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Статті в журналах з теми "Oxygen mismatch":
1
Detterich, Jon A., Roberta Kato, Adam Bush, Patjanaporn Chalacheva, Derek Ponce, Madushka De Zoysa, Payal Shah, et al. "Sickle cell microvascular paradox—oxygen supply‐demand mismatch." American Journal of Hematology 94, no. 6 (April 19, 2019): 678–88. http://dx.doi.org/10.1002/ajh.25476.
2
Petersson, Johan, and Robb W. Glenny. "Gas exchange and ventilation–perfusion relationships in the lung." European Respiratory Journal 44, no. 4 (July 25, 2014): 1023–41. http://dx.doi.org/10.1183/09031936.00037014.
Анотація:
This review provides an overview of the relationship between ventilation/perfusion ratios and gas exchange in the lung, emphasising basic concepts and relating them to clinical scenarios. For each gas exchanging unit, the alveolar and effluent blood partial pressures of oxygen and carbon dioxide (PO2andPCO2) are determined by the ratio of alveolar ventilation to blood flow (V′A/Q′) for each unit. Shunt and lowV′A/Q′ regions are two examples ofV′A/Q′ mismatch and are the most frequent causes of hypoxaemia. Diffusion limitation, hypoventilation and low inspiredPO2cause hypoxaemia, even in the absence ofV′A/Q′ mismatch. In contrast to other causes, hypoxaemia due to shunt responds poorly to supplemental oxygen. Gas exchanging units with little or no blood flow (highV′A/Q′ regions) result in alveolar dead space and increased wasted ventilation,i.e.less efficient carbon dioxide removal. Because of the respiratory drive to maintain a normal arterialPCO2, the most frequent result of wasted ventilation is increased minute ventilation and work of breathing, not hypercapnia. Calculations of alveolar–arterial oxygen tension difference, venous admixture and wasted ventilation provide quantitative estimates of the effect ofV′A/Q′ mismatch on gas exchange. The types ofV′A/Q′ mismatch causing impaired gas exchange vary characteristically with different lung diseases.
3
Guo, Er-Jia, Yaohua Liu, Changhee Sohn, Ryan D. Desautels, Andreas Herklotz, Zhaoliang Liao, John Nichols, John W. Freeland, Michael R. Fitzsimmons, and Ho Nyung Lee. "Oxygen Diode Formed in Nickelate Heterostructures by Chemical Potential Mismatch." Advanced Materials 30, no. 15 (March 7, 2018): 1705904. http://dx.doi.org/10.1002/adma.201705904.
4
Niu, Guangda, Siyu Wang, Jiangwei Li, Wenzhe Li, and Liduo Wang. "Oxygen doping in nickel oxide for highly efficient planar perovskite solar cells." Journal of Materials Chemistry A 6, no. 11 (2018): 4721–28. http://dx.doi.org/10.1039/c8ta00161h.
5
Fernández Sanjulián, Javier, Madhu Chennabasappa, Susana García-Martín, Gwilherm Nénert, Alain Wattiaux, Etienne Gaudin, and Olivier Toulemonde. "Oxygen vacancy ordering in SrFe0.25Co0.75O2.63 perovskite material." Dalton Transactions 46, no. 5 (2017): 1624–33. http://dx.doi.org/10.1039/c6dt03927h.
Анотація:
An oxygen-vacancy ordering related to the “314” model known for the Sr3Y1Co4O10.5 oxide is proposed for Sr4FeCo3O10.52 material despite there is neither A-site ordering nor A-site mismatch.
6
Yuzawa, Izumi, Sava Sakadžić, Vivek J. Srinivasan, Hwa Kyoung Shin, Katharina Eikermann-Haerter, David A. Boas, and Cenk Ayata. "Cortical Spreading Depression Impairs Oxygen Delivery and Metabolism in Mice." Journal of Cerebral Blood Flow & Metabolism 32, no. 2 (October 19, 2011): 376–86. http://dx.doi.org/10.1038/jcbfm.2011.148.
Анотація:
Cortical spreading depression (CSD) is associated with severe hypoperfusion in mice. Using minimally invasive multimodal optical imaging, we show that severe flow reductions during and after spreading depression are associated with a steep decline in cerebral metabolic rate of oxygen. Concurrent severe hemoglobin desaturation suggests that the oxygen metabolism becomes at least in part supply limited, and the decrease in cortical blood volume implicates vasoconstriction as the mechanism. In support of oxygen supply-demand mismatch, cortical nicotinamide adenine dinucleotide (NADH) fluorescence increases during spreading depression for at least 5 minutes, particularly away from parenchymal arterioles. However, modeling of tissue oxygen delivery shows that cerebral metabolic rate of oxygen drops more than predicted by a purely supply-limited model, raising the possibility of a concurrent reduction in oxygen demand during spreading depression. Importantly, a subsequent spreading depression triggered within 15 minutes evokes a monophasic flow increase superimposed on the oligemic baseline, which markedly differs from the response to the preceding spreading depression triggered in naive cortex. Altogether, these data suggest that CSD is associated with long-lasting oxygen supply-demand mismatch linked to severe vasoconstriction in mice.
