Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 50
Filtrar
1.
Small ; : e2402842, 2024 Jun 23.
Artículo en Inglés | MEDLINE | ID: mdl-38923165

RESUMEN

The nacre-inspired multi-nanolayer structure offers a unique combination of advanced mechanical properties, such as strength and crack tolerance, making them highly versatile for various applications. Nevertheless, a significant challenge lies in the current fabrication methods, which is difficult to create a scalable manufacturing process with precise control of hierarchical structure. In this work, a novel strategy is presented to regulate nacre-like multi-nanolayer films with the balance mechanical properties of stiffness and toughness. By utilizing a co-continuous phase structure and an extensional stress field, the hierarchical nanolayers is successfully constructed with tunable sizes using a scalable processing technique. This strategic modification allows the robust phase to function as nacre-like platelets, while the soft phase acts as a ductile connection layer, resulting in exceptional comprehensive properties. The nanolayer-structured films demonstrate excellent isotropic properties, including a tensile strength of 113.5 MPa in the machine direction and 106.3 MPa in a transverse direction. More interestingly, these films unprecedentedly exhibit a remarkable puncture resistance at the same time, up to 324.8 N mm-1, surpassing the performance of other biodegradable films. The scalable fabrication strategy holds significant promise in designing advanced bioinspired materials for diverse applications.

2.
Biomacromolecules ; 24(7): 3127-3137, 2023 07 10.
Artículo en Inglés | MEDLINE | ID: mdl-37276461

RESUMEN

The relationship between the density of the entangled amorphous network and the ductility of oriented poly(l-lactide) (PLLA) films is explored based on the preferential hydrolysis of the amorphous regions in phosphate buffer solution (PBS). PLLA films with a balance of ductility and stiffness have been prepared by the "casting-annealing stretching" based on mechanical rejuvenation, and the structural evolution and mechanical properties at different hydrolysis durations have been identified. Various stages are found during the transition of ductility to brittleness for hydrolyzed PLLA films. First, the elongation at break for hydrolyzed PLLA films remains unchanged in the first stage of hydrolysis and then gradually decreases. Eventually, the films turn to be brittle in the third stage. The strain-hardening modulus (GR) of the hydrolyzed films is utilized to reflect the density of the entangled amorphous network, and a gradual decrease of GR with hydrolysis time indicates the decisive role of the amorphous entanglement network in the mechanical rejuvenation-induced ductility of PLLA. The quantitative relationship between the entangled amorphous network and the stress-induced ductility of PLLA films is revealed. The dependence of deformation behavior on entangled amorphous network density is closely correlated to activated primary structure during deformation. The intact chain network plays a crucial role in sufficiently activating the primary structure to yield and disentanglement during the subsequent necking. These findings could advance the understanding of the PLLA's ductility induced by mechanical rejuvenation and offer guidance for awakening the intrinsic toughness of PLLA.


Asunto(s)
Poliésteres , Poliésteres/química , Resistencia a la Tracción , Hidrólisis
3.
Biomacromolecules ; 23(9): 3990-4003, 2022 09 12.
Artículo en Inglés | MEDLINE | ID: mdl-35960547

RESUMEN

The hierarchical microstructure evolution of an emerging biobased odd-odd polyamide 5,13 (PA5,13) films under the thermo-mechanical field, stepping from hydrogen bond (H-bond) arrangement to the crystalline morphology, has been investigated systematically. It is found that the reorganization of H-bonds under the thermo-mechanical field plays a crucial role in the crystallization of PA5,13. Especially, it is revealed that the crystallization process under the thermo-mechanical field develops along the chain axis direction, while lamellar fragmentation occurs perpendicular to the chain axis. Consequently, a stable and well-organized H-bond arrangement and lengthened lamellae with significant orientation have been constructed. Laudably, an impressive tensile strength of about 500 MPa and modulus of about 4.7 GPa are thus achieved. The present study could provide important guidance for the industrial-scale manufacture of high-performance biobased odd-odd PAs with long polymethylene segment in the dicarboxylic unit combined with a large difference between the polymethylene segments in the dicarboxylic and diamine units.


