The experience of shared decision-making for people with asthma: A systematic review and metasynthesis of qualitative studies.

OBJECTIVES: To identify, describe and synthesise the views and experiences of adults living with asthma regarding shared decision-making (SDM) in the existing qualitative literature METHODS: We conducted a comprehensive search of 10 databases (list databases) from inception until September 2023. Screening was performed according to inclusion criteria. Tools from the Joanna Briggs lnstitute were utilised for the purposes of data extraction and synthesis in this study. The data extraction process in this study employed the Capability, Opportunity and Motivation Model of Behaviour (COM-B model) as a framework, and a pragmatic meta-aggregative approach was employed to synthesise the collected results. RESULTS: Nineteen studies were included in the metasynthesis. Three synthesised themes were identified: the capability of people living with asthma, the opportunities of people living with asthma in SDM, and the motivation of the people living with asthma in SDM. CONCLUSIONS: We have identified specific factors influencing people living with asthma engaging in SDM. The findings of this study can serve as a basis for the implementation of SDM in people living with asthma and provide insights for the development of their SDM training programs. The ConQual score for the synthesised findings was rated as low. To enhance confidence, future studies should address dependability and credibility factors. PRACTICE IMPLICATIONS: This review contemplates the implementation of SDM from the perspective of people living with asthma, with the aim of providing patient-centred services for them. The results of this review can benefit the implementation of SDM and facilitate information sharing. It offers guidance for SDM skills training among adults living with asthma, fosters a better doctor-patient relationship and facilitates consensus in treatment decisions, thereby enabling personalised and tailored medical care. PATIENT OR PUBLIC CONTRIBUTION: Three nursing graduate students participated in the data extraction and integration process, with two students having extensive clinical experience that provided valuable insights for the integration.

Self-management theories, models and frameworks in patients with chronic heart failure: A scoping review.

AIM: The aim of this study was to synthesize the self-management theory, model and frameworks of patients with chronic heart failure, focusing on construction process, methods and existing problems. BACKGROUND: Although the self-management theories have been created and verified for those patients with chronic heart failure, no reviews have been performed to integrate these theories. DESIGN: A scoping review of recent literature (without a date limit) was conducted. METHODS: A comprehensive literature search was performed. If the study reported the construction of a self-management theory, model or framework about chronic heart failure cases, it would be included in the review. RESULTS: Fourteen studies were included, which could be categorized into situation-specific theory, middle-range theory and other theory models (including conceptual model, hypothetic regression model and identity description model). It also includes the update and validation of theories, the situation-specific theoretical of caregiver contributions extended from situation-specific theories and the nurse-led situation-specific theory in different contexts. CONCLUSION: Self-management might contribute to start an education programme before patients with chronic heart failure (CHF) begin their chronic disease live as an individual. Our scoping review indicates that a series of self-management theories, models and frameworks for CHF patients have been developed, but more studies are still needed to validate and support these theories according to their cultural contexts.

Cas14a1-advanced LAMP for ultrasensitive and visual Pathogen diagnostic.

Clustered regularly interspaced short palindromic repeats (CRISPR)/Cas enzymes have been widely applied for biosensor development, combined with various isothermal amplification strategies (IAS) to boost sensitivity and specificity. Currently, the unstable assay and tedious manipulation usually hinder its practical applications. Here, a Cas14a1-advanced LAMP assay (CALA) combined with Rapid Extraction of Bacterial Genomic DNA (REBGD) is proposed for pathogen detection. For rapid CALA, a single stranded fluorescence reporter and ssDNA-gold nanoparticles (AuNPs) are used as signal indicators to establish ultrasensitive and visual platforms. This assay displays precise detection of bacteria, which can achieve an ultrasensitive limit of detection (LOD) 10 aM target genomic DNA. Furthermore, the high reliability of pathogen diagnostic for contrived samples is validated through the rapid visual CALA platform, demonstrating the promising practical testing availability of pathogen detection.

Nurse managers' perceptions and experiences of caring behavior for clinical nurses: a multicenter survey.

