MET Exon 14 skipping mutation inhibitors capmatinib and tepotinib with tolerable toxicity profile. In the GEOMETRY mono-1 trial, capmatinib was especially active in treatment-naïve patients supporting the upfront testing of this oncogenic driver. Tepotinib demonstrated superior activity in the pretreated patients in the VISION trial. Savolitinib is another MET TKI that has shown efficacy in the first- and second-line settings, including patients with aggressive pulmonary sarcomatoid carcinoma. These studies have demonstrated that these TKIs can cross the blood brain barrier and demonstrated some activity toward CNS metastases. MET Exon 14 skipping mutation is detected by NGS-based testing of liquid or tissue biopsies, with preference for RNA-based NGS. The activity of capmatinib and tepotinib is limited by the development of acquired resistance. Current research is focused on strategies to overcome resistance and improve the effectiveness of these agents. Our aim is to review the current status of MET Exon 14 skipping mutation as it pertains NSCLC.METex14 skipping mutations occur in about 3–4% of lung adenocarcinoma patients and 1–2% of patients with other lung cancer histology. The MET receptor tyrosine kinase and its ligand hepatocyte growth factor (HGF) are established oncogenic drivers of NSCLC. A mutation that results in loss of exon 14 in the MET gene leads to dysregulation and inappropriate signaling that is associated with increased responsiveness to MET TKIs. Results from GEOMETRY mono-1 and VISION Phase I/II clinical trials demonstrated significant clinical activity in patients treated with the  EGFR, BRAF, KRASG12C, and ERBB2, rearrangements in ALK, ROS1, RET, and NTRK, MET amplification or exon 14 skipping mutations, PD-L1 expression, and tumor mutational burden. Therapies targeting these biomarkers have demonstrated greater efficacy when compared to chemotherapy [Comprehensive genomic testing is now standard of care in the management of advanced/metastatic non-small cell lung cancer (NSCLC). Genomic testing identifies common or uncommon actionable genomic alterations that impact therapeutic decision making , 2. The otherapy .MET exon 14 skipping mutations (METex14) or activating mutations, MET gene amplification, and MET protein overexpression. However, the presence of MET exon 14 skipping mutations is currently, the best-defined predictive biomarker for the use of MET tyrosine kinase inhibitors (TKIs). MET exon 14 skipping mutations occur in about 3–4% of patients with adenocarcinomas and in about 1–2% of patients with other NSCLC histology (squamous and sarcomatoid lung cancer) [METex14 with other oncogenic drivers is not common, METex14 and MET amplification have been reported together [METex14 and MET amplifications are associated with poor prognosis in patients with NSCLC.The mesenchymal–epithelial transition (MET) is a tyrosine kinase receptor that is mostly expressed in epithelial cells, whose natural ligand is the hepatocyte growth factor (HGF). MET signaling has been demonstrated to involve cell proliferation, migration, invasion, and survival . Genomic cancer) . It appe cancer) . MET gen cancer) . While ctogether . Both MEMET exon 14 skipping treated with currently available therapies are poor. The results from the GEOMETRY mono-1 and VISION trials, respectively, led to the recent regulatory approval of capmatinib, and tepotinib was granted priority review for the treatment of this population of NSCLC patient with advanced disease. These results validate MET exon 14 skipping mutations as important oncogenic targets and underscore the need for routine testing by liquid or tissue biopsies.MET TKIs are divided into types I (subtype Ia and Ib), II, and III. Type Ia inhibitors  block ATP binding to prevent phosphorylation/activation of the receptor; type Ib inhibitors  are more specific for MET than type Ia inhibitors. Type II inhibitors  competitively bind a hydrophobic pocket adjacent to the ATP-binding site. Type III  inhibitors bind allosteric sites rather than the ATP-binding site . Generalc-MET is known to be expressed in epithelial cells of various organs including pancreas, liver, kidney, prostate, muscle, and bone marrow. When HGF binds to c-MET, the receptor undergoes homodimerization with subsequent phosphorylation of two tyrosine residues Y1234 and Y1235, located in the catalytic loop of the TK domain. Subsequently, Y1349 and Y1356 located within the carboxy-terminal tail also become phosphorylated, forming a tandem SH2 recognition motif. This results in recruitment of signaling effectors, including the adaptor proteins growth factor receptor-bound protein 2 (GRB2), src homology 2 domain-containing (SHC), v-crk sarcoma virus CT10 oncogene homolog (CRK) and CRK-like (CRKL); effector molecules phosphatidylinositol 3-kinase (PI3K), phospholipase Cg (PLCg) and SRC, the src homology 2 domain-containing 5’ inositol phosphatase (SHP2); and the signal transducer and activator of transcription STAT3. Unique to c-MET is its assemblage with GRB2-associated binding protein 1 (GAB1) which is a multi-adaptor protein that creates binding sites for additional downstream receptors upon phosphorylation. GAB1 can either bind directly to c-MET or indirectly via GRB2. Downstream responses of c-MET activation include AKT-mediated cell survival, STAT3-mediated cell proliferation, and ERK/MAPK-mediated cellular migration and invasion [Negative regulation of c-MET is necessary for maintaining a tightly controlled activity. The Y1003 site is a negative regulatory site which is located in the juxtamembrane domain that acts by recruiting c-CBL. Regulation of c-MET also occurs via its binding to various protein tyrosine phosphatases (PTPs). These PTPs remove phosphoryl groups on the tyrosines within the c-MET kinase or docking sites. Lastly, binding of PLCg to c-MET activates protein kinase C (PKC) which can negatively regulate receptor phosphorylation and activity. Aside from PKC activation, increases in intracellular calcium levels may also result in the negative regulation of c-MET .MET exon 14 skipping mutations result in base substitutions or indels (likely deletions) that disrupt the branch point of intron 13, the 3′ splice site of intron 13, or the 5′ splice site of intron 14 [MET exon 14 skipping alterations, as they exhibit highly diverse sequence compositions, making these mutations difficult to detect. The loss of METex14 results in increased MET stability, prolonged signaling upon HGF stimulation, and increased oncogenic potential. MET exon 14 skipping mutations may be may due to genomic deletions ranging in size from a 2-base pair deletion to 193-base pair deletion affecting the splice acceptor or splice donor site, or point mutations involving Y1003 [ntron 14 . The regng Y1003 .MET exon 14 skipping alterations are a challenge for diagnostic molecular testing. They exhibit high diversity in sequence composition, many variants are novel, and more than half are indel mutations (up to 3 kb), which are difficult to detect [MET exon 14 skipping mutations can be detected by immunohistochemistry, real-time RT-PCR, and by Sanger sequencing [MET, since tissue samples are limited. However, not all patients are able to receive comprehensive genomic profiling, and up to 40% of tissue biopsies are not adequate for molecular testing [o detect . These vo detect . Additioquencing , 18. Uti testing , 20.Liquid biopsies are a well-validated, FDA-approved molecular diagnostic tool that leverage circulating cell-free DNA (cfDNA) shed from advanced-stage solid tumors, which can be interrogated for tumor-specific alterations utilizing hybrid-capture digital next-generation sequencing . NumerouMET exon 14 mutations and c-MET overexpression [Capmatinib is a small molecule MET inhibitor which has been shown to effectively inhibit the MET pathway both in vitro and in vivo . In a Phpression .MET exon 14 skipping mutation or MET amplification according to gene copy number in tumor tissue). Capmatinib was dosed at 400 mg BID. The study showed that among patients with a MET exon 14 skipping mutation, overall response rate was 41% (95% CI: 29–53) of 69 patients who had received one or two lines of therapy previously and in 68% (95% CI: 48–84) of 28 patients who were treatment naive; the median duration of response was 9.7 months (5.6 to 13.0) and 12.6 months (5.6 to NE), respectively , with a median duration of response of 11.1 months  in the combined biopsy group, by independent review. The response rate was 48%  among 66 patients in the liquid biopsy group and 50%  among 60 patients in the tissue biopsy group; 27 patients had positive results according to both methods. The investigator-assessed response rate of 56%  was similar irrespective of the previous therapy received for advanced or metastatic disease  who progressed after previous systemic chemotherapy or unable to receive chemotherapy [METex14 skipping alterations were enrolled in this study. The median age of study participants was 68.7 years, 92.9% had stage IV disease, 60% received prior systemic chemotherapy and 35.7% had more aggressive pulmonary sarcomatoid carcinoma (PSC). At baseline, 24.3% of patients had brain metastases.Savolitinib is a selective oral otherapy . SeventyFGFR1, EGFR, and KRAS gene amplification at the time of disease progression has been reported as a mechanism of resistance to savolitinib in a case report [At a median follow-up of 17·6 months, the IRC-assessed objective response rate was 49·2% in the tumor response evaluable set, and 42.9% in the full analysis. The median PFS was 6.9 months ( with a 50% maturity) and median OS was 14 months. The PFS was reported to be clinically significant in the subgroup of patients with PSC. Treatment-related serious adverse events of grade 3 or more occurred in 32 (46%) patients, the most frequent of which were liver function and peripheral edema. Treatment-related serious adverse events occurred in 27.5% of patients, the most frequent of which were abnormal liver function (4.3%), hypersensitivity reaction (2.9%), and pyrexia (2.9%). Emergence of e report .METEx14 mutation instead of chemotherapy or immune checkpoint inhibitors (ICIs) upfront [METEx14, the efficacy of ICIs in this group is underwhelming. In a large study of 1,387 lung cancer cases, the expression of PDL1 was reportedly high in 49% of MET mutated cases (compared to 29% of MET wild type), while tumor mutation burden was significantly lower in MET mutated cancers compared to wild-type tumors [METEx14 mutations were associated with high (≥ 50%) PD-L1 expression; but the ORR with immunotherapy was low at 17% and median PFS 1.9 months [METex14 NSCLC, of whom 13 received an immune checkpoint inhibitor in the second-line setting, six patients had prolonged progression-free survival (> 18 months) [The current NCCN guidelines favor first-line treatment with single-agent targeted therapy for patients with e tumors . In a ree tumors . In anot months) . Another months) . FurtherMET exon 14 skipping mutation. Unfortunately, the response magnitude and duration of response are limited by primary and acquired resistance to MET TKIs. The molecular mechanisms of this resistance are not clearly elucidated.MET TKIs have shifted the paradigm in the treatment of patients with MET exon 14 mutant allele, and off-target resistance mediated by the activation of bypass signaling. There are two kinds of MET TKIs: type I and type II MET TKIs based on its binding interaction [There have been several established mechanisms of resistance to MET TKIs such as on-target resistance driven by kinase domain mutations affecting drug binding to the receptor or its ATP affinity, amplification of eraction , 42. Typeraction –45. Typeeraction . Type I eraction .. In contrast, mutations in residues L1195 and F1200 confer resistance to type II MET inhibitors [KRAS amplifications, KRAS mutations [NF1/RASA1 mutations [PI3KCA mutations, EGFR activation have been shown to drive acquired resistance to MET inhibitors [EGFR amplifications have also been detected in tumor samples from patients whose tumors developed resistance to MET TKIs [MET mutations in residues D1228 and Y1230 confer resistance to type I MET TKI by weakening the chemical bonds between the drug and its receptor , 47, 48.hibitors , 49. It hibitors , 49. Offutations , 47, 50,utations , PI3KCA hibitors , 53. AcqMET