Asunto(s)
Nylons , Enlace de Hidrógeno , Resistencia a la Tracción
4.
Zhongguo Dang Dai Er Ke Za Zhi ; 22(7): 684-689, 2020 Jul.
Artículo en Zh | MEDLINE | ID: mdl-32669161

RESUMEN

OBJECTIVE: To compare the efficacy of domestic and imported caffeine citrate in the treatment of apnea in preterm infants. METHODS: A total of 98 preterm infants with a gestational age of 28 - <34 weeks between April 2018 and December 2019 were enrolled. They were randomly administered with domestic (n=48) or imported caffeine citrate (n=50) within 6 hours after birth. The therapeutic effects, complications, adverse effects and clinical outcomes were compared between the two groups. RESULTS: There were no significant differences in the incidence of apnea within 7 days after birth, daily frequency of apnea, the time of apnea disappearance, the failure rate of intubation-surfactant-extubation strategy, the time of non-invasive assisted ventilation, the duration of oxygen therapy, the duration of caffeine citrate therapy, the length of hospital stay, blood gas analysis results, liver and kidney function testing results between the two groups (P>0.05). There were no significant differences in the incidence of complications and the mortality rate between the two groups (P>0.05). There was no significant difference in the incidence of adverse effects between the two groups (P>0.05). CONCLUSIONS: The efficacy and safety of domestic caffeine citrate in the treatment of apnea are similar to those of imported caffeine citrate in preterm infants.


Asunto(s)
Apnea , Cafeína/uso terapéutico , Citratos/uso terapéutico , Enfermedades del Prematuro , Apnea/tratamiento farmacológico , Método Doble Ciego , Humanos , Lactante , Recién Nacido , Recien Nacido Prematuro , Estudios Prospectivos
5.
Biomacromolecules ; 20(7): 2754-2762, 2019 07 08.
Artículo en Inglés | MEDLINE | ID: mdl-31125205

RESUMEN

Substantial adsorption of water vapor triggered by hydrogen-bonding interactions between water molecules and cellulose chains (or nanoplates) is hard to avoid in nanocomposite films, although the addition of nanoplates can improve the oxygen (or carbon dioxide) barrier property. In the present work, an effective strategy is raised to decline adsorption by weakening hydrogen-bonding interactions via chemical cross-linking by epichlorohydrin (ECH) without sacrificing the homogeneous dispersion of nanoplates. The generated microdomain structure of the chemical cross-linking reaction via ECH is explicitly revealed by micro-Raman imaging. Unambiguously, Raman maps of scanning elucidate the distribution and morphology of physical and chemical cross-linking domains quantitatively. The chemical cross-linking domains are nearly uniformly located in the matrix at a low degree of cross-linking, while the interconnected and assembled networks are formed at a high degree of cross-linking. ECH boosts the formation of chemical cross-linking microdomains, bringing out the terrific water vapor barrier property and alleviating the interfacial interactions in penetration, consequently magnifying the water contact angle and holding back the water vapor permeability. Our methodology confers an effective and convenient strategy to obtain remarkable water vapor-resistant cellulose-based films that meet the practical application in the packaging fields.


Asunto(s)
Celulosa/química , Epiclorhidrina/química , Nanocompuestos/química , Agua/química , Celulosa/farmacología , Reactivos de Enlaces Cruzados/química , Reactivos de Enlaces Cruzados/farmacología , Epiclorhidrina/farmacología , Enlace de Hidrógeno/efectos de los fármacos , Permeabilidad/efectos de los fármacos , Espectrometría Raman , Vapor
6.
Biomacromolecules ; 15(5): 1676-86, 2014 May 12.
Artículo en Inglés | MEDLINE | ID: mdl-24650138

