HIV/AIDS is a tremendous public health crisis, with a call for its eradication by 2030. A human rights response through civil society engagement is critical to support and sustain HIV eradication efforts. However, ongoing civil engagement is a challenge.This study aimed to demonstrate the use of Twitter data to assess public sentiment in support of civil society engagement.Tweets were collected during World AIDS Days 2014 and 2015. A total of 39,940 unique tweets (>10 billion users) in 2014 and 78,215 unique tweets (>33 billion users) in 2015 were analyzed. Response frequencies were aggregated using natural language processing. Hierarchical rank-2 nonnegative matrix factorization algorithm generated a hierarchy of tweets into binary trees. Tweet hierarchy clusters were thematically organized by the Joint United Nations Programme on HIV/AIDS core action principles and categorized under HIV/AIDS Prevention, Treatment or Care, or Support.Topics tweeted 35 times or more were visualized. Results show a decrease in 2015 in the frequency of tweets associated with the fight to end HIV/AIDS, the recognition of women, and to achieve an AIDS-free generation. Moreover, an increase in tweets was associated with an integrative approach to the HIV/AIDS response. Hierarchical thematic differences in 2015 included no prevention discussion and the recognition of the pandemic’s impact and discrimination. In addition, a decrease was observed in motivation to fast track the pandemic’s end and combat HIV/AIDS.The human rights–based response to HIV/AIDS eradication is critical. Findings demonstrate the usefulness of Twitter as a low-cost method to assess public sentiment for enhanced knowledge, increased hope, and revitalized expectations for HIV/AIDS eradication. The United Nations’ sustainable development goals (SDGs) seek a holistic and balanced approach to social, economic, and environmental aspects of development ,2. The SThe MDGs resulted in the expansion of 15 million people living with HIV/AIDS (PLWH) on life-saving antiretroviral (ARV) drugs ,4,7. AltThe utilization of social networking sites (SNSs) for civil society activism ,9 is a pDuring the World AIDS Days of December 1, 2014, and December 1, 2015, tweets about HIV/AIDS were collected from Twitter via a Google Chrome–based version of NCapture, a Web crawler that captures internet-based text . The strNatural language processing was conducted to identify and depict topics of collected tweets about HIV/AIDS. Tweets were cleaned and transformed to a vector form and N-gram . An N-grClustering, the process of grouping a set of words into classes of similar topics, was conducted . Hierarccluster words: “fight, today, support, cure, love”; associated theme: Combat HIV/AIDS). Major themes were refined through review and discussion, with our experts (MO and RB), to shape the final coding structure. Themes were organized based on UNAIDS core action principles  for guiding a comprehensive response to HIV/AIDS .A coding framework was used to interpret and explore the data and to identify perceptions of the HIV/AIDS pandemic. Tweet hierarchy raw data clusters were characterized based on words in each cluster of nln and ln by subject matter experts . An increase was also observed in the frequency of tweets associated with the recognition of barriers to HIV/AIDS eradication . A moderate decline was observed in tweets associated with ending the epidemic  and the provision or utilization of services . A significant decrease in tweet frequency associated with combating the epidemic  was also observed .Efforts for Targeted HIV/AIDS Eradication led to 2 nln. First, Reduce Stigma (nln) followed in order of descent by (1) Fast Track the End of the Pandemic (nln), (2) Expression of HIV/AIDS Solidarity and Consciousness (nln), (3) AIDS-Free Generation (ln), (4) Treatment for HIV/AIDS (nln), and (5) Recognition of the Pandemic (ln). Second, Combat HIV/AIDS (nln) followed in order of descent by (1) Celebrities or Industries (ln), (2) Support PLWH (nln), (3) Honor PLWH (nln), (4) Prevent HIV/AIDS (nln), (5) Spread HIV/AIDS Awareness (nln), (6) Commitment to End the Pandemic (ln), and (7) Save Lives: Infected and At Risk and Halt Infections  Save Lives: Infected and At Risk (ln), (2) Spread HIV/AIDS Awareness (nln), and (3) Informational Resources from Governmental Organizations (ln). The tweet cluster of Honor PLWH followed in order of descent by (1) Expression of HIV/AIDS Solidarity (nln), (2) Reduce Stigma (ln), and (3) Support PLWH (ln) versus Commitment to End the Pandemic (ln) followed in order of descent by (4) Discrimination of PLWH (nln), (5) Recognition of the Pandemic (ln), and (6) Treatment for HIV/AIDS (ln) versus Impact of HIV/AIDS Pandemic (ln) followed in order of descent by (7) AIDS-Free Generation (nln), (8) Halt Infections (nln), and (9) Fast Track the End of the Pandemic (nln) versus Combat HIV/AIDS (nln) followed in order of descent by (10) Celebrities or Industries  Informational Resources from Governmental Organizations, (2) Halt Infections, (3) AIDS-Free Generation, and (4) Prevent HIV/AIDS (2014 only).In Prevention, 1 overarching theme emerged. The theme was Access to Services, including the individual themes of (1) Treatment for HIV/AIDS (2015 increase), (2) Save Lives: Infected and At Risk (2015 increase), and (3) Impact of the HIV/AIDS Pandemic (2015 only), and Expand Programs, including the individual themes of (1) Efforts for Targeted HIV/AIDS Eradication and (2) Fast Track the End of the Pandemic (2015 decrease).In Treatment or Care, 2 overarching themes emerged: Safeguard Human Rights, including the individual themes of (1) Spread HIV/AIDS Awareness (2015 increase), (2) Recognition of the Pandemic (2015 increase), (3) Honor PLWH (2015 increase), (4) Expression of HIV/AIDS Solidarity and Consciousness (2015 increase), (5) Combat HIV/AIDS (2015 decrease), and (6) Support PLWH; Partnerships and Alliances, including the individual themes of: (1) Commitment to End the Pandemic (2015 increase) and (2) Celebrities or Industries (2015 decrease); and Eliminate Discrimination and Stigma, including the individual theses of (1) Reduce Stigma and (2) Discrimination of PLWH . This may further reflect the need to re-engage the public in purposeful discussions and to reinvigorate grassroots efforts [Reduced Stigma remained a second-level tweet in 2015, with 2014 data acknowledging the lesbian, gay, bisexual, transgender, and queer community and 2015 data discussing the need to end stigma [Discrimination of PLWH emerged in 2015. This may potentially reflect the November 2014 UNAIDS Fast-Track Strategy report, with zero discrimination recognized as the main target to end HIV/AIDS [In 2015, all themes increased on the hierarchy under Support, except  efforts . The thed stigma ,11,30,31d stigma  and contd stigma ,31. EsseHIV/AIDS ,30. ResuHIV/AIDS ,31.Hierarchical differences also revealed absence of tweets in 2015 mentioning women. This is of great concern; issues of gender minorities must be addressed or eradication efforts may be thwarted. The focus on key populations does very little to change gender inequality . Women aThe generalizability of this study is limited because of the English-only analysis and the use of 1 SNS  . We did Our ambitious targets are critical to the pandemic and are possible with the support of technology and social media outlets such as Twitter ,16. CiviOur study’s demonstration of Twitter utilization to explore HIV/AIDS public sentiment can guide targeted social movement campaigns aimed to address grassroots level barriers and heighten public motivation necessary to drive eradication. We also demonstrated the feasibility of the use of cost-effective social networking technologies to identify health-related communication and the utilization of such platforms to support improved outcomes. In fact, with the ever-increasing amount of social media data and the unique and refined analytic approaches such as ours, HIV/AIDS researchers and global health professionals will soon be able to build upon and enhance their methods, to accurately monitor and support a variety of HIV-related issues, and outcomes.


There has been a significant rise in global antibiotic use in recent years. Development of resistance has been linked to easy accessibility, lack of regulation of sale, increased tendency to self-medicate and the lack of public knowledge. The increase in antibiotic misuse, including self-medication, has not been well documented in developing countries. Antibiotic use prior to visiting health facilities has been found to be prevalent in developing countries. It has been identified by some studies to increase the likelihood of missed diagnoses and influence the outcome of bacteriological tests. This study is aimed at determining the prevalence of prior antibiotic use through a cross-sectional survey of patients undergoing laboratory tests at two health facilities in Ghana. Face-to-face questionnaires were used to interview 261 individuals chosen by random sampling of patients visiting the bacteriology laboratory of the hospitals within a two-month period. The questionnaire investigated participant demographic characteristics, knowledge about antibiotics and the nature of antibiotic use. Antibiotic property detection bioassay was performed on patient’s urine sample using a disk diffusion method to accurately determine antibiotic use within 72 hours. Culture results were used as an index to evaluate the effect of prior antibiotic use on bacteriological tests. Out of a 261 participants enrolled, 19.9%  acknowledged using antibiotics prior to their visit to the laboratory during the study period. On the contrary, 31.4%  of participants’ urine samples were positive for antimicrobial activity. Participants within the age ranges of 20–30, 31–40 and 41–50 years had significantly lower odds of urine antimicrobial activity. Participants who had urine antimicrobial activity were more likely to have no growth on their culture plates than participants who had no urine antimicrobial activity . The most commonly used antibiotics were the penicillins, fluoroquinolones and metronidazole. Although, majority of the participant (54.8%) had knowledge of antibiotics, most of them had inadequate information on their proper use. The commonest indications for antibiotic use were aches and pains (30.3%), diarrhoea (43.3%) and urinary tract infections (28.0%). Prior antibiotic use was found to increase the likelihood of obtaining a culture negative result and can affect the outcome of bacteriological tests. Antibiotic use has risen markedly in recent years. A report by the Centre for Disease Dynamics, Economics and Policy (CDDEP) showed that global antibiotic consumption rose by more than 30% from 2000 to 2010 . Unsurpret al. (2014) detected antimicrobial agents in the urine of 64% out-patients reporting to two hospitals , this association was not significant (p>0.05).et al. 1999, found a slightly lower prevalence of urine antimicrobial activity (25.1%) amongst 203 out-patients in Taiwan . Peni. Peni2]..6% admitWhile a majority of the participants reported that they obtained their antibiotics via physician prescription, a considerable portion admitted to self-medicating with antibiotics at some point prior to the study. Although legislation in Ghana demands that antibiotics be obtained only by prescription, antibiotics are still easily obtained over the counter . This coEscherichia coli (n = 29) and Candida spp.(n = 21). The higher prevalence of Escherichia coli is understandable since it is the most common urinary pathogen [The most commonly isolated organisms were pathogen . More thpathogen .It must be noted that the study was limited by small sample size and short duration (2 months). Thus the results are not comprehensive enough to make it generalizable. Another limitation was the inability to include in-patients at the Bomso Clinic, which could also have had an effect on the data analysis.This study has shown that nearly a third of patients had used antibiotics prior to their bacteriological laboratory tests. It has also shown that prior antibiotic use  increases the likelihood of obtaining culture negative results and thus influences the outcome of laboratory results. These findings confirm the need for health workers to advise patients against using antibiotics before seeking healthcare for any illness. It also re-emphasizes the need for clinicians to obtain their samples for bacteriology cultures before giving antibiotics.The discrepancy between patients reporting of antibiotic use and the bioassay results shows that patient are unlikely to give an accurate history of their antibiotic use. Thus, a more accurate method such as the disk diffusion bioassay can be used in identifying prior antibiotic use in patients presenting to health facilities. There is the possibility that some patients may not actually know that the drug they had taken was an antibiotic. Furthermore, it may also be possible that patients were afraid of some unknown repercussions if they revealed that they had taken antibiotics. Health care providers should ensure that patients are very relaxed in their presence and should encourage patients to provide accurate information and at the same time reassuring patients that they will not suffer any consequences if they give only the right information.Penicillins were the most commonly used class of antibiotics amongst patients in the study.Another important finding of the study was that although a considerable number of the participants were aware of antibiotics and their purpose, they have poor knowledge on the proper use of antibiotics.S1 File(XLSX)Click here for additional data file.S2 File(DOCX)Click here for additional data file.


