Photoinduced magnetism in the ferromagnetic semiconductors

We study the enhancement of the magnetic transition temperature $T_c$ due to incident light in ferromagnetic semiconductors such as EuS. The photoexcited carriers mediate an extra ferromagnetic interaction due to the coupling with the localized magnetic moments. The Hamiltonian consists of a Heisenberg model for the localized moments and an interaction term between the photoexcited carriers and the localized moments. The model predicts a small enhancement of the transition temperature in semi-quantitative agreement with the experiments.Comment: 5 pages, 5 figure

Method of variational calculation of influence of the propulsion plants of forestry machines upon the frozen and thawing soil grounds

The forests, which grow in the conditions of complete expansion of the perpetually frozen ground, are unique forests in accordance with their taxational characteristics, quality indicators of the felled timber, and the ecological functions, which these forests perform in the nature. They are characterised by the low biological productivity, as well as by the high vulnerability due to climatological changes and human economic activities. It is fair to say that conservation of the permafrost is one of the main functions of the forests, which grow within the cryolithozone. Because of this, it is necessary to ensure special regimes for the forestry management and forest exploitation within the forests of the cryolithozone. We formulated the variational problem in order to determine influence of the changeability of the physical and mechanical properties of the thawing soil ground at the boundary with the permafrost ground. © 2019 SERSC

Fibre damage in the manufacture of advanced three-dimensional woven composites

Fibre damage caused by the weaving of three-dimensional (3D) fabric preforms for advanced composite materials is investigated. A Jacquard loom was used to weave continuous fibreglass yarns into a 3D orthogonal woven fabric. Samples of warp and through-thickness yarns that form the 3D fabric were taken from the loom at different stages in the weaving process to examine for fibre damage and determine their residual tensile properties. It was discovered that the fibres are abraded against each other and the loom machinery during weaving, and the resulting abrasion damage and removal of sizing agent causes a reduction in yarn strength of between 30 and 50% depending on the type of yarn. Some fibres are also broken during weaving, and this causes a small reduction to the yarn stiffness and contributes to the large loss in yarn strength. The implication of these findings for the design of advanced 3D woven composites in structural applications is discussed

Effect of weaving damage on the tensile properties of three-dimensional woven composites

This research paper examines the damage mechanisms and reductions to the tensile properties of E-glass yarns during weaving of three-dimensional (3D) fabrics for polymer-based composites. The paper also assesses the influence of weaving damage to load-bearing glass yarns on the tensile properties of 3D orthogonal woven composites. It is found that damage occurs to yarns at most stages of the 3D weaving process due to abrasion and breakage caused when sliding against the loom machinery, The abrasion damage causes a large reduction (similar to30%) to the tensile strength of the dry woven yarns, although the tensile stiffness remains unaffected. The damage and reduction to the tensile properties of the dry yarns at different weaving stages are described. Tensile studies performed on single yarn/resin composites and larger coupons of 3D orthogonal woven composite; reveal that weaving damage is responsible for a significant reduction to the tensile strength

Involvement of miRNAs in Placental Alterations Mediated by Oxidative Stress

Oxidative stress (OS) is known to be strongly involved in a large number of fetal, neonatal, and adult diseases, including placental disorders, leading to pregnancy loss and stillbirths. A growing body of research links OS to preeclampsia, gestational diabetes, obesity, spontaneous abortion, recurrent pregnancy, preterm labor, and intrauterine growth restriction. While a considerable number of miRNAs have been related to physiological functions and pathological conditions of the placenta, a direct link among these miRNAs, placental functions, and OS is still lacking. This review summarizes data describing the role of miRNAs in placental pathophysiological processes and their possible impact on OS damaging responses. As miRNAs can be found in circulation, improving our understanding on their role in the pathogenesis of pregnancy related disorders could have an important impact on the diagnosis and prognosis of these diseases

The Mathematical Model of Forestry Machines Impact on Cryolitozone Forest Soils

In the Russian Federation, the permafrost zone are gaining increasing importance due to wood procurement operations. Active timber harvesting, accompanied by the simultaneous development of wood processing enterprises in the Far Eastern Federal District, leads to the depletion of available and exploitable forests in southern and central Siberia, Buryatia, and Khabarovsk territory. The exploitation of modern forestry machines, wheeled forwarders, in particular, broadens the question of their effectiveness. In specific production and geotechnical conditions, the cross-country ability and technological productivity of wheeled forwarders are of particular relevance. These circumstances, combined with the need to minimise technological pressure on the ecological environment raise the problem of optimisation of the forest machines. We developed a mathematical model for calculating parameters of the defrosting soil destruction process occurring at the border with the permafrost zone. The mathematical model allows assessment of the possible value depth of the induced track at the stage of the project design. The assessment is conducted with the account of the forest machine's technical and maneuvering capabilities in specific natural and industrial conditions. © 2020 - IOS Press and the authors. All rights reserved

Theoretical approaches to logging trail network planning: Increasing efficiency of forest machines and reducing their negative impact on soil and terrain

A good part of the forest that survived active logging during the previous period of industrialization is now in remote areas: on steep slopes, in waterlogged or permafrost areas. There, especially on the slopes, the use of land disproportionately affects ecological processes, specifically hydrological (e.g., peak waves, suspended load, etc.). Organizing off-trail transport of log timber under such conditions is a challenge associated with specific difficulties. Almost any cutting area has sites of different capacity (stand volume per ha), which require the use of high flotation machines and have habitats that cannot be disturbed. The frequency of trips to cutting areas increases with the stand volume in these areas, but there are areas that machines have to drive round. Areas with weak soils need forest machines to carry less weight or to use additional attachments to hold the load. Unfavourable grades need the bundle to be limited in weight to maintain the tractive effort of a skidder. Because this activity is carried out with a high impact on ecology, it calls for a mathematical model and technique to evaluate logging routes and to assess the impact that logging activities have on the forest soil and subsoil and on the forest in general. This paper is devoted to the creation and justification of such a technique and offers an algorithm for careful forest use and forest-friendly logging. © 2019 IOS Press. All rights reserved