A moving-actuator type electromechanical total artificial heart.II. Circular type and animal experiment

A new type of electromechanical total artificial heart (TAH) based on circular rolling-cylinder mechanism was developed to overcome critical problems in motor-driven artificial hearts such as large size and difficulties in fitting the heart to atrial remnants and arterial vessels. Its performance and reliability were evaluated in mock circulation and in an animal implant experiment. The total weight and volume of the pump is 650 g and 600 mL, respectively. This new pump was implanted in a calf for total heart replacement and 96 h of survival was achieved. The whole system, including pump, controller, and control algorithm performed well enough to improve the prospect of eventual clinical application of our TAH system.     

An intelligent remote monitoring system for artificial heart.

A web-based database system for intelligent remote monitoring of an artificial heart has been developed. It is important for patients with an artificial heart implant to be discharged from the hospital after an appropriate stabilization period for better recovery and quality of life. Reliable continuous remote monitoring systems for these patients with life support devices are gaining practical meaning. The authors have developed a remote monitoring system for this purpose that consists of a portable/desktop monitoring terminal, a database for continuous recording of patient and device status, a web-based data access system with which clinicians can access real-time patient and device status data and past history data, and an intelligent diagnosis algorithm module that noninvasively estimates blood pump output and makes automatic classification of the device status. The system has been tested with data generation emulators installed on remote sites for simulation study, and in two cases of animal experiments conducted at remote facilities. The system showed acceptable functionality and reliability. The intelligence algorithm also showed acceptable practicality in an application to animal experiment data.     

A Pneumatic Pressure Cycling System for an Artificial Heart

Included in this paper is a discussion of the operating principle, design, construction and testing of a stroke-limited, transistorized, pneumatic pressure cycling system for a single-chambered artificial heart. The system is free of valve-stiction catastrophes, and reveals that conventional calculations of heart power based on mean blood pressure, cardiac output and kinetic energy of the aortic blood should be augmented substantially to account for turbulence, valve resistance and pneumatic feedline distensibility. Graphs are presented to illustrate the over-all performance data.     

Greater than 500-mW CW kink-free single transverse-mode operation of weakly index guided buried-stripe type 980-nm laser diodes

This is the first report of greater than 500-mW CW kink-free single transverse-mode operation of 980-nm laser diodes with a weakly index guided buried-stripe type structure. The device exhibited a kink-free level of 545 mW and maximum optical output power of over 650 mW limited by thermal saturation and showed no catastrophic optical damage, in addition, a currently on-going aging test at 350 mW optical output power at 50/spl deg/C has shown stable operation. Using a can-sealed LD, we also fabricated a co-axial type module with a two-lens system and a lensed-fiber. The coupling efficiency between the LD and a single-mode fiber was calculated to be approximately 78% and we have confirmed 300 mW kink-free fiber output operation. These figures are also the highest reported operation levels for 980-nm co-axial type modules.     

A Battery‐ and Leadless Heart‐Worn Pacemaker Strategy

Over the past half‐century, cardiac pacing technology has adhered to one basic system. However, many pacemaker‐related complications are related to this system, particularly in terms of the power supply and leads. Here, for the first time a heart‐worn pacemaker strategy is presented, which allows batteryless powering and leadless pacing. The batteryless feature is attained via heart‐extrusion energy scavenging through a micromachined piezoelectric thick film transducer. A record in vivo output current of 30 µA is obtained in an adult swine by the implanted piezoelectric transducer, which can effectively drive a commercial cardiac pacemaker. The exocardial pacing method is demonstrated by this batteryless pacemaker functions without a device or leads placed within the cardiac chambers. Lead‐ or batteryless options are being explored as new basic features of cardiac pacemakers. The presented heart‐worn pacemaker strategy may be useful in future pacing technology.     

Development of a microcontroller-based automatic control system forthe electrohydraulic total artificial heart

An automatic physiological control system for the actively filled, alternately pumped ventricles of the volumetrically coupled, electrohydraulic total artificial heart (EHTAH) was developed for long-term use. The automatic control system must ensure that the device: (1) maintains a physiological response of cardiac output, (2) compensates for any nonphysiological condition, and (3) is stable, reliable, and operates at a high power efficiency. The developed automatic control system met these requirements both in vitro, in week-long continuous mock circulation tests, and in vivo, in acute open-chested animals (calves). Satisfactory results were also obtained in a series of chronic animal experiments, including 21 days of continuous operation of the fully automatic control mode, and 138 days of operation in a manual mode, in a 159-day calf implant     

The Exercise-Responsive Cardiac Pacemaker

The heart has two properties: rhythmicity and contractility. Rhythmic contractions are initiated by the heart's pacemaker, the sinoatrial node, which lies in the right atrium. If the sino-atrial node fails, or if its electrical excitations are not propagated to the ventricles (the main pumping chambers), they wil still contract rhythmically but at a rate that is sometimes too slow to provide enough cardiac output to sustain consciousness. It is for this reason that rhythmic electrical stimuli are delivered to the ventricles in order to increase cardiac output to a level adequate to permit the subject to perform routine daily tasks. The technique of applying rhythmic electrical stimuli to the ventricles is called cardiac pacemaking; it can be achieved in several interesting ways, as this paper will describe.     