7
Fujii, Miki, Chieri Hata, Munetada Ukita, Chie Fukushima, Chihiro Matsuura, Yoshie Kawashima-Ohya, Koji Tomobe, and Tsuyoshi Kawashima. "Characterization of a Thermostable 8-Oxoguanine DNA Glycosylase Specific for GO/N Mismatches from the Thermoacidophilic ArchaeonThermoplasma volcanium." Archaea 2016 (2016): 1–10. http://dx.doi.org/10.1155/2016/8734894.
Анотація:
The oxidation of guanine (G) to 7,8-dihydro-8-oxoguanine (GO) forms one of the major DNA lesions generated by reactive oxygen species (ROS). The GO can be corrected by GO DNA glycosylases (Ogg), enzymes involved in base excision repair (BER). Unrepaired GO induces mismatched base pairing with adenine (A); as a result, the mismatch causes a point mutation, from G paired with cytosine (C) to thymine (T) paired with adenine (A), during DNA replication. Here, we report the characterization of a putative Ogg from the thermoacidophilic archaeonThermoplasma volcanium. The 204-amino acid sequence of the putative Ogg (TVG_RS00315) shares significant sequence homology with the DNA glycosylases ofMethanocaldococcus jannaschii(MjaOgg) andSulfolobus solfataricus(SsoOgg). The six histidine-tagged recombinant TVG_RS00315 protein gene was expressed inEscherichia coliand purified. The Ogg protein is thermostable, with optimal activity near a pH of 7.5 and a temperature of 60°C. The enzyme displays DNA glycosylase, and apurinic/apyrimidinic (AP) lyase activities on GO/N (where N is A, T, G, or C) mismatch; yet it cannot eliminate U from U/G or T from T/G, as mismatch glycosylase (MIG) can. These results indicate that TvoOgg-encodingTVG_RS00315is a member of the Ogg2 family ofT. volcanium.
8
Li, Xiang, Yaming Liu, Wei Bi, Jinglei Bi, Ruiyun Guo, Rui Li, Chaoqi Wang, et al. "Lattice-mismatch-induced growth of ultrathin Pt shells with high-index facets for boosting oxygen reduction catalysis." Journal of Materials Chemistry A 8, no. 32 (2020): 16477–86. http://dx.doi.org/10.1039/d0ta05410k.
9
Shen, Qiang, Shiliang Huang, and Timothy Q. Duong. "T2*-weighted fMRI time-to-peak of oxygen challenge in ischemic stroke." Journal of Cerebral Blood Flow & Metabolism 36, no. 2 (October 6, 2015): 283–91. http://dx.doi.org/10.1177/0271678x15606461.
Анотація:
T2*-weighted MRI of transient oxygen challenge (OC) showed exaggerated OC percent changes in the ischemic tissue at risk compared to normal tissue. One ambiguity is that regions with high vascular density also showed exaggerated OC percent changes. This study explored time-to-peak (TTP) of the OC percent changes to improve the utility of T2*-weighted OC MRI. Experiments were performed longitudinally at 30 min, 150 min and 24 h after transient (60-min) stroke in rats. Ischemic core, normal, and mismatch tissue were classified pixel-by-pixel based on apparent diffusion coefficient and cerebral blood flow. Major findings were: (i) Delayed OC TTP was localized to and corresponded well with the perfusion-diffusion mismatch. (ii) By contrast, the exaggerated OC percent changes were less localized, with changes not only in the at-risk tissue but also in some areas of the contralesional hemisphere with venous vessel origins. (iii) The OC time-course of the mismatch tissue was biphasic, with a faster initial increase followed by a slower increase. (iv) At-risk tissue with delayed TTP and exaggerated OC was normal after reperfusion and the at-risk tissue was mostly (83 ± 18%) rescued by reperfusion as indicated by normal 24-h T2. OC TTP offers unique information toward better characterization of at-risk tissue in ischemic stroke.
10
Shen, Weida, and Joshua L. Hertz. "Ionic conductivity of YSZ/CZO multilayers with variable lattice mismatch." Journal of Materials Chemistry A 3, no. 5 (2015): 2378–86. http://dx.doi.org/10.1039/c4ta03892d.
Дисертації з теми "Oxygen mismatch":
1
Karihtala, P. (Peeter). "Oxidative damage and counteracting mechanisms in breast carcinoma." Doctoral thesis, University of Oulu, 2006. http://urn.fi/urn:isbn:9514279530.
Анотація:
Abstract
Breast cancer is the leading cause of death from cancer among Finnish women, but the ultimate causation of carcinogenesis still remains unclear. Reactive oxygen species (ROS) is a collective term for several types of reactive oxygen metabolites that are continuously generated in human cells mainly as by-products of aerobic respiration. ROS, including nitric oxide and its derivatives, play highly important roles in cell physiology. If ROS production exceeds the capacity of detoxification systems, principally antioxidant enzymes, oxidative stress is said to occur. This state is known to contribute to all stages of carcinogenesis.
