Antimicrobial resistance (AMR) is considered as a global health and development threat. During COVID-19 pandemic, there has been an increase in antimicrobial resistance. Health care providers (HCPs) play the main role in facing antibiotic resistance because they have the authority to prescribe antibiotics during clinical practice as well as in promoting patients’ compliance with therapies and avoid self-medication. So, this study will serve as an important source of information in context with Covid19 pandemic in Egypt. The data was collected using a validated standardized self-administered online questionnaire compromised of four sections: socio-demographic data of the HCPs, the general knowledge on antibiotics and AMR, the HCP attitude towards antibiotic prescription and AMR and the practice in applying the appropriate antibiotic prescription. Most of HCPs (93.7%) recorded good knowledge level about antibiotic prescription and antimicrobial resistance with mean score of knowledge13.21 ± 1.83. About 79% of HCPs recorded a positive attitude towards proper antibiotic prescription with mean score of attitudes 63.02 ± 7.68. Fifty four percent of HCPs demonstrated a good level of practice with mean score of practice 9.75 ± 2.17. In conclusion, HCPs in our study have a good level of knowledge and attitude about antibiotics. However lower level of proper practice towards the problem of AMR in COVID19 era was noticed. Implementation of effective policies and guidelines is crucial to evaluate the antimicrobial use especially in the COVID-19 era to reduce the unintended consequences of the misuse of antibiotics and its impact on AMR. Antimicrobial resistance (AMR) is considered as a global health and development threat. Bacterial infections that are unsuccessfully treated due to antibiotic resistance was reported to cause mortality rate of at least 700,000 people per year worldwide and are expected to kill 10 million people per year by 2050, at a cost of US$100 trillion in lost output to the global economy. The World Health Organization (WHO) has announced AMR as a major global problem and started a global action plan to combat AMR [Corona virus disease COVID-19), which is caused by the severe acute respiratory syndrome coronavirus 2 (SARS Cov2), had caused 764,474,387 confirmed cases, including 6,915,286 deaths as reported on 26 April 2023 by WHO [, which iA large proportion of COVID-19 patients need hospitalization and are at a great risk of developing hospital-acquired bacterial and fungal infections , 11. ManInitial studies had raised concerns about the long-term impact of the COVID-19 pandemic on prevalence and predictors of antibiotic prescription in COVID-19 Patients. These studies had reported that antibiotics are commonly prescribed to patients with COVID-19 despite the relatively low prevalence of bacterial co-infection (less than 10%). A previous study in India found that bacterial and fungal super infections were uncommon in hospitalized COVID-19 patients. Most of super infections were nosocomial and caused by Extensively Drug Resistant (XDR) bacteria because of antibiotic overuse at that time. Poor Infection control and empirical over-use of broad-spectrum antimicrobials are two practices that should be avoided to prevent future epidemics of XDR organisms .Another study conducted in France found that general practitioners (GPs) tended to overprescribe broad-spectrum antibiotics for extended periods of time for COVID-19 patients as well as other viral infections. They had a higher, but not statistically significant, ratio of azithromycin over all other antibiotics .Inappropriate antibiotic prescriptions in COVID-19 patients can cause major complications such as increased bacterial resistance, adverse drug reactions, clostridioides difficile infections and renal impairment , 17. As Health care providers (HCPs) play the main role in facing antibiotic resistance because they have the authority to prescribe antibiotics during clinical practice as well as in promoting patients’ compliance to therapies and avoid self-medication . UnfortuMinimizing the use of antibiotics is the best way to stop the spread of AMR, and this can be done by changing prescribing practices. Evidence-focused questionnaires like knowledge, attitude, and practices (KAP) surveys can be used to analyze the factors influencing medical doctors’ prescribing behaviors .In a systemic review published in 2017, discussing the antimicrobial resistance in Africa, reported that more than a 33% of the African countries did not have recent published data about AMR although they noticed high level of antibiotics resistance in these African countries . This reIn Egypt, antimicrobial therapy was mostly prescribed empirically. As reported in the Egyptian National Action Plan for Antimicrobial Resistance, only in 4% of antimicrobials prescribed based on culture for community acquired infections and in 18% of antimicrobials prescribed for Hospital Acquired Infections. Inappropriate prescriptions may be caused by knowledge gaps in antibiotics uses and resistance development as well as a lack of legal characteristics in antibiotic distribution .There were a limited number of previous KAP studies, and most were conducted before the pandemic. Prescribers may change their practice only when their knowledge, attitudes, thoughts, skills, and knowledge are integrated with each other, resulting in a reduction in antibiotic prescribing. This will in turn reduce the development and spread of infections that are resistant to antibiotics .Recently, an Egyptian study published in 202 reported a good level of knowledge about antibiotics with low levels of positive attitude and proper practice towards the problem of AMR before COVID-19 pandemic. They also reported that only (15.4%) of the Egyptian HCPs referred to national antibiotic guidelines as the main reference of data about antibiotic resistance and stewardship program contrasted with (19.8%) who used the international guidelines which are considered unacceptable low rate of using both national and international guidelines .It is a hot issue to resolve the problem of antibiotic usage during COVID-19 pandemic among prescribers to limit the development of resistance. To the best of our knowledge, this is the first national study that identifies knowledge, characterizes practices, and describes the attitude of Egyptian prescribers towards antibiotic use during COVID-19 pandemic. So, this study will serve as an important source of information in context with Covid19 pandemic for other health care professionals to improve practice of antibiotic prescription. Moreover, this study will help health officials and policy makers in designing an evidence-based education and advocacy plan on prevention of antibiotic resistance in Egypt.A cross sectional analytic online based study was conducted to assess KAP of health care providers (HCPs) toward antibiotics prescription and its resistance in context with COVID19 pandemic in Egypt. We hypothesized that HCPs had good knowledge with less positive attitude and malpractices regarding antibiotics prescription during COVID-19 pandemic.2 as reported in 2018 [The study was conducted in governmental and private hospital in Egypt, officially the Arab Republic of Egypt. The Arab Republic of Egypt spans the northeast corner of Africa. Egypt is one of the most populous countries in Africa and the Middle East. The estimated population is about 99.38 million with a population density of Egypt as a whole is 48 people per km in 2018 . Egypt, Healthcare Providers including physicians and dentist working governmental and private hospitals in Egypt dealing with patients and handling antibiotics for the treatment of cases. Participants were recruited to study during the period between January 2022 and July 2022. According to the Egyptian Medical Syndicate, the Ministry of Health (MoHP) had 213,000 licenced physicians as of September 2020. However, of those registered, only two fifths, or 82,000, actually practice in the country .Physicians aged from 25 to 65 years, including medical doctors (MD), internist and various clinical specialties  were included from the study.Radiologists, and basic sciences doctors were excluded. Egyptian physicians working outside Egypt or in annual leaves.Convenience sampling method was implemented. The sample size was Calculated to be 317 participants based on a reported previous proportion of adequate knowledge among Egyptian health care physicians (71.6%) with a margin of error (5%) . Then afThe data was collected using a validated standardized self-administered online questionnaire used before in Egypt . The queThe data was downloaded from the Google form and checked for any missing answers. SPSS version 23 was used to analyze data. Mean and S.D were calculated for quantitative variables. Categorical data was analyzed by computing percentages. Categorical data were compared using Chi-square test (χ2test). P-value of ≤0.05 was considered statistically significant. The associations between the binary outcome variables (good versus poor knowledge and favorable versus unfavorable attitude) of the respondents on antibiotics usage and resistance with the independent socio-demographic characteristics of participant such as age, gender, level of education and work institutions of the respondents were analyzed.For knowledge score, a score of “1” was assigned to every correct answer and ‘0’ for every wrong answer. The total score was added, and it ranged from 0 to18. A cut off value for good knowledge level is equal to or above 60% of total marks while, those who scored below that was defined as “poor” knowledge on antibiotics use and antibiotic resistance. Similarly, for the attitude related questions, a score of 5 to 1 was assigned to each question according to the selected answer on the Likert scale then the total score was added. The total score ranged from 17 to 85. Those who scored equal or above 60% of marks were considered as “favorable attitude” but when the scores were less than that, it was considered as “unfavorable attitude towards antibiotics prescription and AMR. For assessing practice, antibiotic prescription practice was calculated by giving one point for each selected step. The total score ranged from 1 to 4. Practice level ≥60% of marks was categorized as an appropriate practice.The study was approved by the Research Ethics Committee, Faculty of Medicine, Suez Canal University (Research 4605#).The structured questionnaire was merged into online Google form. The URL link was distributed among healthcare providers. A clear statement was included in the beginning of the questionnaire form that completion of it indicates participant’s consent to participate in the study.A clear statement was included in the beginning of the questionnaire form that completion of it indicates participant’s consent to publish the results of this study.The current study included 350 Egyptian health care providers (HCPs). Below half of HCPs (42.8%) live in Ismailia city while the remaining 57.1% were from another eleven governorates which are (Suez (18.5%), Cairo(14.2%), Sharkya (7.1%), North Sinai(4.5%), Portsaid(2.8%) Menofia(2.5%),Qena(1.5%),Minya(1.5%), Gharbia(1.5%), Dakahlya (1.5%), and Alexandria(1.5%). Males represented half of the sample (50.3%). The mean age of participants was 34.75 ± 7.41. Almost all the participants were physicians and only one participant was dentist. Near a quarter of the studied participants (24.6%) had obtained Medical Decorate (MD) degree while 34% had master’s degree. The highest percentage of HCPs (171 HCPs) were working in university Hospitals (48.9%), while the lowest percentage (12 HCPs) were worked in private clinics (3.4%). Three