This paper presents the compression failure process of basalt fiber concrete with recycled aggregate and analyzes the main factors of basalt fiber and recycled aggregate affecting the compressive strength of recycled concrete. The damage mechanism of recycled aggregate concrete is analyzed by the acoustic emission technique. With the method of acoustic emission (AE) b-value analysis, the evolution and failure process of recycled concrete from the initial defect microcrack formation to the macroscopic crack is studied. Based on the AE clustering analysis method, the damage state of recycled concrete under load grade is investigated. Finally, the failure mode of recycled concrete is explored according to the RA-AF correlation method. The results show that when the concrete reaches the curing age, the strength grade of basalt fiber regenerated coarse aggregate concrete is the highest. The basalt fiber increases the strength of regenerated fine concrete by 4.5% and the strength of coarse concrete by 5%, and reduces the strength of fully recycled aggregate concrete by 6.7%. The b-value divides concrete into three stages: initial damage, stable development of internal damage, and internal damage. The variation of AE energy, count, and event number is related to AE activity and crack growth rate. Matrix cracking is the main damage state of concrete, which is greatly affected by the strength of cement mortar. The load grade of fiber cracking in fully recycled aggregate, recycled fine aggregate, and recycled coarse aggregate concrete is 65, 90, and 85%, respectively. Basalt fiber increases the tensile failure event point of recycled concrete and delays the cracking of recycled concrete under compression. When the load grades of fully recycled fiber, recycled fine aggregate fiber, and recycled coarse aggregate fiber concrete are 65–95, 90–100, and 85–100%, respectively, the tensile failure activity increases. Since the reform and opening up, China has made remarkable achievements in infrastructure construction. However, about 600 million tons of construction waste is also generated in China every year, of which concrete waste accounts for 30–35% . How to Although the failure mechanism of recycled aggregate is similar to that of natural aggregate, there are great differences in their physical properties. The density of recycled aggregate is low, and old mortar and microcracks are commonly adhered to the surface ,3. The lAcoustic emission (AE) technology has been adopted by many structural tests, and the test principle is shown in Abouhussien and Hassan used the AE location method to study the internal damage of concrete and revealed the importance of AE characteristic parameters to detect concrete construction . WatanabScholars and experts have done a lot of research on the AE characteristics of concrete and fiber reinforced concrete, and have achieved corresponding results. However, research into the damage mechanism of basalt fiber recycled concrete remains lacking. In this paper, based on the existing research, using AE non-destructive testing as the technical means, and the aggregate collocation method and basalt fiber as the research variables, the design ratio of one natural concrete and six kinds of recycled concrete is designed. According to b-value, cluster analysis, and RA-AF, the evolution mechanism, damage state, and failure mode of concrete cracks are studied in depth by using the test method of AE to detect the compressive concrete. It is expected to provide a theoretical basis and guidance for engineering practice. 3 and 2401 kg/m3, the bulk density was 1484 kg/m3 and 1630 kg/m3, and the porosity was 46.8% and 43.6%, respectively. The water absorption rate of recycled coarse aggregate was 1.89%, the mud content of recycled fine aggregate was 6.22%, and the volume ratio of chopped basalt fiber was 0.1%. The concrete water-cement ratio was 0.3, and the design strength was C50. The curing temperature was 20 ± 2 °C, the humidity was more than 95%, and the curing period was 28 days. The physical performance indexes are shown in The cementitious materials used in the test were P.O42.5 ordinary Portland cement and type I high calcium fly ash. Physical performance indexes are shown in In the test, the proportion of materials in each part of the cement mortar and the continuous grading of coarse aggregate were kept unchanged, and the aggregate mix method and basalt were taken as the research variables. One kind of natural concrete mix proportion and six kinds of recycled aggregate concrete mix proportions were designed. In the reference concrete, the coarse and fine aggregates were natural aggregates, and the test number was recorded as J1. In fully recycled concrete and fiber fully recycled concrete, the aggregate was all recycled aggregate, and the test number was recorded as J2, J3. In the recycled/fiber recycled fine aggregate concrete, the fine aggregate was crushed slag, the coarse aggregate was natural, and the test number was recorded as J4, J5. In the recycled/fiber recycled coarse aggregate concrete, the coarse aggregate was recycled coarse aggregate, the fine aggregate was natural river sand, and the test number was recorded as J6, J7. The concrete mix design is shown in The size of the concrete test piece was 150 mm × 150 mm × 150 mm. Three parallel test pieces were poured in each proportion. The test started when the curing age of the test piece reached 28 days. The AE test instrument was a Micro-II-Express 8-channel AE system and a R15I-AST longitudinal wave probe produced by Physical Acoustics of the United States. The probe size was 30 mmOD × 30 mmH, and AE real-time monitoring was maintained during the whole loading process. The arrangement of the AE probe and an experimental diagram is shown in The factors influencing the compressive strength of concrete at 3, 7, and 28 days are discussed in According to the results of the table, when the concrete age is 3, 7, and 28 days, the strength of fully recycled concrete is reduced by 8, 9.2, and 6.7%, the strength of recycled fine aggregate concrete is increased by 1.9, 2.7, and 4.5%, and the strength of recycled coarse aggregate concrete is increased by 5.4, 1.7, and 5.0%. Basalt fiber improves the compressive strength of recycled fine and coarse aggregate concrete, but fails to improve the strength grade of fully recycled concrete. The reason is, in the fully recycled concrete, the water absorption of coarse and fine aggregate is large, and the sand ratio of fine aggregate is also relatively large. The cement paste content of the concrete is also lower than the other two recycled concrete proportions, and the fiber is wrapped by the cement paste to improve the mortar interface effect of the concrete, which leads to the concrete strength grade being reduced by the concrete mixed with basalt fiber. In conclusion, the best ratio of strength grade is J1, J2, and J7.The stress-strain curve of concrete is shown in fc, the elastic strain energy gathered in the testing machine is greater than the strain energy absorbed by the specimen, which leads to the sudden destruction of the specimen, and the descending section of the measured specimen is not obvious. In this test, the concrete has high compressive strength and good compactness performance, so in the measured stress-strain curve of concrete, the linear elastic stage is relatively long, while the failure and failure decline stage is relatively short and steep.Compared with ordinary strength concrete, the stress-strain curve of concrete has some differences because the higher the concrete strength grade, the longer the linear elastic characteristics, high strength mortar, and aggregates, which affect the concrete bondability, compactness, and create fewer microcracks. The final damage is often aggregate damage, due to brittleness, and is the most obvious steep decline period. The second reason is that this test adopts the stress loading method as the ordinary testing machine. When the concrete reaches the axial compressive strength A represents the amplitude of the AE signal, Amin represents the minimum amplitude of AE at each time, n is the number of event points at each time period, and e is the natural constant.Exploring the crack evolution process of concrete materials when they are damaged by compression can effectively detect and provide feedback on the actual damage process of concrete. Because the elastic wave is similar to the seismic wave in the damage of concrete materials, the b-value analysis in the seismic field is cited to analyze the crack development process when the concrete is damaged under compression. The maximum likelihood estimation method (MLE)  is selecAccording to the variation law of AE energy and b-value, along with load grade, the damage and destruction process of concrete is divided into three stages. The stage division is shown in Phase I is the initial damage stage of the material. In this stage, the growth of microcracks and micropores is relatively small. The influence of the material density and friction between the surface of the test piece and the pressure bearing iron plate of the press have a sharp increase in AE energy. In Phase Ⅱ, the internal damage stage of the material develops steadily, and the concrete microcracks develop slowly, in which AE value size b fluctuates smoothly, and the AE energy surge is not obvious. Phase Ⅲ is the material internal damage stage. In this stage, without the fiber doping ratio of concrete, the AE b-value is mainly a downward trend, and the internal microcracks of the specimen quickly become macrocracks. In the concrete proportioning of basalt fiber, b-value or volatility will increase. This is because fiber fracture and the fracture of microcracks occur simultaneously, thus increasing the proportion of microcracks and causing a change in b-value. In this phase, the AE energy appears to surge. The specimen internally releases a huge amount of strain energy until the specimen loses effectiveness and is destroyed.When the b-value appears at an inflection point with obvious rise or fall, it means there has been a transformation of concrete in the damage stage. In the mix ratio of non-fiber concrete, the initial defect is large, the number of microcracks is in the majority, and the b-value tends to increase as a whole. In the proportion of concrete mixed with fiber, the fiber reduces the initial defects of the concrete, there are fewer microcracks, and the variation rule of b-value tends to decrease.It needs to be pointed out here that in the concrete mix ratio of J6 and