Our aim was to determine aerobic capacity, [Lac], and work efficiency at sea level (SL) and HA during maximum exercise in miners acclimatized to CIHH at 3,800 m. Eight volunteer miners acclimatized to CIHH at HA (> 4 years) performed an exercise test at SL and HA. The test was performed on the 4th day at HA or SL and consisted of three phases: Rest (5 min); Exercise test, where the load was increased by 50 W every 3 min until exhaustion; and a Recovery period of 30 min. During the procedure VO2, transcutaneous arterial saturation , and HR (bpm) were assessed at each step by a pulse oximeter and venous blood samples were taken to measure [Lac] and hemoglobin concentration. No differences in VO2 and [Lac] in SL vs. HA were observed in this CIHH miner population. By contrast, a higher HR and lower SpO2 were observed at SL compared with HA. During maximum exercise, a reduction in VO2 and [Lac] was observed without differences in intensity (W) and HR. A decrease in [Lac] was observed at maximum effort (250 W) and recovery at HA vs. SL. These findings are related to an increased work efficiency assessment such as gross and net efficiency. This study is the first to show that miners exposed to CIHH maintain their work capacity (intensity) with a fall in oxygen consumption and a decrease in plasmatic lactate concentration at maximal effort at HA. These findings indicate that work efficiency at HA is enhanced.We previously showed that arterial oxygen content during maximum exercise remains constant at high altitude (HA) in miners exposed to chronic intermittent hypobaric hypoxia (CIHH). Nevertheless, information about VO Exposure to hypoxia conditions, such as high altitude (HA), limits oxygen transport from the air into the muscle, affecting work capacity . The samEarly studies showed that during acclimatization at HA , in subjects exposed to progressive exercise, lactate production was reduced at maximum effort in correlation with the altitude reached . Other sOver the last 30 years, mining activity in Chile has relocated miners that normally live at SL lowlands to work at HA . This altitude shift is called the “Chilean model of Chronic Intermittent Hypobaric Hypoxia (CIHH) exposure,” which is characterized by alternating periods of work at HA and rest periods at low altitude <1,000 m .2 max) to decrease at HA with a maintained oxygen transport capacity , where an inverse relation between the miner’s exposure time with a decrease in physical performance was observed . A seconcapacity . A thirdntensity . AdditioTwelve voluntary subjects were enrolled in the study; all miners live at low altitude  and work at HA . All volunteers are heavy truck operators and have experience with CIHH for more than 4 years. Their shift pattern was 7 days of work at HA followed by 7 days resting at SL . All sub2, %) and heart rate  were assessed by a pulse oximeter , with the sensor placed on an ear lobe . For lactate and hemoglobin concentration (Hb) and hematocrit measurements, blood samples were taken by intravenous catheter inserted from the brachial vein allowing for blood sample collection during the rest period, at the end of each load  during the exercise test and during recovery 30 min after the end of the test. For each sample, 3 ml of venous blood was collected in a tube with EDTA. Blood samples were centrifuged immediately after collection , plasma fraction was frozen in liquid nitrogen. Afterward, plasma samples were stored at −80°C until perform assay.All tests were performed at day 4 of the shift work at HA and at day 4 of the shift work at SL . The stu2) was calculated using the following equation: CaO2 (ml O2/dl) = 1.34 (ml O2/gHb) × Hb (g/dl) × SpO2 (%) (Lactate concentration ([Lac]) was determined by spectrophotometry using a commercial kit , according to the manufacturer’s specifications, and values were expressed as mmol/L. Hematological determinations were made using a hematological counter  and hemoglobin concentration (g/dl) was measured. Oxygen content (CaOSpO2 (%) , where tGross efficiency (%) was defined as the ratio of work accomplished divided by the energy expended multiplied by 100. Net efficiency (%) was defined as the ratio between work accomplished divided by energy expended at rest multiplied by 100. To calculate values of gross efficiency or net efficiency, values of oxygen consumption were converted to W/kg and intensity was expressed in W/kg . Significant differences were analyzed using ANOVA followed by a Newman-Keuls test. To evaluate the significant differences between HA and SL, paired p < 0.05). By contrast, oxygen saturation was significantly lower in the HA condition than the SL condition (p < 0.05). No significant difference was observed between the SL and HA conditions in plasma lactate concentration at rest , and PETO2 and hemoglobin concentration (only HA).Resting and maximal values of cardiorespiratory and metabolic variables after exercise in SL and HA conditions are shown in EV increased by 8.8 and 8.5 times, respectively (p < 0.05). This increase can be partially explained by an increase in RR (2.4 times at SL and 3.2 times at HA) and an increase in the tidal volume (3.1 times at SL and 3.4 times at HA). When we express values such as ventilation divided by VO2 (VE/VO2), a significant increase in the respiratory stimulus could be observed at HA in comparison with SL conditions  and ventilation divided by VCO2 (VE/VCO2) obtained values of 76.7 ± 0.9 and 36.5 ± 3.6, p < 0.05, respectively. The heart rate response during maximal exercise showed no differences between SL and HA. The oxygen saturation response at maximal exercise performed at SL showed a significant decrease in oxygen saturation (p < 0.05) with a maintained hemoglobin concentration and oxygen content. By contrast, in the HA condition, the decrease in the oxygen saturation is higher than SL, and an increase in the hemoglobin concentration (p < 0.05) and a maintained oxygen content was observed . These results suggest an increment in work efficiency evaluated at HA compared to the same volunteer at SL.2 max obtained at HA compared with SL at the same intensity, we calculated values of gross efficiency and net efficiency obtained during steady state for exercise performed at SL and HA. In gross efficiency at HA is higher than gross efficiency at SL  and for the first time related these variables with work efficiency. Our results show that work capacity (intensity) is maintained despite the fall in oxygen consumption, supporting the idea that there is an increase in work efficiency and a fall in plasma [Lac] during maximal exercise at HA.The present study contributes new data of VO2 and lactate metabolism during increased exercise intensity  at SL with simulated altitude or real HA exposure, and testing natives or non-natives after a period of chronic exposure to simulated hypobaric hypoxic conditions or at real altitude conditions, and after deacclimatization . In thesntensity . However2 max (near to 29%) observed in our population at 3,800 m of HA, data observed in the same population at SL are similar to values reported in the literature , since in our population intensity was maintained, similar to that described previously by our laboratory at the same altitude at an intensity of 200 W . However, this article did not report any information about the intensity reached during the test at SL or HA . In this case, we did not observe a difference in pH between SL and HA. If our calculations are correct, we can suggest that the buffer capacity in our population is maintained. However, future studies are necessary to demonstrate this speculative approach.Additionally, we know that repeated resistance training increases aerobic capacity given by an increase in mitochondrial volume density, and in hypoxic conditions, this effect is largely increased . A similntration , consideNowadays, studies of the CIHH model that evaluate exercise and measure lactate concentration are scarce. Prior to our study, the only similar article was carried out in a group of soldiers who performed a regular ascent to HA for 11 days, followed by 3 days at SL for 6 months. During the first days of arrival or descent, the maximum oxygen consumption and lactate concentration were evaluated. Under these exposure conditions, maintenance of oxygen consumption and an increase in plasma lactate concentration at HA were reported in subjects exposed to CIHH . These rOur study did not perform any invasive evaluation, such as muscle biopsy or lactate metabolism with marked radionuclides, due to pressure from workers’ union and company reasons. Future studies that consider measurements in a larger population of workers and/or the requirements of an animal model are needed to obtain a better understanding of the mechanisms underlying physiological altitude adjustments in the population with exposure to CIHH.In conclusion, our previous studies showed an almost stable maintenance of oxygen content during a maximal exercise test performed in miners with chronic intermittent exposure to hypoxia at 3,800 m. The present study is the first to show that, in this population, work capacity (intensity) is maintained with a drop in oxygen consumption during a maximum exercise test, which supports that an increase in work efficiency at HA is associated with a lower concentration of lactate.The datasets generated for this study are available on request to the corresponding author.The studies involving human participants were reviewed and approved by Ethics Committee of the Facultad de Medicina of the Universidad Católica del Norte, Chile. The patients/participants provided their written informed consent to participate in this study.FM and JO conceived and designed the study. JO and DJ supervised the overall study. RC-J performed the statistical analysis. DM, RC-J, and JO contributed to sample and data collections. All authors drafted the report and contributed to the interpretation of the results, critical revision of the manuscript, and approval of the final manuscript. FM is the guarantor.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.


