Introduction. Radioresistance of cancer cells is a serious problem in radiation therapy of tumor diseases. Radiosensitizers make malignant cells more sensitive to radiation and increase the effectiveness of radiation therapy; however, their widespread clinical use is limited by significant side effects. The development and study of new radiosensitizers seems to be an urgent task of modern pharmacology.Aim. The purpose of this work was to study the effectiveness of lithium ascorbate as a radiosensitizer under the influence of photon and neutron radiation in wide dose range.Materials and methods. Evaluation of the biological effect was carried out using the tumor line of prostate cancer PC-3. We used a cyclotron to produce neutron radiation and a Cobalt-60 source to produce gamma radiation.Results and discussion. We have proved an increase in the cytotoxic effect with the combined use of different types of ionizing radiation and lithium ascorbate. The resistance of the prostate cancer line to gamma radiation at an absorbed dose of 0.5–3.0 Gy was revealed. It was shown that tumor cells of prostate cancer are more sensitive to the effects of the study drug in minimal concentrations in combination with neutron irradiation compared to gamma radiation in the same absorbed dose. The main mechanism of the radiosensitizing action of lithium ascorbate is the local induction of oxidative stress, which synergistically enhances the action of ionizing radiation.Conclusion. The combination of lithium ascorbate with neutron radiation leads to a more pronounced resulting cytotoxic effect. An increase in the concentration of lithium ascorbate led to the pro-oxidative action with an increase in the damaging effect on cells.

Annotation. A study of the effects of the influence of nanosecond repetitively-pulsed microwave radiation (10 GHz, pulse duration – 100 ns, maximum power flux density – 140 W/cm 2 ) on the healing of burn wounds in rats in real time after irradiation with pulse repetition rates of 8 and 13 Hz was carried out. Comparison of the results of the 4-fold local irradiation of wounds showed that repetitively-pulsed microwave radiation with an intensity of 140 W/cm 2 at a pulse repetition rate of 8 Hz more effectively accelerates wound healing processes in comparison with exposure to a pulse repetition rate of 13 Hz. This conclusion is based on a more rapid decrease in the area of the wound surface in animals. The obtained result gives grounds to consider the use of repeti-tively-pulsed microwave radiation in medical practice as promising

Abstract Possibility of application fibrous additives of a natural origin in an ice matrix as the reinforcing additives is investigated. As a matrix, fresh ice water was used, reinforcing additives — hay fiber 10 mm long and 0.5–1 mm thick and basalt fiber produced by Plant of Basalt Materials LLC (Pokrovsk, Sakha Republic (Yakutia)) with a thickness of 9–12 µm and 40 mm long. The volume content of hay fibers was 10, 20, 30%. The density of chaotic styling of basalt fiber in a single layer was about 3 mm / mm2. Magnitude of breaking load was determined experimentally when tested according to three-point bending pattern. It is shown, that introduction fibrous additives a natural origin leads two - to triple increase of ultimate bending strength of fresh ice. During the tests, unreinforced ice samples fractured brittle along the loading force, and reinforced samples showed viscous fracture and an increase in breaking load due to the mechanical adhesion of reinforcing fibers to ice matrix.

A series of internal-pressure failure tests of steel thin-walled cylindrical shells (vessels) is carried out to measure the crack growth rate in the course of breaking current-conducting strips. The experiments use a specially designed measuring setup based on a precision converter of the signals from resistance thermometers and Terkon thermocouples interfaced with a computer. The crack velocity is measured during straight-line crack propagation and crack branching.

The possibility of using fibrous fillers of natural origin in an ice matrix as a reinforcing additive is investigated. It is shown that the introduction of fillers leads to a two- to threefold increase in the bending tensile strength of fresh ice.

Изучен результат сборки светособирающих комплексов в клетках пурпурной серной бактерии Thiorhodospira ( T .) sibirica , штамм Kir‑3, при подавлении биосинтеза каротиноидов дифениламином (ДФА). Из полученных клеток были выделены комплексы LH2 (В800-850 и В800-830) с разным составом каротиноидов. Максимального ингибирования биосинтеза каротиноидов (~90% от контроля) удалось добиться при концентрации ингибитора 53,25 мкМ (9 мг/л). Установлено, что изменения в качественном и количественном составе каротиноидов не влияют на сборку комплексов В800-830 и В800-850. Предполагается, что в популяции ДФА‑комплексов LH2 из T . sibirica , штамм Kir‑3, могут собираться как бескаротиноидные комплексы, так и комплексы, содержащие одну-две молекулы каротиноидов. Эти результаты подтверждают гипотезу о том, что каротиноиды не требуются для сборки комплексов В800-850 и В800-830.

