The movements of two ultrasound echo signals, believed to arise from the anterior mitral leaflet and from the mitral ring, were studied in 30 normal subjects and in 100 heart-catheterization patients. Fifty patients had proven mitral stenosis. The echo from the anterior mitral leaflet is shown to have a complex pattern of movement. This pattern is analyzed into the opening and closing movements...

Tracheoesophageal speakers can achieve speech without digital occlusion by using a tracheostoma valve. Laryngectomized patients who are successful with this device can regain considerable freedom. However, little is known about which valve suits the patient best. Valve aerodynamics may give a guideline for its use. Three major tracheostoma valves, each divided into four subtypes, were repeatedl...

It is a matter of force. It is a balance of valve closing force and tethering force that affects mitral valve coaptation. Ischemic mitral regurgitation develops secondary to left ventricular dysfunction generally with structurally normal leaflets. However, it seems it is not simply a matter of force when we see the fact that valve leaflets histologically change after myocardial infarction. The ...

An implantable manually-actuated drug delivery device, consisting of a refillable drug reservoir, flexible cannula, check valve, and suture tabs, was investigated as a new approach for delivering pharmaceuticals to treat chronic ocular diseases. Devices are fabricated by molding and bonding three structured layers of polydimethylsiloxane. A 30 gauge non-coring needle was used to refill the rese...

Due to their ease of fabrication, facile use and low cost, ice valves have great potential for use in microfluidic platforms. For this to be possible, a rapid response speed is key and hence there is still much scope for improvement in current ice valve technology. Therefore, in this study, an ice valve with enhanced thermal conductivity and a movable refrigeration source has been developed. An...

Doubt has been cast upon the valvular origin of the first heart sound since the finding of a delay between the cross-over of the ventricular and atrial pressure tracings and the sound attributed to closing ofthe corresponding atrio-ventricular valve. There is a similar delay after the left ventricular pressure falls below that in the left atrium before the occurrence of the opening snap in mitr...

Analytical solutions to the time-dependent, nonlinear equation governing incompressible, one dimensional flow in a pipe are presented. The flow is pressure-driven, and a valve on the pipe controls the flow rate. Power-law losses and an exponential closing action of a valve are assumed. Four different approximation methods are used. Of these, perturbation and Adomian’s decomposition are seen to ...

ABSTRACT Stringent NOx and particulate emission constraints require high levels of exhaust gas recirculation. In this paper we model and analyze a Variable Valve Timing methodology that in steady-state achieves large levels of internal Exhaust Gas Recirculation (iEGR) or residual charge in Compression Ignition Direct Injection (CIDI) engines. Current external Exhaust Gas Recirculation (eEGR) te...

In support of our disruption mitigation profram, a fast gas valve has been constructed and tested on TEXTOR at FZJ Juelich. Its main features have been shown to be: ~1! rapid response time: 0.5 ms; ~2! amount of injected gas: variable, 2–1000 mbar3l; ~3! linear dependence of the number of injected particles on the gas pressure; ~4! capability of working in a strong magnetic field; ~5! sort of g...

Motion and position of both mitral leaflets were studied in five normal dogs 1-11 wk after radiopaque markers were sutured on the valve cusps and on the mitral annulus. Cinefluorograms and cineangiograms (100-120 frames/s) of left atrium and left ventricle were used to study cusp motion and intraventricular flow patterns, and to detect mitral regurgitation during sinus rhythm (42-184 beats/min)...