quarters of HCPs (248) (70.9%) didn’t attend any training/ educational course for antibiotics prescription .The main sources of information about antibiotic prescription and resistance were international antibiotic guidelines, followed by advice from older colleagues and internet representing 21.1%, 17.7% and 13.7% respectively . Most ofRegarding the relation between sociodemographic characteristics and level of knowledge, there were no statistically significant risk factors for bad knowledge level . On the The increase of antibiotic resistance is of a great global health concern. With the complexity of COVID19 pandemic, antibiotic resistance has increased due to the over and misuse of antibiotics. Although the diagnosis of COVID19 has been more efficient nowadays but antibiotic treatment is still being prescribed by HCPs as a precaution . Health In poor and middle-income countries, insufficient training and education of HCPs regarding proper antimicrobial use is one of the most important risk factors that affects antimicrobial resistance . In our The main sources of information about antibiotic prescription and resistance in our study were international antibiotic guidelines, followed by advice from older colleagues and internet representing 21.1%, 17.7% and 13.7% respectively. In a study held in Zimbabwe, they stated that national guidelines were the main source for guiding prescribing in routine practice (93%). Other sources of information to support prescribing were textbooks in (70%), discussions with colleagues (63%) and professional meetings (62%) .Knowledge obviously reflects the practice of individuals as it is the base for good practice. The knowledge of HCPs regarding antibiotic use and resistance especially during COVID-19 era is of a great importance. Physicians, Pharmacists, and Dentists are the professionals who are in the front line having the authority to prescribe and give antibiotics to the patients, so they must be fully aware of the associated risks with this practice. In the present study most of the HCPs (93.7%) recorded good knowledge level about antibiotic prescription and antimicrobial resistance with mean score of knowledge13.21 ± 1.83. In a study carried out by Seaton et al. in United Kingdom, respondents reported strong knowledge on antimicrobial resistance and high trust in fulfilling their antibiotic stewardship programme within everyday practices (92.7%) . Also, iRegarding the attitude dimension, in our study 79% of HCPs recorded a positive attitude towards proper antibiotic prescription with mean score of attitudes 63.02 ± 7.68. On the other side, lower levels of positive attitude were recorded (49%) by Nwafia et al. . In CheoBelow half of our study participants of HCPs demonstrated a good level of practice. Other study by Muradyan et al. reported 63% good level of practice among practitioners . AlthougIn order to improve a doctor’s attitude and practice towards incorrect prescribing, organised interventions are needed. In this situation, antimicrobial stewardship programmes (ASPs) can play a significant role in limiting the misuse of antibiotics in hospitals. However, it is unknown to what extent hospitals have implemented standardized ASPs, and there is a lack of key implementation data and facts on the rollout of ASPs, particularly in low- and middle-income countries. Hospitals lack the tracking and documenting of antibiotic usage for the purpose of submitting it to a provincial, national, or international database . The CDCThe study included different specialties of health care providers from several work institutions. The study used a validated data collection tool. The limitation that data was collected online due to precautions of COVID19 using a convenient sampling method which might affect generalization of our results. The relatively small sample size, which may not accurately represent the actual KAP of physicians in EGYPT as a whole. Although, Participants were from 12 governorates, a larger sample size and random sample would have been preferable to produce a more broadly applicable result. The need for Internet access to complete the questionnaire was yet another restriction because not all HCPSs had enough time during the COVID 19 pandemic to access the internet to fill in the questionnaire which might resulted in selection bias. A cross-sectional survey cannot clarify the cause-effect relationship. The study didn’t assess some variables that may affect prescription practice such as workload, shifts and work stress during the Covid19 pandemic. Almost all participants were physicians. The sample didn’t include different categories of HCPs.Health care practitioners in our study have a good level of knowledge and attitude about antibiotics however lower level of proper practice towards the problem of AMR in COVID19 era was noticed. Low rates for attending courses and education programmes about antibiotic uses and resistance were found. Implementation of effective policies and guidelines is crucial to evaluate the antimicrobial use especially in the COVID-19 era to reduce the unintended consequences of the misuse of antibiotics and its impact on AMR. Moreover, healthcare institutes must ensure that healthcare practitioners receive training and education for proper antimicrobial prescribing. The bulk of the essential components of antimicrobial stewardship are either missing or "Under Process," which points to serious gaps in the practice. If ignored, these gaps will cause severe problems and ultimately have an impact on how effectively antibiotics are used in hospitals. Stakeholders should implement antibiotic stewardship programmes quickly in hospitals to stop the spread of antibiotic resistance and improve antibiotic therapy. Evaluation of the barriers is needed to make future plans on improving awareness of and access to antibiotic resources, encouraging HCWs to use these resources and encouraging them not to prescribe when they feel antibiotics are not required. Behavioural change strategies should be implemented to reach effective and positive behaviours towards antibiotics use.


Culturing has been the cornerstone of microbiology since Robert Koch first successfully cultured bacteria in the late nineteenth century. However, even today, the majority of microorganisms in the marine environment remain uncultivated. There are various explanations for the inability to culture bacteria in the laboratory, including lack of essential nutrients, osmotic support or incubation conditions, low growth rate, development of micro-colonies, and the presence of senescent or viable but nonculturable (VBNC) cells. In the marine environment, many bacteria have been associated with dormancy, as typified by the VBNC state. VBNC refers to a state where bacteria are metabolically active, but are no longer culturable on routine growth media. It is apparently a unique survival strategy that has been adopted by many microorganisms in response to harsh environmental conditions and the bacterial cells in the VBNC state may regain culturability under favorable conditions. The resuscitation of VBNC cells may well be an important way to cultivate the otherwise uncultured microorganisms in marine environments. Many resuscitation stimuli that promote the restoration of culturability have so far been identified; these include sodium pyruvate, quorum sensing autoinducers, resuscitation-promoting factors Rpfs and YeaZ, and catalase. In this review, we focus on the issues associated with bacterial culturability, the diversity of bacteria entering the VBNC state, mechanisms of induction into the VBNC state, resuscitation factors of VBNC cells and implications of VBNC resuscitation stimuli for cultivating these otherwise uncultured microorganisms. Bringing important microorganisms into culture is still important in the era of high-throughput sequencing as their ecological functions in the marine environment can often only be known through isolation and cultivation. Candidatus”, but they may still have great importance in ecology and as the cause of disease in aquatic organisms. Multiple species of “Candidatus” have been described on the basis of DNA sequences and a few characteristics without the availability of pure cultures. For example, “Candidatus Syngnamydia venezia” has been reported as the causal agent of epitheliocystis in broad nosed pipefish  media and did not initially produce visible colonies. These organisms were truly obligate oligotrophs  at low temperature (4 °C), exhibited a decline in culturability on conventional culture media under normal culture conditions. However, a portion of the non-culturable population remained viable when they were detected by the direct viable count (DVC) procedure developed by Kogure et al.  and Edwardsiella tarda , Betaproteobacteria , Gammaproteobacteria , Epsilonproteobacteria , Bacteroidetes , Actinobacteria  and Firmicutes  (Table Proteobacteria and Bacteroidetes), although 25 species comprised Gram-positive non-sporulating bacteria (affiliated to phyla Actinobacteria or Firmicutes). Some other Gram-positive bacteria, notably Bacillus and Clostridium species, could form endospores, which is the first reported bacterial survival state .Bacterial species reported to enter the VBNC state are phylogenetically distributed: The list of microbial species currently discovered to enter the VBNC state mainly reflects the research interest of scientists, which includes pathogen taxa , those associated with food safety or environmental applications, rather than the actual existence of this survival process in natural microbial communities  being quicker and more sensitive.Detection in the absence of culturing initially focused on microscopy  that can initiate the cascade of cellular events leading to the VBNC state have been reported. The physical factors include high/low temperature, high/low salinity (osmotic stress), sub-optimal pH, sub-optimal redox conditions, sunlight, irradiation, drying, pulsed electric field and high-pressure stress. The chemical factors include nutrient starvation, antibiotic pressure, food preservatives, disinfectants , nitrite, heavy metals, organic pollutants or exposure to other toxic compounds  is low temperature  Tween 20 allowed the VBNC coccoid cells of Sal. enterica serovar Typhi to regain culturability, again within 24–48 h, and the resuscitated cells remained virulent as evidenced by animal infectivity experiments  that was produced during biofilm formation process in a serum-based medium  signal molecules have been reported to correlate with the resuscitation of cells from the VBNC state , were shown to have an important role in promoting resuscitation of VBNC cells  catalase allowed the VBNC cells of Sal. enterica to return to culturability  may be biological mediators for the resuscitation of some bacteria from the VBNC state. For example, the VBNC cells of 11–1012 microbial species in the natural environment may be grown on laboratory culture media ; a micro-aerobic organism isolated from well water in Japan. Subsequently, the addition of Rpf-containing culture supernatant from Mic. luteus enhanced the isolation of the biphenyl-degrading bacteria from PCB-contaminated soils of e-waste recycling sites in Taizhou, China (Su et al. In recent years, some resuscitation stimuli have been used successfully to recover bacteria from natural environments. Rpf protein (Mukamolova et al. Mic. luteus had a strong ability to promote the resuscitation of VBNC cells of a high-G + C Gram-positive Rhodococcus sp. DS471, which was isolated from soil. Moreover, the introduction of recombinant Rpf protein from Mic. luteus enabled the isolation of some unique bacterial species, which belonged to the genera Arthrobacter, Bacillus, Bordetella, Mycobacterium, Nocardiopsis, Novosphingobium and Pandoraea. Also, Rpf treatment significantly enhanced cellulase activity of the microbial community in mature compost produced from household and agro‐industrial wastes in China (Su et al. Rhodococcus erythropolis, and showed that Rpf could promote the resuscitation of the VBNC cells of Rho. erythropolis as well as efficiently improve the growth of normal Rho. erythropolis culture.Beside the application of Rpf-containing culture supernatant, the use of recombinant Rpf protein has attracted attention. For example, Ding et al.  demonstrSodium pyruvate was used successfully as a resuscitation stimulus, leading to the recovery of bacteria from natural environments. In this connection, Mu et al.  developeMarine microorganisms exist in an ever-challenging environment, and only a small proportion may be cultivated using currently available techniques. There are a variety of explanations for the inability to culture bacteria in the laboratory, including the use of unsuitable cultivation methods, neglected slow-growing microorganisms, the inability to communicate among microbial cells in pure culture, cell damage induced by oxidative stress of fast-growing bacteria, and the existence of VBNC bacteria. Many Gram-negative bacteria and nonsporulating Gram-positive bacteria can enter the VBNC state, which is a complicated metabolic strategy of bacteria to survive for long-term under adverse conditions. It is assumed that the VBNC response of bacteria is a common process, which may occur in the wider scope of bacterial taxa. In this regard, VBNC cells could constitute a huge reservoir of natural bacteria, which cannot be cultured easily with ordinary cultivation methods. Various resuscitating stimuli, which are able to revert VBNC cells to a metabolically active and culturable state on conventional bacteriological media, have been identified, including physical and chemical stimuli, active proteins, and biological stimuli. However, most studies of VBNC bacteria have focused on pure cultures in the laboratory rather than on environmental bacteria. Stimuli that are currently used on model or indicator strains may well be used to recover cells from the VBNC state in natural environments. Indeed, some resuscitation stimuli have recently been used successfully to recover bacteria from natural environments. Resuscitating indigenous microorganisms from environments may provide a new approach to explore crucial populations, which may play key roles in ecological processes or have great value for industrial applications, and deserve more attention and effort. In addition, different bacterial taxa may adopt different ways to resuscitate, and this point warrants further investigation.


This paper presents experimental results on the influence of concrete composition factors on the criterion characterizing the ratio between the compressive strength of activated low-cement concrete and clinker consumption. The investigation was carried out using mathematical planning of the experiments. Experimental and statistical models describing the influence of the fly ash, activating additive (microsilica), consumption of cement and aggregates, as well as the superplasticizer on the strength of low-cement concrete under normal hardening conditions and after steaming were obtained. The values of the clinker efficiency criterion and the mineral additive cementing efficiency coefficient were calculated, and models of these parameters were obtained for the investigated concrete compositions. It was shown that the activating effect of microsilica yields an increase in ash cementing efficiency and clinker efficiency criterion in concrete. Using the obtained models, an example for calculating the ash cementing efficiency coefficient is given. Both the costs of the main material, the energy resources, and the environmental impact of cement production are associated with the clinker. Increasing the value of criterion L = cmf/C is especially important for low-cement concrete, the technology for which is attracting more and more attention of researchers and manufacturers [3). For high-strength concrete, it can reach 0.2 or more.An important indicator of cement concrete’s economic and environmental efficiency is the ratio between the strength it achieves  can be found from the equation:W = W0 − DW is the change in the concrete mixture water demand when adding additives. W0 and DW are the concrete mixture water content without and with the mineral additives, respectively. At ΔW < 0, the additive effect decreases, and at ΔW > 0, it increases. At For concretes of equal strength with the same workability, the saving of cement Δc.e.K for an active mineral additive allows finding (C/W)m and designing the concrete composition containing an active mineral additive with a given hardened concrete strength. The value of c.eK is usually found experimentally and depends on the cement consumption and the additive content. The value of c.eK for complex mineral additives are presented and analyzed. The novelty of this approach is that the models enable assessment of the main technological factors and evaluation of the effectiveness of adding active components into low-cement concrete containing mineral additives.In the present study, statistical models of criterion L for low-cement ash-containing concrete and, based on them, the calculated values of Cement–ash concrete was made using Portland cement CEM I  with compressive strength class 32.5, strength after two days–13 MPa, and strength after 28 days–44.5 MPa. Fly ash from Ladyzhyn TPP (Ukraine) was used as the additive in concrete mixtures. The chemical composition of the Portland cement and ash is given in 2/kg, and the pozzolanic activity after 7 days was 15 mg/g, after 28 days was 45 mg/g, and after 60 days was 65 mg/g. To increase the activity of the fly ash, a microsilica additive was used. The microsilica contained 93% ultradispersed amorphous SiO2; it was characterized by a specific surface area of 19,000 m2/kg and a pozzolanic activity of 420 mg/g.The ash had a specific surface of 310 mTo solve the problems in the frame of this study, mathematical experiment planning methods  were useWhen planning the experiment, the following concrete structure parameters were taken as factors:msV) in the total volume of the active mineral additive (ashV—volume of fly ash);cV—cement volume);wV—water volume);aV—aggregate volume);spV—volume of naphthalene–formaldehyde type superplasticizer).The conditions for experiment planning and the factor variation range are shown in MS, Ash, C, W, A, and SP are the consumption of the activator (microsilica), ash, Portland cement, water, aggregate, and superplasticizer, respectively, kg/m3; ρ is the components density, kg/m3.Transition from the concrete structure parameters to the component’s consumption can be easily carried out using equations assuming that the absolute volume of the concrete mixture is equal to the sum of the volumes of its individual components:5 plan close to D-optimal [c.eK., are given in The experiment planning matrix for the Ha-optimal  is given-optimal ,22 and aThe concrete compositions for the tested specimens were obtained according to the conditions given in −Concrete compressive strength after 28 days of normal curingStatistical processing of the experimental results allowed us to obtain mathematical models of the concrete strength after 28 days of normal curing, the strength of the concrete subjected to steaming, the corresponding criteria L, and the cementing efficiency coefficients of the mineral admixture. The obtained models were considered adequate with a confidence level of 95%, which is considered satisfactory for concrete technology . The mod−Concrete compressive strength after steaming−Criterion L for concrete compressive strength after 28 days of normal curing−Criterion L for concrete compressive strength after steaming−c.eK for concrete compressive strength after 28 days of normal curingCementing efficiency coefficient −c.eK for concrete compressive strength after steamingCementing efficiency coefficient X1 (part of the activator (microsilica) in the volume of mineral additive). A lower effect was caused by factor X2   a. Factornfluence b. Factor Neville , the ratX1 and X5 in the models (Equations (10) and (11)), which is evident in There was a significant interaction of factors The investigated factors affected the concrete strength after steaming in a similar way . Thus, tBased on the experimentally obtained values of the strength at normal curing and after steaming, the values of L as the efficiency criterion for the use of cement and its main component, clinker, and the cementing efficiency coefficient of the mineral additive were calculated at all points of the experiment. Based on these values, mathematical models of criterion L and the coefficient of cementing efficiency for activated fly ash were obtained. Following the obtained mathematical models of criterion L (Equations (12) and (13)), this criterion varied from 0.03 to 0.26 MPa/kg at normal curing a and froAll the investigated factors had a positive effect on criterion L, similar to the effect on the concrete strength. Accordingly, the maximum value of the criterion was observed at the maximum content of the activator (microsilica), fly ash, and superplasticizer.c.eK acquires negative values . For a more convenient graphical solution of the mathematical models (Equations (14) and (15)), a obtained . Accordi3): cement (C)—123 kg; water (W)—118 L; ash—135 kg; microsilica (MS)—70 kg; sand (S)—648 kg; crushed stone (CS)—1377 kg; superplasticizer (SP)—2.6 kg. Density of concrete components: cement—ρc = 3100 kg/m3, ash—ρAsh = 2600 kg/m3; microsilica—ρms = 2500 kg/m3, superplasticizer—1100 kg/m3, water—1000 kg/m3.Example. Calculate the cementing efficiency coefficient of fly ash when used as an activator of microsilica, if the concrete with activated fly ash has after 28 days of hardening a compressive strength of 21 MPa. Concrete composition of (per 1 mSolution.X1) is:The part of the activator (microsilica) in the volume of the active mineral additive (2.X2) is:The part of the active mineral additive in the binder volume (3.X3) is:The part of the binder in the binding paste volume (4.X5) is:The part of the superplasticizer in the aqueous solution (5.c.eK is:From Equation (14) or according to the nomogram , the valc.eK = 0.11.A set of experimental–statistical dependences of strength, criterion L, and cementing efficiency coefficient at normal hardening and steaming was obtained for cement–ash concrete with microsilica additive and a naphthalene–formaldehyde-type superplasticizer using the mathematical experiment planning method.The analysis of the obtained models made it possible to establish the range of changes of the studied parameters and their influence on the concrete composition factors. It has been found that activation by mineral additive (fly ash), due to the addition of microsilica in presence of a superplasticizer yields a twofold increase in the concrete strength at normal hardening, and after steaming the strength increases about 2.5 times.3 exhibited the maximum efficiency criterion L; these compositions contained the maximum microsilica and superplasticizer values.The compositions of cement–ash concrete with a cement consumption of 100–140 kg/mTo find the fly ash cementing efficiency coefficient values, a corresponding nomogram was created. It allowed taking into account the influence of the cement, ash, activating mineral, and superplasticizer consumption and the concrete hardening conditions.The obtained cementing efficiency coefficient can be used to calculate compositions of concrete containing fly ash.


Ninety-eight (93%) participants refrain from using antibiotic prophylaxis, and sixty-eight (65%) use prophylaxis if complicating factors exist. If asymptomatic bacteriuria is present, approximately 54 (52%) participants omit UDS and reschedule the procedure until antimicrobial susceptibility testing is available. Seventy-eight (78%) participants do not have a standard procedure for antibiotic prophylaxis in their department. Part of the strategy against the development of bacterial resistance is the optimized use of antibiotics, including antibiotic prophylaxis in urodynamics. Establishing a standard procedure is necessary and purposeful to harmonize both aspects in the field of urological diagnostics.Antibiotic prophylaxis contributes substantially to the increase in antibiotic resistance rates worldwide. This investigation aims to assess the current standard of practice in using antibiotic prophylaxis for urodynamics (UDS) and identify barriers to guideline adherence. An online survey using a 22-item questionnaire designed according to the Checklist for Reporting Results of Internet E-Surveys (CHERRIES) was circulated among urologists and gynecologists in Austria, Germany, and Switzerland between September 2021 and March 2022. A total of 105 questionnaires were eligible for analysis. Out of 105 completed surveys, most responders ( Urodynamics (UD) is an important diagnostic tool for assessing lower urinary tract dysfunctions . Due to A total of 105 questionnaires  were eliA total of 98 (93%) participants do not routinely use antibiotic prophylaxis for UDS. If antibiotics for prophylaxis in UDS are utilized, the participants use oral cephalosporins, sulphonamides, or nitrofurantoin in either a single-shot application or administration for up to five days. Sixty-eight (65%) participants prescribe antibiotic prophylaxis in distinct situations, such as catheterized patients (36 (35%)), patients performing intermittent self-catheterization (18 (18%)), those undergoing dipstick analysis (40 (39%)) or sediment examination (23 (22%)), those suspicious of a UTI without clinical symptoms, those with the presence of NLUTD (16 (16%)), and those with a post-void residual volume (PVR) (15 (15%)) . In the case of asymptomatic bacteriuria, 54 (52%) participants omitted UDS and awaited antimicrobial susceptibility testing. The occurrence of symptomatic post-procedural UTI was reported by 29 colleagues (28%). The absolute number of infectious complications ranges from 1 to 20 annually. In addition, specific antimicrobial stewardship programs (AMS) and their implementation were surveyed. Most responders have the recourse of using dedicated AMS teams (69%), whereas 20 (19%) are actively involved in those institutions. The majority of the responders (78 (78%)) have no standard operating procedures regarding antibiotic prophylaxis prior to urodynamics.We conducted a multinational questionnaire to gain insights into the current standard of practice in peri-procedural antibiotic prophylaxis in UDS. Most responders do not routinely prescribe antibiotic prophylaxis for UDS. However, approximately 65% of the responders prescribe routine antibiotic prophylaxis in particular situations, such as for indwelling catheter, NLUTD, post-void residual, and intermittent residual self-catheterization patients. Dipstick urine analysis on the day of the scheduled UDS without routine sediment analysis was most frequently performed. On the contrary, urine cultures are not performed regularly, but are reserved for patients with complicating factors, such as an indwelling catheter. In the case of asymptomatic bacteriuria (ASB), more than half of the responders omit UDS and prescribe antibiotic therapy according to antimicrobial susceptibility testing prior to UDS. The guidelines fail to offer guidance regarding infection screening before UDS. Taking urine cultures before UDS would offer a great level of safety for patients but increase the cost and administrative effort. Dipstick analysis often lacks sensitivity to clinical indifferent symptoms . InfectiAMS finds its way into general practice, where partakers do not usually collaborate. Overall, the participants have no standard operating procedure concerning antibiotic prophylaxis. Our survey uncovered considerable heterogeneity in the overall management of antibiotic prophylaxis in UDS. There is no general standard of care in the primary evaluation before planned diagnostic intervention and effective antibiotics before urodynamics. Additionally, the use of ASB before UDS deeply divides healthcare professionals, and the necessity of targeted prophylaxis is unfathomable. The same applies to the choice of antimicrobial agent in case of treatment, depicted by the broad spectrum of antibiotics used before UDS. Strict AMS guideline adherence is essential to unifying antibiotic prophylaxis regimens among urologists and gynecologists performing UDS. The collected data depict the level of diversity and divisiveness in the relevance of ASB and dosage of therapeutics, duration of prophylaxis, as well as the overall choice of agent. Unnecessary antibiotic prophylaxis therapies should be strictly avoided, and antimicrobial stewardship programs should be installed to provide low-threshold information and counselling concerning targeted therapy. Other studies have shown the benefit of AMS programs in lowering evolution pressure, especially for multi-drug-resistant organisms (MDRO) . InapproInterdisciplinary collaborations should be instigated at every level of healthcare. New processes to reduce antibiotics’ overall prescription and administration must be evaluated and implemented, and barriers that limit adequate therapy should be removed. The multidisciplinary approach is necessary to address multifaceted, complex interventions. AMS programs promote and monitor the correct usage of antibiotics, and subsequently, enable the reduction of the number of patients with MDRO. Failed antimicrobial stewardship is jointly responsible for the ongoing evolution of MDRO. The overuse of fluoroquinolones provides an excellent example of a failed AMS. Even though striking evidence exists concerning the use of fluoroquinolones, there is a lot of it . On the Clear recommendations are mandatory for greater guideline adherence, and standard operating procedures should be developed. Kranz et al. have shown crucial problems in guideline adherence, e.g., it contains ambiguous and complicated flowcharts and tables, and its conversion into clinical practice is difficult and impracticability ,31. To iThe main goal and common ground should be encouraging strategies to tackle rising antibiotic resistance rates. The pre-emptive sparing of antibiotics in every utilization level is required to lower the burden on the evolution of antibiotic resistance. Ultimately, the main objective is avoidance of symptomatic UTI after UDS, which entails prolonged antibiotic therapy, increased costs and morbidity, and reduces the patient’s comfort and well-being.This study inherently has several limitations since we distributed a non-validated questionnaire survey. Furthermore, we gathered a relatively small, German-speaking, sample of urologists and gynecologists in Austria, Germany, and Switzerland. Therefore, we must consider the possibility of a relevant selection bias. There is a high likeability only physicians with interests in UDS and AMS attended the survey increasing the likelihood of a selection bias.A multinational survey was conducted among specialists in urological infections according to the reporting guidelines for surveys found on the equator-network.org, an international initiative providing robust reporting guidelines . The surThe target population was urologists and gynecologists performing urodynamics in Austria, Germany, and Switzerland. The goal was to have only one person per department participate in the survey.® . It was tested for usability by all the co-authors before setting it up online. The questionnaire was available from the 1 September 2021 to the 1 of March 2022. An invitation was sent out via the Working Group “Urological Functional Diagnostics and Urology of Women” and “Infectiology and Hygiene” of the German Society for Urology e.V. and all the contacts of the co-authors. Altogether, six reminders were sent out.The survey was transferred to the online platform, SurveyMonkeyThe investigation was performed in accordance with the ethical standards of the institutional and national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. Consent for this investigation was not mandatory, and no personal data were stored throughout the process. Survey participation was voluntary, and no incentives were offered. Only complete questionnaires were analyzed. The Kolmogorov–Smirnov test was used to preliminarily assess the numeric distribution for each numeric variable. Descriptive statistics were made using the mean and standard deviation (SD) for normal distribution or with the median and interquartile range (IQR) for non-parametric data using SPSS Version 27.There is a restricted level of agreement on the standard of care in UDS concerning the necessity of using antibiotic prophylaxis, the choice of agent, and the duration. Strong, elaborated, comprehensible, and well-disseminated guidelines are prerequisites for clarity and adherence. Strict AMS and standard operating procedures are essential in sparing antibiotics, tackling antibiotic resistance rates, and unifying the procedures for UDS. Given the common nature of genitourinary infections in general, urologists are at the forefront of challenging antibiotic overconsumption, especially when they use recommendations that are contrary to the guidelines. This survey offers new insights into the current standard of practice in peri-procedural antibiotic prophylaxis in UDS and depicts the often slow-paced penetration of guidelines into everyday practice.


