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1.
Zhen Ci Yan Jiu ; 45(7): 541-7, 2020 Jul 25.
Artigo em Chinês | MEDLINE | ID: mdl-32705827

RESUMO

OBJECTIVE: To investigate the effect of electroacupuncture (EA) on intestinal Toll-like receptor 4 (TLR4) and nuclear factor-kappa B (NF-κB) in obese rats, so as to explore the mechanism of action of acupuncture in losing weight. METHODS: A total of 50 male Wistar rats were randomly divided into control and model groups. High-fat feed was used to establish a rat model of obesity, and after modeling, the 24 rats were randomly divided into model group, TLR4 inhibitor group, and EA group, with 8 rats in each group. The rats in the EA group were given EA at "Guanyuan" (CV4), "Zhongwan "(CV12), "Zusanli" (ST36), and" Fenglong" (ST40), 10 minutes each time, 3 times a week, and those in the TLR4 inhibitor group were given intraperitoneal injection of TAK-242 three times a week; the course of treatment was 8 weeks for both groups. Body weight and blood glucose were measured every two weeks. Co-immunoprecipitation was used to observe the interaction between TLR4 and NF-κB p65 in the intestinal tissue; electrophoretic mobility shift assay was used to measure the activity of NF-κB p65; Western blot was used to measure the protein expression of TLR4, phosphorylated nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor alpha (p-IκBα), and NF-κB p65; quantitative real-time PCR was used to measure the mRNA expression of TLR4, NF-κB p65, and IκBα. RESULTS: Compared with the control group, the model group had significant increases in body weight, blood glucose, and protein and mRNA expression of TLR4 and NF-κB p65 (P<0.01, P<0.05), as well as significant enhancement in the interaction between TLR4 and NF-κB p65 and activity of NF-κB p65 (P<0.05,P<0.01). Compared with the model group, the EA group had a significant reduction in body weight (P<0.05), both of the EA group and the TLR4 inhibitor group had significant reductions in blood glucose, and protein and mRNA expression of TLR4, p-IκBα, and NF-κB p65 (P<0.05,P<0.01), as well as significant reductions in the activity of NF-κB p65 (P<0.01). CONCLUSION: EA can effectively regulate intestinal TLR4, inhibit the interaction between TLR4 and NF-κB p65, and reduce the activity of NF-κB p65, which may be a potential mechanism of EA in reducing body weight and blood glucose in obese rats.

2.
Phys Chem Chem Phys ; 2020 Jan 24.
Artigo em Inglês | MEDLINE | ID: mdl-31976989

RESUMO

Using ambient-pressure X-ray photoelectron spectroscopy, here we report the real-time monitoring of dynamic surface composition evolution of Cu3Au(100) in response to the imposed environmental stimuli. Segregation of Au to the pristine surface under ultrahigh vacuum annealing leads to the phase separation with pure Au at the surface and alloyed Au in the subsurface. Upon switching to an oxidizing atmosphere, oxygen adsorption drives the surface segregation of Cu along with inward migration of pure Au to the subsurface. Switching to a H2 atmosphere results in oxygen loss from the oxygenated surface, thereby promoting Au surface segregation and reverting the surface to the pristine state with the Au termination. These measurements demonstrated the tunability of the surface composition of the binary alloy by utilizing the interplay between the tendency of segregating a more noble constituent to the surface and the tendency to segregate the more reactive one with the chemical stimuli.