To explore the widely unstudied role of ROS and cell redox state modulating enzymes in breast carcinomas, the extent of ROS-derived macromolecule damage and the expression of the vast majority of known antioxidant enzymes were assessed in a large series of breast carcinomas, and the results were compared to the patients' clinicopathological parameters. The results were also compared to angiogenesis, DNA repair enzymes, cell proliferation, NF-κB, p53 expression, and survival. Immunohistochemistry was the main method applied, but western blotting and immunoelectron microscopy were also used.
There is extensive oxidative damage in breast carcinomas, which seems to associate with tumor development. Oxidative macromolecule damage is notable even in stage I tumors. Cell redox state regulating enzymes, such as peroxiredoxin V, thioredoxin, thioredoxin reductase, and glutamate-cysteine ligase, associate with more aggressive phenotypes of tumors, including larger primary tumors, growth of metastases, increased cell proliferation, and poor differentiation. This indirectly suggests that cell redox state modulating enzymes may be inductive of tumor promotion in an oxidated environment. The results of this thesis support the importance of ROS in all stages of carcinogenesis. These observations are largely in line with the previous studies on different carcinomas, but there seem to be certain carcinoma type specific differences in the expression of these enzymes. Since the expression of given cell redox state modulating enzymes distinctly associates with clinicopathological parameters, these enzymes may be useful as prognostic indicators and facilitate the choice of appropriate treatment in the future.
2
Dupuy, Diane. "Comportement thermomécanique de composites réfractaires oxyde-carbone." Thesis, Limoges, 2015. http://www.theses.fr/2015LIMO0108.
Анотація:
Cette thèse avait pour objectif d’étudier les relations existant entre la microstructure de réfractaires alumine-carbone utilisés en coulée continue dans l’industrie sidérurgique et leurs propriétés thermomécaniques. Le travail réalisé ici s’inscrit dans une logique composite, en déterminant les propriétés thermomécaniques des constituants séparément et en analysant ensuite les propriétés des matériaux multiphasiques. Différents systèmes de matériaux modèles ont été étudiés en s’intéressant à deux échelles : agrégats et matrice. Ces matériaux sont constitués d’une part, d’un squelette de graphite et d’agrégats d’alumine et d’autre part d’une matrice carbonée chargée en petits grains d’alumine. La liaison carbone de ces matériaux résultant de la pyrolyse d’une résine phénolique, les propriétés thermomécaniques des matériaux modèles élaborés ont été analysées à la fois pendant et après le traitement thermique de pyrolyse. L’évolution des propriétés au cours de la pyrolyse des échantillons réticulés a mis en évidence l’apparition d’un léger endommagement en fin de montée en température, et un endommagement plus prononcé lors du refroidissement. Cet endommagement résulte d’un différentiel de dilatation thermique entre les grains d'alumine et la liaison carbone. L'influence de ces effets microstructuraux sur le comportement mécanique des matériaux pyrolysés a été étudiée grâce à des essais de traction, mettant en évidence un comportement non-linéaire assez marqué. Des relations entre la fraction volumique et les propriétés physiques clés des matériaux ont pu être établies. Par ailleurs, les résultats obtenus ont montré qu’un changement de composition relativement peu important peut modifier radicalement les propriétés thermomécaniques de ces matériaux. Cette étude sur des matériaux modèles a permis de dégager des pistes pour une amélioration des compositions industriellesThe present thesis aimed at investigating the relationships existing between the microstructure of alumina-carbon refractories used in steel continuous casting and their thermomechanical properties. The work realized here fall within a composite approach, by determining thermomechanical properties of the single constituents of the materials and analyzing then the properties of the heterogeneous composites. Different systems of double scale model materials, constituted of graphite and alumina aggregates in one hand, and of carbon matrix loaded with fine alumina grains on the other hand were studied here. The carbon bond of these materials resulting from pyrolysis of phenolic resin, the thermomechanical properties of the elaborated model materials were analyzed both during and after the pyrolysis heating treatment. The properties evolutions of the cured samples during the pyrolysis highlighted a slight damage during the end of heating and important damage during cooling, due to a thermal expansion mismatch between the alumina grains and the resin/carbon bond. The influence of the thermal damage has been investigated thanks to tensile tests on the pyrolyzed materials, which exhibit a rather strong non-linear behavior. Relationships between volume fraction and physical key-properties of the materials have been established. Besides, the obtained results highlighted that a small change in composition can drastically change the thermomechanical properties of these materials. This overall study on model materials allowed to develop some ideas in order to improve industrial compositions
3
Jacquin, Laurent. "Déséquilibre d’oxygénation et lésions myocardiques aiguës : approche clinique en service d’accueil des urgences." Thesis, Lyon, 2021. https://n2t.net/ark:/47881/m6736qrr.
