Possible superconductivity in brain

The unprecedented power of the brain suggests that it may process information quantum-mechanically. Since quantum processing is already achieved in superconducting quantum computers, it may imply that superconductivity is the basis of quantum computation in brain too. Superconductivity could also be responsible for long-term memory. Following these ideas, the paper reviews the progress in the search for superconductors with high critical temperature and tries to answer the question about the superconductivity in brain. It focuses on recent electrical measurements of brain slices, in which graphene was used as a room-temperature quantum mediator, and argues that these measurements could be interpreted as providing evidence of superconductivity in the neural network of mammalian brains. The estimated critical temperature of superconducting network in brain is rather high: 2063 plus-minus 114 K. A similar critical temperature was predicted in the Little's model for one-dimensional organic chains linked to certain molecular complexes. A reasonable suggestion is that superconductivity develops in microtubules inside the neurons of brain.Comment: Preprint of a review paper, 10 pages, 13 figures, Journal of Superconductivity and Novel Magnetism, ISSN: 1557-1939, accepted, in productio

Observation of the Curie Transition in Palladium Bionanomaterial Using Muon Spin Rotation Spectroscopy

Palladium bionanomaterial was manufactured using the sulfate-reducing bacterium, Desulfovibrio desulfuricans, to reduce soluble Pd(II) ions to cell-bound Pd(0). The material was examined using a Superconducting Quantum Interference Device (SQUID) to observe bulk magnetisation over the temperature range 10 – 300 K and by Muon Spin Rotation (μSR), which is a probe of the local magnetic environment inside the sample, over the temperature range 200 – 700 K. Results from SQUID were used to model the temperature dependence of ferromagnetic and paramagnetic components of the bulk magnetisation and, by extrapolation, to predict the Curie transition temperature. Results from μSR confirmed the accuracy of the prediction to within 20 K. The Curie transition, which started at 528 K, was shown to be spread over a wide ( 100 K) range. This was attributed to dependence of the transition on particle size and the range of particle sizes in the population. A competing contribution to the overall magnetisation was observed due to partial thermal decomposition of the organic component of the material. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3533

Visualization of Spin Polarized States in Biologically-Produced Ensembles of Ferromagnetic Palladium Nanoparticles

We report visualization of spin polarized states in macroscopic ensembles of biologically-produced ferromagnetic palladium nanoparticles using the Faraday effect-based technique of magneto-optical imaging. The ferromagnetic palladium only exists in the form of nanoparticles. Large quantities of palladium nanoparticles may be synthesized via biomineralization from a Pd2+ solution. The ferromagnetic Pd nanoparticles are formed in the periplasmic space of bacteria during the hydrogen-assisted reduction of Pd2+ ions by hydrogenases. The ferromagnetism in Pd comes from itinerant electrons. A high Curie temperature of ferromagnetic palladium, about 200 degrees centigrade above room temperature, would allow for a range of room-temperature magnetic applications. The processes of the isolation of electron spins in separate nanoparticles, spin hopping, spin transport and spin correlations may even form a basis of quantum computing. So far, measurements of the magnetic properties of Pd nanoparticles (PdNP) have been limited by integral techniques such as SQUID magnetometry, magnetic circular dihroism and muon spin rotation spectroscopy ( SR). In the present study, ferromagnetic Pd nanoparticles are characterized using the technique of magneto-optical imaging. This allows visualization of the spin polarization by the variations in the intensity of polarized light. To perform measurements at relatively low magnetic fields, a spin injection from a colossal magnetoresistive material has been used. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3533

Pulsed Laser Deposition of Rocksalt Magnetic Binary Oxides

Here we systematically explore the use of pulsed laser deposition technique (PLD) to grow three basic oxides that have rocksalt structure but different chemical stability in the ambient atmosphere: NiO (stable), MnO (metastable) and EuO (unstable). By tuning laser fluence, an epitaxial single-phase nickel oxide thin-film growth can be achieved in a wide range of temperatures from 10 to 750 {\deg}C. At the lowest growth temperature, the out-of-plane strain raises to 1.5%, which is five times bigger than that in a NiO film grown at 750 {\deg}C. MnO thin films that had long-range ordered were successfully deposited on the MgO substrates after appropriate tuning of deposition parameters. The growth of MnO phase was strongly influenced by substrate temperature and laser fluence. EuO films with satisfactory quality were deposited by PLD after oxygen availability had been minimized. Synthesis of EuO thin films at rather low growth temperature prevented thermally-driven lattice relaxation and allowed growth of strained films. Overall, PLD was a quick and reliable method to grow binary oxides with rocksalt structure in high quality that can satisfy requirements for applications and for basic research

