This paper presents research on the impact of fly ash addition on selected physical and mechanical parameters of concrete made with slag cement. Experimental tests were carried out to measure the migration of chloride ions in concrete, the tightness of concrete exposed to water under pressure, and the compressive strength and tensile strength of concrete during splitting. Six series of concrete mixes made with CEM IIIA 42.5 and 32.5 cement were tested. The base concrete mix was modified by adding fly ash as a partial cement substitute in the amounts of 25% and 33%. A comparative analysis of the obtained results indicates a significant improvement in tightness, especially in concrete based on CEM IIIA 32.5 cement and resistance to chloride ion penetration for the concretes containing fly ash additive. In the concretes containing fly ash additive, a slower rate of initial strength increase and high strength over a long period of maturation are shown. In accordance with the presented research results, it is suggested that changes to the European standardization system be considered, to allow the use of fly ash additive in concrete made with CEM IIIA 42.5 or 32.5 cement classes. Such a solution is not currently acceptable in standards in some European Countries. Research on low-emission concrete, also called green concrete, is focused on waste recycling ,2 and thFly ash (FA) is a by-product of the coal dust combustion process in heat plants and power plants, and after passing the certification process, it can be used as an additive to concrete. The use of FA and blast furnace slag as an additive to cement and concrete mixtures allows for waste recycling, reduces the cost of producing building materials, reduces the carbon footprint of concrete, and has a positive effect on selected physical properties of concrete.Numerous experimental tests on concrete mixes have shown a significant improvement in the tightness of concrete after the application of FA additive. The positive effect of the addition of FA to cement and concrete mixes is closely related to the properties, quantity, and quality of the FA used . SignifiIn , GolewskIt is worth noting that fly ash can be obtained from various sources of waste recycling. Rutkowska et al.  studied To date, the conducted studies have focused on the properties of concrete with fly ash additive based on CEM I cement. The EN 206+A1:2016-12 standard  allows tstandard  does notIncreased stable strength and very good dynamics of strength increase over long periods of maturation;Low heat of hydration ;High resistance to the action of corrosion factors, especially sulfates ;Lower water and salt absorption ;Resistance to chloride penetration and reinforcement corrosion ;Low capillary porosity ;Good workability of the mix;Stability of volume;Resistance to the destructive action of alkali from cement in concrete with reactive aggregate ;Light color, allowing for its use in the production of architectural concrete.CEM III cement has the following properties:Van Noort  indicateBecause there is a significant amount of blast furnace slag in proportions from 35% to 65%, CEM III cement can be classified as an ecological cement binder, with a low carbon footprint and high recyclability properties. Slag is a by-product in the metallurgy industry resulting from the smelting of iron ore in a blast furnace. Because of its hydraulic properties, blast furnace slag is a valuable cement component. The use of blast furnace slag in cement allows the amount of Portland clinker to be reduced, which is favorable for ecological reasons. The production of Portland clinker is a highly energy-intensive process that has a negative influence on the environment .w/c = 0.45, and the minimum content of CEM I or CEM IIA cement is 320 kg/m3.The main areas of application of concrete with CEM III binder are foundation slabs, massive foundation footings, diaphragm walls, and structural elements of underground tanks. This is due to the need to provide low concrete shrinkage, resistance to sulfate aggression, or a low heat of hydration. Foundation slabs are designed in exposure class XD3 because of their susceptibility to corrosion due to chloride. According to the standard EN 206+A1:2016-12 , for expImproved workability and stability of the concrete mix;Reduced effects of water release from concrete—less “bleeding”;Increased tightness.Properties resulting from the use of fly ash additive to concrete include:These characteristics are extremely important when making foundation slabs.In , Bijen dThe purpose of this research is to demonstrate how the use of fly ash as an additive constituting more than 25% by weight of CEM IIIA N LH HSR NA cement with strength classes 32.5 and 42.5 affects the physical and mechanical properties of concrete; in particular, its tightness and the migration of chloride ions.3 for the XD3 exposure class. However, for concrete with additives, the minimum cement content was reduced to 270 kg/m3. Simultaneously, the standard [It should be noted that currently, in some countries, such as Poland, Denmark, and UK, the use of fly ash for concrete based on CEM III cement is not allowed by the standard  and its tandards . In the tandards , the minstandard  allows tThe results of the tests carried out in this work indicate a positive influence of fly ash additive on the properties of concrete made by using CEM IIIA LH HSR NA cement of strength classes 32.5N and 42.5N. The results of experimental tests that measured strength properties and resistance to water and chloride ion penetration for concrete made of CEM IIIA LH HSR NA cement with strength classes 32.5N and 42.5N, with and without fly ash additive, were analyzed. The experimental results show that it is possible to obtain concrete based on slag cement with fly ash additive with very good tightness and resistance to chloride corrosion without impairing concrete’s strength properties. The tests were carried out for the addition of fly ash, constituting 25% and 33% of cement weight. The justification for the use of such an amount of fly ash additive is the guidelines of standard EN 206+A1:2016-12 , for theThe samples for testing were prepared for three series of concrete mixes, using CEM IIIA 42.5N cement and three series of concrete mixes made using CEM IIIA 32.5N cement. The series of concrete mixes differed in the amount of fly ash additive substituted for slag cement. Slag cement CEM IIIA 42.5 and CEM IIIA 32.5;Fly ash;Fine aggregate—pit sand with a maximum size of 2.0 mm;Coarse aggregate—natural gravel with a minimum and maximum size of 2.0 and 8.0 mm;Lignosulfonate- and naphthalene-based admixture;Polycarboxylate-based admixture;Pure laboratory pipeline water.For testing, the following materials were used:CEM IIIA 42.5N LH HSR NA and CEM IIIA 32.5N LH HSR N slag cements  were used for testing the concrete series, denoted by CM1 and CM2, respectively. The physical parameters, mechanical parameters, and chemical properties of these cements, made available by the producer, are presented in As an additive to concrete, fly ash originating from hard coal combustion in the Kozienice CHP plant located in central Poland (Kozienice) was used. The used FA has pozzolanic properties, consists mainly of spherical grains, and is certified in the 1+ system, meeting the requirements of the EN 450-1 standard .Fineness: category N, below 12%;Loss on ignition: category A, below 5%.FA was characterized by the following parameters:3S2;Mullite A2;Quartz SiO2O3;Hematite Fe3O4.Magnetite FeThe detailed results of the chemical and phase composition  of fly aThe compounds contained in the phase composition are listed in order of decreasing percentage share of FA weight.w/c = 0.45 without the addition of fly ash. Next, the composition of reference concrete mixes was modified by adding fly ash, with the simultaneous reduction of cement and sand aggregate and the assumption of unchanged The tests were carried out for six series of concrete mixtures made using CEM IIIA 42.5N cement , and using CEM IIIA 32.5N cement . The reference concrete mixes CM1-0 and CM2-0 meet the requirements of exposure class XD3 and were designed assuming the value of standard , only foThe consistency of the concrete mix was tested using the falling cone method, in accordance with EN 12350-2 .nssmD was used, determined in accordance with [2 solution. The value of the nssmD coefficient was determined on the basis of the voltage applied, the temperature of the anolyte measured at the beginning and end of the test, as well as the depth at which chloride ions penetrated, which was measured on an axially split sample. The study was conducted within 48 h.The chloride ion migration coefficient in hardened concrete was determined according to the method presented in the NT BUILD 492 standard . The tesnce with . The chlThe value of the chloride ion migration coefficient in the transient state was calculated according to the NT BUILD 492 standard , using tU—value of voltage used (V);T—average value of the initial and final temperature of the anode liquid (°C);L = 50 mm—sample height;t—duration of the test (h).Concrete water tightness testing for samples of all series was carried out after 120 days of maturation. The tests were performed on cubic samples with a side dimension of 150 mm, whose side surfaces were protected with waterproofing resin. The samples were exposed to pressurized water. For this purpose, an apparatus for testing the water permeability of concrete 55-C0246/6  was used. The device consists of a steel frame with clamps with a hydraulic system, valves, a water pressure indicator, and transparent measuring burettes. The apparatus is adapted for simultaneous testing of up to six cubic samples, and enables water supply at a maximum pressure of 10 bar. The water pressure was increased every 24 h by 0.2 MPa, in the range of 7.4–8.0 MPa. The final pressure, corresponding to a water resistance of 80 m, was maintained for 24 h. The samples were then split, and the depth of water penetration into the concrete was measured using an electronic caliper. From the results of measurements of the depth of water penetration into concrete, the average depth of water penetration into concrete was calculated for the tested samples:mw—average depth of water penetration into concrete (mm);iw—maximum depth of water penetration into concrete in the ith sample;n—number of samples tested.Cubic samples with side dimensions equal to 100 mm were tested to measure the concrete compressive strength. The tests were carried out for concrete recipes CM1-0, CM1-25, CM-33 and CM2-0, CM2-25 and CM2-33 in subsequent periods of concrete maturation from 1 to 234 days. Samples were stored in accordance with the standard [Concrete tensile strength at splitting was tested in accordance with the standard . Six cubct,splf—tensile strength of concrete during splitting (MPa);F—splitting force (N);d—dimension of the sample side (mm).The results of consistency tests presented in A comparative analysis of the obtained results of the chloride ion migration test for the three analyzed recipes indicates a significant increase in resistance to the penetration of aggressive chlorides into concrete in which FA additive was used. The measurement parameters used during the testing are shown in The category of resistance to the penetration of chloride ions with the designation “good” was obtained, both in the case of concrete without the addition of FA, i.e., CM1-0, and in the case of concrete CM1-25, in which FA was used in the amount of 25% of the cement weight. However, comparing the average values of the chloride ion migration coefficient, one can notice a clear reduction in its value, in the case of concretes containing FA additive. The average value of the coefficient obtained for CM1-25 concrete is 26% lower than the value of the coefficient obtained for CM1-0 concrete, while for CM1-33 concrete containing the largest amount of ash (33% of the cement weight), the coefficient value is as much as 43% lower. In addition, CM1-33 concrete was classified in the highest category of resistance to chloride ion penetration, defined as “very good”. The reduction in the chloride ion migration coefficient for concrete samples containing FA additive is directly related to the average depth of chloride ion penetration. In CM1-0 concrete, the depth of ion penetration is almost double that of CM1-33 concrete.One of the results obtained for the CM1-33.3 series was rejected because of microcrack induction.During the tests, no water permeation through the concrete sample was found in any case. The results in mw determined for concrete with the addition of less ash (CM1-25) is 10% smaller than the value determined for concrete without the addition of ash (CM1-0), and with the maximum ash addition (CM1-33), it is smaller by as much as 19%. In turn, in concretes made on the basis of CEM IIIA 32.5 cement, the addition of FA causes a decrease in the average value mw by 68% for CM2-25 concrete and by as much as 87% for CM2-33 concrete compared with the average value mw obtained for concrete without FA addition, i.e., CM2-0.The mean value of the water penetration depth The results of the compressive strength tests are summarized in Among CM2 concretes with long-term maturation, i.e., more than 90 days, the strength of CM2-33 concrete is observed to increase in relation to CM2-25 concrete by 4%, as shown in According to the results of this research, it can be stated that FA, as an addition to concrete based on slag cement, causes a decrease in the strength of concrete, after both the early and the long-term maturation of concrete. However, the use of FA additive in amounts above 30% in concrete based on CEM IIIA 32.5 cement does not rapidly cause a reduction in concrete compressive strength, as was observed in the case of concrete based on Portland cement .The impact of FA addition on the development of compressive strength after long-term concrete maturation was also analyzed. The results of this analysis are shown in Considering the concrete maturation time, which was 120 days, it can be concluded that the influence of the FA addition on the tensile strength of concrete made from slag cement is consistent with the results obtained for concrete based on Portland cement .The conducted tests indicate the usefulness of using type II additive in the form of FA for concrete containing blast furnace slag cement. The presented test results indicate that the addition of FA to concrete mixtures based on slag cements leads to an increase in concrete tightness and resistance to chloride aggression. Both these parameters are particularly important when making such structural elements as foundation slabs. The use of tight concrete resistant to the penetration of adverse and aggressive external factors is extremely important, not only for concrete durability but also for protecting reinforced concrete structures against corrosion. Limitation in the penetration of chloride ions is particularly important for protecting reinforcement steel against corrosion. Corrosion caused by chlorides is extremely dangerous because of its initially asymptomatic course. Consequently, it causes the formation of permanent damage to the reinforcement, which can lead to the sudden destruction of the structure. The phenomenon of corrosion caused by chlorides is additionally enhanced by moisture. For the analyzed concrete recipes, after using FA additive, a significant increase in the resistance of concrete to the penetration of chloride ions and water was observed. An increase in these parameters was observed with an increase in the amount of FA used. The results of the conducted tests indicate a significant reduction in the penetration of concrete by water after the application of FA additive for concretes using CEM IIIA cements, of both classes 42.5 and 32.5. The relationship between the depth of penetration of water and the depth of penetration of chloride ions into concrete was determined. Significantly limiting the depth of water penetration into concrete based on CEM IIIA 32.5 and 42.5 slag cements by using FA additive will significantly reduce the penetration depth of chloride ions, which is particularly important in the case of structures that are designed for exposure class XD3 and exposed to substantial chloride aggression.After a short maturation time, the FA addition significantly reduced the concrete’s compressive strength in both CM1 and CM2 concretes. With the elongation of maturation time, an increase in the strength of concrete containing FA additive was observed. Moreover, in the second phase of maturation, from day 56, the CM2-33 concrete based on CEM IIIA 32.5 cement and containing a maximum of 33% FA additive was found to have higher strength than the CM2-25 concrete containing 25% FA additive. Comparing the results of the tests, it can be seen that concrete based on CEM III 32.5 cement with the addition of FA has a much greater resistance to water penetration and a greater reduction in strength in the initial maturation phase than concrete based on CEM III 42.5 cement with the same percentage of FA additive. In concrete with CEM III 32.5 cement, neither compressive strength nor tensile strength at splitting decreases proportionally to the increase in the FA additive content, as is observed with concrete with CEM IIIA 42.5 cement. The test results also indicate the usefulness of using FA as an additive to concrete based on CEM IIIA 32.5 cement, since there is a significant improvement in concrete tightness. Nevertheless, it should be remembered that the strength of concrete is reduced during the initial time of concrete maturation, which must be considered when designing it. In light of the test results obtained, changing the national standardization systems to allow the addition of fly ash to concretes based on CEM IIIA 42.5 and 32.5 slag cements is an issue worth considering.The following conclusions were made from the results obtained during the research.The addition of fly ash increases the tightness and resistance to the penetration of chloride ions of concrete made of slag cement.Fly ash reduces the depth of penetration of water under pressure into concrete based on CEM IIIA 32.5 slag cement, to a greater extent than that based on CEM IIIA 42.5 cement. The addition of FA reduced the depth of water penetration under pressure by 19% for CM1-33 concrete, and by as much as 87% for CM2-33 concrete, compared with reference concretes that did not contain fly ash.mw is proportional to the decrease in the average depth of the penetration of chloride ions into concrete m,totx. The proportionality coefficient for this reduction is in the range The relationship between the resistance of concrete to water penetration under pressure and resistance to chloride ion penetration is demonstrated. A comparison of the test results obtained for concretes CM1-0, CM1-25, and CM1-33 indicates that the effect of FA addition on reducing the mean value of the water penetration depth under pressure into concrete FA addition to concrete based on slag cement reduces compressive strength during the initial and long-term maturation times. In the case of concrete based on CEM IIIA 42.5 cement, the reduction in compressive strength after the application of FA additive in amounts of 25% and 33% by the weight of cement is similar and does not exceed 5%. This applies to both the standard maturation period, i.e., after 28 days, as well as the extended maturation period, i.e., after 190 days. Concrete based on CEM IIIA 32.5 slag cement after using FA additive is characterized by a significant reduction in compressive strength, which after 28 days of maturation, is 23% (series CM2-25). After the long maturation period of over 120 days, the reduction in compressive strength of concretes containing FA additive does not exceed 10%.The use of FA additive for concretes based on slag cement in amounts of up to 33% by weight of cement is beneficial. The conducted research shows that the FA addition of 33% compared with the addition of 25% by the weight of cement in concrete based on CEM IIIA 42.5 cement does not significantly affect compressive strength and, in the case of concrete based on CEM IIIA 32.5 cement, even causes an increase in this strength. These observations refer to both standard and long maturation periods. The increased addition of fly ash significantly increases the tightness of concrete and its resistance to the penetration of chloride ions.k factor at XD1-3 concrete exposure for CEM IIIA cement classes as well.Consideration should be given to allowing the use of the


The typical pollution events were highly consistent with the evolution path of fine aerosol compelled by extreme weather. The ozone concentration and the atmospheric oxidation capacity can be stably maintained at a low level when NO2 concentration remained at 50–70 μg/m3, no matter how much the AQI was. Meanwhile, ozone concentration in the downwind suburban was as low as the central city and soared in few stations amid post-lockdown, simultaneous the correlation between ozone and other pollutants converted from negative to positive. The trajectory indicated that the pollution sources during the lockdown and pre-lockdown were basically Southern Russia, Inner Mongolia, and the three provinces of Northeast China, the pollution from the Bohai Sea provoked ozone pollutants in Shenyang to rebound briskly amid post-lockdown, the pollution of neighboring countries and areas would have a stronger impact on air quality under the effect of lockdown.During the eruption of COVID-19, a citywide lockdown was executed from 26 January to 23 March 2020, in Shenyang, in which the ozone pollution has recorded significant variations. This paper mainly anatomized the comprehensive characteristics and evolution trends of ozone pollution based on the lockdown period in the first half of 2020. Using the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model and cluster analysis method to establish backward trajectories and channels, the spatial transport process of ozone in the preset period and the causation of typical ozone pollution events were investigated in depth. The results demonstrated that: The ozone concentration pollution in the first half of 2020 was increased than last year. During the lockdown period, the basic pollutants levels were lower than that in pre-lockdown under different proportions, except O The COVID-19 epidemic broke out on a global scale in 2020, and global health is undergoing an emergency. Nearly 90% of the countries around the world have imposed stringent social isolation measures against the pandemic. Huge economic losses and unprecedented economic catastrophe were aroused under the shutdown of global social activities [2 levels over China during lockdown (10–25 February 2020) compared to pre-lockdown (1–20 January 2020) were recognized by satellite data from NASA and the European Space Agency [2 in Almaty, Kazakhstan reduced sharply by 49% and 35%, respectively, during the lockdown compared with the pre-lockdown, except O3 levels mounted by 15% [10, SO2 and NO2 on 2 March 2020, which decreased by 75%, 49% and 96%, respectively [2.5, PM10 and NO2 concentrations during the lockdown, resulting in a significant reduction of 40%, 32% and 13%, respectively [3 titration of NO [The lockdown caused by the epidemic had a positive impact on environmental air and water quality . Decrease Agency . Concentectively . Anotheron of NO .http://www.nhc.gov.cn/), and created good conditions for accelerating the resumption of employment and fabrication throughout the country [2.5 governance begins to improve significantly after years of efforts. From 2013 to 2017, the average ozone concentration in 74 major cities increased by 20% [3-8 h, whose concentration in Changchun was 138 μg/m3 in 2017 [3 in 2018 in Harbin [3 in 2018, 166 µg/m3 in 2017) [The Chinese government has adopted rapid and drastically defensive measures to block the spread of the COVID-19 epidemic. Countless provinces and cities across the country have successively initiated first-level responses to major public health emergencies , which s country . In thisd by 20% . As the d by 20% ,16. JudgLiaoning Province is an important coastal province in the three Eastern Provinces of China. As the capital of Liaoning Province, Shenyang, located in the center of Northeast Asia and Bohai economic circle, along with the Liaodong Peninsula, is regarded as a comprehensive transportation hub connecting the Yangtze River Delta, Pearl River Delta and Beijing–Tianjin–Hebei to the Kanto region. The research on air pollution in Northeast China has been lacking in recent years, of which the ozone pollution in Shenyang was the most omitting related research covered from 2013 to 2017, methods included the characteristics and differences of basic concentration variations, the effects of meteorological elements and ozone precursors  and the 3, PM2.5, PM10, NO2, SO2 and CO at 9 national controlled sampling stations from 1 January to 30 June 2020, from Shenyang Ecological Environment Monitoring Center of Liaoning Province, as well as hourly meteorological data from Shenyang Meteorological Observatory, in which O3 was treated by the sliding eight-hour average method, MDA8 represents the daily maximum eight-hour average ozone concentration specified in the Ambient Air Quality Standard (GB3095-2012). The nine national control stations include Cultural Road (CTR), Lingdong Street (LDS), Forest Avenue (FRA), Dongling Road (DLR), Riverside Road (RSR), Xinxiu Street (XXS), Jingshen Street (JSS), Hunnan East Avenue (HEA), and Taiyuan Street (TYS). The location information of the monitoring station is shown in This study obtained hourly data of Air quality index (AQI) and six kinds of basic pollutants of OWe used the comprehensive index method to make descriptive statistics on the ozone pollution concentration data of Shenyang in 2020, evaluate the total scale, average level, relative level and dispersion degree of pollutants, and summarize its comprehensive characteristics and evolution trend. Before the data analysis, the hourly concentration of pollutants was processed by 8-h moving average, and the daily and monthly mean values were obtained according to the processed values. The standard deviation analysis and inter-annual deviation analysis of the pollutant concentration were carried out. We applied the HYSPLIT model and established a transmission channel to analyze the special pollution events, which was also supplemented by the vorticity evolution at 500 mb sea level pressure and fine aerosol optical thickness in East Asia from Modern-Era Retrospective analysis for Research and Applications (MERRA-2 Greenbelt MD USA). All appendices are placed at the end of the text. Finally, we set three periods according to the epidemic lockdown order and made a comparative analysis of the data to determine whether the lockdown effect existed. The correlation analysis was used to reveal the correlation between meteorological factors and pollutants, and the Kriging interpolation method was used to analyze the spatial ozone distribution.The HYSPLIT model used in the long-distance transmission research in this paper is developed by the National Oceanic and Atmospheric Administration (NOAA) with Air Resources Laboratory (ARL) , combineD is the distance between any two trajectories; t is the trajectory transmission time; i is the backward trajectory number; j is the stop point number; x is the number of trajectories in the cluster; dj is the spatial distance between the jth stop points of the two trajectories; dij is the spatial distance from the jth stop point in the ith backward trajectory to the corresponding stop point of the average trajectory; SPVAR is space variation of each group of trajectories; TSV is total space variation.The calculation formula of SCA is as follows:In addition, the trajectories of the four events were connected together in the order of first backward then forward, to form a complete transmission channel to determine the whole process path of the source and destination of the pollutants.According to the order of the Shenyang COVID-19 Pneumonia Epidemic Prevention and Control Headquarters (No. 1), Shenyang has initiated the first-level response to the COVID-19 epidemic from 0:00 on 26 January 2020. From this moment, the city officially closed the city. According to order No. 9, since 23 March 2020, Shenyang has officially unblocked, with fully resumed work and production, and normal living order has been restored. Consequently, the data obtained in the first half of 2020 were divided into three periods as follows: 1 to 25 January as pre-lockdown (Previous lockdown); 26 January to 23 March as lockdown; 24 March to 30 June as post-lockdown.We perceived four special stages of ozone pollution and marked them out in 3-MDA8 exceeded the second-level standard in 2018. The highest value appeared on 24 June, reaching 288 μg/m3, which was 29 μg/m3 higher than the maximum on 24 May in 2019. In 2019, the degree of ozone pollution decreased, with 33 days exceeding the standard, and the seasonal variation throughout the year weakened. Compared with 2019, the daily ozone concentration in the first half-year of 2020 grew with an average ratio of 8.9%, the average daily ozone MDA8 concentration (96.24 μg/m3) increased by 1.4% and 1.2% lower than that in 2018. As same as 2019, the ozone concentration in 2020 began to exceed the standard in late April  plays an intermediate role in O3 and NO2 [2 and O3 are interrelated through the rapid titration reaction of NO with O3, producing NO2, especially at urban sites, the comprehensive oxidation capacity (Ox) of the atmosphere can be evaluated by observing O3 and NO2. As shown in 3), when the atmospheric oxidation capacity and ozone pollution remained at a meager level at this stage. Combined with the correlation results  is an air quality assessment standard issued by the Chinese government in March 2012 to protect public health. It is an important index used to describe the degree of air cleanliness or pollution and its impact on human health, which can assess the health effects of breathing polluted air for hours or days. As shown in rol zone .In order to have a more detailed understanding of ozone pollution in the first half of 2020, we defined four ozone pollution periods as pollution events. Event 1 occurred during the long New year holiday. Affected by epidemic control instructions and festivals, residents needed to reserve materials in large quantities, resulting in frequent human activities and increasing man-made emissions. Event 2 arose when the majority of residents left their accommodation where they have stayed for more than two weeks and began to expand the scope of their activities. Both events 3 and 4 occurred amid post-lockdown, in which the ozone concentration had already climbed hastily. It can be clearly found that the relative humidity was relatively lower than the around value during the four events in As shown in −5/sec, which was not conducive to the diffusion of pollutants and led to the accumulation of pollutants locally. Eventually, ozone pollution reached a peak in the first half of the year.Wind speed in western China was extremely fast, with a large span and transition, which led to the rapid blowing of pollutants to the Pacific region. Event 3 appeared on April 16 was quite special; the transmission channels formed a spiral path with a rotation of 360 degrees. Thus, we investigated the meteorological data of the day , recogni2, PM10, and PM2.5 have dropped significantly [2.5 concentration dropped by 24.9% year–on–year, with the Yangtze River Delta stood ahead. Both ground and tropospheric NO2 concentrations were reduced by 20% to 30%, and the CO concentration was reduced by 17% year–on–year [2 decreased by 34.4%, AQI by 37.1%, PM2.5 by 46.4%, PM10 by 39.5%, SO2 by 45.6%, and CO by 43.3%, details were shown in 3 and NO2 in 3 and NO2 was not affected, and the peak value of ozone affected by titration still appeared after the valley value of NO2, regardless of whether there was a lockdown or not. What is different was that regardless of whether it was under lockdown control or not, the variations fluctuations of single-peak ozone and single-valley nitrogen dioxide throughout the day were delayed overall. Existing research concerning the ozone in Shenyang from 2013 to 2015 reported that its daily variation peaks generally appeared at 14:00–15:00 [The epidemic lockdown was a turning point for the environment, and it is necessary to discuss the ozone pollution in stages and analyze the impact of the lockdown. Affected by the epidemic, the air quality throughout the country has increased in the meanwhile, among which the NOficantly ,36. The –on–year . Figure 2 was normally negative. The change of the correlation between them in this stage and the extremely low NO2 caused by the decrease of ozone titration reaction in a short time revealed the main reasons. The influence of external factors was not ruled out. During the lockdown, only SO2 was negatively correlated with ozone with an extremely weak correlation. The concentration of SO2 and CO did not rebound as quickly as other pollutants but continued to decline during post-lockdown. As the main pollutant in winter, SO2 was greatly affected by coal-burning during the heating stage; it was normal that the concentration continued to drop.The lockdown also caused an attractive alteration. As shown in the correlation visualization results in The extreme lockdown measures taken during the epidemic greatly cut off the pollution source emissions. Nonetheless, a simple analysis of the variations in the observed concentration of local pollutants was not enough. The pollutant concentrations of each monitoring station were spatially interpolated, as shown in We used the HYSPLIT model to process the backward trajectories of the three preset periods, and four trajectories were clustered in each period to facilitate the source analysis of the pollution. As shown in 3 to the ground, resulting in the increase of surface O3 concentration. At the same time, it can also aggravate the horizontal diffusion, dilute the high O3 concentration, and greatly improve the pollution of ozone.Throughout the first half of 2020, the overall fluctuation of ozone pollution has increased. On one hand, adverse meteorological conditions led to high ozone concentration, which was further confirmed by the analysis of four special ozone pollution events in the first half of the year. In the case of high humidity, the free Hydrogen and hydroxyl radicals contained in water vapor quickly decomposed ozone into oxygen molecules and reduced the ozone concentration, causing a negative correlation between ozone and humidity ,46. Surf2.5 may bring the potential risk of increased ozone content. When the concentration of PM2.5 in the atmosphere decreased significantly, it would lead to an increase of light radiation, which was beneficial to the formation of ozone. At the same time, the inhibition of particles on the photochemical process results in the decrease of atmospheric oxidation ability, which was the possible reason for the decrease of near-surface ozone concentration in 2020 [2.5 while failing to regulate the proportion of NOx and VOCs, ultimately aggravating ozone pollution. Compared with previous years, the overall ambient air quality was further improved in 2018–2019; government work has achieved breakthrough results; nevertheless, ozone pollution became protruding. Furthermore, in the first quarter of 2020, the domestic ozone concentration increased by 3.4% from year to year, and 8.1% in April, while PM2.5 concentration fell by about 15% year–on–year. Research showed that O3-MDA8 continued to grow at an average rate of 4.6% every year [On the other hand, precursor pollutants also play an indispensable role. Numerous studies have shown that a remarkable reduction in PM in 2020 . China hery year , and Lia3, NO2, particulate matter was positively correlated with ozone all-cause mortality [3 was the highest proportion of the six basic pollutants, and the meager ozone pollution would cause higher mortality rate [2 and O3, coupled with the fact that both are associated with health effects, has also led to recent interest [2 concentration has a very important effect on ozone. The ozone concentration was the highest when the NO2 concentration was low, which also verified that the reduction of NO titration led to less ozone consumed and accumulated NO2. When AQI and NO2 concentrations in Shenyang reached standards, not only the atmospheric oxidation capacity turns into the weakest, but also the ozone concentration was in a steady-state. Most importantly, when NO2 reached 50–70μg/m3, ozone pollution would not affected by the comprehensive assessment index of air pollution. This characteristic proved the importance of coordinated ozone treatment, and the judgment of oxidation capacity could assist in determining the emission reduction ratio of ozone precursors in the future.There was also sufficient and robust evidence that the short-term exposure to Oortality ,52, the ity rate . The cheinterest . In our 2.5 (46.4%), NO2 has the smallest drop, but also reached 34.4%. On the contrary, the ozone concentration increased continuously during this period, with an increase of 69.7%. This study also found that the correlation between ozone and other pollutants was reversed during and after the strict implementation of the lockdown measures; ultimately, the reason was that the ozone titration effect was greatly reduced. Affected by the epidemic, the spatial distribution of ozone pollution in Shenyang in 2020 changed in different periods but was consistent with the same period in previous years. Shenyang has always followed the regular pattern that the concentration in the central urban area was lower than that in the suburbs [Similar to much other literature on research results of pollutant variations from the perspective of epidemic lockdown ,56, duri suburbs . In 2020During the period of the epidemic, the lockdown measures greatly improved air pollution, but ozone pollution was more serious than before, and the pollution concentration was higher than that in previous years. After the unsealing of the epidemic, concentrations of various pollutants in the study area rebounded swiftly, and the long-distance transmission channel also made the pollution sources in Shenyang more complex. Considering the factors discussed comprehensively, the higher ozone levels in the lockdown period was not only caused by the long-distance transmission and simple increase of ozone concentration but also due to the reduced titration from reduced nitric oxide, and less ozone was consumed.2 (−34.4%), PM2.5 (−46.4%), PM10 (−39.5%), SO2 (−45.6%) and CO (−43.3%) level, while O3-MDA8 increased by 60.4% amid post-lockdown than lockdown period, and 172.2% than pre-lockdown period. Moreover, the peak time of the daily variations of ozone and nitrogen dioxide was delayed, and the correlation between ozone and other pollutants transformed from negative to positive during the lockdown period. Of paramount importance, it was found for the primary time that no matter how much was the AQI value, the ozone concentration stably maintained at the standard level when NO2 concentration stained at a low level (50–70 μg/m3), which confirmed the prominence of coordinated ozone treatment. As for the four pollution events, we established the transmission channel by HYSPLIT to characterize the whole pollution paths of the source and whereabouts intuitively and found out that they were highly consistent with the evolution path regarding the high pollution region of fine aerosol compelled by high wind speed and low-pressure anticyclone involving by abnormal meteorological systems. Meanwhile, compared with the previous years, the spatial distribution of ozone pollution changed little. The ozone concentration in the northwest of Shenyang was all higher than that in the southeast region, of which the high value was distributed in the north of the urban area, the concentration in the downwind suburban was as low as the central city. High temperature and low humidity were still the main reasons for the overall increase in ozone temperature during post-lockdown. The abnormal phenomena of some stations, such as CTR, were related to the increase of traffic emissions and human activities. As the interaction between pollutants was very complex, the rapid increase in ozone pollution was even more related to the motion of the atmosphere. The HYSPLIT results demonstrated that the pollution source was consistent before and during the lockdown, and the trajectory basically consists of the long-distance transmission in southern Russia, dust impact in Inner Mongolia and short-range input from the three eastern provinces. The pollutants from the transmission channels in eastern Russia and the Bohai Sea after unsealing was one of the reasons for the hasty rebound of all pollutants. The backward trajectory analysis demonstrated that because of the different times and specific measures of lockdown, the pollution of neighboring countries, including Russia and Mongolia and the surrounding areas of Shenyang, would have a stronger impact on air quality under the effect of long-distance transmission.A multifaceted evaluation of the current ozone pollution in Shenyang revealed the impact of long-term lockdown on the environmental situation. Overall, the lockdown did not have a positive effect on ozone pollution, which still proliferated constantly. The results of the corresponding period analysis showed that the ozone concentrations during the lockdown in 2020 were 1.4% higher than that in 2019 and 1.2% lower than that in 2018. In general, compared with last year, ozone pollution was more serious in the first half of 2020. Comparing the variations of pollutants during the lockdown with the pre-lockdown period, it came across that the average concentration of AQI decreased by 37.1%, so did NOThis study corroborates the complexity of air pollution in Shenyang, and there is an urgent to further conduct the source distribution of ozone as well as the deep relationship of ozone precursors. The COVID-19 lockdown is an excellent opportunity to test environmental parameters and improve air quality. We should not only perceive the effect of short-term lockdown as an alternative policy measure to depress pollution, the economic impact and the cost-effectiveness of decision-makers in determining such controls also need to be perceived to accomplish systematic environmental control measures.


Cells are constantly suffering genotoxic stresses that affect the integrity of our genetic material. Genotoxic insults must be repaired to avoid the loss or inappropriate transmission of the genetic information, a situation that could lead to the appearance of developmental abnormalities and tumorigenesis. To combat this threat, eukaryotic cells have evolved a set of sophisticated molecular mechanisms that are collectively known as the DNA damage response (DDR). This surveillance system controls several aspects of the cellular response, including the detection of lesions, a temporary cell cycle arrest, and the repair of the broken DNA. While the regulation of the DDR by numerous kinases has been well documented over the last decade, the complex roles of protein dephosphorylation have only recently begun to be investigated. Here, we review recent progress in the characterization of DDR-related protein phosphatases during the response to a DNA lesion, focusing mainly on their ability to modulate the DNA damage checkpoint and the repair of the damaged DNA. We also discuss their protein composition and structure, target specificity, and biochemical regulation along the different stages encompassed in the DDR. The compilation of this information will allow us to better comprehend the physiological significance of protein dephosphorylation in the maintenance of genome integrity and cell viability in response to genotoxic stress. Most of these adducts might directly or indirectly undergo the formation of single-strand breaks (SSB) that arise when one of the two strands of the DNA duplex is severed. This relatively-easily-to-repair lesion might evolve into a more dangerous form of DNA damage, the double-strand break (DSB), where both DNA strands are simultaneously excised. To counter all these distinctive types of genetic alterations, cells have acquired specialized systems that detect the lesions, signal their presence and, at last, mediate their repair in order to safeguard the stability of our genome. The orchestration of these processes is tightly regulated by the activation of a highly evolutionarily conserved and sophisticated network that is generically termed as the DNA damage response (DDR). When the DDR fails or the rate of DNA damage exceeds the capacity of the pathway to cope with it, the increased accumulation of DNA alterations can lead to the appearance of mutations, thus subjecting cells to a higher risk of malignant transformation [The maintenance of genome integrity is an essential feature of cellular physiology. Our hereditary information encoded in DNA is intrinsically susceptible to alteration, being continually threatened by both endogenous and environmental genotoxic stresses that could alter our genomic material. Environmental sources of DNA damage include several DNA damaging agents, such as ionizing radiation (IR), ultraviolet radiation (UV), alkylating compounds, viral infections and chemotherapeutic drugs. On the other hand, multiple endogenous factors can also compromise genome integrity, such as reactive oxygen species that are generated during cell metabolism or unavoidable errors of certain cellular processes, such as DNA replication or meiotic recombination. These endogenous DNA damaging agents may cause hydrolysis, oxidation, alkylation or the mismatching of DNA bases, thus hazarding the stability of the genetic material . It has ormation ,3. As a ormation ,4,5.At the molecular level, the DDR is a complex signaling pathway that is integrated by a large number of factors that actively contribute to the organization of the multiple cellular events that are enclosed in the response. Though most of these events are, in principle, independent processes, cells have to precisely coordinate them in space and time to guarantee the accurate restoration of the DNA molecule . As withDuring the last few years, there has been an increasing interest in the molecular mechanisms behind the regulation of the DDR. In response to a DNA lesion, several DDR-specific kinases transmit the signal from the sensors to numerous biological processes across the cell by phosphorylating multiple DDR components at specific serine and threonine residues ,10. ImpoProtein phosphatases can be classified into different groups on the basis of their sequence, structure and catalytic mechanisms . These gRecently, new evidences have demonstrated that protein phosphatases cooperate in the regulation of the DDR, not only by promoting cell cycle re-entry after the DNA lesion has been restored but also by playing important roles in the execution of different steps of the repair process. In this regard, it has been postulated that each phosphatase could work on different DNA structures during different steps of the repair process and in response to different types of DNA damage . SupportIn this review, we summarize recent discoveries about the role of DDR-phosphatases during the generation of a DNA adduct. We also focus our attention on the physiological significance of these enzymes during the repair of a DNA lesion, how their enzymatic activity is regulated, and what their targets are in the process. This compilation will allow us to acquire a complete picture of the importance of protein dephosphorylation during the execution of the DNA damage response. Checkpoints are signal transduction pathways that coordinate DNA damage with DNA repair and cell cycle progression. After a DNA breakage has been inflicted, the first priority of the cell is to detect it as quickly and efficiently as possible in order to elicit an accurate activation of the DNA damage checkpoint. The timely activation of this checkpoint restricts damaged cells to premature entry into mitosis and stimulates the activity of repair factors involved in the restoration of the DNA lesion. The DNA damage checkpoint is initiated by the recognition of the DNA lesion by the phosphatidyl inositol kinase-like kinase (PIKK) Mec1/ATR and Tel1/ATM  Figure . The recThough the activation of the DNA damage checkpoint is mainly driven by the phosphorylation events of its components, their steady state phosphorylation must be highly regulated by kinases and phosphatases that work in tandem. This kinase-phosphatase balance allows for the tight control of the response and prevents cells from an unnecessary activation of the signal in the absence of DNA damage. PP1 is one of the most active phosphatases in the cell and is responsible for the dephosphorylation of one third of all phospho-proteins . It is cXenopus eggs extracts. These experiments demonstrated that PP1 and its regulatory element Repo-Man [One of the first observations that pointed to the PP1 phosphatase as a main regulator of the DDR came from experiments in Repo-Man ,40 are vRepo-Man   is another important PP1-binding factor with implications in the initiation of the damage response. PNUTS can be attached to the α, β and γ isoforms of mammalian PP1 via its RVxF motif , targetiPP2A is a serine/threonine phosphatase that belongs to the PPP family of phosphatases. Like PP1, PP2A is composed of a catalytic subunit, a scaffold subunit, and multiple regulatory elements. The catalytic subunit (PP2Ac) binds to a structural subunit (PP2Aa/PR65) to generate the core of the enzyme. This structure can interact with a wide range of regulatory elements  to form the active heterotrimeric PP2A holoenzyme complex . The larOne of the first realizations of the role of PP2A in the regulation of the DDR came from the observation that its scaffold subunit PP2A-A interacts in vivo with ATM in mammalian cells . The PP2PPP2R3A/B130 expression, a regulatory subunit of the PP2A complex, by the histone deacetylases HDAC1/HDAC2 [Xenopus in response to DNA damage [Little is known about the molecular mechanism that controls PP2A–ATM interaction in the DDR. Interestingly, it has been proposed that ATM activation in response to replicative stress relies on the suppression of C1/HDAC2 . This reC1/HDAC2   on hydregulated . Moreoveegulated  . CDC14 is one of the most studied families within the DUSPs, proteins that are characterized by their ability to dephosphorylate both phosphotyrosine and phosphoserine/phosphothreonine residues in their substrates . A speciS. cerevisiae and humans, respectively), which colocalized to stalled replication forks after replication stress. Interestingly, the Flp1 nucleolar release induces a positive feedback loop that ends up with the complete activation of Cds1, thus triggering a proficient activation of the DNA damage checkpoint [Schizosaccharomyces pombe. It has been demonstrated that mammalian CDC14B is also excluded from the nucleolus in response to DNA damage [During the last few years, it has become evident that the CDK is a master regulator of the DDR. Therefore, it is intuitive to think that CDC14 might also have relevant roles in the damage response by counteracting CDK substrates. The first realization of a function of CDC14 in the regulation of the DNA damage checkpoint activation came from the observation that Flp1 (fission yeast ortholog of CDC14) translocates from the nucleolus to the nucleoplasm in response to replication stress induced by HU treatment . Nowadayeckpoint   or by repair pathways that rely on the searching of an intact homologue sequence that serves as donor for the repair (HR)  Figure . HomologLately, it has been well documented that multiple factors involved in DNA repair are activated by phosphorylation events ,102. TheXenopus and human cells that PP1 interacts, dephosphorylates, and activates DNA–PKcs in response to DNA damage [In addition to the role of PP1 in controlling the DNA damage checkpoint response, this phosphatase also participates in DNA repair by modulating several factors of the repair machinery. The breast and ovarian cancer type 1 susceptibility protein BRCA1 is involved in the execution and coordination of various aspects of the DNA damage response, including DNA repair and checkpoint control ,104,105.A damage  , enhanced chromatin compaction, slow replication fork progression and inefficient DNA repair . AnotherDrosophila melanoganster) induces the accumulation of persistent γH2AX foci, high levels of Ku70 phosphorylation, and DNA repair failures that lead to the appearance of chromosome aberrations [The first realization of a role of PP2A in DNA repair came from the observation that HeLa cell extracts treated with okadaic acid resulted in a drastic deficiency in NER execution . Soon afrrations . These rIn addition to the role of PP2A in regulating NEHJ, the phosphatase has also been implicated in HR. In this regard, it has been shown that PP2A coimmunoprecipitates and colocalizes at DNA damage foci with γ-H2AX . Taking Another target of PP2A with a role in the repair of a DSB is RPA . It is kFinally, it is important to remark that PP2A might be indirectly involved in the restoration of a DNA break through its ability to negatively regulate the DNA damage checkpoint see . It has S. cerevisiae PP4 complex, was required for Rad53 dephosphorylation during treatment and recovery from methyl methanesulfonate (MMS). In the absence of Psy2, both the dephosphorylation of Rad53 and resumption from replicative stress are delayed, even though genome replication is eventually completed by the firing of late origins of replication. These results indicate that the PP4 complex is directly implicated in the stabilization of stalled or collapsed replication forks by acting over Rad53 [S. cerevisiae [Similarly to PP2A, PP4 is also involved in DNA repair by acting over multiple factors that are implicated in the restoration of a DNA lesion. Curiously, most of the PP4 targets identified in response to a DNA lesion are also PP2A substrates, suggesting that both phosphatases might have redundant functions in DNA repair. The first realization of the role of PP4 in the repair of DNA lesions came from the observation that Psy2, the Pph3 regulatory subunit of the er Rad53 . Recentler Rad53   allows cells to re-enter in the cell cycle in response to an irreparable DNA break. Even though the role of Cdc5/PLK1 is vital to endorse a full checkpoint recovery, its individual activity is not enough to override the DNA damage checkpoint. Since most of the DNA damage checkpoint routes rely on the active phosphorylation of their components, it is intuitive to think that dephosphorylation events by DNA-damage specific phosphatases might participate in the silencing of the damage response when the DNA lesion has been fixed. Indeed, recent discoveries have put forward protein phosphatases as active enzymes that are essential to re-establish the phosphorylation status of multiple DDR targets during cell recovery. Therefore, in this section, we focus our attention on the role of different phosphatases in DNA damage checkpoint recovery, their targets in the process, and the fundamental principles behind their regulation during cell cycle re-entry.Once the DNA lesion has been repaired, cells have to deactivate the DNA damage checkpoint to allow for cell cycle resumption. This process, generically termed as DNA damage checkpoint recovery, relies mainly on the Polo-like kinase 1 protein PLK1. In human cells, the PLK1-dependent phosphorylation of both WEE1 and Claspin targets them for proteasomal degradation, thus restraining the negative effect that these factors exert over the CDK activity ,131 Fig. A similS. pombe screening to identify genes that, when overexpressed, were able to override the DNA damage checkpoint and re-enter into the cell cycle even in the presence of DNA damage. In this screening, the overexpression of Dis2 (main subunit of the PP1 complex in the fission yeast) was enough to abrogate Chk1 phosphorylation and activation in vivo [Candida albicans) endorses a hyper-phosphorylation state of Rad53 upon MMS treatment [The role of PP1 in cell cycle recovery upon exposure to DNA damage was initially anticipated in a  in vivo   and Cdc55 (PP2A regulatory element) were isolated in a screening to identify genes that were toxic to cdc5-1 mutants when overexpressed [Xenopus, PP2A regulates mitotic entry by acting over CDC25 [S. cerevisiae, the final acceptor of PP2A seems to be the WEE1 homologue Swe1 [S. pombe both Wee1 and Cdc25 are controlled by PP2A and its regulatory subunit Pab1 [The role of PP2A in an undamaged cell cycle progression was originally discovered when realizing that its lack of activity resulted in a precocious mitotic entry of fission yeast cells . The samxpressed . Though er CDC25 , in S. cgue Swe1 . By contnit Pab1 .Xenopus have shown that Greatwall is actively inhibited by the DDR in response to DNA damage, thus allowing for PP2A activation during the initial stages of the repair process [Recently, it has become clear that PP2A activity is negatively regulated by the Greatwall kinase . The mit process . Once th process   targeting the phosphatase to proteasomal degradation [As other DDR-related phosphatases, the activity of WIP1 is tightly regulated along the damage response in order to avoid precocious dephosphorylation of DNA repair factors that could affect the correct restoration of the DNA lesion. At the transcriptional level, r events . Importaradation . In respradation . Thus, tOver the last few years, there has been the realization that the regulation of the DDR is vital to ensure genome stability. Consequently, there has been a burst in the number of studies headed to determine the fundamental principles behind the pathway and the regulatory mechanisms behind this biological process. While phosphorylation of multiple targets by DDR-kinases and their implications in the execution of the response is a well-known process, less is known about the importance of the DDR-phosphatases, their targets in the process, and their implication in genome integrity. Fortunately, we have recently started to focus our attention in the distinctive role of each DDR-related phosphatase in the control of the DNA repair process and their implications in the correct execution of the DDR. These discoveries have put forward a new concept in the field, where protein phosphatases are not passive members of the DDR but highly regulated enzymes with fundamental implications in the orchestration of the repair pathway. Taking into account the close relationship between DDR efficiency and cell transformation, it is intuitive to think that protein phosphatases could act as tumor suppressors. Supporting this notion, numerous carcinoma cells present an altered expression pattern and mutations in the sequence of several protein phosphatases ,170,171.


The aim of the study was to present characteristics of patients transported in incubators by crews of Helicopter Emergency Medical Service (HEMS) and Emergency Medical Service (EMS) of the Polish Medical Air Rescue as well as the character of their missions. The study was based on the method of retrospective analysis of neonatal transports with the use of transport incubators by the crews of HEMS and EMS of the Polish Medical Air Rescue. The study covered 436 medical and rescue transports of premature babies and full-term newborns in the period between January 2012 and December 2018. The study group consisted mainly of male patients (55.05%) who, on the basis of the date of delivery, were qualified as full-term newborns (54.59%). During the transport their average age was 37.53  days, and their average body weight was 3121.18 (SD 802.64) grams. A vast majority of neonatal transports were provided with the use of a plane (84.63%), and these were medical transports (79.36%). The average transport time was 49.92 (SD 27.70) minutes with the average distance of 304.27 km (SD 93.05). Significant differences between premature babies and full-term newborns were noticed in terms of age and body weight at the moment of transport, diagnosis based on the International Statistical Classification of Diseases and Related Health Problems (ICD-10), the most commonly used medications , National Advisory Committee for Aeronautics (NACA) scale rate as well as the mission type and the presence of an accompanying person. The issue of decreasing the death rate of mothers and children under the age of five has always been one of the major goals of all human health activities both internationally and locally. One may notice a particular significance of limiting the death rate of children under the age of 5, including the death rate of newborns. It has become an important point of interest in recent years and is now a great challenge when it comes to ensuring health and development of human capital in the whole world. According to the international data, the mortality of children up to 28 days of age decreased at a much slower rate than that of children aged from 29 days to 5 years, and the death of newborns is responsible for more than two-fifths of deaths of children under 5 years of age annually ,2,3,4,5.The progress in reducing neonatal death rate is made in perinatal care, which is a component of comprehensive measures aimed at providing both a mother, a fetus and a newborn with appropriate multifaceted care during pregnancy, delivery and in the postnatal period. This care is ensured by the cooperation of various specialists who create interdisciplinary teams. In order to improve the perinatal care in Poland, a three-stage model of perinatal care was created in the 1990s ,9,10. InThe transport of a newborn whose life is threatened to a center with a higher level in the referral system in Poland is performed by a ground-based specialist N ambulance or by Helicopter Emergency Medical Service (HEMS) and Emergency Medical Service (EMS) of medical air rescue ,12. GrouIt was precisely the issue of the distance and the necessity of transport that contributed to the authors’ study aimed at presenting the characteristics of both the patients transported in incubators of the Polish Medical Air Rescue crews and the missions themselves.The study was based on the method of retrospective analysis of neonatal transports with the use of an incubator by the crews of HEMS and EMS of Polish Medical Air Rescue. The study covered all medical and rescue transports of premature babies and full-term newborns with a birth weight not exceeding 5000 g in the period between January 2012 and December 2018 in the whole territory of Poland. The exclusion criteria were cases in which transport orders were cancelled, the mission was not undertaken due to bad weather conditions or technical problems and situations in which the doctor of the transport crew disqualified the patient due to too severe clinical condition. After exclusion of cases in accordance with the exclusion criteria, 436 cases of neonatal transports were qualified for the final analysis. The chief executive officer of the Polish Medical Air Rescue granted his consent to conduct the study, while the retrospective nature of the study did not require the consent of the Bioethics Committee.The study was carried out on the basis of medical and operational documentation of HEMS and EMS crews of Polish Medical Air Rescue. During the process of the documentation analysis the following information was obtained: The date and destination, the data concerning characteristics of transported patients, main diagnoses based on the International Statistical Classification of Diseases and Related Health Problems (ICD-10), parameters of clinical condition of patients, medical emergency procedures, medications used during the transport as well as the information related to the characteristics of the completed transportations.NACA 0—no body injuries or illnesses;NACA 1—body injuries or illnesses in case of which medical care is not necessary;NACA 2—body injuries or illnesses that require examination and treatment, but with no need of hospitalization;NACA 3—body injuries or illnesses with no acute life threat but requiring hospitalization;NACA 4—body injuries or illnesses that may lead to deterioration of vital signs;NACA 5—body injuries or illnesses posing a great threat to life;NACA 6—body injuries or illnesses leading to sudden cardiopulmonary arrest;NACA 7—fatal body injuries or illnesses ,16.The National Advisory Committee for Aeronautics (NACA) scale was used to compare the clinical condition of patients. This is a commonly used scale to assess the severity of injury or disease in pre-hospital conditions in Western European countries. This scale distinguishes 8 groups of patients according to the impairment of life-supporting functions and symptoms of injury, illness or poisoning:n) and percentage (%) are used to describe the qualitative data, while mean (M) and standard deviation (SD) are used to describe the quantitative data.The data obtained in the process of documentation analysis were analyzed statistically with the use of STATISTICA program, version 13.2 . The quantity  was implemented to assess the chance of particular congenital malformations in the examined group of patients. The accepted materiality level was p < 0.05.The Shapiro–Wilk normality test was used to verify the normality of the distribution of quantitative variables. The Chi-squared test was adopted in order to assess statistically significant differences between qualitative variables, while the Mann–Whitney non-parametric The study covered 436 cases of neonatal transports carried out by HEMS and EMS Polish Medical Air Rescue crews. The study group consisted mainly of male patients (55.05%) who, on the basis of the date of delivery, were qualified as full-term newborns (54.59%). The average age of patients during transport was 37.53 days (SD 43.53), and the average body weight of babies during transport was 3121.18 g (SD 802.64). The main diagnoses were congenital heart malformations, which constituted more than two-fifths of all cases (41.28%). The analysis of vital signs and clinical condition of patients during transport showed that the vast majority of patients in incubators were conscious during transport (73.17%), their skin coloring was normal (80.96%), there was no cyanosis (89.91%) and no respiratory effort (78.21%). The average breath count was 36.36 per minute (SD 16.95), saturation 93.55% (SD 6.49), heart rate 141.86 beats per minute (SD 17.27), systolic pressure 141.86 mmHg (SD 17.27), diastolic pressure 45.23 mmHg (SD 10.62) and NACA was 3.66, indicating a moderate to severe clinical condition. The most common medical emergency procedure needed by transported patients was intubation (27.29%), and the most commonly used medications were glucose (44.04%) and prostaglandin E1 (33.03%) .p < 0.0001); body weight during transport (p < 0.0001); diagnosis based on the ICD classification 10 (p < 0.05); the most commonly used medications: Prostaglandin E1 (p < 0.0001), glucose (p < 0.05), furosemide (p < 0.05) and vitamins (p < 0.05) as well as the rate of the NACA scale (p < 0.05). The analysis shows that in the group of preterm infants who were older at the time of transport, cardiovascular malformations, congenital malformations of the gastrointestinal tract and respiratory disorders originating in the perinatal period as well as congenital malformations of the nervous system were more common. Glucose and vitamins were administered more often than in the group of full-term newborns. The group of full-term newborns was characterized by higher body weight during transport and more severe clinical condition, as indicated by the NACA scale (p < 0.05). These patients received prostaglandin E1 (p < 0.0001) and furosemide (p < 0.05) more often than premature babies. In other cases no statistically significant dependencies were found (p > 0.05)  .p < 0.05). However, there were no statistically significant correlations between the classification of the patients on the basis of the date of delivery and the reference level of the target hospital, time of transport, care and time of the receipt of the call to patient transfer and the transport distance (p > 0.05) , and during the transport the patients were accompanied by a parent (47.90%). The stated dependencies were statistically significant ( > 0.05) .Since it is not always possible to predict the occurrence of defects, illnesses or premature birth, there is often a need to transfer newborn babies to an appropriate center as late as after their birth ,11,17. TThe first stage of the study was to analyze the characteristics of the patients transported in incubators. The results of the authors’ own study showed that the patients transported in incubators were mainly males. During the transport, their average age was 37.53 days and their body weight was 3121.18 g, while on the basis of the date of delivery they were qualified as full-term newborns. Moss et al. 2005) in the study on the safety of neonatal transport found out that among the transported patients there were mainly newborns whose average gestational age was 32 weeks and birth weight was 1850 g 05 in the.The most common reason for transporting patients in incubators by Medical Air Rescue crews in the analyzed material were congenital heart malformations. On the other hand, the study carried out by Frid et al. (2018) showed that the main indications for neonatal transport were therapeutic hypothermia after perinatal asphyxia, extremely preterm birth and respiratory failure . AdditioThe issue of premature births, i.e., before the 37th week of pregnancy and prematurity, together with its consequences, is a challenge for governments and health care worldwide ,26,27,28The clinical condition of patients transported in incubators by the Polish Medical Air Rescue crews in the analyzed material was stable. Respiratory rate was 36.36 per minute, saturation 93.55%, heart rate 141.86 beats per minute, systolic pressure 76.60 mmHg, diastolic pressure 45.23 mmHg, while the NACA 3.66 scale value indicated moderate to severe clinical condition of patients. In the study of Bastug et al. (2016) on children transported and treated in the Neonatal Intensive Care Unit of the Erciyes University, Faculty of Medicine in Turkey, the average heart rate after transport was 134 beats per minute in the group of patients weighing 501–1500 g, 145 beats per minute in the group of patients weighing 1501–2500 g and 139 beats per minute in the group of patients weighing above 2500 g. The respiratory rate values were as follows: The group with the body weight of 501–1500 g: 55 breaths per minute, the group with the body weight of 1501–2500 g: 52 breaths per minute and the group with the body weight exceeding 2500 g: 54 breaths per minute. The differences between individual groups were statistically significant . StudiesIn the further part of the study, the authors focused on the most frequently undertaken medical emergency procedures and medications used during neonatal transport. The analysis of the authors’ own study showed that the transported patients most often required intubation, mechanical ventilation and oxygen therapy. The most commonly used medications were antibiotics, prostaglandin E1, glucose, furosemide and vitamins. According to Yan Leung et al. (2019), nearly 70% of all transported patients required various procedures during transport. Furthermore, it was proved that the transported infants most often required assisted ventilation, oxygen therapy, inotropic support, sedation and prostaglandin infusion. Moreover, infants in whom complications occurred during transportation were more likely to require intubation and support with inotropic drugs . In AbduAccording to the assumptions regarding the treatment of newborn children requiring specialist care that cannot be obtained in the center where they were born, it is necessary to transport them to the center that will provide comprehensive and multi-faceted diagnostic and therapeutic procedures as well as appropriate care ,18,19,20The study on the contribution of the Polish Medical Air Rescue in the rescue procedure in case of severe upper limb injuries was conducted by Gałązkowski et al. (2014). Their study showed that the average inter-hospital air transport time of patients with severe upper limb injuries was 75.8 min and the total transport time—172.3 min . WejnarsThis study is the first retrospective analysis of patient transports in incubators performed by Helicopter Emergency Medical Service and Emergency Medical Service of the Polish Medical Air Rescue between 2012 and 2018. We would like to point out that the study has some limitations. The analysis covers only the information contained in the documentation of HEMS and EMS crews, without any knowledge of the further management or survival of the examined patients. However, these limitations do not affect the quality of the study. Further research on neonatal transport is necessary in order to comprehend this problem better and to provide the best and highest quality of care for the youngest patients who require transportation.Among the patients transported in incubators by the HEMS and EMS air ambulance crews between 2011 and 2018 there were mainly males who, on the basis of the date of delivery, were qualified as full-term newborns. Most of the neonatal transports were carried out by an airplane as they were medical transports to the tertiary care center in the referral system.Significant differences between preterm infants and full-term newborns were found in the case of age and body weight at the time of transport, diagnosis based on the ICD classification 10, the most commonly used medications , NACA scale value as well as the type of mission and presence of an accompanying person during the transport.Among preterm infants, the odds ratio is higher if there is a possibility of congenital malformations of the circulatory, gastrointestinal, nervous and respiratory system originating in the perinatal period.


