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OBJECTIVES: To investigate the clinical characteristics and prognosis of pneumococcal meningitis (PM), and drug sensitivity of Streptococcus pneumoniae (SP) isolates in Chinese children. METHODS: A retrospective analysis was conducted on clinical information, laboratory data, and microbiological data of 160 hospitalized children under 15 years old with PM from January 2019 to December 2020 in 33 tertiary hospitals across the country. RESULTS: Among the 160 children with PM, there were 103 males and 57 females. The age ranged from 15 days to 15 years, with 109 cases (68.1%) aged 3 months to under 3 years. SP strains were isolated from 95 cases (59.4%) in cerebrospinal fluid cultures and from 57 cases (35.6%) in blood cultures. The positive rates of SP detection by cerebrospinal fluid metagenomic next-generation sequencing and cerebrospinal fluid SP antigen testing were 40% (35/87) and 27% (21/78), respectively. Fifty-five cases (34.4%) had one or more risk factors for purulent meningitis, 113 cases (70.6%) had one or more extra-cranial infectious foci, and 18 cases (11.3%) had underlying diseases. The most common clinical symptoms were fever (147 cases, 91.9%), followed by lethargy (98 cases, 61.3%) and vomiting (61 cases, 38.1%). Sixty-nine cases (43.1%) experienced intracranial complications during hospitalization, with subdural effusion and/or empyema being the most common complication [43 cases (26.9%)], followed by hydrocephalus in 24 cases (15.0%), brain abscess in 23 cases (14.4%), and cerebral hemorrhage in 8 cases (5.0%). Subdural effusion and/or empyema and hydrocephalus mainly occurred in children under 1 year old, with rates of 91% (39/43) and 83% (20/24), respectively. SP strains exhibited complete sensitivity to vancomycin (100%, 75/75), linezolid (100%, 56/56), and meropenem (100%, 6/6). High sensitivity rates were also observed for levofloxacin (81%, 22/27), moxifloxacin (82%, 14/17), rifampicin (96%, 25/26), and chloramphenicol (91%, 21/23). However, low sensitivity rates were found for penicillin (16%, 11/68) and clindamycin (6%, 1/17), and SP strains were completely resistant to erythromycin (100%, 31/31). The rates of discharge with cure and improvement were 22.5% (36/160) and 66.2% (106/160), respectively, while 18 cases (11.3%) had adverse outcomes. CONCLUSIONS: Pediatric PM is more common in children aged 3 months to under 3 years. Intracranial complications are more frequently observed in children under 1 year old. Fever is the most common clinical manifestation of PM, and subdural effusion/emphysema and hydrocephalus are the most frequent complications. Non-culture detection methods for cerebrospinal fluid can improve pathogen detection rates. Adverse outcomes can be noted in more than 10% of PM cases. SP strains are high sensitivity to vancomycin, linezolid, meropenem, levofloxacin, moxifloxacin, rifampicin, and chloramphenicol.
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Empiema , Hidrocefalia , Meningitis Neumocócica , Efusión Subdural , Lactante , Femenino , Masculino , Humanos , Niño , Recién Nacido , Adolescente , Meningitis Neumocócica/tratamiento farmacológico , Meningitis Neumocócica/epidemiología , Meropenem , Vancomicina , Levofloxacino , Linezolid , Moxifloxacino , Estudios Retrospectivos , Rifampin , Streptococcus pneumoniae , CloranfenicolRESUMEN
BACKGROUND: Dysphagia is a common symptom seen in stroke patients, it not only affects patients' nutrition supply, but also causes aspiration pneumonia. To solve the problem of nutritional support for patients with dysphagia after stroke, nasogastric tubes are routinely indwelling to provide nutrition in China. However, this feeding method sometimes causes food reflux, aspiration, pneumonia, and often affects the patients' comfort and self-image acceptance. AIM: The aim of this study was to determine whether a new feeding method called intermittent oroesophageal (IOE) tube feeding compared with continuous nasogastric tube feeding as a practical and beneficial mean of decreasing the rate of stroke associated pneumonia (SAP), and improving patients' swallowing function, comfort, psychological status. DESIGN: This was an assessor-blinded, single-center, randomized controlled trial. METHODS: Ninety-seven hospitalized stroke patients with dysphagia in the rehabilitation department from January to December 2018 were randomized to a control group and an intervention group. Patients in both groups received routine nursing, rehabilitation treatment and swallowing therapy. Patients in the intervention group were given IOE tube feeding, while those in the control group were fed by indwelling nasogastric tube. Outcomes were assessed at admission, discharge or the end of the tube feeding. RESULTS: The incidence of SAP in the intervention group was 16.33% lower than that (31.25%) in the control group; the comfort score (2.08 ± .64), anxiety score (10.98 ± 2.28), depression score (7.39 ± 2.16) were lower than those (3.02 ± .70), (12.10 ± 2.18), (8.42 ± 2.34) in the control group. The improvement rate of swallowing function in the intervention group was 83.67% higher than that (66.67%) in the control group (all P < .05). CONCLUSIONS: The IOE tube feeding compared with continuous tube feeding may reduce the incidence of SAP, and improve patients' swallowing function, comfort, psychological status in patients with dysphagia after stroke.
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Trastornos de Deglución/terapia , Deglución , Nutrición Enteral/métodos , Estado Nutricional , Neumonía por Aspiración/prevención & control , Rehabilitación de Accidente Cerebrovascular/métodos , Accidente Cerebrovascular/terapia , Anciano , China , Trastornos de Deglución/diagnóstico , Trastornos de Deglución/etiología , Trastornos de Deglución/fisiopatología , Nutrición Enteral/efectos adversos , Femenino , Estado de Salud , Humanos , Masculino , Salud Mental , Persona de Mediana Edad , Neumonía por Aspiración/diagnóstico , Neumonía por Aspiración/etiología , Neumonía por Aspiración/fisiopatología , Recuperación de la Función , Factores de Riesgo , Accidente Cerebrovascular/complicaciones , Accidente Cerebrovascular/diagnóstico , Accidente Cerebrovascular/fisiopatología , Rehabilitación de Accidente Cerebrovascular/efectos adversos , Factores de Tiempo , Resultado del TratamientoRESUMEN
An enantioselective [4 + 1] cycloaddition reaction of ortho-quinone methides and bromomalonates using a quinine and BINOL derived phase-transfer catalyst is described. With high yields and enantioselectivities, the method provided a variety of optically active dihydrobenzofurans, which represent a valuable structural motif present in numerous naturally occurring and biologically active molecules.
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Indolquinonas/química , Indolquinonas/síntesis química , Malonatos/química , Malonatos/síntesis química , Catálisis , Reacción de Cicloadición , EstereoisomerismoRESUMEN
The ratio of intercellular to ambient CO2 concentrations (c i/c a) plays a key role in ecophysiology, micrometeorology, and global climatic change. However, systematic investigation on c i/c a variation and its determinants are rare. Here, the c i/c a was derived from measuring ecosystem fluxes in an even-aged monoculture of rubber trees (Hevea brasiliensis). We tested whether c i/c a is constant across environmental gradients and if not, which dominant factors control c i/c a variations. Evidence indicates that c i/c a is not a constant. The c i/c a exhibits a clear "V"-shaped diurnal pattern and varies across the environmental gradient. Water vapor pressure deficit (D) is the dominant factor controls over the c i/c a variations. c i/c a consistently decreases with increasing D. c i/c a decreases with square root of D as predicted by the optimal stomatal model. The D-driving single-variable model could simulate c i/c a as well as that of sophisticated model. Many variables function on longer timescales than a daily cycle, such as soil water content, could improve c i/c a model prediction ability. Ecosystem flux can be effectively used to calculate c i/c a and use it to better understand various natural cycles.
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Dióxido de Carbono/análisis , Ecosistema , Hevea/metabolismo , Luz , Modelos Teóricos , Fotosíntesis , Hojas de la Planta/metabolismo , Presión de VaporRESUMEN
A highly enantioselective allylic C-H alkylation reaction of allylarenes with pyrazol-5-ones has been established by the cooperative catalysis of a chiral palladium complex and chiral Brønsted acid to afford a wide spectrum of functionalized chiral N-heterocycles with an all-carbon quaternary stereogenic center in high yields and with high levels of enantioselectivity (up to 96% ee), wherein the chiral ligand and phosphoric acid showed synergistic effect on the control of stereoselectivity. In addition, a palladium-catalyzed asymmetric allylic C-H alkylation of 1,4-pentadienes with pyrazol-5-ones has been realized to furnish highly functionalized pyrazol-5-ones in high enantioselectivities. In this case, the chiral ligand controls the stereoselectivity while the achiral Bronsted acid, 2-fluorobenzoic acid, turns out to be a better cocatalyst than the chiral phosphoric acid. The installation of electron-deficient substituents at 3,3'-positions of binaphthyl backbone of chiral phosphoramidites is actually beneficial to the allylic C-H oxidation due to their survival in the presence of quinone derivative oxidants. These allylic C-H alkylation reactions undergo smoothly under mild conditions and tolerate a wide range of substrates. The resultant highly functionalized chiral pyrazol-5-ones have been applied to the preparation of more structurally diverse heterocycles by classical transformations.
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The underlying mechanism of gemcitabine resistance during breast cancer treatment remains unclear. Glucose regulated protein 78 (GRP78) frequently triggered by anticancer agents, was substantially elevated in gemcitabine resistant sublines. Ectopic expression of GRP78 changes gemcitabine chemosensitivity and apoptosis levels in breast cancer cells. Further experiments showed an involvement of caspase 9, not caspase 8, in gemcitabine resistance and GRP78-mediated chemosensitivity, suggesting that mitochondria apoptotic pathway was activated by GRP78. This finding was further supported by the observations of AKT activation, Bcl-2 increase, Bax and Bim decrease. Conclusively, GRP78 plays a vital role in gemcitabine resistance and clinical strategy to improve gemcitabine efficacy in breast cancer by manipulating GRP78 should be explored.
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Apoptosis , Neoplasias de la Mama/tratamiento farmacológico , Neoplasias de la Mama/metabolismo , Desoxicitidina/análogos & derivados , Proteínas de Choque Térmico/metabolismo , Proteínas Proto-Oncogénicas c-akt/metabolismo , Antimetabolitos Antineoplásicos/administración & dosificación , Neoplasias de la Mama/patología , Desoxicitidina/administración & dosificación , Relación Dosis-Respuesta a Droga , Chaperón BiP del Retículo Endoplásmico , Humanos , Células MCF-7 , Mitocondrias/efectos de los fármacos , Mitocondrias/metabolismo , Transducción de Señal/efectos de los fármacos , GemcitabinaRESUMEN
Acquisition of gemcitabine resistance in breast cancer has not been fully clarified. Prior studies suggest that miRNAs are important to chemoresistance in solid tumors and we confirmed that miR-21 is involved in the development of gemcitabine resistance. Epithelial-to-mesenchymal transition (EMT) and AKT pathway activation were noted to be important to this resistance as well. PTEN, a direct target gene of miR-21, was significantly downregulated in gemcitabine-resistant breast cancer cells and restoration of PTEN expression blocked miR-21-induced EMT and gemcitabine resistance. Our data offer novel insight into gemcitabine resistance in breast cancer and suggest that miR-21 may be used to predict optimal breast cancer therapy and may be a potential therapeutic target for reversing gemcitabine resistance.
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Antimetabolitos Antineoplásicos/farmacología , Neoplasias de la Mama/patología , Desoxicitidina/análogos & derivados , Resistencia a Antineoplásicos/genética , Transición Epitelial-Mesenquimal/genética , MicroARNs/metabolismo , Animales , Antimetabolitos Antineoplásicos/uso terapéutico , Neoplasias de la Mama/tratamiento farmacológico , Línea Celular Tumoral , Movimiento Celular , Desoxicitidina/farmacología , Desoxicitidina/uso terapéutico , Regulación hacia Abajo/genética , Femenino , Regulación Neoplásica de la Expresión Génica , Humanos , Células MCF-7 , Ratones , Ratones Endogámicos BALB C , Ratones Desnudos , MicroARNs/antagonistas & inhibidores , Fosfohidrolasa PTEN/fisiología , Proteínas Proto-Oncogénicas c-akt/fisiología , ARN Neoplásico , ARN Interferente Pequeño/genética , Transducción de Señal , Ensayos Antitumor por Modelo de Xenoinjerto , GemcitabinaRESUMEN
A highly selective multicomponent carbonyl allylation reaction of 1,3-butadienes, aryldiazonium tetrafluoroborates, and aldehydes has been established under the combined catalysis of palladium acetate and chiral anion phase transfer to render the favorable assembly of chiral Z-configured homoallylic alcohols in high yields and with excellent levels of enantioselectivity.
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A highly diastereoselective Pd-catalyzed carbonyl allylation of aldehydes and isatins directly using simple acyclic olefins as allylating reagents is described. This transformation is actually a sequential process consisting of a Pd-catalyzed oxidative allylic C-H borylation and an allylboration of carbonyls accelerated by phosphoric acid, wherein a wide scope of olefins could be tolerated. The oxidant is revealed to play a key role in the successful realization of the allylic C-H activation-based allylation.
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2-Amino-3-cyano-4H-chromenes show great potential as novel anticancer agents. Here we report a quinine-catalyzed highly enantioselective formal 4 + 2 cycloaddition of ortho-quinone methides and malononitrile, providing a unique approach to 4-arylvinyl, 4-aryl and 4-vinyl 2-amino-3-cyano-4H-chromenes with excellent yields and enantioselectivities. Moreover, this reaction can be performed in up to 6 mmol scale without any noticeable loss of yield and stereoselectivity.
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Benzopiranos/síntesis química , Indolquinonas/química , Nitrilos/química , Quinina/química , Benzopiranos/química , Catálisis , Ciclización , Estructura Molecular , EstereoisomerismoRESUMEN
The effect of blend ratio and pH on the physical properties of surimi-gelatin composite films was investigated. Tensile strength (TS), film water solubility and soluble proteins of composite films increased with the increasing proportion of gelatin, while elongation at break (EAB) decreased. The TS of neutral films with the same ratio of surimi and gelatin were lowest, while increased at acidic or alkaline conditions. Similar tendency was also found in protein solubility and surface hydrophobicity of the film-forming solutions. On the other hand, the film water solubility and soluble proteins of neutral composite films were higher than those of acidic and alkaline films. Furthermore, it was revealed that the dissolved surimi and gelatin proteins could form strong composite films, which were insoluble in water. These results suggested that dissolved proteins were mainly involved in the formation of surimi-gelatin composite films.
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Previous research showed that microRNA-612 (miR-612) has inhibitory effects on cell proliferation, migration, invasion, and metastasis of hepatocellular carcinoma (HCC). AKT2 was confirmed to be a direct target of miR-612, through which the epithelial-mesenchymal transition (EMT) and metastasis of HCC were inhibited. Our present findings reveal that miR-612 is able to suppress the stemness of HCC by reducing the number and size of tumorspheres as well as clone formation in soft agar, and to relieve drug resistance to cisplatin and 5-fluorouracil. In addition, miR-612 hampered the capacity of tumorigenesis in NOD/SCID mice and redistributed the tumor invasive frontier of miR-612-modulating cells. Finally, our findings suggest that Wnt/ß-catenin signaling is required in the regulation of EMT-associated stem cell-like traits by miR-612.
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Carcinoma Hepatocelular/patología , Transición Epitelial-Mesenquimal/efectos de los fármacos , Neoplasias Hepáticas/patología , MicroARNs/fisiología , Células Madre Neoplásicas/efectos de los fármacos , Animales , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Cisplatino/farmacología , Resistencia a Antineoplásicos/efectos de los fármacos , Fluorouracilo/farmacología , Células Hep G2 , Humanos , Masculino , Ratones , Ratones Endogámicos NOD , Ratones SCID , Invasividad Neoplásica/prevención & control , Trasplante de Neoplasias , Células Madre Neoplásicas/fisiología , Vía de Señalización Wnt/fisiología , beta Catenina/efectos de los fármacos , beta Catenina/fisiologíaRESUMEN
While surfactants are widely used in phosphogypsum, their interactions with the phosphogypsum-water interface remain unclear. This study investigates the impact of three types of surfactants, namely polycarboxylate-based surfactant (PCE-TPEG), naphthalene-based surfactant (NS), and melamine-based surfactant (MS), on the performance of phosphorus building gypsum (PBG). Additionally, a nanoscale model of the PBG-surfactant-water interface is constructed using molecular dynamics to elucidate the mechanisms underlying the interaction between different surfactants and PBG at multiple scales. The results demonstrate that all surfactants enhance the mechanical properties of PBG. PCE-TPEG exhibits the most pronounced improvement. In the model, PCE-TPEG molecules likely undergo comb-like adsorption, while NS and MS molecules tend to adsorb on both ends of the crystal plane. Changes in the potential difference between CaSO4·2H2O and H2O, as well as between CaSO4·2H2O and the surfactant, play a crucial role in adsorption. PCE-TPEG, NS, and MS molecules tend to spread horizontally in a vacuum state. With the addition of water molecules, they transition to spatial adsorption. Ca2+ easily interacts with -COO- and -SO3- groups, leading to reduced migration and flexibility of the main chain. The adsorption process of surfactants at the gypsum-water interface occurs spontaneously and Electrostatic forces are the main driving factor. This study contributes to a more comprehensive understanding on the behaviour of the phosphorus building gypsum/surfactant composites.
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Sulfato de Calcio , Tensoactivos , Tensoactivos/química , Simulación de Dinámica Molecular , Agua/química , FósforoRESUMEN
BACKGROUND: Brucellosis is a severe zoonotic disease that is often overlooked, particularly in impoverished countries. Timely identification of focal complications in brucellosis is crucial for improving treatment outcomes. However, there is currently a lack of established indicators or biomarkers for diagnosing these complications. Therefore, this study aimed to investigate potential warning signs of focal complications in human brucellosis, with the goal of providing practical parameters for clinicians to aid in the diagnosis and management of patients. METHODS: A multi-center cross-sectional study was conducted in China from December 2019 to August 2021. The study aimed to investigate the clinical characteristics and complications of patients with brucellosis using a questionnaire survey and medical record system. The presence of warning signs for complications was assessed using univariate and multivariate logistic regression models. Receiver operating characteristic (ROC) curves and the area under the curve (AUC) were used for variable screening and model evaluation. RESULTS: A total of 880 participants diagnosed with human brucellosis were enrolled. The median age of the patients was 50 years [interquartile range (IQR): 41.5-58.0], and 54.8% had complications. The most common organ system affected by complications was the osteoarticular system (43.1%), with peripheral arthritis (30.0%), spondylitis (16.6%), paravertebral abscess (5.0%), and sacroiliitis (2.7%) being the most prevalent. Complications in other organ systems included the genitourinary system (4.7%), respiratory system (4.7%), and hematologic system (4.6%). Several factors were found to be associated with focal brucellosis. These factors included a long delay in diagnosis [odds ratio (OR) = 3.963, 95% confidence interval (CI) 1.906-8.238 for > 90 days], the presence of underlying disease (OR = 1.675, 95% CI 1.176-2.384), arthralgia (OR = 3.197, 95% CI 1.986-5.148), eye bulging pain (OR = 3.482, 95% CI 1.349-8.988), C-reactive protein (CRP) > 10 mg/L (OR = 1.910, 95% CI 1.310-2.784) and erythrocyte sedimentation rate (ESR) elevation (OR = 1.663, 95% CI 1.145-2.415). The optimal cutoff value in ROC analysis was > 5.4 mg/L for CRP (sensitivity 73.4% and specificity 51.9%) and > 25 mm/h for ESR (sensitivity 47.9% and specificity 71.1%). CONCLUSIONS: More than 50% of patients with brucellosis experienced complications. Factors such as diagnostic delay, underlying disease, arthralgia, eye pain, and elevated levels of CRP and ESR were identified as significant markers for the development of complications. Therefore, patients presenting with these conditions should be closely monitored for potential complications, regardless of their culture results and standard tube agglutination test titers.
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Brucelosis , Diagnóstico Tardío , Humanos , Persona de Mediana Edad , Artralgia/complicaciones , Brucelosis/complicaciones , Brucelosis/diagnóstico , Brucelosis/epidemiología , Proteína C-Reactiva/análisis , Proteína C-Reactiva/metabolismo , Estudios Transversales , Incidencia , Estudios Retrospectivos , AdultoRESUMEN
Endothelial cells (ECs) are critical for angiogenesis, and microRNAs play important roles in this process. We investigated the regulatory role of microRNAs in ECs of hepatocellular carcinoma (HCC) by examining the microRNA expression profile of human umbilical vein endothelial cells (HUVECs) in the absence or presence of human HCC cells, and identified miR-146a as the most highly upregulated microRNA. Furthermore, we revealed that miR-146a promoted the expression of platelet-derived growth factor receptor α (PDGFRA) in HUVECs, and this process was mediated by BRCA1. Overexpression of PDGFRA in the ECs of HCC tissues was associated with microvascular invasion and predicted a poorer prognosis. These results suggest that miR-146a plays a key role in regulating the angiogenic activity of ECs in HCC through miR-146a-BRCA1-PDGFRA pathway. MiR-146a and PDGFRA may emerge as potential anti-angiogenic targets on ECs for HCC therapy.
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Carcinoma Hepatocelular/genética , Neoplasias Hepáticas/genética , MicroARNs/genética , Receptor alfa de Factor de Crecimiento Derivado de Plaquetas/genética , Proteína BRCA1/metabolismo , Carcinoma Hepatocelular/metabolismo , Carcinoma Hepatocelular/patología , Células Endoteliales/metabolismo , Células Endoteliales/patología , Regulación Neoplásica de la Expresión Génica/genética , Células Endoteliales de la Vena Umbilical Humana , Humanos , Neoplasias Hepáticas/metabolismo , Neoplasias Hepáticas/patología , MicroARNs/metabolismo , Neovascularización Patológica/tratamiento farmacológico , Neovascularización Patológica/metabolismo , Neovascularización Patológica/patología , Receptor alfa de Factor de Crecimiento Derivado de Plaquetas/metabolismo , Transducción de Señal/genética , Regulación hacia ArribaRESUMEN
The combination of a palladium complex with a chiral phosphoramidite ligand and a chiral phosphoric acid enables the first highly efficient asymmetric allylic alkylation of pyrazol-5-ones with allylic alcohols, affording multiply functionalized heterocyclic products in high yields with excellent enantioselectivities that would be of great potential in the synthesis of pharmaceutically interesting molecules.
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Compuestos Alílicos/síntesis química , Compuestos Organometálicos/química , Paladio/química , Ácidos Fosfóricos/química , Propanoles/química , Pirazolonas/química , Alquilación , Compuestos Alílicos/química , Catálisis , Estructura Molecular , EstereoisomerismoRESUMEN
Medium-density fibreboards (MDFs) and particleboards are engineered woods well-known for durability and structural strength. Wood shavings or discarded wooden products can be used for MDF and particleboard production. However, engineered woods are hard to manage at the end of their useful life due to the utilisation of binders or resins, which are known forms of carcinogens. Like other wood products, MDFs and particleboards can either be recovered for material recycling or energy recovery or sent to the landfill. This paper aims to identify the sustainable circular economy pathways for waste MDF and particleboard management, comparing three different scenarios: landfill, recycling, and energy recovery (incineration) via life cycle assessment methodologies (LCA). Life cycle assessment has been conducted using ReCiPe methodology of conducting life cycle assessment. The data analysis was conducted in MS Excel using @Risk v8.2 add-on function. The analysis was based on relative contribution of the impacts across the individual life cycle stages and the specific toxicity impacts were represented on a tornado chart to reflect the percentage spread of impacts across the life cycle phase. Finally, uncertainty analysis was conducted using Monte Carlo Simulation. The results showed that material recovery is preferred over energy recovery for most of the impact categories. However, energy recovery is preferred in the case of climate change and fossil fuel depletion. For both types of engineered wood products considered in this paper, end-of-life management of engineered woods has less impact than the production process. Toxicity impacts are the greatest for energy recovery compared with landfill and material recovery.
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To address the poor characteristics of low strength and poor toughness in phosphogypsum-based construction material, this study investigates the influence of different diameters, lengths, and dosages of polyvinyl alcohol (abbreviated as PVA) fibers on the workability and mechanical properties of phosphogypsum-based construction material. The results show that as the length and dosage of PVA fibers increase, the flowability of the slurry gradually decreases, and the setting time also shortens. With an increase in the diameter of PVA fibers, the rate of decrease in flowability slows down, and the rate of shortening of setting time also gradually slows down. Moreover, the inclusion of PVA fibers significantly improves the mechanical strength of the specimens. When PVA fibers with a diameter of 15 µm, length of 12 mm, and dosage of 1.6% are used, the phosphogypsum-based construction material reinforced with PVA fibers exhibits optimal performance. Under this mixing ratio, the strength values of the specimens for flexural strength, bending strength, compressive strength, and tensile strength are 10.07 MPa, 10.73 MPa, 13.25 MPa, and 2.89 MPa, respectively. Compared to the control group, the strength enhancements are 273.00%, 164.29%, 15.32%, and 99.31%, respectively. SEM scanning of the microstructure provides a preliminary explanation for the mechanism of how PVA fibers affect the workability and mechanical properties of phosphogypsum-based construction material. The findings of this study can provide a reference for the research and application of fiber-reinforced phosphogypsum-based construction material.
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Phosphogypsum is an industrial by-product from the wet preparation of phosphoric acid. Phosphorus building gypsum (PBG) can be obtained from phosphogypsum after high-thermal dehydration. Improving the mechanical properties of PBG is of great significance to extending its application range. In this paper, PBG was modified by adding nano-CaCO3. Specifically, this study, conducted on 0.25-2% nano-CaCO3-doped PBG, tested effects on the fluidity, setting time, absolute dry flexural strength, absolute dry compressive strength, water absorption and softening coefficient of PBG, followed by its microscopic analysis with SEM and XRD. The experimental results showed that, with an increase in nano-CaCO3 content, the fluidity and setting time of PBG-based mixes were decreased. When the content was 2%, the fluidity was 120 mm, which was 33% lower than that of the blank group; the initial setting time was 485 s, which was 38% lower than that in the blank group; the final setting time was 1321 s, which was reduced by 29%. Nano-CaCO3 evidently improved the absolute dry flexural strength, absolute dry compressive strength, water absorption and softening coefficient of PBG to a certain extent. When the content was 1%, the strengthening effect reached the optimum, with the absolute dry flexural strength and absolute dry compressive strength being increased to 8.1 MPa and 20.5 MPa, respectively, which were 50% and 24% higher than those of the blank group; when the content was 1.5%, the water absorption was 0.22, which was 33% lower than that of the blank group; when the content approached 0.75%, the softening coefficient reached the peak of 0.63, which was 66% higher than that of the blank group. Doping with nano-CaCO3 could significantly improve the performance of PBG, which provides a new scheme for its modification.