J7, there were many original defects in the recycled coarse aggregate, which continued to be damaged in the whole loading process and generate AE signals. The AE energy in this concrete changed without obvious regularity, so the concrete could not be divided into stages for analysis.According to When the load level is 10–60%, the growth rate of the count, AE energy, and number of event points decrease, the rise time decreases, the AE activity gradually decreases from the initial maximum, and the microcrack growth rate slows down. When the load level is 60–70%, the increase of count, AE energy, and number of event points is relatively stable, AE activity is stable, and microcrack expansion is stable. When the load level is 70–90%, the increase of count, AE energy, and number of event points is rapid, and the crack rapidly expands. When the load level is 90–100%, the increase of count, AE energy, and number of event points is low; when the rise time increases, the microcracks gather to form macrocracks, the AE activity decreases, and at this time, the concrete fails. In J3, when the load level is 10–50% and 60–80%, the count, AE energy, number of event points, and rise time increase evenly, the AE activity is stable, and the microcracks expand steadily. When the load level is 50–60%, the count, AE energy, and number of event points increase rapidly, the AE phenomenon is active, and the microcracks expand rapidly. When the load level is 80–100%, the increase rate of the count, AE energy, and number of event points decreases, the AE activity decreases, and concrete damage occurs. Through the comparative analysis of J2 and J3, after the basalt fiber is added, the cracking of fully recycled concrete is stable in the early stage, but in the late damage process, the peak value rises earlier, and the failure of concrete occurs earlier.In J4, the load level of the count, AE energy, number of event points, and increasing speed of rise time is 30–80%. At this stage, the microcracks appear quickly, and the AE activity is enhanced. The load grades of count, AE energy, number of event points, and rise time decrease are 10–30% and 80–100%. In this stage, the growth rate of microcracks decreases, and the AE activity decreases. In the 80–100% stage, microcracks gradually gather to form macrocracks, and the concrete is damaged. The change rule of J5 and J3 is similar, but the load levels of ring count, AE energy, and the number of event points that increase steadily, increase faster, and slow down are 20–60%, 80–90%, 10–20% and 90–100%, respectively. According to the comparative analysis of J4 and J5, doping basalt fiber reduces the AE activity of the early concrete under compression, but in the later failure stage, the fiber failure causes the AE phenomenon to be active and delays the rise time of the peak value, which inhibits the damage and failure of the recycled fine aggregate concrete.During the whole process of J6 compression, the count, AE energy, and the number of event points increase steadily, the load level is 90–100%, and the rise time increases; J7 has the same development trend as J3 and J5, and the load levels of the count, AE energy, and the number of event points are 30–70%, 10–30%, 70–90%, and 90–100%, respectively. Compared with J6, J7 lags behind the rise time of the peak value, which shows that fiber plays a role in delaying the failure of recycled coarse aggregate concrete.n variables X1n~X, and the n variables are divided into X1K~X class. Let iN be the number of variables in class ii X, and im be the mean of these variables. The distance formula adopts European distance, and the specific operation is as follows:m1k~m;Randomly and evenly select k observation samples as the initial clustering center x is divided into class P.If:Recalculate each cluster center:im no longer changes.Repeat steps (2) and (3) until the The k-means clustering algorithm is the most classical clustering method. The basic idea of the algorithm is to cluster with k points in space as the center and classify the objects closest to them. Through the iterative method, the values of each clustering center are updated successively until the best clustering results are obtained. Suppose the sample data are The amplitude and peak frequency of AE are used as the parameters of cluster analysis, and the system clustering method in IBM SPSS Statistics 24 is adopted to obtain the optimal clustering number according to the relationship between the clustering correlation coefficient and the number of categories. The first obvious inflection point appears, and the curve gradually flattens, so this point can be selected as the optimal clustering number. According to According to the relevant literature ,37,38,39According to the results of cluster analysis, matrix cracking is wide value low peak frequency, interface debonding is medium value medium peak frequency, and fiber cracking is narrow value high peak frequency. Because there are many microcracks and holes on the surface of recycled aggregate, there are many uneven impurities along with old mortar with low strength on the surface. Thus, the recycled aggregate is prone to serious damage under pressure, resulting in high-frequency AE event points. Therefore, the peak frequency of recycled aggregate concrete is higher than that of natural concrete J1.In the mixed proportion of recycled concrete, basalt fiber leads with the lower peak frequency of concrete matrix cracking and interface debonding because fiber improves the aggregate interface and cement mortar matrix and reduces the occurrence of high-frequency event points. When the concrete is going to be damaged, the fiber cracking effect is obvious, resulting in high-frequency event points, so the peak frequency is high. The peak frequency of recycled concrete can be the boundary point between fiber cracking and interface debonding. According to the clustering results, it can be seen that the limit peak frequency of fiber cracking and interface debonding in the recycled aggregate concrete is 250–300 kHz; the limit peak frequency of fiber cracking and interface debonding in the recycled fine aggregate concrete is 180–200 kHz; the peak frequency of 400 kHz in the recycled coarse aggregate concrete is the boundary point of interface debonding and fiber cracking.By comparing the damage state of concrete caused by the coarse aggregate, fine aggregate, and basalt fiber, the main influencing factors of concrete compression damaged state are explored.RA and AF in the AE characteristic parameters is related to the failure type of concrete materials, which can effectively identify the failure type of concrete materials.The failure modes of concrete under compression include tensile failure and shear failure. The correlation between RA is defined as the ratio of rising time to amplitude in μs/V, as shown in Formula (2), and AF is defined as the ratio of ringing count to duration in kHz, as shown in Formula (3). There are differences between RA and AF values in shear damage and tensile damage. In tensile damage mode, due to the release of energy, the related AF values will be higher. Conversely, RA values associated with shear damage patterns are higher due to longer rise time and duration. The unit of amplitude in the original AE data of this test is (dB), which needs to be converted to (V). The conversion formula is shown in Formula (4).RA-AF values into two categories. The concrete failure activity is closely related to the AE event point. In In the data analysis, the k-means clustering analysis method in IBM SPSS Statistics 24 is used to divide The number of AE event points of natural concrete is more than that of recycled concrete because, in natural concrete, there are fewer initial defects and fewer micro cracks on the surface of natural aggregate than that on the surface of recycled aggregate; moreover, the aggregate strength is higher. As such, the interface strength of aggregate mortar is greater than recycled aggregate concrete, which eventually leads to the increase of concrete compression duration and more AE event points. After doping basalt fiber, the shear tensile failure event points in recycled concrete increase obviously, because fiber delays the transverse and longitudinal cracking of the concrete, and more AE event points are needed to counteract the effect of fiber on concrete cracking. At the same time, fiber cracking is also accompanied by the occurrence of event points, which eventually leads to an increase of AE cumulative event points.As shown in In this paper, the RA-AF value of concrete is divided into two clusters by cluster analysis method. (1)The compressive strength of concrete was greatly affected by the method of aggregate collocation. The strength of J7 was the highest, and that of J4 was the lowest. When the concrete reached the curing age, the strength of full recycled concrete decreased by 6.7%, and the strength of recycled fine aggregate concrete and recycled aggregate concrete increased by 4.5% and 5.0%, respectively. The best ratios of strength grade were J1, J2, and J7, all of which were over 62 MPa.(2)Based on the b-value analysis of acoustic emission, the transformation process of concrete microcracks and macrocracks was explored from the mechanism. At the same time, combined with the analysis of AE energy, the concrete damage was divided into three stages: the initial damage of the material, the stable development of internal damage of the material, and the damage to the internal damage of the material. Basalt fiber could effectively inhibit the crack growth rate in the early stage of recycled concrete. In the later stage of failure, fiber led to the early failure of recycled concrete but delayed the failure of recycled fine/coarse aggregate concrete.(3)There were two damage states of matrix cracking and interface debonding in common natural/recycled concrete and three damage states of matrix cracking, interface debonding, and fiber cracking in fiber recycled concrete. Matrix cracking, the main damage state of concrete, was wide value low peak frequency, the interface debonding was medium value medium peak frequency, and the fiber cracking was narrow value high peak frequency.(4)In fully recycled/recycled fine/recycled coarse/aggregate concrete, the peak frequencies of the boundary point between fiber cracking and interface debonding were 250~300, 180~200, and 400 kHz, respectively, and the nodes of fiber cracking were 65%, 90%, and 85% of the load grade, respectively. The better the mortar strength was, the larger the ratio of matrix cracking damage was. The higher the amount of natural coarse aggregate, the greater the ratio of interface damage. The greater the rate of fiber cracking was, the greater the rate of interface debonding damage of recycled coarse and fine aggregate concrete.(5)When the load levels were 65–95%, 90–100%, and 85–100%, basalt fiber improved the tensile failure activity of recycled/recycled fine aggregate/recycled coarse aggregate concrete. The addition of basalt fiber reduced the shear failure of recycled fine and coarse aggregate concrete, and when the load grade reached 70%, the shear failure of fully recycled concrete was enhanced by basalt fiber.In this paper, the AE characteristic parameters of recycled concrete in the process of compression were collected by the test method of monitoring concrete compression in the whole process of AE, and the influence factors of concrete compressive strength were explored by taking aggregate mix mode and fiber as research variables. The AE b-value method was used to analyze the crack evolution process of recycled concrete in the process of compression, and AE cluster analysis was used to analyze the main damage state of recycled concrete in the process of compression. Finally, the AE RA-AF correlation method was used to explore the damage mode of concrete in the process of damage. The following conclusions were drawn:


