Matthew Nielsen

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To analyze neural activity using magnetoencephalography (MEG) and functional magnetic resonance imaging (fMRI), we developed a method for fixing equivalent current dipoles of MEG in activation areas of fMRI. It includes a procedure for dividing large fMRI activation volumes into subvolumes in each of which a dipole is placed and another procedure for(More)
RF pulsewidth modulation (PWM) has been proposed as an efficiency improving technique for power amplifiers (PAs) handling varying envelope signals. The core idea is to modulate the varying envelope into a square-wave signal such that the width of each pulse is varied according to the envelope, and any phase information is contained in the timing of the(More)
This paper presents the design of a RF pulse width modulator (RF-PWM) for switched-mode power amplification of varying envelope signals. The general idea is to modulate the varying envelope signal using squarewave signals with varying width and subsequently drive a class D-type power amplifier. The linearity in the modulator is ensured by a novel(More)
The COFIN project studied existing remote-sensing Lidar data on concentration fluctuations in atmospheric dispersion from continuous sources at ground level. Fluctuations are described by stochastic models developed by a combination of statistical analyses and surface-layer scaling. The statistical moments and probability density distribution of the(More)
Nitric oxide (NO) is an ubiquitous signaling molecule of intense interest in many physiological processes. Nitric oxide is a highly reactive free radical gas that is difficult to deliver with precise control over the level and timing that cells actually experience. We describe and characterize a device that allows tunable fluxes and patterns of NO to be(More)
PURPOSE To evaluate the apparent diffusion coefficient (ADC) of skeletal muscle based on signal intensity (SI) attenuation vs. increasing b values and to determine ADC differences in skeletal muscles between genders, age groups and muscles. MATERIALS AND METHODS Diffusion-weighted images (b values in the range of 0-750 s/mm2 at increments of 50 s/mm2) of(More)
Wind vector observations from 85 ERS-2 SAR using CMOD4, and daily wind vector maps for five years from the Quikscat scatterometer archive at IFREMER/CERSAT are used to estimate wind patterns near the Horns Rev wind farm located in the North Sea, Denmark. At this site a large offshore wind farm (80 2MW-turbines) is in operation. The study includes spatial(More)
1 Introduction Since MEG and EEG inverse problems are "ill-posed" (i.e., solutions cannot be uniquely determined), additional information such as fMRI and PET activation data can be used to impose additional constraints [1]-[6]. For example, fMRI data were used to fix the locations of equivalent current dipoles at activation areas [1][2][5] or to give(More)