To determine a crack growth direction, we propose to take into account constant T-stresses and the higher-order terms in the expansion of the stress field at a crack tip by representing them as a function of the angular distribution of T-stresses. A modified criterion is suggested for determining a crack growth direction using the maximum tangential stresses with allowance for the angular distribution of T-stresses at a crack tip.

The open porosity of wear-resistant modified coatings is investigated, and their macrostructure is analyzed. A statistical method is proposed for describing the formation of porosity in the laminar structure of a powder coating. The matrix of transition probabilities is determined for a uniform Markov chain. The porosity of a coating on a smooth substrate is calculated.

Изучено прямое действие синглетного кислорода на бактериохлорофилл (БХл) светособирающих комплексов в мембранах четырех видов пурпурных несерных и серных фотосинтезирующих бактерий с каротиноидами и без каротиноидов. Установлено, что БХл в образцах без каротиноидов, как правило, более устойчив к действию синглетного кислорода по сравнению с контролем. Предполагается, что каротиноиды не нужны для защиты БХл светособирающих комплексов бактерий от синглетного кислорода, а в классической работе Griffith et al . [1] процесс апоптоза клеток бескаротиноидных мутантов, который включает разрушение комплексов, появление мономерного БХл и генерацию последним синглетного кислорода с последующим окислением самого БХл, был ошибочно приписан защитной функции каротиноидов.

The change in the impact toughness of the gas main steel after operation for 50 years is studied. The mechanical properties of the pipe steel before and after operation are compared.

An estimate is made of the ultimate condition of main gas pipelines after long-term operation in the North by determining the impact strength of samples from the pipe material (in various conditions), and correlation of the values obtained with the speed of sound in materials.

The long-term safe operation of vertical steel storage tanks (VSSTs) for petroleum products in remote regions of the Far North implies objective timely detection of various types of emerging and existing defects with further provision for the monitoring of their development. The poor infrastructure and climatic features of the northern regions, as well as the time and material resources spent on preparing the standard scope of VSST testing adversely affect the performance and quality of its implementation. Therefore, taking these circumstances into account, a different approach is needed to inspect VSSTs operating in the hard-to-reach regions of the Far North. Taking the peculiarities of operating VSSTs at low temperatures in the Far North into account and based on the analysis of emergencies and accidents resulting from the degradation of VSST metal structures, the sources of damage are identified, the main problems of detecting planar flaws leading to catastrophic failures of VSSTs are shown, and a modified method is proposed for the local loading of bearing VSST members when conducting their acoustic-emission (AE) testing.

The problems of ensuring the reliability and safe operation of long-running hazardous industrial facilities, in particular gas pipelines, after 50 years of operation are considered. The goal of the work is developing a method for assessing metal embrittlement of long-running main gas pipelines (MG) using a non-destructive method for monitoring and improving operational reliability. Experimental studies of the samples of the pipes of the main gas pipelines revealed the parameters most sensitive to the processes of structural degradation. The applicability of those parameters to assessing the degree of degradation is substantiated. Analysis of the results of mechanical and acoustic studies revealed correlation with an essentially large value of the correlation coefficient. Based on this correlation, a method for assessing the toughness has been developed. The experimentally obtained limit values of the studied characteristics at which the operation of the structure becomes dangerous are presented. A flowchart has been developed for monitoring changes in the toughness of the gas pipeline steel after long-term operation. The experimental results and developed method for estimating the limiting state of the gas pipeline material were used during technical diagnostics of non-project sections of the Mastach — Berge — Yakutsk gas pipeline to determine real operational characteristics and form a database of the studied indicators for their further monitoring. The proposed method will improve the efficiency of accumulated information on the structural reliability and provide the possibility of assessing the degree of pipe metal degradation without conducting mechanical tests and making samples in the process of technical diagnostics thus reducing the material costs for conducting scheduled maintenance of the pipelines.