This paper presents a new generation of compliant piezoelectric microconveyers for microobjects based on the cooperation of arrayed direct-drive standing wave ultrasonic actuators. A method using an equivalent electromechanical circuit is proposed for estimating and analysing the optimum driving force. On the basis of the proposed method, the friction drive optimization of the micro-robot is pe...

Afterload-induced changes in myocardial relaxation are a mechanism for diastolic dysfunction when afterload is elevated beyond certain limits. The present study investigated the effects of acute afterload and preload changes on the position of the end-diastolic (ED) pressure-volume (P-V) relation. Beat-to-beat afterload elevations were induced in seven open-chest rabbits by gradually occluding ...

We studied the effect of an isolated increase in preload on isovolumetric relaxation in the intact dog heart and isometric relaxation in isolated cardiac muscle (dog and rat) preparations. In eight anesthetized dogs, 8 to 12 ml of blood was infused into the left ventricle during a single diastole. The exponential time constant (T) of isovolumetric relaxation was measured in single-beat experime...

BACKGROUND Monitoring of cardiac preload by determination of pulmonary artery occlusion pressure (PAOP) has been traditionally used to guide fluid therapy to optimize cardiac output (CO). Since factors such as intrathoracic pressure and ventricular compliance may modify PAOP, volumetric estimators of preload have been developed. The PiCCO system is able to measure CO and intrathoracic blood vol...

Significant differences exist among textbook definitions for the terms preload and afterload, leading to confusion and frustration among students and faculty alike. Many faculty also chose to use in their teaching simple terms such as "end-diastolic volume" or "aortic pressure" as common-usage approximations of preload and afterload, respectively, but these are only partial representations of t...

STATEMENT OF PROBLEM Loosening or fracture of the abutment screw are frequent complications in implant dentistry and are detrimental to the long-term success of the restorations. However, little is known about the factors influencing the stability of the screw-abutment complex. PURPOSE The purpose of this study was to investigate the influence of lubricant action during implant assembly on sc...

In tissue the Young’s modulus cannot be assumed constant over a wide deformation range. For example, direct mechanical measurements on human prostate show up to a threefold increase in Young’s modulus over a 10% deformation. In conventional elasticity imaging, these effects produce strain-dependent elastic contrast. Ignoring these effects generally leads to suboptimal contrast (stiffer tissues ...

Many studies have been carried out to determine the performance of energy dissipators proposed by different authors, mainly analyzing hysteretic loops loading and unloading. Likewise, authors sought simple, easy manufacture economical designs. Based on above, analysis a passive bidirectional dry friction dissipator system is presented, whose main characteristic implementation layer elements as ...

Using a multielectrode conductance catheter to estimate continuous left ventricular volume we determined the end-systolic pressure-volume relationship (ESPVR) in situ in open-chest anesthetized dogs. Dogs (n = 8) were studied in the control state and after pharmacologic sympathectomy (hexamethonium) and surgical vagotomy both before and after the administration of dobutamine. ESPVR was measured...

BACKGROUND Assessment of cardiac preload is important for clinical management of some emergencies related to hypovolemia. Effects of acute simulated hypovolemia on Doppler blood flow velocity indices of tricuspid valve (TV) and superior vena cava (SVC) were investigated in order to find sensitive Doppler indices for predicting right ventricular preload. METHODS Doppler flow patterns of SVC an...