The deformation performance of recycled aggregate concrete can be effectively improved when basalt fiber is reasonably added. In this paper, the effects of the basalt fiber volume fraction and the length–diameter ratio on the uniaxial compression-related failure characteristics, feature points of the complete stress–strain curve and the compressive toughness of recycled concrete under different replacement rates of recycled coarse aggregate were studied. The results showed that with the increase in the fiber volume fraction, the peak stress and peak strain of basalt fiber-reinforced recycled aggregate concrete first increased and then decreased. With the increase in the fiber length–diameter ratio, the peak stress and strain of the basalt fiber-reinforced recycled aggregate concrete first increased and then decreased, whereas the effect of the length–diameter ratio on peak stress and strain of the basalt fiber-reinforced recycled aggregate concrete was clearly smaller than that of the fiber volume fraction. Based on the test results, an optimized stress–strain curve model of concrete under uniaxial compression was proposed for the basalt fiber-reinforced recycled aggregate concrete. Furthermore, it was found that the fracture energy is more suitable for evaluating the compressive toughness of the basalt fiber-reinforced recycled aggregate concrete than the tensile–compression ratio. Recycled aggregate concrete (RAC) refers to a type of green and low-carbon concrete  which taConcrete toughening technology includes base toughening and fiber toughening . Base toCurrently, the research on BF for the improvement of concrete toughness focuses on the influence of BF volume content, length and other influencing factors on concrete compressive toughness, tensile toughness and flexural toughness. Wang Yi  took theWang Qi  took theIn summary, this paper explored the effects of the BF volume fraction  and length–diameter ratio  on the deformation performance of RAC under compression through the uniaxial compression test. Based on the complete stress–strain curve, the effect of BF characteristic parameters on the compressive toughness of RAC was analyzed; this provides a reference for the current engineering design of BFRAC.The cementitious materials used in this test were ordinary Portland cement (P·O 42.5) and grade I silica fume (SF). The main chemical composition and physical properties of cement and SF are shown in Vf) is the percentage of BF volume to the volume of BFRAC. The length–diameter ratio (l/d) is the ratio of the fiber length (l) to the fiber diameter (d). The replacement rate of recycled coarse aggregate (r) is the percentage of the volume of recycled coarse aggregate in the volume of coarse aggregate. The specimen numbers were grouped according to The design strength grade of the base concrete was C40, and the specific mix proportion is shown in The size, number and curing method of the test specimen were in accordance with the “Standard Test Method for Physical and Mechanical Properties of Concrete” (GB/T 50081-2019). The size of the compressive strength test block was 100 mm × 100 mm × 100 mm, and the size of prismatic specimen was 150 mm × 150 mm × 300 mm for the uniaxial compression test; three samples were made for each group. In order to improve the dispersion performance of the BF in the concrete, the BF was pretreated at a high temperature (300 °C), and a variety of mixing methods were compared and analyzed. The mixing method shown in The cube compressive strength test was performed in accordance with the specification “Standard Test Method for Physical and Mechanical Properties of Concrete” (GB/T 50081-2019). In order to obtain a more ideal complete stress–strain curve under axial compression, a rigid auxiliary element was added to the press in this test. In the elastic stage, the force was used to control the loading. The loading speed was 0.8 KN/s; this was 80% of the axial compressive strength of concrete. In the convex ordinate of the ascending curve, displacement control was used; the loading speed was 0.002 mm/s. When the residual strength of the descending curve was 60% of the axial compressive strength, the displacement control loading rate was adjusted to 0.004 mm/s. When the load was 30% of the peak load, the test stopped. The test device is shown in (1) Effect of fiber volume fractionBy analyzing the increase rate of the BF on the compressive strength of the NC and the RAC, it was found that the maximum increase rate of BF on the compressive strength of the RAC was greater than that of the NC. When the length–diameter ratio was 1200 and the volume fraction was 0.20%, the compressive strength of the RAC with the replacement rates of 50% and 100% increased by 18.31% and 24.0%, respectively, when compared with that of non-doped RAC. However, Liu’s results showed that the best compressive strength improvement was achieved when the fiber volume fraction was 0.2%. However, the increase rate was only 8% which may be caused by uneven fiber dispersion [(2) Effect of fiber length–diameter ratioThe difference was that for the BFRAC of recycled coarse aggregate with the replacement rate of 100%, when the fiber volume fraction of BFRAC was less than 0.15%, the compressive strength of the BFRAC decreased with the increase in the BF length–diameter ratio. This is mainly because when the recycled coarse aggregate had a replacement rate of 100%, and the fiber content was the same, with the increase in its length–diameter ratio, the fiber length increased, and the fluidity of the mixture gradually decreased. At the same time, the “reservoir” effect of the recycled coarse aggregate further reduced the fluidity of the mixture, resulting in the difficult removal of bubbles coated in the mixture during the pouring process. Thus, a weak point was formed inside the specimen, which accelerated the destruction of the concrete and led to the reduction in compressive strength.When the fiber volume fraction was greater than 0.10%, the saturated 3D mesh structure was gradually formed in the RAC due to the “bridging effect” of fibers, and the number of fibers decreased with the increase in the length–diameter ratio. Therefore, the 3D mesh structure tended to saturate first and then become unsaturated, and there was a critical saturation point. The above result suggests that the compressive strength of RAC increases first and then decreases.(1) Effect of fiber volume fraction on tensile strength(2) Effect of fiber length–diameter ratio on tensile strengthThe result of the comprehensive analysis indicated that both the BF volume fraction and the length–diameter ratio affected the compressive strength and tensile strength of the BFRAC in unison, and the BF volume fraction had a more significant effect on the mechanical properties of concrete. Influenced by the dispersion performance of BF in concrete, when the volume fraction of BF did not exceed the optimal volume fraction, the 3D mesh structure formed in concrete was gradually saturated with the increase in the BF volume fraction, such that its compressive strength increased. When the volume fraction of the BF exceeded the optimal volume fraction, the probability of the BF clumping in concrete increased, thus affecting the compressive strength of concrete. As the BF continued to increase, the probability of fiber clumping also continued to increase. Subsequently, a large defect was formed inside the concrete, thus greatly reducing the strength of concrete.When the BF volume fraction was small, the mechanical properties of concrete were mainly affected by the length–diameter ratio. The larger the length–diameter ratio, the longer the fiber length, and the more easily the fiber would exist in a curve shape in concrete. The bond property between fiber and cement mortar was optimized. With the further increase in the length–diameter ratio, the cross phenomenon easily appeared between the fibers, thus having an adverse effect on the concrete. However, when the volume fraction of the BF was large, since a certain length of fiber-base bond can ensure the full play of BF’s mechanical properties, as the fiber length–diameter ratio got larger, its length was also extended; the phenomenon of fiber crossing was also more likely to occur, thus having adverse effects on concrete. At the same volume fraction, when the length–diameter ratio was larger, the number of fibers was smaller. To achieve a certain number of 3D mesh structures, more fibers would be needed, thus leading to the increase in the optimal volume fraction.1 can reflect the toughness and crack resistance of concrete materials. The tensile–compression ratio αDuring the curing phase, the sealing water is absorbed by the unhydrated cement particles, and the hydration reaction occurs, thus increasing the density of RAC. However, BF is distributed in a three-dimensional disorderly direction after RAC stirring. A mechanical meshing force and an adsorption adhesion force will be formed between the interface of fiber and the cement matrix , which fThe failure process of the RAC specimens is similar to that of the NC specimens. Under uniaxial compression, the crack development rate of the RAC and the NC specimens was fast. After the peak stress, the concrete specimen suddenly cracked into two independent blocks, showing brittle failure. However, the crack growth rate of the BFRC and BFRAC specimens was slow during loading. At the late loading stage, only a small quantity of concrete debris on the surface of the specimen flaked off. The specimen was still in its whole state at the last moment of loading, showing obvious ductility. From the perspective of the crack development process, the failure mode of the NC and the RAC was oblique shear failure, which developed from the corners of both ends to the middle of the specimen. The angle between the failure surface and the load vertical line was nearly 60~70°, while the angle between the failure surface and the load vertical line was more than 75° for the BFRAC and the BFRC. After the specimen was destroyed, the surface micro-cracks of the concrete with BF were significantly more than those without BF, and the maximum crack width was significantly smaller than that of the concrete without BF. The failure sections of the BFRC and the BFRAC specimens indicated that the BF was mainly pulled out from the concrete, and the “crackling” sound of BF was heard during the failure process.The distribution of cracks on the surface of the specimen indicated that with the increase in the fiber volume fraction, the width of the main crack on the surface of the specimen tended to decrease, while the number of micro-cracks gradually increased. This is because BF can reduce the probability of micro-cracks forming and spreading in the base when the specimen is subjected to uniaxial longitudinal pressure. When the micro-cracks in concrete began to extend and expand under the vertical load, overlapped BF at both ends of the cracks acted as a bridge, so as to inhibit and constrain crack growth. With the increase in the fiber volume fraction, the three-dimensional distribution range of fiber in concrete was wider, and the inhibition effect of fiber on the development of micro-cracks in concrete was stronger. With the increase in the macro-crack width, the microfiber was constantly pulled out and broken, which effectively delayed and prevented the crack expansion. Therefore, the specimen exhibited an increase in fine cracks, while the width of the main crack decreased.With the increase in the length–diameter ratio, the formation velocity of the main cracks and the total number of cracks on the surface of the BFRC specimens first decreased and then increased. The main reason is that when the BF’s length–diameter ratio is less than the optimal length–diameter ratio with the same fiber content, the fiber anchorage length at both ends of the micro-crack increases with the increase in the length–diameter ratio, and the inhibition effect on micro-crack growth is enhanced. When BF length–diameter ratio is greater than the optimal length–diameter ratio, the fluidity of the mixture decreases gradually with the increase in the length–diameter ratio. Therefore, it is difficult to remove the bubbles coated in the mixture during the casting process, and many weak spots are formed in the specimen. Under the action of a compression load, the weak point will become the inducing factor for crack development, so the total number of cracks increases. However, due to the increase in initial micro-cracks, the probability of forming a penetrating main crack increases, thus resulting in the rapid formation of the main crack.The peak point of the stress–strain curve of concrete most directly indicates the bearing capacity and deformation capacity of concrete before failure. Different feature points on the stress–strain curve indicate the distribution, expansion and fracture of cracks in concrete ,23.