RESUMEN

A local shear flow field was feasibly generated by pulling the ramie fiber in single fiber reinforced poly(lactic acid) (PLA) composites. This was featured by an ultrahigh shear gradient with a maximum shear rate up to 1500 s(-1), a level comparable to that frequently occurring during the practical polymer processing. To distinguish shear-induced self-nucleation and ramie fiber-induced heterogeneous nucleation, the shear history was classified by pulling the fiber for 5 s (pulled sample) and pulling out the fiber during 10 s (pulled-out sample), while the static fiber-induced crystallization was carried out as the counterpart. As a result of the ultrahigh shear gradient, the combination of primary shear-induced nucleation in the central region and secondary nucleation in the outer layer assembled the unique hierarchical superstructures. By comparing the architectural configurations of interphases formed in the static, pulled, and pulled-out samples, it was shown that the hierarchical cylindrites underwent the process of self-nucleation driven by the applied shear flow, very different from the formation of fiber-induced transcrystallinity (TC) triggered by the heterogeneous nucleating sites at the static fiber surface. The twisting of transcrystallized lamellae may take place due to the spatial hindrance induced by the incredibly dense nuclei under the intense shearing flow, as observed in the synchrotron X-ray diffraction patterns. The influence of chain characteristics on the crystalline morphology was further explored by adding a small amount of poly(ethylene glycol) (PEG) to enhance the molecular mobility of PLA. It was of interest to find that the existence of PEG not only facilitated the growth rates of TC and cylindrites but also improved the preferential orientation of PLA chains and thus expanded the ordered regions. We unearthed lamellar units that were composed of rich fibrillar extended chain crystals (diameter of 50-80 nm). These results are of importance to shed light on tailoring crystalline morphology for natural fibers reinforced green composite materials. Of immense practical significance, too, is the crystalline evolution that has been tracked in the simple model penetrated with an ultrahigh shear gradient, which researchers have so far been unable to replicate during the practical melt processing, such as extrusion and injection molding.


Asunto(s)
Ácido Láctico/química , Polímeros/química , Ácido Láctico/síntesis química , Estructura Molecular , Tamaño de la Partícula , Poliésteres , Polietilenglicoles/química , Polímeros/síntesis química , Propiedades de Superficie
7.
Biomacromolecules ; 15(11): 4054-64, 2014 Nov 10.
Artículo en Inglés | MEDLINE | ID: mdl-25245861

RESUMEN

The notion of toughening poly(lactic acid) (PLA) by adding flexible biopolymers has generated enormous interest but has yielded few desirable advances, mainly blocked by the sacrifice of strength and stiffness due to uncontrollable phase morphology and poor interfacial interactions. Here the phase control methodology, that is, intense extrusion compounding followed by "slit die extrusion-hot stretching-quenching" technique, was proposed to construct well-aligned, stiff poly(butylene succinate) (PBS) nanofibrils in the PLA matrix for the first time. We show that generating nanosized discrete droplets of PBS phase during extrusion compounding is key to enable the development of in situ nanofibrillar PBS assisted by the shearing/stretching field. The size of PBS nanofibrils strongly dependent on the PBS content, showing an increased average diameter from 83 to 116 and 236 nm for the composites containing 10, 20, and 40 wt % nanofibrils, respectively. More importantly, hybrid shish-kebab superstructure anchoring ordered PLA kebabs were induced by the PBS nanofibrils serving as the central shish, conferring the creation of tenacious interfacial crystalline ligaments. The exceptional combination of strength, modulus, and ductility for the composites loaded 40 wt % PBS nanofibrils were demonstrated, outperforming pure PLA with the increments of 31, 51, and 72% in strength, modulus, and elongation at break (56.4 MPa, 1702 MPa, and 92.4%), respectively. The high strength, modulus, and ductility are unprecedented for PLA and are in great potential need for packaging applications.


Asunto(s)
Butileno Glicoles/química , Tecnología Química Verde/métodos , Ácido Láctico/química , Nanofibras/química , Polímeros/química , Ensayo de Materiales/métodos , Poliésteres , Resistencia a la Tracción , Sustancias Viscoelásticas/síntesis química
8.
Carbohydr Polym ; 337: 122088, 2024 Aug 01.
Artículo en Inglés | MEDLINE | ID: mdl-38710544

