Carbon nanotubes for polarization sensitive terahertz plasmonic interferometry.

We report on helicity sensitive photovoltaic terahertz radiation response of a carbon nanotube made in a configuration of a field-effect transistor. We find that the magnitude of the rectified voltage is different for clockwise and anticlockwise circularly polarized radiation. We demonstrate that this effect is a fingerprint of the plasma waves interference in the transistor channel. We also find that the presence of the helicity- and phase-sensitive interference part of the photovoltaic response is a universal phenomenon which is obtained in the systems of different dimensionality with different single-particle spectrum. Its magnitude is a characteristic of the plasma wave decay length. This opens up a wide avenue for applications in the area of plasmonic interferometry.

Photon Transport in a Bose-Hubbard Chain of Superconducting Artificial Atoms.

We demonstrate nonequilibrium steady-state photon transport through a chain of five coupled artificial atoms simulating the driven-dissipative Bose-Hubbard model. Using transmission spectroscopy, we show that the system retains many-particle coherence despite being coupled strongly to two open spaces. We find that cross-Kerr interaction between system states allows high-contrast spectroscopic visualization of the emergent energy bands. For vanishing disorder, we observe the transition of the system from the linear to nonlinear regime of photon blockade in excellent agreement with the input-output theory. Finally, we show how controllable disorder introduced to the system suppresses nonlocal photon transmission. We argue that proposed architecture may be applied to analog simulation of many-body Floquet dynamics with even larger arrays of artificial atoms paving an alternative way towards quantum supremacy.

Manifestation of plasmonic response in the detection of sub-terahertz radiation by graphene-based devices.

We report on the sub-terahertz (THz) (129-450 GHz) photoresponse of devices based on single layer graphene and graphene nanoribbons with asymmetric source and drain (vanadium and gold) contacts. Vanadium forms a barrier at the graphene interface, while gold forms an Ohmic contact. We find that at low temperatures (77 K) the detector responsivity rises with the increasing frequency of the incident sub-THz radiation. We interpret this result as a manifestation of a plasmonic effect in the devices with the relatively long plasmonic wavelengths. Graphene nanoribbon devices display a similar pattern, albeit with a lower responsivity.

Electronic Transport and Possible Superconductivity at Van Hove Singularities in Carbon Nanotubes.

Van Hove singularities (VHSs) are a hallmark of reduced dimensionality, leading to a divergent density of states in one and two dimensions and predictions of new electronic properties when the Fermi energy is close to these divergences. In carbon nanotubes, VHSs mark the onset of new subbands. They are elusive in standard electronic transport characterization measurements because they do not typically appear as notable features and therefore their effect on the nanotube conductance is largely unexplored. Here we report conductance measurements of carbon nanotubes where VHSs are clearly revealed by interference patterns of the electronic wave functions, showing both a sharp increase of quantum capacitance, and a sharp reduction of energy level spacing, consistent with an upsurge of density of states. At VHSs, we also measure an anomalous increase of conductance below a temperature of about 30 K. We argue that this transport feature is consistent with the formation of Cooper pairs in the nanotube.

[NEURONAL DIFFERENTIATION OF PC12 CELL LINE AND MURINE NEURAL STEM CELLS ON THE CARBON NANOTUBES FILMS].

The study of the interaction of nerve cells with specially designed substrates (scaffolds) with different surface characteristics at the nanoscale is a necessary step in the development of methods of stimulation of regeneration of nervous tissues, as well as to create next generation of bioelectronic devices. A promising material for such scaffolds may be carbon nanotubes (CNT) that are flexible films of graphene rolled into nano-sized cylindrical tubes. CNT were produced by chemical deposition from the gas phase. The analysis of the PC12 cells cultivated on quartz glass coated by carbon nanotubes films using electron and light microscopy has shown that CNT stimulate the proliferation and do not inhibit neuronal differentiation of PC12 cells. We have found that it is possible to obtain differentiated neurons from murine neural stem cells on the quartz glasses covered with CNT films. The data obtained indicate that the CNT films produced by chemical deposition from the gas phase onto quartz glass may be used as the electro conductive scaffold to obtain and study the functions of neural cells and possibly of mature neurons.

[The interaction between nerve cells and carbon nanotube networks made by CVD process investigation].

In this research we investigate neuroblastoma cells cultivated on single-walled carbon nanotubes networks made by CVD method on silicon substrates. The complex analysis of grown cells made by atomic force, electron microscopy and Raman spectroscopy was carried out and the effect of nanotube growth process on proliferation factor was investigated. It is shown that despite of a weak decrease in proliferation, cell morphology remains unchanged and no physical or chemical interaction between carbon nanotubes and cells is observed. The results of the research can be used to investigate the interaction between conductive nanomaterials and cells for the development of neural replacement implants. Also they can be useful in bio-electronic interface investigation of signal propagation in neurons.

Visually triggered K-complexes: a study in New Zealand rabbits.

K-complexes are the EEG elements recorded during the state of developing sleep and during slow wave sleep. They are the only EEG components which can be elicited by sensory stimulation during sleep. The peculiarity of New Zealand rabbits to sleep with their eyes open allows the use of visual stimuli to elicit K-complexes. Experiments were performed with three rabbits. For visual stimulation, an elongated screen illuminated by LED flashes was attached to an implant on the animal's skull. The screen covered 20-120° of the visual field of one eye, and moved with the head during animal motion. One-millisecond flashes (15-s interval) were used during daytime in an illuminated room. Flashes elicited evoked responses, which, during the first stages of sleep, were often accompanied by K-complexes. The induced K-complexes were recorded from electrodes located both above visual and somatosensory areas. Evoked responses to visual stimuli were also recorded from both pairs of electrodes, although they were generated exclusively in the visual cortex. Correlation analysis showed that visual evoked responses and K-complexes induced by this stimulation were generated in visual cortex, and passively spread to the electrodes above the somatosensory area. Investigation of the latencies of induced K-complexes revealed two time windows when these complexes could be seen. Within each window there was no correlation between latency and amplitude of K-complexes. There was also no correlation between amplitudes of the visual evoked responses and K-complexes elicited by these responses. We propose that visual stimulation in light sleep temporarily opens a gate for some independent external signals, which evoke activation of the visual cortex, reflected in K-complexes.

Respiration restitution in rats following its termination in immersion hypothermia.

Rats were cooled in water until attaining profound hypothermia and respiratory arrest. After removal from water, 0.5% solution of Na2EDTA was administered intravenously. This led to a drop of blood [Ca2+] by 20-30% from the baseline and promoted recovery of respiration following its arrest lasting 10.3±1.4 min. By the 30th minute of Na2EDTA administration, respiration rate increased to 32.3±5.2 cycles per minute and respiration amplitude reached 68±4% of the baseline level. This effect was observed without special warming of the rats. It was concluded that the period during which the organism maintains viability in respiration arrest and disturbances in respiratory center are still reversible is prolonged under conditions of profound hypothermia.

Tunnel field-effect transistors for sensitive terahertz detection.

The rectification of electromagnetic waves to direct currents is a crucial process for energy harvesting, beyond-5G wireless communications, ultra-fast science, and observational astronomy. As the radiation frequency is raised to the sub-terahertz (THz) domain, ac-to-dc conversion by conventional electronics becomes challenging and requires alternative rectification protocols. Here, we address this challenge by tunnel field-effect transistors made of bilayer graphene (BLG). Taking advantage of BLG's electrically tunable band structure, we create a lateral tunnel junction and couple it to an antenna exposed to THz radiation. The incoming radiation is then down-converted by the tunnel junction nonlinearity, resulting in high responsivity (>4 kV/W) and low-noise (0.2 pW/[Formula: see text]) detection. We demonstrate how switching from intraband Ohmic to interband tunneling regime can raise detectors' responsivity by few orders of magnitude, in agreement with the developed theory. Our work demonstrates a potential application of tunnel transistors for THz detection and reveals BLG as a promising platform therefor.

Mechanism of suppression of physiological functions in hypothermia and means for their stimulation without body warming.

Cold-suppressed thermoregulatory reactions and respiration in rats in deep hypothermia (rectal body temperature (25-22 degrees C) were shown to be stimulated by injecting disodium ethylenediaminetetraacetic acid (EDTA) solution into the blood stream of cold rats at a dose of 16.5 mg/100 g (0.0045 mmol/100 g). EDTA binds Ca2+ ions in the blood, forming complexes. Increases in cold shivering and pulmonary respiration (by 5 min after the start of administration) coincided with a reduction in the blood Ca2+ concentration by 42-45% of normal. By 15 min after the start of the EDTA injection, the blood Ca2+ concentration returned to the normal level present in cold rats before EDTA treatment. This was accompanied by suppression of cold shivering and pulmonary respiration. Repeated injection of EDTA into the blood stream produced a new drop in blood Ca2+ and repeated stimulation of cold shivering and pulmonary respiration.

[A biophysical approach to the investigation of physiological processes]. / Biofizicheskii podkhod k issledovaniiu fiziologicheskikh protsessov.

It was shown that understanding the mechanism of rhythmic excitation in cells and tissues requires the combination of physiological and biophysical approaches. Systemic studies of changes in the physicochemical characteristics of the object were carried out by a protocol that takes into account the mode of rhythmic excitation and the functional sate of the object being studied. The validity of the approach was proved in studies of rhythmic excitation in somatic nonmyelinic and myelinic nerves, and in model systems. The approach can be used in studies of many physiological processes.

[Effect of lipid monolayers on diffusion of oxygen through the air/water interface]. / Vliianie lipidnykh monosloev na diffuziiu kisloroda cherez granitsu razdela vozdukh/voda.

