Chi-Hsiao Yeh

Late-Outgrowth Endothelial Cells Attenuate Intimal Hyperplasia Contributed by Mesenchymal Stem Cells After Vascular Injury

Objectives—Mesenchymal stem cells (MSCs) are one of a number of cell types undergoing extensive investigation for cardiac regeneration therapy. It has not yet been determined whether this cell therapy also substantially contributes to vascular remodeling of diseased vessels. Methods and Results—Human MSCs and a variety of progenitor and vascular cells were used for in vitro and in vivo experiments. Wire-induced vascular injury mobilized MSCs into the circulation. Compared with human aortic smooth muscle cells, MSCs exhibited a 2.8-fold increase in the adhesion capacity in vitro (P<0.001) and a 6.3-fold increase in vivo (P<0.001). In all animal models, a significant amount of MSCs contributed to intimal hyperplasia after vascular injury. MSCs were able to differentiate into cells of endothelial or smooth muscle lineage. Coculture experiments demonstrated that late-outgrowth endothelial cells (OECs) guided MSCs to differentiate toward an endothelial lineage through a paracrine effects. In vivo, cell therapy with OECs significantly attenuated the thickness of the neointima contributed by MSCs (intima/media ratio, from 3.2±0.4 to 0.4±0.1, P<0.001). Conclusions—Tissue regeneration therapy with MSCs or cell populations containing MSCs requires a strategy to attenuate the high potential of MSCs to develop intimal hyperplasia on diseased vessels.

Hydrodynamic Simulation of an Orbital Shaking Test for the Degradation Assessment of Blood-Contact Biomedical Coatings

Biomedical coatings are used to promote the wear resistance and the biocompatibility of a mechanical heart valve. An orbital shaking test was proposed to assess the durability of the coatings by the amount material eroded by the surrounding fluid. However, there is still a lack of understanding with regards to the shaker’s rotating conditions and the corresponding physiological condition. This study implemented numerical simulations by establishing a fluid dynamic model to evaluate the intensity of the shear stress under various rotating speeds and diameters of the shaker. The results are valuable to conduct in vitro tests for estimating the performance of biomedical coatings under real hemodynamic conditions and can be applied to other fluid-contact implants.

Decreased Hemolysis and Improved Hemodynamic Performance of Synchronized Bileaflet Mechanical Valve

PURPOSE This study compared the performance of a newly patented synchronized valve (SV) with that of a commercially available (CAV) bileaflet mechanical heart valve. DESCRIPTION A high-speed camera was used to record the leaflet kinematics of the SV vs the CAV along the flow channel. Transvalvular energy loss, effective orifice area, and hemolysis ratios were obtained using a mock circulatory system at two fixed pulse rates and at various cardiac outputs with a fixed aortic pressure. EVALUATION The rotational radius and inertia of the SV was lower than that of the CAV during valve closure. For heart rates and at cardiac outputs of 7, 5, and 4 L/min, the ratio of total energy loss to effective energy of the SV was significantly less than the CAV, whereas the effective orifice area of the SV was significantly larger than that of CAV. The hemolysis ratio after 4 hours was significantly higher in the CAV than in the SV for both pulse rates. CONCLUSIONS The synchronized leaflet motion mitigated leaflet rebound and regurgitation during valve closure, which could decrease energy loss, increase the effective orifice area, and reduce hemolysis.

IMPROVING DETECTION TECHNIQUE FOR FLIGHT RECORDERS OF THE DISTRESS AIRPLANES CRASHED INTO OCEAN BY INTEGRATING INERTIAL NAVIGATION SYSTEM INTO UNDERWATER LOCATOR BEACON

Flight recorder, used to analyze distress reasons, is equipped with underwater locator beacon (ULB) for being detected and recovered easily in sea. According to the recovery report for the Air France flight no. AF447 distress airplane, it nearly took two years and cost 40 million US dollars to search and recover the flight recorders. Apparently, future aviation safety could be greatly improved if earlier recovery of the flight recorders would reveal the crash reasons sooner. Therefore, this paper is aimed to develop an enhanced ULB, which integrates inexpensive inertial navigation system (INS) into ULB, for a cost-effective and time-saving operation of search and recovery in the future. This new equipment is anticipated to directly provide the location of flight recorders to the search and recovery authority. From the static and dynamic tests, maximum position errors are below 50 m when the standalone INS operates in a duty cycle of 78 seconds. From the case report of AF447 aircraft crush, the time taken from 38,000 feet (=11,582 m) descent to sea level is about 3 minutes and 30 seconds. Over this time frame, the maximum position error is about 140 m owing to the nearly linear drift property of the INS. Thus, the proposed INS-aided ULB approach should be feasible to the search and recovery mission.

Effects of Sheet Resistance on mc-Si Selective Emitter Solar Cells Using Laser Opening and One-Step Diffusion

In order to simplify process procedure and improve conversion efficiency (η), we present new steps of laser opening and one-step POCl3 diffusion to fabricate selective emitter (SE) solar cells, in which heavily doped regions (HDR) and lightly doped regions (LDR) were formed simultaneously. For HDR, we divided six cells into two groups for POCl3 diffusion with sheet resistance () of 40 Ω/sq (for group A) and 50 Ω/sq (for group B). The dry oxidation duration at a temperature of 850°C was 18, 25, and 35 min for the 3 different cells in each group. This created six SE samples with different pairings for the HDR and LDR. The optimal cell (sample SE2) with values of 40/81 Ω/Sq in HDR/LDR showed the best η of 16.20%, open circuit voltage () of 612.52 mV, and fill factor (FF) of 75.83%. The improvement ratios are 1.57% for η and 14.32% for external quantum efficiency (EQE) as compared with those of the two-step diffusion process of our previous study. Moreover, the one-step laser opening process and omitting the step of removing the damage caused by laser ablation especially reduce chemistry pollution, thus showing ecofriendly process for use in industrial-scale production.