TKIs . TherefoThe prognosis with lung cancer remains poor as it remains the leading cause of cancer-related death in the USA. Current therapeutic strategies include traditional chemotherapy, radiation therapy, targeted therapies, and immunotherapies. Actionable mutation within tumors drives the efficacy of targeted therapy. However, tumor heterogeneity remains a challenge for identifying the patient population that may benefit from specific targeted therapy .MET exon 14 skipping mutations were more frequent in women than men, were less likely to be associated with a history of smoking, and were associated with a significantly older age. MET exon 14 skipping mutation have also been associated with poor prognosis, but were not associated with an increased risk for stage IV disease [A meta-analysis of 11 studies with a total of 18,464 patients with NSCLC showed that  disease , 56.MET exon 14 skipping mutation inhibitors capmatinib, tepotinib, and savolitinib have been proposed for the treatment of adult patients with metastatic NSCLC whose tumors harbor this mutation, irrespective of tumor histology. These TKIs have demonstrated durable response in both untreated and pretreated patients. In treatment-naïve patients, capmatinib demonstrated ORR of 68%, disease control rate of 96.4%, and duration of response of 12.6 months. In previously treated patients, the ORR is 41%, disease control rate is 78.3%, and duration of response is 9.7 months. Thirteen evaluable patients in the cohorts with MET exon 14 skipping had brain metastasis at baseline [The baseline  and intrIn the tepotinib VISION trial, at a median follow-up of 17.4 months, oral tepotinib led to an independently assessed objective response rate (ORR) of 46.5% among the 99 participants with locally advanced or metastatic disease who had been followed up for a minimum of 9 months at data cutoff. There were no complete responses, as all responses were partial and lasted for a median of 11.1 months. Median progression-free survival was 8.5 months and the overall survival data were not mature. In all, 43 patients were treatment-naïve, while the remaining 56 had received at least one prior line of therapy, but the ORRs by independent review were comparable to that of the overall cohort, at 44.2% and 48.2%, respectively. This was also the case for most other subgroups, with the largest difference seen for patients with versus without a smoking history, for whom the respective ORRs were 56.5% and 35.6% [MET exon 14 skipping mutation. However, sensitivity to type II kinase inhibitors such as cabozantinib is maintained, thereby providing the rational for sequential therapy [Despite the durable responses seen with these agents, acquired resistance remains a challenge as in all TKIs. Acquisition or emergence of preexisting clones with mutations in the MET activation loop Y1230  or D1228  has been shown to mediate resistance to type I MET TKI such as crizotinib in NSCLC with  therapy , 59. Inc therapy . Drug swMET exon 14 skipping as target are currently undergoing clinical trials (Table MET exon 14 skipping is currently enrolling in Europe and Japan. Antibody–drug conjugates like telisotuzumab vedotin (ABBV-399), which is a first-in-class conjugate of a MET antibody, ABT-700, and the antimicrotibule agent momomethyl auristatin E have been proposed. Other highly selective MET inhibitors like glumetinib have shown robust antitumor activity in preclinical models and are currently being studied in Phase I/II trials. Boxitinib (APL-101) is also a selective MET inhibitor under investigation in Phase I/II trials as a single agent in patients harboring MET exon 14 skipping mutation (Table MET Exon 14 skipping mutation inhibitors in the small cell lung cancer space.A multitude of new agents and rational combination of agents with ls Table . A randoon Table . A searcMET exon 14 skipping mutations or activating mutations, MET gene amplification, and MET protein overexpression, but the presence of MET exon 14 skipping mutations is presently the best-defined oncogenic driver and predictive biomarker for the use of MET TKIs. Given the prevalence of MET exon 14 skipping mutations and the poor outcomes in these patients, MET Exon 14 skipping mutations will continue to be an attractive therapeutic target. As far as we know, MET Exon 14 skipping mutation has not been found in small cell lung cancer.The molecular biology and therapeutic implications of MET alterations in NSCLC continue to evolve. Genomic alterations in MET include In conclusion, in the era of precision medicine, it is imperative to evaluate each patient individually. Molecular profiling of the tumor is an essential component of this clinical evaluation process. MET inhibitors are now established TKIs in the treatment of NSCLC patients with exon 14 skipping mutation, which is present in 3–4% of patients with adenocarcinomas and 1–2% of patients with other histologies. The challenge remains overcoming resistance to these new agents.


Up to 56% of antibiotics prescribed in the ambulatory setting in the United States are inappropriately prescribed, with 30% of those determined to be unnecessary. In order to increase transparency and education about antibiotic prescribing in our ambulatory clinics at our institution, we implemented quarterly scorecards demonstrating antibiotic prescribing trends for primary care prescribers. This pre-post interventional study analyzed the impact of prescriber scorecards on antibiotic prescribing, with the intervention consisting of real-time education and presentation of baseline data via scorecards. Prescribers were educated on the scorecard project via live meetings in Nov-Dec 2020. In Dec 2020, prescribers were sent individual emails describing their baseline antibiotic prescription rate (defined as number of prescriptions per 100 patient encounters), de-identified comparison data for other prescribers within their individual clinic, and average rate of the top 10% of prescribers with the lowest prescription rates. Baseline data was from prescriptions dated Jan-Mar 2020. The email also explained the project and shared that quarterly scorecards would be distributed in 2021. Baseline data was compared to prescription data from Jan-Mar 2021. Knowing the COVID-19 pandemic resulted in significantly fewer encounters for respiratory infections, data was also analyzed with respiratory diagnoses removed from the dataset. In the pre-intervention period, 11,769 antibiotics were prescribed during 92,239 encounters for a prescription rate of 12.8 (95%CI: 12.5-13.0). Of 96,449 encounters in the post-intervention period, 7,326 antibiotics were prescribed for a rate of 7.6 . When respiratory diagnoses were removed, prescription rates were 6.1 (95%CI: 5.9-6.2) in the pre-group, compared to 6.3 . When analyzed by prescriber, significant decreases were seen in prescriptions by physicians  while increases were seen in prescriptions by advanced practice prescribers. Antibiotic scorecards sent to prescribers may result in reduced antibiotic prescribing, but further research is needed to elucidate the impact of the scorecards in light of the COVID-19 pandemic. All Authors: No reported disclosures


Escherichia coli using five antibiotics, before measuring collateral effects on resistance to other paired antibiotics. During both isolation and phenotyping, we varied conditions in ways relevant in nature . This revealed that local abiotic conditions modified expression of resistance against both the antibiotic used during isolation and other antibiotics. Consequently, local conditions influenced collateral sensitivity in two ways: by favoring different sets of mutants  and by modifying expression of collateral effects for individual mutants. These results place collateral sensitivity in the context of environmental variation, with important implications for translation to real-world applications.Mutations conferring resistance to one antibiotic can increase (cross-resistance) or decrease  resistance to others. Antibiotic combinations displaying collateral sensitivity could be used in treatments that slow resistance evolution. However, lab-to-clinic translation requires understanding whether collateral effects are robust across different environmental conditions. Here, we isolated and characterized resistant mutants of IMPORTANCE When bacteria become resistant to an antibiotic, the genetic changes involved sometimes increase (cross-resistance) or decrease  their resistance to other antibiotics. Antibiotic combinations showing repeatable collateral sensitivity could be used in treatment to slow resistance evolution. However, collateral sensitivity interactions may depend on the local environmental conditions that bacteria experience, potentially reducing repeatability and clinical application. Here, we show that variation in local conditions  can influence collateral sensitivity in two ways: by favoring different sets of mutants during bacterial resistance evolution  and by modifying expression of collateral effects for individual mutants. This suggests that translation from the lab to the clinic of new approaches exploiting collateral sensitivity will be influenced by local abiotic conditions. As a result of antibiotic use, resistance is increasing in bacteria , necessi5–5–10–in vitro studies showed that different replicate populations exposed to the same antibiotic sometimes acquire collateral sensitivity to another antibiotic and sometimes do not  reduced pH (pH 6.5), as found in certain body compartments, including abscesses and parts of the gastrointestinal (GI) tract  between five pairs of antibiotics, each in four different experimental environments. Each antibiotic pair consisted of a selection antibiotic (which we used in mutant isolation) and a paired antibiotic . We chose pairs of antibiotics indicated by past work to at least sometimes display collateral sensitivity interactions , 6. The I) tract , 24; (iiI) tract ; and (ivI) tract .Escherichia coli K-12 MG1655 in the absence of antibiotics, before screening for antibiotic-resistant mutants, on agar with the selection antibiotic  for the relevant selection antibiotic and paired antibiotic, again across all four sets of abiotic conditions  was grown in liquid cultures (without antibiotics) overnight. (b) The cultures were transferred to agar with the same environmental conditions as during overnight growth  and the selection antibiotic at selection concentration. If there was growth after 48 h (resistant mutants), single colonies were picked and subjected to whole-genome sequencing (c). (d) For each mutant, dose response curves were measured against the selection antibiotic and a paired antibiotic in all four abiotic environments . From these curves we could calculate the antibiotic-free growth, the IC90 of the selection antibiotic, the IC90 of the paired antibiotic, and the growth at selection concentration (selection antibiotic only) for each mutant in each assay environment. (e) The same workflow was used for the other four antibiotic pairs, but using the selection and paired antibiotics given in the table. Although we show only single replicates here, we grew and selected 92 independent populations for each environment-antibiotic combination . We randomly chose up to 6 mutants to sequence and phenotype for each combination  The ancestral strain . Similarly, mutants selected in the same selection environment tended to have mutations affecting the same genes more often than mutants selected in different selection environments . Looking at each selection antibiotic separately, there was an effect of selection environment for cefuroxime  and streptomycin  but not trimethoprim and gentamicin (corrected P > 0.05). For streptomycin, the major differences were between the mutations selected in the low-pH environment and those in other selection environments. For cefuroxime, we found mutations in the penicillin-binding protein gene ftsI, but only in the presence of bile . Mutated genes influenced IC90 of chloramphenicol , GASC , and antibiotic-free growth . Mutated genes interacted with environment to influence IC90 of chloramphenicol , GASC , and antibiotic-free growth . Download FIG S2, TIF file, 0.3 MB.Phenotypes for chloramphenicol selected strains. (a) Nitrofurantoin resistance; (b) chloramphenicol resistance; (c) GASC of chloramphenicol; (d) antibiotic-free