Staphylococcus aureus biofilms. However, the emergence of rifampin resistance strongly limits its use. Combinatorial therapy of antibiotics and bacteriophages may represent a strategy to overcome the resistance. Here, we evaluated the activity of staphylococcal bacteriophage Sb-1 in combination with different antibiotics against the biofilms of 10 rifampin-resistant S. aureus clinical strains, including MRSA and MSSA. S. aureus biofilms formed on porous glass beads were exposed to antibiotics alone or combined with Sb-1 simultaneously or staggered (first Sb-1 for 24 h followed by antibiotic). Recovered bacteria were detected by measuring growth-related heat production at 37°C  and the biofilm eradication was assessed by sonication of beads and plating of the resulting sonication fluid. Minimum biofilm eradication concentration (MBEC) was defined as the lowest concentration of antibiotic required to kill all adherent bacteria, resulting in absence of growth after plating the sonication fluid. Tested antibiotics presented high MBEC values when administered alone . The simultaneous or staggered combination of Sb-1 with daptomycin showed the highest activity against all MRSA biofilms, whereas the exposure to Sb-1 with vancomycin showed no improved anti-biofilm activity. Staggered administration of Sb-1 and flucloxacillin, cefazolin, or fosfomycin improved the antibiofilm activity in four out of six MSSA, whereas simultaneous exposure exhibited similar or lesser synergy. In conclusion, the combinatorial effect of Sb-1 and antibiotics enabled to eradicate rifampin-resistant S. aureus biofilms in vitro.Rifampin plays a crucial role in the treatment of staphylococcal implant-associated infection, as it is the only antibiotic capable of eradicating  Staphylococcus aureus is one of the most common organisms causing implant-associated infections, such as periprosthetic joint infections (PJI), fracture-related infections (FRI), or spinal implant-associated infections  and vancomycin, daptomycin, or fosfomycin against methicillin-resistant S. aureus (MRSA). In addition, rifampin is added to treat staphylococcal infections in patients who undergo debridement with retention or implant re-implantation in one- or two-stage exchange  clinical strains (four MRSA and six MSSA) and the MRSA ATCC 43300 and MSSA ATCC 29213 laboratory strains.Phage Sb-1 is one of the best characterized and fully sequenced lytic  Georgia . Its gen Georgia . Moreovepatients . HoweverCC 43300 . In thisTen RRSA clinical isolates collected between 2015 and 2019 were included in this study. The clinical isolates were used from the biobank collection, which is part of the prospective institutional PJI cohort. The study was approved by the institutional ethical committee (EA1/040/14) and was conducted in accordance with the most recent iteration of the Declaration of Helsinki. According to the ethical approval, participants’ informed consent was waived, and all data were pseudonymized. Moreover, MRSA ATCC 43300 and MSSA ATCC 29213 laboratory standard strains were used in this study. Bacteria were stored at −80°C using a cryovial bead preservation system . The staphylococcal phage Sb-1 was supplied by the Eliava Institute  and stored at 4°C.Vancomycin , daptomycin , fosfomycin , gentamicin injectable solution , flucloxacillin , cefazolin , and rifampin  were provided from the respective manufacturers.5 CFU/ml was used. Two fold serial dilutions of each antibiotic were prepared in sterile polystyrene round-bottom tubes to a final volume of 1 ml in inoculated medium and incubated for 24 h at 37°C. The MIC was defined as the lowest concentration of antibiotic that completely inhibited visible growth. BHI broth medium was supplemented with calcium chloride (40 μg/ml) and glucose 6-phosphate (25 μg/ml) when testing daptomycin and fosfomycin, respectively. All experiments were performed in triplicates.MIC for each antibiotic was determined by the broth macrodilution assay (BMD) in brain heart infusion broth . An inoculum of approximately 5 × 10The bacterial susceptibility to Sb-1 was evaluated in terms of efficacy of plating (EOP) as previously described . The EOP6 PFU/ml Sb-1 phage and sub-MBBC concentrations of antibiotics. By simultaneous application, biofilms were exposed to antibiotics and Sb-1 during 24 h at 37°C. By staggered application, biofilms were exposed first to Sb-1 for 24 h and then to antibiotic for a further 24 h at 37°C. Evaluation of a staggered application of antibiotic followed by phage was discarded based on the unfavorable results observed in previous studies , as previously reported . Briefly studies .For samples where no heat production was detected, the complete biofilm eradication was determined by CFU counting of the sonicated beads after the microcalorimetric assay, and the minimum biofilm-eradicating concentration (MBEC) was defined as the lowest concentration of antibiotic required to kill all adherent bacteria, resulting in absence of any growth after plating of the sonication fluid (detection limit: <20 CFU/ml) . All expphage/MBECalone ratio, where MBECphage corresponds to the obtained MBEC value of an antibiotic tested in combination with the phage, and the MBECalone represents the obtained MBEC value of the same antibiotic when tested alone. Synergy was defined as a ratio ≤ 0.25, which correlated with a reduction of more than 2xMBECalone. We combined and tested only concentrations of antibiotic that could reveal a synergistic effect with Sb-1 based on the MBEC values of the single antibiotic to be combined .The effect of phage–antibiotic combinations against biofilms was assessed as in a previous study , determiS. aureus was determined by BMD and by plating of sonication fluid, respectively. The obtained MIC and MBEC values are summarized in The antimicrobial activity of antibiotics against planktonic and biofilm Both ATCC strains were susceptible to all antibiotics according to the EUCAST breakpoints , except The antibiofilm activity of different antibiotics against the ATCC strains was evaluated by monitoring for 48 h the heat produced by biofilm bacteria still viable on the beads (after the exposure to the antibiotics) re-inoculated in fresh medium . On the S. aureus strains were susceptible to Sb-1 infection, showing EOP ratios ranging from 0.3 to 0.9 , in three strains (75%) when exposure to Sb-1/gentamicin staggered combination and in two (50%) strains exposed to staggered Sb1/fosfomycin or to simultaneous Sb-1/gentamicin combination. No synergistic effect was observed when the biofilm of tested clinical strains was exposed to either simultaneous or staggered Sb-1/vancomycin combination, in contrast to the finding with MRSA ATCC 43300 strain.Among six MSSA isolates, synergistic effect was observed in four strains (67%) after staggered exposure to Sb-1/flucloxacillin or to Sb-1/cefazolin, and in three strains (50%) with simultaneous Sb-1/flucloxacillin combination. Only staggered but not simultaneous Sb-1/fosfomycin combination revealed a synergistic effect against four strains (67%), whereas simultaneous or staggered Sb-1/gentamicin combination showed synergism against three strains (50%). None of the tested simultaneous or staggered phage/antibiotic combinations presented an improvement in the antimicrobial activity compared to the action of each antimicrobial agent alone against MSSA5 biofilm.Moreover, no synergism was found with Sb-1 and rifampin combination against MRSA or MSSA .S. aureus orthopedic implant-associated infections  were also observed with staggered administration of Sb-1 with fosfomycin. Fosfomycin has been shown to act synergistically with other antibiotics against biofilms of different bacterial species, including MRSA, in part probably because of its broad-spectrum bactericidal activity (Low MBECactivity . In addiactivity .Previous studies revealed synergistic effects by combining phage with an antibiotic for which the bacteria strain was resistant . In our in vitro. Our work highlights that findings obtained testing ATCC strains may differ from the outcome with clinical isolates, but also among the different strains, implying that selecting an appropriate phage–antibiotic combinatorial therapy will be highly dependent on the strain causing the infection as well as on the specific antibiofilm efficacy of the phage, more than its lytic spectrum. Moreover, there is substantial evidence that many antibiotics can interfere with phage infection activity—especially at concentrations exceeding measured minimum inhibitory concentrations—and thus with phage primary pharmacodynamic properties. Hence, further preclinical and clinical studies are essential to support the development of phage/antibiotic combination therapy with particular isolates. Factors that point toward a more personalized approach for the successful treatment of antibiotic-resistant implant-associated infections.When trying to draw conclusions or make clinical extrapolations, it is important to consider the small number of tested strains in our study. We aimed to provide the first original data on the combinatorial effect of Sb-1 and different antibiotics to eradicate RRSA biofilms The original contributions presented in the study are included in the article/LW and TT performed the experiments with the contribution of MG. MG, LW, and TT analyzed the data. MG and TT drafted the manuscript with the contribution of LW and AT. All authors conceived and designed the experiments and revised and approved the final version of this manuscript.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


BRAF、HER2、MET、RET等少见驱动基因改变肺癌患者的靶向药物的选择仍然较少。近年来免疫检查点抑制剂在肺癌治疗中取得了一定的疗效，但因为少见驱动基因突变的肺癌患者本身样本量少，开展大规模临床随机对照试验尚存在一定的困难，目前此类患者接受免疫检查点抑制剂治疗的疗效情况仍不明确。本文将对目前已掌握的免疫检查点抑制剂治疗BRAF、HER2、MET、RET等少见驱动基因改变肺癌患者的临床研究结果进行综述，以期在一定程度上为临床工作提供一些依据和参考。驱动基因的发现及针对驱动基因的靶向治疗已显著提高了肺癌患者的生存质量和时间，但目前对于


Is emphasizing improved communication, teamwork, and clinical best practices associated with reductions in antibiotic use across a large number of US hospitals?Clostridioides difficile infection rates, including critical access hospitals, rural hospitals, and hospitals without infectious diseases specialists. The greatest reduction in antibiotic use was observed in sites most actively engaged in the Safety Program.In this quality improvement study of 402 hospitals, implementation of the Agency for Healthcare Research and Quality Safety Program was associated with a reduction in antibiotic use and hospital-onset The Agency for Healthcare Research and Quality Safety Program resources, now publicly available, may be useful in teaching frontline clinicians to become stewards of their antibiotic use. Regulatory agencies and professional organizations recommend antibiotic stewardship programs (ASPs) in US hospitals. The optimal approach to establish robust, sustainable ASPs across diverse hospitals is unknown.To assess whether the Agency for Healthcare Research and Quality Safety Program for Improving Antibiotic Use is associated with reductions in antibiotic use across US hospitals.A pragmatic quality improvement program was conducted and evaluated over a 1-year period in US hospitals. A total of 437 hospitals were enrolled. The study was conducted from December 1, 2017, to November 30, 2018. Data analysis was performed from March 1 to October 31, 2019.The Safety Program assisted hospitals with establishing ASPs and worked with frontline clinicians to improve their antibiotic decision-making. All clinical staff  were encouraged to participate. Seventeen webinars occurred over 12 months, accompanied by additional durable educational content. Topics focused on establishing ASPs, the science of safety, improving teamwork and communication, and best practices for the diagnosis and management of infectious processes.Clostridioides difficile laboratory-identified events per 10 000 PD were a secondary outcome.The primary outcome was overall antibiotic use (days of antibiotic therapy [DOT] per 1000 patient days [PD]) comparing the beginning (January-February 2018) and end (November-December 2018) of the Safety Program. Data analysis occurred using linear mixed models with random hospital unit effects. Antibiotic use from 614 hospitals in the Premier Healthcare Database from the same period was analyzed to evaluate contemporary US antibiotic trends. Quarterly hospital-onset P < .01). Antibiotic use decreased by 30.3 DOT per 1000 PD . Similar changes in antibiotic use were not observed in the Premier Healthcare Database. The incidence rate of hospital-onset C difficile laboratory-identified events decreased by 19.5% .Of the 437 hospitals enrolled, 402 (92%) remained in the program until its completion, including 28 (7%) academic medical centers, 122 (30%) midlevel teaching hospitals, 167 (42%) community hospitals, and 85 (21%) critical access hospitals. Adherence to key components of ASPs  improved from 8% to 74% over the 1-year period (The Agency for Healthcare Research and Quality Safety Program appeared to enable diverse hospitals to establish ASPs and teach frontline clinicians to self-steward their antibiotic use. Safety Program content is publicly available. This quality improvement study examines the use of the Agency for Healthcare Research and Quality Safety Program for antibiotic stewardship across US hospitals. Antibiotic stewardship programs are limited in their resources to provide real-time assistance with all antibiotics prescribed in a hospital, leading to lost opportunities to improve antibiotic prescribing. Moreover, teaching clinicians to incorporate stewardship concepts into their clinical practice supports the durability of stewardship principles in daily patient care. In response to drawbacks of the traditional top-down ASP approach, the Agency for Healthcare Research and Quality (AHRQ) established the AHRQ Safety Program for Improving Antibiotic Use .Antibiotic stewardship programs (ASPs) are being established across the US in response to the negative consequences associated with antibiotic overuse.4 We discuss the structure, implementation, and outcomes of the Safety Program in 402 hospitals across the US.In addition to assisting hospitals with establishing sustainable ASPs, an overarching goal of the Safety Program is to provide frontline clinicians with tools to incorporate stewardship principles into routine decision-making by underscoring the importance of communication around antibiotic prescribing and equipping frontline clinicians with best practices in the diagnosis and treatment of common infectious processes. The underpinnings of the Safety Program are largely drawn from the Comprehensive Unit-Based Safety Program method, an approach to make health care safer by emphasizing improved teamwork, clinical best practices, and the science of safety.SQUIRE) reporting guideline.5The Safety Program was conducted from December 1, 2017, to November 30, 2018, and data analysis was performed from March 1 to October 31, 2019. Any acute care facility  in the US was eligible to participate, with a predetermined maximum enrollment of 500 sites. Each site identified a medical and pharmacy ASP director. All clinical staff were encouraged to be involved in the Safety Program, including physicians, pharmacists, physician assistants, nurse practitioners, and nurses, and each individual was provided unique credentials to access content. Continuing education credits were provided. This study followed the Standards for Quality Improvement Reporting Excellence  per month per participating unit to the Safety Program website beginning in March 2018 , and access to a Safety Program email address for additional questions. An external quality improvement expert well-versed in large-scale implementation programs in hospital settings6 Before the onset of the Safety Program, 2 of us (P.D.T. and S.E.C.) performed a systematic review to determine key components of successful ASPs  events per 10 000 PD for the participating units as a proxy for C difficile infection.9 Individualized quarterly data reports were provided to each site to assess progress over the course of the Safety Program and compare similar units and hospital types  per 1000 patient days (PD). Monthly antibiotic use data were submitted for 50 intravenous or oral antibiotics from January 1 to December 31, 2018, beginning the month following the onset of the Safety Program  with the January-February baseline. Changes in overall DOT per 1000 PD during the intervention based on select hospital and unit characteristics were also estimated.To investigate whether there was an association between high engagement in the Safety Program and greater reduction in antibiotic use, we performed a stratified analysis comparing changes in antibiotic use between units that completed an average of 10 or more TARFs per month  with those that completed less than 10 TARFs per month. In addition, a subgroup analysis of changes in fluoroquinolone  DOT per 1000 PD from the beginning to the end of the Safety Program were compared, because a large focus of the Safety Program was reducing unnecessary fluoroquinolone use.C difficile LabID events, with the additional assumption that the number of events followed a Poisson distribution, given that C difficile LabID events are relatively rare. Incidence rate ratios described changes in C difficile infection rates over time.A linear mixed model with random hospital unit effects was used to assess changes in overall antibiotic use from baseline (January-February 2018) to the end of the Safety Program (November-December 2018), as well as from baseline to each bimonthly period. A generalized linear model with random hospital unit effects was used to estimate changes from quarter 1 (January 2018-March 2018) to each of the subsequent 3 quarters for hospital-onset 10 Hospitals that provided days of antibiotic therapy per 1000 PD for all antibiotics included in the Safety Program and for all months from January to December 2018 were included in the Premier Healthcare Database cohort. Entropy balancing was used to ensure a similar distribution of academic and nonacademic hospitals as well as intensive care unit and general wards in the Premier Healthcare Database cohort in an attempt to mirror the Safety Program. Hospitals that participated in the Safety Program were excluded from the Premier Healthcare Database cohort. In total, 1711 units located in 614 hospitals in the Premier Healthcare Database were included in the analysis. Antibiotic use data from January-February to November-December and from baseline to each subsequent bimonthly period in the Premier Healthcare Database cohort were analyzed using an identical approach as antibiotic use data from Safety Program sites. The presumed residual heterogeneity of the Premier Healthcare Database cohort compared with the Safety Program cohort , precluded direct comparisons between the Safety Program and Premier Healthcare Database cohort antibiotic use data. Data analyses were conducted using SAS, version 9.4 (SAS Institute Inc). Findings were considered significant at P < .05 with 2-sided testing.Antibiotic use data from the Premier Healthcare Database, a database containing drug use information for approximately one-fourth of hospitalizations in the US, were analyzed to provide information on temporal antibiotic changes during the period of the Safety Program.P < .01).Overall, 437 hospitals enrolled in the AHRQ Safety Program; of these, 402 (92%) hospitals, which included 476 units, remained in the Safety Program until its completion. The eFigure in the The AHRQ Safety Program website had 11 650 unique users. There was a median of 561 attendees per webinar ; on average, 511 participants (91%) described the content as excellent and 45 participants (8%) described the content as very good, as reported through blinded