Physical model for effects of microwaves on nucleoids in living cells: role of carrier frequency, modulation and DC and AC magnetic field

The effect of static and alternating magnetic fields on the conformation of nucleoids in cells of different types is considered. The model of slow and nonuniform rotation of the charged DNA domain is used. An equation is obtained for the resonance frequencies of the alternating magnetic field.

Stick-slip nonuniform rotation distortion correction in distal scanning optical coherence tomography catheters

We present a robust and fiducial-marker-free algorithm that can identify and correct stick-slip distortion caused by nonuniform rotation (or beam scanning) in distally scanned catheters for endoscopic optical coherence tomography (OCT) images. This algorithm employs spatial frequency analysis to select and remove distortions. We demonstrate the feasibility of this algorithm on images acquired from ex vivo rat colon with a distally scanned DC motor-based endoscope. The proposed algorithm can be applied to general endoscopic OCT images for correcting nonuniform rotation distortion.

Stability of synchronous regimes in unbalanced rotors on elastic base

The stationary dynamics of an unbalanced rotor (vibrator) on a movable base (linear oscillator) under excitation by a driving torque is studied with focusing on the stability of 1:1 stationary regimes of rotation and oscillation. This problem was well studied previously in the first approximation, dealing, in fact, with averaged regimes, mainly in the framework of asymptotic procedures. We use an efficient analytical procedure, proposed in our previous works for another problem, which sequentially separates the averaged regimes and deviations from them. Describing in the first approximation the known features of the synchronous stationary regimes under consideration, this approach in the second approximation results in the analytical solution for nonuniform rotation whose exactness is confirmed in the numerical simulation. The solution enables us to reveal possibility of parametric instability for oscillations of the rotor angular velocity and to describe two possible mechanisms of this instability. It is shown that the known condition of stability of stationary synchronous rotation-oscillation regimes is only necessary but not sufficient criterion, and two additional necessary conditions of stability are obtained and confirmed by the numerical simulation.