Анотація:
Dans ce travail de thèse, nous nous sommes intéressés en première partie aux critères de déséquilibre d’oxygénation impliqués dans la survenue d’un infarctus de type 2. Nous avons exploré chez 610 patients l’association entre les paramètres de ces critères et la survenue de lésions myocardiques aiguës, et d’infarctus de type 2, ainsi que la relation entre ces paramètres et l’extension de l’atteinte du myocarde. Nos résultats ne montraient pas de lien entre l’amplitude du déséquilibre d’oxygénation et la survenue de lésions myocardiques aiguës. Il n’y avait également pas de corrélation avec l’importance de ces lésions. Nous n’avons donc pas pu définir de seuils restrictifs stricts considérés comme facteur de stress myocardique significatif. Dans la deuxième partie, nous avons comparé le devenir à court terme et à distance des patients admis avec une condition de déséquilibre d’oxygénation en fonction de la présence d’une lésion myocardique, ou d’un infarctus de type 2, et évaluer l’association de ces entités pathologiques avec la mortalité et les évènements cardiovasculaires. Dans cette population de 824 patients, la survenue de lésions myocardiques aiguës non-ischémiques ou d’infarctus de type 2 conduisait à une mortalité hospitalière élevée à plus de 20% et y était significativement associée après ajustement sur les caractéristiques des patients. A plus long terme chez les survivants, le devenir était dépendant des comorbidités sans implication de la survenue de ces lésions myocardiques initiales, avec des taux de mortalité de 27 à 35 % et d’évènements cardiovasculaires de 23 à 40%. Nous avons proposé de confronter ces résultats dans une autre étude, menée prospectivement, avec un suivi standardisé à 6 mois des patients admis en déséquilibre d’oxygénation, dont nous détaillons la méthodologie. Cette cohorte est constituée de 670 patients dont l’analyse des données est en cours. Enfin, dans une troisième partie, nous nous sommes focalisés sur les 675 personnes âgées, qui représente plus de 80% de notre cohorte, pour déterminer les facteurs associés à la survenue de ces lésions myocardiques et infarctus de type 2 en fonction des classes d’âge. Nous avons retrouvé des profils de patients très dépendants de ces classes, liés aux évolutions épidémiologiques du vieillissement. L’individualisation des infarctus de type 2 au sein des lésions myocardiques aiguës n’était cependant pas évidente, de même que l’impact sur la mortalité qui reposait essentiellement sur le poids des comorbiditésIn the first part, we were interested in the criteria of oxygen supply/demand imbalance involved in the occurrence of a type 2 infarction. We explored in 610 patients the association between the parameters of these criteria and the occurrence of acute myocardial injury and type 2 infarction, as well as the correlation between these parameters and the extent of myocardial injury. Our results did not show any association between the importance of oxygen mismatch and the occurrence of acute myocardial injury. There was also no correlation with the magnitude of such injury. Therefore, we could not define strict restrictive thresholds that could be considered a significant myocardial stressor. In the second part, we compared the short-term and the long-term outcomes of patients admitted with an oxygen supply/demand imbalance condition according to the presence of myocardial injury or type 2 infarction and assessed the association of these pathological entities with mortality and major cardiovascular events. In this population of 824 patients, the occurrence of myocardial injury or type 2 infarction led to high in-hospital mortality of more than 20% and was significantly associated with it after adjustment for patient characteristics. In the follow-up of survivors, the outcome was dependent on comorbidities without the involvement of the occurrence of these initial myocardial injuries, with mortality rates of 27 to 35% and major cardiovascular events of 23 to 40%. We proposed to compare these results in another study, conducted prospectively, with a standardized 6-month follow-up of patients admitted for oxygenation failure, the methods of which are detailed here. This cohort consists of 670 patients whose data are currently being analyzed. Finally, in the third part, we focused on the 675 elderly patients, who represent more than 80% of our cohort, to determine the factors associated with the occurrence of these myocardial injuries and type 2 infarction according to age classes. We found very dependent patient profiles in these classes, linked to the epidemiological changes of aging. However, the individualization of type 2 myocardial infarction within acute myocardial lesions was not obvious, nor was the impact on mortality, which was essentially based on the burden of comorbidities
Книги з теми "Oxygen mismatch":
1
Gattinon, Luciano, and Eleonora Carlesso. Acute respiratory failure and acute respiratory distress syndrome. Oxford University Press, 2015. http://dx.doi.org/10.1093/med/9780199687039.003.0064.
Анотація:
Respiratory failure (RF) is defined as the acute or chronic impairment of respiratory system function to maintain normal oxygen and CO2 values when breathing room air. ‘Oxygenation failure’ occurs when O2 partial pressure (PaO2) value is lower than the normal predicted values for age and altitude and may be due to ventilation/perfusion mismatch or low oxygen concentration in the inspired air. In contrast, ‘ventilatory failure’ primarily involves CO2 elimination, with arterial CO2 partial pressure (PaCO2) higher than 45 mmHg. The most common causes are exacerbation of chronic obstructive pulmonary disease (COPD), asthma, and neuromuscular fatigue, leading to dyspnoea, tachypnoea, tachycardia, use of accessory muscles of respiration, and altered consciousness. History and arterial blood gas analysis is the easiest way to assess the nature of acute RF and treatment should solve the baseline pathology. In severe cases mechanical ventilation is necessary as a ‘buying time’ therapy. The acute hypoxemic RF arising from widespread diffuse injury to the alveolar-capillary membrane is termed Acute Respiratory Distress Syndrome (ARDS), which is the clinical and radiographic manifestation of acute pulmonary inflammatory states.
2
Gattinon, Luciano, and Eleonora Carlesso. Acute respiratory failure and acute respiratory distress syndrome. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780199687039.003.0064_update_001.
Анотація:
Respiratory failure (RF) is defined as the acute or chronic impairment of respiratory system function to maintain normal oxygen and CO2 values when breathing room air. ‘Oxygenation failure’ occurs when O2 partial pressure (PaO2) value is lower than the normal predicted values for age and altitude and may be due to ventilation/perfusion mismatch or low oxygen concentration in the inspired air. In contrast, ‘ventilatory failure’ primarily involves CO2 elimination, with arterial CO2 partial pressure (PaCO2) higher than 45 mmHg. The most common causes are exacerbation of chronic obstructive pulmonary disease (COPD), asthma, and neuromuscular fatigue, leading to dyspnoea, tachypnoea, tachycardia, use of accessory muscles of respiration, and altered consciousness. History and arterial blood gas analysis is the easiest way to assess the nature of acute RF and treatment should solve the baseline pathology. In severe cases mechanical ventilation is necessary as a ‘buying time’ therapy. The acute hypoxemic RF arising from widespread diffuse injury to the alveolar-capillary membrane is termed Acute Respiratory Distress Syndrome (ARDS), which is the clinical and radiographic manifestation of acute pulmonary inflammatory states.
3
Hedenstierna, Göran, and Hans Ulrich Rothen. Physiology of positive-pressure ventilation. Oxford University Press, 2016. http://dx.doi.org/10.1093/med/9780199600830.003.0088.
Анотація:
During positive pressure ventilation the lung volume is reduced because of loss of respiratory muscle tone. This promotes airway closure that occurs in dependent lung regions. Gas absorption behind the closed airway results sooner or later in atelectasis depending on the inspired oxygen concentration. The elevated airway and alveolar pressures squeeze blood flow down the lung so that a ventilation/perfusion mismatch ensues with more ventilation going to the upper lung regions and more perfusion going to the lower, dependent lung. Positive pressure ventilation may impede the return of venous blood to the thorax and right heart. This raises venous pressure, causing an increase in systemic capillary pressure with increased capillary leakage and possible oedema formation in peripheral organs. Steps that can be taken to counter the negative effects of mechanical ventilation include an increase in lung volume by recruitment of collapsed lung and an appropriate positive end-expiratory pressure, to keep aerated lung open and to prevent cyclic airway closure. Maintaining normo- or hypervolaemia to make the pulmonary circulation less vulnerable to increased airway and alveolar pressures, and preserving or mimicking spontaneous breaths, in addition to the mechanical breaths, since they may improve matching of ventilation and blood flow, may increase venous return and decrease systemic organ oedema formation (however, risk of respiratory muscle fatigue, and even overexpansion of lung if uncontrolled).
4
van Lier, Felix, and Robert Jan Stolker. Preoperative assessment and optimization. Edited by Jonathan G. Hardman. Oxford University Press, 2017. http://dx.doi.org/10.1093/med/9780199642045.003.0040.
Анотація:
Perioperative cardiovascular complications (including myocardial ischaemia and myocardial infarction) are the predominant cause of morbidity and mortality in patients undergoing non-cardiac surgery. The pathophysiology of perioperative myocardial infarction is complex. Prolonged myocardial ischaemia due to the stress of surgery in the presence of a haemodynamically significant coronary lesion, leading to subendocardial ischaemia, and acute coronary artery occlusion after plaque rupture and thrombus formation contribute equally to these devastating events. Perioperative management aims at optimizing the patient’s condition by identification and modification of underlying cardiac risk factors and diseases. The first part of this chapter covers current knowledge on preoperative risk assessment. Current risk indices, the value of additional testing, and new preoperative cardiac risk makers are investigated. During recent decades there has been a shift from the assessment and treatment of the underlying culprit coronary lesion towards a systemic medical therapy aiming at prevention of myocardial oxygen supply–demand mismatch and coronary plaque stabilization. In the second part of this chapter, risk-reduction strategies are discussed, including β-blocker therapy, statins, and aspirins. A central theme in this chapter will focus on long-term cardiovascular risk reduction. Patients who undergo non-cardiac (vascular) surgery are particularly prone to long-term adverse cardiac outcomes. The goal of perioperative cardiovascular risk identification and modification should not be limited to the perioperative period, but should extend well into the postoperative period.
