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1.
Appl Opt ; 60(26): 8046-8049, 2021 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-34613066

RESUMO

We demonstrate a compact and efficient Ho:YLF slab laser that is pumped by a self-made Tm:YAP slab laser. The maximum output power of 125 W at 2064 nm was obtained with the incident pump power of 245 W. To the best of our knowledge, this is the first report for an Ho:YLF laser oscillator to reach hundred-watts-level output power. The slope efficiency with respect to the incident pump power was 62.5%, and the optical-to-optical conversion efficiency was 51%. The RMS instability of the maximum output power was measured to be 0.24% in 30 min. The beam quality factors M2 were 475 and 1.59 in the x and y directions, respectively.

2.
J Cell Mol Med ; 25(20): 9740-9752, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34533278

RESUMO

Nitazoxanide (NTZ) is a broad-spectrum antiparasitic and antiviral drug (thiazole). However, although NTZ has been extensively used, there are no reports concerning its toxicology in vertebrates. This study used the zebrafish as a vertebrate model to evaluate the safety of NTZ and to analyse the related molecular mechanisms. The experimental results showed that zebrafish embryos exposed to NTZ had cardiac malformation and dysfunction. NTZ also significantly inhibited proliferation and promoted apoptosis in cardiomyocytes. Transcriptomic analysis used compared gene expression levels between zebrafish embryos in the NTZ treatment and the control groups identified 200 upregulated genes and 232 downregulated genes. Analysis by Kyoto encyclopaedia of genes and genomes (KEGG) and gene ontology (GO) showed that signal pathways on cardiomyocyte development were inhibited while the oxidative stress pathways were activated. Further experiments showed that NTZ increased the content of reactive oxygen species (ROS) in the hearts of zebrafish. Antioxidant gadofullerene nanoparticles (GFNPs) significantly alleviated the developmental toxicity to the heart, indicating that NTZ activated the oxidative stress response to cause embryonic cardiomyocyte injury in zebrafish. This study provides evidence that NTZ causes developmental abnormalities in the cardiovascular system of zebrafish.

3.
Ecotoxicol Environ Saf ; 222: 112514, 2021 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-34280841

RESUMO

Pendimethalin (PND) is one of the best sellers of selective herbicide in the world and has been frequently detected in the water. However, little is known about its effects on cardiac development. In this study, we used zebrafish to investigate the developmental and cardiac toxicity of PND. We exposed the zebrafish embryos with a serial of concentrations at 3, 4, and 5 mg/L at 5.5-72 h post-fertilization (hpf). We found that PND exposure can reduce the heart rate, survival rate, and body length of zebrafish embryos. Furthermore, we identified many malformations including pericardial and yolk sac edema, spinal deformity, and cardiac looping abnormality. In addition, PND increased the expression of reactive oxygen species and malondialdehyde and reduced the activity of superoxide dismutase (Antioxidant enzymes); We examined the expression of cardiac development-related genes and the apoptosis markers, and found changes of the following marker: vmhc, nppa, tbx5a, nkx2.5, gata4, tbx2b and FoxO1, bax, bcl-2, p53, casp-9, casp-3. Our data showed that activation of Wnt pathway can rescue the cardiac abnormalities caused by PND. Our results provided new evidence for the toxicity of PND and suggested that the PND residual should be treated as a hazard in the environment.


Assuntos
Embrião não Mamífero , Peixe-Zebra , Compostos de Anilina , Animais , Apoptose , Cardiotoxicidade/metabolismo , Embrião não Mamífero/metabolismo , Estresse Oxidativo , Peixe-Zebra/metabolismo , Proteínas de Peixe-Zebra/genética , Proteínas de Peixe-Zebra/metabolismo
4.
Ecotoxicol Environ Saf ; 220: 112385, 2021 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-34082241

