Antibiotics were empirical in 7720 infections (85.6%), with an increase in appropriate antibiotic indications during the second period (p < 0.001). The main indication for antibiotic adjustment was de-escalation, increasing in the second period (p = 0.045). Despite the high rate of antibiotic use in PICUs, our results showed a significant increase in appropriate antibiotic use and adjustment following the implementation of AMS programs.Antibiotic misuse in pediatric intensive care units (PICUs) can lead to increased antimicrobial resistance, antibiotic-triggered side effects, hospital costs, and mortality. We performed a multicenter, prospective study, analyzing critically ill pediatric patients (≥1 month to ≤18 years) admitted to 26 Spanish PICUs over a 3-month period each year (1 April–30 June) from 2014–2019. To make comparisons and evaluate the influence of AMS programs on antibiotic use in PICUs, the analysis was divided into two periods: 2014–2016 and 2017–2019 (once 84% of the units had incorporated an AMS program). A total of 11,260 pediatric patients were included. Total antibiotic prescriptions numbered 15,448 and, overall, 8354 patients (74.2%) received at least one antibiotic. Comparing the two periods, an increase was detected in the number of days without antibiotics in patients who received them divided by the number of days in PICUs, for community-acquired infections ( Undoubtedly, antibiotic resistance has become one of the greatest threats of our time. Not 100 years have passed since the discovery of antibiotics transformed healthcare practices, heralding an abrupt deceleration of mortality coinciding with the first clinical use of sulfonamides in 1935 and penicillin in 1942 [In recent years, antimicrobial stewardship (AMS) programs have become the cornerstone of slowing the development of antimicrobial resistance, optimizing not only the treatment of infections but also reducing adverse effects that result from the overuse of antimicrobials, as well as reducing the associated costs ,6. SeverIn today’s challenging environment, with no immediate prospects for any new broad-spectrum antibiotics, especially against enterobacteria, and an aging and/or compromised patient population, the implementation of AMS practices has shown to decrease antimicrobial use by 22–36%, as observed in both large and small community hospitals . In SpaiFurthermore, with a view to developing a surveillance system for healthcare-associated infections (HAI), a multicenter registry of HAIs in Spanish Pediatric Intensive Care Units (PICUs) was created in 2007 . This waThe data included in this far-reaching registry provide important information not only about the overall rates of HAI but also about the use of antibiotics, the microorganisms isolated, and the resistance profile. It is considered a national and international benchmark for HAIs in PICUs. This study offers novel information for use in the field, data on the use of broad-spectrum antibiotics and HAIs being scarce in the literature ,14, as aA prospective, multicenter observational study was conducted in 26 PICUs in Spain, over a 3-month period each year  from 2014 to 2019. The reason for choosing these particular months was that it is a time of the year with a medium workload, so it is estimated that the data are more accurate.The subjects included were hospitalized pediatric patients (≥1 month and ≤18 years of age) who required admission to the PICU during the study period. All patients were admitted before the study period began (1 April) and those who were hospitalized in the PICUs after 30 June were excluded.n = 5) of them had not yet done so. By 2016, only 55% (n = 17) of the units had established one of these programs. However, by 2019, 84% (n = 26) of the PICUs had incorporated an AMS program. To test the hypothesis that AMS programs may influence antibiotic use, the analysis was divided into two 3-year periods, 2014–2016 and 2017–2019, for comparison.Patients registered by all of the PICUs participating in the National Nosocomial Infections Surveillance System were included in this study. However, at the beginning of the data collection period, not all of the PICUs had implemented an AMS program. We conducted a recurring survey among these 31 units in order to determine exactly when they did implement an AMS program. By the end of the study period, 16%  that was used within the 48 h period before the onset of the infection, even if it was only used intermittently ,18. TablThe primary outcome was to determine changes in the use of antibiotics over time, considering the influence of the implementation of AMS programs. The antibiotic use indicators considered were:Outside-PICU antibiotic use: Antibiotics prescribed for infections diagnosed once the patient was hospitalized for more than 48 h in a hospital ward.Inside-PICU antibiotic use: Antibiotics prescribed for infections diagnosed once the patient was hospitalized for more than 48 h in the PICU.Antibiotic-free days: The difference between the duration of the antibiotic course(s) and the length of stay in the PICU. Antibiotic use ratio: The number of patients who received antibiotics with respect to the total number of patients included in the study. Antibiotic-free days ratio: The number of days without antibiotics in patients who received them divided by the number of days these patients spent in the PICU. Global antibiotic-free days ratio: The number of days without antibiotics, considering all the patients with respect to the overall number of days they were in the PICU .Physicians at the participating hospitals entered all the clinical data for each patient admitted to the PICU during the study period into a standardized online registry. The parameters collected for this analysis included demographic characteristics, pediatric risk of mortality (PRISM) score and Glasgow score at admission, comorbid medical conditions, predisposing factors for infections, diagnosis at admission, community-acquired infections, HAIs acquired outside and inside the PICU, device-associated HAIs, microbiological data, length of stay (LOS), antibiotics used, and antibiotic susceptibility profile ,11.®, IBM . Categorical variables were indicated as frequency (n) and percentage (%), while continuous variables were summarized as median and interquartile range (IQR) because they were not normally distributed. The comparison of qualitative variables was performed using the χ2 test or Fisher’s exact test. Continuous variables were compared using the Mann–Whitney U test when not normally distributed. Probability values of less than 0.05 were considered statistically significant.The statistical analysis was performed using SPSS 25.0 Statisticsn = 6368) were males and the median age was 43.2 months (IQR 10–115 months). n = 317) presented at least one device-related HAI during their stay in the PICU. The total number of HAIs was 390, and the overall rate of HAI was 6.3 per 1000 patient-days. The most frequent device-related HAI was VAP, with 110 episodes, followed by CAUTI, with 105 episodes, and CLABSI, with 90 episodes.A total of 11,260 pediatric patients were included in the registry from 2014 to 2019. Among them, 56.6%  received at least one antibiotic during their PICU stay. The ratio of antibiotics per patient prescribed antibiotics, meaning the average number of antibiotic prescriptions given to each patient who required them, showed a progressive decrease until 2019, when it skyrocketed to 2014 levels .n = 2201, 14.2%), followed by the suspicion of a HAI acquired outside the PICU , other non-surgical prophylaxis , and unknown reason for prescription . Upon comparing these antibiotic indications between the time periods (2014–2016 vs. 2017–2019), the only statistically significant differences detected were among HAIs acquired outside the PICU  and unknown reasons for prescription . The detailed results regarding the number of antibiotics prescribed for each indication are included in Surgical prophylaxis was the main indication for antibiotics, with a total of 5024 (32.5%) antibiotics used. Community-acquired infection was the second most common antibiotic indication, with 4690 (30.4%) antibiotic prescriptions. The suspicion of a HAI acquired inside the PICU was the third most common reason for prescribing antibiotics . Regarding suspected community-acquired infections, 4310 antibiotics (92.7%) were empirical and 340 (7.3%) were pathogen-targeting. As for suspected outside-PICU-acquired HAIs, 1726 (82.1%) of the prescriptions were empirical and 375 (17.8%) were pathogen-targeting. Finally, as regards suspected inside-PICU-acquired HAIs, 1684 (77%) of these antibiotics were empirical and 504 (23%) were pathogen-targeting therapies. There were statistically significant differences between the three groups and the empirical or pathogen-targeting therapies, with all p-values < 0.001. There was a total of 9013 courses of antibiotics prescribed due to suspected infections. The indication of antibiotic therapy was empirical in 7720 suspected infections (85.6%) and in 1219 (13.5%) cases was pathogen-targeting therapy, with no differences between the two periods (n = 1972) and the distribution was similar in community-acquired infections (24.7%), outside-PICU-acquired HAIs (23.4%), and inside-PICU-acquired HAIs (26.7%). Empirical antibiotic therapy was considered inappropriate in 12.1% of all cases (n = 957): 11.3%, 12.3%, and 13.8%, respectively, for the aforementioned groups. No statistically significant differences were observed as regards the appropriate or inappropriate prescription and the type of suspected infection , p = 0.231. In 45.7% of the indications (n = 3621), negative cultures were found: 45.5% in community-acquired infections, 47.9% in outside-PICU-acquired HAIs, and 43.8% in inside-PICU-acquired HAIs, with statistically significant differences between them (p = 0.011).Empirical therapy was considered appropriate when microorganisms were susceptible in vitro to antibiotics. In this sample, the empirical prescriptions were appropriate in 24.9% of cases (p < 0.001) and a parallel significant decrease in negative cultures (p < 0.001). No statistically significant differences were detected for inappropriate indications (p = 0.162).An increase in appropriate antibiotic indications was detected when comparing the two periods, as shown in n = 5512), no modifications were made and 20.2% were suspended early, while an antibiotic adjustment was made in 14.2% of the prescriptions. No statistically significant changes were detected over time regarding antibiotic adjustment, early suspension, or absence/presence of a change in antibiotics. p < 0.001. Early suspension was more frequent in suspected community-acquired infections (21.8%) than in inside-PICU-acquired HAIs (20.5%) and outside-PICU-acquired HAIs (16.1%), with p < 0.001.In up to 65.7% of the antibiotics indicated for empirical treatment , followed by a poor clinical evolution  and a need to increase the antibiotic spectrum . p = 0.045), without clear differences regarding the other items: increasing the spectrum, 13.7% vs. 12.9%, p = 0.696; poor clinical outcome, 31.9% vs. 27%, p = 0.062; new resistances, 1.6% vs. 0.8%, p = 0.227; and toxicity, 3.5% vs. 4.4%, p = 0.426.The main indication of the 1,189 antibiotic adjustments was reducing the antibiotic spectrum in favor of a narrower one (p = 0.049. Reducing the antibiotic spectrum was more frequent for inside-PICU-acquired HAIs (44%) than for community-acquired infections (39.9%) and outside-PICU-acquired HAIs (37.7%), with n = 485) of the cases. Antibiotic adjustment due to poor clinical evolution was more frequent in community-acquired infections (32.9%) and outside-PICU-acquired HAIs (32.8%) than in inside-PICU-acquired HAIs (22.8%), with p = 0.004. The increase of the antibiotic spectrum was more frequent in inside-PICU-acquired HAIs (17.5%) and outside-PICU-acquired HAIs (14.9%) than in community-acquired infections (8.7%), with p = 0.001.Out of the 9013 antibiotic courses prescribed for a suspected infection, de-escalation was practiced in 5.4%  was surprising, as this is mostly used for serious nosocomial infections that are more likely to be contracted in ICUs. This is probably attributable to a greater effort to implement AMS programs in PICUs than in general wards.The number of antibiotics prescribed empirically was very high (85.6%). Pathogen-targeting therapy was greater for HAIs, most likely due to the poor performance of blood cultures in pediatric patients infected in the community. In fact, when analyzing the rates of appropriate antibiotic use, in 45.7% of the prescriptions it was impossible to detect whether antibiotic therapy was actually appropriate because of negative cultures, with a significantly lower percentage of negative cultures shown for inside-PICU-acquired HAIs.Comparing the two different periods, we saw a significant increase in terms of appropriate antibiotic use, with a decreasing trend in the use of antibiotics in patients with negative cultures.An important finding in our study was that up to 20.2% of the antibiotics were discontinued early. In addition, modifications were made to the antibiotic therapy in up to 14.2% of the cases where these were prescribed. The main cause for this adjustment (40.8%) was de-escalation in favor of a narrower spectrum, which was significantly more frequently seen with inside-PICU-acquired HAIs. Ying Guo et al.  performeWe also found a statistically significant increase in de-escalation being carried out during the second period, attributable to AMS interventions in physicians’ prescriptions. In line with our observations, Al-Omari et al.  stated tWe acknowledge that our study has some limitations. We report a progressive increase in the number of PICUs that implemented AMS programs; by 2016, 55% of these centers had established such programs. We expect the effects of these programs on antibiotic policies to be less remarkable for those units with a short trajectory.Another limitation was the fact that we did not assess the impact that maximum PICU occupancy may have on antibiotic prescription, as this phenomenon occurs during the winter season. On the other hand, the sample is very homogeneous because we compared the same months during each year and the healthcare centers included were of the same complexity, with no major changes in staff and patient structure in the PICUs included.There is a clear association between antibiotic use and antibiotic resistance, but there is much less evidence to support the concept that reducing antibiotic use actually leads to improvements in antibiotic susceptibilities . The cleAntibiotics exert selection pressures on bacterial populations, thus contributing to the development of antibiotic-resistant bacteria. Removing this pressure, however, does not guarantee that the resident microflora will lose the antibiotic-resistance genes. Cook et al.  reportedAMS programs may be considered as pivotal contemporary healthcare policies which have some of the greatest impacts on both patient outcomes and healthcare costs. They should thus be a top priority for all healthcare providers, otherwise there may be serious long-term impacts whose ramifications we cannot currently comprehend. In today’s clinical environment, especially in pediatric areas, antimicrobials are being unnecessarily prescribed to treat mainly viral infections, which implies not only an unnecessary cost but a risk to patients as well as to public health.We have already emphasized the importance of antibiotic stewardship programs in PICUs. Our results show that AMS programs are related to prescribing appropriate antibiotics and also to reducing the use of broad-spectrum antibiotics, which could be the key to slowing the development of antimicrobial resistance. Moreover, after the implementation of AMS programs, we found a statistically significant increase in the number of antibiotics that were adjusted to target a narrower spectrum, which is a practice that has consequences for public health.Our study highlights the importance of implementing AMS programs, which have been shown to be effective in reducing antimicrobial utilization, altering prescribing behavior and encouraging the appropriate use of antibiotics. This will help our healthcare systems better tackle both current and future challenges, such as controlling antimicrobial resistance. Further studies are required on clinical outcomes, hospital costs, indirect expenses such as antibiotic side effects, earlier transitions to oral therapy, length of hospital stay, and readmissions. In addition, future long-term studies are needed that focus mainly on mortality and antimicrobial resistance in the pediatric population.


Boronic esters prepared by condensation of boronic acids and diols have been widely used as dynamic covalent bonds in the synthesis of both discrete assemblies and polymer networks. In this study we investigate the potential of a new dynamic-covalent motif, derived from TetraAzaADamantanes (TAADs), with their adamantane-like triol structure, in boronic ester-based covalent adaptable networks (CANs). The TetraAzaADamantane-boronic ester linkage has recently been reported as a more hydrolytically stable boronic ester variant, while still having a dynamic pH response: small-molecule studies found little exchange at neutral pH, while fast exchange occurred at pH 3.8. In this work, bi- and trifunctional TetraAzaADamantane linkers were synthesised and crosslinked with boronic acids to form rubber-like materials, with a Young’s modulus of 1.75 MPa. The dynamic nature of the TetraAzaADamantane networks was confirmed by stress relaxation experiments, revealing Arrhenius-like behaviour, with a corresponding activation energy of 142 ± 10 kJ/mol. Increasing the crosslinking density of the material from 10% to 33% resulted in reduced relaxation times, as is consistent with a higher degree of crosslinking within the dynamic networks. In contrast to the reported accelerating effect of acid addition to small-molecule TetraAzaADamantane complexes, within the polymer network the addition of acid increased relaxation times, suggesting unanticipated interactions between the acid and the polymer that cannot occur in the corresponding small-molecules analogues. The obtained boronate-TetraAzaADamantane materials were thermally stable up to 150°C. This thermal stability, in combination with the intrinsically dynamic bonds inside the polymer network, allowed these materials to be reprocessed and healed after damage by hot-pressing. The poor recyclability of most modern plastics, in particular of thermoset materials, has created a focus on making more sustainable and better recyclable materials. This recyclability issue can be tackled by incorporating dynamic covalent bonds  inside cvia reactions with diols or poly-ols, which usually result in the formation of soft (hydro)gels gels . Howeverdro)gels  was founSOXH3 , which iSOXH3 .This TAAD moiety was then further investigated . It was In this work, we investigate the potential of the TAAD moiety in dynamic CANs. To this end, bifunctional boronic acid linkers and bi- and trifunctional TAAD linkers were designed and synthesised, as shown in 2000 with 4-formylphenylboronic acid and subsequently reducing the formed imine bond  groups in a boronate ester network, different linker molecules were synthesised. Both a linear bifunctional boronic acid and TAAD linker were prepared, as well as a trifunctional TAAD linker to enable crosslinking. For the linear boronic acid crosslinker it was chosen to react bis-amine terminated PPGine bond . For thepara-substituted phenylboronic acids  and loss modulus (G″) between 0.1 and 1 MPa over the frequency domain of 0.01–100 rad/s. Extensional DMA showed that the material had a Young’s modulus of 1.75 MPa, corresponding to a soft rubber. The temperature sweep from 4°C to 170°C  with temperature, which will yield the activation energy Ea of relaxation process due to bond exchange. To this end, the relaxation behaviour of the boronate-TAAD network was investigated in the temperature range of 90°C–130°C. The observed relaxation time τ decreased from 2,478 s at 90°C to 18 s at 130°C, as can be seen in A defining feature of CANs is their ability to undergo stress relaxation by dynamic bond exchange. The time for the material to relax imposed stress generally shortens with an increase in temperature, since the dynamic bond exchange becomes faster. This allows faster network rearrangement and thus faster stress relaxation. The Arrhenius equation can be applied to the dependence of the relaxation time  of the material increased by one order of magnitude with increasing crosslink density from 10% to 33%, as can be seen in Having established that a TAAD-based CAN could be prepared with a 10% crosslinker content, the effect of the crosslink density on the CAN’s material properties was investigated. Additional CANs with 20% and 33% crosslinks were prepared and compared. Frequency sweeps  did not e sweeps  did showKa of the added acid was found to correlate with the shortening of the material relaxation time. Combined with the reported findings , ranging from 0.25 wt% to 10 wt%. The relaxation behaviour of these materials was then measured and evaluated, as shown in i.e., the addition of acid did not simply lead to faster relaxation. In contrast, at low PTSA content (0.25–0.5 wt%) an increase in the relaxation time of the material compared to the material without PTSA was observed. These materials displayed a relaxation time that is about one order of magnitude longer than the original acid-free material. At moderate PTSA content (1–5 wt%) the relaxation time is still generally longer than without PTSA, but it started to decrease until at 5 wt% PTSA the material had a relaxation time similar to the control without PTSA. At high PTSA content (5–10 wt%) again an increase in relaxation time was observed. While the precise underlying mechanism of these trends remains unclear, one possible explanation might be that the PTSA is partially excluded from the network due to unfavourable interactions between the apolar aromatic ring of the acid and the polar building blocks, thus reducing its effectiveness as a catalyst while possibly introducing crystalline regions in the matrix. Another possible explanation could be an interaction with the secondary amines of the PBA-PPG-PBA linker. PTSA could protonate the secondary amines of this linker, resulting in the formation of charged nitrogen species similar to polyelectrolyte complexes, which often become stiff and brittle upon drying  exchange under acidic conditions (pH 3.8), the corresponding CANs could already undergo (stress) relaxation under neutral conditions. Surprisingly, the addition of acid did not have a further accelerating effect on the exchange. The boronate-TAAD material showed complete self-healing after multiple thermal reprocessing cycles and Arrhenius analysis gave a relatively high activation energy of 142 ± 10 kJ/mol for the crosslink relaxation process compared with regular boronic esters.This first investigation into boronate-TAAD networks showed that the novel boronate-TAAD linkages can indeed be used to develop CANs. Coupled to the relatively simple synthesis of the TAAD moiety, this unique boronate-TAAD linkage offers an interesting alternative to the more commonly used boronic esters.


In order to verify the feasibility of using FRP grid and mortar reinforcement technology to enhance the blast resistance of concrete arch structures, this paper designed and fabricated FRP grid and mortar reinforced concrete arch structures and conducted blast resistance tests in the field. A detailed design of anti-explosion scheme was carried out before the experiment. The tests were conducted to observe the structural cracking, concrete collapse, and reinforcement peeling of FRP grid and mortar reinforced concrete arch under the explosion. In order to compare the anti-explosion performance with the protective arch structures in other literature, the explosion of 2 kg TNT with a blast distance of 600 mm was selected. After the explosion, it was found that the blast resistance of the FRP grid and mortar reinforced concrete arch was significantly higher than that of the unreinforced arch, and the concrete arch reinforced with FRP grid and mortar has a better damage patterns and improved blast resistance performance than that of the FRP and steel plate reinforced arch. According to the research results, the FRP grid and mortar composite reinforcement technology can be used to enhance the blast resistance of arch structures in protection projects. As a special form of structure, the arch structure has more excellent force performance than other structural members, such as beams and slabs. This is mainly because it can transform the vertical load into horizontal thrust at the foot of the arch, thus reducing the bending moment and shear force caused by the load. This advantage is why the arch structure often used in the construction of various practical projects, such as the top of the tunnel lining and the bridge cavity underneath the bridge. Likewise, arch structures have many applications in the field of defense engineering, such as aircraft caverns.The arch structure as protective engineering may be subject to dynamic loads, such as blast impacts and earthquakes, and may lose its load-bearing capacity ,2. For tIn recent years, the development of science and technology has led to the emergence of various new advanced weapons, which put forward higher requirements for the resistance of protective engineering. Many underground projects built according to the original technology have not been able to give full play to the role of protection. Concrete structural members subjected to blast load behave differently compared to quasi-static loaded members ,4. ConcrFiber-reinforced composites (FRP) can be used to strengthen RC arches. Researchers found that FRP strengthening plays an important blast protective role in the concrete arch. Indeed, its effects in controlling the shearing crack and spalling, decreasing the dynamic deformation of the arch structure, and improving the structural stability are remarkable . FRPs haMany scholars have conducted studies on the use of FRP materials to enhance the blast resistance of concrete structures ,12,13. XZhao Chengjie et al.  systematIn addition to enhancing the blast resistance of concrete arches, enhancing the static performance of arches by FRP materials is also a research focus. Zhang Xu et al.  carried The FRP grid , as a neCombined with previous research, in order to propose a more convenient, reliable, and cost-effective reinforcement method to improve the anti-explosion performance of the protective arch structures, the FRP grid and mortar composite reinforcement form is proposed, and the anti-explosion experiment of the composite arch was designed and conducted in the field. Considering the actual situation that reinforcement can only be carried out on the inner surface of the structure in the process of strengthening and renovation of the actual arch structure, in this paper, based on the previous study, the FRP grid is used instead of FRP cloth, and the ordinary mortar is used instead of polyurea in the inner surface strengthening of the arch structure. The feasibility of FRP grid and mortar composite reinforcement form is clarified through the experimental study of the blast resistance performance of FRP grid and mortar reinforced concrete arch.The internal span of the arch is 1000 mm, the thickness is 100 mm, and the transverse width is 500 mm, as shown in Using basalt fiber-reinforced composite (BFRP) as the reinforcing material, In the experiment, the type of explosive used for air blast is TNT. As a type of chemical explosion, TNT explosion is an extremely rapid energy release process. In this instant, the energy contained in TNT is released at a very fast rate, and transformed into other forms of energy, such as kinetic energy, light, heat, etc. The shock wave generated by the explosion on the concrete elements of the effect is obvious. Air blast refers to a certain amount of equivalent TNT block placed at a certain distance from the top of the arch structure explosion, as shown in As shown in After the explosion of 2 kg TNT at 600 mm from the upper surface of the arch, the FRP grid and mortar composite reinforced concrete arch structure showed plastic damage, and the damaged area was near the arch vault where it was closer to the explosive. A crack distributed basically along the axis of the arch, as shown in From In the literature , the antArch A4 uses steel plate battens to anchor the bonded CFRP sheets. Due to the impact effect, the steel plate exactly fell off and the CFRP sheets debonded, the bolts were pulled out of the concrete, leaving a wide concrete crack, as shown in A comparison with arches A1 and A4 reveals that the concrete arches reinforced with FRP grid and mortar all have different degrees of improvement in damage patterns and improved blast resistance performance. Since the FRP grid is anchored to the concrete arch by anchor nails, the number of anchor nails is larger and the force is more uniform, which can provide better anti-blasting performance for the composite arch under dynamic load. The FRP grid and mortar reinforced arch can limit the appearance of large cracks in the arch structure by forming many small cracks in the reinforcement layer. This type of reinforcement can effectively inhibit the further expansion of concrete cracks, disperse large cracks into small ones, and effectively improve the overall working performance of the arch structure.The blast resistance of FRP grid and mortar reinforced concrete arch was significantly higher than that of the unreinforced arch. The FRP grid and mortar composite reinforcement technology can be used to enhance the blast resistance of arch structures in protection projects.By analyzing the blast resistance test results and comparing them with the FRP and steel plate reinforced arch in the literature, the concrete arch reinforced with FRP grid and mortar has different degrees of improvement in damage patterns and improved blast resistance performance. The new composite grid and mortar reinforcement is useful for controlling crack expansion, inhibiting concrete spalling, and improving structural loading performance. This type of reinforcement can effectively inhibit the further expansion of concrete cracks, disperse large cracks into small ones, and effectively improve the overall working performance of the arch structure.From the viewpoint of maintaining the integrity of the blast-resistant structure, the new FRP grid and mortar reinforcement method is more advantageous than the traditional reinforcement method and can reduce the reinforcement cost while realizing the blast resistance effectiveness.In this paper, the excellent material properties of FRP are successfully applied to the reinforcement and fabrication of the protective concrete arch structure. The reinforcement method of using the FRP grid & mortar at the bottom of the arch is proposed. The FRP grid and mortar reinforced concrete arch structure was designed and fabricated, and the blast resistance experiment was conducted in the field. The feasibility of FRP grid and mortar composite reinforcement form is clarified through the experimental study. It is concluded that:This paper only studies the reinforcement and anti-explosion performance of the semicircular arch structure. Since the mechanical properties of the arch will change with the change of the central angle, in the future, the reinforcement research of arch structures with different central angles can be carried out. In addition, the arch structure in this research is made of ordinary concrete. In order to reasonably match the mechanical properties of the material, the strength of the mortar used for reinforcement is not high. In the next step, ultra-high-performance mortar can be used to strengthen the high-strength concrete arch structure.


The coronavirus disease 2019 (COVID-19) pandemic has influenced antibiotic consumption over a long period, with variability in trends among studies. We conducted this systematic review to explore and compare the effect of the pandemic on overall and individual antibiotic consumption in 2020 with that in 2019.This systematic literature review was conducted using PubMed, EMBASE, and Web of Science databases. Data on antibiotic consumption in Japan was sourced from the Japan Surveillance of Antimicrobial Consumption.A total of 1,442 articles and reports were screened, and 16 eligible articles were reviewed. The included studies were conducted in Jordan, Australia, Canada, UK, Japan, Brazil, India, China, and the EU. There was no study from African and Southeast Asian Countries. Overall, antibiotic consumption in the community consistently reduced in 2020. Studies from Australia, Canada, Portugal, Spain, the UK, Japan, and the European Union reported both decreases in overall and selected individual antibiotics consumption. In contrast, hospital-based studies reported both increases and decreases. Hospital-based studies in Lebanon, Spain, Italy, India, and the UK reported an increase in antibiotic consumption in 2020. Studies reporting an interruption of antibiotic stewardship programs during the pandemic also reported increases in antibiotic consumption for hospitalized patients in 2020 compared with that in 2019.Our results showed a different trend between communities and hospitals in antibiotic consumption during 2020 compared to 2019. The continuity of the antibiotic stewardship program might have influenced the antibiotic consumption trend variability among hospitals in 2020. Alongside this, the lack of information on antibiotic consumption from low-income countries and limited reports from middle-income countries revealed gaps that need to be urgently filled. Antimicrobial-resistant (AMR) bacterial infections—which cause longer hospital stays and higher treatment costs and mortality rates—have been regarded as one of the biggest global health issues , 2. DeatThe coronavirus disease COVID-19) pandemic has impacted many aspects of our daily lives, including economics , social  pandemichttps://amrcrc.ncgm.go.jp/surveillance/Surveillance_en.html) (DeepL.com). The entire procedure of the systematic review was conducted by two independent reviewers: MF and NNH.An electronic literature search of the PubMed, Web of Science, and EMBASE databases was conducted. The search terms used were  AND consumption AND (COVID-19 OR SARS-CoV-2). The antibiotic consumption in Japan and Japanese hospitals were identified using data from the Japan Surveillance of Antimicrobial Consumption (JSAC) database (en.html) . The seaA study was considered eligible if it met all the following inclusion criteria: 1) involved human participants; 2) reported annual overall antibiotic consumption in 2019 and 2020; 3) quantified antibiotic consumption at a hospital or hospital department or area or country level; and 4) controlled number of inpatients or admissions when they reported hospital-based consumption. A study was considered ineligible if it met any of the following exclusion criteria: 1) only involved non-human subjects; 2) only reported quantified antibiotic consumption among specially selected study participants based on their health conditions ; 3) indirect measurements to quantify antibiotic consumption ; 4) failed to report the measuring unit of antibiotic consumption; 5) hospital-based study that did not control the number of patients when they reported the quantity of antibiotic consumption; and 6) failed to report the quantity of total antibiotic consumption, 7) case reports, review, opinion, and/or study protocol.The most accurate index that reflected antibiotic use among the targeted populations was antibiotic consumption. However, some studies used antibiotic prescription or dispensation as a proxy of consumption because of the difficulty in accurately measuring antibiotic consumption at the community level. Therefore, community-based studies reporting antibiotic prescriptions and/or dispensations were also included.The main objective of this study was to explore trends in antibiotic consumption over a long period during the COVID-19 pandemic. Therefore, studies that reported the annual consumption of antibiotics in both 2019 and 2020 were initially considered in this review. In addition, studies that reported a quasi-annual consumption  were included in this review. Studies that exclusively focused on antibiotic consumption during the first wave of the COVID-19 pandemic were excluded.Several studies reported the statistical significance of the change in the quantity of antibiotic consumption during the study years. In this case, their categorization of the trend of this change was followed, namely an increase, no significant change, or a decrease. In contrast, some studies reported only the total quantity of annual antibiotic consumption without any statistical analysis. In this case, their categorization of the trend was followed, namely a ≥10% change between 2019 and 2020. These studies were classified into increase or decrease categories. The remaining studies were classified as the no-change category.Quality assurance of the studies was conducted using a graded scale. The seven criteria were considered in the graded scale: 1) source of antibiotic consumption data was described; 2) antibiotics considered in the study were reported; 3) study period was reported, 4) pre-COVID-19 pandemic antibiotic consumption quantity was reported; 5) antibiotic consumption quantity during the COVID-19 pandemic (or in 2020) was reported; 6) antibiotic consumption quantity was controlled by the number of inpatients and/or inhabitants; and 7) antibiotic consumption quantity was controlled by the number of days of treatment. The scores of the seven criteria were added, and the quality of the study was categorized as follows: low, 0–2; medium, 3–5; and high, 6–7. Based on these criteria, there were no low-quality studies .Through an electronic literature search, 1,441 articles were identified. In addition, one article was identified from the JSAC database. After excluding 172 duplicated articles, 1,270 articles were reviewed and 1,204 articles were excluded by titles and abstracts because they were clearly not relate to our current study. Full text of remaining 66 articles were reviewed, and finally, 16 articles were included in this systematic review –28 Figu. Eight sThese hospital-based studies were conducted in Lebanon, Spain, Italy, India, Brazil, China, and the UK , 23–28. Similarly, Andrews et al. reported a decrease in antibiotic prescriptions in the community in 2020 and an increase in hospital admissions in England . They alThe interruption or reduction of antibiotic stewardship programs during the COVID-19 pandemic has been reported by Grau et al. , Macera The economies of countries were categorized according to the World Bank country and lending groups . HospitaOur systematic review results revealed a consistent decrease in community antibiotic consumption –22. In cAll the studies identified in our systematic review reported a decrease in antibiotic consumption at the national level –22. The Increased public awareness regarding infectious disease control was a positive side effect of the COVID-19 pandemic. However, regardless of the benefits of strict regulations such as city/country lockdown and state of emergency in COVID-19 control, the pandemic has affected the economy  and mentContrary to the consistent decrease in overall antibiotic consumption in the community, there was a different trend in antibiotic consumption in hospitals , 23–28. One study from Spain reported an interrupted antibiotic stewardship program in 66 acute care hospitals and increased antibiotic consumption . In contOur review results showed that the studies were mostly published in high-income countries. Only one community-based study was reported from a middle-income country (Jordan)  and threThis review excluded studies that exclusively focused on patients with specific comorbidities, including COVID-19. However, the magnitude of the effect of antibiotic consumption on COVID-19 patients could not be distinguished from hospital- or department-level antibiotic consumption, even though this effects the overall antibiotic consumption trend. National-level studies  included both outpatient and inpatient antibiotic consumption. Thus, although the main interest was antibiotic use in the community, this report included inpatient antibiotic use. Because of the type of data, we could not distinguish between these data in some community- and national-level studies. In addition, the variability of the size of the targeted population could not be directly considered in the current study.During the COVID-19 pandemic, all community- and national-level studies reported an overall decrease in antibiotic consumption. This could be because of the reduction in infectious disease cases induced by social and individual control of infection. In contrast, hospital inpatients' antibiotic consumption was reported to decrease or increase depending on the hospital. This could be because of the increase in the ratio of more severe patients during the pandemic and the interruption of antibiotic stewardship programs. Thus, hospitals that reported an interruption of antibiotic stewardship programs in 2020 also reported an increase in antibiotic consumption. Our results highlight the importance of continuing antibiotic stewardship programs even while implementing amendments to manage to the pandemic. In addition, the review showed a research output gap between low- and middle-income countries. More studies evaluating the effect of the COVID-19 pandemic on antibiotic consumption should be conducted in these countries.The original contributions presented in the study are included in the article/MF, DL, and OO: initial conception and design of the study. MF and N-HN: systematic review and data extraction. MF, N-HN, DL, SF, and OO: contribution to drafting manuscript editing/reviewing. All authors approved the final version of the manuscript.MF was supported by the Japan Agency for Medical Research and Development (project code: 22fk0108630h0001) and the University of Tsukuba's review paper-editing project. The funders do not play a role in this review results.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.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.


The need for low-cost raw materials is driven by the fact that iron ore tailings, a prevalent kind of hazardous solid waste, have created major environmental issues. Although many studies have focused on using iron ore tailing (IOT) in concrete and have reported positive results, readers may find it difficult to accurately assess the behaviors of IOT in concrete due to the scattered nature of the information. Therefore, a comprehensive assessment of IOT in concrete is necessary. This paper thoroughly reviews the characteristics of concrete that contains IOT such as fresh properties, mechanical properties and durability at different age of curing. The outcome of this review indicates that by using IOT, concrete’s mechanical properties and durability improved, but its flowability decreased. Compressive strength of concrete with 20% substitution of IOT is 14% more than reference concrete. Furthermore, up to 40% substitution of IOT produces concrete that has sufficient flowability and compactability. Scan electronic microscopy results indicate a weak interfacial transition zone (ITZ). The optimum IOT dosage is important since a greater dose may decrease the strength properties and durability owing to a lack of fluidity. Depending on the physical and chemical composition of IOT, the average value of optimum percentages ranges from 30 to 40%. The assessment also recommends areas of unsolved research for future investigations. Concrete is a raw material often utilized in construction and serves as the foundation for all infrastructure projects and construction projects worldwide ,2,3,4,5.The demand for natural resources has increased along with the continuous rise in living standards, and increasingly more industrial waste is being created . Reusing2 emissions.Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs. The term “sustainable building” describes management that is responsible for formulating a welcoming atmosphere that takes ecological and resources development into consideration ,21,22. OOwing to worries about potentially hazardous social and environmental effects of waste, the tendency of rising solid waste output has created its environmental disposal a critical problem. Recycling industrial trash is one strategy to reduce these problems ,34,35. IThe preparation and performance testing of concrete containing iron mine tailings have made some progress in recent years, owing to efforts by domestic and international academics. Research  that useA brief literature review on IOT shows that it has credibility to be used in concrete. Although many researchers focus on the utilization of IOT in concrete and reported a positive response, knowledge is scattered and readers feel difficulty in easily judging the behaviors of IOT in concrete. Therefore, a comprehensive review is required for IOT in concrete. This review provides a detailed study on the physical and chemical properties of concrete containing IOT—when fresh, and its hardening and durability after curing. Microstructure analyses were also reviewed. Finally, the review also identifies research gaps for future studies. Scanning electron microscopy (SEM) images of the two aggregates are shown in 2), gibbsite, hematite (Fe2O3), and chamosite , as shown in 3) are also found in the spectrum. According to research, quartz makes up most of the natural sand while other minerals are also present in the tailings [tailings . When cetailings .materiaIn comparison to regular concrete under the same conditions, the slumps and fluidity of concrete mixed with IOT decreased, as indicated in According to research, the first slump value improved as IOT content grew, especially when IOT substitution was less than 30% and water content remained constant. The combination that included 30% IOT had the largest drop, measuring 195 mm, together with good cohesion and water retention. The reason for this was that the finer IOT made the mortar more fluid, which reduced the coarse aggregate’s resistance to motion. However, when the IOT content increased and reached a level of 30% or more, the slump value began to decline. This was done to avoid the concrete mixture becoming too thick if there was too much IOT in the finer-size powder . The IOTThe fineness modulus for IOT is 1.05, which is less than half the minimum 2.3 value required by the ASTM C33 standard for sand , reducinFor instance, the bleeding capacity at 30 min was lowered by 52% and the bleeding rate by 48% for the mix containing 30% IOT. The bleeding tests also revealed that when the IOT content was lower than 30%, the bleeding rate increased after 30 min. The finer size of IOT with a particular surface, which decreased the quantity of free water in the mixture compared to natural river sand, should be blamed for the decrease in bleeding rate and bleeding capacity .The results of the compacting factor test vary from 0.89 to 0.92, as shown in In contrast to 28-day conventional cured counterparts, the heat-treated specimens had greater CS. This may be accounted for by the acceleration of the hydration process during high-temperature curing, which results in a notable increase in strength at a young age. The quick hydration products that form around the unhydrated cement grains, on the other hand, impede further hydration and increase porosity, which has a detrimental effect on the strength development . The CS It should be highlighted that concrete made with 12% iron waste had a 15% higher CS than regular concrete after 28 days. The mix ratio was primarily intended to provide 33 MPa at 28 days, but more may be achieved at 7 days by adding 12% iron waste, which is equivalent to 35 MPa. Therefore, using 12% iron waste in concrete may be advised if the concrete has to attain its maximum CS in the shortest amount of time . The CS At 28 days, however, all the tailing mortars had a strength reduction of 10 to 17% whereas the control mix still had an FS of 18.6 MPa. The flexural strength of T0 reached 22.5 MPa after 90 days, and the strength difference between T0 and the tailing mortars widened even more. When the tailings concentration was between 20 and 50%, the FS decreased by around 20% and by 29% for T100. The control mix’s FS was equivalent to that of its 28-day standard cured counterpart for steam curing, while all of the tailing mortars had strengths that were greater than those of their 28-day standard cured counterparts and were comparable to the control mix . The staThe previous findings demonstrate that water absorption decreases as IOT concentration increases, making UHPC mortars very impermeable. The mortars’ macropores and micropores fill with fine IOT particles as the hydration products rise . TherefoThe Coulomb electric flux test, which is used for the chloride permeability rating, is used to assess the impact of IOT on the planned UHPC’s chloride resistance. The findings are displayed in In general, shrinkage is considered as a significant durability characteristic of hardened concrete. Concrete durability may be reduced if harmful contaminants enter via fractures caused by dry shrinkage ,74. The The ITZ between the paste and MS seems to be extremely thick as the curing age increased, there are hardly any noticeable flaws, and the connection between them looks to be very strong at 28 days, as shown in T40 has the maximum compressive strength at age 28. As shown in 2) and calcium carbonate (CaCO3) into CaO and CO2, respectively, and the evaporation of water (from liquid activator and C-S-H) and water at various temperatures [2(CH), which occurred between 447 and 462 °C. Wei et al. [2 is decomposed by the addition of IOT, resulting in the creation of C-S-H. However, even after the addition of 30% IOT, an endothermic peak that corresponds to the breakdown of Ca(OH)2 can still be seen, proving that not all of the Ca is transformed into C-S-H. By consuming Ca(OH)2, the addition of IOT causes the matrix to produce more C-S-H. Calculating the mass loss at 440 °C, which is caused by the breakdown of Ca(OH)2, may be used to determine the quantity of Ca(OH)2. Ca(OH)2 amounts are shown in 2 contents decrease, indicating its conversion to C-S-H. The findings of the rising compressive strength are further supported by the lowered Ca(OH)2 and the resulting creation of more C-S-H. The weight loss at about 120 °C caused by the evaporation of water  rises with the concentration of IOT, indicating that calcium silicate hydrate gel is being produced as a result of the addition of IOT. The IOT’s role in the development of calcium silicate hydrate gel is demonstrated by the reduced Ca(OH)2 and the resulting formation of additional C-S-H.The weight loss in the references IOT10, IOT20, and IOT30 was attributed to the breakdown of portlandite (Ca(OH)eratures . Accordieratures , clear ei et al.  discover2 index of the planned UHPC with IOT has to be assessed since IOT replaces some of the cement. A carbon footprint is used to evaluate how sustainable a constructed UHPC is, and 2 emission (kg/m3). It is evident that the installation of IOT reduces CO2 emissions. For instance, a typical UHPC mixture without IOT emits 690.96 kg/m3 of CO2 [Owing to its superior mechanical qualities compared to conventional concrete, UHPC may be considered an environmentally benign material. As a result, it is possible to create lightweight concrete structures while using less raw resources overall. Additionally, because of its great resilience, concrete may have a longer service life and lower cost maintenance in the future. In addition to the benefits already described, the emission CO3 of CO2 .2 emission is still 672.06 kg/m3 [2 discharges for the UHPC mixture. Additionally, the application of IOT in UHPC may lessen the burden on landfills brought on by IOT. In general, IOT may be utilized to create an advanced, ecofriendly UHPC. Therefore, from the standpoint of an environmentally responsible UHPC design, it makes sense to employ IOT as the cementitious material.When IOT is added at a 30% concentration, this number is dramatically lowered to 470.42 kg. IOT has also been used to substitute for river sand as the fine aggregate. However, according to the reference, even with 100% replacement, the COResearch reported in  found thPhysical properties show that IOT particles are rough and angular, which reduce the flowability of concrete.The chemical composition and XRD analysis of IOT show that IOT has the ability to be utilized as a binding material.Fresh properties of concrete such as slump flow and compactability decrease with added IOT. However, up to 40% substitution of IOT shows that concrete has sufficient flowability and compactability. Furthermore, for higher doses, a plasticizer is recommended.To certain limit, mechanical strength improves with IOT substitution due to micro filling voids and pozzolanic reaction. Different researchers recommend different optimum doses. However, the typical optimum dose varies from 30 to 40%. However, a higher dose of IOT (greater 40%) adversely affects the mechanical strength of concrete.Compressive strength of concrete with 20% substituted IOT is 14% more than reference concrete.Water absorption, chloride ion penetration, and dry shrinkage decrease considerably with the substitution of IOT.SEM results indicate that ITZ (cracks) improved with the substitution IOT due to filling voids and pozzolanic reaction.The performance of concrete with incorporated IOT is reviewed for several studies carried out during the last ten years. More than 80 papers were critically examined and summarized in this work. The following conclusions may be made in light of this review:Finally, the overall studies recommend that up to 40% IOT has the credibility to be used in concrete without any harmful effect on strength and durability properties.Although IOT enhanced concrete strength and durability properties, its low tension capacity results in sudden collapse without any indication. Therefore, more study is suggested to enhance the tensile strength of dune-based sand with the addition of fibers. Additionally, as IOT adversely affects the flowability of concrete, further research is recommended to apply a treatment . A detailed investigation of IOT as fine aggregate at elevated temperatures should be conducted.


We examined the use of antibiotics for acute respiratory infections in an urgent-care setting.Retrospective database review.The study was conducted in 2 urgent-care clinics staffed by academic emergency physicians in San Diego, California.Visits for acute respiratory infections were identified based on presenting complaints.The primary outcome was a discharge prescription for an antibiotic. The patient and provider characteristics that predicted this outcome were analyzed using logistic regression. The variation in antibiotic prescriptions between providers was also analyzed.In total, 15,160 visits were analyzed. The patient characteristics were not predictive of antibiotic treatment. Physicians were more likely than advanced practice practitioners to prescribe antibiotics . For every year of seniority, a provider was 1.03  more likely to prescribe an antibiotic. Although the providers saw similar patients, we detected significant variation in the antibiotic prescription rate between providers: the mean antibiotic prescription rate within the top quartile was 54.3% and the mean rate in the bottom quartile was 21.7%.The patient and provider characteristics we examined were either not predictive or were only weakly predictive of receiving an antibiotic prescription for acute respiratory infection. However, we detected a marked variation between providers in the rate of antibiotic prescription. Provider differences, not patient differences, drive variations in antibiotic prescriptions. Stewardship efforts may be more effective if directed at providers rather than patients. The treatment of acute respiratory infections  is the most common reason for antibiotic prescriptions in the outpatient setting. Systematic reviews have revealed that antibiotics provide little to no symptomatic relief for the common cold, acute otitis media in children, maxillary sinusitis, sore throat, and acute bronchitis. The number needed to prevent rare complications of acute respiratory infections (ARIs), such as mastoiditis or pneumonia, is >4,000 cases. However, it has been estimated that antibiotics are prescribed in more than one-half of outpatient visits for ARI. This is unfortunate because antibiotics are associated with diarrhea, allergic skin reactions, anaphylaxis, and the development of resistance in the individual taking the antibiotic.The rapid growth of antibiotic-resistant infections is a significant public health problem; curbing unnecessary use of antibiotics in the healthcare setting is one part of the solution. There has been a large increase in the use of retail and urgent-care clinics, where ARIs are frequently seen. However, the antibiotic utilization patterns in this setting have not been specifically examined.Understanding the characteristics of ARI antibiotic practices can inform efforts to reduce their unnecessary use. Previous studies have generally relied on large outpatient survey databases.In this retrospective review, we examined the use of antibiotics for ARI in patients in the urgent-care setting. We also investigated specific predictors of antibiotic use not available for study in large databases  and the variation between provider antibiotic prescription rates.The study setting consisted of 2 urgent-care centers serving suburban populations associated with an academic healthcare system. The combined annual census comprises ∼20,000–30,000 visits. The providers included emergency physicians (EPs), nurse practitioners (NPs), and physician assistants (PAs). NPs and PAs were combined in the analysis and are referred to as advanced practice practitioners (APP). In these urgent-care centers, physicians and APPs generally encounter the same types of patients. No physician or APP trainees worked at these sites. Data on cases between September 2016 and November 2019 were obtained from electronic medical records. All ARI-presenting complaints were taken from the 50 most common complaints, including congestion, cough, ear pain, fever, flu-like symptoms, pharyngitis, sinus problems, sore throat, and throat pain. Cases with a secondary chief complaint were also excluded; these were often found to have confounders, such as a chief complaint of “UTI.” Cases with missing data were excluded.Sanford Guide to Antimicrobial Therapy. Antibiotics included amoxicillin, amoxicillin-clavulanic acid, azithromycin, cefdinir, clindamycin, penicillin G, and penicillin V. We excluded other antibiotics, such as doxycycline and fluroquinolones, that theoretically could be used for ARI. In a preliminary review of our data, the incidence of their use was small and was often associated with non-ARI use, including UTI and cellulitis. Thus, these were excluded to minimize error.The primary outcome was the presence of a discharge prescription for antibiotics in patients presenting to a urgent-care clinic with an ARI presenting complaint of ARI. A review of the most common ARI antibiotics was obtained from the Predictors of discharge prescription were determined a priori. They included both patient and provider characteristics. Patient characteristics included age, sex, and whether the patient was there for a repeat visit, which was defined as a visit within 2 weeks of the initial visit (both visits had to be for an ARI). In the provider analysis, those providers with <30 patient visits were excluded to decrease random error. This study was reviewed and approved by the local institutional review board.Provider characteristics included years since training graduation , sex, provider type (physician vs APP), and whether the provider was a high prescriber of antibiotics. Providers were ranked according to the rate at which an antibiotic was prescribed for ARI visits: a high-prescribing provider was defined as above the 75th percentile and low prescribers were below the 25th percentile. Years since training graduation were obtained from departmental records, direct inquiry by e-mail, or through the website Doximity.Patient, visit, and provider characteristics are also reported. The 2 most common antibiotics were assessed in each complaint group. Predictive factors for antibiotic prescription were assessed using unadjusted (single predictor) and adjusted (multipredictor) logistic regression. Effect sizes were summarized using odds ratios and 95% confidence intervals (CIs). No predictors were prespecified. The final multipredictor model was determined using backward model selection based on the Wald test with a threshold of inclusion of 0.20. Univariable results for high antibiotic prescribers were included as a reference but were not included in the final model because there was a correlation with the other variables.Variations in the rate of antibiotic prescription for ARIs among urgent-care providers who saw at least 30 patients are also reported. The coefficient of variation (COV) was used to quantify variations, defined as the standard deviation divided by the mean value. These values were generated to quantify the variation among providers in terms of the antibiotic prescription rate. Patients with ARI are seen by providers in urgent-care settings in a somewhat random manner; this suggests that any variation seen is not driven by patient factors. To confirm this, age and presenting complaints were compared between high and low antibiotic prescribers and between physicians and APPs. Analyses were performed using SPSS for Mac version 26 software .In total, 19,549 patients with the 50 most common chief complaints were identified as having ARIs between 2017 and 2019. We excluded 1,956 cases who had a second chief complaint and 2,433 cases with missing data, leaving 15,160 cases for analysis. Patient, provider, and visit characteristics are listed in Table Table Figure To determine whether patient-level factors were driving this variation, the age and chief-complaint distribution are compared between high and low prescribers, as well as between APPs and physicians Table . No sign As of 2018, 78% of urgent-care clinics are located in suburban areas. It is not clear how the association with an academic medical center would affect results. The literature on antibiotic use for ARI generally relies on large national surveys, such as the National Ambulatory Medical Care Survey; this should be considered when comparing results to our study.This study had several limitations. This multisite study within a single health system may not have external validity in other practice settings or existing literature. The 2 urgent-care clinics in our study, associated with an academic medical center in southern California, serve a suburban population. The Western region generally has a lower rate of antibiotic prescription compared to the Northeast, South, and Midwest regions.One benefit of this single-center study was access to variables that are infrequently studied, such as provider sex, seniority, and professional degree. However, the numbers were small for certain categories of providers, and we were unable to include these variables in the multivariable analysis. We did not find that a repeated visit for an ARI predicted receiving an antibiotic prescription; however, this result was limited to repeated visits within our system because visits outside our system were not captured. The rates for bronchitis and pharyngitis were both ∼60%; we recorded rates of 33% and 32.4%, respectively,. We found less of a difference for sinusitis patients: nationally, the rate is ∼70%, and we recorded a rate of 60%. The lower antibiotic rate could be due to differences in patient population, study methodology, or chance. An alternative hypothesis could be the association of this urgent-care center with an academic medical center, which may be worthy of further study.In this study of antibiotic use for ARI in urgent-care patients, the rate of antibiotic use was lower than that generally found in the literature. The overall antibiotic prescription rate for ARIs is ∼60%; we recorded a rate of 35%. This was the case in the present study. We did not study patient race; again, with some exceptions, this factor is generally weakly predictive of receiving an antibiotic for ARI.In general, neither patient age nor sex has been found to predict antibiotic prescription for ARI. discovered that older male providers were more likely to prescribe antibiotics, whereas Jones et al (2015) noted no difference. Suda et al (2016) reported that APPs were increasing their rate of prescribing antibiotics while physicians were decreasing their rate; however, physicians still prescribed antibiotics at a higher rate. Shaver et al (2019) also determined that patients seen by APPs were less likely to receive antibiotics. However, Frost et al (2018) found that APPs prescribe more, and Jones et al (2015) reported no difference between physicians and APPs.In this study, provider sex did not predict prescribing an antibiotic, but older providers and physicians (compared to APPs) were more likely to provide a prescription. However, the existing literature examining provider characteristics is inconsistent. McKay et al (2019)In summary, we did not detect consistent identifiable patient or provider characteristics that can predict antibiotic prescriptions for ARIs. In our analysis, provider characteristics were more predictive than patient characteristics but were still only weakly predictive. Variation was measured between different variables, including geographic regions, insurance plans, and specialties. However, only 2 studies have recorded variations in ARI treatment between providers, both of which were drawn from large databases. We discovered that significant variation is not surprising, but it is novel because we present it in the urgent-care population specifically, and it was among providers seeing the same population of patients.Variation in the rate of antibiotic prescription for ARIs has been well established. However, persistently high rates of overuse suggest that there is still work to be done. Our data, showing high variation in rates of antibiotic utilization among providers seeing the same types of patients, suggest that efforts directed toward providers, not patients, might be more effective.Antibiotic stewardship programs can decrease antibiotic use.


The originality of this paper was the use of our own production method for the fine aluminum powder through atomizing the recycled molten waste of this metal using concentrated jets of nitrogen. Additionally, the waste melting technique involved our own microwave heating method. A high weight proportion of calcined gypsum (maximum 82.3%) represented the main concrete binder. Using moderate contents of coal fly ash (3.6–11.1%) together with perlite (4.6–6.4%) to reduce the pore size and silica fume (0.3–1.2%) with pozzolanic properties, the aim was to obtain a macrostructure characterized by a very low pore size and to increase the compressive strength (by up to 4.1 MPa), despite the relatively low density (below 641 kg/m3). An industrial method of increasing the mechanical strength by steam curing fresh concrete was applied.A cellular concrete with a fine porous structure was experimentally made using the corrosion technique for aluminum powder as an expanding agent in an aqueous solution of Ca(OH) Cellular (aerated) concrete as a construction material has been designed and industrially manufactured since the first decades of the 20th century. The Swedish architect Axel Eriksson patented the production technique for this concrete type by mixing limestone and ground slate  in termsIn another study , particlIn , the funThe application of aerated concrete in construction has highlighted several advantages compared to common concrete, as it can maintain a comfortable climate in the building while reducing the heating cooling costs, it is fire-resistant, it shows resistance to earthquake activities, it is environmentally sustainability, and it provides effective insulation for sound ,4.3), thermal conductivity (0.06–0.40 W/mK), and compressive strength (0.4–15 MPa). The compressive strength is strongly influenced by the curing conditions. Autoclaved concretes (cured with steam at high pressure) have higher mechanical strength compared to concretes with common binder and common curing conditions.Cellular concretes are considered as synthetic materials, with the hardened binder having a homogeneously distributed porous structure . AccordiCurrently, there are several known manufacturing variants for aerated concrete, depending on the nature of the binding component  and the type of siliceous component , as well as the curing conditions  .2 and 25.4% CaO or 7% wollastonite containing 53.4% SiO2 and 34.7% CaO). The choice of mineral additives took into account their influence on the hydration of the clinker minerals and the formation of the hardened cement paste structure. The characteristics of the experimentally manufactured concretes were density values of 580 kg/m3 (in the case of using diopside) and 600 kg/m3 (in the case of using wollastonite), compressive strength values of 3.3 MPa (in the case of using diopside) and 3.1 MPa (in the case of using wollastonite), as well as the thermal conductivity values of 0.131 W/mK (diopside) and 0.135 W/mK (wollastonite).The experimental production of non-autoclaved aerated concrete with mineral additives was tested according to . Portlan3) , and molecular hydrogen. The process took place at room temperature. Theoretically, the general reaction that characterizes the process of hydrogen release together with the solid phase, called katoite (which enters the molten mass), using aluminum powder in an aqueous solution of Ca(OH)2 is as follows:According to , in whic2+ and OH− ions , coal fly ash, perlite, silica fume, CMC, and aluminum powder. The oxide compositions of coal fly ash, perlite, and silica fume are shown in The solid materials used in the experiment and noted above were calcined gypsum  used in the experiment was produced by the team of authors at the Romanian companies Cosfel Actual and Daily Sourcing and Research using an original installation for molten metal atomization . The coaIn order to test the manufacture of cellular concrete without the cement and aggregates usually used in making traditional building concrete, the modern solution for the mixture, including calcined gypsum, hydrated lime, coal fly ash, perlite, silica fume, carboxymethyl cellulose (CMC), and aluminum powder (as an expanding agent), as well as distilled water, was adopted in the four experimental variants shown in 2 in the aqueous solution, which facilitates the corrosion of aluminum powder in order to release hydrogen as a foaming gas for cellular concrete manufacture, was used within the limits of 5.0–7.8%.It was experimentally found that there was a correlation with the coal fly ash/perlite/silica fume weight ratio in the starting mixture, which influences the fineness and uniformity of the cellular concrete’s porous structure. The four variants were adopted so that the proportions of coal fly ash increased from 3.6 to 11.1%. Correspondingly, the increase in fly ash content involved a reduction in the perlite proportion from 6.4 to 4.6% and a decrease in the silica fume content from 1.2 to 0.3%. The calcined gypsum content as the main binder of the concrete was reduced from 82.3 to 74.7%, corresponding to its substitution with coal fly ash. Having a role as a foam stabilizer, CMC was used at a constant weight proportion of 0.5% in all tested variants. Hydrated lime, as the supplier of Ca(OH)The details of the mixture’s preparation process were as follows. The mixing after dosing the solid components  was performed by mechanical stirring. Distilled water was poured over the mixture after its homogenization. During this time, the stirring of the mixture continued. After forming the slurry, it was poured into a metal mold with removable walls and allowed to expand freely. The temperature range at which the preparation of fresh concrete was carried out was 70–80 °C . The relatively low density together with the thermal conductivity over a range of low values (0.129–0.144 W/mK) contributed decisively to the heat-insulating properties of the cellular concrete. In a relationship of inverse proportionality to these properties, the concrete porosity increased with the decreases in density and thermal conductivity values from 74.2 to 75.9%. The main mechanical characteristic (compressive strength) simultaneously increased with the increases in bulk density and thermal conductivity, reaching a maximum value of 4.1 MPa in the case of the specimen corresponding to variant 1, largely due to the minimal content of coal fly ash and the maximal contents of perlite and silica fume, respectively, which allowed a homogeneous structure with small pores to be obtained. Regarding the water absorption in the concrete mass, the values varied between 2.6 and 3.5 vol.%. According to the previous literature observations, a material in which the volume of the voids (pores) is smaller and the volume of the ceramic solid mass is higher absorbs more moisture compared to a similar material containing more voids. Thus, the volume of water absorbed by the specimen corresponding to variant 1 reached the maximum value of 3.5 vol.% under the conditions in which this sample had the highest bulk density and the lowest porosity.The characteristics of the cellular concrete samples made under the technical conditions presented in the paper corresponded to the adopted objectives. Thus, the bulk density values were within the estimated limits  and the maximum content of coal fly ash (11.1%) were used, showed a relatively inhomogeneous pore distribution in the cross-section. This physical characteristic led to a decrease in compressive strength by almost 50% compared to the concrete specimen corresponding to variant 1, although the bulk density and thermal conductivity values remained at a low level.The cross-section appearance of the cellular concrete specimens is shown in The microstructural homogeneity of the cellular concrete specimens was investigated by examining the pictures shown in The major advantage of cellular concrete is its light weight, which saves the support structures of the building , meaning high degree of thermal and acoustic insulation is achieved. Additionally, due to the porous structure, the cellular concrete ensures the important economy of material used in the manufacturing process.2O2) and calcium carbide (CaC2), the aluminum powder has the ability to generate a porous structure in the concrete, releasing hydrogen, oxygen, and acetylene. Among these, the use of aluminum powder is the most often applied as an aerating agent [Together with hydrogen peroxide . The interest of concrete manufacturers is to obtain high mechanical strength under conditions where the density is kept at a low level. This goal in terms of quality became achievable by applying the steam curing method.4·0.5H2O) was the main binder of the mixture, with adequate physical, thermal, and ecological properties for building concretes. Coal fly ash was introduced into the mixture due to its contribution to improving the properties of the concrete. The inorganic filler perlite was adopted for its ability to reduce the pore size. Due to the pozzolanic properties, silica fume was also added into the mixture. The adopted foaming agent was aluminum powder prepared using the authors’ original method from aluminum waste melted via unconventional microwave heating. The nitrogen distributed in converging jets upon contact with the molten aluminum jet allowed the atomization of the melt and its capture in a metal enclosure with water-cooled walls in the form of particles with grain sizes below 10 μm. Hydrated lime Ca(OH)2 dissolved in distilled water provided the aqueous solution that facilitated the corrosion reaction of the fine aluminum particles with the release of hydrogen as an expansion gas. The fresh concrete was cured by periodical blowing steam at 0.3 bar and 75 °C under laboratory conditions in a room that was permanently heated to 80 °C for 8 h, of which the steam blowing last for 3.5 h. Of the four variants tested, variant 1, in which the weight proportions of the mixture components were 82.3% calcined gypsum, 5% hydrated lime, 3.6% coal fly ash, 6.4% perlite, 1.2% silica fume, 0.5% CMC, 1% aluminum, and 41.6% water, was considered optimal. The main experimentally identified characteristics of the cellular concrete were its bulk density of 641 kg/m3, porosity of 74.2%, thermal conductivity of 0.144 W/mK, compressive strength of 4.1 MPa, water absorption rate of 3.5 vol.%, and pore size range of 0.2∓1 mm. In comparison with the data from the literature, the characteristics of the experimentally produced cellular concrete were excellent, the concrete being suitable for building applications.The objective of the work was making a high-strength cellular concrete with a relatively low density. The main components of traditional concrete (cement and aggregate) were not used in this experiment. Calcined gypsum (CaSO


With the rapid development of urbanization, the construction industry consumes a lot of cement and produces a large amount of construction waste. To overcome this situation, the rational use of recycled aggregate produced from waste concrete is one of solutions. In some countries, the building industry has approved the use of recycled coarse aggregates in concrete, with some limits. However, practically all existing standards and regulations prohibit the use of recycled fine aggregate (RFA) in concrete. Therefore, study on improving the performance of RFA concrete is vital. In this study, the effects of fly ash and GGBS on concrete with RFA were investigated. Compressive strength, pore structure, drying shrinkage and accelerated carbonation were tested. The correlation between the pore structure and properties of concrete was analyzed. The results show that adding fly ash and GGBS to RFA concrete increased its compressive strength, modified pore structure, reduced drying shrinkage, and even achieved higher compressive strength and lower drying shrinkage than normal concrete. The compressive strength was mainly affected by the capillary pores, and the carbonation was mainly affected by the gel pores. Howev3 ,7, 317 M3 . Therefo3 .Several studies have been conducted on the properties of RFA concrete. Gholampour et al.  studied On the other hand, some studies have shown that the application of cementitious materials in concrete can improve durability, reduce long-term deformation, and modify the pore structure. It has been reported that cementitious materials enhance the workability, improve the performance of concrete at high temperatures, and inhibit the alkali-aggregate reaction . Fly ashThe purpose of this study was to enhance the compressive strength and durability performance of RFA concrete by adding cementitious materials, and to analyze the influence of microstructure on the mechanical properties and durability of RFA concrete. The optimal addition rate of fly ash or GGBS in RFA concrete was obtained. After adding supplementary cementitious materials, RFA concrete had higher strength and lower drying shrinkage than ordinary concrete. In addition, the influence of pore volume of different pore diameters on the compressive strength and durability of RFA concrete was analyzed. The micropores in RFA concrete were divided into harmful pores, small harmful pores, and harmless pores according to diameter. The results of this study will provide a basis for the application of RFA in practical engineering.Sea sand (S) and M standard RFA conforming to JIS A 5022  were useOPC as defined in JIS R 5210 , supplem3, and the unit coarse aggregate amount was 945 kg/m3. A total of 12 concrete mixes were prepared: the control concrete, concrete containing sea sand replaced with RFA (50% by volume), four mixes containing cement replaced with FA or MFA (10% and 15% by weight), two mixes containing cement replaced with GGBS (30% and 45% by weight), and four mixes with cement replaced (30% and 45% by weight) by FA and GGBS using ternary binders (the ratio of FA to GGBS was 1 or 0.5). In the process of concrete production, the aggregates were all surface dry. The mix proportions of the concrete cast in this experiment are shown in According to JIS A 1108 , testingThe “Method of measurement for length change of mortar and concrete” described in JIS A 1129-2  was used2 concentration of 2.0%, 20 °C, and RH of 65% for 7, 28, 56, and 91 days. The depth of carbonation was tested at a specified age by splitting the specimen at right angles to the length direction and immediately spraying the split surface with 1% phenolphthalein solution to measure the depth-stained red purple. The carbonation depth of was measured at five points on each side , and the average was taken as the carbonation depth. The carbonation depth was modelled by Equation (1):0.5).The accelerated carbonation experiment was conducted according to JIS A1153  using 40Porosity was measured by mercury intrusion porosimetry (MIP). The samples were prepared by crushing a specimen (φ100 × 200 mm) that had been cured in water at 20 °C to the specific material age and sieving the powder to obtain particles of 2.5 to 5.0 mm. The hydration reaction was stopped by immersion in acetone, and then the powder was dried under vacuum for 72 h before use. The porosity was tested at 7, 28, and 91 days to investigate the development of the pore structure of concrete.2 might result in abundant CSH, resulting in modified pore structure and improved long-term strength, which is ultimately responsible for the improvement in the mechanical performance [The pozzolanic reaction between fly ash and Ca(OH)formance ,63,65. TZhao et al.  reported2 to diffuse into concrete.The accelerated carbonation experiment results are shown in 2 in fly ash concrete compared to normal concrete [concrete ,82, whicconcrete .2, resulting in a decrease in the pH of the concrete [concrete . When thWhen the total FA and GGBS content was constant, increasing the FA content increased the carbonation velocity coefficient.The pore volume of concrete containing 30% cementitious materials did not change substantially, whereas that containing 45% cementitious materials was different. The total pore volume of concrete containing the blended admixture was larger than that containing only GGBS; while the volume of the pores at 0.05–2 µm did not change much, the volume of the pores at 0.01–0.05 µm increased. The experimental results prove that the activity of pozzolanic reaction of GGBS is greater than that of fly ash, so the pore volume of concrete mixed with GGBS only had a higher pore volume at pore diameters of less than 0.01 µm. Furthermore, we found that the incorporation of GGBS decreased the volume of pores with a diameter greater than 0.01, and the incorporation of fly ash had little effect on the volume of pores. with a diameter of 0.05–2µm but increased the volume of pores with a diameter of 0.01–0.05µm.Based on MIP-determined trials, Mindess et al.  defined 2) for the 0.01–36 µm pore volume were the highest. However, the 7-day compressive strength had a good correlation with the 0.05–2 μm pore volume. In 2 of 0.87. Therefore, for the compressive strength, pores with a diameter greater than 0.05 μm can be termed harmful pores, 0.01–0.05 μm small harmful pores, and less than 0.01 μm harmless pores.Based on the relationship between pore volume and pore diameter, we analyzed the correlation between the compressive strength of concrete at each age and the total pore volumes of 0.01–36, 0.05–36, 0.003–2, 0.01–2, and 0.05–2 μm. 2 of 0.83. Thus, the carbonation velocity coefficient of concrete was linearly related to the volume of pores with diameters less than 0.01 µm.Adding fly ash and GGBS to RFA concrete increased its compressive strength. M50BS45 and M50FA15BS15 exhibited similar 91-day compressive strengths with normal concrete. Therefore, the compressive strength of RFA concrete can be effectively improved by the use of cementitious materials.Replacement of cement with fly ash or GGBS significantly decreased the drying shrinkage of the RFA concrete. The drying shrinkage of all specimens in this experiment reached the level of ordinary concrete, and even lower than that of ordinary concrete. M50FA15BS15 showed 16.5% lower drying shrinkage, M50BS45 and M50FA15BS30 showed around 25% lower drying shrinkage than normal concrete.Increasing the cementitious (fly ash and GGBS) materials content decreased the carbonation resistance of RFA concrete. Fly ash had a greater effect on carbonation than GGBS.Incorporating FA or GGBS into concrete modified the pore structure of concrete, and reduced the volume of capillaries larger than 0.05 μm. In addition, the compressive strength was mainly affected by capillary pores (greater than 0.01 μm or 0.05 μm), and the carbonation was mainly affected by gel pores (less than 0.01 μm).For compressive strength, pores with a diameter greater than 0.05 μm are considered harmful pores, 0.01–0.05 μm are considered small harmful pores, and less than 0.01 μm are considered harmless pores.


The coarse aggregate–mortar interface transition zone (ITZ) has a great influence on the mechanical properties of concrete, which cannot be easily studied using laboratory tests in the mesoscale. In this paper, a series of axial compression tests were conducted using the discrete element method (DEM) on concrete specimens for four phases: coarse aggregates, mortars, aggregate–mortar interface transition zones, and voids. The effects of ITZ strength on macroscopic stress and microscopic cracks under different strength reduction factors were investigated through axial compression testing. With the increase in interface transition strength, the compressive strength of the concrete becomes stronger; moreover, the number of cracks decreases, and the anisotropy of contact orientation becomes weaker. Meanwhile, the direction of crack development and the damage mode of compressed concrete specimens were also dependent on the coarse aggregate–mortar interface strength coefficient. As the material with the highest strength-to-price ratio, concrete has played a revolutionary role in the world’s architectural history over the past century. In 1965, Fanran  and fillThe contributing factors to the properties of the interface transition zone have been studied widely. For example, silica fume can fill the holes created by the cement’s exothermic reaction and improve the density of the interface between the aggregate and mortar ,5. An adAmong the many simulation methods, the discrete element method (DEM) proposed by Cundall in 1971 ,11 has uAt present, the main analysis points of ITZ effect are focused on macro mechanical properties ,20,21, sR, A, I, and J are the radius, area, moment of inertia, and polar moment of inertia of the bond cross sections, respectively.The parallel bond model (PBM) developed by D.O. Potion and P.A. Cundall  was used3 was selected as a reference experiment [Herein, the axial laboratory compression test on the concrete specimen with a size of 50 × 50 × 50 mmperiment , in whicperiment ,24,25 waperiment . The conE), stiffness ratio (k), bonding effective modulus , according to parameters calibrated by previous studies ,17,26. Tσy) field in the specimen at an axial strain level of 0.0011, at which the stress in the stress–strain curve reaches maximum of 28.7 MPa. The stress distribution in the specimen is inhomogeneous, and the maximum stress zone accumulated around the outlines of the coarse aggregate, shown in red, is 57.3 MPa. Compared with the peak stress in the stress–strain curve, the maximum stress in the specimen can reach two times the peak stress of the specimen; meanwhile, the weak stress parts also formed around the voids in the specimen, shown in blue in the figure, which demonstrate that the existence of coarse aggregates and voids increases the inhomogeneous stress field and stress concentration in the specimen. R), and the reduction factors are listed as 0.2, 0.4, 0.6, 0.8, and 1.0 in five tests, respectively. The maximum shearing strength  is taken as a mesoscopic characteristic index in which f is the ratio of contact force over the mean contact force, and it can be calculated using the following Equation (2):N is the total number of intervals; k is the number of intervals; and NR is the amount of contact force in the k interval. For example, k is the number of contact force, which when divided by mean contact force ranges from k−1 to k.f < 1 and the strong contact force interval with f > 1. It can be clearly seen that with the increase in R, the probability of weak contact force decreases and the probability of strong contact force increases. Therefore, the ITZ strength will affect the proportion of the strong contact force-chain inside the specimen, so the internal force transmitted by the concrete increases, corresponding to the stronger load capacity of the concrete.E(θ) [E(θ) represents the proportion of the contact whose direction is within D θ around the E(θ) and has the following properties:Contact orientation is the probability of a contact force-chain forming in all directions, which can be described by the density function E(θ) , and E(θE(θ), it can be approximated by a Fourier series:aθ represents the principal direction of normal contact and a is the anisotropy coefficient. When a = 0, the specimen is anisotropic, and this characteristic will be more obvious as a increases.Due to the periodicity of a can examine the level of the anisotropy of each specimen. Integrating the Fourier series of E(θ) gives:Hence, the index a can be expressed as:aθ can be expressed as:The anisotropy index R and axial strain ε. Overall, the contact orientation of the specimen remains vertical during loading. However, when the strain is 0.2%, the contact force in the specimen is so small that the contact orientation changes significantly.According to Equations (8) and (9), the anisotropy of each specimen can be obtained. a and strain ε. The figure shows that as the strain increases, a also increases, especially after plastic strain, since the occurrence of failure will enhance the anisotropic properties of the specimen. Moreover, improving R will decrease the anisotropy index a of the specimen, indicating that enhancing the ITZ strength will make the particles inside the specimen display more balanced stress in all directions.The anisotropy indices are reflected in In this paper, a four-phase concrete model based on the real damage surface of concrete was established by PFC2D. The model can reflect the mechanical properties of concrete well by considering the effects of ITZ strength. On this basis, compression tests were carried out with different ITZ strength coefficients.R ≥ 0.8, which is the same as previous studies [In the tests, macro mechanical strength curves are first studied; the peak stress of concrete increases as the ITZ strength increases, and the corresponding effects can be ignored after  studies ,20. FurtThe micro crack and contact characteristics are subsequently studied; with the increase in ITZ strength, the initial cracks are transformed from an ITZ zone into a void zone, and the crack’s number and elevation increase. Meanwhile, the concrete is prone to brittle failure and the concrete will be damaged from shearing to tensile. For microscopic perspective, as the ITZ strength increases, the force-chain quantity and strength of the specimen will increase, and the contact anisotropy will become weaker. The specimen with low ITZ strength has a fragile and instable contact net, which resulted in crack development and contact anisotropy. Therefore, a relatively stable force-chain structure has a great influence on the mechanical properties of concrete.In summary, the ITZ strength has a great impact on the mechanical properties of concrete when the surface is too small. Controlling the minimum quality of ITZ is the basic requirement to ensure the effectiveness of concrete.