growth for the isolates resistant to chloramphenicol, where we have genotyping information. Thick lines show the mean phenotypic value for the 4 strains with mutations in Copyright © 2021 Allen et al.2021Allen et al.https://creativecommons.org/licenses/by/4.0/Creative Commons Attribution 4.0 International license.This content is distributed under the terms of the 10.1128/mSystems.01055-21.8TABLE S1E. coli K-12 MG1655 reference) or the start position for multi-base-pair mutations. “Gene” is the gene(s) that was mutated; where there are two genes separated by a slash, the mutation occurred between them. The number in brackets represents either the nucleotide position from the start of the gene for mutations in coding regions or the distances to the neighboring genes in the case of intergenic mutations (minus and plus signs indicate upstream and downstream). “Gene mutated” is the gene influenced by the mutation, either because the mutation occurred in that gene or because the mutation affects the promoter region of that gene (as determined by breseq). Genes with a superscript 1 were intergenic mutations where breseq did not assign a gene, but we manually identified which promoter was influenced based on promoter information (https://ecocyc.org/). Genes with a superscript 2 are synonymous mutations; these are listed here and in hemB was mutated in other isolates, so we assigned this large deletion as affecting hemB. In some isolates, we could not identify any mutations, so no mutations information is given, but coverage is still reported. We were able to identify mutations in 84 of the strains. Download Table S1, DOCX file, 0.1 MB.Mutations identified in the 110 strains genotyped. Mutations were identified by breseq, run in consensus mode, using the genotype of the ancestral strain as a reference. All mutations detected by breseq are shown. “Sample Code” is shorthand for each mutant . Antibiotic abbreviations: CFR, cefuroxime; CHL, chloramphenicol; GEN, gentamicin; STR, streptomycin; TRM, trimethoprim. “Position” is the position in the genome that was mutated  , mutants selected against streptomycin and tested against tetracycline , and mutants selected against trimethoprim and tested against nitrofurantoin  but not for mutants selected against cefuroxime and tested against gentamicin . We found several genes that were consistently associated with collateral sensitivity to paired antibiotics , such as ubi mutants, which were on average collaterally sensitive to cefuroxime   , which in turn leads to a reduced membrane potential and hence reduced influx of aminoglycosides   compared ± 0.71) . For ind< 0.001) , and atp < 0.01) . Mutatio10.1128/mSystems.01055-21.3FIG S390 of antibiotics compared across directly and indirectly selected mutants and ancestral strain. Panels show resistance (IC90) to (a) cefuroxime, (b) gentamicin, (c) streptomycin, (d) trimethoprim, (e) tetracycline, (f) nitrofurantoin, (g) chloramphenicol, and (h) polymyxin B in the 4 different abiotic environments for all relevant strains. Strains shown are mutants directly selected with the same antibiotic (red box plots), mutants selected with another antibiotic , and the ancestral strain (yellow lines). See keys in individual panels for the specific drugs used for selection of mutants. Box plots show medians and interquartile ranges across all individual mutants measured under the relevant conditions (where the score for each mutant is first averaged across replicate assays). Data for the ancestral strain are the means of all independent estimates of IC90 under the relevant conditions (mean n = 4.8); error bars show standard errors of the means. y axes are log transformed and vary between panels. For the ancestral strain, assay environment had the strongest effects on resistance to gentamicin , streptomycin , and polymyxin , although only for gentamicin was this effect significant after accounting for multiple testing. All IC90 comparisons reported in the text are relative to the ancestral IC90 in the same abiotic environment. This could in theory influence the main effect of assay environment on collateral effects, as reported in the text (seen for the selection-paired drug combinations cefuroxime-gentamicin and trimethoprim-nitrofurantoin). However, we see the same main effect of assay environment in these two combinations when we use absolute IC90 of the paired drug for resistant mutants instead of IC90 relative to the ancestor . We also see a significant effect for streptomycin-selected mutants , which was not significant using IC90 relative to the ancestor (see the text). Download FIG S3, TIF file, 0.5 MB.ICCopyright © 2021 Allen et al.2021Allen et al.https://creativecommons.org/licenses/by/4.0/Creative Commons Attribution 4.0 International license.This content is distributed under the terms of the 90 to nitrofurantoin: χ23 = 20.6; corrected P < 0.01). Mutants selected at high temperature  had significant collateral sensitivity. Mutations in phoPQ, which were associated with relatively high sensitivity to nitrofurantoin  (90 (not relative to the ancestor).Expression of average collateral effects to paired antibiotics also varied depending on the abiotic conditions during exposure to these antibiotics. For mutants selected against cefuroxime and trimethoprim, there was a significant effect of assay environment on average resistance to the paired antibiotics, relative to the ancestor under the same conditions  . Note th< 0.001) . Qualita< 0.001)  if we us29 = 38.3; corrected P < 0.001). For some mutants, this variation led to a switch between cross-resistance and collateral sensitivity, such as cpxA mutants  and pH  environments but were susceptible to cefuroxime at high temperature . cpxA is part of a two-component regulator which responds to misfolded proteins in the periplasm, activating the Cpx response, which has been shown to confer resistance to aminoglycosides (cpxA (as in our mutants) have the Cpx pathway locked into an activated state  of each mutant to its corresponding selection antibiotic in all four abiotic conditions: assay environment did not significantly alter the observed variation of IC90 among genotypes . Furthermore, we found no evidence that average IC90 was higher for mutants tested in sympatric environments (selection environment = assay environment) than in allopatric environments (selection environment ≠ assay environment), as would be the case if the mutations we detected conferred bigger increases in resistance in the abiotic conditions they were selected in . Thus, variation across assay environments of the relative changes in resistance (measured as IC90) conferred by different resistance mutations did not explain why we isolated different mutants in different conditions  may depend on local abiotic conditions . We founected in , 34 , measured in four sets of abiotic conditions (assay environment). Each panel shows mutants selected for resistance to the drug indicated for the panel, with the resistance to this selection drug as ICironment . MutantsCopyright © 2021 Allen et al.2021Allen et al.https://creativecommons.org/licenses/by/4.0/Creative Commons Attribution 4.0 International license.This content is distributed under the terms of the 90. Therefore, GASC potentially provides additional information about why some types of mutants were associated with particular selection environments. GASC was calculated from the same dose-response curves as the IC90 and was positively correlated with IC90 across all mutants   . For cefuroxime-resistant mutants, GASC varied significantly among sets of mutants selected under different abiotic conditions, with bile-selected mutants performing best  (ftsI mutants) . Note that ftsI mutants also had relatively high IC90 on average . Our rationale here was that the mutations most beneficial during our screen (and most likely to result in formation of viable colonies) are not necessarily the mutations that confer the largest increases in IC 0.0001) . For tri< 0.001) , and the< 0.001)  varied a < 0.05) . Thus, amutants) . Consistmutants) . Despite average , althougfor GASC . In summ10.1128/mSystems.01055-21.5FIG S590 for 48 mutants, each measured against the relevant selection drug in each of the four assay environments. Each point is from an independent dose-response assay, with IC90 and GASC calculated from the same data. The different measures are transformed according to the way that the variables are input into the relevant models. These measures are highly correlated . Download FIG S5, TIF file, 0.1 MB.Correlation between GASC and ICCopyright © 2021 Allen et al.2021Allen et al.https://creativecommons.org/licenses/by/4.0/Creative Commons Attribution 4.0 International license.This content is distributed under the terms of the 10.1128/mSystems.01055-21.6FIG S6E. coli with different drugs in different environments. The number of populations in which resistance was seen (one or more resistant colonies) varied with the combination of antibiotic and selection environment . The dashed line shows the maximum number of independent mutants . Download FIG S6, TIF file, 0.1 MB.Number of independent wells (of 92) which had resistant colonies after plating Copyright © 2021 Allen et al.2021Allen et al.https://creativecommons.org/licenses/by/4.0/Creative Commons Attribution 4.0 International license.This content is distributed under the terms of the 90s . Relative to the ancestral strain in the absence of antibiotics , most types of resistant mutants showed evidence of growth costs, with 29 of the 57 mutants showing at least a 20% reduction in mean growth relative to the ancestor in one or more environment. However, this varied depending on the selection antibiotic   .F4,16 = 107, corrected P < 0.001; gentamicin, F5,12 = 23.0, corrected P < 0.001; streptomycin, F6,10 = 15.5, corrected P < 0.001; trimethoprim, F3,18 = 358, P < 0.001). For example, streptomycin-resistant mutants with mutations in atpG grew relatively poorly , as did trimethoprim-resistant mutants with phoPQ mutations . For all selection antibiotics, variation of antibiotic-free growth among different genotypes depended on the local abiotic conditions . Despite this, we did not find any evidence of matching between mutants and their selection environments in terms of antibiotic-free growth . In summary, local abiotic conditions modified the costs of resistance for our genotypes in the absence of antibiotics, but this did not explain the distribution of genotypes across selection environments in our mutant screen.For all selection antibiotics, mean antibiotic-free growth varied depending on which gene was mutated (y poorly  (differeutations  (differeacr) (marR and phoPQ) (ftsI and rpsL)  , global d phoPQ) , 40 and nd rpsL) –43, suggd rpsL) –, 45, whid rpsL) –, 47. In –E. coli .cpxA mutants only in a single environment at 37°C, we would have observed only that they mediate cross-resistance between gentamicin and cefuroxime  that have been found in previous studies  with additions to create variations in environmental conditions for basal, pH, and bile media. Basal medium (the base condition) is LB buffered at pH 7.0 with 0.1 M sodium hydrogen phosphate (Na2HPO4 and NaH2PO4). pH medium (acidic pH) is LB buffered at pH 6.5 with 0.1 M sodium hydrogen phosphate. Bile medium is LB with the addition of 0.5 g/liter of bile salts and buffered at pH 7.0 with 0.1 M sodium hydrogen phosphate. The temperature treatment uses the basal medium but is incubated at 42°C. When these conditions were on solid media , we instead used LB agar (Sigma-Aldrich), but other temperature and medium additions were the same. For overnight culture prior to assay, we incubated at 37°C in diluted LB .We used E. coli strain for each of the 4 selection environments , incubated for 20 h in the absence of antibiotics. Each entire culture was then transferred to a well of a 24-well plate containing 1 ml of agar corresponding to the same selection environment as the prior liquid culture plus one of five antibiotics at selection concentration . These selection concentrations were approximately equal to MICs for the ancestor. This meant the ancestral strain was effectively inhibited, but mutants with even moderately increased resistance could grow. A higher selection concentration was used for the aminoglycosides  in the pH medium because of the