Carbon Dioxide Output Research Articles

Origin of inorganic carbon dioxide associated with hydrocarbon generation: Evidence from hydrous pyrolysis experiments and natural and shale gases

Inorganic carbon dioxide with heavier δ13C values frequently occurs in natural gases or shale gases generated from marine source rocks. To provide a better understanding on the origin of inorganic CO2 associated with hydrocarbon generation, hydrous pyrolysis experiments were conducted utilizing source rocks of different depositional environments and varying carbonate mineral concentrations, at a fixed temperature 350 °C, and lithostatic pressure 50 MPa and fluid pressure 28 MPa for 48 h. Carbon dioxide yields, concentrations in gaseous products, and δ13C values tend to increase in proportion to the carbonate mineral concentrations of the original source rocks. The results showed that carbonate mineral dissolution might be the principal source of inorganic carbon dioxide generated in the experiments. Based on the δ13C values of carbon dioxide produced in the hydrous pyrolysis experiments both in this study and in the literature, we suggest that inorganic CO2 show δ13C values heavier than −8‰, organic CO2 show δ13C values lighter than −16‰, and CO2 with mixed origins show δ13C values ranging from −16 to −8‰. We further discussed the origins of CO2 in the marine Ordovician natural gases of the Ordos Basin, in the marine Miocene CO2-dominated natural gases of the Yinggehai Basin, and in the marine Silurian shale gases of the Sichuan Basin. With a majority of δ13C values higher than −8‰, a major inorganic origin from carbonate mineral dissolution were suggested for CO2 in the natural and shale gases of the above basins.

Innovative ways to control dust and explosion safety of mine workings

Ensuring dust and explosion safety during underground coal mining is one of the most important tasks of industrial safety and labor protection departments. The main method of preventing explosions of coal dust settled in mine workings is to process them with stone dust (rock dusting). The traditional methods of quality control of rock dusting include radioisotope, optical and chemical methods. To implement them, the devices are equipped with environmentally harmful radioactive elements, expensive optical sensors, desiccants and replaceable flasks with chemical reagents, which increases the cost of analysis and its duration. The measurement error of these devices is 10 % or more. The main purpose of the study is to develop and substantiate a new method for monitoring the dust and explosion safety of mine workings, which will be devoid of the disadvantages of the methods mentioned above. It is proposed to evaluate the quality of rock-dust distribution by a fundamentally new way – thermogravimetric. The method was tested on the dust of coal mines in Kuzbass and the Vorkuta basin, including dust samples taken in mines with actual explosions. The article presents the results of experimental studies of the processes of thermal destruction of coal and stone dust mixtures. The non-overlapping intervals of the thermogravimetric reaction are identified: moisture yield (35-132 °С); volatile matter yield from coal (380-580 °С); thermal degradation of limestone with carbon dioxide yield (650-850 °С). Methods and mathematical dependencies for processing significant and qualitative identification characteristics of thermogravimetric curves in determining the content of non-combustible components in a sample of mine dust are considered.

MXene based core-shell flame retardant towards reducing fire hazards of thermoplastic polyurethane

Amounts of heat and toxic fumes are released during the combustion of polymeric materials, which severely threats to the human health and causes the environmental pollution. Therefore, it is vital to find an effective way to address these problems. Herein, titanium carbide (Ti 3 C 2 T x ) and chitosan (CS) were firstly adopted to functionalize ammonium polyphosphate (APP) via the microencapsulation and layer-by-layer assembly. Afterwards, the as-synthesized core-shell-structured hybrid (APP@CS@Ti 3 C 2 T x ) was used to enhance the interface compatibility, thermal stability and fire safety of thermoplastic polyurethane (TPU) composites. The results demonstrated that the APP@CS@Ti 3 C 2 T x hybrid presented a strong interface interaction with the TPU matrix. Besides, TPU/APP@CS@Ti 3 C 2 T x composites exhibited the improved thermal stability. The TPU composite containing 9.5APP@CS@0.5Ti 3 C 2 T x achieved V-0 rating in the UL-94 testing. The cone calorimetry results illustrated that introduction of 9.5APP@CS@0.5Ti 3 C 2 T x into TPU caused remarkable reduction in the total heat release (73.0%) and total smoke release (77.3%). Furthermore, the total carbon monoxide yield and total carbon dioxide yield of TPU/9.5APP@CS@0.5Ti 3 C 2 T x were significantly decreased by 75.3% and 75.3%, respectively, compared to those of pure TPU. The synergistic charring effect between APP@CS and Ti 3 C 2 T x , the thermal oxidization action and “tortuous path” effect of Ti 3 C 2 T x nanosheets combined with the trapping effect of APP@CS resulted in the dramatically improved fire resistance of the polymeric material. This work offers an innovative strategy to fabricate the high-performance polymer composites with superior fire safety.

