In this study, the strength characteristics, deformation characteristics and damage characteristics of three kinds of specimens, namely, surrounding rock, cemented paste backfill (CPB) and a surrounding rock-CPB combination, were studied by uniaxial compression testing using rice husk ash and slag as cementing materials, and the mechanical properties of the combination specimens with different height ratios were also analyzed. The results showed that the surrounding rock specimens were the strongest, followed by the composite body, and the CPB was the weakest. The relationship between different height ratios of the assemblage and the cut line modulus was found according to the fitted curves. The CPB specimens and the surrounding rock specimens showed ductile damage, while the assemblage specimens showed brittle damage. There are many hidden dangers in mines, and safety is a major cause of concern. To solve the safety problems of mining areas after mining operations have ceased, paste filling methods are widely used to solve the problems of uneven settlement and collapse in areas where rock was removed5. Cement, the cementitious material that was used in previous fillings, not only consumes a large amount of energy but also causes some environmental impact. The search for a replacement for cement has become a direction of development for filling technology6. The use of solid waste as the main research material for CPB can make full use of resources and at the same time protect the environment. Thus, finding a CPB material that can meet production needs and is economical and reasonable will be the key to solving the problem8.Mineral resources are the essential material basis of China's economy, and mining results in the formation of a many areas where rock was removed, resulting in surface subsidence, subsidence and deformation and other destructive phenomena2, which can be used as a CPB cementitious material10. Scanning electron microscopy (SEM) was used to observe the microstructure, and the observations showed that the C–S–H gel produced by the hydration of RHA was dense and acted as a CPB11. RHA replacement of cement improved the compressive, tensile and flexural strength of concrete13, which reduced the creep of concrete and improved the durability and uniformity of concrete15. Similar to the current common mineral admixtures, such as silica fume (SF)16, slag (SS)17, and fly ash (FA)18, RHA has high volcanic ash activity and is also added to concrete.RHA is a waste residue from the combustion of rice husk fuel, and its main component is SiO19 investigated the compressive mechanism of rock package fillers and found that encapsulated rock could enhance the uniaxial compressive strength (UCS) and elastic modulus (EM) of the backfill material. Fu et al.20 investigated the effect of structural parameters on the creep mechanical properties of composite specimens of surrounding rock and filling body (SR-FB). Li et al.21 conducted uniaxial compression tests on coal-rock, rock-coal and rock-coal-rock combination samples. It was concluded that the rock-coal-rock combination samples exhibited plastic damage, while the coal-rock and rock-coal combination samples exhibited brittle damage. Zhao et al.22 investigated the synergistic deformation mechanism of CPB specimens consisting of tantalum-niobium mine tailings and rocks under different ratios of cement tailings, and the results showed that the overall strength of the composite was comparable to the strength of a single CPB specimen, the modulus of elasticity increased with the decrease in the strength ratio of the specimen, and the damage modes of the CPB mainly exhibited shear damage and tensile damage. He et al.23 performed uniaxial compression acoustic emission (AE) experiments on single cement stone and cement stone-rock combinations with different cement tailings ratios to study the crack evolution of samples at different stages. Liu et al.24 investigated the mechanical properties of coal in coal-rock assemblages, and the compressive strength of coal-rock specimens increased with increasing rock strength and decreased with increasing coal-rock height ratio. Pan et al.25 investigated the deformation characteristics and loading damage of coal-rock assemblages with different coal-rock height ratios and found that the uniaxial compressive strength of coal-rock assemblages increased with increasing coal-rock height. Chen et al.26 conducted experimental and numerical studies on the response of rock-coal, coal-rock and rock-coal-rock composite structures under triaxial compression. The experimental data showed that the mechanical parameters of rock-coal-rock composites were better than those of rock-coal and coal-rock combinations, and the failure of rock assemblages mainly occurred in coal. Yu et al.27 conducted triaxial compression tests on laboratory specimens containing rock and backfill to understand the effect of the rock/backfill volume fraction and perimeter pressure on strength and fracturing in rock backfill systems. Li et al.28 conducted uniaxial compression tests on composite samples consisting of sandstone and cemented gangue-fly ash backfill (CGFB) to investigate their deformation and damage characteristics. Tan et al.29 designed a composite structure made of cement tailings backfill (CTB) and rock core (RC) and investigated its mechanical properties, damage process, damage characteristics and microstructural features. Liang et al.30 analyzed the displacement and stress field evolution characteristics of the overlying strata in backfill mining by physical modeling, and the backfill improved the stress distribution, reduced the stress concentration in the surrounding rock, and helped to prevent the progressive destruction of the overlying strata. Li et al.31 investigated the creep properties of rock bodies under different seepage conditions and effectively described the whole change process of rock creep properties according to the model.In underground mineral mining, CPB is used in the mining void to support the rock around the quarry by forming a common load-bearing CPB-perimeter rock laminar combination, which is crucial to mine stability. The mechanical properties of the CPB materials and the interaction mechanism and combination form have a significant effect on the overall synergistic deformation mechanism and the support effect of the surrounding rock. In view of the importance of the CPB-perimeter rock laminate assemblage, scholars have explored the mechanical properties and proportional optimisation design of the assemblage in recent years. Wang et al.Most of the above studies focused on the mechanical properties of different composite specimens under uniaxial conditions, and there were fewer studies on different heights and types of CPB-perimeter rock composites and fewer studies on RHA slag as a cementing material. In this study, five different types of CPB-surrounding rock combinations with height ratios of 1:9, 1:3, 3:1, 9:1, and 1:1 and two different types of CPB-surrounding rock combinations were used to compare and analyze their cut-line modulus values and compressive strength fitting curves. The stress‒strain curves and deformation damage characteristics between the combinations and single CPB and single surrounding rock were compared and analyzed to provide a basis for evaluating destabilization damage in mines. The results of this study have some significance to guide the practices of mining and filling voids in mines.2 and Al2O3, and the aggregate was made from tailing sand taken from Fuxin Mongol Autonomous County Yuan Phosphorus Mining Co. The alkali exciter was water–glass from Jiashan Yourui Refractories, and NaOH was used to adjust it to the modulus required for the experiments.The main materials for this experiment consisted of RHA, slag, aggregate, water glass and NaOH. The RHA was taken from a mining area in Hubei, and impurities were removed through simple screening. The slag was made from S95 slag produced by Shandong Kangjing New Material Technology Co., Ltd. with the main chemical composition of CaO, SiOThe uniaxial compressive strength of the rock was tested using a triaxial testing machine (model TAW-2000), as shown in Fig. 32. The above materials and proportions were used to make the surrounding rock slurry and filling slurry, and the slurry was poured into the Φ 50 mm × L 100 mm mold that had been well oiled. After 1 d, the slurry was shaped and demolded and then placed in a constant temperature and humidity curing chamber  for 28 d to obtain the specimens of the surrounding rock and CPB. The experiments were conducted in strict accordance with the GB/T50266-2013 Engineering Rock Test Standard, and the uniaxial compressive strength was measured using a rock triaxial testing machine. The experimental results are shown in Table The gelling materials used in this experiment were RHA and slag, the aggregate was tailing sand, and the exciter solution materials were NaOH, water glass and water. The RHA accounted for 10% of the cementing material, the fixed slurry concentration was 83%, the alkali-activated modulus was 1.0, the amount of alkali used was 4% of the mass of the cementing material, and the water-cement ratio was 0.35The test combination as shown in Fig. The unconfined compressive strength test was performed on three groups of specimens of CPB, net slurry and combined body and the surfaces of the specimens were polished smooth before testing. The corresponding mechanical test data were obtained by using a TAW-2000 rock triaxial testing machine. There were three CPB specimens, T1 ~ T3, and three net slurry specimens, J1 ~ J3, in each group, and there were six CPB specimens, A1 ~ A6, B1 ~ B6, C1 ~ C6, D1 ~ D6, and E1 ~ E6 in each group, totaling 36 specimens. As the composition and structure of the materials of each specimen were different, the magnitudes of their strengths differed greatly, and the corresponding changes in each type of specimen were studied by stress‒strain curves.The stress‒strain diagram of the T group CPB specimen is shown in Fig. The changing patterns of the stress‒strain curves of three net slurry specimens at an age of 28 d under uniaxial compression testing are shown in Fig. As shown in the figure, the specimens of Group J were in contact with the top plate of the press when the strain was 0 ~ 0.2. In the rising stage, the stress increased to 10 MPa, the strain was 0.2 ~ 0.7, and the curve was depressed and bent downward. When the stress increased to more than 10 MPa and the strain was 0.7 ~ 1.0, the stress continued to grow upward, the stress‒strain relationship was positive, and the curve was steeper, indicating that the strength increased faster. The J3 curve fluctuated, and the test block showed crack expansion. The curve reached the ultimate load, the stress no longer increased, the specimen cracks expanded to penetration damage, the curve fluctuated down, and the bearing capacity decreased. The curve was divided into two parts. One part was in the rising stage. Starting from the 0 point, microcracks