Obvious Stress Research Articles

Research on the Performance of a New External Occlusion Device for Pressure Vessel Leakage

Given the advantages and disadvantages of the existing plugging technology, a new type of external sealing device for pressure vessel leakage is proposed, which has the advantages of fast installation speed, small installation resistance, and stronger adaptability to the leakage surface. The connecting rod propulsion mechanism provides power, uses the fluidity of materials in the annular cavity to adapt to the complex curved surface, and carries out real-time monitoring and self-healing of the plugging process. Through the establishment of a finite element model of conventional top pressure plugging and the new type of external sac plugging method, simulation analysis of the leakage point and the pressure distribution around the crack leak has shown that: in the installation process of the new type of external liquid sac plugging device, a pressure-equalizing contact area and a sealing area are formed around the leakage point, and there is no obvious stress concentration phenomenon. When the thickness of the gasket is low, the deformation is uniform, which overcomes the problems of insufficient adaptability of the gasket in the conventional jacking method, and enhances the stability and reliability of emergency plugging.

Cadmium-induced oxidative stress, metabolic dysfunction and metal bioaccumulation in adult palaemonid shrimp Palaemon macrodactylus (Rathbun, 1902)

The Palaemonid shrimp Palaemon macrodactylus is widely distributed in coastal areas and estuaries which are easily contaminated by various pollutants. However, the responses of this species to environmental toxicants are not well described. In the present study, adult individuals of P. macrodactylus were exposed to gradient concentrations of Cadmium (Cd) to evaluate its acute toxic effects, including bioaccumulation, induced oxidative stress and changed energy metabolism in this species. The medium lethal concentration (LC50) of Cd at 24 h, 48 h, 72 h, and 96 h were 2.60, 0.88, 0.49 and 0.37 mg/L, respectively. Cd bioaccumulations in tissues of shrimp increased in a concentration-dependent manner, and higher concentration (50% 96 h-LC50, 0.185 mg/L) of Cd exposure led to a maximum increase of Cd concentration by 14.8, 145.5 and 15.8 folds in gill, hepatopancreas and abdominal muscle. Cd exposure caused a significant inhibition on the activity of catalase (CAT), and total superoxide dismutase (T-SOD), decrease in the total antioxidant capacity (T-AOC), and an increase of malonadehyde (MDA) content, which indicated a damage to the antioxidant system of shrimp. Meanwhile, Cd exposure also led to a significant up-regulation in the expression level of metallothionein gene (MT), and down-regulations at the mRNA level of heat shock protein 70 (HSP70) and CAT. Moreover, Cd exposure significantly inhibited the oxygen consumption rate (22%), and increased the ammonia excretion rate (43%), hence lead to a significant decrease of the O:N ratio (45%) in shrimp. The results indicated that Cd exposure could induce obvious oxidative stress, energy metabolic dysfunction and bioaccumulation of Cd in P. macrodactylus. The data obtained from the present study would provide useful information for further understanding on the toxicological mechanism of Cd to crustaceans in coastal areas and estuaries.

The effect of ultrasonic vibration on stress-strain relations during compression tests of aluminum alloys

Complete understanding of ultrasonic interaction with aluminum alloys is essential to promote application of ultrasonic-assisted friction stir welding process in manufacturing industry. In this study, the ultrasonic-assisted compression tests were performed to investigate the effect of ultrasonic vibration on the stress-strain characteristics of AA2024-T3 alloy. At the same time, AA6061-T6 alloy was also tested, and the stress-strain relations for both alloys were compared and analyzed to study the influence of material properties on the variation of stress-strain characteristics under ultrasonic assisted compression. It was found that on the stress-strain curves of AA2024-T3 there are an obvious and transient stress reduction concave point at the beginning of ultrasonic exertion, a hysteresis of stress recovery and a short-term small hardening phenomenon after the ultrasonic exertion stopped. The results laid foundation for process optimization of ultrasonic-assisted friction stir welding of AA2024-T3.

