QS/A), and the flow ratio of the left pulmonary artery (LPA) to right pulmonary artery (RPA) (QL/R) was more close to 1, while both the proportion of high wall shear stress (WSS) areas and power loss decreased. The case of PDA nonclosure demonstrates that the aortic oxygen saturation (Sao2) increased, while the systemic oxygen delivery (Do2) decreased. In general, for the CS model with three typical PA dysplasia, the changing trends of hemodynamic parameters during the spontaneous closing process of PDA were roughly identical, and nonclosure of PDA had a series of hemodynamic advantages, but a larger PDA may cause excessive PA perfusion and was not conducive to reducing cyanosis symptoms.A central shunt (CS) was an important surgery of systemic-to-pulmonary shunt (SPS) for the treatment of complex congenital heart diseases with decreased pulmonary blood flow (CCHDs-DPBF). There was no clear conclusion on how to deal with unclosed patent ductus arteriosus (PDA) during CS surgery. This study expanded the knowledge base on PDA by exploring the influence of the closing process of the PDA on the hemodynamic parameters for the CS model. The initial three-dimensional (3D) geometry was reconstructed based on the patient's computed tomography (CT) data. Then, a CS configuration with three typical pulmonary artery (PA) dysplasia structures and different sizes of PDA was established. The three-element windkessel (3WK) multiscale coupling model was used to define boundary conditions for transient simulation through computational fluid dynamics (CFD). The results showed that the larger size of PDA led to a greater systemic-to-pulmonary shunt ratio ( For infants with congenital heart disease and insufficient pulmonary blood flow, the systemic-to-pulmonary shunt (SPS) is the most commonly used clinical palliative surgical method, which mainly includes modified the Blalock-Taussig shunt (MBTS) and central shunt (CS) , 2. AmonAlwi et al.  have iniThis research began with an analysis of the clinic data from patients with preoperative PDA nonclosure and decreased pulmonary blood flow who were prepared to receive a CS palliative surgery. Considering the effects of different types of PA dysplasia, the three-dimensional (3D) model of CS with three typical PA structures was established based on the preoperative computed tomography (CT) data in the clinic, including CS models with left pulmonary artery (LPA) dysplasia, symmetrical PA dysplasia, and right pulmonary artery (RPA) dysplasia. Also, the process of PDA spontaneous closure was simplified to six different relative sizes of PDA. Eventually, the transient simulation results were calculated by the CFD solver, and the effects of PDA in CS with different PA dysplasia were analyzed through multiple hemodynamic parameters.DCS (where DCS indicates the diameter of CS) was created as the latest initial nonclosure PDA. Finally, the model of CS with symmetrical PA dysplasia is shown in This study was based on a 12-day-old infant with pulmonary atresia and symmetrical PA dysplasia and nonclosure PDA. Due to insufficient pulmonary blood flow, the surgeon implemented the CS operation on this patient. We consciously selected this kind of clinically controversial case on how to deal with PDA as the research object. To study the hemodynamics of such patients, the initial 3D geometry was rebuilt with this patient's 138-slice CT image collected in preoperation. And to eliminate the influence of the complexity of the AAO inlet cross-sectional shape on the calculation process and results, the AAO inlet was simplified to a circle and made an appropriate extension in the axial direction. Then, a 3.5 mm CS configuration was created in the 3D model based on the choice in the clinical CS surgery. The original irregularly shaped PDA was discarded, and with the axis of the original rebuilt PDA, a circular tube with a size of 1.5DRPA = 4 mm, DLPA = 4 mm, where DRPA and DLPA indicate the diameters of the RPA and LPA, respectively); the PA structure with LPA dysplasia ; and the PA structure with RPA dysplasia . The 3D geometry of LPA (RPA) dysplasia was created through adjusting the size of LPA (RPA) and unchanging the initial position of LPA (RPA), based on the model of symmetrical PA dysplasia. The reconstructed structures are exhibited in Figures The previous research showed that the hemodynamic environment was greatly affected by different types of RPA and LPA structures . Thus, wα) was used to define the size of PDA:DPDA and DCS indicate the diameters of the PDA and CS, respectively.There will be a flow competition relationship in the PA due to the shunt blood being provided by both the CS and the nonclosure PDA. To highlight the impact of this competitive flow on the hemodynamics of patients after surgery, and considering the PDA being spontaneously closed for the postoperative patients, the relative sizes (α) decreased from 150% to 0 in this study. For CS models with each typical PA structure, six different relative sizes of PDA were established to correspond with six different degrees of PDA closure: the initial PDA nonclosure (α = 150), PDA gradually closing , and PDA completely closed (α = 0). This study discarded the model with the relative size of PDA being α = 25% due to the undersized PDA always bringing about lower mesh quality for the model and affecting the accuracy of the simulation. Taking the case of PA structures with symmetrical PA dysplasia as an example, the changing processes of the PDA gradually closing are demonstrated in The spontaneously closing process of PDA was simplified to the process of PDA relative sizes  to get the grid independence test. According to the test results, the power loss change less than 1% was taken as the evaluation standard, and the final selected global element size was 0.4 mm to reduce the cost of calculation. Additionally, the boundary-fitted prism layers were defined with the first layer size being 0.1 mm and increased by a height ratio of 1.15 and 5 layers in total. The value of wall Y plus was checked to ensure the mesh quality of the boundary-fitted prism layer. Finally, the above grid parameter settings were adopted in all models, and the mesh information for the model with symmetrical PA dysplasia and nonclosure of PDA is described in The 3D reconstruction models with tetrahedral elements and triangular prisms just for the boundary-fitted prism layers were meshed. The results of Benim et al.  show thaIn this study, a three-element windkessel (3WK) model consists of two resistors, and one capacitor was used to prescribe the outlet boundary conditions of the 3D vascular model , and theR0 and R1 indicate the flow resistance at the proximal and distal ends, respectively; P0(0), Pd, and P(t) are the proximal pressure, the downstream pressure, and the outlet pressure at the initial time, respectively; C represents the compliance of the blood vessel; and Q(t) is the outlet volume flow rate.According to the 3WK model shown in R0, R1, and C in the case of the CS model with symmetrical PA dysplasia were calculated based on the clinical parameters and previous studies [R0) at each outlet is inversely proportional to the square of the cross-sectional area of the outlet and the compliance (C) value is proportional to the cube of the outlet radius; then, the 3WK parameters of the unilateral PA dysplasia model can be calculated based on the symmetrical PA dysplasia model. Finally, the pulse pressure method was used to calibrate the parameter values of the 3WK model [The 3WK model parameters  studies –22. Sinc studies , we haveWK model , 25, andUser-defined functions are used to customize outlet boundary conditions during the simulation, and considering the calculation accuracy and workload, the second-order Runge-Kutta method was used to discretize the integral term. According to the measurement data provided by Di Molfetta et al. , the sim3 [K-omega based Shear Stress Transport (SST) solver was set as the turbulence calculation mode [−6, and the total calculation time length is five cardiac cycles with 0.5 s for each cycle. Finally, the number of time steps in a single cardiac cycle was set to 1000, and transient CFD simulation was conducted to obtain the characteristics of the flow field.All models have used the same calculation method; the blood was assumed to an incompressible Newtonian fluid, with the dynamic viscosity of 0.0035 Pa·s. And the density was 1060 kg/m3 , 28. It 3 . Additioion mode , and a sQS/A) was usually used to express the volume flow of shunt blood:Qshunt and QAAO indicate the total volume flow in the pulmonary circulation and the inlet of AAO during a cardiac cycle, respectively.The main purpose of CS surgery was to provide a certain amount of shunt blood for the pulmonary circulation through establishing an artificial shunt, which could increase the body's blood oxygen content and reduce the patient's cyanosis symptoms and promotes the development of the PA –32. TherQL/R) was adopted to evaluate the patient's LPA and RPA perfusion after surgery:QLPA and QRPA indicate the flow volume in the LPA and RPA within one cardiac cycle, respectively.Studies have confirmed that promoting the balanced distribution of pulmonary blood flow after CS surgery is crucially important . Thus, tThe power loss and the indexed power loss (iPL) are an important indicator for evaluating hemodynamics after CS surgery; especially for patients with poorly developed cardiac function, the excessive power loss will affect the patient's capacity to perform physical activities after surgery , 35:(5)p is the static pressure of the blood in the resting state, ρ is the density of the blood, v is the flow velocity of the blood at the border of the inlet and outlet of the 3D model, Q is the volume flow of the blood at the inlet and outlet of the 3D model, and N represents the total calculation time steps in a cardiac cycle.Among them, 2) and aortic oxygen saturation (Sao2) are as follows:QS and QP indicate the volume flow into the systemic circulation and the volume flow into the pulmonary circulation, respectively. According to clinical statistics [C2PVo) flowing into the ventricle through the pulmonary circulation and the oxygen consumption (CVo2) of the body were 0.22 mLo2/mL and 0.874 mLo2/s, respectively.The calculation of blood oxygen content after surgery is an important indicator for evaluating the central shunt, and it is closely related to whether