Ray optics in flux avalanche propagation in superconducting films

Experimental evidence of wave properties of dendritic flux avalanches in superconducting films is reported. Using magneto-optical imaging the propagation of dendrites across boundaries between a bare NbN film and areas coated by a Cu-layer was visualized, and it was found that the propagation is refracted in full quantitative agreement with Snell's law. For the studied film of 170 nm thickness and a 0.9 mkm thick metal layer, the refractive index was close to n=1.4. The origin of the refraction is believed to be caused by the dendrites propagating as an electromagnetic shock wave, similar to damped modes considered previously for normal metals. The analogy is justified by the large dissipation during the avalanches raising the local temperature significantly. Additional time-resolved measurements of voltage pulses generated by segments of the dendrites traversing an electrode confirm the consistency of the adapted physical picture.Comment: 4 pages, 4 figure

Stray-fields-based magnetoresistance mechanism in Ni80Fe20-Nb-Ni80Fe20 trilayers

We report on the transport and magnetic properties of hybrid trilayers and bilayers that consist of low spin-polarized Ni80Fe20 exhibiting in-plane but no uniaxial anisotropy and low-Tc Nb. We reveal a magnetoresistance effect that is pronounced. In our trilayers the magnetoresistance exhibits an increase of two orders of magnitude when the superconducting state is reached: from the conventional normal-state values 0.6 % it goes up to 1000 % for temperatures below Tc. In contrast, in the bilayers the effect is only minor since from 3% in the normal state increases only to 70 % for temperatures below Tc. Magnetization data of both the longitudinal and transverse magnetic components are presented. Most importantly, we present data not only for the normal state of Nb but also in its superconducting state. Strikingly, these data show that below its Tc SC the Nb interlayer under the influence of the outer Ni80Fe20 layers attains a magnetization component transverse to the external field. By comparing the transport and magnetization data we propose a candidate mechanism that could motivate the pronounced magnetoresistance effect observed in the trilayers. Adequate magnetostatic coupling of the outer Ni80Fe20 layers is motivated by stray fields that emerge naturally in their whole surface due to the multidomain magnetic structure that they attain near coercivity. Atomic force microscopy is employed in order to examine the possibility that such magnetostatic coupling could be promoted by interface roughness. Referring to the bilayers, although out-of-plane rotation of the magnetization of the single Ni80Fe20 layer is still observed, in these structures magnetostatic coupling does not occur due to the absence of a second Ni80Fe20 one so that the observed magnetoresistance peaks are only modest.Comment: 9 pages, 7 figure

Yet another Freiheitssatz: Mating finite groups with locally indicable ones

The main result includes as special cases on the one hand, the Gerstenhaber--Rothaus theorem (1962) and its generalisation due to Nitsche and Thom (2022) and, on the other hand, the Brodskii--Howie--Short theorem (1980--1984) generalising Magnus's Freiheitssatz (1930).Comment: 5 pages. A Russian version of this paper is at http://halgebra.math.msu.su/staff/klyachko/papers.ht

Dendritic flux avalanches in a superconducting MgB2 tape

MgB2 tapes with high critical current have a significant technological potential, but can experience operational breakdown due to thermomagnetic instability. Using magneto-optical imaging the spatial structure of the thermomagnetic avalanches has been resolved, and the reproducibility and thresholds for their appearance have been determined. By combining magneto-optical imaging with magnetic moment measurements, it is found that avalanches appear in a range between 1.7 mT and 2.5 T. Avalanches appearing at low fields are small intrusions at the tape's edge and non-detectable in measurements of magnetic moment. Larger avalanches have dendritic structures