双声光器件调制的同步性对Nd:YAG脉冲激光输出的影响

在脉冲Nd：YAG激光器的谐振腔内,用最大输出功率为120W的声光电源,同时驱动2个正交放置的器件,进行声光调制。实验研究了2个声光器件不同的开启时间对激光脉冲输出的影响。研究结果表明,双声光器件的开启时间的同步性对激光输出脉冲有较大的影响,当两器件开启时间差大于5ns时,声光器件不能对调制光进行有效关断;当两器件的开启时间大于18ns时,有效调制输出的激光脉冲能量下降了20％。     

一种基于dsPIC的新型反激逆变器的实现

PV（Photovoltaic）光伏并网发电系统的核心就是逆变器。文中设计并实现了一种新型反激逆变器,详细论述了其系统原理、主要模块设计、主要参数设计,并给出了系统测试结果。该逆变器采用SCR（可控硅）全桥结构,使用平均电流模式控制方法产生与网同步的正弦输出电流,具有输出波形好,失真度低,对通信设备无干扰等优点。     

Permanent circulatory support systems at the Pennsylvania StateUniversity

Permanent circulatory support systems are required for patients in whom myocardial damage is irreversible and cardiac transplantation is not possible. Two systems are described which provide long term circulatory support: the left ventricular assist system and the total artificial heart. These systems are based on the design of a pusher plate actuated blood pump, driven by a small brushless dc electric motor and rollerscrew driver. An implantable motor controller maintains suitable physiologic flow rates for both systems and controls left-right balance in the total artificial heart. Other parts of the system include an intra-thoracic compliance chamber, transcutaneous energy and data transmission system, and internal and external batteries.     

Real-time cardiac output estimation of the circulatory system underleft ventricular assistance

A method for indirect and real-time estimation of the cardiac output of the circulatory system supported by the left ventricular assist device (LVAD) is proposed. This method has low invasiveness and is useful for clinical applications of the LVAD since it needs only two measurements: the rate of blood outflow from the LVAD and the aortic pressure. The method is based on a system identification technique for the time-series model of the cardiovascular system and requires less computational time than other methods with similar estimation accuracy. Hence, the method could be implemented in a personal computer system and realize online, real-time estimation of the instantaneous outflow rate of the natural heart. Results obtained in vitro using a mock circulatory system and in vivo using an adult goat show that the method can yield a fairly high correlation coefficient between the true stroke volume of the natural heart and its estimate of more than 0.99 (in vitro) or 0.95 (in vivo). The estimation method thus appears suitable for clinical use     

Effects of Unphysiological Factors on Cardiac Output Regulation During Artificial Heart Pumping

Several Factors affecting artificial heart output were studied employing two mathematical models of prosthetic hearts, i.e., sac and diaphragm heart models. The stroke volume sensitivity to changes in venous pressure was analyzed by numerical computations. Increased inflow valve resistance, increased pump vacuum pressure, decreased elasticity of the ventricular sac or diaphragm and decreased size of the ventricle were shown to depress artificial heart function. In total prosthetic heart replacement experiments in calves, the resistance at the junction of the right heart to the natural atrium was measured by varying the pump vacuum pressure. When the vacuum pressure exceeded ?20 mmHg, the orifice resistance to flow increased approximately 4 times. Optimizing the above factors, a prosthetic heart should be designed that provides sufficient flow with a pump vacuum pressure not greater than ?20 mmHg.     

Dual Extra Cardiac Pacemaker

A cardiac stimulator for evaluation of mechanical and electrical response to arrhythmias is described. It drives the heart at preselected rates and can stop the basic driving, introduce two extra stimulations and return to basic rate with a single switch. Three output circuits enable independent amplitude regulation for the basic pacing and each extra stimuli. The two extra pulses can be transferred to the heart through either single or separate electrodes.     

