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1.
ACS Appl Mater Interfaces ; 13(27): 32226-32241, 2021 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-34210116

RESUMO

The touchstone for bone replacing or anchoring trauma implants, besides resorption, includes functional ankylosis at a fixation point and replacement by viable functional neo-bone tissues. These parameters redefined the concept of "resorbability" as "bioresorbability." Interference screws are the most commonly used resorbable anchoring implants for anterior cruciate ligament (ACL) reconstruction (surgery). Over the years, the bioresorbable screw fixation armamentarium has amplified countless choices, but instability and postimplantation complications have raised concerns about its reliability and efficacy. Owing to this interest, in this work, bioactive glass fiber-reinforced plastic (BGFP) composites with (BGFPnb5) and without (BGFP5) niobicoxide composing multiplexed network modifiers are reported as bioresorbable bone-anchoring substitutes. These synergistically designed composites have a fabricated structure of continuous, unidirectional BG fibers reinforced in an epoxy resin matrix using "melt-drawing and microfabrication" technology. The BGFP microarchitecture is comprised of multiplexed oxide components that influence bioactive response in a distinctive lophelia atoll-like apatite formation. Furthermore, it assists in the proliferation, adherence, and migration of bone marrow-derived mesenchymal stem cells. It also exhibits superior physicochemical characteristics such as surface roughness, hydrophilic exposure, distinctive flexural strength, and bioresorption. Thus, it induces restorative bone osseointegration and osteoconduction and actuates periosteum function. In addition, the BGFP influences the reduction of DH5-α Escherichia coli in suspension culture, demonstrating potential antibacterial efficacy. In conclusion, the BGFP composite therapeutic efficacy demonstrates distinctive material characteristics aiding in bone regeneration and restoration that could serve as a pioneer in orthopedic regenerative medicine.


Assuntos
Substitutos Ósseos/química , Substitutos Ósseos/farmacologia , Vidro/química , Periósteo/efeitos dos fármacos , Plásticos/química , Regeneração Óssea/efeitos dos fármacos , Cristalografia por Raios X , Teste de Materiais , Osseointegração/efeitos dos fármacos , Periósteo/fisiologia , Próteses e Implantes
3.
J Chromatogr A ; 1651: 462311, 2021 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-34146960

RESUMO

Compound-specific isotope analysis of chlorine (CSIA-Cl) is a practicable and high-performance approach for revelation of transformation processes and source identification of chlorinated organic pollutants. This study conducted CSIA-Cl for typical polychlorinated organic pollutants using gas chromatography-high resolution mass spectrometry (GCHRMS) with an alternate injection mode using perchloroethylene (PCE) and trichloroethylene (TCE) as model analytes. PCE and TCE standards from two manufacturers were employed for method development, and chlorine isotope ratio calculation schemes were evaluated by experiment and numerical simulation. The achieved precision (standard deviation of isotope ratios) was up to 0.21‰ for PCE and 0.43‰ for TCE. The limits of detection for CSIA-Cl of were 0.05 µg/mL (0.05 ng on column), and the linearities were 0.05-1 µg/mL. Two isotope ratio calculation schemes, i.e., one using complete molecular isotopologues and another using the first pair of neighboring chlorine isotopologues of each analyte, were evaluated in terms of accuracy and precision. The complete-isotopologue scheme showed evidently higher precision and was more competent to reflect trueness than the isotopologue-pair scheme and the two schemes could present completely different outcomes. The method has been successfully applied to PCE and TCE reagents from different suppliers, a trichloromethane reagent, and a plastic material. The relative isotope ratio variations (Δ37Cl) of PCE and TCE in the reagents and plastic material were from -1.84±0.7‰ to 15.12±0.85‰. The analytes from different sources could mostly be discerned from each other by chlorine isotope ratios. This study will be conducive to transformation process elucidation and source identification of for PCE and TCE, and facilitate CSIA-Cl using GC-MS for more polychlorinated organic pollutants, particularly in selection and optimization of isotope ratio calculation schemes.