Частини книг з теми "Oxygen mismatch":
1
van Beek, Johannes H. G. M. "Hypoxia in Saline-Perfused Heart May be Due to Mismatch of Regional Metabolism and Perfusion." In Oxygen Transport to Tissue XI, 499–507. Boston, MA: Springer US, 1989. http://dx.doi.org/10.1007/978-1-4684-5643-1_55.
2
Bihari, D. J. "Mismatch of the Oxygen Supply and Demand in Septic Shock." In Septic Shock, 148–60. Berlin, Heidelberg: Springer Berlin Heidelberg, 1987. http://dx.doi.org/10.1007/978-3-642-83108-9_13.
3
Crea, Filippo, and Gaetano Antonio Lanza. "Myocardial ischaemia: definition and causes." In ESC CardioMed, edited by William Wijns, 1325–29. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780198784906.003.0327.
Анотація:
Myocardial ischaemia is caused by a mismatch between myocardial oxygen demand and myocardial blood flow supply, which results in myocardial suffering and, when prolonged, injury. The main mechanisms of myocardial ischaemia include atherothrombotic lesions of epicardial coronary vessels, which may result in chronic and acute ischaemic syndromes; coronary artery spasm, which is mainly responsible for variant angina; and abnormalities in coronary microvascular function, which can cause or contribute to myocardial ischaemia in various clinical settings.
4
Gattinoni, Luciano, Mattia Busana, and Eleonora Carlesso. "Acute respiratory failure and acute respiratory distress syndrome." In The ESC Textbook of Intensive and Acute Cardiovascular Care, edited by Marco Tubaro, Pascal Vranckx, Eric Bonnefoy-Cudraz, Susanna Price, and Christiaan Vrints, 863–79. Oxford University Press, 2021. http://dx.doi.org/10.1093/med/9780198849346.003.0065.
Анотація:
Respiratory failure (RF) is defined as the acute or chronic impairment of respiratory system function to maintain normal oxygen and CO2 values when breathing room air. ‘Oxygenation failure’ occurs when O2 partial pressure (PaO2) value is lower than the normal predicted values for age and altitude and may be due to ventilation/perfusion mismatch or low oxygen concentration in the inspired air. In contrast, ‘ventilatory failure’ primarily involves CO2 elimination, with arterial CO2 partial pressure (PaCO2) higher than 45 mmHg. The most common causes are exacerbation of chronic obstructive pulmonary disease (COPD), asthma, and neuromuscular fatigue, leading to dyspnoea, tachypnoea, tachycardia, use of accessory muscles of respiration, and altered consciousness. History and arterial blood gas analysis is the easiest way to assess the nature of acute RF and treatment should solve the baseline pathology. In severe cases mechanical ventilation is necessary as a ‘buying time’ therapy. The acute hypoxemic RF arising from widespread diffuse injury to the alveolar-capillary membrane is termed Acute Respiratory Distress Syndrome (ARDS), which is the clinical and radiographic manifestation of acute pulmonary inflammatory states.
5
Crea, Filippo, and Gaetano Antonio Lanza. "Myocardial ischaemia: definition and causes." In ESC CardioMed, edited by William Wijns, 1325–29. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780198784906.003.0327_update_001.
Анотація:
Myocardial ischaemia is caused by a mismatch between myocardial oxygen demand and myocardial blood flow supply, which results in reversible myocardial suffering and, when prolonged, in irreversible injury. The main causes of myocardial ischaemia include (1) atherosclerotic flow-limiting stenoses which are responsible for chronic stable angina; (2) coronary thrombus superimposed on an atherosclerotic plaque which is responsible for acute coronary syndromes; (3) coronary artery spasm which is responsible for vasospastic angina; and (4) coronary microvascular dysfunction which is responsible for microvascular angina and can also contribute to myocardial ischaemia in various clinical settings. Functional alterations (thrombus, spasm, and microvascular dysfunction) may act on angiographically normal coronary arteries or arteries presenting stenoses of variable severity. Less frequent coronary causes of myocardial ischaemia include spontaneous coronary artery dissection, myocardial bridge, coronary thromboembolism, an abnormal origin of the right or left coronary artery, and ascending aorta dissection involving coronary ostia. Finally, myocardial ischaemia can occur in the presence of severe left ventricular hypertrophy as observed in aortic stenosis and hypertrophic cardiomyopathy.
Тези доповідей конференцій з теми "Oxygen mismatch":
1
Marchionni, Paolo, Maria Laura Palazzi, Lorenzo Scalise, Virgilio Paolo Carneilli, and Stefano Nobile. "Computerized assessment of shunt and Ventilation-Perfusion mismatch in oxygen dependent infants." In 2018 IEEE International Symposium on Medical Measurements and Applications (MeMeA). IEEE, 2018. http://dx.doi.org/10.1109/memea.2018.8438793.