The electromechanical impedance model of the piezoelectric ceramics in a free state can be used for screening and quality control in the structural health monitoring community, but the derivation process of the existing model is usually complicated. This paper describes a novel theoretical derivation methodology based on the assumption of zero-stress on the free boundary of the one-dimensional transducer, which can simplify the derivation of the model to a large extent. To assess the accuracy of the model, a signal processing method based on frequency shifting transformation and the Pearson correlation coefficient is also proposed to calculate the similarity between theoretically predicted and experimentally measured data. Two different piezoelectric ceramics were used in experiments to verify the effectiveness of the model. Experimental results convincingly demonstrate that the assumption proposed in this paper possesses good feasibility for one-dimensional thin-walled piezoelectric ceramics and the model has excellent precision. Over the past decade, electromechanical impedance (EMI) based on piezoelectric ceramics (PZT) emerged as a cost-effective technique in structural health monitoring (SHM) and non-destructive testing (NDT) communities. The EMI technique has been widely used for damage detection in typical engineering structures, such as infrastructures, composites, and mechanical equipment.At present, the SHM techniques are mainly based on the PZT sensor array to acquire the serving condition in real-time. Hence, the properties of PZT have a great influence on the monitoring accuracy, which may lead to poor detection results if the PZT used in the sensing network has a difference. The priori to the monitoring of structural condition with the EMI technique is the screening of PZT sensors before mounting on the host structures. It is significant to test and determine the performance of a PZT in its free state when excited by an alternating electric charge. For a better understanding of the PZT spectroscopy in its free state, a relevant theoretical model needs to be established to reveal the characteristics of rectangular PZT signals changing with excitation frequency in its longitudinal direction.Research workers have made substantial efforts to the analytical and numerical modeling of various aspects in the EMI field up to date. Liang et al.  firstly Apart from the above-mentioned researchers who proposed their physical models of EMI, there is also much other work reported by scholars. The scope of these investigations covered structural identification and damage diagnosis, signal processing, and damage localization. For instance, Zhang et al.  proposedHowever, the majority of previous investigations were mainly focused on the fundamentals of PZT-structure interaction, damage localization, and diagnosis in the coupled state. Only a few studies concentrated on impedance spectroscopy of PZT under free conditions. The spectroscopy of a free PZT can be used for determining the sensors’ selection and its layout for the subsequently coupled scenarios that integrate the PZT with monitored structures, such as the surface-mounted or embedded PZT. To sum up, it is significant to derive a model aiming at PZT in a free state to assess its performance.In this paper, a novel derivation of the PZT theoretical model in a free state was described by considering the two assumptions: (1) zero-stress boundary condition, and (2) longitudinal vibration in 1-direction. Then the theoretical model for one-dimensional can be deduced. By verifying the proposed EMI model with experiments, the effectiveness and accuracy of the model can be convincingly demonstrated. Furthermore, the model can be used for predicting the PZT spectroscopy by inputting mechanical and electrical parameters, which has favorable guidance in promoting the monitoring results and improving the cost-effectiveness in the field of SHM.2l, width w, and thickness h. The PZT is assumed to undergo the longitudinal expansion along the 1-direction induced by the electric field E3 in thickness polarization, as shown in E3 is produced by applying the harmonic voltage between the top electrode and bottom electrode, which is defined by A thin-walled rectangular PZT has a length of l >> w >> h, then the motions in three directions can be considered as uncoupled. Assuming the displacement in 1-direction is u1 and the vibration in a longitudinal direction (1-direction) is regarded as a predominant mode.Defining the size in length, width, and thickness meets the correlation of 2 E3 is uniform over the PZT, the related derivative is a constant zero, i.e., According to the above-mentioned assumption that the electric field x from the centroid under dynamic equilibrium condition. The illustration of the infinitesimal element of the PZT is shown in Assuming that there is an infinitesimal element of the PZT and the length of the element is defined as According to Substituting Equation (1) into Equation (2) and solving then yields Equation (3):According to Hooke’s Law and a correlation between displacement and strain, Equation (3) can be transformed into Equation (4):x = 0, u = 0, the general solution of this PDE can be obtained, as shown in Equation (5):By solving the governing wave equation ), as shown in Equation (4), and applying the initial value, i.e., S1 is the strain in a longitudinal direction (1-direction). D3 is the electric displacement of the PZT. d31 is the piezoelectric strain coefficient. T1 is the axial stress in 1-direction. Considering the thin-walled rectangular PZT vibrates longitudinally in 1-direction, the piezoelectric constitutive relations can be simplified, as described in Equation (7):T1 can be deduced as Equation (8):According to the Equation (7), the expression of S1 can be determined by Equation (9):In the light of “displacement-strain” relation, the equation of T1, as shown in Equation (10):Substituting Equation (9) into Equation (8), then yields the expression of Assuming that the thin-walled rectangular PZT is vibrating longitudinally, the boundary condition can be regarded as a “free” state, which means that the stress on the boundary of PZT is zero, as shown in Equation (11):A can be given by Equation (13):Substituting Equation (10) into Equation (11), the Equation (12) can be obtained. Then the expression of to-be-determined constant Hence, Equation (5) can be further determined as the following Equation (14):According to Equation (7), the electric displacement can be deduced as Equation (15):Due to the correlation between the electric displacement and current, the expression of current over the PZT surface can be deduced as shown in Equation (16):Considering the definition of the electric field, i.e., η and dielectric loss factor δ are separately defined. The Young’s modulus and dielectric coefficient taking the loss effect into account can be expressed by Equations (20) and (21):Practically, there are mechanical and dielectric losses when the PZT is excited by the harmonic voltage. Thus the mechanical loss factor Then the formulae of admittance and impedance can be further transformed into the following complex expressions, as shown in Equations (22) and (23):The Equations (22) and (23) are practically formulae of the PZT under the free conditions in a longitudinal direction. Compared with the existing model, the derivation process is much simpler based on zero-stress assumption on the PZT boundary presented in this paper.To demonstrate the effectiveness and applicability of the formulae proposed in this paper, two verifying experiments were designed and conducted. In addition, to simulate the free state of PZT, a simple fixture was also machined and used for clamping the centroid of PZT.For convincingly demonstrating the predicted curve with the EMI model presented in the theoretical section, two different PZTs were applied in the experiments. The thin-walled rectangular PZTs used in experiments were provided by the Shanghai Institute of Ceramics, PZT-5A (numbered PZT#1) and PZT-5A1 (numbered PZT#2). The size of PZT-5A and PZT-5A1 are separately 40 mm × 5 mm × 0.34 mm and 11.72 mm × 3 mm × 0.78 mm in length, width, and thickness direction. The properties of PZT with electrodes coated silver on both sides are enumerated in The fixture used for clamping the PZT was made of 6061-T6 aluminum alloy. Two nylon bolts were adopted to constrain the PZT to prevent the top and bottom electrodes from short-circuiting, as shown in During the experiments, the resistance and reactance signals were acquired in terms of the above-mentioned experimental setup. Owing to the discrepancy among PZTs in materials and sizes, there are also some differences in their sampling frequency scopes. Because the PZTs under free condition are easily excited, the frequency scope of the main peak was also considered. The interference was also found in our laboratory when the frequency was less than 10 kHz. Therefore, the testing frequency scope from 10 kHz to 200 kHz was finally selected. More precisely, as to PZT-5A (numbered PZT#1), the scope of frequency ranges from 10 k–200 kHz, while the PZT-5A1 (numbered PZT#2) ranges from 50 k–200 kHz. The data points are 800 in each experiment, which means that the uniform sample interval is 237.5 Hz and 187.5 Hz, respectively.R) and imaginary part  of the impedance of PZT under free condition can be calculated.Based on the Equation (23) and the properties enumerated in As mentioned above, to demonstrate the model’s effectiveness in this paper, two kinds of piezoelectric ceramics, PZT#1 and #2, were adopted. The experimental and theoretical curve of PZT#1 determined by Equation (23) is comparatively shown in Although the magnitude of deviation changes with the frequency scope, it can be observed that the magnitude of the two curves is small enough on the whole. The range of vertical coordinates are confined up to 14 Ω, and the magnitude in the frequency scope where the Peak-1 situated is only from 0 to 8 Ω. Thus, the accuracy of the EMI model was proved preliminarily.x and y represent experimental and theoretical data, respectively. x and y. x and y. i is the data-counter and N is the total number of acquired data points.In order to further quantify the effectiveness and accuracy of the theoretical model for free PZT, an index of Pearson correlation coefficient (CC) was introduced to evaluate the similarity of signals between the experimental and theoretical curves. The expression of Pearson CC is defined by Equation (25).Furthermore, a new method was presented in this paper on signal processing when assessing the similarity between theoretical and experimental curves in terms of CC index. The signal processing and similarity assessment between the two curves follows the procedure shown with a flow chart in According to Equation (25) and To evaluate the similarity between the experimental and theoretically predicted curves, the Pearson CC was also calculated in terms of Equation (25) and To further study the effectiveness of the EMI model presented in this paper, another experiment with PZT#2 was also conducted. Substituting the properties of PZT#2 listed in In the frequency scope ranging from 50–200 kHz, the comparative resistance plots for PZT#2 are shown in Similar to the scenario of PZT#1, the Pearson CC of PZT#2 is also calculated, which is 0.9145. Hence, according to the value of Pearson CC, the effectiveness of the EMI model for PZT under free condition can be further validated.The comparative reactance plots for PZT#2 are shown in Using the method presented above to evaluate the similarity between the two curves shown in This paper presents an investigation on the EMI theoretical model derived with an assumption of zero-stress on the boundary of 1D thin-walled PZT that can vibrate freely in a longitudinal direction. To study the effectiveness of the EMI model proposed, experiments were conducted.(1)A simplified derived process based on the assumption of zero-stress on the PZT boundary was proposed.(2)A signal processing method of “frequency normalization” was proposed to evaluate the similarity of the EMI model by comparing frequency shifting and magnitude scaling to verify its effectiveness.The EMI model is a universal one for the 1D PZT in a free state. It can be used for accurately predicting the resistance and reactance signatures in terms of piezoelectric ceramic material parameters and geometric size. Then the behavior of any 1D thin-walled PZT under free conditions is obtained. Hence, the modeling of a free PZT has potential for the screening and quality control before integrating it with monitored host structures, which could improve the cost-effectiveness in the field of PZT-based SHM adequately. The work presented in this paper mainly includes the following two aspects of novelties:To evaluate the presented model’s effectiveness, a series of experiments were conducted by using piezoelectric ceramics, which were PZT#1 and #2. The theoretically predicted curves with the presented EMI model showed excellent accuracy when compared with the measured corresponding resistance and reactance signals. The comparative results between the theoretical and experimental of the real part and imaginary part of impedance signatures demonstrated the reasonability of the assumption and similarity assessment method proposed in this paper. Furthermore, this method has the potential application prospect of improving the cost-effectiveness and obtaining better monitoring results.