Assuntos
Cloro/análise , Simulação por Computador , Poluentes Ambientais/análise , Cromatografia Gasosa-Espectrometria de Massas/métodos , Halogenação , Compostos Orgânicos/análise , Fracionamento Químico , Indicadores e Reagentes , Isótopos , Análise Numérica Assistida por Computador , Plásticos/química , Padrões de Referência , Tricloroetileno/análise , Tricloroetileno/química
4.
J Mater Chem B ; 9(23): 4746-4762, 2021 06 16.
Artigo em Inglês | MEDLINE | ID: mdl-34095937

RESUMO

The surfaces of indwelling catheters offer sites for the adherence of bacteria to form biofilms, leading to various infections. Therefore, the development of antibacterial materials for catheters is imperative. In this study, combining the strong antibacterial effect of a quaternary ammonium salt (QAS) and the high biocompatibility of tannic acid (TA), we prepared a quaternary tannic acid (QTA) by grafting a synthesized quaternary ammonium salt, dimethyl dodecyl 6-bromohexyl ammonium bromide, onto TA. To prepare antibacterial catheters, QTA was blended with thermoplastic polyurethane (TPU) via melt extrusion, which is a convenient and easy-to-control process. Characterization of the TPU blends showed that compared with those of the QAS, dissolution rate and biocompatibility of QTA were significantly improved. On the premise that the introduction of QTA had only a slight effect on the original mechanical properties of pristine TPU, the prepared TPU/QTA maintained satisfactory antibacterial activities in vitro, under a flow state, as well as in vivo. The results verified that the TPU/QTA blend with a QTA content of 4% is effective, durable, stable, and non-toxic, and exhibits significant potential as a raw material for catheters.


Assuntos
Antibacterianos/farmacologia , Materiais Biocompatíveis , Cateteres/microbiologia , Plásticos/química , Poliuretanos/química , Taninos/farmacologia , Testes de Sensibilidade Microbiana , Propriedades de Superfície
5.
Ultrason Sonochem ; 76: 105627, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-34130189

RESUMO

New biotechnological processes using microorganisms and/or enzymes to convert carbonaceous resources, either biomass or depolymerized plastics into a broad range of different bioproducts are recognized for their high potential for reduced energy consumption and reduced GHG emissions. However, the hydrophobicity, high molecular weight, chemical and structural composition of most of them hinders their biodegradation. A solution to reduce the impact of non-biodegradable polymers spread in the environment would be to make them biodegradable. Different approaches are evaluated for enhancing their biodegradation. The aim of this work is to develop and optimize the ultrasonication (US) and UV photodegradation and their combination as well as dielectric barrier discharge (DBD) plasma as pre-treatment technologies, which change surface properties and enhance the biodegradation of plastic by surface oxidation and thus helping bacteria to dock on them. Polylactic acid (PLA) has been chosen as a model polymer to investigate its surface degradation by US, UV, and DBD plasma using surface characterization methods like X-ray Photoelectron Spectroscopy (XPS) and Confocal Laser Microscopy (CLSM), Atomic Force Microscopy (AFM) as well as FT-IR and drop contour analysis. Both US and UV affect the surface properties substantially by eliminating the oxygen content of the polymer but in a different way, while plasma oxidizes the surface.


Assuntos
Plásticos/química , Poliésteres/química , Reciclagem/economia , Propriedades de Superfície
6.
Molecules ; 26(11)2021 May 27.
Artigo em Inglês | MEDLINE | ID: mdl-34072199

RESUMO

Food contact materials (FCM) are defined as the objects and materials intended to come into direct or indirect contact with foodstuff, while food contact articles are defined as objects, being equipment, containers, packaging and various utensils which are clearly intended to be used for the manufacture, preparation, conservation, flow, transport or handling of foodstuffs [...].