2
Fujii, Shuntaro, Hideki Takeuchi, Soichi Morita, Tatsushi Yagi, Shohei Hamada, Toshiro Sakamoto, Shinji Kawaguchi, et al. "Analysis of the Effects of Boron Transient Enhanced Diffusion on Threshold Voltage Mismatch in Steep Retrograde Doping NMOSFETs with Inserted Oxygen Layers." In 2020 IEEE International Symposium on the Physical and Failure Analysis of Integrated Circuits (IPFA). IEEE, 2020. http://dx.doi.org/10.1109/ipfa49335.2020.9260584.
3
De la Torre Pari, S. A., F. F. H. Aragón, L. Villegas-Lelovsky, and D. G. Pacheco Salazar. "A DFT study of structural and electronic properties of anatase TiO2 phase with Ni and oxygen vacancies impurities." In VIII Simpósio de Estrutura Eletrônica e Dinâmica Molecular. Universidade de Brasília, 2020. http://dx.doi.org/10.21826/viiiseedmol2020136.
Анотація:
In the present work, first-principle theory using the functional density theory (DFT) was used in the ABINIT software package using the PBE pseudopotential (norm-conserving pseudopotentials). To determine the structural parameters such as lattice constant, Bulk modules, and energy formation, for the TiO2 anatase phase doped with substitutional and interstitial nickel impurity, oxygen vacancies (VO) are also included in the present work. For this study, the 2x1x1 supercells with 24 atoms and 2x2x1 with 48 atoms were used. Different types of Ni dopants and oxygen vacancies were considered for energy formation using the 2x2x1 supercell. Our results show that the values of network parameters, minimum energy, and Bulk modulus remain constant with the supercell's growth. With the inclusion of Ni in the supercell substituting the Ti-ions, the unit cell volume (V) exhibits a decrease in agreement with ionic radii mismatch between Ti and Ni atoms. However, when entry as an interstitial form a significant increase is shown. The preliminary results of the energy of formation analyzed for the Ni defects show that it is more probable for an interstitial Ni than for a substitutional Ni.
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De la Torre Pari, S. A., F. F. H. Aragón, L. Villegas-Lelovsky, and D. G. Pacheco Salazar. "A DFT study of structural and electronic properties of anatase TiO2 phase with Ni and oxygen vacancies impurities." In VIII Simpósio de Estrutura Eletrônica e Dinâmica Molecular. Universidade de Brasília, 2020. http://dx.doi.org/10.21826/viiiseedmol2020106.
Анотація:
In the present work, first-principle theory using the functional density theory (DFT) was used in the ABINIT software package using the PBE pseudopotential (norm-conserving pseudopotentials). To determine the structural parameters such as lattice constant, Bulk modules, and energy formation, for the TiO2 anatase phase doped with substitutional and interstitial nickel impurity, oxygen vacancies (VO) are also included in the present work. For this study, the 2x1x1 supercells with 24 atoms and 2x2x1 with 48 atoms were used. Different types of Ni dopants and oxygen vacancies were considered for energy formation using the 2x2x1 supercell. Our results show that the values of network parameters, minimum energy, and Bulk modulus remain constant with the supercell's growth. With the inclusion of Ni in the supercell substituting the Ti-ions, the unit cell volume (V) exhibits a decrease in agreement with ionic radii mismatch between Ti and Ni atoms. However, when entry as an interstitial form a significant increase is shown. The preliminary results of the energy of formation analyzed for the Ni defects show that it is more probable for an interstitial Ni than for a substitutional Ni.
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Mesrati, N., H. Ajhrourh, N. Du, and D. Treheux. "Thermal Spraying On Graphite." In ITSC 1998, edited by Christian Coddet. ASM International, 1998. http://dx.doi.org/10.31399/asm.cp.itsc1998p1507.
Анотація:
Abstract In order to expand the fields of application and to improve the performance of graphite (Cg), it is necessary to reduce its permeability towards of oxygen and to limit its reactivity and especially its oxidation. It is, therefore, essential to protect it from the environment through the use of ceramic coatings. Adhesion between ceramic coatings and graphite is controlled by the mechanical stresses in the coatings and the thermodynamic work of adhesion. Different metal-graphite systems were examined which showed that the adhesion particularly depended on the thermal expansion coefficient mismatch between the two materials and on metal carbide stability. Thus, the rote of the addition on the graphite surface of elements such as Cr, Mo, Al, Si, O on the adhesion of metals or ceramics to graphite has been identified.
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Latzel, S., R. Vaßen, and D. Stöver. "A New Environmental Barrier Coating System on Carbon-Fiber Reinforced Silicon Carbide Composites." In ITSC2003, edited by Basil R. Marple and Christian Moreau. ASM International, 2003. http://dx.doi.org/10.31399/asm.cp.itsc2003p1625.