RESUMEN

The construction of the preferred orientation structure by stretching is an efficient strategy to fabricate high-performance cellulose film and it is still an open issue whether crystalline structure or amorphous molecular chain is the key factor in determining the enhanced mechanical performance. Herein, uniaxial stretching with constant width followed by drying in a stretching state was carried out to cellulose hydrogels with physical and chemical double cross-linking networks, achieving high-performance regenerated cellulose films (RCFs) with an impressive tensile strength of 154.5 MPa and an elastic modulus of 5.4 GPa. The hierarchical structure of RCFs during uniaxial stretching and drying was systematically characterized from micro- to nanoscale, including microscopic morphology, crystalline structure as well as relaxation behavior at a molecular level. The two-dimensional correlation spectra of dynamic mechanical analysis and Havriliak-Negami fitting results verified that the enhanced mechanical properties of RCFs were mainly attributed to the stretch-induced tight packing and restricted relaxation of amorphous molecular chains. The new insight concerning the contribution of molecular chains in the amorphous region to the enhancement of mechanical performance for RCFs is expected to provide valuable guidance for designing and fabricating high-performance eco-friendly cellulose-based films.

9.
Int J Biol Macromol ; 261(Pt 2): 129829, 2024 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-38296134

RESUMEN

Three-dimensional interpenetrating and hierarchically porous carbon material is an efficient catalyst support in water remediation and it is still a daunting challenge to establish the relationship between hierarchically porous structure and catalytic degradation performance. Herein, a highly porous silica (SiO2)/cellulose-based carbon aerogel with iron-based catalyst (FexOy) was fabricated by in-situ synthesis, freeze-drying and pyrolysis, where the addition of SiO2 induced the hierarchically porous morphology and three-dimensional interpenetrating sheet-like network with nitrogen doping. The destruction of cellulose crystalline structure by SiO2 and the iron-catalyzed breakdown of glycosidic bonds synergistically facilitated the formation of electron-rich graphite-like carbon skeleton. The unique microstructure is confirmed to be favorable for the diffusion of reactants and electron transport during catalytic process, thus boosting the catalytic degradation performance of carbon aerogels. As a result, the catalytic degradation efficiency of tetracycline under light irradiation by adding only 5 mg of FexOy/SiO2 cellulose carbon aerogels was as high as 90 % within 60 min, demonstrating the synergistic effect of photocatalysis and Fenton reaction. This ingenious structure design provides new insight into the relationship between hierarchically porous structure of carbon aerogels and their catalytic degradation performance, and opens a new avenue to develop cellulose-based carbon aerogel catalysts with efficient catalytic performance.


Asunto(s)
Carbono , Compuestos Heterocíclicos , Carbono/química , Hierro/química , Dióxido de Silicio , Celulosa/química , Porosidad , Tetraciclina/química , Antibacterianos , Catálisis
10.
Int J Biol Macromol ; 260(Pt 2): 129566, 2024 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-38253148

RESUMEN

Despite great potential in fabrication of biodegradable protective membranes by electrospinning of poly(lactic acid) (PLA) nanofibers, it is still thwarted by smooth surfaces and poor electroactivity that challenge the promotion of electret properties and long-term air filtration performance. Here, a microwave-assisted synthetic method was used to customize dielectric TiO2 nanocrystals of ultrasmall and uniform dimensions (∼30 nm), which were homogeneously embedded at beaded PLA nanofibers (PLA@TiO2, diameter of around 280 nm) by the combined "electrospinning-electrospray" approach. With small amounts of TiO2 (2, 4 and 6 wt%), the nanopatterned PLA@TiO2 nanofibrous membranes (NFMs) were characterized by largely increased dielectric constants (nearly 1.9), surface potential (up to 1.63 kV) and triboelectric properties (output voltage of 12.2 V). Arising from the improved electroactivity and self-charging mechanisms, the nanopatterned PLA@TiO2 NFMs exhibited remarkable PM0.3 filtration properties (97.9 %, 254.6 Pa) even at the highest airflow rate of 85 L/min, surpassing those of pure PLA membranes (86.2 %, 483.7 Pa). This was moreover accompanied by inhibition rates of 100 % against both E. coli and S. aureus, as well as excellent UV-blocking properties (UPF as high as 3.8, TUVA of 50.9 % and TUVB of 20.1 %). The breathable and electroactive nanopatterned PLA NFMs permit promising applications in multifunctional protective membranes toward excellent UV shielding and high-efficiency removal of both PMs and pathogens.


Asunto(s)
Nanofibras , Nanofibras/química , Staphylococcus aureus , Escherichia coli , Poliésteres/química , Antibacterianos/farmacología , Antibacterianos/química
11.
Zhonghua Wai Ke Za Zhi ; 51(9): 796-9, 2013 Sep.
Artículo en Zh | MEDLINE | ID: mdl-24330958

RESUMEN

OBJECTIVE: To evaluate the novel method of combinedly use of occluder and bare stent in the treatment of aortic dissection with distal tear at visceral branches. METHODS: From April 2010 to September 2012, 6 patients (5 male and 1 female patients, aged from 29 to 62 years, mean 47.2 years) were diagnosed as Stanford type B aortic dissection that been revealed by CT angiography. The main tears were sealed with stent-grafts firstly, and then the tears at the visceral branch area were evaluated that impossible to close spontaneously. Atrium septal defect occluder and ventricular septal defect were implanted at the tears with the anterior disc in false lumen, while the posterior disc in the true lumen. After that, the bare stents were implanted in the true lumen to pull the occluders on the aortic wall. RESULTS: Among the 6 procedures, occluders were successfully implanted in 5 cases, and 1 failed anchoring at the tear, and the alternative method of coils embolization was applicated. After all the procedures, the immediate aortogrophy revealed that the false lumen disappeared in the 5 cases that occluders were used, and the visceral branches were all patent. No paraplegia, lesion of visceral organs or other complications occurred. All the cases were followed at least 5 months. There was one endoleak due to a non-sealed tear at the descending aorta, one new-occurred small tear in the descending aorta but with no communication to the false lumen. CONCLUSIONS: The combinedly use of occluder and bare stent in the treatment of aortic dissection with tears at the visceral branch area is a sum of two simple technique plus each other. It is easily to master. The lesions at the aortic that ordinary stent-grafting incapable to seal are successfully solved then. The huge trauma of open or hybrid procedures are avoided.


Asunto(s)
Disección Aórtica , Implantación de Prótesis Vascular , Disección Aórtica/cirugía , Aneurisma de la Aorta/cirugía , Aneurisma de la Aorta Torácica/cirugía , Humanos , Stents
12.
Artículo en Inglés | MEDLINE | ID: mdl-38048182

RESUMEN

Despite the great promise in the development of biodegradable and ecofriendly air filters by electrospinning of poly(lactic acid) (PLA) nanofibrous membranes (NFMs), the as-electrospun PLA nanofibers are generally characterized by poor electroactivity and smooth surface, challenging the exploitation of electrostatic adsorption and physical interception that are in need for efficient removal of pathogens and particulate matters (PMs). Herein, a combined "electrospinning-electrospray" strategy was disclosed to functionalize the PLA nanofibers by direct anchoring of highly dielectric BaTiO3@ZIF-8 nanohybrids (BTO@ZIF-8), conferring simultaneous promotion of surface roughness, electret properties (surface potential as high as 7.5 kV), and self-charging capability (∼190% increase in tribo-output voltage compared to that of pure PLA). Benefiting from the well-tailored morphology and increased electroactivity, the electrospun-electrosprayed PLA/BTO@ZIF-8 exhibited excellent PM-capturing performance (up to 96.54% for PM0.3 and 99.49% for PM2.5) while providing desirable air resistance (only 87 Pa at 32 L/min) due primarily to the slip flow of air molecules over the nanohybrid protrusions. This was accompanied by excellent antibacterial properties (99.9% inhibition against both Staphylococcus aureus and Escherichia coli), arising presumably from the synergistic effects of enhanced reactive oxygen species (ROS) generation, plentiful ion release, and surface charges. Our proposed strategy opens up pathways to afford exceptional combination of high-efficiency and low-resistance filtration, excellent antibacterial performance, and mechanical robustness without sacrificing the biodegradation profiles of PLA NFMs, holding potential implications for efficient and long-term healthcare.

