Poly(vinylidene fluoride) (PVDF) membranes have been extensively applied to scientific research and industrial process due to its outstanding properties such as high thermal stability, good chemical ...resistance and membrane forming properties. This article provides an overview of recent progress on the application and modification of PVDF membranes. The applications include water treatment, membrane distillation, gas separation, pollutants removal, bioethanol recovery, separator for lithium ion battery, support for preparing composite membranes, etc. Subsequently, on the basis of two major problems of PVDF membranes in applications, i.e., membrane fouling and membrane wetting, the hydrophilic modification and hydrophobic modification methods are comprehensively reviewed. Finally, the key issues associated with the modification of PVDF membranes for actual applications are discussed. This paper may provide an insight for the development of PVDF membranes in future.
•A broad overview of applications of PVDF membranes is presented.•Hydrophilic modification to reduce membrane fouling in water treatment.•Hydrophobic modification to improve wetting resistance in membrane contactor.•Improving membrane preparation process and modifying existing membranes.
The pandemic of coronavirus disease 2019 (COVID‐19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), has caused an unprecedented global social and economic impact, and ...high numbers of deaths. Many risk factors have been identified in the progression of COVID‐19 into a severe and critical stage, including old age, male gender, underlying comorbidities such as hypertension, diabetes, obesity, chronic lung diseases, heart, liver and kidney diseases, tumors, clinically apparent immunodeficiencies, local immunodeficiencies, such as early type I interferon secretion capacity, and pregnancy. Possible complications include acute kidney injury, coagulation disorders, thoromboembolism. The development of lymphopenia and eosinopenia are laboratory indicators of COVID‐19. Laboratory parameters to monitor disease progression include lactate dehydrogenase, procalcitonin, high‐sensitivity C‐reactive protein, proinflammatory cytokines such as interleukin (IL)‐6, IL‐1β, Krebs von den Lungen‐6 (KL‐6), and ferritin. The development of a cytokine storm and extensive chest computed tomography imaging patterns are indicators of a severe disease. In addition, socioeconomic status, diet, lifestyle, geographical differences, ethnicity, exposed viral load, day of initiation of treatment, and quality of health care have been reported to influence individual outcomes. In this review, we highlight the scientific evidence on the risk factors of severity of COVID‐19.
Background and aims
The outbreak of coronavirus disease 2019 (COVID‐19) caused by severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) infection has recently spread worldwide and been ...declared a pandemic. We aim to describe here the various clinical presentations of this disease by examining eleven cases.
Methods
Electronic medical records of 11 patients with COVID‐19 were collected, and demographics, clinical manifestations, outcomes, key laboratory results, and radiological images are discussed.
Results
The clinical course of the eleven cases demonstrated the complexity of the COVID‐19 profile with different clinical presentations. Clinical manifestations range from asymptomatic cases to patients with mild and severe symptoms, with or without pneumonia. Laboratory detection of the viral nucleic acid can yield false‐negative results, and serological testing of virus‐specific IgG and IgM antibodies should be used as an alternative for diagnosis. Patients with common allergic diseases did not develop distinct symptoms and severe courses. Cases with a pre‐existing condition of chronic obstructive pulmonary disease or complicated with a secondary bacterial pneumonia were more severe.
Conclusion
All different clinical characteristics of COVID‐19 should be taken into consideration to identify patients that need to be in strict quarantine for the efficient containment of the pandemic.
Clinical manifestations of COVID‐19 range from asymptomatic cases to patients with mild and severe symptoms, with or without pneumonia. Laboratory detection of the viral nucleic acid can yield false‐negative results, and serological testing of virus‐specific IgG and IgM antibodies should be used as an alternative for diagnosis. Patients with common allergic diseases did not develop distinct symptoms and severe courses. Cases with a pre‐existing condition of chronic obstructive pulmonary disease or complicated with a secondary bacterial pneumonia were more severe.
Background
The pandemic of coronavirus disease 2019 (COVID‐19) caused by severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) infection has made widespread impact recently. We aim to ...investigate the clinical characteristics of COVID‐19 children with different severities and allergic status.
Methods
Data extracted from the electronic medical records, including demographics, clinical manifestations, comorbidities, laboratory and immunological results, and radiological images of 182 hospitalized COVID‐19 children, were summarized and analyzed.
Results
The median age was 6 years, ranging from 3 days to 15 years, and there were more boys (male‐female ratio about 2:1) within the studied 182 patients. Most of the children were infected by family members. Fever (43.4%) and dry cough (44.5%) were common symptoms, and gastrointestinal manifestations accounted for 11.0%, including diarrhea, abdominal discomfort, and vomiting. 71.4% had abnormal chest computed tomography (CT) scan images, and typical signs of pneumonia were ground‐glass opacity and local patchy shadowing on admission. Laboratory results were mostly within normal ranges, and only a small ratio of lymphopenia (3.9%) and eosinopenia (29.5%) were observed. The majority (97.8%) of infected children were not severe, and 24 (13.2%) of them had asymptomatic infections. Compared to children without pneumonia (manifested as asymptomatic and acute upper respiratory infection), children with pneumonia were associated with higher percentages of the comorbidity history, symptoms of fever and cough, and increased levels of serum procalcitonin, alkaline phosphatase, and serum interleukins (IL)‐2, IL‐4, IL‐6, IL‐10, and TNF‐α. There were no differences in treatments, duration of hospitalization, time from first positive to first negative nucleic acid testing, and outcomes between children with mild pneumonia and without pneumonia. All the hospitalized COVID‐19 children had recovered except one death due to intussusception and sepsis. In 43 allergic children with COVID‐19, allergic rhinitis (83.7%) was the major disease, followed by drug allergy, atopic dermatitis, food allergy, and asthma. Demographics and clinical features were not significantly different between allergic and nonallergic groups. Allergic patients showed less increase in acute phase reactants, procalcitonin, D‐dimer, and aspartate aminotransferase levels compared with all patients. Immunological profiles including circulating T, B, and NK lymphocyte subsets, total immunoglobulin and complement levels, and serum cytokines did not show any difference in allergic and pneumonia groups. Neither eosinophil counts nor serum total immunoglobulin E (IgE) levels showed a significant correlation with other immunological measures, such as other immunoglobulins, complements, lymphocyte subset numbers, and serum cytokine levels.
Conclusion
Pediatric COVID‐19 patients tended to have a mild clinical course. Patients with pneumonia had higher proportion of fever and cough and increased inflammatory biomarkers than those without pneumonia. There was no difference between allergic and nonallergic COVID‐19 children in disease incidence, clinical features, and laboratory and immunological findings. Allergy was not a risk factor for developing and severity of SARS‐CoV‐2 infection and hardly influenced the disease course of COVID‐19 in children.
There is no difference between allergic and nonallergic children in clinical features and laboratory/immunological findings, and allergy is not a risk factor for COVID‐19. The majority (97.8%) of infected children were not severe, and 24 (13.2%) of them had asymptomatic infections. Laboratory results were mostly within normal ranges, and only a small ratio of lymphopenia (3.9%) and eosinopenia (29.5%) was observed. Higher proportion of patients with pneumonia have fever, cough, comorbidities, and increased inflammatory biomarkers (procalcitonin, alkaline phosphatase and serum interleukins (IL)‐2, IL‐4, IL‐6, IL‐10, and TNF‐α) than those without pneumonia. Abbreviations: AD, atopic dermatitis; AR, allergic rhinitis; AST, aspartate aminotransferase, AURI, acute upper respiratory infection; COVID‐19, coronavirus disease 2019; DA, drug allergy; FA, food allergy; PCT, procalcitonin; SARS‐CoV‐2, severe acute respiratory syndrome coronavirus 2; TNF, tumor necrosis factor.
With the rapidly increasing demands on water resources, fresh water shortage has become an important issue affecting the economic and social development in many countries. As one of the main ...technologies for producing fresh water from saline water and other wastewater sources, reverse osmosis (RO) has been widely used so far. However, a major challenge facing widespread application of RO technology is membrane fouling, which results in reduced production capacity and increased operation costs. Therefore, many researches have been focused on enhancing the RO membrane resistance to fouling. This paper presents a review of developing antifouling RO membranes in recent years, including the selection of new starting monomers, improvement of interfacial polymerization process, surface modification of conventional RO membrane by physical and chemical methods as well as the hybrid organic/inorganic RO membrane. The review of research progress in this article may provide an insight for the development of antifouling RO membranes and extend the applications of RO technology in water treatment in the future.
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► The progress in the development of antifouling reverse osmosis membranes. ► Exploration of new monomers and improvement of fabrication process. ► Surface modification of conventional RO membrane by physical and chemical methods. ► Development of hybrid organic/inorganic RO membrane with good fouling resistance.
Due to unique redox property, visible light photoredox catalysis is emerging as a powerful tool in synthetic organic chemistry. This review summarizes the previous researches employing visible light ...photoredox catalysts for difunctionalization of alkenes. Display omitted
Due to unique redox property, visible light photoredox catalysis is emerging as a powerful tool in synthetic organic chemistry. This review summarizes the previous researches employing visible light photoredox catalysts for difunctionalization of alkenes.
The development of catalytic enantioselective transformations, enabling the construction of complex molecular scaffolds from simple precursors, has been a long-standing challenge in organic ...synthesis. Recent achievements in transition-metal catalyzed enantioselective functionalizations of carbon–hydrogen (C–H) bonds represent a promising pathway toward this goal. Over the last two decades, iridium catalysis has evolved as a valuable tool enabling the stereocontrolled synthesis of chiral molecules via C–H activation. The development of iridium-based systems with various chiral ligand classes, as well as studies of their reaction mechanisms, has resulted in dynamic progress in this area. This review aims to present a comprehensive picture of the enantioselective functionalizations of C–H bonds by chiral iridium complexes with emphasis on the mechanisms of the C–H activation step.
A simple and facile room-temperature solution-phase synthesis was developed to fabricate a spherical covalent organic framework with large surface area, good solvent stability and high ...thermostability for high-resolution chromatographic separation of diverse important industrial analytes including alkanes, cyclohexane and benzene, α-pinene and β-pinene, and alcohols with high column efficiency and good precision.
Purpose
Continuous fiber reinforced thermoplastic composites (CFRTPCs) are becoming more significant in industrial applications but are limited by the high cost of molds, the manufacturing ...boundedness of complex constructions and the inability of special fiber alignment. The purpose of this paper is to put forward a novel three-dimensional (3D) printing process for CFRTPCs to realize the low-cost rapid fabrication of complicated composite components.
Design/methodology/approach
For this purpose, the mechanism of the proposed process, which consists of the thermoplastic polymer melting, the continuous fiber hot-dipping and the impregnated composites extruding, was investigated. A 3D printing equipment for CFRTPCs with a novel composite extrusion head was developed, and some composite samples have been fabricated for several mechanical tests. Moreover, the interface performance was clarified with scanning electron microscopy images.
Findings
The results showed that the flexural strength and the tensile strength of these 10 Wt.% continuous carbon fiber (CCF)/acrylonitrile-butadiene-styrene (ABS) specimens were improved to 127 and 147 MPa, respectively, far greater than the one of ABS parts and close to the one of CCF/ABS (injection molding) with the same fiber content. Moreover, these test results also exposed the very low interlaminar shear strength (only 2.81 MPa) and the inferior interface performance. These results were explained by the weak meso/micro/nano scale interfaces in the 3D printed composite parts.
Originality/value
The 3D printing process for CFRTPCs with its controlled capabilities for the orientation and distribution of fiber has great potential for manufacturing of load-bearing composite parts in the industrial circle.
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