The stochastic resonance of magnetosomes fixed in the cytoskeleton

The rotation of microscopic magnetic particles, magnetosomes, embedded into the cytoskeleton and subjected to a magnetic field and thermal noise was considered. The dynamics of magnetosome is shown to comply with the conditions of the stochastic resonance under not too tight constraints on the character of particle fastening. The excursion of regular rotations attains the value of the order of radian, which facilitates explaining the biological effects of low-frequency weak magnetic fields and geomagnetic fluctuations.     

Plasmonically Tunable Blue-Shifted Emission from Coumarin 153 in Ag Nanostructure Random Media: A Demonstration of Fast Dynamic Surface-Enhanced Fluorescence

Enhancement of intensity and wavelength tunability of emission are desirable features for light-emitting device applications. We report on the large and tunable blue shift (60 nm) in emission from an environment-sensitive fluorophore (Coumarin153) embedded in Ag plasmonic random media. Coumarin 153 having emission at 555 nm, show a systematic blue shift (to 542, 503 and 495 nm) upon infiltration into random media fabricated by Ag nanowires of different aspect ratio (hence, surface plasmon resonances at 426, 445 and 464 nm). The blue shift is due to the fast dynamic surface-enhanced fluorescence mechanism and can be tuned by controlling the surface plasmon resonance and hotspot density in random media. Enhanced emission at desired wavelength is achieved by using nanostructures having higher extinction coefficient but same-surface plasmon resonance. Ag nanostructures of different aspect ratio used for fabricating the random media are synthesized by chemical route.     

Microwave absorption by magnetic nanoparticles in organisms

An estimate of the rate of absorption of the electromagnetic microwaves by magnetic nanoparticles in organisms is presented. The absorption takes place due to the energy dissipation at the ferromagnetic resonance. Based on the known solution of the Landau-Lifshitz equation, the imaginary part of the complex magnetic susceptibility is evaluated that gives the absorption rate. It is shown that even in the conditions of thermal isolation of the particles, their temperature growth would be insignificant at absorption of the emission with the energy flux density of the order of 1 mW/cm2, and the given mechanism is unrelated to the observable effects of low-intensity microwaves.     

Two types of magnetic biological effects: individual and batch effects

Frequency distributions of the magnetic effects values have been calculated based on the results of about 120 thousand single trials during psychophysical testing of 40 people under normal conditions and exposure to the hundredfold weakened geomagnetic field. Two types of such distributions were shown to be attributed to a) the individual reactions to the change of a magnetic field and b) the batch magnetic effect on the set of the individual reactions. The methodological consequences significant for detecting magnetic biological phenomena and studying their nature are discussed.     

The paradox of magnetobiology: analysis and prospects for solution

The wording, content, and corollaries of the so-called "kT problem" are considered. The problem points to the paradox of the biological effects of weak low-frequency magnetic fields. The conventional wording of the problem contains implicit assumptions the analysis of which shows their incomplete physical validity.     

The temperature factor and magnetic noise under the conditions of stochastic resonance of magnetosomes

The influence of magnetic noise on the dynamics of magnetic nanoparticles under the conditions of stochastic resonance is considered. The effect of the magnetic noise is shown to be equivalent to the growth of the effective thermostat temperature for the particles at the permanent actual temperature of the medium. This regularity may be used for testing the hypothesis on the involvement of magnetic nanoparticles in the formation of biological effects of weak magnetic fields.     

Influence of the compensation of the geomagnetic field on human cognitive processes

The influence of the compensation of the geomagnetic field to a level less than 0.4 microT on human cognitive processes has been studied. Forty persons took part in the study; they were divided by sex and age into four groups. The cognitive abilities of the persons were tested. Each person took part in two experiments: in control conditions and under the exposure to zero magnetic field. A 45-min exposure to zero magnetic field caused statistically significant changes in five of eight parameters of the cognitive tests. The magnitude of the effects varied between 1.3 and 6.2%, with an average value for all tests being 2.1% (p < 0.002, MANOVA). Exposure to zero magnetic field led predominantly to an increase in the number of errors and the time the task was performed as compared with the controls. Men passed the tests in zero magnetic field better than women, and young people did it better than aged persons. Groups of persons were distinguished that responded differently to zero magnetic field, the differences being not related to the age or gender.     

Rotation of biological systems in a magnetic field: slitting of spectra for some magnetobiological effects

The interference mechanism for biological reception of weak magnetic fields was studied with consideration for the own molecular rotations of ion-protein complexes. An additional rotation of a biological system is shown to decrease the biological effect of "magnetic vacuum" and split spectral peaks from the effects of static magnetic field.     

The method for studying of the "magnetic vacuum" effect on color memory in humans

The method for studying the effects of weak magnetic fields and "magnetic vacuum" on the psychophysiological state of a human organism is proposed. This method includes the system of the exposure of a human organism to uniform constant and alternating magnetic fields and the system of computerized psychological tests. The influence of the weakening of constant magnetic field on the psychophysiological state of human organisms was studied. The short-term color memory and reaction rates of 30 subjects have been examined in the local geomagnetic field and in a magnetic field which was reduced in 10 and more times. Statistically significant differences in the color memory test was found in the magnetic field 4 +/- 1 microT in comparison with the results in the geomagnetic field. In the magnetic field 0 +/- 1 microT, slight impairment of color memory was found. Preliminary results in the test of reaction rates showed the tendency to slowing down the reaction rates in the weakened magnetic fields.     

A computer method for the evaluation of Paramecium motor activity using video records of their movement

A method for the evaluation of Paramecium caudatum motility was proposed as a tool for the investigation of magnetobiological as well as other physical and chemical effects. The microscopically observed movement of paramecia is recorded and processed using a special software program. The protozoan motility is determined as a function of their mean velocity in a definite time. The main advantages of the method are that it is easily modified for determining various characteristics of the motor activity of paramecia and that the video data obtained can be reused.