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1.
J Am Chem Soc ; 2020 Jul 20.
Artigo em Inglês | MEDLINE | ID: mdl-32687344

RESUMO

Nanoconfinement imposes physical constraints and chemical effects on reactivity in nanoporous catalyst systems. In the present study, we lay the groundwork for quantitative single-molecule measurements of the effects of chemical environment on heterogeneous catalysis in nanoconfinement. Choosing hydrophobicity as an exemplary chemical environmental factor, we compared a range of essential parameters for an oxidation reaction on platinum nanoparticles (NPs) confined in hydrophilic and hydrophobic nanopores. Single-molecule experimental measurements at the single particle level showed higher catalytic activity, stronger adsorption strength, and higher activation energy in hydrophobic nanopores than those in hydrophilic nanopores. Interestingly, different dissociation kinetic behaviors of the product molecules in the two types of nanopores were deduced from the single-molecule imaging data.

2.
ACS Nano ; 2020 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-32639718

RESUMO

Stability against reshaping of metallic fcc nanocrystals synthesized with tailored far-from-equilibrium shapes is key to maintaining optimal properties for applications such as catalysis. Yet Arrhenius analysis of experimental reshaping kinetics, and appropriate theory and simulation, is lacking. Thus, we use TEM to monitor the reshaping of Pd nanocubes of ∼25 nm side length between 410 °C (over ∼4.5 h) and 440 °C (over ∼0.25 h), extracting a high effective energy barrier of Eeff ≈ 4.6 eV. We also provide an analytic determination of the energy variation along the optimal pathway for reshaping that involves transfer of atoms across the nanocube surface from edges or corners to form new layers on side {100} facets. The effective barrier from this analysis is shown to increase strongly with the degree of truncation of edges and corners in the synthesized nanocube. Theory matches experiment for the appropriate degree of truncation. In addition, we perform simulations of a stochastic atomistic-level model incorporating a realistic description of diffusive hopping for undercoordinated surface atoms, thereby providing a visualization of the initial reshaping process.

3.
Environ Sci Pollut Res Int ; 27(18): 23062-23072, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32333345

RESUMO

Photo-Fenton processes have been widely studied in wastewater treatment. In this research, the degradation of bisphenol A (BPA) was carried out in a new heterogeneous photo-Fenton process. The ethylenediamine-N,N'-disuccinic acid (EDDS) was used as chelating agent in this system with two different kinds of commercially available nanosized hematite (30 nm and 80 nm) addition. The results showed that the present of EDDS could enhance the degradation efficiency. And can be concluded that the degradation efficiency is better in the system with 30 nm hematite. The TEM, XRD, and specific surface area were conducted to understand the different characteristics of the two size hematite. The adsorption experiments of BPA and EDDS on hematite proved that there was little adsorption of BPA while the EDDS was adsorbed much more on hematite, which has confirmed Fe(III) and EDDS can form Fe(III)-EDDS complex. The effects of different parameters including hematite loading, H2O2, and EDDS concentrations on the degradation process were investigated. According to the results, the optimum condition for BPA degradation using 30 nm (0.8 g L-1 hematite, 0.1 mmol L-1 H2O2, and 1.2 mmol L-1 EDDS) and 80 nm (0.6 g L-1 hematite, 0.05 mmol L-1 H2O2, and 1.2 mmol L-1 EDDS) hematite were selected. It was confirmed that the ·OH plays an important role in the oxidation process through attacking the BPA molecule and produce hydroxyl addition derivative. In addition, O2 can react with electron (e-) and holes (h+) produced by iron oxide under UV irradiation to create 1O2, which could work as potential reactive species to oxidize BPA.


Assuntos
Compostos Férricos , Peróxido de Hidrogênio , Compostos Benzidrílicos , Oxirredução , Fenóis
4.
Nanoscale ; 2020 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-32242595

RESUMO

The molecular basis for the high cis-alkene selectivity over intermetallic PtSn for alkyne semi-hydrogenation is demonstrated. Unlike the universal assumption that the bimetallic surface is saturated with atomic hydrogen, molecular hydrogen has a higher barrier for dissociative adsorption on intermetallic PtSn due to the deficiency of Pt three-fold sites. The resulting molecular behavior of adsorbed hydrogen on intermetallic PtSn nanoparticles leads to pairwise-hydrogenation of three alkynes to the corresponding cis-alkenes, satisfying both high stereoselectivity and high chemoselectivity.

