Fraction Of Carbon Dioxide Research Articles

Effect of thermal boundary condition and turbulent models on the combustion simulation of ethylene-fueled scramjet combustor

Wall thermal boundary conditions and turbulent models can affect flow and combustion simulations but are seldom considered in the turbulent modeling of supersonic combustors. This work investigated the effect of thermal boundary conditions and four turbulent models on turbulent combustion in a cavity-stabilized scramjet combustor. Results showed that the thermal boundary condition had a noticeable influence on the temperature fields. Changing the thermal boundary condition from zero gradient to a fixed lower temperature considerably reduced the maximum temperature but did not affect the temperature distribution. The fixed temperature boundary condition generated a slightly larger reaction heat release near the upper region of the cavity. However, the mass fraction of carbon dioxide was low for a fixed low temperature. The pressure increased near the rear of the cavity but decreased elsewhere at a fixed temperature. Reynolds-averaged models (k-epsilon, k-omega, and realizable k-epsilon) tend to over-predict the temperature and turbulent kinetic energy but under-predict the mass fraction of carbon dioxide. The detached Eddy simulation also under-predicts carbon dioxide but predicts a more accurate temperature.

Control of the flame and flow characteristics of a non-premixed bluff body burner using dielectric barrier discharge plasma actuators

Reducing emissions and improving combustion are necessary steps to reach greener combustion systems. In this study, the effect of employing an annular plasma actuator mounted on the surface of a bluff body in a non-premixed burner is numerically investigated. Activating the plasma actuator induces an ionic wind near the surface of the bluff body that modifies the flow features. While the previous relevant studies were mainly focused on volume dielectric barrier plasma discharges, this study investigates the influences of surface plasma discharges. Also, the effect of plasma actuator position, fuel-to-air velocity ratio, and the size of the bluff body are investigated. The characteristics of the flow and temperature fields, the mass fraction of carbon monoxide and carbon dioxide inside the burner in the presence, and the absence of a plasma actuator are analyzed. Also, spatial mixing deficiency (SMD) is used to evaluate the plasma actuator's influence on the reactants' mixing. The results show that among various configurations of annular plasma actuators, positioning the plasma actuator on the bluff body surface acting upwards near the air duct, strengthens the external recirculation region which leads to a favorable change in the characteristics of the flame inside the burner. With the activation of the plasma actuator, the spatial mixing deficiency (SMD) values decrease by an average of 12.75%, showing improvement in mixing, and the flame becomes more uniform compared to the baseline case leading to the reduction of CO concentration. In addition, the root of the flame is strengthened and the height of the body of the flame measured from the bluff body surface is reduced by about 43%. For both low and high fuel-to-air velocity ratios, the presence of a plasma actuator leads to a positive effect on the flame structure. For a high fuel-to-air velocity ratio, the external recirculation area has a favorable size. The created flame is elongated and the root of the flame is entirely away from the burner. When the plasma actuator is active, it causes the flame to get closer to the burner tip. For various diameters of the bluff body, the plasma actuator showed reasonable capability in altering the flame behavior. For larger bluff body diameters, the plasma actuator strengthens both recirculation zones, especially the external recirculation zone, leading to a uniform and shorter flame.

Reconstructing annual XCO2 at a 1 km×1 km spatial resolution across China from 2012 to 2019 based on a spatial CatBoost method

