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1.
Nanoscale ; 12(2): 755-762, 2020 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-31829368

RESUMO

Efficient photocatalytic conversion of CO2 into energy-rich chemicals is of great significance for both environmental conservation and alleviating the energy crisis. However, convenient synthesis of low-cost, durable and eco-friendly photocatalysts with a novel morphology or structure for highly selective photocatalytic CO2 reduction remains a challenge. Herein, Co3O4 hierarchical nanosheets were synthesized by calcination of novel cobalt metal-organic framework (MOF) nanosheets prepared by a facile oil bath method. In such Co MOF nanosheets, 1,4-naphthalenedicarboxylic acid was chosen as the organic linker, rather than the commonly used 2-methylimidazole for ZIF-67. After thermal treatment in air, the obtained Co3O4 inherited the 2D morphology of its MOF template and evolved into hierarchical nanosheets which were composed of small nanoparticles. Benefiting from the large surface area, abundant mesoporous structure and good capability towards the separation and transfer of photo-generated charge carriers induced by less internal oxygen vacancies, the Co3O4 hierarchical nanosheets showed a CO generation rate of 39.70 µmol h-1 in visible-light photocatalytic CO2 reduction, which was superior to that of Co3O4 nanoparticles and commercial Co3O4. What's more, a CO selectivity of 77.3% was achieved, which is among the highest of cobalt-based spinel oxide photocatalysts for CO2 conversion.

3.
Angew Chem Int Ed Engl ; 58(40): 14197-14201, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31385423

RESUMO

Bimetal-S-O composites have been rarely researched in electrochemical reduction of CO2 . Now, an amorphous Ag-Bi-S-O decorated Bi0 catalyst derived from Ag0.95 BiS0.75 O3.1 nanorods by electrochemical pre-treatment was used for catalyzing eCO2 RR, which exhibited a formate FE of 94.3 % with a formate partial current density of 12.52 mA cm-2 at an overpotential of only 450 mV. This superior performance was attributed to the attached amorphous Ag-Bi-S-O substance. S could be retained in the amorphous region after electrochemical pre-treatment only in samples derived from metal-S-O composites, and it would greatly enhance the formate selectivity by accelerating the dissociation of H2 O. The existence of Ag would increase the current density, resulting in a higher local pH, which made the role of S in activating H2 O more significantly and suppressed H2 evolution more effectively, thus endowing the catalyst with a higher formate FE at low overpotentials.

4.
Drug Deliv ; 26(1): 63-69, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30744429

RESUMO

The influence of chiral excipient D-chitosan (CS) on the stereoselective release of racemic ketoprofen (rac-KET) microspheres has been investigated in comparison to those microspheres containing individual enantiomers in vitro and in vivo. Stereoselectivity was observed in vitro release test, with R-KET release slightly higher than that of S-KET, especially in 3% rac-KET loading microspheres. Stereoselectivity is dependent on the content of chiral excipient and pH of release medium. A molecular docking study between CS and KET enantiomers further revealed that S-KET has a stronger interaction with CS compared to R-KET. Moreover, the plasma concentration of KET enantiomers in rats shows substantial differences, as the plasma levels of S-KET were higher than those of R-KET. Plasma levels of enantiomers from the R-KET microspheres had similar stereoselectivity as rac-KET microspheres. The S/R ratio of rac-KET microspheres was significantly lower than that of rac-KET suspension (regular-release formulation) (p<.05), and the differences is 3-5 fold. Besides, rates of R-KET converted to S-KET exhibited differences between rac-KET microspheres and suspension. Similar results were also found between R-KET microspheres and suspension. All investigations suggest that the chitosan interacting preferentially with S-KET to R-KET significantly affect the stereoselective pharmacokinetics of rac-KET from chitosan microspheres in rats.


Assuntos
Anti-Inflamatórios não Esteroides/administração & dosagem , Quitosana/administração & dosagem , Sistemas de Liberação de Medicamentos/métodos , Cetoprofeno/administração & dosagem , Microesferas , Animais , Anti-Inflamatórios não Esteroides/química , Anti-Inflamatórios não Esteroides/metabolismo , Quitosana/química , Quitosana/metabolismo , Avaliação Pré-Clínica de Medicamentos/métodos , Feminino , Cetoprofeno/química , Cetoprofeno/metabolismo , Masculino , Simulação de Acoplamento Molecular/métodos , Ratos , Ratos Sprague-Dawley , Estereoisomerismo
5.
Chemistry ; 25(21): 5472-5479, 2019 Apr 11.
Artigo em Inglês | MEDLINE | ID: mdl-30693990

RESUMO

The metal-controlled self-assembly of organometallic molecular cylinders from a series of imidazo[1,5-a]pyridine-based tris-NHC ligands is described in this report. The imidazo[1,5-a]pyridinium salts H3 -L(PF6 )3 (L=4 a-4 c) were treated with 1.5 equivalents of Ag2 O to yield the trinuclear AgI hexacarbene cages [Ag3 (L)2 ](PF6 )3 (L=4 a-4 c), in which three AgI are sandwiched between the two tricarbene ligands. The silver(I) complexes [Ag3 (L)2 ](PF6 )3 underwent a facile transmetalation reaction in the presence of 3 equivalents of [AuCl(tht)] (tht=tetrahydrothiophene) to furnish the trinuclear AuI cylinder-like cages [Au3 (L)2 ](PF6 )3 (L=4 a-4 c) without destruction of the metallosupramolecular structure. The new hexacarbene assemblies feature a large cavity that can easily accommodate a molecule of dimethyl sulfoxide as molecular guest. This is the first study of a unique "host-guest" system containing an organometallic cylinder-like cage derived exclusively from poly-NHC ligands.

6.
J Hazard Mater ; 361: 329-337, 2019 01 05.
Artigo em Inglês | MEDLINE | ID: mdl-30245255

RESUMO

Fluorescent CdTe nanocrystals (NCs) capped with beta-cyclodextrin (ß-CD) are successfully synthesized by host-guest supramolecular assembly of the hydrophobic alkyl chains of N-acetyl-l-cysteine (NAC) on the surface of CdTe NCs and eco-friendly ß-CD via the promising simple hydrothermal method in our experiments. The as-prepared NCs display better stability and lower toxicity compared with traditional those only capped with NAC. Specially, cytotoxicity experiments to human umbilical vein endothelial cells in vitro and zebrafish embryo toxicological tests in vivo are performed to determine the toxicity of CdTe NCs. For their practical applications, the promising red-luminescent NCs are employed as stable and low poison red phosphors to fabricate white light-emitting diodes (WLEDs) with remarkable color-rendering index (CRI) being 91.6. This research offers significance for solving the difficulty in toxicity and instability of heavy metal based NCs, which has potential applications in future optoelectronic devices and biomarkers.

7.
Brief Bioinform ; 20(5): 1913-1924, 2019 09 27.
Artigo em Inglês | MEDLINE | ID: mdl-30032279

RESUMO

In the genetic system that regulates complex traits, metabolites, gene expression levels, RNA editing levels and DNA methylation, a series of small and linked genes exist. To date, however, little is known about how to design an efficient framework for the detection of these kinds of genes. In this article, we propose a genome-wide composite interval mapping (GCIM) in F2. First, controlling polygenic background via selecting markers in the genome scanning of linkage analysis was replaced by estimating polygenic variance in a genome-wide association study. This can control large, middle and minor polygenic backgrounds in genome scanning. Then, additive and dominant effects for each putative quantitative trait locus (QTL) were separately scanned so that a negative logarithm P-value curve against genome position could be separately obtained for each kind of effect. In each curve, all the peaks were identified as potential QTLs. Thus, almost all the small-effect and linked QTLs are included in a multi-locus model. Finally, adaptive least absolute shrinkage and selection operator (adaptive lasso) was used to estimate all the effects in the multi-locus model, and all the nonzero effects were further identified by likelihood ratio test for true QTL identification. This method was used to reanalyze four rice traits. Among 25 known genes detected in this study, 16 small-effect genes were identified only by GCIM. To further demonstrate GCIM, a series of Monte Carlo simulation experiments was performed. As a result, GCIM is demonstrated to be more powerful than the widely used methods for the detection of closely linked and small-effect QTLs.

8.
World J Gastroenterol ; 24(40): 4596-4605, 2018 Oct 28.
Artigo em Inglês | MEDLINE | ID: mdl-30386109

RESUMO

AIM: To evaluate the outcomes of furazolidone- and amoxicillin-based quadruple therapy for treatment of Helicobacter pylori (H. pylori) infection and identify predictors of failed eradication. METHODS: Patients with H. pylori infection treated with furazolidone, amoxicillin, bismuth, and proton pump inhibitor therapy (January 2015 to December 2015) who received the 13C-urea breath test > 4 wk after treatment were evaluated. Demographic and clinical data including prior H. pylori treatment attempts, medication adherence, alcohol and cigarette consumption during therapy, and treatment-related adverse events were recorded by reviewing medical records and telephone surveys. H. pylori eradication rates for overall and subgroups were evaluated. Multivariate analysis was performed to identify independent predictors of failed H. pylori eradication. RESULTS: Of the 992 patients treated and retested for H. pylori infection, the overall eradication rate was 94.5% [95% confidence interval (CI): 94.1%-95.9%]. H. pylori eradication rate of primary therapy was 95.0% (95%CI: 93.5%-96.5%), while that of rescue therapy was 91.3% (95%CI: 86.8%-95.8%). Among the 859 patients who completed the study protocol, 144 (17%) reported treatment-related adverse events including 24 (3%) leading to premature discontinuation. On multivariate analysis, poor medication adherence [adjusted odds ratio (AOR) = 6.7, 95%CI: 2.8-15.8], two or more previous H. pylori treatments (AOR = 7.4, 95%CI: 2.2-24.9), alcohol consumption during therapy (AOR = 4.4, 95%CI: 1.5-12.3), and possibly smoking during therapy (AOR = 1.9, 95%CI: 0.9-4.3) were associated with failed H. pylori eradication. CONCLUSION: Furazolidone- and amoxicillin-based quadruple therapy for H. pylori infection in an area with a high prevalence of clarithromycin resistance demonstrated high eradication rates as primary and rescue therapies with a favorable safety profile. Patient education targeting abstinence from alcohol during therapy and strict medication adherence may further optimize H. pylori eradication.


Assuntos
Amoxicilina/uso terapêutico , Antibacterianos/uso terapêutico , Anti-Infecciosos Locais/uso terapêutico , Furazolidona/uso terapêutico , Infecções por Helicobacter/tratamento farmacológico , Helicobacter pylori/efeitos dos fármacos , Adulto , Consumo de Bebidas Alcoólicas/efeitos adversos , Consumo de Bebidas Alcoólicas/prevenção & controle , Antiácidos/uso terapêutico , Antibacterianos/farmacologia , Bismuto/uso terapêutico , Testes Respiratórios , Claritromicina/uso terapêutico , Farmacorresistência Bacteriana , Quimioterapia Combinada/métodos , Feminino , Infecções por Helicobacter/microbiologia , Helicobacter pylori/isolamento & purificação , Humanos , Masculino , Adesão à Medicação/estatística & dados numéricos , Pessoa de Meia-Idade , Educação de Pacientes como Assunto , Inibidores da Bomba de Prótons/uso terapêutico , Falha de Tratamento
9.
Adv Mater ; 30(52): e1803475, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30393968

RESUMO

Methods allowing construction of macroscopic programmed materials in a flexible and efficient fashion are highly desirable. However, the existing approaches are far removed from such materials. A new self-healing-driven assembly (SHDA) strategy to fabricate various programmed materials by using uniform gel beads (microsize of 212 µm or millimeter size of 4 mm) as building blocks is described here. In virtue of hydrogen bonds and host-guest interactions between gel beads, a series of linear, planar, and 3D beaded assemblies are fabricated via SHDA in microfluidic channels in a continuous and controlled manner. From the perspective of practical applications, the use of gel assemblies is exploited for tissue engineering with controlled cells coculture, as well as light conversion materials toward white-light-emitting diodes (WLEDs). The SHDA strategy developed in this study gives a new insight into the facile and rapid fabrication of various programmed materials toward biological tissue and optoelectronic device.

10.
Front Plant Sci ; 9: 1146, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30186292

RESUMO

Understanding the genetic function of the forage quality-related traits, including crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), hemicellulose (HC), and cellulose (CL) contents, is essential for the identification of forage quality genes and selection of effective molecular markers in sorghum. In this study, we genotyped 245 sorghum accessions by 85,585 single-nucleotide polymorphisms (SNPs) and obtained the phenotypic data from four environments. The SNPs and phenotypic data were applied to multi-locus genome-wide association studies (GWAS) with the mrMLM software. A total of 42 SNPs were identified to be associated with the five forage quality-related traits. Moreover, three and two quantitative trait nucleotides (QTNs) were simultaneously detected among them by three and two multi-locus methods, respectively. One QTN on chromosome 5 was found to be associated simultaneously with CP, NDF, and ADF. Furthermore, 3, 2, 2, 5, and 2 candidate genes were identified to be responsible for CP, NDF, ADF, HC, and CL contents, respectively. These results provided insightful information of the forage quality-related traits and would facilitate the genetic improvement of sorghum forage quality in the future.

11.
ACS Appl Mater Interfaces ; 10(37): 31603-31609, 2018 Sep 19.
Artigo em Inglês | MEDLINE | ID: mdl-30152231

RESUMO

Hybrid organic-inorganic and all-inorganic metal halide perovskite nanocrystals (PNCs) have aroused extensive attention from both academic and industrial researchers, considering their excellent performance in optoelectronic applications. Herein, we develop a facile and time-saving strategy to synthesize NH2CH═NH2PbBr3 (NH2CH═NH+, FA) PNCs at room temperature. Benefiting from this facile method, high-quality FAPbBr3 PNCs with photoluminescence quantum yield up to 76% and narrow full width at half-maxima of 20 nm can be produced on a large scale. Moreover, anion-exchange reactions run by using FAPbBr3 as a template, producing various PNCs with different anion constituents. By manipulating the ratios of two different anions, a series PNCs with various bright photoluminescence ranging from 452 to 646 nm could be done. On account of superior and adjustable photoluminescence over the visible spectral region, FAPbBr3 PNCs can be applied as a promising color-converting material in liquid-crystal display (LCD) backlight, white light-emitting diode (WLED), and inkjet printing pattern. As a proof of concept, FAPbBr3 PNCs with green emission were integrated in WLED and LCD backlight, accomplishing a color rendering index of 87.5 and a wide color gamut of 116%, respectively.

12.
ACS Appl Mater Interfaces ; 10(31): 26233-26240, 2018 Aug 08.
Artigo em Inglês | MEDLINE | ID: mdl-29989395

RESUMO

The copper nanoflowers, assembled by sub-2 nm rough nanowires with high catalytic active (200) facets, are prepared by a prompt and simple method with cetyltrimethylammonium bromide (CTAB) as a capping agent. The CTAB plays a vital role in the synthesis process, whereas the copper nanorod arrays assembled by copper nanoparticles are obtained without CTAB. The copper nanoflowers are used as catalysts in oxygen reduction reactions and exhibit excellent electrocatalytic activity, which shows nearly the same activity compared with the commercial Pt/C catalyst, attributing to the nanoflower-exposed higher catalytic active (200) facets. Furthermore, the nanoflowers can avoid methanol-poison effect and show better long-term operation stability. The density functional theory was used to calculate the atom energy of Cu(100) facets and Cu(111) facets. Both of O2 dissociation and H2O activation on the facets are very easy. However, the difference between Cu(100) facets and Cu(111) facets is the adsorption and dissociation energy of O2, and the adsorption and activation of oxygen molecule is much easier on Cu(100) facets than on Cu(111) facets because of the more open nature of (100) facets.

13.
Zhongguo Shi Yan Xue Ye Xue Za Zhi ; 26(3): 917-921, 2018 Jun.
Artigo em Chinês | MEDLINE | ID: mdl-29950243

RESUMO

Hematopoietic stem cells (HSC) are a class of stem cells with self-renewal and multipotent differentiation into a variety of blood cells and are most thoroughly studied, maturely applied in the clinic adult stem cell. Function of HSC is closely associated with metabolic regulation. The metabolic state mainly maintains HSC living in hypoxic bone marrow microenvironment depending on glycolysis for energy metabolism, and keeping low reactive oxygen species (ROS) level. Proteins like Hif-1, FoxO3, ATM, PTPMT1 protect HSC from ROS injury, maintaining HSC in hypoxic state. In addition, glucose metabolism-related enzymes, glutamine, fatty acid oxidation, purine and amino acid metabolism also play important roles in metabolic regulation of HSC. In this review the research progress on metabolism regnlation mechanisms of HSC is summurized, focusing on the mechanisms releted with oxydation metabolism regulation, carbohydrate metabolism level, purine metabolism and aminoacide metabolism.


Assuntos
Células-Tronco Hematopoéticas , Medula Óssea , Diferenciação Celular , Oxirredução , Espécies Reativas de Oxigênio
14.
Nanoscale ; 10(15): 6936-6944, 2018 Apr 19.
Artigo em Inglês | MEDLINE | ID: mdl-29594270

RESUMO

The synthesis of ultrathin metal nanosheets (NSs) attracts broad scientific and technological interest, and it still remains a challenge for non-noble metals like nickel due to their intrinsic cubic symmetry and high surface energy. Herein, we report a NiO intermediated solvothermal method towards the synthesis of ultrathin Ni NSs (thickness < 3 nm) using N,N-dimethylformamide as the solvent and n-butylamine as the shape controlling reagent. The growth of the ultrathin Ni NSs follows an intermediate mechanism which was proved by the results obtained by means of transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray absorption spectra (XAS) and X-ray photoelectron spectroscopy (XPS). Under solvothermal conditions, the nickel acetylacetonate precursor was first reduced to a NiO NS intermediate, then reduction occurred and NiO NSs were reduced to Ni NSs. The synthesized ultrathin Ni NSs predominately in a metallic state showed high selectivity (88.0-92.0%) towards styrene (ST) in the phenylacetylene (PA) semihydrogenation reaction under mild conditions (323 K, 1 atm of hydrogen) in a broad PA conversion range (2.0-98.0%). The low coverage of oxygen atoms on the Ni NS surface is proposed to account for the high ST selectivity, as indicated by density functional theory (DFT) calculations.

15.
Zhongguo Zhong Yao Za Zhi ; 42(14): 2784-2788, 2017 Jul.
Artigo em Chinês | MEDLINE | ID: mdl-29098838

RESUMO

A solvent diffusion method was used to prepare pegylated asiatic acid (AA) loaded nanostructured lipid carriers (p-AA-NLC), and the ligated intestinal circulation model was established to observe the absorption and distribution in small intestine. The concentration of AA in bile after oral administration of p-AA-NLC was detected by HPLC in healthy SD rats to indirectly evaluate the oral absorption promoting effect of PEG-modified namoparticles. The results showed that the penetration of p-AA-NLC was enhanced significantly and the transport capacity was increased greatly in small intestinal after PEG modification. As compared with the normal nanoparticles (AA-NLC), the Cmax of the drug excretion was increased by 76%, the time to reach the peak (tmax ) was decreased and the elimination half-life t1/2 was doubled in the rats after oral administration of p-AA-NLC, and the AUC0→t was 1.5 times of the AA-NLC group, indicating that the oral bioavailability of AA-NLC was significantly improved by hydrophilic modification of PEG.


Assuntos
Portadores de Fármacos , Nanopartículas , Triterpenos Pentacíclicos/farmacocinética , Polietilenoglicóis , Administração Oral , Animais , Meia-Vida , Absorção Intestinal , Lipídeos , Tamanho da Partícula , Triterpenos Pentacíclicos/administração & dosagem , Ratos , Ratos Sprague-Dawley
16.
Asian Pac J Trop Med ; 10(5): 524-527, 2017 May.
Artigo em Inglês | MEDLINE | ID: mdl-28647192

RESUMO

OBJECTIVE: To analyse the genetic variability of EG95 sequences and provide guidance for EG95 vaccine application against Echinococcus granulosus (E. granulosus). METHODS: We analysed EG95 polymorphism by collecting total 97 different E. granulosus isolates from 12 different host species that originated from 10 different countries. Multiple sequence alignments and the homology were performed by Lasergene 1 (DNASTAR Inc., Madison, WI), and the phylogenetic analysis was performed by using MEGA5.1 (CEMI, Tempe, AZ, USA). In addition, linear and conformational epitopes were analysed, including secondary structure, NXT/S glycosylation, fibronectin type III (FnIII) domain and glycosylphosphatidylinositol anchor signal (GPI-anchor). The secondary structure was predicted by PSIPRED method. RESULTS: Our results indicated that most isolates overall shared 72.6-100% identity in EG95 gene sequence with the published standard EG95 sequence, X90928. However, EG95 gene indeed has polymorphism in different isolates. Phylogenetic analysis showed that different isolates could be divided into three subgroups. Subgroup 1 contained 87 isolates while Subgroup 2 and Subgroup 3 consisted of 3 and 7 isolates, respectively. Four sequences cloned from oncosphere shared a high identity with the parental sequence of the current vaccine, X90928, and they belonged to Subgroup 1. However, in comparison to X90928, several amino acid mutations occurred in most isolates besides oncosphere, which potentially altered the immunodominant linear epitopes, glycosylation sites and secondary structures in EG95 genes. All these variations might change their previous antigenicity and thereby affecting the efficacy of current EG95 vaccine. CONCLUSIONS: This study reveals the genetic variability of EG95 sequences in different E. granulosus isolates, and proposed that more vaccination trials would be needed to test the effectiveness of current EG95 vaccine against distinct isolates in different countries.

17.
Biomed Rep ; 6(2): 181-187, 2017 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-28357070

RESUMO

The aim of the present study was to predict and analyze the secondary structure, and B and T cell epitopes of Echinococcus granulosus antigen 5 (Ag5) using online software in order to investigate its immunogenicity and preliminarily evaluate its potential as an effective antigen peptide vaccine for cystic echinococcosis. The PortParam program was used to analyze molecular weight, the theoretical isoelectric point, instability index and other physicochemical properties. The secondary structure of the Ag5 protein was predicted using Self-Optimized Prediction method With Alignment and the tertiary structure of the Ag5 protein was predicted using 3DLigandSite together with Center for Biological Sequence Analysis Prediction Servers. Furthermore, the Immune Epitope Database software was used to predict B cell epitopes, and T cell epitopes were predicted with the BioInformatics and Molecular Analysis Section and SYFPEITHI programs. The results demonstrated that α-helixes, ß-turns, random coils and extended strands account for 23.35, 10.95, 41.32, and 24.38% of the secondary structure of the Ag5 protein, respectively. Ten potential B cell epitopes of Ag5 were identified as the amino acids sequences 27-39, 70-80, 117-130, 146-168, 250-262, 284-293, 339-349, 359-371, 403-412 and 454-462, and seven potential T cell epitopes were identified as the amino acid sequences 52-60, 57-65, 182-190, 231-239, 273-281, 318-326 and 467-475. Thus, ten B cell epitopes and seven T cell epitopes were identified on Ag5, suggesting the strong immunogenicity of this protein, which could be applied to design antigen peptide vaccines for echinococcosis.

18.
J Am Chem Soc ; 139(6): 2267-2276, 2017 02 15.
Artigo em Inglês | MEDLINE | ID: mdl-28099028

RESUMO

Ruthenium is a promising low-temperature catalyst for Fischer-Tropsch synthesis (FTS). However, its scarcity and modest specific activity limit its widespread industrialization. We demonstrate here a strategy for tuning the crystal phase of catalysts to expose denser and active sites for a higher mass-specific activity. Density functional theory calculations show that upon CO dissociation there are a number of open facets with modest barrier available on the face-centered cubic (fcc) Ru but only a few step edges with a lower barrier on conventional hexagonal-closest packed (hcp) Ru. Guided by theoretical calculations, water-dispersible fcc Ru catalysts containing abundant open facets were synthesized and showed an unprecedented mass-specific activity in the aqueous-phase FTS, 37.8 molCO·molRu-1·h-1 at 433 K. The mass-specific activity of the fcc Ru catalysts with an average size of 6.8 nm is about three times larger than the previous best hcp catalyst with a smaller size of 1.9 nm and a higher specific surface area. The origin of the higher mass-specific activity of the fcc Ru catalysts is identified experimentally from the 2 orders of magnitude higher density of the active sites, despite its slightly higher apparent barrier. Experimental results are in excellent agreement with prediction of theory. The great influence of the crystal phases on site distribution and their intrinsic activities revealed here provides a rationale design of catalysts for higher mass-specific activity without decrease of the particle size.

19.
Nanoscale ; 9(3): 1154-1165, 2017 Jan 19.
Artigo em Inglês | MEDLINE | ID: mdl-28009923

RESUMO

For the first time, shape-tunable Pt-Ir alloy nanocatalysts including both single-crystalline (nano-octahedra (NOs), nano-truncated octahedra (NTOs), nanocubes (NCs)) and polycrystalline (nanocluster flowers (NCFs), nanowires (NWs), nano-short-chains (NSCs), and nano-octahedral stars (NOSs)) ones were synthesized with a facile one-pot solvothermal method, via precise control of the facet-selective agents (Br- and I-). The surface effects of Pt-Ir alloy nanocatalysts for oxygen electrode reaction in acidic solution were intensively investigated. Pt-Ir alloy nanocatalysts showed enhanced catalytic activities for the oxygen evolution reaction (OER), which were 1.6 to 2.0 times those of the commercial Ir/C catalyst and the Pt/C-Ir/C mixture at an overpotential of 0.25 V. The catalytic activity for the OER exhibited a positive correlation with the proportion of surface IrOx species, but was restricted by the surface alloying effect. Besides the change of the intermediate adsorption state, the dissociation of water was also confirmed to be effective as the rate-determining step of the Pt-Ir alloy nanocatalysts. The catalytic activity for the oxygen reduction reaction (ORR) decreased with the increase of surface IrOx species. Pt-Ir nano-short-chains (NSCs) exhibited 1.3 times the catalytic activity as that of the commercial Pt/C catalyst at 0.80 V and 0.85 V, owing to the higher proportion of the (110) facets with irregular step sites exposed after the annealing treatment at 350 °C. The unique structure could prevent the mass transfer process from being obstructed by adsorbed bisulfate anions and oxidized species on the surfaces. Pt-Ir NSCs exhibited a catalytic efficiency of 46.7% and were considered to be a promising URFC catalyst.

20.
World J Gastroenterol ; 23(47): 8321-8333, 2017 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-29307992

RESUMO

AIM: To determine whether fructo-oligosaccharide (FOS) affects visceral sensitivity, inflammation, and production of intestinal short-chain fatty acids (SCFA) in an irritable bowel syndrome (IBS) mouse model. METHODS: Mice were randomly assigned to daily oral gavage of saline solution with or without FOS (8 g/kg body weight) for 14 d. Mice were further assigned to receive either daily one-hour water avoidance stress (WAS) or sham-WAS for the first 10 d. After 2 wk, visceral sensitivity was measured by abdominal withdrawal reflex in response to colorectal distension and mucosal inflammation was evaluated. Gas chromatography, real-time reverse transcription PCR, and immunohistochemistry assays were used to quantify cecal concentrations of SCFA, intestinal cytokine expression, and number of intestinal mast cells per high-power field (HPF), respectively. RESULTS: Mice subjected to WAS exhibited visceral hypersensitivity and low-grade inflammation. Among mice subjected to WAS, FOS increased visceral hypersensitivity and led to higher cecal concentrations of acetic acid (2.49 ± 0.63 mmol/L vs 1.49 ± 0.72 mmol/L, P < 0.05), propionic acid (0.48 ± 0.09 mmol/L vs 0.36 ± 0.05 mmol/L, P < 0.01), butyric acid (0.28 ± 0.09 mmol/L vs 0.19 ± 0.003 mmol/L, P < 0.05), as well as total SCFA (3.62 ± 0.87 mmol/L vs 2.27 ± 0.75 mmol/L, P < 0.01) compared to saline administration. FOS also increased ileal interleukin (IL)-23 mRNA (4.71 ± 4.16 vs 1.00 ± 0.99, P < 0.05) and colonic IL-1ß mRNA (2.15 ± 1.68 vs 0.88 ± 0.53, P < 0.05) expressions as well as increased mean mast cell counts in the ileum (12.3 ± 2.6 per HPF vs 8.3 ± 3.6 per HPF, P < 0.05) and colon (6.3 ± 3.2 per HPF vs 3.4 ± 1.2 per HPF, P < 0.05) compared to saline administration in mice subjected to WAS. No difference in visceral sensitivity, intestinal inflammation, or cecal SCFA levels was detected with or without FOS administration in mice subjected to sham-WAS. CONCLUSION: FOS administration intensifies visceral hypersensitivity and gut inflammation in stress-induced IBS mice, but not in the control mice, and is also associated with increased intestinal SCFA production.


Assuntos
Hipersensibilidade Alimentar/imunologia , Mucosa Intestinal/imunologia , Intestinos/imunologia , Síndrome do Intestino Irritável/imunologia , Oligossacarídeos/imunologia , Animais , Citocinas/metabolismo , Modelos Animais de Doenças , Ácidos Graxos Voláteis/metabolismo , Feminino , Humanos , Mucosa Intestinal/patologia , Intestinos/citologia , Intestinos/patologia , Síndrome do Intestino Irritável/patologia , Mastócitos/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Limiar Sensorial , Estresse Psicológico/complicações
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