(1) Peak stressAs depicted in (2) Peak strainPeak strain is the strain corresponding to peak stress. As depicted in The OA stage was in the linear elastic stage, and there was no crack on the surface of the specimen. In this stage, the BF’s toughening and cracking resistance was not fully at work and was close to that of ordinary concrete.The AB stage was the meso-crack propagation stage. The initial crack inside the specimen gradually expanded with the increase in load, and small cracks parallel to the loading direction appeared on the surface of the specimen. When the load exceeded 80% of the peak stress, relatively clear macroscopic cracks appeared on the surface of the specimen. When the load reached the peak stress, the macroscopic cracks on the surface of the specimen gradually expanded, gathered and crossed to form macroscopic main cracks. At this stage, the BF crack resistance effect was obvious, which can inhibit the development of micro-cracks and the generation of new cracks in concrete.The BC stage was the macro-fracture stable extension section. After reaching peak stress, the stress began to decrease as the load continued to increase. This phenomenon of stress reduction with deformation increase, namely strain softening, is an important feature of common concrete and BFRC under uniaxial compression. Compared with ordinary concrete, the number and development rate of BFRC cracks increased.The CD stage was the fracture instability failure stage. As the strain continued to increase, the stress decreased slowly, and the macroscopic main crack on the surface of the specimen gradually formed a penetrating crack; crack width increased with the increase in load. At this stage, the BF mainly played a bridging role by mostly pulling out.In the OA stage, the stress and strain of the BFRAC and the RAC increased linearly, whereas the stress–strain curve of BFRAC was basically on the left of RAC, thus indicating that the stiffness of BFRAC was greater than that of RAC. At the AB stage, the stress increased steadily while the strain increased at a higher rate, and the slope of the curve gradually decreased; the stiffness of the specimen degraded. With the increase in axial deformation, the stress–strain curve of the BFRAC was still on the left of the RAC. At this stage, the effect of the BF on RAC crack resistance began to appear. At the BC stage, after the RAC reached the peak load, the specimens failed rapidly and the load dropped sharply, and the RAC showed the characteristics of brittle failure. At this stage, the rate of decline of the BFRAC curve was relatively slow, and the stress–strain curve was located on the upper side of the RAC. The main reason is that, at this stage, fiber and concrete worked together in coordination. The BF played a role in the form of bridge stress, across the crack interface transfer stress, thus effectively avoiding the phenomenon of “one crack, two stages”. In the CD stage, the stress–strain curve of the BFRAC decreased gradually and became flat. At this stage, the BF was pulled out and broken into large quantities, and the specimen was seriously damaged. Meanwhile, RAC and NC showed no flat segment, which showed a split and two segments in macro.The stress–strain curve of concrete under uniaxial stress lays an experimental data basis for structural design and nonlinear analysis . ScholarThe complete stress–strain curve of BFRC was predicted using the three models of Guo Zhenhai  (Model 1(1)The curve passes through the origin and point of coordinates.(2)At  the slope is 0.(3)(4)At present, the stress–strain curve equation of concrete is generally expressed in a dimensionless way, that is, In this paper, the sectional equation proposed by Guo Zhenhai was adopted, and the equation of the ascending section of the BFRAC compression stress-strain curve isThe equation of the descending section is expressed asAccording to the analysis in a value increased first and then decreased with the increase in the fiber volume fraction, and the overall change range was small. The a values of the BFRC, the BFRAC-50% and the BFRAC-100% were 2.08–2.27, 2.04–2.18 and 1.96–2.12, respectively. Therefore, the average a values of the BFRC, the BFRAC-50% and the BFRAC-100% were 2.19, 2.12 and 2.06. b value change curve of the BFRAC. As depicted in b value decreased first and then increased with the increase in the fiber volume fraction. The distribution range of the b value was 0.78~1.53, and the variation range was larger than that of the a value on the whole, thus proving that the effect of the BF on the descending section of the RAC was greater than that on the ascending section.Parameter a represents the ratio of the initial elastic modulus of concrete axial compression to the peak secant modulus . Figure F [β is the fiber bond coefficient; Vf is fiber volume fraction; lf is fiber length; df is the fiber diameter.In order to better describe the effect of the BF on the RAC stress–strain, a fiber strengthening factor F ,8,33,34 b and F was obtained through data regression analysis, and the results are listed in The bond coefficient is related to the geometric characteristics of the fiber: since BF is a flexible fiber it mostly exists in the form of curve in concrete. Compared with the round straight fiber, the bond performance is better. Therefore, the BF bond coefficient was set at 0.75 . The relBy substituting Equations (4)–(6) into Equation (2), the constitutive model of the descending section of the stress–strain curve of BFRAC under uniaxial compression load can be obtained.T) surrounded by the curve and coordinate axis is defined as the fracture energy of uniaxial compression failure [T can be obtained from Equation (7) [Axial compression toughness reflects the ability of concrete to absorb energy when it continues to bear the load after cracking. Fracture energy is an important toughness index for concrete . In orde failure ,37, whiction (7) .(7)T=∫0T values of each group can be obtained from Equation (7) as shown in The It can be seen that the toughness of the BFRAC under uniaxial compression increased first and then decreased with the increase in the fiber strengthening factor. When the fiber strengthening factor was 2.4, the fiber volume fraction 0.20% and the aspect ratio 1200, the toughness of the BFRC, the BFRAC-50% and the BFRAC-100% increased by 11.32%, 21.96 and 26.59, respectively, when compared with the control group.The analysis of the tension–compression ratio and fracture energy indicated that the tension–compression ratio increased first and then decreased with the change in BF volume fraction; this was consistent with the effect of the BF on the basic mechanical properties of RAC, whereas the corresponding optimal fiber volume fraction was different. According to the fracture energy index, the maximum increase rate of BFRAC toughness was higher than that of the control group, which was higher than that of the tensile–compression ratio. The result of the comprehensive analysis of the influence law and the increase effect of the BF on the compressive properties of the RAC reveals that fracture energy is more suitable for evaluating the compressive toughness of BFRAC.The paper focuses on the study of the basic mechanical properties and the uniaxial compression constitutive relationship of basalt fiber recycled concrete. It discusses the influence of the volume fraction and the length–diameter ratio of basalt fiber on mechanical properties, including the axial compression strength, peak strain and compression toughness. It also establishes a theoretical full curve model combined with current research and the characteristics of basalt fiber recycled concrete. The compression toughness of BFRAC is quantitatively evaluated by the tension–compression ratio and the uniaxial compression failure fracture energy. In accordance with the calculation and analysis results, the following conclusions were obtained:(1) Basalt fiber (BF) can effectively improve the compressive strength and splitting tensile strength of recycled aggregate concrete (RAC). The compressive strength of basalt fiber-reinforced recycled aggregate concrete (BFRAC) with 50% and 100% replacement ratios was 18.31% and 24.0%, higher than that of RAC without fiber, respectively. The maximum increase rates of the splitting tensile strength were 32.84% and 31.61%, respectively.(2) The peak stress and peak strain of the RAC increased first and then decreased with the increase in the BF volume fraction. The effect of the BF length–diameter ratio on RAC peak stress and peak strain was small. The peak stress of the BFRAC with 50% and 100% replacement rates had maximum increase rates of 23.15% and 26.94%, respectively, and the peak strain of this concrete had maximum increase rates of 29.03% and 29.15%, respectively.(3) Based on the stress–strain curve analysis of the BFRAC uniaxial compression, a fiber strengthening factor considering the influence of the fiber length–diameter ratio and the volume fraction was introduced to establish the stress–strain curve expression of the BFRAC uniaxial compression. The correlation coefficient was more than 0.85, which provides a theoretical basis for the engineering application of BFRAC.(4) Compared with the tensile–compression ratio, the compressive failure fracture is more suitable for evaluating the toughness of BFRAC under compression. Compared with the control group, the toughness of the BFRAC with 50% and 100% replacement rates increased by 21.96% and 26.59%, respectively. BF has a good effect on improving the toughness of recycled concrete, which is helpful to realize the large-scale application of recycled concrete.