3.
Nat Commun ; 11(1): 305, 2020 Jan 16.
Artigo em Inglês | MEDLINE | ID: mdl-31949160

RESUMO

Surface and subsurface are commonly considered as separate entities because of the difference in the bonding environment and are often investigated separately due to the experimental challenges in differentiating the surface and subsurface effects. Using in-situ atomic-scale transmission electron microscopy to resolve the surface and subsurface at the same time, we show that the hydrogen-CuO surface reaction results in structural oscillations in deeper atomic layers via the cycles of ordering and disordering of oxygen vacancies in the subsurface. Together with atomistic calculations, we show that the structural oscillations in the subsurface are induced by the hydrogen oxidation-induced cyclic loss of oxygen from the oxide surface. These results demonstrate the propagation of the surface reaction dynamics into the deeper layers in inducing nonstoichiometry in the subsurface and have significant implications in modulating various chemical processes involving surface-subsurface mass transport such as heterogeneous catalysis, oxidation, corrosion and carburization.

4.
ACS Omega ; 4(3): 4888-4895, 2019 Mar 31.
Artigo em Inglês | MEDLINE | ID: mdl-31459672

RESUMO

Sn-based alloy materials are strong candidates to replace graphitic carbon as the anode for the next generation lithium-ion batteries because of their much higher gravimetric and volumetric capacity. A series of nanosize Sn y Fe alloys derived from the chemical transformation of preformed Sn nanoparticles as templates have been synthesized and characterized. An optimized Sn5Fe/Sn2Fe anode with a core-shell structure delivered 541 mAh·g-1 after 200 cycles at the C/2 rate, retaining close to 100% of the initial capacity. Its volumetric capacity is double that of commercial graphitic carbon. It also has an excellent rate performance, delivering 94.8, 84.3, 72.1, and 58.2% of the 0.1 C capacity (679.8 mAh/g) at 0.2, 0.5, 1 and 2 C, respectively. The capacity is recovered upon lowering the rate. The exceptional cycling/rate capability and higher gravimetric/volumetric capacity make the Sn y Fe alloy a potential candidate as the anode in lithium-ion batteries. The understanding of Sn y Fe alloys from this work also provides insight for designing other Sn-M (M = Co, Ni, Cu, Mn, etc.) system.

5.
ACS Appl Mater Interfaces ; 11(38): 34889-34894, 2019 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-31466439

RESUMO

High-nickel layered oxides, such as NMC 811, are very attractive high energy density cathode materials. However, the high nickel content creates a number of challenges, including high surface reactivity and structural instability. Through a wet chemistry method, a Li-Nb-O coated and substituted NMC 811 was obtained in a single step treatment. This Li-Nb-O treatment not only supplied a protective surface coating but also optimized the electrochemical behavior by Nb5+ incorporation into the bulk structure. As a result, the 1st capacity loss was significantly reduced (13.7 vs 25.1 mA h/g), contributing at least a 5% increase to the energy density of the full cell. In addition, both the rate (158 vs 135 mA h/g at 2C) and capacity retention (89.6 vs 81.6% after 60 cycles) performance were enhanced.

6.
Sci Rep ; 9(1): 2075, 2019 02 14.
Artigo em Inglês | MEDLINE | ID: mdl-30765831

RESUMO

Concrete is susceptible to cracking owing to drying shrinkage, freeze-thaw cycles, delayed ettringite formation, reinforcement corrosion, creep and fatigue, etc. Continuous inspection and maintenance of concrete infrastructure require onerous labor and high costs. If the damaging cracks can heal by themselves without any human interference or intervention, that could be of great attraction. In this study, a novel self-healing approach is investigated, in which fungi are applied to heal cracks in concrete by promoting calcium carbonate precipitation. The goal of this investigation is to discover the most appropriate species of fungi for the application of biogenic crack repair. Our results showed that, despite the significant pH increase owing to the leaching of calcium hydroxide from concrete, Aspergillus nidulans (MAD1445), a pH regulatory mutant, could grow on concrete plates and promote calcium carbonate precipitation.

7.
Chem Commun (Camb) ; 54(53): 7342-7345, 2018 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-29911221

RESUMO

We report in situ atomic-scale transmission electron microscopy observations of the surface dynamics during Cu2O reduction. We show inhomogeneous oxide reduction caused by the preferential adsorption of hydrogen at step edges that induces oxygen loss and destabilizes Cu atoms within the step edge, thereby resulting in the retraction motion of atomic steps at the oxide surface.