appeared during the rising stage of the curve, and with increasing load, the cracks expanded. When the ultimate stress was reached, the cracks were still expanding, although the stress no longer increased, and the curve went downward. Microcracks appeared during the rising stage with limited crack expansion. In the falling stage, the falling curves of J2 and J3 under the stress‒strain curve were more turbulent, the stress fluctuated and decreased, there was obvious residual strength, and the crack expansion increased.The combination specimens were first compared with Group A and Group D. For the two specimens of Group A in Fig. As shown in Fig. Table The above table shows the results of this type of compression test. From 1 to 3, the compressive strength and cut line modulus of the specimen from Group A were the highest, 15.15 MPa and 7.25 GPa, respectively. The results for Group B were the second highest, with compressive strength decreased by 24% and cut line modulus decreased by 49%. For Group C, the compressive strength decreased by 43%, and the cut line modulus decreased by 62%. The compressive strength of Group D was reduced by 39% and the modulus of cut line was reduced by 60%. The compressive strength of Group E was reduced by 33% and the modulus of cut line was reduced by 57%. From Groups 1 to 3, the order of compressive strength was A-B-E-D-C, and the order of cut line modulus was A-B-E-D-C.From Groups 4 to 6, the compressive strength and cut line modulus of specimen A were the highest, 16.74 MPa and 9.72 GPa, respectively. The results for Group B were the second highest, with a 29% reduction in compressive strength and a 52% reduction in cut line modulus. Group C had the highest compressive strength and cutline modulus, respectively. The compressive strength of Group C decreased by 47%, and the cut line modulus decreased by 71%. The compressive strength of Group D decreased by 42%, and the cut line modulus decreased by 66%. The compressive strength of Group E decreased by 35%, and the cut line modulus decreased by 60%. From Groups 4 to 6, the order of compressive strength from largest to smallest was A-B-E-D-C, and the order of cut line modulus from largest to smallest was A-B-E-D-C.For the two types, Groups 1 ~ 3 and Groups 4 ~ 6, for the specimens with the same height ratio, Groups 4 ~ 6 were higher than Groups 1 ~ 3 in both compressive strength and cut-line modulus. When the height ratio was Group A, the compressive strength and cut line modulus of the assemblage were most obviously affected by the different distributions above and below the surrounding rock-CPB. From the results, the compressive strength and cut line modulus of the two groups were slightly different, but their values were similar. It was obvious from the above test data that the mechanical parameters, such as compressive strength and cut line modulus, of different composite specimens were not the same under the influence of different height ratios and different pressures on the upper side of the material. To analyze the specific influence of different height ratios and different pressures on the compressive strength and cut line modulus of the structural specimens, compressive strength, cut line modulus and cut line modulus curves were obtained for different heights and different pressures. The relationship curves of compressive strength and cut line modulus with different heights and different compression conditions are shown in Fig. The analysis shows that the peak strength of the surrounding rock was 4 ~ 5 times that of the CPB specimen, the peak strength of the combined specimen was 1–2 times that of the CPB specimen, and the peak strength of the surrounding rock specimen was 2 ~ 5 times that of the combined specimen. For the three specimens, the preliminary stress–strain slope of the CPB was smaller, the curve increase rate was smaller for the other two specimens, and the growth was slightly slower. The slope was steepest for the surrounding rock and second steepest for the combined body. For the peak strength and modulus of elasticity, the surrounding rock specimen were the largest, second-largest for the composite specimen, and smallest for the CPB specimen.There was a relationship between the structural specimens of assemblies with different height ratios and compressive strengths. When the height of the surrounding rock increased beyond a certain limit, the rebound deformation of the surrounding rock was violent, which led to a certain fluctuating trend for the overall strength of the structural specimen. Therefore, we used various fitting methods to analyze the relationship between different height ratios of the assemblage and compressive strength.Figure Figure The cut line modulus, which reflects the average stiffness of the rock in rock mechanics, was applied to study the difference. Here, the slope of the line connecting the 50% peak compressive strength point with the origin of the coordinates was chosen as the value of the cut line modulus, i.e.,The complex correlation coefficients of the three fitting methods in Groups 1 ~ 3 were 0.9192, 0.8800, and 0.9777. The complex correlation coefficients of the exponential and logarithmic and polynomial fitting in Groups 4 ~ 6 were 0.9199, 0.8843, and 0.9843, respectively. All of these showed better fitting characteristics, and the R2 values were larger for Groups 4–6. The highest results for polynomial fitting indicated that the polynomial fitting could better characterize the quantitative relationship between different height ratios and the compressive strength of the cemented fill. In addition, the interaction between the surrounding rock and the CPB affected the compressive strength of the composite specimen. The overall strength of the composite body was significantly weakened with the increasing thickness of the upper material, and the cut line modulus and strength were reduced. When the height ratio reached 3:1, the height reached a certain limit, and the strength showed rising fluctuations. Compared with the specimen of Group C with a height ratio of 3:1, the stress curve of the specimen of Group D appears to rebound, and there was a certain rise in the elastic modulus. However, due to the low overall strength, the damage started at the lower peak strength.The stress‒strain curve of the CPB is shown in Fig. The stress‒strain diagram of the surrounding rock specimen is shown in Fig. The stress‒strain curve of the CPB-sandstone composite specimen is shown in Fig. In the first stage, the surrounding rock, CPB and composite specimens all exhibited an obvious depression. In the second stage, the CPB, sandstone and composite specimens all showed nearly linear growth, but the growth was more obvious for the composite specimen. In the third stage, the slope of the curve of each specimen gradually decreased to zero. In the fourth stage, the CPB specimen maintained a high residual stress, the stress fluctuated and decreased for the sandstone specimen, and the stress fluctuated and decreased for the composite specimen. In the fourth stage, the CPB specimens maintained high residual stress, the sandstone specimens underwent fluctuating decreasing stress and the assemblage specimens underwent rapidly decreasing stress.The bending deformation damage characteristics of cast and natural stacked assemblages were different, and the strengths were also different. When the rock specimen was subjected to axial pressure only and there was no lateral pressure, the damage form was mainly tensile damage and shear damage where the shear damage form was divided into conjugate bevel and single bevel shear damages. The test CPB, sandstone and composite specimens underwent tensile damage and single bevel shear damage, and a variety of damage forms coexisted. The rock specimens were damaged, small pieces spalled and made brittle cracking sounds, and there were fluctuations in the decline and residual strength, which corresponded to ductile damage. The CPB damage was ductile without a loud noise, and the combined specimen underwent a change to brittle damage with a rapid drop in stress.The surrounding rock specimen was the strongest, followed by the combined body, and the CPB was the weakest. The average values of the compressive strengths of the CPB and surrounding rock were 7.13 MPa and 31.35 MPa, respectively, and the strength of the CPB under the upper layer of surrounding rock was higher than that of the upper layer of the CPB combination. From Groups 1 ~ 3 and 4 ~ 6, the order of compressive strengths from large to small was A-B-E-D-C, and the order of cut line moduli from large to small was A-B-E-D-C.From the stress‒strain diagram, the damage process of CPB specimens under uniaxial compression was divided into four stages: microfracture closure stage, elastic stage, yielding stage and damage stage. The CPB specimens fell gently in the damage stage, the surrounding rock specimens fluctuated and fell in the damage stage, and the combined body specimens fell rapidly.The CPB and surrounding rock specimens had obvious post-peak residual strength after the failure stage, which was mainly manifested as ductile failure. The combination specimen was directly destroyed after the elastic stage, and the bearing capacity was instantly lost, which eventually led to the instability and failure of the entire combination sample, which was brittle failure.According to research published in the literature, most materials, such as coal-rock and cement tailings, were selected in previous research on the mechanical properties of the assemblage to study the mechanical properties and the mechanism of synergistic deformation, while research on RHA slag was less common. In this paper, for the first time, the use of RHA and slag as cementitious materials, the use of alkali excitation to stimulate the activity, and the use of tailings sand as aggregate were explored to prepare a new type of CPB. Through the uniaxial compression test, the mechanical properties and damage characteristics of the three kinds of specimens were studied, and an in-depth analysis of the change stage of its specimens was conducted. Results for different types of layering and different mixing ratios showed that interactions between the surrounding rock and CPB affected the compressive strength of the assemblage specimens.In the experimental process, uniaxial compression experiments were used to study the mechanical strength characteristics based on the compressive strength and cut line modulus. The results were fitted with functions to analyze the relationship between the height ratio of the assemblage and the compressive strength. Additionally, the deformation characteristics of different specimens were analyzed through their stress‒strain curves. In future research, true triaxial tests will be used to study the mechanical properties of filling bodies as well as the acoustic characteristics and damage forms of assemblies with different thicknesses. These future studies will make it possible to continue to explore this subject at a deeper level.


Cutting fluids are the most effective method to lower the cutting temperature and decrease the cutting tool wear. At the same time, the cutting fluids influence the corrosion resistance property of the machined surface. In this study, chlorinated paraffin (CP), which is a common additive in the cutting fluid, was selected as the research objective to study its corrosion resistance property. The passivation effect of CP with different concentrations on the machined surface of stainless steel was studied. Electrochemical measurements and surface morphology investigation were used to characterize the passivation effect of CP with different concentrations. The test results showed that the corrosion resistance of stainless steel in the cutting fluid was enhanced with the increase in CP additive. This reason is that the charge transfer resistance increases and the corrosion current density decreases with the increase in CP additive. The X-ray photoelectron spectroscopy (XPS) results show that the proportion of metal oxides on the processed surface of the stainless steel sample was increased from 20.4% to 22.0%, 32.9%, 26.6%, and 31.1% after adding 1 mL, 2 mL, 4 mL and 6 mL CP in the cutting fluid with a total volume of 500 mL, respectively. The oxidation reaction between CP and the stainless steel sample resulted in an increase in metal oxides proportion, which prevented the stainless steel sample from corrosion in cutting fluid. Stainless steel, which contains 9–12 wt% chromium, is widely used in industrial  fields. The workpiece and cutting tool in the environment suffer extremely high temperature and pressure , so chloThe oxidation properties of CP make it a potential anti-corrosion agent. As mentioned in literature ,21,22,23At present, electrochemical measurements are the primary method for the research of corrosion and passivation. In the electrochemical measurements, the relationship between the given voltage and the output current helps us understand corrosion or passivation behavior indirectly ,26,27,28In this study, the passivation behavior of stainless steel in the cutting fluid with chlorinated paraffin (CP) of different content was studied using several characterization methods. The potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were selected for obtaining corrosion current density and charge transfer resistance, respectively. Scanning electron microscope (SEM) and energy disperse spectroscopy (EDS) were selected for the surface morphology observation and the characterization of the elemental composition of the passivation film, respectively. X-ray photoelectron spectroscopy (XPS) was selected for the characterization of the reaction-generated products.Icorr reflects the corrosion rate directly. The electrochemical parameter Icorr is the ratio of corrosion current and contact area. The corrosion current and corrosion potential are determined in the intersection point of anodic polarization curve and cathodic polarization curve. A higher Icorr value means a higher corrosion rate. The potentiodynamic polarization curves obtained in deionized water and E206 cutting fluid in the absence and presence of different concentrations of CP are shown in Icorr (μA cm−2), corrosion potential Ecorr (V), and Tafel slope, which are shown in Icorr values of CP-added groups were lower than E4 blank group.The potentiodynamic polarization measurement was used to measure the corrosion sensitivity of the stainless steel sample with CP of different content added in the E206 cutting fluid. In this study, Icorr value of the stainless steel sample in deionized water was considerably less than that in the cutting fluid environment. It meant the utilization of cutting fluid indeed posed a risk of corrosion. All the Icorr values obtained from groups with the addition of CP were lower than that obtained from the E4 blank group, so the corrosion resistance of stainless steel in E206 cutting fluid could be effectively improved by adding CP.It was found that the Epp). It can be observed that a significant drop of current density appeared in the interval from 1.1 V to 2.5 V with the addition of CP, so a significant passivation zone appeared (range d–e in Epp depended on the oxidation of Cr to Cr3+ [Epp of 1.1 V) and E4-CP4 (Epp of 1.16 V) reached the Epp at almost the same potential. The Epp of group E4-CP6 appeared at 1.25 V, and group E4-CP1 reached the biggest Epp of 1.44 V. The most-generated product under this condition is dense film of Cr2O3, which protects the stainless steel sample from corrosion.The final potential of polarization measurement was increased from −0.6 V to 3.0 V and the complete anodic polarization curve is shown in  to Cr3+ . Group EEsp), which depended on the oxidation from Cr3+ to Cr6+ [3. Groups E4-CP1, E4-CP2, E4-CP4, and E4-CP6 reached the Esp at 2.46 V, 2.35 V, 2.5 V, and 2.46, respectively. The secondary passive state of anode electrode in alkaline solutions was consistent with literature [E = Esp − Epp) was 1.02 V, 1.25 V, 1.34 V, and 1.21 V when 1 mL, 2 mL, 4 mL, and 6 mL CP was added, respectively. A larger passivation zone means better corrosion resistance. This result indicated that CP promoted the oxidation reaction on the surface of stainless steel sample. CP promoted the generation of passivation film on the surface of the stainless steel sample. The main composition of this passivation film needs to be further characterized using elemental analysis methods, such as EDS and XPS.Then, the current density continued to increase as the potential increased and reached the transpassive state  measurements were performed after the polarization tests. It was utilized to obtain the passivation film information of the sample surface. The experiments and fitting results of the Nyquist plot are shown in Rs), the outer layer constant phase element (CPE1), the passivating film pseudo resistance (Rfilm) [Rct). All the above parameters were fitted by Zview software .The Bode plot contains the phase angle-frequency plot, and the module of impedance-frequency plot is shown in  (Rfilm) ,36,37, tRs in each set of experiments were around 35 Ω·cm−2, resulting from an electrolyte environment with similar conductivity as shown in T is the imaginary admittance of the CPE, where n gets closer to 1, the more it tends to be a pure capacitor [Rfilm that most of the Rfilm values decreased with the addition of CP. It was relevant to the formation of low-impedance porous metal hydroxides in the outer layer. The inner layer of the passivation film became thicker with the addition of CP, which was relevant to the generation of high-impedance and dense metal oxides film on the stainless steel sample surface. This was also reflected in the change of passive film resistance Rct. Rct is relevant to the corrosion rate directly. A higher Rct means a smaller corrosion rate. Rct is inversely proportional to Icorr [Rct values in the presence of CP were greater than the E4 blank group.The equivalent circuit was proposed as shown in apacitor . As listapacitor . It can to Icorr . As listfilm were slightly smaller than the E4 blank group. It is relevant to the thinning of the outer corrosion film on the stainless steel sample surface. All the values of CPE2 were smaller than the E4 blank group and all the values of Rct were larger than the E4 blank group. It is relevant to the formation of the thicker inner passivation film on the stainless steel sample surface. It can be speculated that the outer layer CPE1 tends to increase, while the pseudo resistance Rfilm tends to decrease, which is attributed to the formation of porous metal hydroxides in the outer layer. The inner layer CPE2 tends to decrease, while the charge transfer resistance Rct tends to increase, which is attributed to the formation of dense metal oxides in the inner layer. The results of EIS measurements show good consistency with the results of potentiodynamic polarization measurements.In summary, after adding CP, the values of CPE1 were slightly larger and the values of RFour typical surface structures in this work are presented in It can be seen from these SEM photos that the original polished surface is relatively smooth, with only minor scratches after polishing with #800, #1000, #2000, and #4000 sandpaper in sequence. The experimental error caused by variation of surface roughness was reduced effectively, which is helpful for the implementation of electrochemical measurements. The EDS analysis of the stainless steel sample surface was carried out to identify the elemental composition of the different regions. As shown in As shown in Through the SEM and EDS analysis results of the stainless steel sample surface, it was found that a large area of pits and defects appeared on the surface of the stainless steel sample after the electrochemical test. It was attributed to the forced loss of electrons on the stainless steel sample surface during the strong polarization process (range a–b) in The composition of the corrosion scale on the stainless steel sample surface was analyzed by XPS. The signal of Fe 2p, Cr 2p, O 1s, and Cl 2p was used to discuss the composition of the corrosion scale. To ensure the reliability of results, the high-resolution spectra of each element were fitted in exactly the same way . A simil3O4 (710.4 eV), Fe2O3 (710.8 eV), FeCl3 (711.3 eV), and α-FeOOH (711.8 eV), respectively. Fe 2p exhibited two different valence states of +2 and +3, while α-FeOOH owned the largest peak area among all iron species in each group. This result is consistent with the SEM image shown in 2O3 (576.8 eV), Cr(OH)3 (577.3 eV), and CrO3 (578.3 eV), respectively. The dense chromium oxide protected stainless steel from corrosion. Cl 2p was decomposed into two kinds of peaks attributed to organic chloride (200 eV) and metal chloride (198–199 eV). The signal of Cl 2p was relatively small, which is consistent with the EDS results, as shown in The fitting results including binding energy (BE/eV), full width half maximum (FWHM/eV), and area of each peak are shown in The change of O 1s spectrum showed that CP promoted the oxidation of the stainless steel sample. O 1s was decomposed into three peaks, attributed to metal oxides (529–530 eV), metal hydroxides (530–532 eV), and bounded water (532–534 eV) ,47. The The formulation of XPS quantification calculation is presented by Equations (2)–(4) :(2)Am′=AChlorinated paraffin promotes the generation of metal oxidation corrosion scale, which contributed to the better corrosion resistance of stainless steel sample. Chlorinated paraffin is prone to REDOX reactions with metal in the stainless steel sample surface where iron and chromium are oxidized. According to the reaction below:Initially, the metal ions undergo a hydrolysis reaction to form metal hydroxides according to the reaction:Then, the part of the metal hydroxide continues to oxidize to form metal oxides according to the reaction:Meanwhile, part of the metal hydroxides and metal oxides react with chloride ions to form metal chloride according to the reaction:3. The inner layer of the corrosion scale was mainly composed of dense metal oxides such as Cr2O3 and CrO3. These results are in agreement with the explanation of equivalent circuits to the corrosion scale. Corrosion resistance of the stainless steel sample in the environment containing CP is better than that in the pure cutting fluid environment, which is attributed to the presence of dense metal oxide corrosion scale.In summary, CP can promote the surface oxidation of the stainless steel sample. The outer layer of the corrosion scale was mainly composed of porous metal hydroxides such as α-FeOOH and Cr(OH)The material selected for the research is a kind of hard-to-machine stainless steel, usually used in the manufacturing of turbine blades. The main component of stainless steel is shown in 2, and a Ag/AgCl reference electrode (RE), which is fully immersed in KCl solution (3 mol/L). The working electrode was encapsulated with epoxy resin. The working surface of the stainless steel was polished to the average surface roughness Ra of lower than 100 nm, which is measured by Zygo 9300 . The stainless steel samples were processed by ultrasonic cleaning in ethanol for 5 min and then washed with deionized water before each experiment. The platinum has little polarization in the electrochemical process. To prevent the pollution of the reference electrode by cutting fluid, which may lead to a slight change of reference potential during the experiments, a salt bridge containing 3 mol/L KCl solution was attached to the reference electrode. The tip of the reference electrode and the salt bridge are a porous ceramic junction that allows a low flow rate of cutting fluid to prevent pollution of reference potential by the cutting fluid and prevent pollution of cutting fluid by the reference potential.In this study, commercial water-based cutting fluid E206 from Master Chemical Co., Ltd.  and CP (40% Cl element containing) were selected for the research of passivation behavior. The total volume of prepared cutting fluid is 500 mL for each group. The volume of E206 stock solution is a constant 20 mL, expressed in the volume fraction of 4%, which group is abbreviated as E4. In addition, chlorinated paraffin of 1 mL, 2 mL, 4 mL, and 6 mL were added in the group of E4, which are abbreviated as E4-CP1, E4-CP2, E4-CP4, and E4-CP6, respectively. The pH of the solution is between 8 and 9. Another blank group of deionized water was set. All the glassware used in this experiment was washed with ethanol and deionized water. All the cutting fluid was prepared freshly with deionized water before the experiment. A conventional three-electrode electrochemical cell was selected for this study. It contains a working electrode (WE) mentioned, a platinum foil counter electrode (CE) with an area of 1 cmEcorr), corrosion current (Icorr), and Tafel slope can be obtained by the potentiodynamic polarization curve which reflects the corrosion rate directly. The range of potential was set as follows: the initial potential from −0.8 V to the final potential 0.6 V, and the scan rate to 1 mV/s. In addition, the final potential of another group was increased to 3.0 V to obtain the complete anodic polarization curve which was used to investigate the chemical process on the sample surface before and after adding CP. The electrochemical impedance spectroscopy (EIS) measurement was carried out after the polarization measurement attempt to obtain the information of the passivation film. The sinusoidal electrical signal with an amplitude of 5 mV and frequency from 106 Hz to 1 Hz was applied to the working electrode under the open circuit potential to obtain the passive film information of the working electrode surface. All the above electrochemical tests were performed by CHI 660E electrochemical workstation . The electrochemical workstation was stabled for 30 min before electrochemical measurements.All the electrodes were immersed in the cutting fluid for 30 min before electrochemical tests to obtain a stable open circuit potential (OCP), which is the potential between the reference potential and the working electrode. However, there is no current flow in the above period. All the electrochemical tests were performed under the stable OCP. The potentiodynamic polarization measurement was performed immediately. There is a current flow between the working electrode and the counter electrode, and the direction of the current changes in the process, which is called polarization current. Parameters such as corrosion potential , were performed for the observation of surface morphology and the element analysis of surface film products. The EDS analysis requires high energy, which contributed to electron beam energy set to 15 kV, and the analysis mode is point mode. EDS analysis was conducted in and around the reaction-generated product target, respectively. The XPS, provided by Thermo Fisher Scientific  with an Al Kα source, was performed for the analysis of reaction-generated products. The reaction-generated products can be identified by distinguishing the binding energies of different substances. In this study, the element variation of Fe, Cr, O, and Cl on the processed surface was investigated. The results of the EDS and the XPS analysis are the key information for the explanation of the passivation mechanism.In this study, passivation behavior of the stainless steel in the E206 cutting fluid with the addition of chlorinated paraffin has been investigated by electrochemical measurements and elemental analysis methods. It was found that the corrosion process of stainless steel in the E206 cutting fluid was alleviated by adding CP. It is related to the formation of a metal oxide layer on the electrode surface. There is a good correspondence between the results of electrochemical measurements and elemental analysis. The corrosion resistance of the stainless steel sample in cutting fluid can be enhanced as CP is added. The corrosion resistance was primarily attributed to the electronegativity of halogen substituents of CP, which result in the formation of dense metal oxides as the passivation film.


To analyse: (1) Changes in clinical parameters and in the use of social healthcare resources by patients with alcohol abuse disorder between the six months prior to the start of the pandemic and the first year of the pandemic. (2) The factors related to a worsening of clinical parameters among patients with alcohol abuse disorder.A retrospective and observational study of a population who have been diagnosed with alcohol abuse disorders according to their primary health care (PHC) electronic medical records was performed. The total sample was made up of 11,384 patients. The variables  were collected in three different time periods: (i) six months before the onset of the strict lockdown, (ii) six months following the end of lockdown and (iii) from six to twelve months after the end of lockdown. Paired Student’s T-test and a multivariate logistic regression were performed.Along the first year after the onset of the pandemic, between 44% and 54% of the patients suffered a decline in every clinical parameter. The number of PHC nursing, GP visits and social worker visits reduced significantly. As regards the associated factors related to deterioration of alcohol abuse disorder, being younger than 40 years old, having an income of over 18,000 euros/year and not having visited the social worker were associated with a worsening of the disorder.These results suggest that the impact of COVID-19 on this group has been high, and the social care offered to these patients plays a significant role in minimising the repercussions of the pandemic. Alcohol dependence and alcohol abuse or harmful use cause substantial morbidity and mortality . It is eAlcohol use disorder is associated with important life events and problems. Since 2019, people may have consumed alcohol to reduce the intensity of negative feelings caused by the outbreak of the COVID-19 pandemic , 7. To cIn relation to changes in alcohol consumption patterns during the COVID-19 pandemic, several studies and reviews have been carried out, mainly performed on the general population, the results of which diverge significantly , 12–16. In addition, the impact of the COVID-19 crisis on essential healthcare services is of great concern, as healthcare systems and particularly Primary Health Care (PHC) have been focused on treating and detecting cases of the infection, following up positive cases and contact tracing. According to the results of the PULSE survey carried out by the World Health Organization (WHO) in 105 countries, most (90%) have suffered interruptions in essential healthcare services since the beginning of the pandemic . These iTo the best of our knowledge, few studies have been performed which analyse the effect of the COVID-19 pandemic that consider not only the effects of the lockdown but also the health, social, political, and economic crisis, looking specifically at people with a history of alcohol abuse disorder, and using a longitudinal, ecological and community methodology. The use of data from PHC records allows us to quantify changes in clinical parameters, as well as the consumption of healthcare resources, with such changes possibly indicating a modification in the state of the illness. Primary healthcare is the gateway to the health system, and the closest community healthcare resource to the population. Furthermore, epidemiological analyses using real world data (RWD) such as data from primary healthcare records provide results related to decision-making from the perspective of health and social care.Hence, the aims of this study are to analyse changes in clinical parameters and in the use of social healthcare resources by patients with alcohol abuse disorder between the six months prior to the start of lockdown and the twelve months after it was lifted. We will be focusing on primary healthcare patients diagnosed with alcohol abuse disorder in one of Spain’s 17 ‘autonomous communities’, Aragon, situated in the north of the country. We also aim to analyse the factors related to a worsening of clinical parameters among these patients.This is a retrospective, ecological and observational study of a population in northern Spain (Aragon) over the age of 16 who have been diagnosed with alcohol abuse disorders according to their primary health care electronic medical records (EMR), using RWD. This massive complex and varied data set led to the use of technological tools to be processed. The clinical data management system of the Aragonese Health Service (BIGAN) collected all the data generated by the health system and anonymized them. This big data tool made it possible to build a database that included sociodemographic and clinical information of those patients older than 16 years with EMR in Primary Care and with a diagnosis of alcohol abuse disorder at least 6 months before the declaration of the state of alarm in Spain.The sample consisted of all patients with an open EMR held by health centres in the Autonomous Community of Aragon (Spain) with a diagnosis of alcohol abuse disorder at least 6 months before the declaration of the state of alarm in Spain (14/09/2019). Accordingly, the inclusion criteria were: (i) over 16 years old, (ii) registered diagnosis of alcohol abuse disorder ). The exclusion criterion was to minimise inconsistencies in the data.The total sample that met these criteria was made up of 11,384 patients. Due to the universal nature of the healthcare system and the absence of other PHC providers, the data obtained in the study is considered representative of practically 100% of the studied population.Data on sociodemographic variables, chronic comorbidities, analytical parameters, COVID-19 