We propose a new approach to optimization of electrical stimulation of the vestibular nerve and improving the transfer function of vestibular implant. A mathematical model of the vestibular organ is ...developed based on its anatomy, the model premises, 3D-analysis of MRI and CT images, and mathematical description of physical processes underlying propagation of alternating electric current across the tissues of vestibular labyrinth. This approach was tested
in vitro
on the rat vestibular apparatus and had been examined anatomically prior to the development of its mathematical model and equivalent electrical circuit. The experimental and theoretical values of changes of the gain—phase characteristics of vestibular tissues in relation to location of the reference electrode obtained in this study can be used to optimize the electrical stimulation of vestibular nerve.
Experimental data on electric signal transmission through tissues of the vestibular organ of a guinea pig are presented. Stimulating electrodes are implanted in three ampullae of semicircular canals ...to which an alternating voltage of 170 mV is applied. The receiving electrode is implanted in the termination of vestibular nerves. The impedance of the vestibular organ tissues has been measured depending on the stimulating signal frequency. It is shown that the amplitude phase characteristics of the resulting signal at the termination of the vestibular nerves depend on the position of the stimulating electrodes and on the stimulating signal frequency. The presence of conductive disturbance currents and their influence on the resulting signal waveforms are established. A method for eliminating the influence of the conductive disturbance currents by means of application of additional electric pulses with a certain phase shift to the stimulating electrodes is suggested.
We present the results of joint observations of ozone and temperature in the middle atmosphere above Tomsk in December–January 2012–2013 and in December–February 2014–2015 during stratospheric ...warmings. The results of simultaneous microwave observations of ozone in Peterhof (60° N, 30° E) and Tomsk (56° N, 85° E) in the winter of 2013–2014 are also given. Ground-based microwave radiometry and laser diagnostics were used in the observations. Microwave radiometry and lidar technology allow us to study ozone and temperature variations during large-scale wave disturbances in the middle atmosphere such as stratospheric warming.
The results of ground-based microwave observations of ozone in the middle atmosphere in Apatity (67° N, 33° E) during three winters (2017–2018, 2018–2019 and 2019–2020) are presented. Long-term ozone ...observations were carried out during the period of minimum solar activity for cycles 24 and 25. A mobile microwave spectrometer with an operating frequency of 110.8 GHz was used in the measurements, which allows tracking the behavior of ozone in the middle atmosphere with a 15-min time resolution. The microwave ozone data from ground-based measurements are compared with the MLS/Aura onboard data. Ground and airborne data are compared with the data of contact measurements with ozonesondes at Sodankyla st. (67° N, 27° E). In addition, MLS/Aura data from mid-atmospheric temperature soundings are used to interpret perturbations in the ozone layer associated with sudden stratospheric warmings. A significant influence sudden stratospheric warming on the ozone vertical distribution at altitudes of 22–60 km was found. At the same time, the scale of mesospheric ozone variability (60 km) over Apatity is comparable or exceeds the known model calculations for assessing the impact of solar proton events and auroral electron precipitation on the ozone of the polar regions.
A theoretical and experimental study was performed of a frequency dependence of the amplitude-phase characteristics of the vestibular nerve stimulation signal and its changes during passage from the ...stimulating electrodes to the end of the vestibular nerve. To assess the influence of leakage currents on the change in the stimulating current pulse, a physico-mathematical model of the vestibular organ and electrical processes occurring in its tissues was developed on the basis of experimental data on electrophysical and anatomical characteristics of the vestibular labyrinth tissues by the example of a guinea pig. The calculations and measurements of the frequency dependence of the amplitude-phase characteristics of the stimulating signal at a recording electrode located in the Scarp’s ganglion are performed. It is established that the influence of leakage currents on the signal amplitude at the recording electrode is significant in the entire frequency range considered. Compensation of the influence of leakage currents will improve the stimulating signal quality and increase the transfer function of the vestibular implant.
Diagnostic features of a catastrophic aridization of climate, desertification, and paleoecological crisis in steppes of the Lower Volga region have been identified on the basis of data on the ...morphological, chemical, and microbiological properties of paleosols under archeological monuments (burial mounds) of the Middle Bronze Age. These processes resulted in a certain convergence of the soil cover with transformation of zonal chestnut (Kastanozems) paleosols and paleosolonetzes (Solonetz Humic) into specific chestnut-like eroded saline calcareous paleosols analogous to the modern brown desert-steppe soils (Calcisols Haplic) that predominated in this region 4300–3800 years ago.