Long-time-series, high-resolution datasets of the column-averaged dry-air mole fraction of carbon dioxide (XCO2) have great practical importance for mitigating the greenhouse effect, assessing carbon emissions and implementing a low-carbon cycle. However, the mainstream XCO2 datasets obtained from satellite observations have coarse spatial resolutions and are inadequate for supporting research applications with different precision requirements. Here, we developed a new spatial machine learning model by fusing spatial information with CatBoost, called SCatBoost, to fill the above gap based on existing global land-mapped 1° XCO2 data (GLM-XCO2). The 1-km-spatial-resolution dataset containing XCO2 values in China from 2012 to 2019 reconstructed by SCatBoost has stronger and more stable predictive power (confirmed with a cross-validation (R2 = 0.88 and RSME = 0.20 ppm)) than other traditional models. According to the estimated dataset, the overall national XCO2 showed an increasing trend, with the annual mean concentration rising from 392.65 ppm to 410.36 ppm. In addition, the spatial distribution of XCO2 concentrations in China reflects significantly higher concentrations in the eastern coastal areas than in the western inland areas. The contributions of this study can be summarized as follows: (1) It proposes SCatBoost, integrating the advantages of machine learning methods and spatial characteristics with a high prediction accuracy; (2) It presents a dataset of fine-scale and high resolution XCO2 over China from 2012 to 2019 by the model of SCatBoost; (3) Based on the generated data, we identify the spatiotemporal trends of XCO2 in the scale of nation and city agglomeration. These long-term and high resolution XCO2 data help understand the spatiotemporal variations in XCO2, thereby improving policy decisions and planning about carbon reduction.

Improved Constraints on the Recent Terrestrial Carbon Sink Over China by Assimilating OCO‐2 XCO2 Retrievals

AbstractThe magnitude and distribution of China's terrestrial carbon sink remain uncertain due to insufficient observational constraints; satellite column‐average dry‐air mole fraction carbon dioxide (XCO2) retrievals may fill some of this gap. Here, we estimate China's carbon sink using atmospheric inversions of the Orbiting Carbon Observatory 2 (OCO‐2) XCO2 retrievals within different platforms, including the Global Carbon Assimilation System (GCAS) v2, the Copernicus Atmosphere Monitoring Service, and the OCO‐2 Model Inter‐comparison Project (MIP). We find that they consistently place the largest net biome production (NBP) in the south on an annual basis compared to the northeast and other main agricultural areas during peak growing season, coinciding well with the distribution of forests and crops, respectively. Moreover, the mean seasonal cycle amplitude of NBP in OCO‐2 inversions is obviously larger than that of biosphere model simulations and slightly greater than surface CO2 inversions. More importantly, the mean seasonal cycle of the OCO‐2 inversions is well constrained in the temperate, tropical, and subtropical monsoon climate zones, with better inter‐model consistency at a sub‐regional scale compared to in situ inversions and biosphere model simulations. In addition, the OCO‐2 inversions estimate the mean annual NBP in China for 2015–2019 to be between 0.34 (GCASv2) and 0.47 ± 0.16 PgC/yr (median ± std; OCO‐2 v10 MIP), and indicate the impacts of climate extremes (e.g., the 2019 drought) on the interannual variations of NBP. Our results suggest that assimilating OCO‐2 XCO2 retrievals is crucial for improving our understanding of China's terrestrial carbon sink regime.

The carbon sink in China as seen from GOSAT with a regional inversion system based on the Community Multi-scale Air Quality (CMAQ) and ensemble Kalman smoother (EnKS)

Abstract. Top-down inversions of China's terrestrial carbon sink are known to be uncertain because of errors related to the relatively coarse resolution of global transport models and the sparseness of in situ observations. Taking advantage of regional chemistry transport models for mesoscale simulation and spaceborne sensors for spatial coverage, the Greenhouse Gases Observing Satellite (GOSAT) retrievals of column-mean dry mole fraction of carbon dioxide (XCO2) were introduced in the Models-3 (a flexible software framework) Community Multi-scale Air Quality (CMAQ) and ensemble Kalman smoother (EnKS)-based regional inversion system to constrain China's biosphere sink at a spatiotemporal resolution of 64 km and 1 h. In general, the annual, monthly, and daily variation in biosphere flux was reliably delivered, attributable to the novel flux forecast model, reasonable CMAQ background simulation, well-designed observational operator, and Joint Data Assimilation Scheme (JDAS) of CO2 concentrations and natural fluxes. The size of the assimilated biosphere sink in China was −0.47 Pg C yr−1, which was comparable with most global estimates (i.e., −0.27 to −0.68 Pg C yr−1). Furthermore, the seasonal patterns were recalibrated well, with a growing season that shifted earlier in the year over central and south China. Moreover, the provincial-scale biosphere flux was re-estimated, and the difference between the a posteriori and a priori flux ranged from −7.03 Tg C yr−1 in Heilongjiang to 2.95 Tg C yr−1 in Shandong. Additionally, better performance of the a posteriori flux in contrast to the a priori flux was statistically detectable when the simulation was fitted to independent observations, indicating sufficient to robustly constrained state variables and improved fluxes estimation. This study serves as a basis for future fine-scale top-down carbon assimilation.