infection, and use of healthcare resources were collected from PHC records for the three distinct periods. The first measurement was taken from the records from the 6 months before the onset of the pandemic, which began with a strict lockdown (14/09/2019 to 14/03/2020). The second period covers the 6 months following the end of this lockdown during the first wave (03/05/2020 to 04/11/2020), and the third measurement was taken from the records for months 6–12 after the end of lockdown (05/11/2020 to 05/05/2021). The measurements taken during lockdown have not been included because there is an extremely small number of assessments and therefore there was not enough statistical power.Sociodemographic variables: sex, age, individual´s income collected from prescription charge records , social service assistance at primary health centres, and residence in a rural or urban area .Data on chronic comorbidities presenting a prevalence of over 5% in the general population  were col2 are indicative of kidney malfunction. In cases where an increase in these parameters or a decrease in glomerular filtration was found , it was considered that the disease had deteriorated.Analytical parameters related to chronic alcohol consumption were included: glutamic pyruvic transaminase (GPT), glutamic oxaloacetic transaminase (GOT), blood creatinine, and glomerular filtration. An increase in these parameters and a decrease in the last one indicate a deterioration of the illness. The main variables that indicate deterioration are GPT and GOT, which reflect decreased liver function due to alcohol consumption. The normal values for GPT are between 8 and 35 IU/L for males, and between 6 and 25 IU/L for females. The values for GOT used as a normal reference point are between 8 and 30 IU/L for men, and between 6 and 25 IU/L for women. Normal blood creatinine levels are between 0.7 and 1.3 mg/dL for men, and between 0.6 and 1.1 mg/dL for women. Finally, glomerular filtration has been calculated taking age and sex into account. Values lower than 60 mL/min/1.73mInfection with COVID-19 during the study period, classified as yes/no.Use of healthcare resources by these patients was assessed by looking at use of PHC services. This included the number of ordinary or continuous care visits to the health centre or home visits by the nurse or General practitioner (GP), the number of visits to other health professionals at the health centre , and the use of hospital services  for each of the periods under study.The sample size allowed the use of parametric methods . FirstlyTo determine variations in the analytical parameters, the differences between the GPT, GOT, blood creatinine and glomerular filtration levels for each period  were calculated. Patients with data before the outbreak of the pandemic and 6 months and/or 12 months after were included. To compare the differences in the use of healthcare resources for each period, a paired Student’s T-test was used. For those variables with a frequency of less than 100, a Wilcoxon rank test was used.To analyse associated factors related to the possible worsening of the illness, a multivariate logistic regression was performed. Worsening of the illness was considered to have taken place when GPT and/or GOT values increased, which was analysed as dependent variable. The independent variables were sex; age ; income according to prescription charge bracket ; social assistance ; residence in a rural or urban area; chronic comorbidities (categorised as not presenting comorbidity or presenting another chronic disease); and COVID-19 infection.Statistical analysis was carried out using IBM SPSS Statistic 21  and R 4.The Study Protocol was approved by the Aragon Clinical Research Ethics Committee (PI20-175). All procedures contributing to this work comply with the ethical standards of the Aragon Clinical Research Ethics Committee  and with the Helsinki Declaration of 1975, as revised in 2008. Data were obtained from clinical records provided in a non-identifiable format by the Aragon Health Service. The processing, notification, and transfer of personal data were carried out in accordance with Regulation (EU) 2016/679 of the European Parliament and Spanish Organic Law 03/2018 on the Protection of Personal Data and the guarantee of digital rights.In Aragon, on 14/09/2019 there were 11,384 patients diagnosed with alcohol abuse disorder by their GP, with males accounting for 84.1% of the total. These patients’ mean age is 56.04 (13.05), 71.5% of them had an annual income of less than 18,000 euros, and 8.1% had been infected with COVID-19. In terms of the presence of comorbidities, dyslipidaemia (45.3%), nicotine addiction (44.1%), hypertension (35.5%), depression and anxiety (35.5%), back pain (23.7%) and neoplasia (22.2%) were the most frequent chronic conditions in the study population. The analytical parameters that can indicate liver damage were found to show normal levels in both males  and females  before the pandemic outbreak. Other analytical parameters such as blood creatinine and glomerular filtration also showed normal levels. Table As for new diagnoses of psychiatric comorbidity in this population, in the 6 months before the lockdown, there were 115 (1%) new diagnoses of nicotine addiction, 186 (1.6%) of depression and anxiety, 92 (0.8%) of insomnia and 15 (0.1%) attempted suicides. However, in the 6-month period after lockdown and the 6 months thereafter, there were, respectively, 31 (0.3%) and 11 (0.1%) new diagnoses of nicotine addiction, 143 (1.3%) and 34 (0.3%) of depression and anxiety, 69 (0.6%) and 19 (0.2%) of insomnia, and 20 (0.2%) and 2 (0.01%) suicide attempts. As can be observed, there is a decrease in the incidence of psychiatric pathology.The number and percentage of patients with alcohol abuse disorder and their clinical parameters  at 6 months and 12 months post-lockdown are shown in Table As is seen in Table As regards the associated factors related to deterioration of alcohol abuse disorder, to examine the patients whose GPT and/or GOT levels worsened at 6 months or 12 months post-lockdown, a multivariable logistic regression was performed, the results of which are displayed in Table This study analyses the evolution of a sample consisting of patients who had been diagnosed with alcohol abuse disorder before the COVID-19 pandemic, at least six months before lockdown. Exposure to other serious infectious diseases (SARS) has already been associated with alcohol abuse/dependence . NeverthSome studies show results which indicate that the population with alcohol use disorder increased their alcohol consumption during the health crisis , 26–28, This disparity in results may be explained by the data resources used, but also by the periods under study and the care provided during the COVID-19 pandemic. Some studies , 29, 31 The point of data collection may be also relevant when explaining the results, since some studies analysed data during lockdown, and immediately or 6 months after it was lifted , 29. OurFear of infection and the collapse of the healthcare system, especially primary care services, during every wave of the pandemic has interrupted continuous healthcare services for all patients , 32, 33.To overcome these interruptions, telemedicine was established as the most frequently used option to replace in-person appointments and to offer psychosocial support to patients , 34. TelThe increase in demand for social services in the first months after the pandemic is also significant, reflected by the notable increase in the number of consultations with social workers. This data, according to Druss´ study , is consLooking at the long term, it is worth highlighting the increase in the number of visits to specialised care and hospital admissions at 12 months post-lockdown. This may indicate a physical and psychological imbalance in these patients’ health. This idea is supported by most of the existing literature , 42–44. Factors associated with a worsening of clinical parameters include having an income of over 18,000 euros/year and not having visited the social worker at the health centre. In relation to patient’s socio-economic situation, several studies have evaluated the cross-sectional relationship between socio-economic status and alcohol abuse, concluding that medium and high incomes were correlated with a greater frequency of alcohol abuse, higher than among those with a lower income , 46. In On the other hand, in relation to visits to a health centre social worker, during the first year of the pandemic various studies indicate that there has been a negative impact on the quality of life of those sick with COVID-19 and of the general population, at a physical, mental, social and economic level , 58, as The results of our study may help improve the prevention and health care of people with alcohol use disorder. The factors related to a worsening of this disease make it possible to know the most vulnerable population. In this way, preventive strategies must address different population groups and, especially, the one obtained in this study: being under 40 years of age, having an income of more than 18,000 euros/year and not having visited the social worker. These results, added to the increase in demand after the pandemic, make it necessary to strengthen the specialized care network of the health system, offering greater coverage. Special mention for social work professionals as a key player in the care of people with alcohol abuse disorder.Our study has some significant strengths. Its main strength is the availability of a large population database and the use of clinical-administrative data from the electronic health records of Primary Care. The evidence generated provides greater knowledge about the consequences of the pandemic in vulnerable populations such as patients with alcohol use disorder. On the other hand, it has limitations. The first limitation is that we have considered only data from electronic medical records in three time periods, what prevented knowing changes in clinical parameters during all the twelve months. The second limitation is that we do not have access to a quantified record of alcohol consumption in standard drinking units, nor to some of the specific structured questionnaires used in PC such as the CAGE or the Alcohol Use Disorders Identification Test (AUDIT). The third limitation is that we have considered an increase in the analytical parameters as an indication of deterioration, without determining whether these increases were significant. If we compare clinical parameters before and after the pandemic, these increases may not be significant , but mayIt would be interesting to carry out studies with a qualitative approach. That would give us more information about the perceptions that these patients have about the impact of COVID-19 on their health. Also, the use of geographic information systems would allow us to represent through maps the most affected basic health areas identifying geographic clusters.Our study sheds some light on the consequences of the COVID-19 pandemic in a large sample of people diagnosed with alcohol abuse disorder from a longitudinal, ecological and community perspective. The results suggest that the impact of COVID-19 on this group has been high, and the social care offered to this group of patients plays a significant role in minimising the repercussions of the pandemic.


