Articles de revues : « CO2 challenge »

1

Ziegler, Marc. « The Challenge of CO2 Limits ». MTZ worldwide 80, n^o 12 (8 novembre 2019) : 3. http://dx.doi.org/10.1007/s38313-019-0154-5.

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Gitelman, Darren R., Isak Prohovnik et Thomas K. Tatemichi. « Safety of Hypercapnic Challenge : Cardiovascular and Neurologic Considerations ». Journal of Cerebral Blood Flow & ; Metabolism 11, n^o 6 (novembre 1991) : 1036–40. http://dx.doi.org/10.1038/jcbfm.1991.172.

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The hemodynamic, cerebrovascular, and neurologic effects of hypercapnia with 4% and 6% CO2 were retrospectively reviewed in 217 patients referred for regional CBF (rCBF) procedures. Inhalation of CO2 significantly increased rCBF, blood pressure, and pulse from baseline. The findings suggest a higher incidence of side effects with 6% CO2 concentration and an equivalent vasoreactivity to 4%. We recommend the use of 4% CO2 for hypercapnic stimulation, and present safety guidelines for its use.

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Westerhoff, Martin. « Sports Car Powertrains No Greater CO2 Challenge ». MTZ worldwide 77, n^o 11 (14 octobre 2016) : 8–13. http://dx.doi.org/10.1007/s38313-016-0141-z.

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Green, J. E. « Civil aviation and the environmental challenge ». Aeronautical Journal 107, n^o 1072 (juin 2003) : 281–99. http://dx.doi.org/10.1017/s0001924000013579.

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Abstract In the coming century, the impact of air travel on the environment will become an increasingly powerful influence on aircraft design. Unless the impact per passenger kilometre can be reduced substantially relative to today’s levels, environmental factors will increasingly limit the expansion of air travel and the social benefit that it brings. This essay considers the three main impacts, noise, air pollution around airports and influence on climate change. Of the three, impact on climate change is taken to have the greatest long-term importance and is discussed at the greatest length. It is argued that, of the three main contributors to climate change from aircraft – CO2 emissions, NOX emissions and the creation of persistent contrails – it is the last two which are the most promising targets. Ways of reducing the impacts of these two are discussed and it is noted that, in each case, the best environmental result is likely to entail some increase in CO2 emissions. It follows that regulatory or economic measures to reduce impact on climate should be framed so as to do just that. Measures framed purely in terms of CO2 emissions are likely to be counter-productive. Nevertheless, the design of aircraft to reduce fuel burn and hence CO2 emission remains a key long-term objective; the essay considers the potential offered by new technology and new design concepts in this arena.

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Valença, Alexandre M., Antonio Egidio Nardi, Isabella Nascimento, Walter A. Zin et Márcio Versiani. « Carbon dioxide test as an additional clinical measure of treatment response in panic disorder ». Arquivos de Neuro-Psiquiatria 60, n^o 2B (juin 2002) : 358–61. http://dx.doi.org/10.1590/s0004-282x2002000300003.

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OBJECTIVE: We aim to determine if a treatment with a dose of clonazepam - 2 mg/day, for 6 weeks, blocks spontaneous panic attacks and the ones induced by the inhalation of 35% carbon dioxide (CO2) in panic disorder (PD) patients. The CO2 challenge-test may be a useful addition tool for measuring the pharmacological response during the initial phase (6 weeks) in the treatment of PD. METHOD: Eighteen PD patients drug free for a week participated in a carbon dioxide challenge test. Fourteen had a panic attack and were openly treated for a 6-week period with clonazepam. At the end of the 6-week period they were submitted again to the CO2 challenge test. RESULTS: After 6 weeks of treatment with clonazepam, 12 of 14 PD patients (85.7%) did not have a panic attack after the CO2 challenge test. Just 2 of 14 patients (14.3%) had a panic attack after the CO2 challenge test. Ten of 14 (71.4%) PD patients had panic free status after clonazepam treatment. The 2 patients who had a panic attack in the sixth week, after the CO2 test, did not have panic free status after the treatment with clonazepam. CONCLUSION: The CO2-test may be a valid tool for testing and predicting the drug response.

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Morland, Bjørn H., Gaute Svenningsen et Arne Dugstad. « The Challenge of Monitoring Impurity Content of CO2 Streams ». Processes 9, n^o 4 (24 mars 2021) : 570. http://dx.doi.org/10.3390/pr9040570.

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Carbon capture and storage has gained increased attention during the last decade, and several full-scale projects are currently being planned. From economic and public acceptance point of view it is important to ensure that the transportation system is operated in a safe manner, avoiding threats such as corrosion or formation of solid matters. Thus, routine chemical analyses are required to ensure that the CO2 stream complies with the required specifications. The CO2 will usually be transported in the liquid or supercritical state (high pressure), which makes the practicalities around chemical analyses difficult. Phase transition from liquid or supercritical state to gaseous state may also introduce several physiochemical effects that may affect the analyses. This paper discusses technical and practical challenges with CO2 stream analyses experienced in a joint industry project that studied corrosion and chemical reactions in a simulated CO2 transport system.

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Pols, Henk J., Roos C. Hauzer, Jaap A. Meijer, Kees Verburg et Eric J. Griez. « Fluvoxamine Attenuates Panic Induced by 35% CO2 Challenge ». Journal of Clinical Psychiatry 57, n^o 11 (15 novembre 1996) : 539–42. http://dx.doi.org/10.4088/jcp.v57n1107.

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Wolff, Eric, Christoph Kull, Jerome Chappellaz, Hubertus Fischer, Heinz Miller, Thomas F. Stocker, Andrew J. Watson et al. « Modeling past atmospheric CO2 : Results of a challenge ». Eos, Transactions American Geophysical Union 86, n^o 38 (2005) : 341. http://dx.doi.org/10.1029/2005eo380003.

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Perna, Giampaolo, Barbara Barbini, Silvia Cocchi, Angelo Bertani et Mariangela Gasperini. « 35% CO2 challenge in panic and mood disorders ». Journal of Affective Disorders 33, n^o 3 (mars 1995) : 189–94. http://dx.doi.org/10.1016/0165-0327(94)00088-q.

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Rising, Bruce. « CO2 Seen as Multidecade Challenge for Power Industry ». Natural Gas & ; Electricity 35, n^o 3 (17 septembre 2018) : 15–20. http://dx.doi.org/10.1002/gas.22080.

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Peng, Shin-Lei, Harshan Ravi, Min Sheng, Binu P. Thomas et Hanzhang Lu. « Searching for a truly “iso-metabolic” gas challenge in physiological MRI ». Journal of Cerebral Blood Flow & ; Metabolism 37, n^o 2 (20 juillet 2016) : 715–25. http://dx.doi.org/10.1177/0271678x16638103.

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Hypercapnia challenge (e.g. inhalation of CO2) has been used in calibrated fMRI as well as in the mapping of vascular reactivity in cerebrovascular diseases. An important assumption underlying these measurements is that CO2 is a pure vascular challenge but does not alter neural activity. However, recent reports have suggested that CO2 inhalation may suppress neural activity and brain metabolic rate. Therefore, the goal of this study is to propose and test a gas challenge that is truly “iso-metabolic,” by adding a hypoxic component to the hypercapnic challenge, since hypoxia has been shown to enhance cerebral metabolic rate of oxygen (CMRO2). Measurement of global CMRO2 under various gas challenge conditions revealed that, while hypercapnia (P = 0.002) and hypoxia (P = 0.002) individually altered CMRO2 (by −7.6 ± 1.7% and 16.7 ± 4.1%, respectively), inhalation of hypercapnic-hypoxia gas (5% CO2/13% O2) did not change brain metabolism (CMRO2 change: 1.5 ± 3.9%, P = 0.92). Moreover, cerebral blood flow response to the hypercapnic-hypoxia challenge (in terms of % change per mmHg CO2 change) was even greater than that to hypercapnia alone (P = 0.007). Findings in this study suggest that hypercapnic-hypoxia gas challenge may be a useful maneuver in physiological MRI as it preserves vasodilatory response yet does not alter brain metabolism.

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Bows, A. « Aviation and climate change : confronting the challenge ». Aeronautical Journal 114, n^o 1158 (août 2010) : 459–68. http://dx.doi.org/10.1017/s000192400000395x.

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Abstract Each year greenhouse gas emissions remain high the climate mitigation and adaptation challenges grow. The economic downturn was already in train in 2008, yet concentrations of CO2 increased unabated. Without concerted effort across all sectors there will be little chance of avoiding ‘dangerous climate change’ and the aviation sector has a clear role to play. Current and forthcoming technologies, operational practices and behavioural change offer widespread opportunities for other sectors to mitigate their CO2 emissions in absolute terms, but as they do so, aviation will become an increasingly important player. By comparing a range of global cross-sector emission scenarios with existing aviation projections, this paper illustrates the importance of understanding the future context with regard to other sectors when assessing the aviation industry’s potential impact. Given growth projections for aviation and the relatively slow pace of technological change, aviation’s proportion of 2050 global CO2 emissions is low only in those global cross-sector emission scenarios where there is a high probability of ‘dangerous climate change’. For a ‘reasonable’ (>50%) chance of avoiding ‘dangerous climate change’, the most technologically radical scenarios for aviation make up 15% of global CO2 in 2050 and conventional scenarios exceed the carbon budget entirely. Only by recognising that aviation’s currently projected emissions are incompatible with avoiding ‘dangerous climate change’ can the industry fully grasp the challenge of accelerating innovation and managing demand to deliver a more sustainable route to 2050 and beyond.

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Cosci, F., T. De Gooyer, K. Schruers, C. Faravelli et E. Griez. « The influence of ethanol infusion on the effects of 35% CO2 challenge. A study in panic disorder patients and healthy volunteers ». European Psychiatry 20, n^o 3 (mai 2005) : 299–303. http://dx.doi.org/10.1016/j.eurpsy.2004.06.009.

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AbstractAlcohol and panic disorders co-occur at a rate that exceeds chance significantly. Early experimental work suggests that alcoholic subjects, compared to non-alcoholics, are less sensitive to sodium lactate and that alcohol intake reduces the response to a 35% CO2 challenge in Panic Disorder patients. The present study documents the direct pharmacological effect of ethanol infusion on CO2 induced panic.MethodsAccording to a placebo-controlled, double-blind, randomized, cross-over design 10 drug free panic disorder patients and 16 healthy volunteers underwent a 35% CO2 challenge after intravenous infusion of a moderate dose of ethanol on one test day and of placebo on another test day.ResultsCompared to the placebo condition, the effect of the CO2 challenge was significantly smaller after ethanol infusion (P = 0.041).DiscussionA moderate dose of ethanol decreased the response to a 35% CO2 without inducing pre challenge sedation.ConclusionThe results comfort earlier findings of a direct pharmacological effect of ethanol on panic.

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Schutters, Sara IJ, Wolfgang Viechtbauer, Inge J. Knuts, Eric JL Griez et Koen RJ Schruers. « 35% CO2 sensitivity in social anxiety disorder ». Journal of Psychopharmacology 26, n^o 4 (6 janvier 2012) : 479–86. http://dx.doi.org/10.1177/0269881111430750.

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The 35% carbon dioxide (CO2) challenge is a well-established model of panic. This study aimed to investigate 35% CO2 sensitivity in patients with social anxiety disorder (SAD) compared with patients with panic disorder (PD) and normal controls. First, a 35% CO2 challenge was conducted including 16 patients with generalized SAD, 16 with PD and 16 normal subjects. Outcome was assessed by a Visual Analogue Scale for Fear (VAS-F) and the Panic Symptom List (PSL). Second, meta-analyses of fear and panic scores were performed, including data from the present experiment and from previous 35% CO2 challenge studies in patients with SAD. The present 35% CO2 challenge found equal increases in VAS-F and PSL in patients with SAD compared with normal controls, whereas the CO2 response in patients with PD was significantly stronger than in controls. The meta-analyses confirmed the experimental data from this study, and in addition showed an intermediate panic rate in SAD patients, in between that of normal controls and patients with PD. In conclusion, neither our experiment nor the meta-analyses found evidence for a similarly exaggerated 35% CO2 sensitivity in SAD and PD, suggesting that the pathogenesis of SAD is different from PD, although patients with SAD may be slightly more sensitive than non-anxious controls.

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Secchinato, Kaio Felippe, Pedro Henrique Rodrigues Da Silva, Ana Paula Afonso Camargo, Octávio Marques Pontes-Neto et Renata Ferranti Leoni. « Cerebrovascular reactivity mapping without hypercapnic challenge in patients with carotid artery stenosis ». Revista Brasileira de Física Médica 13, n^o 2 (28 décembre 2019) : 62. http://dx.doi.org/10.29384/rbfm.2019.v13.n2.p62-65.

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Vascular reactivity represents the ability of the vascular smooth muscle to dilate or contract in response to changes in metabolic demand or vasoactive stimulus. More specifically, the cerebrovascular reactivity (CVR) has raised interest in several studies that point to its potential to predict stroke risk in patients with cerebrovascular disease. CVR mapping is typically performed using carbon dioxide (CO2) inhalation, breath-holding, or acetazolamide injection as vasoactive challenges, while magnetic resonance imaging (MRI) based on the blood oxygenation level-dependent (BOLD) contrast is acquired. However, such challenges of hypercapnia depend on additional equipment and cooperation of the subjects, limiting their applications, especially in elderly patients. Therefore, the objective of the present study was to map the CVR using resting-state MRI-BOLD, with no hypercapnic challenge, considering the variations in BOLD signal associated with variations in the arterial partial pressure of CO2. The CVR maps obtained with resting data showed a high correlation with those obtained by the conventional experiment with CO2 inhalation (r > 0.70). In addition, the CVR changes observed for the patients were consistent with their clinical reports. These results show that the mapping of CVR obtained with resting-state data may become a useful alternative in the detection of perfusion changes in clinical applications when the hypercapnic challenge is not feasible.