13.
ACS Appl Mater Interfaces ; 15(32): 38867-38877, 2023 Aug 16.
Artículo en Inglés | MEDLINE | ID: mdl-37542460

RESUMEN

Multilayer structures are not only applied to manipulate properties of synthetic polymer materials such as rainbow films and barrier films but also widely discovered in natural materials like nacre. In this work, in situ formation of an interconnected multi-nanolayer (IMN) structure in poly(butylene adipate-co-terephthalate) (PBAT)/poly(butylene succinate) (PBS) cocontinuous blends is designed by an extensional flow field during a "casting-thermal stretching" process, combining the properties of two components to a large extent. Hierarchical structures including phase morphology, crystal structure, and lamellar crystals in IMN films have been revealed, which clearly identifies the crucial role of extensional flow. The oriented PBAT phase in the IMN structure can be beneficial to the epitaxial growth of PBS crystals onto the PBAT nanolayers, thus improving interfacial adhesions. Furthermore, intense extensional stress can also promote crystallinity and thicken the lamellar structure. Given such distinct features in the fully biodegradable films, a simultaneous enhancement in tear strength, tensile strength, and puncture resistance has been achieved. To the best of our knowledge, the tear strength of IMN films about 285.9 kN/m is the highest level in the previous works of this system. Moreover, the proposed fabrication way of the IMN structure is facile and scalable, which is highly expected to be an efficient strategy for development of structured biodegradable polymers with excellent comprehensive properties.

14.
ACS Macro Lett ; 12(7): 880-887, 2023 Jul 18.
Artículo en Inglés | MEDLINE | ID: mdl-37343235

RESUMEN

Cellulose-based dielectrics with attractive dielectric performance are promising candidates to develop eco-friendly electrostatic energy storage devices. Herein, all-cellulose composite films with superior dielectric constant were fabricated by manipulating the dissolution temperature of native cellulose, where we revealed the relationship among the hierarchical microstructure of the crystalline structure, the hydrogen bonding network, the relaxation behavior at a molecular level, and the dielectric performance of the cellulose film. The coexistence of cellulose I and cellulose II led to a weakened hydrogen bonding network and unstable C6 conformations. The increased mobility of cellulose chains in the cellulose I-amorphous interphase enhanced the dielectric relaxation strength of side groups and localized main chains. As a result, the as-prepared all-cellulose composite films exhibited a fascinating dielectric constant of as high as 13.9 at 1000 Hz. This work proposed here provides a significant step toward fundamentally understanding the dielectric relaxation of cellulose, thus developing high-performance and eco-friendly cellulose-based film capacitors.

15.
ACS Appl Mater Interfaces ; 15(19): 23701-23710, 2023 May 17.
Artículo en Inglés | MEDLINE | ID: mdl-37140941

RESUMEN

Polypropylene (PP) serves as an excellent commercialized polymer dielectric film owing to its high breakdown strength, excellent self-healing ability, and flexibility. However, its low dielectric constant causes the large volume of the capacitor. Constructing multicomponent polypropylene-based all-organic polymer dielectric films is a facile strategy for achieving high energy density and efficiency simultaneously. Thereinto, the interfaces between the components become the key factors that determine the energy storage performance of the dielectric films. In this work, we propose to fabricate high-performance polyamide 513 (PA513)/PP all-organic polymer dielectric films via the construction of abundant well-aligned and isolated nanofibrillar interfaces. Laudably, a significant enhancement in the breakdown strength is achieved from 573.1 MV/m of pure PP to 692.3 MV/m with 5 wt % of PA513 nanofibrils. Besides, a maximum discharge energy density of about 4.4 J/cm2 is realized with 20 wt % of PA513 nanofibrils, which is about 1.6-folds higher than pure PP. Simultaneously, the energy efficiency of samples with modulated interfaces maintains higher than 80% up to 600 MV/m, which is much higher than pure PP of about 40.7% at 550 MV/m. This work provides a new strategy to fabricate high-performance multicomponent all-organic polymer dielectric films on an industrial scale.

16.
Biomacromolecules ; 13(11): 3858-67, 2012 Nov 12.
Artículo en Inglés | MEDLINE | ID: mdl-23072455

RESUMEN

The effect of shear flow and carbon nanotubes (CNTs), separately and together, on nonisothermal crystallization of poly(lactic acid) (PLA) at a relatively large cooling rate was investigated by time-resolved synchrotron wide-angle X-ray diffraction (WAXD) and polarized optical microscope (POM). Unlike flexible-chain polymers such as polyethylene, and so on, whose crystallization kinetics are significantly accelerated by shear flow, neat PLA only exhibits an increase in onset crystallization temperature after experiencing a shear rate of 30 s(-1), whereas both the nucleation density and ultimate crystallinity are not changed too much because PLA chains are intrinsically semirigid and have relatively short length. The breaking down of shear-induced nuclei into point-like precursors (or random coil) probably becomes increasingly active after shear stops. Very interestingly, a marked synergistic effect of shear flow and CNTs exists in enhancing crystallization of PLA, leading to a remarkable increase of nucleation density in PLA/CNT nanocomposite. This synergistic effect is ascribed to extra nuclei, which are formed by the anchoring effect of CNTs' surfaces on the shear-induced nuclei and suppressing effect of CNTs on the relaxation of the shear-induced nuclei. Further, this interesting finding was deliberately applied to injection molding, aiming to improve the crystallinity of PLA products. As expected, a remarkable high crystallinity in the injection-molded PLA part has been achieved successfully by the combination of shear flow and CNTs, which offers a new method to fabricate PLA products with high crystallinity for specific applications.


Asunto(s)
Ácido Láctico/química , Nanocompuestos/química , Nanotubos de Carbono/química , Polímeros/química , Frío , Cristalización , Microscopía de Polarización , Poliésteres , Difracción de Rayos X
17.
Int J Biol Macromol ; 207: 927-940, 2022 May 15.
Artículo en Inglés | MEDLINE | ID: mdl-35364194

RESUMEN

Up to now, unbalanced mechanical properties and poor heat resistance have become two major problems of polylactic acid (PLA). In this study, the coupling between Cellulose nanocrystal (CNC) and strong shearing field formed a unique hierarchical structure. Compared with pure PLA, the tensile strength of DPIM PLA/CNC increased from 57.9 MPa to 79.6 MPa without sacrificing the toughness of PLA, and the vicat softening temperature of DPIM PLA/CNC increased from 60 °C to 155 °C. The microstructure of PLA/CNC composites was analyzed by SEM, SAXS and WAXD, and it was found that the coupling effect of CNC and strong shear flow field could significantly change the crystallization behavior of PLA. CNC could increase PLA shish length from 251 nm to 889 nm under the action of shear field. At the same time, due to this coupling effect, more PLA shish-kebab structures were induced at the interface. This special hierarchical structure composed of CNC and PLA Shish-Kebab is of great significance and can provide important guidance for achieving the balance of strength and toughness of polymer materials.


Asunto(s)
Celulosa , Nanopartículas , Celulosa/química , Nanopartículas/química , Poliésteres/química , Dispersión del Ángulo Pequeño , Difracción de Rayos X
18.
Front Neurol ; 13: 1049543, 2022.
Artículo en Inglés | MEDLINE | ID: mdl-36523347

RESUMEN

Background: Endovascular therapy (EVT) is complex in the context of intracranial atherosclerosis (ICAS)-related large vessel occlusion (LVO) and the re-occlusion rates are high due to residual stenosis, the procedure time is long and the optimal EVT technique is unclear. The Balloon AngioplaSty with the dIstal protection of Stent Retriever (BASIS) technique is a novel thrombectomy technique that allows emergent balloon angioplasty to be performed via the wire of the retrieval stent. Our study presents our initial experience with the BASIS technique in ICAS-related LVO and assesses its feasibility. Method: In patients with ICAS-related LVO treated with BASIS, clinical and angiographic data were retrospectively analyzed. Angiographic data included first-pass reperfusion (PFR), the rate of residual stenosis, distal emboli, and re-occlusion post-procedure. The Extended Thrombolysis in Cerebral Infarction (eTICI) scale was used to assess reperfusion extent, and an eTICI score ≥2b was defined as successful perfusion. Clinical outcome was evaluated at 3 months (modified Rankin score [mRS]), and an mRS ≤ 2 was defined as a good clinical outcome. Results: A total of seven patients with ICAS-related LVO were included, and the median age of the patients was 76 years. All patients achieved eTICI 3 reperfusion and FPR. The residual stenosis rate ranged from 5 to 10%. None of the patients had re-occlusion post-procedure. The median puncture-to-reperfusion time was 51 min. None of the patients had a symptomatic cerebral hemorrhage, re-occlusion, distal embolism, and dissection. Good clinical outcomes were observed in four patients (4/7, 57.1%), and 1 patient (1/7, 14.3%) died. Conclusion: The BASIS technique is feasible and safe for treating acute ICAS-related LVO.

19.
Nutrients ; 14(17)2022 Aug 31.
Artículo en Inglés | MEDLINE | ID: mdl-36079859

RESUMEN

Abnormal vasorin (Vasn) expression occurs in multiple diseases, particularly liver cancers. Vasn knockout (KO) in mice causes malnutrition, a shortened life span, and decreased physiological functions. However, the causes and underlying mechanisms remain unknown. Here, we established Vasn KO C57BL/6J mice by using the CRISPR/Cas9 system. The animals were weighed, and histology, immunohistochemistry, electronic microscopy, and liver function tests were used to examine any change in the livers. Autophagy markers were detected by Western blotting. MicroRNA (miRNA) sequencing was performed on liver samples and analyses to study the signaling pathway altered by Vasn KO. Significant reductions in mice body and liver weight, accompanied by abnormal liver function, liver injury, and reduced glycogen accumulation in hepatocytes, were observed in the Vasn KO mice. The deficiency of Vasn also significantly increased the number of autophagosomes and the expression of LC3A/B-II/I but decreased SQSTM1/p62 levels in hepatocytes, suggesting aberrant activation of autophagy. Vasn deficiency inhibited glycogen-mediated mammalian target of rapamycin (mTOR) phosphorylation and activated Unc-51-like kinase 1 (ULK1) signaling, suggesting that Vasn deletion upregulates hepatocyte autophagy through the mTOR-ULK1 signaling pathway as a possible cause of diminished life span and health. Our results indicate that Vasn is required for the homeostasis of liver glycogen metabolism upstream of hepatocyte autophagy, suggesting research values for regulating Vasn in pathways related to liver physiology and functions. Overall, this study provides new insight into the role of Vasn in liver functionality.


Asunto(s)
Proteínas Reguladoras de la Apoptosis , Glucógeno , Proteínas de la Membrana , Serina-Treonina Quinasas TOR , Animales , Proteínas Reguladoras de la Apoptosis/genética , Autofagia/genética , Hepatocitos/metabolismo , Proteínas de la Membrana/genética , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Serina-Treonina Quinasas TOR/genética , Serina-Treonina Quinasas TOR/metabolismo
20.
J Hazard Mater ; 423(Pt A): 127054, 2022 02 05.
Artículo en Inglés | MEDLINE | ID: mdl-34481389

RESUMEN

Currently, many catalysts are inconvenient to separate from water, and the solvents used in the preparation process are not environmentally friendly, resulting in low recovery efficiency and secondary pollution. In this study, the magnetic and porous regenerated cellulose/carbon nanotubes/Fe3O4 nanoparticles (RC/CNTs/Fe3O4 NPs) composites were synthesized for activation of peroxydisulfate (PDS) in a green alkaline-urea system. The RC/CNTs/Fe3O4 NPs-PDS system achieved 100% removal of bisphenol A compared with CNTs (~64.6%), RC (~0%) or Fe3O4 NPs (~0%), which was closely related to the introduction of defects and functional groups, nitrogen doping and conductive networks. Interestingly, the strong interaction between CNTs and the sheath-like protective layer formed by urea on the cellulose surface promotes the introduction of nitrogen into the composites at the preparation temperature of 70 °C. Moreover, the mechanism of the system was found to be a typical non-radical pathway. Fortunately, there is no leaching of iron ions in the system, and the effects of the actual waterbody, initial pH, and different anions are negligible. The recycling and separation experiments revealed the practicality and superiority of the composite. This work provides a feasible and sustainable strategy for the application of natural cellulose-supported catalysts.


Asunto(s)
Nanotubos de Carbono , Compuestos de Bencidrilo , Celulosa , Fenoles
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA