Mark W. Keller

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BACKGROUND Although it has been demonstrated in short-term preparations that ischemia with early reperfusion results in coronary vascular injury manifested by abnormal endothelium-dependent relaxation and increased permeability to plasma proteins, it has not been clear whether these abnormalities are permanent or reversible. METHODS AND RESULTS In a(More)
The purpose of this study was to determine whether the behavior of sonicated albumin microbubbles accurately mimics red blood cell flow in the microcirculation and is thus consistent with their use as in vivo tracers of red blood cell flow during myocardial contrast echocardiography. Accordingly, microbubbles prepared from fluorescein-conjugated albumin and(More)
BACKGROUND This prospective study was designed to test the hypothesis that the assessment of left ventricular systolic function at the time of emergency room (ER) presentation provides valuable diagnostic and prognostic information in patients with cardiac-related symptoms. METHODS AND RESULTS The study is based on a 2-year follow-up of 171 consecutive(More)
We derive equations for the phase noise spectrum of a spin torque oscillator in the macrospin approximation for the highly symmetric geometry where the equilibrium magnetization, applied field, anisotropy, and spin accumulation are all collinear. This particular problem is one that can be solved by analytical methods, but nevertheless illustrates several(More)
We have fabricated ballistic cavities from a two-dimensional GaAs electron gas in which the Fermi energy can be varied independent of cavity shape. For each cavity, we have measured the magnetoconductance G(B) of many individual members of an ensemble, with each member labeled by its Fermi energy. We find that G(B) of a single ensemble member does not(More)
This article describes the production, analysis, and reproducibility of forming microbubbles for contrast ultrasound imaging. The sonication method used to generate microbubbles was tested by four independent observers, and a subsequent laser particle counter analysis of microbubble size and concentration determined the reproducibility of the method. The(More)
A single-electron transistor (SET) is used to detect tunneling of single electrons into individual InGaAs self-assembled quantum dots (QDs). By using an SET with a small island area and growing QDs with a low density we are able to distinguish and measure three QDs. The bias voltage at which resonant tunneling into the dots occurs can be shifted using a(More)
We have fabricated single-Cooper-pair transistors in which the spatial profile of the superconducting gap energy was controlled by oxygen doping. The profile dramatically affects the switching current vs gate voltage curve of the transistor, changing its period from 1e to 2e. A model based on nonequilibrium quasiparticles in the leads explains our results,(More)
—We have developed a seven-junction electron pump for use in a new standard of capacitance based on measuring the voltage produced when a known charge is placed on a capacitor. This new pump, with an error per pumped electron of 152 2 210 09 , is about 30 times more accurate than a five-junction pump made previously at NIST. By careful design of the pump(More)