It was shown that statistical methods of chemometrics such as projection on latent structures provided the opportunity to distinguish SERS of MG from 100 ppm RhB in a mixture, whereas separation of MEF signals are feasible even for a mixture of MG and 1 ppm RhB due to two-photon excitation.We proposed a novel method of nanostructure preparation for observation of surface-enhanced Raman spectroscopy (SERS) and metal-enhanced fluorescence (MEF) based on the deposition of gold nanoparticles (GNPs) above the thin dye film by dry aerosol printing. We detected various enhanced SERS and MEF signals of films of malachite green (MG) and rhodamine B (RhB) mixtures, depending on the surface packing density of Au NPs on the strip, and found the optimum one to achieve the 3.5 × 10 Sensitive detection of trace analytes in complex environmental compounds is a pivotal demand in various fields of life ranging from food and chemical safety  and biolIn such an approach the initial samples are irretrievably destroyed, which is prohibitive in specific applications, for example, in the course of investigations of pigments and dyes in valuable paintings for the purposes of authentication and restoration.Nowadays, innovative methods for the non-destructive characterization of works of art are proposed worldwide. For instance, a mobile laser emission spectrometer for quantitative and qualitative elemental analysis of paintings directly in the halls of museums  and port−9 M on Au nanorods coated with PNIPAM and Rhodamine B of 10−4 M on Ag and ZnO nanoparticle substrates have been detected by the SERS technique [SERS is a powerful technique for the identification of traces of molecules down to the single-molecule-level  that canechnique ,21,22. Technique .The phenomenon of plasmon enhancement of a signal is used both in the SERS method and in metal-enhanced fluorescence (MEF) applications ,25. SeveFor the identification of dyes and pigments in real applications such as forensic and heritage science, where it is important to save the exterior appearance of the objects, non-destructive, highly sensitive methods of sample preparation are preferred . The exiTraditional methods of producing nanostructures, such as vacuum deposition and photolithography, which are multistage and include high temperature treatment and the use of aggressive resists, etchants and developers, are incompatible with the assigned task.This is why dry aerosol printing , which aThus, the goal of this research is to fabricate gold nanoparticles strips (GNPS) using the original, non-traditional method of sample preparation for SERS, which is based on dry aerosol printing gold nanoparticles onto the surface of dye/painted films. Then, to investigate the ability of the obtained strips to enhance SERS and luminescence signals for detection of small amount of analyte in the mixture, mixtures of xanthene dye Rhodamine B (RhB), as a small impurity in the film of the triarylmethane dye malachite green (MG), is used as a model system. MG is an effective quencher of RhB fluorescence in liquid solutions. At the same time, MG has a low quantum yield of luminescence in fluid liquids, but it demonstrates moderate luminescence in solid films. The SERS effect of GNPS was examined for near resonance and off resonance of RhB excitation. The effect of GNPS on the luminescence of the dye mixture of RhB and MG was tested under the conditions of two-photon excitation with femtosecond pulses of 976 nm and single-photon excitation at 488 or 561 nm.2) until the films were completely dry, in air atmosphere, for SERS  and scanning electron microscopy  investigations, respectively. To achieve the homogeneity of the film thickness, the glass substrate was periodically slowly turned when the solution reached the edge of the substrate.Solutions of malachite green  and Rhodamin B  were prepared in chromatography 2-propanol  without further purification, with a concentration of 10 and 1 g/L, correspondingly. Then, mixtures of dyes with mass fractions of 1, 10, and 100 ppm of Rodamin B diluted in malachite green were fabricated by simple mixing. To get thin films of the dyes’ mixtures, one drop (2 µL of solution) was deposited on the surface of quartz or indium tin oxide (ITO) glasses . In the thermal optimizer with a temperature of 950 °C, the synthesized gold nanoparticles changed their size and acquired a spherical-like shape in the heated atmosphere [In the spark discharge generator, the nanoparticles were synthesized by the electrical erosion of gold electrodes in an argon–hydrogen flow . SERS measurements were performed using a Senterra Raman microscope  with the following parameters: (1) excitation wavelength 785 nm, which is beyond the absorption peaks of both MG and RhB, excluding the mainly complex energy interplay between pigments though the field enhancement factors of plasmonic NPs (which can still be exploited); and (2) the mode of the minimum available laser power of 1 mW with the simultaneous use of a microscopic objective with a low numerical aperture (0.25) to eliminate bleaching effects, as well as to more effectively deal with surface heterogeneity on a submicron level. Laser scanning microscope (LSM) studies were performed on the LSM-980 multicolor laser scanning microscope . The measurements were made using a sensitive GaAsP PMT detector, which allowed working with laser powers of microwatt scale, as well as making multiple lambda scans of the same sample area without any bleaching. The excitation wavelengths were chosen to be: (1) 561 nm, which is close both to LSPR position and absorption maxima of RhB; (2) 488 nm, which is close to the absorption deep of MG; and (3) 976 nm , which is far from the absorption bands of both pigments and utilizes their ability for multiphoton luminescence with the aid of a plasmonic subsystem.Projection on latent structures (PLS)  was usedThe dye films were substantially uniform over the surface of the substrates, regardless the rhodamine B concentration. The average thickness measured by optical profilometer was 220 ± 35 nm.The surface packing density of nanoparticles on the dye films was influenced by the formation conditions of the strips for all films, independent of rhodamine B concentration. The typical microstructure of strips of gold nanoparticles deposited on dye films is presented in This spectral feature of the strip of Au NPs is of interest for obtaining the Raman spectrum of light when excited by a 785 nm laser in the near-IR range since this wavelength falls into the spectrum of the electromagnetic field of the plasmon system. At the same time, the wavelength of 785 nm is rather far from the resonance bands of dyes and, at a moderate laser power, does not excite dye fluorescence undesirable for Raman spectroscopy. The wavelengths of the SERS excitation sources were 785 and 532 nm. On the one hand, the wavelength of 785 nm is distant from the plasmon absorption bands of dyes; on the other hand, it is contained within the infrared tail of the GNPS plasmon resonance band . Thus, nThe SERS effect greatly depends on near-field distribution around gold nanoparticles and formation of “hot spots” on the surface. Since GNPS on dye mixture films of RhB and MG have the form of disordered particle aggregates, SERS spectra were measured at 11 randomly selected points for each experimental strip. Raman spectra without SERS was measured on the 11 random points of RhB and MG film outside the GNPs strip. The enhancement was determined as the ratio of the averaged area under the Raman spectra curves with and without SERS .5, while decreasing GNPs strip density expectedly diminished SERS enhancement. For the first and second lines with higher GNPS density, the upper layers of gold nanoparticles can shield the down layer located in contact with the dye film, which can also lead to a signal decrease.−1. It was obtained by averaging all spectra from subplots. Error bars qualitatively suggest the distribution of hot spots in the GNPS. As expected, in a close-packed band, the relative error of the averaged spectrum is lower than in a less dense band. This observation suggests that the distribution of hot spots is wider in low-density films.The dependence of the enhanced Raman signal on the density of the nanoparticle layer per dye layer, shown in The results of the PLS calibration are presented in The prediction vs. measurement plot c shows tThe results shown in −5. Stark [Since the preparation method of the dye films ensures their uniformity, the difference in the shape of the luminescence spectra cannot be associated with the inhomogeneous distribution of rhodamine B molecules in the dye films on the substrate. The shape of the PL spectra is influenced by the distinction between the enhancement factor for malachite green and rhodamine B at different excitation wavelengths. MG is known to be an effective RhB quencher. Nevertheless, RhB luminescence is observed. In a mixture of RhB and MG, the near-field electromagnetic behavior around the plasmonic structure in various regions encourages the luminescence of the two dyes in different ways. Malachite green (MG) is an organic dye with almost no fluorescence when in solution by itself with a quantum yield of 7.9 × 105. Stark  and Schm5. Stark  have not5. Stark ,53,54,55Simultaneous observation of the Raman and fluorescence enhancement of dyes under the strip of randomly closed packed gold nanoparticles means that an intense electromagnetic field through the strip was generated. The interaction of a metal nanostructure with electromagnetic radiation is markedly determined by the free conduction electrons in a metal, which are dedicated by localized surface plasmons ,56. SurfSERS,MEF  can be expressed analytically as a function of the excitation wavelength λex, the radiation wavelength λex, and the distance d between the molecule and the surface of a metal nanoparticle. The significant SERS and MEF cross section σSERS,MEF  is achieved by the amplification of the EM field in “hot spots”, which is formalized through the enhancement factor of the EM field MEM  [An explanation of the effect of SERS and MEF under a strip of randomly and closed packed Au nanoparticles is based on the mechanism of the electromagnetic field (EM) enhancement in hot spots ,63,64. T λem, d) ,66.ex, λem).Since, in our experiments, we have randomly packed nanoparticles on the surface, the parameter d is difficult to formalize and we are restricted to the consideration of only the expression of MEM |2 = |Ehot spot (λex)/Ein (λex)|2 and |M2|2 = |Ehot spot (λem)/Ein (λem)|2 are EM enhancement factors corresponding to the interaction of the plasmon resonance with incident light λex, (|M1(λex)|2) and Raman scattering of light, or fluorescent light λem, (|M2(λem)|2), respectively.Let |MEM|MEF , the fluorescence decay rate can also increase by a factor of |Md|2 times due to the transfer of energy from the molecule to the metal surface [MEF  = σFL  × |MEM|2/|Md|2.In the case of MEF σ surface ,55,56. TSERS ~|MEM|2 σRS .Thus, according to the EM model of amplification, the SERS cross section will be expressed as σ2 and the coefficient |Md|2 depend on the wavelengths λex and λem, this circumstance can be regarded as a qualitative explanation of the dependence of the envelope curve for luminescence spectrum on the excitation wavelength.The experiment showed that both the SERS effect and the MEF are enhanced under a strip of randomly closed packed Au nanoparticles. Moreover, the SEF effect amplificated itself both in the case of single-photon excitation at wavelengths of 488 and 561 nm and with two-photon excitation at 976 nm. Since the overall enhancement factors |MEM|The novel method of nanostructure preparation was developed to get the SERS and enhanced photoluminescence signals. The proposed technique is predicated on the aerosol printing deposition of 144 nm gold nanoparticle strips above the thick dye films prepared from a solution of mixtures of 1, 10, and 100 ppm rhodamine B in malachite green. This method can have a significant advantage for the identification of dyes and pigments in real applications, such as heritage arts, due to the deposition of nanoparticles above the paint and usage of the highly sensitive PL and SERS techniques directly on the art object without sample selection. That fact leads to the detection of traces of dyes with further non-destructive removal of nanoparticles from the object of art, resulting in its conservation for the next generation in its initial conditions.5 was achieved on the strip with a surface packing density of 97%. Only 100 ppm rhodamine mixed with malachite can be proven to be distinguished in SERS spectra by statistical processing using the projection on latent structures procedure, whereas, in the luminescence spectra, it is possible to detect the enhancement effect and separate malachite and rhodamine even at a concentration of 1 ppm by the aid of multi-photon excitation.It was found that the SERS effect depends on the location of the hot spots and the surface packing density of metal nanoparticles on the dye film. The enhancement factor of 3.5 × 10