The penetration resistance of the new material Basic Magnesium Sulfate Cement (BMSC) is studied through comprehensive application of an experimental and numerical simulation method. This paper consists of three parts. The first part introduces the preparation of Basic Magnesium Sulfate Cement Concrete (BMSCC) and the study of its dynamic mechanical properties. In the second part, on-site testing was carried out on both BMSCC and an ordinary Portland cement concrete (OPCC) target, and the anti-penetration performance of the two materials was analyzed and compared from three aspects: penetration depth, crater diameter and volume, and failure mode. In the last part, the numerical simulation analysis was carried out based on LS-DYNA, and the effects of factors, such as material strength and penetration velocity on the penetration depth, are analyzed. According to the results, the BMSCC targets have better penetration resistance performance than OPCC under the same conditions, mainly manifested in smaller penetration depth, smaller crater diameter and volume, as well as fewer cracks. Concrete is widely used as a structural material in modern civil engineering due to its high compressive strength, good durability, and strong ability to protect reinforcement. Currently, reinforced concrete structures are mostly adopted in protective engineering and fortifications among various countries. Therefore, researching the penetration effect of projectiles on concrete structures is essential. Over the past hundred years, scientists from various countries have conducted detailed research on the penetration for concrete materials by using the following three methods.The first method is on-site testing. Due to the limitation of research conditions, initially the penetration resistance research of concrete materials was conducted in various countries, mainly by tests of field live projectile, and then a large amount of data were obtained and analyzed to derive corresponding empirical formulas, such as the Petry formula , the BRLThe second one is theoretical analysis. Theoretical analysis of concrete penetration caused by projectiles is mainly focused on building an engineering analysis model based on a single mechanism, of which the most representative is the cavity expansion approximation theory. Bishop  first prThe third one is numerical simulation. In recent years, with the rapid development of computer technology and gradually matured calculation methods, numerical simulation has increasingly become the main mean of studying penetration problems. Currently, the HJC model and the RHT model are the commonly used concrete constitutive models. Holmquist et al.  proposed2·MgSO4·7H2O  [2 produced in lithium extraction from salt lakes through a certain process of calcination. Another main raw material, MgSO4, is widely available in the byproducts of magnesium desulfurization method used in thermal power plants and steel plants. Therefore, compared with OPC, BMSC is more energy-saving and environmentally friendly. Currently, research on BMSC concrete mainly focuses on mix proportion design and static mechanical properties [MgO is commonly used as an expansive agent to improve the crack resistance of face slab concrete  and late7 phase) . Zhu et 7 phase)  comparedoperties ,34. A syIn this study, on-site testings and numerical simulations were carried out on the projectile penetration of BMSC concrete and OPC concrete with different strength grades. The results, including penetration depth, crater diameter and volume, and failure mode, are analysed and discussed. These results show the influence of different cements, concrete strengths, and projectile velocities on the penetration performance of the target.4·7H2O), 23.5% grade I fly ash (FA), and 0.5% core admixture . The physical and mechanical properties of the BMSC are listed in (1) BMSC: Main raw materials are calcined 50.6% Light-burned MgO (LBM), 25.4% industrial-grade magnesium sulfate heptahydrate  Fine aggregate: river sand produced in Ganjiang was provided by Jiangsu Liyang Laijiang Concrete Co., Ltd., with an apparent density of 2650 kg/m3, and a packing density of 1440 kg/m3. It is classified as 10~20 mm continuous gradation.(3) Coarse aggregate: crushed stone was provided by Anhui Xingyuan mineral Co., Ltd., with a particle content of 4.8% in faller gill, a crushability index of 10.4%, an apparent density of 2610 kg/mBased on Cylindrical targets measuring Ø30 × 25 cm were designed. The target adopts a 5 mm-thick steel hoop mold. The middle part in the height direction of the inner side of the steel hoop is welded to 4 pairs of L-shaped reinforcement symmetrically around the center of the circle. The long part is 10 cm, and the bending part is 4 cm  of the head of 3.To prevent the cylindrical target from rolling, a wooden wedge was used to secure it onto the target platform. This ensured that the distance between the smooth-bore gun’s barrel outlet and the back of the concrete targets remained fixed at 6 m. At the same time, the surface of the target is perpendicular to the barrel of the smooth-bore gun, and the axis of the barrel is aligned with the center of the target.The initial velocity of the projectile is controlled by the charge. After the experiment, the residual velocity of the projectile is determined through high-speed photography. At the same time, the diameter, volume, and depth of the bullet hole on the surface of the target are measured, and the penetration depth is obtained through calculation. All experimental results are summarized in The penetration depth of target is an important basis for evaluating the penetration resistance of materials. The comparison of penetration depths of concrete targets with different strength grades has been shown in The LS-DYNA finite element pre-processing program was used for modeling, the basic unit of which is g-cm-μs. A Solid164 three-dimensional entity unit was used for projectile and concrete models. During the grid division process, grid cells were defined by their densities. As shown in The Johnson-Cook elastic–plastic model was selected for the projectile material, which can accurately describe the behavior of metal materials under large deformations, high strain rates, and high temperatures. For the concrete target, the isotropic Johnson-Holmquist-Concrete material model was adopted, which takes into account failure and is related to strain rate. Model parameters are shown in The contact–collision interface between the projectile and the target’s interface model is defined using the symmetric penalty method. The specific contact type is defined by using the keyword *CONTACT_ERODING_SURFACE_TO_SURFACE, where the projectile is the main surface, and the target is the secondary surface. As the concrete element is deleted after reaching the ultimate stress, a new contact surface will be defined inside the material. Based on practical test results, non-reflecting boundary conditions are set for the external and bottom surfaces of the cylindrical target, and symmetrical constraints are imposed on the 1/4 section of both the target and projectile.Numerical simulations were conducted for all test conditions of the BMSCC and OPCC target, and the comparison between the simulated values and experimental values is shown in In order to study the variation of penetration depth of BMSC concrete with concrete strength and penetration velocity of projectile, the numerical simulation method was adopted in this paper. The target model is a cylinder with diameter of 30 cm and height of 50 cm. The parameters of the model and materials are shown in (1)The on-site test results have shown that projectile velocity and concrete strength both have significant effects on the penetration resistance of the BMSCC target. The greater the initial velocity of the projectile, the greater the penetration depth of the target. Besides, when the initial velocity of the projectile is the same, the penetration depth of the BMSCC target will decrease with increasing concrete strength.(2)The crater diameter and volume increase with the increase in BMSCC strength when the projectile velocity is the same. When analyzing the failure mode of target, the craters are all funnel-shaped, with radial cracks at the edges, and the larger the velocity of the projectile, the more cracks and the larger the width.(3)The model parameters shown in (4)Material properties also have an impact on the penetration resistance of concrete, which is obtained through on-site testing and numerical simulations. The BMSCC targets have better penetration resistance performance than OPCC under the same conditions, mainly manifested in smaller penetration depth, smaller crater diameter, and volume, as well as fewer cracks.