the patient needs further intervention after surgery , 37. Accatistics , 39, theQS/A and QL/R of the three typical PA configuration models with the CS. With the relative sizes of PDA (α) decreased from 150 to 0, QS/A of the case with symmetrical PA dysplasia, LPA dysplasia, and RPA dysplasia gradually decreased from 0.73 to 0.56, 0.77 to 0.58, and 0.78 to 0.59, respectively. This analysis found that the nonclosure of PDA increases the QS/A value of the CS model, and the QS/A value will gradually decrease following the α decrease. In most cases, QL/R > 1, which indicates that more blood flow was in LPA than RPA. The only two exceptions were the cases of RPA dysplasia when α was 150 and 125; the corresponding value of QL/R was 0.97 and 0.94, respectively. A further novel finding was that the nonclosure of PDA was associated with lower QL/R than the closure of PDA.As detailed in 2 and the Sao2 when the PDA was gradually closed are shown in 2 of the symmetrical PA dysplasia, the LPA dysplasia, and the RPA dysplasia models with the nonclosure of PDA (closure of PDA) was 2.19 mLo2/s (3.45 mLo2/s), 1.83 mLo2/s (3.38 mLo2/s), and 1.98 mLo2/s (3.09 mLo2/s), respectively. It appears that with the gradual atresia of PDA, Sao2 will gradually decrease while the Do2 gradually increases, which has opposite effects for the patients.For the three typical PA configuration models with the CS, the changes of the Dot = 0.12 s) was selected as the research object. The proportion of different WSS distribution was plotted for the CS configuration with the three typical PA structures , which indicated that this size of PDA has less impact on the risk of PA overflow. Moreover, QS/A is closely related to Do2 and Sao2. The cyanosis phenomenon in patients becomes alleviated with the increase of Do2 and Sao2, which is the main purpose of SPS surgery. However, the nonclosure of PDA may cause a lower Do2 and higher Sao2 in our study due to the overlarge QS/A causing too little blood involved in the systemic circulation. Such results are beneficial to the development of PA, but not conducive to reducing the cyanosis phenomenon.Compared with the CS model when the PDA is in the atretic state, the nonclosure PDA is equivalent to providing an additional shunt channel from the systemic circulation to the pulmonary circulation. These results demonstrated that under the shunt diameter of 3.5 mm, CS has been able to provide sufficient PA perfusion for the research subjects when the PDA was closed. However, the presence of PDA led to an increase in the erfusion . Thus, fQL/R is close to 1, which is the infusive result and could promote the balanced development of LPA and RPA. For the model with RPA dysplasia, the case of PDA closure with QL/R = 5.22 indicates that CS is not suitable for this patient, and combined with the research of Mitra and McNamara [QL/R value is reduced to 2.06 similar to the MBTS in the PDA nonclosure. Therefore, for the case of PDA nonclosure, CS will lead to more uniform pulmonary blood flow distribution than BT. In general, if promoting the balanced development of the LPA and RPA after CS surgery is the most important goal, a PDA that remains in the conductive state can be the first choice.The CS structure and PA have a strong geometric sensitivity, which may cause asymmetrical blood flow distribution in the LPA and RPA when the PDA was closed. And this result will be improved in the case of PDA nonclosure; especially for the models with symmetrical PA dysplasia or LPA dysplasia in the PDA nonclosure states, McNamara , MBTS coOur study demonstrates that nonclosure of PDA tends to result in lower power loss and iPL of the CS model with three typical PA dysplasia structures, and retaining the initial PDA reduces the power loss of the CS model by more than 30% compared with the PDA closed. The value of power loss and iPL is negatively correlated with PDA size, while the structural difference of PA has little effect on this changing trend. Lower power loss is beneficial to reduce the burden on the heart of patients with hypoplastic cardiac function and provide patients with a better quality of life in postoperation . This imα < 50), keeping the PDA nonclosure may increase the risk of shunt blockage. It is recommended to manually turn off PDA in CS operation when α is smaller than 50.The unclosed PDA is considered an additional shunt pipe, which can greatly reduce the probability of complete blockage of the systemic-to-pulmonary shunt and plays a positive role in preventing SPS failure caused by early acute shunt thrombosis. From the result, the case of PDA nonclosure has shown the homogeneous WSS distribution and the smaller proportion of high WSS areas. The high WSS will mediate the activation of platelets, and in the area of low flow rate, the activated platelets will aggregate and combine with the coagulation protein in the low blood flow areas, which is a precursor to thrombosis . Therefo2 are negatively correlated with the relative size of PDA, while Sao2 is positively correlated with it, which is consistent with the result of MBTS with nonclosure of PDA in Zhang et al.'s study [The shunt blood for pulmonary circulation provided by the CS and the PDA are mixed in the PA, which resulted in a complicated blood flow pattern at the junction, while the blood velocity distribution of the CS structure is more uniform. In addition, the surgeon cannot ignore the changes in hemodynamic parameters during the process of PDA spontaneously closed and how to deal with different sizes of PDA before surgery. Our results clearly show that the power loss, RPL, and Do's study .This study focuses on the influence of the diameter of PDA and PA on hemodynamics, and the diameter of blood vessels may be one of the most important factors affecting hemodynamics . HoweverQS/A) of CS surgery is positively correlated with the size of PDA, and a larger PDA may cause excessive PA perfusion and is not conducive to increasing oxygen delivery to reduce cyanosis symptoms. Moreover, it cannot be ignored that different PA structures have obvious effects on QS/A, QL/R, and oxygen transfer. There is no gold standard for how to manage PDA during CS surgery, the specificity of the cardiovascular geometry and physical condition in different patients limits the application scope of our research results, and multiple hemodynamic parameters should be considered comprehensively according to the characteristics of different patients to achieve the best surgical effect.For the CS model with symmetrical PA dysplasia, LPA dysplasia, and RPA dysplasia, respectively, the changing trends of hemodynamic parameters during the spontaneous closing process of PDA were roughly identical. Nonclosure of PDA has a series of advantages, which could provide more uniform pulmonary blood flow to promote the balanced development of LPA and RPA, as well as reduce power loss to decrease the heart workload and reduce the proportion of high WSS areas to prevent postoperative shunt thrombosis. Besides, the dual shunt is beneficial in preventing early acute shunt failure. However, the gradual closure of PDA will make these advantages nonexistent. It is worth noting that the systemic-to-pulmonary shunt ratio (


Recycling of raw materials and is crucial for the production of new products for the global economy. The aim here is, on the one hand, to reduce energy consumption, and, on the other hand, to obtain materials with similar functional properties. The study undertook research on the possibility of processing AlSi11 aluminum chips by compaction and co-extruding to obtain a product in the form of a flat bar with mechanical properties not lower than those of the cast materials. The performed tests and the developed technique allowed to obtain flat bars with more favorable mechanical properties  than the castings (YS ≥ 70 MPa ≥ 150 MPa). The weldability evaluation tests revealed that the material is susceptible to porosity. The presence of pores, which reduces the cross-section (up to 60%), reduces the tensile strength (up to 20 MPa). The typical joint structure and plasticity is obtained, which indicate the possibility of tensile strength improvement. Sustainable economic development constantly puts emphasis on searching for methods of manufacturing products with minimal energy consumption and minimal input of materials from primary sources. A highly effective way to achieve these goals is to close the material cycle in the economy by recycling waste materials and scrap. It is of particular importance in the case of light metals and their alloys, which due to their properties constitute an important material group in the global economy. Currently, the world production of primary aluminum is around 50 million tons per year, and the demand for aluminum has been steadily increasing in recent years at the rate of 2.4% per annum .2 [2. [2 each year. Hence, there is a lot of research and experimental work related to the simulation of aluminum production and recycling and models allowing for the reduction of CO2 emissions [However, it should be taken into account that aluminum alloys are the most energy-consuming raw materials already at the production stage in the initial extraction processes from primary sources . The mos2 . It is a2 [2.  On a glomissions , increasmissions  or prelimissions .Almost all modern aluminum recycling is based on the processes of melting scrap. Various types of melting furnaces are used for this purpose, from gas furnaces, which are relatively cheap, to technologically advanced electric furnaces, which are equipped with special charge-introduction systems into the liquid metal . In the In recent years, there has been a lot of research work on the recycling of aluminum alloy chips using modern and innovative techniques without the liquid phase ,23,24,25To reduce a losses can be the recycling carried out at a temperature much lower than the melting point. At low temperatures the intensive oxidation is not observed which allow the direct processing of the fragmented fractions of scrap . This poSuch materials can be mechanically synthesized and strengthened by the addition of metal oxides ,14 or suGronostajski J.Z. et al.  carried 36H70O4Zn [Koch A. et al.  used alu6H70O4Zn . In the cyclic extrusion compression back pressure (CECBP) technique fine chips of AA 6061 alloy were pre-compacted under a high pressure and then subjected to the forging process, which allowed high compaction of the fragmented material, resulting in similar hardness as in the case of solid material . BaffariIn summary, a review of previous studies shows that although the properties and structure of materials after consolidation are well-known, there are no reports on the possibility of joining them by welding, which results from the limited weldability of the casting alloys due to the high porosity of the material after casting ,27. HencThe paper presents the results of the tests carried out for the recycled AlSi11 alloy, made to determine the influence of the chip size on mechanical properties of extruded bars and its weldability. The material for the tests was eutectic aluminum alloy of AlSi11 grade in the form of a commercial ingot with dimensions of 70 mm × 100 mm × 700 mm. The chemical composition and mechanical properties of ingots and filer metal for welding are presented in The samples manufacturing plan is shown in The reference material, with which the two types of chips were compared, was a solid ingot cast by gravity into a steel crucible with a diameter of 40 mm and a height of 60 mm A. The di1. Cold compaction A. Molded2. Hot co-extrusion B. The chThe material prepared in the form of flat bars was cut into sections of 150-mm long, then V-beveled, maintaining the bevel angle of 30° (groove angle 60°) and the threshold of 1 mm. The distance between the joined elements was 1 mm . Before Samples of the base material (bars) and welded joints used in the tests were determined in accordance with The extruded flat bars (profiles), intended for welding, were tested in terms of quality assessment and meeting the requirements of EN 1706  coveringThe joints were visually inspected in order to identify the possible welding defects. Visual examinations were carried out maintaining a direct path between the observer and the sample. The lighting during the test was 550 lx. Samples were taken from the joints for metallographic and mechanical properties tests using the BP05d electro-erosion machine . The samples for the microstructure tests were mounted in Bakelite with carbon filler resin on the CITOPRESS-1 device . The metallographic specimens were ground on water-based abrasive papers and polished with the use of diamond pastes with a gradation up to 1 μm and the OPS polishing agent.Metallographic specimens were used in macroscopic, microscopic, and SEM examinations. Macroscopic observations of the joints were carried out using the Leica S9 stereoscopic microscope , while the observations of the joints microstructure were made using light microscopy (LM) using Leica DM/LM  and scanning electron microscopy (SEM) using Phenom XL . SEM observations were carried out at a beam-accelerating voltage of 20 kV. Chemical composition analyzes were performed using SEM-EDS . 3·s−1. The obtained fractures were subjected to macroscopic observations using the Stemi 305 stereoscopic microscope  and the scanning electron microscope  used in metallographic research.The mechanical properties in the static tensile test were made with a Zwick Roell Z050 testing machine  on samples with base dimensions of 15 mm × 5 mm. The tension speed was 8∙10Density was measured using the displacement volume method using a laboratory balance XA 120/250.4Y . Measurements were made on samples with dimensions of 15 mm × 40 mm with an measurement accuracy of 0.001 g. The porosity of the material was analyzed on the basis of macroscopic photographs using Sigma Scan Pro software .The surface morphology of the flat bars obtained by hot co-extrusion is shown in 3. This indicates that the obtained results are in the range of the measurement error.Measurements of the density of the materials did not reveal any significant differences between the different processing states , where tThe microscopic observations (LM/SEM) revealed a similar structure in all the tested materials. The reference material (M1) is characterized by relatively large areas of α-Al phase, against which there are visible precipitations in the form of massive and lamellar form corresponding to the primary silicon crystals and brittle intermetallic phases . In the Hardness measurements revealed that M3 material is characterized by the highest hardness amounting to approx. 75 HV2, which is approx. 15 HV2 higher than the original material, while for material M2 the hardness recorded is approx. 65 HV2 . In addiThe obtained results of tests of materials in the state after hot extrusion show that the reference material M1 is characterized by a relatively low porosity and a fine-grained structure. Porosity occurs both in the reference material and obtained from chips, and has a similar morphology and is evenly distributed over the cross-section. Profiles made of fine (M3) and large chips (M2) have a lower porosity than casting material (M1), while in the M2, a greater number of large precipitates and the presence of impurities bands associated with extrusion are observed. For samples obtained from large chips (M2), delamination in the form of strips arranged parallel to the material flow during extrusion was observed. The materials obtained from chip recycling have a fine-grained structure and more favorable strength properties than the M1 material , Table 7Visual tests showed the regular shape of the welds made on all flat bars, regardless of the method of their production. This indicates that the welding parameters used should ensure high-quality joints. In the case of samples W2 and W3 made of flat bars corresponding to materials M2 and M3, an increase in the height of the excess weld metal in relation to M1 was noted and no visible scaling of the weld in both joints was observed. Detailed observation of surface revealed a typical morphology of the weld face W2 with very small pores see B. In addMacroscopic observations in the cross-section of the joints  revealedMicroscopic examinations carried out with the use of LM and SEM revealed a change in the morphology of silicon precipitates and intermetallic phases in all welds D in relaThe results of testing the mechanical properties of welded joints are shown in All fractures are characterized by a quasi-plastic fracture. In the case of W1 the material is deformed, but cracking was due to the presence of brittle Si-plates precipitation and intermetallic phases A. The loHardness distributions (HV2) in the cross-section of the welded joint W1 revealed an increase in hardness compared to the base material by approx. 15 HV2 A. In theThe test results show that while it is possible to produce a material in the form of a flat bar or a strip of recycled chips with mechanical and plastic properties meeting the requirements for castings, these materials show a high tendency to porosity and lower mechanical properties during welding.The tests of materials after hot co-extruding have shown that, regardless of the size of the chips used, it is possible to obtain good mechanical properties, i.e., YS > 120 MPa, UTS = 167 Mpa, and A > 11%. The obtained results are consistent with the values . This shMIG arc welding of flat bars revealed the presence of significant porosity of the welds, and the gas voids cover a significant part of the cross-section (up to 60% for W3)—3/100 g of the weld metal, and at the temperature slightly below the melting point (solidus) it decreases to a value below 0.036 cm3/100 g of weld metal [The gases were found in the base material, and as a result of heating to high temperature and melting the edges, they escaped into the liquid metal. The gas favoring the formation of porosity is hydrogen, the solubility of which in liquid aluminum increases with increasing temperature, where at 660 °C it is 0.69 cmld metal . As a reThe study of mechanical properties shows that the strength of the obtained joints is much lower (over 60%) than that of the base material . Here, t3). The tests revealed that it is possible to obtain materials by recycling, which will have a favorable structure with lamellar and acicular precipitates of silicon and intermetallic phases, and also favorable mechanical properties meeting the requirements for eutectic castings such as AlSi11 alloy. The degree of porosity (up to 60%) obtained by compaction and extrusion does not differ from the porosity observed for cast alloys, which is indicated by similar density results  it is approx. 27%, and for fine chips (W3) approx. 60%. However, the degree of porosity does not clearly affect the mechanical properties of the joints, where the lower porosity (27%) and higher hardness 38 HV2 in W2 do not prevent the formation of the small cross-sectional area being the shear plane in the static tensile test (UTS 60 MPa). Larger pores, but evenly distributed in the cross-section of the welds (W3), have no effect on higher tensile strength (UTS 20 MPa), behaving similar to metal foams during tension . Summing up, the obtained results show that while it is possible to recycle casting aluminum alloy chips and obtain, by extruding, full-value materials, which may also be economically feasible , furtherThe size of the chips used in the recycling process affects the mechanical properties of the materials after co-extrusion, where more favorable properties are obtained for thick chips (UTS upto.224 MPa);Chip size affects the porosity of welded joints, where lower porosity (27%) is obtained for thick chips, while the distribution of pores (gas voids) in the cross-section is uneven, and greater (60%) for fine chips, which results in less favorable mechanical properties .The type of chips used did not affect the structure of the weld and the character of the fracture, and the increase in porosity was reflected in the height of the excess weld metal;The tests performed revealed the possibility of obtaining metallic continuity of the AlSi11 alloy, the equally low quality of the obtained joints indicates that joining tests should be performed using other welding methods with a limited amount of heat input into the material, i.e., friction stir welding (FSW).Overall, the research showed that:


Bisphenol A (BPA) is a substance used in the manufacture of plastics which shows multidirectional adverse effects on living organisms. Since the main path of intoxication with BPA is via the gastrointestinal (GI) tract, the stomach and intestine are especially vulnerable to the impact of this substance. One of the main factors participating in the regulation of intestinal functions is the enteric nervous system (ENS), which is characterized by high neurochemical diversity. Neuregulin 1 (NRG1) is one of the lesser-known active substances in the ENS. During the present study (performed using the double immunofluorescence method), the co-localization of NRG1 with other neuronal substances in the ENS of the caecum and the ascending and descending colon has been investigated under physiological conditions and after the administration of BPA. The obtained results indicate that NRG1-positive neurons also contain substance P, vasoactive intestinal polypeptide, a neuronal isoform of nitric oxide synthase and galanin and the degree of each co-localization depend on the type of enteric plexus and the particular fragment of the intestine. Moreover, it has been shown that BPA generally increases the degree of co-localization of NRG1 with other substances. Bisphenol A (BPA) is an organic synthetic substance which is used in the manufacture of plastics around the world and therefore contained in a wide range of objects of everyday use, including domestic appliances, toys, bottles, conserve tin liners, office supplies, dental materials, amongst many other things ,2. BPA mHowever, it should be pointed out that the main vector of intoxication of living organisms with BPA is through the gastrointestinal (GI) tract . TherefoThe ENS is located in the wall of the GI tract and is characterized by a very complicated construction and a high degree of independence from the central nervous system ,13. The The enteric neurons are characterized by a high degree of heterogeneity with regard to their neurochemical characterization, which enables the synthesis of active substances by neuronal cells ,16. BesiNRG1 is a 44-kD glycoprotein belonging to the neuregulin family, which, in turn, is a part of the group of epithelial growth factors affecting ErbB receptors, and plays a key role in the development of the organism through the regulation of apoptosis, angiogenesis and cell survivability ,18. In tOne of the ways to better understand the functions of lesser-known neuronal substances is the study of their co-localization with other better-known factors in the same nervous structures, since previous investigations have shown that neuronal substances synthesized and occurring in the same neurons most often play similar and/or complementary roles ,27,28. TDuring this study, all neuronal factors studied were found in NRG1-like immunoreactive (LI) neurons located in all types of enteric plexus within the porcine caecum and the ascending and descending colon both under physiological conditions and after BPA administration. The degree of co-localization of NRG1 with other substances depended on the type of enteric plexus and the fragment of the intestine.Under physiological conditions, the largest number of NRG1-positive cells in all types of enteric plexus were also immunoreactive to nNOS , which wAdministration of low and high doses of BPA caused an increase in the degree of co-localization of NRG1 with all other substances studied in all types of enteric plexus, and more visible changes were observed with higher doses of BPA . The cleThe changes on the level of about 10 pp in comparison to the control animals were also observed under the impact of a high dose of BPA in populations of neurons NRG1+/VIP+ in the MP and NRG1+/SP+ in the OSP, as well as in animals treated with a low dose of BPA in neurons simultaneously immunoreactive to NRG1+/SP+ located in the ISP . In turnUnder physiological conditions in the MP and ISP, the degree of co-localization of NRG1 with other substances studied was similar to that observed in the caecum . The mosLess numerous were NRG1+/VIP+ and NRG1+/SP+ neurons, whereas the smallest degree of co-localization was observed for neurons immunoreactive to NRG1 and GAL, whose percentage did not exceed 20% of NRG1-positive cells in each type of enteric plexus . The sitThe administration of BPA generally caused, likewise in the caecum, an increase in the degree of co-localization of NRG1 with other substances studied. The only exception was the number of NRG1+/nNOS+ neurons in the OSP, which did not undergo statistically significant changes under the impact of a low dose of BPA . In turnUnder physiological conditions, the degree of co-localization of NRG1 with all other substances studied in the enteric neurons located in the descending colon was higher than in other parts of the large intestine .This phenomenon was particularly pronounced in the case of NRG1+/GAL+ neurons, which formed the largest population of NRG1–LI neuronal cells in the OSP and ISP . In thesIn the descending colon, low doses of BPA caused the least pronounced changes among all segments of the large intestine studied. Such doses did not result in statistically significant changes in the percentage of NRG1+/SP+ neurons located in all types of the enteric plexus, NRG1+/nNOS+ neurons in the MP and OSP, or in NRG1+/VIP+ cells in the ISP . In turnHigh doses of BPA in the descending colon (similar to the caecum and ascending colon) caused an increase in the degree of co-localization of NRG1 with all other substances studied in all types of enteric plexus . The mosDuring the present study, NRG1 was observed in the enteric neurons located in all types of enteric plexus within the porcine large intestine, which is in agreement with previous studies in which this substance was noted in the ENS of other mammal species, including humans ,24. NRG In the light of the present study, the relatively large number of NRG1-positive enteric neurons also showed the presence of nNOS and/or VIP, which may suggest that NRG1 (similar to both of these substances) may perform inhibitory functions in the large intestine. Such a conclusion follows from the fact that both VIP and NO are the two most important intestinal inhibitory factors. They affect the smooth muscles, leading to hyperpolarization of the muscular fibres and therefore to inhibition of intestinal motility ,40,41. TIn turn, the co-localization of NRG1 with SP, which is an important factor participating in sensory conduction, may also indicate that NRG1 displays such activity and may occur in the sensory enteric neurons. This thesis is all the more probable since previous studies have suggested the participation of neuronal NRG1 in the conduction of sensory and/or pain stimuli . MoreoveGAL, the next substance observed during the present study in NRG1-positive enteric cells, shows different effects on the intestinal muscles (similar to SP), depending on the particular fragment of the GI tract and on the precise animal species. For instance, GAL induces muscle contraction in rats and guinea pigs, while in dogs it has relaxatory effects ,50. MoreApart from the neurochemical characterization of NRG1-positive enteric neurons under physiological conditions, changes after the administration of BPA were observed. The changes noted in this study, together with those noted in previous publications where the impact of BPA on the total number of NRG1-positive nervous structures was described , may sugDue to the multidirectional adverse effects of BPA on living organisms, the exact mechanisms of observed changes are difficult to define. They may result from the known direct neurotoxic and neurodegenerative impact of BPA on the nervous system , the infThese functions of NRG1 are also confirmed in the current study by co-localization with other substances included in the experiment. It should be emphasized that all neuronal factors whose co-localization with NRG1 were investigated in this study have previously been described as substances involved in the neuroprotective mechanisms. However, the substance that is best known, and which is the strongest in this regard, is VIP, whose neuroprotective activity relies on the influence of the glial cells located around the enteric neurons . Other sHowever, it cannot be excluded that the changes observed may be connected with the immunomodulatory and pro-inflammatory activity of BPA, which in the previous studies was described as a factor causing clear changes in the immunological system ,60,61. OOf course, it should be pointed out that the present study has some limitations. Firstly, it is not clear what mechanisms are at the root of changes in the neurochemical characterization of NRG1-positive enteric neurons and whether these changes are the result of fluctuations in the expression (protein or mRNA) of the substances studied or of changes in transport within neuronal cells. The effect of the observed changes on the function of the large intestine is also unexplained. Further investigations are indispensable for the clarification of these issues.In conclusion, the present study, for the first time, has shown that NRG1-positive enteric neurons located in the large intestine are characterized by considerable diversity in terms of neurochemical characterization. Substances which co-localize with NRG1 are involved in various regulatory processes. This fact, together with the presence of NRG1 in all types of enteric plexus, suggests that NRG1 participates in the regulation of diverse intestinal activity, including motility, secretory activity and intestinal and mesenteric blood flow. Moreover, changes in neurochemical characterization of NRG1-positive neurons under the impact of BPA may suggest that these neurons take part in pathological processes connected with the adverse effect of this toxic substance. However, the elucidation of these issues requires further study.The present study was conducted on 15 immature eight-week-old female Piétrain x Duroc pigs, which were kept under standard laboratory conditions. Twice a day the animals received commercial feed appropriate to their species and age and they were given water ad libitum. All activities carried out during the study received agreement from the Local Ethics Committee in Olsztyn (Poland) (decision numbers 28/2013 of 22 May 2013 and 65/2013/DLZ of 27 November 2013).After an adaptive period, the animals were divided into three groups of five pigs each: (1) a control (C) group, which received empty capsules; (2) a low dose (LD) group, to which capsules with BPA at a dose of 0.05 mg/kg b.w./day were given; and (3) a high dose (HD) group, in which animals were treated with capsules containing BPA at a dose of 0.5 mg/kg b.w./day. All animals received capsules for 28 days in the same way, i.e., capsules