Antibiotic misuse is a serious public health problem worldwide. National health authorities release clinical practice guidelines (CPGs) to guide general practitioners (GPs) in their choice of antibiotics. However, despite the large-scale dissemination of CPGs, GPs continue to prescribe antibiotics that are not recommended as first-line treatments. This nonadherence to recommendations may be due to GPs misunderstanding the CPGs. A web interface displaying antibiotic prescription recommendations and their justifications could help to improve the comprehensibility and readability of CPGs, thereby increasing the adoption of recommendations regarding antibiotic treatment.This study aims to design and evaluate a web interface for antibiotic prescription displaying both the recommended antibiotics and their justifications in the form of antibiotic properties.A web interface was designed according to the same principles as e-commerce interfaces and was assessed by 117 GPs. These GPs were asked to answer 17 questions relating to the usefulness, user-friendliness, and comprehensibility and readability of the interface, and their satisfaction with it. Responses were recorded on a 4-point Likert scale (ranging from “absolutely disagree” to “absolutely agree”). At the end of the evaluation, the GPs were allowed to provide optional, additional free comments.The antibiotic prescription web interface consists of three main sections: a clinical summary section, a filter section, and a recommended antibiotics section. The majority of GPs appreciated the clinical summary  and filter  sections, whereas 48.7% (57/117) of them reported difficulty reading some of the icons in the recommended antibiotics section. Overall, 82.9% (97/117) of GPs found the display of drug properties useful, and 65.8% (77/117) reported that the web interface improved their understanding of CPG recommendations.The web interface displaying antibiotic recommendations and their properties can help doctors understand the rationale underlying CPG recommendations regarding antibiotic treatment, but further improvements are required before its implementation into a clinical decision support system. Antibiotic misuse is a serious public health problem worldwide ,2. It exNational health authorities release clinical practice guidelines (CPGs) to guide GPs in their choice of antibiotics. CPGs contain evidence-based recommendations from a group of experts based on scientific publications. However, despite the large-scale diffusion of CPGs, GPs continue to prescribe antibiotics that are not recommended for first-line treatment  ,8. This lost or hidden in large amounts of text [An antibiotic prescription web interface displaying not only recommendations of antibiotics but also their justifications could help improve the GPs’ comprehensibility and readability of CPGs, thereby increasing the adoption of recommendations regarding antibiotic treatment. The justifications for antibiotic recommendations can be found within CPG documents, but they are often  of text ,13. A qu of text ,13 for a of text ,15. For It is not easy to display the recommended antibiotics and their properties in a readily usable interface ,17. In tIn this study, we aim to (1) design a web interface for antibiotic prescription presenting recommendations and justifications, in the form of an e-commerce interface displaying antibiotics and their properties, and (2) evaluate the readability and utility of this interface for improving the GPs’ comprehension of CPGs.The elements involved in medical decision-making for antibiotic prescription have been previously identified based on analyses of clinical guidelines  and clinThe best way to organize these elements into the proposed web interface was determined by reviewing and analyzing the content of the following:Health care interfaces: However, no interface with a design similar to that of an e-commerce interface was retrieved.Several well-known e-commerce websites for booking trips or hotels and web-based stores: A panel of websites were reviewed and the interface of four selected e-commerce websites  were analyzed in greater detail. This analysis revealed that these interfaces contained three common main sections: a summary section, a result section, and a filter section . The samsummary section of e-commerce interfaces usually displays the search criteria entered by the user when searching for a product . In our web interface, the elements “patient profiles” and “diseases”  were considered as search criteria.The filter section of e-commerce interfaces usually displays optional parameters that users can click to filter the products selected in response to the initial search criteria . In our web interface, elements relating to certain generic patient conditions that are taken into account during drug prescription  were considered as optional parameters.The result section of e-commerce interfaces usually displays the products recommended after both the search criteria and the optional parameters entered by the user have been taken into account. The characteristics of the products are usually also displayed in the form of icons to facilitate product comparison . In the web interface, the elements “antibiotic” and “antibiotic properties” were considered as products and characteristics, respectively. The antibiotics recommended in CPGs and the properties used by CPG experts to make those recommendations would then be displayed. A previous study identified seven preference properties  that are currently used by experts for making recommendations [Finally, the ndations . AntibioThe utility of the interface for improving GPs’ comprehension of CPGs and their readability was evaluated using a questionnaire tailored to the study.GPs were contacted via emails sent to medical networks in the Île-de-France region (including Paris) and by word of mouth, between March 25 and April 25, 2018. A reminder was sent 15 days after the first contact was made. For inclusion in the study, GPs had to be in training or practicing in primary care. The evaluation was voluntary and anonymous.A web-based evaluation was carried in three steps. First, the participating GPs were asked to answer five sociodemographic questions. Their responses were rendered anonymous. Next, the GPs were asked to use the web interface for the use case “young adult woman with uncomplicated pyelonephritis.” The information displayed on the web interface was derived from a knowledge base describing 11 infectious diseases, 50 antibiotics, and 21 patient profiles, constructed based on French CPGs and clinical expertise (a description of this knowledge base is available in the literature ). Then, The web interface for antibiotic prescription was divided into three main sections, as in most e-commerce websites :clinical summary section, located at the top of the interface, displays a short summary of the clinical situation defined by both the disease and the profile of the patient .The filter section, located at the top left of the interface, can be used to filter the recommended drugs according to patient-specific conditions such as drug allergies, renal failure, pregnancy, and/or breastfeeding.The recommended antibiotics section, located in the center of the interface, displays the recommended drugs, with justifications in the form of drug properties. These preference properties are represented by seven icons. Each icon is shown in a different color, as follows: green, if the recommended antibiotic satisfies the property; red, if the recommended antibiotic does not satisfy the property; and grey, if no information is available. For each recommended drug, the recommendation rank is displayed with a numbered thumbs-up icon, as per the CPGs.The legend located at the bottom of the interface highlights the icons used in the recommended antibiotics section and displays hypertextual links to the original CPGs.The Given the opportunistic nature of the recruitment method used, it is difficult to estimate accurately how many GPs received the invitation email. The number of GPs contacted was estimated to range between 850 and 880.In total, 117 GPs working within distinct GP surgeries accepted the invitation and assessed the web interface. More than half  were female. More than three-fourths  were under 40 years of age and had been in practice for less than 10 years. More than half  were working in private practice .Overall, 82.9% (97/117) of GPs found the display of drug properties useful (95% CI 76-90); 65.8% (77/117) reported that the interface improved their understanding of CPG recommendations (95% CI 57-74), and 59.8% (70/117) considered the interface useful for clinical practice (95% CI 51-69), as shown in Only 54.7% (64/117) of all GPs were satisfied with the global interface (95% CI 46-64), probably because of dissatisfaction with some of the icons. Indeed, the majority of GPs appreciated the clinical summary  and filter  sections, whereas 48.7% (57/117) of them reported difficulties understanding some of the icons .Five of the eight icons were considered sufficiently readable. The icons for recommended rank, ecological adverse effects, and taste were considered easily understandable by more than 80% of GPs; both the precious class and the side effects icons were considered comprehensible by more than 60% of all GPs. By contrast, three icons were not sufficiently readable; icons for antibacterial spectrum and convenient protocol were considered poorly understandable by nearly half the GPs and that for efficacy level was considered poorly understandable by about 84% of GPs .Some GPs said that they found the web interface interesting but that it could take time for them to get familiar with it. They suggested several areas for improvement .For the clinical summary section, GPs suggested displaying more details about the probable causal microbes, patient history, treatment, and signs of gravity. For the filter section, they suggested adding filters for hepatic conditions and galenic forms. Regarding the recommended antibiotics section, the GPs thought it included too much information and needed to be simplified to improve readability. For example, some GPs said that only the most important properties should be displayed and that other properties should be hidden and accessible only on request . Surprisingly, some GPs reported that some properties were not important for the choice of antibiotic, whereas these properties were used by CPG experts in the formulation of recommendations . Other GPs also had doubts about the nonprecious class property because they did not understand what this meant. Conversely, other GPs suggested including additional properties such as drug cost, drug-drug interactions, and contraindications. Some others said that some of the icons were not sufficiently intuitive and required revision. They suggested, for example, replacing the efficacy level by a graduated scale, speedometer, or weapon symbol. Finally, some GPs said that they thought the web interface could be useful for shared decision-making with patients.An interface for antibiotic prescription displaying the recommendations and their justifications was designed and assessed. The web interface was divided into three main sections: a clinical summary section, a filter section, and a recommended antibiotics section enlisting recommended antibiotics and their properties displayed as icons. Overall, 82.9% of participating GPs found the display of drug properties useful, and 65.8% of them reported that the interface helped to improve their understanding of CPG recommendations. Nevertheless, the interface requires further improvement before its implementation in a clinical decision support system (CDSS).Despite 82.9% of the GPs reporting that they found the display of antibiotic properties useful, 48.7% reported difficulty in reading the corresponding icons. Starren et al  describeThe interface displayed the recommendations and the elements required for antibiotic prescription according to the experts writing CPGs. However, the qualitative analysis of the free comments highlighted the following: (1) some properties were considered important by CPG experts but not by GPs ; (2) GPs considered other properties not mentioned in CPGs to be important ; and (3) some properties are currently used by CPGs experts but are not understood by GPs . This gap between real-life practice and writing CPGs should be considered when designing CDSS interfaces. Thus, interfaces should also include the properties used by GPs in real-life practice, even if the evidence for their use is poor or not given in CPGs. For example, with regard to antibiotic prescription, Krishnakumar et al  developeThe participating GPs were recruited via emails sent to medical networks and by word of mouth. This mode of recruitment was chosen because it is faster and cheaper than traditional approaches ,28. HoweGraphs have also been used for drug comparisons, such as Rxplore [Other types of interfaces have been developed for comparing drugs in medical domains. With regard to Dopamine , for ins Rxplore  for the  Rxplore  for chem Rxplore . As antiOther interfaces have been developed for the empiric prescription of antibiotics in primary care, for example, IAAP Smart phone , ARI SmaA web interface for antibiotic prescription presenting drug recommendations and their justifications was designed following the basic framework of an e-commerce interface. The justifications of CPG recommendations were displayed in the form of antibiotic properties, which was considered useful by more than three-fourths of GPs and helpful for understanding CPGs by two-thirds of GPs evaluating the interface. Further improvements are required before the implementation of this interface in a CDSS.


