Letteratura scientifica selezionata sul tema "Restriction du flux sanguin"
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Articoli di riviste sul tema "Restriction du flux sanguin"
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Passeri, Aurélien, e Abd-Elbasset Abaidia. "Restriction du flux sanguin et rééducation : une revue parapluie des revues systématiques et des méta-analyses". Kinésithérapie, la Revue 23, n. 255 (marzo 2023): 30. http://dx.doi.org/10.1016/j.kine.2022.12.052.
Testo completo
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Planque, F., e B. Tamalet. "L’exercice avec restriction du flux sanguin (BFR) : une mode ? Une alternative ? Une méthode miracle ? L’expérience du centre médical FFF de Clairefontaine". Journal de Traumatologie du Sport 38, n. 2 (giugno 2021): 94–100. http://dx.doi.org/10.1016/j.jts.2021.02.002.
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Gerstner, Aline. "Le cerveau gère le flux sanguin". Pour la Science N° 501 - juillet, n. 7 (7 gennaio 2019): 13. http://dx.doi.org/10.3917/pls.501.0013.
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Gerstner, Aline. "Un contrôle cérébral du flux sanguin". Cerveau & Psycho N° 112, n. 7 (7 gennaio 2019): 10a. http://dx.doi.org/10.3917/cerpsy.112.0010a.
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Bresson-Dumont, H., e F. Aptel. "Le flux sanguin oculaire dans le glaucome". Journal Français d'Ophtalmologie 34, n. 6 (giugno 2011): 413–15. http://dx.doi.org/10.1016/j.jfo.2011.03.008.
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Bourdin, G., e J. Y. Bayle. "Èvaluation non invasive du flux sanguin pulmonaire dans l’hypertension pulmonaire". Revue des Maladies Respiratoires 23 (gennaio 2006): 120. http://dx.doi.org/10.1016/s0761-8425(06)72448-2.
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Frédéric VIN. "Cas Clinique". Les pathologies vasculaires (anciennement ANGEIOLOGIE) 71, n. 02 (1 giugno 2019): 2. http://dx.doi.org/10.54695/mva.71.02.2193.
Testo completoAbstract (sommario):
Les anévrysmes veineux superficiels sont le siège deturbulence du flux sanguin. Un cas clinique d’un patient avecthrombose d’un anévrysme de la veine basilique du bras estprésenté. Une mutation du facteur V Leiden a été retrouvécomme facteur de risque. Afin d’éviter une récidive, uneexérèse avec phlébectomie a été réalisée sous anesthésielocale par tumescence
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Colné, Patrick. "Le flux sanguin de l’artère vertébrale vu sous toutes les coutures". Kinésithérapie, la Revue 6, n. 55 (luglio 2006): 52–53. http://dx.doi.org/10.1016/s1779-0123(06)70201-7.
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Bruder, N., O. Lévrier, O. M. Stordeur, D. Pellissier, G. Salamon e G. F.R.ançois. "R433 Effet de l'hypotension sur le flux sanguin des malformations arterioveineuses cerebrales (MAV)". Annales Françaises d'Anesthésie et de Réanimation 17, n. 8 (gennaio 1998): 1027. http://dx.doi.org/10.1016/s0750-7658(98)80549-2.
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Geiser, Martial, Charles Riva e Ulrich Diermann. "Mesure du flux sanguin choroïdien au moyen d'un nouvel instrument laser Doppler confocal". Klinische Monatsblätter für Augenheilkunde 214, n. 05 (maggio 1999): 285–87. http://dx.doi.org/10.1055/s-2008-1034795.
Testo completoTesi sul tema "Restriction du flux sanguin"
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Fortin, Jean-François. "Influence de la restriction du flux sanguin à l'échauffement sur l'oxygénation musculaire et la performance lors de sprints répétés chez des joueurs de football américain". Master's thesis, Université Laval, 2019. http://hdl.handle.net/20.500.11794/34441.