surveys at the conclusion of each webinar. There was an average of 470 downloads per item from the Safety Program website (eTable in the P = .008). Evaluating bimonthly antibiotic use, the largest decrease occurred between January-February and March-April (P = .009).Comparing January-February with November-December 2018, antibiotic use decreased from 900.7 to 870.4 DOT per 1000 PD . For 276 units that completed an average of 10 or more TARFs per month, antibiotic use decreased from 912 to 877 DOT per 1000 PD; −34.2 DOT (P < .01), suggesting that units more actively engaged in the Safety Program were more likely to see a decrease in antibiotic use.Changes in antibiotic use between high engagement units and units with low to average engagement were compared. For 200 units that completed an average of less than 10 TARFs per month, antibiotic use decreased from 861 to 845 DOT per 1000 PD between January-February and November-December 2018; −15.6 DOT (P = .62) from 648 in January-February to 639 DOT per 1000 PD in November-December for the Premier Healthcare Database sample. Furthermore, when comparing January-February with March-April, the period of the largest decrease in antibiotic use in the Safety Program, overall antibiotic use in the Premier Healthcare Database cohort increased from 648 to 660 DOT per 1000 PD.In contrast to the Safety Program, there were no significant reductions in antibiotic use observed in the Premier Healthcare Database cohort when comparing January-February with November-December 2018. Overall antibiotic DOT per 1000 PD decreased by −9.0 .The number of hospital-onset C difficile infection across 402 US hospitals, comparing the beginning and end of the 1-year program, with the greatest reductions in units highly engaged in the Safety Program. A large proportion of hospitals were underresourced. Forty-one percent of sites had 100 hospital beds or less, including 85 critical access hospitals, 43% did not have access to infectious diseases specialists, and 35% self-described as rural hospitals.The AHRQ Safety Program for Improving Antibiotic Use is the largest hospital antibiotic stewardship quality improvement initiative in the US to date. It contributed to a decrease in overall antibiotic use and 12 Despite these barriers, we observed a decrease in antibiotic use in the initial year of the Safety Program. The Safety Program simultaneously provided comprehensive training to ASP leads as well as frontline clinicians and included live webinars as well as durable educational material, content to increase buy-in for stewardship principles , and training on collating and feeding-back antibiotic use data, all of which expedited the establishment and augmentation of ASPs. Hospitals with nascent or no ASPs are encouraged to access the Toolkit Implementation Guide for Acute Care Antibiotic Stewardship Programs to emulate the approaches used in the Safety Program  the influence of seasonal changes, (2) expected secular variations, or (3) inaccuracies with submitted antibiotic use data, each described in further detail below. Because the Safety Program was a quality improvement initiative and not a research study, we limited data collection to information necessary to improve local antibiotic prescribing practices. We did not want to discourage resource-limited hospitals , traditionally excluded from large quality improvement initiatives, from participating by requesting data that would be overly onerous to obtain. As such, we did not collect antibiotic use data in the year before the Safety Program to serve as a control group.29 More specifically, antibiotic use increases in the winter months. Suda and colleagues24 investigated antibiotic prescriptions in the US over a 5-year period and reported that they were almost 25% higher in winter months (defined as the first and last quarters of each year) compared with summer months. Similarly, an evaluation of antibiotic consumption in British Columbia over a 4-year period revealed that antibiotic use during quarters 1 and 4 were 22% greater than in quarters 2 and 3.29 Although seasonal changes may have influenced the high antibiotic prescribing rate observed in January-February in the Safety Program, seasonality was unlikely to have factored prominently into our findings, given that both the beginning  and end  of the Safety Program occurred in winter months. Moreover, antibiotic use data from the Premier Healthcare Database indicate that antibiotic use was similar in January-February and November-December 2018. In addition, we do not have evidence from the literature suggesting that antibiotic use in January-February is generally higher than November-December.33Seasonal changes are an important determinant of antibiotic prescribing rates.34 an upsurge in the lay and scientific literature focusing on antibiotic-associated harm,41 an enhanced evidence base supporting shorter durations of therapy than historically prescribed,43 and recommendations for minimizing prescribing for common indications, such as perioperative prophylaxis44 or asymptomatic bacteriuria,45 antibiotic use may have decreased over time in participating hospitals independent of the Safety Program.Decreased antibiotic use during the course of the Safety Program may have reflected secular changes. With a growing understanding of the need for judicious antibiotic prescribing due to public health campaigns,To explore whether Safety Program antibiotic use changes represented secular trends, we obtained 2018 data from the Premier Healthcare Database. In contrast to the Safety Program, no significant reductions in antibiotic use were observed from January-February to November-December in the Premier Healthcare Database cohort. Moreover, no significant reductions in antibiotic use were observed between January-February and March-April in the Premier Healthcare Database cohort, the period with the sharpest decline in antibiotic use in the Safety Program cohort. Comparisons between the Safety Program and the Premier Healthcare Database cohort should be interpreted cautiously because some important information was not available for the hospitals contributing data to the Premier Healthcare Database cohort. Important missing information included antibiotic stewardship infrastructure, ongoing quality improvement activities, and access to infectious diseases specialists. Furthermore, critical access hospitals were not represented in the Premier Healthcare Database cohort. These limitations notwithstanding, antibiotic use data from the Premier Healthcare Database cohort do not suggest temporal trends indicating a reduction in antibiotic use over the 2018 calendar year.46 evaluated antibiotic use across more than 300 US hospitals using the Truven Health MarketScan Hospital Drug Database from 2006 to 2012 and did not observe decreases in overall antibiotic use during this 7-year period. Goodman and colleagues47 performed an almost identical analytic approach as Baggs et al, using the Premier Healthcare Database from 2016 to 2017 to investigate antibiotic use data across 576 US hospitals and found total antibiotic consumption was not substantially different from antibiotic use data published almost a decade earlier.46 These data do not provide strong support for the narrative that antibiotic use was expected to naturally decline over the 2018 calendar year. In addition, with the recommendation of The Surviving Sepsis Campaign Bundle: 2018 Update that all elements of the Severe Sepsis/Septic Shock Early Management Bundle be initiated within 1 hour of emergency department presentation, it is plausible that antibiotic use would be anticipated to gradually increase during 2018.48We explored the literature to understand whether antibiotic use has followed a decreasing trend over the past several years. Baggs and colleaguesThe study has limitations. In addition to the aforementioned discussion of the lack of a control group and seasonality concerns, we cannot discount the possibility of inaccuracies with antibiotic data collection by participating sites. Our lack of access to protected health information precluded our ability to ensure the integrity of antibiotic use data submitted from hospitals or an evaluation of appropriate antibiotic use. Nonetheless, rigorous steps were followed to maximize the likelihood of valid data submission as previously described.C. difficile infection rates across 402 US hospitals. The Centers for Medicare & Medicaid Services required that hospitals—including critical access hospitals—implement ASP by March 30, 2020, as a condition of participation.49 Hospitals that had not yet established ASPs likely included large numbers of resource-limited hospitals, similar to many that participated in the Safety Program. The Safety Program was able to demonstrate that establishing ASPs and training frontline clinicians may improve antibiotic use, even in hospitals without infectious diseases–trained physicians or pharmacists. In fact, we were able to train clinicians—often staff pharmacists—to become stewardship leaders in their facilities. Because all content from the Safety Program is publicly available,6 use of Safety Program resources provides opportunities for hospitals across the US seeking to improve antibiotic use by establishing or strengthening existing ASPs and teaching frontline clinicians to become self-stewards of their antibiotic use.The AHRQ Safety Program for Improving Antibiotic Use was associated with a significant decrease in overall antibiotic use and hospital-onset


To study the seismic performance of embedded polyvinyl chloride (PVC) pipe confined reinforced high-strength concrete (PVC-RHC) columns, five specimens are designed for cyclic loading test, which include three PVC-RHC column specimens, an embedded circle steel tube confined reinforced high-strength concrete (CST-RHC) column specimen, and a reinforced high-strength concrete (RHC) column specimen. The failure mechanism and morphology are revealed by experiments. The influences of PVC pipe diameter, axial compression ratio, and concrete strength on seismic performance indexes are analyzed. The research results indicate thhe following: all specimens displayed shear baroclinic failure. Compared with RHC specimens, the hysteretic curves of the PVC-RHC specimen and CST-RHC specimen were fuller; furthermore, their energy dissipation capacity, deformation, and ductility were more beneficial. With the increase of the diameter–length ratio and axial pressure, the energy dissipation capacity and deformation capacity of PVC-RHC specimens decreased. The shear bearing capacity of the PVC-RHC specimen calculated with “concrete structure design code” (GB 50010-2010) was smaller than the test results by 25%, showing an excessive safety margin. Thus, according to the failure mechanism of the PVC-RHC specimen, a new calculation formula of shear bearing capacity is deduced, which is in good agreement with the experimental results. Owing to the advantages of high strength, little deformation, and good durability, reinforced high-strength concrete (RHC) is widely used in long-span, heavy-duty, and high-rise buildings ,2,3. HowLarge relevant universities and research institutes have also carried out some tests on PVC pipe-constrained concrete. Through the axial compression test of a PVC plastic pipe confined concrete column, C.E.Kurt found that the PVC plastic pipe improved the mechanical properties of core concrete by providing a constraining force . It is pHowever, the relevant research of the PVC-RHC has not been reported in the literature at present. In order to reveal its failure mechanism and seismic performance, the low-cyclic loading test of the PVC-RHC is carried out. It is expected to provide new technical support for the further promotion and application of high-strength concrete.Five short-column specimens were designed for the low-cyclic loading test, including three PVC-RHC specimens (PVC-RHC-1−PVC-RHC-3), a circle steel tube (CST)-RHC specimen, and an RHC specimen. The PVC pipe diameter , axial compression ratio , and concrete strength  were considered as the main parameters. The parameters of the specimens are shown in All specimens have the same external dimensions. The cross-section of the test section was 200 × 200 mm with the height of 300 mm. The size of the loading end was 200 × 300 × 400 mm, which was embedded with four M24 high-strength bolts for connection with the actuator. The size of the fixed end was 900 × 220 × 360 mm, where the horizontal longitudinal bar was 14 mm HRB400 , and the stirrup was 8 mm HRB335 with spacing of 50 mm. The longitudinal rebar and stirrup were HRB400 and HRB335, respectively, with the ratio of 2.543% and 1.273%, respectively. The cross-section and reinforcement situation of specimens are shown in Ordinary portland cement of 42.5 MPa.Medium coarse river sand.Crushed rock aggregate, which had a maximum size of 20 mm and a minimum size of 5 mm.The main constituent materials are described as follows:fcu represents the cube compressive strength of concrete. fy and fu represent the yield strength and ultimate strength, respectively. Es is the elastic modulus. The physical properties determined on steel and the PVC pipe were obtained using the MTS  electro-hydraulic servo testing machine  co. LTD, Shanghai, China), as shown in In the test, high-strength concrete was stirred by mixer in the laboratory on the spot. AF-C polycarboxylic acid superplasticizer  was adopted in the tests. The column members and the corresponding concrete test block strength tests are performed at the same time. The average compressive strength of the high-strength concrete cube and the concrete mix proportion are shown in A cantilever-type pseudo-static loading device was used in the test. In the loading process, the vertical load was applied and kept constant through the hydraulic jack, and then the horizontal repeated load was applied by the electro-hydraulic servo actuator of 500 kN. The loading process includes the load-controlled phase and displacement-controlled phase, as shown in The horizontal load and displacement of the cylinder top are collected automatically by the electro-hydraulic servo actuator control system. The strain of concrete, steel bar, and PVC pipe is collected by Strain Collection DH3820 . The arrangement of strain gauges is shown in The cracks and failure modes are shown in Furthermore, this test component mainly consists of three parts—the external reinforced concrete, the pipe, and the concrete core pillar inside the pipe. In destructing, the external reinforced concrete part is cracked first. Then, the surface concrete falls off and the reinforcement is exposed. As the apparent change of the inner steel pipe (PVC pipe) and the core column cannot be observed directly during the test, it can be seen through the analysis of the test points and the numerical simulation verification analysis of the seismic performance test of the high-strength concrete column restrained with the PVC pipe by the Abaqus method. After the external reinforced concrete part is out of work, with the progress of the load, for the PVC pipe core column, when the PVC pipe reaches the limit, the internal high-strength concrete has not reached the strength limit. For the steel pipe core column, the steel pipe reaches first. After yielding, the internal concrete was crushed and the test specimen reached its limit state.It can be seen from the failure morphology of the specimens that, except for the reinforced high-strength concrete column specimens restrained by ordinary stirrup, the final failure morphology of all the specimens presented diagonal cross oblique cracks. Because of the existence of the internal core of confined concrete columns with steel tubes, after cracking, the reinforced high-strength concrete column specimens confined with pipes formed many thin bending cracks and oblique cracks, which can prevent or reduce the appearance of main cracks and avoid the situation of forming main cracks quickly in the reinforced high-strength concrete columns confined with ordinary stirrup constraints, and ductility and energy dissipation capacity are obviously improved.Compared with the reinforced high-strength concrete specimens, the hysteretic curves of the embedded PVC pipe and steel tube confined reinforced high-strength concrete specimens were fuller and the deformation capacity was stronger, among which the embedded steel tube specimen appeared the most significant, indicating that the measures of the embedded PVC pipe can enhance the energy dissipation capacity and deformation capacity of the reinforced high-strength concrete short columns.Compared with PVC-RHC-1, PVC-RHC-3 with a smaller diameter of the PVC pipe had a fuller hysteresis curve, stronger energy dissipation capacity, and slower intensity decay in the later stage. It can be seen that the seismic energy dissipation and deformation capacity of the specimen are significantly affected by the PVC pipe diameter. It is also very important to consider a reasonable area ratio of the PVC pipe concrete core column in the design stage. Under the condition of similar strength concrete, the area enveloped by hysteretic curve of PVC-RHC-2 of a higher axial compression ratio was larger than that of the specimen PVC-RHC-1, but the bearing capacity was less stable and the deformation ability was weakened in the later period; with the increase of shear span ratio, the hysteresis curve of the specimen was longer and narrower, the energy dissipation capacity was weakened, and the ultimate deformation was small, indicating that the seismic deformation ability of specimen decreased with the increase of the axial compression ratio and shear span ratio.After connecting the peak points of each level of loading in the same direction, the skeleton curves of each specimen were obtained as shown in As can be seen from the figure, the ratio of peak load to yield load of all specimens was between 1.16 and 1.58, with a high safety reserve. For the reinforced high strength concrete column specimens restrained by ordinary stirrup, after reaching the peak load, the bearing capacity stability was weaker, the descending section was steep, and the deformation ability was bad. After embedding pipes, it can be seen that the peak load of the reinforced high-strength concrete column specimens PVC-RHC-1 and CST-RHC restrained with the embedded PVC pipe and steel tube increased by 8.0% and 10.6%, respectively, compared with that of the RHC specimen. Moreover, the descending section of the skeleton curve was more gentle, the limit displacement increased, and the ductility performance was improved. In particular, the late deformation performance of the specimens embedded with the steel pipe was improved more significantly.Comparing the skeleton curve of the specimen PVC-RHC-1 with that of the specimen PVC-RHC-3, it can be seen that, with the increase of the PVC pipe diameter, the initial stiffness of the specimen also increased, but the peak load did not increase much, about 1.5%. After the peak value, it dropped steeply, the strength attenuation was accelerated, the stiffness degraded obviously, and the deformation ability became worse in the later stage. This may be because the wall of the PVC pipe was smooth and the bond strength of concrete was small. When the PVC pipe diameter increased, the thickness of the concrete cover accordingly became thin, which likely produced the bond slip effect between the PVC pipe and concrete. The two parts of concrete inside and outside the PVC pipes could not work well, causing the earlier specimen cracking, but with a larger area of large diameter constraint of the core concrete, the initial stiffness was larger. As the horizontal load increased to the peak, the lateral deformation of the core concrete increased sharply inside the tubes, owing to the extrusion of the PVC pipe wall, the expending effect of the peripheral expansion concrete protective layer was obvious, leading to thinner prismatic concrete block convex drum crushing to fall off, which caused the bearing capacity to decrease and fail. In the experiment, it can also be seen that, in the PVC-RHC-1 specimen, the concrete dropped largely.n increased from 0.25 to 0.45, the specimen peak load increased by 22.6%, but the stiffness degradation and intensity attenuation was accelerated, the limit deformation was reduced, and ductility became worse. This is because, when improving the axial compression ratio appropriately, it made it slow and limited the internal micro cohere emergence and development of cracks, improved the aggregate interlocking, strengthened the bolt pin effect of longitudinal reinforcement, and raised the shear bearing capacity of the components. However, after the fracture development was inhibited, the internal savings of energy dissipation cannot be dissipated. The P-Δ effect was more significant because of the large deformation in the late load. This caused the principal stress and principal compressive strain of concrete to increase sharply, weakening the plastic deformation capacity of the concrete and, at the same time, the internal energy was suddenly released, leading to the rapid destruction of the specimen and worse ductility.Under the condition of approximation with concrete strength, when the axial compression ratio The measured bearing capacity and displacement of the specimens are shown in The cracking load and yield load of the soil column specimens were about 54.9% and 71.5% of the peak load, respectively; those of the PVC-RHC specimens were about 51% and 71.7%, respectively; and those of the CST-RHC specimens were 59.6% and 66.7%, respectively. It can be seen that the cracking load was slightly reduced by using the PVC pipe in the ordinary stirrup confined high-strength concrete column. The steel tube can restrain or slow down the cracking of concrete, but the yield load reduced.