Microsurgery of Cell Membrane with Femtosecond Laser Pulses for Cell Fusion and Optical Injection

We report on results of using femtosecond laserscalpel for microsurgery of plasma membrane ofliving cells. Femtosecond laser pulses were appliedto initiate cell fusion as well as to performreversible permeabilization of cell membranerequired for efficient injection of extrinsicsubstances into the target cells. Laser-based cellfusion of mammalian embryo blastomeres as wellas fusion of cell bodies of neurons of molluskLymnaea stagnalis were successfully carried out byapplying single femtosecond laser pulses (secondharmonic of a Cr:Forsterite laser system) 620 nm,100 fs with the fluences of 0.42-0.71 J/cm2. It wasshown that the fusion of cells was completed within5-60 minutes depending on the cell type. Successfulpermeabilization of a cell membrane andoptoinjection of a membrane impermeable dye wasperformed with the help of a compact laser systemfor cell microsurgery DissCell-F (ytterbium laser,1050 nm, 75 MHz, ~115 fs). In both cases the laserirradiation parameters were thoroughly optimized toachieve high viability of treated cells and highefficiency of the procedures of cell fusion andoptical injection

Electronic and magnetic properties of [Fe(3-MeO-Qsal)2]Y•n solvent (n = 0,1) complexes

[Fe(3-MeO-Qsal)2]Y (Y = PF6, BF4, NCS, NO3, BPh4) compounds were synthesized using the diffusion method and studied by the electron spin resonance and the magnetic susceptibility methods in the temperature range (5-300) K. Coexistence of spatially separated high-spin and low-spin fractions in these compounds was observed. Low-spin fraction of all compounds reveals the antiferromagnetic correlations at low temperatures. High-spin fraction of complexes with Y = PF6 demonstrate the weak ferromagnetic properties due to exchange interaction between complexes in whole temperature range. Influence of outer-sphere anion on the spin state, the electronic properties of low-spin Fe(III) complexes is demonstrated

Compensation of a Relative Drift of Satellites due to the Earth Oblateness by Low-Thruster with a Given Direction

Abstract: The preprint is devoted to control algorithm development to nullify a relative secular drift due to the Earth oblateness in Formation Flight motion. It is assumed a chief satellite orbit to be circular and its orbit not to be controlled to maintain the formation. Deputy satellite is equipped with a passive magnetic attitude control system with permanent magnet alongwith the principal inertia axis and low-propulsion thruster alongwith the same direction. The investigation how to eliminate the relative secular drift by a limited control is carried out. The limitation consists in a constraint of direction and magnitude of feasible control. In the present work the control to eliminate the relative secular drift is analytically developed. Analytical results are approved by numerical simulation of the satellite motion like the first Russian nanosatellite TNS-0 N1.Note: Research direction:Theoretical and applied problems of mechanic

Spin crossover properties of Fe(III) complexes in [Fe (bzacen)(tvp)]BPh<inf>4</inf>·nSolv chain structures: EPR study

© 2020 John Wiley & Sons, Ltd. Two types of Fe(III) polynuclear iron(III) 1D-chain coordination compounds of the general formula [Fe (L)(tvp)]BPh4 nSolv, where L = dianion of N,N′-ethylenebis (benzoylacetylacetone)2,2′-imine (bzacen), tvp = 1,2-di(4-pyridyl)ethylene were synthesized and studied by the electron paramagnetic resonance (EPR) and magnetic susceptibility methods in the temperature range (100–300) К. Two types of spin-variable complexes are formed depending on the time of precipitation of the complexes from the same solution leading to differently solvated species. They have different characteristics of the local ligand field and the spin transition behavior. The thermodynamic parameters of spin transitions were determined from the temperature dependence of the EPR signals integral intensity. The energy levels splitting values obtained by analyzing g-factors of low-spin Fe(III) centers evidenced not only on the crucial role of low-symmetry distortions on the principal possibility of spin-crossover processes, but also on the temperature peculiarities of spin transitions

How to optimize preconditioners for the conjugate gradient method: a stochastic approach

Abstract: The conjugate gradient method (CG) is usually used with a preconditioner which improves efficiency and robustness of the method. Many preconditioners include parameters and a proper choice of a preconditioner and its parameters is often not a trivial task. Although many convergence estimates exist which can be used for optimizing preconditioners, they typically hold for all initial guess vectors, reflecting the worst convergence rate. To account for the mean convergence rate instead, in this paper, we follow a simple stochastic approach. It is based on trial runs with random initial guess vectors and leads to a functional which can be used to monitor convergence and to optimize preconditioner parameters in CG. Presented numerical experiments show that optimization of this new functional usually yields a better parameter value than optimization of the functional based on the spectral condition number.Note: Research direction:Programming, parallel computing, multimedi

Determination of Parameters of the Laboratory Facility for Testing of Magnetic Hysteresis Damper

Abstract: Laboratory facility which comprises a string suspended disk with permanent magnet and hysteresis rod located within an external artifical magnetic field is considered. The analysis of motion equation of the disc was developed in a framework of three hysteresis models for the rod. They are: Rayleigh model, “parallelogram” model and “saturated” model. Required parameters of the models are estimated for 4-79-permalloy. The algorithm which allows us to compute an allowable factor of the air viscosity friction according to the given external magnetic field intensity and vice versa is developped. It is shown that an appropriate choice of the external magnetic field intensity can provide domination of the hysteresis decrement from the rod over the decrement due to viscous friction of the disc on air, and thus we can simulate the satellite attitude dynamics in laboratory environment.Note: Research direction:Theoretical and applied problems of mechanic