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    PublicationOpen Access
    Haemodynamic recovery properties of the torsioned testicular Artery Lumen
    (Nature Publishing Group (NPG), 2017) Göktaş, Selda; Pişkin, Şenol; Çapraz, Can T.; Çakmak, Yusuf O.; N/A; Department of Mechanical Engineering; Yalçın, Özlem; Ermek, Erhan; Pekkan, Kerem; Other; Faculty Member; Department of Mechanical Engineering; School of Medicine; College of Engineering; 218440; 109991; 161845
    Testicular artery torsion (twisting) is one such severe vascular condition that leads spermatic cord injury. In this study, we investigate the recovery response of a torsioned ram testicular artery in an isolated organ-culture flow loop with clinically relevant twisting modes (90°, 180°, 270° and 360° angles). Quantitative optical coherence tomography technique was employed to track changes in the lumen diameter, wall thickness and the three-dimensional shape of the vessel in the physiological pressure range (10–50 mmHg). As a control, pressure-flow characteristics of the untwisted arteries were studied when subjected to augmented blood flow conditions with physiological flow rates up to 36 ml/min. Both twist and C-shaped buckling modes were observed. Acute increase in pressure levels opened the narrowed lumen of the twisted arteries noninvasively at all twist angles (at ∼22 mmHg and ∼35 mmHg for 360°-twisted vessels during static and dynamic flow experiments, respectively). The association between the twist-opening flow rate and the vessel diameter was greatly influenced by the initial twist angle. The biomechanical characteristics of the normal (untwisted) and torsioned testicular arteries supported the utilization of blood flow augmentation as an effective therapeutic approach to modulate the vessel lumen and recover organ reperfusion.
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    PublicationOpen Access
    Stability of three-phase ternary-eutectic growth patterns in thin sample
    (Elsevier, 2018) Bottin-Rousseau, Sabine; Faivre Gabriel; Akamatsu, Silvere; Department of Mechanical Engineering; Şerefoğlu, Melis; Yücetürk, Sinan; Researcher; Department of Mechanical Engineering; College of Engineering
    Near-eutectic ternary alloys subjected to thin-sample directional solidification can exhibit stationary periodic growth patterns with an ABAC repeat unit, where A, B, and C are the three solid phases in equilibrium with the liquid at the eutectic point. We present an in-situ experimental study of the dynamical features of such patterns in a near-eutectic IneIn2BieSn alloy. We demonstrate that ABAC patterns have a wide stability range of spacing l at given growth rate. We study quantitatively the ldiffusion process that is responsible for the spacing uniformity of steady-state patterns inside the stability interval. The instability processes that determine the limits of this interval are examined. Qualitatively, we show that ternary-eutectic ABAC patterns essentially have the same dynamical features as two-phase binary-eutectic patterns. However, lamella elimination (low-l stability limit) occurs before any Eckhaus instability manifests itself. We also report observations of stationary patterns with an [AB]m[AC]n superstructure, where m and n are integers larger than unity.