No abstract

Sunlight energy is potentially excellent for small drones, which can often operate during daylight hours and fly high enough to avoid cloud blockade. However, the best solar cells provide limited power, compared to conventional power sources, making their use for aerial vehicles difficult to realize, especially in rotorcraft where significant lift ordinarily generated by a wing is already sacrificed for the ability to hover. In recent years, advances in materials (use of carbon-fiber components, improvement in specific solar cells and motors) have finally brought solar rotorcraft within reach. Here, the application is explored through a concise mathematical model of solar rotorcraft based on the limits of solar power generation and motor power consumption. Multiple solar quadcopters based on this model with majority solar power are described. One of them has achieved an outdoor airtime over 3 hours, 48 times longer than it can last on just battery alone with the solar cells carried as dead weight and representing a significant prolongation of drone operation. Solar-power fluctuations during long flight and their interaction with power requirements are experimentally characterized. The general conclusion is that solar cells have reached high enough efficiencies and can outperform batteries under the right conditions for quadcopters.

Owing to shortage of donor hearts, the ventricular assist device is used as a bridging therapy to heart transplantation. However, thrombus formation is a critical complication during ventricular assist device circulatory support that might result in ischemic infarction of end organs. Here, we report a patient diagnosed with decompensated dilated cardiomyopathy and cardiogenic shock who underwent emergent extracorporeal life support, and subsequent temporary bilateral ventricular assistance with the CentriMag device (Levitronix LLC, Waltham, MA). Daily transthoracic echocardiography did not detect any thrombus formation, and no stroke event occurred during biventricular support. During eventual orthotopic heart transplantation, transesophageal echocardiography detected a huge thrombus in the left ventricle. We removed the biventricular assist device, excised the recipient heart, cleaned up the thrombus, and then implanted the donor heart successfully. No stroke or transient neurological deficit was noted during or after the transplantation. The patient was discharged 14 days after transplantation. No major adverse cardiovascular event was noted during 2 years of outpatient follow-up.