpenAIRE

OHNO Sanae; FUKUDA Shin-ichi

2003-01-01

Since the onset of the Asian crisis, what characterizes the East Asian exchange rates has been a topic of considerable discussion. In the pre-crisis period, the de facto pegs to the U.S. dollar sometimes destabilized the real "effective" exchange rates of these currencies. Several economists have, thus, proposed the desirability of intermediate exchange rate regimes in East Asia that might stabilize their effective exchange rates. The post-crisis experience in East Asia, however, taught us th...

First-order-reversal-curve analysis of exchange-coupled SmCo/NdFeB nanocomposite alloys

International Nuclear Information System (INIS)

Pan, Mingxiang; Zhang, Pengyue; Ge, Hongliang; Yu, Nengjun; Wu, Qiong

2014-01-01

Exchange-coupled SmCo 5 /Nd 2 Fe 14 B nanocomposite magnets have been fabricated by ball milling of the micrometer sized SmCo 5 and Nd 2 Fe 14 B powders. The influence of Nd 2 Fe 14 B content on the microstructure and magnetic properties of these hybrid alloys was investigated. The alloys that show strong intergrain exchange-coupling behavior with (BH) max =2.95 MGOe was obtained when the two hard phases are well coupled. A first-order-reversal-curve (FORC) analysis was performed for both SmCo 5 single-phase magnet and SmCo 5 /Nd 2 Fe 14 B hybrid magnet; the FORC diagrams results show two major peaks for the hybrid magnets. In both cases, the magnetization reversal behaviors for these alloys were discussed in detail and are consistent with the results of δM plots. - Highlights: • Exchange-coupled SmCo 5 /Nd 2 Fe 14 B nanocomposite magnets were studied. • Magnetization reversal behaviors of the hybrid magnet were discussed. • The FORCs analysis is taken to identify the optimal conditions for hybrid magnet

Influences of soil volume and an elevated CO[sub 2] level on growth and CO[sub 2] exchange for the crassulacean acid metabolism plant Opuntia ficus-indica

Energy Technology Data Exchange (ETDEWEB)

Nobel, P.S.; Cui, M.; Miller, P.M.; Luo, Y. (UCLA-DOE Lab., Univ. of California, Los Angeles, CA (United States))

1994-01-01

Effects of the current (38 Pa) and an elevated (74 Pa) CO[sub 2] partial pressure on root and shoot areas, biomass accumulation and daily net CO[sub 2] exchange were determined for opuntia ficus-indica (L.) Miller, a highly productive Crassulacean acid metabolism species cultivated worldwide. Plants were grown in environmentally controlled rooms for 18 weeks in pots of three soil volumes (2600, 6500 and 26000 cm[sup 3]), the smallest of which was intended to restrict root growth. For plants in the medium-sized soil volume, basal cladodes tended to be thicker and areas of main and lateral roots tended to be greater as the CO[sub 2] level was doubled. Daughter cladodes tended to be initiated sooner at the current compared with the elevated CO[sub 2] level but total areas were similar by 10 weeks. At 10 weeks, daily net CO[sub 2] uptake for the three soil volumes averaged 24% higher for plants growing under elevated compared with current CO-2 levels, but at 18 weeks only 3% enhancement in uptake occurred. Dry weight gain was enhanced 24% by elevated CO[sub 2] during the first 10 weeks but only 8% over 18 weeks. Increasing the soil volume 10-fold led to a greater stimulation of daily net CO[sub 2] uptake and biomass production than did doubling the CO[sub 2] level. At 18 weeks, root biomass doubled and shoot biomass nearly doubled as the soil volume was increased 10-fold; the effects of soil volume tended to be greater for elevated CO[sub 2]. The amount of cladode nitrogen per unit dry weight decreased as the CO[sub 2] level was raised and increased as soil volume increased, the latter suggesting that the effects of soil volume could be due to nitrogen limitations. (au) (30 refs.)