Seismic responses of the densely distributed caves of the Mogao Grottoes in China

Some of the largest and best-preserved Buddhist art treasure houses in the world, namely the Mogao Grottoes, are located at the northwest edge of the region of the Qinghai-Tibet plateau and are adjacent to the Altun and Qilian mountains, where the geotectonic activity is intense and large earthquakes have occurred. Future earthquakes are one of the major threats to the caves of the Mogao Grottoes; therefore, it is important that their dynamic performance is studied when an earthquake occurs. To understand the dynamic performance of the densely distributed caves under the effect of earthquakes, as well as the long-term stability of the Mogao Grottoes, the stress distribution, deformation characteristics, and peak-acceleration amplification factor were analysed under rare-earthquake conditions using a finite-difference element. The numerical study revealed that the most dangerous state of the caves is the initial time when an earthquake occurs. The obvious tensile stress concentration appeared at the top and the bottom of the caves of the middle floor; the main damage was caused by the shear failure towards the direction of the free face and not by the tensile failure. A large permanent horizontal displacement of the caves occurred after an earthquake, mostly at the densely distributed caves of the middle floor. The acceleration amplification effect of the middle-floor caves was significant; the Fourier amplitudes of the acceleration (which were monitored in all caves) were significantly magnified at the frequencies of 3 ~ 4 Hz and 7 ~ 9 Hz, whereas the Fourier amplitudes of the acceleration which were monitored in the middle-floor caves were almost amplified within the entire frequency range. Although the maximum stress was within the allowed limit and no tensile failure occurred, great permanent inhomogeneous horizontal displacements and large accelerations could have a negative effect on the stability of caves and the preservation of wall paintings. Moreover, it was assumed that the calculation results could serve as a type of guidance and as advice on the preventive protection of the Mogao Grottoes.

Silicone stressed response of crayfish (Procambarus clarkii) in antioxidant enzyme activity and related gene expression.

Organosilicon has been widely used in various fields of industry and agriculture due to its excellent properties, such as high and low temperature resistance, flame retardant, insulation, radiation resistance and physiological inertia. However, organosilicon toxicity in aquatic animals is seldom known. In this research, two typical silicone or silane coupling agents (KH-560 (3-Glycidoxypropyltrimethoxysilane) and KH-570 (3-Methacryloxypropyltrimethoxysilane)) were used in a hydroponic experiment to evaluate the effects on survival rate, antioxidant response and gene expression in red swamp crayfish (Procambarus clarkii). Crayfishes were grown in black aquaculture boxes containing different concentrations (0, 10, 100 and 1000mgL-1) of KH-560 and KH-570 for 72h, and then crayfish samples were harvested and separated into tissues of carapace, gill and muscle for analysis. The results showed that silicone significantly increased malondialdehyde (MDA) content in muscle by 17%-38% except for the treatment of 100mgL-1 KH-570, and reduced the survival rate of crayfish. Additionally, silicone KH-570 increased the activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) by 15%-31%, 17%-35%, and 9%-46%, as well as the contents of ascorbate (AsA) and glutathione (GSH) by 19%-31%, and 23%-29% respectively, in muscle tissue, and similar results occurred in KH-560. In the carapace, however, SOD activity was significantly decreased at high concentrations level of both silicone treatments. Moreover, silicon (Si) content was higher in the abdominal muscle of crayfish after silicone treatment. Assay of gene expression showed an obvious increasing expression of antioxidant related genes (Sod1, Sod2, Cat1, Cat2, and Pod1, Pod2) under silicone stress. The above results suggested that silicone caused an obvious stress response in crayfish in both biochemical and molecular levels.

Oxidative Stress From Exposure to the Underground Space Environment.

There are a growing number of people entering underground spaces. However, underground spaces have unique environmental characteristics, and little is known about their effects on human health. It is crucial to elucidate the effects of the underground space environment on the health of humans and other organisms. This paper reviews the effects of hypoxia, toxic atmospheric particles, and low background radiation in the underground space environment on living organisms from the perspective of oxidative stress. Most studies have revealed that living organisms maintained in underground space environments exhibit obvious oxidative stress, which manifests as changes in oxidants, antioxidant enzyme activity, genetic damage, and even disease status. However, there are few relevant studies, and the pathophysiological mechanisms have not been fully elucidated. There remains an urgent need to focus on the biological effects of other underground environmental factors on humans and other organisms as well as the underlying mechanisms. In addition, based on biological research, exploring means to protect humans and living organisms in underground environments is also essential.