Assuntos
Contaminação de Alimentos/análise , Embalagem de Alimentos/instrumentação , Embalagem de Alimentos/tendências , Tecnologia de Alimentos/métodos , Alimentos , Plásticos/química , Antioxidantes/química , Cromatografia Líquida de Alta Pressão , Espectrometria de Massas , Medição de Risco , Segurança
7.
J Food Sci ; 86(7): 3219-3227, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-34118069

RESUMO

The manufacture of single-use plastic items uses fossil fuels, and releases greenhouse gases. Plastic waste is also harmful to humans and wildlife. Recent attention towards the regulation or elimination of plastic straws has led to the development of many alternatives to single-use plastic straws, some intended to be disposed of immediately after use, and others to be cleaned and reused. Unfortunately, anecdotes are widespread of inferior sensory experiences from such alternatives, with straws either losing stability when wet, imparting negative flavor properties to a beverage, or feeling unpleasant in the mouth. Despite such reports, little formal research exists categorizing these alternatives. Here, we examine popular choices for straw materials in a focus group (n = 9) and in a consumer sensory test (n = 102), as well as testing the durability of straws when soaked in water. Cornstarch straws offered the most similar sensory experience to plastic, whereas options such as paper, wheat, pasta, and rice straws all scored low on mouthfeel and flavor liking, with off-flavors commonly reported in beverages consumed with these straws. A Kano analysis (n = 193) to determine the factors consumers find essential in drinking straws confirmed the most important to be that no flavors were imparted to beverages when used. Finally, a consumer survey (n = 579) confirmed that straw consumers primarily use them out of default availability; most use them only if they are given without asking, and most would readily give up plastic straws, but may be unfamiliar with other options. PRACTICAL APPLICATION: Plastic straws contribute to waste and result in the release of greenhouse gases in their manufacture. Despite this, they provide a superior sensory experience compared to other options. Here, we review aspects of this experience, along with consumers motivations for using straws.


Assuntos
Bebidas/análise , Água Potável/química , Aromatizantes/análise , Plásticos/análise , Plásticos/química , Humanos , Nigéria , Paladar/fisiologia
8.
J Food Sci ; 86(7): 2872-2885, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-34146411

RESUMO

Enzyme-based time-temperature integrators (TTIs) were applied to indicate the ripeness of plastic-container-packaged kiwifruit. The hypothesis was that the ethylene gas production, an indication of kiwifruit ripeness, depends on the time-temperature history. The market-purchased, unripe kiwifruit was assumed to be stored in a plastic container to ripen at home, as common practice in Korea. The kinetics of ethylene gas production and TTI color change was found to be suitable for the indication. The Arrhenius activation energy (Ea ) of the ethylene gas production and color changes of lipase-, amylase-, and laccase-based TTIs were 41.60 ± 10.87 kJ/mol, and 42.76 ± 9.57, 100.28 ± 6.84, and 30.49 ± 4.41 kJ/mol, respectively. Kiwifruit firmness was also tested as a practical, major quality factor. The Ea of the firmness changes was 39.66 ± 4.64 kJ/mol. In scenarios tests, the firmness could be most accurately predicted from the lipase-based TTI color. Overall, the lipase-based TTI was found to be the best in terms of the similarity of the Ea and the prediction accuracy. PRACTICAL APPLICATION: Currently, there is no commercially available indicator that can determine the ripeness of packaged kiwifruit. Although an ethylene gas indicator is possible, it has been difficult to commercialize because the gas may leak in the package. An indicator on plastic containers with kiwifruit, as is common in Korea, has been developed using a conventional time-temperature integrator (TTI). The hypothesis was that the production of ethylene gas, indicating kiwi ripening, is also dependent on the time-temperature history. It was found that the TTI color change over time was suitable for judging suitable kiwifruit hardness, a major kiwifruit ripeness index.