reduced efficacy against the ancestral strain in this environment (E. coli populations (each plated from a separate overnight culture grown in the absence of antibiotics) for each combination of 4 selection environments and 5 selection antibiotics. After incubation, each agar well was checked for the appearance of resistant colonies  according to the manufacturer’s instructions. Libraries were produced using the Illumina Nextera XT kit. Sequencing was performed on the Illumina HiSeq 4000 platform with 150-bp paired-end reads at the Functional Genomic Center, Zürich, Switzerland . Reads wftsI (phoQP) or having very closely related functions . In one mutant, we found a large deletion affecting multiple genes, including hemB, which was also altered in some other mutants; this mutation was designated as affecting hemB. This list of genes and gene sets was used in PERMANOVA (see “Statistics”). Sixteen mutants had multiple mutations affecting multiple genes ; in the other such cases, we categorized each mutant according to mutated genes known to be involved in resistance to the selection antibiotic . The ch600) using a spectrophotometer . Due to the time taken to read 64 plates, incubation and plate reading was staggered and the order was randomized. Some mutants failed to regrow during overnight incubation, resulting in some assay wells not being inoculated. To filter out these false negatives, we excluded OD600 scores from assay plates that were <0.03, but only if the OD600 in the overnight well (prior to inoculation of the assay well) was also <0.03 (both after subtracting blanks).We selected 75 strains with genotypic information to phenotype (and the ancestor), excluding mutants where very similar genotypes were already represented. Resistance of all mutants and the ancestral strain was quantified using broth dilution. For each antibiotic, we assayed each combination of strain, assay environment, and antibiotic concentration in four biological replicates, each in a separate temporal block. In each block of assays, we used a frozen master plate containing all strains organized in one of three randomized layouts  to inoculate a single preculture plate . We then incubated the preculture plate for 3 h before using it to inoculate all the overnight plates . Overnight cultures were then used to inoculate the assay plates using a pin replicator. Each mutant was tested against the relevant selection and paired antibiotics, and the ancestor was tested against all antibiotics, each at 8 concentrations (including zero) in each assay environment. After culturing assay plates for 20 h, we agitated the plates to resuspend bacteria and then measured the biomass of bacteria by optical density at 600 nm (OD90) of the selection antibiotic, (ii) growth at selection concentration (GASC) for the selection antibiotic, (iii) IC90 of the paired antibiotic, and (iv) growth in the absence of antibiotics. These phenotypes were calculated from the dose-response relationship data for the selection and paired antibiotics (for each replicate separately). We fitted a Hill function using nonlinear least-squares analysis in R (A × nk)/(nk + nC), where OD is the measured optical density and C is the antibiotic concentration. A is then the asymptote, k is the inflection point of the curve, and n is the Hill parameter controlling curve steepness. Thus, growth in the absence of antibiotics is equal to A, so for each combination of mutant and assay environment, antibiotic-free growth is the mean of the A parameters across all dose-response curves for this strain and environment. The IC90 for the selection and paired antibiotics can be calculated using the following formula, taking the parameters from the relevant fitted curve.For each mutant strain, we calculated four phenotypes: (i) 90% inhibitory concentration . In all cases, there was a strong correlation between the fit-dependent and fit-independent measures . We estmeasures .10.1128/mSystems.01055-21.7FIG S7P < 0.001). The red lines indicate exact identity. Download FIG S7, TIF file, 0.2 MB.Correlation between the 4 phenotypes measured when calculated using a method that requires a fitted Hill function (fit dependent) and a method that does not require a fitted Hill function (fit independent). Points represent values calculated from individual replicate dose-response measurements. Only points where both fit-dependent and fit-independent methods were calculated are plotted. The correlation measured by Pearson’s correlation coefficient is given at the bottom right of each panel; in all cases, this was significant  relative to the mean of the ancestral strain (log2 transformed) measured in the same environment. This controlled for any effects of assay environment on antibiotic inhibition of the ancestral strain .We treated the mutants selected for resistance against different antibiotics as independent data sets, due to the difficulty in comparing resistance across multiple antibiotics. This meant that we had only 5 independent mutants for chloramphenicol, which limited our ability to draw conclusions about this antibiotic. Therefore, we do not discuss the chloramphenicol-resistant mutants in the text, but they are included in the supplemental information for completeness . In eachl strain  and normFor each of the 4 phenotypes across the 4 antibiotic data sets, we fitted two mixed effects models . The fix10.1128/mSystems.01055-21.10TABLE S3Table S3, DOCX file, 0.03 MB.Significance of terms from phenotypic models reported in the text. Models A and B were separately fitted to the different phenotypes. The models were independently simplified to the minimal models by dropping nonsignificant (α = 0.05) terms (not included in higher-order interactions), as described in more detail in Materials and Methods. Grey cells are significant at an α value of 0.05 and are thus kept in minimal models. For the fixed-effect terms, cells are black if terms were still considered significant after multiple-testing correction ; this was tested only for fixed effects. Download Copyright © 2021 Allen et al.2021Allen et al.https://creativecommons.org/licenses/by/4.0/Creative Commons Attribution 4.0 International license.This content is distributed under the terms of the In both models, we included a nested random effect of strain  on intercept [+(1|Strain) in the lmer function] to account for variation between strains . We alsoF test for fixed-effects models and a likelihood ratio test (χ2 statistic) for mixed models. When the main effect of genotype is involved in a significant higher-order interaction (genotype: assay_environment) the main effect cannot be dropped, so significance is instead reported with an F test (on a type III ANOVA), regardless of whether the model contains random effects. For mixed models, the approximate degrees of freedom are calculated using lmerTest . These are reported in the text as corrected P values, and values below 0.05 are considered significant.For both the genotype and phenotype models, we tested 4 data sets (from four antibiotic combinations) for similar effects in parallel, therefore, when reporting the results of these tests, we give https://doi.org/10.5061/dryad.6m905qg16). Genomic data are relative to the reference genome of Escherichia coli K-12 MG1655 and have been uploaded as SNP tables relative to this reference in the Dryad data file.All raw data are available on Dryad (


Acquired immunodeficiency syndrome (AIDS) is a chronic and incurable disease. People with human immunodeficiency virus (HIV) require lifelong care. Traditional Chinese Medicine (TCM) has played an important role in AIDS treatment since the year 2004. TCM offers many advantages including a rich resource of Chinese herbs, lower cost and fewer side effects. In addition to the widespread use of antiviral therapy, TCM offers unique humanistic care and holistic adjustment of the body system. To date, more and more patients are benefiting from TCM not only in China. In this article, we describe the feasibility of treating AIDS with TCM. In developing countries with limited medical resources and a lack of health knowledge among the population, most patients with AIDS live in poor areas with limited opportunities to receive Western medical care, other than free antiviral therapy.Being a chronic and controllable infectious disease, treatment and research related to human immune-deficiency virus (HIV) or acquired immunodeficiency syndrome (AIDS) has been ongoing for more than 30 years ,2. ChinaIn clinical practice, Traditional Chinese Medicine (TCM) has a theoretical basis and a profound cultural heritage, with a rich accumulation of clinical experience. Under the guidance of TCM theory, Chinese medicine practitioners have used TCM to successfully treat numerous infectious diseases, such as severe acute respiratory syndrome, influenza A virus sub-type H1N1, epidemic encephalitis, hepatitis, and COVID-19 . TCM and+ T-cell count and HIV viral load. TCM is more concerned with the clinical complaints of patients with AIDS, including abnormal symptoms and signs, lower level of quality of life (QOL), complications, opportunistic infections, and side effects of combination anti-retroviral therapy (cART) and not merely CD4+ T cell counts and viral lead-time is based on clinical practice with humanistic characteristics, a holistic approach, syndrome differentiation, and flexible prescription, which lead many Chinese medicine practitioners and patients to believe that TCM can treat any complex disease.There are a large number of TCM hospitals and clinics in China, where millions of patients receive TCM treatment and services every day. TCM involves a variety of approaches including qigong, Chinese herbs, acupuncture, and moxibustion. Patients often seek treatment with TCM alone or in combination with WM to manage HIV/AIDS, and this conventional practice has flourished in China. The unrecognized efficacy of TCM in the treatment of AIDS might be owing to fundamental differences in the two kinds of medicine. The gold standard diagnostic criteria of the World Health Organization (WHO) for AIDS are CD4TCM treatment of AIDS is a process of continuous improvement. Since 2004, the State Administration of Traditional Chinese Medicine of China has executed a pilot program for the use of TCM to treat patients with AIDS in conjunction with anti-retroviral drugs and has sponsored many AIDS-related science and technology projects , and wit+ T cell counts, reducing plasma HIV viral loads, reducing opportunistic infections, improving QOL, counteracting the effects of anti-retroviral drugs, promoting immune function recovery, and increasing survival of patients with AIDS. TCM offers many advantages including a rich resource of Chinese herbs, lower cost, and fewer side effects.TCM has multiple effects , such asSigns and symptoms  are more common among patients with AIDS who have lower immune function , which mvs. after 1.09±1.60) and scores for fatigue and anorexia in the TCM group were significantly lower than those in the control group after treatment (fatigue: 0.41±0.89 vs. 0.59±0.92 and anorexia: 0.13±0.49 vs. 0.45±0.84). The study findings suggest that Immune No. 2 granules have a certain therapeutic effect on fatigue and anorexia symptoms in patients with AIDS who have a low viral load and low immune status after cART.A multi-center, randomized, double-blind, controlled clinical trial demonstrated the effects of Immune No. 2 granules on signs and symptoms of patients with AIDS who had low viral loads and low immune status after cART . A totalet al. [Meng et al.  reportedet al. [Ma et al.  randomizet al. [Xu et al.  reportedQOL is an individual's perception of their life in the context of the culture and value systems in which they live and in relation to their goals, expectations, standards and concerns . The QOLet al. [Jin et al.  reportedet al. [Weng et al.  reportedet al. [Xu et al.  reportedAIDS remains a highly fatal disease. Survival rates reflect the lethality of the disease and can be used to evaluate the long-term curative effect of AIDS treatments.et al. [Zhao et al.  reportedIn a 6-year retrospective cohort study , 1,666 pet al. [Xu et al.  reportedThe morbidity and mortality of AIDS has been reduced since the introduction of cART, but adverse effects of these drugs remain inevitable. Antiviral strategies are limited in developing countries because patients must adhere to treatment for their entire life. It very important to seek more realistic methods to reduce the side effects of cART drugs.A multi-center, randomized, double-blind, placebo controlled clinical trial evaluated the efficacy and safety of TCM in reducing cART adverse reactions . 