Simultaneous improvement of plasticity and strength of metallic glasses by tailoring residual stress: Role of stress gradient on shear banding

Inducing residual stress in metallic glasses (MGs) is recognized to be beneficial for plasticity but the mechanisms on how it affects shear band nucleation, propagation and multiplication remain poorly understood. With the aid of experimental and computational approaches, we address this issue by comparatively studying the deformation behavior of two types of MG samples, which were individually prepared by surface imprinting and photo-chemical etching but having similar surface patterns. Results showed that the imprinted MGs exhibit simultaneously enhanced plasticity and compressive strength, while the etched ones show limited plasticity improvement and reduced strength. The enhanced mechanical properties of the imprinted MGs are attributed to the compressive residual stresses generated near the surfaces, rather than the resultant geometrical pits. Finite element analysis revealed that the residual stress induces obvious stress gradient and inhomogeneous plastic deformation, which facilitate heterogeneous nucleation of multiple shear bands near the surfaces. Complementary atomistic simulations further revealed that the stress gradient resulting from the residual stress slows down the shear banding dynamics and causes deflection and branching, which consequently promotes shear band multiplication during propagation. This work uncovers the interactions between the residual stresses and shear bands, which are useful for processing MGs with desirable mechanical properties.

Experimental Research on In-situ Monitoring of Coalbed Methane Extraction Pipes in a Coal Mine Working Face

To study the stress and deformation characteristics of the coalbed methane (CBM) extraction pipe and to overcome the obstruction of the CBM extraction channel, an in-situ monitoring test of the extraction pipe was performed based on a coal mine working face in the Huainan mining area. According to the data of CBM overrun and field situation, the in-situ stress and deformation test of the CBM extraction pipes was designed and implemented, and the actual stress variation and deformation of the extraction pipe in the borehole was measured, which revealed the mechanical properties of the CBM extraction pipe as the working face advanced. The results show that the stress value of each measuring point increased as the working face advanced, and there was obvious stress concentration at the depth of 50 m. When the working face was ~35 m away from the test hole, there was a major increase in the stress growth rate. This work has guiding significance for the reasonable selection of CBM extraction pipes and optimization of extraction schemes in deep coal mines.

Dynamic responses of loess tunnels with different cross sections under the action of earthquakes, rainwater seepage and trains

Four tunnel models with different cross sections were established, and the models were coupled with fluid models to investigate rainwater seepage-, earthquake- and train-induced effects. The displacements, stresses and pore water pressures of key points in the loess tunnels were analyzed, and the dynamic response patterns of loess tunnels under the influence of earthquakes, rainwater seepage and train loading were obtained. The results show that the dynamic responses of loess tunnels with different cross sections vary. Although the patterns of acceleration and displacement in the four loess tunnel sections are basically identical, the peaks of acceleration and displacement are lowest in the circular tunnel and highest in the rectangular tunnel. Furthermore, obvious stress differences exist among the different sections. The stress is lowest in the circular loess tunnel, intermediate in the curved-wall and straight-walled arch tunnels, and highest in the rectangular tunnel. The pore water pressures of loess tunnels increase with increasing depth, but the differences are not large. Shaking-table testing of a curved tunnel was carried out, and the results were consistent with the numerical results.

Evolution of nano-cracks in single-crystal silicon during ultraprecision mechanical polishing

Abstract The evolution of nano-cracks in mono-crystalline silicon during three-body polishing was investigated by three-dimension molecular dynamics (MD) simulations and theoretical calculations. Atomic displacement, coordination numbers (CN), temperature and stress during the polishing process are studied in detail. The results show that cracks will close rather than expand in ultraprecision mechanical polishing process. The simulation results show two different ways for crack closure due to different crack inclinations: the coordinated displacement of atoms and the phase transformation filling of atoms. Crack closure will result in significant changes in CN. Furthermore, the crack closure effect is the best at 600 K. The calculation shows an obvious uneven stress distribution along the crack line in the polishing process. In addition, the distribution of the normal stress and shear stress at the lower tip of cracks are related to the mode of closure, indicating that simulation is related to the calculated stresses in theoretical model.

Cluster modeling of the short-range correlation of acoustically emitted scattering signals

As a widely used measurement technique in rock mechanics, spatial correlation modeling of acoustic emission (AE) scattering signals is attracting increasing focus for describing mechanical behavior quantitatively. Unlike the statistical description of the spatial distribution of randomly generated AE signals, spatial correlation modeling is based mainly on short-range correlation considering the interrelationship of adjacent signals. As a new idea from percolation models, the covering strategy is used to build the most representative cube cluster, which corresponds to the critical scale at peak stress. Its modeling process of critical cube cluster depends strongly on the full connection of the main fracture network, and the corresponding cube for coverage is termed the critical cube. The criticality pertains to not only the transition of local-to-whole connection of the fracture network but also the increasing-to-decreasing transition of the deviatoric stress with an obvious stress drop in the brittle failure of granite. Determining a reasonable critical cube guarantees the best observation scale for investigating the failure process. Besides, the topological connection induces the geometric criticality of three descriptors, namely anisotropy, pore fraction, and specific surface area, which are evaluated separately and effectively. The results show that cluster modeling based on the critical cube is effective and has criticality in both topology and geometry, as well as the triaxial behavior. Furthermore, the critical cube length presents a high confidence probability of being correlated to the mineral particle size. Besides, its pore fraction of cube cluster is influenced strongly by the critical cube length and confining pressure.