RESUMO

Sulfometuron methyl (SM) is a widely used herbicide and thus leading to accumulation in the environment. The toxicity assessments of SM in model organisms are currently rare. In the present study, zebrafish were utilized for evaluating the detrimental effects of SM in aquatic vertebrates. Zebrafish embryos were exposed to 0, 10, 20, and 40 mg/L SM from 5.5 to 72 h post-fertilization (hpf), respectively. Consequently, SM exposure resulted in increasing the mortality rate and reducing hatching rate in larval zebrafish at 10, 20, and 40 mg/L SM-treated groups. The reduced numbers of immune cells (neutrophils and macrophages) were observed after SM exposure by a dose-dependent manner. The inflammatory responses (TLR4, MYD88, IL-1ß, IL-6, IL-8, IFN-γ, IL-10, and TGF-ß) were measured to estimate immune responses. Anti-inflammatory factors (IL-10 and TGF-ß) were down-regulated in all the treated groups and significantly altered at 40 mg/L exposure group. Additionally, behavioral tests suggested that SM treatment significantly increased the total distance, average speed, and maximum acceleration of larval zebrafish during light-dark transition and subsequently enzymology test displayed the same trend to locomotor behaviors. The content significantly increased in oxidative stress, as reflected in ROS level in all the treated groups. The numbers of cell apoptosis were significantly increased at 20, and 40 mg/L and the highest concentration group induced the substantial increment (P < 0.001) of apoptosis-related genes including p53, Bax/Bcl-2, caspase-9, and caspase-3. In summary, our results demonstrated that exposure to SM caused toxicity of development, immune system, locomotor behavior, oxidative stress, and cell apoptosis at the early developmental stages of zebrafish.


Assuntos
Embrião não Mamífero/efeitos dos fármacos , Herbicidas/toxicidade , Compostos de Sulfonilureia/toxicidade , Peixe-Zebra/crescimento & desenvolvimento , Animais , Apoptose/efeitos dos fármacos , Catalase/metabolismo , Citocinas/genética , Citocinas/metabolismo , Regulação da Expressão Gênica no Desenvolvimento/efeitos dos fármacos , Larva/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Espécies Reativas de Oxigênio , Superóxido Dismutase/metabolismo , Poluentes Químicos da Água/toxicidade
5.
Environ Pollut ; 274: 116539, 2021 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-33549839

RESUMO

Bifenazate is a novel acaricide for selective foliar spraying and is widely used to control mites in agricultural production. However, its toxicity to aquatic organisms is unknown. Here, a zebrafish model was used to study bifenazate toxicity to aquatic organisms. Exposure to bifenazate was found to cause severe cardiotoxicity in zebrafish embryos, along with disorders in the gene expression related to heart development. Bifenazate also caused oxidative stress. Cardiotoxicity caused by bifenazate was partially rescued by astaxanthin (an antioxidant), accompanied by cardiac genes and oxidative stress-related indicators becoming normalized. Our results showed that exposure to bifenazate can significantly change the ATPase activity and gene expression levels of the calcium signaling pathway. These led to heart failure, in which the blood accumulated outside the heart without entering it, eventually leading to death. The results indicated that bifenazate exposure caused cardiotoxicity in zebrafish embryos through the induction of oxidative stress and inhibition of the calcium signaling pathway.


Assuntos
Cardiotoxicidade , Peixe-Zebra , Animais , Carbamatos/metabolismo , Cardiotoxicidade/metabolismo , Embrião não Mamífero/metabolismo , Hidrazinas , Estresse Oxidativo
6.
Proc Natl Acad Sci U S A ; 118(2)2021 01 12.
Artigo em Inglês | MEDLINE | ID: mdl-33376206

RESUMO

Planarian flatworms regenerate their heads and tails from anterior or posterior wounds and this regenerative blastema polarity is controlled by Wnt/ß-catenin signaling. It is well known that a regeneration blastema of appendages of vertebrates such as fish and amphibians grows distally. However, it remains unclear whether a regeneration blastema in vertebrate appendages can grow proximally. Here, we show that a regeneration blastema in zebrafish fins can grow proximally along the proximodistal axis by calcineurin inhibition. We used fin excavation in adult zebrafish to observe unidirectional regeneration from the anterior cut edge (ACE) to the posterior cut edge (PCE) of the cavity and this unidirectional regeneration polarity occurs as the PCE fails to build blastemas. Furthermore, we found that calcineurin activities in the ACE were greater than in the PCE. Calcineurin inhibition induced PCE blastemas, and calcineurin hyperactivation suppressed fin regeneration. Collectively, these findings identify calcineurin as a molecular switch to specify the PCE blastema of the proximodistal axis and regeneration polarity in zebrafish fin.


Assuntos
Nadadeiras de Animais/fisiologia , Calcineurina/metabolismo , Regeneração/fisiologia , Animais , Polaridade Celular/fisiologia , Extremidades/fisiologia , Transdução de Sinais , Cicatrização/fisiologia , Peixe-Zebra/metabolismo , Proteínas de Peixe-Zebra
7.
Ecotoxicol Environ Saf ; 205: 111339, 2020 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-32961491

RESUMO

Famoxadone-cymoxanil is a new protective and therapeutic fungicide, but little research has been done on it or its toxicity in aquatic organisms. In this study, we used zebrafish to investigate the cardiotoxicity of famoxadone-cymoxanil and the potential mechanisms involved. Zebrafish embryos were exposed to different concentrations of famoxadone-cymoxanil until 72 h post-fertilization (hpf), then changes of heart morphology in zebrafish embryos were observed. We also detected the levels of oxidative stress, myocardial-cell proliferation and apoptosis, ATPase activity, and the expression of genes related to the cardiac development and calcium-signaling pathway. After famoxadone-cymoxanil exposure, pericardial edema, cardiac linearization, and reductions in the heart rate and cardiac output positively correlated with concentration. Although myocardial-cell apoptosis was not detected, proliferation of the cells was severely reduced and ATPase activity significantly decreased, resulting in a severe deficiency in heart function. In addition, indicators of oxidative stress changed significantly after exposure of the embryos to the fungicide. To better understand the possible molecular mechanisms of cardiovascular toxicity in zebrafish, we studied the transcriptional levels of cardiac development, calcium-signaling pathways, and genes associated with myocardial contractility. The mRNA expression levels of key genes in heart development were significantly down-regulated, while the expression of genes related to the calcium-signaling pathway (ATPase [atp2a1], cardiac troponin C [tnnc1a], and calcium channel [cacna1a]) was significantly inhibited. Expression of klf2a, a major endocardial flow-responsive gene, was also significantly inhibited. Mechanistically, famoxadone-cymoxanil toxicity might be due to the downregulation of genes associated with the calcium-signaling pathway and cardiac muscle contraction. Our results found that famoxadone-cymoxanil exposure causes cardiac developmental toxicity and severe energy deficiency in zebrafish.


Assuntos
Acetamidas/toxicidade , Embrião não Mamífero/efeitos dos fármacos , Fungicidas Industriais/toxicidade , Coração/efeitos dos fármacos , Estrobilurinas/toxicidade , Poluentes Químicos da Água/toxicidade , Peixe-Zebra/metabolismo , Animais , Apoptose/efeitos dos fármacos , Sinalização do Cálcio/efeitos dos fármacos , Sinalização do Cálcio/genética , Cardiotoxicidade , Regulação para Baixo , Embrião não Mamífero/metabolismo , Embrião não Mamífero/patologia , Regulação da Expressão Gênica no Desenvolvimento/efeitos dos fármacos , Coração/embriologia , Frequência Cardíaca/efeitos dos fármacos , Fatores de Transcrição Kruppel-Like/genética , Fatores de Transcrição Kruppel-Like/metabolismo , Estresse Oxidativo/efeitos dos fármacos , Peixe-Zebra/crescimento & desenvolvimento , Proteínas de Peixe-Zebra/genética , Proteínas de Peixe-Zebra/metabolismo
8.
Macromol Rapid Commun ; 41(17): e2000307, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32767468

RESUMO

Yolk-shell magnetic nanoparticles@nitrogen-enriched Carbon nanostructures with a magnetic core and a hollow nitrogen-enriched carbon shell exhibit considerable promise in various applications, such as drug delivery, heterogenous catalysts, removal of metal ions and organic pollutants, and screening of biomolecules, due to their strong magnetic response, unique cavities, and the selective absorption ability of nitrogen-enriched groups. However, their complicated synthesis always involves possible surface modification, layer-by-layer deposition of a sacrificial middle layer and an outer nitrogen-enriched layer on magnetic nanoparticles, subsequent carbonization, and final removal of the sacrificial middle layer. Herein, yolk-shell Fe3 O4 @nitrogen-enriched carbon nanostructures are constructed based on NH4 + ion-induced one-step deposition of SiO2 and Resorcinol-3-aminophenol-formaldehyde cocondensed resin (R-APF) dual layers onto poly acrylic acid-modified Fe3 O4 nanoclusters without any extra surface modification. The N-Carbon shell thickness of the yolk-shell Fe3 O4 @Void@N-Carbon nanostructure can be finely tailored though tailoring the feeding amount of aminophenol and resorcinol to tune the thickness of the outer R-APF resin shell onto Fe3 O4 @SiO2 intermediate particles. This NH4 + ion-induced one-pot deposition of double layers can effectively promote synthesis efficiency of this kind of yolk-shell nanostructure.


Assuntos
Nanopartículas , Dióxido de Silício , Aminofenóis , Carbono , Formaldeído , Resorcinóis
9.
Nat Commun ; 11(1): 3884, 2020 Aug 04.
Artigo em Inglês | MEDLINE | ID: mdl-32753658

RESUMO

Integrating nitrogen species into sp2-hybridized carbon materials has proved an efficient means to improve their electrochemical performance. Nevertheless, an inevitable mixture of nitrogen species in carbon materials, due to the uncontrolled conversion among different nitrogen configurations involved in synthesizing nitrogen-doped carbon materials, largely retards the precise identification of electrochemically active nitrogen configurations for specific reactions. Here, we report the preparation of single pyrrolic N-doped carbon materials (SPNCMs) with a tunable nitrogen content from 0 to 4.22 at.% based on a strategy of low-temperature dehalogenation-induced and subsequent alkaline-activated pyrolysis of 3-halogenated phenol-3-aminophenol-formaldehyde (X-APF) co-condensed resins. Additionally, considering that the pseudocapacitance of SPNCMs is positively dependent on the pyrrolic nitrogen content, it could be inferred that pyrrolic nitrogen species are highly active pseudocapacitive sites for nitrogen-doped carbon materials. This work gives an ideal model for understanding the contribution of pyrrolic nitrogen species in N-doped carbon materials.

10.
Opt Lett ; 45(15): 4216-4219, 2020 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-32735262

RESUMO

We propose a novel, to the best of our knowledge, cascade recurrent neural network (RNN)-based nonlinear equalizer for a pulse amplitude modulation (PAM)4 short-reach direct detection system. A 100 Gb/s PAM4 link is experimentally demonstrated over 15 km standard single-mode fiber (SSMF), using a 16 GHz directly modulated laser (DML) in C-band. The link suffers from strong nonlinear impairments which is mainly induced by the mixture of linear channel effects with square-law detection, the DML frequency chirp, and the device nonlinearity. Experimental results show that the proposed cascade RNN-based equalizer outperforms other feedforward or non-cascade neural network (NN)-based equalizers owing to both its cascade and recurrent structure, showing the great potential to effectively tackle the nonlinear signal distortion. With the aid of a cascade RNN-based equalizer, a bit-error rate (BER) lower than the 7% hard-decision forward error correction (FEC) threshold can be achieved when the receiver power is larger than 5 dBm. Compared with traditional non-cascade NN-based equalizers, the training time could also be reduced by half with the help of the cascade structure.