Δu is for ultimate displacement, with a decline period of 0.85 times the peak load of the displacement. Δy is the yield displacement, based on the general bending moment method.The ductility coefficient and displacement angle between the layers of each specimen are also given in It can be seen from the table that the displacement ductility coefficient of the reinforced high-strength column restrained by the ordinary stirrup is 1.94, while the displacement ductility coefficient of the reinforced high-strength specimen restrained by the embedded PVC pipe is within the range of 3.28−4.61, most of which is greater than 3, that is, the ductility of reinforced high strength column restrained by the embedded PVC pipe is better than that restrained by the ordinary stirrup. When cracking, the elastic interlayer displacement angle and limit interlayer displacement angle of all specimens were 1/173−1/76 and 1/48−1/15, respectively, both of which exceeded the limit of the interlayer displacement angle in the code, indicating that reinforced high-strength concrete columns have strong lateral and collapse resistance. Compared with the specimen RHC, the reduction rate of the elastic inter-layer displacement angle mean value of PVC-RHC-1 and PVC-RHC-3 of specimens was slower, and the increase in the amplitude of the limit elastic–plastic inter-layer displacement angle mean value was larger, indicating that the PVC pipe equipped with an appropriate pipe diameter could enhance the deformation ability of components in the later stage, improving its collapse resistance.he is usually used, as shown in The energy dissipation capacity of a structure or component is an important factor for judging its seismic performance. The equivalent damping ratio eh of each specimen tends to increase with the increase of displacement, that is, the energy dissipation capacity is good in the later stage. The equivalent viscous damping coefficient eh (between 0.241 and 0.309) is higher than that of the ordinary stirrup (he = 0.130), which indicates that the measure of the reinforced high-strength concrete embedded PVC pipe column can significantly improve the energy dissipation capacity of the specimen. The equivalent viscous damping coefficient of the specimen CST-RHC is the highest, which indicates that the energy-dissipation capacity of high-strength concrete with the steel tube is stronger. For the specimens that are both equipped with PVC pipes, the later stage energy consumption capacity of the smaller-diameter PVC-RHC-3 is stronger than that of the larger-diameter specimen PVC-RHC-1. In addition, under the condition of approximately the same strength concrete, the energy consumption of the specimen increases with the increasing axial pressure ratio. This is because the axial pressure is small, and the lateral strain of concrete is also small, so steel tubes in the constraints of the effect are not apparent. In the scope of the experiment, with the increase of axial pressure, the constraint effect of core concrete is enhanced, so the energy dissipation performance of the specimens is enhanced with the increase of the ratio of axial compression.As can be seen from the figures, the viscous damping coefficient Fn/F1 between the maximum horizontal load in the cycle and the maximum horizontal load in the first cycle at the same displacement amplitude is used to express the strength attenuation of the specimen under this cycle. The component intensity attenuation degree of intensity attenuation coefficient is λ, and the attenuation coefficient of the measured part of the specimen strength with the displacement ratio (Δ/Δy) changes in the relationship is shown in The ratio It can be seen from the figure that the strength attenuation of all specimens is accelerated with the increase of loading displacement and loading cycle times, indicating that the specimens’ ability to continue to resist the seismic action decreases after being subjected to a certain seismic action. The main reason is that, with the increase of loading displacement and cycle times, the bearing capacity of concrete decreases slowly in the early stage of loading owing to the gradual cracking of concrete; in the later stage, the concrete spalling and compression falls off and the steel damage accumulates seriously. As a result, the effective bearing area of components decreases sharply, leading to the rapid decline of bearing capacity. Along with the increase of the displacement, despite the concrete crushing loss of large area, in the late loading, the intensity attenuation of the reinforced high-strength concrete embedded with the PVC pipe and steel tube columns is still relatively slower than reinforced high-strength concrete. Among them, the strength attenuation of embedded steel tube specimens is more stable, showing that the distribution of the PVC tube and steel tube can effectively confined the core concrete to improve its performance, causing the bearing capacity to slow down and improving the stability of the intensity attenuation. With the increase of the axial compression ratio, the stability of strength attenuation decreases. PVC-RHC-2 had a lower number of loading cycles and a lower limit displacement than PVC-RHC-2 before failure, and the range of bearing capacity attenuation under the action of each cycle increased.K represents the stiffness changes of specimens. Δ/Δy) curve.The secant stiffness Δ/Δy equals 3, all the stiffness of the specimens were greater than 35% of the initial stiffness. When loading to the failure point, the average residual stiffness of all specimens except ordinary reinforced high-strength concrete specimens is greater than 21%, indicating that the lateral stiffness of reinforced high-strength concrete confined with the PVC pipe and steel tube column had a strong stability, and the influence is most significantly affected by the axial compression ratio.As can be seen from the figure, with the increase of the displacement amplitude, the stiffness of each specimen presented a trend of first fast and then slow degradation. This is mainly because, in the early stage of loading, a large number of oblique and bending cracks appeared in the root of the specimen, which made the early stiffness degradation faster. As the load continues to increase, the damage degree of concrete increases and gradually drops out of work. At this time, cracks are fully developed and almost no new cracks appeared. The plastic deformation of steel increased, which further reduced the stiffness of the members. The initial stiffness of each specimen varied greatly. The specimens with a large axial compression ratio had the highest initial stiffness, which was about 1.92 times that of the specimens with a large axial compression ratio. When At present, there are no reports on the calculation methods for the ultimate bearing capacity of high-strength concrete columns embedded with PVC pipes. Owing to the complex shearing mechanism of reinforced concrete specimens and considering the low tensile strength of PVC pipes, in order to facilitate engineering applications, the structure in accordance with China’s current “Code for Design of Concrete Structures” (GB 50010-2010)  is prefeV is as follows:λ is the shear span ratio, ft is the tensile strength of the concrete, b is the section width, h0 is the effective height of the section, fyv is the yield strength of the stirrup, Asv is the cross-sectional area of the stirrup, s is the pitch of the stirrup, and N is the axial pressure.The test shows that the failure mode of reinforced high-strength concrete constrained with the PVC pipe column is shear baroclinic failure, and the stirrup bends when it breaks, and its strength is fully exerted. According to the current concrete standard structural column of China, the calculation formula of the ultimate shear capacity Vc was compared with the measured value Vt, as shown in Vt to Vc is 1.26. Therefore, it is feasible and safer to use the current standard calculation method to calculate the shear bearing capacity of the new type of confined concrete structure column. Owing to the lack of experimental data and the complexity of shear problems, the refined calculation method for the ultimate shear bearing capacity of this new type of confined concrete column needs to be further studied.Equation (3) is used to calculate the specimen. The calculated result V is the ultimate bearing capacity of reinforced high-strength concrete columns embedded pipes; VT is the shear force of the PVC pipes (or steel tube) and high-strength concrete, and VT = VT1 + VT2 + VT3, where VT1, VT2, and VT3 are the shear capacity of the pipe, the shear capacity of the concrete, and the axial pressure for the shear capacity of the component, respectively; and Vrhc is the shear force of periphery of the high-strength concrete.The shearing problem of reinforced concrete specimens is very complex. When it comes to the embedded PVC pipes, the calculation of the shear bearing capacity of reinforced high-strength concrete columns embedded PVC pipes is more complex. On the basis of the research results of the concrete-filled steel tube and composite structure at home and abroad ,20,21, t(1) Shear Capacity of PVC Pipe High-Strength ConcreteNeglect the contribution of the PVC pipe hoop on the shear strength of concrete;The PVC pipe meets the von Mises yield criterion;Axial pressure is evenly distributed along the cross-section of the specimens.At present, the systemic research of the calculation method for the shear capacity of PVC high-strength concrete is lacking. Considering that the mechanism of PVC pipe confining core concrete is similar to that of steel pipe, the shear strength of the PVC high-strength concrete force calculation model and method is established, which is based on the theory of shear performance in the concrete confined steel tube. In order to simplify the calculation, the following basic assumptions are made with reference to the research on the concrete-filled steel tube:fTy ≈ 0.6fT, where fT is the ultimate strength of the PVC pipe or the yield strength of the steel tube. When the shear span ratio λ = 0, the pipe is in a pure shear state; when the shear span ratio λ is more than 0.5, the pipe damage has typical bending failure characteristics. When the pipe is in these two specific critical states, the calculation formula of the shear bearing capacity VT1 can be obtained according to the classical mechanics [VT1 means the shear capacity, which includes VP1 as the shear capacity of the PVC pipe and Va1 as that of the steel tube; AT is the cross-sectional area of the PVC pipe or the cross-sectional area of the steel tube; r1, r2 are the inner and outer diameters of pipe, respectively; and λ = H/r2, where H is the height of the pipe. When the shear span ratio is 0 < λ < 0.5, the shear capacity of the pipe is determined by interpolation.It is assumed that the PVC pipe and the steel pipe satisfy the von Mises yield criterion, and the shear strength echanics .