5.
ACS Appl Mater Interfaces ; 12(20): 23002-23009, 2020 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-32338862

RESUMO

Multifunctional metal-organic frameworks (MOFs) that possess permanent porosity are promising catalysts in organic transformation. Herein, we report the construction of a hierarchical MOF functionalized with basic aliphatic amine groups and polyvinylpyrrolidone-capped platinum nanoparticles (Pt NPs). The postsynthetic covalent modification of organic ligands increases basic site density in the MOF and simultaneously introduces mesopores to create a hierarchically porous structure. The multifunctional MOF is capable of catalyzing a sequential Knoevenagel condensation-hydrogenation-intramolecular cyclization reaction. The unique selective reduction of the nitro group to intermediate hydroxylamine by Pt NPs supported on MOF followed by intramolecular cyclization with a cyano group affords an excellent yield (up to 92%) to the uncommon quinoline N-oxides over quinolines. The hierarchical MOF and polyvinylpyrrolidone capping agent on Pt NPs synergistically facilitate the enrichment of substrates and thus lead to high activity in the reduction-intramolecular cyclization reaction. The bioactivity assay indicates that the synthesized quinoline N-oxides evidently inhibit the proliferation of lung cancer cells. Our findings demonstrate the feasibility of MOF-catalyzed direct synthesis of bioactive molecules from readily available compounds under mild conditions.

6.
Org Lett ; 2020 Apr 17.
Artigo em Inglês | MEDLINE | ID: mdl-32301619

RESUMO

Cobalt-catalyzed highly branched- and enantioselective allylic alkylation of malononitriles has been developed. Chiral γ,δ-unsaturated malononitriles could be synthesized with >20:1 branched/linear regioselectivity and up to 99% enantiomeric excess from easily accessible racemic allylic carbonates under mild reaction conditions. The electron-rich and sterically less hindered bisoxazolinephosphine ligand is essential to realize the high reactivity in the carbon-carbon bond formation process.

7.
Medicine (Baltimore) ; 99(12): e19577, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32195970

RESUMO

RATIONALE: The diagnosis of anaplastic lymphoma kinase (ALK)-negative inflammatory myofibroblastic tumors (IMT) remains challenging because of their morphological resemblance with spindle cell sarcoma with myofibroblastic characteristics. PATIENT CONCERNS: A 69-year-old female patient presented with loco-regional recurrent IMT several times within 8 years after primary treatment and neck lymph node metastasis 3.5 years after last recurrence. DIAGNOSIS: The primary, recurrence, and lymph node metastasis lesions were diagnosed as ALK-negative IMTs based on the histopathological features. INTERVENTIONS: Biopsy samples were obtained during repeated surgeries and evaluated for genomic alterations during first and recurrent presentations. The evaluation was done using pathway-driven massive parallel sequencing, and genomic alterations between primary and recurrent tumors were compared. OUTCOMES: Copy number gains and overexpression of mouse double minute 2 homolog (MDM2) and cyclin dependent kinase 4 (CDK4) were observed in the primary lesion, and additional gene amplification of Discoidin Domain Receptor Tyrosine Kinase 2 (DDR2), Succinate Dehydrogenase Complex II subunit C (SDHC), and thyroid stimulating hormone receptor (TSHR) Q720H were found in the recurrent tumors. Metastases to the neck lymph node were observed 3.5 years after recurrence. LESSONS: Our results indicated genetic evolution in a microscopically benign condition and highlighted the importance of molecular characterization of fibro-inflammatory lesions of uncertain malignant potential.


Assuntos
Granuloma de Células Plasmáticas/metabolismo , Neoplasias de Cabeça e Pescoço/secundário , Recidiva Local de Neoplasia/patologia , Neoplasias de Tecido Muscular/metabolismo , Quinase do Linfoma Anaplásico/metabolismo , Quinase 4 Dependente de Ciclina/metabolismo , Diagnóstico Diferencial , Feminino , Amplificação de Genes , Granuloma de Células Plasmáticas/patologia , Neoplasias de Cabeça e Pescoço/patologia , Sequenciamento de Nucleotídeos em Larga Escala/métodos , Humanos , Metástase Linfática , Mediastino/patologia , Pessoa de Meia-Idade , Miofibroblastos/patologia , Neoplasias de Tecido Muscular/patologia , Neoplasias de Tecido Muscular/radioterapia , Proteínas Proto-Oncogênicas c-mdm2/metabolismo
8.
Artigo em Inglês | MEDLINE | ID: mdl-32196846