IgG4-related disease (IgG4-RD) often affects multiple organs and tissues, especially the kidneys, and is characterized by interstitial nephritis, obstructive nephropathy, and in rare cases glomerulopathy (including membranous nephropathy).In this article, we report a patient with nephrotic syndrome as the only initial manifestation. Membranous nephropathy was confirmed by renal biopsy, but without any renal interstitial lesions. The nephrotic syndrome completely resolved after treatment with immunosuppressants but recurred after drug withdrawal, which was accompanied by acute kidney injury. Ultimately, IgG4-related interstitial nephritis with membranous nephropathy was confirmed by a second renal biopsy. After routine administration of steroids and cyclophosphamide, renal function returned to normal after 2 months, and nephrotic syndrome was ameliorated after 5 months.Special attention should be paid to this rare condition in the clinical setting. In patients with membranous nephropathy (MN) that is accompanied by multi-system damage, impaired renal function, elevated IgG4 levels , negative PLA2R, and/or renal interstitial plasma cell infiltration, the possibility of IgG4-related kidney disease (IgG4-RKD) should be carefully assessed. Elevated serum IgG4 levels were found in patients with autoimmune pancreatitis (AIP)  in 2001,A 46-year-old male patient was hospitalized in March 2015 because of bilateral lower extremity edema, and a diagnosis of nephrotic syndrome was made. The patient displayed evidence of chronic bilateral lacrimal gland inflammation, with exophthalmos, tearing, and bulbar conjunctival hyperemia. Laboratory test results are shown in Table +, CD138+, IgG+, and IgG4+ cells (approximately 30% of IgG+ cells) , and prednisone acetate was continued at 10 mg/day for maintenance. His renal function returned to normal after 2 months, and nephrotic syndrome was ameliorated after 5 months. The patient has been closely followed-up to date Fig. .Fig. 3FlIgG4-RKD is any form of renal involvement in IgG4-RD , 7, whicOur current patient had an initial disease manifestation of MN, which manifested as nephrotic syndrome. The disease was alleviated after treatment but relapsed upon drug withdrawal, and renal insufficiency was very serious. After the second renal biopsy, a pathological diagnosis of IgG4-TIN with MN was made. Comparison of the results of the two renal biopsies confirmed that the MN found during the first attack was also associated with IgG4-RKD. Thus, IgG4-RKD can be initially manifested as MN, followed by TIN. IgG4-RD is a cause of secondary MN [How can this early identification of IgG4-MN in patients with MN be achieved? First, MN patients often have multi-system injuries, in which the possibility of IgG4-RKD involvement should be identified. In our current case, during the first disease attack, the patient had unexplained binocular chronic lacrimal gland inflammation. He also had exophthalmos, epiphora, and congestive conjunctiva. Chronic dacryocystitis is an infection of the lacrimal sac that is typically associated with nasolacrimal duct obstruction , which wTIN is the most common initial manifestation of IgG4-RKD, whereas IgG4-RKD with MN as its initial manifestation is much rarer. In patients with MN accompanied by multi-system damage, impaired renal function, elevated IgG4 , negative PLA2R, and/or renal interstitial plasma cell infiltration, the possibility of IgG4-RKD should be carefully assessed.


As there is rapid increase in international travel to tropical and subtropical countries, there will likely be more people exposed to diarrheal pathogens in these moderate to high risk areas and subsequent increased concern for traveler’s diarrhea. The disease may appear as a mild clinical syndrome, yet a more debilitating presentation can lead to itinerary changes and hospitalization. As bacterial etiologies are the most common causative agents of TD, the use of antibiotic prophylaxis to prevent TD has been reported among travelers for several years. The most common type of antibiotic used for TD has changed over 50 years, depending on many influencing factors. The use of antibiotic prophylaxis for TD prevention in travelers is still controversial, mainly because of difficulties balancing the risks and benefits. Many factors, such as emerging drug resistance, side effects, cost and risk behavior need to be considered. This article aims to review antibiotic prophylaxis from the 1950s to 2000s, to describe the trend and reasons for different antibiotic use in each decade. We conclude that prophylactic antibiotics should be restricted to some high-risk travelers or short-term critical trips. International travel is rapidly increasing, with 1.2 billion travelers in 2016, and Asian and Pacific regions being particularly popular . IncidenEscherichia coli (ETEC) and enteroaggregative E. coli (EAEC) [Campylobacter, Giardia and Shigella have frequently been reported to cause TD in travelers in the Indian subcontinent [Campylobacter is the most common pathogen isolated from travelers returning from Southeast Asia [The causative pathogens of TD vary in each region, but bacteria are the most common, followed by viruses and protozoa. In Latin America and the Caribbean, the most common pathogens causing TD are enterotoxigenic i (EAEC) , 18. In i (EAEC) . As wellontinent , 21. Intast Asia , 22. Incast Asia .Travelers to remote areas far from medical facilities are often advised to take antibiotics when symptoms of TD develop . In contTraditionally, standard pre-travel consultations include advice to “boil it, cook it, peel it, or forget it” to prevent TD ; neverthantibiotics, travel, diarrhea, neomycin, furazolidone, doxycycline, trimethoprim/sulfamethoxazole, erythromycin, mecillinam, bicozamycin, ciprofloxacin, norfloxacin, azithromycin and rifaximin. All search articles yielded 616 in numbers. Inclusion criteria were papers written in English and related to the use of antibiotics as prophylaxis for TD. Overall, 27 studies were included in this review, to illustrate the trend of antibiotic use in the prevention of TD over the past 50 years  prophylaxis resulted in a significantly higher reduction of TD incidence in college students traveling to Guadalajara, Mexico when compared with a placebo and TMP alone , 50. Admly 1980s . DermatoEmerging drug resistance resulted in the need to find new regimens for the chemoprophylaxis of TD Fig. . In earlDiscovery of quinolone antibiotics gave researchers hope to prevent traveler’s diarrhea, as this group of antibiotics is highly effective against gram-negative pathogens including Enterobacteriaceae . The earCampylobacter species has been reported, particularly in Southeast Asia [Antibiotic resistance to fluoroquinolones, especially in ast Asia –68. Broaast Asia , 70. In ast Asia , 71.The protective effect of azithromycin against dysenteric diarrhea has been accidentally discovered during malaria chemoprophylaxis efficacy trial in Kenya in 1995. A total of 231 volunteers were divided into 4 arms: azithromycin 250 mg daily, azithromycin 1000 mg weekly, doxycycline 100 mg daily, or placebo. Result showed that only 2.6% of volunteers in the daily or weekly azithromycin groups developed dysentery, while 13.9% of volunteer in doxycycline or placebo group developed dysentery in the same period, so the estimated protective efficacy of azithromycin was 81% . UnfortuSide effects and development of resistance among extraintestinal bacteria means the use of absorbable (systemic) antibiotics to prevent TD has been discouraged . In the Studies in short-term travelers to Mexico, using various regimens of rifaximin for 14 days, demonstrated protective efficacies ranging from 28 to 72% , 33, 35.E. coli in several countries [Low to moderate efficacy of rifaximin has been observed in several studies, however the majority of the studies –36 did nountries .Several factors need consideration when prescribing prophylactic antibiotics for the prevention of TD. Individual risk assessment, including type of population Table , travel Host microbiome may be an important factor involved in protecting travelers from TD. Alterations in native gut microbiome, known as dysbiosis, are known to be associated with travel . IngestiCampylobacter strains from Southeast Asia. Hence, fluoroquinolones should not be prescribed as prophylactic antibiotic for TD in travelers traveling to Southeast Asia. Unfortunately, data for antibiotic resistance are unavailable in some regions of the world, especially in low- and middle-income countries [Other factors may affect the efficacy of prophylactic antibiotics, such as the predominant pathogens present in each geographical region and their pattern of antibiotic resistance . Drug reountries . The curAlthough TD is perceived as a self-limiting disease, it represents a substantial socioeconomic burden from traveler’s perspective . This ilCurrent recommendations suggest that antibiotic prophylaxis for TD may be prescribed selectively in some travelers, especially in high-risk short-term travelers . RifaximTrends in antibiotic use for TD prevention have been changing over several decades. Prophylactic antibiotic prescribing for TD should always include an individual risk assessment, including type of traveler, their destination, travel purpose, itineraries, drug side effects, and cost-benefit analysis. The global increase in antibiotic resistance limits the choice of antibiotics. In the past, doxycycline, TMP/SMX or fluoroquinolones may have been effective for TD prevention; however currently, minimally-absorbed rifaximin is recommended for travelers.