Background: Most antibiotic use occurs in ambulatory settings. Antibiotic prescribing for children living in the United States in medically underserved areas or in populations is not well understood.Objective: To characterize antibiotic prescribing for children in a practice-based research network (PBRN).Design and Methods: In this retrospective cohort study, we characterized oral antibiotic prescribing in a large PBRN. Patients aged 0–17 years with at least 1 in-person visit between January 1, 2014, and December 31, 2018, at 1 of 25 primary-care clinics located within the WWAMI  region of the Practice and Research Network (WPRN) were included. Data were extracted from DataQUEST, a centralized data repository from included primary-care clinics. Encounters for wellness visits or those lacking a diagnosis code and patients with complex chronic conditions were excluded. Diagnoses were categorized using International Classification of Disease, Ninth Revision (ICD-9) and ICD-10 codes. Oral antibiotics prescribed within 3 days of an encounter were associated with that encounter. Demographic data included age, sex, race, and ethnicity. Antibiotic appropriateness was determined using a previously published 3-tiered classification system using diagnosis codes as always, sometimes, or never appropriate. Patient-level data (ZIP codes) were used to designate medically underserved areas (MUAs) and medically underserved populations (MUPs). Antibiotic prescribing was then analyzed within these groups. Results: In total, 37,314 patients across 206,845 encounters were included, of which 34,601 encounters (17%) resulted in antibiotic prescription (Table 1). Of those, appropriateness data were available for 34,286 (99%). Of the antibiotics prescribed, 14% were always appropriate, 57% were sometimes appropriate, and 27% were never appropriate (1% missing). In total, 64% and 35% of encounters occurred with patients from an MUA and MUP, respectively. Conclusions: Targets to improve oral antibiotic prescribing for children in a large PBRN include antibiotic prescribing for diagnoses that never require an antibiotic. Larger comparative studies may focus on the role (if any) that MUA/MUP has on antibiotic prescribing.Disclosures: None


Strigolactones (SLs) are a unique and novel class of phytohormones that regulate numerous processes of growth and development in plants. Besides their endogenous functions as hormones, SLs are exuded by plant roots to stimulate critical interactions with symbiotic fungi but can also be exploited by parasitic plants to trigger their seed germination. In the past decade, since their discovery as phytohormones, rapid progress has been made in understanding the SL biosynthesis and signaling pathway. Of particular interest are the diversification of natural SLs and their exact mode of perception, selectivity, and hydrolysis by their dedicated receptors in plants. Here we provide an overview of the emerging field of SL perception with a focus on the diversity of canonical, non-canonical, and synthetic SL probes. Moreover, this review offers useful structural insights into SL perception, the precise molecular adaptations that define receptor-ligand specificities, and the mechanisms of SL hydrolysis and its attenuation by downstream signaling components. Strigolactones (SLs) are a recently discovered class of phytohormones that have become the focus of numerous research studies in the last decade. SLs garner much attention because of their central role in modulating an increasingly wide range of plant-developmental and plant-environmental processes. Since their first discovery, SLs have been characterized to have remarkable dual function as both exogenously secreted signaling molecules and endogenous hormones.Striga plants   . SLs whep yields . While Sp yields .As hormones, SLs were first identified to have endogenous roles in regulating shoot branching . Later sDue to this central role of SL signaling in plant development and plant-environment interactions, the research on the mode of SL perception has become a main focus with over 50 studies in 17 species at the genetic, phenotypic, biochemical, and structural level. Over the past decade, these studies have revealed a complex mode of perception and signaling in plants. A major leap in understating SLs perception is the identification of their receptor protein which also acts as an active catalytic enzyme . Since tStriga, taking on the name strigol  which is connected to a common butenolide ring (D-ring) through the conserved 2′R configured enol-ether linkage  Fig. 1)Fig. 1).The ongoing identifications of diverse SLs reveal a variability in the C-ring configuration and provide further classification of SLs that are originally derived from 5-Deoxystrigol (5DS) with β-oriented C-ring as strigol-type , and SLsSolanum lycopersicum (Sl), SlCYP722C was found to be necessary for the synthesis of orobanchol-type SLs   . The LBOlactone) . Additiolactone) , 2019. Olactone) , b.Arabidopsis, maize, and poplar produce both canonical and non-canonical SLs. Therefore, further identification of new metabolic precursors and SLs biosynthesis enzymes will illuminate the diversification of canonical and non-canonical SLs across plants.Interestingly, some plant species such as Both canonical and non-canonical SLs are generally unstable compounds that can spontaneously disintegrate into inactive ABC and D-ring products in alkaline conditions . Additio5DS and GR24ent–5DS are retained as a racemic mixture ( ±)-GR24 and referred as rac-GR24 or maintained as pure enantiomers. Molecules lacking the A-ring and AB-ring of GR24 such as GR7 and GR5 were also shown to be bioactive Striga germination stimulants , the GR compounds such as GR24, GR7 and GR5 , named aimulants . rac-GR2nagement . Howevermination , b or domination . Therefomination , b. Thismination . This inmination , furanonmination   , Xilatonn planta .Interestingly, a group of sulfonamide-related compounds called cotylimides (CTLs) which lacks the D-ring has been identified  Fig. 3)Fig. 3). Striga. Another antagonist molecule, soporidine, was identified in a chemical screen and was shown to bind Striga HTL (ShHTL) and inhibit Striga germination Striga. Amination . Recentlmination . Lastly,mination  Oryza sativa)  . This wa sativa) . Then, ttor KAI2 . Followitor KAI2 , MedicagMedicago , barley Medicago , poplar Medicago , pea  . First dStriga SL receptor, ShHTL7, has been proposed as a hyper-sensitive receptor in planta . ShHTL7 strigol   on the loop connecting αT1–αT2 helices (Physcomitrella patens (Pp), the ancestral D14 family proteins have an altered pocket size, due to a S166A substitution in the loop connecting αT2-αT3 , can harbor substitutions that alter ligand selectivity between paralogs or orthologs . Among tArabidopsis, shows that swapping three endogenous residues W153L, F157T, and G190T , are sufficient to switch the karrikin (KAR) receptor, KAI2, to an SL receptor  have been used to determine various intermediate states in ligand hydrolysis. Two studies by Yao et al. have proposed an intermediate state where the D-ring of SL becomes covalently linked between the catalytic serine at C5′ of SL) and the histidine (at C1′ of SL) , C and E5′ of SL Perception and hydrolysis of SLs has been considered to be the very first step of the much larger cascade of the signaling pathway. Three key proteins are required to transduce the SL signal: the SL receptor D14, the D3/MAX2 (DWARF 3/ MORE AUXILLARY BRANCHES 2) ubiquitin (Ub) ligase F-box protein, and the target for proteasomal degradation, the transcriptional co-repressor proteins D53/SMXLs (DWARF 53 / SUPRESSOR OF MAX2-LIKE) . These kThrough structural examinations in vitro, one model has been proposed wherein SL hydrolysis is required for complex formation . A crystD218A, that lacks enzymatic activity yet can complement the atd14 mutant phenotype in an SL-dependent manner. In this model, the active signaling state of D14 is triggered upon intact SL binding, but not by hydrolysis intermediate(s) or product(s). Therefore, it is proposed that the hydrolysis functions to deactivate the bioactive SLs postsignal transduction, but not for complex formation. Given the slow turnover of SL receptors compared to the proteasomal degradation rate of the target substrates in SL signaling, hydrolysis of SLs may not be required for D14-SL-D3-D53 complex formation (In another model of SL complex formation, hydrolysis is not required for signal transduction . This isormation .This has been further supported by other studies  centeredStriga infestation impacts Sub-Saharan Africa, the Middle East, and parts of Asia, particularly by parasitizing and decimating staple cereal crops such as maize and sorghum (Striga without a host, which will result in death of the obligate parasite (Striga before planting crops. Another strategy for crop protection is the development of antagonists that can target the Striga SL receptors to inhibit SL-dependent seed germination (A deeper understanding of SL biosynthesis, their catalysis, and the structure of their receptors has allowed for the development of targeted agonists and antagonists not only as research tools, but also for agricultural applications. Synthetic SLs have the potential to serve a more potent or specific function than natural SLs and could provide a precise control of SL-influenced processes without off-target effects . Hence,  sorghum . To thisparasite . This prmination .In addition, synthetic SLs can be utilized for precision farming to improve crops. Due to SLs’ role in inhibiting branching, SL antagonists can be used as yield stimulants by increasing the number of productive branches or tillers in crops such as grains . AlternaOverall, our understanding of the SL signaling pathway in the past decade has been increasingly advanced. In this review we highlight the central aspects of SL diversity, perception, and hydrolysis, however, there are many other facets and open questions that remain to be addressed. These include further elucidation of diversified SL biosynthesis, the precise molecular mechanism of the signal transduction cascade, the implications of SL crosstalk with other phytohormones, and the application of SLs in agriculture.


The vibration process applied to fresh concrete is an important link in the construction process, but the lack of effective monitoring and evaluation methods results in the quality of the vibration process being difficult to control and, therefore, the structural quality of the resulting concrete structures difficult to guarantee. In this paper, according to the sensitivity of internal vibrators to vibration acceleration changes under different vibration media, the vibration signals of vibrators in air, concrete mixtures, and reinforced concrete mixtures were collected experimentally. Based on a deep learning algorithm for load recognition of rotating machinery, a multi-scale convolution neural network combined with a self-attention feature fusion mechanism (SE-MCNN) was proposed for medium attribute recognition of concrete vibrators. The model can accurately classify and identify vibrator vibration signals under different working conditions with a recognition accuracy of up to 97%. According to the classification results of the model, the continuous working times of vibrators in different media can be further statistically divided, which provides a new method for accurate quantitative evaluation of the quality of the concrete vibration process. Reinforced concrete is the most used building material in the world today. The selection of appropriate raw materials and the use of appropriate technology can lead to strong building structures ,2,3. AmoHowever, insufficient vibration time causes problems such as honeycomb structure, voids, and exposed reinforcement in the concrete mixture, while too long a vibration time causes segregation and the uneven distribution of aggregates ,7. This Taking internal vibrator vibration construction as an example, the single vibration process of concrete mixtures is mainly divided into two stages: vibrator insertion and pull-out. The key to vibration process monitoring is to determine the stage in which the vibrator is working, and the duration of vibrator working in each stage is recorded to obtain the actual energy acting on the concrete mixture and quantify the quality of the concrete vibration processing. Burlingame  believedThe above studies were limited to the monitoring of the plain concrete vibration process. In actual engineering, concrete structures usually included steel mesh to improve mechanical properties , and theIn order to solve the above problems, this paper studied and determined the sensitivity of acceleration signals to high-frequency vibration, and a vibration medium identification method based on vibration acceleration signals of concrete vibrators was proposed. A multi-scale convolutional neural network (MCNN) was used to classify the vibrator acceleration signals, which can identify the stages of the vibration process and accurately classify the duration of the vibration process. This paper has provided a new basis for the quantitative evaluation of the quality of vibration processing and has helped to monitor potential construction quality problems.X is rod head displacement, mm; A is amplitude, mm; f is the frequency, Hz; and t is time, s.An internal vibrator is widely used and suitable for various types of concrete projects. According to structural composition and vibration mode, vibrators can be divided into pendulum-type and eccentric-type vibrators. The internal initiation structures of the two types of vibrators are shown in Vibration is a dynamic quantity, and simple harmonic vibration is the simplest form of vibration. In addition to vibration displacement, vibration velocity and acceleration are often used in vibration analysis . The vibE is vibration energy, J; C is a constant, depending on the stiffness and damping of concrete; m is the mass of concrete under vibration, kg; A is the maximum amplitude of concrete, m; f is vibration frequency, Hz; and t is the vibrating time, s.In the process of concrete vibration, the vibrator generated high-frequency vibration when working, producing energy transfer inside the concrete. According to the American Concrete Institute (ACI) research report ACI 309 , the forEquations (1) and (2) can be obtained as follows:ba is the acceleration of the distance between the shaken concrete and the vibrator b m, m/s2.By combining Equations (3) and (4), the vibration energy per unit time can be written as:ζ0 is boundary damping, ζm is material damping, and a0 is vibrator acceleration.According to the literature ,26, the According to Equations (5) and (6) and simplified constant terms, Equation (7) can be obtained:This represents the total damping of the vibration system.According to Equation (7), when the vibrator is unloaded, the damping is small and the vibrator acceleration reaches its peak. When the vibrator is inserted into the concrete, the damping increases, causing the vibrator acceleration to decrease. At the same time, the existence of steel bars in concrete presents obvious obstacles to the propagation of vibration energy, which leads to a further increase in the vibration system damping and the corresponding reduction in vibrator acceleration. According to the research of Alexander , He 28]28], and When the vibrator is working, it interacts with the mixture, and the properties of the mixture medium are also fed back to the vibrator and characterized by the change in vibration parameters. Therefore, for the analysis and study of the concrete vibration process, the vibrator acceleration is selected as the main parameter to reflect the vibrator’s working state more sensitively. Based on this, the method of accurately identifying the properties of the vibration medium is proposed.The mechanism between the vibrator and concrete in the process of concrete vibration was described in detail in The above device is used to measure the vibration acceleration data of 50 mm diameter vibrators of different brands (only differentiated by place of origin). The vibration signal is simply analyzed, and the main frequency of vibration is obtained through spectrum analysis. According to Equations (1) and (2), in simple harmonic vibration, the amplitude (maximum displacement X max) and acceleration can be interconverted and have the same frequency, which can reflect the amplitude of vibration. However, according to the measured parameters listed in When the vibrator vibrates in reinforced concrete, it is difficult to obtain accurate data for variable load vibration signal analysis by traditional vibration analysis methods such as amplitude analysis, frequency spectrum analysis, phase analysis, and waveform analysis in the face of heterogeneous media. The physical model and vibration signal identification method rely on expert experience, which cannot meet the real-time, fast, and accurate identification requirements of concrete vibration technology.With the development of sensor technology and information technology, the use of machine learning algorithms provides a new solution for mechanical intelligent fault diagnosis because of their powerful data processing ability. According to the depth of the network structure, machine learning can be divided into either shallow or deep learning . Deep leA concrete vibrator is a rotating machine that generates vibration through the internal rotor rotating at high speed. For the identification of the vibration medium in the vibration process, concrete as a vibration medium is not uniform, and the addition of reinforcement can make the load change, and a single-scale convolution kernel is not conducive to learning vibration signal characteristics under load change. If only a single-scale convolution kernel is used in a single-layer convolution layer, other features of different fineness are easily ignored. A multi-scale convolutional neural network (MCNN) can extract features of different fineness from complex signals, considering the multi-scale characteristics displayed by vibration signals . In ordeTherefore, a multi-scale convolutional neural network combined with a self-attention feature fusion mechanism (SE-MCNN) was proposed to identify the vibration medium. The self-attention mechanism was used for the weighted fusion of multi-scale features to obtain the final features that can accurately identify the medium type. The structure of the SE-MCNN model is shown in The media identification process based on SE-MCNN is shown in Step 1: Sensors are used to collect vibrator vibration signals under different vibration media, and the signals are truncated into individual samples and labeled.Step 2: Labeled samples are randomly divided into training sets and test sets. The training set is used to train the SE-MCNN network. The loss function of the model optimizes the model parameters through gradient backpropagation. After several iterations, model training is completed.Step 3: The test set is input into the trained SE-MCNN model to identify the type of vibration medium of unknown signals, and the recognition accuracy is calculated through known labels to verify the effectiveness of the model.In order to verify the feasibility of the above method and the accuracy of model recognition, an experiment was designed. The specific test scheme was as follows: Two wooden molds were made and vibration isolation sponges were pasted inside to eliminate the influence of the template-reflected vibration waves on the test. The structure size is shown in The test was divided into five groups according to the different vibrators. In each group of tests, the concrete in the mold is poured out and re-stirred after the end of the first vibration to ensure that the fluidity of the mixture in the second test was the same as that in the first test. During the test, each vibrator was vibrated in each medium for 30 s to ensure that sufficient vibration signals were collected for MCNN model training and verification.The vibration signals collected above were de-noised, then normalized and labeled. Finally, the dataset was divided into training and test sets according to a 7:3 ratio. This was used to train and test the SE-MCNN recognition model, and the recognition accuracy was 96.1%. According to the identification results of the vibrator vibration medium, the vibration process stage of the vibrator can be finely divided, which provided the basis for accurate quantitative evaluation of vibration quality.Vibration signals usually exhibit multi-scale characteristics. In the SE-MCNN model, convolution layers with different kernel sizes are used to extract the multi-scale information of the vibrator signals. However, the increasing number of scales not only brings more information to the model but also increases the complexity and training difficulty of the network, resulting in unnecessary calculation loss. In addition, with the deepening of the fault diagnosis model and the increase in convolutional modules, the extracted features become more separable. However, the deepening of the model will inevitably complicate the modeling and easily lead to overfitting.In this paper, the scale and depth of the model framework were determined to be 3 after several iterations of training and optimization. Detailed model parameters are shown in In order to evaluate the recognition ability of the network after training, Due to the time-sensitivity of the concrete vibration process, many researchers ,43,44,45Concrete was poured into the two wooden molds described in W is the accumulated energy of vibration and it is the duration of vibration in each stage.The above vibration signals were input into the trained SE-MCNN model for recognition and classification. The model divided the batch size of vibration signals into 500. As the sampling frequency was 20,000 Hz, the duration of each group of signal points was 0.025 s. The classification results are listed in Thus, the cumulative vibration energy can be calculated according to the amplitude of the real-time acceleration signal and the vibration duration of each stage after classification. Combined with the energy threshold , the quaBased on the characteristics of the vibration acceleration signal for comprehensive and effective monitoring of high-frequency vibration, this paper studies the ability of acceleration to characterize the medium attribute information of concrete in the process of vibration and determines the direct correlation and sensitivity of vibrator acceleration signals to the identification and analysis of the medium under vibration.Through the introduction of a vibration signal analysis method, a multi-scale convolutional neural network combined with a self-attention feature fusion mechanism (SE-MCNN) was proposed to identify the vibration medium, which can accurately identify and classify the vibrator “pull-out”, “insertion into plain concrete”, “insertion into reinforced concrete” three main vibration process stages. The identification accuracy of this method was up to 97.0% and the stability was good.According to the recognition and classification results of model vibration signals, the complete vibration construction process is finely divided into different stages, and the actual working duration of vibrators at each stage is calculated using statistical signal time-domain information. The vibration duration at different stages is combined with the vibration energy formula to calculate the parameters of the actual vibration energy absorbed by the concrete at each stage. Combined with the threshold parameters of vibration energy, a precise quantitative evaluation method for concrete vibration quality is proposed.The application of the model and method can not only monitor the working state of the vibrator but also provide quantitative statistical parameters of the quality of the vibration processing for practical engineering, plugging a gap in field vibration quality evaluation. If the proposed method is combined with wireless communication, accurate real-time quality monitoring and feedback of the vibration process can be provided for on-site construction quality supervisors to ensure high-quality construction utilizing concrete vibration.This paper classified and identified vibrator acceleration signals and finely divided the vibrating process into different stages. The following conclusions can be drawn and prospects identified:


Antibiotics are administered to livestock at subtherapeutic levels to promote growth, and their degradation in manure is slow. High antibiotic concentrations can inhibit bacterial activity. Livestock excretes antibiotics via feces and urine, leading to their accumulation in manure. This can result in the propagation of antibiotic-resistant bacteria and antibiotic resistance genes (ARGs). Anaerobic digestion (AD) manure treatment technologies are gaining popularity due to their ability to mitigate organic matter pollution and pathogens, and produce methane-rich biogas as renewable energy. AD is influenced by multiple factors, including temperature, pH, total solids (TS), substrate type, organic loading rate (OLR), hydraulic retention time (HRT), intermediate substrates, and pre-treatments. Temperature plays a critical role, and thermophilic AD has been found to be more effective in reducing ARGs in manure compared to mesophilic AD, as evidenced by numerous studies. This review paper investigates the fundamental principles of process parameters affecting the degradation of ARGs in anaerobic digestion. The management of waste to mitigate antibiotic resistance in microorganisms presents a significant challenge, highlighting the need for effective waste management technologies. As the prevalence of antibiotic resistance continues to rise, urgent implementation of effective treatment strategies is necessary. The worldwide livestock industry is predicted to increase, and as a result, the use rate of therapeutic antibiotics in the livestock industry is expected to exceed 100,000 tons by 2030 per year . The amoThe use of antibiotics in livestock production is primarily non-therapeutic, serving to promote growth and prevent disease . These aAntibiotics are not just used in clinical settings to treat diseases in people. Antibiotics are also used in the livestock husbandry, administered in subtherapeutic doses in concentrated animal feed to promote feed conversion efficiency, growth and disease prevention . Antibio(1)Polyether antibiotic: monensin, narasin, lasalocid, and salinomycin;(2)Fluorochinolones: enrofloxacin, ofloxacin, norfloxacin, danofloxacin;(3)Sulphonamides: sulphadimidine, sulphamethoxazole, trimethoprim, sulphadoxine;(4)Macrolides: azithromycin, clarithromycin, clindamycin, erythromycin, roxithromycin, spiramycin, tylosin, and vancomycin;(5)Tetracyclines: chlortetracycline, doxycycline, oxytetracycline, and tetracycline;(6)b-Lactams, penicillins: amoxicillin, ampicillin, oxacillin, piperacillin, benzylpenicillin, cloxacilin, dicloxacilin, flucloxacillin, methicillin, phenoxymethylcillin, mezlocillin, and nafcillin.Livestock are treated therapeutically and subtherapeutically with many antibiotic classes, , includiIn Shandong, China, 126 pig manure samples taken from 21 animal-feeding operations showed tetracyclines (85–97%), sulphonamides (52%), and macrolides (5%) ; the sam−1 or L−1 but can exceed 200 mg·kg−1 or L−1 [−1 or L−1 [−1 [The concentrations of antibiotics in manure usually range from 1 to 10 mg·kg1 or L−1 , while i1 or L−1 . The acc L−1 [−1 . As indiThe measurement of antibiotics in complex matrices such as biological sludge and soil is not standardized, making comparisons between studies difficult. The majority of research does not even describe the manure storage and management practices prior to sampling when reporting results. The liquid/solid antibiotic partitioning affects the outcomes. In contrast to overall concentration, sampling leaching manure reveals the percentage of antibiotics in the solid phase. During storage, the majority of antibiotic residues in manure combine to form stable compounds with soluble organics. Some antibiotics become mobile when manure is applied to fields and contaminate the soil and groundwater in the area. The features of the antibiotic, the soil, and the hydrological effects all play a role in this. Understanding the rates of biodegradation and the potency of degraded antibiotics in various situations requires more investigation .ARGs give resistance to nine significant families of antibiotics, including fluoroquinolone, chloramphenicol, and amphenicol (FCA), tetracyclines (tet), sulfonamides (sul), β-lactams (bla), and macrolide-lincosamide-streptogramin B (MLSB). The ARG classes that are most frequently found in cattle manure are tet, sul, erm, fca, and bla . Van BoeGlobally, the livestock business utilizes around 60,000 tons of antibiotics per year, such for basic veterinarian care, prophylaxis, and growth promotion is a significant contributor of ARGs to the environment . VariousSalmonella, E. coli, and Listeria, can be present in biowaste, and proper handling and treatment of this waste is crucial to prevent the spread of pathogens and protect public health. Pathogens present in food, water, or air can pose a risk to human health when proper waste management and treatment practices are not followed. Factors such as the increase in food waste, animal manure, and other biowaste, combined with inadequate pathogen inactivation during waste management, can contribute to the spread of biosafety-related diseases [If pathogens are not effectively inactivated prior to the use of manure in crop cultivation or discharge into the environment, there is a risk of foodborne illness due to the potential contamination of crops or water sources. Common foodborne pathogens, such as diseases . Livestodiseases . Manure diseases .p < 0.01). The study included 63 investigations of fecal coliform inactivation, 51 investigations of E. coli inactivation, and 38 investigations of salmonella inactivation. More data were available for mesophilic AD processes than for either ambient or thermophilic AD processes, indicating a preference for mesophilic systems. Understanding and quantifying the effect of different parameters on pathogen inactivation is critical for balancing the operating conditions of pathogen inactivation and bio-methane production.To achieve effective pathogen inactivation while producing bio-methane, it is crucial to comprehend and measure the impact of different operational conditions on the inactivation of pathogens. Ma et al.  performeThe microbiome is largely shaped by the temperature, but the microbial populations in the digester may have an impact on the proliferation of ARGs . StudiesIn AD, acidogenic bacteria and methanogenic bacteria interact syntrophically. However, their growth kinetics, nutrition, and optimal environment factors have distinctions between them. Researchers have proposed the acidogenic phase followed by the methanogenic phase (two-stage AD) to give the best growth conditions for each microbial community . HoweverThe performance of ADs and the digester microbiota depend on solids residence time (SRT), according to numerous research studies. Only a small number of studies, meanwhile, specifically looked into how SRTs affected how ARGs turned out. Ma et al.  looked aThe AD with total solids ≥ 15% is called solid or dry AD. In addition to having better volumetric methane production than wet AD, residues of dry AD are frequently applied to agriculture land without dewatering procedures . AccordiFor AD to function properly, the carbon-to-nitrogen ratio, toxicity, pH, moisture, and trace element levels must all be optimized . Co-digeSince the topic of antibiotic use and ARGs are still relatively new, there is still a need to establish a comprehensive body of existing knowledge corresponding to diverse manure treatment procedures and feedstock characteristics. Future research and current understanding are anticipated to contribute to the development of better treatment techniques that can potentially lessen the load of ARGs that waste materials could potentially release into the environment. It is critical to develop standardized techniques for assessing the impact, degradation, and fate of various antibiotics and their metabolites during anaerobic digestion in order to reliably, compare data from different studies. It is necessary to concentrate on kinetic and metabolic modeling and simulation of inhibition, recovery, and adaptive processes in order to evaluate the impact of culture matrices, solid content, and the composition of the organic manure fraction on the de-radiation dynamic of various antibiotics during anaerobic digestion. Research is particularly essential to ascertain how to most accurately predict the relative relevance of physical and chemical vs. living organism breakdown processes for different types of antibiotics. It is important to understand and quantify the impacts of manure fractioning on the anaerobic breakdown of antibiotics in different manure classes, antibiotics kinds, reactor designs, and operations. For design purposes, it is vital to investigate how various anaerobic reactor designs and operations affect the kinetic data for antibiotic parent chemicals and their metabolites. To avoid problems with operations caused by the harmful effects of high concentrations of antibiotics on anaerobic digestion, it is important to look into how to process staging and adjustment affect things. The possibility of psychrophilic anaerobic digestion of different livestock manures for the removal of antibiotics and antibiotic-resistant microbes has not been studied.The influence of operational parameters  and environmental variables  on the production of ARB and ARGs during wastewater treatment.The identification of novel mechanisms of ARG development as well as the determination of the dominant processes of ARG development .Future research should focus on the wider spectrum of ARBs and ARGs resistance, including fluoroquinolone, ertapenem, and levofloxacin resistance.Antibiotic resistance in microorganisms is a difficult problem that necessitates advancements in livestock waste treatment procedures. Antibiotic resistance among infections is increasing the demand for efficient treatment methods. The following are some of the knowledge gaps and research needs for the future:In conclusion, it was evident that optimizing various process parameters could successfully eliminate ARGs during AD. Previous research has identified certain fundamental factors that influence the proliferation of ARGs in AD. However, the interactions between different process factors often led to contradictions in prior findings. Therefore, further research is required to fully comprehend how the interplay between various process factors impacts the proliferation of ARGs in AD. Additionally, continued development of conductive additives and pre-treatment procedures is crucial to provide dual solutions for better biogas generation and ARG management, ensuring economic sustainability of AD while also decreasing the danger of digestate for land application.


Electronic continuous surveillance databases are ideal for monitoring antibiotic use (ABU) in hospitalised patients for antibiotic stewardship programmes (ASP). However, such databases are scarce in low-resource settings. Point prevalence surveys (PPS) are viable alternatives. This report describes ABU and identifies ASP implementation improvement areas in Limpopo Province, South Africa.V was used to assess the strength of these associations.This cross-sectional descriptive study extracted patient-level ABU data from patients’ files using a modified global PPS tool. Data were collected between September and November 2021 at five regional hospitals in Limpopo Province, South Africa. All patients in the wards before 8 a.m. on study days with an antibiotic prescription were included. Antibiotic use was stratified by Anatomic Therapeutic Chemical and Access, Watch, Reserve classifications and presented as frequencies and proportions with 95% confidence intervals (CI). Associations between categorical variables were assessed using the chi-square test. Cramér’s p = 0.005, Cramér’s V = 0.2). Lower respiratory tract infection , skin and soft tissue infections (SST) , and obstetrics and gynaecology prophylaxis  were the common diagnoses for antibiotic prescriptions. The three most prescribed antibiotic classes were imidazoles , third-generation cephalosporins  and combination penicillin . Access antibiotics accounted for 70.2% (292/416) of prescriptions and Watch antibiotics for 29.6% (123/416) . Reasons for prescribing and treatment plans were documented in 64.9% (270/416) (95% CI 60.3–69.5) and 21.4% (89/416) (95% CI 17.3–25.3) of prescriptions, respectively.Of 804 inpatients surveyed, 261 (32.5%) (95% CI 29.2–35.7) were prescribed 416 antibiotics, 137 were female (52.5%) and 198 adults (75.9%). One hundred and twenty-two (46.7%) patients received one antibiotic, 47.5% (124/261) received two, and 5.7% (15/261) received three or more antibiotics. The intensive care units had a higher ABU  compared to medical  and surgical  wards (The study serves as a baseline for ABU surveillance at the five regional hospitals in Limpopo Province. Lack of documentation indicates poor prescribing practices; ASP should address gaps by deploying evidence-based, multifaceted and stepwise interventions.The online version contains supplementary material available at 10.1186/s13756-023-01306-z. The global increase and variation in antibiotic use (ABU) , 2 driveIncreasing ABU necessitates measures to ensure optimal use and monitoring , 3, 16. An electronic continuous surveillance database will be ideal for collecting ABU surveillance data to guide evidenced-based ASP interventions; however, such databases are scarce in low-resource settings , 21. WitThere is evidence of ASP in the South African public and private sectors , 28–36; A cross-sectional descriptive research design was used to collect data from hospitalised patients' files from the Limpopo Province's five regional hospitals  between 07 September and 16 November 2021. Regional hospitals in the South African public sector context are secondary care facilities that operate on a 24-h basis . Each ofA paper-based PPS data collection tool was developed using the global PPS and WHO-PPS as the basis , 45, witThe study population consisted of all patients admitted to the hospital ward before 8 a.m. on the day of the PPS with at least one systemic antibiotic prescribed. To prevent denominator inaccuracies, all patients admitted after 8 a.m. on the day of the survey were excluded. Due to the unstable and continual transfer of patients to the wards or other hospitals, patients admitted to the emergency care department were excluded.On the antibiotic level, this study included antibacterials for systemic use  and antiprotozoals  used as antibacterial agents. Topical antibiotics, antimycobacterials, antivirals and antifungals were excluded. All wards at the five study centres were included and categorised according to their activities: medical, surgical, and intensive care units. All outpatient departments were excluded.The files of hospitalised patients with an antibiotic prescription were used as a data source for patient-level demographic and antibiotic prescription data. The demographic data collected for each patient on antibiotic therapy comprised age, weight and sex. For each antibiotic prescribed, the dose, route , prescriber type , diagnosis, indication, and treatment start date were collected. The diagnosis of the prescribed antibiotics was collected by applying standardised categories adopted from the global PPS protocol , 45. TheA set of prescribing quality indicators was also collected for each prescribed antibiotic: antibiotic written in the generic name (“yes/no”), prescribing reason documented in notes (“yes/no”), South African standard treatment guidelines (STGs) adherence (“yes/no/not assessable/no information”), antibiotic treatment plans documented (“yes/no”) and whether prescribed treatment was empirical or targeted. Additional patient care indicators adapted from a global consensus study  were alsTo minimise denominator complexity caused by new admissions and discharges, ward data collection was completed on the same day. We visited surgical wards the day after elective surgical interventions were scheduled to collect data about prophylaxis in the previous 24 h. Data from each hospital had to be collected within one week and during weekdays.®) version 28. Patient demographics and hospital characteristics were reported as frequencies and proportions stratified by sex , age (adults (above 18 years)/paediatric (18 years and younger), healthcare-associated infections risk factors, bed occupancy rate, and ward type. In this study, ABU was determined at the patient level  and at the antibiotic level  and was stratified by ward activity, source of infection, diagnosis, ATC and AWaRe classifications. The overall, mono or combination therapy and ward activity ABUs were determined by dividing the number of patients who received an antibiotic by the total number of eligible patients (admitted). ABU by ward activity was categorised as medical, surgical and intensive care units. The antibiotic per patient ratio was determined by dividing the total number of prescribed antibiotics by the number of patients with at least one prescribed antibiotic on survey days.Data were analysed using Statistical Package for the Social Sciences  and diagnoses/site of infection . To determine commonly prescribed antibiotics, individual antibiotic agents were ranked from the highest to the lowest according to their prescribing frequency and assigned their respective ATC level 4 and AWaRe classifications. ABU frequencies and proportions were also described according to the AWaRe classification and stratified by hospital, ward activity, age, prescriber type, source of infection and diagnosis. At an antibiotic level, overall antibiotic prescribing quality indicators were described using frequencies and proportions of the "yes" choice. The "yes, no, unknown, not applicable" choices were used to determine patient-level indicators of patient care quality using frequency and proportions.p-value of 0.05 for statistical significance to assess the relationship between categorical variables . For practical significance interpretation, Cramér's V ≥ 0.6 was deemed a strong association, 0.3–0.5 moderate, 0.1–0.2 weak and < 0.1 no association.For statistical inferences, ABU, prescribing and patient care indicators were represented as frequencies and proportions with 95% confidence intervals. We used the Chi-square test with a In the five hospitals, 804 of the 1463 available beds were occupied, resulting in a bed occupancy rate of 55.0%. In 2020, the five hospitals had 340 660 inpatient days. Two-hundred and sixty-one (261) of the 804 hospitalised patients satisfied the study's inclusion criteria (inpatients with at least one antibiotic prescription) (Table Baseline demographic data are shown in Table p = 0.000), with a weak association between the two variables (Cramér’s V = 0.2) (Table Table 2) Table . In termn = 13) were indicated for healthcare-acquired infection. The most prevalent antibiotic classes in SAP were extended-spectrum penicillins  and imidazole derivatives , whereas the majority  of sulphonamides-trimethoprim combinations were prescribed for medical prophylaxis , followed by healthcare-acquired infection  and surgical prophylaxis  , 3GC 20.7%, 86/416) and combination penicillins 18.5%, 79/416) , with a weak association between the variables (Cramér’s V = 0.2). Paediatric patients were prescribed a higher proportion of Access antibiotics , while adult patients were prescribed a higher proportion of Watch antibiotics . The relationships between age groups and the prescribing prevalence of Access and Watch antibiotics were statistically significant (p = 0.000), with a strong association between the variables (Cramér’s V = 1.0).The antibiotic prescribing pattern according to the WHO AWaRe classification is summarised in Table Indicators for antibiotic prescribing and the quality of patient care are presented in Table Diagnostic specimens were taken in only 11.9% (31/261) (95% CI 8.0–15.8) of the patients, whereas results were available in 45.2% (14/31) (95% CI 27.6–62.7) of the cases. However, 95.7% (250/261) (95% CI 93.5–98.2) of patients were current on antibiotic therapy, totalling 41 missing doses. Thirty-six of 261 patients (13.8%) (95% CI 9.6–18.0) were identified for probable intravenous to oral switch therapy, whereas 17 patients (6.5%) (95% CI 3.5–9.5) were identified for renal dose adjustment, and six patients (2.5%) (95% CI 0.5–4.1) were identified for therapeutic drug monitoring.This study used an adapted PPS tool to describe ABU in five public sector regional hospitals in Limpopo Province, South Africa, as a baseline for future comparison. Antibiotics were prescribed to approximately one-third (32.5%) of patients, which is similar to earlier South African public sector studies (31.0% and 33.6%) , 40. TheOne hundred and twenty-two (46.7%) patients received one antibiotic, 124 (47.5%) received two, and 15 (5.7%) received three or more antibiotics. Carefully chosen combination therapy is useful, and reporting it may indicate ASP intervention areas , 38–40.In our study, the intensive care unit ABU was the highest (68.6%), followed by medical (31.5%) and surgical (28.5%) wards. A similar trend was observed in a Western Cape Province tertiary hospital . The intSimilar to global trends , the mosOverall LRTIs, SST, obstetrics and gynaecology prophylaxis were the most common diagnoses for antibiotic prescriptions. This was comparable to previous South African studies , 39. GloStaphylococcus aureus and Streptococcus species [Globally, including in South Africa and Limpopo Province, traffic accidents, self-harm, and interpersonal violence are the leading causes of injury to SST , 54, 55. species . In this species , 56.Imidazoles were the frequently prescribed antibiotic class, followed by 3GCs and combination penicillins, correlating with global trends , 8. The Klebsiella pneumonia predominance in South Africa [Acinetobacter baumannii in South Africa [The five commonly prescribed antibiotic agents were metronidazole, ceftriaxone, amoxicillin with an enzyme inhibitor, ampicillin and gentamycin, which is consistent with earlier South African studies –40. The h Africa . Meropenh Africa ), which h Africa .According to the WHO's 2021 AWaRe classification , 70.2% oAntibiotic prescribing quality indicators are important for identifying the appropriateness of prescribing and establishing and monitoring the effectiveness of ASP interventions . ParenteClostridium difficile infection; hence, an area for persuasive prospective audit and feedback ASP interventions to reduce SAP[In our study, there were 59 prescriptions for SAP, of which 34.5% were prolonged (> 24 h), which is lower than findings from early South African adult (73.2%) and paediatric 66.7%) studies , 40. Proeduce SAP, 65, 66..7% studiThe adherence to antibiotic prescribing to clinical guidelines is associated with improved patient outcomes, including decreased mortality, length of stay, improved quality and lower costs in the direction of targeted prescribing , 68. TheThe documentation of antibiotic prescribing reasons was 64.9%, which is lower than the global benchmark (76.9%)  and findIn our study, the proportion of antibiotic prescriptions targeting specific pathogen(s) was 3.4%, lower than global levels (9.8% to 22.3%) , 8, 26, Our study revealed additional areas for clinical ASP interventions, including intravenous to oral switch therapy, renal-dose adjustment, and therapeutic drug monitoring, which are considered advanced and costly ASP interventions . FinallyThe following limitations were noted in this study. A PPS is limited by its cross-sectional study design since data were collected over a short period; this approach did not account for seasonal variation in diseases and antibiotic prescriptions. A more accurate estimate of inpatient ABU may have been obtained by conducting this survey over several periods using serial or a seasonal repeated PPS. This study was conducted in regional (secondary) hospitals, and its findings cannot be generalised to other levels of care  as global and national evidence suggests ABU heterogeneity by hospital type , 38, 40.The study serves as a baseline for ABU surveillance at the five regional hospitals in Limpopo Province. Lack of documentation indicates poor prescribing practices; ASP should address gaps by deploying evidence-based, multifaceted and stepwise interventions. , 73.Additional file 1. Table S1: Antibiotic use among inpatients at five regional hospitals in Limpopo Province, stratified by patient age.