Анотація:
Abstract Carbon-fiber-reinforced silicon carbide composites (C/SiC) are promising materials for high temperature light weight structural components. However, a protective coating is necessary to prevent the oxidation of the carbon, especially at temperatures above 400 °C. Also the silica scale, which often forms on top of the C/SiC, must be protected from water vapor contact as the silica scale is not stable under these conditions. Hence, a protective coating, an Environmental Barrier Coating (EBC), is needed to shelter the material from the environmental influences of oxygen and water vapor. Current EBC systems employ multiple layers, each serving unique requirements. However, any mismatch in the coefficients of thermal expansion (CTE) leads to internal stress and results in crack formation. In this case, oxygen and water vapor penetrate through the EBC, reducing the lifetime of the component. Mullite (Al6Si2O13) is used in many known EBC systems on silicon-based ceramics either as an EBC itself or as a bondcoat. Due to its low CTE and its sufficient thermal cycling behaviour, mullite was chosen in this investigation as a first layer. As mullite suffers loss of SiO2 when exposed to water vapor at high temperatures, an additional protective top coat is needed to complete the EBC system. Different oxides were evaluated to serve as top coat, especially high temperature oxides with low coefficients of thermal expansion (LCTE). An Environmental Barrier Coating containing mullite as bondcoat and a LCTE oxide as a top coat is proposed. Both layers were applied via atmospheric plasma spraying. Results on the influence of processing conditions on the microstructure of single mullite and LCTE oxide layers and also mullite / LCTE oxide systems will be presented. Special emphasis was directed towards the crystallinity of the mullite layer, and in the top layer towards low porosity and reduced crack density.
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Haag, J. Ch, A. Hildebrandt, H. Ho¨nen, M. Assadi, and R. Kneer. "Turbomachinery Simulation in Design Point and Part-Load Operation for Advanced CO2 Capture Power Plant Cycles." In ASME Turbo Expo 2007: Power for Land, Sea, and Air. ASMEDC, 2007. http://dx.doi.org/10.1115/gt2007-27488.
Анотація:
In this paper two different power plant processes with their current optimized layouts of the AZEP project and the recently started OXYCOAL-AC project are presented. Both processes are designed for CO2-capture combined with oxygen membrane technology. As a consequence of the implementation of a membrane module there will be essential changes in the plant layout involving modifications to the turbomachinery designs due to the different working medium and interactions of different cycle components. Furthermore, there are different loops included for recirculation of the combustion gas constituents CO2 and H2O. Although, the processes presented have different boundary conditions regarding the selection of fuel and gross power output, they have in common the need for new turbomachinery designs. These two processes are thermodynamically analyzed and compared both at design point and at off-design (part-load operation) mode. Main focus are the different operation modes of AZEP and different turbomachinery layouts for OXYCOAL-AC. Special attention is paid to the modeling of the crucial components common for both power plant processes e.g. the oxygen membrane, the turbine and the compressors. The thermodynamic studies aim at analyzing a) the requirements on turbomachinery at the design point, b) how to reduce the level of requirements for the compressor and the turbine and c) the operation and potential of mismatch for the turbomachinery during part-load operation. Simplified turbomachinery maps and a simplified black box 1-D model of the membrane module and the heat exchangers are used within a commercial heat- and mass-balance program for simulation of part-load operation of both processes. The objective of this conceptual study is the investigation of parameter changes caused by the interaction of process components.
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Vahedi, Nasser, Qasim A. Ranjha, and Alparslan Oztekin. "Numerical Study of High Temperature Thermochemical Energy Storage Using Co3O4/CoO." In ASME 2018 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/imece2018-86329.
Анотація:
Large-scale solar power generation becomes feasible using concentrated solar power plants, as the received heat is collected at high temperatures compatible with power cycle operations. The main drawback of solar power generation is the intermittent nature of available solar irradiation, which results in a mismatch between collected heat and electrical demand. Thermal energy storage (TES) systems are the options to resolve this problem by storing excess heat during high solar irradiance and releasing at off-sun conditions. Thermochemical energy storage (TCES) systems have the potential to store the solar energy at high temperatures suitable for CSP plants’ operations because of the higher energy density of the TCES materials than those used for sensible and latent heat storage options. In TCES, the heat is stored in the form of thermo-chemical energy using an endothermic reaction and is released by carrying out the reverse exothermic reaction. TCES using cobalt oxide redox (reduction/oxidation) reaction is selected for this study because of its unique features suitable for high temperature thermal energy storage. A reactor with the cylindrical fixed bed is considered, in which air flows through the bed during charging and discharging modes. Air is used as heat transfer fluid (HTF) and as the reactant gas supplying oxygen. Transient mass and energy transport equations are solved along with reaction kinetics equations using finite element method. Charging and discharging processes are investigated. The effect of geometrical and operational parameters including the material properties on overall storage and retrieval process has been studied. It was shown that the bed porosity plays a dominant role in the reactor performance. The increase in the bed porosity improves the reactor performance for both charging and discharging mode.