Background and Objectives: International institutions together with the World Health Organisation recommend the teaching of BLS in schools. Therefore, the objective of this research was to study the feasibility of teaching CPR and AED through the flipped classroom, exploring the medium- and long-term retention of knowledge and practical skills among high school students. Materials and Methods: The sample consisted of 260 secondary schoolchildren  and 123 in the control group (CG)) between 12 and 14 years old (M = 12.75 ± 1.02). Results: The data revealed that the EG obtained better post-course results in the correct position of the hands (p = 0.011), the depth of external cardiac compression (p > 0.001), and the mean time to apply an effective shock with the AED (p = 0.013). The CG obtained better results in compressions with complete chest re-expansion (p = 0.025). These differences disappeared at 6 months (p > 0.05) and 12 months (p > 0.05). Conclusions: A training program based on the flipped classroom is as effective and viable as traditional training, although more efficient since it is applied in less time, in the sequence of action in BLS, CPR skills, and the application of an effective shock with an AED. Training in basic life support (BLS) and using an automated external defibrillator (AED) of the general population is widely recognised to promote a positive attitude towards cardiopulmonary resuscitation (CPR) . AdditioCPR and AED training in schools is considered an essential and effective part of disseminating knowledge, skills, and positive attitudes towards CPR and AED among the general population ,4,5 sincIt has long been established that BLS and AED courses improve knowledge immediately after application, while knowledge and skill retention have been explored less ,12. PrevThe existing literature advocates an annual 2-h BLS and AED training from the age of 12 ,17. UnfoThe aim of this research was to compare the flipped classroom with traditional teaching and to explore the medium- and long-term retention of knowledge and practical skills learned among secondary schoolchildren after a CPR and AED course.A quasi-experimental design including post-test measurements  with folTwo secondary schools in northwestern Spain were invited to participate in the research. As an inclusion criterion, it was proposed that only students who did not have a physical or mental disability that prevented them from learning and performing basic CPR manoeuvres and use of the AED in the 1st and 3rd years of secondary education would participate in this research. The schoolchildren who correctly answered the questions regarding the sequence of action for a person with possible cardiac arrest and the correct order of application of an effective shock were rejected from the investigation. Schoolchildren who did not participate in the entire process or were admitted to the educational centre after the start of the study were excluded. In addition to this, the informed consent of their parents or legal guardians was necessary for participation in this study.The following tools were used in the research’s development, and the variables mentioned below were gathered:The ad hoc questionnaire used was made up of questions related to (1) the socio-demographic data of the schoolchildren ; (2) previous training received in BLS (yes/no); (3) sequence of action for a person with possible cardiac arrest  call; 5. position of the hands and initiation of external chest compressions); and (4) correct order of AED application . Questions (3) and (4) were scored as correct or incorrect according to the answers and the order given by the schoolchildren since these answers were out of order and they had to number them in the correct order of execution.2. The space used for this part of the research was cosy and allowed for the schoolchildren participants’ privacy. The room was occupied by the researchers and one person from the educational centre’s management staff for each gender. In both schools, the measurements were conducted uniformly and in accordance with the standard methods.The weight and height of each schoolchild were assessed barefoot and in comfortable clothing using a scale and a stadiometer, respectively. The body mass index (BMI) was calculated using the formula weight (Kg)/(height (m))The Laerdal Resusci Anne CPR mannequin with SkillReporter software version 2.4  was used to perform CPR and collect data. It was exclusively programmed for chest compressions.The variables related to the quality of CPR execution collected were % total quality of hands-only CPR (75–100%); total compressions in 1 min (100–120) and 2 min (200–240); % of correct hand positioning during compressions (100%); compression depth (50–60 mm); and % of compressions with complete re-expansion (100%). Variables were categorised as achieved/not achieved.Prior to performing the external cardiac compressions, the researchers used a checklist to record whether the schoolchildren executed the following actions: scene security, consciousness assessment, breathing assessment, emergency medical system (EMS) call, positioning of the hands, and initiation of external chest compressions.The source of instruction for using an AED was the Laerdal AED trainer, a simulation of the HeartStart FR2+ Philips Defibrillator. The following variables were collected to record the use of the AED: 1. effective shock; 2. execution safety; 3. quality shock; 4. errors made; and 5. time to give an effective shock. An effective shock was considered one for which no errors were made that altered the target of the shock . Execution safety was considered if the schoolchildren were not in contact with the mannequin at the time of the shock. A quality shock was considered one for which no errors were made, the shock was performed safely, and the execution order  was correct.To carry out this research, the management of the 2 educational centres was contacted; the objective of the study was explained; and, later, a letter was sent to the parents and/or legal guardians explaining the objective, purpose, design, and procedure of the study , in addition to the declaration of confidentiality, voluntary participation, and the possibility of withdrawing the schoolchildren from the study at any time they wished.The required sociodemographic data  were recorded once the parents’ signed informed consent was obtained. In order to assist the construction of the training programmes in the control group (CG)  and the experimental group (EG) (flipped classroom training programme), the schoolchildren were then randomised by natural groups (belonging to the same group-classroom and school). An ad hoc questionnaire was presented to the participating schoolchildren before the training programmes to ascertain their background knowledge of BLS.A 50-min theoretical–practical course with instructor-led training in BLS and AED was provided to the CG. During this time, focus was placed on the value of performing hands-only CPR without pausing and using the AED in accordance with the guidelines set forth by the European Resuscitation Council (ERC) . Assurinhttps://www.youtube.com/watch?v=ZQdwoRf-TLg (accessed on 17 October 2022)), and another on the use of AEDs, lasting 3 min 57 s (https://www.youtube.com/watch?v=6W4zbqWWDs20 (accessed on 17 October 2022).; both have been used in other similar studies [The EG was given the same ad hoc questionnaire as the CG but through the virtual classroom in the physical education subject of each educational centre. This questionnaire had to be answered to gain access to 2 short videos; one of external cardiac massage of compressions only, lasting 3 min and 20 s  and experimental (EG) groups in terms of age, weight, height, and body mass Index. To check whether the previous training received, the sequence of action in terms of CPR and AED, and gender were similar in both groups, the chi-square test was used. After the training process was applied in both groups, to evaluate the differences between groups (CG vs. EG) in terms of the sequence of action for a person with possible cardiac arrest, as well as the achievement or not of quality external cardiac compression parameters and the application of the AED in terms of effective discharge, performance safety, and objective quality, the chi-square test with Cramer’s V statistic was used at each of the time points . The independent samples t-test was used to establish the differences in the times of application of an effective shock. Cohen’s d statistic was used to establish statistical power . SPSS software  was used for all statistical analyses. The level of significance was set at p > 0.05.Quantitative variables were expressed as measures of central tendency (means and standard deviation), and categorical variables were expressed as frequencies and percentages, as appropriate. The M = 12.79; SD = 1.03) participated, with a mean weight of 54.96 kg (±12.22) and a mean height of 162.76 cm (±9.42). Of these 260 schoolchildren, 117 (45.0%) were girls and 143 (55.0%) were boys.Initially, 309 schoolchildren were included in the study; however, 49 were excluded for completing the initial questionnaire’s CPR and AED action sequence questions properly. Finally, a total of 260 schoolchildren aged 12–14 years  and the EG . A total of 91 schoolchildren participants (CG = 40 and EG = 51) were assigned to re-test after six months of training, and 169 schoolchildren participants (CG = 83 and EG = 86) were assigned to re-test after twelve months, on the basis of the availability of educational centres .The initial characteristics of both groups appear in p = 0.034; Cramer’s V = 0.163, p = 0.034), in favour of the CG (97.6% vs. 89.5%).The results for the CG and EG groups at the three time points analysed  are shown in 2 = 6.450; p = 0.011, Cramer’s V = 0.158; p = 0.011). In addition to this, 101 schoolchildren (73.7%) in the EG managed to perform the correct depth range (50–60 mm) compared with 63 schoolchildren (51.2%) in the CG . Regarding compressions with complete re-expansion (100%), statistically significant differences were found in favour of the CG versus the EG (48.0% vs. 34.3%) . At 6 and 12 months after training, the statistically significant differences disappeared, and similar results were obtained in both groups  since in 100% of some occasions and close to 100% of others, the schoolchildren discharged the shock without touching the mannequin.Regarding the performance of the shock without any error, the percentages were again similar in both training groups (CG vs. EG), with no statistically significant differences at the three time points . However, the number of schoolchildren who applied the AED shock without any errors decreased in both groups when the time points were compared with each other (post-training vs. 6 months vs. 12 months).p = 0.013; Cohen’s d = 0.328). These times decreased at 6 months of training compared with post-training and subsequently increased at 12 months. Even so, the times obtained at 12 months compared with the post-training times were still lower, although the percentage of schoolchildren who were capable of applying an effective shock decreased.The mean times of the schoolchildren who managed to perform an effective shock with the AED were significantly better in the EG after training (The objective of this research was to study the feasibility of teaching CPR and AED use with flipped-classroom methodology (EG) compared with a traditional teaching method and to explore the medium- and long-term retention of knowledge and practical skills among secondary schoolchildren, considered a target population in the position “kids save lives” promoted by the ERC .The results obtained regarding the knowledge acquired after the application of the training methods indicate that both produced an increase in the knowledge and skills of schoolchildren ,28,29,30The BLS action sequence, as in previous studies ,31, was Despite this, both training processes resulted in a large number of schoolchildren being able to follow the steps of this action sequence without significant differences between the CG and the EG . This abRegarding the quality of the skills in performing CPR , approxiIn more detail, the performance of quality external cardiac compressions is closely related to the anthropometry of schoolchildren ,40. ThusThe percentage of compressions with complete re-expansion is also an indication of the quality of the external cardiac compressions so that the chest is fully released ,33. WhenThe adequate rate of compressions, which could be internalised by the feedback given by the mannequin during training , dependsThe percentages of performing the sequence in the correct order without committing any error in the application of the AED were low in both groups, and this percentage decreased at 6 and 12 months after the training. These findings are in line with what was proposed by the ERC on education for resuscitation , which iRegarding the simulation of an effective shock with the AED, and after receiving the training, the percentage of schoolchildren who managed to perform an effective shock was almost 100% in both groups (CG and EG), a percentage that was maintained in those schoolchildren evaluated at 6 months . HoweverRegarding the safety in the simulation of the application of a shock with the AED, almost 100% performed it correctly in both groups (CG vs. EG) and at all time points  .Lastly, when evaluating the time spent applying an effective shock with the AED, the schoolchildren who were able to apply it did so in just over 60 s, a time similar to that in previous studies with a population of similar age ,49. ThesThe limitations found were (1) the assignment to the control (CG) and experimental group (EG) was not random and (2) the study involved a simulation on a mannequin, and therefore, the results must be taken with caution since we do not know how the schoolchildren would react in a real situation.The results obtained in this study highlight that training through the flipped classroom is feasible and can be implemented in the normal development of classes in schools without interrupting their normal development or modifying the time structure of the didactic sessions (50 min). In addition, it allows the implementation of the teaching of the sequence of action for a person with possible cardiac arrest, the learning of quality cardiac compressions, and the correct execution of the steps to follow to apply an effective shock with an AED with the same results as traditional teaching but in less training time, according to the standards recommended by international institutions , so thatFor this reason, it is considered that training courses in BLS with mixed methodology should be promoted, in which the theoretical part can be worked on by secondary schoolchildren at home, and in this way, more emphasis can be placed on practical training, in which secondary schoolchildren obtain the amount optimal training necessary for proper performance of BLS and AED skills. Even so, it is recommended to refresh the action sequence and CPR before 6 months and skills in the application of an effective shock between 6 and 12 months.