Physiological Responses of an Arctic Crustose Coralline Alga (Leptophytum foecundum) to Variations in Salinity.

In the Beaufort Sea, Arctic crustose coralline algae (CCA) persist in an environment of high seasonal variability defined by naturally low pH ocean water and high magnitude freshwater pulses in the spring. The effects of salinity on the CCA Leptophytum foecundum were observed through a series of laboratory and field experiments in Stefansson Sound, Alaska. We found that salinity (treatments of 10, 20, and 30), independent of pH, affected L. foecundum physiology based on measurements of three parameters: photosynthetic yield, pigmentation, and calcium carbonate dissolution. Our experimental results revealed that L. foecundum individuals in the 10-salinity treatment exhibited an obvious stress response while those in the 20- and 30-salinity treatments were not significantly different for three parameters. Reciprocal in situ transplants and recruitment patterns between areas dominated by CCA and areas where CCA were absent illustrated that inshore locations receiving large pulses of freshwater were not suitable for CCA persistence. Ultimately, spatially and temporally varying salinity regimes levels affected distribution of CCA in the nearshore Arctic. These results have implications for epilithic benthic community structure in subtidal areas near freshwater sources and highlight the importance of salinity in CCA physiology.

Effects of ignition position on explosion of premixed propane‐air in a T‐type pipe

AbstractIgnition position has an important influence on gas explosion, but few researches have been done on the ignition position in T‐type pipe. In this paper, an experimental and numerical study of horizontal and vertical ignition positions in a T‐type pipe has been presented. Results show that the ignition position has a great influence on the flame propagation velocity, flame structure and explosion pressure. In the case of vertical ignition, the maximum pressure appears near the T‐type bifurcation, and there is an obvious stress concentration on the upper side wall of the bifurcation. In the case of horizontal ignition, the maximum pressure appears at the right end of the pipe, and a weak stress concentration occurring at the splitting point. When flame passing through the bifurcation, it takes 12 ms longer than ignition on horizontal, but the time for flame propagates from ignition to the end is less. The “tulip flame” forms three times after flame propagates the bifurcation when ignition on horizontal, but there is no “tulip flame” while ignition on vertical. In the case of vertical ignition, the scale of the vortex at the bifurcation is larger than that in the horizontal. The turbulent kinetic energy is mainly in the horizontal section when ignition on vertical, while it is mainly in the vertical pipe if ignition on horizontal.

Overexpression of a Monodehydroascorbate Reductase Gene from Sugar Beet M14 Increased Salt Stress Tolerance

Monodehydroascorbate reductase (MDHAR), a key enzyme to reduce monodehydroascorbate (DHA) to ascorbic acid (AsA), plays an important role in maintaining the level of ascorbic acid in plant cells. It helps to remove reactive oxygen species and regulate cellular redox homeostasis. In this study, we cloned a MDHAR gene from a sugar beet M14 line (BvM14). The full-length BvM14-MDHAR was 1737 bp, and its ORF contained 1059 bp encoding the MDHAR of 352 amino acids. In addition, we expressed the coding sequence of BvM14-MDHAR in Escherichia coli and purified the BvM14-MDHAR protein with high enzymatic activity. Quantitative real-time PCR analysis revealed that the BvM14-MDHAR was up-regulated in the BvM14 roots under salt stress. To investigate the functions of the BvM14-MDHAR, it was constitutively expressed in Arabidopsis thaliana. The transgenic plants exhibited an obvious salt stress tolerance phenotype, as evidenced by longer roots, higher fresh weight and chlorophyll contents, as well as higher AsA/DHA levels than wild-type (WT) seedlings under salt stress. In addition, the overexpression seedlings showed higher activities of MDHAR and dehydroascorbate reductase (DHAR) and decreased cell membrane damage compared to WT. The results showed that the BvM14-MDHAR confers salt tolerance through its activity in redox regulation. It is a potential target for enhancing crop salt stress tolerance through genetic engineering and molecular breeding effort.