536 patWendan granule is composed of eight Chinese herbs to alleviate adverse gastrointestinal effects caused by cART . The incet al. [Jiang et al.  observedDanggui Shaoyao San, a well-known Chinese herbal formula, has been used to treat cART-induced liver dysfunction . StudiesSome individuals exhibit failed or incomplete recovery of CD4+ cell counts despite viral load suppression after continuous cART. This phenomenon is defined as suboptimal immune recovery or poor immune reconstitution (IR) . IR is dTCM has been used to promote IR and some studies have proven that TCM has an important role in IR. A randomized, double-blind, placebo-controlled clinical trial tested a Chinese herbal formulation (Immune No. 2) with respect to IR in patients with HIV/AIDS after cART . The stu+, CD45RA+, and CD8+ T-cell counts, reducing HIV virus load, improving clinical symptoms and signs, and increasing body weight in patients.Another randomized, double-blind, placebo parallel controlled clinical trial investigated a Chinese herbal formulation (Zhongyan-4) in treating patients with HIV/AIDS in the early or middle stages . The tri+ T-cell count have been adopted in TCM. Some results demonstrate that TCM shows promise in reducing HIV viral loads, increasing CD4+ T cell counts, as well as improving other immunological indicators. Compared with HIV viral loads, CD4+ T cell counts are more frequently examined in TCM clinical trials.The indexes viral load and CD4et al. [+ cell counts. Compared with the ART group during the first 6 months, CD4+ T cell counts among patients in the TCM group and TCM combined with ART group exhibited a steady rise. CD4+ T cell counts in the TCM, and combined groups remained much lower than those in the ART group during the first 3 years, but these overtook the ART group in the fourth year.Sun et al.  reported+ T cell counts among patients with HIV/AIDS who were treated with cART over a 14-year period [A retrospective cohort study analyzed the efficacy of TCM therapy on long-term trends in CD4r period . The stuet al. [Li et al.  observedThe efficacy of a Chinese herbal formulation (Xiang A1 capsule) in AIDS has been demonstrated in a randomized, double-blind, double dummy, controlled clinical trial . Sixty eet al. [+ T cell counts among patients with AIDS in the asymptomatic stage. Sixty patients were randomly divided into a control group (cART) and treatment group (Jianpi Yishen decoction+cART). After 12 months, the Chinese medical syndrome score decreased and CD4+ T cell counts increased significantly in both groups; however, these changes were greater in the TCM+cART group than in the cART group. Thus, the combination of cART and Jianpi Yishen decoction may improve symptoms in asymptomatic patients with AIDS and increase CD4+ T cell counts.Song et al.  observedet al. [+ and CD8+ T cells. They found that patients with HIV/AIDS exhibited an improved immune activation profile following Fuzheng Paidu granule treatment. The potential mechanism of action for Fuzheng Paidu granule appears to lie in its ability to up-regulate CD38 and HLA-DR expression on CD4+ T cells, and down-regulate these on CD8+ T cells, thereby modulating immune activation of CD4+ and CD8+ T cells.Jiang et al.  reportedet al. [+ T-cell counts decreased in both groups after 11 months, cell counts declined less significantly in the Aining group than in the control group. Significant improvement of symptoms such as fatigue, anorexia, nausea, diarrhea, and skin rash were observed in the Aining granule group. However, there was no significant difference between the two groups in viral load after treatment.Wang et al.  reportedThe safe medication use is a basic principle consistently followed by TCM specialists. Whether TCM is safe remains controversial. Only few studies have reported some mild side effects of TCM, indicating that it is a relatively safe treatment option . TreatmeTreating AIDS using TCM is decided not only according to the needs of the patient but also according to the availability and side effects of antiviral drugs. In some regions of China, individuals can easily receive TCM treatment by consulting with Chinese medicine practitioners and via other approaches. First, the national TCM project is the main mode for receiving TCM treatment. The State Administration of Traditional Chinese Medicine of China has carried out a trial program, with different fixed preparations and additional TCM treatments supplied to participants in five different provinces of China. Second, the free clinic model is very convenient. Patients usually do not have to inform Chinese medicine practitioners of their HIV status at an ordinary TCM clinic when they see a doctor, and the CMP usually makes a diagnosis and treats according to the patient's clinical information using a TCM approach. Third, the self-management model of TCM is popular. Individuals can easily receive TCM treatment or health care whenever they wish. Using over-the-counter herbal medicines and preparations for tea and medicinal meals as well as non-drug therapy  are popular modes of health management in TCM.TCM has an important role in AIDS treatment, offering unique humanistic care and holistic adjustment of the body system. The use of TCM has become more common among people living with HIV, and increasingly more patients with AIDS are benefiting from TCM. Some research has shown encouraging results, and numerous evidence-based high-quality clinical studies have confirmed the effectiveness and safety of a TCM approach in managing HIV, alone or in combination with WM. Previous studies have mainly focused on younger patients with AIDS, with few studies among older patients. Therefore, active promotion and further high-level evidence in support of TCM treatment for HIV/AIDS are needed.


The present study experimentally and numerically investigated the impact behavior of composite reinforced concrete (RC) beams with the pultruded I-GFRP and I-steel beams. Eight specimens of two groups were cast in different configurations. The first group consisted of four specimens and was tested under static load to provide reference results for the second group. The four specimens in the second group were tested first under impact loading and then static loading to determine the residual static strengths of the impacted specimens. The test variables considered the type of encased I-section (steel and GFRP), presence of shear connectors, and drop height during impact tests. A mass of 42.5 kg was dropped on the top surface at the mid-span of the tested beams from five different heights: 250, 500, 1000, 1500, and 1900 mm. Moreover, nonlinear Finite Element (FE) models were developed and validated using the experimental data. Static loading was defined as a displacement-controlled loading and the impact loading was modeled as dynamic explicit analysis with different drop velocities. The validated models were used to conduct a parametric study to investigate the effect of the concrete compressive strength on the performance of the composite beams under static and impact loadings. For the composite specimen with steel I-sction, the maximum impact force was 190% greater than the reference specimen NR-I at a drop height of 1900 mm, whereas the maximum impact forces for the specimens composite specimens with GFRP I-sction without and with shear connectors were 19% and 77%, respectively, more significant than the reference beam at the same drop height. The high stiffness for the steel I-beams relative to the GFRP I-beam was the reason for this difference in behavior. The concrete compressive strength was more effective in improving the impact behavior of the composite specimens relative to those without GFRP I-beams. Hybrid construction using combined materials is essential for achieving performance targets such as durability, sustainability, seismic resistance, and speedy construction. Because composite materials are simple, buildable, and cost-competitive, they give a consistent performance and are the best choice. Pultruded Glass Fiber Reinforced polymer (GFRP) I-beams are a new type of Fiber Reinforced Polymer (FRP) composite that are developed using pultrusion. These new beams are recommended for bridge construction due to their superior corrosion resistance and higher compressive and flexural strength ,2. The bPrevious studies explored different types of composite beams under the effect of impact loading. Tabiei et al.  investigNonlinear Finite Element (FE) models were developed and calibrated to analyze the impact behavior of composite RC beams with pultruded GFRP materials ,6,7,8. AComposite RC beams with pultruded GFRP beams are widely used for bridge construction due to their superior corrosion resistance and higher compressive and flexural strength ,2. HowevEight specimens of two groups were cast in different configurations, as listed in The overall length of the specimens was 3000 mm with a clear span of 2750 mm, as shown in Concrete specimens were prepared and tested to determine the compressive strength, splitting tensile strength, modulus of rupture, and modulus of elasticity of concrete. Three standard cubes of dimensions 150 mm × 150 mm × 150 mm and three standard cylinders of dimensions 150 mm × 300 mm were tested by a universal compression machine to determine the compressive strength of concrete. The splitting tensile strength of concrete was determined according to ASTM C496-96  by usingThe mechanical properties of steel bars and steel plates, such as yield tensile strength and ultimate tensile strength, were evaluated according to ASTM A370-19 . Three sThe mechanical properties of the GFRP I-section, such as compressive and tensile strength and elastic modulus, were examined. The compression tests were conducted following ASTM D695 . FifteenBeam specimens of group one were tested as simply-supported beams under a monotonic concentrated load at the mid-span up to failure using a 1000 kN capacity hydraulic universal testing machine, as shown in 2). Just before the hammer struck the beam, the velocity and kinetic energy were calculated by Equations (1) and (2), respectively.The hammer has the potential energy When the hammer hit the beam, the hammer’s momentum was rapidly transferred to the beam. As a response, the hammer’s momentum was reduced. This resulted in a reduction in the hammer’s kinetic energy and an increase in the beam’s energy. This sudden energy transfer between the hammer and the beam led to a rapid build-up of stress in the beam. The momentum . The longitudinal and transverse steel reinforcement were modeled using three-dimensional truss elements (T3D2) with a linear kinematic hardening model. The pultruded GFRP I-profile was simulated using an 8-node doubly curved thick shell element with reduced integration (S8R). The impactor in the impact loading case was modeled by a discrete rigid shell that rotated 360° to create the cylindrical shape.bo⁄fco), coefficient (K), and viscosity parameters (μ). These parameters were established from previous analyses and were implemented in this study.The concrete damage plasticity (CDP) model was employed to model the behavior of the tested specimens to consider the concrete cracking and crushing. The response of the CDP model under uniaxial tensile loading was characterized by a linear–elastic stress-strain relationship up to the value of the failure stress. The stress-strain curves were used to describe the compressive and tensile behaviors, as shown in y, ultimate stress fu, and plastic strains, as illustrated in The steel I-beam, longitudinal steel rebars, and stirrups were modeled as a non-linear relationship adopted by , as showThe numerical model employed the general static processes by using the displacement-controlled loading. The suggested model was validated using experimental data from the tested specimens NR, CG, and CGC. The assembled FE model for the composite specimen CGC is shown in The numerical model employed the dynamic explicit step to apply the impact loading. The suggested model