Is the variation in the compressive strength of concrete across the thickness of horizontally cast elements negligibly small or rather needs to be taken into account at the design stage? There are conflicting answers to this question. In order to determine if the compressive strength of concrete varies across the thickness of horizontally cast elements, ultrasonic tests and destructive tests were carried out on core samples taken from a 350 mm thick slab made of class C25/30 concrete. Special point-contact probes were used to measure the time taken for the longitudinal ultrasonic wave to pass through the tested sample. The correlation between the velocity of the longitudinal ultrasonic wave and the compressive strength of the concrete in the slab was determined. The structure of the concrete across the thickness of the slab was evaluated using GIMP 2.10.4. It was found that the destructively determined compressive strength varied only slightly (by 3%) across the thickness of the placed layer of concrete. Whereas the averaged ultrasonically determined strength of the concrete in the same samples does not vary across the thickness of the analyzed slab. Therefore, it was concluded that the slight increase in concrete compressive strength with depth below the top surface is a natural thing and need not be taken into account in the assessment of the strength of concrete in the structure. The view that the compressive strength of concrete varies across the thickness of horizontally cast elements  is seldom expressed in the literature on the subject. Opinions as to the significance of this variation are widely divided, as the following survey of literature indicates.The research published by Stawiski ,2,3 provc ≤ 1.0 MPa/cm. The increase of 1.0 MPa/cm in the strength of concrete in the lower situated layers relative to the top layer suggested by Stawiski [Stawiski  proposedStawiski  seems toOn the basis of ultrasonic tests of the compressive strength across the thickness of samples taken from cut out pieces of 40, 45 and 60 mm thick floorings made of cement mortars, Hoła, Sadowski and Hoła A. [Petersons in  found thIn monograph , DąbrowsYuan, Ragab, Hill and Cook  found thNeville  found thNeville  ascribedAccording to standard , the comTherefore, the questions arises: Is the variation in the compressive strength of concrete across the thickness of horizontally cast elements negligibly small or rather needs to be taken into account at the design stage?3), fly ash additive (60 kg/m3), plasticizer (2.43 kg/m3), water (170 kg/m3) and 1879 kg/m3 of natural aggregate  were used in the concrete mix for the slab construction. The latter had been compacted by means of an immersion vibrator and cured for 28 in the laboratory conditions defined in standard [In order to verify the phenomenon of concrete compressive strength variation across the thickness of horizontally cast elements, samples with diameter d = 100 mm height h = 350 mm , taken fstandard . The slaL of ultrasonic wave passage through concrete was measured in two perpendicular directions. No concrete/probe coupling material was used. The probes were set perpendicularly to the tested side surface of the sample . The details of the operation of exponential heads with point-to-point contact with the examined surface are described in detail in the paper [A Unipan Materials Tester Type 543 with point-contact exponential probes  and a frhe paper .L of the longitudinal ultrasonic wave along the height of the core samples with d ≅ 100 mm were quite constant (except for the top layers). The mean velocity CL of ultrasonic wave propagation in the samples (01–06) taken perpendicularly to the top surface of the slab was CL1 = 3.54 km/s, a standard deviation sCL1 = 0.13 km/s and a variation coefficient νCL1 = 3.67%. In the case of the samples (07–12) taken parallel with the top of the slab, the following were obtained: CL2 = 3.45 km/s, sCL2 = 0.072 km/s and νCL2 = 2.09%. On the basis of the obtained velocities CL of the longitudinal ultrasonic wave in the range: CL = 3.5–4.5 km/s, it can be assessed [assessed  whether L of the longitudinal ultrasonic wave in the inner layers of the concrete are due to local concrete defects  or local strengthening with larger aggregate grains. Lower velocities CL of the longitudinal ultrasonic wave were registered in the samples (01–06) taken perpendicularly to the top surface of the slab .The concrete strength values  yielded Standard  states tm(18),is = 31.45 MPa . The mean standard deviation amounted to s = 0.49 MPa. The coefficient k1 = 1.48 was assumed. The characteristic compressive strength of the concrete in the structure  was determined on the basis of standard [ck,is = min(fm(18),is − k1 × s; fis,lowest + 4) = . Thus the characteristic cube compressive strength of the concrete determined on samples taken perpendicularly to the top surface of the slab amounted to fck,is = fck,is,cube = 30.72 MPa.The mean compressive strength of the concrete, determined on the 18 samples taken perpendicularly to the top surface of the slab, amounted to fstandard , from thm(18),is = 31.11 MPa . The mean standard deviation amounted to s = 0.81 MPa. The characteristic cube compressive strength of the concrete, determined on the samples taken parallel with the top surface of the slab, amounted to fck,is =  = 29.91 MPa. The cube strength determined on the samples taken parallel to the top surface of the slab was 3% lower than the strength determined on the samples taken perpendicularly to the top surface of the slab. This confirms the observation that the strength of core samples drilled out horizontally is lower  thanck,is,cube values, the actual strength class of the concrete in the structure is estimated to be fck,is,cube = 30.72 MPa and 29.91 MPa, respectively. When the correction factor of 0.85 is applied, this gives the concrete strength class respectively fck,is,cube = 36.1 MPa and 35.2 MPa, which corresponds to at least concrete class C25/30.On the basis of the obtained fL were correlated with the mean compressive concrete strengths fis. When calculating the mean longitudinal ultrasonic wave passage velocity CL, the values from the areas of disturbances near the ends of the samples were rejected. The correlation curve was scaled according to the procedure described in standard [CL,b = 2.39CL2 − 7.06CL + 4.2 for CL = 2.4–5.0 km/s, was adopted. Then, the differences δf between experimental compressive strength fis and the strength obtained from base curve fCL, as well as the mean value δfm(n) of the differences and standard deviation s were determined. The shift of the base correlation curve was calculated from the relation Δf = δfm(n) − k1·s for coefficient k1 = 1.48 [CL = fCL,b + Δf has the form fCL = 2.39CL2 − 7.06CL + 25.09. The obtained curve only slightly differs from the curves determined separately for samples 01 ÷ 06 and 07–12.On the basis of the measurements, the mean longitudinal ultrasonic wave passage velocities Cstandard  ,is = 29.80 MPa  and the mean standard deviation to s = 0.66 MPa. Hence, the characteristic compressive strength of the concrete amounted to fck,is = fck,is,cube ≤  =  = 28.82 MPa. When the correction factor of 0.85 was taken into account, concrete class C25/30 was obtained. The concrete class determined on the basis of the compressive strength values obtained from the correlation curve confirmed the destructively determined class of the concrete.The class of the concrete in the structure was determined on the basis of the concrete compressive strength values obtained from the correlation curve fCL = 2.39·CL2 − 7.06·CL + 25.09, it was possible to trace the variation of the compressive strength of the concrete along the height of the analyzed samples. With the corrected correlation curve: fAn analysis of the concrete compressive strength values for the particular samples 01–06  taken peThe averaged compressive strength results obtained from the ultrasonic measurements showed , howeverThe ultrasonic tests indicate that the variation in the compressive strength of concrete along the height of the sample is minimal and random. It can even be considered as negligible. The obtained results do not corroborate Stawiski’s theses ,2,3, butThe decreases in the compressive strength of the concrete occurring at the ends of the samples taken perpendicularly to the top plane of the slab (samples 01–06) and at the edge constituting the side edge of the slab for the samples taken parallel with the top plane of the slab (samples 07–12) were found to be interesting.The following conclusions emerge from the investigations of the compressive strength of concrete carried out on core samples taken perpendicularly to and parallel with the top surface of the approximately 35 cm thick element, using different testing methods (the ultrasonic method and the destructive method):The obtained compressive strength increments across the thickness of the placed layer of concrete do not corroborate Stawiski’s theses ,2,3, butThe concrete compressive strength determined on core samples only slightly depends on the depth of where the sample came from (provided the ingredients of the concrete do not segregate as it is being placed and compacted).The use of the ultrasonic method for testing concrete with point-contact exponential probes showed the variation in concrete strength along the height of the core sample could be quite accurately evaluated and areas of lower quality concrete could be indicated. This was mainly from the thick layer (approximately 30–40 mm) extending from the top edge and the thick layer (approximately 30–50 mm) extending from the bottom edge of the samples 01–06 taken perpendicularly to the upper plane of the element. Further, from the thick layer (approximately 20–80 mm) extending from the edge constituting the side plane of the slab for the samples taken parallel with the top plane of the element (samples 07–12). The decline in the strength of the concrete in the upper part of samples 01–06 is caused by the bleeding of water from the concrete mixture (the bleeding phenomenon ) and theFrom the point of view of the assessment of the concrete structure, supplementary tests on the slab in the future should be carried out using ultrasonic tomography ,21.The ultrasonic method of testing concrete by means of point-contact exponential probes enables the accurate assessment of the quality of concrete  along the height of a core sample drilled out perpendicularly to the placed layer.The concrete compressive strength destructively determined along the height of the placed layer of concrete changed slightly (by 3%—samples 01–06) with a depth below the top surface of the element. The averaged concrete strength determined on the basis of the ultrasonic tests of the same samples did not vary across the thickness of the analyzed slab.