Contrasting impact of forestry-drainage on CO2 balance at two adjacent peatlands in Finland

Science.gov (United States)

Lohila, Annalea; Minkkinen, Kari; Penttilä, Timo; Launiainen, Samuli; Koskinen, Markku; Ojanen, Paavo; Laurila, Tuomas

2014-05-01

Fate of carbon in peatlands after drainage has been a subject of many studies, particularly at agriculturally managed sites, but also at sites prepared for forestry. In general, the drainage of peatlands has been considered to trigger the decomposition rate of peat and to cause carbon dioxide (CO2) emissions from the peat into the atmosphere. However, there is not yet full consensus on what are the main regulating factors of the carbon balances in forested peatlands, and do all the forested peatland even act as a source of carbon into the atmosphere. In this study we compare the CO2 exchange rates at two adjacent peatland sites in southern Finland, drained for forestry about 40 years earlier. The pair of sites with similar climatic conditions offer an excellent case for studying the mechanisms controlling the carbon balances of forestry-drained peatlands. The sites differ from each other only by fertility, which has an impact on, e.g., tree growth rate. At both sites, CO2 and energy fluxes have been measured with the eddy covariance method over the course of 4 years, but not simultaneously. We have also built at both sites an automatic system consisting of six transparent closed chambers which collect data on the CO2 exchange of the forest floor vegetation (including tree roots) and soil around the year. This enables us to quantify the carbon uptake potential of the ground layer and the peat decomposition rates and helps us to understand the differences between the sites. The results show that the pine and dwarf-shrub-dominated site (nutrient-poor) is a large CO2 sink. The site with a mixture of spruce, birch and pine and lesser ground vegetation (nutrient-rich), on the contrary, has a close-to-neutral CO2 balance, despite the much higher tree growth rate there. In this presentation we will compare the general dynamics and climatic responses of CO2 exchange at the sites, compare the magnitude and factors causing interannual variation, and discuss potential reasons

North America's net terrestrial CO2 exchange with the atmosphere 1990–2009

Science.gov (United States)

King, A.W.; Andres, R.J.; Davis, K.J.; Hafer, M.; Hayes, D.J.; Huntzinger, Deborah N.; de Jong, Bernardus; Kurz, W.A.; McGuire, A. David; Vargas, Rodrigo I.; Wei, Y.; West, Tristram O.; Woodall, Christopher W.

2015-01-01

Scientific understanding of the global carbon cycle is required for developing national and international policy to mitigate fossil fuel CO2 emissions by managing terrestrial carbon uptake. Toward that understanding and as a contribution to the REgional Carbon Cycle Assessment and Processes (RECCAP) project, this paper provides a synthesis of net land–atmosphere CO2 exchange for North America (Canada, United States, and Mexico) over the period 1990–2009. Only CO2 is considered, not methane or other greenhouse gases. This synthesis is based on results from three different methods: atmospheric inversion, inventory-based methods and terrestrial biosphere modeling. All methods indicate that the North American land surface was a sink for atmospheric CO2, with a net transfer from atmosphere to land. Estimates ranged from −890 to −280 Tg C yr−1, where the mean of atmospheric inversion estimates forms the lower bound of that range (a larger land sink) and the inventory-based estimate using the production approach the upper (a smaller land sink). This relatively large range is due in part to differences in how the approaches represent trade, fire and other disturbances and which ecosystems they include. Integrating across estimates, "best" estimates (i.e., measures of central tendency) are −472 ± 281 Tg C yr−1 based on the mean and standard deviation of the distribution and −360 Tg C yr−1 (with an interquartile range of −496 to −337) based on the median. Considering both the fossil fuel emissions source and the land sink, our analysis shows that North America was, however, a net contributor to the growth of CO2 in the atmosphere in the late 20th and early 21st century. With North America's mean annual fossil fuel CO2 emissions for the period 1990–2009 equal to 1720 Tg C yr−1 and assuming the estimate of −472 Tg C yr−1 as an approximation of the true terrestrial CO2 sink, the continent's source : sink ratio for this time period was

In-plane and perpendicular exchange bias in [Pt/Co]/NiO multilayers

Energy Technology Data Exchange (ETDEWEB)

Lin, K.W.; Guo, J.Y.; Chang, S.C.; Ouyang, H. [Department of Materials Science and Engineering, National Chung Hsing University, Taichung 402 (China); Kahwaji, S.; Van Lierop, J. [Department of Physics and Astronomy, University of Manitoba, Winnipeg, R3T 2N2 (Canada); Phuoc, N.N.; Suzuki, T. [Information Storage Materials Laboratory, Toyota Technological Institute, Nagoya 468-8511 (Japan)

2007-12-15

Exchange bias in [Pt/Co]/NiO multilayers were studied as a function of film thickness and [Pt/Co] layer repetition. A strong temperature dependence of the coercivity, H{sub c}, and exchange bias field, H{sub ex}, was observed for the thick and thinnest [Pt/Co]/NiO multilayers. While the thinnest [Pt(3 nm)/Co(1.25 nm)]{sub 4}/NiO multilayers exhibits no in-plane exchange bias field, a perpendicular H{sub ex} {sub perpendicular} {sub to} {proportional_to} -150 Oe at 80 K was measured. By contrast, the thickest [Pt(12 nm)/Co(10 nm)]{sub 1}/NiO multilayers exhibited an in-plane H{sub ex//}{proportional_to}-600 Oe (with H{sub ex//}{proportional_to}-1300 Oe at 5 K) with no measurable perpendicular exchange bias field. The estimated interfacial exchange coupling energy implies the effective Co layer thickness contributing to the exchange bias is effective only in Co layer in contact with NiO bottom layer. AC susceptibility and the temperature dependence of H{sub ex} show that the a 1.25 nm thick Co component enables perpendicular exchange bias with a reduced blocking temperature T{sub B}{proportional_to}200 K, compared to that (T{sub B}{proportional_to}250 K) for the thick [Pt/Co]/NiO multilayers. This is attributed to disordered CoPt phases that formed due to intermixing between Co and Pt during deposition. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

On exchange rate misalignments in the Eurozone's peripheral countries

Science.gov (United States)

Grochová, Ladislava; Plecitá, Klára

2013-10-01

In this paper we model equilibrium exchange rates for the Eurozone's countries on the basis of the Behavioural Equilibrium Exchange Rate approach, which assumes, that equilibrium exchange rates are in the long run affected by economic fundamentals. To assess the degree of exchange rate misalignment for the Eurozone's peripheral countries - Portugal, Ireland, Greece and Spain - the gap between the actual and the modelled equilibrium exchange rate value is calculated. Our results show that Spain, Portugal and Ireland had their real exchange rates in equilibrium when they joined the Eurozone; however their real exchange rates have been persistently overvalued since the beginning of the 2000s. Greece, on the other hand, has experienced diminishing undervaluation at the beginning of its membership in the Eurozone and since 2009 has exhibited an overvalued real exchange rate.

A new assessment of floating exchange rates

OpenAIRE

Waimann, D. R.

1981-01-01

The switch to floating exchange rates during the 1970s has given economists the first comprehensive opportunity to assess the arguments for and against floating. Much new work has been done on various aspects of floating exchange rate behaviour. This article attempts a limited survey of the evidence concerning two important issues—whether floating exchange rates are inherently unstable and whether they harm international trade.

Elevated atmospheric CO2 increases microbial growth rates and enzymes activity in soil

Science.gov (United States)

Blagodatskaya, Evgenia; Blagodatsky, Sergey; Dorodnikov, Maxim; Kuzyakov, Yakov

2010-05-01

Increasing the belowground translocation of assimilated carbon by plants grown under elevated CO2 can cause a shift in the structure and activity of the microbial community responsible for the turnover of organic matter in soil. We investigated the long-term effect of elevated CO2 in the atmosphere on microbial biomass and specific growth rates in root-free and rhizosphere soil. The experiments were conducted under two free air carbon dioxide enrichment (FACE) systems: in Hohenheim and Braunschweig, as well as in the intensively managed forest mesocosm of the Biosphere 2 Laboratory (B2L) in Oracle, AZ. Specific microbial growth rates (μ) were determined using the substrate-induced respiration response after glucose and/or yeast extract addition to the soil. We evaluated the effect of elevated CO2 on b-glucosidase, chitinase, phosphatase, and sulfatase to estimate the potential enzyme activity after soil amendment with glucose and nutrients. For B2L and both FACE systems, up to 58% higher μ were observed under elevated vs. ambient CO2, depending on site, plant species and N fertilization. The μ-values increased linearly with atmospheric CO2 concentration at all three sites. The effect of elevated CO2 on rhizosphere microorganisms was plant dependent and increased for: Brassica napus=Triticum aestivumyeast extract then for those growing on glucose, i.e. the effect of elevated CO2 was smoothed on rich vs. simple substrate. So, the r/K strategies ratio can be better revealed by studying growth on simple (glucose) than on rich substrate mixtures (yeast extract). After adding glucose, enzyme activities under elevated CO2 were 1.2-1.9-fold higher than under ambient CO2. This indicates the increased activity of microorganisms, which leads to accelerated C turnover in soil under elevated CO2. Our results clearly showed that the functional characteristics of the soil microbial community (i.e. specific growth rates and enzymes activity) rather than total microbial biomass

High Precision Stable Isotope Measurements of Caribic Aircraft CO{sub 2} Samples: Global Distribution and Exchange with the Biosphere

Energy Technology Data Exchange (ETDEWEB)

Assonov, S. S. [Max Planck Institute for Chemistry, Mainz (Germany); Joint Research Centre, Institute for Reference Materials and Measurements (JRC-IRMM), European Commission, Geel (Belgium); Brenninkmeijer, C. A.M.; Schuck, T. J. [Max Planck Institute for Chemistry, Mainz (Germany); Taylor, P. [Joint Research Centre, Institute for Reference Materials and Measurements (JRC-IRMM), European Commission, Geel (Belgium)

2013-07-15

In 2007-2009 JRC-IRMM, in collaboration with the project CARIBIC (Civil Aircraft for Regular Investigation of the atmosphere Based on an Instrument Container, www.caribicatmospheric. com), conducted systematic measurements aimed to study the global distribution of CO{sub 2} isotopic composition. A large data set for the upper troposphere-lowermost stratosphere and free troposphere was obtained. For the first time it is demonstrated how CO{sub 2} isotope signals reflect global scale variability in air mass origin. Tight correlations observed arise either from stratosphere/troposphere mixing or from mixing of background air and air masses affected by CO{sub 2} sources and sinks, over long distances and throughout the seasons. The high quality {delta}{sup 18}O(CO{sub 2}) data prove to be a useful tracer reflecting long range CO{sub 2} transport and also CO{sub 2} exchange with land biosphere and soils. The data provide a benchmark for future comparisons and are available for modelling studies. (author)

Magnetization reversal dynamics in exchange-coupled NiO - Co bilayers

International Nuclear Information System (INIS)

Camarero, J.; Pennec, Y.; Bonfim, M.; Vogel, J.; Pizzini, S.; Fontaine, A.; Cartier, M.; Fettar, F.; Dieny, B.

2001-01-01

We performed a detailed study of the magnetization reversal in polycrystalline exchange-coupled NiO/Co bilayers over 10 decades of field sweep rate dH/dt for different NiO and Co thicknesses. For all sweep rates and thicknesses, the symmetry of the hysteresis loops shows that an identical pinning strength has to be overcome in both directions of the reversal. At low dH/dt the reversal is governed by domain wall displacement while domain nucleation is dominant at higher ones. The dH/dt at which the transition between the two regimes takes place depends on the relative thickness of the NiO and Co layers. It increases (decreases) when the Co (NiO) thickness is increased. Experimentally, it was found that the energy barrier varies linearly with the square root of the area corresponding to the activation (Barkhausen) volume which is consistent with a random walk model of the coupling between antiferromagnetic and ferromagnetic layers. The results can be explained in terms of a thermally activated switching of the NiO magnetization dragged by the Co reversal. [copyright] 2001 American Institute of Physics

Extraction of Co ions from ion-exchange resin by supercritical carbon dioxide

International Nuclear Information System (INIS)

Ju, Min Su; Koh, Moon Sung; Yang, Sung Woo; Park, Kwang Heon; Kim, Hak Won; Kim, Hong Doo

2005-01-01

There are a number of liquid treatment processes for eliminating radioactive ionic contaminants in nuclear facilities. One of the most common treatment methods for aqueous streams is the use of ion exchange, which is a well-developed technique that has been employed for many years in the nuclear industry. More specifically speaking, systems that ion exchange method is applied to in nuclear power plants are liquid radioactive waste treatment system, chemical and volume control system, steam generator blowdown treatment system, and service water supply system. During the operation of nuclear power plants, radioactive contaminants such as Co-60, Mn-54, Fe-59 and Cs-137 are contained in liquid radioactive wastes. And the wastes containing small amount of uranium are generated in nuclear fuel cycle facilities. To treat the liquid radioactive waste, we usually install ion exchangers rather than evaporators due to their simplicity and effectiveness, and this trend is increasing. However, the ion exchange process produces large volume of spent organic resin, and has some problems of radiation damage and thermal instability. And the reuse of the resin is limited due to the degradation of ion-exchanging ability. For this reason, were should consider a better method to expand the lifetime of the resin or to reduce the volume of radioactive resin wastes by extracting radioactive contaminants located in the resin. Supercritical fluid CO 2 has many good points as a process solvent that include low viscosity, negligible surface tension, and variable selectivity. And supercritical fluids have physical properties of both liquid and gas such as good penetration with a high dissolution capability. Supercritical fluids have been widely used in extraction, purification, and recovery processes. A number of workers applied supercritical CO 2 solvent for cleaning of precision devices and waste treatments. Since supercritical CO 2 has its mild critical point at 31 and 73.8bar as .deg. C

Anion-Exchange Membrane Fuel Cells with Improved CO2 Tolerance: Impact of Chemically Induced Bicarbonate Ion Consumption.

Science.gov (United States)

Katayama, Yu; Yamauchi, Kosuke; Hayashi, Kohei; Okanishi, Takeou; Muroyama, Hiroki; Matsui, Toshiaki; Kikkawa, Yuuki; Negishi, Takayuki; Watanabe, Shin; Isomura, Takenori; Eguchi, Koichi

2017-08-30

Over the last few decades, because of the significant development of anion exchange membranes, increasing efforts have been devoted the realization of anion exchange membrane fuel cells (AEMFCs) that operate with the supply of hydrogen generated on-site. In this paper, ammonia was selected as a hydrogen source, following which the effect of conceivable impurities, unreacted NH 3 and atmospheric CO 2 , on the performance of AEMFCs was established. As expected, we show that these impurities worsen the performance of AEMFCs significantly. Furthermore, with the help of in situ attenuated total reflection infrared (ATR-IR) spectroscopy, it was revealed that the degradation of the cell performance was primarily due to the inhibition of the hydrogen oxidation reaction (HOR). This is attributed to the active site occupation by CO-related adspecies derived from (bi)carbonate adspecies. Interestingly, this degradation in the HOR activity is suppressed in the presence of both NH 3 and HCO 3 - because of the bicarbonate ion consumption reaction induced by the existence of NH 3 . Further analysis using in situ ATR-IR and electrochemical methods revealed that the poisonous CO-related adspecies were completely removed under NH 3 -HCO 3 - conditions, accompanied by the improvement in HOR activity. Finally, a fuel cell test was conducted by using the practical AEMFC with the supply of NH 3 -contained H 2 gas to the anode and ambient air to the cathode. The result confirmed the validity of this positive effect of NH 3 -HCO 3 - coexistence on CO 2 -tolerence of AEMFCs. The cell performance achieved nearly 95% of that without any impurity in the fuels. These results clearly show the impact of the chemically induced bicarbonate ion consumption reaction on the realization of highly CO 2 -tolerent AEMFCs.

Model Uncertainty and Exchange Rate Forecasting

NARCIS (Netherlands)

Kouwenberg, R.; Markiewicz, A.; Verhoeks, R.; Zwinkels, R.C.J.

2017-01-01

Exchange rate models with uncertain and incomplete information predict that investors focus on a small set of fundamentals that changes frequently over time. We design a model selection rule that captures the current set of fundamentals that best predicts the exchange rate. Out-of-sample tests show

Model Uncertainty and Exchange Rate Forecasting

NARCIS (Netherlands)

R.R.P. Kouwenberg (Roy); A. Markiewicz (Agnieszka); R. Verhoeks (Ralph); R.C.J. Zwinkels (Remco)

2013-01-01

textabstractWe propose a theoretical framework of exchange rate behavior where investors focus on a subset of economic fundamentals. We find that any adjustment in the set of predictors used by investors leads to changes in the relation between the exchange rate and fundamentals. We test the

First-principles study of mechanical, exchange interactions and the robustness in Co{sub 2}MnSi full Heusler compounds

Energy Technology Data Exchange (ETDEWEB)

Akriche, A., E-mail: akricheahmed@gmail.com [Laboratoire de Microscope Electronique et Sciences des Matériaux, Université d’Oran des Sciences et de la Technologie-USTO, Mohamed Boudiaf, Faculté de physique, Département de Génie Physique, Oran (Algeria); Bouafia, H. [Laboratoire de Génie Physique, Université Ibn-Khaldoun, Tiaret 14000 (Algeria); Hiadsi, S. [Laboratoire de Microscope Electronique et Sciences des Matériaux, Université d’Oran des Sciences et de la Technologie-USTO, Mohamed Boudiaf, Faculté de physique, Département de Génie Physique, Oran (Algeria); Abidri, B. [Laboratoire des Matériaux Magnétiques, Université Djillali Liabés, Sidi Bel-Abbes (Algeria); Sahli, B. [Laboratoire de Génie Physique, Université Ibn-Khaldoun, Tiaret 14000 (Algeria); Elchikh, M.; Timaoui, M.A.; Djebour, B. [Laboratoire de Microscope Electronique et Sciences des Matériaux, Université d’Oran des Sciences et de la Technologie-USTO, Mohamed Boudiaf, Faculté de physique, Département de Génie Physique, Oran (Algeria)

