Cardiac Output Monitoring by Impedance Cardiography During Treadmill Exercise

We have modified impedance cardiography for monitoring cardiac output during stress tests. We adapted an ensemble-averaging technique for eliminating motion artifacts. We applied an array consisting of four spot ECG electrodes for impedance cardiogram (ICG) monitoring and compared it to conventional encircling band electrodes. We tested ten normal adults, compared the cardiac output obtained by our ICG monitoring system to that simultaneously obtained by the carbon dioxide (CO2) rebreathing method at rest and during three levels of treadmill exercise. The results show that the correlation coefficient between the spot electrode ICG and the CO2 rebreathing method is r = 0.90, and between the band electrode ICG and the CO2 rebreathing method is r = 0.96. If we use the peak-to-valley height of dz/dt instead of the peak height of dZ/dt in computing cardiac output, the correlation coefficient between the spot electrode ICG and the CO2 rebreathing method can be improved to r = 0.95.     

A Simple Device for Closed Loop Heart Rate Control During Cardiac Rehabilitation

During unsupervised exercise for cardiac rehabilitation or conditioning, it is desirable to reach and maintain a predetermined heart rate (without overshooting) selected according to age, health, and cardiac status of the patient. Because there is no simple and inexpensive heart rate controller, most exercise protocols are specified in terms of patient work load-often speed and torque of a stationary bicycle. In these protocols the actual heart rate achieved will depend on the patients physical condition and fatigue as the exercise progresses.     

Continuous Thermal Measurement of Cardiac Output

A thermal-dilution technique for the continuous measurement of cardiac output has been developed. It employs pulmonary-artery sensing of low-level periodic thermal signals generated in the right ventricle of the heart. A resistive element in a modified Swan Ganz?catheter is energized with a periodic electrical waveform. The resulting thermal signal is diluted by blood flow and attenuated by mixing within the heart. Sensed by a thermistor in the pulmonary artery, the thermal signal is processed by a microprocessor-based instrument using a suitable mathematical model. With multiple signal frequencies, separate estimates of the flow-dependent and mixing-dependent attenuation components become possible, allowing continuous monitoring of cardiac output. This technique works well in anesthetized, mechanically ventilated animals, even with average power levels as low as 4 W and corresponding temperature increases of a few hundredths of a degree centigrade. Based on measurements of pulmonary artery thermal noise spectra in humans, we infer that similar performance levels should be attainable with mechanically ventilated human subjects. However, noise spectra from spontaneously breathing critically ill patients suggest that signal-to-noise ratios would be less than satisfactory in that group unless increased signal power is allowed or improved algorithms are developed.     

用于泵浦固体激光器的激光二极管线阵的输出特性

从实验上测量了激光二极管线阵的输出特性,研究了温度、电流对输出功率、光谱特性,以及偏振特性的影响,为设计全固态激光器提供有益的参考。     

半导体抽运铷蒸气输出2.8W线偏振铷激光

半导体抽运碱金属蒸气激光器(DPAL)是一种具有广阔应用前景的激光器,近年来发展迅速。使用碱金属铷所需要的中心波长为780nm的半导体激光器线阵作抽运源,采用平面衍射光栅搭建Littrow外腔将线宽压窄至0.13nm,并使用斩波器将半导体激光变为脉冲输出形式。采用透镜组合对窄线宽半导体激光进行光束扭转整形,整形后光斑近似为方形。半导体激光经线宽压窄和光束整形后,被聚焦进铷蒸气泡,泡内充入79kPa甲烷作为缓冲气体。控制铷蒸气泡温度为145℃,注入谐振腔的抽运光峰值功率为最高13W时,获得了峰值功率2.8W的线偏振铷激光输出,光-光转换效率达21%。     

Continuous Cardiac Output Measurement: Aspects of Doppler Frequency Analysis

From the suprasternal notch blood flow velocity in the aorta can be measured non-invasively by a Doppler probe. Integration over systole after frequency analysis gives a measure of stroke volume if a separate diameter observation is incorporated. Frequency analysis by a zero crossing counter or by a set of parallel phaselock loops was less effective than a set of bandpass filters. Observations on dogs, baboons and humans before and after exercise or surgery suggest the indications to be useful. Application to judging heart failure by the effect of introducing a volume load is indicated. Changes in output also are measured in freely moving subjects.     

Theoretical Considerations Regarding the Optimization of Cardiac Assistance by lntraaortic Balloon Pumping

A lumped parameter model representing the effects of cardiac assistance by intraaortic balloon pumping was developed. The model permits closed-form calculations of important hemodynamic events in the system. The equations derived from the model were used to determine pumping parameters for optimum assistance. The model indicates that, in the ideal case, optimization of assistance requires instantaneous inflation of the balloon to maximum volume at end systole and instantaneous complete deflation at end diastole. Since an impulse flow rate is not realizable in practice, the model was used to investigate the effects of finite inflation/deflation periods. In general, it was found that fast inflation/deflation rates give higher benefits than slow rates. The optimal time to begin inflation is end systole. Timing of deflation was shown to involve a tradeoff between lower end diastolic pressure (achieved with early deflation) and increase of mean diastolic pressure and cardiac output (achieved with late deflation). The model's predictions were validated using a nonlinear distributed parameter digital computer model previously described. The lumped model results should make possible a quantitative as well as a simple approach to automatic control of in-series cardiac assistance.     

Effects of Induced Motor Gestures on Vocal Output

The communicative act is a complex phenomenon involving gestural and expressive, as well as vocal, components. In the present experiment, the relationship between gestural and vocal components was studied by imposing an arbitrary gesture on a speaker and examining its effect on his verbal output. Subjects either performed or viewed a circular or linear gesture, and were required to simultaneously produce either short stories or words in restricted categories. Analysis of the story protocols showed a significant effect of gesture type in both the observed and produced conditions. No such effect was found for word production. These results suggest that meaning was conveyed by the gestures, and that the gestural and vocal systems are not independent during the communicative act. Furthermore, the gesture is capable of constraining the content of vocal output at the ideational level of production (stories), but not at the level of production of individual words.     

CCD片上放大器直流输出电压影响因素分析

对电荷耦合器件(CCD)片上放大器直流输出电压的主要影响因素进行了研究,通过对不同源漏工艺、不同栅下注入剂量工艺条件对直流输出的影响分析,指出有效沟道长度和放大管栅下注入是CCD片上放大器直流输出电压的主要影响因素。     

Theoretical Validation of the Thermal Dilution Method for Cardiac Output Determination

The basic formula of the thermal dilution method for the measurement of cardiac output is proven for pulsatile flow, assuming constant stroke rate, equal stroke volumes, and ideal ventricular mixing. Firstly, for an ideal thermistor of negligible response time which presents the temperature of the blood in the pulmonary artery as a step function; then it is shown that the area under the curve of temperature versus time is independent of the response time of the thermistor; hence, the formula holds for all thermistors.     

Automated Computation of Cardiac Output and Shunts from Indicator Dilution Curves

A method for automatic computation of cardiac outputs using a digital computer program written in FORTRAN IV is presented. The program also computes the ratio of pulmonary to systemic flows so that the dye curve may be used for shunt detection and quantification as well.     

离轴激光雷达几何重叠因子的计算与实验测定

介绍了一台直接探测的用于大气气溶胶测量的离轴激光雷达系统,分别从理论计算和实验测量两方面给出了该激光雷达系统中几何重叠因子的求解方法.结果显示,实验法所得几何重叠因子随距离的分布曲线和理论计算所得结果基本吻合,且实验法所得系统几何重叠因子随距离的分布曲线随日期基本不变,说明所介绍的用于求解系统几何重叠因子的实验方法是可行的.     

A New Technique for Obtaining Values of Cardiac Output in Rapid Succession

Cardiac output was measured in dogs using 5 percent saline as the indicator and a new type of electrically calibrated catheter-tip conductivity cell in the aorta. Paired values of cardiac output were compared using the direct Fick method. It was found that saline cardiac outputs overestimated the Fick values by about 15 percent on the average. Use of the electrically calibrated catheter-tip conductivity cell in the aorta is very easily applied; it does not require special preparation of the indicator or mixing calibration solutions and does not require withdrawal of blood. Cardiac output measurements can be made every few minutes.     

三结GaAs电池损伤对输出特性的影响研究

针对发生损伤后三结GaAs电池的电学特性进行了研究。从三结电池的等效电路模型出发,根据光伏效应相关理论,建立了GaAs三结电池损伤分析模型,具体计算了损伤发生在不同位置时,光电池输出电压、功率、效率的变化。结果表明,顶结发生热熔损伤对电池的电学特性影响最大,将直接导致光电转换效率下降17.23%。中结发生热熔损伤对电池的电学特性影响次之, 将引起4.23%的效率下降。底结损伤对电池的电学特性影响相对最小,所导致的光电转换效率下降量为2.42%。     

Mapping of Cardiac Electrophysiology Onto a Dynamic Patient-Specific Heart Model

Electrophysiological cardiac data mapping is an essential tool for the study of cardiac rhythm disorders, such as atrial fibrillation. Over the past decade, various advanced cardiac mapping systems have been developed to create detailed cardiac maps and assist physicians in diagnosis and therapy guidance. While these systems have increased the ability to study and treat cardiac arrhythmias, inherent limitations exist. The objective of this paper is to describe and evaluate a system that extends current approaches to cardiac mapping, to create a dynamic cardiac map, using patient-specific cardiac models. This paper details novel approaches to collecting a stream of electrophysiological cardiac data, registering the data with patient-specific dynamic cardiac models, and displaying the data directly on the dynamic model surface, giving a more accurate and comprehensive visualization environment when compared to current systems. To validate the system, a series of laboratory and in vivo experiments were conducted. In the laboratory studies, the system was used to test the user's ability to accurately locate a landmark in physical space, as well as their ability to accurately navigate to a virtual location. In the in vivo studies the overall system performance was compared to an existing electrophysiological recording system, where right atrial cardiac maps were created during sinus and paced cardiac rhythms. The results showed that the new dynamic cardiac mapping system was able to maintain high accuracy in locating physical and virtual landmarks, while being able to create a dynamic cardiac map displayed on a dynamic cardiac surface model.      

Source-Field Relationships for Cardiac Generators on the Heart Surface Based on Their Transfer Coefficients

We consider three different types of equivalent sources over a closed surface enclosing all the electrical cardiac generators: the (in situ) potential, the (in situ) normal current density, and the (macroscopic) transmembrane potential on the heart surface. The last equivalent source, which behaves as a double layer, is derived from the bidomain (bisyncytia) model for anisotropic cardiac muscle. This model predicts that if ratios of intracellular to interstitial conductivity along all directions are equal, field potential can be calculated only using surface integrals. The volume integral arising from the tissue anisotropy of cardiac muscle vanishes in that case. For each type of source under study, we give the field potential in a bounded inhomogeneous volume conductor in the form of an integral equation. We also derive the conditions which the lead field (or the transfer coefficients) must satisfy. The in situ potential and normal current are related to the cardiac sources in a complex way, but their lead fields are independent of conductivity of heart muscle, whereas the transmembrane potential is directly involved as a source term, but the lead field depends on the anisotropy of the heart muscle.     

An Algorithm for the Automated Determination of Cardiac Output by the Stewart-Hamilton Method

An algorithm is described for the digital computer determination of cardiac output by the Stewart-Hamilton method. The algorithm is concerned with the choice of a window over which a negative exponential is fitted to the indicator dilution data to eliminate the effects of recirculated indicator. Trials of the algorithm are reported, and it is found to be suitable for clinical use.     

Effects of Resonator Loss on Output Characteristics of Ring Microresonator Filter

The ring microresonator filter considering resonator inner loss is analyzed theoretically, which has one input port and two output ports, Some universal relations for coupling of optical power between microresonator and dielectric waveguides are presented. The analytical expressions of filter bandwidth or the full width at half maximum （FWHM）, free spectral range and finesse of resonator are derived. The characteristics of the ring microresonator filter are discussed numerically. It is demonstrated that the loss of the ring resonator reduces the peak value of transmission, widens the filter bandwidth, and reduces the finesse of the resonator filter.     

电荷泵法研究FLASH擦工作时带带隧穿引起的界面损伤

FL ASH在擦操作的过程中 ,带带隧穿产生的空穴注入将会在 Si O2 / Si O2 界面和氧化层中产生带电中心 (包括界面态和陷阱 ) ,影响电路的可靠性 .利用电荷泵方法 ,通过应力前后电荷泵电流的改变确定出界面态和陷阱电荷的空间分布 ,为 FL ASH单元设计与改进可靠性 ,提供了理论和实验基础     

电荷泵法研究FLASH擦工作时带带隧穿引起的界面损伤

FLASH在擦操作的过程中,带带隧穿产生的空穴注入将会在SiO2/SiO2界面和氧化层中产生带电中心(包括界面态和陷阱),影响电路的可靠性.利用电荷泵方法,通过应力前后电荷泵电流的改变确定出界面态和陷阱电荷的空间分布,为FLASH单元设计与改进可靠性,提供了理论和实验基础.