were given orally before the morning feeding. After 28 days, all animals were euthanized. For this purpose, the animals were first pre-medicated with an intramuscular injection of Stresnil  and later (after about 30 min) an overdose of sodium thiopental  was given intravenously.Immediately after euthanasia, the fragments of the selected part of the large intestine were collected. Approximately three-centimetre-long fragments of the caecum , the ascending  and descending  colon were included in the study. Immediately after collection, the intestinal fragments were put into 4% buffered paraformaldehyde (pH 7.4) for 1 h. The tissues were then rinsed in a phosphate buffer for three days and stored in 18% phosphate-buffered sucrose at 5 °C. After at least three weeks the intestinal fragments were frozen at −22 °C and cut using a cryostat . Slices of the intestine were mounted on microscopic slides and stored at −22 °C until further study.3, 0.25% Triton x-100 and 0.05% thimerosal in PBS . The next stage of the labelling was the incubation of intestinal slices with a mixture of two antibodies obtained from various species and directed against neuronal factors studied in a humidity chamber . One of the antibodies was directed against NRG1, and the second was directed against one of the other substances studied. The list of antibodies is presented in The slices of the intestine underwent the double immunofluorescence technique according to the method described previously . The prop < 0.05 (*) and as highly significant at p ≤ 0.01 (**) and p ≤ 0.001 (***).After labelling, the intestinal fragments were evaluated under an Olympus BX51 microscope using epi-fluorescence and appropriate filter sets. To define the neurochemical characterization of NRG1-positive enteric neurons, at least 400 such neurons located in each type of the enteric plexus in each animal were checked for the presence of each of the other neuronal substances studied  Only well-stained and visible neurons, whose colour was clearly different from the surrounding area, were included in the study. The neurochemical characterization of NRG1-positive neurons was presented as a percentage of neurons containing SP, GAL, VIP or nNOS in relation to the total number of NRG1-like immunoreactive (LI) cells, which was considered as 100%. For example, when, during the co-localization study of NRG1 and SP, 400 cells immunopositive to NRG1were evaluated and the presence of SP was noted in 100 cells, the value was presented as 25%. In order to exclude the possibility of the same cells being double-counted, the intestinal slices included in the study were located at least 200 µm apart from each other. The data were pooled and presented as the mean ± SEM. A statistical analysis was performed with a one-way analysis of variance (ANOVA), with Bonferroni’s Multiple Comparison post hoc test using Statistica 12 software . Differences were considered significant at


This paper presents the design, fabrication, and testing of a novel three-dimensional (3D) three-fingered electrothermal microgripper with multiple degrees of freedom (multi DOFs). Each finger of the microgripper is composed of a V-shaped electrothermal actuator providing one DOF, and a 3D U-shaped electrothermal actuator offering two DOFs in the plane perpendicular to the movement of the V-shaped actuator. As a result, each finger possesses 3D mobilities with three DOFs. Each beam of the actuators is heated externally with the polyimide film. The durability of the polyimide film is tested under different voltages. The static and dynamic properties of the finger are also tested. Experiments show that not only can the microgripper pick and place microobjects, such as micro balls and even highly deformable zebrafish embryos, but can also rotate them in 3D space. The manipulation of microobjects with high flexibility has long been a hot and seemingly never satisfactory topic for both scientists and engineers ,2. ThougIn designing microgrippers, choosing a proper actuation mechanism can largely affect the structure and performance of the microgripper. The shape memory alloy (SMA) actuators are usually utilized as actuation of microgrippers with large deformation. However, the SMA actuators have low force and are high cycle time, and are difficult to control because of their thermomechanical nonlinearities ,24,25. EThis work proposes a novel 3D electro-thermal microgripper which can provide multi DOFs with three fingers. Each finger is composed of a novel 3D U-shaped actuator and a V-shaped actuator. The 3D U-shaped actuator and the V-shaped actuator provide two DOFs and one DOF, respectively. The two DOFs provided by the 3D U-shaped actuator are in a plane perpendicular to the motion of the V-shaped actuator, so that each finger will possess 3D motion capability. With three fingers, the 3D microgripper can not only grip microobjects more firmly, but can also rotate them in 3D space. The 3D microgripper is fabricated with 3D printing. The nickel-chromium alloy in the polyimide film is utilized to convert input voltage to thermal energy for heating the beams.This work is organized as follows. In The schematic structure of the novel 3D electrothermal microgripper is shown in The V-shaped actuator presents a symmetric configuration, where two slanted beams are connected in the shuttle at a certain angle and the inclination of the beams facilitates the in-plane movement. When the polyimide film transfers heat to the beams of the V-shaped actuator, thermal expansion caused by joule heating pushes the shuttle outward, as shown in 2, 5120 N·mm2, and 15,000 N·mm2 respectively. The bending stiffness of polyimide film is much smaller than that of the pair of beams of the 3D U-shaped and the beam of V-shaped actuator, so the polyimide film can be bend with deformation of the actuator beams and only bring little extra stiffness to the actuator. The resistance of the polyimide film with the size of 6 × 22 mm and 6 × 50 mm is 15.625 Ω and 40 Ω, respectively. It is found that the change of resistance is very weak when applied with a set of voltages [The polyimide electrothermal film is used to provide external heat source to the beams, as shown in voltages .The experimental setup consists of a controllable direct current (DC) power supply, a manual manipulator, the 3D microgripper, and a microscope, as shown in Durability of the polyimide electrothermal film is of great importance to the life of the 3D microgripper. In order to test the durability of the electrothermal film, a set of voltages are applied to the polyimide film. First, a voltage is applied to the polyimide film for one minute to heat the polyimide film sufficiently. After cooling down for one minute, another cycle of application of voltage is performed. The sizes of the polyimide films for the V-shaped actuator and the 3D U-shaped actuator are 6 × 22 mm and 6 × 50 mm, respectively. As shown in The experimental results show that the polyimide film can be used repeatedly for many times without causing obvious decrease in output displacements. This is ideal and satisfactory for micro manipulation applications considering the cheap price (8 yuan) and replaceability.The static displacement of the 3D U-shaped actuator is tested as shown in The static responses of the V-shaped actuator are tested under different voltages (with increment of 1 V), as shown in The displacement of the 3D U-shaped actuator and V-shaped actuator of the 3D microgripper driven separately is presented in the above two sub-sections. Now, the displacement of the 3D U-shaped actuator and the V-shaped actuator driven simultaneously is measured. Due to the displacement characteristics of the two opposite sides of the 3D U-shaped actuator are the same, as shown in When the voltage of polyimide film on the V-shaped actuator is set to be 6V, we apply different voltages to the polyimide film on the 3D U-shaped actuator and measure the displacement of 3D U-shaped actuator, as shown in The experimental results show that the displacement of 3D U-shaped actuator and V-shaped actuator driven at the same time is almost the same, with minor differences, as when driven alone. Though there are mutual thermal effects between the 3D U-shaped actuator and the V-shaped actuator, the effect is small and can be omitted.With three flexible fingers, the 3D manipulation of microobjects using the fabricated microgripper is demonstrated in this section. The overall flowchart of picking and rotating strategy is depicted in In order to clearly observe the rotation of the micro ball during the operation, marking points were made on the surface of the micro ball, and the rotation angle of the micro ball can be calculated according to the movement of the mark points. In addition, there is a white line from the center of the micro ball to the mark point, which is used to indicate the movement state of the micro ball, and it can be seen clearly the movement of the micro ball. As shown in In order to clearly observe the rotation of zebrafish embryos during the operation, marking points were made on the surface of the zebrafish embryo, and a white line was drawn along the center of zebrafish embryo to the mark point to describe the movement state of zebrafish embryo. As shown in L = X2 − X1, and then the rotation angle N of the microobject is calculated by The rotation angle of the microobject caused by the 3D microgripper is calculated according to the position change of the marked points on the microobject, as shown in In this work, we have designed and fabricated a novel 3D electrothermal microgripper with three fingers. Each finger is composed of a V-shaped actuator and a 3D U-shaped actuator, which provides one and two DOFs in 3D space respectively. The 3D microgripper is fabricated using 3D metal printing and the polyimide film is utilized as the external heat source. Experimental testing has been performed to demonstrate satisfactory durability of the microgripper. In addition, static and dynamic performances have also been tested. With designed operation methods, both the micro ball with a diameter of 2 mm and the zebrafish embryo with a diameter of around 600~800 microns can be handled freely. Furthermore, with the collaboration of three fingers, the microgripper can rotate the microobjects in 3D space. Based on the 3D microgripper, our ongoing work focuses on the controlling, force sensing, and 3D micro visions.


Magnesium alloys, due to their unique properties, low density and high strength properties, are becoming more frequently used in industrial applications. However, a limitation of their use may be the need to ensure high abrasive wear resistance and corrosion resistance. Therefore, magnesium alloys are often protected by applying protective coatings. The paper presents the influence of the modification of the electrolyte composition, with or without the addition of borax, on the morphology (observed by SEM method) and phase composition  of the formed layers on the AZ91 magnesium alloy, and their abrasive wear  and corrosion resistance , especially in chloride solutions. It has been clearly demonstrated that the modification of the electrolyte composition significantly impacts the final properties of the protective coatings on the AZ91 alloy formed by the plasma electrolytic oxidation (PEO) process. On the basis of the results, it was found that the new type of PEO coatings with the borax addition, compared to base PEO coatings, showed significantly higher abrasion resistance and an order of magnitude lower corrosion rate. Moreover, their specific properties, such as, high mechanical properties and excellent castability, made them widely used in transport and production of computers, communications and consumer electronics (3C) manufacturing in order to meet environmental protection and energy saving requirements [Magnesium and its alloys, due to their density, are classified into the group of so-called “irements ,2.17Al12 intermetallic phase, but also improves its corrosion resistance. The key factor, however, is the volumetric share of the phase formed and the place and distribution of its crystallization [β-phase (Mg17Al12) possesses a continuous nature and is finely divided, the corrosion resistance increases [17Al12 formed as intergranular precipitates, microgalvanic cathodes occur, decreasing the corrosion resistance of magnesium alloys [17Al12 particles, distributed discontinuously in structure and, thus, due to their relatively high cathodic potential, contribute to decreasing the corrosion resistance of the material [Unfortunately, a certain limitation in the use of magnesium and its alloys may be its higher chemical activity compared to other commonly used non-ferrous alloys, such as aluminum. As a consequence, it exhibits lower corrosion resistance ,4. Therelization . When thncreases . On the m alloys . Zinc ism alloys . HoweverIn order to protect the surface of magnesium alloys and, thus, enable their widespread applications, regardless of the environmental conditions in which they would be used, in recent years, different coating technologies have been developed ,14. The 2B4O7·10H2O), which is widely used in various industrial applications [One of the main advantages of applying the PEO coating to the surface of the material is the increase of their resistance to corrosion and abrasion . Howeverications ,26. Boraications  or its cications ,27. For ications  showed tIn this study, the properties of the coatings produced on the magnesium alloy AZ91 using the PEO process were investigated. The influence of the modification of the electrolyte composition, with or without the addition of borax, on the morphology and phase composition of the formed layers and their abrasive wear and corrosion resistance, especially in chloride solutions, was analyzed.The AZ91 magnesium alloy (MgAl9Zn1) was melted in a resistance furnace  at a temperature of 680–700 °C using an SF6 protective atmosphere. Then the ingots were prepared by the coquille casting method. The PEO coatings were applied to the samples after their casting, without any prior special preparation or degreasing of their surfaces. During the PEO process, the electrolyte temperature was controlled and kept below 20 °C. The sample was the anode and the stainless-steel container containing the electrolyte was the cathode. The diagram of the entire PEO system was presented in The type and the used designation of the samples were presented in −1 with a 40 mA current and 40 kV tube voltage. The qualitative analysis was performed using HighScore Plus software . The phase composition was identified on the basis of data contained in the International Centre for Diffraction Data (ICDD) PDF-4+ catalogue.The surface and cross-sectional morphology, as well as the elemental composition of the PEO coatings and alloys, were examined by scanning electron microscopy (SCIOS FEI), equipped with an energy-dispersive spectrometer (EDS). X-ray diffraction  was carried out to determine the phase composition of the coatings. The rectangular specimens were scanned in Bragg–Brentano geometry in a 2θ range of 10° to 100°, using Cu-Kα radiation. The scanning rate was 1.5°·minn to the ball holder. The friction force Ft was measured continuously during the test using the extensometer. The tests were carried out at room temperature under dry sliding conditions.The coefficient of friction and the wear resistance of the coatings were determined in the ball-on-disc tests, using a UMT-2MT universal mechanical tester , by rotating the sample against a stationary ball . The loaBall diameter, load and the radius of the sliding circle were experimentally selected through preliminary analysis in such a way that the expected abrasion of the coating did not occur too early, preferably in the middle of the test . In the The corrosion resistance of the coatings was evaluated using the immersion method (500-h exposure) in an inert salt spray in 5% aqueous NaCl solution with pH 6.6 ÷ 7.2 at 35 °C.2. The reference electrode was a chlorosilver Ag/AgCl electrode (containing 3M KCl), and a steel wire (SS316) served as the counter-electrode. The experiments were carried out in 0.1M NaCl aqueous solution. Linear sweep voltammetry (LSV) was performed at a scan rate of 0.001 V/s after an initial 1800 s exposure in solution to stabilize the open circuit potential (OCP). All measurements were made at room temperature.To further evaluate the corrosion resistance of PEO coatings, electrochemical tests were performed. For this purpose, AUTOLAB PGSTAT302N potentiostat/galvanostat was used. In each test, a traditional three-electrode system was used, where the sample working electrode was the tested sample with surface exposed size of 1 cmSEM images of the surface and cross-sections of PEO coatings formed on AZ91 alloy were presented in The element content (at. %) was determined from the EDS results shown in . The ana0.93Al0.07 (card no. 04-003-5282) crystallized in a hexagonal structure. This phase appears for all samples. Furthermore, signals attributable to the Mg17Al12 (card no. 04-005-4961), and MgO (card no. 01-085-5649) phases are observed, but their signal intensities are much lower. The results suggest that the building blocks of these types of coatings closely depend on the composition of the alloy as well as the electrolyte. A consistent feature for all such coatings is the presence of a small number of oxides (MgO), which were formed according to Equations (1) and (2).The main phase identified is Mg2SiO4 are also observed, which is known by the name forsterite or olivine in mineral databases. It is a magnesium orthosilicate  formed by fusion of stoichiometric amounts of magnesium and silicon oxides at 1900 °C (such a temperature may occur during the microplasma oxidation process). Mg2SiO4 was formed according to Equation (3):Moreover, slight amounts of 17Al12 phase is not unusual, especially for cast alloys of the Mg-Al system. However, the transition phase may be the result of thermal phenomena  occurring during the plasma discharge. In the PEO processes, the magnesium substrate acts as an anode in silicate-based electrolytes; thus, the magnesium dissolution reaction (Equation 4) occurs under a strong electric field that produces magnesium ions.The presence of the Mg42−, OH−, from the electrolyte to the substrate, at high potentials. When the concentrations of these ions at the electrode/electrolyte interface reach a critical value, film forming reactions occur.The formation of oxide films on magnesium is due to the external diffusion of magnesium ions, flow from the substrate to the electrolyte, and the internal diffusion of SiOThe results of the ball-on-disc friction measurements on AZ91 cast alloy protected with the PEO coating was shown in On the other hand, the behaviour of the COF curve recorded for the PEO coating made on AZ91 alloy in the electrolyte containing the addition of borax also showed an increase in the initial stage, but it was not so rapid and its stabilization with the value of about 0.6 took place after ~3500 s of the analysis. Moreover, this type of PEO coating was not damaged until the end of the test, the behaviour of the COF curve was stable, and no visible signs of abrasion were observed.Examination of the surface of the samples after immersion in salt spray revealed surface defects and pitting, regardless of the composition of the electrolyte used in the PEO process to create the protective coating. However, for a sample covered by the base PEO process, the number and size of pits are much larger than for the sample protected when a modified PEO electrolyte was used. The coating destruction mechanism is caused by the formation of numerous new pitting corrosion centers, which grow and interconnect, mainly visible as a large dark area (hole) covering a large part of the surface on base PEO coating a. On the−3 for further corrosion tests and quality assessment of the produced coatings. The widespread presence of chlorides in the surrounding environment and their complexing properties and increasing the electrolyte conductivity resulted in the selection of an aqueous NaCl solution with a concentration of 0.1 mol dmcorrE, corri, Rp and the corrosion rate of the tested materials clearly confirm the significant influence of PEO coatings on the protection of magnesium alloys against corrosion. The corrosion rate was reduced by two orders of magnitude. Moreover, the obtained results indicate a significant advantage of PEO coatings modified with the addition of borax, because their corrosion rate value is an order of magnitude lower compared to the base PEO coating. The recorded results are in accordance with the results obtained from the salt spray tests, wherein, for the case of the sample protected with the base PEO coating, active dissolution of the material was observed, while for the PEO coating modified with borax, the sample was attacked only in points at the discontinuity of the coating.On the basis of the recorded curves, it was found that after the application of the PEO coating to the surface of the magnesium alloy, there was a decrease of almost two orders of magnitude in the value of the cathode current density  was also observed in macro mode, as shown in Based on the observations, it can be concluded that the most intense corrosion processes took place on the AZ91 alloy surface a, which Based on the presented results, it has been clearly demonstrated that the modification of the electrolyte composition significantly impacts the final properties of the PEO coatings. The coatings made on the AZ91 magnesium alloy in the electrolyte containing the addition of borax showed much greater abrasive wear resistance and corrosion resistance, especially in chloride solutions, compared to the coatings made in the solution without borax addition, and in relation to the AZ91 alloy itself. Moreover, the addition of borax to the electrolyte did not change the phenomenon of the formation and growth of the protective coating applied on the AZ91 magnesium alloy. The use of the PEO coating modified with the addition of borax changed the active dissolution of the magnesium alloy to pitting corrosion of the alloy in the places of discontinuity/porosity of the coating, which was confirmed by both visual observations and the results of the polarization test. Their corrosion rate was an order of magnitude lower than that for the base PEO coatings. Moreover, PEO coatings with the addition of borax, in contrast to the base PEO coatings, were not damaged until the end of the ball-on-disc test, and no signs of abrasion were visible on their surface.


The application of concrete containing mineral admixtures was attempted in Northwest China in this study, where the environment has the characteristics of low humidity and large temperature variation. The harsh environment was simulated by using an environmental chamber in the laboratory and four types of concrete were prepared, including ordinary concrete and three kinds of mineral admixture concretes with different contents of fly ash and blast-furnace slag. These concretes were cured in the environmental chamber according to the real curing conditions during construction. The compression strength, fracture properties, SEM images, air-void characteristics, and X-ray diffraction features were researched at the early ages of curing before 28 d. The results showed that the addition of fly ash and slag can improve the compression strength and fracture properties of concrete in the environment of low humidity and large temperature variation. The optimal mixing of mineral admixture was 10% fly ash and 20% slag by replacing the cement in concrete, which can improve the compression strength, initial fracture toughness, unstable fracture toughness, and fracture energy by 23.9%, 25.2%, 45.3%, and 22.6%, respectively, compared to ordinary concrete. Through the analysis of the microstructure of concrete, the addition of fly ash and slag can weaken the negative effects of the harsh environment of low humidity and large temperature variation on concrete microstructure and cement hydration. In the past three decades, the economy of China developed rapidly. In 2019, China’s GDP reach USD 14.343 trillion, ranking second in the world. However, there is an imbalance between the east and the west of China, and the infrastructure construction is relatively weak in the Northwest China. According to the GDP data of 2019, the total GDP of western region is USD 2.983 trillion, accounting for 20.8% of the national GDP; while the eastern region is USD 7.444 trillion, accounting for 51.9%. In recent years, China has accelerated the pace of infrastructure construction in the Northwest. From 2015 to 2019, China’s road construction investment had increased by 32.6%. In 2019, China completed CNY 10,049.8 billion in road construction investment in the Northwest [Existing research has proven that the humidity and temperature in the curing environment have an impact on the mechanical characteristics and microstructure of concrete. When concrete is cured in a dry environment, the water inside the concrete will evaporate to the outside, resulting in the chaos of ion migration inside the concrete and weakening the hydration products in the interface transition zone (ITZ) . AM SoliIn recent years, an effective method of adding mineral admixtures was adopted by scholars to improve the performance of concrete ,10,11. AIn the process of infrastructure construction in Northwest China, the use of concrete with mineral admixtures may be able to withstand the harsh environment and bring considerable economic benefits. However, there were few studies that paid attention to the characteristics of concrete containing mineral admixtures in such a complex environment. Only Jiang et al.  investig2/kg in this study. The fine aggregate utilized was natural river sand with a fineness modulus of 2.85 and an apparent density of 2640 kg/m3. The coarse aggregate was natural crushed stone with a particle size of 5−20 mm and an apparent density of 2760 kg/m3. The used superplasticizer, working as a water reducing admixture, had a water-reducing rate of 25–30%. The water used in the tests was local tap water.The Portland cement of P.O. 42.5  was useTwo kinds of mineral admixtures were adopted in this research, including fly ash and blast-furnace slag. The fly ash is first level in Class F according to the Chinese national standard GB/T 1596-2017 , and theIn the laboratory trials, four groups of concrete with a strength grade of C 45 were manufactured according to the Chinese national standard JGJ 55-2011 , and theIn each group of concrete, six specimens were prepared, including three cube specimens with size of 100 mm × 100 mm × 100 mm for compression strength tests and three prism specimens with size of 100 mm × 100 mm × 515 mm for fracture tests. When the prisms were manufactured, a steel plate with a dimension of 100 mm × 40 mm × 3 mm was welded in the middle of the concrete mold to prefabricate a notch with a width of 3 mm and a depth of 40 mm in the specimens, as shown in An environmental chamber was utilized to simulate the environment of low humidity and large temperature variation in Northwest China. The meteorological data from 1990 to 2020 were analyzed, and the most adverse environmental state was implemented by the environmental chamber: The humidity was maintained at 35%, and the temperature changed periodically from −5 °C to 40 °C every day. From 1:00 a.m. to 6:00 a.m., it was a constant of −5 °C. Then, the temperature gradually raised to 40 °C from 6:00 a.m. to 14:00 p.m. This high temperature remained until 20:00 p.m. and gradually dropped to −5 °C at 1:00 a.m. the next day. The detailed change process of humidity and temperature in one day was displayed in After cured for one day under indoor conditions, the concrete specimens were demolded and then placed into the environmental chamber. In order to simulate the real curing condition during construction, a layer of water-saturated geotextile (sprinkling water every day) was covered on the concrete specimens in the first 14 d. Then the geotextile was removed to expose the concrete to the environmental chamber with no sprinkling water from 14 to 28 d.fcc is the compression strength of the cube specimen (MPa), P is the peak load during the compression test (N), and A is the bearing area of the specimen (mm2).The compression strength tests were conducted according to the Chinese national standard GB/T 50081-2019 . When thDue to the harsh environment in the western region of China, concrete is prone to fine cracks during curing. These microcracks will develop, connect, and merge into one or more macrocracks, which can expand gradually and may lead to structural damage. Traditional strength measurements cannot study the effect of cracks on the structure, so the early-age fracture properties of the concretes were detected by a method of three-point bending test at the ages of 3 d, 7 d, 14 d, and 28 d. The tests were carried out by using an electro-hydraulic servo universal testing machine of type WAW-1000 , as shown in After facture tests, the double-K fracture mode  was usedTo research the influence of mineral admixture on the internal microstructure of concrete under the harsh environment. Scanning electron microscope (SEM) observation for concrete was conducted. After fracture tests, the concrete specimens were cut into cube samples with side length less than 10 mm. The cubes were dried in an oven for 24 h at a temperature of 60 °C and then placed into anhydrous ethanol to prevent further hydration . Before Cutting the concrete specimens to make an observation surface, which must be perpendicular to the casting surface. The observation surface was smoothened and washed several times until it was flat with only pores and void left. Drying the specimens at a temperature of 105 ± 5 °C before detection.Observing the smooth surface by using the hardened concrete pore structure analyzer. The observation area was divided into multiple sub-areas with the same size and each sub-area was taken photos. These photos were binarized for determining the number of air-voids and the chord length by the linear traverse method.According to the collected information, the hardened concrete pore structure analyzer calculated the air-void system parameters of concrete, including the air content, average air-void size, and spacing factor. The air content can be considered as the porosity of concrete. The spacing factor represents the average distance between any point in the concrete matrix and the air-void, and a lower value of spacing factor means more air-voids in the observation area.The internal pore structure of concrete can explain its mechanical properties, so the linear traverse method  was usedFor each group of concrete, three observation surfaces were prepared, and the air-void system parameters were the average values of the three specimens.To study the hydration degree of cement in concrete, crumb inside concrete was dried and grounded into power for X-ray diffraction test to detect the phase composition by using an X-ray diffractometer. During the test, the scanning speed was 0.15 s/step, the step length was 0.013 mm, and the scanning angle range is 5–70°.2 and Al2O3 in fly ash and slag can react with Ca(OH)2 in the presence of water and produced calcium silicate hydrate and calcium sulphoaluminate hydrate, resulting in the consumption of Ca(OH)2 and the promotion of the hydration reaction [The early-age compression strengths of the four types of concrete were displayed in reaction . After 1reaction . Moreovereaction , the earTo research the growth rule of the strength of concrete in the environment of low humidity and large temperature variation, the ratios of concrete compression strength to its 28-day strength of OC and F10S20 concrete were plotted in The load-CMOD (P-CMOD) curves of the four types of concrete at early ages were plotted in From In fracture tests, the initial fracture toughness and unstable fracture toughness represent the ability of concrete to resist cracking and resist crack propagation, respectively. The fracture toughness of concretes versus curing age was shown in Fracture energy represents the consumed energy by unit crack area in the process of expansion. The variation of fracture energy of the four types of concretes with curing age was shown in The interface transition zone is the weakest and most sensitive area inside the concrete, and the breakdown of concrete often starts here . In the From the experimental results of mechanical characteristics, F10S20 concrete revealed the best performance among the three types of concrete with mineral admixtures. One of the reasons for this was that F10S20 concrete had higher content of slag and lower content of fly ash. Slag with high contents of calcium oxide can participate in the hydration process of cement at the early age and improve the hydration products in concrete . The actFrom the SEM images of OC and F10S20 concrete, the influence of mineral admixture on the internal microstructure of concrete can be clearly observed, as shown in To investigate the influence of low humidity and large temperature variation on the concretes, three air-void parameters of OC and F10S20 concrete versus curing age were detected, including porosity, average air-void size, and spacing factor, as shown in The air-void size distribution of OC and F10S20 concrete at different ages was drawn in 4), calcium hydroxide (Ca(OH)2), silica (SiO2), calcium carbonate (CaCO3), and calcium silicate (CnS) in concrete, and SiO2 had the highest diffraction peak. This was because the test sample contained a certain amount of sand, which was mainly composed of silica. Ca(OH)2, as the hydration product, can reflect the hydration degree in concrete. From 2 in the four types of concrete was as follows: OC > F10S20 > F15S20 > F15S15. OC concrete had the highest cement content in the four kinds of concrete, resulting in the highest amount of Ca(OH)2 at the curing age of 28 d. Slag contained more CaO, which can generate Ca(OH)2 with water. Therefore, F10S20 and F15S20 concrete, which had higher slag content, had higher Ca(OH)2 content than F15S15. Moreover, the diffraction peaks of CaSO4 (2θ = 11.67°) in the concrete with mineral admixtures was higher than that in OC concrete, indicating that more CaSO4 was produced in concrete because of the addition of fly ash and slag. The produced CaSO4 and AFt can both fill in the pores and improve the compaction of concrete.X-ray diffraction can be used to analyze the phase composition in concrete, through which the hydration characteristics of concrete can be studied. This paper investigated the early-age mechanical characteristics and microstructures of concrete with mineral admixtures under the environment of low humidity and large temperature variation. Four types of concrete, including ordinary concrete and three kinds of mineral admixtures concrete, were prepared and cured in an environmental chamber, which was used to simulate the real curing condition during construction in Northwest China. The compression strength, fracture properties, SEM images, air-void characteristics, and X-ray diffraction features of concrete were researched. The following conclusions can be drawn.Under the simulative curing environment during construction, the compression strength of ordinary concrete was higher before the first 3 d but was surpassed by the concrete with mineral admixtures after exposure to the curing environment of low humidity and large temperature variation. The fracture properties of concrete increased in the first 14 d and decreased in the last 14 d during the curing period, and the fracture toughness of the mineral admixture concrete was higher than the ordinary concrete. Among the three kinds of concrete containing mineral admixtures, F10S20 concrete showed the best performance, whose compression strength, initial fracture toughness, unstable fracture toughness, and fracture energy were 23.9%, 25.2%, 45.3%, and 22.6% higher than OC concrete, respectively, at the curing age of 28 d.The addition of fly ash and slag can weaken the negative effects of the harsh environment of low humidity and large temperature variation on concrete microstructure and cement hydration. Firstly, the mineral admixture can reduce the pores in the concrete caused by drying shrinkage and temperature variation and can reduce the size of the pores. Secondly, fly ash and slag can improve the hydration degree in concrete, even under the condition of lacking water.Even though the experimental design in this research was specific, including adopting the environmental parameters of Northwest China and few kinds of concrete with mineral admixtures being prepared, the research results can still provide valuable theoretical guidance for the application of mineral admixtures concrete in the environment of low humidity and large temperature variation.