The dependence of the diffusion current on the depth of immersion of the electrode was studied by polarography using an open platinum electrode. As the electrode was brought from the depth of the liquid phase to its surface, an increase in the current under aerobic conditions was observed, due to diffusion of oxygen through the interface. The formation of lipid monolayers of phosphatidylcholine, stearic acid, hexadecanol, octadecanol, eicosanol, and docosanol on the water surface led to a decrease in diffusion current; the effect being most pronounced at a minimal depth of immersion of the electrode. The maximum value of the relative decrease in diffusion current R was obtained for docosanol monolaers. It was shown that the R value increases with increasing surface pressure in monolayers of phosphatidylcholine and stearic acid. It is assumed that the decrease in diffusion flow of O2 in the presence of monolayers is caused by the formation of an energy barrier that prevents the sorption of O2, which is related to the presence of hydrocarbon chains weakly interacting with oxygen.

[Thermotropic changes in the conductivity of black bilayers from egg phosphatidylethanolamine]. / Termotropnye izmeneniia provodimosti chernykh bisloev iz iaichnogo fosfatidilétanolamina.

Current fluctuations in black bilayers from phosphatidyl ethanolamine obtained from egg lecithin were registered in the temperature region of the main phase transition of this phospholipid and the bilayer--hexagonal phase transition about 35 degrees; they correspond to the conductivity changes of hundreds of pSm. This transition takes place in the same temperature region as shown by 31P-NMR and depolarization of light-scattering method in phosphatidyl ethanolamine multilamellar liposomes. The scheme of bilayer transformation into hexagonal phase in the temperature region of lipid polymorphic transition is discussed.

[Characteristics of immune response to diphtheria anatoxin in children with different immune status during the second age-scheduled revaccination]. / Osobennosti formirovaniia immunnogo otveta na difteriinyi anatoksin u detei s raznym immunnym statusom pri vtoroi vozrastnoi revaktsinatsii.

The dynamics of the intensity of specific antidiphtheria immunity after the second age-scheduled revaccination was studied in 129 practically healthy children. The study revealed that the formation of immunity depended on the initial functional state of the immune system before the injection of diphtheria toxoid. Three variants of immune response were determined and the immune status corresponding to each of these variants was characterized. As shown in this study, children with the hyperergic character of immune response were characterized by relatively high initial titers of antitoxin, and the injection of an additional dose of the antigen led to the prolonged state of hyperimmunization with the subsequent decrease of the intensity of immunity by half, registered in the catamnestic observation for 4 years. Children with the hypo- and normoergic variants of immune response were characterized by the most stable immune response to diphtheria toxoid, and during the catamnestic observation they formed the levels of antibody titers 2.5- to 3-fold higher than before immunization. But the protection characteristics in children with the third variant were the lowest among the children under study.

[The characteristics of the development of immunity with a primary immunization complex using adsorbed DTP vaccine]. / Osobennosti formirovaniia immuniteta pri pervichnom komplekse immunizatsii AKDS-vaktsinoi.

The intensity of immunity, depending on immune response variants characterized by the definite composition of the T and B lymphocyte subpopulation in peripheral blood, was studied in 70 practically healthy young children after the primary complex of immunization with adsorbed DPT vaccine. The most stable immune reaction was shown to appear in children with the hyperergic and normoergic variants of immune response to diphtheria and tetanus toxoids, while the reaction to pertussis antigen was essentially weaker both after the second vaccination and after the first revaccination. In children with the hypoergic variant of immune response to all components of adsorbed DPT vaccine the resulting immune reaction was 2.5-3 times weaker than in children of other groups.

[Regulation of Na, K-ATPase activity in nerves during propagation of rhythmic excitation]. / Reguliatsii aktivnosti Na, K-ATFazy v nerve pri provedenii ritmicheskogo vozbuzhdeniia.

The changes of Na, K-ATPase activity of the isolated squid, crab, frog, and rat nerves depended on the stimulation frequency: at the frequency specific for each nerve the maximum deviation from initial resting level occurred. During a certain stimulation the maximum deviation of SH-group content and Na/K ratio as well as of Na, K-ATPase activity developed while the level of acetylcholine esterase activity (AEA) remained at its minimum. The data obtained suggest the mechanism of Na, K-ATPase activity in nerve under rhythmic propagation of excitation. In the resting nerve the minimum level of the acetylcholine concentration is kept because of the AEA. Under stimulation the membrane depolarization induces changes of the protein conformation suppressing the AEA. This results in an increase of the acetylcholine concentration in the nerve which leads to an increase of Na+ influx and K+ efflux. The changes of Na/K ratio in the nerve activate the transport ATPase.

[Relationship between the concentration of vitamin A in the liver of the lesser suslik, Citellus pygmaeus, and the altitude of its habitat]. / Soderzhanie vitamina A v pecheni malogo suslika Citellus pygmaeus v zavisimosti ot vysoty obitaniia

With the increase of the altitude of habitation of the ground-squirrel C. pygmaeus the content of vitamin A in its liver decreases. It is suggested that low vitamin A content of the liver in mountain animals is due to the increased utilization of vitamin A and carotenoids which provides for adaptation of these animals to lower partial oxygen pressure and lower temperature.