11.
Chemosphere ; 259: 127380, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32634720

RESUMO

Fomesafen is widely used in agriculture and can be detected in the environment and agricultural products. Research on the developmental toxicity of fomesafen in animals is currently very limited. Here, we used zebrafish as an animal model to evaluate the toxicity of fomesafen in developing aquatic vertebrates and higher animals. From 6h to 72h following fertilization, exposure of zebrafish embryos to 5, 10 and 20 mg/L of fomesafen resulted in pericardial edema, a reduction in heart rate, shortening of body length, and yolk sac edema. Fomesafen reduced the number of immune cells such as neutrophils and macrophages, increased the expression of a number of inflammatory factors, induced the up-regulation of the oxidative stress response and apoptosis, and disrupted the activity of enzymes related to nerve development, which affected the motility of the embryos. In conclusion, the results provide new evidence for the comprehensive assessment of fomesafen toxicity in aquatic vertebrates.


Assuntos
Benzamidas/toxicidade , Embrião não Mamífero/efeitos dos fármacos , Desenvolvimento Embrionário/efeitos dos fármacos , Herbicidas/toxicidade , Animais , Apoptose/efeitos dos fármacos , Estresse Oxidativo/efeitos dos fármacos , Regulação para Cima , Peixe-Zebra/embriologia , Peixe-Zebra/metabolismo
12.
Opt Express ; 27(25): 36953-36964, 2019 Dec 09.
Artigo em Inglês | MEDLINE | ID: mdl-31873466

RESUMO

The computational complexity and system bit-error-rate (BER) performance of four types of neural-network-based nonlinear equalizers are analyzed for a 50-Gb/s pulse amplitude modulation (PAM)-4 direct-detection (DD) optical link. The four types are feedforward neural networks (F-NN), radial basis function neural networks (RBF-NN), auto-regressive recurrent neural networks (AR-RNN) and layer-recurrent neural networks (L-RNN). Numerical results show that, for a fixed BER threshold, the AR-RNN-based equalizers have the lowest computational complexity. Amongst all the nonlinear NN-based equalizers with the same number of inputs and hidden neurons, F-NN-based equalizers have the lowest computational complexity while the AR-RNN-based equalizers exhibit the best BER performance. Compared with F-NN or RNN, RBF-NN tends to require more hidden neurons with the increase of the number of inputs, making it not suitable for long fiber transmission distance. We also demonstrate that only a few tens of multiplications per symbol are needed for NN-based equalizers to guarantee a good BER performance. This relatively low computational complexity signifies that various NN-based equalizers can be potentially implemented in real time. More broadly, this paper provides guidelines for selecting a suitable NN-based equalizer based on BER and computational complexity requirements.

13.
Opt Lett ; 43(8): 1870-1873, 2018 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-29652386

RESUMO

We propose a numerical and totally automatic phase aberration compensation method in digital holographic microscopy. The phase aberrations are extracted in a nonlinear optimization procedure in which the phase variation of the reconstructed object wave is minimized. Not only phase curvature but also high-order aberrations could be corrected without extra devices. The correction is directly carried out with the wrapped phase map, which is not affected by phase unwrapping or fitting errors. Numerical simulation proves that the proposed method is more accurate than the conventional surface fitting method without selecting a cell-free background. Experimental results demonstrate the availability of the proposed method in real-time analysis of living cells.


