An Artificial Lens Capsule with a Lens Radial Stretching System Mimicking Dynamic Eye Focusing

Presbyopia is a common eye disorder among aged people which is attributed to the loss of accommodation of the crystalline lens due to the increasing stiffness. One of the potential techniques to correct presbyopia involves removing the lens substance inside the capsule and replacing it with an artificial lens. The development of such devices, e.g., accommodating intraocular lenses (AIOLs), relies on the understanding of the biomechanical behaviour of the lens capsule and the essential design verification ex vivo. To mimic the eye’s dynamic focusing ability (accommodation), an artificial lens capsule (ALC), from silicone rubber accompanied by a lens radial stretching system (LRSS) was developed. The ALC was manufactured to offer a dimension and deforming behaviour replicating the human lens capsule. The LRSS was calibrated to provide a radial stretch simulating the change of diameter of capsules during accommodating process. The biomechanical function of the ALC was addressed by studying its evolution behaviour and reaction force under multiaxial stretch from the LRSS. The study highlighted the convenience of this application by performing preliminary tests on prototypes of ophthalmic devices (e.g., AIOLs) to restore accommodation.

Impact of rotation on the evolution of convective vortices in collapsing stars

We study the impact of rotation on the hydrodynamic evolution of convective vortices during stellar collapse. Using linear hydrodynamics equations, we study the evolution of the vortices from their initial radii in convective shells down to smaller radii where they are expected to encounter the supernova shock. We find that the evolution of vortices is mainly governed by two effects: the acceleration of infall and the accompanying speed up of rotation. The former effect leads to the radial stretching of vortices, which limits the vortex velocities. The latter effect leads to the angular deformation of vortices in the direction of rotation, amplifying their non-radial velocity. We show that the radial velocities of the vortices are not significantly affected by rotation. We study acoustic wave emission and find that it is not sensitive to rotation. Finally, we analyze the impact of the corotation point and find that it has a small impact on the overall acoustic wave emission.

Flow of Magnetohydrodynamic Micropolar Fluid Induced by Radially Stretching Sheets

We investigate the flow of a micropolar fluid between radial stretching sheets. The magnetohydrodynamic (MHD) nonlinear problem is treated using the homotopy analysis method (HAM) and the velocity profiles are predicted for the pertinent parameters. The values of skin friction and couple shear stress coefficients are obtained for various values of Reynolds number, Hartman number, and micropolar fluid parameter.

NORMAL MODE ANALYSIS OF A SINGLE-WALLED CARBON NANOTUBE BASED ON MOLECULAR DYNAMIC: A SINGULAR VALUE DECOMPOSITION STUDY

The complete set of significant normal modes of a single-walled carbon nanotube has been extracted using singular value decomposition analysis of this molecular dynamics data. The first part of this study focuses on an isolated single-walled carbon nanotube performed with NVE Molecular Dynamic simulations. Singular value decomposition analysis is then done on this data. Normal modes are excited with an initial radial stretching given to all the atomic coordinates. For the case with 5% initial radial stretching given to the carbon nanotube, the two strongest modes involve radial breathing motion combined with a very slow rotational motion of individual rings of the nanotube. There is good agreement between the calculated frequency of radial breathing modes and published experimental measurements, as also the inverse scaling of this frequency with tube diameter. The coupling between these two motions weakens for a smaller initial perturbation. The next eight most significant modes are divided into two classes. The first class is characterized by mz = 0, i.e., axial uniformity and produces azimuthal variation in the radial positions of atoms, with a finite azimuthal mode number. The second class of modes has mθ = 0, with mz = 1 and 2, are with radial uniformity and leads to shifts in the X- and Y-centroid locations of different rings. Mode frequency and the associated spatial distortion are thus obtained for all the above-mentioned modes. Under NPT conditions, similar to laboratory conditions, i.e., at a constant temperature and pressure, mode frequencies change only slightly, but the hierarchy of modes is slightly different. External excitation produced at one of the normal mode frequencies, corresponding to centroid motion with (mθ = 0, mz = 1), shows a significant and steady increase in the amplitude of centroid displacement. Excitation at the second harmonic frequency leads to an initial increase in displacement amplitude, but eventual saturation. These conclusions are important for the application of carbon nanotubes in nanodevices, e.g., as nanomotors.