A method is introduced for the spectral analysis of complex noisy signals containing several frequency components. It enables components that are independent to be distinguished from the harmonics of nonsinusoidal oscillatory processes of lower frequency. The method is based on mutual information and surrogate testing combined with the wavelet transform, and is applicable to all situations where complex signals are encountered, including applications in astrophysics, engineering, and electrical circuits, as well as physiology and biology.
COBISS.SI-ID: 8318804
The adhesion of cells to a nanorough titanium implant surface with sharp edges is considered. The basic assumption was that the attraction between the negatively charged titanium surface and a negatively charged osteoblast is mediated by charged proteins with a distinctive quadrupolar internal charge distribution. It is concluded that osteoblasts are most strongly bound along the sharp convex edges or spikes of nanorough titanium surfaces where the magnitude of the negative surface charge density is the highest.
COBISS.SI-ID: 8562772
A number of methods were proposed to measure sagittal vertebral inclination (SVI) in lateral radiographic projections in the form of spinal curvature or segmental angulation. A systematic analysis of the manual and computerized measurements in sagittal computed tomography (CT) cross-sections has not been performed yet. In this study, SVI was systematically evaluated for 28 vertebrae in CT images by three observers using six manual and two computerized measurements. Manual measurements were obtained in sagittal cross-sections by manually identifying the vertebral body corners, which defined the lines of SVI (superior and inferior tangents, anterior and posterior tangents, mid-endplate and mid-wall lines) against reference horizontal or vertical lines. Computerized measurements were obtained by manually identifying the vertebral centroids, which initialized an automated method that evaluated SVI by searching for the planes of maximal symmetry of vertebral bodies in two dimensions (2D) and in three dimensions (3D). The mid-wall lines proved to be the most reproducible and reliable manual measurements (1.0 degree and 1.4 degrees standard deviation, SD). The computerized measurements in 3D were more reproducible and reliable (0.9 degrees and 1.3 degrees SD) and also most consistent with the mid-wall lines (2.1 degrees SD and 1.7 degrees mean absolute difference, MAD). In terms of speed and operator-friendliness, the computerized measurements may represent an adequate alternative to manual measurements.
COBISS.SI-ID: 8373332