The selectivity in the simultaneous detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA) has been an open problem in the biosensing field. Many surface modification methods were carried out for glassy carbon electrodes (GCE), including the use of graphene oxide and amino acids as a selective layer. In this work, molecular dynamics (MD) simulations were performed to investigate the role of serine oligomers on the selectivity of the AA, DA, and UA analytes. Our models consisted of a graphene oxide (GO) sheet under a solvent environment. Serine tetramers were added into the simulation box and were adsorbed on the GO surface. Then, the adsorption of each analyte on the mixed surface was monitored from MD trajectories. It was found that the adsorption of AA was preferred by serine oligomers due to the largest number of hydrogen-bond forming functional groups of AA, causing a 10-fold increase of hydrogen bonds by the tetraserine adsorption layer. UA was the least preferred due to its highest aromaticity. Finally, the role of hydrogen bonds on the electron transfer selectivity of biosensors was discussed with some previous studies. AA radicals received electrons from serine through hydrogen bonds that promoted oxidation reaction and caused the negative shifts and separation of the oxidation potential in experiments, as DA and UA were less affected by serine. Agreement of the in vitro and in silico results could lead to other in silico designs of selective layers to detect other types of analyte molecules. The discovery of graphene has opened the era of two-dimensional nanomaterials for different uses. Graphene is a two-dimensional sp2 hybridized carbon atom packed in a hexagonal lattice ,2,3. DueMany studies showed that using a cyclic voltammetry (CV) or differential pulse voltammetry (DPV) with glassy carbon electrodes (GCE) can detect AA, DA, and UA up to the micromolar limit of detection ,21,22. HIn this study, to gain more insight into the selective mechanisms of the polymerized L-serine and graphene oxide decorated on the GCE in a solvent environment, atomistic molecular dynamics (MD) simulations were performed for the model systems  consistiSix atomistic MD simulations were performed: (a) GO + AA, (b) GO + DA, (c) GO + UA, (d) GO + SE + AA, (e) GO + SE + DA, and (f) GO + SE + UA . The firFor systems decorated with serine tetramers, tetraserines lying across the GO formed a primary layer over the surface. The tetraserine layer selectively interacts with some analyte molecules and thus shields them away from the GO surface and facilitates the stacking between analyte molecules. n) as a function of distance from the surface were calculated between the analyte molecules and the GO surface for the systems of AA, DA, and UA adsorbed on GO without serine tetramers  was 8.63 for AA at the 0.48 nm distance, while the higher Cn of 9.93 was found for DA at the same distance. For UA, 9.73 molecules formed the first adsorption layer, and the remaining 2.36 UA molecules were adsorbed in the second layer. Binding constants were found at 0.62, 1.16, and 1.03 M−1 for AA, DA, and UA, respectively, suggesting that UA was the most energetically favorable analyte for the bare GO. The planar structure of UA could increase the surface area for binding and promote the van der Waals contacts. n at the first adsorption layer was decreased to 4.63, and the binding constant was substantially dropped to 0.15 M−1. Similar to AA, the decreased first RDF peak of DA on the GO surface when decorated by tetraserines was observed along with the higher probability distribution at a further distance. This also demonstrated the shielding effects of tetraserines, but the effects on DA were less significant than those on AA. The Cn at the first adsorption layer for DA on the GO surface was decreased to 7.80, and the binding constant was decreased to 0.45 M−1. For UA, however, only a slight decrease of the first RDF peak was observed, suggesting that the binding of UA on the GO surface was mostly unaffected by tetraserine. Only a small decrease of the Cn at the first adsorption layer and the binding constant were found at 9.69 and 1.01 M−1, respectively. The absorption of analytes on the GO surface was affected by the presence of tetraserine, as shown in n. Comparing the RDF profiles of AA, DA, and UA on the tetraserine surfaces in −1 for AA binding was significantly higher than the 0.18 M−1 for DA and 0.11 M−1 for UA binding. Coordination numbers and binding constants calculated from the first adsorption layers on GO were in concurrence with the analysis of minimum distances, in which AA molecules were the most affected and the UA molecules were the least affected by tetraserine decoration. UA/kAA = 1.66 M−1) were found for systems without tetraserines when considering the binding constants. On the other hand, clear differences (kUA/kAA = 6.73 M−1) in the binding constants were found for systems with tetraserines. These results suggested that tetraserine was unequally affected and was selective for the binding of AA, UA, and DA, which was due to the intrinsic properties of the analyte molecules. The high affinity of AA binding on the tetraserine surface shown in In the previous section, our MD simulations and RDF analysis illustrated the selective adsorption of AA, DA, and UA analytes on the GO surface decorated by tetraserines. The selectivity was contributed by the binding preference of AA on tetraserines and UA on the GO surface. Due to a large number of polar functional groups, a tetraserine in n and a carbonyl (C=O) oxygen atom of the neighboring amino acids  oxygens was found at 0.22 nm. Now, consider the distances between hydrogen bond donors in an AA molecule  oxygens of tetraserine as acceptors, the amine group at the tetraserine backbone and the hydroxyl group at the tetraserine sidechain acted as donor atoms for hydrogen bonding but were less dominant than the carboxyl (COO-) acceptors.Hydrogen bond analysis was then performed between the analytes and the tetraserine decorated substrates by counting the number of events that meet these criteria: (1) the distance between a donor atom and an acceptor atom was less than 0.35 nm, and (2) bending angle made by a group of donor-hydrogen-acceptor was less than 30°. It was found that the number of hydrogen bonds between the analytes and GO in 680 chlorophylls was facilitated by hydrogen bonding of the tyrosine with a deprotonated histidine residue. The phenol group of the tyrosine received electrons from the imidazole ring of the histidine and gave away the proton. After the first charge transfer, the phenol became a phenoxyl radical, for which the adiabatic ionization and the oxidation potential for the electron transfer to P680 became lower [In this work, atomistic molecular dynamics simulations were used to provide atomistic details on the selectivity of a GO electrode modified by serine oligomers for the simultaneous detections of the AA, DA, and UA molecules. Our model systems consisted of a small GO flake and several analyte molecules. Adsorption of analyte molecules of the GO flakes was monitored either in the presence or in the absence of tetraserines. It was found that the role of intrinsic molecular properties of the three analytes promoted the hydrogen bonding with the tetraserines, which became a selective layer. Molecular mechanisms of the enhanced selectivity by serine oligomers addressed by the MD simulations were in concurrence with our differential pulse voltammetry results of simultaneous detection of AA, DA, and UA. The largest negative shift found for the oxidation potential of AA corresponded to the highest number of hydrogen bonds with serine oligomers. Meanwhile, the smallest negative shift found for the oxidation potential of UA corresponded to the lowest number of hydrogen bonds with serine oligomers see . The higme lower . Analogome lower . TherefoAgreement of the in vitro and in silico results demonstrated the importance of the intrinsic properties, e.g., local polarity of functional groups, on the binding specificity and sensitivity of the electrode to the analytes. In addition, the simulation techniques had been validated for other designs of selective layers to detect other analytes, based-on the electro-polymerization of other biopolymers. However, not all molecular features of the real electrode system in vitro were depicted in the current in silico molecular model due to the limited simulation computing resource. Calibration of the model with the larger experimental dataset was also needed for more accurate prediction. 3 SPC [The 3D structure of a model graphene oxide nanosheet with dimensions of 20.94 nm × 22.56 nm in 3 SPC  solvated3 SPC , each sy3 SPC  at 300 K3 SPC . After all simulations were completed, water molecules were deleted from the trajectory files. Minimum distances were measured between the closest atom pairs from each analyte molecule and the GO surface to monitor the adsorption of each molecule on the bare GO and the tetraserine-decorated GO surface. Then, radial distribution functions (RDF) and coordination numbers (Cn) were calculated as a function of closest distance from the GO surface for the GO + AA, GO + DA, and GO + UA systems without serine tetramers. RDF and Cn of analyte molecules were calculated both from the GO surface and from serine tetramers for the GO + SE + AA, GO + SE + DA, and GO + SE + UA systems decorated by serine tetramers. To further quantify the adsorption of analyte molecules, the binding constant (k) was calculated from the cumulative average number of analytes at the first adsorption layer (N) by using Equation (1). Numbers of hydrogen bonds formed (1) between analytes and GO and (2) between tetraserine and GO were also calculated along all the trajectories. The cut-off distance between the donor atom and the acceptor atom of a hydrogen bond was set to 0.35 nm, and the bending angle cut-off was set to 30°. Finally, the RDF between hydrogen bond donor atoms of the analytes and all the oxygen atoms of the tetraserines was also calculated to display the contribution of each atom to selective binding of the analytes on the tetraserine surface.