Detection and characterization of higher order nonlinearities in the oscillations of Definity at higher frequencies and very low acoustic pressures
Notice bibliographique
Résumé
The oscillation dynamics of phospholipid shell microbubbles (MBs) (e.g. Definity) exhibiting subharmonic (SH) oscillations has been widely investigated for high frequency ultrasonic imaging of the vascular bed. However, many aspects of the behavior of these MBs have remained unexplored, partly due to an extra degree of complexity imposed by the nonlinear behavior of the shell, leading to "compression only" behavior. Full understanding of the dynamics of these MBs at higher frequencies will aid in the design of optimal ultrasonic exposure parameters and MB properties to improve the current SH imaging protocols. The dynamics of Definity MBs were investigated both numerically and experimentally. Polydisperse dilute solutions of Definity were sonicated separately at frequencies of 25 and 55 MHz using pulse trains of 30 cycles with a Vev0770 ultrasonic machine. For each sonication the driving pressure was varied between 100 kPa to 3.8 MPa. The backscatter signals from single MBs were iso la ted and analyzed. The Marmottant model for lipid shell MBs was numerically solved for a wide range of MB sizes and driving acoustic pressures at frequencies of 25 and 55 MHz. The results of the numerical simulations were visualized using bifurcations diagrams (MB expansion ratio versus MB size and acoustic pressure and buckling radius). Analysis of the signals extracted from the oscillations of single Definity MBs revealed, for the first time, that in addition to the conventional SH of order 1/2, SHs of the higher order of 1/3, 1/4 and 1/5 can be observed at very low acoustic pressures (~200 kPa) at both frequencies (25 and 55 MHz). These results contradict the predictions of the viscoelastic models (e.g. Hoff) which require very high acoustic pressures (~2.5 MPa) for the generation of higher order SHs at high frequencies (e.g. 55MHz). In order to investigate the origin of these oscillations, the bifurcation structure of the Marmottant model was generated. In very good agreement with experimental results, numerical results reveal the generation of higher order subharmonics in the dynamics of lipid shell MBs at pressure levels as low as 200kPa. Depending on the initial size of the MBs, simulations predict the generation of the oscillations including period 2 (P2), P3 and up to PS. Results of the simulations using the bifurcation diagrams showed that compression only behavior is the most probable reason for the occurrence of higher order SHs at very small pressure values. These results suggest that the value for the buckling radius is of great importance in the generation and order of higher order SHs. To our best knowledge, this is the first time that the numerical classification and experimental observation of the higher order SHs in the dynamics of MBs undergoing buckling and rupture is shown.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».