Dynamics of superconducting qubits with exactly solvable bias pulses

The dynamics of a quantum two-state system (qubit) with external control bias pulses of special shapes is considered. The bias pulses represent the potentials for which the Schrödinger equation can be solved exactly. The probability to register a definite direction of the current in a loop and its time-averaged values are calculated for the flux qubit; calculations are performed both analytically and numerically in the presence of relaxation and decoherence within the framework of the density matrix formalism. It is demonstrated that there exist external bias pulses for which the definite current direction probability is a monotonically increasing function of time that approaches a limiting value exceeding 1/2. The probability to find the system in the excited state is calculated, and the possibility of inverse population in a properly driven two-state system is demonstrated given that the relaxation and decoherence rates are small enough.     

Intracavity control of a 200-W continuous-wave Nd:YAG laser by a micromachined deformable mirror

A silicon micromachined membrane deformable mirror with a diameter of 10 mm, reflectivity of better than 99.8%, and a surface deflection range of 3mum has been used for intracavity control of an industrial 200-W cw Nd:YAG laser. When it was placed in the resonator, the mirror demonstrated continuous (more than 40-h) stable operation under an ~550-W cw optical load, with beam diameters in the range 3-6 mm. Periodic modulation of the curvature of the deformable mirror with a frequency of 250 Hz produced quick switching between stable and unstable resonator configurations, which resulted in pulse-period Q -switched generation with average power in the range 50-200 W, modulation depth from 95% to 10%, and an M(2) parameter of 6.5 to 30.     

Activation Radionuclides in the Process of Irradiation of a Niobium Target at the Cyclone 18/9 HC Cyclotrone

Physics of Atomic Nuclei - The accumulation of long-lived radionuclides (LRNs) produced in water [18O]H2O under irradiation at the Cyclone 18/9 HC cyclotron with a niobium target and an input...     

Application of intracellular microelectrophoresis to analysis of the influence of the low-level microwave radiation on electrokinetic properties of nuclei in human epithelial cells

Intracellular microelectrophoresis was applied to investigate the electrokinetic properties of human buccal epithelium cell nuclei after exposure of cells to microwaves of wavelengths of 8 mm (f = 37.5 GHz) and 16 mm (f = 18.75 GHz) at a surface power density of 0.2 mW/cm(2). Irradiated or nonirradiated cells were suspended in a flat microelectrophoretic chamber and exposed to an electric field of 15 V/cm at a current flow of 0.1 mA. The cells, whose nuclei altered their intracellular location towards the anode of the externally applied electric field, were considered to have negatively charged nuclei. The percentage of cells with electrophoretically movable nuclei was determined as the value of electronegativity of cell nuclei (ENN). Microwaves induced changes of ENN during irradiation of 15-60 s. If cells of a donor had an elevated initial level of ENN, it decreased during irradiation. On the contrary, if cells of another donor had a low initial ENN level, irradiation induced ENN increase. No significant difference between the action of microwaves of wavelengths of 8 mm and 16 mm was found. However, microwave irradiation caused an increase in membrane permeability for the in vivo dye indigo Carmine in cells of all donors irrespectively of the initial levels they showed. This suggests that electrokinetic properties of nuclei in cells do not only depend on cell membrane permeability.     

Thresholds for nonlinear recording of fluorescent centers in chromone-doped polymer films

Nonlinear recording of stable fluorescent microstructures in PMMA films doped with photosensitive compound 2-(furan-2-yl)-3-(thiophen-2-carbonyl)-chromen-4-one is investigated. Energy and power density thresholds for recording stable fluorescent marks and for film destruction and photobleaching of the fluorescent marks by laser pulses were measured in wide spectral (from 530 to 620 nm) and temporal (from 80 to 7 ns) ranges. The evidences of the sequential two-step excitation mechanism for the studied dye are presented. It was shown that picosecond pulse duration range is preferable for two-photon data recording. Quasi-Gaussian and donut shaped fluorescent marks with almost the same cross-section were recorded by femtosecond pulses with rather small difference in energies.     

Numerical analysis of the flutter of a shallow shell

The stability of vibrations of a shallow shell that is rectangular in plant in a gas flow is studied for an arbitrary vector of flow velocity. Mathematically, the problem is shown to reduce to an ill-conditioned computational problem. To solve this problem, we propose a numerical saturation-free algorithm that allows one to obtain a sufficiently accurate solution for a grid containing 169 (13×13) nodes. In calculations for cylindrical and spherical shallow shells, new mechanical effects concerning the vibration modes and the dependence of the critical flutter velocity on the direction of the flow-velocity vector were found. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 40, No. 6, pp. 97–102, November–December, 1999.