This Research Topic, led by myself and Dr. Yang Deng, together with an editorial team including Dr. Xihong Zhao, Dr. Nguyen Thi Thanh Hanh, and Dr. Viduranga Y. Waisundara, contains a total of 24 excellent manuscripts. As the background of this topic was concerned, a viable but non-culturable (VBNC) state, a unique state in which a number of bacteria respond to adverse circumstances, was first discovered in 1982  and dead (negative), the VBNC state is an exceptionally important and eventually unavoidable topic for microbiologists, but also commonly underestimated and even controversial. Just lately in 2021, an opinion article entitled “Viable but non-culturable cells' are dead,” had been published (Song and Wood, All submitting authors had made an important contribution to this Research Topic. Exceptionally and importantly, as far as our knowledge can reach, this is the first time that researchers have validated the “Control” of the VBNC state, which represents a milestone and breakthrough in the field of VBNC. In a few articles in this Research Topic, relevant studies had been conducted on As concluded, the articles in this Research Topic have made contributions to the relevant field, however, a few opinions have been proposed as controversial in this topic. It should not be surprising as in the VBNC field, more studies had been conducted and previously unclear questions had been better documented. In contrast, seen from the accepted articles in this Research Topic and several opinions articles in the relevant field, the VBNC field has drawn wide attention and great interest from microbiologists. Based on the intrinsic importance of the VBNC state, confusion in the definitions between VBNC and persister cells, as well as the standardization of accurate determination of VBNC cells, we strongly suggest an urgent need for a comprehensive article from microbiologists with expertise in VBNC, to answer essential questions such as “what is the definition of VBNC and what is the difference between VBNC and persister cells” and “how to standardly and accurately determine VBNC cells.”ZX wrote the editorial. All authors approved the manuscript.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.


Bovine mastitis results in substantial problems in terms of animal health, food safety, and profitability of farmers. Methionyl-methionine dipeptide confers protection in the bovine mammary epithelial cells as evidenced by our previous transcriptomic study at the molecular level. However, whether the metabolic production of Met-Met confers protection remains unknown. In this study, Met-Met significantly suppressed LPS-induced TNF-α, IL-8, AP-1, and MCP-1 expression; reversed decreased tryptophan, phenylalanine, and histidine levels; and inhibited LPS-induced palmitic acid and stearic acid levels as well as purine metabolism disorder. Overlapping metabolites were mainly involved in the cysteine and methionine metabolism, fatty acids biosynthesis, and purines degradation. These metabolites and pathways might contribute to the protective action of methionyl-methionine.IL-8, TNF-α, AP-1, and MCP-1 were reduced by pretreating with 2 mM Met-Met after LPS exposure. Metabolomics profiling analysis demonstrated that LPS induced significant alteration of metabolites, including decreased tryptophan, phenylalanine, and histidine levels and increased palmitic acid and stearic acid levels as well as purine metabolism disorder, whereas Met-Met reversed these changes significantly. Pathways analysis revealed that overlapping metabolites were mainly enriched in the cysteine and methionine metabolism, fatty acids biosynthesis, and purines degradation. Correlation networks showed that the metabolic profile was significantly altered under the conditions of inflammation and Met-Met treatment. Collectively, Met-Met might relieve MAC-T cell inflammation via hydrolysate methionine, which further changes the processes of amino acid, purine, and fatty acid metabolism.Our previous transcriptomic study found that methionyl-methionine (Met-Met) exerts an anti-inflammatory effect in the bovine mammary epithelial cell (MAC-T) at a molecular level. However, evidence of whether the metabolic production of Met-Met confers protection was scarce. To investigate the inflammatory response and metabolite changes of Met-Met in lipopolysaccharide (LPS)-induced inflammation of MAC-T, mass spectrometry-based metabolomics and qPCR were conducted. The increased levels of  With the intensive development of the dairy industry, mastitis caused by Gram-negative bacteria in the environment has attracted much attention . For thiStreptococci and Staphylococci) are based on targeted antibiotics [Escherichia coli (E. coli) is not satisfactory, becase the use of extended-duration therapy to treat E. coli significantly increases costs without improving clinical outcomes of mastitis [Several efficient programs are utilized to control bovine mastitis. At present, most of the clinical treatments for mastitis resulting from Gram-positive bacteria  contains two DL-methionines that modulate bovine blood polymorphonuclear cells’ inflammatory status and help the resolution of inflammation after LPS stimulation . BesidesE. coli O111:B4) was purchased from Sigma Company .Met-Met was provided by ChinaPeptides Co., Ltd. . The certificates of mass spectrometry (MS) and high-performance liquid chromatography (HPLC) analysis of Met-Met are uploaded to the 6 cells/mL and incubated with or without Met-Met (2 mM) for 6 h and then stimulated by fresh media containing LPS (1 μg/mL) for 1, 3, 6, and 12 h. For the metabolic experiment, MAC-T was treated with Met-Met (2 mM) for 6 h and further co-incubated with 1 μg/mL LPS for 3 h, and then the supernatant was removed and the cells were collected for metabolomic analysis. Each experiment was divided into four groups, i.e., the control group , inflammation group , anti-inflammatory group , and dipeptide group . Finally, MAC-T was obtained for further analyses.The MAC-T was cultured in Dulbecco’s modified Eagle’s medium  containing 1% penicillin/streptomycin , 5 μg/mL insulin (Sigma), 1 μg/mL hydrocortisone, and 10% fetal bovine serum (FBS) (Gibco) . The finTNF-α), interleukin 8 (IL-8)) and inflammatory mediators (activator protein 1 (AP-1), monocyte chemotactic protein 1 (MCP-1)) were selected to evaluate the inflammatory response after LPS stimulation. The relative expression of genes was normalized to the special internal reference ribosomal protein S9 (RPS9) [−∆∆CT method. The primer sequences of the genes are described in TNF-α, IL-8, and RPS9 refer to previous studies [The total RNA of MAC-T was collected using Trizol reagent . The quality of total RNA was assessed by an Agilent 2100 , and the samples with an RNA integrity number (RIN) larger than 7.6 were selected for subsequent experiments. The total RNA (1 μg) was reverse transcribed into cDNA by the PrimeScript RT reagent kit . Quantitative RT-PCR was carried out in the 7500 real-time PCR system  with SYBR Premix Ex Taq (TaKaRa). PCR conditions were as follows: 95 °C for 30 s, 40 cycles of 95 °C for 5 s, and 60 °C for 34 s. The specificity of amplification was evaluated by the melt curve of an additional 15 s at 95 °C, 1 min at 60 °C, and 15 s at 95 °C. Several genes related to cytokines (tumor necrosis factor-α (9 (RPS9) ,18,19. T studies ,21.2O , and adequately vortexed. The homogenate was sonicated at 4 °C (30 min/once × 2), incubated for 60 min at −20 °C to precipitate the protein, and centrifuged . The supernatants were collected and dried under vacuum and then stored at −80 °C. The sample was redissolved in 100 μL of acetonitrile/water , adequately vortexed, and then centrifuged . The supernatants were collected for LC-MS/MS analysis.In all, 12 samples (4 groups × 3 samples per group) were delivered to Shanghai Applied Protein Technology Co., Ltd.  for liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. Every sample was thawed at 4 °C, mixed with 1 mL of cold methanol/acetonitrile/HAll samples were analyzed using a chromatographic column (ACQUIY UPLC BEH (100 mm × 2.1 mm 1.7 µm)). Column temperature (25 °C) and flow rate (0.3 mL/min) were selected as separation conditions. Mobile phase A was 25 mM ammonium acetate and 25 mM ammonium hydroxide in water , while mobile phase B was acetonitrile . The gradient was 85% B for 1 min and was linearly reduced to 65% in 11 min, then reduced to 40% in 0.1 min and kept for 4 min, and then increased to 85% in 0.1 min, with a 5-min re-equilibration period employed. After separation by ultra-high performance liquid chromatography (UHPLC), all samples were analyzed by a Triple TOF 6600 mass spectrometer . The parameters of the MS were as follows: ion source gas 1, 60; ion source gas 2, 60; curtain gas, 30; source temperature, 600 °C; and ion spray voltage floating (ISVF), ±5500 V. In MS acquisition, the instrument was set to acquire over the m/z range 60–1000 Da, and the accumulation time was set at 0.20 s/spectra.https://www.genome.jp/kegg/, accessed on 20 July 2020) and Human Metabolome Database . The metabolites with high confidence were validated by comparing the retention time and MS/MS spectra of commercial reference standards. The LC-MS data were analyzed using SIEVE software . Partial least squares discriminant analysis (PLS-DA) and orthogonal partial least squares discriminant analysis (OPLS-DA) were performed using SIMCA-P 14.1 software . Differential metabolites were detected according to the variable importance in the projection (VIP > 1.0) of PLS-DA and p values (p < 0.1) calculated by student’s t-test. Then, the differential metabolite data were uploaded into the MetaboAnalyst web server  to determine the metabolic pathway distribution and to perform metabolite–metabolite interaction analysis.The metabolites were identified by comparing the MS/MS spectra with the spectra in the Kyoto Encyclopedia of Genes and Genomes database . * TNF-α and IL-8 were prominently higher at 3 (3.77 and 4.36-fold) and 6 h (2.65 and 2.36-fold) than those at 1 (1.18 and 1.21-fold) and 12 h (2.19 and 2.34-fold) when compared the LPS group with the CON group. Treatment with Met-Met +LPS significantly suppressed the expression of TNF-α at 1  (p < 0.05) (p < 0.01)  (p < 0.01) (p < 0.05)(p < 0.05)  (p < 0.01)   A, 3 (1.6 < 0.05) B, and 6  < 0.01) C except  < 0.01) A, 3 (0.6 < 0.01) B, 6 (1.0p < 0.05)C, and 12 < 0.05) D when co < 0.05) A and 12  < 0.01) D. The le < 0.05) A in the  < 0.05) B–D. Inte and 3 h A,B.2Y of PLS-DA provides an estimate of how well the model fits Y, and Q2 is an estimate of how well the model predicts X. Two hundred permutation test models  and P-value (VIP >1 and p < 0.1), eight differential metabolites (DMs) were identified in Met-Met vs. CON, of which four were upregulated and four were downregulated . According to the biochemical characteristics and biological processes, these DMs and metabolic pathways could be further divided into three categories: amino acid metabolism, purine metabolism, and fatty acid metabolism  were identified. Among these metabolites, the overexpression of 10 overlapping metabolites was founded in LPS-induced inflammation, while their expression was downregulated by Met-Met A. In conTNF-α and IL-8, and the inflammatory mediators AP-1 and MCP-1. Met-Met exhibited a suppressive effect on these proinflammatory cytokines under LPS