A Constitutive Model for Cemented Tailings Backfill Under Uniaxial Compression

Constitutive model is the foundation describing the mechanical properties of materials. Cemented tailings backfill (CTB) plays an important role in goaf filling. However, a universally applicable constitutive model for CTB has not been proposed yet. In this paper, a two-stage constitutive model of CTB under uniaxial compression was established, based on the Weibull distribution density function, the strain equivalence principle and the damage mechanics theory. Eight groups of CTB samples with a diameter of 50 mm and a height of 100 mm prepared with different solid contents (70-78 wt%) and cement-sand ratios (1/4-1/10) were subjected to uniaxial compression tests to verify the validity of the theoretical model. The compared results showed that the predictions of the proposed constitutive model agreed well with the experimental results. The following conclusions were also obtained: (i) Solid content and cement-sand ratio had a significant effect on the basic mechanical parameters of the CTB samples, especially at the peak stress; (ii) The constitutive model of CTB was similar to that of the ordinary cement mortar M5, but with obvious residual stress; (iii) The failure mode of the CTB specimens under uniaxial compression was mainly tensile failure. The results presented in this paper contribute to a better understanding of the uniaxial compression characteristics of CTB and lay an important foundation for future research.

Changes in Antioxidant Enzymes Activity and Metabolomic Profiles in the Guts of Honey Bee (Apis mellifera) Larvae Infected with Ascosphaera apis.

The fungus Ascosphaera apis, an obligate fungal pathogen of honey bee brood, causes chalkbrood disease in honey bee larvae worldwide. Biological characteristics of the fungal pathogen and the molecular interactions between A. apis and honey bees have been studied extensively. However, little is known about the effects of A. apis infection on antioxidant enzyme activities and metabolic profiles of the gut of honey bee larvae. In this study, sandwich enzyme-linked immunosorbent assay and LC-MS based untargeted metabolomic analysis were employed to determine the changes in the specific activities of antioxidant enzymes and the metabolomic profiles in gut tissues of A. apis-infected larvae (105 A. apis spores per larva) and controls. Results showed that specific activities of superoxide dismutase, catalase and glutathione S-transferase were significantly higher in the guts of the control larvae than in the guts of the A. apis-infected larvae. The metabolomic data revealed that levels of 28 and 52 metabolites were significantly higher and lower, respectively, in the guts of A. apis-infected larvae than in the guts of control larvae. The 5-oxo-ETE level in the infected larvae was two times higher than that in the control larvae. Elevated 5-oxo-ETE levels may act as a potential metabolic biomarker for chalkbrood disease diagnosis, suggesting that A. apis infection induced obvious oxidative stress in the honey bee larvae. The levels of metabolites such as taurine, docosahexaenoic acid, and L-carnitine involved in combating oxidative stress were significantly decreased in the gut of A. apis-infected larvae. Overall, our results suggest that A. apis infection may compromise the ability of infected larvae to cope with oxidative stress, providing new insight into changing patterns of physiological responses to A. apis infection in honey bee larvae by concurrent use of conventional biochemical assays and untargeted metabolomics.

The gut-microbiota-testis axis mediated by the activation of the Nrf2 antioxidant pathway is related to prepuberal steroidogenesis disorders induced by di-(2-ethylhexyl) phthalate.

Di-(2-ethylhexyl) phthalate (DEHP) is a common plasticizer, which is known to be an environmental endocrine-disrupting chemical that can jeopardize the male reproductive system. Prepuberal exposure to DEHP leads to steroidogenesis disorders. However, the specific mechanism remains ambiguous. Therefore, Sprague Dawley (SD) rats underwent prepuberal DEHP exposure at a dose of 500 mg/kg per day through gavage. Additionally, the resulting testicular injury was evaluated to confirm the disturbed steroidogenesis. Changes in testicular histology, significant reduction of serum testosterone (P < 0.01) and luteinizing hormone (P < 0.001), and significantly decreased expressions of steroidogenic acute regulatory protein (P < 0.01) and 3-beta-hydroxysteroid dehydrogenase (P < 0.05) were found in DEHP-treated rats. DEHP exposure resulted in obvious intestinal damage and oxidative stress imbalance, primarily in the jejunum. Both the activation of the nuclear factor-E2-related factor 2 (Nrf2) signaling pathway and alterations of microbiota profiles were observed in all three gut specimens, but were most notable in the jejunum. We hypothesize that the gut-microbiota-testis axis, which is mediated by the activation of the Nrf2 antioxidant pathway, could be involved in the dysfunction of prepuberal steroidogenesis induced by DEHP.