The number of copies of ribosomal genes of fungi and archaea varied within 107–109 copies of genes/g soil. The biomass of microorganisms  varied from 0.023 to 0.840 mg/g soil. The share of mycobiota in the microbial biomass ranged from 90% to 97%. The number of prokaryotes was not large and varied from 1.87 × 108 to 1.40 × 109 cells/g of soil, while the biomass of fungi was very significant and varied from 0.021 to 0.715 mg/g of soil. The length of actinomycete mycelium was small—from 0.77 to 88.18 m/g of soil, as was the length of fungal hyphae—an order of magnitude higher (up to 504.22 m/g of soil). The proportion of fungal mycelium, an active component of fungal biomass, varied from 25% to 89%. Most (from 65% to 100%) of mycobiota propagules were represented by specimens of small sizes, 2–3 microns. Thus, it is shown that, despite the extreme position on the mainland land of Fennoscandia, local soils had a significant number of microorganisms, on which the productivity of ecosystems largely depends.The soil microbiome of the Barents Sea coast of the Kola Peninsula is here characterized for the first time. The content of copies of ribosomal genes of archaea, bacteria, and fungi was determined by real-time PCR. Reserves and structure of biomass of soil microorganisms such as total biomass of fungi and prokaryotes, length and diameter of mycelium of fungi and actinomycetes, proportion of mycelium in biomass, number of spores and prokaryotic cells, proportion of small and large fungal propagules, and morphology of mycobiota spores were determined. The largest number of ribosomal gene copies was found for bacteria (from 6.47 × 10 The relevance of studying polar regions is constantly increasing due to the rapid and sensitive response of Arctic ecosystems to global climate change . ExtremeMost of the Arctic territories are located in remote areas with partial or complete lack of infrastructure, which greatly complicates their study. At the same time, it is very important to understand the potential of the Arctic ecosystems for understanding its existence and recovery under conditions of an ever-increasing anthropogenic load, as well as for identifying microorganisms with a biotechnological potential.One of these areas is the Kola Peninsula, which is the subarctic part of Fennoscandia and the Scandinavian Peninsula, as well as the extreme continental land of northwestern Russia, almost the entire territory of which is located beyond the Arctic Circle in natural zones of southern tundra, forest tundra, and northern taiga .Long-term studies of the chemical and biological properties of the region’s soils were carried out in the subaerial biotopes ,4,5, whiSoil microorganisms carry out biogeochemical cycles and quickly respond to environmental changes . For thiMost of the soil microbiological studies on the Kola Peninsula were carried out using the classical microbiology methods ; therefore, it is very important to confirm or refute the previously put forward hypotheses using modern methods of molecular genetic analysis . Modern research methods also make it possible to study new groups of microorganisms, such as archaea, which have not previously been studied by classical methods. In addition, this group is of great interest to science in view of poor knowledge of it.The research aimed to investigate the microbial communities  of the subaqueous soils of the Barents Sea coast, to compare them with the subaerial soils of the region, and to identify the potential.In the northwest of the peninsula, the climate is arctic maritime; in other parts it is more continental and moderately cold. Summer is cool, winter, thanks to the influx of heat from the Barents Sea, is very warm for its latitude. The average annual temperature is about 0 °C, the average temperature of the warmest month (July) is from 8 to 12 °C, the coldest (February) is from −8 to −11 °C. Thaws occur throughout the winter. Frosts are possible for most of the growing season; snow can fall during any month. The frost-free period is about 110–120 days. The average annual rainfall is about 375 mm. Characteristic features of the climate are frequent strong winds and very high air humidity (up to 95–100%) ,8.Relief of the Kola Peninsula is represented by denudation-tectonic and denudation flat-topped mountain ranges, hills, low ridges, plateaus, and low basement plains with moraine ridges and lakes . The higOn the coasts of the Murmansk region, within the tundra zone and forest–tundra, marching communities are found only fragmentarily since the geomorphological features of the coasts are unfavorable for the formation of halophytic vegetation. Communities of sandy and pebble beaches along the entire coast of the Murmansk region, both in the tundra and taiga zones, belong to the Honckenyo–Elymion arenariae group  Tx. 1966 . The beach communities of the Murmansk coast are typical of the subarctic coasts in the tundra and forest–tundra subzones and belong to syntaxa of predominantly subarctic, boreal, and moderate distribution, which gives the considered areas commonality with more southerly boreal territories . To avoid inaccuracies and confusion, in this article we distinguish between “object” and “sample”. Objects are selected territories. Samples are small amounts of soil taken from the objects of study. The study focused on the substrates of the coastal areas of the Barents Sea coast . The objects of study are the territories on the coast of the Pechenga Bay (near the settlement of Pechenga) and the Kola Bay  . The midAt each site (object of research), representative sampling points were selected, taking into account vegetation and type of coast. Samples were taken in five replicates. A total of 55 samples were taken and analyzed. For microbiological analysis, soil samples weighing 20–30 g were collected from a depth of 0–10 cm into aseptic plastic containers, which were stored at −18 °C for fluorescence microscopy and at −70 °C for molecular analyzes. Characteristics of the sites are shown in 1 is the area of preparation, μm2; a is the number of cells in one field of view ; n is the dilution rate of the bacterial mixture, mL; V is the volume of the drop applied to the glass, mL; S2 is the area of the field of view, μm2; and C is the weighed substrate specimen, 1 g.The total number of prokaryotes was determined using direct microscopy with a Zeiss Axioskop 2 plus  luminescent microscope . Preparations from the soil suspension were stained with acridine orange . Soil  at a magnification of 400. Soil suspension preparations (1:100 dilution) were stained with fluorescent dye calcofluor white .2; and n is the dilution rate, mL. Cell desorption from the soil was performed using a vortex MSV-3500 (Latvia) at 3500 rpm for 10 min. The (10 μL) was applied to the glass and distributed over an area of 2 cm × 2 cm, then the glass was fixed in a burner flame and stained with CW  for 15–20 min immediately before viewing under a microscope with a UV light source. Three glass preparations were prepared from each soil sample; in each, cells were counted for 90 fields of view. The calculation of the number of fungal cells per 1 g of the substrate was carried out according to the formula1 is the area of the preparation (μm2); a is the average length of mycelium fragments in the field of view (μm); n is the dilution index of the suspension (mL); v is the volume of the drop applied to the glass (ml); v is the volume of the drop applied to the glass (mL); S2 is the area of the microscope field of view (μm2); c is the sample portion (d). Fungal biomass (mg/g soil) was calculated assuming that the spore density was 0.837 g/cm3, and the mycelium density was 0.628 g/cm3 [The length of the fungal and actinomycetal mycelia in 1 g of soil was calculated as follows: 28 g/cm3 . The con28 g/cm3 .w/v in TAE) with further visual DNA and RNA detection using the Gel Doc XR + System . Total RNA was used as the template for cDNA synthesis using the MMLV RT kit . Extracted DNA, RNA, and cDNA samples were stored at −70 °C until further analyses.Total DNA was extracted and purified from 0.25 g of each spatial soil or manure replicate using the DNeasy PowerSoil Kit . Total RNA was extracted and purified from 2 g of all samples, except soils of sampling 4, using the RNeasy PowerSoil Total RNA Kit  and phenol/chloroform/isoamyl alcohol 25:24:1 saturated with 10 mM Tris  and 1 mM EDTA. The homogenization step was performed with a Precellys 24 homogenizer , program 5 . Co-extracted DNA was removed from RNA samples using RNase-free DNase . DNA and RNA quality was estimated by electrophoresis in agarose gels  using the following protocol: 3 min at 95 °C, followed by 49 cycles of 95 °C for 10 s, 50 °C for 10 s, and 72 °C for 20 s. Melting curve analysis was done to check amplicon length. Gene copy numbers were estimated using a regression equation for each assay relating the cycle threshold (Ct) value to the known number of copies in the standard solutions. All sample and standard reactions were performed in triplicate, and average values were calculated.For manure and each soil sample, 1 μL of DNA from three replications was used separately to quantify the copy numbers of archaeal, bacterial, and fungal ribosomal genes. Similarly, the copy numbers of bacterial gene transcripts were quantified in cDNA replicates. Gene and gene transcript abundances were estimated using EvaGreen Supermix . Primers Eub338/Eub518   to 2.85 × 109/g soil in the second beach of Pechenga (sample Pech3-sl) . In general, the smallest number of archaea was found on coast in the village Roslyakovo, the largest—in the village Pechenga. For most of the samples , the number of archaea was about 108 copies of gene/g soil.The number of 16S rRNA gene copies of archaea varied from 6.68 × 10ech3-sl) A. For sa9/g soil A. Values9/g soil on the second beach of the Pechenga sandy soil (sample Pech2-sd) to 3.02 × 1011/g soil in the soil under the Pechenga grass (sample Pech-sl) . For most of the samples , the number of copies of ribosomal genes of bacteria was on the order of 1010–1011 copies of genes/g soil. The difference in the number of ribosomal copies of bacterial genes in sandy soil and coastal soil was more pronounced than for the archaea group: in sand it was an order of magnitude lower than in soil. Thus, number of 16S rRNA gene copies of bacteria in sandy soil varied from 6.47 × 109 to 4.63 × 1010/g soil; and in the coastal soil, from 5.23 × 1010 to 3.02 × 1011/g of soil. The smallest number of bacteria, such as archaea, was found on the Roslyakovo coast, the largest number—in Pechenga.The number of 16S rRNA gene copies of bacteria varied from 6.47 × 10Pech-sl) B. Values7/g soil in the flooded sand of Roslyakovo (sample Ros-sl) to 4.46 × 109/g soil in the soil under the Pechenga grass (sample Pech-sl3) . For most samples , the number of fungi was on the order of 108–109 gene copies/g of soil. The number of ITS rRNA gene copies of fungi, such as bacteria, in sandy soil was an order of magnitude less than in the coastal soil and varied from 4.28 × 107 to 4.96 × 108/g soil, while in soil it varied from 1.07 × 109 to 4.46 × 109/g soil. The largest number of fungi, as well as other groups of microorganisms, was isolated in the substrates of the Pechenga coast, the smallest—in the Roslyakovo area.The number of ITS rRNA gene copies of fungi varied from 4.28 × 10ech-sl3) . Values The biomass of fungi in studied coastal substrates varied from tens to hundreds of mg/g . In sandThe proportion of mycelium, an active component of fungal biomass, in the studied samples varied greatly from 25% to 89%. The length of the mycelium of fungi varied from several to hundreds of meters per gram of soil. The minimum of mycelium (up to complete absence) was noted in sandy soil near Pechenga (Pech2-sd), as well as in soil and sand of Roslyakovo . On the Pechenga coast, all samples of the coastal soil showed a high content of fungal mycelium . There was slightly less mycelium in the sandy substrate of Roslyakovo (195.30 m/g soil) and Belokamenka (190.21 m/g soil).4 cells/g soil; however, in coastal soil of Pechenga (Pech2-sl), their number reached 105 cells/g soil. Most (from 65% to 100%) of mycobiota propagules were represented by specimens of small sizes, 2–3 microns. The smallest proportion of small propagules (65.3–87.8%) was found in the same samples where large spores and yeasts with a characteristic size of 5 μm were found—in sandy soil of Belokamenka (Bel-sd), in soil of Pechenga , and in the flooded sand of Roslyakovo (Ros2-sd). An abundance of large propagules (in the samples where they were registered) was about 103 cells/g of soil. About 68% of the propagules were round in shape, with a smooth surface: 15%—round and rough; 12%—oval with a smooth surface; 5%—oval with irregularities.The proportion of thin (less than 3 μm in diameter) mycelium of fungi in the studied soils was relatively high (up to 42%). In most samples, the number of unicellular fungal propagules (spores and yeasts) was 10In general, the coastal areas of Kola and Belokamenka turned out to be the poorest locations  in terms of mycobiota biomass. Roslyakovo was much richer in this respect—0.120 mg/g of soil. Most of the fungi were found in Pechenga—0.342 mg/g of soil.The biomass of prokaryotes in the sandy soil varied from 0.63 to 2.84 µg/g of the substrate and in the soil—from 2.13 to 5.69 µg/g of soil . The low8 cells/g soil) were found in the sand on the Pechenga coast (Pech-sd). The maximum of prokaryotes (1.40 × 109 cells/g soil) was found in the soil on the coast of Pechenga (Pech-sl). Half of the samples were characterized by the number of prokaryotes 108, and half by 109 cells/g soil. Most (up to 61%) of prokaryotic cells were small nanoforms. As well as for mycobiota, Kola and Belokamenka were themselves poor locations  in terms of prokaryotic biomass. Roslyakovo was much richer in this respect—2.09 μg/g of soil. Most prokaryotes were found in Pechenga—2.40 mg/g soil.The number of prokaryotes in the studied soils ranged from hundreds of millions to a billion cells per gram of soil . The smaDue to active anthropogenic activity on land and sea in the Kola Peninsula region, local ecosystems are severely disturbed. Communities of microorganisms quickly respond to external influences; therefore, their qualitative and quantitative indicators can be indicators of the state of ecosystems. For this reason, the aim of the study was to compare the state of indicators of the subaqueous (marine) and soil  microbiome of the Barents Sea coast of the Kola Peninsula. Previously, the microbe of substrates on the Barents Sea coast of the Kola Peninsula was not investigated by real-time PCR and luminescence microscopy. The originality of the work lies in the simultaneous use of methods of classical and molecular microbiology to test one hypothesis. This study determined the content of copies of ribosomal genes of archaea, bacteria, and fungi, as well as the reserves and structure of the biomass of soil microorganisms .7 to 109 /g soil. This is a fairly high value, given the northern geographic location of the research objects. The number of copies of the 16S rRNA ribosomal genes of bacteria on average was 2 orders of magnitude higher than for archaea and fungi. We assume that the low amount of organic matter in local soils stimulates the growth of bacteria, since this group of microorganisms is capable of carrying out many stages of biogeochemical cycles of nutrients. The biomass of fungi varied from tens to hundreds of mg/g of soil, and the biomass of prokaryotes, from tenths to units of μg/g of soil. Such a significant difference is probably associated with the cell size of these groups of microorganisms. Fungal cells are much larger than those of archaea and bacteria, while their physical density is approximately the same. This is why the mass of fungi was greater than the mass of prokaryotes. The length of the mycelium of fungi varied from units to hundreds of meters per gram of soil, and the length of the mycelium of actinomycetes—from tenths to tens of meters per gram of soil. This pattern is easily explained by the fact that usually the body of fungi consists almost entirely of mycelium, while the organism of many bacteria is unicellular. Thus, bacteria prevailed in abundance in the studied substrates of the Kola Peninsula, and fungi prevailed in weight.It was shown that the number of copies of the ribosomal 16S rRNA genes of archaea and ITS rRNA of fungi in the analyzed samples varied from 10The number of copies of the 16S rRNA ribosomal genes of archaea in coastal soils is, on average, 2–3 orders of magnitude lower than in forest and urban soils of the northern taiga zone of the Kola Peninsula and is comparable with that in the forest–tundra zone . We beliThe number of 16S rRNA gene copies of bacteria in the studied coastal soils is lower than in the urban and forest soil of northern taiga and forest–tundra zones of Kola Peninsula . ProbablThe number of copies of the ribosomal genes ITS rRNA of fungi in the studied samples is, on average, an order of magnitude lower than in the urban soils of the northern taiga zone of the Kola Peninsula, but is comparable with the soils of the forest–tundra zone . Conside10–1011 copies of genes/g of soil, while in 82% of samples the number of fungi was about 108–109 copies of genes/g of soil, while in 63.4% of samples, the number of archaea was about 108 copies of genes/g soil. The largest number of ribosomal copies of genes of all groups of microorganisms was noted on the coast of the settlement Pechenga, the smallest—in Roslyakovo. Apparently, this result was obtained because the Pechenga Bay and the soils of its environs have the least anthropogenic load, limiting the growth of microorganisms.Thus, bacteria dominated in the microbial complex of soils and grounds on the Barents Sea coast of the Kola Peninsula. For most samples (82%), their number was about 10For some objects, real-time PCR and luminescence microscopy methods obtained opposite data, such as biomass was either low or the number of copies of ribosomal genes was too high, or vice versa. This can be explained by an irregular distribution of genetic material over cells of microorganisms ,27. ThusFungal biomass. In the studied substrates of the Barents Sea coast, biomass of mycobiota was less than in background landscapes of the Kola Peninsula ,7, but iDespite the fact that soil is the natural habitat of most of the fungi, it often creates unfavorable conditions for the development of mycobiota propagules . TherefoKola and Belokamenka sites were themselves poor, while Roslyakovo and Pechenga sites were the richest locations in fungi. We believe that this may be due to the high degree of pollution of the soils of these locations with oil products, which some fungi can use as a nutrient substrate .9 cells/g of soil) in the analyzed soils is comparable in an order of magnitude with that for soddy-podzolic soils of central Russia [Biomass of prokaryotes. The abundance and biomass of prokaryotes in the studied soils of the Barents Sea coast of the Kola Peninsula was low, as in other Arctic territories—Taimyr , Novaya l Russia ,41,42. Tl Russia ,44. The l Russia ,46. Therl Russia . Presumal Russia . UsuallyThe number of prokaryotes, as well as fungi, was minimal in the sites of Kola and Belokamenka, but it was maximal in the sites of Roslyakovo and Pechenga. This may be due to the high content of oil products in the soils. Depending on the physical and chemical properties, oil products can both inhibit the growth of microorganisms and serve as a nutrient substrate for them.In general, the abundance of petroleum products did not significantly affect the number of all groups of microorganisms studied. We believe that this is primarily due to the non-critical concentration of hydrocarbons for the vital activity of most soil archaea, bacteria, and fungi. The main factor influencing the growth and development of microorganisms was the content of organic carbon in the soil, which was consistent with the work of many microbiologists ,49,50.For the first time, using a complex of classical and molecular genetic microbiological methods, the soil microbiome of the Barents Sea coast of the Kola Peninsula was characterized. It was shown that, despite the extreme position on the mainland land of Fennoscandia, local soils have a significant number of microorganisms, on which the productivity of ecosystems largely depends. For the analyzed sandy soils, the number of copies of ribosomal genes was maximal, but the biomass of microorganisms was minimal, while the coastal soils were characterized by an inverse relationship. The largest number of copies of ribosomal genes in the substrates of the coastal area was found for bacteria. The number of the ribosomal gene copies of fungi and archaea was 2 orders of magnitude less than that of bacteria. Mycobiota prevailed in the microbial biomass and ranged from 90% to 97%. The proportion of fungal mycelium varied from 25% to 89%. Most of the propagules of mycobiota were represented by specimens of small sizes, 2–3 microns. Thus, even in the oligotrophic conditions of the Subarctic zone, microorganisms are able to actively develop, colonizing substrates that are not very suitable for other forms of life. We believe that such microbiological indicators as the number of ribosomal genes, the number of cells, the length of the mycelium, and the biomass reserves can be effectively used to detect anthropogenic disturbances in polar ecosystems.


