Robert W. Johnson

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Fast changing, increasingly complex, and diverse computing platforms pose central problems in scientific computing: How to achieve, with reasonable effort, portable optimal performance? We present SPIRAL that considers this problem for the performance-critical domain of linear digital signal processing (DSP) transforms. For a specified transform, SPIRAL(More)
We discuss the design and implementation of a compiler that translates formulas representing signal processing transforms into efficient C or Fortran programs. The formulas are represented in a language that we call SPL, an acronym from Signal Processing Language. The compiler is a component of the SPIRAL system which makes use of formula transformations(More)
SPIRAL is a generator for libraries of fast software implementations of linear signal processing transforms. These libraries are adapted to the computing platform and can be re-optimized as the hardware is upgraded or replaced. This paper describes the main components of SPIRAL: the mathematical framework that concisely describes signal transforms and their(More)
The passive permeability of isolated chromaffin vesicles to H+ and the internal pH of the vesicles under various conditions were measured. Potentiometric measurements of K+ and H+ fluxes in the presence of selected ionophores and uncouplers indicated that the membrane is highly impermeable to both protons and potassium. deltapH across the chromaffin granule(More)
Sensory processing deficits are a hallmark of schizophrenia and can be demonstrated by recording auditory evoked potentials (AEPs) elicited in response to closely paired click stimuli. In nonschizophrenic humans, as well as in rats, the amplitude of the response to the second click is reduced (filtered) compared with the first. In contrast, schizophrenics,(More)
Diminished evoked response to repeated auditory stimuli, an example of sensory gating normally present in human subjects, is often absent in schizophrenics. To examine the mechanism of the normal response and to delineate possible sites of its abnormality in psychosis, it would be desirable to reproduce the phenomenon in laboratory animals. In this study,(More)
INTRODUCTION This study evaluated whether cyclosporine (CsA) could be eliminated from a sirolimus (Rapamune, rapamycin, SRL)-CsA-steroid (ST) regimen at 3 months. METHODS This was an open-label study conducted in Europe, Australia, and Canada. Upon enrollment, 525 primary (90%) or secondary (10%) renal allograft recipients with cadaveric (89%) or living(More)
A new classification method for CT/discography was developed. The Dallas discogram description (DDD) related five separate categories of information. Degeneration and annular disruption were regarded as separate phenomena. Additionally, provoked pain response, contrast volume, and miscellaneous information were recorded. Discogram findings of 59 patients(More)
The effect of the transmembrane potential (delta psi) and the proton concentration gradient (delta pH) across the chromaffin granule membrane upon the rate and extent of catecholamine accumulation was studied in isolated bovine chromaffin granules. Freshly isolated chromaffin granules had an intragranular pH of 5.5 as measured by [14C]methylamine(More)
We have investigated those factors which influence the range of movement after total knee arthroplasty, including sex, age, preoperative diagnosis and preoperative flexion deformity and flexion range. We also compared cemented and cementless tibial fixation, the influence of collateral ligament and lateral parapatellar releases and of replacement of the(More)