Stochastic Dynamics of Magnetosomes in Cytoskeleton

Rotations of microscopic magnetic particles, magnetosomes, embedded into the cytoskeleton and subjected to the influence of an ac magnetic field and thermal noise are considered. Magnetosome dynamics is shown to comply with the conditions of the stochastic resonance under not-too-tight constraints on the character of the particle's fastening. The excursion of regular rotations attains the value of order of radian that facilitates explaining the biological effects of low-frequency weak magnetic fields and geomagnetic fluctuations. Such 1-rad rotations are effectively controlled by slow magnetic field variations of the order of 200 nT.Comment: LaTeX2e, 7 pages with 3 figure

Field dependence of spin-lattice relaxation of Nd3+ ions in y3Al5O12 crystals

Our studies involve measuring spin-lattice relaxation times for Nd3+ ions in yttrium-aluminum garnets over the temperature range 4-50 K at 9.25 and 36.4 GHz for different orientations of the external magnetic field in relation to the crystallographic axes. The temperature dependence of the relaxation rate is described by T1 -1=ATn + b exp(-ΔAT), where n varies from sample to sample, with n=1 for "perfect" samples (i.e., with the longest relaxation times). Here A is approximately 130 cm-1, which is the energy of the excited Kramers doublet of the neodymium ion closest to the ground state, and this makes it possible to interpret the second term in T1 -1 as the contribution of two-stage relaxation proceeding through the intermediate level Δ. A strong field dependence of these processes has been discovered: when the frequency was increased fourfold, the relaxation rate increased by a factor of 10. The effect is a specific manifestation of the degeneracy of the excited level, breaking of the symmetry of the crystalline field due to lattice defects, and the prevalence of deformations of a certain type in the spin-lattice interaction. ©1997 American Institute of Physics

High temperature superconductivity at the interface Ba0.8Sr0.2TiO3/La2CuO4

The reported study was funded by Russian Scientific Foundation, research project No. 18-12-00260

Investigation of high conductivity area at the interface between Ba0.8Sr0.2TiO3 and LaMnO3 after effect of electric field on Ba0.8Sr0.2TiO3 ferroelectric film

The reported study was funded by Russian Scientific Foundation, research project No. 18-12-00260

Effect of magnetic field on high conductivity area at the interface of heterostructure Ba0.8Sr0.2TiO3/LaMnO3

The reported study was funded by Russian Scientific Foundation, research project No. 18-12-00260

Single Electron Spin Decoherence by Nuclear Spin Bath: Linked Cluster Expansion Approach

We develop a theoretical model for transverse dynamics of a single electron spin interacting with a nuclear spin bath. The approach allows a simple diagrammatic representation and analytical expressions of different nuclear spin excitation processes contributing to electron spin decoherence and dynamical phase fluctuations. It accounts for nuclear spin dynamics beyond conventional pair correlation models. As an illustration of the theory, we evaluated the coherence dynamics of a P donor electron spin in a Si crystal.Comment: 37 pages, 13 figure

Experimental Substantiation of Feasibility of Using Enzymatic Fibrin Hydrolyzate-Based Medium to Obtain Components of Chemical Cholera Vaccine

The aim of the study was to experimentally substantiate the possibility of using a nutrient medium based on enzymatic fibrin hydrolyzate in order to obtain specific components of chemical cholera vaccine: cholerogen-anatoxin and O-antigen. Materials and methods. We used production strains of Vibrio cholerae 569B and V. cholerae M-41. Submerged low-volume cultivation was carried out in a laboratory fermenter for 8 hours, with automatic maintenance of cultivation parameters and feeding with glucose on the nutrient medium based on enzymatic fibrin hydrolyzate, containing (1.0±0.1) g/l of amine nitrogen, pH being (8.0±0.1). Cholerogen-anatoxin and O-antigens were obtained from detoxified formalin-treated centrifugates of culture liquids. The specific activity of V. cholerae antigens at the stages of cultivation and isolation was determined applying immunochemical methods. The preparation of the finished dosage form of the cholera vaccine and the coating of the tablets with an enteric coating was carried out in accordance with the regulatory documentation. Results and discussion. It has been shown that cultivation on the medium based on enzymatic fibrin hydrolyzate provides a stable growth of the biomass of V. cholerae production strains with a high level of specific activity of antigens. Comparative analysis of the main properties of the finished dosage form of laboratory batches with a commercial batch of chemical cholera vaccine has demonstrated compliance with the requirements of regulatory documentation. The results obtained has led us to conclusion that it is feasible to use the nutrient medium based on enzymatic fibrin hydrolyzate for cultivating production strains and obtaining specific components of the cholera vaccine

Comparison of dynamical decoupling protocols for a nitrogen-vacancy center in diamond

We perform a detailed theoretical-experimental study of the dynamical decoupling (DD) of the nitrogen-vacancy (NV) center in diamond. We investigate the DD sequences applied to suppress the dephasing of the electron spin of the NV center induced by the coupling to a spin bath composed of the substitutional nitrogen atoms. The decoupling efficiency of various DD schemes is studied, including both periodic and periodic pulse sequences. For ideal control pulses, we find that the DD protocols with the Carr-Purcell-Meiboom-Gill (CPMG) timing of the pulses provides best performance. We show that, as the number of control pulses increases, the decoupling fidelity scaling differs qualitatively from the predictions of the Magnus expansion, and explain the origin of this difference. In particular, more advanced symmetrized or concatenated protocols do not improve the DD performance. Next, we investigate the impact of the systematic instrumental pulse errors in different periodic and aperiodic pulse sequences. The DD protocols with the single-axis control do not preserve all spin components in the presence of the pulse errors, and the two-axis control is needed. We demonstrate that the two-axis control sequence with the CPMG timing is very robust with respect to the pulse errors. The impact of the pulse errors can be diminished further by symmetrizing this protocol. For all protocols studied here, we present a detailed account of the pulse error parameters which make strongest impact on the DD performance. In conclusion, we give specific recommendations about choosing the decoupling protocol for the system under investigation.Comment: 16 pages, 11 figure