exposure. Consistently, compared with the control group, Met-Met treatment alone significantly decreased the levels of TNF-α, IL-8, AP-1, and MCP-1. Although there is little literature about the suppressive effect of Met-Met on inflammation, our recent study found that Met-Met has a similarly inhibitive impact on the expression of TNF-α and IL-8 [TNF-α and IL-1β in different types of bovine epithelial cells [IL-8 might impair neutrophil migration, leading to greater E. coli invasion; therefore, the animal model needed to be further conducted to determine the optimal concentration of Met-Met. Bovine mastitis caused by lipopolysaccharide leads to severe economic loss for farmers . In thisand IL-8 . Besidesand IL-8 . Severalal cells ,25. In t2S in cells [TNF-α to enhance host immunity [Amino acids play a fundamental role in the inflammatory response. The synthesis of antigen-presenting molecules, immunoglobulins, and cytokines in the innate and acquired immune systems requires amino acids as materials, and individual amino acids participate directly or indirectly in the immune response through their intermediates, such as histamine, glutathione (GSH), nitric oxide (NO), and superoxide ,27,28. Min cells . GSH canin cells . There iin cells , and thein cells . The difin cells . In our immunity . An impoimmunity . In the IL-12 and increasing IL-10 production [Histidine creates histamine through decarboxylase in the mammary gland . Histamioduction . Our resPurine metabolism is associated with amino acid metabolism through the purine nucleotide cycle and plays an important role in energy supply, metabolic regulation, and coenzyme production . Purine IL-8. In our study, LPS induced a significant upregulation of palmitic acid, whereas this trend was adjusted by treatment with Met-Met, suggesting that Met-Met might relieve inflammation via the palmitic acid metabolism pathway. Similarly, stearic acid can aggravate inflammation by inducing superoxide to activate NLRP3 inflammasomes [Fatty acids can regulate the immune metabolism of animals and cells by affecting the intensity and duration of inflammation. Palmitic acid is a saturated fatty acid that can activate the NFκB pathway through toll-like receptors and generate reactive oxygen species to cause endoplasmic reticulum stress . Additiommasomes . In our This study demonstrated that Met-Met alleviated MAC-T inflammation via hydrolysate methionine. Methionine and cysteine metabolism, purine metabolism, and fatty acid metabolism could be responsible for the inflammatory response of Met-Met . This re


All concrete mixtures satisfied targeted air content and slump ranges but exhibited significantly different mechanical and durability properties. The CaO-activated GGBFS concretes showed different strength levels, depending on the type of additive. The added CaCl2 was the most effective, but Ca(NO3)2 was the least effective at increasing mechanical strength in the CaO-activated GGBFS system. The OPC concrete showed the most excellent freezing–thawing resistance in the durability test, but only the CaO-activated GGBFS concrete with CaCl2 exhibited relatively similar resistance. In addition, the chemical resistance was significantly dependent on the type of acid solution and the type of binder. The OPC concrete had the best resistance in the HCl solution, while all CaO-activated GGBFS concretes had relatively low resistances. However, in the H2SO4 solution, all CaO-activated GGBFS concretes had better resistance than the OPC concrete. All concrete with sulfate ions had ettringite before immersion. However, when they were immersed in HCl solution, ettringite tended to decrease, and gypsum was generated. Meanwhile, the CaO-activated GGBFS concrete with CaCl2 did not change the type of reaction product, possibly due to the absence of ettringite and Ca(OH)2. When immersed in an H2SO4 solution, ettringite decreased, and gypsum increased in all concrete. In addition, the CaO-activated concrete with CaCl2 had a considerable amount of gypsum; it seemed that the dissolved C-S-H and calcite, due to the low pH, likely produced Ca2+ ions, and gypsum formed from the reaction between Ca2+ and H2SO4.This study examined the mechanical and durability properties of CaO-activated ground-granulated blast-furnace slag (GGBFS) concretes made with three different additives (CaCl With global warming, abnormal climates are occurring worldwide, causing many problems ,2. The i2 emissions, accelerating global warming  was identified in GGBFS, and GGBFS primarily consisted of an amorphous phase. On the other hand, dicalcium silicate (C2S), tricalcium silicate (C3S), tetracalcium aluminoferrite (C4AF), tricalcium aluminate (C3A), and gypsum (CaSO4) were identified in OPC [Particle size distribution results  show thad in OPC . 2, Ca(HCOO)2, and Ca(NO3)2, respectively, as additives, and their material proportions were determined via previous studies [4 to enhance the early compressive strength of the binders.The material proportions of binders used to produce concrete samples are shown in  studies ,24,25. NThe mixture proportions of concrete are given in 3) to test determine compressive strength, split strength, elastic modulus, and chemical resistance, and samples in prism molds (10 × 10 × 40 cm3) for freezing and thawing cycle tests. The fresh concrete samples were compacted and cured at 23 °C and 99% relative humidity.For concrete production, all mixing procedures followed the Korea Standard (KS) F 2403 . The fre3).Slump and air content were examined according to the KS F 2402 and KS F 2421 ,31. The Freezing and thawing cycle resistance tests were performed using 14-day cured samples, and all experimental procedures followed by KS F 2456 . In addi2SO4 solutions, and the solutions were replaced once in 4 weeks. The weight changes were measured at 3, 7, 14, 28, 56, and 91 days after immersion to identify the evolution of reaction products. On each weight measurement, three identical specimens were weighed. Analysis of XRD and TGA identified reaction products after 28, 56, and 91 days of immersion. The exposed samples were fractured and finely ground using a mortar and pestle. In addition, XRD and TGA were conducted once for each measurement day and mixture proportion. In addition, SDT Q600  was used to measure the reaction products of each sample with a heating rate of 30 °C/min from 25 to 1000 °C in a nitrogen atmosphere in an alumina pan.Chemical resistance tests were carried out according to ASTM C 267 . The 28-2 was the most effective in increasing strength, while Ca(NO3)2 was the least effective. Compressive strengths of hardened concretes are shown in cr) was 45 MPa. The compressive strength was 48 MPa for P-CON, but the CaO-activated GGBFS concretes gained only about 10 to 30 MPa, significantly lower compressive strength than fcr. The mixture proportion of concrete was designed following the Concrete Standard Specification in Korea , and theThe split strengths are presented in The measured elastic modulus values of concrete samples are given in When comparing the experimental values with the calculated values from the ACI and CEB-FIP models, the models showed significantly higher elastic modulus than the measured values. Previous studies similarly reported that the ACI and CEB-FIP models tended to overestimate the elastic modulus of OPC concrete, and it was observed for all types of concretes in this study ,39,40. The dynamic elastic modulus of P-CON and C-CON decreased down to about 60% up to 300 cycles, while those of F-CON and N-CON were not measured because they were damaged significantly before reaching 300 cycles. Thus, F-CON and N-CON are vulnerable to freezing and thawing cycles.It is worth noting that although C-CON and F-CON had similar compressive strengths and elastic modulus, they showed significantly different resistances to freezing and thawing cycles. However, a sample with a higher drop of the dynamic modulus tended to show a steeper decrease in the weight. Thus, the strength itself was a less accurate indicator than the dynamic modulus for estimating the ability to resist freezing and thawing cycles in this study.For OPC concretes, KS F 2456  determin2SO4 solutions are shown in 2SO4 aqueous solutions yielded different results; the most considerable weight loss occurred in P-CON, followed by N-CON, F-CON, and C-CON, in order.The results of chemical resistance tests using 5% HCl and 5% H2SO4), the pH of the concrete was lowered, resulting in the change of hydration products. When concrete samples were immersed in acid solutions 6Cl(H2O)2) was found. The HCl solution likely lowered the pH of P-CON, resulting in removing OH− of Ca(OH)2 [− ions from HCl and Ca2+ ions from Ca(OH)2. In addition, regeneration of Ca(OH)2 was observed at the 91-day sample. It seemed that as the chemical resistance test proceeded, Ca(OH)2 was regenerated by a complex chemical reaction; more research will likely be needed for the regeneration of Ca(OH)2.In the HCl solution, the change of the reaction products was investigated using the XRD and TG/DTG analysis, shown in  Ca(OH)2 ,42, and 42−)  had ettringite before immersion. When immersed in HCl solution, the DTG analysis showed that ettringite tended to decrease, and gypsum was generated; F-CON exhibited the most prominent decrease of ettringite, while N-CON displayed the slightest change in ettringite peak. Previous studies [2 before immersion. In addition, the weight loss occurred in the vicinity of 800 to 900 °C in CaO-activated concrete, which might be the recrystallization of C-S-H [The XRD showed that all samples with sulfate ion 2 at the P-CON sample and crystallization were observed. It is worth noting that ettringite is relatively more susceptible to the drying process of sample preparation than other cementitious reaction products and, thus, ettringite can often be underestimated in quantity in XRD and TG/DTG [2SO4 solution in TG/DTG was not precisely consistent with that of XRD; however, careful interpretation enabled us to recognize the approximate tendency of the product change.d TG/DTG ,47. Unfo2SO4 solution, ettringite became unstable and decomposed, producing gypsum. In the samples that had ettringite before immersion 2 before immersion (2+ ions (or Ca(OH)2) when the pH is lowered. In the TG/DTG results, the decrease in calcite peak was—relatively—clearly seen, but the decrease in C-S-H peak was difficult to observe because the C-S-H peak below 200 °C overlapped with the peaks of ettringite and gypsum, making it challenging to analyze. However, when referring to the other study results [2+ ions can produce gypsum from the reaction with H2SO4 in C-CON. On the other hand, in the case of P-CON, the coexistence of Ca(OH)2 generally prevents chemical deterioration of C-S-H [However, note that gypsum can also form from the reaction between Ca(OH)position ,41. For mmersion b. Previo results ,50,51, Cof C-S-H ,52; thus2, Ca(HCCO)2, and Ca(NO3)2), and compared their properties with those of Portland cement concrete. Detailed conclusions are summarized as follows:All CaO-activated GGBFS concretes satisfied the targeted air content and slump ranges. However, they exhibited lower mechanical properties  than OPC concrete.2 was the most effective at increasing strength and elastic modulus, while the additive Ca(NO3)2 was the least effective.In the CaO-activated GGBFS system, the additive CaCl2 and Ca(NO3)2 were destroyed before 300 cycles; however, the one made with CaCl2 had a relatively comparable resistance in the freezing and thawing cycles test to OPC concrete.In the freezing and thawing cycle test, the CaO-activated GGBFS concretes with added Ca(HCOO)The strength was a less accurate indicator than the dynamic modulus for estimating the ability to resist freezing and thawing cycles in this study.2SO4 solutions showed significantly different results depending on the type of acid solutions. In a 5% HCl solution, although weight loss was observed in all immersed samples, the OPC concrete had the most excellent resistance, while the CaO-activated GGBFS concrete with Ca(NO3)2 was the most vulnerable. However, in 5% H2SO4 aqueous, the most considerable weight loss occurred in the OPC concrete.The chemical resistance tests using 5% HCl and 5% H42−) 2 and Ca(NO3)2) had ettringite before immersion. When they were immersed in HCl solution, their DTG results showed that ettringite tended to decrease, and gypsum was generated; however, the CaO-activated GGBFS concrete with CaCl2 did not change the type of reaction product in the HCl solution, possibly due to the absence of ettringite and Ca(OH)2 before immersion.In XRD, all concrete with added sulfate ion 2 and H2SO4 in all concrete samples. In particular, the concrete without ettringite  had a considerable amount of gypsum formation; in this concrete, dissolved C-S-H and calcite, due to the low pH, likely produced Ca2+ ions, and gypsum formed from the reaction between Ca2+ and H2SO4.When immersed in HThis study examined the mechanical and durability properties of three types of CaO-activated GGBFS concretes made with three different additives (CaCl


Antimicrobial resistance poses a significant threat to public health and safety across the globe. Many factors contribute to antibiotic resistance, most especially are the concerns of excessive prescribing and misuse of antibiotics. Because patient expectations for antibiotics may contribute to prescriber pressures, experts recommend targeting antimicrobial stewardship (AMS) education efforts towards prescribers as well as patients in outpatient settings. Undergraduate university students are a unique and promising target population for AMS efforts because they are in a transformative life stage of social, cognitive, and physical development in which they are learning to independently care for themselves without the presence or influence of parents. By introducing AMS education during this transition, university students may adopt positive antibiotic use behaviors that they will carry throughout their lives. Not only will their personal health be improved, but widespread adoption of AMS in university settings may have a broader effect on public health of present and future generations. Despite public health opportunities, minimal research has examined AMS in university health settings. This article explores current evidence on knowledge, attitudes, and use of antibiotics among university students and discusses opportunities for AMS initiatives in college and university health settings. Antimicrobial resistance poses a significant threat to public health and safety across the globe. According to the Centers for Disease Control and Prevention (CDC), patients in the United States incur over 2.8 million antibiotic-resistant infections annually, resulting in over 35,000 deaths . In addiMany factors contribute to antibiotic resistance, most especially are the concerns of excessive prescribing and misuse of antibiotics. Outpatient clinical settings account for approximately 80–90% of antibiotic prescriptions, and half of these prescriptions are deemed inappropriate or unnecessary . MultidiTo address the issue of patient expectations for antibiotics, experts recommend targeting AMS education efforts towards patients as well as prescribers ,14,15,16Although the typical university student is young and healthy, many students will seek out medical attention for illness or injury at some point during their studies. In the American College Health Association’s National College Health Assessment survey, university students consistently report respiratory illnesses/infections, urinary tract infections (UTIs), and acne among the most frequent medical diagnoses received from a healthcare provider . Young pUniversity students participating in a qualitative study in United Arab Emirates admitted to engaging in frequent antibiotic use/misuse citing several influencing factors, such as easy access to antibiotics without a prescription, advice from friends/family, time constraints associated with classes, and clinic visit costs . StudentNot only is antibiotic resistance a risk with increased antibiotic use in this population, but also antibiotic-related adverse drug events are a concern. In a 2018 U.S. study, young adults aged 20–34 were twice as likely as older adults to seek medical attention for antibiotic-related adverse drug events at the emergency department . This evCultural context must also be considered when examining antibiotic use and misuse of university students from different countries. The presence of infectious illnesses, access to antibiotics, surveillance, and government regulations are significantly different in low- and middle-income countries (LMICs) compared to high-income countries (HICs).According to Tattevin et al., LMICs located in Sub-Saharan Africa and Asia are disproportionately affected by infectious disease and antimicrobial resistance, which is likely a result of weak government regulations, counterfeit and over-the-counter sales of antimicrobials, lack of surveillance/diagnostic testing capability, and poor prescribing practices . In a syIndividuals living in HICs, such as the United States, United Kingdom, and Australia, are estimated to consume the highest number of antibiotics with 25 defined daily doses (DDD) per 1000 persons per day compared to 10–20 DDD per 1000 persons per day in LMICs . Though Evidence directly quantifying the use and misuse of antibiotics in university students is limited; therefore, most studies have focused on students’ self-reported knowledge and attitudes. In a survey-based study exploring common myths of antibiotic use, Shahpawee et al. found 51% of students in Brunei were adequately knowledgeable about antibiotics and antimicrobial resistance . AlthougKnowledge and attitudes of university students in health-related majors  may differ from the general university student population. According to several studies, students in health-related majors consistently demonstrated higher levels of knowledge and attitudes regarding antibiotic use/misuse and antibiotic resistance ,24,30,31Though university students are engaged in formal education, they are at risk for low health literacy regarding use of antibiotics and antibiotic resistance. Students have potential during their transitional college years to improve their health literacy related to AMS, resulting in lifelong reduction of expectations for and consumption of unnecessary antibiotics . Shared p < 0.01) and clearly explained the rationale for prescribing or not prescribing an antibiotic (p < 0.01) [In a pilot quality improvement project, Moes et al. provided an example of using AMS educational tools and shared decision-making to improve knowledge and attitudes for university students in a student health clinic . Student < 0.01) .AMS is essential to improve antibiotic use among university students, however, studies related to AMS initiatives in college and university health settings are rarely published. Throughout the literature, recommendations for university-based AMS initiatives include provider-focused education to improve prescribing and communication, student-focused education, student health clinic educational handouts, interprofessional learning experiences, and social media campaigns ,30,31,32Colleges and universities are optimal settings to apply the CDC’s Core Elements of Outpatient Antibiotic Stewardship, a framework designed for outpatient clinics to help improve antibiotic prescribing and use . The CDCMany student health clinics have on-campus pharmacies to facilitate stronger AMS collaboration between pharmacists and prescribers. University clinics and pharmacies located in countries where over-the-counter antibiotics are legally permitted can commit to only dispensing antibiotics to students who have a valid prescription. Universities can also implement a collaborative, multidisciplinary approach to AMS by engaging faculty experts and students in health sciences departments  in AMS research, program development, and outreach. In addition, student health clinics should incorporate procedures and electronic medical record features to aid in auditing and reporting antibiotic prescribing practices for high-priority diagnoses, such as UTIs and respiratory illnesses ,15. ElecAnother advantage in student health clinics is accessibility. Typically, student health clinics are conveniently located on campus and visits are of minimal to no cost to students. Providers may experience less pressure and more confidence introducing “watchful waiting” in this setting because students can avoid the added costs and inconvenience associated with typical follow-up appointments in outpatient settings . BecauseGlobal context must be considered before implementing AMS initiatives in the college and university setting. According to Tattevin et al., AMS initiatives that work well in HICs, such as those mentioned in In this article, we provide an overview of current evidence that suggests university students have knowledge and attitude deficits related to safe and appropriate antibiotic use, and they are at risk to develop antibiotics misuse behaviors. We also highlight opportunities for AMS in college and university health settings and include a model for how to apply the CDC’s Core Elements of Outpatient Antimicrobial Stewardship to these settings. Whereas current evidence supports the need for enhanced AMS initiatives in this population, gaps and limitations exist. Additional and more rigorous studies are needed to directly measure antibiotic use and identify specific approaches to AMS in this population. Cultural context and government policies must be considered when studying antibiotic use and misuse in the university student population as the expectation for and availability of antibiotics varies from country to country. We hope this article generates interest in university students as a focus for new outpatient AMS research and practice initiatives.With 20 million students enrolled in universities across the U.S., the introduction of AMS efforts through on campus student health clinics could have a significant impact on public health . Univers


In this study, we aimed to explore the effect of concrete short columns confined by flax/glass fiber hybrid-reinforced epoxy resin (FFRP/GFRP) composites. Taking the same fiber hybrid ratio and different paving orders as parameters, analysis of the axial compressive mechanical properties of eight groups of FFRP/GFRP composite-confined concrete short columns, including one group of flax fiber-reinforced epoxy resin (FFRP) composite-confined concrete short columns and one group of unconstrained concrete short column, was conducted. The effects of different layering sequences on failure modes, load–displacement curves, energy dissipation ductility and the stress–strain relationship of hybrid composite-confined concrete short columns were analyzed. The results show that the axial compression failure modes of FFRP/GFRP composite-confined concrete short columns with the same hybrid ratio and different paving sequences were basically the same, and the CC-H6 group was the most prominent. The ultimate bearing capacity and axial deflection were 91.05% and 11.49% higher than those of the control group (CC-FFRP), and the energy dissipation coefficient was also the largest, at 9.79. The failure trend of the stress–strain curve of the confined concrete short column specimens was basically the same, and the stress and axial strain of the members were increased by 247.9~292.5% and 486.7~701.0%, respectively. Synthetic fiber-reinforced polymer composites have excellent mechanical properties, including a glass fiber tensile strength of 3400~3700 MPa and a carbon fiber tensile strength of 3500~4500 MPa ,2,3,4, a3) and good low-cost characteristics [In recent years, composite materials consisting of natural plant fibers, such as flax, jute, ramie, hemp, etc., have attracted the attention of researchers in various fields. They have the advantages of being lightweight, high-strength, degradable, economic, practical, and providing environmental protection, and they meet the needs of the current international development trend ,15,16. Aeristics ,18,19. Ceristics ,21.Nauman Wahab et al. employed a jute–polyester hybrid fiber (JFRP) composite material to reinforce a concrete cylinder for an axial compression test . The resIn this experiment, flax fibers were used as the plant fibers, which have a low price and high specific strength, while glass fibers were used as the synthetic fibers. Using the hand paste method to prepare the flax/glass fiber hybrid-reinforced epoxy resin (FFRP/GFRP) composites with the same hybrid ratio, different layer sequences were used to observe how they affect the performance of confined concrete short columns with regard to axial compression, the failure modes of the axial compression performance test, load–displacement curves, ductility and the energy stress–strain relationship. This study could provide a reference for practical engineering applications and help to meet the performance and strength requirements of different structures in practical applications.2 and volume density of 1.5 g/cm3) was purchased from Harbin Flax Textile Co., Ltd., Harbin, China. Bidirectional glass fiber no-twist gauze  was purchased from China Jushi Group Co., Ltd., Jiaxing, China.Bidirectional flax fiber twisted yarn cloth  and ASTM D2344/D2344M , as shown in Epoxy-impregnated A and B adhesives (MH-301), for which the density is 1.2 g/cmIn this paper, the Portland cement (P.O. 42.5) was produced by Harbin Cement Co., Ltd., Harbin, China. The fine aggregate was selected as natural river sand in Harbin City, with particle sizes less than 4.75 mm and good grading. The coarse aggregate was selected as 10~20 mm basalt gravel, and the water reducer used FND naphthalene water reducer, with a water reduction rate of 22%.The casting mold adopted the electric flux circular test mold with a diameter of 100 mm and a height of 200 mm. The designed strength of the concrete was C30, and the appropriate mix ratio was selected according to the design specification of the ordinary concrete mix ratio As shown in (2)The flax fiber sheet was cut to a certain size and put into the ultrasonic cleaning machine  for reaction for 40 min to remove impurities, and then was taken out and dried for later use. The flax fiber and glass fiber sheet was cut to a size of 400 mm × 300 mm and put into the oven. The drying treatment was conducted at a constant temperature of 60 °C until a constant weight was attained, and then the sample quality was measured, and data were recorded;(3)We mixed the composite according to the mass proportion 2:1, configured group A and group B with epoxy resin impregnation glue, and used a glass rod to stir the impregnation glue until the color distribution was uniform. Then, the impregnation glue was coated on the surface of the specimen, and the fiber sheet was wound around the concrete cylinder in the direction of fibers several times, and the internal bubbles were extruded. We repeated the above steps to the specified number of coating layers, then coated the outermost layer with epoxy resin adhesive (as shown in (4)After curing for 7 days at room temperature, the upper and lower parts of all specimens were leveled. If the end of the specimen was uneven, the stress concentration phenomenon occurred under the action of axial compressive stress, leading to the specimen breakage in advance. The end leveling was mainly made of high-strength gypsum. The high-strength gypsum added with an appropriate amount of water was stirred evenly and coated on the end of the specimen. The gypsum was compacted with a flat slide plate and the upper and lower ends were made sufficiently level, as shown in (5)Finally, we determined the paste position of the test strain gauge and polished it smooth for later use.The wrapping method was layered—that is, after each layer of epoxy resin was administered, a layer of fiber cloth was wrapped around the column, and this step was repeated a total of eight times. A quarter of the circumference (80 mm) was taken as the lap length, and the lap position of each layer could not overlap. In the test, due to the weak end constraint, three layers of flax fibers with a width of 4 cm were affixed to the upper and lower ends of the component in the test. The operation steps of the restraint wrapped specimen were as follows:The maximum compression force of the hydraulic testing machine used in this test was 500 t, and the average compression rate was 0.5 MPa/s. The ultimate bearing capacity and axial/circumferential strain data were collected. The test point layout of the specimen is shown in The control in the test process was also very crucial, which was an important factor related to the quality of the test data. Therefore, a series of measures were taken in this test to ensure the accuracy and reliability of the test data.(1)After wrapping the fiber around the concrete cylinder, the surface of the cylinder was leveled with a plastic scraper, and the composite material was uniformly wrapped in the concrete cylinder, so that the compression of the cross-section was uniform.(2)We adopted the method of laser wiring to determine the specific sticking position of strain gauge to ensure it was horizontal and vertical. It was then carefully polished with fine sandpaper until smooth.(3)Special glue was used for strain gauge bonding to better force the strain gauge and material together, prevent the risk of damage in advance, and record more accurate and effective data.(4)In order to ensure that the specimen was subjected to uniform load and axial compression, the upper and lower ends of the specimen were made of high-strength gypsum as the leveling layer, so as to avoid local stress of the specimen.(5)Before the test, the pressure sensor was calibrated and the strain gauge was checked again to check that it was intact.The following measures were taken to reduce the errors in the test:The failure mode of the specimen is shown in The concrete cylinder restrained by the pure flax fiber sheet is in the elastic stage at the initial loading stage. The mechanical behavior of the whole specimen is similar to that of the unrestrained concrete cylinder, and the surface of the specimen does not change significantly. As the load continues to increase, the binding effect of fiber cloth is gradually revealed, the toroidal volume of specimens begins to expand, and the toroidal tensile strain value of the FFRP composites increases rapidly. When the axial load reaches about 60% of the ultimate load, the cylinder expands and breaks in the middle, the internal concrete strength increases over the limit, some of the fibers fracture, along with the load increasing, and the thrum becomes larger and more and more intensive, until the specimen, with a crackling sound, is destroyed, and the ultimate bearing capacity peaks, releasing energy. The failure mode is cracking in the middle of the cylinder first, and then spreading to both ends. Most of FFRP composite materials and concrete fragments splash, which is dangerous to a certain extent. A large number of concrete fragments scatter around the test bed, and the core concrete is seriously damaged, as shown in The failure mode of the HFRP composites (H1-H8) is shown in In general, the failure process of plain concrete cylinder is mainly circumferential expansion, and vertical cracks appear on the periphery during the axial compression performance test, leading to longitudinal cracks along the concrete cylinder. Because the compressive strength of concrete material is 10 times its tensile strength, it cannot prevent the development of longitudinal cracks. The damaged concrete surface cracks, divides, and then falls off. The cracks between the concrete fragments extend in the same direction as the loading axis. Compared with the concrete cylinder without restraint treatment, the concrete cylinder wrapped with flax/glass fiber can have a better restraint effect. Using this method, the volumetric expansion and crack development of the concrete cylinder under compression conditions are limited, and the peak load and overall failure deformation of the concrete cylinder are obviously increased under the joint action of axial and peripheral wrapping forces. Because the lateral binding force of HFRP composites is fully exerted, and the upper and lower parts are strengthened, the lateral deformation of the end part is small, the deformation of the middle part is large, the fracture of the composite plate is neat, and the core concrete is in the conical failure form.uP and uδ are the ultimate load and axial ultimate deflection of concrete cylindrical members under failure. ΔuP and Δuδ are the percentage of improvement in the bearing capacity and deflection of concrete cylinders after being reinforced with fiber cloth. It can be found that the ultimate bearing capacity of the unconstrained cylinder is only 253.19 kN and the axial deflection is 6.02 mm. The bearing capacity of concrete cylinders is improved obviously by using fiber cloth to restrain them, mainly because FRP provides circular restraint, which improves the bearing capacity. When the flax/glass fiber hybrid composites were used to restrain concrete members at the same mixture ratio, CC-H6 showed the most outstanding performance. Compared with the control group (CC-FFRP), the ultimate bearing capacity of CC-H6 was increased by 91.05%, and its axial deflection was also increased by 11.49%. The ultimate bearing capacity of CC-H5 is not greatly improved, but the deflection extension is improved by 27.87%, which is similar to the conclusion regarding the mechanical properties of HFRP composites in Above all, the test results show that on the one hand, the flax/glass fiber hybrid composite material can effectively enhance the axial compression performance of the concrete column, the ultimate bearing capacity of the concrete column is enhanced, and the effectiveness of the structure constraint is verified, and on the other hand, the axial deflection of concrete cylinder is improved, and the deformation resistance of concrete cylinder is improved. Therefore, HFRP-reinforced concrete columns not only improve the bearing capacity, but also meet the ductility requirements of the structure.cuE to describe the change in the specimen in the process of absorbing stress energy, as shown in Ductility is mainly determined by the amount of energy absorbed by the concrete member during the stress process. The less energy is absorbed, the worse the ductility and the weaker the deformation resistance. In order to further explore the influence of the constraint on energy dissipation capacity, this chapter introduces λ is defined to represent the improvement effect of FRP composite material on the energy dissipation performance of concrete cylindrical members.Its value is the area of the curve formed by the load–displacement curve of axial compression and the horizontal axis—that is, the integral solution of the curve is carried out from zero axial displacement to the maximum deflection displacement. The energy dissipation coefficient cuE represents the energy dissipation of the concrete cylindrical member constrained by FRP composite materials, and coE represents the energy dissipation of unconstrained concrete cylindrical member. In the axial compression test, the energy dissipation coefficient λ of the concrete cylindrical member constrained by FRP composite materials is shown in Equation (1): λ was 2.27. However, CC-H5 performs the worst in the reinforcement of hybrid fibers, and the energy dissipation coefficients of CC-H1, CC-H2, CC-H3, CC-H4, CC-H7 and CC-H8 are similar, ranging between those of CC-H5 and CC-H6, which is also consistent with the results obtained in When the axial compression test is carried out on the concrete cylindrical member wrapped with FRP composite restraint, the core concrete part is passively restrained. As shown in ω, its value is being equal to the measured values of the constraints of cylindrical concrete specimens the unconfined concrete column specimens’ measured values divided by the measured values of the unconfined concrete column specimens, and the unit is expressed as a percentage. Then, the effective utilization coefficient k is introduced to express the relationship between the effective circumferential ultimate strain of FRP composite-confined concrete and the ultimate strain of composite performance test, and its magnitude is the ratio of the above two. fcc′, εcc, εec, and εuc represent the ultimate axial stress, the ultimate axial strain, the effective circumferential strain of the FRP composite-confined concrete cylindrical specimens and the ultimate strain value of FRP sheet tensile performance test, respectively. fω and εω are the ultimate stress and strain improvement coefficient values of the concrete cylinders constrained by FRP composites, respectively, and the calculation results are shown in To further research into composite cylinders regarding the strength and ductility increase rate of confined concrete, this paper introduces the improved coefficient of As can be seen from The test results also show that the ultimate strain of FRP composites in the tensile performance test is much greater than the effective circumferential fracture strain of its sheet-confined concrete cylinder in the axial compression performance test. The main reasons may be as follows: in the process of specimens subjected to axial compression, the uneven transverse expansion of the internal concrete and the existence of cracks or holes on the surface of the concrete are prone to stress concentration, leading to the local tensile fracturing of FRP composites in advance. When FRP composites are wrapped by bending, their denaturation ability and energy dissipation ductility will be reduced, and there will inevitably be bubbles after manual operation, so this phenomenon will occur.(1)The axial compression failure modes of HFRP-confined concrete cylindrical members are basically the same; cracking occurs in the middle part first and spreads to both ends, and the internal core concrete is seriously damaged in a cone shape, which is in obvious contrast to FFRP-confined specimens.(2)The load–displacement curve of HFRP composite-confined concrete cylinders subjected to axial compression performance test shows that the failure trend is basically consistent throughout the loading process. The ultimate bearing capacity of the CC-H6-confined concrete cylindrical specimen is 91.05% higher than that of the control group (CC-FFRP), and its axial deflection is 11.49% higher than that of the control group. The ultimate bearing capacity of CC-H5 is increased by 84.8%, but the deflection extension is increased by 27.87%. There is no significant difference in the influence of other hybrid layers on the axial compressive performance of concrete columns, and ranged between the values observed for the CC-H6 and CC-H5 groups.(3)The strength and ductility of concrete columns confined by HFRP can be significantly improved. The CC-H6 group has the largest energy dissipation coefficient (9.79), and its confined concrete columns have the best ductility and seismic performance. CC-H5 performs poorly, and its energy dissipation coefficient is 5.95. The energy dissipation coefficient values of CC-H1, CC-H2, CC-H3, CC-H4, CC-H7 and CC-H8 groups are similar.(4)The failure trend of the stress–strain curves of FRP-confined concrete cylinders is basically the same, and the main difference is in the failure process of the second stage, which depends on the comprehensive mechanical properties of each HFRP composite. The ultimate stress and elastic modulus of the CC-H6-confined concrete cylinder are obviously higher than other combinations. Further comparison shows that the stress and axial strain of HFFRP composite-confined concrete cylindrical members are increased by 247.9~292.5% and 486.7~701.0%, respectively. The axial stress of CC-H6-constrained specimens increased the most, but the axial strain improvement effect was not good, while the effect of CC-H5 was the opposite, which was mainly related to the different fiber layering sequence. The improvement effect of other HFRP-constrained specimens ranged between that of CC-H5 and CC-H6.In this experiment, the axial compression performance test of HFRP composite-confined concrete cylindrical specimens with the same hybrid ratio is studied. The test design method, test content and loading scheme are introduced. The failure mode, characteristic load, strength and ductility of the compression members and stress-circumferential/axial strain relationship are analyzed and discussed. Based on the results of the study and characterization, the hybrid method is feasible in practical engineering applications, and the following conclusions can be drawn:


The latter processinvolving ammonia loss marks a difference with the prevailing chloridereplacement in protic solvent, pointing to the effect of a low-polarityenvironment.Methionine (Met)plays an important role in the metabolism of cisplatinanticancer drug. Yet, methionine platination in aqueous solution presentsa highly complex pattern of interconnected paths and intermediates.This study reports on the reaction of methionine with the active aquaform of cisplatin,  Itsuse in chemotherapy has been pivotal for over 40 years, and cisplatinis still considered a first-choice drug for several solid tumors,including head and neck and testicular cancers. In the cell environment,cisplatin undergoes hydrolysis, producing the corresponding aqua complex cis-[PtCl(NH3)2(H2O)]+, which is able to act as a platinating agent for DNA. Cisplatinreactivity is oriented preferentially toward the nucleophilic N7 ofguanine, producing 1,2-intrastrand cross-links and thus inhibitingDNA transcription and replication.6 In spite of DNA being the main cisplatin target, platinum(II) ishighly thiophilic and prone to interact with sulfur-donor ligands,which are mainly represented in the biological media by S-containingamino acids, i.e., cysteine and methionine, in peptides and proteins.18 It is worth noting that several proteins, not limited to serum transportsystems and metal detoxification enzymes, are reported to be implicatedin both the pharmacological and pharmacokinetic profiles of cisplatin.19 In order to improve our understanding of cisplatininteraction with peptides at a molecular level, in recent years westarted to explore its binding motifs with proteinogenic amino acids,such as histidine21 and methionine,22 using electrospray ionization mass spectrometry (ESI-MS), high-resolutionFourier-transform ion cyclotron resonance (FT-ICR) mass spectrometry,and infrared multiple photon dissociation (IRMPD) spectroscopy combinedwith density functional theory (DFT) ab initio calculations.IRMPD spectroscopy is a powerful tool that allows one to reveal thevibrational features of mass-selected ions by monitoring the fragmentationproduced by the absorption of photons that are resonant with the ionvibrational modes.27 Varying the photon energy allows us to obtain an IRMPD spectrumthat can be compared with calculated IR spectra in order to gain structuralinformation. It is worthy of note that the species is assayed in thegas phase, in the absence of solvent and associated band-broadeningeffects. IRMPD spectroscopy has been extensively used for the vibrationaland structural characterization of transition metal complexes of bothcatalytic and biological relevance.34 In particular, cisplatin related platinum(II) complexes have beencharacterized.36 Previous reports have highlighted the versatilityof ESI-MS together with the specificity of IRMPD spectroscopy in deliveringdetailed structural information on the monofunctional complexes cis-[PtCl(NH3)2(AA)]+,where AA is either Met or His.22 Furthermore, solutions of cisplatinand a simple ligand , assayed by ESI-MS and IRMPD spectroscopyhave revealed the presence and role of the encounter complexes {cis-[PtCl(NH3)2(H2O)]+·L}.38 These species are formed by thediffusion controlled encounter of the aqua complex of cisplatin withthe incoming ligand L and are the early actors in the substitutionreaction of metal complexes in aqueous media, conforming to the Eigen–Wilkinsreactant preassociation model.42 In the reported cases, the role of the encountercomplex along the substitution reaction path of the cisplatin aquacomplex with model ligands was assessed by observing the reactionto occur in the isolated species after collisional- or photoactivation,while IRMPD spectroscopy has afforded its vibrational and structuralfeatures. Moving one step further in assaying the cisplatin reactionwith nucleophiles approaching the biomolecular targets, herein isreported the isolation and characterization of the adduct formallyobtained by the preassociation of cisplatin aqua complex with methionine,[PtCl(NH3)2(H2O)(Met)]+. This species may be taken as a model for the early intermediatein the platination reaction of peptides presenting methionine residues.43 The [PtCl(NH3)2(H2O)(Met)]+ complex is isolated in the gas phase under long-lived conditionswhere it can be structurally assayed and activated. The reaction pathsand intermediates are characterized by ESI-MS and IRMPD spectroscopy,backed by quantum chemical calculations. The dilute environment allowsfor fine control of the reaction occurring at the singly molecularlevel. This point may be significant in view of the multifaceted natureof the cisplatin reaction even with a simple molecule such as theamino acid methionine in aqueous solution. The reaction of cisplatinwith methionine leads in fact to a variety of complexes where theamino acid performs as either mono- or bidentate-ligand, with a majorend product being a cis-[Pt(NH3)2Met-]+/2+ chelate.45 The reactionis dependent on pH because in strongly acidic conditions the cis-[Pt(NH3)2Met-]2+ complex is preferentially formed, subsequently evolving to the morestable cis-[Pt(NH3)2Met-]2+ at a higher pH.46 In the presenceof 2 mol equiv of Met, diastereomeric cis-[Pt)2] bis-chelate complexes are observed.44Withinthe broad range of antineoplastic agents present in therapy,cisplatin 2(H2O)]+, primarily formed in solution, has been examinedstarting from the preassociation adduct with the target Met reactant.The monosubstitution and bidentation processes and intermediates arecharacterized by both experimental and computational methods.To summarize, an in depth understanding of the reactivitybehaviorof cisplatin with a simple amino acid target such as Met in an aqueousmedium is highly difficult to achieve due to a complex pattern ofinterconnected paths and by the contribution of different hydrolyzedforms of cisplatin.l-methionine fromcommercial sources were used as received. Stock aqueous solutionsof l-methionine and of cisplatin were prepared at 10–3 M concentration, mixed in 1:1 molar ratio, and dilutedwith water to reach a final concentration of 5 × 10–5 M in each analyte in methanol/water (1:1 v/v). The solution of cisplatinwas allowed to stand overnight prior to use.Cisplatin and Complexesof interest were obtained by ESI-MS of the solution prepared as describedabove. Typical ESI conditions were a flow rate of 120 μL/h,a capillary spray voltage set at −4.5 kV, nebulizer at 12 PSI,drying gas flow at 5 L/min, and drying gas temperature at 300 °C.–1) and the X–H stretching ranges (2900–3700 cm–1). The fingerprint range was explored using the beamline of the IRfree electron laser (FEL) of the Centre Laser Infrarouge d’Orsay(CLIO). The electron energy of the FEL was set at 38 and 44 MeV inseparate runs to optimize the laser power in the frequency rangesof interest. The IR beamline is coupled with a hybrid FT-ICR tandemmass spectrometer (APEX-Qe Bruker) equipped with a 7.0 T activelyshielded magnet and coupled to a quadrupole–hexapole interfacefor mass-filtering and ion accumulation.49 The charged complexes of interest were mass selected in the quadrupoleand collisionally cooled for 300 ms in the hexapole with argon asbuffer gas, prior to IR irradiation. The isolated complexes were irradiatedfor 0.3–0.5 s with the IR FEL light, after which the resultingmass spectrum was recorded.IRMPD spectroscopy experiments were performed using two instrumentalsetups, covering different ranges of the IR spectrum, namely, theIR fingerprint  bondstretching modes were investigatedwith a tunable KTP/KTA optical parametric oscillator/amplifier lasersystem  pumped by a non seeded Nd:YAG laser(Continuum Surelite II). The IR light is allowed to enter an ion trapmass spectrometer , as describedpreviously.–1) in the case of the OPO/OPA but is much broader  in the case of CLIO IR-FEL. As a result, the IRMPD bandwidthobserved in the 2900–3700 cm–1 range is smallerthan that observed in the 900–1900 cm–1 region.Since electrosprayed ions are thermalized through multiple low-energycollisions at room temperature, it has been proposed51 that, while the IRMPD bandwidth is essentially controlledby ion temperature in the former range, it is controlled by the IR-FELbandwidth in the latter.IR-FELs have been shown to be particularly well-suitedfor drivingnoncoherent IRMPD processes. The IR-FEL at CLIO provides ∼8μs long trains of picosecond pulses delivered at 25 Hz. Thehigh peak power (∼80 μJ per picosecond pulse) and the16 ns time between two consecutive picosecond pulses are probablyat the origin of the high IRMPD performance of IR-FELs. Conversely,the OPO/OPA laser used here delivers nanosecond pulses, which is determinedby the Nd:YAG pulse length (∼5 ns). A typical pulse energyis 20–25 mJ, which is on the order of magnitude of an IR FELmacropulse energy (∼40 mJ). Lasers also differ by their bandwidth,which is controlled by the Nd:YAG pump (3–4 cmR (R = −ln[Iparent/(Iparent + ∑Ifragment)], where ln standsfor natural logarithm and Iparent and Ifragment are the intensities of the precursorand fragment ions, respectively)as a function of the wavenumber.52IRMPD spectra are obtained by plottingthe photofragmentation yield 3)2(H2O)(Met)]+ and [PtCl(NH3)(Met)]+ complexes, usingthe Multiple Minimum Monte Carlo (MMMC) method with AMBER FF, implementedin Macromodel 9.6.53 For each isomer, similarconformations were grouped into clusters and their representativestructures were minimized at the B3LYP/6-311+G level of theory,using the pseudopotential LANL2DZ for platinum. Then, a visual inspectionwas performed in order to devise additional conformers that mighthave escaped from the conformational search.A conformational search was performedfor both + were also computed at theωB97X-D/BS1//B3LYP/BS1level of theory to include the effect of long-range interactions inthe energetics.The relative energies of [PtCl(NH3)2(H2O)(Met)]+ and [PtCl(NH3)(Met)]+ complexes, in the 900–1900 and2900–3700 cm–1 ranges, were scaled by 0.974and 0.957, respectively.37Harmonic frequencies computed for [PtCl of 15 cmcis-[PtCl(NH3)2(H2O)]+, obtained by thefirst reactive event involving hydrolysis of cisplatin in aqueoussolution was found to yield the substitution product cis-[PtCl(NH3)2(Met)]+ when a 1:1 solutionof cisplatin and Met in 50% aqueous methanol was examined by ESI-MS.22 Both reactant and product ions were thoroughlycharacterized by IRMPD spectroscopy, and the cis-[PtCl(NH3)2(Met)]+ complex was found to largelyconform to a Met-S-ligated species.55 A preferentialattack to the S-site of methionine is in accordance with the metal“softness”. Sampling by ESI was then able to interceptthe transient charged complexes en route to the thermodynamicallyfavored chelate complexes. It is recognized that ligand replacementoccurs in solution by a multistep sequence outlined in 39 The firststep is a diffusion controlled entry of the incoming ligand L intothe second coordination sphere of the metal ion complex. The rate-limitingevent regards L/H2O (as in the present example) interchangebetween the two coordination spheres.The aqua complexof cisplatin, cis-[PtCl(NH3)2(H2O)]+·L}, although MS alone does not allow us to discriminatefrom an isomeric {cis-[PtCl(NH3)2(L)]+·H2O} species or even from a lesslikely five-coordinate complex. Henceforth it is thus referred toas generically [PtCl(NH3)2(H2O)(L)]+.ESI-MS delivers inthe gas phase and reveals the presence of ions formally correspondingto {Supporting Information, SI) displaysisotopic clusters congruent with cis-[PtCl(NH3)2(Met)]+ and [PtCl(NH3)2(H2O)(Met)]+ composition at m/z 412 and 430, respectively .Both ions have been assayed by IRMPD spectroscopy in the 900–1900cm–1 (IR fingerprint) and in the 3100–3700cm–1  ranges. 3)2(H2O)(Met)]+. The photofragmentation process occurs by parallel routesinvolving a loss of either Met or H2O, with the latterprocess partly accompanied by a subsequent loss of NH3,as displayed in Figure S2. The dissociationof [PtCl(NH3)2(H2O)(Met)]+ ions 2(H2O)]+·Met} complex,holding Met in the outer coordination sphere, while H2Oloss could reflect the external coordination of water, as in {cis-[PtCl(NH3)2(Met)]+·H2O}. However, this option is rather discarded in view of theIRMPD profile recorded along the two dissociation channels, as reportedin Figure S3, which do not seem to presentsignificant differences. In other words, both fragmentation routesare endured by the same species.The ESI mass spectrum of a cisplatin/Met solution]+ ions 2, followcis-[PtCl(NH3)2(Met)]+ ions, obtained by displacementby Met of the aqua ligandin cis-[PtCl(NH3)2(H2O)]+ ions, are characterized by the IRMPD spectrum depictedin trans-[PtCl(NH3)2(Met)]+ ions.22 The IRMPD process involves a loss of NH3, and the same cleavage occurs readily under collision induceddissociation, which has led to a proposal of the formation of a stablechelate complex.22 To gain structural information,the [PtCl(NH3)(Met)]+ complex, obtained by collisioninduced dissociation, was assayed by IRMPD spectroscopy . The slowed rate of multiple photon absorption by less active oscillatorsmay be counteracted by collisional deactivation. As a result, thephotoframentation process that needs to reach a relatively high-energythreshold is inhibited. This finding is well--documented to affectIRMPD spectroscopy.56troscopy 1C. This cis-[PtCl(NH3)2(H2O)(Met)]+ and [PtCl(NH3)(Met)]+ is due, to elucidate ion structures, onemay note common features in the three spectra displayed in –1 (compatible withO—H stretching) and a band at ca. 1750 cm–1 (in the C=O stretch range), which suggests the presence ofan unperturbed carboxylic group. Hence, the carbonyl group does notseem to be coordinated to the metal in any of the sampled species.While an analysis of theIRMPD spectra of cis-[PtCl(NH3)2(Met)]+ → [PtCl(NH3)(Met)]+ + NH3), the process may lead to ch1 and ch2 isomers depending on whether the precursoris an S- or N-ligated platinated methionine complex, respectively(Reasoning on a chelate complex formation as the outcomeof the second dissociation step in ectively2.cis-[PtCl(NH3)2(Met)]+ ion was found to largely consistof an S-platinated complex,22 so that theresulting chelate complexes are expected to belong mainly to the ch1 class. It is worthy of note that the observed cis-[PtCl(NH3)2(Met)]+ →[PtCl(NH3)(Met)]+ + NH3 process isa reactivity behavior specific of the unsolvated cis-[PtCl(NH3)2(Met)]+ complex. Inprotic solvent, ligand displacement preferentially involves chlorideas the leaving group. Furthermore, isomers ch1 and ch2 can exist as pairs of epimers, ch1_ss/ch1_sr and ch2_ss/ch2_sr, whereCα and S atoms are both chiral centers. While Cα is always in S configuration (l-methionine), the S atom can be in either R or S configuration, which leads to different stericstrain inferences.However, the monofunctional 2+ atoms. The relevantconformations are summarized in ch2_ss_b_1). As mentioned earlier, while Cα has an S configuration coming from l-methionine, the sulfuratom depending on the chelation reaction can be either S or R , S, and Ptr S or R 3, and foch1 and ch2 isomers. Their relative Gibbs energy (kJ mol–1) is reported in parentheses. An extended set of geometries lyingin low-energy minima is shown in Figure S5. The lowest Gibbs energy structure is ch2_ss_b-1, characterizedby a hydrogen bond linking C=O and NH2 groups ofthe amino acid ligand. The sulfur atom has S configuration,and consequently, the methyl group is in axial position.ch1 isomer, ch1_sr_b_1, is characterizedby CH3 in equatorial position with the Cl atom as the neighboringgroup, as shown in ch1_ss_b_3  is 5.0 kJ mol–1 higherin energy because of the repulsive interactions generated by the methylgroup in axial position.On the contrary, thelowest energy structure in the set of conformersof the ch2 isomers are generallylower in energy than the corresponding ch1 structures,indicating that the platinated complex is more stable when Cl, ratherthan NH3, is in a trans position to sulfur. Ch2_ss_b_1 and ch1_sr_b_1 isomers are characterizedby the COOH group in equatorial position, whereas the ch1_ss_a_2 isomer (Met)]+ generated by dissociation of cis-[PtCl(NH3)2(Met)]+ is reportedin ch1 and ch2 isomers. The 3100–3700 cm–1 range presentsa single absorption at 3563 cm–1, which can be accountedfor by the OH stretching of the methionine carboxylic group. The fingerprintregion (900–1900 cm–1) shows several features,with the most pronounced ones appearing at 1777, 1280, and 1148 cm–1.The IRMPD spectrum of + (Met)]+ 1.3)(Met)]+ is likely toreflect the isomeric distributionof the reactant complex, cis-[PtCl(NH3)2(Met)]+, which has already been experimentallyassessed.22 In particular, methionine bindingin the early monofunctional complex was found to involve almost exclusivelythe thioether function. Thus, the family of ch1 conformersshould be largely predominant in the chelate complex. This expectationis confirmed by experimental evidence. As a matter of fact, in spiteof being very similar, the calculated spectra of the most stable conformersof ch1 and ch2 (such as ch1_sr_b_1 and ch2_ss_b_1) show a few distinct differences inthe low wavenumber range, which can guide the attribution of the assayedion. The most notable difference is the NH3 umbrella mode,which is calculated at 1282 cm–1 for ch1_sr_b_1, in good agreement with the experiment, while in ch2_ss_b_1 it is blue-shifted at 1305 cm–1. The experimentalbands match fairly well with the calculated vibrational modes of ch1_sr_b_1 and ch1_ss_a_2, which are very closein energy (1.5 kJ mol–1) and pertain to the samefamily. It is reasonable that the assayed ion population comprisesboth of them. The assignment of the vibrational modes is reportedin Table S1 in the SI.Therefore, the assayed gas-phasepopulation of + ionsformed in the gas phase by the dissociation of unsolvated cis-[PtCl(NH3)2(Met)]+ complexesdisplay vibrational features consistent with a chelate complex derivedfrom an S-Met ligated precursor. Diastereomeric forms (SS and SR) likely coexist, depending on the chiralityof the coordinated thioether sulfur.It maythus be inferred that [PtCl(NHcis-[PtCl(NH3)2(Met)]+ reportedin previous work22 have provided the basisto obtain the starting geometries of the formal five-coordinate complexes,possibly responding to either {cis-[PtCl(NH3)2(H2O)]+·(Met)} or {cis-[PtCl(NH3)2Met]+·(H2O)}, indicated here as ec1 and ec2, respectively. The former complex is an aqua platinum complex witha Met molecule in outer coordination, while in the second one, Metentered the first coordination sphere and water is noncovalently boundon the periphery.The optimized structures of ec2-type ion to be thermodynamically favored,and the lowest energy structure is represented by ec2_1, where water is externally bound to cis-[PtCl(NH3)2(Met)]+ by means of two H bonds 2(L)(H2O)]+ complexes, where L is a simple ligand.38 In ec2_1, the COOH group is characterized by anti-geometry, allowing a hydrogen bond between the carboxylicH atom and the NH2 lone pair. A similar structure withCOOH in syn conformation, ec2_2, is5.5 kJ mol–1 higher in energy .This arrangement  complex) has been found to be thefavored one also in other examples of [PtCl(NHcis-[PtCl(NH3)2(H2O)]+·Met},wheremethionine is externally bound on the edge of the aqua complex, is ec1_1, placed at 52.2 kJ mol–1 Gibbs energyrelative to ec2_1 (cis-[PtCl(NH3)2(H2O)]+ by establishing two strong H-bonds with the water molecule,through the carbonyl oxygen and the nitrogen atoms. Moreover, an intramolecularhydrogen bond NH2···S is observed withinmethionine. Specifically, the H bond involving NH2 andthe water H atom is significantly strong (r = 1.42Å) with a consequent lengthening of the O–H bond (1.12Å). These values suggest that such an intermolecular hydrogenbond (O–H···NH2) may represent anexample of the so-called “hydrogen bridge”, where theH atom is shared and/or continuously transferred between two groups,57 leading to an equilibrium between {cis-[PtCl(NH3)2(H2O)]+·Met}and {cis-[PtCl(NH3)2(OH)]·MetH+}. It is found that the proton transfer can indeed occur,and the lowest energy structures of the corresponding isomers, ec1_2 and ec1_3, are only 0.7 and 1.5 kJ mol–1 higher in energy, respectively. In the presence ofa basic functional group the prototropic neutral form of the aquacomplex of cisplatin is obtained within the encounter complex,37 as verified here. One can speculate that theadduct of cisplatin aqua complex and externally coordinated Met isin fact a dynamically equilibrating mixture of {cis-[PtCl(NH3)2(H2O)]+·(Met)}and {cis-[PtCl(NH3)2(OH)]·(MetH+)} ions, where the two partners interact by a strong hydrogenbridge.The lowest energy geometry of {to ec2_1 6. In thiec1 familyof [PtCl(NH3)2(H2O)(Met)]+ complexes  lie at a relativelyhigher energy (>60 kJ mol–1 with respect to thereference ec2_1) and are not expected to contribute significantlyto the sampled population. An extended set of optimized structuresfor both ec1 and ec2 families of isomersis displayed in Figures S7 and S8. In spiteof specific search, no five-coordinate platinum complexes have beenfound lying in an energy minimum.Additional optimized structures for the 3)2(H2O)(Met)]+ ions was investigatedin order to unveil the structure of sampled complex, aiming to discriminatebetween an encounter complex on the reactant, {cis-[PtCl(NH3)2(H2O)]+·(Met)},or on the product, {cis-[PtCl(NH3)2(Met)]+·(H2O)}, side. To this end,the calculated IR spectra for the two isomer families ec2 and ec1 are examined against the experimental IRMPDspectrum. 3)2(H2O)(Met)]+ together with the calculated spectra of ec2_1, the lowest lying structure, and ec1_1, ec1_2, and ec1_3, the three most stable geometriesof the ec1 class. The large energy gap (52.2 kJ mol–1) between ec2_1 and ec1_1 is in agreement with the well-known bias for platinum binding tothio-containing nucleophiles.18 However, the relative thermodynamic stability may not predict whichof the two isomer families is actually present. In fact, as alreadyreported,38 the ESI process may not be able to deliver{cis-[PtCl(NH3)2(L)]+·(H2O)} like complexes in spite of them being generallylower in energy. The fragmentation pattern, privileging water loss,may reflect either the direct cleavage of noncovalently bound water(from an ec2 isomer) or the ligand replacement eventwithin vibrationally activated ec1 ions, followed byleaving group departure. As already underlined, both photofragmentationpaths arise from a single species or common mixture of isomers . Assaying [PtCl(NH3)2(H2O)(Met)]+ ions by IR spectroscopyis therefore mandatory to distinguish between ec2 and ec1 in order to comprehend the role of the sampled ion inthe line of events related to the interaction of cisplatin with methionine.TheIRMPD spectrum of + allowed by the analysisof the computational results thus points to an ion mixture comprising{cis-[PtCl(NH3)2(H2O)]+·(Met)} and {cis-[PtCl(NH3)2(HO)]·(MetH+)}. In any case,the noncovalent complex includes a cisplatin aqua complex associatedwith externally bound methionine. However, the most stable isomeris rather {cis-[PtCl(NH3)2(Met)]+·(H2O)}, and the question rises why this isnot the observed species. An insight into this issue is provided bythe energy profile for the ligand exchange reaction described in thefollowing paragraph.The interpretation of the IRMPD spectrum of [PtCl(NHcis-[PtCl(NH3)2(H2O)]+·(Met)}encounter complex of the reactant pair, namely, ec1_1. IRMPD spectroscopy has allowed us to clarify that this complex isprone to undergo ligand displacement when activated by multiple photonabsorption leading to the product {cis-[PtCl(NH3)2(Met)]+·(H2O)} complex(represented here by the lowest energy geometry of ec2_1) that promptly releases water. Thus, while recording the activevibrational frequencies, one also observes ligand exchange reactivity.The two encounter complexes are separated by an activation barrierof 71 kJ mol–1, corresponding to the relative enthalpyof the transition state depicted in Figure S10, in the transition state, the elongation of the H2O–Pt bond (2.41 Å) is assisted by a H-bond involvingthe amino group of Met (1.71 Å). An incipient S–Pt bond(2.85 Å) is simultaneously formed with an overall five-coordinategeometry at the metal center. The angle formed by the entering S–Pt-leavingOH2 (S–Pt–O) is 76.1°, in agreementwith a typical entering ligand–metal-leaving ligand angle (<90°).61 The Cartesian coordinates of the transition state are reported in Table S3. Note that, starting from the geometryof the encounter complex ec1_1, a reorientation of theMet side chain is needed for the sulfur atom to attack the metal centerand for displacing the water molecule. IRC calculations were performedto verify that the transition state structure is indeed connectedwith ec1-type (reactant) and ec2-type (product) minima. The correspondingoptimized geometries are given in Figure S11.In the calculated profile shown in cis-[PtCl(NH3)2(Met)]+·(H2O)} complex,in spite of being the most stable, is not in fact observed. The cis-[PtCl(NH3)2(Met)]+ ions,that are formed in solution and characterized in the gas-phase byIRMPD spectroscopy, are delivered by ESI due to progressive desolvation.However, the ESI conditions, promoting solvent departure, combinedwith the relatively low binding energy of water in this complex 2(Met)]+·(H2O)}. In contrast, the {cis-[PtCl(NH3)2(H2O)]+·(Met)}encounter complex lies in a fairly deep well relative to dissociationof the two partners (requiring 141 kJ mol–1) andit may thus be observed. The ligand substitution reaction in solutionis clearly not fast enough to turn all cisplatin aqua complexes inthe monofunctional Met derivative. Once delivered in the gas phaseand activated by multiple photon absorption (or else by collisioninduced dissociation), the {cis-[PtCl(NH3)2(H2O)]+·(Met)} encountercomplex undergoes ligand substitution, finally releasing water. Theend products are lower in energy than the transition state for liganddisplacement so that all complexes passing the activation barrierproceed to freely dissociate. At the same time, the high thresholdenergy for Met dissociation explains the highly unbalanced photofragmentationratio for Met versus H2O departure, which is consistentwith the behavior of comparable systems previously reported.38 Thus, the energy profile provides a neat account for the reactionoccurring in the naked encounter complex of the two partners as retrievedfrom solution.The energy profile may explainwhy the {3 departure 2(H2O)(Met)]+ composition has been unequivocallyassigned to the {cis-[PtCl(NH3)2(H2O)]+·(Met)} complex (rather than tothe {cis-[PtCl(NH3)2(Met)]+·(H2O)} isomer) and the [PtCl(NH3)(Met)]+ ion to a chelate complex deriving from the S-Metligated cis-[PtCl(NH3)2(Met)]+ intermediate. Vibrational excitation of the {cis-[PtCl(NH3)2(H2O)]+·(Met)}encounter complexes is found to activate the H2O/Met ligandexchange process rather than dissociation into the free reactant pair, cis-[PtCl(NH3)2(H2O)]+·Met. This finding is well-accounted for by the computedenergy profile. Finally, NH3 loss in the formation of the[PtCl(NH3)(Met)]+ chelate complex indicatesthat a low-polarity medium may significantly affect the process ofleaving group departure.The structure of the assayed intermediates has been obtainedbyIRMPD spectroscopy aided by the analysis of computed IR spectra forcandidate structures. By these means, the ion at