Excessive and inappropriate use of antibiotics in hospitalised patients contributes to the development and spread of antibiotic resistance. Implementing a stewardship programme to curb the problem requires information on antibiotic use. This study describes a multicentre point prevalence of antibiotic use among paediatric inpatients in Ghana.Data were extracted from a multicentre point prevalence survey of hospital acquired infections in Ghana. Data were collected between September 2016 and December 2016 from ten hospitals through inpatient folder and chart reviews using European Centre for Disease Control (ECDC) adapted data collection instrument. From each site, data were collected within a 12-h period (8 am to 8 pm) by a primary team of research investigators and a select group of health professionals from each participating hospital.n = 251, 49.6%) were prescribed two antibiotics at the time of the survey. The top five classes of antibiotics prescribed were third generation cephalosporins  aminoglycosides , second generation cephalosporins , beta lactam resistant penicillins  and nitroimidazoles . The majority of antibiotics  were prescribed for community acquired infections. The top three agents for managing community acquired infections were ceftriaxone , gentamicin  and cefuroxime .Among 716 paediatric inpatients, 506 : 67.2 to 74.0%) were on antibiotics. A significant proportion of antibiotics (82.9%) was prescribed for infants compared to neonates (63.9%) and adolescents (60.0%). The majority of patients (This study points to high use of antibiotics among paediatric inpatients in Ghana. Cephalosporin use may offer an important target for reduction through antibiotic stewardship programmes. Antibiotic resistance is a public health threat of global proportions . It is aAntibiotic resistance, though a natural phenomenon, has been accentuated by inappropriate use of antibiotics which selects for and contributes to the spread of resistant bacteria –13. StraTo develop antimicrobial stewardship programmes, there is a need to acquire accurate baseline data on antibiotic prescription practice . As an an = 8195) in 2017 for a total bed capacity of 12,806.The report presented here on antibiotic use in patients ≤18 years is a sub-analysis to a multicentre point prevalence survey of hospital acquired infections. The study design was a retrospective patient record review using data collection instrument. The study was conducted among in-patients at ten hospitals in Ghana between September and December 2016 . DetailsData were collected from patient folders and treatment charts using standardised forms adapted from the European Centre for Disease Control (ECDC) . Data reData on antibiotic use was recorded when a patient was actively on antibiotics at the time of the survey. As per ECDC guidelines, indication for antibiotic use was assigned to either community acquired infection  or hospital acquired infection . Unknown indications included antibiotic treatments with missing information on origin of active infection. Diagnosis of infection was categorised according to anatomic systems , 25: eyep-values < 0.05 were considered statistically significant. We categorized our study as neonates if ≤28 days; and infants if > 28 days to ≤2 years. In the Ghanaian healthcare system, patients aged 0 up to 13 years are attended to in paediatric departments whilst those > 13 years are seen at adult departments. We thus assigned the term children if aged > 2 years to ≤13 years, and adolescents if aged > 13 years to ≤18 years.Data was analysed using Access (Microsoft Office 2016) and Statistical Package for Social Sciences . Antibiotics were classified according to the Anatomical Therapeutic Chemical Classification System (ATC) . We compData was collected from 2 tertiary hospitals, 3 secondary hospitals, and 5 primary hospitals Table . The incA total of 849 inpatients under the age of 18 years were included. Among these, 133 neonates were healthy and only in hospital because their mothers had not been discharged home. None of these received antibiotics and they were excluded from further analyses, leaving a total of 716 patients included for analysis. Baseline demographic data are shown in Table p = 0.0001). The proportion of antibiotic use among infants (82.9%) was significantly higher compared to antibiotic use in neonates (63.9%) and adolescents (60.0%) but similar to the proportion of use among children  were prescribed two antibiotics whereas fewer received one antibiotic , three antibiotics  or four antibiotics . This trend was observed among the neonatal, infant and adolescent populations, but not for children who were more likely to receive one antibiotic : 67.2 to 74.0] received at least one antibiotic at the time of the survey. There was a significant difference between the proportions of patients receiving antibiotics in regional hospitals (83.4%), tertiary (65.6%) and district hospitals  were third generation cephalosporins , aminoglycosides , second generation cephalosporins , beta lactam resistant penicillins  and nitroimidazoles . The proportion of third generation cephalosporin used was similar at the three hospital levels, i.e. tertiary , regional , district . Similar proportions of aminoglycosides were used in tertiary  and regional  hospitals, whereas significantly lower proportion were used in district hospitals  compared to tertiary hospitals (p = 0.03). A significantly higher proportion of second generation cephalosporins were used in district hospitals  compared to tertiary  and regional hospitals . Carbapenems were only used in tertiary hospitals . Of third generation cephalosporins prescribed, ceftriaxone was the commonest  compared to ceftazidime  and cefpodoxime . Among the aminoglycosides, gentamicin  and amikacin  were the only prescribed agents, with amikacin being prescribed only in tertiary hospitals. Cefuroxime (n = 103) was the only prescribed second generation cephalosporin in all healthcare facilities. Cloxacillin (n = 83) and metronidazole (n = 82) represent the only agents used across all healthcare facilities in the beta lactam resistant penicillin and nitroimidazole classes respectively. Among carbapenems, meropenem was the only agent prescribed (n = 7) ; cloxacillin ; ampicillin ; amikacin ; and cefotaxime  , cefuroxime , gentamicin , ampicillin , crystal penicillin  and metronidazole  were the top six antibiotics used. Among children, the five most common antibiotics used were ceftriaxone (n = 66 (21.8%), cefuroxime , gentamicin , ciprofloxacin  and amoxicillin-clavunalic acid .The five most common antibiotics used among neonates were gentamicin , gentamicin  and cefuroxime . The common agents used for surgical prophylaxis were metronidazole , amoxicillin-clavulanic acid  and cefuroxime .Out of the 831 antibiotics prescribed, 508 (61%) were prescribed for community-acquired infections, 86 (10.3%) for hospital-acquired infections, 197 23.7%) for prophylaxis and 40 (4.8%) for unknown reason , followed by the respiratory system  and skin, soft tissue, bone and joint infections  , ceftriaxone  and ampicillin . For respiratory tract infections, gentamicin , cefuroxime  and ceftriaxone  were the three most commonly used antibiotics. The top three antibiotics prescribed for skin, soft tissue, bone and joint purposes were metronidazole , cloxacillin  and clindamycin .Based on the anatomic site, antibiotics were mainly prescribed for undefined reasons n = 28, 39.5%To the best of our knowledge this study presents one of the few multicentre studies on antibiotic use among hospitalised paediatric patients from Africa and the first from Ghana. It provides current patterns of antibiotic prescribing practices in this population in Ghana and can serve as a baseline for future comparison. We observed that 71% of the hospitalised paediatric and adolescent patients were prescribed antibiotics with a high percentage of use among infants and neonates. This figure is comparable to a 69.4% rate of antibiotic use observed among children in a recent single site study from Korle-bu Teaching Hospital in Ghana . The ratThe lowest antibiotic use was reported for tertiary hospitals. This may be attributed to the fact that doctors in tertiary hospitals have more opportunities for rational antibiotic use: through participation in continuing education, consultations with senior physicians, and research –17, 30. In our study, we observed a very high rate of parenteral antibiotic use, especially in tertiary hospitals. It has been suggested that high rates of parenteral antibiotic use persists among children because of limited options for oral broad spectrum antibiotics with appropriate formulations and the challenges of oral administration of medications in young children . SimilarThe highest use of gentamicin, amikacin, ampicillin and cloxacillin was in the neonatal age group. These agents are recommended by the standard treatment guidelines of Ghana and by other international guidelines for neonatal infections , 43. OurThe use of broad spectrum antibiotics among children is a quality indicator for antibiotic prescribing as it can lead to the development and spread of antibiotic resistance . Use of Reducing antibiotic consumption through stewardship programmes is a major global strategy being advanced to curb the development and spread of antibiotic resistance , 51–55. This study has some potential limitations. Although the data presented here gives a good situation report of publicly funded health facilities, findings may not be directly extended to private healthcare facilities. We recorded the duration of antibiotic treatment, but the appropriateness and length of antibiotic use was not assessed at the individual level, nor was the indication for culture before antibiotic therapy. This could have provided significant information to guide antibiotic stewardships strategies and may be considered in future surveys. Another limitation is the study’s time window. Being a point prevalence study, information on antibiotic use was collected at a single point in time over the period between September and December 2016. This design would not capture the seasonality of infections and antibiotic prescriptions. Conducting this survey throughout multiple time points would have allowed for a more robust estimate of inpatient antibiotic prescribing in Ghana. However, we did not have the necessary capacity to repeat this multi-site point prevalence study more than once. Despite these limitations we believe the use of standardized international protocol  for our Our study shows high use of antibiotics among paediatric inpatients in Ghana. It also highlights key differences in antibiotic use among neonates and the other paediatric population; neonates are likely to be prescribed an aminoglycoside and a penicillin as opposed to the dominant use of cephalosporins among the other age groups. Studies of the appropriateness of antibiotic use are urgently needed to guide antibiotic stewardship strategies aiming at reducing the use of agents such as cephalosporins in order to conserve their lifespan.


Applying an ecological framework to bacterial antibiotic responses improves understanding of population recovery. An essential property of microbial communities is the ability to survive a disturbance. Survival can be achieved through resistance, the ability to absorb effects of a disturbance without a notable change, or resilience, the ability to recover after being perturbed by a disturbance. These concepts have long been applied to the analysis of ecological systems, although their interpretations are often subject to debate. Here, we show that this framework readily lends itself to the dissection of the bacterial response to antibiotic treatment, where both terms can be unambiguously defined. The ability to tolerate the antibiotic treatment in the short term corresponds to resistance, which primarily depends on traits associated with individual cells. In contrast, the ability to recover after being perturbed by an antibiotic corresponds to resilience, which primarily depends on traits associated with the population. This framework effectively reveals the phenotypic signatures of bacterial pathogens expressing extended-spectrum β-lactamases (ESBLs) when treated by a β-lactam antibiotic. Our analysis has implications for optimizing treatment of these pathogens using a combination of a β-lactam and a β-lactamase (Bla) inhibitor. In particular, our results underscore the need to dynamically optimize combination treatments based on the quantitative features of the bacterial response to the antibiotic or the Bla inhibitor. A disturbance is a biological, chemical, or physical event that affects a community  and there are many methods to quantify the bacterial antibiotic responses   (12). HoHere, we apply these concepts to the analysis of bacterial pathogens that produce extended-spectrum β-lactamases (ESBLs), which are becoming increasingly prevalent and can degrade many β-lactam antibiotics—the most widely used class of antibiotics . There was a slight, but significant, decrease in fluorescence for A = 1 μg/ml . Overall, Bla production is not induced by exposure to this range of antibiotic concentrations.We also tested whether the antibiotic induced the production of Bla by using fluorocillin, a substrate that fluoresces green when degraded by Bla, allowing the real-time visualization of Bla activity. After incubating the isolate with different concentrations of cefotaxime for 3 hours, we added fluorocillin to the sonicated culture to quantify the total Bla present. There was no significant increase in fluorescence as a function of antibiotic concentration  at the PT50%). With increasing antibiotic concentrations, more cells will lyse in the process of degrading the antibiotic, thus increasing the resulting recovery time. The more resilient a population is, the faster it can return to a normal state after being perturbed by an antibiotic. We define resilience as the inverse of the treated population’s T50%  and the net growth rate of an untreated population (ρ0) at the same time. When dealing with the experimental data, our analysis accounts for the time delay in lysis caused by a β-lactam (We quantify resistance as the ability of the population to not deviate from the pre–antibiotic treatment state (as quantified by the growth rate). Mathematically, we define resistance as the ratio between the minimum net growth rate in the presence of an antibiotic in a treated population , the population’s recovery displays a decline in both resistance and resilience because the antibiotic concentration is high enough to induce some lysis, slow the net growth rate, and delay the recovery time. Once the antibiotic concentration is high enough to induce a population crash (A > 5 μg/ml), the recovery of the population shifts to being dominated by resilience. If the antibiotic concentration exceeds the threshold for population recovery, the resulting resilience and resistance will be minimal. This resistance-resilience framework effectively reveals the phenotypic signature of each strain . The sensitivity analysis revealed that all parameters affect resilience to varying degrees, depending on the antibiotic concentration. Resilience is sensitive to the maximum lysis rate (STγ= 0.9 ± 0.02), Bla activity (ξ = 0. 03 ± 0.01). These parameters determine the collective ability of the population to remove the antibiotic, underscoring the notion that resilience is a population-level trait.Global sensitivity analysis was used to determine which parameters influenced resistance and resilience under a range of antibiotic concentrations. Briefly, the Sobol method calculates resilience and resistance for a range of parameter values and breaks down the variation for each into fractions that can be attributed to one or more parameters  of antibiotic for each level of the Bla inhibitor was unique for each isolate . Here, tResistance and resilience provide a powerful framework to dissect the contributions of different factors underlying a population’s response to a disturbance. Despite their appeal, resistance and resilience have had limited applications for understanding population responses due to differing definitions (0 = 0). Hence, it can be applied to diverse situations. For example, some bacteria are resistant to xeric stress due to the disturbance triggering their adaptive mechanisms  in response to neutral or negative perturbations, as both metrics can be uniquely defined from the time course of the population, as long as the minimum net growth rate of the treated population can be measured before the control population reaches its carrying capacity . For instance, cell-to-cell variability in gene expression can cause fluctuations in single-cell growth and death rates when in the presence of a disturbance  has mutated the end of a peptidoglycan strand, a component necessary for cell wall synthesis and the target for vancomycin , 0.4% glucose, 0.2% casamino acids (Teknova), 0.5% thiamine (Sigma), 2 mM MgSO4, and 0.1 mM CaCl2]. For overnight cultures, we inoculated single colonies from an agar plate into 2 ml of M9 and incubated them for 12 hours at 30°C.We characterized bacterial isolates from a library assembled by the Duke Hospital’s Division of Infectious Diseases. This library consists of approximately 80 isolates that have been identified as ESBL producers. Unless otherwise noted, 600 by adding the appropriate volume of M9 (fig. S9). The culture was then diluted 1000-fold in fresh M9, and the appropriate amount of cefotaxime (Sigma) was added to achieve a range of concentrations from 0 to 300 μg/ml. A 96-well plate (Costar) was loaded with 200 μl of culture per well and topped with 50 μl of mineral oil (Sigma) to prevent evaporation. The plate was loaded into a Tecan Infinite M200 PRO microplate reader (chamber temperature maintained at 30°C), and OD600 readings were measured every 10 min for 48 hours with intermittent plate shaking. Unless otherwise noted, each condition tested consisted of four technical replicates that, when averaged, did not need to include error bars.One milliliter of overnight culture was washed , and the OD was adjusted to 0.5 OD600 by adding the appropriate volume of M9. The culture was then diluted 1000-fold in 4 ml of fresh M9, and the appropriate amount of cefotaxime was added to achieve final concentrations of 0, 10, or 100 μg/ml. The cultures were incubated at 37°C for 6 hours. At this time, lawns of sensitive cells were prepared by spreading 5 μl of the 1000-fold diluted MC4100 culture onto agar plates. Supernatant from the cultures incubated with cefotaxime were prepared by spinning down 0.5 ml of culture with clavulanic acid . Four microliters of the supernatant was dropped into the center of the agar plates, which were then incubated for 16 hours at 37°C. The zones of inhibition were recorded by a camera.ESBL-producing isolate I and sensitive strain MC4100 were cultured in M9 for 12 hours at 30°C (fig. S10). One milliliter of each overnight culture was washed , and the OD was adjusted to 0.5 ODOvernight cultures of ESBL isolates I to IV and sensitive cells (MG1655) were prepared by inoculating a colony in LB for 12 hours at 37°C. ESBL cultures were washed and diluted, as in the “Measuring time courses” section, and the appropriate amount of cefotaxime (Sigma) was added to achieve 50 μg/ml in M9. Exogenous Bla (Sigma) was prepared in phosphate-buffered saline (PBS) and added to the ESBL cultures to achieve concentrations ranging from 1 to 100 μg/ml. MG1655 was washed and diluted, as in the “Measuring time courses” section, and the appropriate amount of carbenicillin (Genesee) was added to achieve 100 μg/ml. Exogenous Bla was prepared in PBS and added to the MG1655 cultures to achieve concentrations ranging from 1 to 20 μg/ml. Time courses were measured by a Tecan Spark and a Tecan M200 plate reader for the ESBL isolates and MG1655, respectively, as in the “Measuring time courses” section.After conducting a 24-hour time course, as described in the “Measuring time courses” section, cultures that had been exposed to cefotaxime doses of 0, 2, and 200 μg/ml were diluted 10-fold in fresh M9 (antibiotic free) and incubated at 37°C for 3 hours (fig. S11). The recovered cultures were then used to run another time course using the same antibiotic concentrations used in the previous round of treatment.600 and green fluorescent protein (GFP) readings were measured every 10 min for 1.5 hours. The GFP measurements of the sonicated samples were plotted over time, and the slope was calculated. The slope was normalized by the relevant culture’s OD measurement. A one-way ANOVA was used to determine any significant differences between the conditions.One milliliter of overnight culture was washed  and diluted 1000-fold in fresh M9. The appropriate amount of cefotaxime (Sigma) was added to achieve 0, 1, 10, and 100 μg/ml. The cultures were incubated for 3 hours at 30°C. For each culture, 1 ml was kept on ice to preserve the population density at the 3-hour time point. Two milliliters was spun down  and resuspended in 2 ml of water before being sonicated  to release periplasmic Bla. The sonicated culture was diluted 10-fold in water and then treated with 0 or 1 μM fluorocillin. A 96-well plate was loaded with 200 μl of each culture (whole cells), sonicated with and without fluorocillin, and topped with 50 μl of mineral oil. The plate was loaded into a Tecan Infinite M200 PRO microplate reader (chamber temperature maintained at 25°C), and OD600 and GFP readings were measured every 10 min for 1.5 hours. The GFP measurements of the samples were plotted over time, and the slope was calculated. The slope was normalized by the whole cell’s OD measurement.ESBL-producing isolates were incubated with cefotaxime  for 12 hours at 30°C. At that point, the culture was centrifuged  to separate the supernatant and whole cells. The supernatant was removed, and whole cells were resuspended in fresh M9. A portion of the whole cells was removed and sonicated  to release Bla from the periplasmic space. Bla activity in each component  was quantified by adding 1 μM fluorocillin and monitoring the change in green fluorescence with a plate reader. A 96-well plate was loaded with 200 μl of each mixture and topped with 50 μl of mineral oil. The plate was loaded into a Tecan Infinite M200 PRO microplate reader (chamber temperature maintained at 25°C), and ODThe preparation of cells, antibiotic, and 96-well plate were prepared as in the “Measuring time courses” section. When the cefotaxime was added, clavulanic acid potassium salt (Sigma) was also added to achieve final concentrations ranging from 0 to 5 μg/ml.Culture was prepared as in the “Bacterial strains, growth media, and culturing conditions” section except that the culture dilution ranged from 100- to 100,000-fold. Cultures were exposed to cefotaxime (0 or 100 μg/ml), time courses were measured by a plate reader, and the final cell density after 30 hours was recorded.MATLAB  was used to plot and characterize the time courses obtained from the plate reader .et al.’s ordinary differential equation model (n), extracellular Bla concentration (b), nutrient level (s), and β-lactam concentration (a).The interaction between a β-lactam and a bacterial population expressing a Bla can be simplified to the interactions between four main components: population density, antibiotic concentration, nutrient level, and Bla concentration. To model bacteria that constitutively produce Bla and lyse due to antibiotics degrading the cell wall, we modified Tanouchi n(0) = 0.4, b(0) = 0, a(0) = 0:300, and s(0) = 4 were used for all the simulations. We assume that the growth rate of cells (g) is limited by s, following the Monod kinetics. We assume the lysis rate (l) can reach a maximum of γ and depends on a following the Hill kinetics and g. dB and dA are the natural decay rates of extracellular Bla and antibiotic, respectively. κb is the rate at which Bla degrades the antibiotic. ξ is a weighting factor for how much nutrients are recycled upon cell lysis, and h is the Hill coefficient. See the Supplementary Materials for parameter values and full model development.Initial conditions of