A significant part of reinforced concrete structures is subjected to intensive environmental impact during operation. This can cause local destruction and failure of buildings if obligatory measures are not taken to protect them from corrosion. This is especially true for industrial buildings, where the environment could be contaminated with aggressive products or waste. An important issue is the development of methods for calculating the load-bearing capacity and serviceability of reinforced concrete structures with corrosion damage. The main reason for this is the necessity to determine the durability and reliability of buildings and structures and the estimation of their safe operation time. As corrosion damages of concrete are a critical issue, more detailed experimental studies are needed. This paper presents experimental studies of concrete prisms under the simultaneous action of an aggressive environment and a constant level of compressive force. In total, 32 prisms under different loading conditions and in different aggressive medium were tested. Samples were divided in series, for which different load levels were chosen ( Intensive environmental impact is an important problem for concrete and reinforced concrete structures which are currently operated. This effect could be the reason for local destruction and failure of buildings ,2,3,4,5.Physical and chemical processes during corrosion are considered in a number of recent studies ,16,17,18One of the parameters of the concrete corrosion resistance is its water resistance, which can be increased, both by design measures and with special additives in the concrete . It is eAs the alternative to cementitious binder concretes, new types of acid-resistant concretes have been developed and studied. As the result of the research in , the posMany studies concern the effect of corrosion on modified concrete ,23,24,25Additives, which modify the concrete structure and properties, are of considerable interest as the means to increase its corrosion resistance. The authors of ,27,28,29An important issue is the development of methods for calculating the load-bearing capacity and serviceability of reinforced concrete structures with corrosion damages. The main reason is the necessity of determination of the durability and reliability of buildings and structures, as well as the assessment of their safe operation time. Most researchers ,44,45,46As Webster  states, Thus, in recent times, studies dedicated to qualitive and quantitative assessment of corrosion processes in concrete with the use of accelerated corrosion tests are widespread ,37. GeneElectrical measurement methods of chemical processes in concrete were also conducted by Kusak et al. ,39,40, CNamely, in ,42, fundIt could be summarized that quantitative evaluation of concrete corrosion in recent research studies is circumscribed by analysis of experimental data, based on mass or cross-section loss during the corrosion process. However, there are the number of issues of the reinforced concrete structures with corrosion damage of concrete, which are not sufficiently studied yet. Therefore, further investigation of this urgent issue and more detailed experimental studies of the effect of corrosion on concrete damage are required.3) and air-absorbing additive “Chrysoair”  were used. The dosage of the super-plasticizer was 1.2 kg for 100 kg of cement and 0.035 kg of the air-absorbing additive for 100 kg of cement.Experimental research included testing of prism samples, made of concrete with the following characteristics: Prisms were made of concrete with components ratio C:S:Gr = 1:1.01:2.28 and water-cement ratio W/C = 0.32. Additionally, the super-plasticizer “Chrysofluid” . Detailed characteristics of the concretes used during the experiment are provided in c = 2.04 and coefficient of non-uniformity Cv = 2.0. The granulometric curve for fine aggregates is presented in Fine and coarse aggregates were tested with the use of the sieve analysis procedure. As the fine aggregate, quartz sand from Slavutych quarry of the Khmelnytsky region  was used, without impurities and with a size modulus of Mmax and minimum dmin diameter of gravel grains were 20 and 3 mm, respectively. Fractional composition of coarse aggregates mostly contained 5..10 and 10..20 mm grains. The granulometric curve for coarse aggregates is presented in As the coarse aggregate, granite crushed stone from the Selishche quarry of the Rivne region  was used. Maximum DThe experimental study of concrete was performed by testing prism samples of 100 mm × 100 mm × 400 mm size according to regulations of DSTU B B.2.7–214: 2009, EN 206:2013.Samples were subjected to the action of an acid-liquid environment and axial compression in order to study the change of physical and mechanical properties of concrete under loading over time, taking into account corrosion damages of concrete.In order to study the effect of stress on the development of corrosion processes in concrete over time, 4 series of prisms were loaded with different values of initial stresses, equal to (a)Only the central compressive force without aggressive medium,(b)Simultaneous influence of compressive force and aquatic medium,(c)Simultaneous influence of compressive force and aggressive environment.Series 1–4 of prisms belonged to the main part of the research see . For eacThe following symbols were used for the marking of prisms: P—prism, and L—tested for long-term loading see . The marSeries 5 contained 4 prisms, tested in the air, subjected to long-term loading.Series 6 contained 6 prisms, tested in the air, subjected to short-term loading.Series 7 contained 6 prisms, tested on shrinkage.Series 8 contained 4 prisms, tested in aquatic medium, subjected to long-term loading.In order to take into account the whole range of various factors, which have an influence on the destruction process, series 5–8 of control samples were tested:In total, 32 prisms were tested under different conditions .Concrete prisms were tested according to the developed technique on the special stand. The constant value of compressive force was provided with the use of powerful springs.During the first 24 h after concreting, the samples were covered with plastic wrap to prevent heat loss during cement hydration. After that, the strength setting was continued at the external temperature of 20 °C and constant humidification. Concrete samples were released from the formwork on the 3rd–4th day after concreting.In order to determine the initial physical and mechanical characteristics of the studied material, control samples were investigated see . Thus, 3Micro-indicators for the determination of shrinkage deformations were fixed on 6 prisms, that were not subjected to loading (series 7).In order to assess the water resistivity of concrete, 4 samples were tested in aquatic medium under long-term loading (series 8).Simultaneously with the loading of concrete prisms, concrete cubes of 100 mm × 100 mm × 100 mm size were immersed in the aggressive environment of the same concentration in special containers of 120 mm× 120 mm× 120 mm size, in cubic form. The purpose of this experiment was observation of the corrosion depth and strength characteristics of cube samples.2SO4 with 10% concentration was used. Such concentration of the acid medium enabled the accelerated modeling of the aggressive environment impact and the assessment of the structure behavior in particular conditions. By type, these are corrosion processes that develop in concrete under the action of water containing chemicals that react with the components of cement stone and belong to highly aggressive medium. A similar environment takes place in some chemical plants, galvanic shops, chimneys of thermal power stations and reinforced concrete structures of scrubbers in emergency situations. In addition, the creation of such aggressive environment allows to simulate the effect of an aggressive environment and the simultaneous action of the load in a relatively short period of time.As the aggressive medium, the solution of sulfuric acid HPrism samples were loaded on a specially made power stand  to a givNext, special containers with aggressive medium were fixed on experimental samples of concrete prisms, and the joints were carefully sealed. Before the beginning of the experiments, the geometric dimensions, the base for concrete deformation measurement and the mass of the samples were carefully recorded using a caliper and electronic scales. During the research, these values were constantly monitored. Additionally, during the experiment, the temperature, ambient humidity and acid concentration were constantly monitored. When the acid concentration changed by more than 1%, the acid solution was replaced. It should be noted that the age of the concrete prisms from the moment of concreting until the beginning of the testing was 520 days. During this time, the main part of shrinkage deformations occurred, and the shrinkage processes of concrete were almost stabilized, which could be confirmed by the readings of devices on prisms studied for shrinkage (series 7).Measurements of longitudinal deformations of concrete were performed daily, while cross-sectional dimensions and the weight of samples were controlled every 10 days. Besides the measurement of deformations after the destruction of prisms, X-ray phase analysis of cement stone and study of the concrete microstructure were also performed in order to detect corrosion products and changes in the concrete structure. X-ray phase analysis was performed on an X-ray machine, DRON-2. For X-ray phase analysis, samples were taken from each sample from the surface and from the depth of concrete prisms. The concrete microstructure  was studied with the use of the raster electron microscope TESLA BC—300 .Samples were taken in the form of specimens with dimensions of 10 mm × 10 mm × 15 mm so that they included the outer and inner layers of the studied material. Therefore, it was possible to trace the changes in the microstructure of concrete in different areas. In order to obtain the clear idea of the concrete microstructure, the images of the samples were magnified 1000 times and fixed on photographic film. In order to analyze the microstructure of concrete, three photographs were taken: the first at the surface, the second at the distance of 4–6 mm and the third at the distance of 10–15 mm from the surface.According to the accepted research method of the concrete deformability under long-time impact of aggressive medium and compressive forces, four series of concrete prisms were tested. For series 1, the load level was equal to 0.25During the experiment, according to the accepted technique, the sizes of the cross-section and changes of deformations of concrete were measured. Destruction processes in concrete, which were observed during the test, were caused by concrete corrosion. For better understanding of deterioration processes, which are the issue of this study, it is necessary to provide a detailed explanation on the main mechanisms of concrete destruction. In general, concrete corrosion could be identified with chemical reactions of acid with components of cement stone, containing calcium.The chemical reaction could be described by Equation (1):4·2H2O in Equation (1) is gypsum. As gypsum is the salt of sulfuric acid, it simultaneously proceeds to the sulfate corrosion (see Equation (2)):CaSO2O3·CaSO4·32H2O). Under conditions of repeated wetting and drying, ettringite crystals tend to absorb additional moisture, which causes their expansion. Expanded crystals become the reason for localized crystallization pressure and internal stresses. After that, due to macroscopic expansion of the hardened material, the destruction of concrete proceeds.As the result of this reaction (2), the crystals of ettringite or “cement bacillus” are formed  and (2) describe the formation of ettringite crystals. It is important to note that the corrosion process envies different chemical processes between the components, so that the destruction of the structural element is the result of a combination of different chemical processes. 