(5)VT1=Va2 trend along with the shear span ratio is shown in The tests have shown that, when the concrete-filled steel tube reached the ultimate shear bearing capacity, the hoop strain value of the steel pipe was not large, which means that the restraining effect of the steel pipe on the core concrete was not very remarkable. Therefore, when calculating the shear strength of the core concrete, the beneficial effect of the steel tube on the improvement of the shear strength of the core concrete can be neglected. The measured shear bearing capacity of the steel core concrete Vp2 is as follows:As the strength of the PVC pipe is low, it is recommended to take the lower limit envelope of the shear strength of the PVC core core with the shear span ratio curve lack of research data. The fitting expression of PVC shear bearing N is the axial pressure of the concrete pipe of the PVC pipe (steel tube). When N > 0.4 (fTA + fcAc), take N = 0.4 (fTA + fcAc) to calculate the PVC pipe (steel tube) shear capacity of concrete columns. ξ is the axial pressure influence coefficient of the shear capacity of pipe concrete.In the same condition, when the axial pressure effect is still present in the tubular concrete column, the shear bearing capacity of the tubular concrete column will also increase. The added value is the contribution of the axial pressure. The contribution value of the axial pressure against shear is as follows:ΨTN, where ΨT is the area ratio of the high-strength concrete of the pipe, which refers to the ratio of the cross-sectional area ATc of the high-strength concrete of the pipe to the total cross-sectional area A.The distribution of axial pressure in the confined high-strength concrete columns embedded PVC pipe (steel pipe) is very complicated. To simplify the calculation, it is assumed that the axial pressure is evenly distributed along the entire section of the specimen, that is, the axial pressure of the high-strength concrete part of the PVC pipe (steel tube) is ξ of the pipe concrete shear capacity decreases with the increase of the shear span ratio λ and the axial pressure ratio n, and the factors affecting ξ are more complicated. Generally, the axial pressure influence coefficient ξ of the steel tube (PVC pipe) is taken as 0.10.It can be seen from (2) Shear Capacity of High-Strength ConcreteVrhc is the shear ultimate bearing capacity of the high-strength concrete part of the peripheral reinforcement; fyv is the yield strength of the stirrup; ΨT is the area ratio of the high-strength concrete of PVC pipe and steel tube; and ATc is the cross-sectional area of the pipe concrete.For the reinforced high-strength concrete columns embedded PVC pipe, in addition to the influence of axial pressure, the shear bearing capacity of the external reinforced high-strength concrete mainly includes the shear bearing capacity of high-strength concrete and the shear bearing capacity of the stirrup. Therefore, this part adopts Equation (10) for calculation:(3) Analysis of Calculation ResultsAccording to the superposition method, the shear ultimate bearing capacity of reinforced high-strength concrete embedded with the PVC pipe is calculated as shown in (1)λ ≤ 2.5), the failure mode of the reinforced high-strength concrete column embedded PVC pipe is shear barocliny failure. The influence of the axial compression ratio, shear span ratio, and other parameters on the failure mode was not obvious.When the shear span ratio is not large ((2)Compared with the reinforced high strength concrete column restrained with the ordinary stirrup, the hysteretic curve of the high strength concrete column with the PVC pipe and steel tube inside is fuller, the peak load is increased, the strength attenuation in the later stage is slow, the decline section of the skeleton curve is gentle, the limit deformation is large, and the ductility is good.(3)The restraint effect of the PVC pipe and steel tube is similar, which can provide an effective restraint effect and effectively enhance the seismic energy dissipation and deformation capacity of the reinforced high strength concrete column.(4)For specimens with the same configuration of the PVC pipe, with the increase in the axial compression ratio and shear span ratio, the ductility becomes worse, and the value of PVC pipe diameter has an impact on its seismic performance. It is not that the larger the pipe diameter, the better; there is a problem with the value of the reasonable pipe diameter ratio.(5)The ductility of the high-strength concrete column can be effectively improved by adopting measures of the internal PVC pipe, and the displacement ductility coefficient is greater than 3 in most cases. The lateral displacement angle of the limit exceeds the limit of the displacement angle between the layers of the concrete frame in the code.(6)In order to facilitate the calculation of shear strength of the concrete column confined by the PVC pipe, a simplified calculation method is adopted. According to the formula of the current concrete specification, the safety surplus is about 25%.In this paper, the hysteretic behavior of embedded PVC pipe confined reinforced high strength concrete columns was investigated. The following conclusions can be drawn:


Heroin leukoencephalopathy is associated with 'Chasing the dragon,' which is a heroin vapour inhalation method that is different from smoking or sniffing heroin. The clinical presentation ranges from mild to severe disease. Mild disease is characterized by inattentiveness and ataxia. In moderate diseases, extrapyramidal symptoms predominate, and finally, severe disease is characterized by generalized motor impairment, with death occurring in two-third of cases. We now report a rare presentation of the disease in a 60-year-old female with a past medical history of heroin abuse who presented to ED with signs and symptoms of confusion and restlessness. MRI brain without contrast showed diffuse symmetric increased intensity signals throughout the white matter. Electroencephalogram (EEG) revealed mild diffuse slowing with no lateralization. The patient was started on Vitamin E and was transferred to a rehab facility with following up neurology as an outpatient. Leukoencephalopathy, due to heroin inhalation colloquially known as 'chasing the dragon,' is a rare complication of heroin abuse. 'Chasing the dragon' a term derived from the method of inhalation of heroin fumes that is different from sniffing or smoking heroin . A smallA 60-year-old Caucasian female with the unknown past medical history presented to the emergency department via her sister for evaluation of altered mental status. The patient was a poor historian, and most of the history was obtained from the patient's sister. As per collateral, the patient had been behaving "differently" for the past month. The patient was unaware of why she was in the hospital. She replied, 'does not know' to almost every question. She denied fever, headache, dizziness, nausea, vomiting, muscle weakness, sensory deficit, gait abnormality, hallucination, homicidal or suicidal ideation. She also denied smoking or any illicit drug use; however, her sister reported the patient has been inhaling heated vapours of heroin for an unknown duration.On examination, she looked confused and restless, was alert and oriented to person and place but not to time, and intermittently laughing throughout the interview. CNS examination revealed normal strength and sensation in all extremities, including proprioception. No gait abnormalities or nystagmus was observed.Laboratory investigations done on admission, including complete blood count and metabolic panel, were unremarkable; WBC 8.3 k/ul, Hb 13.3 g/dl, platelets 392 k/ul, creatinine (Cr) 0.7 mg/dl, sodium (Na) 135 mmol/l, potassium (K) 4.8 mmol/l. The urine drug screen was negative. The CT head was unremarkable. MRI brain without contrast showed diffuse symmetric increased intensity signals throughout the white matter (Figures The patient was started on Vitamin E 400 IU twice daily and was transferred to a rehab facility with following up neurology as an outpatient. She was counselled regarding abstaining from heroin.Heroin inhalation causing leukoencephalopathy was first initially described in a report from the Netherlands . InhaledThe clinical presentation ranges from mild to severe disease. Mild disease is characterized by inattentiveness, ataxia, and confusion. In moderate diseases, extrapyramidal symptoms predominate, and finally, severe disease is characterized by generalized motor impairment with death occurring in two-thirds of cases ,4. In adCharacteristic MRI findings include symmetrically increased T2 and T2-FLAIR signal intensity in the cerebellum, posterior cerebrum, and posterior limbs of the internal capsule. Grey matter affected in anoxic encephalopathy is usually spared . EEG usuThere is no established treatment for heroin leukoencephalopathy. Kriegstein AR et al. reported clinical improvement in patients treated with antioxidants, including coenzyme Q . This clHeroin induced leukoencephalopathy is a rare complication of heroin abuse. Diagnosis should be considered in a patient with a history of 'chasing the dragon' and neurobehavioral changes. Our patient presented only with mild symptoms of confusion and restlessness. Clinical features with a history of heroin use, along with MRI findings, helped establish the diagnosis and starting treatment.