Comparison of Injection Meglumine Antimoniate with a Combination of Injection Meglumine Antimoniate and Carbon Dioxide Fractional Ablative Laser in Treatment of Cutaneous Leshmaniasis

Aim: To see the efficacy of meglumine antimoniate alone in comparison with combination of meglumine antimoniate and CO2 ablative laser among patients with cutaneous leishmaniasis. Study design: Quasi-experimental study. Place and duration of study: Department of Dermatology, Pakistan Emirates Military Hospital, Rawalpindi from 9th July 2020 to 8th January 2021. Methodology: Sixty patients (30 in each group) diagnosed cases of cutaneous leishmaniasis by skin biopsy or slit skin smear were enrolled. In group A; intramuscular injection of meglumine antimoniate (dose 20 mg/kg daily) was administered for 28 days and group B was treated with intramuscular meglumine antimoniate injection along with fractional C02 ablative laser. Standard digital photography was done before start of treatment and then every 2 weeks. Results: Efficacy of meglumine antimoniate alone was observed in 60% of patients while it was 86.7% when combined with fractional CO2 ablative laser. Better outcome was observed when such patients were treated with both meglumine antimoniate and fractional CO2 laser. Efficacy was measured after 6 x weeks in all patients of both groups. Clinical Implication: Hence CO2 lasers are latest modality of treatment with minimal side effects and can be used in treatment of patients with cutaneous leishmaniasis. Conclusion: Efficacy of meglumine antimoniate plus fractional CO2 laser found to be higher as compared to meglumine antimonate alone in treating cutaneous leishmaniasis. Keywords: Cutaneous leishmaniasis, CO2 fractional ablative laser, Meglumine antimoniate, Slit skin smear

The effect of minimal and high flow anesthesia on optic nerve sheath diameter in laparotomic gynecological surgery

Background/Aim: Optic nerve sheath diameter (ONSD) is a surrogate parameter for intracranial pressure. This study evaluated the effect of anesthetics on ONSD in women undergoing surgery. We aimed to measure the effect of minimal and high flow anesthesia techniques on expiratory/inspiratory oxygen and carbon dioxide fraction values, hemodynamic parameters, and the optic nerve sheath diameter by ultrasonography in open gynecological surgeries.
 Methods: In the present prospective cohort study, 80 patients who planned laparotomic gynecological surgery were divided into two groups: a high flow of 2 L/min and a minimum flow of 0.5 L/min. Anesthesia was maintained with 50% oxygen-50% air at 2 L/min and desflurane at 1.1 MAC in Group 1 (n=40) and 50% oxygen-50% air at 0.5 L/min and desflurane at 1.1 MAC in Group 2 (n=40). After 10–15 min, group 2 was administered minimal flow with 50–60% oxygen and 40–50% air at 0.5 L/min desflurane, and 10 min before the end of the surgery, the patients were switched to high flow with 50% oxygen-50% air at 2 L/min.
 Results: Decreasing heart rates were higher in Group 2 (T0 P=0.001, T2 P=0.007, T3 P=0.035). There was a significant positive correlation between EtCO2 at the 60th min and optic nerve sheath diameter measurements in the minimal flow group (left ONSD r=0.440, P=0.004, right ONSD r=0.473, P=0.002). Although inspiratory oxygen values in Group 2 did not fall below 32%, it was lower than Group 1 except for the last measurement time.
 Conclusion: Minimal flow anesthesia is as safe as high flow in terms of effects on optic nerve sheath diameter and oxygenation parameters in laparotomic gynecological surgery.