Assuntos
Actinidia/crescimento & desenvolvimento , Etilenos/análise , Frutas/crescimento & desenvolvimento , Plásticos/química , Actinidia/química , Frutas/química , Cinética , República da Coreia , Temperatura , Fatores de Tempo
9.
ACS Appl Mater Interfaces ; 13(16): 19193-19199, 2021 Apr 28.
Artigo em Inglês | MEDLINE | ID: mdl-33871260

RESUMO

Bio-based plastics that can supplant petroleum-derived materials are necessary to meet the future demands of sustainability in the life cycle of plastic materials. While there are significant efforts to develop protein-based plastic materials for commercial use, their application is limited by poor processability and limitations in mechanical performance. Here, we present a bovine serum albumin (BSA)-based resin for stereolithographic apparatus (SLA) 3D printing that affords bioplastic objects with shape-memory behavior. We demonstrate that the native conformation of these globular proteins is largely retained in the 3D-printed constructs and that each protein molecule possesses a "stored length" that could be revealed during mechanical deformation (extension or compression) of the 3D bioplastic objects. While the plastically deformed objects could retain this state for an indefinite period of time, heating the object or submerging in water allowed it to return to its original 3D-printed shape.


Assuntos
Fenômenos Mecânicos , Plásticos/química , Impressão Tridimensional , Soroalbumina Bovina/química , Animais , Bovinos , Força Compressiva , Testes Mecânicos , Água/química
10.
Int J Mol Sci ; 22(7)2021 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-33800567

RESUMO

Plastic pollution is one of the crucial global challenges nowadays, and biodegradation is a promising approach to manage plastic waste in an environment-friendly and cost-effective way. In this study we identified the strain of fungus Trichoderma viride GZ1, which was characterized by particularly high pectinolytic activity. Using differential scanning calorimetry, Fourier-transform infrared spectroscopy techniques, and viscosity measurements we showed that three-month incubation of polylactide and polyethylene terephthalate in the presence of the fungus lead to significant changes of the surface of polylactide. Further, to gain insight into molecular mechanisms underneath the biodegradation process, western blot hybridization was used to show that in the presence of poly(ethylene terephthalate) (PET) in laboratory conditions the fungus produced hydrophobin proteins. The mycelium adhered to the plastic surface, which was confirmed by scanning electron microscopy, possibly due to the presence of hydrophobins. Further, using atomic force microscopy we demonstrated for the first time the formation of hydrophobin film on the surface of aliphatic polylactide (PLA) and PET by T. viride GZ1. This is the first stage of research that will be continued under environmental conditions, potentially leading to a practical application.


Assuntos
Hypocreales/metabolismo , Plásticos/química , Poliésteres/química , Polietilenotereftalatos/química , Biodegradação Ambiental , Varredura Diferencial de Calorimetria , Microscopia de Força Atômica , Polímeros/química , Espectroscopia de Infravermelho com Transformada de Fourier , Propriedades de Superfície , Viscosidade , Microbiologia da Água , Poluentes Químicos da Água
11.
Ecotoxicol Environ Saf ; 217: 112207, 2021 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-33866287

RESUMO

Microplastics (MPs) are emerging pollutants that act as a carrier of toxic pollutants, release toxic substances, and aggregate in biota. The adsorption behavior of MPs has recently become a research hot spot. The objective of this study was to summarize the main mechanisms by which MPs adsorb organic pollutants, introduce some mathematical models commonly used to study the adsorption behavior of MPs, and discuss the factors affecting the adsorption capacity from three perspectives, i.e., the properties of MPs and organic pollutants, and environmental factors. Adsorption kinetics and isothermal adsorption models are commonly used to study the adsorption of organic pollutants on MPs. We observed that hydrophobic interaction is the most common mechanism by which MPs adsorb organic pollutants, and also reportedly controls the portion of organic pollutants. Additionally, electrostatic interaction and other non-covalent forces, such as hydrogen bonds, halogen bonds, and π-π interactions, are also mechanisms of organic pollutant adsorption on MPs. The particle size, specific surface area, aging degree, crystallinity, and polarity of MPs, and organic pollutant properties (hydrophobicity and dissociated forms) are key factors affecting adsorption capacity. Changes in the pH, temperature, and ionic strength also affect the adsorption capacity. Current research on the adsorption behavior of MPs has mainly been conducted in laboratories, and in-depth studies on the adsorption mechanism and influencing factors are limited. Therefore, studies on the adsorption behavior of MPs in the environment are required, and this study will contribute to a better understanding of this topic.