Breathing patterns in people with exercise-induced laryngeal obstruction.

Exercise‐induced laryngeal obstruction (EILO) is common, but we lack readily available diagnostic tools. The larynx represents an important point of resistance in the airways, and we therefore hypothesized that EILO is associated with characteristic breathing patterns possible to record from a standard incremental ergospirometry test. We studied 24 individuals with moderate/severe EILO and 20 individuals with no‐EILO, mean (SD) age 17 (6.1) and 24 (6.4) years, respectively. EILO versus no‐EILO was verified from maximal continuous laryngoscopy treadmill exercise (CLE) tests, which also included ergospirometry. We described the relationships between minute ventilation (V˙E) versus tidal volume (V T) and V˙E versus carbon dioxide output (V˙CO2), using respectively quadratic and linear equations, and applied adjusted regression models to compare ergospirometry data and curve parameters. Compared to the no‐EILO group, the group with EILO had prolonged inspiratory time (T in), lower breathing frequency (B f), lower V˙E, and lower inspiratory flow rate (V˙in) at peak exercise. Mathematical modeling of the breathing pattern relationships was feasible in both groups, with similar coefficients of variation. For V˙E versus V T, the mathematical curve parameters were similar. For V˙E versus V˙CO2, the slope was similar but the intercept was lower in the EILO group. EILO was associated with prolonged T in, lower B f, V˙E, and V˙E. The relationship between V˙E versus V T was similar, whereas for V˙E versus V˙CO2, the slope was almost parallel but shifted downward for the EILO group. Most ergospirometry data overlapped, except V˙in which discriminated between EILO and no‐EILO in a promising way.

Comprehensive Study of Heart Rate Recovery and Altered Ventilatory Response to Exercise in Patients with Obstructive Sleep Apnea

Abstract Background Obstructive sleep apnea (OSA) is a chronic disorder that results in many cardiovascular disorders including hypertension, arrhythmias and congestive heart failure (CHF). Polysomnography is the gold standard for diagnosis of OSA, even though up to 93% of women and 82% of men with moderate to severe OSA still remain undiagnosed. Cardiopulmonary exercise testing (CPXT) has been conventionally used for evaluation of coronary artery diseases and rehabilitation of cardiac patients. Modern systems allow for the analysis of gas exchange at rest, during exercise, and during recovery and also yield measures of oxygen uptake (V O2), carbon dioxide output (V CO2), and minute ventilation (V E) together with heart rate, blood pressure, electrocardiography findings, and symptoms. This may have clinical utility if added to the available screening tools used to identify OSA. Aim of study To assess altered ventilatory response and heart rate recovery in response to exercise in patients with obstructive sleep apnea and their relation to its severity. Methods and Results Case control study was enrolled including 30 patients with obstructive sleep apnea (OSA) divided according to severity (5 mild, 8 moderate and 17 severe) and 15 control healthy overweight with sedentary lifestyle individuals. The two groups underwent cardiopulmonary exercise testing and different pulmonary and cardiac parameters were calculated. Greater VE, VE/VCO2, VE/VO2 ratios and VE/VCO2 slope were statistically significant regarding the patients group (P < 0.001, F = 69.053, 104.381, 140.806 and 68.010 respectively according to ANOVA test). OSA patients had a reduced maximal exercise capacity expressed as lower VO2 peak, decreased breathing reserve (BR) and VO2 at anaerobic threshold compared to control group (P < 0.001, F = 22.597, 68.773 and 82.90 respectively). Delayed heart rate recovery (HRR) and weaker chronotropic response (CR) in patients with OSA than in controls with negative relationship to severity of OSA were proved (p < 0.001, F = 119.493 and 91.271 respectively). The study revealed elevated maximal systolic BP (max SBP), diastolic BP (max DBP) and recovery SBP in the following 2 minutes after exercise in patients with OSA relative to their healthy controls with positive relationship to the severity of OSA (P < 0.001, F = 37.129, 169.275 and 244.609 respectively). Conclusion Patients with OSA demonstrated exaggerated ventilatory response to exercise and autonomic dysfunction reflected by measurement of heart rate variability and reduced maximal exercise capacity than healthy controls. Abbreviations OSA, CHF, CPXT, VO2, VCO2, VE, VE/VCO2, VE/VO2, VE/VCO2, BR, CR, HRR, max SBP and max DBP.