Assuntos
Holografia/métodos , Microscopia de Contraste de Fase/métodos , Osteoblastos/citologia , Algoritmos , Animais , Interpretação de Imagem Assistida por Computador/métodos , Camundongos
14.
Sensors (Basel) ; 18(3)2018 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-29510547

RESUMO

The diverse density (DD) algorithm was proposed to handle the problem of low classification accuracy when training samples contain interference such as mixed pixels. The DD algorithm can learn a feature vector from training bags, which comprise instances (pixels). However, the feature vector learned by the DD algorithm cannot always effectively represent one type of ground cover. To handle this problem, an instance space-based diverse density (ISBDD) model that employs a novel training strategy is proposed in this paper. In the ISBDD model, DD values of each pixel are computed instead of learning a feature vector, and as a result, the pixel can be classified according to its DD values. Airborne hyperspectral data collected by the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) sensor and the Push-broom Hyperspectral Imager (PHI) are applied to evaluate the performance of the proposed model. Results show that the overall classification accuracy of ISBDD model on the AVIRIS and PHI images is up to 97.65% and 89.02%, respectively, while the kappa coefficient is up to 0.97 and 0.88, respectively.

15.
Macromol Rapid Commun ; 38(22)2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-29027296

RESUMO

Functional polymer-grafting silica nanoparticles hold great promise in diverse applications such as molecule recognition, drug delivery, and heterogeneous catalysis due to high density and uniform distribution of functional groups and their tunable spatial distance. However, conventional grafting methods from monomers mainly consist of one or more extra surface modification steps and a subsequent surface polymerization step. A monomer protonation-dependent surface polymerization strategy is proposed to achieve one-step uniform surface grafting of cross-linked poly(4-vinylpyridine) (P4VP) onto core-shell Fe3 O4 @SiO2 nanostructures. At an approximate pH, partially protonated 4VP sites in aqueous solution can be strongly adsorbed onto deprotonated silanol groups (SiO- ) onto Fe3 O4 @SiO2 nanospheres to ensure prior polymerization of these protonated 4VP sites exclusively onto Fe3 O4 @SiO2 nanoparticles and subsequent polymerization of other 4VP and divinylbenzene monomers harvested by these protonated 4VP monomers onto Fe3 O4 @SiO2 nanoparticles, thereby achieving direct grafting of cross-linked P4VP macromolecules onto Fe3 O4 @SiO2 nanoparticles.


Assuntos
Óxido Ferroso-Férrico/química , Nanopartículas/química , Polivinil/química , Dióxido de Silício/química , Adsorção , Concentração de Íons de Hidrogênio , Nanopartículas/ultraestrutura , Polimerização , Propriedades de Superfície , Termogravimetria , Água/química
16.
Chem Asian J ; 11(24): 3534-3540, 2016 Dec 19.
Artigo em Inglês | MEDLINE | ID: mdl-27787941

RESUMO

Ni-based magnetic catalysts exhibit moderate activity, low cost, and magnetic reusability in hydrogenation reactions. However, Ni nanoparticles anchored on magnetic supports commonly suffer from undesirable agglomeration during catalytic reactions due to the relatively weak affinity of the magnetic support for the Ni nanoparticles. A hierarchical yolk-shell Fe@SiO2 /Ni catalyst, with an inner movable Fe core and an ultrathin SiO2 /Ni shell composed of nanosheets, was synthesized in a self-templating reduction strategy with a hierarchical yolk-shell Fe3 O4 @nickel silicate nanocomposite as the precursor. The spatial confinement of highly dispersed Ni nanoparticles with a mean size of 4 nm within ultrathin SiO2 nanosheets with a thickness of 2.6 nm not only prevented their agglomeration during catalytic transformations but also exposed the abundant active Ni sites to reactants. Moreover, the large inner cavities and interlayer spaces between the assembled ultrathin SiO2 /Ni nanosheets provided suitable mesoporous channels for diffusion of the reactants towards the active sites. As expected, the Fe@SiO2 /Ni catalyst displayed high activity, high stability, and magnetic recoverability for the reduction of nitroaromatic compounds. In particular, the Ni-based catalyst in the conversion of 4-nitroamine maintained a rate of over 98 % and preserved the initial yolk-shell structure without any obvious aggregation of Ni nanoparticles after ten catalytic cycles, which confirmed the high structural stability of the Ni-based catalyst.

17.
ACS Appl Mater Interfaces ; 8(32): 21046-54, 2016 Aug 17.
Artigo em Inglês | MEDLINE | ID: mdl-27463101

RESUMO

UV-triggered self-healing of single microcapsules has been a good candidate to enhance the life of polymer-based aerospace coatings because of its rapid healing process and healing chemistry based on an accurate stoichiometric ratio. However, free radical photoinitiators used in single microcapsules commonly suffer from possible deactivation due to the presence of oxygen in the space environment. Moreover, entrapment of polymeric microcapsules into coatings often involves elevated temperature or a strong solvent, probably leading to swelling or degradation of polymer shell, and ultimately the loss of active healing species into the host matrix. We herein describe the first single robust SiO2 microcapsule self-healing system based on UV-triggered cationic polymerization for potential application in aerospace coatings. On the basis of the similarity of solubility parameters of the active healing species and the SiO2 precursor, the epoxy resin and cationic photoinitiator are successfully encapsulated into a single SiO2 microcapsule via a combined interfacial/in situ polymerization. The single SiO2 microcapsule shows solvent resistance and thermal stability, especially a strong resistance for thermal cycling in a simulated space environment. In addition, the up to 89% curing efficiency of the epoxy resin in 30 min, and the obvious filling of scratches in the epoxy matrix demonstrate the excellent UV-induced healing performance of SiO2 microcapsules, attributed to a high load of healing species within the capsule (up to 87 wt %) and healing chemistry based on an accurate stoichiometric ratio of the photoinitiator and epoxy resin at 9/100. More importantly, healing chemistry based on a UV-triggered cationic polymerization mechanism is not sensitive to oxygen, extremely facilitating future embedment of this single SiO2 microcapsule in spacecraft coatings to achieve self-healing in a space environment with abundant UV radiation and oxygen.

18.
Chem Asian J ; 10(12): 2651-9, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-26282338

RESUMO

Robust nitrogen-enriched Fe3O4@carbon nanospheres have been fabricated as a catalyst scaffold for Pt nanoparticles. In this work, core-shell Fe3O4@3-aminophenol/formaldehyde (APF) nanocomposites were first synthesized by a simple hydrothermal method, and subsequently carbonized to Fe3O4@N-Carbon nanospheres for in situ growth of Pt nanocrystals. Abundant amine groups were distributed uniformly onto Fe3O4@N-Carbon nanospheres, which not only improved the dispersity and stability of the Pt nanocrystals, but also endowed the Pt-based catalysts with good compatibility in organic solvents. The dense three-dimensional cross-linked carbon shell protects the Fe3O4 cores against damage from harsh chemical environments, even in aqueous HCl (up to 1.0 M) or NaOH (up to 1.0 M) solutions under ultrasonication for 24 hours, which indicates that it can be used as a robust catalyst scaffold. In the reduction of nitrobenzene compounds, the Fe3O4@N-Carbon@Pt nanocatalysts show outstanding catalytic activity, stability, and recoverability.

19.
Opt Lett ; 36(7): 1056-8, 2011 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-21478981

RESUMO

Based on repetition frequency-dependent excited state absorption (ESA) upconversion (UC) luminescence, a method to measure the lifetime of an IR intermediate level is proposed so long as ESA UC luminescence can occur in the rare earth ions. The feasibility of this idea is demonstrated via a theoretical simulation. A Er(3+):LiNbO3 crystal ESA UC luminescence under femtosecond laser excitation is used to illustrate this measurement method, and the obtained 1.5 µm lifetime of 2.31 ms is shorter than previous reported values. This method can obviate the influence of radiation trapping effect on lifetime measurement, which is crucial in the traditional pulse sampling technique.


Assuntos
Raios Infravermelhos , Medições Luminescentes/métodos , Absorção , Lasers de Estado Sólido , Fatores de Tempo
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