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- ItemImpedimetric Analysis of Trabecular Bone Based on Cole and Linear Discriminant Analysis(Lausanne : Frontiers Media, 2021) Wei, Wenzuo; Shi, Fukun; Kolb, Juergen F.A spatially unambiguous characterization of electrical properties of osseous tissues is important for the therapy of osteopathy via electrical stimulation. Accordingly, the study aimed to characterize the highly inhomogeneous composition and structures of different anatomical regions of trabecular bone based on their electrical properties. The electrical properties of 64 porcine trabecular bone samples were analyzed in a parallel plate electrode configuration and compared with published results. Therefore, a novel method, combining traditional Cole model with a linear discriminant analysis (LDA), was developed to discriminate the different regions, i.e., femur head, greater trochanter, and femur neck. Possible mechanisms behind the distinction for different regions could be interpreted from both methods. Respective adjacent regions with similar structure and composition could be distinguished from statistically significant differences of Cole parameters, i.e., α (p < 0.01) and R∞ (p < 0.05). The latter was correlated especially with water content, indicating an association of individual differences in microstructures in particular with conductivity. Conversely, different regions were unambiguously discriminated with LDA based on permittivity or conductivity. Contributions to the discrimination were explicitly reflected by the coefficients of the derived LDA features. A clear distinction was obtained especially for a frequency response at 950 kHz. Moreover, predictions for the classification of unspecified samples assigned them correctly to their origin with a success of 92.9%. The combination of both methods offers the possibility for a spatially resolved and eventually patient specific discrimination and evaluation of bone tissues and their response to therapies, notably electrical stimulation.
- ItemSi:P as a laboratory analogue for hydrogen on high magnetic field white dwarf stars(London : Nature Publishing Group, 2013) Murdin, B.N.; Li, J.; Pang, M.L.Y.; Bowyer, E.T.; Litvinenko, K.L.; Clowes, S.K.; Engelkamp, H.; Pidgeon, C.R.; Galbraith, I.; Abrosimov, N.V.; Riemann, H.; Pavlov, S.G.; Hübers, H.-W.; Murdin, P.G.Laboratory spectroscopy of atomic hydrogen in a magnetic flux density of 10 5 T (1 gigagauss), the maximum observed on high-field magnetic white dwarfs, is impossible because practically available fields are about a thousand times less. In this regime, the cyclotron and binding energies become equal. Here we demonstrate Lyman series spectra for phosphorus impurities in silicon up to the equivalent field, which is scaled to 32.8 T by the effective mass and dielectric constant. The spectra reproduce the high-field theory for free hydrogen, with quadratic Zeeman splitting and strong mixing of spherical harmonics. They show the way for experiments on He and H 2 analogues, and for investigation of He 2, a bound molecule predicted under extreme field conditions.