2SO4 could react with calcium components, Ca(OH)2, which results in a chemical reaction of neutralization. Therefore, C-S-H phases are destructed, and the concrete material is deteriorated, which causes the loss of mass and decrease of dimensions.Simultaneously with ettringite formation, the acid aggressive medium HAnother crucial destruction mechanism is the carbonation, which progresses in the following way: The carbon dioxide enters the concrete pores from the atmosphere and causes the carbonation reaction with interstitial water. After that, calcium hydroxide “hydrated lime” is converted. As the calcium hydroxide provides high values of pH of concrete, its destruction lowers the pH of concrete stone to the values up to 8–9 and also degrades the passivation of the reinforcement .Important issues in concrete corrosion are reactions of alkalis in concrete with aggregates. These processes are generally called alkali reactions and cause tension stresses due to components’ expansion, after which swelling and cracks appear .Among chemical causes of concrete destruction are also internal and external sulphate reactions . The proThrough the experimental research, diligent observations and a detailed analysis of the specifics of the deterioration process were made. During the whole test period, white precipitate was constantly released on the samples, which were immersed in the sulfuric acid.This substance is the product of concrete corrosion, which was formed due to chemical reactions (see Equations (1) and (2)). The white sediment was gypsum, which, as a result of reaction (2), formed the crystals of ettringite or “cement bacillus”. At the same time, the cross-sectional dimensions of the concrete samples constantly decreased see a.In the described experiments, the cross-sectional dimensions were recorded by direct measurement with the caliper with an accuracy of 0.05 mm.Experimental studies have shown that the sizes of the cross-section (width b and height h) decreased during the test, almost linearly see a. At theParameters of the aggressive medium could have a significant impact on the corrosion process, as they may act as initiators or inhibitors of the corrosion rate. On the other hand, changes in the moisture content or its temperature can be considered as indicators of the intensity of chemical reactions. Therefore, during the experiment, the temperature and environmental humidity were constantly monitored b,c. RecoThe average air humidity was 85.1% and was almost equal to its initial level see c. DuringThus, it could be assumed that temperature and humidity did not have a critical influence on the studied deterioration process.ult, applied by the power stand on the residual cross-sectional area, S . Further analysis will be more representative in coordinates of stress values, which corresponded to each loading level. Values of stresses were determined by dividing the load, Na, S see .The constant decreasing of the cross-section of prisms led to an increase of the stress level, c − tε). Additionally, graphs showing changes of stress level over time (t) and graphs of coordinates (cσ − cε) were composed. The graphs show the average values of corresponding parameters for prism-twins ):ult/S are provided in In order to represent changes in concrete strength due to corrosion, experimental and theoretical values of the ratio Nbc. For the concrete prisms tested in the air and water, no destruction occurred, and the stress level in concrete remained constant. A slight increase in deformations of concrete due to shrinkage or swelling and creep was observed. In concrete prisms immersed in water, the deformations of concrete creep were balanced by swelling deformations, and therefore total deformations remained unchanged.Analysis of the results of experimental studies shows that the destruction of concrete prisms in sulfuric acid was due to the corrosion of concrete. Corrosion processes caused the linear decrease in the cross-sectional size of prisms over time. The cross-sectional area of the experimental samples decreased according to quadratic dependency. The decrease in the cross-sectional area caused an increase in stresses in the concrete and in flexibility, which led to the destruction of concrete prisms. The destruction took place at a stress level lower than the initial strength of concrete. The reason is the decrease in the strength of concrete with corrosion damages during long-term loading, which could be taken into account by the coefficient of working conditions of concrete in an aggressive environment, γThe analysis also shows that the methodology of valid norms in all cases does not allow to determine with sufficient accuracy the strength of compressed concrete elements with corrosion damages. The difference between theoretical and experimental values was about 12.3% to 19.5% see . In geneAfter the destruction of concrete prisms subjected to the impact of sulfuric acid, the cut of the prisms in the zone adjacent to the place of concrete destruction was performed with a diamond saw . As a reThese results could also be confirmed by X-ray phase analysis . StudiesAnalysis of the results of experimental studies shows that the destruction of concrete prisms in sulfuric acid was due to concrete corrosion. As a result of concrete corrosion, a contact layer with lower physical and mechanical characteristics was formed. The thickness of the contact layer for samples of series 2 was 1.5 times smaller than for series 1. This could be explained by the use of chemical additives in samples of series 2 and more careful selection of concrete components. In the contact layer of the prism concrete, the presence of the corrosion product ettringite was detected, which causes the formation of microcracks. These microcracks become stress concentrators in concrete. This explains the decrease in the concrete strength during long-term loading, which could be taken into account by the coefficient of working conditions of concrete in an aggressive environment.c-εσ” diagrams were obtained and specifics of stress and deformation changes over time were identified. These results bring us to the conclusion that reasons for the destruction of concrete prisms are the presence of corrosion damages in the concrete and the cross-section reduction. For different series of samples, different exposure times in an aggressive environment were required for destruction: for series 1–106 days, for series 2–79 days, for series 3–56 days and for series 4–89 days. Decreases of cross-sectional sizes were also controlled and recorded. Namely, the relative reduction of the area for samples of series 1 was on average 63–65%, whereas for series 2, 3 and 4 this number reached 46–50%, 34–37% and 4–51%, respectively. Therefore, the load level has a significant influence on the residual load-bearing capacity of samples, subjected to corrosion. In addition, ultimate loads were calculated with the use of the theoretical approach and compared with experimental results. As the theoretical values were on average 15–17% higher than the obtained experimental values, it could be assumed that the stresses in the concrete at the moment of destruction were less than the value of the concrete prism strength. Therefore, exhaustion of the load-bearing capacity of concrete samples is associated not only with the cross-section decrease, but also with the reduction of material strength characteristics.Experimental research conducted in this work detailed the study of stress–strain of concrete samples, subjected to simultaneous action of aggressive impact and constant loading. As a result, changes of cross-section dimensions of samples were recorded, “The ultimate deformations of concrete with corrosion damages, which correspond to the prismatic strength of concrete in comparison with concrete without corrosion damage, were lower by 18% for material with In order to obtain reliable information about the corrosion mechanisms, which cause a reduction of the physico-mechanical characteristics of the concrete, X-ray phase analysis with the use of an electron microscope was performed. It was identified that along the section contour, a partially degraded layer of concrete was formed with a thickness of 1.5–3.7 mm, with corrosive microcracks and corrosion products. Comparison of the microstructure of intact and corrosion-damaged concrete layers enabled to indicate gypsum and ettringite crystals, which are corrosion products and are the reason for additional initial stresses in concrete.It could be concluded that according to the results of the experimental research, deterioration of concrete in aggressive environments is associated with two significant aspects: the decrease of cross-sectional dimensions and changes of physico-mechanical characteristics of the material. It was identified that theoretical algorithms for the calculation of the load-bearing capacity of damaged concrete elements overestimate strength characteristics and do not fully represent the corrosion mechanisms. It was also shown that the intensity of exhaustion of samples’ strength to a large extent depends on the level of load applied and environmental conditions.Findings of this study are important and need to be taken into consideration when the sustainability of corroded concrete structures is evaluated.