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Schruers, K. R. J., H. van de Mortel, T. Overbeek et E. Griez. « Symptom profiles of natural and laboratory panic attacks ». Acta Neuropsychiatrica 16, n^o 2 (avril 2004) : 101–6. http://dx.doi.org/10.1111/j.0924-2708.2004.0084.x.

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Background:Little accurate information is available about the symptomatology of real-life panic attacks and about how well they are reproduced by an experimental model such as the 35% CO2 challenge.Method:Real-life panic symptoms were assessed in a group of 67 panic disorder patients, using daily life monitoring. Panic symptoms elicited by a 35% CO2 challenge were assessed in 61 panic disorder patients, and their frequency was compared with the real-life symptoms.Results:The most frequent real-life symptoms were palpitations, dizziness and trembling. The 35% CO2 challenge reproduced well the majority of real-life symptoms.Conclusion:The findings suggest that the 35% CO2 challenge is a marker for spontaneous panic attacks, which are considered the core of panic disorder.

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Asad, Syed Muhammad, Shuja Ansari, Metin Ozturk, Rao Naveed Bin Rais, Kia Dashtipour, Sajjad Hussain, Qammer H. Abbasi et Muhammad Ali Imran. « Mobility Management-Based Autonomous Energy-Aware Framework Using Machine Learning Approach in Dense Mobile Networks ». Signals 1, n^o 2 (18 novembre 2020) : 170–87. http://dx.doi.org/10.3390/signals1020010.

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A paramount challenge of prohibiting increased CO2 emissions for network densification is to deliver the Fifth Generation (5G) cellular capacity and connectivity demands, while maintaining a greener, healthier and prosperous environment. Energy consumption is a demanding consideration in the 5G era to combat several challenges such as reactive mode of operation, high latency wake up times, incorrect user association with the cells, multiple cross-functional operation of Self-Organising Networks (SON), etc. To address this challenge, we propose a novel Mobility Management-Based Autonomous Energy-Aware Framework for analysing bus passengers ridership through statistical Machine Learning (ML) and proactive energy savings coupled with CO2 emissions in Heterogeneous Network (HetNet) architecture using Reinforcement Learning (RL). Furthermore, we compare and report various ML algorithms using bus passengers ridership obtained from London Overground (LO) dataset. Extensive spatiotemporal simulations show that our proposed framework can achieve up to 98.82% prediction accuracy and CO2 reduction gains of up to 31.83%.

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Mukherjee, Soumya, Nivedita Sikdar, Daniel O’Nolan, Douglas M. Franz, Victoria Gascón, Amrit Kumar, Naveen Kumar et al. « Trace CO2 capture by an ultramicroporous physisorbent with low water affinity ». Science Advances 5, n^o 11 (novembre 2019) : eaax9171. http://dx.doi.org/10.1126/sciadv.aax9171.

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CO2 accumulation in confined spaces represents an increasing environmental and health problem. Trace CO2 capture remains an unmet challenge because human health risks can occur at 1000 parts per million (ppm), a level that challenges current generations of chemisorbents (high energy footprint and slow kinetics) and physisorbents (poor selectivity for CO2, especially versus water vapor, and/or poor hydrolytic stability). Here, dynamic breakthrough gas experiments conducted upon the ultramicroporous material SIFSIX-18-Ni-β reveal trace (1000 to 10,000 ppm) CO2 removal from humid air. We attribute the performance of SIFSIX-18-Ni-β to two factors that are usually mutually exclusive: a new type of strong CO2 binding site and hydrophobicity similar to ZIF-8. SIFSIX-18-Ni-β also offers fast sorption kinetics to enable selective capture of CO2 over both N2 (SCN) and H2O (SCW), making it prototypal for a previously unknown class of physisorbents that exhibit effective trace CO2 capture under both dry and humid conditions.

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Seddon, Kate, Kelly Morris, Jayne Bailey, John Potokar, Ann Rich, Sue Wilson, Paolo Bettica et David J. Nutt. « Effects of 7.5% CO2 challenge in generalized anxiety disorder ». Journal of Psychopharmacology 25, n^o 1 (16 mars 2010) : 43–51. http://dx.doi.org/10.1177/0269881110364270.

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Bocola, V., M. D. Trecco, Giovanni Fabbrini, C. Paladini, A. Sollecito et N. Martucci. « Antipanic Effect of Fluoxetine Measured by CO2 Challenge Test ». Biological Psychiatry 43, n^o 8 (avril 1998) : 612–15. http://dx.doi.org/10.1016/s0006-3223(97)00221-7.

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Ruddiman, William F. « The challenge of modeling interglacial CO2 and CH4 trends ». Quaternary Science Reviews 27, n^o 5-6 (mars 2008) : 445–48. http://dx.doi.org/10.1016/j.quascirev.2007.11.007.

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Smits, Jasper A. J., Alicia E. Meuret, Michael J. Zvolensky, David Rosenfield et Anke Seidel. « The effects of acute exercise on CO2 challenge reactivity ». Journal of Psychiatric Research 43, n^o 4 (janvier 2009) : 446–54. http://dx.doi.org/10.1016/j.jpsychires.2008.05.009.

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Kaye, Joey, Peter Soothill, Moira Hunt et Stafford Lightman. « Responses to the 35% CO2 challenge in postpartum women ». Clinical Endocrinology 61, n^o 5 (novembre 2004) : 582–88. http://dx.doi.org/10.1111/j.1365-2265.2004.02133.x.

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Corrêa-Afonso, Alessandra Marques, Luciano Bachmann, Cíntia Guimarães de Almeida, Regina Guenka Palma Dibb, Silmara Aparecida Milori Corona et Maria Cristina Borsatto. « CO2-lased enamel microhardness after brushing and cariogenic challenge ». Journal of Biomedical Optics 18, n^o 10 (21 octobre 2013) : 108003. http://dx.doi.org/10.1117/1.jbo.18.10.108003.

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Eilts, Peter. « The Challenge of CO2 Limits for Heavy Commercial Vehicles ». ATZheavy duty worldwide 12, n^o 3 (septembre 2019) : 66. http://dx.doi.org/10.1007/s41321-019-0040-8.

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Ren, Shaoxuan, Dorian Joulié, Danielle Salvatore, Kristian Torbensen, Min Wang, Marc Robert et Curtis P. Berlinguette. « Molecular electrocatalysts can mediate fast, selective CO2 reduction in a flow cell ». Science 365, n^o 6451 (25 juillet 2019) : 367–69. http://dx.doi.org/10.1126/science.aax4608.

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Practical electrochemical carbon dioxide (CO2) conversion requires a catalyst capable of mediating the efficient formation of a single product with high selectivity at high current densities. Solid-state electrocatalysts achieve the CO2 reduction reaction (CO2RR) at current densities ≥ 150 milliamperes per square centimeter (mA/cm2), but maintaining high selectivities at high current densities and efficiencies remains a challenge. Molecular CO2RR catalysts can be designed to achieve high selectivities and low overpotentials but only at current densities irrelevant to commercial operation. We show here that cobalt phthalocyanine, a widely available molecular catalyst, can mediate CO2 to CO formation in a zero-gap membrane flow reactor with selectivities > 95% at 150 mA/cm2. The revelation that molecular catalysts can work efficiently under these operating conditions illuminates a distinct approach for optimizing CO2RR catalysts and electrolyzers.

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Chalmers, H., et J. Gibbins. « Carbon capture and storage : The ten year challenge ». Proceedings of the Institution of Mechanical Engineers, Part C : Journal of Mechanical Engineering Science 224, n^o 3 (1 mars 2010) : 505–18. http://dx.doi.org/10.1243/09544062jmes1516.

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Carbon capture and storage (CCS) could play a significant role in reducing global CO2 emissions. It has the unique characteristic of keeping fossil carbon in the ground by allowing fossil fuels to be used, but with the CO2 produced being safely stored in a geological formation. Initial versions of the key component technologies are at a sufficient level of maturity to build integrated commercial-scale demonstration plants. If CCS is to reach its full potential to contribute to global efforts to mitigate the risk of dangerous climate change, it is urgent that a number of actions begin now in order to be ready for CCS deployment from around 2020 using proven designs that can be built in large numbers. This article discusses some key challenges for CCS, with a focus on development in the next decade, highlighting the potential benefits of a two tranche programme for integrated commercial-scale demonstration to develop proven reference plant designs and reviewing the importance of distinguishing between different classes of CCS according to their ability to significantly reduce CO2 emissions associated with fossil fuel use. It also identifies some ongoing CCS projects and initiatives and examines some possible implications of current policy discussions for technology development.

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Brys, Miroslaw, Clive M. Brown, Harald Marthol, Renate Franta et Max J. Hilz. « Dynamic cerebral autoregulation remains stable during physical challenge in healthy persons ». American Journal of Physiology-Heart and Circulatory Physiology 285, n^o 3 (septembre 2003) : H1048—H1054. http://dx.doi.org/10.1152/ajpheart.00062.2003.

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The effects of physical activity on cerebral blood flow (CBF) and cerebral autoregulation (CA) have not yet been fully evaluated. There is controversy as to whether increasing heart rate (HR), blood pressure (BP), and sympathetic and metabolic activity with altered levels of CO2 might compromise CBF and CA. To evaluate these effects, we studied middle cerebral artery blood flow velocity (CBFV) and CA in 40 healthy young adults at rest and during increasing levels of physical exercise. We continuously monitored HR, BP, end-expiratory CO2, and CBFV with transcranial Doppler sonography at rest and during stepwise ergometric challenge at 50, 100, and 150 W. The modulation of BP and CBFV in the low-frequency (LF) range (0.04–0.14 Hz) was calculated with an autoregression algorithm. CA was evaluated by calculating the phase shift angle and gain between BP and CBFV oscillations in the LF range. The LF BP-CBFV gain was then normalized by conductance. Cerebrovascular resistance (CVR) was calculated as mean BP adjusted to brain level divided by mean CBFV. HR, BP, CO2, and CBFV increased significantly with exercise. Phase shift angle, absolute and normalized LF BP-CBFV gain, and CVR, however, remained stable. Stable phase shift, LF BP-CBFV gain, and CVR demonstrate that progressive physical exercise does not alter CA despite increasing HR, BP, and CO2. CA seems to compensate for the hemodynamic effects and increasing CO2 levels during exercise.

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Monni, Noemi, Eduardo Andres-Garcia, Katia Caamaño, Víctor García-López, Juan Modesto Clemente-Juan, Mónica Giménez-Marqués, Mariangela Oggianu et al. « A thermally/chemically robust and easily regenerable anilato-based ultramicroporous 3D MOF for CO₂ uptake and separation ». Journal of Materials Chemistry A 9, n^o 44 (2021) : 25189–95. http://dx.doi.org/10.1039/d1ta07436a.

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A novel anilato-based 3D ultramicroporous MOF is reported, displaying a significant balance of high CO2 separation from CO2:N2 and CO2:CH4 gas mixtures, high thermal stability and high regenerability, a challenge in the separation technology industry.

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Ouanonou, A., Y. Zhang et L. Zhang. « Changes in the Calcium Dependence of Glutamate Transmission in the Hippocampal CA1 Region After Brief Hypoxia-Hypoglycemia ». Journal of Neurophysiology 82, n^o 3 (1 septembre 1999) : 1147–55. http://dx.doi.org/10.1152/jn.1999.82.3.1147.

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Using the model of hypoxia-hypoglycemia (HH) in rat brain slices, we asked whether glutamate transmission is altered following a brief HH episode. The HH challenge was conducted by exposing slices to a glucose-free medium aerated with 95% N2-5% CO2, for ∼4 min, and glutamate transmission in the hippocampal CA1 region was monitored at different post HH times. In slices examined ≤8 h post HH, CA1 synaptic field potentials are comparable in amplitude to controls, but are less sensitive to experimental manipulations designed to attenuate intracellular Ca2+ signals, as compared with controls. Reducing calcium influx, by applying a nonspecific calcium channel blocker Co2+ or lowering external Ca2+, attenuated CA1 synaptic potentials much less in challenged slices than in controls. Buffering intracellular Ca2+ by bis-( o-aminophenoxy)- N,N,N′,N′-tetraacetic acid-AM (BAPTA-AM) attenuated CA1 synaptic potentials in control but not in slices post HH. Furthermore, minimally evoked excitatory postsynaptic currents displayed a lower failure rate in post-hypoxic CA1 neurons compared with controls. Based on these convergent observations, we suggest that evoked CA1 glutamate transmission is altered in the first several hours after brief hypoxia, likely resulting from alterations in intracellular Ca2+homeostasis and/or Ca2+-dependent processes governing transmitter release.

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Rosenthal, Guy, Rene O. Sanchez-Mejia, Nicolas Phan, J. Claude Hemphill, Christine Martin et Geoffrey T. Manley. « Incorporating a parenchymal thermal diffusion cerebral blood flow probe in bedside assessment of cerebral autoregulation and vasoreactivity in patients with severe traumatic brain injury ». Journal of Neurosurgery 114, n^o 1 (janvier 2011) : 62–70. http://dx.doi.org/10.3171/2010.6.jns091360.

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Object Cerebral autoregulation may be altered after traumatic brain injury (TBI). Recent evidence suggests that patients' autoregulatory status following severe TBI may influence cerebral perfusion pressure management. The authors evaluated the utility of incorporating a recently upgraded parenchymal thermal diffusion probe for the measurement of cerebral blood flow (CBF) in the neurointensive care unit for assessing cerebral autoregulation and vasoreactivity at bedside. Methods The authors evaluated 20 patients with severe TBI admitted to San Francisco General Hospital who underwent advanced neuromonitoring. Patients had a parenchymal thermal diffusion probe placed for continuous bedside monitoring of local CBF (locCBF) in addition to the standard intracranial pressure and brain tissue oxygen tension (PbtO2) monitoring. The CBF probes were placed in the white matter using a separate cranial bolt. A pressure challenge, whereby mean arterial pressure (MAP) was increased by about 10 mm Hg, was performed in all patients to assess autoregulation. Cerebral CO2 vasoreactivity was assessed with a hyperventilation challenge. Local cerebral vascular resistance (locCVR) was calculated by dividing cerebral perfusion pressure by locCBF. Local cerebral vascular resistance normalized to baseline (locCVRnormalized) was also calculated for the MAP and hyperventilation challenges. Results In all cases, bedside measurement of locCBF using a cranial bolt in patients with severe TBI resulted in correct placement in the white matter with a low rate of complications. Mean locCBF decreased substantially with hyperventilation challenge (−7 ± 8 ml/100 g/min, p = 0.0002) and increased slightly with MAP challenge (1 ± 7 ml/100 g/min, p = 0.17). Measurements of locCBF following MAP and hyperventilation challenges can be used to calculate locCVR. In 83% of cases, locCVR increased during a hyperventilation challenge (mean change +3.5 ± 3.8 mm Hg/ml/100 g/min, p = 0.0002), indicating preserved cerebral CO2 vasoreactivity. In contrast, we observed a more variable response of locCVR to MAP challenge, with increased locCVR in only 53% of cases during a MAP challenge (mean change −0.17 ± 3.9 mm Hg/ml/100 g/min, p = 0.64) indicating that in many cases autoregulation was impaired following severe TBI. Conclusions Use of the Hemedex thermal diffusion probe appears to be a safe and feasible method that enables continuous monitoring of CBF at the bedside. Cerebral autoregulation and CO2 vasoreactivity can be assessed in patients with severe TBI using the CBF probe by calculating locCVR in response to MAP and hyperventilation challenges. Determining whether CVR increases or decreases with a MAP challenge (locCVRnormalized) may be a simple provocative test to determine patients' autoregulatory status following severe TBI and helping to optimize CPP management.

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El Mays, Tamer Y., Mahmoud Saifeddine, Parichita Choudhury, Morley D. Hollenberg et Francis H. Y. Green. « Carbon dioxide enhances substance P-induced epithelium-dependent bronchial smooth muscle relaxation in Sprague–Dawley rats ». Canadian Journal of Physiology and Pharmacology 89, n^o 7 (juillet 2011) : 513–20. http://dx.doi.org/10.1139/y11-052.

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Hypocapnia and hypercapnia constrict and relax airway smooth muscle, respectively, through pH- and calcium (Ca2+)-mediated mechanisms. In this study we explore a potential role for the airway epithelium in these responses to carbon dioxide (CO2). Contractile and relaxant responses of isolated rat bronchial rings were measured under hypocapnic, eucapnic, and hypercapnic conditions. Substance P was added to methacholine precontracted bronchial rings with and without epithelium. The role of Ca2+ was assessed using Ca2+-free solutions and a Ca2+ channel blocker, nifedipine. The effects of pH were assessed in solutions with HEPES buffer. Hypocapnic challenge increased the organ bath’s pH and increased bronchial smooth muscle resting tension. This effect was abolished with HEPES buffer and partially inhibited by nifedipine. Hypocapnic conditions suppressed substance P-induced epithelium-dependent relaxation, whereas hypercapnia augmented the response. The epithelial hypocapnic effect was pH dependent, whereas the hypercapnic effect was pH independent. CO2 had no effect on the epithelial independent smooth muscle agonists methacholine and isoproterenol. In conclusion our data indicate that, in addition to the effects of pH and Ca2+, CO2 affects airway smooth muscle by a pH-independent, epithelium-mediated mechanism. These findings could potentially lead to new treatments for asthma involving CO2-sensing receptors in the airways.

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Hua, J., M. Wang, Deqiang Zhang, X. Pei, Xiaoyu Zhao et X. Ma. « A three dimensional cadmium-mixed ligands coordination polymer with CO2 adsorption ability ». Журнал структурной химии 63, n^o 12 (2022) : 103658. http://dx.doi.org/10.26902/jsc_id103658.

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Carbon dioxide (CO2) is an important metabolite and biological signal gas, and the adsorption of the CO2 is not only a challenge but also an important research field of bio-inorganic chemistry and coordination chemistry. A coordination polymer (CP) [Cd(tib)(1,4-NDC)]·3H2O (CdTN) has been prepared by the solvothermal reactions of 1,3,5-tris(1-imidazolyl) benzene (tib) and 1,4-naphthalenedicarboxylic acid (1,4-H2NDC) with Cd2+. The result of X-ray single-crystal analysis shows that CdTN is a two-fold interpenetrating 3D framework with {42·65·83}{42·6} topology. CdTN was further characterized by powder X-ray diffraction (XPRD), IR spectroscopy, thermogravimetric analysis (TGA), and elemental analysis. Notably, further research showed that CdTN possesses the ability in CO2 adsorption at low temperature.

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Freed, AN, et Adkinson NF. « Dry air-induced late phase responses in the canine lung periphery ». European Respiratory Journal 3, n^o 4 (1 avril 1990) : 434–40. http://dx.doi.org/10.1183/09031936.93.03040434.

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Although controversial, late phase responses in asthmatic subjects have been reported several hours after exercise. We previously showed that exposure to dry air increases collateral system resistance (Rcs) in the canine lung periphery, and produces acute airway responses analogous to those that characterize human exercise-induced asthma. We used a dual wedged bronchoscope technique in anaesthetized male mongrel dogs to monitor Rcs in: 1) control segments continuously exposed to 200 ml.min-1 of 5% CO2 in air and 2) dry air challenged segments exposed to 2000 ml.min-1 5% CO2 for 5 min. We examined Rcs at 5 min and approximately 5 h post-challenge in an attempt to document late phase airway obstruction. Five min after dry air challenge Rcs initially increased 114 +/- SE 22%; contralateral control segments remained unchanged (n = 9). Five hour post-challenge, Rcs in dry air exposed segments was elevated 81 +/- 20% above pre-challenge baseline (p less than 0.01); contralateral control segments did not change significantly over the 5 h period. Cell profile analyses of lavage samples at 5 hours revealed that neutrophils and eosinophils were significantly increased (p less than 0.03) in dry air challenged segments when compared to controls. Leukotriene C4/D4 concentration in lavage was correlated (p less than 0.02) with neutrophil infiltration. Thus, we conclude that the canine lung periphery represents a reproducible model of a dry air-induced late phase reaction.

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Aizawa, Takafumi. « Process Development of CO2-Assisted Polymer Compression for High Productivity : Improving Equipment and the Challenge of Numbering-Up ». Technologies 7, n^o 2 (8 mai 2019) : 39. http://dx.doi.org/10.3390/technologies7020039.

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The CO2-assisted polymer compression method is used herein to prepare porous polymer materials by bonding laminated polymer fiber sheets using a piston in the presence of CO2. In this work, the CO2 flow line connections were moved from the pressure vessel to the piston to increase productivity, which makes the pressure vessel free-moving and the processing time of sample introduction and removal seemingly zero. In addition, a numbering-up method suitable for CO2-assisted polymer compression is proposed and verified based on the variability of the products. The variability of the product was evaluated using porosity, which is one of the most important properties of a porous material. It is found that the CO2 exhaust process, specific to this method, that uses high-pressure CO2, causes product variation, which can be successfully suppressed by optimizing the CO2 exhaust process.

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Goldner, A., N. Herold et M. Huber. « The challenge of simulating warmth of the mid-Miocene Climate Optimum in CESM1 ». Climate of the Past Discussions 9, n^o 3 (26 juin 2013) : 3489–518. http://dx.doi.org/10.5194/cpd-9-3489-2013.

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Abstract. The mid-Miocene Climatic Optimum (MMCO) is an intriguing climatic period due to its above-modern temperatures in mid-to-high latitudes in the presence of close-to-modern CO2 concentrations. We use the recently released Community Earth System Model (CESM1.0) with a slab ocean to simulate this warm period, incorporating recent Miocene CO2 reconstructions of 400 ppm. We simulate a global mean annual temperature (MAT) of 18 °C, ~4 °C above the pre-industrial value, but 4 °C colder than the global Miocene MAT we calculate from climate proxies. Sensitivity tests reveal that the inclusion of a reduced Antarctic ice sheet, eastern equatorial Pacific Ocean temperature anomalies, increased CO2 to 560 ppm, and variations in obliquity only marginally improve model-data agreement. All MMCO simulations have an equator to pole temperature gradient which is at least ~ 10 °C larger than the reconstruction from proxies. The MMCO simulation most comparable to the proxy records requires a CO2 concentration of 800 ppm. Our results illustrate that MMCO warmth is not reproducible using the CESM1.0 forced with CO2 concentrations reconstructed for the Miocene or including various proposed Earth system feedbacks; the remaining discrepancy in the MAT is comparable to that introduced by a CO2 doubling. The models tendency to underestimate proxy derived global MAT and overestimate the equator to pole temperature gradient suggests a major climate problem in the MMCO akin to those in the Eocene. Our results imply that this latest model, as with previous generations of climate models, is either not sensitive enough or additional forcings remain missing that explain half of the anomalous warmth and pronounced polar amplification of the MMCO.

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Liu, Peiying, Jill B. De Vis et Hanzhang Lu. « Cerebrovascular reactivity (CVR) MRI with CO2 challenge : A technical review ». NeuroImage 187 (février 2019) : 104–15. http://dx.doi.org/10.1016/j.neuroimage.2018.03.047.

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Caldirola, Daniela, Giampaolo Perna, Cinzia Arancio, Angelo Bertani et Laura Bellodi. « The 35% CO2 challenge test in patients with social phobia ». Psychiatry Research 71, n^o 1 (mai 1997) : 41–48. http://dx.doi.org/10.1016/s0165-1781(97)00038-3.

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Richey, J. Anthony, Meghan E. Keough et Norman B. Schmidt. « Attentional Control Moderates Fearful Responding to a 35% CO2 Challenge ». Behavior Therapy 43, n^o 2 (juin 2012) : 285–99. http://dx.doi.org/10.1016/j.beth.2011.06.004.

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Wang, Qiang, Kehao Hu, Ruxing Gao, Leiyu Zhang, Lei Wang et Chundong Zhang. « Hydrogenation of Carbon Dioxide to Value-Added Liquid Fuels and Aromatics over Fe-Based Catalysts Based on the Fischer–Tropsch Synthesis Route ». Atmosphere 13, n^o 8 (4 août 2022) : 1238. http://dx.doi.org/10.3390/atmos13081238.

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Hydrogenation of CO2 to value-added chemicals and fuels not only effectively alleviates climate change but also reduces over-dependence on fossil fuels. Therefore, much attention has been paid to the chemical conversion of CO2 to value-added products, such as liquid fuels and aromatics. Recently, efficient catalysts have been developed to face the challenge of the chemical inertness of CO2 and the difficulty of C–C coupling. Considering the lack of a detailed summary on hydrogenation of CO2 to liquid fuels and aromatics via the Fischer–Tropsch synthesis (FTS) route, we conducted a comprehensive and systematic review of the research progress on the development of efficient catalysts for hydrogenation of CO2 to liquid fuels and aromatics. In this work, we summarized the factors influencing the catalytic activity and stability of various catalysts, the strategies for optimizing catalytic performance and product distribution, the effects of reaction conditions on catalytic performance, and possible reaction mechanisms for CO2 hydrogenation via the FTS route. Furthermore, we also provided an overview of the challenges and opportunities for future research associated with hydrogenation of CO2 to liquid fuels and aromatics.

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Ortas, Ibrahim. « The role of mycorrhiza in food security and the challenge of climate change ». International Journal of Agricultural and Applied Sciences 3, n^o 1 (20 juin 2022) : 1–11. http://dx.doi.org/10.52804/ijaas2022.311.

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Before the Industrial Revolution, the concentration of CO2 in the atmosphere was 280 ppm and in time increasing fossil fuels use increased CO2 concentration up to 416 ppm in a preset time. Meanwhile, increasing population growth (around 8 billion) has also started to put serious pressure on soil ecosystem for more food production demand. With the demand for more food production, intensive chemical inputs and soil cultivation practices applied to the soil has increased the amount of CO2 released to the atmosphere. Increasing CO2 concentration in the atmosphere triggers global warming and climate change which is negatively affect plant growth and consequently food security. In order to ensure food security under climate change conditions, it seems that the need to re-enact nature's own mechanisms has arisen. In this context, it is aimed to reduce the effect of climate changes by keeping more carbon as a sink by operating the effects of plant root mechanisms on the soil health according to ecological principles. Under long term filed conditions the effects of different soil-plant managements, especially mycorrhiza fungi, were investigated. Since 1996, several researches have been carried out under long-term field studies to see the effect of mycorrhizal fungi and other microorganisms on carbon sequestration, as well as the emission of CO2 from the greenhouse gases to the atmosphere. Regularly CO2 flux, emissions, photosynthesis rate, C, N sequestration and yield parameters are measured. Data are yearly evaluated. Results revealed that under long-term field conditions, organic fertilizers application and mycorrhizal inoculation sequestered more carbon in soil profile. It has been shown that, using animal manure, compost, biochar, nitrogen-fixing bacteria and mycorrhizal fungi significantly kept more carbon in plant tissue and soil. It is determined that there is an increase of 1.5 ppm CO2 concentration in atmosphere per year. It has been determined that especially long-term addition of organic matter and management of natural mycorrhizae increase soil organic carbon and accordingly soil quality and productivity increase. As the effect of climate change and population growth have significant negative impact on food security, definitely a new agriculture revelation is needed to overcome of climate and food security problem. Soil and plant management must be managed according to low-input ecological principles.

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Cosci, Fiammetta, Koen Schruers, Carlo Faravelli et Eric Griez. « The influence of alcohol oral intake on the effects of 35% CO2 challenge. A study in healthy volunteers ». Acta Neuropsychiatrica 16, n^o 2 (avril 2004) : 107–9. http://dx.doi.org/10.1111/j.0924-2708.2004.0077.x.

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Objective:Alcohol use disorders and panic disorder co-occur at a rate that exceeds chance significantly. The underlying mechanism of alcoholism associated with anxiety has rarely been examined using experimental methodologies. The present study in healthy volunteers tested whether alcohol consumption reduces anxiety associated with a panic-challenge procedure (35% CO2 challenge).Methods:The study design was placebo-controlled, double-blind, randomized. Eight healthy volunteers were enrolled; all subjects had an alcohol and a placebo oral intake according to a crossover design. After each consumption the subjects underwent the 35% CO2 challenge and a series of anxiety symptom assessments.Results:After the alcohol intake, the subjects presented a significant reduction in the anxiety state associated with the challenge procedure. The Panic Symptom List score is significantly lower after alcohol intake (P = 0.032), as compared with the placebo, and the Visual Analogue Anxiety Scale shows a trend to be lower after alcohol intake (P = 0.111).Conclusions:Moderate doses of alcohol acutely decrease the response to a 35% CO2 challenge in healthy volunteers. These results lend support to the pharmacological anxiolytic effect of alcohol and suggest that this property may reinforce the drinking behaviour among those with high levels of anxiety.

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Wang, Wanhua, Haixia Li, Ka-Young Park, Taehee Lee et Fanglin (Frank) Chen. « Improving the Performance for Direct Electrolysis of CO₂ in Solid Oxide Electrolysis Cell with Sr_1.9Fe_1.5Mo_0.5 O₆ _- _δ Electrode Via Infiltration of Pr₆O₁₁ Nanoparticles ». ECS Meeting Abstracts MA2022-02, n^o 47 (9 octobre 2022) : 1778. http://dx.doi.org/10.1149/ma2022-02471778mtgabs.

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High temperature direct CO2 electrolysis based on solid oxide electrolysis cell (CO2-SOEC) is a promising technology to convert carbon dioxide to carbon monoxide with a high current density and Faradaic efficiency. The exploration for suitable cathodes with desirable catalytic activity is a grand challenge for the development of CO2-SOEC. Sr2Fe1.5Mo0.5O6 - δ is often used as the cathode material for SOEC, but suffers from insufficient activity for CO2 reduction reaction (CO2RR). In this work, nanoscale Pr6O11 was infiltrated into the Sr1.9Fe1.5Mo0.5O6 - δ (SFM) electrode to promote the CO2RR performance in SOEC. The optimal loading of Pr6O11 is systematically investigated. At 800°C, the current density of the Pr6O11 infiltrated SFM cathode with a Pr6O11 loading of 13.4wt.% reaches 1.58 A/cm2 at 1.5V, which is 2.5 times higher than that of SFM cathode (0.63 A/cm2) at the same operating conditions. X-ray photoelectron spectroscopy characterization and temperature-programmed desorption of CO2 measurements indicate that the adsorption and desorption ability of CO2 of SFM cathode are improved by the infiltration of Pr6O11. Further, the polarization resistance of SFM cathode has significantly decreased with the infiltrated Pr6O11. These results demonstrate that the infiltration of Pr6O11 is a promising approach for increasing CO2RR activity. Acknowledgements Financial support from the U.S. Department of Energy (DE-EE0009427) and NASA EPSCoR (Grant # 80NSSC20M0233) is greatly appreciated.

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Ballamine, Abderrahmane, Abdellah Kotni, Jean-Pierre Llored et Sylvain Caillol. « Valuing CO₂ in the development of polymer materials ». Science and Technology for Energy Transition 77 (2022) : 1. http://dx.doi.org/10.2516/stet/2021001.

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Reducing the concentration of carbon dioxide in the atmosphere is a major challenge for humanity as well as for living species on Earth. Not least because of the adverse effects of climate warming caused by the anthropological emissions of the CO2. We are interested in a complementary approach to capturing and storing CO2, which is to use CO2 as a raw material for chemical reactions. Specifically, it is a question of using the CO2 for the synthesis of certain types of biocompatible polymers. For the time being, these remain restricted to polycarbonates for economic reasons. The use of CO2 is also motivated by its abundance as a potentially unlimited source of carbon. The challenge of this chemical process is to use appropriate catalysts to synthesize polycarbonates in sufficient quantities and with interesting physical properties. There is also talk of producing biodegradable and biocompatible polycarbonates to ensure a relatively green footprint compared to conventional polycarbonate production processes.

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Huneke, Nathan T. M., M. John Broulidakis, Angela Darekar, David S. Baldwin et Matthew Garner. « Brain Functional Connectivity Correlates of Response in the 7.5% CO2 Inhalational Model of Generalized Anxiety Disorder : A Pilot Study ». International Journal of Neuropsychopharmacology 23, n^o 4 (14 mars 2020) : 268–73. http://dx.doi.org/10.1093/ijnp/pyaa019.

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Abstract Background The 7.5% CO2 inhalational model can be used to explore potential treatments for generalized anxiety disorder. However, it is unknown how inter-individual variability in the functional architecture of negative affective valence systems might relate to anxiogenic response in this model. Methods A total of 13 healthy volunteers underwent functional magnetic resonance imaging during a passive emotional face perception task. We explored task-evoked functional connectivity in the potential threat system through generalized psychophysiological interaction analysis. Within 7 days, these participants underwent prolonged 7.5% CO2 inhalation, and results from the generalized psychophysiological interaction analysis were correlated with CO2 outcome measures. Results Functional connectivity between ventromedial prefrontal cortex and right amygdala positively correlated with heart rate and subjective anxiety, while connectivity between midcingulate cortex and left amygdala negatively correlated with anxiety during CO2 challenge. Conclusions Response to CO2 challenge correlated with task-evoked functional connectivity in the potential threat system. Further studies should assess whether this translates into clinical populations.

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Koukouzas, Nikolaos, Pavlos Tyrologou, Dimitris Karapanos, Júlio Carneiro, Pedro Pereira, Fernanda de Mesquita Lobo Veloso, Petros Koutsovitis, Christos Karkalis, Eleonora Manoukian et Rania Karametou. « Carbon Capture, Utilisation and Storage as a Defense Tool Against Climate Change : Current Developments in West Macedonia (Greece) ». Energies 14, n^o 11 (5 juin 2021) : 3321. http://dx.doi.org/10.3390/en14113321.

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In West Macedonia (Greece), CO2 accounts as one of the largest contributors of greenhouse gas emissions related to the activity of the regional coal power plants located in Ptolemaida. The necessity to mitigate CO2 emissions to prevent climate change under the Paris Agreement's framework remains an ongoing and demanding challenge. It requires implementing crucial environmentally sustainable technologies to provide balanced solutions between the short-term needs for dependency on fossil fuels and the requirements to move towards the energy transition era. The challenge to utilise and store CO2 emissions will require actions aiming to contribute to a Europe-wide CCUS infrastructure. The Horizon 2020 European Project "STRATEGY CCUS "examines the potential for CO2 storage in the Mesohellenic Trough from past available data deploying the USDOE methodology. Research results show that CO2 storage capacities for the Pentalofos and Eptachori geological formations of the Mesohellenic Trough are estimated at 1.02 and 0.13 Gt, respectively, thus providing the potential for the implementation of a promising method for reducing CO2 emissions in Greece. A certain storage potential also applies to the Grevena sub-basin, offering the opportunity to store any captured CO2 in the area, including other remote regions.

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Olabi, A. G., Tabbi Wilberforce, Enas Taha Sayed, Nabila Shehata, Abdul Hai Alami, Hussein M. Maghrabie et Mohammad Ali Abdelkareem. « Prospect of Post-Combustion Carbon Capture Technology and Its Impact on the Circular Economy ». Energies 15, n^o 22 (17 novembre 2022) : 8639. http://dx.doi.org/10.3390/en15228639.

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The sudden increase in the concentration of carbon dioxide (CO2) in the atmosphere due to the high dependency on fossil products has created the need for an urgent solution to mitigate this challenge. Global warming, which is a direct result of excessive CO2 emissions into the atmosphere, is one major issue that the world is trying to curb, especially in the 21st Century where most energy generation mediums operate using fossil products. This investigation considered a number of materials ideal for the capturing of CO2 in the post-combustion process. The application of aqueous ammonia, amine solutions, ionic liquids, and activated carbons is thoroughly discussed. Notable challenges are impeding their advancement, which are clearly expatiated in the report. Some merits and demerits of these technologies are also presented. Future research directions for each of these technologies are also analyzed and explained in detail. Furthermore, the impact of post-combustion CO2 capture on the circular economy is also presented.

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Goldner, A., N. Herold et M. Huber. « The challenge of simulating the warmth of the mid-Miocene climatic optimum in CESM1 ». Climate of the Past 10, n^o 2 (13 mars 2014) : 523–36. http://dx.doi.org/10.5194/cp-10-523-2014.

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Abstract. The mid-Miocene climatic optimum (MMCO) is an intriguing climatic period due to its above-modern temperatures in mid-to-high latitudes in the presence of close-to-modern CO2 concentrations. We use the recently released Community Earth System Model (CESM1.0) with a slab ocean to simulate this warm period, incorporating recent Miocene CO2 reconstructions of 400 ppm (parts per million). We simulate a global mean annual temperature (MAT) of 18 °C, ~4 °C above the preindustrial value, but 4 °C colder than the global Miocene MAT we calculate from climate proxies. Sensitivity tests reveal that the inclusion of a reduced Antarctic ice sheet, an equatorial Pacific temperature gradient characteristic of a permanent El Niño, increased CO2 to 560 ppm, and variations in obliquity only marginally improve model–data agreement. All MMCO simulations have an Equator to pole temperature gradient that is at least ~10 °C larger than that reconstructed from proxies. The MMCO simulation most comparable to the proxy records requires a CO2 concentration of 800 ppm. Our results illustrate that MMCO warmth is not reproducible using the CESM1.0 forced with CO2 concentrations reconstructed for the Miocene or including various proposed Earth system feedbacks; the remaining discrepancy in the MAT is comparable to that introduced by a CO2 doubling. The model's tendency to underestimate proxy derived global MAT and overestimate the Equator to pole temperature gradient suggests a major climate problem in the MMCO akin to those in the Eocene. Our results imply that this latest model, as with previous generations of climate models, is either not sensitive enough or additional forcings remain missing that explain half of the anomalous warmth and pronounced polar amplification of the MMCO.

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Leibold, Nicole K., Daniel LA van den Hove, Wolfgang Viechtbauer, Gunter Kenis, Liesbet Goossens, Iris Lange, Inge Knuts et al. « Amiloride-sensitive cation channel 2 genotype affects the response to a carbon dioxide panic challenge ». Journal of Psychopharmacology 31, n^o 10 (25 janvier 2017) : 1294–301. http://dx.doi.org/10.1177/0269881116686880.

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Until recently, genetic research into panic disorder (PD) has had only limited success. Inspired by rodent research, demonstrating that the acid-sensing ion channel 1a (ASIC1a) is critically involved in the behavioral fear response to carbon dioxide (CO2) exposure, variants in the human homologue gene amiloride-sensitive cation channel 2 (ACCN2) were shown to be associated with PD. However, the relationship between changes in brain pH and ACCN2, as done in rodents by CO2 exposure, has not been investigated yet in humans. Here, we examined this link between the ACCN2 gene and the response to CO2 exposure in two studies: in healthy volunteers as well as PD patients and using both behavioral and physiological outcome measures. More specifically, 107 healthy volunteers and 183 PD patients underwent a 35% CO2 inhalation. Negative affect was assessed using visual analogue scales and the panic symptom list (PSL), and, in healthy volunteers, cardiovascular measurements. The single nucleotide polymorphism rs10875995 was significantly associated with a higher emotional response in PD patients and with an increase in systolic as well as diastolic blood pressure in healthy subjects. In all measurements, subjects homozygous for the T-allele showed a heightened reactivity to CO2. Furthermore, a trend towards an rs685012 genotype effect on the emotional response was found in PD patients. We provide the first evidence that genetic variants in the ACCN2 are associated with differential sensitivity to CO2 in PD patients as well as healthy volunteers, further supporting ACCN2 as a promising candidate for future research to improve current treatment options.

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Hahn, Christopher. « (Invited) Steering Electrocatalytic CO₂ Reduction Reactivity Using Microenvironments ». ECS Meeting Abstracts MA2022-02, n^o 49 (9 octobre 2022) : 1879. http://dx.doi.org/10.1149/ma2022-02491879mtgabs.

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A key challenge in electrocatalysis is co-designing the catalyst and its microenvironment to work in concert to efficiently steer complex reaction networks. First, I will describe the development of a tandem catalysis strategy on Au/Cu electrocatalysts to control the potential energy landscape of the CO2 and CO reduction at length scales beyond the active site and achieve synergistic catalytic activity for alcohols superior to that of either Cu or Au. Next, I will provide examples of CO2 reduction on catalysts supported on gas diffusion electrodes to discuss how the intrinsic catalysis and mass transport are interconnected through microenvironments, leading to emergent catalytic properties under industrially relevant reaction rates. Finally, I will conclude by providing our perspective on key remaining challenges to the scale-up of CO2 electrolyzers within the context of electrifying the chemicals manufacturing sector.

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