Rheological properties of dense medium suspension for coal preparation

ABSTRACT Dense medium preparation is widely used in coal preparation, and the rheology of dense medium suspension is a key factor affecting the coal separation performance. The rheological properties of dense medium suspensions in coal preparation with density from 1.40 g/cm3 to 1.80 g/cm3 were investigated. A linear fitting correction method for measuring the viscosity of suspension with a rotary viscometer is proposed, which reduces the measurement error of suspension viscosity caused by particle sedimentation. The rheological equation of dense medium suspensions with 0-30% slime was determined. It has no obvious yield stress and can be described using a pseudoplastic fluid model. Proper addition of 0-7% kaolinite will increase the apparent viscosity of the suspensions, but it will not affect the characteristics of the pseudoplastic fluid in the suspension.

L-Carnitine protects against 1,4-benzoquinone-induced apoptosis and DNA damage by suppressing oxidative stress and promoting fatty acid oxidation in K562 cells.

Widespread occupational and environmental exposure to benzene is unavoidable and poses a public health threat. Studies of potential interventions to prevent or relieve benzene toxicity are, thus, essential. Research has shown l-carnitine (LC) has beneficial effects against various pathological processes and diseases. LC possesses antioxidant activities and participates in fatty acid oxidation (FAO). In this study, we investigated whether 1,4-benzoquinone (1,4-BQ) affects LC levels and the FAO pathway, as well as analyzed the influence of LC on the cytotoxic effects of 1,4-BQ. We found that 1,4-BQ significantly decreased LC levels and downregulated Cpt1a, Cpt2, Crat, Hadha, Acaa2, and Acadvl mRNA expression in K562 cells. Subsequent assays confirmed that 1,4-BQ decreased cell viability and increased apoptosis and caspase-3, -8, and -9 activities. It also induced obvious oxidative stress and DNA damage, including an increase in the levels of reactive oxygen species and malondialdehyde, tail DNA%, and olive tail moment. Additionally, the mitochondrial membrane potential was significantly reduced. Cotreatment with LC (500 μmol/L) relieved these alterations by reducing oxidative stress and increasing the protein expression levels of Cpt1a and Hadha, particularly in the 20 μmol/L 1,4-BQ group. Thus, our results demonstrate that 1,4-BQ causes cytotoxicity, reduces LC levels, and downregulates the FAO genes. In contrast, LC exhibits protective effects against 1,4-BQ-induced apoptosis and DNA damage by decreasing oxidative stress and promoting the FAO pathway.

FUNCTIONAL STATE OF OMON FIGHTERS BEFORE AND AFTER TRIP

Introduction. The study of the physiological status of representatives of power structures at different stages of service is very relevant.Purpose: a comprehensive assessment of the functional state of the body of OMON fighters before and after a 4-month business trip on perform a special task associated with health and life risks. Materials and methods. 34 OMON fighters of the Komi Republic were examined before the trip and after a 4-month trip to the North Caucasus, where they constantly experienced stress. To assess the functional state of the body, a complex of anthropometric, physiometric, psychophysiological, physiological and biochemical studies was used.Results and its discussion. Before the trip, the fighters showed an increase in the time of the visuomotor reaction, the index of functional changes, the myocardium index, the centralization index, the activity index of regulatory systems, blood pressure indicators and other changes that indicate the activation of free radical oxidation processes, and the appearance in individuals of prenosological and even premorbid conditions. In most of the examined patients, a shift in the autonomic balance was found towards strengthening the sympathetic link in the regulation of heart rhythm. Hypovitaminosis was found in many fighters. After a trip, the functional state deteriorated in most indicators (increased blood pressure, personal anxiety, cholesterol, etc., decreased life index and hemoglobin content, etc.) and the number of people with depleted regulatory systems almost doubled.Conclusion. In general, the body of OMON fighters experiences increased functional stress with signs of obvious stress both before a trip to an area dangerous for health and life, and in the first days after returning to places of permanent residence in the North. In this regard, they need additional health and rehabilitation measures related to optimization of the regime of work and rest, activation of physical education, rationalization of nutrition and strengthening the work on the psychological impact.