To observe the dynamic changes in oxidative stress and the expression levels of antioxidant and oxidative parameters in the blood and synovial fluid in the osteochondral defects of the rabbit knee joints and to explore the significance. n = 10), a model control group (n = 10), and an osteochondral defect group (n = 10). The osteochondral defect model of rabbit knee joint was constructed by medial parapatellar arthrotomy. The expression levels of glutathione (GSH), malondialdehyde (MDA), superoxide dismutase (SOD), and 8-hydroxydeoxyguanosine (8-OHdG) in peripheral venous blood and knee synovial fluid of the three groups were measured at the end of the 4th, 8th, and 12th weeks after treatment.  Thirty New Zealand white rabbits were randomly selected and divided into a blank control group (P < 0.05); higher expression levels of MDA and 8-OHdG in the blood and synovial fluid of the osteochondral defect group compared with those of the other two groups were obtained (P < 0.05). At the end of the 4th, 8th, and 12th weeks, the expression levels of MDA and 8-OHdG in the blood and synovial fluid of the osteochondral defect group presented an upward trend (P < 0.05).  The expression levels of GSH and SOD in the blood and synovial fluid in the osteochondral defect group at the end of the 8th and 12th weeks were observably lower than those of the other two groups ( The osteochondral defects initiate the oxidative stress in the body, which is presented as the decrease of GSH and SOD expression, and the upregulation of MDA and 8-OHdG expression. Osteoarthritis (OA) is the most common joint degenerative disease in the world, to which the middle-aged and elderly population are more susceptible . More thn = 10), a model control group (n = 10), and an osteochondral defect group (n = 10). Laboratory animal disposal complied with animal ethics requirements.Thirty New Zealand rabbits, specific pathogen-free (SPF), 6 months old, 15 males and 15 females, weighing 3.0-3.5 kg, were purchased from Chongqing Weston Biomedical Technology Co., Ltd. During the experiment, standard laboratory diet and drinking water were given. After 1 week of adaptive feeding, the animals were randomly divided into a blank control group  software was used to analyze the data obtained from the study. The measurement data conforming to the normal distribution were represented as (P > 0.05). See Tables No significant difference in the levels of GSH, MDA, SOD, and 8-OhdG in the synovial fluid and blood of the three groups before operation was found (P > 0.05), as shown in Tables Compared with the blank control group, the model control group and the osteochondral defect group yielded a downward trend of the GSH and SOD in the blood and synovial fluid and an upward trend of the MDA and 8-OHdG at the end of the fourth week; however, the differences were not considered statistically significant (P < 0.05). See Tables In contrast to the blank control group, apparently lower levels of GSH, MDA, SOD, and 8-OHdG in the synovial fluid and blood of the other two groups at the 8th week were observed P < 0.0. See TabP < 0.05).Tables P > 0.05). Compared with before surgery, the expression levels of MDA and 8-OHdG in the synovial fluid and blood saw a surge at the end of the 8th and 12th weeks (P < 0.05). See Figures In the osteochondral defect group, GSH and SOD in the blood and synovial fluid before surgery and at the end of the fourth, eighth, and twelfth weeks rose gradually, yet no statistical differences were detected (With the aging of population, the incidence of OA has been presenting a rising trend, with osteochondral degradation being the most quintessential pathological change. Oxidative stress is involved in the pathogenesis of hypertension, atherosclerosis, diabetes, osteoporosis, and cancer. It is also known to cause and accelerate the aging process. Although exercise of the knee joint has numerous benefits for human health, it is also often claimed to induce oxidative stress since exercise increases ROS generation. Several studies have demonstrated that exercise increases the plasma 8-OHdG level. As mentioned above, oxidative stress plays a crucial role in the development of osteochondral degradation , 7, the This study explored the dynamic changes of oxidative stress during the repair of osteochondral defects in the classic animal model of knee osteochondral defects in New Zealand white rabbits. We found that at the end of the fourth week, there was no significant difference in the expression levels of GSH, MDA, SOD, and 8-OHdG among the three groups, which suggested a similar condition without significant difference in terms of degree of oxidative stress among the three groups. However, at the end of the 8th and 12th weeks, compared with the other two groups, the expression levels of MDA and 8-OHdG in the osteochondral defect group witnessed an elevation, while the expression levels of GSH and SOD plummeted, which indicated that osteochondral defects gave rise to an upregulation of oxidative stress in the body. Ostalowska et al.  found anIn summary, the repair process of osteochondral defects slowly initiates the body's oxidative stress, which upregulates the expression levels of oxidation markers but inhibits the expression levels of antioxidant markers in the body. It implies that the intervention of the degree of oxidative stress in the repair of osteochondral defects may be of great significance to the diagnosis, treatment, and prognosis of OA. Recent studies have shown that the activation of adenylate-activated protein kinase impedes the viability of osteoblasts under oxidative stress conditions, which in turn hinders the balance of bone metabolism . Therefo


The compatibility between crop straw and Portland cement greatly restrict the application of crop straw in cement-based materials. In this study, rice straw fibers with different pretreatments were added to ordinary Portland cement (OPC), and the influence of different rice straw fiber (RF) content on the hydration process of OPC was measured using calorimeter tests. Additionally, compatibility between RF and OPC was evaluated using the inhibitory index. As a result, steam explosion treatment of rice straw removed most hemicellulose and post-treatment bleaching was used for delignification. As compared with the pure OPC, addition of RF inhibited the hydration of OPC, and the inhibition degree reduced with the increase in pretreatment degree of RF. The inhibitory index grade of different RF filled OPC (RF-OPC) samples is directly related to hemicellulose and lignin content. Compared with lignin, hemicellulose has a greater influence on cement hydration. Without considering the influence of other components, the RF-OPC samples with hemicellulose content of 1.54 wt.% reached the inhibitory index extreme grade, and the hemicellulose content of 2.05 wt.% led to the cessation of cement hydration. The inhibitory index of the samples with 2.05 and 0.85 wt.% lignin content is moderate and low grade, respectively. In addition, the results of XRD patterns and SEM images are consistent with those of heat of hydration. In terms of mechanical properties of cement-based composites with 10 wt.% rice straw fibers, pretreatment of fibers is beneficial to improving the fracture toughness of the samples. The application of plant fibers in cement-based materials has attracted great interest of researchers in recent years because of the low cost, high specific modulus and low density compared with synthetic fiber. Page et al.  investigAccording to statistics, agricultural residues around the world reached 100 billion tons, and plants accounted for more than 80 percent of the residues . China iIn view of the above analysis, cement-based composite reinforced with plant fibers provides an effective approach for the utilization of crop straw and sustainable development strategy of building materials, which is of great significance to the increasingly serious energy shortage and environmental pollution problems. However, the compatibility between the plant fibers and Portland cement greatly restrict the application of plant fibers in cement-based materials. On the one hand, the main components of plant fibers affect the hydration of cement and delay the main hydration reactions of cement . On the 2 and the pretreatment with NaOH significantly changed the compatibility between cement and the coir fiber.Castro et al.  evaluateX-ray diffraction (XRD) of the composite samples filled with different types and various quantities of rice straw fibers were measured over 7 days. In addition, the inhibitory index was used to express the compatibility degree between rice straw fibers with different pretreatments and OPC. The objectives were to assess compatibility between rice straw fibers and ordinary Portland cement as well as provide an academic basis for the application of crop straw in cement materials in the future.In this study, we studied the compatibility between rice straw with different pretreatments and ordinary Portland cement (OPC) to provide a theoretical basis for the engineering application of crop straw in cement-based materials. For the above purpose, untreated and pretreated rice straw fibers with different contents were added to OPC. The heat of hydration and In this study, rice straw fibers (RFs) were obtained from farms in the Province of Sichuan, China. To observe the influence of the main components of RF involved in the hydration heat of OPC, pristine rice straw fibers (RF1) were pretreated in the laboratory. Firstly, RF1 treated by steam explosion (RF2) were obtained after the steam explosion pretreatment at 2.5MPa with a solid to liquid ratio of 3:1 for 25 min. Then, to remove the lignin of RF2, RF2 were immersed into hydrogen peroxide aqueous solution together with ozone blowing, and the rice straw fibers treated by bleaching once (RF3) were obtained. The same bleaching process produced the rice straw fibers treated with twice bleaching (RF4). The specific pretreatment process and condition of rice straw was described in Reference [X-ray fluorescence (XRF) as shown in A Chinese standard Graded P·O 42.5 type Portland cement (OPC) was used in this study, the chemical components of OPC were determined by −1, with a resolution of 0.5 cm−1. Bamboo cellulose fibers were mixed with KBr and ground, subsequently being pressed into a tablet for FTIR measurement.The morphological observations of the different rice straw fiber were carried out on an EVO 18 scanning electron microscope (SEM) made by Zeiss In Jena, Germany. The SEM images were obtained by an electronic microscope model with a 20 kV electron beam. FTIR measurements were conducted using a Spectrum One Autoima spectrometer device made by PerkinElmer OPTICS in America. A total of 24 scans were performed for each sample in the range of 400 to 4000 cmW/S) ratio of 1.0 were carried out using an isothermal conduction calorimeter (TAM Air) at the temperature of 20 ± 0.1 °C for a period of 7 days. The hydration heat of the reference OPC sample without RF was measured with the same W/S ratio and test time. The hydration heat of each formulation was obtained from three individual tests.In this study, the quantities of four rice straw fibers replacing the OPC in the composite pastes were 0–10% by weight (wt.%); the mix proportion of the composite samples and the content of the main components are shown in Q) of each formulation, we calculated the inhibitory index (I) of the rice straw fibers filled with cement-based composite samples (RF-OPC) as the following equation:I is the inhibitory index of RF-OPC samples, Q is the total hydration heat of 7 days of per unit OPC in the reference samples (J/g), Q’ is the total hydration heat of 7 days of per unit OPC in RF-OPC samples (J/g), H is the time to reach the max rate of hydration heat in the reference samples (h), H’ is the time to reach the max rate of hydration heat in RF-OPC samples (h), S is the max hydration heat increment in the reference samples (J/g/h) and S’ is the max hydration heat increment in RF-OPC samples (J/g/h).According to the relevant literature ,21,24, tW/S of 1.0 was placed into a plastic bottle under curing conditions of 20 ± 2 °C and humidity exceeding 90% for 3 and 7 days. Then, the samples were sliced from the hardened composite samples and immersed in alcohol for 7 days to stop the hydration until measurement. The composite samples for XRD analysis were dried at a temperature of 60 °C and then ground into powders (≤45 μm). After that, the samples were measured on a Rigaku D/max-1400 diffractometer  with a step interval and scanning speed of 0.02° and 8°/min, respectively.XRD analysis were performed to observe the influence of the rice straw with different pretreatments on the hydration process of OPC. Each test paste consisting of 20 g of sample with Additionally, the composite samples filled with 10 wt.% RF were prepared, and pure cement paste was used as reference sample. The composite samples were prepared using a slurry vacuum de-watering technique. Firstly, RFs were stirred by a Joyoung household soybean milk maker for 2.5 min, then OPC was added and stirred at 1500 rpm in a planetary mixer for an additional 2.5 min. After that, the slurry was transferred to a casting box with size of 160 × 40 mm, superfluous water was absorbed by vacuum and then the samples were pressed at 3.2 MPa for 5 min. The samples were cured at a temperature of 20 ± 2 °C and relative humidity exceeding 90% for 7 and 28 days. For each mixture series, six rectangular samples with the size of 160 × 40 × 8 mm were prepared.MOR) and fracture toughness (FT) were measured using the following equations:P refers to the maximum load, l represents the support span, b is the width of the specimen and d stands for the thickness of the specimen. Fracture energy was calculated by integration of the load-deflection curve to the point where the load had dropped to 50% of its maximum value. The results were obtained according to the average value of the six samples.The three-point bending tests were performed using a WSM-10kN universal testing machine of SENS company in Shenzhen, China. In the bending tests, the span and deflection rate were 100 mm and 0.5 mm/min, respectively. The ultimate flexural strength  made by Zeiss In Jena, Germany at 20 kV accelerating voltage.− due to the reaction between H2O2 and oxygen radicals released from the ozone. In addition, the ozone also could degrade the residual lignin as described in Reference [Hemicellulose, lignin and cellulose are the main components of the plant fibers. Cellulose is the essential component of all the plant fibers, and cellulose type determines the mechanical strength of the plant fibers . As a kieference .The length, diameter and the aspect ratio of the rice straw fibers are provided in −1) was present in all samples, indicating presence of a large number of associated hydroxyl groups and extremely hydrophilicity. The sharp peak of the C-H bond stretching vibration was revealed at 2917 cm−1, embodying the saturated alkane chain in the chemical structure of plant fibers, such as the phenylpropane structure in the molecular structure of lignin, methylene and a small amount of methyl on the carbon shelf of cellulose and hemicellulose molecules [−1 represents the absorption peak of water due to excellent hydrophilicity of the pure cellulose [−1 represents the skeleton vibration of the benzene ring within fiber [−1 represent the C-H stretching vibration peak, C-H bending vibration peak and O-H bending vibration peak, respectively. In addition, the absorption peak near 1054 cm−1 and shoulder peak on both sides are the typical absorption peaks of natural cellulose, and 783 cm−1 represents the C-H bending vibration peak outside the lignin benzene ring [The FTIR spectrums of four rice straw fibers are shown in ellulose . The smain fiber ,31, whicene ring .The heat of hydration curves of the composite samples with different rice straw fibers within 7 days are shown in In According to the hydration curves of Combining As shown in Through the above analysis, it can be found that RF not only reduces the hydration heat of OPC but also delays the main hydration reactions of OPC. The reduction degree of hydration heat and the decreased hydration reactions increase with the increase in RF content. In case of the same RF content, addition of 5 wt.% RF1, RF2, RF3 and RF4 results in the total hydration heat evolution within 7 days decreasing to 64.5%, 97.9%, 98.9% and 99.0% of the reference sample, respectively, while addition of 10 wt.% RF1, RF2, RF3 and RF4 leads to the total hydration heat evolution within 7 days decreasing to 2.4%, 71.8%, 95.2% and 94.9% of the reference sample, respectively. The above results are attribute to variation of the contents of main components of the fibers. Steam explosion destroys the water extractives and removes the hemicellulose component of rice straw fiber . Due to The inhibitory index of the composite samples was calculated by the values of the total hydration heat in the first 7 days, the hydration time needed to reach max rate of hydration heat and the max rate of hydration heat increment of the inhibited OPC, as shown in The results for the inhibitory index of different RF-OPC samples are directly related to contents of hemicellulose, lignin and cellulose ,21. As s2+ ions, slowing the OPC hydration. Therefore, the extractives of plant fibers are involved in free calcium sequestration in the process of hydration of OPC and change the formation process of the hydration products, leading to composites with lower mechanical properties. Thus, the influence of RF1 on the hydration of OPC is in agreement with results reported by Olorunnisola [A diagram of the inhibition grade versus the content of hemicellulose, lignin and cellulose is shown in unnisola  for rattunnisola  investigIn order to understand the distribution of the four rice straw fibers in the cement matrix and the combination between different straw fibers and the cement matrix, the morphological characteristics of the fracture of the composite samples with 10% fiber content were observed using a scanning electron microscope. As shown in Steam explosion treatment of rice straw fibers removes most hemicellulose, while the action of bleaching treatment gets rid of lignin.The hydration process of the composite samples is similar to that of OPC except the 90OPC-10RF1 sample. In addition, the hydration heat of the composite samples is affected by both the pretreatment degree of rice straw fiber and fiber content.The inhibitory index value of different RF-OPC samples is directly related to hemicellulose and lignin content of rice straw fibers. In particular, the content of hemicellulose significantly affects cement hydration. When the hemicellulose content was 1.54 wt.% in the composite sample, the inhibitory index reached the extreme grade, and the hydration of OPC stopped when the hemicellulose content was 2.05 wt.%.Combining XRD and SEM analysis of the different rice straw fibers filled cement-based composite samples, better compatibility and adhesion were observed between the pretreated fibers and OPC due to removal of hemicellulose and lignin.In this study, compatibility between rice straw fibers with different pretreatments and OPC was evaluated by measuring the hydration process and hydration heat of OPC with different types and contents of rice straw fibers. The following conclusions are drawn:In this work, the compatibility between rice straw and OPC was studied. In the next step, influence of other crop straw and plant fibers on the hydration of OPC can be considered, so as to provide more theoretical research for the application of crop straw in building materials.


Nanosystems for targeted delivery and remote-controlled release of therapeutic agents has become a top priority in pharmaceutical science and drug development in recent decades. Application of a low frequency magnetic field (LFMF) as an external stimulus opens up opportunities to trigger release of the encapsulated bioactive substances with high locality and penetration ability without heating of biological tissue in vivo. Therefore, the development of novel microencapsulated drug formulations sensitive to LFMF is of paramount importance. Here, we report the result of LFMF-triggered release of the fluorescently labeled dextran from polyelectrolyte microcapsules modified with magnetic iron oxide nanoparticles. Polyelectrolyte microcapsules were obtained by a method of sequential deposition of oppositely charged poly (PAH) and poly(sodium 4-styrenesulfonate) (PSS) on the surface of colloidal vaterite particles. The synthesized single domain maghemite nanoparticles integrated into the polymer multilayers serve as magneto-mechanical actuators. We report the first systematic study of the effect of magnetic field with different frequencies on the permeability of the microcapsules. The in situ measurements of the optical density curves upon the 100 mT LFMF treatment were carried out for a range of frequencies from 30 to 150 Hz. Such fields do not cause any considerable heating of the magnetic nanoparticles but promote their rotating-oscillating mechanical motion that produces mechanical forces and deformations of the adjacent materials. We observed the changes in release of the encapsulated TRITC-dextran molecules from the PAH/PSS microcapsules upon application of the 50 Hz alternating magnetic field. The obtained results open new horizons for the design of polymer systems for triggered drug release without dangerous heating and overheating of tissues. Nanotechnologies gain much attention due to the unique physical and chemical properties of its products having a ground-breaking impact in a range of fields such as chemistry, biology, and engineering. The fields of nanomedicine and drug delivery have undergone rapid development over the past decades. In contrast to the usual administration of a drug substance, targeted delivery of the encapsulated formulation allows to increase the selectivity of the therapeutic effect, ensure its prolonged action, and reduce side effects. To achieve this goal, tremendous efforts have been made to modifying the surface of carriers with antibodies and other ligands to increase their affinity to the target sites ,2. TheseAmong a wide variety of the drug delivery vehicles, the polyelectrolyte multilayer capsules (PECs) obtained by the method of layer-by-layer adsorption of macromolecules on the surface of sacrificial colloid particles deserves special attention ,9. The P3O4/poly capsules due to application of 50 kHz alternating magnetic field B O4. At room temperature, at the [B] sites, a fast electronic exchange occurs between Fe3+ and Fe2+, which leads to the averaged valence of Fe2.5+ at [B] sites. At T = 120 K, the electron exchange at the [B] sites is “frozen”, and the Verwey transition takes place. In maghemite, all iron ions are in the Fe3+ state, and it can be considered as non-stoichiometric magnetite, where some of the octahedral cationic sites are vacant (Fe3+)A [Fe5/33+1/3]B O4. The ratios of Fe ions in (A) and [B] sublattices in γ-Fe2O3 and Fe3O4 are 1:1.67 and 1:2, respectively.In the crystal structures of magnetite FeThe Mössbauer spectra of the obtained nanoparticles are shown in δ, hyperfine magnetic field at the iron nucleus hfH, and quadrupole coupling constant q, our computational model also allows us to obtain the average magnetic anisotropy energy KV for the given ensemble of nanoparticles and the relative width of the size distribution of magnetic domains ΔD/D0. Here K is the constant of magnetic anisotropy, and V is the average volume of the magnetic domain.The analysis of the spectra was carried out within the model of the magnetic dynamics of ferromagnetic nanoparticles . An exam2O3 maghemite. The parameters obtained are presented in When approximating the Mössbauer spectra at different temperatures, two magnetic components corresponding to iron ions in the octahedral [B] and tetrahedral (A) magnetic sublattices were used. The ratio of the areas of the components corresponding to the A and B sites was fixed either as 1:1.67 or 1:2. The model was fitted for all spectra of the sample simultaneously. This allows one to find the most self-consistent solution for each spectrum. The model demonstrated good agreement with the experiment  when usiAδ = 0.376 (2) mm/s and Bδ = 0.471 (3) mm/s correspond to Fe3+ ions in the high-spin state  at tetra- and octa-sites of γ-Fe2O3, respectively. No traces of ferrous ions related to magnetite were observed in Mössbauer spectra. The maghemite γ-Fe2O3 phase was also observed in previous work, where similar polyelectrolyte microcapsules modified by iron oxide nanoparticles were studied -sites and the magnetic anisotropy constant in bulk maghemite and in the studied nanoparticles  are in a superparamagnetic state, while larger particles can be in a spin-blocking or magnetically ordered state, and they are responsible for the observed hysteresis.The magnetization curve for the nanoparticles is shown in It is known that superparamagnetic blocking temperature depends on the characteristic time of the experiment. The time-scale of Mössbauer spectroscopy is much less than the time-scale of magnetometry measurement. As shown above, in the Mössbauer spectrum at room temperature, we do not observe doublet lines characteristic of the superparamagnetic state. Mössbauer spectroscopy indicates that the spin-blocking temperature of nanoparticles is above room temperature.M0, and the magnetic anisotropy has an axial form and its energy is described by the parameter KV, where K is the constant of magnetic anisotropy, and V is the average volume of the magnetic particle.The theoretical processing of the magnetization curve was carried out within the generalized Stoner–Wohlfarth relaxation model ,44,45,46In the model, the particles have the shape of elongated ellipsoids with the anisotropy axis coinciding with the axis of rotation of the ellipsoid. We assume a random distribution of the directions of the anisotropy axes of particles in the sample. Accordingly, for each particle, the anisotropy axis is randomly directed in space.exH) is less than the critical field of the particle magnetization reversal (CH), then the magnetic moments of the particles can jump under the influence of thermal excitations.In the initial state , the magnetic moment of the particle is in one of two possible positions in the local energy minima. If the external magnetic field  indicates that this interaction is rather weak [It was found that the average size of the magnetic domain is in good agreement with the average size of nanoparticles, which was obtained from the TEM data. This suggests that the resulting nanoparticles are predominantly single-domain. The positive value of the parameter her weak ,44.Accordingly, to the theoretical concepts, the synthesized MNPs can implement Brownian relaxation of the magnetic moment, and can be used as local strain mediators due to the magneto-mechanical effect.3 particles. The reversal of Zeta-potential during the layers deposition indicates the successful formation of multilayers shell  is 2.6 ± 0.5 and 2.8 ± 0.4 µg/mL, respectively.Concentration of the magnetic nanoparticles in the shell was calculated from concentration of iron ions :The dynamic part of optical density is described by the sum of two components, which compete with each other. The attraction to the walls of the cuvette reduces the concentration of microcapsules in the area of beam path, which reduces the scattering of light by the microcapsules. LFMF, forming in the electromagnet air gap, in practical is not uniform. The inhomogeneity of the generated magnetic field, according to the manufacturer, is no more than 5%. Intensity of magnetic field increases near the core that leads to attraction of MNPs. Due to the oscillation of the magnetic field, the emerging forces alternately attract the capsules to the poles of the magnet. However, due to the inertial motion of the capsules and the rotation of magnetic nanoparticles in the shell, the oscillation of the magnetic field cannot fully compensate for the initial displacement of the microcapsules. In contrast, the release of TRITC-dextran from microcapsules increases the optical density through absorption. The process of release from microcapsules and diffusion of TRITC-dextran into the beam region are slower than the attraction of microcapsules to the walls of the cuvette. Thus, at the beginning of the process, the optical density curve decreases. Then the role of the release process begins to grow, and the second and third components become balanced.S0, A, B, S0, B, 0, B are common for all samples and do not depend on frequency of magnetic field. The calculated values of those parameters are S0 = 0.585 ± 0.002, B = 0.831 ± 0.005. Others calculated parameters are shown in To calculate the parameters from the Equation (2), namely The value of parameter A is of a special interest. As can be seen from the 2O3 maghemite magnetic nanoparticles were synthetized by precipitation method by R. Massart. The characteristics of the tailor-made nanoparticles were analyzed in order to obtain an effective drug delivery system with remote release of the encapsulated component. The results demonstrate the perspectives of the nanoparticles application as the magneto-mechanical actuators due to their ability to the Brownian relaxation. The multilayer composite microcapsules were developed on the base of sacrificial vaterite templates from PAH and PSS polyelectrolytes and the synthesized nanoparticles, which are uniformly distributed over the shells. The TRITC-dextran-loaded microcapsules permeability triggered by LFMF was investigated at 100 mT and frequencies of 30–150 Hz range. A low-frequency magnetic field of 50 Hz was found to be the most pronounced to selectively increase the permeability of magnetically sensitive microcapsules to the high molecular weight TRITC-dextran. We present here a proof-of-concept and expect this effect to be much stronger for low molecular weight substances, which are mainly used in medicine. Our findings could provide a perspective application of the microcapsules with LFMF-triggered permeability for controlled release of drugs without dangerous heating and overheating of the biological tissues.We demonstrate that permeability of composite magnetic microcapsules can be triggered by non-heating low frequency magnetic field. For this purpose, the single-domain γ-Fe


However, the positive effects of the ultrasonic vibration were weakened at low temperatures; consequently, the IMCs layer became discontinuous at the bottom of the nugget zone and the welding defects also formed. The ultrasonic vibration accelerated the dynamic recrystallization and refined the microstructures in the nugget zone due to the increased strain rate and stored energy. As a result, the UaFSW joint exhibited a better mechanical performance in comparison to the FSW joint, and the increment in the peak tensile load/elongation was more than twice. In addition, the UaFSW joint failed in the nugget zone along with the Al/steel interface, and the fracture mode was a mixture of ductile and brittle.A dissimilar AA7075/Q235 butt-lap joint was fabricated via ultrasonic-assisted friction stir welding (UaFSW), and the characteristics of the UaFSW joint were investigated systematically. The acoustoplastic effect of the ultrasonic vibration led to the softening of the materials and enhanced the material flow during welding, decreasing the volume of welding defects in the nugget zone of the UaFSW joint. With the help of ultrasonic vibration, a smooth and thin intermetallic compounds (IMCs) layer could generate along the Al/steel interface at the top of nugget zone, which possibly consisted of Al Currently, Al/steel hybrid components have been widely applied in the transportation system, aimed at reducing both the weight and the fuel consumption of vehicles ,2. HowevAs mentioned above, the IMCs layer forms at the Al/steel interface during FSW, and moreover, the strength of the joints varies depending on the thickness of the IMC layer ,12. The The positive effects of UaFSW on the welding quality can be outlined based on references ,20,21,22So far, UaFSW is mainly utilized to elevate the welding quality of butt- and lap-joints, while the data on the butt-lap joint is scarce. Compared with the simple butt- or lap-joint, fabricating the butt-lap joint becomes more difficult because of its asymmetrical structure. Currently, the butt-lap joint is widely used in the train industry , and theRolled AA7075 and Q235 steel were chosen as the base metal (BM) in this work, and the nominal chemical compositions of AA7075/Q235 can be seen in 3:C2H5OH was 1:24) and AA7075 was by the Keller’s reagent (the volume fraction of HF:HCL:HNO3:H2O was 2:3:5:90). Differently, the samples for SEM analysis were only mechanically polished in order to avoid the falling out of IMCs layer and second-phase particles caused by etching. The type of SEM detection was the secondary electron. Both the grain size and the recrystallization fraction of Al in the NZ were counted using EBSD technique, and the EBSD samples were electro-polished using the perchloric acid–ethanol solution (the volume fraction of HCLO4:C2H5OH was 1:9), and the scanning step of EBSD selected here was 0.36 µm. Besides, transmission electron microscopy  was also used to observe the second-phase particles in the matrix of AA7075. The TEM samples were jet electro-polished at −25 °C with the nitric acid–methanol solution (the volume fraction of HNO3:CH3OH was 7:3).In order to analyze the microstructural characteristics of dissimilar Al/steel butt-lap joints, optical microscopy , scanning electron microscopy , and electron back-scattered diffraction  were employed. For OM observation, the FSW and UaFSW joints were mechanically polished and etched: Q235 was etched by the nitric acid–ethanol solution  was employed to measure the distribution of hardness through the whole joint; the tested line was along the mid-thick of upper AA7075 plate, which started from Q235 at the advancing side and ended in AA7075 at the retreating side. Each tested line contained 30–40 measured points and the distance between the adjacent measured points was 0.5 mm. The test load and dwelling time are 50 gf and 5 s, respectively. Moreover, the mechanical performance of joint was evaluated by the tensile test . The tensile specimens were produced perpendicular to the welding direction with a gauge of 40 mm length and 10 mm width  dissThe overviews of a dissimilar Al/steel butt-lap joint fabricated by FSW and UaFSW joints are shown in 5Fe2 and Al13Fe4 phases. The above inference can also be supported by references [13Fe4 phase was firstly generated and then transformed into the Al5Fe2 phase during FSW.The microstructural evolution of the Al/steel interface is analyzed by SEM, as shown in ferences , which rAt the bottom of the NZ, the welding defects are detected in both the FSW and UaFSW joints a,b, indiD is the final grain diameter of DRX, Q is the activation energy, T is the welding temperature, and a, b, and R are constants. Thus, it can be inferred that fine grains can be obtained using a low welding temperature or high strain rate. Shi et al. [C is the materials constant, AN is the nucleation rate, and G is the growth rate. It has been reported that both AN and G increased with the increase of the stored energy, and the stored energy had a more marked effect on the former than the latter [The NZ of the joint is mainly located in the aluminum side due to the offset of the stir tool and, meanwhile, a small amount of steel is stirred into the aluminum matrix, acting as the strengthening particles. The grain morphology of aluminum in the NZ is shown in i et al.  stated ti et al. ,37. There latter . Thus, fe latter  reportedThe images of failure specimens are shown in It is still difficult to obtain a sound Al/steel butt-lap joint via UaFSW at this time, and much work is needed to be done in the future. The authors propose one possible way to elevate the quality of the Al/steel butt-lap joint: the energy input of a single ultrasonic source may be not sufficient enough for the butt-lap structure, and thus, a doubling or tripling of ultrasonic sources can be employed in order to increase the energy input.(1)5Fe2 and Al13Fe4 phases. However, the acoustoplastic effect was weakened at low temperatures. As a result, both welding defects and discontinuous IMCs layers formed at the bottom of the NZ;Compared with FSW, the material flow during UaFSW was enhanced, decreasing the volume of welding defects in the NZ. Moreover, the IMCs layers at the top of the NZ became smooth and thin due to the acoustoplastic effect of ultrasonic vibration, and the IMCs layer was mainly comprised of Al(2)The application of ultrasonic vibration accelerated the DRX process, and the fraction of recrystallization increased from 55% to 77%. Besides, superimposing ultrasonic vibration led to better grain refinement in the NZ, which was caused by the increased strain rate and stored energy. In comparison to the FSW joint, the tensile properties of the UaFSW joint were elevated, and a 1.5 KN (or 200%) increment in the peak tensile load (or elongation) was obtained for the UaFSW joint. Meanwhile, the fracture mode of the UaFSW joint shifted from ductile at the top of the NZ to brittle at the bottom of the NZ.The microstructural/mechanical evolutions of dissimilar Al/steel butt-lap joints fabricated via UaFSW were investigated in the present study, and the following results can be summarized: