Anders Helgeland

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Line integral convolution (LIC) is a powerful texture-based technique for visualizing vector fields. Due to the high computational expense of generating 3D textures and the difficulties of effectively displaying the result, LIC has most commonly been used to depict vector fields in 2D or over a surface in 3D. We propose new methods for more effective volume(More)
In this paper, we present an interactive texture-based method for visualizing three-dimensional unsteady vector fields. The visualization method uses a sparse and global representation of the flow, such that it does not suffer from the same perceptual issues as is the case for visualizing dense representations. The animation is made by injecting a(More)
BACKGROUND AND PURPOSE The Chiari I malformation, characterized by tonsils extending below the foramen magnum, has increased CSF velocities compared with those in healthy subjects. Measuring the effect of tonsillar herniation on CSF flow in humans is confounded by interindividual variation. The goal of this study was to determine the effect of herniated(More)
Right: Volume rendering of hurricane data at time (t = 44) in the simulation. This roughly corresponds to the time in the left image. ABSTRACT To provide an effective visualization of three-dimensional time-varying vector fields is one of the current challenges in scientific visualization. In this poster, we propose and study methods and strategies for more(More)
In 23 hypertensive men, aged 47-55, propranolol reduced serum high-density-lipoprotein (HDL) cholesterol by 13% reduced the ratio of HDL to low-density-lipoprotein (LDL)+very-low-density-lipoprotein (VLDL) cholesterol by 15%, increased total triglycerides by 24%, and increased serum uric acid by 10%. Prazosin reduced total serum cholesterol by 9%, LDL+VLDL(More)
Coronary heart-disease (C.H.D.) had been reviewed as a "manager's disease". However, deaths from C.H.D. are now said to be more common in groups from the lower social classes than in those of higher socioeconomic status. We have examined wheather these differences in C.H.D. mortality can be explained by differences in the conventional risk factors for C.H.D.
This study was initiated by the scientifically interesting prospect of applying advanced visualization techniques to gain further insight into various spatio-temporal characteristics of turbulent flows. The ability to study complex kinematical and dynamical features of turbulence provides means of extracting the underlying physics of turbulent fluid motion.(More)
OBJECT The effect of craniovertebral decompression surgery on CSF flow dynamics in patients with Chiari malformation Type I (CM-I) has been incompletely characterized. The authors used computational fluid dynamics to calculate the effect of decompression surgery on CSF flow dynamics in the posterior fossa and upper cervical spinal canal. METHODS(More)
BACKGROUND AND PURPOSE CSF fluid dynamics in healthy subjects and patients with Chiari I have been characterized during rest with phase-contrast MR imaging and CFD. CSF flow velocities and pressures in the nonresting state have not been adequately characterized. We used computer simulations to study CSF dynamics during increased heart rates in the normal(More)
Enalapril, atenolol, and hydrochlorothiazide were compared in a double-blind randomised parallel study in general practice. 436 patients with mild to moderate hypertension were included at 76 centres. A two-week placebo run-in period was followed by 16 weeks of monotherapy. The initial doses were: enalapril 20 mg; atenolol 50 mg; and hydrochlorothiazide 25(More)