1
In the second millennium BC, humidization of the climate led to the divergence of the soil cover with secondary formation of the complexes of chestnut soils and solonetzes. This paleoecological crisis had a significant effect on the economy of the tribes in the Late Catacomb and Post-Catacomb time stipulating their higher mobility and transition to the nomadic cattle breeding.
. Several lumped and distributed parameter models of the inner ear have been proposed to improve vestibular implant stimulation. The models should account for all significant physical phenomena that ...influence the current propagation, such as the electrical double layer (EDL) and medium polarization. The electrical properties of the medium are reflected in the electrical impedance; therefore, the study aimed to measure the impedance in the guinea pig inner ear and construct its equivalent circuit.
. The electrical impedance was measured from 100 Hz to 50 kHz between a pair of platinum electrodes immersed in 0.9% NaCl saline solution using sinusoidal voltage signals. The Randles circuit was fitted to the measured impedance in the saline solution in order to estimate the EDL parameters (C,W,andRct) of the electrode interface in saline. Then, the electrical impedance was measured between all combinations of the electrodes located in the semicircular canal ampullae and the vestibular nerve in the guinea pig
. The extended Randles circuit considering the medium polarization (Ri,Re,Cm) together with EDL parameters (C,Rct) obtained from the saline solution was fitted to the measured impedance of the guinea pig inner ear. The Warburg element was assumed negligible and was not considered in the guinea pig model.
. For the set-up used, the obtained EDL parameters were:C=27.09*10-8F,Rct=18.75kΩ.The average values of intra-, extracellular resistances, and membrane capacitance wereRi=4.74kΩ,Re=45.05kΩ,Cm=9.69*10-8F,respectively.
. The obtained values of the model parameters can serve as a good estimation of the EDL for modelling work. The EDL, together with medium polarization, plays a significant role in the electrical impedance of the guinea pig inner ear, therefore, they should be considered in electrical conductivity models to increase the credibility of the simulations.
Soil-archeological soil studies on the kurgan burial site ‘Peregruznoe’, located to the north of the Yergeninskaya upland 80 km from the city of Volgograd, Russia, were performed. For the first time, ...data on the structure of soil cover in the dry steppe zone during Sarmatian times (AD 1) were obtained. From paleosol data it was established that, in the second half of the first century AD, the prevailing humid climate progressively changed to more arid conditions similar to those of the modern time. Using the methodology and theoretical conceptions of archaeological soil science, the age of the monuments investigated was detailed. For one of the kurgans, the original technology involved in erecting the monument was reconstructed and the time of year when construction had taken place was determined. Principally, new information on the details of the funeral rites of the Middle Sarmatian tribes in the Lower Volga region was obtained.
•Methodology of archeological soil science for kurgans studies was applied.•The structure of past soil cover in dry-steppe zone of Eastern Europe (AD 1) was analyzed.•A stepwise aridization of climate in the Lower Volga region was fixed in soil properties.•Relative age, the technology, and original architecture of kurgans were elucidated.•Funeral rites of the Middle Sarmatian tribes were detailed.
The population density and total biomass of microbial communities were determined in chestnut soils and solonetzes of the dry steppe zone in the Lower Volga region with the use of the methods of ...sequential fractionation of the soil and direct counting. The mean weighted values of the population density of the microbial communities in the soil profiles (A1 + B1 + B2 horizons) in the studied soils varied within 3.8–8.0 × 10¹¹cells/g of soil. The total microbial biomass in the soils of the Privolzhskaya Upland reached 0.9–2.4 mg C/g of soil; in the soils of the Ergeni Upland, it was 20 to 75% lower. The microbial cells in the soils of the Privolzhskaya Upland were larger than those in the soils of the Ergeni Upland. Sequential fractionation of the soil prior to direct counting contributed to the more complete assessment of the population density of the microbial communities.
Living green microalgae morphologically identified as
Muriella terrestris
and
Heterochlorella luteo-viridis
have been cultivated from buried soil samples of a Middle Sarmatian kurgan (1st Century ...AD.). Paleosols for which the algal flora has been studied have a microalgal pool with a substantially lower abundance and taxonomic diversity than modern humus horizons. We discuss the probable reasons for the preservation of microalgae viability in paleosols over a period of 200 years after their burial. The first find of the green alga
Hemiflagellochloris kazakhstanica
in Russia was discovered in fine solonchakous solonetz, buried approximately 40 years ago as result of plowing of the kurgan. The structures of algal-cyanobacterial assemblages of modern background soils are also considered.