Testo completoAbstract (sommario):
La capacité à répéter des sprints (CRS) est un déterminant majeur de la performance au football américain. Les méthodes d’entraînement de la CRS visent essentiellement l’amélioration de la capacité à résister à la fatigue neuromusculaire. Il est généralement admis que l’amélioration du métabolisme oxydatif a pour effet d’accroître la CRS en atténuant l’impact des facteurs à l’origine de la diminution progressive de la performance. Outre l’entraînement, l’échauffement peut lui aussi affecter positivement la CRS en accélérant la cinétique de VO2 et en augmentant la consommation d’O2 dans le muscle. La restriction sanguine à l’exercice (BFR) est une technique de manipulation du flux sanguin. La méthode consiste à appliquer, pendant l’exercice, une pression modérée sur les membres inférieurs ou supérieurs au moyen de brassards spécialisés ou de bandages élastiques (practical BFR). Elle déclenche un ensemble de modifications physiologiques qui s’apparentent à celles induites par l’échauffement. Le BFR pourrait donc amplifier les effets de l’échauffement et affecter positivement la CRS. L’étude insérée dans ce mémoire a été élaborée afin de vérifier cette hypothèse. Nos résultats démontrent que l’utilisation du BFR à l’échauffement permet d’augmenter le volume sanguin local et d’élever la saturation musculaire en O2 pendant certaines périodes d’un test de sprints répétés complété immédiatement après l’échauffement. Bien que ces adaptations physiologiques n’aient pas influencé positivement la performance lors des douze sprints du test, elles pourraient produire un effet ergogénique pendant une activité de plus longue durée, comme lors d’un match de football américainRepeated-sprint ability (RSA) is an important determinant of performance in American football. Athletes and coaches use varied interventions to enhance RSA, with the goal of delaying the onset of fatigue. Many authors have suggested that increasing the oxidative metabolism through appropriate training could mitigate the influence of the limiting factors that cause fatigue and thereby enhance RSA. Aside from physical training, a well-conducted warm-up may also enhance RSA by acutely improving skeletal muscle VO2 and VO2 kinetics. The so-called blood-flow restriction (BFR) technique is a compression method that allows manipulating blood flow to skeletal muscles. BFR is employed during exercise and does not elicit complete ischemia. The pressure applied to the limbs with cuffs or elastic wraps (practical BFR) is sufficient to impede the venous outflow but maintains some of the arterial inflow. The BFR-induced acute adaptations mimic some of the mechanisms of a warm-up, and could thereby potentiate the effects of a warm-up on RSA. The study presented later in this paper examined this hypothesis. Our results suggest that performing BFR during warm-up may increase local blood volume and muscle O2 saturation during some parts of a subsequent RSA test. Although the BFR warm-up did not clearly impact performance, the altered physiological responses could prove beneficial to American football players and other team-sport athletes in longer activities involving multiple bouts of maximal efforts, such as games
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Desanlis, Julien. "Haemodynamic and cardiorespiratory acute and chronic responses to different blood flow restrictions at rest and during exercise". Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASW008.
Testo completoAbstract (sommario):
L'ischémie induite par un brassard gonflé au repos (Ischemic Preconditioning, IPC) ou à l'effort (Blood Flow Restriction, BFR) affecte les paramètres de la chaîne de transport de l'oxygène, en fonction de la pression appliquée. Cette hypoxie locale est utilisée pour optimiser les effets de l'entraînement. L'objectif de ce travail de thèse est donc d'étudier les réponses et adaptations hémodynamiques et cardio- respiratoires à différents niveaux de restriction du flux sanguin, au repos ou à l'effort. Afin d'étudier les réponses hémodynamiques au repos, la fiabilité des mesures d'oxygénation musculaire obtenues avec de la spectroscopie infrarouge (NIRS) est testée. Les études menées dans ce travail doctoral montrent une excellente fiabilité des mesures intra-session, mais un manque de fiabilité inter-sessions. Au repos, l'oxygénation musculaire est affectée différemment entre une occlusion vasculaire partielle ou complète. Cependant, la réponse n'est pas différente entre une pression suprasystolique absolue et individualisée. A l'effort, quatre semaines d'entraînement aérobie à haute intensité couplé à différents niveaux de BFR améliorent la performance lors de l'épreuve maximale incrémentée et l'efficience à intensité sous-maximale, sans distinction entre les pressions d'occlusion. Ces résultats ouvrent des perspectives de recherche sur les processus physiologiques impliqués dans les réponses à l'hypoxie locale et suggèrent des applications du BFR dans l'entraînement aérobie pour améliorer les paramètres cardiovasculaires et respiratoiresIschaemia induced by an inflated cuff at rest (Ischemic Preconditioning, IPC) or during exercise (Blood Flow Restriction, BFR) affects the oxygen transport chain, depending on the cuff pressure. This local hypoxia is used to optimise training effects. The objective of this thesis is to study the haemodynamic and cardio-respiratory responses and adaptations to different levels of blood flow restriction, at rest or during exercise. The reliability of muscle oxygenation values obtained using near-infrared spectroscopy (NIRS) is studied to enable further investigations of haemodynamic responses. The results show excellent intra-session reliability but a lack of inter-session reliability. At rest, muscle oxygenation is significantly affected by partial and complete occlusions differently. However, no significant differences are observed between absolute and individualised supra-systolic pressures. During exercise, four weeks of high-intensity aerobic training with various BFR levels improve cycling performance in a maximal incremental test and submaximal efficiency, regardless of the training pressure used. The results of the present PhD manuscript provide research perspectives on the physiological processes involved in responses to local hypoxia and suggest applications of BFR in aerobic training to improve cardiovascular and respiratory parameters
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DELESALLE, JEAN-CHRISTOPHE. "Semeiologie i. R. M. Du flux". Lille 2, 1989. http://www.theses.fr/1989LIL2M106.
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Castier, Yves. "Remodelage vasculaire associé à une augmentation chronique du flux sanguin". Paris 7, 2007. http://www.theses.fr/2007PA077051.
Testo completoAbstract (sommario):
Toute altération des conditions hémodynamiques (flux ou pression), hormonales ou métaboliques, ou encore tout traumatisme induisent dans les vaisseaux un processus d'adaptation, conduisant à terme à un remaniement de la paroi, le remodelage vasculaire. Afin d'étudier les mécanismes moléculaires et cellulaires qui sous-tendent deux types de remodelage vasculaire associés à une modification chronique du flux, nous avons dans un premier temps mis au point un modèle de fistule unilatérale carotido-jugulaire chez la souris. Ce modèle murin a l'avantage de ne pas entraîner de modifications hémodynamiques systémiques. Ensuite, à l'aide de ce modèle, nous avons démontré que les radicaux libres oxygénés jouent un rôle majeur dans la dilatation artérielle associée à une augmentation chronique du flux. Plus spécifiquement, nous avons montré que la NADPH oxydase comprenant la sous-unité p47phox était un pourvoyeur important des radicaux libres oxygénés produits en réponse à l'augmentation des contraintes de cisaillement. De plus, nos résultats suggèrent que le péroxynitrite (ONOO-), qui résulte de la réaction entre le NO avec Fanion superoxyde, active les métalloprotéases, favorisant ainsi l'élargissement artériel. Par ailleurs, nous avons caractérisé Phyperplasie intimale qui se développe au niveau de l'anastomose carotido-jugulaire chez les animaux fistulisés. Nous avons montré que seules les cellules progénitrices endothéliales étaient recrutées au sein de la lésion d'hyperplasie intimale dans notre modèle, participant probablement à la formation de microvaisseaux, alors que les cellules progénitrices musculaires lisses ne contribuaient pas à la formation de la lésionAll change in haemodynamic conditions (blood flow or pressure), in hormonal or metabolic status, and ail traumatism or external constriction of the vessel can lead to vascular remodeling. We have studied the vascular remodeling associated with chronic changes in blood flow. We developed a mouse model of peripheral arteriovenous fistula, Connecting the common carotid artery with the jugular vein, which does not modify the blood pressure. Using transgenic animals and different strains of the mouse available we studied two different aspects of the vascular remodeling associated with a chronic increase in blood flow. We demonstrated that reactive oxygen species play a fundamental role in flow-induced vascular enlargement. Moreover, we showed that NADPH oxidase comprising p47phox subunit is the major generator of shear stress-induced reactive oxygen species in the vascular wall. Together with NO derived from eNOS activation, reactive oxygen species produce peroxynitrite, which in ail probability accounts for MMP activation and enlargement of flow-loaded vessels. We characterized the neointimal hyperplasia at the site of the anastomosis that evolves after the creation of an arteriovenous in our mouse model and we investigated the role of progenitor cells in the neointima formation. We showed that smooth muscle cells of the neointima lesion do not originale from bone marrow stem cells. Conversely, the lesion contains microvessels of which a significant number of endothelial cells are derived from bone marrow stem cells
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MATROUGUI, KHALID. "Controle du tonus vasomoteur des arteres de resistance : role de la pression et du flux sanguin". Paris 7, 1998. http://www.theses.fr/1998PA077316.
Testo completoAbstract (sommario):
Dans les arteres de resistance, la pression provoque une vasoconstriction (tonus myogenique, tm) et le debit engendre une dilatation endothelium-dependante (dfd). Dans l'hypertension arterielle (hta), le tm et la dfd semble perturbes au moins dans certains territoires vasculaires. Toutefois, la nature des alterations de la dfd et du tm reste a determiner. Nos experiences ont ete realisees sur des arteres mesenteriques de resistance provenant de rats normotendus (wky) et de rats genetiquement hypertendus (shr) perfusees in situ ou in vitro. Ces arteres de resistance possedent un tonus basal induit par la pression intravasculaire et module par la dfd. L'endothelium joue un role important dans la dfd sans etre implique dans le tm. Les voies de la no-synthase et de la cyclooxygenase sont impliquees dans la dfd chez le rat wky, mais pas chez le shr. Le flux et la pression peuvent induire la synthese et la liberation d'angiotensine ii et d'endotheline. L'angiotensine ii en activant ses recepteurs de type 2 (vasodilatateurs) participe a la dfd chez le rat wky, alors que chez le shr elle diminue la dfd en activant ses recepteurs de type 1 (vasoconstricteurs). L'endotheline est liberee dans les deux souches sous l'effet du flux et diminue la dfd en activant ses recepteurs et-a. Cet effet est plus important chez le shr. Chez les rats soumis a un regime riche en nacl qui provoque un effondrement du systeme renine-angiotensine, nous avons mis en evidence une dfd et un tm diminues dans les deux souches. Les effets du nacl pourraient etre dus a une perturbation de mecanotransducteurs na +-dependants de la matrice extracellulaire. Ainsi, dans les arteres mesenteriques de resistance, le tonus basal issu de l'interaction entre la dfd et
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Nourhashemi, Mina. "Analyse multimodale du couplage neurovasculaire chez le nouveau-né". Thesis, Amiens, 2018. http://www.theses.fr/2018AMIE0059/document.
Testo completoAbstract (sommario):
Une exploration multimodale permettrait d'identifier les biomarqueurs précoces du CNV permettrait de déterminer leur caractère prédictif. Chapitre (3): Dans ce chapitre, les résultats présentés montrent que l'augmentation maximale de la température était plus élevée dans le cerveau néonatal que dans le cerveau adulte. Chapitres (4 et 5): Le but principal de cette thèse était de fournir une approche multimodale du CNV et de la régulation neurovasculaire dans le cerveau du nouveau-né prématuré. Chapitre (4): Les résultats montrent que le volume sanguin cérébral régional (rCBV) et le rCMRO2 (Cerebral metabolic rate of oxygen) exercent une influence prédominante sur le débit sanguin cérébral régional (rCBF) à l'état de repos chez le prématuré. Chapitre (5): Les bouffées d'activité électroencéphalographique caractéristiques chez les nouveau-nés au repos se sont révélés couplées à une réponse hémodynamique transitoire complexes avec différents types de réponses incluant: (a) des réponses hémodynamiques stéréotypées positives (augmentations de HbO, CBF et CMRO2, diminution de HbR), (b )des réponses hémodynamiques négatives (augmentations de HbR, diminutions de HbO avec des diminutions de CBF et CMRO2), (c) des augmentations et des diminutions à la fois de HbO -HbR et de CMRO2 sans modification du CBF. Malgré des profils de réponse hémodynamique différents qui reflètent l'immaturité et la complexité des systèmes vasculaires et des réseaux neuronaux, l'établissement d'un couplage neurovasculaire a été caractérisé avec une évolution en fonction de l'âgeNeurovascular coupling (NVC) has become the key aspect for understanding brain function. A multimodal exploration would aim to identify the early NVC biomarkers and determine their predictive character. Paper (1): In this chapter, the photothermal interaction of NIR laser on human tissues were modelled in silico. The results demonstrated the safety of the noninvasive optical evaluation of the brain function and the maximum temperature increase was higher in the neonatal brain than in the adult brain. Paper (2 & 3): The main purpose of this thesis was to provide a multimodal view of the NVC and cerebrovascular regulation in the neonatal premature brain. Paper (2): Key findings included that rCBV and rCMRO2 have a predominant driving influence on rCBF at the resting-state in the preterm neonatal brain. Paper (3): The bursts of electroencephalographic activity in neonates in resting state were found to be coupled to a transient hemodynamic response involving different types of hemodynamic response including: (a) positive stereotyped hemodynamic responses (increases in HbO, decreases in HbR together with increases in CBF and CMRO2), (b) negative hemodynamic responses (increases in HbR, decreases in HbO together with decreases in CBF and CMRO2), (c) Increases and decreases in both HbO-HbR and CMRO2 together with no changes in CBF. The establishment of neurovascular coupling system was observed as a function of age. High coherence was observed between the cerebral hemodynamic (vascular) and electrical (neuronal) oscillations which was less in the non-encephalopathic newborns than in the two pathological groups
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Bauer, Daniela. "Modélisation mécanique par approche continue et discrète des variations du flux sanguin dans la peau et validation expérimentale". Phd thesis, Université de Technologie de Compiègne, 2004. http://tel.archives-ouvertes.fr/tel-00007943.
Testo completoAbstract (sommario):
L'irritation mécanique de la peau entraîne une vasodilatation sur la ligne de la griffure suite à la libération de l'histamine des mastocytes et une vasodilatation dans les alentours liée à la stimulation des récepteurs de douleurs. Le réseau vasculaire est décrit par un modèle continu et un modèle discret. Les modèles consistent en trois couches. Le modèle continu décrit la première et la troisième couche (irrigation et drainage) comme milieux poreux bidimensionnels horizontaux. Le modèle discret tient compte de la structure de l'arbre vasculaire. La couche intermédiaire est décrite comme modèle de compartimentation. La vasodilatation a été mesurée en utilisant la Vélocimétrie Laser Doppler. Les résultats expérimentaux et numériques ont été comparés à l'aide du modèle de Bonner et al., qui est basé sur le spectre de fréquence du signal Doppler.
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Sarkis, Albert. "Flux sanguin rénal médullaire et natriurèse de pression chez le rat de souche lyonnaise : effets de l'angiotensine II". Lyon 1, 2002. http://www.theses.fr/2002LYO1T190.
Testo completoAbstract (sommario):
La 4e de couverture indique : "La circulation médullaire rénale est un facteur déterminant de la natriurèse de pression (PNa), phénomène qui joue un rôle important dans la régulation à long terme de la pression artérielle. Les objectifs principaux de ce travail étaient : i) de comparer les caractéristiques du flux sanguin rénal (FSR) médullaire chez le rat génétiquement hypertendu de souche lyonnaise (LH) et son contrôle normotendu bas (LL) afin de mieux comprendre les altérations de la PNa que présente le rat LH et ii) de préciser le rôle de l'angiotensine II (Ang II) dans la régulation du FSR médullaire chez les rats LH dont l'hypertension nécessite un système rénine-angiotensine intact pour se développer. Les fonctions rénales ont été étudiées chez le rat anesthésié placé en expansion volémique. Le FSR médullaire a été mesuré par la technique laser Doppler, mise au point au sein du laboratoire. Dans ces conditions expérimentales, les résultats obtenus montrent que sous régime normosodé, le FSR médullaire est bien autorégulé chez le rat LH alors qu'il augmente avec la pression de perfusion rénale (PPR) chez le rat LL. Le régime riche en sel diminue le FSR médullaire du rat LH ainsi que sa capacité d'autorégulation (Sarkis et Coll. , Am J Hypertens 2002, 15, 212-216). Chez les rats LL et LH, l'Ang II induit une réponse médullaire biphasique caractérisée par une vasoconstriction rapide suivie d'une vasodilatation plus tardive qui sont dose-dépendantes et médiées par la stimulation des récepteurs de type 1 à l'Ang II et non de type 2. La vasodilatation tardive est essentiellement due à une libération secondaire de prostaglandines et de monoxyde d'azote. Enfin, le rat LH diffère du rat LL par une vasoconstriction plus marquée et une vasodilatation très atténuée (Sarkis et Coll. , Am J Physiol, Accepté pour publication). En conclusion, ces résultats démontrent l'existence d'une altération de la circulation médullaire chez le rat LH qui se manifeste par une vasodilatation réduite lors d'une élévation de la PPR ou après administration d'Ang II. Ils suggèrent que ces anomalies, possiblement à l'origine de la diminution de la PNa, pourraient être liées à un déficit des systèmes vasodilatateurs médullaires. "
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Guesdon, Pascal. "Rôle de l'activation musculaire sur la dynamique des écoulements veineux". Paris 7, 2007. http://www.theses.fr/2007PA077054.
Testo completoAbstract (sommario):
Nous présentons un montage expérimental qui modélise le processus de drainage des veines musculaires pendant l'activation des muscles du mollet. Un tube collabable est placé verticalement dans une enceinte hermétique connectée à un réservoir capable de fournir des pressions extérieures contrôlées. Dans le cas d'un drainage correspondant à une marche rapide, nous montrons qu'un phénomène de limitation de débit se produit et que le drainage se fait lentement. Nous présentons des simulations numériques qui montrent qu'un passage critique, similaire aux ondes de choc dans les fluides compressibles, est à l'origine du phénomèneWe present an experimental setup representing muscular draining in the lower leg. A collapsible tube is placed vertically in a hermetic chamber connected to a variable pressure tank. With the help of electrovalves we study a draining corresponding to walking. When the external pressure is raised a phenomenon of flow limitation appears and the draining time is very long. We also present numerical simulations showing that a critical passage subcritical supercritical originates the flow limitation
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HARTMANN, ALINE. "Contribution a l'etude de la microcirculation pulpaire chez le rat et l'homme (doctorat : biologie et biomateriaux du milieu buccal et osseux)". Paris 7, 1997. http://www.theses.fr/1997PA07GE01.
Testo completoCapitoli di libri sul tema "Restriction du flux sanguin"
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MIRAUX, Sylvain ,., Frank KOBER e Emmanuel Luc BARBIER. "Imagerie vasculaire : flux et perfusion". In Les enjeux de l’IRM, 147–76. ISTE Group, 2023. http://dx.doi.org/10.51926/iste.9113.ch6.
Testo completoAbstract (sommario):
Une description des méthodes qui permettent de réaliser des angiographies, des cartes de perfusion tissulaire (débit, volume sanguin) ou des cartes de perméabilité vasculaire, avec ou sans agent de contraste (effets de relaxivité, de susceptibilité magnétique, marquage de spin artériel), dans différents organes comme le cerveau ou le cœur.
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VENTRE, Jeanne, José-Maria FULLANA, Pierre-Yves LAGRÉE, Francesca RAIMONDI e Nathalie BODDAERT. "Modèles d’ordre réduit du flux sanguin : application aux sténoses artérielles". In Écoulements biologiques dans les grands vaisseaux, 163–83. ISTE Group, 2023. http://dx.doi.org/10.51926/iste.9065.ch6.
Testo completoAbstract (sommario):
Quatre modèles d'ordre réduit sont proposés pour simuler les écoulements sanguins. Ils sont tous issus des équations de Navier-Stokes. Les interactions fluide-structure sont prises en compte via une loi de pression correspondant à divers comportements de paroi. Les applications concernent les effets d'entrée, la solution de Womersley et la sténose artérielle. Le modèle multi-anneau donne les meilleurs résultats.
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Corfield, Penelope J. "Aristocrats, Plutocrats and Cross-Class Gentlemen". In The Georgians, 245–65. Yale University Press, 2022. http://dx.doi.org/10.12987/yale/9780300253573.003.0013.
Testo completoAbstract (sommario):
This chapter reviews the concept of ‘civil society’ and social interconnectedness for the Georgians. It highlights that the concept conveyed a secular sphere of human interaction, with shared values and peaceable intentions. The chapter then jumps to discuss the unwritten rules in Britain which welded society together—and guided social ‘upstarts’ on how to behave. While British society at first glance still seemed highly traditional, headed by kings, dukes, and earls, the chapter reveals that it was in a prolonged state of flux at all social levels. It emphasizes that the old landed aristocracy was merging with a new plutocracy, with some tensions in the process, to form a porous and broad-based ‘upper class’. The chapter then surveys one sign of social flexibility: the extension of the honours system. It also considers the marked long-term restriction in the number of hereditary titles.
Atti di convegni sul tema "Restriction du flux sanguin"
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Umekawa, Hisashi, Mamoru Ozawa e Takeshi Sanami. "Restriction of Critical Heat Flux by Critical Flow Condition in Capillary Tube". In ASME 2003 1st International Conference on Microchannels and Minichannels. ASMEDC, 2003. http://dx.doi.org/10.1115/icmm2003-1073.
Testo completoAbstract (sommario):
Critical heat flux (CHF) is a very important design factor of boiling channel, then, so many investigations have been conducted so far. In the case of small diameter channel, the main interest is related with the heat removal of high heat flux component. Therefore, CHF of that system should be predicted by DNB condition. On the other hand, CHF under low heat flux condition in small channel can be considered as the relation with two kinds of restrictions. In this investigation, the confirmation of the relationship of two restrictions in CHF was principal purpose. The CHF of this system was basically decided by the dryout condition, but it deviated from the dryout under certain conditions. In those conditions, the critical flow condition achieved in lower heat flux compared with that of the dryout. Owing to this restriction of the flow rate by critical flow condition, pseudo CHF condition occurs. Experimental results have expressed these relationships between CHF and critical flow condition well.
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Büsing, F., FA Hägele, A. Nas, J. Hummel e A. Bosy-Westphal. "Impact of energy flux on changes in glucose metabolism with caloric restriction and overfeeding". In Ernährung 2018 – Ernährung ist Therapie und Prävention. Georg Thieme Verlag KG, 2018. http://dx.doi.org/10.1055/s-0038-1647155.
Testo completo
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Mohammed, H., T. Yusaf e Y. Salman. "Experimental Investigation of Free Convection Heat Transfer With Entrance Restriction Placed at Top of a Vertical Circular Tube". In ASME 8th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2006. http://dx.doi.org/10.1115/esda2006-95229.
Testo completoAbstract (sommario):
A free convection from the inside surface of vertical circular tube with a uniformly heated surface (constant wall heat flux) was investigated experimentally for laminar air flow in the ranges of RaL from 6.9 × 108 to 5 × 109. The effect of restriction lengths placed at top position of the heated tube on the surface temperature distribution and the local and average heat transfer coefficient were studied. The experimental apparatus consists of aluminum tube with 900mm length and 30mm inside diameter. The entry restrictions were included a circular tube of same diameter as the heated tube but with different lengths of 60cm, 90cm, 120cm, 150cm, and 180cm. It was found that the surface temperature along the tube surface higher values for restriction with length of 180cm and smaller values for the restriction with length of 120cm. The results showed that the local Nux and average Nusselt number Nu were higher values for the restriction with length of 120cm and smaller values for the restriction with length of 180cm. The results obtained are correlated by dimensionless groups as Log NuL against Log RaL for each case and proposed a general correlation for all cases.
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Fan, Yanfeng, e Ibrahim Hassan. "The Effect of Inlet Orifice on Critical Heat Flux and Flow Boiling Heat Transfer in Single Horizontal Microtube". In ASME 2013 Heat Transfer Summer Conference collocated with the ASME 2013 7th International Conference on Energy Sustainability and the ASME 2013 11th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/ht2013-17284.
Testo completoAbstract (sommario):
Flow oscillation is a crucial issue for the development of flow boiling heat transfer in the applications. Inlet orifice has been proven be an option to eliminate the oscillation. However, the effects of inlet orifice on critical heat flux and flow boiling heat transfer coefficient are lack of study. In this work, the effects of inlet restriction on critical heat flux and heat transfer coefficient in single horizontal microtube under uniform heating condition is experimentally investigated using FC-72 as working fluid. A stainless steel microtube with an inner diameter of 889 μm is selected as main microtube. Two smaller microtubes are assembled at the inlet of main microtube to achieve the restriction configurations of 50% and 20% area ratios. The experimental measurement is carried out at mass fluxes ranging from 160–870 kg/m2·s and heat fluxes varying from 6–170 kW/m2. Two saturation pressures, 10 and 45 kPa, are tested. The experimental results of critical heat flux and two phase heat transfer coefficient obtained in the microtube without orifice are compared with the existing correlations. The addition of an orifice does not enhance the normal critical heat flux but increases the premature critical heat flux. In aspect of heat transfer, the orifice shows improvement on heat transfer coefficient at low mass flux and high saturation pressure.
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Angatkina, Oyuna, e Andrew Alleyne. "Model Predictive Control of a Pumped Two-Phase Cooling System With Microchannel Heat Exchangers". In ASME 2018 Dynamic Systems and Control Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/dscc2018-9143.
Testo completoAbstract (sommario):
Two-phase cooling systems provide a viable technology for high–heat flux rejection in electronic systems. They provide high cooling capacity and uniform surface temperature. However, a major restriction of their application is the critical heat flux condition (CHF). This work presents model predictive control (MPC) design for CHF avoidance in two-phase pump driven cooling systems. The system under study includes multiple microchannel heat exchangers in series. The MPC controller performance is compared to the performance of a baseline PI controller. Simulation results show that while both controllers are able to maintain the two-phase cooling system below CHF, MPC has significant reduction in power consumption compared to the baseline controller.
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Reilly, Sean W., e Ivan Catton. "Characterization of Vapor Escape Restriction in Biporous Wicks With Monolayers for Thermal Ground Plane Optimization". In ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-12618.
Testo completoAbstract (sommario):
Developing better heat pipes requires advancement of technology in all aspects of construction. In this paper I am investigating the effect of vapor pathways on the performance of biporous wicks in heat pipes. Biporous evaporator wicks, generated by sintering copper particles into semi-uniform clusters, were demonstrated to achieve high flux, heat transfer performance for use in heat pipes by Semenic (2007). The effective thermal conductivity of thick biporous wicks at high heat fluxes was found to be reduced because the region next to the wall dried out prematurely, allowing the wall interface temperature to rise well above the saturation temperature. One possible way to reduce the size of the wall-wick interface dry-out region is to sinter a thin layer of uniform size particles on the wall as suggested by Seminic. The boiling curve for this “double layer” wick diverges from a standard “single layer” biporous wick at the point of nucleation by reducing the wall temperature, and concurrently the overall temperature drop across the wick needed to drive a given heat flux. The temperature drop across the wick is reduced because the thin layer of particles between the biporous wick and the wall reduces the wall-wick interface resistance and also provides additional capillary channels underneath the biporous wick. Experimental data supports this hypothesis by showing a clear divergence between measured wall temperatures for the double layer wick from its single layer counterpart with an indication that smaller cluster sizes in the biporous wicks perform better at lowering the superheat required to obtain high fluxes. In this work, we are looking to compare the performance of these wicks to similarly sized blocks of copper in order to investigate the performance increase offered by the wicks. In order to investigate this phenomenon we ran experiments in a similar manner to previous experiments done by Reilly (2009), but a plate was inserted into the chamber above the wick to restrict the vapor flow. To determine the behavior in the copper we ran several simulations in COMSOL (a finite element software used for doing conduction analysis) of copper disks at different representative thicknesses. We ran experiments with the plate at several heights above the wick, going so far as to place the plate flush with the upper surface of the wick to force vapor back through the wick laterally. By comparing the results between these two sets of experiments we were able to deduce that even in the case where there was no open space above the wick for vapor to escape, we were still able to double the performance with respect to a system of solid copper.
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Fan, Yanfeng, e Ibrahim Hassan. "New Predictive Methodology for the Onset of Flow Instability in Single Horizontal Microtube With an Inlet Orifice". In ASME 2013 Heat Transfer Summer Conference collocated with the ASME 2013 7th International Conference on Energy Sustainability and the ASME 2013 11th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/ht2013-17283.
Testo completoAbstract (sommario):
A new methodology to predict the onset of flow instability (OFI) in single horizontal microtube with inlet orifice is proposed. The predictive methodology states that OFI occurs as the pumping power under no heating condition is equal to the pumping power under heating condition in the microtube at the same volume rate. Since the pumping power can be simply described as the product of volume rate and pressure drop cross the microtube, the heat flux at OFI is determined as the two-phase pressure drop under heating condition is equal to the single-phase pressure drop under no heating condition at same flow rate. The addition of inlet orifice increases the pumping power under no heating condition. The increased pumping power by orifice delays the onset of flow instability. The predictive methodology is validated by comparing the predicted heat flux at OFI with our previous experimental data in the microtubes with three different inlet restriction ratios. The result shows that the proposed method is capable of prediction of heat flux at OFI with a deviation of 30% and mean absolute error of 13% at mass flux less than 2000 kg/m2·s.
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Feng, Zhaozan, Guomeng Song, Fan Xia, Bin Liu, Jinfeng Yang e Kai He. "An Experimental and Modeling Study on Device- and System-Level Two-Phase Cooling for High-Heat-Flux Application". In ASME 2024 7th International Conference on Micro/Nanoscale Heat and Mass Transfer. American Society of Mechanical Engineers, 2024. http://dx.doi.org/10.1115/mnhmt2024-121519.
Testo completoAbstract (sommario):
Abstract A multi-microchannel two-phase cold plate made of copper is tested for temperature rise and flow resistance to verify its feasibility for heat dissipation in high-heat-flux devices such as GPU, as well as programmed with EES (Engineering Equation Solver) to predict its temperature profile and pressure drop across the device. The microchannel cold plate has a channel height of 3mm, a channel width of 0.3mm, a fin thickness of 0.2mm, a total width of 50mm, and a total length of 60mm. The 3D model of the cold plate and heat source was imported into COMSOL to complete the three dimensional heat conduction analysis based on the convective flux boundary conditions calculated with EES. Through correlation-based EES coding for thermal and hydraulic behaviors in the cold plate, the heat transfer and flow resistance have been predicted very well. Among the components of the overall pressure drop across the cold plate, the local two phase flow resistances, especially the abrupt bend and restriction of the outlet, play an extremely vital role. Moreover, the adiabatic pressure drop between the micro-channel cold plate and condenser is proved to be a key factor that affects the working pressure or saturation fluid temperature in the cold plate, which in turn determines the temperature rise of the cold plate over the atmosphere. This study provides not only a feasibility analysis for the high-heat-flux cooling solution, but also a reliable and easy-to-use tool for predicting multi-microchannel cooling device and system.
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Wu, Ge Ping, Sui Zheng Qiu, Guang Hui Su e Dou Nan Jia. "Analysis of Flow Instabilities in Forced-Convection Steam Generator". In 14th International Conference on Nuclear Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/icone14-89109.
Testo completoAbstract (sommario):
Because of the practical importance of two-phase instabilities, substantial efforts have been made to date to understand the physical phenomena governing such instabilities and to develop computational tools to model the dynamics. The purpose of this paper is to present a numerical model for the analysis of flow-induced instabilities in forced-convection steam generator. The model is based on the assumption of homogenous two-phase flow and thermodynamic equilibrium of the phases. The thermal capacity of the heater wall has been included in the analysis. The model is used to analysis of flow instabilities in steam generator and to study the effects of system pressure, mass flux, inlet temperature and inlet/outlet restriction, gap size, the ratio of do/di and the ratio of qi/qo on system behavior.
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Cheng, Ping, Guodong Wang e Xiaojun Quan. "Boiling and Condensation in Microchannels". In ASME 2008 First International Conference on Micro/Nanoscale Heat Transfer. ASMEDC, 2008. http://dx.doi.org/10.1115/mnht2008-52387.
Testo completoAbstract (sommario):
The characteristics of boiling of water and condensation of steam in a microchannel under heating or cooling conditions are discussed in this paper. Stable and unstable boiling modes occur in a microchannel, depending on the nucleated bubble size in the microchannel. Stable boiling mode with constant temperature variations exists when the size of the nucleated bubble is less than that of the microchannel diameter, while unstable boiling mode exists when the size of the bubble is greater than the microchannel diameter. The latter is owing to the fact that when a bubble grows to the size of the microchannel, it will expand in both upstream and downstream directions. Subsequently, the reversed flow of vapor bubble is swept downstream by the incoming subcooled liquid, leading to large cyclic fluctuations of temperature and pressure. The amplitude and frequency of these fluctuations depend greatly on the inlet/outlet configurations and the exit vapor quality. By fabricating an inlet restriction on each microchannel, the reversed flow of vapor can be suppressed, resulting in a stable flow boiling mode. Boiling heat transfer coefficient and pressure drop in a microchannel under stable flow boiling conditions are obtained. These data at high vapor qualities are found to be substantially different from the correlations obtained for flow boiling in macrochannels. For condensation in a microchannel, mist flow, annular flow, injection flow, slug/bubbly flow exist depending on mass flux, condensation heat flux, and the location in the microchannel. The occurrence of the injection flow is owing to the instability of the liquid/vapor interface because the surface tension effect is predominant in microchannels. The location, at which the injection flow occurs, depends on the mass flux and the cooling rate of steam. Increase in steam mass flux, decrease in cooling rate and the microchannel diameter tend to enhance instability of the condensate film on the wall, resulting in occurrence of the injection flow further toward the outlet with an increase in occurrence frequency. At low mass fluxes, the pressure drop obtained for condensation in microchannels is substantially different from the correlation equations for macrochannels because of different flow patterns.