8.
Chem Commun (Camb) ; 54(56): 7802-7805, 2018 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-29946607

RESUMO

By controlling the morphology and particle size of the epsilon polymorph of vanadyl phosphate, ε-VOPO4, it can fully reversibly intercalate two Li-ions and reach the theoretical capacity of 305 mA h g-1 over two voltage plateaus at about 4.0 and 2.5 V.

9.
Nat Mater ; 17(6): 514-518, 2018 06.
Artigo em Inglês | MEDLINE | ID: mdl-29736001

RESUMO

The presence of water vapour, intentional or unavoidable, is crucial to many materials applications, such as in steam generators, turbine engines, fuel cells, catalysts and corrosion1-4. Phenomenologically, water vapour has been noted to accelerate oxidation of metals and alloys5,6. However, the atomistic mechanisms behind such oxidation remain elusive. Through direct in situ atomic-scale transmission electron microscopy observations and density functional theory calculations, we reveal that water-vapour-enhanced oxidation of a nickel-chromium alloy is associated with proton-dissolution-promoted formation, migration, and clustering of both cation and anion vacancies. Protons derived from water dissociation can occupy interstitial positions in the oxide lattice, consequently lowering vacancy formation energy and decreasing the diffusion barrier of both cations and anions, which leads to enhanced oxidation in moist environments at elevated temperatures. This work provides insights into water-vapour-enhanced alloy oxidation and has significant implications in other material and chemical processes involving water vapour, such as corrosion, heterogeneous catalysis and ionic conduction.

10.
Nat Mater ; 17(1): 56-63, 2018 01.
Artigo em Inglês | MEDLINE | ID: mdl-29180772

RESUMO

Surface segregation-the enrichment of one element at the surface, relative to the bulk-is ubiquitous to multi-component materials. Using the example of a Cu-Au solid solution, we demonstrate that compositional variations induced by surface segregation are accompanied by misfit strain and the formation of dislocations in the subsurface region via a surface diffusion and trapping process. The resulting chemically ordered surface regions acts as an effective barrier that inhibits subsequent dislocation annihilation at free surfaces. Using dynamic, atomic-scale resolution electron microscopy observations and theory modelling, we show that the dislocations are highly active, and we delineate the specific atomic-scale mechanisms associated with their nucleation, glide, climb, and annihilation at elevated temperatures. These observations provide mechanistic detail of how dislocations nucleate and migrate at heterointerfaces in dissimilar-material systems.

11.
ACS Omega ; 3(7): 7310-7323, 2018 Jul 31.
Artigo em Inglês | MEDLINE | ID: mdl-31458891

RESUMO

ε-LiVOPO4 is a promising multielectron cathode material for Li-ion batteries that can accommodate two electrons per vanadium, leading to higher energy densities. However, poor electronic conductivity and low lithium ion diffusivity currently result in low rate capability and poor cycle life. To enhance the electrochemical performance of ε-LiVOPO4, in this work, we optimized its solid-state synthesis route using in situ synchrotron X-ray diffraction and applied a combination of high-energy ball-milling with electronically and ionically conductive coatings aiming to improve bulk and surface Li diffusion. We show that high-energy ball-milling, while reducing the particle size also introduces structural disorder, as evidenced by 7Li and 31P NMR and X-ray absorption spectroscopy. We also show that a combination of electronically and ionically conductive coatings helps to utilize close to theoretical capacity for ε-LiVOPO4 at C/50 (1 C = 153 mA h g-1) and to enhance rate performance and capacity retention. The optimized ε-LiVOPO4/Li3VO4/acetylene black composite yields the high cycling capacity of 250 mA h g-1 at C/5 for over 70 cycles.

12.
J Phys Chem B ; 122(2): 855-863, 2018 01 18.
Artigo em Inglês | MEDLINE | ID: mdl-29091455

RESUMO

The role of oxygen in the activation of C-H bonds in methane on clean and oxygen-precovered Cu(111) and Cu2O(111) surfaces was studied with combined in situ near-ambient-pressure scanning tunneling microscopy and X-ray photoelectron spectroscopy. Activation of methane at 300 K and "moderate pressures" was only observed on oxygen-precovered Cu(111) surfaces. Density functional theory calculations reveal that the lowest activation energy barrier of C-H on Cu(111) in the presence of chemisorbed oxygen is related to a two-active-site, four-centered mechanism, which stabilizes the required transition-state intermediate by dipole-dipole attraction of O-H and Cu-CH3 species. The C-H bond activation barriers on Cu2O(111) surfaces are large due to the weak stabilization of H and CH3 fragments.

13.
J Phys Chem Lett ; 8(24): 6035-6040, 2017 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-29193974

RESUMO

Using in situ transmission electron microscopy that spatially and temporally resolves the evolution of the atomic structure in the surface and subsurface regions, we find that the surface segregation of Au atoms in a Cu(Au) solid solution results in the nucleation and growth of a (2 × 1) missing-row reconstructed, half-unit-cell thick L12 Cu3Au(110) surface alloy. Our in situ electron microscopy observations and atomistic simulations demonstrate that the (2 × 1) reconstruction of the Cu3Au(110) surface alloy remains as a stable surface structure as a result of the favored Cu-Au diatom configuration.

14.
Nanoscale ; 9(34): 12398-12408, 2017 Aug 31.
Artigo em Inglês | MEDLINE | ID: mdl-28808709

RESUMO

A binary system of tin/indium (Sn/In) in the form of nanoparticles was investigated for phase transitions and structural evolution at different temperatures and compositions. The Sn/In nanosolder particles in the composition range of 24-72 wt% In were synthesized by a surfactant-assisted chemical reduction method under ambient conditions. The morphology and microstructure of the as-synthesized nanoparticles were analyzed by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and X-ray diffraction (XRD). HRTEM and SAED identified InSn4 and In, with some Sn being detected by XRD, but no In3Sn was observed. The differential scanning calorimetry (DSC) thermographs of the as-synthesized nanoparticles exhibited an endothermic peak at around 116 °C, which is indicative of the metastable eutectic melting of InSn4 and In. When the nanosolders were subjected to heat treatment at 50-225 °C, the equilibrium phase In3Sn appeared while Sn disappeared. The equilibrium state was effectively attained at 225 °C. A Tammann plot of the DSC data of the as-synthesized nanoparticles indicated that the metastable eutectic composition is about 62% In, while that of the DSC data of the 225 °C heat-treated nanoparticles yielded a eutectic composition of 54% In, which confirmed the attainment of the equilibrium state at 225 °C. The phase boundaries estimated from the DSC data of heat-treated Sn/In nanosolder particles matched well with those in the established Sn-In equilibrium phase diagram. The phase transition behavior of Sn/In nanosolders leads to a new understanding of binary alloy particles at the nanoscale, and provides important information for their low temperature soldering processing and applications.

15.
Nat Commun ; 8(1): 307, 2017 08 21.
Artigo em Inglês | MEDLINE | ID: mdl-28824169

RESUMO

Directly probing structure dynamics at metal/oxide interfaces has been a major challenge due to their buried nature. Using environmental transmission electron microscopy, here we report observations of the in-place formation of Cu2O/Cu interfaces via the oxidation of Cu, and subsequently probe the atomic mechanisms by which interfacial transformation and grain rotation occur at the interfaces during reduction in an H2 gas environment. The Cu2O→Cu transformation is observed to occur initially along the Cu2O/Cu interface in a layer-by-layer manner. The accumulation of oxygen vacancies at the Cu2O/Cu interface drives the collapse of the Cu2O lattice near the interface region, which results in a tilted Cu2O/Cu interface with concomitant Cu2O island rotation. These results provide unprecedented microscopic detail regarding the redox reactions of supported oxides, which differs fundamentally from the reduction of bulk or isolated oxides that requires the formation of new interfaces between the parent oxide and the reduced phase.Metal/oxide interfaces play an important role in heterogeneous catalysis and redox reactions, but their buried nature makes them difficult to study. Here, the authors use environmental transmission electron microscopy to probe the atomic-level transformations at Cu2O/Cu interfaces as they undergo redox reactions.

16.
Chem Commun (Camb) ; 53(39): 5376-5379, 2017 May 11.
Artigo em Inglês | MEDLINE | ID: mdl-28425514

RESUMO

A Fe-based catalyst exhibits extremely high selectivity (89.6%) besides excellent catalytic activity in gas-phase dimethyl oxalate hydrogenation. The ethanol formation occurs via hydrogenation of methyl acetate instead of ethylene glycol over the active species Fe5C2.


Assuntos
Compostos Inorgânicos de Carbono/química , Etanol/síntese química , Compostos de Ferro/química , Nanoestruturas , Oxalatos/química , Catálise , Hidrogenação , Estrutura Molecular
17.
Hepatology ; 66(1): 136-151, 2017 07.
Artigo em Inglês | MEDLINE | ID: mdl-28194813

RESUMO

Current treatment of intrahepatic cholangiocarcinoma (ICC) remains ineffective because knowledge of ICC carcinogenesis is unclear. Increasing evidence suggests that microRNAs (miRNAs), including miR-191, play an important role in tumorigenesis; but expression and biological functions of miR-191 in ICC remain to be established. This study investigated the functions and underlying mechanisms of miR-191 in ICC. ICC miRNA profiles were generated in five pairs of ICC and matched to normal bile duct tissues by next-generation sequencing technology; ICC miRNA profiles were verified in 18 pairs of ICC tissues and normal bile duct tissues by quantitative RT-PCR. The miR-191-associated mechanisms in ICC were investigated in vitro and in vivo, and clinical outcomes associated with miR-191 were correlated in 84 patients. Our results showed that miR-191 expression was significantly increased in ICC compared with the adjacent normal bile duct tissues (P < 0.001). Overexpression of miR-191 promoted proliferation, invasion, and migration of cholangiocarcinoma cells in vitro and in vivo. The elevated miR-191 expression reduced the expression level of ten-eleven translocation 1 (TET1)-a direct target gene of miR-191 in ICC, which catalyzes demethylation. The reduced TET1 expression level allowed the methylated CpG-rich regions at the p53 gene transcription start site stay methylated, leading to reduced p53 expression level, which compromises p53's anticancer vigor. Finally, miR-191 was found to be an independent risk factor for poor prognosis in patients with ICC (overall survival, hazard ratio = 3.742, 95% confidence interval 2.080-6.733, P < 0.001; disease-free survival, hazard ratio = 2.331, 95% confidence interval 1.346-4.037, P = 0.003). CONCLUSION: Our results suggest that overexpressed miR-191 is associated with ICC progression through the miR-191/TET1/p53 pathway. (Hepatology 2017;66:136-151).


Assuntos
Neoplasias dos Ductos Biliares/genética , Colangiocarcinoma/genética , Regulação Neoplásica da Expressão Gênica , MicroRNAs/genética , Oxigenases de Função Mista/genética , Proteínas Proto-Oncogênicas/genética , Animais , Neoplasias dos Ductos Biliares/patologia , Biópsia por Agulha , Movimento Celular/genética , Proliferação de Células/genética , Colangiocarcinoma/patologia , Estudos de Coortes , Modelos Animais de Doenças , Progressão da Doença , Feminino , Humanos , Imuno-Histoquímica , Masculino , Camundongos , Camundongos Nus , Metástase Neoplásica/genética , Estudos Retrospectivos , Sensibilidade e Especificidade , Transdução de Sinais , Células Tumorais Cultivadas
18.
ACS Nano ; 11(1): 656-664, 2017 01 24.
Artigo em Inglês | MEDLINE | ID: mdl-27960055

RESUMO

Atomic-scale structural dynamics and phase transformation pathways were probed, in situ, during the hydrogen-induced reduction of Fe2O3 nanostructure bicrystals using an environmental transmission electron microscope. Reduction commenced with the α-Fe2O3 → γ-Fe2O3 phase transformation of one part of the bicrystal, resulting in the formation of a two-phase structure of α-Fe2O3 and γ-Fe2O3. The progression of the phase transformation into the other half of the bicrystalline Fe2O3 across the bicrystalline boundary led to the formation of a single-crystal phase of γ-Fe2O3 with concomitant oxygen-vacancy ordering on every third {422} plane, followed by transformation into Fe3O4. Further reduction resulted in the coexistence of Fe3O4, FeO, and Fe via the transformation pathway Fe3O4 → FeO → Fe. The series of phase transformations was accompanied by the formation of a Swiss-cheese-like structure, induced by the significant volume shrinkage occurring upon reduction. These results elucidated the atomistic mechanism of the reduction of Fe oxides and demonstrated formation of hybrid structures of Fe oxides via tuning the phase transformation pathway.

19.
J Chem Phys ; 145(23): 234704, 2016 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-28010088

RESUMO

Using a combination of scanning tunneling microscopy (STM) and density functional theory (DFT) modeling, we determine the mechanism of the atomic structural evolution of the oxygenated Cu(110) surface induced by the reaction of adsorbed hydrogen with chemisorbed oxygen in the Cu(110)-c(6 × 2)-O structure. Our STM observations show that the reconstructed Cu(110)-c(6 × 2)-O surface undergoes a phase transition to the (2 × 1)-O reconstruction in the course of oxygen loss induced by the reaction with H2 gas. Using DFT modeling, we find that the surface phase transition is initiated via the adsorption of molecular hydrogen on the chemisorbed oxygen, which results in the formation of H2O molecules that desorb spontaneously from the surface. The loss of chemisorbed oxygen induces the c(6 × 2) → (2 × 1) transition that involves the diffusion of Cu-O-Cu chains along the ⟨1¯10⟩ direction.

20.
J Phys Chem C Nanomater Interfaces ; 120(27): 14854-14862, 2016 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-27891206

RESUMO

The atomic-scale reduction mechanism of α-Fe2O3 nanowires by H2 was followed using transmission electron microscopy to reveal the evolution of atomic structures and the associated transformation pathways for different iron oxides. The reduction commences with the generation of oxygen vacancies that order onto every 10th [Formula: see text] plane. This vacancy ordering is followed by an allotropic transformation of α-Fe2O3 → γ-Fe2O3 along with the formation of Fe3O4 nanoparticles on the surface of the γ-Fe2O3 nanowire by a topotactic transformation process, which shows 3D correspondence between the structures of the product and its host. These observations demonstrate that the partial reduction of α-Fe2O3 nanowires results in the formation of a unique hierarchical structure of hybrid oxides consisting of the parent oxide phase, γ-Fe2O3, as the one-dimensional wire and the Fe3O4 in the form of nanoparticles decorated on the parent oxide skeleton. We show that the proposed mechanism is consistent with previously published and our density functional theory results on the thermodynamics of surface termination and oxygen vacancy formation in α-Fe2O3. Compared to previous reports of α-Fe2O3 directly transformed to Fe3O4, our work provides a more in-depth understanding with substeps of reduction, i.e., the whole reduction process follows: α-Fe2O3 → α-Fe2O3 superlattice → γ-Fe2O3 + Fe3O4→ Fe3O4.

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