MMP2, MMP9 and tissue inhibitor of metalloproteinases (TIMP1) in the blood of NSCLC patients during therapy . The paper also analyzes differences in the expression of the studied genes in the tumor tissue, as well as data collected in publicly available databases. The results of blood tests showed no differences in the expression of the tested genes during therapy; however, changes were observed in cancerous tissue, which was characterized by higher expression of MMP2 and MMP9, compared to non-cancerous tissue, and unchanged expression of TIMP1. Nevertheless, higher expression of each of the studied genes was associated with shorter patient survival. Interestingly, it was not only the increased expression of metalloproteinase genes, but also the increased expression of the metalloproteinase inhibitor (TIMP1) that was unfavorable for patients.In the course of lung cancer, normal cells are transformed into cancerous ones, and changes occur in the microenvironment, including the extracellular matrix (ECM), which is not only a scaffold for cells, but also a reservoir of cytokines, chemokines and growth factors. Metalloproteinases (MMPs) are among the elements that enable ECM remodeling. The publication focuses on the problem of changes in the gene expression of  K-ras and the EGFR, ALK, BRAF, MEK, MET and TP53 oncogenes [In 2020, more than 2.2 million people worldwide were diagnosed with lung cancer, which was the second most common type of cancer in the population. However, this cancer was characterized by the highest death rate . Most luncogenes . Their sncogenes .Cancer arises as an accumulation of mutations in genes responsible for the proliferation or apoptosis process, which leads to uncontrolled cell growth. Abnormal neoplastic cells are surrounded by normal stromal cells, e.g., fibroblasts; however, neoplasia significantly changes their functioning. A similar process is typical for wound healing or inflammation. This leads to an increase in angiogenesis, turnover of the extracellular matrix (ECM) and tumor cell motility . ExtraceMMP2 gene is constitutively expressed in many tissues, and it is located on chromosome 13. The MMP9 gene is located on chromosome 20, and it is most often expressed by stimuli from various types of transcription factors, such as NFκB [The metalloproteinase family is divided into six subgroups, according to their structure and specificity for the digested protein substrate. One of the subgroups includes gelatinases MMP-2 and MMP-9 with the ability to degrade gelatin ; however as NFκB .The activity of metalloproteinases depends largely on the balance between MMP concentration and tissue inhibitors of metalloproteinases. The disturbed balance in neoplastic disease results not only from altered gene or protein expression of metalloproteinases, but also from tissue inhibitors of metalloproteinases ,12. So fTIMP1 mRNA and two metalloproteinases involved in the neoplastic process, the activity of which is inhibited by TIMP-1 in non-small-cell lung cancer. The gene expression of TIMP1, MMP2 and MMP9 has been assessed in tumor tissue and blood. The results of the analysis were compared to various clinical data. This work attempts to comprehensively describe the changes in gene expression of gelatinases and TIMP1 in NSCLC, as a result of cancer development and progression as well as a consequence of applied treatment.The presented study aims to assess the change, during one year after diagnosis, in the expression of (N = 45) patients with non-small-cell lung cancer. The blood was taken from the subjects at three time points—before tumor removal surgery (N = 45), one hundred days after surgery (N = 39) and one year after surgery (N = 27). The research material also included blood from healthy individuals (N = 38) obtained from the regional blood donation center. The results of NSCLC patients were compared to those of a control group. The research was conducted with the approval of the Bioethics Committee (No. RNN/87/16/EC and KE/952/22). The clinicopathological characteristics of the study group are presented in The research was carried out on RNA isolated from peripheral blood lymphocytes and from neoplastic lung tissue obtained from later Stabilization Solutions Invitrogen (USA) and stored until isolation at −80 °C. In the collected blood samples, red blood cells were lysed with eBioscience 1X RBC Lysis Buffer  and centrifuged. RNAlater Stabilization Solution  was added to the resulting pellet, and the mixture was stored at −80 °C. Total RNA from peripheral blood and cancer tissue of NSCLC patients were isolated using the Total RNA Mini Plus kit from A&A Biotechnology  according to the manufacturer’s protocols. The concentration and purity of the isolated RNA were measured using the spectrophotometric method with an Implen NanoPhotometer . RNA samples whose A260/A280 absorbance ratio was between 1.7 and 2.0 were qualified for the study.Tumor tissue collected intraoperatively was placed in RNAThe obtained RNA samples were reverse transcribed to cDNA. The reaction was performed using High Capacity cDNA Reverse Transcription Kits from Applied Biosystems . Each sample used for the RT reaction had a final RNA concentration of 0.005 µg/mL. The composition of the reaction mixture and the temperature conditions of the reaction were in accordance with the manufacturer’s recommendations. The cDNA obtained in this process was stored at −20 °C until further analysis.GADPH (housekeeping gene), according to the manufacturer’s protocol. The sequences of the primers used for amplification are listed in To assess the presence of cDNA in all tested samples, a PCR reaction was performed using PCR Super Master Mix  for TIMP1, MMP2 and MMP9 in peripheral blood and cancer tissue samples from the patients with non-small-cell lung cancer and the control group. The quantitative amplification reaction was performed on a CFX Connect Real-Time PCR Detection System  with the nonspecific SYBR Green fluorescent dye. The reaction mixture for one sample was composed of 5 µL of iTaq Universal SYBR Green Supermix BioRad (USA), 0.35 µL of each primer , reference genes (GAPDH) and negative control were amplified in parallel. The mean of the obtained Ct values for GAPDH and all tested genes were calculated. To assess the relative level of TIMP1, MMP2 and MMP9 expression, the ΔΔCt method was used due to the similar efficiency of the qPCR of each gene [The real-time PCR method was used to perform the quantitative evaluation of the expression of genes encoding h primer , and RNAach gene .TIMP1, MMP2 and MMP9 genes in lung cancer was supplemented with the analysis of available databases. Thus, it was possible to compare neoplastic tissue and normal tissue as well as to contrast the obtained results with a larger population. For this purpose, the data collected in the UALCAN database [The assessment of changes in the expression of database  were anaThe data collected in the Kaplan–Meier Plotter database  were useU-test, Kruskal–Wallis and ANOVA tests and repeated measures ANOVA were used to assess the differences between the individual populations studied. The log-rank test was used to analyze survival rates in general populations. In all the subsequent calculations, the significance was set at the level of 0.05.The statistical analysis was performed using Statistica 13.1 software . The Shapiro–Wilk test was used to assess the compliance of the distribution of the tested feature with the normal distribution. In order to obtain the compliance of the relative expression coefficients of the studied genes with the normal distribution, they were transformed with the Box–Cox transformant. The Mann–Whitney MMP2, MMP9, TIMP1) in blood and tumor tissue  in the blood 100 days and one year following resection of tumor tissue . The results of the analysis indicate that chemotherapeutic treatment has no effect on the expression of any of the studied genes , and the second those who also received chemotherapy (N = 18). Both groups were compared for changes in the expression of all the tested genes at three time points. However, statistical analysis did not show any difference between the two groups , MMP2  and MMP9 ).Statistical analysis showed no differences in the expression of the genes between the individuals with lung cancer at three time points and the control group (TIMP1 expression during the treatment period (p = 0.035). The main difference was observed 100 days after surgery. In adenocarcinoma, there was an increase in TIMP1 expression 100 days after surgery compared to the baseline expression, while in squamous carcinoma, there was a decrease in TIMP1 expression 100 days after surgery. Interestingly, one year after tumor removal, TIMP1 expression was at a similar level in both histological subtypes of NSCLC. A similar tendency was observed for MMP2 and MMP9, but it was not statistically significant. The study also assessed changes in the expression of all the genes in the blood of the NSCLC patients examined in the course of the treatment in relation to the size of the primary tumor according to the TNM classification. However, the results of the analysis did not show statistically significant changes in the expression of TIMP1 (p = 0.6068), MMP2 (p = 0.1589) or MMP9 (p = 0.3996) in comparison with this parameter. In addition, no differences were found in the expression of all the studied genes at the analyzed time points depending on the presence of lymph node metastases  or histological grade . Moreover, the genes studied during the treatment were not affected by smoking status  or gender   .TIMP1 (p = 0.8535); MMP2 (p = 0.4627) and MMP9 (p = 0.0996)). The expression of the studied genes was at the same level in smokers and non-smokers . No correlation was found between the size of the tumor and the expression of the studied genes  in the neoplastic tissue, also taking into account their combined expression (p = 0.2698). Similarly, a lack of correlation was confirmed for the patients who had tumor cells in the surrounding lymph nodes as compared to those whose lymph nodes were free . No association between histological grade of malignancy and TIMP1 (p = 0.8934), MMP2 (p = 0.9332) or MMP9 (0.9994) expression was confirmed.Due to the lack of correlation between the expression of all the studied genes in the blood and tissue of the NSCLC patients, a separate part of the analysis involved the assessment of changes in expression in tumor samples only. There were no differences in the expression of the studied genes in lung tissue according to tumor histological subtypes , MMP2 (p = 0.9208) or MMP9 (p = 0.8674) in blood before surgical removal of tumor tissue and survival of patients with NSCLC. Similar results were obtained by analyzing the association between the expression of the studied genes in tumor samples and patient survival . The analysis of one-year survival in NSCLC patients showed no differences in the expression of the examined genes in the tumor tissue based on the one-year survival of the patients (TIMP1 (p = 0.7463); MMP2 (p = 0.8729); MMP9 (p = 0.7338)) and in the blood taken before surgical resection (TIMP1 (p = 0.5565); MMP2 (p = 0.1253); MMP9 (p = 0.304)). In addition, an analysis was carried out to assess the impact of the expression of the studied genes on overall survival, taking into account the differences between patients receiving adjuvant chemotherapy (at a more advanced stage of cancer) and those whose treatment procedure included only surgical resection of the tumor. However, the level of expression of MMP2, MMP9 and TIMP1 genes had no effect on overall survival in both study groups, in the blood of patients with adjuvant chemotherapy (TIMP1 (p = 0.997); MMP2 (p = 0.5153); MMP9 (p = 0.7648)) and in the blood of patients without adjuvant chemotherapy (TIMP1 (p = 0.1444); MMP2 (p = 0.2631); MMP9 (p = 0.7029)). Identical results were obtained for tumor tissue patients with adjuvant chemotherapy (TIMP1 (p = 0.3108); MMP2 (p = 0.6402); MMP9 (p = 0.5738)) and without adjuvant chemotherapy (TIMP1 (p = 0.2654); MMP2 (p = 0.69); MMP9 (p = 0.5649)).Survival analysis was performed based on the results of the expression of all the tested genes in neoplastic tissue and in blood prior to the surgical removal of the neoplastic tissue. The patients were divided into two groups based on the median value of the expression of individual genes . Additionally, a one-year survival analysis was performed based on the expression of the MMP2 and MMP9 (p < 0.0001) genes in NSCLC as compared to normal tissue; however, TIMP1 gene expression remained unchanged. Similarly to the results of the experimental analysis, no differences were found in the expression of any of the tested genes between the histological subtypes of the tumor. The analysis did not confirm the effects of smoking status, gender, tumor size or surrounding lymph node involvement on the expression of the studied genes.The analysis of normal and neoplastic tissue, using data collected in the UALCAN database, showed a statistically significantly higher expression of the MMP2 and the survival of patients with lung cancer (p = 0.55). However, analysis of the specific histological subtypes of the tumor showed that in adenocarcinoma, higher expression correlates with shorter survival in NSCLC patients (p < 0.001), whereas for squamous cell carcinoma, no relationship was observed (p = 0.12). Similar results were obtained in the analysis of the length of survival of patients with NSCLC depending on MMP9 expression. Without differentiation of the tumor subtypes, it has been shown that higher MMP9 expression is associated with shorter survival in NSCLC patients. Assessment of a specific histological subtype, as in the case of MMP2, confirmed this relationship for adenocarcinoma only (p = 0.009), but not for squamous cell carcinoma (p = 0.34). The analysis of the relationship between TIMP1 expression and survival time turned out to be very interesting. A statistically significant correlation was observed between lower TIMP1 gene expression and longer survival of patients with lung cancer (p < 0.001). Analyzing the correlation between the expression of the TIMP1 gene and the survival depending on a specific histological subtype of the tumor shows the correlation only in adenocarcinoma (p < 0.001). The results of survival analysis in NSCLC patients with adenocarcinoma are presented in The patient survival analysis was also supplemented with an assessment of data collected in the Kaplan–Meier Plotter database. The analysis confirmed no correlation between the expression of The extracellular matrix (ECM) is present in all types of tissues as a three-dimensional non-cellular structure necessary for the proper functioning of cells, tissues, organs and ultimately whole organisms. The significance of this structure is reflected in the fact that various types of congenital abnormalities in ECM cause disorders that are fatal. The extracellular matrix not only provides the scaffolding in which cells are located, but also is the source of many different factors affecting the process of growth, migration, angiogenesis and survival . Thus, iMMP2, MMP9 and TIMP1 gene expression in the blood of NSCLC patients to determine the prognosis for them. For this purpose, the relationship between the parameters evaluating the stage of cancer and the expression of the studied genes in cancer tissue and blood was examined. The correlation between tissue and blood expression as well as the change in expression within one year after surgical removal of the pathological tissue was also assessed. The presented study was primarily aimed to check the possibility of using the evaluation of MMP2, MMP9 and, interestingly, TIMP1 in tumor tissue or blood. However, no correlation was found in the expression of the investigated genes between tissue and blood. This indicates a similar mechanism regulating the expression of these genes within the tissue, but not throughout the body (no correlation of expression was found between lung tissue and blood samples). Metalloproteinase and tissue metalloproteinase inhibitor genes are regulated by various types of cytokines, chemokines or growth factors [MMP and TIMP genes depends on the sequence of the promoter region. The presence of sequences containing canonical retinoic acid or retinoid X receptor response elements has also been demonstrated on the promoter regions of the MMP2, MMP9 and TIMP1 genes [MMP2 and MMP9 genes is also regulated at the level of post-transcriptional modifications or transcript stability [MMP2 and MMP9 genes which was associated with an unfavorable prognosis for patients [MMP2 and MMP9 concerned only cancer cells and no other cells. This may be due to the activation of the PI3K/Akt/mTOR pathway which is observed in NSCLC tumor cells [MMP2 and MMP9 observed in this disease entity [The results of the analysis showed the presence of correlations between the expression of  factors . Mitogen factors . The regP1 genes . That cotability . An examtability . In the patients . The chaor cells . Activate entity .MMP2, MMP9 and TIMP1 genes in the blood. This suggests a state in which even the use of chemotherapy does not cause a statistically significant change in the expression of the tested genes in the blood. Numerous studies indicate the influence of chemotherapy on the expression of genes of metalloproteinases or tissue inhibitors of metalloproteinases; however, they mainly concern changes involving neoplastic tissue. An example is cisplatin, which is widely used in NSCLC as an adjuvant therapy. Studies on tumor tissue fragments taken from patients before the initiation of treatment with cisplatin and vinorelbine and two weeks after the end of the treatment cycle showed a statistically significant decrease in MMP2 gene expression compared to the baseline [TIMP1 expression showed that its use significantly increased the expression of this inhibitor. The referenced test results describe a change at the level of cancer tissue or cancer cells, but they do not refer to changes in the blood, which only indicates a local change in the expression of metalloproteinase genes after the use of adjuvant chemotherapy [The presented studies showed no effect of the adjuvant treatment on the expression of the baseline . Similarbaseline . Interesotherapy .MMP2 compared to normal tissue. Furthermore, higher expression of MMP2 in tumor tissue samples was associated with shorter survival in patients with adenocarcinoma. Similar results were obtained for the second of the gelatinases, where the tumor tissue was also characterized by the expression of MMP9 above the normal level. Again, a correlation between the level of MMP9 gene expression and the length of survival of patients with adenocarcinoma was confirmed. Studies by Liping Han et al. [MMP9, El-Badrawy et al. confirmed the overexpression of the gene in NSCLC patients relative to controls. These studies were supplemented by a zymographic analysis of proteolytic activity, which also confirmed an increase in MMP-9-derived gelatinolytic activity in tissue samples from NSCLC patients [MMP9 gene in NSCLC cells compared to normal cells. Moreover, a correlation was also observed between the higher MMP-9 activity and the increase in the potential for metastasis of cancer cells [MMP2 and MMP9 was associated with shorter overall survival in NSCLC patients. This may be due to the favorable role of both gelatinases in the progression of cancer. MMP2 and MMP9 participate both in the formation of new blood vessels and lymphangiogenesis, enabling adequate blood supply to the tumor, as well as the penetration of cancer cells into blood and lymphatic vessels. Moreover, both metalloproteinases are involved in the penetration of cells through the basement membrane, allowing the transfer of cancer cells to different sites of the body, giving rise to the process of metastasis [MMP2 and MMP9 is associated with metastatic cell activity in many types of cancer [Analysis of biological samples and information collected from external databases showed that the samples of the NSCLC patients were characterized by a higher gene expression of n et al. , which cn et al. . Addition et al. . Thus, ipatients . Other ser cells . Furtherer cells . Overexptastasis . Overexpf cancer . Moreovef cancer . Most tyTIMP1 expression carried out on available databases, i.e., UALCAN and Kaplan–Meier Plotter, which showed that tumor tissue fragments do not differ in expression from normal tissue. However, it also confirmed that TIMP1 gene expression varied within tumor tissues, and higher expression was associated with shorter patient survival. This leads to the conclusion that TIMP1 overexpression is beneficial for cancer development. Similar conclusions were drawn by Xiao et al., who observed a lower proliferative potential and increased apoptosis in non-small-cell lung cancer cells after silencing the TIMP1 gene [TIMP1 expression and shorter survival in patients with NSCLC [An interesting study was an analysis of MP1 gene . Resultsth NSCLC . A high th NSCLC .MMP2, MMP9 and, interestingly, TIMP1. Overexpression of MMP2 and MMP9 may be associated with increased angiogenesis, metastasis or lack of susceptibility to proapoptotic signals, while increased expression of TIMP1 and other non-metalloproteinase inhibitors may promote excessive deposition of collagen fibers in lung tissue, thus leading to impaired pulmonary function and fibrosis [The findings confirm that cancerous tissue in patients with NSCLC is characterized by a higher expression of fibrosis .MMP2, MMP9 and TIMP1 genes was assessed in the blood of NSCLC patients at three time points, before the tumor removal surgery, 100 days after surgery and one year after surgery, and in the tumor tissue. The study did not confirm the relationship between the level of expression of the studied genes and the length of survival of patients, which could be due to the insufficient number of patients included in the study. This resulted from the need to obtain a homogeneous group of patients who agreed to take blood samples at subsequent time points and appeared for the examination. However, evaluation of the results obtained from external databases confirmed the presence of a relationship between the level of expression of the MMP2, MMP9 and TIMP1 genes and the length of survival of patients. Work on the assessment of the role of the studied genes in NSCLC should also be continued at the level of assessing the concentration of individual proteins or assessing their activity.In the presented study, the expression of The imbalance in the remodeling of the extracellular matrix accompanying the neoplastic process is manifested in changes in the activity of proteolytic enzymes degrading the ECM, e.g., metalloproteinases. To fully understand the process of carcinogenesis, it is necessary to study the changes that also occur in non-cellular structures. Restoring the balance between the production and degradation of the ECM may be an important aspect of therapy against cancer cells. However, inhibition of proteolytic properties alone does not seem to be a perfect solution, which was confirmed by clinical trials on metalloproteinase inhibitors. Perhaps a more targeted approach, taking into account the type of cancer, the stage of cancer or other clinical and demographical aspects, may be crucial.