Concrete structure performance continuously deteriorates during operation, and the performance is simultaneously affected by chloride corrosion and repeated traffic loading. Repeated-loading-induced cracks have an impact on the rate of chloride corrosion. Chloride-induced concrete corrosion also affect the stress level of the structure under loading. Therefore, the coupled effect of repeated loading and chloride corrosion on the structural performance needs to be investigated. An upgraded test device was developed for chloride corrosion testing of unsaturated concrete structures under repeated loading. Based on the experimental results, considering the influence of repeated loading on the moisture diffusion coefficient and the chloride diffusion coefficient, a chloride transport model for unsaturated concrete under the coupled effect of repeated uniaxial compressive loading and corrosion was established. The chloride concentration under coupled loading was determined by the Crank–Nicolson finite difference method and the Thomas algorithm, and then chloride transport under the coupled effect of repeated loading and corrosion was analyzed. The results showed that the stress level and the repeated loading cycles directly affect the relative volumetric water content and chloride concentration in unsaturated concrete. The effect of chloride corrosion is more severe in unsaturated concrete compared to saturated concrete. Concrete exposed to the marine environment is susceptible to various physical and chemical degradation processes. After harmful ions penetrate the concrete, the normal service life of the structure will be shortened . Fulin eSome studies have focused on the chloride transport behavior of saturated concrete under repeated loading ,13,14,15In addition, during operation, concrete structures are subject to continuously repeated loading such as vehicles, wind, waves, etc., which could cause fatigue damage in concrete, increase the connectivity between pores, provide more channels for chloride intrusion, and lead to the corrosion of reinforcements in the structures ,11,12,13Chloride ions in unsaturated concrete are continuously transported into concrete by capillary-absorption-induced convection and by concentration-gradient-induced diffusion . The couIn this paper, chloride transport in unsaturated concrete under the coupled effect of repeated loading and chloride diffusion was investigated. The effects of stress levels and the number of loading cycles on chloride transport were also analyzed. Based on experimental results, a modified chloride transport model of unsaturated concrete was proposed and verified. The proposed model provides a reference for the design, construction, operation, and maintenance of unsaturated concrete structures.According to the recommended dimensions and shapes of concrete specimens subjected to a coupled compressive loading and chloride penetration. in RILEM TC 246-TDC , a totalIn addition, three cubic concrete specimens (150 mm × 150 mm × 150 mm) and three prismatic concrete specimens (150 mm × 150 mm × 300 mm) were constructed to test their ultimate compressive strength. The average value of the ultimate compressive strength of the prism was used as the basis for calculating the maximum load and the minimum load under uniaxial compression repeated loading. In this test, the ultimate compressive strengths of cubic and prismatic concrete were 47.8 MPa and 32.5 MPa, respectively.After 28 days of standard curing, all specimens were placed in a drying system. The initial temperature of the drying system was set to 20 °C. Then, the temperature was increased by 20 °C every two hours until it reached 105 °C . The purTo measure the liquid absorption rate of unsaturated concrete specimens under repeated uniaxial compressive loading, we referred to the test process of Yan , and an The height of the specimens was relatively short; thus, the hydrostatic pressure distribution along the height direction was not significant and could be ignored. In addition, to overcome the influence of liquid gravity on concrete capillary suction, this paper adopted the side suction method. When the valve is closed, the solution in the observed part of the concrete will reduce due to capillary absorption. The amount of liquid absorption of the concrete can be obtained by observing the change in the observed area.4 cycles, 100 × 104 cycles, 150 × 104 cycles, and 200 × 104 cycles. The loading frequency was 4Hz. The loading method was divided into two types: coupled and uncoupled. Coupled loading means that the test specimens were subjected to both chloride corrosion as well as repeated uniaxial compressive loading. For uncoupled loading, specimens were subjected to a chloride corrosion test after the repeated loading and unloading. The testing scenario is detailed in To investigate the influence of repeated uniaxial compression loading on chloride transport in unsaturated concrete, factors such as the stress level and repeated loading cycles were studied. The stress levels were set to 0, 0.15, 0.3, and 0.45. The loading cycles were repeated for 50 × 10Sodium chloride solution was added from the liquid injection part of the liquid storage tank until the solution had reached the specified position in the observation tube. Then, the location of the solution in the observation tube was recorded at specified time intervals according to ASTM C1585-04 , as showThe concentration of chloride in the unsaturated concrete was determined by the drilling core sampling method and selective electrode method. A GERMANN RCT rapid chlorine meter for concrete was used to measure the chloride concentration. A drill with an inner diameter of 50 mm was used to drill six samples in each test specimen. The drilling depths were 1 mm, 6 mm, 11 mm, 16 mm, 21 mm, and 26 mm. The chloride concentration measurement process is shown in To reflect the level of liquid absorption of the unsaturated concrete at varying numbers of loading cycles and stress levels, the measured liquid absorption at different stages was converted into absorption per hour. The absorption rate of unsaturated concrete at each loading stage is shown in As shown in As shown in l, of the change in sodium chloride solution level in the horizontal tube of the test, the accumulated fluid absorption amount i (per unit area) of unsaturated concrete can be deduced using Equation (1).The moisture diffusivity of concrete is related to the liquid absorption rate. By observing the accumulated length, i–t1/2 [i–t1/2 curve is the absorption rate. Taking the test results of coupling loading for 1 million cycles as an example, no matter how the stress level of repeated uniaxial compression loading changes, the i–t1/2 curve of unsaturated concrete is bilinear, corresponding to the initial and secondary liquid absorption stages, respectively, as shown in 1/2). Piecewise linear fitting was performed on the i–t1/2 curve. The average liquid absorption rate under each stress condition was obtained. In this test, four groups of tests were carried out for the load conditions with stress levels of 0 and 0.3. In principle, the liquid absorption of concrete under the same load at the same time should be consistent, but due to the randomness of the concrete material, the liquid absorption slightly changes. The influence of the randomness of the concrete material should be removed in the analysis of the data, where the data are averaged. The average liquid absorption of each specimen was calculated at each stage and the cumulative liquid absorption per unit area of concrete was calculated under this stress level. Then, the average liquid absorption rate under each stress condition was obtained by piecewise linear fitting of the averaged curve. The calculation results are shown in The liquid absorption rate, is generally defined by means of i–t1/2 , where tThe results of the initial and secondary absorption rate of group I in Through the test results of groups I and III, it can be observed that the secondary absorption rate of C-30%-50 is less than that of C-0-50. The secondary absorption rates of C-30%-100, C-30%-150, and C-30%-200 are higher than C-0-100, C-0-150, C-0-200, respectively. This phenomenon shows that in the early stage of transmission, the new damage inside the concrete with a stress level of 30% is not enough to offset the impact of the initial compaction effect of the test specimens. Thus, the secondary liquid absorption rate is lower than the liquid absorption rate without stress. However, as the loading cycles continue to increase, the damage generated inside the concrete gradually offsets the impact of the initial compaction effect. Fatigue damage creates a channel for chloride transport. The secondary liquid absorption rate is greater than the liquid absorption rate without stress. The initial liquid absorption rate is the liquid absorption rate produced during the rapid water filling process of the capillary pores on the concrete surface. It is related to the porosity of concrete and the initial compression effect of repeated loading. However, the secondary liquid absorption rate is the liquid absorption rate produced during the slow filling of capillary pores in the concrete, which is related to the pores and cracks in concrete. When the loading cycles increase, more concrete damage will occur. The damage increases the connectivity between the pores and accelerates the process of moisture transport.The uncoupled loading specimen (UC-30%-100) was compared with the coupled loading specimen (C-30%-100), as shown in SL) with the same number of loading cycles, as shown in LC), micro-cracks in the concrete expand and gradually connect. The number of channels for the transport and migration of chloride increases, which significantly increases the concentration of chloride at various depths inside the unsaturated concrete.The chloride concentration increases first and then decreases with the stress level ; 2/s); and 3). Chloride transport in unsaturated concrete is the result of diffusion and convection. Fick’s law has been used to describe the diffusion of chloride ,33. The concrete . The fluAccording to the mass conservation law of chloride transport in concrete,rete, C′ ,(5)C=C′By substituting Equation (5) into Equation (4), the chloride transfer model of unsaturated concrete can be expressed as:The corrosion of the rebaris only related to the content of free chloride. The reason is that the redox reaction cannot occur with bound chloride and reinforcement. Therefore, when considering the effect of bound chloride, the left side of Equation (6) should be the change in total chloride content with time, and the right side should be the free chloride content.In this paper, the effect of bound chloride in unsaturated concrete is assumed to be linear. The bound coefficient of chloride is defined as In Equation (8), the concentration distribution of free chloride in unsaturated concrete is mainly related to two parameters: the moisture diffusion coefficient, , which cannot be solved independently. In the process of water transport, water not only satisfies the extended Darcy’s Law but also satisfies the law of conservation of mass. Therefore, the control equation of capillary water content can be derived in Equation (9):Equation (8) contains the concentration of free chloride in concrete, According to the unsaturated seepage theory of capillary absorption in porous media, Equation (9) should meet the initial conditions of n is the shape parameter of the diffusion coefficient curve.The moisture diffusivity, pression :(10)Dwθ=s is the relative liquid absorption rate and S is the liquid absorption rate of the specimen, which is the moisture absorption rate when concrete and water are in contact.Based on work by Parlange et al. , the anaS, can be deduced as:According to Equations (10) and (11), the relationship between n is from 4 to 6 [n, the closer the calculated result is to the experimental result. In view of this, Previous studies have shown that the range of the parameter m 4 to 6 ,38, and refS is the liquid absorption rate of the unloaded concrete specimen (mm/min1/2); According to the test results in According to Equations (12) and (13), the moisture diffusion coefficient model under repeated uniaxial compressive loading is derived as:N is the number of repeated loading cycles; The chloride diffusion coefficient model (Equation (15)) in concrete with the introduction of a crack factor and a fatigue parameter under repeated loading given in reference  is as fong to Yu ; N is thIn the initial stage of repeated loading, the accumulated concrete damage is insignificant. The major influence on the chloride transport at this stage is the initial compression effect of the load on the concrete. When the maximum stress level of the repeated uniaxial compressive loading has not reached the critical value, the chloride diffusion coefficient decreases with the increase in stress level. When the maximum stress level of repeated uniaxial compressive loading is greater than the critical value, the diffusion coefficient of chloride increases with the increase in stress level. Referring to a study by Zhang , a quadrThe curing age will also affect the transport of chloride in the concrete. Longer curing times provide sufficient time for the hydration reaction of the cement inside the concrete, resulting in fewer and smaller internal pores. Less and smaller internal pores mean fewer channels for chloride and moisture transport, resulting in a reduced diffusion coefficient. The influence of curing age on the diffusion coefficient of chloride  is:(17)FThe diffusion coefficient of the concrete matrix decreases with the increase in chloride ion erosion time. The reason for this is that with the increase in time, the cement inside the concrete undergoes a secondary hydration reaction, which makes the concrete more compact. The transmission path of chloride ions is reduced, so the chloride ion diffusion coefficient will continue to decrease:Therefore, the influence of the initial compression effect of repeated uniaxial compressive loading, From the test results in According to the above analysis, the suggested correction coefficient is substituted into Equation (10). The relationship between the load factor of the repeated uniaxial compressive loading and the liquid absorption rate of the unsaturated concrete isAccording to the concrete capillary water control equation (Equation (6)) and its approximate analytical solution, the software Matlab was used to calculate the distribution of relative volumetric water content in unsaturated concrete. The relative volumetric water absorption of unsaturated concrete under different stress levels and different loading cycles was calculated by using the average liquid absorption in each stage. The solutions are shown in As shown in When the relative volumetric water content is the same, the stress level has a great influence on the penetration depth, as shown in Based on the water diffusion coefficient model fitted by the test data and the modified chloride diffusion coefficient model, the Crank–Nicolson finite difference method and Thomas algorithm were used to solve the chloride transport model of unsaturated concrete under repeated uniaxial compressive loading (Equation (5)). It is assumed that the initial compression effect of uniaxial compression repeated loading has the same influence on the transport behavior of both water and chloride, namely The chloride concentration distribution in unsaturated concrete under different stress levels and loading cycles was calculated according to the proposed model, as shown in As shown in To analyze the influence of the state of concrete on chloride transport, a normalized chloride transmission law of saturated concrete from the literature  was compThe transport depth of chloride in unsaturated concrete is significantly larger than that in saturated concrete, as shown in Under repeated loading, the liquid absorption rate of unsaturated concrete exhibits an obvious two-stage trend. The liquid absorption rate of unsaturated concrete in the initial stage is mainly related to the stress level in capillary action and repeated loading. The increase in the liquid absorption rate in the second stage is mainly caused by diffusion of chloride through the accumulated damage channels inside the concrete under repeated loading.The internal damage of concrete before chloride exposure leads to changes in the transmission channels of moisture and chloride in the uncoupled test method. Thus, the penetration of moisture and chloride in unsaturated concrete will be overestimated.Fully considering the coupled effect of repeated loading and corrosion, the chloride diffusion coefficient and water diffusion coefficient are modified. The chloride transport model of unsaturated concrete under uniaxial compressive repeated load is established.The penetration depth when the relative moisture content is 0.4 can be used as the critical penetration depth of chloride for unsaturated concrete under coupled action. Repeated loading with a stress level of less than 0.2 will improve the chloride resistance of unsaturated concrete.The chloride transport in unsaturated and saturated concrete is different under the coupled action of repeated loading and corrosion. Unsaturated concrete has a higher chloride concentration and corrosion depth. The effect of chloride is more pronounced in unsaturated concrete.This paper conducted an experimental study on the transport of chloride inside unsaturated concrete under repeated loading. Based on the experimental results, a theoretical model for the calculation of chloride transport inside the unsaturated concrete under repeated uniaxial compressive loading was proposed. The main conclusions can be summarized as follows:


Guidelines for the management of pulmonary nontuberculous mycobacterial (NTM) infections are well defined; however, similar guidelines for the treatment of disseminated or extrapulmonary NTM infections are lacking. This study aimed to describe our institutional experience in the treatment of disseminated and extrapulmonary NTM infections, and to better characterize the disease course, management, and outcomes in this patient population.This single-center retrospective study was conducted at The Ohio State University Wexner Medical Center in patients who were diagnosed with disseminated or extrapulmonary NTM infection from November 1, 2011 to November 1, 2021. Only index cases were included in patients with a documented culture positive for an NTM, and patients with a positive pulmonary culture were only included if they had a documented extra-pulmonary site as well.58 patients met inclusion criteria and 54 were started on antibiotic therapy. 41.4% (N=24) and 31.0% (N=18) were started on two and three antibiotics as initial therapy, respectively. 32 (59.3%) patients required changes to their initial regimen, of which 31.3% (N=10) were changed due to intolerance or adverse event. The mean time to onset of antibiotic intolerance or adverse drug events was 129.4 days (6-404 days). 67.2% (N=39) of patients had documented resolution of their infections, with 7 patients currently on antibiotic therapy at the end of the study period (38.9%).The most common antibiotic classes used included macrolides (64.8%), carbapenems (35.2%), ethambutol (25.9%), and aminoglycosides (22.2%). The antibiotic classes with most frequent intolerances were linezolid (42%), aminoglycosides (31.6%) and clarithromycin (21.0%) at a mean duration of 39.3, 72.2, and 32 days, respectively.Table 1. NTM infection characteristics, including infection site, species breakdown, and disease outcome.Table 2. NTM treatment regimen details and reasons for changing and/or not completing planned antibiotic regimen for all study patients.Table 3. Breakdown of antibiotic classes used in initial treatment regimens for dNTM-infected patients, along with antibiotics that caused patient intolerances. For each antibiotic class that caused intolerance, average time to develop intolerance listed.Treatment of disseminated and extrapulmonary NTM infections typically requires a complicated treatment course due to prolonged durations of multiple antibiotics, patient intolerances to antibiotic classes, and difficulty with determining appropriate end of therapy timing. Additional studies are needed to better outline the ideal antibiotic regimens and duration for disseminated and extrapulmonary NTM infections.All Authors: No reported disclosures


To investigate the impact of the filament winding angle of glass-fiber reinforced plastic (GFRP) on the seismic behavior of GFRP tube ultra-high performance concrete (UHPC) composite columns, this study designs two types of GFRP tube UHPC composite columns. Quasi-static tests are conducted on the specimens subjected to horizontal reciprocating load and axial force, and the skeleton curve characteristics of the structure are analyzed. Furthermore, a finite element analysis model of the composite column is established to explore the effects of the diameter-thickness ratio, circumferential elastic modulus of confined tubes, and tensile strength of concrete on the seismic performance of the composite column. The analysis includes a review of the skeleton curve, energy dissipation capacity, and stiffness degradation of the structure under different designs. The results indicate that the use of GFRP tubes effectively enhances the seismic performance of UHPC columns. The failure mode, peak load, and peak displacement of the composite columns are improved. The finite element analysis results are in good agreement with the experimental results, validating the effectiveness of the analysis model. Extended analysis reveals that the bearing capacity of the specimen increases while the energy dissipation capacity decreases with a decrease in the diameter-thickness ratio and an increase in the circumferential elastic modulus. Although the tensile strength of concrete has some influence on the seismic performance of the specimen, its effect is relatively small. Through regression analysis, a formula for shear capacity suitable for GFRP tube UHPC composite columns is proposed. This formula provides a theoretical reference for the design and engineering practice of GFRP tube UHPC composite columns. In 1994, Larrard ,3. The rThe concrete-filled FRP tube (CFFT) column is an innovative structural system that combines the advantages of concrete and FRP tubes to enhance the strength and ductility of columns by effectively confining the transverse expansion of concrete. In comparison to concrete-filled steel tubes and reinforced concrete structures, FRP tube-confined concrete composite columns exhibit superior heat resistance, corrosion resistance, and insulation properties. The CFFT system has garnered significant attention from researchers, and numerous scholarly studies have been conducted in this area. Mirmiran et al.  conducteCurrently, there are various combinations of concrete-filled FRP tube (CFFT) columns that have been studied. Cao et al. derived a stress–strain model for FRP-constrained rubber-concrete columns considering the cross-sectional shape through theoretical derivation , and LiuIn existing research, the influence of steel bars in the specimens on seismic performance is more significant compared to external GFRP. Additionally, most studies on the effects of parameters such as the thickness and strength of the confined tube on the seismic performance of composite columns are qualitative analyses. There is a lack of a unified standard for the practical application of engineering design methods, and limited research has been conducted on the seismic performance of GFRP tube UHPC composite columns. In order to study the essential factors affecting the seismic performance of this type of structure, the seismic performance of GFRP tube UHPC composite columns is investigated through experimental testing and finite element analysis. This study aims to verify the test results and expand the parameter analysis. The effects of the diameter-thickness ratio, circumferential elastic modulus of the confined tubes, and horizontal bearing capacity of concrete tensile strength specimens are thoroughly examined. Mathematical models are developed to provide guidance for designers in practical applications.In order to design longitudinal reinforcements for lateral resistance materials more reasonably, it is necessary to discuss the stress mechanism of UHPC materials under triaxial compression and seismic loads. Therefore, this study has investigated the seismic performance of GFRP tube UHPC composite columns, providing experimental and theoretical foundations for future research. Two composite columns with GFRP tubes and one UHPC column without GFRP tubes were designed and fabricated. The cross-section of the specimen is depicted in θ kinds of GFRP tubes used in the test, which are 45° and 80°, respectively. The inner diameter d of all composite columns is 150 mm, the wall thickness is t = 3 mm, and the length l is 1500 mm.There are two Each specimen was fabricated following the subsequent steps: Firstly, the inner surface of the GFRP tube required for the test was meticulously cleaned to eliminate any dust or oil residues, ensuring a tight interface between the GFRP and concrete. The concrete mixture was prepared using a JW300 forced concrete mixer, where the measured ultra-high-performance concrete dry mixture, water, and admixtures were thoroughly mixed to form a cohesive gel. Subsequently, the mixture was poured into the GFRP tube through a funnel and conduit (a PVC tube was employed as a mold for the reference column specimen) to ensure the compactness of the concrete placement. Once the pouring was completed, the top of each specimen was covered with plastic film to maintain moisture, and regular watering was performed for proper curing. The manufacturing process of the specimens is illustrated in The GFRP tube utilized in this experimental study is a filament wound tube manufactured by a reputable glass fiber-reinforced plastic company based in Guangdong. The filament winding process involves angles of 45° and 80°. The concrete employed in the test is C130UHPC powder, which is produced by Guangdong Guangzhou New Material Technology Co., Ltd (China). This concrete formulation possesses an expansion rate of 0.02%, enabling it to fulfill the requirements for micro-expansion and self-compaction. The UHPC mix ratio used in the experiment is as follows: C130 dry mixture to admixture to water ratio of 50:0.98:3.17, respectively.In accordance with the prescribed curing conditions for the specimen, a total of six non-standard concrete cubes (100 mm × 100 mm × 100 mm) were cast, as illustrated in Based on the formula proposed by YU and Ding , the comF is the cube failure load (kN), and A is the cube splitting area (mm2).In accordance with the specified curing conditions for the specimen, three non-standard concrete cubes (100 mm × 100 mm × 100 mm) were cast, as depicted in To ensure effective constraints, prefabricated filament-wound glass fiber-reinforced polymer (GFRP) tubes are utilized, with fibers oriented at 45° and 80° relative to the longitudinal axis. In order to evaluate the performance, ring tension tests are conducted following the guidelines specified in ASTM D2290-19 [As depicted in To capture the deformation of the specimen during the entire loading process, three displacement acquisition points have been established. These points are placed to monitor specific aspects of the specimen’s behavior. Displacement Gauge 1: Located at the fixed base of the specimen, this gauge is intended to monitor any potential sliding or movement of the base during the loading process. It helps ensure the stability of the specimen’s foundation. Displacement Gauge 2: Positioned at a height of 750 mm along the column, this gauge is employed to observe the bending deformation of the specimen as it undergoes loading. It provides insights into the specimen’s flexural behavior. Displacement Gauge 3: Placed at the horizontal displacement loading point, this gauge is utilized to monitor the horizontal displacement of the loading point. It helps track any lateral movement or displacement that occurs during the loading process; this is also compared to the actuator displacement output data. For data acquisition, resistive displacement gauges are used at each of these three points. These gauges are designed to measure and record displacement values accurately. The arrangement of the displacement gauges can be referred to in In the low-cycle reciprocating loading test of the column, the column foot area is typically the location where failure occurs. Therefore, to capture strain data accurately, strain gauges are placed at specific heights along the column. The arrangement includes four locations: 0 mm, 150 mm, 300 mm, and 750 mm. At each height, both longitudinal and transverse strain gauges are applied. Additionally, four groups of strain gauges are evenly distributed along the circumference of the column. In total, there are 32 strain gauges used in one specimen. The specific arrangement can be referred to in In the test procedure, the axial force is initially preloaded in a graded manner. The preloading axial force is set at 60% of the actual axial force, which is 120 kN. Throughout the test, the rationality of loading is assessed based on observation data, and the axial force is gradually increased until it reaches the predetermined level. After applying the axial force, horizontal loading is conducted using a displacement control method. The loading scheme follows the guidelines outlined in JGJ/T101-2015 . The horBased on the observations in In By comparing the ultimate displacements of the two types of GFRP-reinforced UHPC composite columns with the ultimate displacement of the UHPC column without GFRP confinement, it is evident that the former has a larger displacement. However, due to the limited number of test samples and budget constraints that prevented repetitive testing, a comprehensive analysis of the seismic performance of GFRP-reinforced UHPC composite columns could not be conducted. Therefore, this study aims to conduct finite element analysis on the test models to gain an in-depth understanding of the seismic performance of composite structures and propose rational design methods.The damage to the GFRP tube is significantly influenced by the dislocation of fibers and the shear behavior of the resin, which poses challenges in studying its behavior . PreviouReferring to Li et al. , the comIt is mentioned that the ANSYS program provides various material models for finite element modeling of GFRP tubes and concrete. In this study, the linear elastic behavior of the GFRP tube is defined using the BISO model in the software. Additionally, the high-strength concrete model confined by the GFRP tube is defined based on an improved Drucker–Prager criterion proposed by the research group .There is no relative slip between the GFRP pipe and the concrete.The stressing process satisfies the conditions of internal and external force balance and longitudinal deformation coordination.The model in this study is established based on the C-2, FC45-2, and FC80-2 specimens tested. Two basic assumptions need to be met:The obtained skeleton curve and full test curves from the test are compared with the numerical simulation results, as shown in The analysis results demonstrate good agreement with the test results, as indicated in There is a difference in the early stiffness of the specimen. This is mainly manifested by the fact that at the beginning of loading, the load values of the simulation results are higher than the test results for the same displacements. Further analysis reveals that the ideal loading conditions used in the finite element simulation do not accurately capture the gap and slip between the specimen and the loading device in the test. This discrepancy results in a higher stiffness in the early stages of the simulation curve. Based on the above analysis, it can be concluded that the material constitutive relation utilized in the finite element analysis effectively reflects the mechanical characteristics of the GFRP tube UHPC composite column under quasi-static testing. Additionally, it can also capture the hysteresis curve of the specimen under different parameters to analyze the energy dissipation capacity of the specimen’s stiffness degradation, thus verifying the effectiveness of the finite element simulation.To ensure the accuracy of both the test and simulation results and to minimize the influence of other factors, a total of 16 specimens were designed using data from the FC45-2 and FC80-2 models. In consideration of practical engineering applications, the seismic performance of these specimens was analyzed in relation to the diameter-thickness ratio, circumferential elastic modulus of the confined tubes, and tensile strength of the concrete. Notably, the discussion on the circumferential elastic modulus of the confined tubes takes into account the commonly used types of FRP materials in structural applications. It is worth mentioning that the majority of circumferential elastic moduli of confined tubes, with various FRP materials and processing methods, fall within the range of 20 to 200 GPa . The desThe skeleton curve provides a macroscopic representation of the seismic performance of each characteristic point (data acquisition points) of the specimen, including displacement, load, ductility, strength degradation, and stiffness degradation. By correlating the specimen data with parameters such as the diameter-thickness ratio, circumferential elastic modulus of the restrained tube, and concrete tensile strength, the skeleton curve depicted in When the circumferential elastic modulus of the constrained tube is set to 54 GPa, 100 GPa, 150 GPa, and 200 GPa, the corresponding peak bearing capacities of the specimen are measured at 16.73 kN, 19.18 kN, 20.88 kN, and 24.92 kN, respectively. In comparison to the FC45-2-A50-T7 specimen with a circumferential elastic modulus of 29 GPa, the peak bearing capacity exhibits a variation range of 9.4%, 25.1%, 36.2%, and 62.6%, respectively. It is evident that an increase in the circumferential elastic modulus of the restrained tube leads to an increase in the peak load displacement and peak load of the specimen.The peak displacement of the specimen is primarily influenced by specimen damage. For specimens with different diameter-thickness ratios and varying concrete tensile strengths, the peak displacement consistently remains at 40 mm. This indicates that an increase in GFRP thickness has a minimal impact on delaying the damage to the core concrete. However, when the circumferential elastic modulus of the restrained tube reaches a certain level, the peak displacement of the FCE20-2-A50-T7-S20 specimen increases from 40 mm to 50 mm. A restrained tube with a higher elastic modulus can effectively restrain the crushed concrete under larger displacements, thereby delaying specimen damage. Additionally, a smaller diameter-thickness ratio results in a steeper decreasing trend after reaching the peak load, while an increase in the circumferential elastic modulus slows down the downward trend of the specimen after reaching the peak load. Therefore, it can be concluded that decreasing the diameter-thickness ratio and increasing the circumferential elastic modulus can delay the damage to the core concrete during the intermediate loading stage, thereby improving the seismic performance of the specimen. However, in the later loading stage, the restraining effect caused by increased thickness rapidly diminishes due to the damage to the GFRP tube, whereas the increase in circumferential elastic modulus continues to provide persistent benefits. In practical engineering applications, the method of increasing the circumferential elastic modulus of restrained tubes should be prioritized to enhance the seismic performance of composite columns.When the concrete tensile strength of the 45° angle specimen is set at 6 MPa, 5 MPa, and 4 MPa, the corresponding peak bearing capacities of the specimen are measured at 15.2 kN, 14.65 kN, and 13.98 kN, respectively. Compared to the FC45-2-A50-T7-S20 specimen with a concrete tensile strength of 7 MPa, the peak bearing capacity exhibits a change range of −0.8%, −4.4%, and −8.8%, respectively. As the tensile strength of the concrete decreases, the peak bearing capacity of the specimen also decreases. Following the peak load, the decreasing trend becomes steeper, although it does not significantly affect the peak displacement of the specimen.iK1 is the equivalent stiffness of stage i loading cycle; iPA1 is the positive peak load of stage i loading the first cycle; i1BP is the negative peak load of stage i loading the first cycle; ΔiA1 is the positive peak displacement of stage i loading the first cycle; ΔiB1 is the negative peak displacement of stage i loading the first cycle; i is the loading series.In this paper, the equivalent stiffness  is used The above calculation results are shown in E can be used to evaluate the energy dissipation capacity of the specimen. The calculation diagram is shown in The energy dissipation capacity of the composite column specimens studied in this paper can be analyzed with reference to the wrapping area of the hysteretic curve. With reference to the building seismic test code , the eneThe energy consumption coefficient of each specimen is obtained, as shown in For the calculation of the seismic bearing capacity of GRFP tube confined UHPC composite columns in this experiment, with reference to the derivation process of the formula for calculating the shear capacity of concrete-filled steel tube in the codes GB50936-2014  and JIN m > 3, the contribution of the GFRP tube to the shear capacity of columns is generally bending failure. In this case, reference is made to the contribution of steel tubes in concrete-filled steel tubes to shear capacity [m is the shear-span ratio of composite columns,In the formula, capacity ,32. CompN to the shear capacity of composite columns, h/2 [For the contribution of axial force e is h/2 .(11)Vn=For the contribution of core concrete to the shear capacity of composite columns, refer to the code , Vc is em is the shear-span ratio,To sum up, the formula for the shear capacity of GFRP tube UHPC composite columns is as follows:Based on the above formula, using the numerical simulation data, regression analysis and correction are carried out. For GRFP tube-confined UHPC composite columns, the following formula is suggested to calculate the shear capacity:According to the experimental results and finite element analysis, the relationship between the coefficient In order to verify the correctness of the formula, specimen analyses for the FC45-2 and FC80-2S specimens and the 16 parameters in sV is the maximum shear capacity measured in the experiment, and gV is the calculated value of the shear capacity formula obtained by regression analysis in this paper.s2 = 0.0032, sample standard deviation s = 0.057, coefficient of variation The GFRP tube has a significant positive impact on enhancing the seismic performance of UHPC. It not only increases the peak load and peak displacement of the column but also effectively improves the failure pattern of the composite structure, preventing concrete fragmentation and peeling phenomena.A finite element analysis model for GFRP tube-confined UHPC composite columns is proposed. Through parameter analysis, it is observed that reducing the diameter-thickness ratio and increasing the circumferential elastic modulus enhance the bearing capacity of the specimen. However, these changes result in a decrease in energy dissipation capacity. Overall, an increase in the circumferential elastic modulus of the confined tube exhibits a more significant effect and demonstrates good persistence. Specimens with higher tensile strength of concrete exhibit larger bearing capacities but worse energy dissipation capacity. In addition, expanding the current database of GFRP tube UHPC composite column tests would significantly contribute to further substantiating the proposed conclusions.By utilizing expanded parameter finite element analysis data and test data, a seismic bearing capacity formula for GFRP tube-confined UHPC composite columns is derived through regression and validated against test results and experimental data from other researchers. The proposed formula aligns well with the results, demonstrating high accuracy and universality. It serves as a valuable reference for designers.This paper focuses on investigating the seismic performance of GFRP tube-confined UHPC composite columns through a quasi-static test with an axial compression ratio of 0.2. A refined numerical analysis model is established to further understand the mechanical characteristics of the composite structure, and a rational calculation method for seismic bearing capacity is proposed. Based on the research conducted, the following conclusions can be drawn: