Numerical solution of the forward magnetic field problem for models with irregular polyhedron discretization taking into account the "demagnetization effect"

A performance-effective numerical method for magnetic field calculation is proposed. The method works with irregular polyhedron discretization which enables us to construct models with magnetic objects of arbitrary shape. As a case study, a model of a well in plane-parallel layer is considered. The model is approximated with dense irregular grid, elements of which are polyhedrons. With the help of conjugate gradient method, we solve "demagnetization effect" equation and calculate total magnetic field on the plane above the well. For a well of 0.25m radius and 8m height "demagnetization effect" is of order of 2% relative to the field induced by the object placed in equivalent of Earth magnetic field. © 2020 American Institute of Physics Inc.. All rights reserved

Mortality from cerebrovascular diseases in the context of municipalities of the Sverdlovsk region

The results of the study indicate that there are significant differences in the municipalities of the Sverdlovsk region in the level of mortality from cerebrovascular diseases in 2017-2018 and the insufficient proportion of patients with acute conditions hospitalized in specialized vascular departmentsРезультаты исследования свидетельствуют о наличии значительных различий муниципальным образованиям Свердловской области по уровню смертности от цереброваскулярных болезней в 2017-2018 годы и недостаточной доле госпитализированных в специализированные сосудистые отделения пациентов с острыми состояниями

ДЕВИТАЛИЗИРОВАННЫЕ СОСУДИСТЫЕ ПРОТЕЗЫ: ИССЛЕДОВАНИЕ IN VIVO

Porcine intrathoracic arteries were devitalized by application of low temperatures and electron beam irradiati- on. The resulted connective tissues vascular scaffolds could be used as the prosthesis of small diameter arteries (≤6 mm). Biocompatibility, immunogenicity degree and thrombogenicity were estimated in the study. Results of electron microscopy are presented. Described treatment reduces an immunogenicity of xenoarteries, their ade- quate functioning during 6 months was shown by means of experimental surgeries. Для девитализации внутренних грудных артерий свиней использовали низкие температуры и облучение потоком электронов. Полученные соединительнотканные сосудистые скаффолды в данном исследовании были использованы в качестве протезов артерий малого диаметра (≤6 мм). В работе изучали биосовме- стимость, степень иммуногенности, тромбогенность девитализированных артерий. Приведены результа- ты электронной микроскопии. Показано снижение иммуногенности девитализированных ксеноартерий. Экспериментальные операции продемонстрировали их адекватное функционирование в течение 6 мес.

A Positive Feedback Synapse from Retinal Horizontal Cells to Cone Photoreceptors

Cone photoreceptors and horizontal cells (HCs) have a reciprocal synapse that underlies lateral inhibition and establishes the antagonistic center-surround organization of the visual system. Cones transmit to HCs through an excitatory synapse and HCs feed back to cones through an inhibitory synapse. Here we report that HCs also transmit to cone terminals a positive feedback signal that elevates intracellular Ca2+ and accelerates neurotransmitter release. Positive and negative feedback are both initiated by AMPA receptors on HCs, but positive feedback appears to be mediated by a change in HC Ca2+, whereas negative feedback is mediated by a change in HC membrane potential. Local uncaging of AMPA receptor agonists suggests that positive feedback is spatially constrained to active HC-cone synapses, whereas the negative feedback signal spreads through HCs to affect release from surrounding cones. By locally offsetting the effects of negative feedback, positive feedback may amplify photoreceptor synaptic release without sacrificing HC-mediated contrast enhancement

Synaptic Transmission from Horizontal Cells to Cones Is Impaired by Loss of Connexin Hemichannels

In the vertebrate retina, horizontal cells generate the inhibitory surround of bipolar cells, an essential step in contrast enhancement. For the last decades, the mechanism involved in this inhibitory synaptic pathway has been a major controversy in retinal research. One hypothesis suggests that connexin hemichannels mediate this negative feedback signal; another suggests that feedback is mediated by protons. Mutant zebrafish were generated that lack connexin 55.5 hemichannels in horizontal cells. Whole cell voltage clamp recordings were made from isolated horizontal cells and cones in flat mount retinas. Light-induced feedback from horizontal cells to cones was reduced in mutants. A reduction of feedback was also found when horizontal cells were pharmacologically hyperpolarized but was absent when they were pharmacologically depolarized. Hemichannel currents in isolated horizontal cells showed a similar behavior. The hyperpolarization-induced hemichannel current was strongly reduced in the mutants while the depolarization-induced hemichannel current was not. Intracellular recordings were made from horizontal cells. Consistent with impaired feedback in the mutant, spectral opponent responses in horizontal cells were diminished in these animals. A behavioral assay revealed a lower contrast-sensitivity, illustrating the role of the horizontal cell to cone feedback pathway in contrast enhancement. Model simulations showed that the observed modifications of feedback can be accounted for by an ephaptic mechanism. A model for feedback, in which the number of connexin hemichannels is reduced to about 40%, fully predicts the specific asymmetric modification of feedback. To our knowledge, this is the first successful genetic interference in the feedback pathway from horizontal cells to cones. It provides direct evidence for an unconventional role of connexin hemichannels in the inhibitory synapse between horizontal cells and cones. This is an important step in resolving a long-standing debate about the unusual form of (ephaptic) synaptic transmission between horizontal cells and cones in the vertebrate retina

Species-Specific Effects of Epigeic Earthworms on Microbial Community Structure during First Stages of Decomposition of Organic Matter

Background: Epigeic earthworms are key organisms in organic matter decomposition because of the interactions they establish with microorganisms. The earthworm species and the quality and/or substrate availability are expected to be major factors influencing the outcome of these interactions. Here we tested whether and to what extent the epigeic earthworms Eisenia andrei, Eisenia fetida and Perionyx excavatus, widely used in vermicomposting, are capable of altering the microbiological properties of fresh organic matter in the short-term. We also questioned if the earthworm-induced modifications to the microbial communities are dependent on the type of substrate ingested. Methodology/Principal Findings: To address these questions we determined the microbial community structure (phospholipid fatty acid profiles) and microbial activity (basal respiration and microbial growth rates) of three types of animal manure (cow, horse and rabbit) that differed in microbial composition, after being processed by each species of earthworm for one month. No differences were found between earthworm-worked samples with regards to microbial community structure, irrespective of type of manure, which suggests the existence of a bottleneck effect of worm digestion on microbial populations of the original material consumed. Moreover, in mesocosms containing cow manure the presence of E. andrei resulted not only in a decrease in bacterial and fungal biomass, but also in a reduced bacterial growth rate and total microbial activity, while no such reduction was found with E. fetida and P. excavatus

Algorithm for solution 3D direct and inverse problem of magnetic prospecting

This paper presents the integral equations of the direct problem of magnetic prospecting with respect to demagnetization. These equations are derived for a two-layer medium model. The method of determining the intensity of a secondary magnetic field for the case of magnetizing by a static field, which potential is a harmonic function, is described. The respective integral equations are written based on the theory of a simple layer potential. An iteration algorithm for solving the three-dimensional structural inverse problem of magnetic prospecting with respect to demagnetization for the sampled medium model is proposed based on the modified method of local corrections. For the method of local corrections, it is important to suggest that a change in the model field is mostly influenced by a change in the geometry of part of the object’s boundary that is the nearest to the point of observation. The main feature of this algorithm allows us to get effective technique for solution of magnetic inverse problem for medium with any numbers of layers. © SGEM 2017. All Rights Reserved

ANALYTICAL REPRESENTATION OF ANOMALOUS MAGNETIC FIELD OF IRON OBJECTS

Using a highly sensitive POS magnetometer, we measured magnetic field from an iron cylinder. The field is approximated by analytical models: a dipole, a rod, a parallelepiped, and a surface model, a set of triangles. We performed a comparison of the actual field and the field of the models

Density block models creation based on isostasy usage

We offer two approaches for construction of block lithosphere models. First is for selection of blocks in mantle only, it is applicable to both two- and three-dimensial models. Second method (3D) helps to select blocks related to known tectonic structures. Usual approach for tectonic maps construction is the gravity field analysis. However, this method is significantly limited because the gravity field includes integral information about density features in lithosphere. This makes impossible to split selected tectonic blocks by depth. Out technique is based on lithostatic pressure calculation. In the 2D case we show the way to split the mantle to blocks with vertical boundaries. Such separation of the mantle can help to diminish discrepancy between model and observed fields. In 3D case we suggest a method, which can be used to construct tectonic structure maps with information about approximate depth and height of each tectonic block. It is based on comparison of known map of tectonic structures with horizontal maps of anomaly lithosphere pressure on different depths. © SGEM 2017. All Rights Reserved.Our research is partly supported by RFBR grant 17-05-00916a