was validated using the experimental data of specimens NR-I, CG-I, and CGC-I. FE models were developed to represent five series impacts by five identical impactors that hit the model at different drop velocities. The contact between the hammer and top surface of the beam was employed as surface-to-surface contact, which used a friction coefficient of 0.35 with tangential behavior. Comparisons between the FE and experimental results of the impact force and mid-span deflection time histories for specimen NR-I, as an example, are shown in A parametric study was carried out to investigate the influence of the concrete compressive strength on the ultimate strength of the composite specimens with the GFRP I-beams under the effect of static and impact loadings.The influence of different concrete compressive strengths of 25 MPa, 35 MPa, and 45 MPa on the static flexural behavior of the analyzed specimens was investigated. The concrete compressive strengths 25 MPa, 35 MPa, and 45 MPa were examined to determine their influences on the load capacity and corresponding mid-span deflection under the effect of impact loads. Variation percentages in the impact load and mid-span deflection were calculated based on the results of the compressive strength 25 MPa as listed in The embedded GFRP I-beam in the RC specimens with and without shear connectors increased the load-bearing capacity by 51% and 65%, respectively, relative to the reference specimen NR. However, this improvement was 100% in the case of using steel I-beam.Increasing the composite interaction between the GFRP I-beam and concrete by means of shear connectors improved the ultimate capacity by 9.5% relative to the composite specimen without shear connectors.For the composite specimen CS-I, the maximum impact force was 190% greater than the reference specimen NR-I at a drop height of 1900 mm whereas the maximum impact forces for specimens CG-I and CGC-I were 19% and 77%, respectively, more significant than the reference beam at the same drop height. The high stiffness for the steel I-beams relative to the GFRP I-beams was the reason for this difference in behavior, where the impact force is proportional to the structural stiffness.The composite specimens CG-I and CGC-I showed reductions in the maximum mid-span deflections relative to the reference specimen NR-I. For the 1900 mm drop height, reductions of 9.4% and 21% were obtained, respectively, whereas the composite specimen CS-I showed a 17% increase in the maximum mid-span deflection due to the high impact force caused by the section’s high stiffness.As the compressive strength increased, the static ultimate load capacity increased and the corresponding deflection decreased. For the composite specimens with GFRP I-beam, the ultimate load capacity was improved by 23% and 40% for compressive strengths 35 MPa and 45 MPa, respectively. However, these improvements were 13% and 22% for the reference specimen NR, respectively. On the other hand, the corresponding deflections were reduced by 60% for the specimen CG. However, these reductions were 23% and 48% for the concrete strength 35 MPa and 45 MPa, respectively, for the specimen CGC. These results confirmed the effectiveness of concrete strength to improve the stiffness of the composite specimens was less pronounced when the shear connectors were used.The impact characteristics of the RC composite specimens with GFRP I-beam were influenced effectively by increasing the compressive strength of concrete. The average increase in the maximum impact load was between 18% and 25% for all specimens when the compressive strength was 35 MPa. However, it was between 30% and 40% when the compressive strength was 45 MPa. Therefore, the concrete compressive strength was more effective in improving the impact behavior of the composite specimens relative to those without GFRP I-beams.The present study experimentally and numerically investigated the impact behavior of composite RC beams with the pultruded I-GFRP and I-steel beams. Eight specimens of two groups were cast in different configurations. The first group consisted of four specimens and was tested under static load to provide reference results for the second group. The four specimens in the second group were tested first under impact loading and then static loading to determine the residual static strengths of the impacted specimens. Moreover, nonlinear FE models were developed and validated using the experimental data. The validated models were used to conduct a parametric study to investigate the effect of the concrete compressive strength on the performance of the composite beams under static and impact loadings. The main conclusions are summarized as follows:It is worth noting that these impact tests were performed to initially unloaded specimens while in reality, the composite RC beams would be loaded and then an impact load would be applied. Therefore, pre-loading before administering impact loads will be the next research focus.


The reinforced concrete-filled steel tube (RCFST) column solves several of the problems of the concrete-filled steel tube (CFST) column in practical engineering applications. Moreover, RCFST has a simple joint structure, high bearing capacity, good ductility, and superior fire resistance. From a structural safety perspective, designers prioritize the creep performance of CFST members in structural design. Therefore, the creep behavior of RCFST columns should be thoroughly investigated in practical engineering design. To study the influence of the creep behavior of RCFST columns under axial compression, this work analyzed the mechanical behavior of composite columns based on their mechanical characteristics under axial compression and established a creep formula suitable for RCFST columns under axial compression. A creep analysis program was also developed to obtain the creep strain–time curve, and its correctness was verified by existing tests. On this basis, the effects of the main design parameters, such as the stress level, steel ratio, and reinforcement ratio, on the creep behavior were determined and analyzed. The creep of the tested composite columns increased rapidly in the early stages (28 days) of load action; the growth rate was relatively low after 28 days and tended to stabilize after approximately six months. The stress level had the greatest influence on the creep of RCFST columns under axial compression, followed by the steel ratio. The influence of the reinforcement ratio on the creep behavior was less. The results of this study can provide a reference for engineering practice. The reinforced concrete-filled steel tube (RCFST) column is formed by placing longitudinal steel bars in a steel tube and pouring concrete into the tube. The steel tubes of RCFST columns do not bear longitudinal load directly; thus, they can play a constraining role on the core reinforced concrete in the early stages of member loading. However, the steel tubes of CFST members typically bear longitudinal load in a normal operation. The outer steel tube provides a limited restraint to the core concrete when it reaches the yield. Consequently, the axial compressive bearing capacity and seismic performance of RCFST columns with steel tube constraints are better than those of CFST columns with the same parameters –3.RCFST column constraints simplify the joints and reduce the design and construction difficulties. The fire failure of an external steel tube under longitudinal load is often considered in CFST columns, and the reinforcement in RCFST columns improves their fire resistance. Thus, any fire damage to the steel tube would have little influence on the fire resistance limit of the columns –6. RCFSTDuring the long-term use of RCFST columns, the concrete in the steel tube undergoes compression creep and the internal force is redistributed between the steel tubes, steel bars, and concrete. The continuous change in the concrete creep affects the strain state of the columns. The creep behavior of concrete is more complicated because the 3D stress state of the concrete is constrained by the external steel tubes. Therefore, the ability to accurately predict the creep behaviors is significant in the application of RCFST columns.Many studies have been conducted on the creep behavior of CFST columns. Furlong  was the Terry et al.  studied In China, Zhong et al.  were theFurthermore, to study the creep of concrete-filled circular steel tubular members under axial compression, Wang et al. –20 used In this study, based on the mechanical characteristics of RCFST composite columns, their mechanical performance was analyzed, and a calculation formula for the axial compression creep was established. Further, a creep analysis program was developed to calculate and analyze the influence of the main design parameters—such as the stress level, steel ratio, and reinforcement ratio, on the creep performance—to provide a reference for engineering practice.For common RCFST members, the maximum load in the elastic stage is approximately in the range of 70%–80% of the ultimate load. For the most practical projects, the service load is typically in the range of 50%–60% of the ultimate load . Therefoσr and σθ are the radial and circumferential stresses at any point on the cylinder wall, respectively. p1 and p2 are the internal and external pressures of the cylinder. r1 and r2 are the internal and external radii of the cylinder. r is the radius at any point on the cylinder.Lamé’s theory of elasticity  is widelr2 = rs+ts , p2 = 0, ts/Rs<<1, Rs, rs, and ρ are the outer radius, inner radius, and the radius at any point on the steel tube, respectively).The stress of the steel tube-reinforced concrete section was calculated using Lamé’s formula. σr = 0. Here, ps is the restraint stress of the steel tube. The circumferential and radial stresses of the steel tube are as follows: The radial and circumferential stresses of the steel tube can be expressed as follows:Es and μs are the elastic modulus and Poisson’s ratio of the steel tube, respectively.The strain of the steel tube can be expressed as follows:σc2 = σc3 = psThe concrete is in the state of equal lateral stress: σc1, Ec, and μc are the longitudinal stress, elastic modulus, and Poisson’s ratio of concrete, respectively.According to Hooke’s law, the strain of the concrete can be obtained as follows:μc varies with the creep:αs = As/Ac. As and Ac are the sectional areas of the steel tube and concrete, respectively. F = 0.16+0.53α, and G = 1.96−1.94α. ϕ is the hoop coefficient. φ = αfs/fck. [σ0] is the ultimate stress of concrete.According to the formula provided by Mao and Wang , μc variεs3 = εc2.The circumferential strain of the steel tube is equal to the radial strain of the concrete, After sorting the above formulas, the following results are obtained.Order ps = nσc1where Nr and Nc are the axial forces of the longitudinal reinforcement and concrete, respectively. Ar and Ac are the sectional areas of the longitudinal reinforcement and concrete, respectively.The initial stress of the concrete is the force on the concrete when there is no creep in the reinforced concrete-filled steel tube columns. The steel tube exhibits a hoop restraint effect on the concrete; therefore, this effect should be considered in the initial stress solution.εr1 = εc1.The longitudinal strain of the longitudinal reinforcement is equal to the longitudinal strain of concrete: The results are as follows:Concrete and steel tubes have different Poisson’s ratios. Under axial compression loading, the steel bar, concrete, and steel tube are in stress simultaneously. The steel tube exhibits a hoop restraint effect on concrete. Under the long-term action of the external load, the concrete will be in the unloading state owing to creep. The stress on the section of the composite columns is redistributed, and transferred to the longitudinal reinforcement and steel tube, thereby increasing the stress of the longitudinal reinforcement and steel tube.ci is the net creep of concrete under multiaxial stress, σu is the stress on concrete under uniaxial stress, and μcp,i is the effective Poisson’s ratio in the i direction and is related to the state of action of σi, σj, and σk. σi, σj, and σk are the stresses in the i, j, and k directions respectively. c is the creep of concrete under uniaxial stress. Because the concrete in the steel tube-reinforced concrete column is in the unloading state during creep, the creep theory for concrete creep is used to analyze the creep of the steel tube-reinforced concrete column.t0 is the loading age, and t is the time.Based on the creep characteristics of reinforced CFST columns, the creep theory of concrete under a multiaxial stress state proposed by Neville  was adopHan and Wang  derived σc2 = σc3 = ps, ps = nσc1.The concrete is in the state of equal lateral stress: μcp,1 is as follows:Therefore, the longitudinal effective Poisson’s ratio c1 can be expressed as The longitudinal creep σc1 is equal to that of concrete under uniaxial stress σu, i.e., σu = σc1.The longitudinal stress of concrete c1 can be reduced toThe longitudinal creep When creep occurs in the reinforced CFST columns, the stress on the section is redistributed; however, this redistribution does not affect the external load. Therefore,The creep of concrete can be expressed as c2 is the radial creep of concrete. Δps is the increase in ps due to the creep.The influence of creep on the transverse deformation of RCFST columns can be expressed as follows:ps is very small, it can be ignored; thus, the lateral creep of concrete can be expressed as μcp,2 is the Poisson’s ratio of the lateral creep of concrete.Because the increment in σu = ps, thenOrder Based on the compatibility condition of the radial deformation, the increment in the steel tube binding force was obtained.From the equal longitudinal deformation of the steel bar and concrete, we have The stress increment of the concrete under creep is as follows:Thus, the creep formula for the composite columns under axial compression is derived:5 MPa, and 0.248, respectively. Six HRB400 bars 18 mm in diameter were used as the longitudinal reinforcement, with a reinforcement ratio of 4%. The concrete grade was C50.Based on the above theory, a calculation and analysis program for the creep of RCFST columns under axial compression was developed. To verify its correctness, the calculated creep strain–time curves were compared with those of test specimens t14-50, t28-50, and t56-50 reported in , as show4 MPa, and the applied load is 653 kN. 4 MPa, and the applied load is 725 kN. 4 MPa, and the applied load is 784 kN. By comparing with the results reported in , the cal5 MPa, 345 MPa, 0.28, C50, and 3.45×104 MPa, respectively. Six HRB400 bars 10 mm in diameter were used as the longitudinal reinforcement; the elastic modulus of the steel bar was 1.97×105 MPa, the initial stress level of concrete nc was 0.35. With the other parameters immutable, the effects of the stress level, wall thickness (content ratio), and reinforcement ratio on the creep behavior were studied.Based on the calculation results, the creep of the RCFST members under axial compression was analyzed. The basic parameters used in the calculation were as follows: the outer diameter, wall thickness, elastic modulus, yield strength, Poisson’s ratio, concrete grade, and elastic modulus of the steel tube were 165 mm, 1.5 mm, 1.88×10The creep strain–time curves of RCFST columns under axial compression with stress levels of 0.45, 0.35, 0.25, and 0.15 were calculated and analyzed using the developed creep analysis program, as shown in Based on the creep analysis program, the creep strain–time curves for steel tube wall thicknesses of 6, 4.5, 3, and 1.5 mm—i.e., steel ratios of 14.02%, 10.61%, 7.14%, and 3.60%—were calculated and analyzed, as shown in Based on the creep analysis program, the creep strain–time curves for reinforcement ratios of 1.47%, 2.20%, 2.93%, and 3.67% were calculated and analyzed, as shown in The above analysis shows that the creep strain increases with the increase in the stress level. When the stress level ranges from 0.15 to 0.45, the creep strain increases by 191.2%, whereas it decreases with the increase in the steel content. When the wall thickness ranges from 1.5 to 6 mm and the steel content ranges from 3.60% to 14.02%, the creep strain is reduced by 28.9%. In comparison, it decreases with the increase in the reinforcement ratio. When the reinforcement ratio ranges from 1.47% to 3.67%, the creep strain is reduced by 18.85%. The stress level had a significant influence on the creep of the composite columns under axial compression, followed by the steel ratio. The influence of the reinforcement ratio on the creep was relatively small.In this study, based on the mechanical characteristics of reinforced concrete-filled steel tubular columns under axial compression, a creep calculation formula for composite columns under axial compression was established on the basis of the multiaxial stress and flow theory of concrete.With the established formula, a creep analysis program was developed, and the creep strain–time curve was derived and analyzed. The results showed that the creep of the composite columns increases rapidly in the initial stages of loading (within 28 days). The growth rate was relatively low after 28 days and tended to stabilize after approximately six months. The creep program was verified by existing tests.On this basis, the influence of the main design parameters on the axial compression creep of the composite columns was determined and analyzed. The stress level had a significant influence on the creep of composite columns under axial compression, followed by the thickness of the steel tube wall (steel ratio). The influence of reinforcement ratio had a relatively small influence on the creep.This study only analyzed the creep characteristics of RCFST columns in the elastic working range; the creep problems in the elastoplastic and plastic stages need to be further studied.S1 Data(XLS)Click here for additional data file.


The data from both models were cleaned using correlated variables, and the initial variables were compared with ti. The main result achieved was the verification of the feasibility of using correlations of variables to clean unnecessary data in order to calculate ti. Additionally, electrical resistivity was identified as one of the main durability indexes for in-service concrete structures exposed to marine environments. This is important because electrical resistivity is a non-destructive and reliable test that can be measured both in the laboratory and in the field very easily.This paper presents a comparison of six index properties collected during durability inspections of five Mexican seaports. Typical durability indicators such as compressive strength, saturated electrical resistivity, ultrasonic pulse velocity, percent total void content, capillary porosity, and chloride concentration profiles were analyzed to obtain empirical correlations with the non-steady-state chloride diffusion coefficient. These indices were compared to determine correlation coefficients that are the most important for obtaining better corrosion initiation forecasting. Two models of corrosion initiation time (t The most widely used material in construction is concrete. The durability of concrete has gained great relevance in the last decades. Hence, a large number of studies have explored the subject, including the analysis of reinforcing steel corrosion , alkali-aggregate reactivity, sulfate attack, freezing and thawing .Deterioration is present in all concrete structures regardless of the quality of their design and construction. This phenomenon has become evident and worrisome for many modern structures (in marine environments) that present strong and premature deterioration, along with low durability . This coThe main mechanism of damage to a reinforced concrete (RC) structure is corrosion, especially in marine environments, and this process impairs structural safety by decreasing the load capacity of structures ,5,6. In Depending on environmental exposure conditions and moisture content of concrete, aggressive agents such as chlorides realize infiltration by using different combinations of transport mechanisms. In addition to chlorides, water and oxygen (necessary for corrosion) penetrate concrete through pores, paste/aggregate interface and microcracks present in the concrete matrix .Several durability tests have been performed to determine the level of attack and aggressiveness of many types of aggressive environments. Permeability, i.e., the resistance of concrete to fluid penetration, is the main property that should be minimized to ensure adequate protection against any type of exposure ,16.Permeability is the ability of a material to allow or limit the passage of fluids and gases through it under a pressure gradient and is affected by different parameters . SeveralMost deterioration processes consist of two stages. In the first stage, the deterioration promoting agents  need to be transported through the capillary pores of concrete toward the reaction zones  before actual chemical or physical deterioration reactions .One of the main causes of corrosion of RC is the presence of chlorides in reinforcing steel. Chlorides affect the service life of structures exposed to this type of aggressive environment. Depending on the particular environmental conditions at each construction site, a single mechanism or several diffusion mechanisms acting in combination may transport chlorides inside concrete ,32. In tPenetrated chlorides generally exist in two main forms within concrete: bound chlorides and free chlorides. Of these two forms, only free chlorides are directly detrimental to the risk of reinforcement corrosion, but some bound chlorides may be released at later stages and added to the free chlorides ,42,43,44Mexico has 16 federal international ports, and all of them have a strong impact on the country’s economy and require strong investments for their maintenance and expansion. In 2006, the impact of the port maritime subsector on the national gross domestic product amounted to 1.6 billion USD and generated around 157,000 jobs . The maiSeveral researchers have investigated the durability of concrete, and the results have broadened our understanding of underlying phenomena and have resulted in improved specifications and design for durability. However, our understanding and application of such results to real structures are still limited. Recently, the Nanocem Consortium  highlighted the need to advance the understanding of key deterioration mechanisms, especially in applications under real construction situations [The present study is focused on obtaining the correlation coefficients between the most important durability indices  and non-steady-state chloride diffusion estimates  based on data gathered from several marine natural exposure sites. The correlation coefficients between these durability indices were analyzed to determine the impact of all these indices in order to validate their individual importance on corrosion initiation predictions in a marine environment.This study analyzes data collected during the durability inspection of 47 reinforced concrete piers  located on five Mexican seaports. These inspections were carried out at the request of Mexico’s Secretariat of Communications and Transportation (SCT), choosing these ports based on their commercial, historical and strategic importance. One seaport is located in the Gulf of Mexico while the other four are located on the Pacific coast. The naming of ports is related to their north to south positions; thus, port 1 is found in the farthest north position, and port 5 is found in the farthest south position . All thenss), effective porosity (EP), total porosity (TP), electrical resistivity (ER) and ultrasonic pulse velocity (UPV). Comparisons are made between the different characteristics measured and analyzed during field inspections to determine which of them are correlated.The data obtained during our inspections consist of the levels of damage of the different structural elements and the details of the physical, mechanical, chemical and electrochemical tests on such elements. With these data, we aim to provide a diagnosis of the status of each port enclosure and to assess the urgency of the need for repair based on the results obtained from the characterization of concrete and the level and incidence of observed damage. In this study, the following characteristics of concrete that make up the different berthing structures of the port enclosures are considered : comprePreventive maintenance can be performed before deterioration spreads if adequate information, modeling and planning are available. Such process maintains the serviceability of buildings and even extends their service life . At presThe most common method to model concrete deterioration caused by chlorides is to adopt a three-phase process, which involves chloride ingress, crack initiation and crack propagation ,58 Figu. The firi)” in the reported Resistivity-based model [i) in addition to the propagation period of corrosion (tp). In the current study, it is used only to determine the initiation period, and it is calculated with two different models.This first phase is called the “initiation time  and diffusion coefficient (Dnss: mm2/s), the chloride concentration (Cx: mass percentage of binders) at a certain depth (x: mm), an estimated initial chloride content (Ci: mass percentage of binders) and a certain time (ti: s) can be expressed as follows:s and Ci, adopts a non-steady-state diffusion coefficient in the model, the procedure of which is described in standard NMX-C-546-ONNCCE-2018.Chloride ingress can be described by Fick’s second law . Under t-variant , this sti), this study uses Equation (2) and takes the chloride threshold value (Cx) as indicated in the NMX-C-523-ONCCE-2016 standard.In order to estimate initiation time , kcl is a constant that depends on the outer concentration of chlorides, ρes is the resistivity of saturated concrete  and σ is the conductivity (inverse of resistivity). In water-saturated concrete, resistivity indicates the level of porosity (pore connectivity) and is, thus, directly related to the transportation phenomena of aggressive agents .The method is based on the relationship between diffusivity and resistance to the movement of electrical loads (ions) established about 100 years ago by A. Einstein. It has been modified by other authors in order to apply the principle to porous media. This relationship is expressed as follows :De = kclHowever, this basic equation is insufficient for modelling the case of concrete life as chlorides are combined with the cement phases and the properties of concrete evolve. Therefore, the following concepts are introduced.Cl) is introduced to take into account the amount of chlorides that do not advance because they combine with the cement phases. For this purpose, Einstein’s relation has been modified by establishing an apparent resistivity as follows [ap: Diffusion coefficient in non-steady state referred to cm3 of the sample in cm2/s obtained according to UNE 83,986 standard;DCl: Environmental exposure factor that takes into account the degree of environmental aggressiveness and chloride content;Fap: Apparent resistivity. It is the value of the effective resistivity multiplied by the reaction factor (rcl).ρDelay factor  represents the resistivity evolution with time. This factor may not be used if accelerated curing is performed or if the structure is more than one year old.x: Minimum concrete cover thickness, cm;ef,0: Effective resistivity at 28 days of curing, Ω cm;ρq: Age factor, (-);0: First age of 28 days in which the value of resistivity is taken;tn: Latest age of analysis. with ages t0 and tn introduced into the same units;tCl: Environmental exposure factor for the initiation period, cm3·Ω/year.FThe new equation (Equation (4)) is, thus, written as follows ,63,66:tie) are not recommended without the additional factors of age or delay (Equation (6)). In this manner, service life can be calculated from the value of the resistivity of concrete and environmental and cement type factors. [i and tp estimates, the present investigation uses only ti.Since the structure’s age is greater than 1 year, then applying any age factor and considering the value of the measured resistivity ) are displayed. The analysis focuses on the global behavior of the data of the five ports as a whole to determine the behavior of concrete with different characteristics and elaborated under different conditions and to determine which index properties of the concrete are the most important from the point of view of durability. For all comparisons, an exponential type trend was proposed to analyze their exponent values and to estimate their degree of correlation. It is important to mention that the data presented are restricted only to concrete cores extractions permitted by the Port Authorities on each of the evaluated reinforced concrete piers. This is due to the commercial, historical and strategic importance of this infrastructure.As described in In the empirical correlation of electrical resistivity (ER) with effective porosity (EP), nss, which is necessary for the application of Fick’s life model, in addition to being determined by a high-uncertainty method (between 20% and 28%) [nss in maritime infrastructure works; similar to ER, Dnss is affected by the type of cement [In and 28%) . This cof cement ,77 and mf cement . This cof cement ,71,78,79In 2 = 0.85).In this comparison , both vaThe comparison between EP and mechanical strength of concrete (fc)  is usefui) was determined for each of the 47 structural elements inspected in the five different ports. As shown in − and the diffusivity of concrete [s .concrete ,65. The − and saturation levels were considerably low, thereby increasing diffusion time. − concentration gradient is low, especially when the surface concentration is very close to the limiting concentration, which is necessary with respect to corrosion initiation. In these cases, the concentration gradient can be equal to or slightly lower than the limiting concentration, which drastically raises the value of ti. This is in accordance with Poulsen and Mejlbro [i.As the Resistivity-based model includes factors that depend on the type of environment to which the studied elements are exposed, both models should be compared by considering which area of each of the elements was analyzed . The correlation is presented in  Mejlbro  .In order to determine whether both models were sensitive to any of the previously analyzed variables, we compared the initiation times of both models and variables. i with EP (mentioned above). EP is a defining parameter for determining the durability of concrete. i . The results of these data are necessary for the estimation of concrete service life and the identification of preventive measures against environmental degradation. Thus, we identified the useful variables or index properties as saturated ER, percent total void content, capillary (or effective) porosity, non-steady state chloride diffusion coefficient, ultrasonic pulse velocity and compressive strength of concrete. By focusing on these concrete properties, an adequate design of concrete structures exposed to corrosive environments can be achieved.2 in the comparison between the ti models analyzed (2 from 0.28 to 0.70 and 0.72 was achieved by, respectively, using correction and elimination of the general trend with the correction and deletion of outlier data; for the air zone, an improvement in R2 from 0.39 to 0.69 and 0.73 was respectively, achieved while for the tidal zone, an improvement in R2 from 0.11 to 0.70 and 0.73 was, respectively, realized.During inspections for the durability of concrete structures, we can determine which data can be considered atypical and be properly treated within the life prediction models by using the correlations of variables for the index properties. analyzed . An incrRegarding the comparison of these variables with the initial time of corrosion, adequate correlations were obtained only for EP, chloride diffusion coefficient and ER. Although all the comparisons show great variability even with the handling of outlier data, the variations may be due to the quality control of each construction and design method, with cement’s quantity and quality varying depending on the design method for concrete mixtures. Another alternative may be the type and quality of aggregates used in each port, as several authors have reported that the characteristics of aggregates can alter the physical properties of concrete ,42,75,82ER is verified as a variable with strong correlations because it relates to four of the five variables analyzed at the level of the index properties of concrete and at the level of calculation of corrosion initiation time. Thus, we conclude that the most decisive property for good concrete performance is ER, which can be used in design and construction control and the inspection stage.


Very good partial response rates (VGPR) or better at the end of induction were 41% in EMN02, 45% in VRD arm, and 47% in ASCT arm of IFM2009 and highest in CASSIOPEIA at 56% in the VTD control group. After ASCT, the VGPR rates were similar at 64% in EMN02, 70% in IFM2009, and 67.3% in CASSIOPEIA (VTD control group).7Indeed, much of the most recent evidence that informs current standard practice stems from the large EMN02, IFM2009, and CASSIOPEIA randomized studies in MM patients with de novo disease eligible for ASCT.7However, differences in eligibility and patient characteristics highlight the problematic nature of cross-trial comparisons. For example, a creatinine clearance (CrCl) of >50 mL/min was required for IFM2009 enrolment, >40 mL/min for CASSIOPEIA but just >15 mL/min for EMN02. In addition, the proportion of cases with high-risk cytogenetic features was 25% in EMN02, 19.4% in IFM2009, and 16% in CASSIOPEIA with differences in the percentage of plasma cells required to exhibit a particular genetic aberration before inclusion in the high-risk group also varied between trials. For example, in the CASSIOPEIA study, >50% of plasma cells examined were required to display deletion 17p compared with >20% in EMN02. Important differences in maintenance therapy protocols are also evident. In IFM2009, lenalidomide 10 mg once daily (OD) maintenance stopped at 1 year but a dose increase to 15 mg OD was permitted, as tolerated. In comparison, lenalidomide 10 mg OD was continued till progression as tolerated with a median duration of 34.3 months maintenance therapy reported in the ASCT arm of EMN02. In addition, while there were 2 cycles of VRD consolidation in the IFM2009 study for all patients randomized to ASCT, 210 of 702 ASCT patients in EMN02 received a double-ASCT following which there was a further randomization to VRD consolidation or no consolidation. Despite the differences in induction regimens, the number of induction cycles received and subsequent trial protocols, median progression-free survival (PFS) rates in the ASCT arms in both EMN02 and IFM2009 are similar at 56.7 months and 50 months, respectively, while the CASSIOPEIA data are not mature enough to report at this point. Overall survival data are also very similar; 75.1% at 5 years in the EMN02 and 81% at 4 years in the IFM2009 studies, respectively.8 These results are underscored by early clinical experience of daratumumab in combination with VCD in MM, where bortezomib was dosed weekly at 1.6 mg/m2. For example, a phase Ib study of Dara-VCD, delivered as induction therapy in MM patients eligible for ASCT led to an impressive post-induction overall response rate and VGPR rate of 94% and 67%, respectively.9 This combination is currently being compared with VTD in the EMN18 randomized study in transplant-eligible MM and additional trials have explored or are investigating daratumumab and other anti-CD38 MAbs (such as isatuximab) in combination with VRD, VTD, and KRD .These outcomes deserve attention as the focus moves to monoclonal antibody (Mab)-based induction combinations. Preclinical studies have highlighted the potential role for cyclophosphamide in enhancing the anti-MM effect of daratumumab via its effects on the MM microenvironment, specifically recruiting macrophages and augmenting antibody-dependent cellular phagocytosis.In the meantime and outside of clinical trials, it seems that VRD is almost certainly the regimen to be most widely employed in treating transplant-eligible MM where VRD is available. However, bearing in mind the outcomes at the end of induction, post-ASCT, and PFS data in EMN02 and IFM2009, we suggest that VCD continues to represent an effective induction regimen that is very well tolerated with predictable and manageable effects on blood count parameters, being both convenient to deliver, well tolerated, and relatively inexpensive.The authors have no conflicts of interest to disclose.