Fluid Components in Cordierite from the Rocks of Epidote-Amphibole Facies of the Muzkol Metamorphic Complex, Tajikistan: Pyrolysis-Free GC-MS Data

The composition of volatile components of cordierite from the Muzkol metamorphic complex was studied using shock destruction with pyrolysis-free gas chromatography-mass spectrometry (GC-MS) with simultaneous IR and Raman spectroscopy. Applying the GC-MS procedure, the component relative concentrations (rel.%) and composition of different zones of cordierite crystals were determined. It was found that the substantially magnesian cordierite was formed with a predominantly aqueous-carbonic acid fluid (from 57.06 to 67.88 rel.% H2O, from 24.29 to 32.95 rel.% CO2). From the center towards the crystal periphery, the molar fraction of carbon dioxide (CO2/(H2O + CO2)) decreases from 0.36 to 0.26, whereas the alkane/alkene ratio increases from 0.80 to 0.88. At least 11 homologous series of organic compounds among the identified volatile components, in addition to water and carbon dioxide, were determined, including oxygen-free aliphatic and cyclic hydrocarbons (paraffins, olefins, cyclic alkanes and alkenes, arenes, polycyclic aromatic hydrocarbons (PAHs)), as well as oxygen-containing (alcohols, esters, aldehydes, ketones, carboxylic acids) and heterocyclic (furans, dioxanes) organic compounds.

MAPPING TRENDS OF CARBON DIOXIDE AND METHANE DURING MOVEMENT CONTROL ORDER IN INDUSTRIAL AREAS IN PENINSULAR MALAYSIA USING GOSAT, GOSAT-2, OCO-2, OCO-3, AND TROPOMI SATELLITES DATA

Abstract. The Malaysian government implemented the Movement Control Order (MCO) from March 18 to May 13, 2020, in an effort to curb the coronavirus disease outbreak that had spread throughout the nation. Utilizing data from GOSAT, GOSAT-2, OCO-2, OCO-3, and TROPOMI, the total column-averaged dry-air mole fraction of carbon dioxide and methane (referred as XCO2 and XCH4) is employed to examine the patterns of both gases throughout the MCO as well as from the same period the prior and following year. The Inverse Distance Weighting (IDW) interpolation method is utilized in mapping the XCO2 and XCH4 for the industrial areas in Peninsular Malaysia. The results revealed that even MCO is implemented, the XCO2 and XCH4 in the industrial areas are increasing year by year. By using satellites data, the XCO2 and XCH4 from large areas can be monitored continuously.

The Joule–Thomson effect of (CO2 + H2) binary system relevant to gas switching reforming with carbon capture and storage (CCS)

The Joule–Thomson effect is one of the important thermodynamic properties in the system relevant to gas switching reforming with CCS. In this work, a set of apparatus was set up to determine the Joule–Thomson effect of binary mixtures (CO2 + H2). The accuracy of the apparatus was verified by comparing with the experimental data of carbon dioxide. The Joule–Thomson coefficients (μJT) for (CO2 + H2) binary mixtures with mole fractions of carbon dioxide (xCO2= 0.1, 0.26, 0.5, 0.86, 0.94) along six isotherms at various pressures were measured. Five equations of state EOSs (PR, SRK, PR, BWR and GERG-2008 equation) were used to calculate the μJT for both pure systems and binary systems, among which the GERG-2008 predicted best with a wide range of pressure and temperature. Moreover, the Joule–Thomson inversion curves (JTIC) were calculated with five equations of state. A comparison was made between experimental data and predicted data for the inversion curve of CO2. The investigated EOSs show a similar prediction of the low-temperature branch of the JTIC for both pure and binary systems, except for the BWRS equation of state. Among all the equations, SRK has the most similar result to GERG-2008 for predicting JTIC.

Quality Evaluation of the Column-Averaged Dry Air Mole Fractions of Carbon Dioxide and Methane Observed by GOSAT and GOSAT-2

Quality Evaluation of the Column-Averaged Dry Air Mole Fractions of Carbon Dioxide and Methane Observed by GOSAT and GOSAT-2

A Case of Radio Frequency Micro-Needling Combined with Carbon Dioxide Fractional Laser for the Treatment of Severe Post-Acne Scarring

Acne scarring is a kind of sequelae of acne, which is the scar left on the patient’s skin after acne occurs and the local inflammation is more serious and not controlled in time. It is a disfiguring skin disease that affects patients physically and mentally because it occurs on the face. The treatment of acne scarring has always been a popular and difficult clinical problem. Gold micro-needling is one of the commonly used treatments for acne scarring. Gold micro-needling can bring about some improvement in the extent of scarring, and is also useful for large areas of post-inflammatory erythema, however, it is less effective for icicle-like, compartmentalized, and elevated scarring. The fractional carbon dioxide laser can accurately grind raised, and irregular scarring, which can significantly improve the unevenness of the skin and make the lesions look more even. We report a case of gold micro-needling combined with fractional carbon dioxide laser for the treatment of severe post-acne scarring.

H2 impact on combustion kinetics, soot formation, and NOx emission of hydrocarbon fuel flames

Soot and carbon dioxide released from internal combustion engines became the key issues when using fossil fuels. The use of zero-carbon fuel, hydrogen, with hydrocarbon fuels can play an important role in reducing the exhaust effect on the environment and mitigating the reliance on nonrenewable energy resources. A numerical approach was executed to elucidate the H2 impact on combustion kinetics, soot formation, and NOx emission of hydrocarbon fuel under premixed and diffusion flame conditions. The results showed that hydrogen deteriorated the formations of particle number density, the volume fraction of soot, carbon monoxide, carbon dioxide and polycyclic aromatic hydrocarbons thru the reduction of small chain hydrocarbons at both premixed and diffusion flame conditions. The soot volume fraction and soot particle number density formation were prevailing in the air region of the combustion chamber at diffusion flame conditions. NO3 produced from fuel-related species such as CHO and air-related species such as NO. H2 reduced the peak molar fraction of small chain HC including CHO related species, resulting in a reduction in NO3 emissions. C3H3 species dominantly participated to reduce the CO2 and NO3 emissions, while C2H2 and C5H4CH2 were the main species to control the soot precursors formation in both HC fuel flames. Besides, NH3 emission was limited by C2H2 in DS flames.

PROMISING TECHNOLOGIES AND EXISTING EXPERIENCE OF CARBON DIOXIDE EXTRACTION FROM PROCESS AND WASTE GASES

The main technologies for carbon dioxide capturing are analyzed. Promising technologies include “before burning” CO2 capture and CO2 injection into depleted oil fields to enhance oil recovery, which make it possible not only to reduce residual oil saturation, but also to reduce carbon dioxide emissions into the atmosphere effectively. The energy costs of amine processes for extracting carbon dioxide from biogas are analyzed with the use of computer simulation. To extract carbon dioxide from process gases a traditional single-flow absorption scheme can be used in which MDEAmod absorbents the optimal in terms of energy performance minimizing. The MDEAmod absorbent is universal and can be used in CO2 extraction processes, including those under high pressure, from various process gases, in which the CO2 content can vary over a wide range of concentrations and reach 45 % (vol.). The use of this absorbent reduces the heat consumption for the regeneration of the saturated sorbent by 1.4–2.5 times compared to 18 % MEA and reduces the absorbent consumption by 30 %. A laboratory unit for extracting target fractions of biomethane and carbon dioxide from biogas has been created. The model calculation results of the amine CO2 extracting from biogas and those obtained on a laboratory unit are quite close and the deviation of the calculated from the experimentally obtained CH4 concentration in biomethane at a pressure in the absorber Pabs = 0.11–0.2 MPa does not exceed 3 %. The results of extracting carbon dioxide from biogas modeling can be used to optimize the technological absorption schemes for the production of biomethane - an analogue of natural gas. Experimental technology has been developed and equipment for the production and decomposition of natural gas and carbon dioxide hydrates has been created. The thermodynamic parameters of hydrate formation by bubbling have been determined, and hydrate samples have been obtained. Thermodynamic trend of pressure difference of 1.5–2 MPa to methane replace with carbon dioxide in hydrates was experimentally established and thus the possibility of replacing methane gas hydrates with carbon dioxide and using this technology for the conditions of developing gas hydrate deposits in the Black Sea was confirmed. Bibl. 30, Fig. 10, Tab. 3.

Analysis of Energy and Density in Treating Hypertrophic Scar After Burn in Children with CO2 Dot Matrix Laser.

Objective: To analyze and compare the effect of the combination of energy and density parameters of CO2 dot matrix laser in the hyperplastic stage of pediatric burn. Materials and Methods: A total of 160 pediatric patients with hypertrophic scar after limb burn from 2017 to 2020 were randomly divided into four parameter groups (n = 40). The patients were treated with ablative fraction carbon dioxide laser, once every 10 weeks. During the interval of laser treatment, Compound Heparin Sodium and Allantoin Gel (Contractubex) was applied externally, tid, and elastic cover or elastic bandage is attached to the affected limb. Scoring based on the Vancouver Scar Scale is performed before each laser treatment, The score before the first treatment was the initial score, which was scored by two people separately, and the average score was calculated. Subsequently, the patients were treated four times and scored. The differences between each treatment and the first score of each parameter group were compared. Under the same energy and different treatment density, the scores after each treatment were compared. Under the same density and different energy, the scores after each treatment were compared. The bleeding and pigmentation of each parameter group were compared. Results: The increase of density can show the therapeutic effect earlier than the increase of energy, and 25mj energy and 10% density have better intervention effect. With the course of disease and the progress of treatment, the correlation between intervention effect and parameters tends to weaken. Comparing the number of cases with different scores between each treatment and the first time, the score in the 5% density group was lower than that in the 10% density group, but there was no significant difference between the 25mj and 17.5mj energy levels in the same density group. The intervention effect of the increase of density on scar was better than that of energy, and the increase of energy and density could aggravate the pain. Conclusion: In pediatric burn hypertrophic scars treated by CO2 dot matrix laser in exfoliation mode, the intervention effect of increasing density is better than that of energy. When setting laser treatment parameters, we should give priority to increasing density and adjust energy according to the effect of treatment and the condition of pain, bleeding and color precipitation. In this study, the best combination of parameters is 17.5mj/10%.

A novel model for the solution gas-oil ratio suitable for CO2-rich reservoir fluids

Reservoir fluids with high carbon dioxide (CO2) fraction in their compositions have been the focus of growing attention due to the increasing importance of CO2 injection in subsurface reservoirs for enhanced oil recovery and carbon capture and sequestration. Their thermophysical behavior has unique characteristics when compared to the behavior of reservoir fluids with low CO2 content. However, empirical models that are extensively used to model the reservoir fluid behavior originally did not cover this particular composition, and their extrapolation to this subset of fluids has been little explored in the literature. This study first evaluates the performance of nine such traditional empirical models for the solution gas-oil ratio (Rs) property of CO2-rich reservoir fluids. Predictions are compared against an experimental database containing 1457 points. The database covers reservoir fluids with CO2 molar content ranging from 0% to 38% and gas-oil ratio (GOR) from 75 scf/STB to 2487 scf/STB. Previous models’ results show rather poor predictions for reservoir fluids with high CO2 content, with high deviations from experimental data and inconsistencies. Therefore, this paper proposes a general Rs model that is able to model reservoir fluids with high CO2 content and high GOR with significant superior performance. The new Rs model predictions present a mean absolute percentage error (MAPE) of 6% and a root mean square error (RMSE) of 27 scf/STB for the aforementioned experimental values. For a test (holdout) dataset containing 173 data points from novel reservoir fluid compositions, the MAPE was 8% and the RMSE was 71 scf/STB. The proposed model outperforms the existing models on both training and test sets, even for reservoir fluids with low or no CO2 content.

Stream metabolism sources a large fraction of carbon dioxide to the atmosphere in two hydrologically contrasting headwater streams

AbstractHeadwater streams are control points for carbon dioxide (CO2) emissions to the atmosphere, with relative contributions to CO2 emission fluxes from lateral groundwater inputs widely assumed to overwhelm those from in‐stream metabolic processes. We analyzed continuous measurements of stream dissolved CO2 and oxygen (O2) concentrations during spring and early summer in two Mediterranean headwater streams from which we evaluated the contribution of in‐stream net ecosystem production (NEP) to CO2 emission. The two streams exhibited contrasting hydrological regimes: one was non‐perennial with relatively small groundwater inflows, while the other was perennial and received significant lateral groundwater inputs. The non‐perennial stream exhibited strong inverse coupling between instantaneous and daily CO2 and O2 concentrations, and a strong correlation between aerobic ecosystem respiration (ER) and gross primary production (GPP) despite persistent negative NEP. At the perennial stream, the CO2–O2 relationship varied largely over time, ER and GPP were uncorrelated, and NEP, which was consistently negative, increased with increasing temperature. Mean NEP contribution to CO2 emission was 51% and 57% at the non‐perennial and perennial stream, respectively. Although these proportions varied with assumptions about metabolic stoichiometry and groundwater CO2 concentration, in‐stream CO2 production consistently and substantially contributed to total atmospheric CO2 flux in both streams. We conclude that in‐stream metabolism can be more important for driving C cycling in some headwater streams than previously assumed.

Cardiorespiratory Coordination Among Intermediate And Novice Female Collegiate Rowers

Elite rowers present high levels of cardiorespiratory performance. Rowers’ on-water performance can be predicted by a cardiopulmonary exercise test (CPET) and related measured parameters such as maximum oxygen uptake test (VO2max), ventilation (VE), heart rate (HR), expired fraction of oxygen (FeO2) and carbon dioxide (FeCO2). However, such testing provides little information about the non-linear dynamic interactions during rowing and the qualitative synergetic reconfigurations between cardiovascular and respiratory systems to adjust to the individual rowing performance. Cardiorespiratory coordination (CRC) has been proposed as a method to measure the co-variation among cardiorespiratory variables during a CPET. PURPOSE: To measure and compare the CRC through principal components analysis (PCA) between intermediate (9) and novice (9) rowers. METHODS: Eighteen females, members of NCAA Division II team, participated based on their off-water performance on 6000 m time trial and training status (i.e., Intermediate vs, Novice) in a discontinuous incremental rowing ergometer test to exhaustion. A variety of cardiorespiratory values were recorded. VE, HR, FeO2, and FeCO2 values during the last two stages before volitional fatigue between intermediate and novice rowers were analyzed by PCA on SPSS vs28. The number of principal components (PCs) and the first PC eigenvalues were computed for each group. RESULTS: While 67% of participants in the intermediate group showed one PC, only 22% of the novice group displayed 1 single PC. The formation of an additional PC in N rowers was the result of the shift of FeCO2 from the PC1 cluster of variables. CONCLUSIONS: Intermediate rowers showed a trend towards lower number of PCs compared to novice rowers, reflecting a higher degree of CRC. These findings point toward a higher efficiency of cardiorespiratory function in intermediate rowers, potentially as a result of improved bicarbonate buffering efficiency during high-intensity exercise. Intermediate rowers presented better gas exchange and relied less on ventilation for a given oxygen consumption. CRC appears as a complementary measure to assess aerobic fitness as well as cardiorespiratory interactions and their response to exercise in rowing may be useful to coaches, athletes and other stakeholders.

Characteristics and source analysis of greenhouse gas concentration changes at Akedala Station in Central Asia

Mole fractions of atmospheric carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and sulfur hexafluoride (SF6) have been continuously measured since September 2009 at the Akedala Station (47°06′N, 87°58′E, 563.3 masl) in China. The station is located in the Central Asia and northwest of China, and it is the only station in that region with background conditions for long-term greenhouse gas observations. Characteristics of the mole fractions, growth rates, and influence of long-distance transport were studied considering data from September 2009 to December 2019. The greenhouse gases concentrations at Akedala Station show a trend of year-on-year growth, with CO2 concentrations ranging from 389.80 × 10−6 to 408.79 × 10−6 (molar fraction of substances, same below), CH4 concentrations ranging from 1890.07 × 10−9 to 1976.32 × 10−9, N2O concentrations ranging from 321.26 × 10−9 to 332.03 × 10−9, and SF6 concentrations ranging from 7.04 × 10−12 to 10.07 × 10−12, the growth rate of which is similar to the decadal average growth rate in the Northern Hemisphere. There exist obvious seasonal variations, with CO2 concentrations showing high in winter and low in summer and CH4 showing a distinct “W”-shaped trend while N2O and SF6 showing little difference between the four seasons. A relatively strong correlation and homology exist among the four greenhouse gases except in summer, and the analysis based on backward trajectories model shows that the Akedala Station is influenced by the airflow from northwest or southwest throughout the year. The Akedala Station is an important atmospheric background station in Central Asia, and its greenhouse gas concentration levels and variation characteristics are significantly different from those of the background stations in the monsoon region. Its degree changes are closely related to local source emissions, monsoon transport, and atmospheric photochemical processes.

Interannual variability in the Australian carbon cycle over 2015–2019, based on assimilation of Orbiting Carbon Observatory-2 (OCO-2) satellite data

Abstract. In this study, we employ a regional inverse modelling approach to estimate monthly carbon fluxes over the Australian continent for 2015–2019 using the assimilation of the total column-averaged mole fractions of carbon dioxide from the Orbiting Carbon Observatory-2 (OCO-2, version 9) satellite. Subsequently, we study the carbon cycle variations and relate their fluctuations to anomalies in vegetation productivity and climate drivers. Our 5-year regional carbon flux inversion suggests that Australia was a carbon sink averaging −0.46 ± 0.08 PgC yr−1 (excluding fossil fuel emissions), largely influenced by a strong carbon uptake (−1.04 PgC yr−1) recorded in 2016. Australia's semi-arid ecosystems, such as sparsely vegetated regions (in central Australia) and savanna (in northern Australia), were the main contributors to the carbon uptake in 2016. These regions showed relatively high vegetation productivity, high rainfall, and low temperature in 2016. In contrast to the large carbon sink found in 2016, the large carbon outgassing recorded in 2019 coincides with an unprecedented rainfall deficit and higher-than-average temperatures across Australia. Comparison of the posterior column-averaged CO2 concentration with Total Carbon Column Observing Network (TCCON) stations and in situ measurements offers limited insight into the fluxes assimilated with OCO-2. However, the lack of these monitoring stations across Australia, mainly over ecosystems such as savanna and areas with sparse vegetation, impedes us from providing strong conclusions. To a certain extent, we found that the flux anomalies across Australia are consistent with the ensemble means of the OCO-2 Model Intercomparison Project (OCO-2 MIP) and FLUXCOM (2015–2018), which estimate an anomalous carbon sink for Australia in 2016 of −1.09 and −0.42 PgC yr−1 respectively. More accurate estimates of OCO-2 retrievals, with the addition of ocean glint data into our system, and a better understanding of the error in the atmospheric transport modelling will yield further insights into the difference in the magnitude of our carbon flux estimates.