The volume expansion of reinforcement corrosion products resulting from the corrosion of steel reinforcement embedded into concrete causes the concrete’s protective layer to crack or spall, reducing the durability of the concrete structure. Thus, it is necessary to analyze concrete cracking caused by reinforcement corrosion. This study focused on the occurrence of non-uniform reinforcement corrosion in a natural environment. The characteristics of the rust layer were used to deduce the unequal radial displacement distribution function of concrete around both angular and non-angular bars. Additionally, the relationship between the corrosion ratio and the radial displacement of the concrete around the bar was established quantitatively. Concrete cracking due to the non-uniform corrosion of reinforcements was simulated using steel bars embedded in concrete that were of uneven displacement because of rust expansion. The distribution of the principal tensile stress around the bar was examined. A formula for calculating the critical radial displacement at the point when cracking began was obtained and used to predict the corrosion ratio of the concrete cover. The determined analytical corrosion ratio agreed well with the test result. The effect factor analysis based on the finite element method indicated that increasing the concrete strength and concrete cover thickness delays concrete cracking and that the adjacent rebar causes the stress superposition phenomenon. Many factors can reduce the durability of a reinforced concrete (RC) structure. Among them, the corrosion of internal reinforcement materials, which is known as reinforcement corrosion, is the primary cause. The volume expansion caused by the corrosion of reinforcing bars in concrete leads to cracking or spalling in the concrete protective layer as corrosion develops, followed by durability failure of the concrete structure ,2. CorroAfter the reinforcement has corroded, an extrusion force on the concrete around the reinforcement is induced by the corrosion products. Under this reinforcement rust expansion force, the concrete cracks further. As the degree of rust corrosion increases, the cracks gradually expand toward the surface of the protective concrete layer. Several theoretical studies have been conducted on the reinforcement rust expansion force. According to an elastic analysis in the cracking process of corroded products, Bazant et al.  proposedExperimental studies on the rust-driven cracking of a concrete protective layer focus mainly on two topics: (1) the time from the rusting of the steel bar to the point when cracks appear on the concrete surface or the corrosion loss at the time of cracking on the concrete surface, and (2) the development of a law to predict the width of cracks on the concrete surface resulting from reinforcement corrosion. Numerous scholars have performed experiments to establish empirical models for the concrete cracking time and crack width. Andrade et al.  performeVarious factors contribute to the cracking of concrete structures due to corrosion expansion, but these factors cannot be comprehensively analyzed using empirical formulas. Previous research findings cannot be applied to other rust crack tests based on a small subset of factors. Therefore, in this study, a steel corrosion rate model was established for the situation in which a protective concrete layer is cracked, with consideration of various factors, such as the concrete cover thickness, water–binder ratio, and diameter of the steel bar.Failure of concrete under the action of the steel rust expansion force is simulated using finite element software or a custom computer program developed for this purpose. Val et al.  studied At present, the standard approach for the simulation of the process of concrete cracking caused by corrosion expansion is the use of a 2D model with a circular hole inside the concrete. However, such a 2D model cannot be used to analyze the interaction between sections, fracture development, or concrete spalling after rust-driven cracking. Therefore, in this study, focusing on the non-uniform corrosion of reinforcement in natural environments, an unequal radial displacement distribution function for concrete around angular and non-angular steel bars was deduced using the characteristics of the rust layer. A mathematical model for the critical radial displacement at the point when the concrete protective layer cracks was obtained in accordance with the results of a numerical regression analysis. The relationship between the radial displacement and the steel corrosion rate was used to obtain a calculation model for the corrosion rate of steel at the time of cracking. The prediction model was used to estimate the cracking time of the protective layer. Finally, the non-uniform rust calculation model was validated by comparing the results of the numerical analysis with experimental results.After the reinforcement materials begin to corrode, corrosion products exert an extrusion force on the concrete around the reinforcement. Under this reinforcement rust expansion force, a radial displacement field is generated in the concrete surrounding the reinforcement. If this radial displacement field can be determined, the volume expansion of the rust product can be simulated via the displacement method. In a real-world application environment, the corrosion of steel in RC members is non-uniform. The concrete side near the protective layer tends to be badly corroded, while the other side exhibits the opposite pattern. The radial displacement field of the reinforcement in angular and non-angular regions can be determined using findings from previous research.r is the original radius of the steel bar, uθ is the corroded thickness at θ under polar coordinate, u1 is the maximum corroded thickness nearest the concrete cover (for the side located bar) or the maximum corroded thickness at the corner of the concrete specimen (for the corner located bar), and u2 is the corroded thickness at the side far away from concrete cover.Reinforcement corrosion is distributed such that the thickness of the rust layer is inversely proportional to the shortest distance to the concrete protective layer. A point closer to the concrete surface corresponds to a thicker rust layer on the rebar. An elliptical model of the rust layer’s outer contour line in a non-angular reinforcement area is proposed. Before the expansion, due to the corrosion of the reinforcing causes the concrete to crack, the reinforcement corrosion is distributed in a semicircle on one side of the concrete protective layer, and the rust layer on the other side of the semicircle is so comparatively small that it is ignored in the calculations . HoweverBased on the results of a previous study , a doublThe concrete cracking process comprises three stages : the rusδ0, the volume of the pore transition zone in unit length is 2πrδ0, and the corrosion volume of the reinforcement material in unit length is sV1. Thus, the volume V1 of the corrosion products is the sum of the pore transition zone volume and the reinforcement corrosion volume, as given by Equation (3).The thickness of the pore transition zone between the steel and concrete is V2. When the pore transition zone is filled with reinforcement corrosion products, the concrete around the reinforcement bar is displaced by the reinforcement rust expansion force. Thus, the expanded volume of the concrete around the reinforcement in unit length (cV) is calculated using the radial displacement around the reinforcement, as indicated by Equation (4). In both stages, the reinforcement corrosion volume in unit length is sV2. Thus, the volume V2 of the corrosion product is the sum of the expanded volume of the concrete and the corrosion volume of the reinforcement, as indicated by Equation (5).The volume of the corrosion product at the concrete cover tensile stress stage and the concrete cover cracking stage is rV of corrosion products is the sum of V1 and V2, as indicated by Equations (6) and (7). The expansion rate of the reinforcement corrosion products is ρ, and the relationship between rV and sV is given in Equation (8). The total corrosion volume of the reinforcement in unit length (sV) is given by Equation (9). The rate of reinforcement corrosion ŋ is given by Equation (10). The relationship between the reinforcement corrosion rate and the radial displacement is given by Equation (11).The total quantity u1 and the minimum radial displacement u2 is given by Equation (12). The radial displacement equation is obtained by including the corrosion rate of the reinforcement (Equations (13) and (14)).Before corrosion expansion forms cracks in the concrete, the reinforcement corrosion is distributed in a semicircle near one side of the concrete protective layer, while the rust layer on the other side of the semicircle remains relatively small. Therefore, according to the literature , the relNon-angular area reinforcement: Angular area reinforcement: u1 and u2, the corrosion rate and the quantity of steel reinforcement corrosion at the point when rust expansion causes the concrete to crack can be determined. According to the characteristics of the steel corrosion layer in the concrete, a mathematical model is obtained for the unequal radial displacement distribution field caused by the effect of steel corrosion on the concrete for both a non-angular and an angular area. The model elucidates the conditions underlying the additional stress field caused by steel corrosion expansion and allows finite element model analysis for predicting the concrete cracks. Moreover, the quantitative relationship between the section loss rate of the non-uniform corroded reinforcement and the radial displacement of the concrete around the steel bars is obtained by analyzing the entire corrosion process that results in concrete cracking.Given the radial displacements At present, there are two approaches for the analysis of the concrete protective layer cracking: the theoretical analytical approach and the experimental approach. The theoretical analysis mainly involves mechanics analysis and finite element analysis. The elastic mechanics analysis approach adopted by scholars involves the consideration of the elastic mechanics of a thick-walled cylinder model in which the expansion force of the corrosion product is assumed to be evenly distributed on the inner wall of the concrete cylinder. However, this assumption is unrealistic. An additional drawback of elastic mechanics analysis is the difficulty of accurate quantitative determination of the damage caused by concrete cracking. Although finite element analysis is a recommended and an accepted method for the analysis of concrete crack damage caused by steel corrosion, an alternative approach—experimentation—must also be considered. The experimental techniques include the impressed-current accelerated test method and the simulation test method. The former is generally widely used by researchers, as it has the advantage of relatively short test time. However, the corrosion results of the impressed-current accelerated test method correlate poorly with natural corrosion conditions. Meanwhile, the simulation test method is poor for simulating the uneven nature of reinforcement corrosion. Compared with the experimental method, the theoretical analysis method’s advantages of a short analysis period and low cost ensure that it plays an important role in the field of concrete crack damage research, including the establishment of a reinforcement corrosion model both before and at the time of concrete cracking ,32,33 anThe concrete constitutive relation refers mainly to the stress–strain relation of concrete subjected to uniaxial and multiaxial stresses. A concrete dispersion crack model is used to describe the nonlinear behavior of concrete caused by isotropic hardening under compression elastoplastic and elastic cracking tension. The compression yield surface and crack detection surface function on the p–q plane (compression damage) is shown in (1)The ratio of the biaxial ultimate compressive stress to the uniaxial ultimate compressive stress;(2)The ratio of the uniaxial tensile ultimate failure stress to the uniaxial ultimate compressive stress;(3)The ratio of the principal plastic strain component under the biaxial ultimate compressive stress to the plastic strain component corresponding to the uniaxial ultimate compressive stress; and(4)The ratio of the principal tensile stress at cracking  to the stress at the time of uniaxial tensile cracking.The nonlinear behavior of concrete under a load is expressed by the model partitions. The isotropic hardening elastoplastic model is used in the pressure–pressure model area and the elastic cracking model is used in other areas. The linear-elastic constitutive relation is adopted before concrete cracking, the crack detection surface (tensile damage) is determined by the stress state and fracture direction at the time of cracking, and the elastic constitutive relation is adopted after cracking. The equivalent hydrostatic pressure and equivalent deviatoric stress are used to express the compressive yield surface and crack detection (tensile damage), respectively. The “Failure Ratios” option defines the shape of the failure surfaces. Four values are necessary to express the model:cf represents the maximum uniaxial compressive stress, cε represents the maximum uniaxial compression strain, and aα is the relevant parameter of the uniaxial compression stress–strain curve.The uniaxial compressive stress–strain relationship of the concrete was defined by the “concrete” option. The uniaxial compressive stress–strain relationship of GB50010-2010  was adopCracking is one of the most important mechanical behaviors of concrete materials. The crack expression and the shape simulation after cracking are key parts of the model. In the numerical analysis of concrete, considering nonlinear behavior, the key problem is how to simulate concrete cracking. In this study, a dispersion cracking model with independent crack detection surfaces was adopted. Concrete cracks develop when the stress reaches the crack detection surface. The fracture directions are then stored and used for subsequent analysis and calculations. Because the damage theory is used, the fracture direction can affect the subsequent calculation once the crack is generated (crack may be open or closed). The subsequent failure behavior of the crack zone was simulated via “tensile hardening,” which must be defined in the concrete cracking model. There are two tension stiffening modes: the post-failure stress–strain relation and the fracture energy crack criterion. The post-failure stress–strain relation mode was used for plain concrete, but its calculation results exhibited mesh sensitivity. To solve this problem, the fracture energy crack criterion mode was adopted. The displacement of the crack surface was 0.05 mm when the stress was 0 in the model. The setting “TYPE=DISPLACEMENT” under the “TENSION STIFFENING” option in the model parameters was used to apply the initial displacement.An RC specimen with a section size of 200 mm × 200 mm was simulated using the finite element analysis model, in which the reinforcement was replaced with an equal diameter hole. C3D8R elements were used to simulate the concrete. C3D8R is a 3D eight-node linear hexahedral solid heat conduction unit that adopts the linear reduction integral of fine mesh division. Structural grid generation technology was adopted, and the grid size was 0.005 m. The meshes around the holes are more refined, in which the grid size was 2 mm. The density and shape of the mesh division must be specified for finite element calculations. A relatively convergent solution can be obtained via trial-and-error calculations with different meshing densities. The steel and concrete were assumed to be perfectly bonded. An “embedded” command was utilized to simulate the interaction between the concrete and steel. Moreover, a fixed connection at the end of the concrete cover was used as a boundary condition. In the cracking analysis, the main tasks included adding the mechanical property parameters of the materials, modifying the analysis types, adding displacement boundary conditions, applying loads, and outputting calculation results.The reinforcement corrosion was assumed to be uniform along the axial direction, such that the reinforcement corrosion expansion could be treated as a plane strain problem. The concrete angle bar model and concrete side bar model were simulated . The surThe main factors influencing concrete cracking include the concrete strength, concrete cover thickness, rebar diameter, and steel position. The influencing factors considered in this study are presented in The elliptical model described above was adopted to analyze the radial displacement field, and radial displacement was applied to simulate the uneven corrosion expansion of the reinforcement. Hinged bearings were set at the model boundary, such that the models were under tension in both the radial and axial directions. To facilitate analysis, initial defects and micro-cracks were ignored in the study. For the reinforcements in the angular and non-angular areas, the radial displacement of the concrete was applied according to Equations (13) and (14).A concrete model with C30 concrete strength, a cover thickness of 30 mm, and a steel diameter of 20 mm was analyzed.u1 = 1 µm for the simulated stress distribution of uncracked concrete, as shown in The nephogram and isoline map of the principal tensile stress was obtained by applying a displacement value of Here, three holes  were arranged evenly. Equal radial displacement was applied to obtain a nephogram and isoline map of the principal tensile stress, as shown in u1 = 2.5 µm was applied, cracks occurred in the concrete around the steel bar. When a radial displacement of u1 = 5 µm was applied, the cracks spread in all directions. When a radial displacement of u1 = 6 µm was applied, cracks appeared in the concrete protective layer. When a radial displacement of u1 = 7.2 µm was applied, cracks penetrated the concrete protective layer. The horizontal and vertical components of the concrete stress values for the cracked surface are shown in A concrete model with C30 concrete strength, a cover thickness of 30 mm, and a steel diameter of 20 mm was analyzed to obtain the critical radial displacement when concrete cracks. When a radial displacement of (1) Concrete Strength Gradeu1 and the tensile strength of the concrete when the concrete protective layer cracks was established, as shown in u1 increases gradually as the tensile strength increases when the concrete cover thickness and rebar diameter remain constant.According to (2) Concrete Cover Thickness and Rebar Diameteru1 and the ratio of the concrete cover thickness to the rebar diameter when the concrete protective layer cracks, as shown in u1 increases gradually as the relative cover thickness increases when the tensile strength of the concrete remains constant.(3) Regression Analysis Datau1 represents the critical radial displacement, tf represents the tensile strength of the concrete, c represents the cover thickness, and d represents the rebar diameter.Factor analysis results indicated that the regression formula considering the critical radial displacement, concrete strength, cover thickness, and rebar diameter could be obtained using multiple logistic regression analyses. The regression model was established using the fitting function of Equation (16), as given in Equation (17).u1 = 4.5 µm was applied, cracks occurred in the concrete around the steel bar. When a radial displacement of u1 = 7.4 µm was applied, the cracks spread in all directions. When a radial displacement of u1 = 11.3 µm was applied, cracks appeared in the concrete protective layer. When a radial displacement of u1 = 11.9 µm was applied, the cracks penetrated the concrete protective layer. The horizontal and vertical components of the concrete stress on the cracked surface are shown in A concrete model with C30 concrete strength, a cover thickness of 30 mm, and a steel diameter of 20 mm were analyzed to determine the critical radial displacement during concrete cracking. When a radial displacement of (1) Concrete Strength Gradeu1 and the tensile strength of the concrete when the concrete protective layer cracks can be determined from u1 increases gradually as the tensile strength increases when the concrete cover thickness and rebar diameter remain constant.The relationship between the radial displacement (2) Relative Concrete Cover Thicknessu1 and the ratio of the concrete cover thickness to the rebar diameter when the concrete protective layer cracks can be determined from u1 increases gradually as the relative cover thickness increases when the tensile strength of the concrete remains constant.The relationship between the radial displacement (3) Regression Analysis Datau1 of the protective layer caused by the non-uniform rust in the non-angular area was corrected in accordance with Equation (18).The critical radial displacement of a non-angular reinforcement area is larger than that of an angular area reinforcement area, as indicated by u1 represents the critical radial displacement, tf represents the tensile strength of the concrete, c represents the cover thickness, and d represents the rebar diameter.Here, Equations (17) and (18), respectively, were substituted into Equation (11), and the steel corrosion rate models for the non-angular and angular areas are given in Equation (19). The regression mathematical model of the steel corrosion rate was obtained using the reinforcement-position correction parameters, as indicated by Equation (20). The radial displacement equation was obtained by including the reinforcement corrosion rate, as indicated by Equations (21) and (22).δ0 represents the thickness of the pore transition zone between the steel and concrete, ρ represents the expansion rate of the reinforcement corrosion products, and k represents the reinforcement-position correction parameter, which is 1 in the angular area and 0.9 for the reinforcement in the non-angular region.Here, Non-angular area reinforcement: Angular area reinforcement:2. The crack width was monitored using a crack width meter. When it was found that the crack width of the specimen surface along the longitudinal reinforcement was 0.10 mm, the broken specimen was removed for rust removal and weighing. The weight loss rate of the reinforcement was the corrosion rate when the protective layer cracked.To validate the formula, a 300 mm × 300 mm × 500 mm RC specimen was tested to determine the rate of steel corrosion. The cementing material used in the experiment was P.O42.5 ordinary Portland cement. Ordinary concrete fine aggregates were made of river sand with a fineness modulus of 2.4. Coarse aggregates were made of basalt gravel with a particle size of 5–20 mm. Both the fine and coarse aggregates satisfied the requirements of the aggregate grading curve. The water-reducing admixture was a polycarboxylic acid superplasticizer with a water reduction rate of 25%–30% (mass fraction), and the mixing water was tap water. The tensile strength of concrete was obtained via a splitting test involving cubic specimens. The splitting tensile strength of the concrete was evaluated for three cubic test blocks with dimensions of 150 mm × 150 mm × 150 mm. To reduce the influence of pouring factors, the same batch of sample curing was adopted. The mixture ratios of the C30 concrete are presented in δ0 was 12.5 µm, and ρ was 2. The mathematical regression model for the steel corrosion rate was simplified to Equation (23). The corrosion rate of the steel reinforcement was evaluated using the weightlessness method. The test and numerical simulation results are presented in After the accelerated corrosion tests, the specimens were cut into slices to analyze the corrosion pattern by microscopy in the inner reinforced mortar. A half sample was used to analyze the corrosion process by using inter-correlation image technique at the upper surface. The rust layer on the mortar was analyzed by using a CCD camera. According to a microscopic test, From this table, the calculated results were close to the experimental results, the error between them was <5%. The error occurred because the phenomenon of the rust products filling the crack gap and the creep effect of the concrete were not considered in the numerical simulation.(1)According to the occurrence of non-uniform corrosion and the characteristics of the rust layer, the unequal radial displacement distribution function of concrete around both an angular and a non-angular bar was deduced.(2)The stress field distribution of the concrete protective layer caused by steel corrosion was summarized, and the presence of adjacent steel bars caused a stress superposition of the concrete between the steel bars.(3)The formula for calculating the critical radial displacement was obtained at the point when cracking begun and used to predict the corrosion ratio of the covering concrete.(4)The mathematical model of the radial displacement at the time cracking occurred was obtained, which is related to the tensile strength of the concrete, the relative protective layer and diameter of rebar.(5)The correctness of the non-uniform rust calculation model was verified by comparing the results of the numerical analysis with the experimental results.As the corrosion of steel bars seriously affects the durability of concrete structures, the analysis of the concrete cracking process caused by reinforcement corrosion has important research significance. For the non-uniform corrosion of steel bars, uneven rust expansion displacement was used to simulate the cracking process of the concrete protective layer using numerical simulation.