An Artificial Autonomic Nervous System That Implements Heart and Pupil as Controlled by Artificial Sympathetic and Parasympathetic Nerves

The autonomic nervous system maintains homeostasis in organisms through complex neural pathways and responds adaptively to changes in the external and internal environment. The fabrication of an artificial autonomic nervous system is reported that replicates combined effects of sympathetic and parasympathetic nerves on cardiac activity and pupillary control, to mimic the regulation of autonomic nervous system to external changes. The artificial autonomic nerve-controlled pupil contraction and relaxation, modulating the rate of heartbeats for normal cardiac rhythm and arrhythmia as reflected by blink rates of a signal indicator. These functions are switched by using a parallel-channeled synaptic transistor with a special n-i-p heterostructure that has a 2D h-BN insulator in the middle to provide barrier against ion injection into the 2D MoS₂ bottom n-channel and enable short-term plasticity as induced by acetylcholine, and the electrochemical doping reaction occurred at the P3HT nanowire p-channels on top to enable relatively long-term plasticity as induced by noradrenaline. Low-energy consumption down to femtojoule and an ultrahigh paired-pulse facilitation index up to ≈455% are demonstrated. An artificial neural network based on device characteristics achieves a high recognition accuracy for electrocardiogram patterns. This study extends insights into artificial nerves-inspired biological signal processing and recognition.     

Low-Frequency Piezoelectric Energy Conversion for an Intrathoracic Artificial Heart

The present paper is concerned with an evaluation of a piezoelectric energy conversion system in which two columns of piezoelectric ceramic disks are excited axially by means of thin metallic shims stacked alternately with the disks. Mechanical energy output is extracted through the expansion and contraction of the Columns. The treatment is based upon the equivalent circuit approach first suggested by Mason. A lever system is used in making the mechanical impedance transformation between the very high force and small displacement of the piezoelectric columns and the low force and relatively large displacement required for an artificial heart. The role of mass loading in improving the power capability and efficiency of the energy converter is clearly indicated. It is concluded that the theoretical energy output per unit mass of material per cycle and the efficiency of conversion are such as to justify a continued developmental effort.     

Coil‐Capacitor Circuit Design of a Transcutaneous Energy Transmission System to Deliver Stable Electric Power

A new transcutaneous energy transmission (TET) system was developed for transmitting electrical power to an implanted device, such as an artificial heart in a patient's body. This new design can maintain a stable output voltage independent of the load resistance. The system includes a compensation capacitor to reduce energy loss and increase power transfer efficiency. Experimental results show that the output voltage of the receiving coil changes very little as the load resistance varies from 14.8 Ω to 15 kΩ, which corresponds to a change in output power from 0.1 to 97 W.     

Development of an implantable motor-driven assist pump system

A motor-driven artificial pump and its transcutaneous energy transmission (TET) system have been developed. The artificial pump consists of a high-speed dc brushless motor driving a ball screw and magnetic coupling mechanism between the blood pump and ball screw. The ball screw transfers high-speed rotary motion into low-speed rectilinear motion by a single component. Magnetic coupling enables active blood filling without applying an excess negative pressure to the pump. The transcutaneous transformer is formed from a pair of concave/convex ferrite cores. This design minimizes lateral motion of the external core. Information on motor voltage is transmitted through the skin by infrared pulses. The motor voltage is regulated by controlling the duty ratio of the square pulse supplied to the primary coil. Pump flow of 5.6 l/min was obtained with a mean outlet pressure of 100 mmHg at a drive rate of 100 bpm under preload of 15 mmHg. The performance of synchronous pumping has been very satisfactory. Continuous pumping was maintained by the backup battery in the case of interruption of TET. 24 W were transmitted by TET system with 78 percent of efficiency. Temperature rise of the internal core was 0.2 C. The developed system is promising as an implantable assist pump system.     

A novel pull-up type RF MEMS switch with low actuation voltage

We report a novel pull-up type radio frequency (RF) microelectromechanical system (MEMS) switch with no elastic deformation of the cantilever involved in the actuation. At a voltage of 4.5V, reliable actuations are achieved such that the movable lower contact pad is pulled up by the electrostatic force to make contact with the upper pad. At a frequency of 50GHz, an insertion loss of 0.5dB, a return loss of 12.4dB, and an isolation of 55dB are obtained from the switch. The measured transient times for switch-on and switch-off are 120 and 130ns, respectively. Compared to the MEMS switches reported thus far, the pull-up type switch shows the best switching speed and isolation characteristic at 50GHz.     

光栅选频单纵模35MW TEACO_2激光系统

本文报道了光栅调频单纵模TEA CO_2激光系统,它由混合型TEA CO_2振荡器和二台TEA CO_2放大器组成,得到脉冲输出能量4.2J,脉宽120ns,功率35MW,可调谱线81条。