Academic literature on the topic 'Anisotopy'

Purpose of this study was to evaluate with diffusion-tensor imaging (DTI) changes of radial diffusivity (RD) and fractional anisotropy (FA) in the optic nerve (ON) and optic radiation (OR) in glaucoma and to determine whether changes in RD and FA correlate with disease severity. Therefore, glaucoma patients and controls were examined using 3T. Regions of interest were positioned on RD and FA maps, and mean values were calculated for ON and OR and correlated with optic nerve atrophy and reduced spatial-temporal contrast sensitivity (STCS) of the retina. We found, that RD in glaucoma patients was significantly higher in the ON (0.74 ± 0.21 versus 0.58 ± 0.17⋅10−3 mm2 s−1;P<0.05) and OR (0.79 ± 0.23 versus 0.62 ± 0.14⋅10−3 mm2 s−1;P<0.05) compared to controls. Aside, FA was significantly decreased (0.48 ± 0.15 versus 0.66 ± 0.12 and 0.50 ± 0.20 versus 0.66 ± 0.11;P<0.05). Hereby, correlation between changes in RD/FA and optic nerve atrophy/STCS was observed (r>0.77). In conclusion, DTI at 3 Tesla allows robust RD and FA measurements in the ON and OR. Hereby, the extent of RD increase and FA decrease in glaucoma correlate with established ophthalmological examinations.

Using an all-electron, full potential first-principles method, we have investigated the topology of charge density and elastic anisotropy of Ti3SiC2 polymorphs comparatively. By analyzing the charge density topology, it was found that the Ti–Si bonds are weaker in β than in α, resulting in a destabilizing effect and lower Young’s modulus in directions between a and c axes for β. On the other hand, the Si–C bonds (absent in α) are formed in β in the c direction. The formation of the Si–C bonds not only mitigates the destabilizing effect of the weaker Ti–Si bonds, but also results in larger Young’s modulus in the c direction. In contrast to the high elastic anisotrophy, the elastic anisotropy of Ti3SiC2 is very low.

We calculate the angular distribution of cosmic rays at a given point of the heliosphere under the assumption that the incoming flux from outer space is isotropic. The static magnetic field is shown to cause no anisotropy provided that the observation point is situated out of the trapped particle area. We consider a coronal ejection model in the form of a static cylinder with an axial homogeneous magnetic field inside. We calculate angular distribution samples in the trapped particle area (inside the cylinder) and show that there is a certain cone of directions with a reduced flux. For the same model with the moving cylinder, the angular distribution samples are calculated for different positions of the observation point outside the cylinder. Anisotropy of order of the ejection to light velocity ratio is shown to arise. The calculated samples are in qualitative agreement with URAGAN muon hodoscope data.

In this work, a model of the surface layer of perfect single crystals is used and the role of surface energy in physical processes occurring in the region of nanosized carbon materials is clarified. Of these, diamond, graphite, carbyne and fullerenes have been investigated. The thickness of the surface layer of diamond with cubic symmetry is 8.2 nm and is a nanostructure. The average size of the synthesized nanodiamond is of the order of ~ 8 nm. The value of the surface energy σhkl calculated by us along the diamond planes (100), (110), and (111) is in good agreement with experiment and other calculations. The thickness of the surface layer of graphite along the a axis is equal to R(I)a = 8.0 nm and also represents a nanostructure. But along the c axis we have a layer thickness of about 1.5 nm and the number of monolayers is only 2. On this c axis, graphite can be created a monolayer by turning it into graphene. The σhkl value calculated by us along the a and c planes of graphite is 25957 and 5515 mJ/m2 , respectively. Carbines represent a polymeric polyyne or cumulene chain composed of sp-hybridized carbon atoms. If we imagine that the thickness of the surface layer of carbyne is stretched into a one-dimensional chain along the c axis, then the length of this chain is up to 200 nm for α-carbyne. The thickness of the surface layer of fullerenes significantly exceeds the thickness of the surface layer of pure metals. The surface energy of fullerenes σhkl increases with an increase in the number of carbon atoms С36 → С96. It also changes in the series (111) → (100) → (110).