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- Phounglamcheik, Aekjuthon, PhD student, 1989-, et al.
(författare)
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Self-Heating of Biochar during Postproduction Storage by O2 Chemisorption at Low Temperatures
- 2022
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Ingår i: Energies. - : MDPI. - 1996-1073. ; 15:1
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Tidskriftsartikel (refereegranskat)abstract
- Biochar is attracting attention as an alternative carbon/fuel source to coal in the process industry and energy sector. However, it is prone to self-heating and often leads to spontaneous ignition and thermal runaway during storage, resulting in production loss and health risks. This study investigates biochar self-heating upon its contact with O2 at low temperatures, i.e., 50–300 °C. First, kinetic parameters of O2 adsorption and CO2 release were measured in a thermogravimetric analyzer using biochar produced from a pilot-scale pyrolysis process. Then, specific heat capacity and heat of reactions were measured in a differential scanning calorimeter. Finally, a one-dimensional transient model was developed to simulate self-heating in containers and gain insight into the influences of major parameters. The model showed a good agreement with experimental measurement in a closed metal container. It was observed that char temperature slowly increased from the initial temperature due to heat released during O2 adsorption. Thermal runaway, i.e., self-ignition, was observed in some cases even at the initial biochar temperature of ca. 200 °C. However, if O2 is not permeable through the container materials, the temperature starts decreasing after the consumption of O2 in the container. The simulation model was also applied to examine important factors related to self-heating. The results suggested that self-heating can be somewhat mitigated by decreasing the void fraction, reducing storage volume, and lowering the initial char temperature. This study demonstrated a robust way to estimate the cooling demands required in the biochar production process.
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| 2. |
- Haeck, Joost D. E., et al.
(författare)
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Percutaneous Coronary Intervention vs Medical Therapy for Coronary Lesions With Positive Fractional Flow Reserve (FFR) but Preserved Pressure-Bounded Coronary Flow Reserve (CFR): A Substudy of the Randomized Compare-Acute Trial
- 2021
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Ingår i: JOURNAL OF INVASIVE CARDIOLOGY. - 1042-3931 .- 1557-2501. ; 33:7, s. E557-E564
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Tidskriftsartikel (refereegranskat)abstract
- Objectives. Performing percutaneous coronary intervention (PCI) for fractional flow reserve (FFR) positive coronary lesions improves clinical outcomes and is recommended by international guidelines. It has been hypothesized that lesions with a positive FFR but a preserved coronary flow reserve (CFR) are less likely to be flow limiting and might best be treated medically. We investigated the association of CFR in FFR-positive lesions with clinical outcomes when treated medically, as well as the treatment effect of PCI vs medical therapy in FFR-positive lesions and a preserved CFR. Methods. We performed a substudy of the randomized, multicenter Compare-Acute trial, in which stabilized ST-segment elevation myocardial infarction (STEMI) patients with non-culprit lesions were randomized to either FFR-guided PCI or medical therapy. Based on baseline and hyperemic pressure gradients, we computed physiologic limits of CFR, the so-called pressure-bounded CFR (pb-CFR), and classified lesions as low (<2) or preserved (>= 2). The primary endpoint was 12-month major adverse cardiac and cerebrovascular event (MACCE) rate, defined as a composite of death from any cause, non-fatal myocardial infarction, revascularization, or cerebrovascular events. Results. A total of 980 lesions from 885 patients were included in this substudy. In lesions with FFR <= 0.80, a total of 249 patients had a pb-CFR<2 and 29 patients had a preserved CFR (pb-CFR >= 2). The rate of MACCE at 1 year was not significantly different between patients with FFR <= 0.80 and pb-CFR <2 vs patients with FFR <= 0.80 and pb-CFR >= 2 (25% vs 17%, respectively; P=.39). Because of randomization, baseline characteristics were well balanced between patients with FFR <= 0.80 and pb-CFR >= 2 treated by either by PCI or medical therapy. Importantly, in patients with FFR <= 0.80 and pb-CFR >= 2, MACCE occurred more frequently in patients treated medically vs patients treated by PCI (44% vs 0%, respectively; P=.01). Conclusions. Preserved or low pb-CFR did not alter clinical outcomes in patients with a positive FFR. Patients with FFR-positive coronary lesions but a preserved CFR had more clinical events when treated medically vs those treated with PCI.
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| 3. |
- De Maria, Giovanni Luigi, et al.
(författare)
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Novel Indices of Coronary Physiology : Do We Need Alternatives to Fractional Flow Reserve?
- 2020
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Ingår i: Circulation. Cardiovascular Interventions. - 1941-7640 .- 1941-7632. ; 13:4
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Forskningsöversikt (refereegranskat)abstract
- Fractional flow reserve is the current invasive gold standard for assessing the ischemic potential of an angiographically intermediate coronary stenosis. Procedural cost and time, the need for coronary vessel instrumentation, and the need to administer adenosine to achieve maximal hyperemia remain integral components of invasive fractional flow reserve. The number of new alternatives to fractional flow reserve has proliferated over the last ten years using techniques ranging from alternative pressure wire metrics to anatomic simulation via angiography or intravascular imaging. This review article provides a critical description of the currently available or under-development alternatives to fractional flow reserve with a special focus on the available evidence, pros, and cons for each with a view towards their clinical application in the near future for the functional assessment of coronary artery disease.
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| 4. |
- Zimmermann, Frederik M., et al.
(författare)
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Fractional flow reserve-guided percutaneous coronary intervention vs. medical therapy for patients with stable coronary lesions : meta-analysis of individual patient data
- 2019
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Ingår i: European Heart Journal. - : Oxford University Press (OUP). - 1522-9645 .- 0195-668X. ; 40:2, s. 180-186
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Tidskriftsartikel (refereegranskat)abstract
- Aims: To assess the effect of fractional flow reserve (FFR)-guided percutaneous coronary intervention (PCI) with contemporary drug-eluting stents on the composite of cardiac death or myocardial infarction (MI) vs. medical therapy in patients with stable coronary lesions. Methods and results: We performed a systematic review and meta-analysis of individual patient data (IPD) of the three available randomized trials of contemporary FFR-guided PCI vs. medical therapy for patients with stable coronary lesions: FAME 2 (NCT01132495), DANAMI-3-PRIMULTI (NCT01960933), and Compare-Acute (NCT01399736). FAME 2 enrolled patients with stable coronary artery disease (CAD), while the other two focused on non-culprit lesions in stabilized patients after acute coronary syndrome. A total of 2400 subjects were recruited from 54 sites world-wide with 1056 randomly assigned to FFR-guided PCI and 1344 to medical therapy. The pre-specified primary outcome was a composite of cardiac death or MI. We included data from extended follow-ups for FAME 2 (up to 5.5 years follow-up) and DANAMI-3-PRIMULTI (up to 4.7 years follow-up). After a median follow-up of 35 months (interquartile range 12-60 months), a reduction in the composite of cardiac death or MI was observed with FFR-guided PCI as compared with medical therapy (hazard ratio 0.72, 95% confidence interval 0.54-0.96; P = 0.02). The difference between groups was driven by MI. Conclusion: In this IPD meta-analysis of the three available randomized controlled trials to date, FFR-guided PCI resulted in a reduction of the composite of cardiac death or MI compared with medical therapy, which was driven by a decreased risk of MI.
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