Thermocatalytic oxidation of a three-component mixture of volatile organic compounds by a titanium dioxide-supported platinum catalyst

To gain a better knowledge for efficient treatment of volatile organic compounds (VOCs), a series of experiments were carried out to assess the potential of titanium dioxide (TiO2)-supported platinum (Pt) catalyst (Pt/TiO2) in low-temperature catalytic oxidation of formaldehyde (FA), acetaldehyde (AA), and toluene (T) (10–100 ppm range) both individually and as a mixture. Accordingly, 100% mineralization of FA (50–200 ppm), AA (10 ppm), and T (10 ppm) was achieved by 1%-Pt/TiO2-R (‘R’ suffix for reduction pretreatment on the catalyst) at 30, 190, and 160 °C, respectively. The carbon dioxide (CO2) yield was used to assess the extent of VOC mineralization in air (as the carrier gas at a flow rate of 0.2 L atm min ̶ 1). Their conversion efficiency was lowered with increases in the pollutant concentration or decreases in the bed mass. Furthermore, the reaction intermediates and catalytic pathways were assessed based on in-situ diffuse reflectance infrared Fourier transform spectroscopy. This study offers valuable insights into the interactive roles between process variables in the low-temperature thermocatalytic oxidation of single and/or multi-component gaseous VOC systems and into the effects of such variables on the overall catalytic performance.

PeakPETCO2 combined with FEV1/FVC predicts vasodilator-responsive patients with idiopathic pulmonary arterial hypertension.

Cardiopulmonary exercise testing and pulmonary function test are important methods for detecting human cardio-pulmonary function. Whether they could screen vasoresponsiveness in idiopathic pulmonary artery hypertension (IPAH) patients remains undefined. One hundred thirty-two IPAH patients with complete data were retrospectively enrolled. Patients were classified as vasodilator-responsive (VR) group and vasodilator-nonresponsive (VNR) group on the basis of the acute vasodilator test. Pulmonary function test and cardiopulmonary exercise testing were assessed subsequently and all patients were confirmed by right heart catheterization. We analyzed cardiopulmonary exercise testing and pulmonary function test data and derived a prediction rule to screen vasodilator-responsive patients in IPAH. Nineteen of VR-IPAH and 113 of VNR-IPAH patients were retrospectively enrolled. Compared with VNR-IPAH patients, VR-IPAH patients had less severe hemodynamic effects (lower RAP, m PAP, PAWP, and PVR). And VR-IPAH patients had higher anaerobic threshold (AT), peak partial pressure of end-tidal carbon dioxide (PETCO2), oxygen uptake efficiency (OUEP), and FEV1/FVC (P all <0.05), while lower peak partial pressure of end-tidal oxygen (PETO2) and minute ventilation (VE)/carbon dioxide output (VCO2) slope (P all <0.05). FEV1/FVC (Odds Ratio [OR]: 1.14, 95% confidence interval [CI]: 1.02–1.26, P = 0.02) and PeakPETCO2 (OR: 1.13, 95% CI: 1.01–1.26, P = 0.04) were independent predictors of VR adjusted for age, sex, and body mass index. A novel formula (=−16.17 + 0.123 × PeakPETCO2 + 0.127×FEV1/FVC) reached a high area under the curve value of 0.8 (P = 0.003). Combined with these parameters, the optimal cutoff value of this model for detection of VR is −1.06, with a specificity of 91% and sensitivity of 67%. Compared with VNR-IPAH patients, VR-IPAH patients had less severe hemodynamic effects. Higher FEV1/FVC and higher peak PETCO2 were associated with increased odds for vasoresponsiveness. A novel score combining PeakPETCO2 and FEV1/FVC provides high specificity to predict VR patients among IPAH.

Exertional ventilation/carbon dioxide output relationship in COPD: from physiological mechanisms to clinical applications.

There is well established evidence that the minute ventilation (V'E)/carbon dioxide output (V'CO2 ) relationship is relevant to a number of patient-related outcomes in COPD. In most circumstances, an increased V'E/V'CO2 reflects an enlarged physiological dead space ("wasted" ventilation), although alveolar hyperventilation (largely due to increased chemosensitivity) may play an adjunct role, particularly in patients with coexistent cardiovascular disease. The V'E/V'CO2 nadir, in particular, has been found to be an important predictor of dyspnoea and poor exercise tolerance, even in patients with largely preserved forced expiratory volume in 1 s. As the disease progresses, a high nadir might help to unravel the cause of disproportionate breathlessness. When analysed in association with measurements of dynamic inspiratory constraints, a high V'E/V'CO2 is valuable to ascertain a role for the "lungs" in limiting dyspnoeic patients. Regardless of disease severity, cardiocirculatory (heart failure and pulmonary hypertension) and respiratory (lung fibrosis) comorbidities can further increase V'E/V'CO2 A high V'E/V'CO2 is a predictor of poor outcome in lung resection surgery, adding value to resting lung hyperinflation in predicting all-cause and respiratory mortality across the spectrum of disease severity. Considering its potential usefulness, the V'E/V'CO2 should be valued in the clinical management of patients with COPD.

Evaluation of Fischer-Tropsch synthesis to light olefins over Co- and Fe-based catalysts using artificial neural network

Currently, energy transition due to fossil fuel negative side effects is taking place. This transition impacts the chemical industry based on light olefins reactions. Plastics, detergents, polymers, and others are mostly produced from such hydrocarbons, which are mainly originated from oil-based and highly energy-consuming processes. Fischer-Tropsch Synthesis (FTS) is a strategic technology capable to transform a given carbon source, including natural gas and biomass, into high added-value hydrocarbons. It is affected by several conditions, such as catalyst design and operating conditions and its feasibility requires a good selection of relevant process variables to optimize light olefins yield. In this work, Machine Learning models were used to predict adequate reaction conditions from the catalytic literature data. Three-layer feedforward neural networks were adjusted using a careful selection of operating conditions and catalyst composition as inputs and carbon monoxide conversion, light olefins selectivity, and carbon dioxide yield as outputs. The results indicate neural network prediction efficacy for FTS most relevant variables, such as temperature and catalyst composition. This work presents the novelty of including more variables in the model compared to recent similar studies, such as catalyst support, active phase, and promoters as inputs; and light olefins selectivity and CO2 yield as outputs. Overall, Fe-based catalyst (standard Fe (1.6 wt%) K/TiO2) presented the highest light olefins selectivity and yield at optimal conditions (T = 500 °C and 20 wt% of active phase), despite showing the highest emission of carbon dioxide.

Economical and preferred walking speed using body weight support apparatus with a spring-like characteristics

BackgroundA specific walking speed minimizing the U-shaped relationship between energy cost of transport per unit distance (CoT) and speed is called economical speed (ES). To investigate the effects of reduced body weight on the ES, we installed a body weight support (BWS) apparatus with a spring-like characteristics. We also examined whether the 'calculated' ES was equivalent to the 'preferred' walking speed (PWS) with 30% BWS.MethodsWe measured oxygen uptake and carbon dioxide output to calculate CoT values at seven treadmill walking speeds (0.67–2.00 m s− 1) in 40 healthy young males under normal walking (NW) and BWS. The PWS was determined under both conditions on a different day.ResultsA spring-like behavior of our BWS apparatus reduced the CoT values at 1.56, 1.78, and 2.00 m s− 1. The ES with BWS (1.61 ± 0.11 m s− 1) was faster than NW condition (1.39 ± 0.06 m s− 1). A Bland-Altman analysis indicated that there were no systematic biases between ES and PWS in both conditions.ConclusionsThe use of BWS apparatus with a spring-like behavior reduced the CoT values at faster walking speeds, resulting in the faster ES with 30% BWS compared to NW. Since the ES was equivalent to the PWS in both conditions, the PWS could be mainly determined by the metabolic minimization in healthy young males. This result also derives that the PWS can be a substitutable index of the individual ES in these populations.

Coking of Stamped Coal Batch. 3. Yield of Chemical Products

Given that coal may be oxidized and the yield of ammonia and hydrogen sulfide cannot be predicted from the volatile matters, mathematical formulas describing the yield of the basic coking products as a function of the elemental composition of the initial stamped coal batch are derived. It is found that, with increase in the content of gas coal (and hence in the volatile matter) in the stamped batch, the coke yield declines, but there is a higher yield of tar, benzene, carbon dioxide, pyrogenetic moisture, and coke-oven gas. The yield of the basic coking products is found to be additive. Hence, the total yield for the enterprise may be calculated, taking account of the characteristics and proportions of stamped and unstamped batch.

Optimisation of two-stage biomass gasification for hydrogen production via artificial neural network

A two-stage gasification has been proven as an effective and robust approach for converting low-valued and/or highly heterogeneous materials i.e. waste, into hydrogen and/or syngas due to its tight control and flexibility in operation. As the gas yield and gas properties depend upon materials and operating conditions, the interactions of operating conditions should not be ignored. However, these have not been able to fully capture experimentally. In this work, an artificial neural network model was developed and validated using experimental data to predict and optimise the gasification process thereby reducing time and costs in developing and testing. The model can predict accurately gas composition and yield corresponding to the variations at the output with a correlation R2 > 0.99. The developed neural network model was then applied for optimising operating conditions of the two-stage gasification for high carbon conversion, high hydrogen yield and low carbon dioxide in nitrogen and carbon dioxide environments. The predicted conditions were tested, and the results agreed well with experimental data. For example, at the optimum operating conditions (900˚C for the 1st stage and 1000 °C for the 2nd stage with a steam/carbon ratio of 3.8 in nitrogen and 5.7 in carbon dioxide environments), the gas yield, hydrogen and carbon dioxide were 96.2 wt%, 70 mol% and 16.4 mol% for nitrogen environment and 97.2 wt%, 66 mol% and 12 mol% for carbon dioxide environment.

Severity does not impact on exercise capacity in COVID-19 survivors

Background: current data on the impact of acute illness severity on exercise capacity and ventilatory efficiency of COVID-19 survivors, evaluated at cardiopulmonary exercise test (CPET), are limited.Methods: in this post-hoc analysis of our previous observational, prospective, cohort study on mechanisms of exercise intolerance in COVID-19 survivors, we aimed at evaluating the impact of acute COVID-19 severity on exercise capacity, pulmonary function testing (PFT) and chest computed tomography (CT) outcomes.Results: we enrolled 75 patients (18 with mild-to-moderate disease, 18 with severe disease, and 39 with critical disease). Mean (standard deviation – SD) follow-up time was 97 (26) days. Groups showed a similar PFT and CT residual involvement, featuring a mildly reduced exercise capacity with comparable mean (SD) values of peak oxygen consumption as percentage of predicted (83 (17) vs 82 (16) vs 84 (15), p = 0.895) among groups, as well as the median (interquartile range – IQR) alveolar-arterial gradient for O2 in mmHg at exercise peak (20 (15–28) vs 27 (18–31) vs 26 (21-21), p = 0.154), which was in the limit of normal. In addition, these patients featured a preserved mean ventilatory efficiency evaluated through the slope of the relation between ventilation and carbon dioxide output during exercise (27.1 (2.6) vs 29.8 (3.9) vs 28.3 (2.6), p = 0.028), without a clinically relevant difference. ConclusionsDisease severity does not impact on exercise capacity in COVID-19 survivors at 3 months after discharge, including a ventilatory response still in the limit of normal.

Effect of Breathing Oxygen-Enriched Air on Exercise Performance in Patients With Pulmonary Hypertension Due to Heart Failure With Preserved Ejection Fraction: A Randomized, Placebo-Controlled, Crossover Trial.

Objective: To evaluate the effects of breathing oxygen-enriched air (oxygen) on exercise performance in patients with pulmonary hypertension due to heart failure with preserved ejection fraction (PH-HFpEF).Methods: Ten patients with PH-HFpEF (five women, age 60 ± 9 y, mPAP 37 ± 14 mmHg, PAWP 18 ± 2 mmHg, PVR 3 ± 3 WU, resting SpO2 98 ± 2%) performed two-cycle incremental exercise tests (IET) and two constant-work-rate exercise test (CWRET) at 75% maximal work-rate (Wmax), each with ambient air (FiO2 0.21) and oxygen (FiO2 0.5) in a randomized, single-blinded, cross-over design. The main outcomes were the change in Wmax (IET) and cycling time (CWRET) with oxygen vs. air. Blood gases at rest and end-exercise, dyspnea by Borg CR10 score at end-exercise; continuous SpO2, minute ventilation (V'E), carbon dioxide output (V'CO2), and cerebral and quadricep muscle tissue oxygenation (CTO and QMTO) were measured.Results: With oxygen vs. air, Wmax (IET) increased from 94 ± 36 to 99 ± 36 W, mean difference (95% CI) 5.4 (0.9–9.8) W, p = 0.025, and cycling time (CWRET) from 532 ± 203 to 680 ± 76 s, +148 (31.8–264) s, p = 0.018. At end-exercise with oxygen, Borg dyspnea score and V'E/V'CO2 were lower, whereas PaO2 and end-tidal PaCO2 were higher. Other parameters were unchanged.Conclusion: Patients with PH-HFpEF not revealing resting hypoxemia significantly improved their exercise performance while breathing oxygen-enriched air along with less subjective dyspnea sensation, a better blood oxygenation, and an enhanced ventilatory efficiency. Future studies should investigate whether prolonged training with supplemental oxygen would increase the training effect and, potentially, daily activity for PH-HFpEF patients.Clinical Trial Registration: [clinicaltrials.gov], identifier [NCT04157660].

Ventilatory efficiency in pulmonary vascular diseases.

Cardiopulmonary exercise testing (CPET) is a frequently used tool in the differential diagnosis of dyspnoea. Ventilatory inefficiency, defined as high minute ventilation (V' E) relative to carbon dioxide output (V' CO2 ), is a hallmark characteristic of pulmonary vascular diseases, which contributes to exercise intolerance and disability in these patients. The mechanisms of ventilatory inefficiency are multiple and include high physiologic dead space, abnormal chemosensitivity and an altered carbon dioxide (CO2) set-point. A normal V' E/V' CO2 makes a pulmonary vascular disease such as pulmonary arterial hypertension (PAH) or chronic thromboembolic pulmonary hypertension (CTEPH) unlikely. The finding of high V' E /V' CO2 without an alternative explanation should prompt further diagnostic testing to exclude PAH or CTEPH, particularly in patients with risk factors, such as prior venous thromboembolism, systemic sclerosis or a family history of PAH. In patients with established PAH or CTEPH, the V' E/V' CO2 may improve with interventions and is a prognostic marker. However, further studies are needed to clarify the added value of assessing ventilatory inefficiency in the longitudinal follow-up of patients.

SLC4A2 anion exchanger promotes tumour cell malignancy via enhancing net acid efflux across golgi membranes

Proper functioning of each secretory and endocytic compartment relies on its unique pH micro-environment that is known to be dictated by the rates of V-ATPase-mediated H+ pumping and its leakage back to the cytoplasm via an elusive “H+ leak” pathway. Here, we show that this proton leak across Golgi membranes is mediated by the AE2a (SLC4A2a)-mediated bicarbonate-chloride exchange, as it is strictly dependent on bicarbonate import (in exchange for chloride export) and the expression level of the Golgi-localized AE2a anion exchanger. In the acidic Golgi lumen, imported bicarbonate anions and protons then facilitate a common buffering reaction that yields carbon dioxide and water before their egress back to the cytoplasm via diffusion or water channels. The flattened morphology of the Golgi cisternae helps this process, as their high surface-volume ratio is optimal for water and gas exchange. Interestingly, this net acid efflux pathway is often upregulated in cancers and established cancer cell lines, and responsible for their markedly elevated Golgi resting pH and attenuated glycosylation potential. Accordingly, AE2 knockdown in SW-48 colorectal cancer cells was able to restore these two phenomena, and at the same time, reverse their invasive and anchorage-independent growth phenotype. These findings suggest a possibility to return malignant cells to a benign state by restoring Golgi resting pH.

Augmented muscle glycogen utilization following a single session of sprint training in hypoxia.

This study determined the effect of a single session of sprint interval training in hypoxia on muscle glycogen content among athletes. Ten male college track and field sprinters (mean ± standard error of the mean: age, 21.1 ± 0.2years; height, 177 ± 2cm; body weight, 67 ± 2kg) performed two exercise trials under either hypoxia [HYPO; fraction of inspired oxygen (FiO2), 14.5%] or normoxia (NOR: FiO2, 20.9%). The exercise consisted of 3 × 30s maximal cycle sprints with 8-min rest periods between sets. Before and immediately after the exercise, the muscle glycogen content was measured using carbon magnetic resonance spectroscopy in vastus lateralis and vastus intermedius muscles. Moreover, power output, blood lactate concentrations, metabolic responses (respiratory oxygen uptake and carbon dioxide output), and muscle oxygenation were evaluated. Exercise significantly decreased muscle glycogen content in both trials (interaction, P = 0.03; main effect for time, P < 0.01). Relative changes in muscle glycogen content following exercise were significantly higher in the HYPO trial (- 43.5 ± 0.4%) than in the NOR trial (- 34.0 ± 0.3%; P < 0.01). The mean power output did not significantly differ between the two trials (P = 0.80). The blood lactate concentration after exercise was not significantly different between trials (P = 0.31). A single session of sprint interval training (3 × 30s sprints) in hypoxia caused a greater decrease in muscle glycogen content compared with the same exercise under normoxia without interfering with the power output.

Evidence of a double anaerobic threshold in healthy subjects.

The anaerobic threshold (AT) is an important cardiopulmonary exercise test (CPET) parameter both in healthy and in patients. It is normally determined with three approaches: V-slope method, ventilatory equivalent method, and end-tidal method. The finding of different AT values with these methods is only anecdotic. We defined the presence of a double threshold (DT) when a ΔVO2 > 15 mL/min was observed between the V-slope method (met AT) and the other two methods (vent AT). The aim was to identify whether there is a DT in healthy subjects. We retrospectively analysed 476 healthy subjects who performed CPET in our laboratory between 2009 and 2018. We identified 51 subjects with a DT (11% of cases). Cardiopulmonary exercise test data at rest and during the exercise were not different in subjects with DT compared to those without. Met AT always preceded vent AT. Compared to subjects without DT, those with DT showed at met AT lower carbon dioxide output (VCO2), end-tidal carbon dioxide tension (PetCO2) and respiratory exchange ratio (RER), and higher ventilatory equivalent for carbon dioxide (VE/VCO2). Compared to met AT, vent AT showed a higher oxygen uptake (VO2), VCO2, ventilation, respiratory rate, RER, work rate, and PetCO2 but a lower VE/VCO2 and end-tidal oxygen tension. Finally, subjects with DT showed a higher VO2 increase during the isocapnic buffering period. Double threshold was present in healthy subjects. The presence of DT does not influence peak exercise performance, but it is associated with a delayed before acidosis-induced hyperventilation.

Global carbon dioxide output of volcanic lakes in the Azores archipelago, Portugal

The Azores archipelago (Portugal) contains 88 lakes, two located inside caves spread across six of the nine volcanic islands of the archipelago; the formation of the lakes is associated with various types of volcanic structures. Surveys were performed on 45 water bodies corresponding to a representative data set and omitting only small ephemeral ponds to extensively research CO2 emissions from the volcanic lakes.The modified accumulation chamber method was used to measure the CO2 flux at the surface of the lakes; 16,119 measurements were performed with flux values ranging from 0 to 20,960 g m−2 d−1. Graphical statistical approaches identified different geochemical populations from the CO2 flux data. Multiple populations associated with limnological and biogenic processes or volcanic/hydrothermal sources were identified in some cases. The influence of these sources was also confirmed by the determined δ13C content of the lakes.The lakes of the Azores emit approximately ~171 × 103 t yr−1 of CO2 into the atmosphere; much of this is released by the Furnas and Furna do Enxofre lakes, both showing mantle-derived CO2 origin. Deep-seated CO2 accounts for approximately 42% of the total degassing.

Efficient catalytic combustion of toluene at low temperature by tailoring surficial Pt0 and interfacial Pt-Al(OH)x species

SummaryExploring highly efficient and low-cost supported Pt catalysts is attractive for the application of volatile organic compounds (VOCs) combustion. Herein, efficient catalytic combustion of toluene at low temperature over Pt/γ-Al2O3 catalysts has been demonstrated by tailoring active Pt species spatially. Pt/γ-Al2O3 catalyst with low Pt-content (0.26 wt%) containing both interfacial Pt-Al(OH)x and surficial metallic Pt (Pt0) species exhibited super activity and water-resistant stability for toluene oxidation. The strong metal-support interaction located at the Al-OH-Pt interfaces elongated the Pt-O bond and contributed to the oxidation of toluene. Meanwhile, the OH group at the Al-OH-Pt interfaces had the strongest adsorption and activation capability for toluene and the derived intermediate species were subsequently oxidized by oxygen species activated by surficial Pt0 to yield carbon dioxide and water. This work initiated an inspiring sight to the design of active Pt species for the VOCs combustion.