RESUMO

Controlling the surface composition of shaped bimetallic nanoparticles could offer precise tunability of geometric and electronic surface structure for new nanocatalysts. To achieve this goal, a platform for studying the intermixing process in a shaped nanoparticle was designed, using multilayered Pd-Ni-Pt core-shell nanocubes as precursors. Under mild conditions, the intermixing between Ni and Pt could be tuned by changing layer thickness and number, triggering intermixing while preserving nanoparticle shape. Intermixing of the two metals is monitored using transmission electron microscopy. The surface structure evolution is characterized using electrochemical methanol oxidation. DFT calculations suggest that the low-temperature mixing is enhanced by shorter diffusion lengths and strain introduced by the layered structure. The platform and insights presented are an advance toward the realization of shape-controlled multimetallic nanoparticles tailored to each potential application.

9.
Chemistry ; 26(33): 7358-7364, 2020 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-32090400

RESUMO

Heptazine-based conjugated polymeric carbon nitrides (PCNs) are promising metal-free photocatalysts, yet their synthesis is challenging due to the electron-deficiency and insolubility of heptazine units. Indeed, heptazine-containing polymers have only been prepared through nucleophilic substitution with amines by using toxic cyameluric chloride as the starting material. Herein, we report the novel and environmentally friendly method for preparing heptazine-based mesoporous PCNs with hydrazone links formed through a simple Schiff base condensation of melem-NH2 and aldehydes. Unlike cyameluric chloride, melem-NH2 is non-toxic, stable, and can be readily obtained from melem and hydrazine in solution. We demonstrate that the hydrazone linkages and the heptazine units synergistically enhance the photocatalytic activity of PCNs in visible-light-driven aerobic oxidation of benzyl alcohol to benzaldehyde. In particular, the polymer constructed from melem-NH2 and p-phthalaldehyde shows 17 times more activity than graphitic carbon nitride (g-C3 N4 ).

10.
Nano Lett ; 20(1): 136-144, 2020 01 08.
Artigo em Inglês | MEDLINE | ID: mdl-31774999

RESUMO

NiFe-layered double hydroxide (LDH) is thought of as a promising bifunctional water-splitting catalyst, owing to its excellent performances for alkaline oxygen evolution reactions (OERs). However, it shows extremely poor activity toward hydrogen evolution reactions (HERs) due to the weak hydrogen adsorption. We demonstrated that the integration of Rh species and NiFe-LDH can dramatically improve its HER kinetics without sacrificing the OER performance. The Rh species were initially integrated into NiFe-LDH as oxidized dopants and metallic clusters (< 1 nm). In 1 M KOH electrolyte, an overpotential of 58 mV is needed to catalyze 10 mA cm-2 HER current density. Furthermore, this catalyst only requires 1.46 V to drive an electrolyzer at 10 mA cm-2. A strong interaction between metallic Rh clusters and NiFe hydroxide during the HER process is revealed. The theoretical calculation shows the Rh ions replace Fe ions as the major active sites that are responsible for OERs.

11.
Nat Commun ; 10(1): 4815, 2019 10 23.
Artigo em Inglês | MEDLINE | ID: mdl-31645571

RESUMO

Nanoconfinement could dramatically change molecular transport and reaction kinetics in heterogeneous catalysis. Here we specifically design a core-shell nanocatalyst with aligned linear nanopores for single-molecule studies of the nanoconfinement effects. The quantitative single-molecule measurements reveal unusual lower adsorption strength and higher catalytic activity on the confined metal reaction centres within the nanoporous structure. More surprisingly, the nanoconfinement effects on enhanced catalytic activity are larger for catalysts with longer and narrower nanopores. Experimental evidences, including molecular orientation, activation energy, and intermediate reactive species, have been gathered to provide a molecular level explanation on how the nanoconfinement effects enhance the catalyst activity, which is essential for the rational design of highly-efficient catalysts.