BACKGROUND: Humanistic care management is a necessary measure to improve the motivation and initiative of clinical nurses and is the foundation to improve the quality of nursing. Understanding the current status and identifying the influencing factors that promote or hinder humanistic care behaviors is essential. This study investigated the current status and experiences of nurse managers' caring behaviors toward clinical nurses. METHODS: We conducted a mixed-methods study with an explanatory sequential design. A survey on the nurse managers' caring behaviors in 101 hospitals from 23 provinces and four municipalities in China was investigated (n = 2022). Then, semi-structured interviews were conducted to obtain information about the participants' experiences associated with the performance of caring behaviors (n = 27). RESULTS: Survey data demonstrated that the nurse managers' overall caring behaviors were moderately good. The total scoring rate was 88.55%, and the overall score was 161.19 ± 20.68. Qualitative data revealed that the capacity of nurse managers and clinical nurses, opportunity, and motivation to implement humanistic care are key influencing factors of caring behaviors. CONCLUSIONS: The results suggested that intrinsic motivation, organizational support, and the humanistic care capabilities of clinical nurses and nurse managers are vital to implementing care behaviors. Thus, successful humanistic care management requires a concerted effort at the individual and organizational levels.

Immunogenicity and protective effects of recombinant bivalent COVID-19 vaccine in mice and rhesus macaques.

Coronavirus disease (COVID-19) is still spreading rapidly worldwide, and a safe, effective, and cheap vaccine is still required to combat the COVID-19 pandemic. Here, we report a recombinant bivalent COVID-19 vaccine containing the RBD proteins of the prototype strain and beta variant. Immunization studies in mice demonstrated that this bivalent vaccine had far greater immunogenicity than the ZF2001, a marketed monovalent recombinant protein COVID-19 vaccine, and exhibited good immunization effects against the original COVID-19 strain and various variants. Rhesus macaque challenge experiments showed that this bivalent vaccine drastically decreased the lung viral load and reduced lung lesions in SARS-CoV-2 (the causative virus of COVID-19)-infected rhesus macaques. In summary, this bivalent vaccine showed immunogenicity and protective efficacy that was far superior to the monovalent recombinant protein vaccine against the prototype strain and provided an important basis for developing broad-spectrum COVID-19 vaccines.

Enhancing the Production of Xenocoumacin 1 in Xenorhabdus nematophila CB6 by a Combinatorial Engineering Strategy.

Xenocoumacin 1 (Xcn1) is an excellent antimicrobial natural product against Phytophthora capsici. However, the commercial development of Xcn1 is hindered by the low yield, which results in high application costs. In this study, multiple metabolic strategies, including blocking the degradation pathway, promoter engineering, and deletion of competing biosynthetic gene clusters, were employed to improve the production of Xcn1, which was increased from 0.07 to 0.91 g/L. The formation of Xcn1 reached 1.94 g/L in the TB medium with the final strain T3 in a shake flask and further reached 3.52 g/L in a 5 L bioreactor, which is the highest yield ever reported. The engineered strain provides a valuable platform for production of Xcn1, and the possible commercial development of the biofungicide. We anticipate that the metabolic engineering strategies utilized in this study and the constructed constitutive promoter library can be widely applied to other bacteria of the genera Xenorhabdus and Photorhabdus.

Ligation-dependent Cas14a1-Activated biosensor for one-pot pathogen diagnostic.

Pathogen identification requires nucleic acid diagnosis with simple equipment and fast manipulation. Our work established an all-in-one strategy assay with excellent sensitivity and high specificity, Transcription-Amplified Cas14a1-Activated Signal Biosensor (TACAS), for the fluorescence-based bacterial RNA detection. The DNA as a promoter probe and a reporter probe directly ligated via SplintR ligase once specifically hybridized to the single-stranded target RNA sequence, with the ligation product transcribed into Cas14a1 RNA activators by T7 RNA polymerase. This forming sustained isothermal one-pot ligation-transcription cascade produced RNA activators constantly and enabled Cas14a1/sgRNA complex to generate fluorescence signal, thus leading to a sensitive detection limit of 1.52 CFU mL-1E. coli within 2 h of incubation time. TACAS was applied in contrived E. coli infected fish and milk samples, and a significant signal differentiation between positive (infected) and negative (uninfected) samples was reached. Meanwhile, E. coli colonization and transmit time in vivo were explored and the TACAS assay promoted the understanding of the infection mechanisms of the E. coli infection, demonstrating an excellent detection capability.

OsOLP1 contributes to drought tolerance in rice by regulating ABA biosynthesis and lignin accumulation.

Rice, as a major staple crop, employs multiple strategies to enhance drought tolerance and subsequently increase yield. Osmotin-like proteins have been shown to promote plant resistance to biotic and abiotic stress. However, the drought resistance mechanism of osmotin-like proteins in rice remains unclear. This study identified a novel osmotin-like protein, OsOLP1, that conforms to the structure and characteristics of the osmotin family and is induced by drought and NaCl stress. CRISPR/Cas9-mediated gene editing and overexpression lines were used to investigate the impact of OsOLP1 on drought tolerance in rice. Compared to wild-type plants, transgenic rice plants overexpressing OsOLP1 showed high drought tolerance with leaf water content of up to 65%, and a survival rate of 53.1% by regulating 96% stomatal closure and more than 2.5-fold proline content promotion through the accumulation of 1.5-fold endogenous ABA, and enhancing about 50% lignin synthesis. However, OsOLP1 knockout lines showed severely reduced ABA content, decreased lignin deposition, and weakened drought tolerance. In conclusion, the finding confirmed that OsOLP1 drought-stress modulation relies on ABA accumulation, stomatal regulation, proline, and lignin accumulation. These results provide new insights into our perspective on rice drought tolerance.

Nursing Home Residents' Perceptions of Challenges and Coping Strategies during COVID-19 Pandemic in China.

Older people in nursing homes are at a high risk of being infected by coronavirus disease 2019 (COVID-19). They also experienced nursing home lockdowns that harm their psychological wellbeing. Better support for this vulnerable population requires understanding their perceptions of challenges and coping strategies during the COVID-19 pandemic. A qualitative descriptive study was conducted using semi-structured interviews. Thematic analysis approach was used to analyze the data. Participants were recruited from six nursing homes in three cities in Hunan Province, China. Fourteen nursing home residents participated in the study. Four themes were identified from interviews and described as: mental stress and coping strategies, self-regulation to respond to lockdown, the lack of social connection and coping strategies, and the need for medical care services and coping strategies. This study revealed that nursing home residents perceived stress during the nursing home lockdown, but they reported initiating activities to maintain health and connections with their families and peers. Resilience improvement interventions are necessary to enable residents' autonomy and develop their resilience in coping with difficulties and hardship during crises. The findings also indicate that a supportive environment with interactions from families, peers, and staffs played a key role in enabling residents' positive health and wellbeing during the lockdown.

Chondroitin Sulfate/Dermatan Sulfate Hybrid Chains from Swim Bladder: Isolation, Structural Analysis, and Anticoagulant Activity.

Glycosaminoglycans (GAGs) with unique structures from marine animals show intriguing pharmacological activities and negligible biological risks, providing more options for us to explore safer agents. The swim bladder is a tonic food and folk medicine, and its GAGs show good anticoagulant activity. In this study, two GAGs, CMG-1.0 and GMG-1.0, were extracted and isolated from the swim bladder of Cynoscion microlepidotus and Gadus morhua. The physicochemical properties, precise structural characteristics, and anticoagulant activities of these GAGs were determined for the first time. The analysis results of the CMG-1.0 and GMG-1.0 showed that they were chondroitin sulfate (CS)/dermatan sulfate (DS) hybrid chains with molecular weights of 109.3 kDa and 123.1 kDa, respectively. They were mainly composed of the repeating disaccharide unit of -{IdoA-α1,3-GalNAc4S-ß1,4-}- (DS-A). The DS-B disaccharide unit of -{IdoA2S-α1,3-GalNAc4S-ß1,4-}- also existed in both CMG-1.0 and GMG-1.0. CMG-1.0 had a higher proportion of CS-O disaccharide unit -{-GlcA-ß1,3-GalNAc-ß1,4-}- but a lower proportion of CS-E disaccharide unit -{-GlcA-ß1,3-GalNAc4S6S-ß1,4-}- than GMG-1.0. The disaccharide compositions of the GAGs varied in a species-specific manner. Anticoagulant activity assay revealed that both CMG-1.0 and GMG-1.0 had potent anticoagulant activity, which can significantly prolong activated partial thromboplastin time. GMG-1.0 also can prolong the thrombin time. CMG-1.0 showed no intrinsic tenase inhibition activity, while GMG-1.0 can obviously inhibit intrinsic tenase with EC50 of 58 nM. Their significantly different anticoagulant activities may be due to their different disaccharide structural units and proportions. These findings suggested that swim bladder by-products of fish processing of these two marine organisms may be used as a source of anticoagulants.

Hrip1 mediates rice cell wall fortification and phytoalexins elicitation to confer immunity against Magnaporthe oryzae.

Magnaporthe oryzae is a potent fungus that adversely affects rice yield. Combinatorial techniques of prevention, toxic chemicals, and fungicide are used to remedy rice blast infection. We reported the role of Hrip1 in cell death elicitation and expression of systematic acquired resistance that could potentially stifle M. oryzae infection. In this study, transcriptome and metabolomic techniques were used to investigate the mechanism by which Hrip1 reprogramed the transcriptome of rice seedlings to confer immunity against M. oryzae. Our results showed that Hrip1 induces cell wall thickening and phytoalexin elicitation to confer immunity against M. oryzae infection. Hrip1 activates key lignin biosynthetic genes and myeloblastosis transcription factors that act as molecular switches for lignin production. Lignin content was increased by 68.46% and more after 48 h onwards in Hrip1-treated seedlings compared to the control treatment. Further analysis of cell wall morphology using the transmission electron microscopy technique revealed over 100% cell wall robustness. Hrip1 also induced the expression of 24 diterpene synthases. These include class I and II terpene synthases, cytochrome P450 subfamilies (OsCYP76M and OsCYP71Z), and momilactones synthases. The relationship between the expression of these genes and metabolic elicitation was analyzed using ultra-performance liquid chromatography-tandem mass spectrometry. Enhanced amounts of momilactones A and B, oryzalactone, and phytocassane A and G were detected in the Hrip1-treated leaves. We also identified seven benzoxazinoid genes (BX1-BX7) that could improve rice immunity. Our findings show that Hrip1 confers dual immunity by leveraging lignin and phytoalexins for physical and chemical resistance. This study provides novel insights into the mechanisms underlying Hrip1-treated plant immunity.

An Inverse Analysis for Establishing the Temperature-Dependent Thermal Conductivity of a Melt-Cast Explosive across the Whole Solidification Process.

Thermal conductivity is one of the most important thermophysical properties of a melt-cast explosive. However, the temperature-dependent thermal conductivity of such explosives cannot be easily measured across the whole solidification process (including the liquid, semi-solid, and solid states). This study used an inverse analysis method to estimate the temperature-dependent thermal conductivity of a 2,4-dinitroanisole/cyclotetramethylenetetranitramine (DNAN/HMX) melt-cast explosive in a continuous way. The method that was used is described here in detail, and it is verified by comparing the estimated thermal conductivity with a prespecified value using simulated measurement temperatures, thereby demonstrating its effectiveness. Combining this method with experimentally measured temperatures, the temperature-dependent thermal conductivity of the DNAN/HMX melt-cast explosive was obtained. Some measured thermal conductivity values for this explosive in the solid state were used for further validation.

Ethylene-responsive factor ERF114 mediates fungal pathogen effector PevD1-induced disease resistance in Arabidopsis thaliana.

APETALA2/ethylene-responsive factor (AP2/ERF) family transcription factors are well-documented in plant responses to a wide range of biotic and abiotic stresses, but their roles in mediating elicitor-induced disease resistance remains largely unexplored. PevD1 is a Verticillium dahliae secretory effector that can induce disease resistance in cotton and tobacco plants. In our previous work, Nicotiana benthamiana ERF114 (NbERF114) was identified in a screen of genes differentially expressed in response to PevD1 infiltration. Here, we found that the ortholog of NbERF114 in Arabidopsis thaliana (ERF114) also strongly responded to PevD1 treatment and transcripts were induced by Pseudomonas syringae pv. tomato (Pst) DC3000 infection. Loss of ERF114 function caused impaired disease resistance, while overexpressing ERF114 (OE-ERF114) enhanced resistance to Pst DC3000. Moreover, ERF114 mediated PevD1-induced disease resistance. RNA-sequencing analysis revealed that the transcript level of phenylalanine ammonia-lyase1 (PAL1) and its downstream genes were significantly suppressed in erf114 mutants compared with A. thaliana Col-0. Reverse transcription-quantitative PCR (RT-qPCR) analysis further confirmed that the PAL1 mRNA level was significantly elevated in overexpressing OE-ERF114 plants but reduced in erf114 mutants compared with Col-0. Chromatin immunoprecipitation-qPCR (ChIP-qPCR) and electrophoretic mobility shift assay verified that ERF114 directly bound to the promoter of PAL1. The gene expression profiles of ERF114 and PAL1 in oestradiol-inducible transgenic plants confirmed ERF114 could activate PAL1 transcriptional expression. Further investigation revealed that ERF114 positively modulated PevD1-induced lignin and salicylic acid accumulation, probably by activating PAL1 transcription.

DEVELOPMENT AND VALIDATION OF AN EXPLAINABLE ARTIFICIAL INTELLIGENCE FRAMEWORK FOR MACULAR DISEASE DIAGNOSIS BASED ON OPTICAL COHERENCE TOMOGRAPHY IMAGES.

PURPOSE: To develop and validate an artificial intelligence framework for identifying multiple retinal lesions at image level and performing an explainable macular disease diagnosis at eye level in optical coherence tomography images. METHODS: A total of 26,815 optical coherence tomography images were collected from 865 eyes, and 9 retinal lesions and 3 macular diseases were labeled by ophthalmologists, including diabetic macular edema and dry/wet age-related macular degeneration. We applied deep learning to classify retinal lesions at image level and random forests to achieve an explainable disease diagnosis at eye level. The performance of the integrated two-stage framework was evaluated and compared with human experts. RESULTS: On testing data set of 2,480 optical coherence tomography images from 80 eyes, the deep learning model achieved an average area under curve of 0.978 (95% confidence interval, 0.971-0.983) for lesion classification. In addition, random forests performed accurate disease diagnosis with a 0% error rate, which achieved the same accuracy as one of the human experts and was better than the other three experts. It also revealed that the detection of specific lesions in the center of macular region had more contribution to macular disease diagnosis. CONCLUSION: The integrated method achieved high accuracy and interpretability in retinal lesion classification and macular disease diagnosis in optical coherence tomography images and could have the potential to facilitate the clinical diagnosis.

Pseudomonas syringae activates ZAT18 to inhibit salicylic acid accumulation by repressing EDS1 transcription for bacterial infection.

Phytopathogens can manipulate plant hormone signaling to counteract immune responses; however, the underlying mechanism is mostly unclear. Here, we report that Pseudomonas syringae pv tomato (Pst) DC3000 induces expression of C2H2 zinc finger transcription factor ZAT18 in a jasmonic acid (JA)-signaling-dependent manner. Biochemical assays further confirmed that ZAT18 is a direct target of MYC2, which is a very important regulator in JA signaling. CRISPR/Cas9-generated zat18-cr mutants exhibited enhanced resistance to Pst DC3000, while overexpression of ZAT18 resulted in impaired disease resistance. Genetic characterization of ZAT18 mutants demonstrated that ZAT18 represses defense responses by inhibiting the accumulation of the key plant immune signaling molecule salicylic acid (SA), which is dependent on its EAR motif. ZAT18 exerted this inhibitory effect by directly repressing the transcription of Enhanced Disease Susceptibility 1 (EDS1), which is the key signaling component of pathogen-induced SA accumulation. Overexpression of ZAT18 resulted in decreased SA content, while loss of function of ZAT18 showed enhanced SA accumulation upon pathogen infection. Furthermore, enhanced resistance and SA content in zat18-cr mutants was abolished by the mutation in EDS1. Our data indicate that pathogens induce ZAT18 expression to repress the transcription of EDS1, further antagonising SA accumulation for bacterial infection.

The Effects of Diosgenin on Hypolipidemia and Its Underlying Mechanism: A Review.

Hyperlipidemia is a disorder of lipid metabolism, which is a major cause of coronary heart disease. Although there has been considerable progress in hyperlipidemia treatment, morbidity and risk associated with the condition continue to rise. The first-line treatment for hyperlipidemia, statins, has multiple side effects; therefore, development of safe and effective drugs from natural products to prevent and treat hyperlipidemia is necessary. Diosgenin is primarily derived from fenugreek (Trigonella foenum graecum) seeds, and is also abundant in medicinal herbs such as Dioscorea rhizome, Dioscorea septemloba, and Rhizoma polygonati, is a well-known steroidal sapogenin and the active ingredient in many drugs to treat cardiovascular conditions. There is abundant evidence that diosgenin has potential for application in correcting lipid metabolism disorders. In this review, we evaluated the latest evidence related to diosgenin and hyperlipidemia from clinical and animal studies. Additionally, we elaborate the pharmacological mechanism underlying the activity of diosgenin in treating hyperlipidemia in detail, including its role in inhibition of intestinal absorption of lipids, regulation of cholesterol transport, promotion of cholesterol conversion into bile acid and its excretion, inhibition of endogenous lipid biosynthesis, antioxidation and lipoprotein lipase activity, and regulation of transcription factors related to lipid metabolism. This review provides a deep exploration of the pharmacological mechanisms involved in diosgenin-hyperlipidemia interactions and suggests potential routes for the development of novel drug therapies for hyperlipidemia.

Risk Stratification Tool for Ischemic Stroke: A Risk Assessment Model Based on Traditional Risk Factors Combined With White Matter Lesions and Retinal Vascular Caliber.

Objective: This study aims to establish a risk assessment model based on traditional risk factors combined with the Fazekas classification of white matter lesions and retinal vascular caliber for screening the patients at high risk of ischemic stroke. Methods: This study included 296 patients (128 cases of ischemic stroke and 168 cases in the normal control group). The basic data of the patients were collected. Color fundus photography was performed after pupil dilation, and the retinal vascular caliber was measured using semiautomated vascular measurement software (IVAN Software, Sydney, Australia). The severity of white matter lesions (WML) on cranial nuclear magnetic fluid-attenuated inversion recovery images were assessed using the Fazekas scale. Moreover, logistic regression analysis was used to establish different risk assessment models for ischemic stroke. The effects of models were evaluated through the receiver operating characteristic (ROC) curve and the Delong test compared area under the curve. Results: The sensitivity and specificity of models 1 (the traditional risk factor model), 2 (the retinal vascular caliber model), 3 (the WML model), and 4 (the combined the traditional risk factor, WML and central retinal artery equivalent (CRAE) model) were 71 and 55%, 48 and 71%, 49 and 67%, and 68 and 68.5% with areas under the curve of 0.658, 0.586, 0.601, and 0.708, respectively. The area under the receiver operating characteristic curve in models 1, 2, 3, and 4 showed statistically significant differences. Moreover, no statistical significance exists in the pairwise comparison of other models. Conclusion: The risk assessment model of ischemic stroke combined with Fazekas grade of WML and CRAE is superior to the traditional risk factor and the single-index model. This model is helpful for risk stratification of high-risk stroke patients.

Verticillium dahliae secretory effector PevD1 induces leaf senescence by promoting ORE1-mediated ethylene biosynthesis.

Leaf senescence, the final stage of leaf development, is influenced by numerous internal and environmental signals. However, how biotic stresses such as pathogen infection regulate leaf senescence remains largely unclear. In this study, we found that the premature leaf senescence in Arabidopsis caused by the soil-borne vascular fungus Verticillium dahliae was impaired by disruption of a protein elicitor from V. dahliae 1 named PevD1. Constitutive or inducible overexpression of PevD1 accelerated Arabidopsis leaf senescence. Interestingly, a senescence-associated NAC transcription factor, ORE1, was targeted by PevD1. PevD1 could interact with and stabilize ORE1 protein by disrupting its interaction with the RING-type ubiquitin E3 ligase NLA. Mutation of ORE1 suppressed the premature senescence caused by overexpressing PevD1, whereas overexpression of ORE1 or PevD1 led to enhanced ethylene production and thereby leaf senescence. We showed that ORE1 directly binds the promoter of ACS6 and promotes its expression for mediating PevD1-induced ethylene biosynthesis. Loss-of-function of ACSs could suppress V. dahliae-induced leaf senescence in ORE1-overexpressing plants. Furthermore, we found thatPevD1 also interacts with Gossypium hirsutum ORE1 (GhORE1) and that virus-induced gene silencing of GhORE1 delays V. dahliae-triggered leaf senescence in cotton, indicating a possibly conserved mechanism in plants. Taken together, these results suggest that V. dahliae induces leaf senescence by secreting the effector PevD1 to manipulate the ORE1-ACS6 cascade, providing new insights into biotic stress-induced senescence in plants.

Effect of Mixed Recycled Aggregate on the Mechanical Strength and Microstructure of Concrete under Different Water Cement Ratios.

Mixed recycled aggregate (MRA) is a kind of recycled aggregate containing discarded bricks and other impurities that is inferior to ordinary recycled concrete aggregate. To study the effect of MRA in concrete, specimens with 100% MRA under different water-cement ratios (W/C) of 0.50, 0.42, 0.36 and 0.30 were prepared, and the mechanical properties and microstructure were tested. Results show that compared with ordinary concrete, the compressive strength of mixed recycled aggregate concrete (MRAC) with the same W/C was reduced by more than 50% at 28 days, but the axial compression ratio was relatively high, reaching over 0.87. Affected by the high water absorption of MRA, the hydration rate of cement slowed, which was beneficial to the long-term development of the properties of MRAC. An appropriate increase in cement content could strengthen MRA and densify the pore structure of MRAC. The research results of this article prove that MRA has high utilization value and could be used to prepare MRAC with application potential using optimal gradation, which is of positive significance for promoting the consumption of construction waste.