Assuntos
Poluentes Ambientais/química , Microplásticos/química , Poluentes Químicos da Água/química , Adsorção , Ligação de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Cinética , Concentração Osmolar , Plásticos/química , Poluentes Químicos da Água/análise
12.
Molecules ; 26(9)2021 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-33922098

RESUMO

More than 23 million tonnes of lignin are produced annually in the US from wood pulping and 98% of this lignin is burnt. Therefore, creating products from lignin, such as plastics, offers an approach for obtaining sustainable materials in a circular economy. Lignin-based copolymers were synthesized using a single pot, solvent free, melt condensation reaction. The synthesis occurred in two stages. In the first stage, a biobased prepolymer consisting of butanediol (BD, 0.8-1 molar content) and a diacid (succinic (SA), adipic (AA) and suberic acids (SuA), with varying amounts of diaminobutane (DAB, 0-0.2 molar content) was heated under vacuum and monitored by Fourier transform infra-red (FTIR) spectroscopy and electrospray ionization-mass spectrometry (ESI-MS). In the second stage, prepolymer was mixed with a softwood kraft lignin (0-50 wt.%) and further reacted under vacuum at elevated temperature. Progression of the polymerization reaction was monitored using FTIR spectroscopy. The lignin-copolyester/amide properties were characterized using tensile testing, X-ray diffraction (XRD), dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) techniques. Lignin co-polymer tensile (strength 0.1-2.1 MPa and modulus 2 to 338 MPa) properties were found to be influenced by the diacid chain length, lignin, and DAB contents. The lignin-copolymers were shown to be semi-crystalline polymer and have thermoplastic behavior. The SA based copolyesters/amides were relatively stiff and brittle materials while the AA based copolyesters/amides were flexible and the SuA based copolyesters/amides fell in-between. Additionally, > 30 wt.% lignin the lignin- copolyesters/amides did not exhibit melt behavior. Lignin-co-polyester/amides can be generated using green synthesis methods from biobased building blocks. The lignin- copolyesters/amides properties could be tuned based on the lignin content, DAB content and diacid chain length. This approach shows that undervalued lignin can be used in as a macromonomer in producing thermoplastic materials.


Assuntos
Amidas/química , Lignina/química , Plásticos/química , Poliésteres/química , Fenômenos Químicos , Estrutura Molecular , Polimerização , Espectrometria de Massas por Ionização por Electrospray , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura , Resistência à Tração , Termogravimetria , Difração de Raios X
13.
Molecules ; 26(9)2021 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-33922162

RESUMO

The present study was aimed to evaluate the suitability of agro-wastes and crude vegetable oils for the cost-effective production of poly-ß-hydroxybutyrate (PHB), to evaluate growth kinetics and PHB production in Alcaligenes faecalis RZS4 and Pseudomonas sp. RZS1 with these carbon substrates and to study the biodegradation of PHB accumulated by these cultures. Alcaligenes faecalis RZS4 and Pseudomonas sp. RZS1 accumulates higher amounts of PHB corn (79.90% of dry cell mass) and rice straw (66.22% of dry cell mass) medium respectively. The kinetic model suggests that the Pseudomonas sp. RZS1 follows the Monod model more closely than A. faecalis RZS4. Both the cultures degrade their PHB extract under the influence of PHB depolymerase. Corn waste and rice straw appear as the best and cost-effective substrates for the sustainable production of PHB from Alcaligenes faecalis RZS4 and Pseudomonas sp. RZS1. The biopolymer accumulated by these organisms is biodegradable in nature. The agro-wastes and crude vegetable oils are good and low-cost sources of nutrients for the growth and production of PHB and other metabolites. Their use would lower the production cost of PHB and the low-cost production will reduce the sailing price of PHB-based products. This would promote the large-scale commercialization and popularization of PHB as an ecofriendly bioplastic/biopolymer.


Assuntos
Agricultura , Alcaligenes/metabolismo , Biopolímeros/biossíntese , Fermentação , Pseudomonas/metabolismo , Resíduos , Biodegradação Ambiental , Biomassa , Biopolímeros/química , Biopolímeros/isolamento & purificação , Cinética , Plásticos/química , Análise Espectral
14.
Nat Chem Biol ; 17(6): 732-738, 2021 06.
Artigo em Inglês | MEDLINE | ID: mdl-33737758

RESUMO

Petrochemical-based plastics have not only contaminated all parts of the globe, but are also causing potentially irreversible damage to our ecosystem because of their non-biodegradability. As bioplastics are limited in number, there is an urgent need to design and develop more biodegradable alternatives to mitigate the plastic menace. In this regard, we report aquaplastic, a new class of microbial biofilm-based biodegradable bioplastic that is water-processable, robust, templatable and coatable. Here, Escherichia coli was genetically engineered to produce protein-based hydrogels, which are cast and dried under ambient conditions to produce aquaplastic, which can withstand strong acid/base and organic solvents. In addition, aquaplastic can be healed and welded to form three-dimensional architectures using water. The combination of straightforward microbial fabrication, water processability and biodegradability makes aquaplastic a unique material worthy of further exploration for packaging and coating applications.


Assuntos
Biofilmes , Plásticos/química , Água/química , Biodegradação Ambiental , Bioengenharia , Escherichia coli/genética , Escherichia coli/metabolismo , Proteínas/química , Solventes , Resistência à Tração
15.
J Vis Exp ; (168)2021 02 10.
Artigo em Inglês | MEDLINE | ID: mdl-33645576

RESUMO

Estimations of soil organic carbon are dependent on soil processing methods including removal of undecomposed plant material. Inadequate separation of roots and plant material from soil can result in highly variable carbon measurements. Methods to remove the plant material are often limited to the largest, most visible plant materials. In this manuscript we describe how electrostatic attraction can be used to remove plant material from a soil sample. An electrostatically charged surface passed close to dry soil naturally attracts both undecomposed and partially decomposed plant particles, along with a small quantity of mineral and aggregated soil. The soil sample is spread in a thin layer on a flat surface or a soil sieve. A plastic or glass Petri dish is electrostatically charged by rubbing with polystyrene foam or nylon or cotton cloth. The charged dish is passed repeatedly over the soil. The dish is then brushed clean and recharged. Re-spreading the soil and repeating the procedure eventually results in a diminishing yield of particulates. The process removes about 1 to 5% of the soil sample, and about 2 to 3 times that proportion in organic carbon. Like other particulate removal methods, the endpoint is arbitrary and not all free particulates are removed. The process takes approximately 5 min and does not require a chemical process as do density flotation methods. Electrostatic attraction consistently removes material with higher than average C concentration and C:N ratio, and much of the material can be visually identified as plant or faunal material under a microscope.


Assuntos
Compostos Orgânicos/química , Material Particulado/análise , Solo/química , Eletricidade Estática , Carbono/análise , Plantas/química , Plásticos/química
16.
Int J Artif Organs ; 44(2): 75-84, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33522378

RESUMO

Polyvinylchloride is universally agreed upon to be the material of choice for tubings and for containers for medical application. Many alterations of the chemical/physical surface conditions, mainly due to an altered extrusion process, could influence its biocompatibility by promoting platelet aggregation. Biocompatibility and safety of the medical device must be preserved, also monitoring the migration of additives within polyvinylchloride during the diffusion process. A large variety of methods are used to verify the correct composition and extrusion of polyvinylchloride but, generally, they need long experimental time and are expensive. The aim of the study is to propose a simple, economic and rapid approach based on Fourier transform-infrared spectroscopy and Coomassie Blue staining. The method has been used to detect chemical and morphological defects caused by an altered extrusion process on 20/75 polyvinylchloride tubings in a blind test. This approach positively identified altered samples in 80% of the cases. The suggested approach represents a reliable and versatile method to detect and monitor surface defects by an easy, inexpensive and reproducible method.


Assuntos
Segurança de Equipamentos/métodos , Cloreto de Polivinila , Diálise Renal/instrumentação , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Propriedades de Superfície , Humanos , Teste de Materiais/métodos , Plásticos/química , Plásticos/uso terapêutico , Agregação Plaquetária , Cloreto de Polivinila/efeitos adversos , Cloreto de Polivinila/química , Cloreto de Polivinila/uso terapêutico
17.
PLoS One ; 16(2): e0246439, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33606752

RESUMO

The plastic hinge is a key factor in the ductile and plastic design of structures and an important basis for the seismic strengthening of structures. The formation and behavior of plastic hinges is critical for the seismic performance of an entire structure. The relocation of plastic hinges away from the beam end is an effective way of addressing brittle failure. In this paper, the cause of the shear buckling failure of prefabricated steel beams with corrugated webs and the strain variation at the flanges of steel beams are theoretically analyzed through structural tests. Based on the analysis results, a local strengthening method is proposed, and the effects of the beam sizes and the strengthening steel plate on the plastic hinges are obtained. In addition, a calculation method for determining the size of the strengthening steel plate that promotes the relocation of the plastic zone away from the beam end is given, a design method for plastic hinge relocation is proposed based on the test data, and its validity is verified.


Assuntos
Materiais de Construção , Plásticos/química , Aço/química , Fenômenos Físicos , Projetos de Pesquisa
18.
Molecules ; 26(4)2021 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-33562272

RESUMO

For many antibacterial polymer fibres, especially for those with natural functional additives, the antibacterial response might not last over time. Moreover, the mechanical performance of polymeric fibres degrades significantly during the intended operation, such as usage in textile and industrial filter applications. The degradation process and overall ageing can lead to emitted volatile organic compounds (VOCs). This work focused on the usage of pine rosin as natural antibacterial chemical and analysed the weathering of melt-spun polyethylene (PE) and poly lactic acid (PLA) polyfilaments. A selected copolymer surfactant, as an additional chemical, was studied to better integrate rosin with the molecular structure of the plastics. The results reveal that a high 20 w-% of rosin content can be obtained by surfactant addition in non-oriented PE and PLA melt-spun polyfilaments. According to the VOC analysis, interestingly, the total emissions from the melt-spun PE and PLA fibres were lower for rosin-modified (10 w-%) fibres and when analysed below 60 ℃. The PE fibres of the polyfilaments were found to be clearly more durable in terms of the entire weathering study, i.e., five weeks of ultraviolet radiation, thermal ageing and standard washing. The antibacterial response against Gram-positive Staphylococcus aureus by the rosin-containing fibres was determined to be at the same level (decrease of 3-5 logs cfu/mL) as when using 1.0 w-% of commercial silver-containing antimicrobial. For the PE polyfilaments with rosin (10 w-%), full killing response (decrease of 3-5 logs cfu/mL) remained after four weeks of accelerated ageing at 60 ℃.


Assuntos
Antibacterianos/química , Polietileno/química , Resinas Vegetais/química , Compostos Orgânicos Voláteis/química , Antibacterianos/farmacologia , Testes de Sensibilidade Microbiana , Pinus/química , Plásticos/química , Plásticos/farmacologia , Poliésteres/química , Polietileno/farmacologia , Polímeros/química , Polímeros/farmacologia , Prata/química , Staphylococcus aureus/efeitos dos fármacos , Têxteis/análise , Compostos Orgânicos Voláteis/farmacologia
19.
Cell Transplant ; 30: 963689720987527, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33426911

RESUMO

Since its outbreak in China, the Coronavirus disease 2019 (COVID-19) pandemic has caused worldwide disaster. Globally, there have been 71,581,532 confirmed cases of COVID-19, including 1,618,374 deaths, reported to World Health Organization (data retrieved on December 16, 2020). Currently, no treatment modalities for COVID-19 (e.g., vaccines or antiviral drugs) with confirmed efficacy and safety are available. Although the possibilities and relevant challenges of some alternatives (e.g., use of stem cells as immunomodulators) have been proposed, the personal protective equipment is still the only way to protect and lower infection rates of COVID-19 among healthcare workers and airway managers (intubators). In this article, we described the combined use of a plastic sheet as a barrier with the intubating stylet for tracheal intubation in patients needing mechanical ventilation. Although conventional or video-assisted laryngoscopy is more popular and familiar to other groups around the world, we believe that the video-assisted intubating stylet technique is much easier to learn and master. Advantages of the video stylet include the creation of greater working distance between intubator and patient, less airway stimulation, and less pharyngeal space needed for endotracheal tube advancement. All the above features make this technique reliable and superior to other devices, especially when a difficult airway is encountered in COVID scenario. Meanwhile, we proposed the use of a flexible and transparent plastic sheet to serve as a barrier against aerosol and droplet spread during airway management. We demonstrated that the use of a plastic sheet would not interfere or hinder the intubator's maneuvers during endotracheal intubation. Moreover, we demonstrated that the plastic sheet was effective in preventing the spread of mist and water spray in simulation models with a mannequin. In our experience, we found that this technique most effectively protected the intubator and other operating room personnel from infection during the COVID-19 pandemic.


Assuntos
COVID-19/terapia , Transmissão de Doença Infecciosa do Profissional para o Paciente/prevenção & controle , Intubação Intratraqueal/instrumentação , Equipamento de Proteção Individual , COVID-19/epidemiologia , COVID-19/transmissão , Humanos , Intubação Intratraqueal/métodos , Distanciamento Físico , Plásticos/química , Taiwan/epidemiologia , Gravação em Vídeo/instrumentação
20.
J Am Chem Soc ; 143(2): 1235-1246, 2021 01 20.
Artigo em Inglês | MEDLINE | ID: mdl-33417768

RESUMO

This report describes an approach for preparing tethered tungsten-imido alkylidene complexes featuring a tetra-anionic pincer ligand. Treating the tungsten alkylidyne [tBuOCO]W≡CtBu(THF)2 (1) with isocyanates (RNCO; R = tBu, Cy, and Ph) leads to cycloaddition occurring exclusively at the C═N bond to generate the tethered tungsten-imido alkylidenes (6-NR). Unanticipated intermediates reveal themselves, including the discovery of [(O2CtBuC═)W(η2-(N,C)-RNCO)(THF)] (11-R) and an unprecedented decarbonylation product [(tBuOCO)W(≡NR)(tBuCCO)] (14-R), on the pathway to the formation of 6-NR. Complex 11-R is kinetically stable for sterically bulky isocyanate R = tBu (11-tBu) and is isolated and characterized by single-crystal X-ray diffraction. Finally, adding to the short list of catalysts capable of ring expansion metathesis polymerization (REMP), complexes 6-NR and 11-tBu are active for the stereoselective synthesis of cyclic polynorbornene.


Assuntos
Alcenos/química , Complexos de Coordenação/química , Plásticos/síntese química , Tungstênio/química , Catálise , Complexos de Coordenação/síntese química , Cristalografia por Raios X , Modelos Moleculares , Estrutura Molecular , Plásticos/química , Estereoisomerismo
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