Analysis of normal human retinal vascular network architecture using multifractal geometry

AIM: To apply the multifractal analysis method as a quantitative approach to a comprehensive description of the microvascular network architecture of the normal human retina. METHODS: Fifty volunteers were enrolled in this study in the Ophthalmological Clinic of Cluj-Napoca, Romania, between January 2012 and January 2014. A set of 100 segmented and skeletonised human retinal images, corresponding to normal states of the retina were studied. An automatic unsupervised method for retinal vessel segmentation was applied before multifractal analysis. The multifractal analysis of digital retinal images was made with computer algorithms, applying the standard box-counting method. Statistical analyses were performed using the GraphPad InStat software. RESULTS: The architecture of normal human retinal microvascular network was able to be described using the multifractal geometry. The average of generalized dimensions (Dq) for q=0, 1, 2, the width of the multifractal spectrum (Δα=αmax - αmin) and the spectrum arms’ heights difference (│Δf│) of the normal images were expressed as mean±standard deviation (SD): for segmented versions, D0=1.7014±0.0057; D1=1.6507±0.0058; D2=1.5772±0.0059; Δα=0.92441±0.0085; │Δf│= 0.1453±0.0051; for skeletonised versions, D0=1.6303±0.0051; D1=1.6012±0.0059; D2=1.5531± 0.0058; Δα=0.65032±0.0162; │Δf│= 0.0238±0.0161. The average of generalized dimensions (Dq) for q=0, 1, 2, the width of the multifractal spectrum (Δα) and the spectrum arms’ heights difference (│Δf│) of the segmented versions was slightly greater than the skeletonised versions. CONCLUSION: The multifractal analysis of fundus photographs may be used as a quantitative parameter for the evaluation of the complex three-dimensional structure of the retinal microvasculature as a potential marker for early detection of topological changes associated with retinal diseases

Statistics of interatomic Ni-Ni bonds in Ni-based ternary solid solutions with non-magnetic elements and their magnetic behaviour

The drop of ferromagnetic moment in the ternary solid solutions Ni1-x-yCuxDy, (D = Zn, Si, Au, Al) is analyzed in terms of the statistical model of the environment-dependent moments. This probabilistic model shows that the disappearing of one Ni atom ferromagnetic moment can be assigned to the replacement of at least four Ni–Ni bindings, out of twelve, in pure nickel. This paper aims at discussing all these features that, from the point of view of macroscopic equilibrium states, are related to the distribution of local bonds, provided by the peripheral electrons of the substitute atoms dissolved in the Ni matrix

Characterization of a Simulated Martian Regolith Ecosystem by Proton Nuclear Magnetic Resonance (NMR) Relaxometry and Fourier Transform Infrared (FT-IR) and Visible (VIS)-Near-Infrared (NIR) Spectroscopies

Of the various Martian soil simulant mixes developed by NASA and Jet Propulsion Laboratory (JPL), three types were chosen that have the closest features to those of the Martian regolith to be analyzed. The characterization of the Martian regolith types was performed the advanced methods of 1H nuclear magnetic resonance (NMR) relaxometry, Fourier transform infrared (FT-IR) spectroscopy and visible (VIS)-near-infrared (NIR) spectroscopy, as well as classical methods such as pH, the electrical conductivity, and the total dissolved solids. These analyses showed that trace water, nitrogen, phosphorus and potassium are present in the Martian regolith simulant. A Martian Garden has been built with the Martian soils, in which various vegetables have been seeded. Among the Fourier Transform infrared (FT-IR) spectra acquired for the plants, a high degree of similarity was observed, which indicates that the substrate ‘Martian regolith simulant of terrestrial soil’ does not significantly influence the structure of the radish, peas and bean leaves, stems, or roots. Nevertheless, the results of 1D 1H nuclear magnetic resonance (NMR) relaxometry indicate that the substrate presents a high influence on the water dynamics in plant pores at the level of roots, stems and leaves and in bound water. A Marsarium was designed and built, where all types of Martian and terrestrial soils were introduced, together with a family of ants. The ants adapted to the imposed conditions, as they dug tunnels in the soils

Fourier and Laplace-like low-field NMR spectroscopy: The perspectives of multivariate and artificial neural networks analyses

Low field Nuclear Magnetic Resonance (LF-NMR) is a rich source of information for a wide range of samples types. These can be hard or soft solids, such as plastics or elastomers; bulk liquids or liquids absorbed in porous materials, and can come from biomaterials, biological tissues, archaeological artifacts, cultural heritage objects. LF-NMR instruments present a significant advance especially for in situ, ex situ and in vivo measurement of relaxation and diffusion. Moreover, high resolution 1D and 2D spectroscopy, as well as magnetic resonance (MR) imaging are available in these fields. In this work we discuss the advanced analysis of the data measured in LF-NMR from the perspectives of tertiary level that implies the analysis on principal components (PCA), and on the quaternary analysis that uses an artificial neural network (ANN). The principles of PCA and ANN are largely discussed. For the PCA analysis, a series of 52 spectra were analyzed, having been recorded in vivo by LF-NMR. Of these spectra, 38 were generated from normal uterus, 7 by uterus tissue with endometrial cancer, and another 7 were obtained from tissues of women with uterine cervical cancer. The PC1 vs PC2 plot was further analyzed using an artificial neural network, and the results are presented as 2D maps of probability. Furthermore, the perspectives of applying an ANN to solve the problem of Laplace-like inversion are discussed. An example of such ANN was presented and the performance was discussed. Finally, a model of complex ANN, capable to sequentially solve this kind of problems specific to LF-NMR is proposed and discussed