2017-01-15

In this work we report the results of ab-initio studies of structural, mechanical, electronic and magnetic properties of Co based Co{sub 2}MnSi Heusler compound in stoichiometric composition. All of which are accurately calculated by the full-potential (FP-LMTO) program combined with the spin polarized generalized gradient approximation in the density functional formalism (DFT). The total energy calculations clearly favor the ferromagnetic ground state. The lattice parameter, elastic constants and their related parameters were also evaluated and compared to experimental and theoretical values whenever possible. In this paper, the electronic properties are treated with GGA+U approach. The magnetic exchange constants temperature has been calculated using a mean field-approximation (MFA). The half-metal to metal transition was observed around 40 GPa. Increasing pressure has no impact on the total magnetic moment or the overall shape of the band structure that indicates the robustness of the electronic structure of this system. - Highlights: • In this work, we have studied some physical properties of Co{sub 2}MnSi Heusler compound. • The exchange-correlation energy is treated within GGA and (GGA+U) approximation. • The electronic band structure shows that Co{sub 2}MnSi is a half-metallic compound.

Diurnal and Seasonal Variations in the Net Ecosystem CO2 Exchange of a Pasture in the Three-River Source Region of the Qinghai-Tibetan Plateau.

Directory of Open Access Journals (Sweden)

Bin Wang

Full Text Available Carbon dioxide (CO2 exchange between the atmosphere and grassland ecosystems is very important for the global carbon balance. To assess the CO2 flux and its relationship to environmental factors, the eddy covariance method was used to evaluate the diurnal cycle and seasonal pattern of the net ecosystem CO2 exchange (NEE of a cultivated pasture in the Three-River Source Region (TRSR on the Qinghai-Tibetan Plateau from January 1 to December 31, 2008. The diurnal variations in the NEE and ecosystem respiration (Re during the growing season exhibited single-peak patterns, the maximum and minimum CO2 uptake observed during the noon hours and night; and the maximum and minimum Re took place in the afternoon and early morning, respectively. The minimum hourly NEE rate and the maximum hourly Re rate were -7.89 and 5.03 μmol CO2 m-2 s-1, respectively. The NEE and Re showed clear seasonal variations, with lower values in winter and higher values in the peak growth period. The highest daily values for C uptake and Re were observed on August 12 (-2.91 g C m-2 d-1 and July 28 (5.04 g C m-2 day-1, respectively. The annual total NEE and Re were -140.01 and 403.57 g C m-2 year-1, respectively. The apparent quantum yield (α was -0.0275 μmol μmol-1 for the entire growing period, and the α values for the pasture's light response curve varied with the leaf area index (LAI, air temperature (Ta, soil water content (SWC and vapor pressure deficit (VPD. Piecewise regression results indicated that the optimum Ta and VPD for the daytime NEE were 14.1°C and 0.65 kPa, respectively. The daytime NEE decreased with increasing SWC, and the temperature sensitivity of respiration (Q10 was 3.0 during the growing season, which was controlled by the SWC conditions. Path analysis suggested that the soil temperature at a depth of 5 cm (Tsoil was the most important environmental factor affecting daily variations in NEE during the growing season, and the photosynthetic photon

Concentration of ions Co(II), Ni(II) at the Tokem-250 carboxylic cation exchange for catalysts development

Science.gov (United States)

Zharkova, Valentina; Bobkova, Ludmila; Brichkov, Anton; Kozik, Vladimir

2017-11-01

Sorption and catalytic properties of the cation exchanger are investigated. It was found that the Tokem-250 has a wide operating range of pH. The value of the effective ionization constant of the functional groups of the cation exchanger (pKa) is 6.59. The Tokem-250 cation exchanger exhibits selectivity to Ni2+ ions to Co2+ (D˜103). This is probably due to the stability of ion-exchange complexes detected by the method of diffuse reflectance electron spectroscopy (ESDD). According to these data, for Co2+ ions, in contrast to Ni2+, tetragonal distortion of octahedral coordination is characteristic, which has a positive effect on the stability of complexes with Co2+. To obtain spherical catalysts on the basis of Tokem-250, cobalt-containing samples of cation exchanger were used. The developed spherical materials have catalytic activity in the reactions of deep and partial oxidation of n-heptane.