12.
Cancers (Basel) ; 11(10)2019 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-31569404

RESUMO

MicroRNAs (miRNAs) have been shown to play a crucial role in the progression of human cancers, including urothelial carcinoma (UC), the sixth-most common cancer in the world. Among them, miR-34a has been implicated in the regulation of cancer stem cells (CSCs); however, its role in UC has yet to be fully elucidated. In this study, bioinformatics and experimental analysis confirmed that miR-34a targets CD44 (a CSC surface marker) and c-Myc (a well-known cell cycle regulator) in UC. We found that, surprisingly, most UC cell lines and patient samples did express miR-34a, although epigenetic silencing by promoter hypermethylation of miR-34a expression was observed only in UMUC3 cells, and a subset of patient samples. Importantly, overexpression of c-Myc, a frequently amplified oncogene in UC, was shown to upregulate CD44 expression through a competing endogenous RNA (ceRNA) mechanism, such that overexpression of the c-Myc 3'UTR upregulated CD44, and vice versa. Importantly, we observed a positive correlation between the expression of c-Myc and CD44 in clinical samples obtained from UC patients. Moreover, overexpression of a dominant-negative p53 mutant downregulated miR-34a, but upregulated c-Myc and CD44, in UC cell lines. Functionally, the ectopic expression of miR-34a was shown to significantly suppress CD44 expression, and subsequently, suppression of cell growth and invasion capability, while also reducing chemoresistance. In conclusion, it appears that aberrant promoter methylation, and c-Myc-mediated ceRNA mechanisms, may attenuate the function of miR-34a, in UC. The tumor suppressive role of miR-34a in controlling CSC phenotypes in UC deserves further investigation.

13.
Diabetol Metab Syndr ; 11: 71, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31462934

RESUMO

Background: Polycystic ovary syndrome (PCOS) has been consistently associated with subsequent gestational diabetes mellitus (GDM). Women with PCOS showed a high prevalence of obesity, which raises the question regarding the role of obesity or PCOS pe ser in development of GDM. In this study we conducted a 2-phase study to compare the risk of GDM and its associated early pregnancy metabolic factors in women with and without PCOS, stratified by pre-pregnancy body mass index (BMI). Methods: A 2-phase design was used in this study. The initial phase of the study included 566 age- and pre-pregnancy BMI-matched singleton pregnant women (242 with and 324 without PCOS). Risk of GDM and associated early-pregnancy risk factors were explored between women with and without PCOS, after stratification by pre-pregnancy BMI. Stratified analysis was conducted in normal weight (pre-pregnancy BMI < 25 kg/m2) and overweight/obese (pre-pregnancy BMI ≥ 25 kg/m2) groups. Subsequently, the findings was confirmed in a separate cohort study with 18,106 participants (877 with and 17,229 without PCOS). Results: Overall, prevalence of GDM is higher in women with PCOS. Results from the initial study showed that in normal-weight subjects, there is a significant increase in GDM prevalence in PCOS women than non-PCOS women (26.5% vs. 16.2%, p = 0.02). Additionally, normal-weight PCOS women showed higher triglycerides levels (1.51 ± 0.84 mmol/L vs. 1.30 ± 0.75 mmol/L, p = 0.02), lower SHBG levels (277.8 ± 110.2 nmol/L vs. 330.5 ± 180.4 nmol/L, p = 0.001) and a possible trend towards higher insulin resistance (LogHoMA-IR 0.70 ± 0.55 vs. 0.57 ± 0.57, p = 0.05) during early pregnancy. However, in overweight/obese group, no difference in risk of GDM was observed between PCOS and non-PCOS subjects (p = 0.7). Results from the independent cohort confirmed the risk for GDM associated with PCOS in normal weight women (p < 0.0001). Conclusion: Consistent findings from the 2-phase study showed an increased risk of GDM in normal-weight, but not overweight/obese PCOS women. Analysis of early-pregnancy risk factors of GDM suggested that the pathogenesis of GDM in normal weight and overweight/obese women with PCOS may be different.

14.
Obes Facts ; 12(4): 407-415, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31261149

RESUMO

OBJECTIVE: Timing of gestational weight gain (GWG) may influence perinatal outcomes differently. This study aimed to find associations of latent GWG patterns with risk of large for gestational age (LGA) in women with overweight or obesity. METHODS: A total of 4,438 women with overweight or obesity were included in the analyses. Latent trajectories of GWG associated with LGA were identified by trajectory analysis. GWG, risk of LGA and early pregnancy factors were compared between these identified groups. RESULTS: This study identified four distinct GWG trajectory groups associated with LGA, each group including, respectively, 78.6, 19.0, 1.4, and 0.9% of the participants. Group 1 presented a typical curve with lower GWG in early pregnancy and relatively higher GWG in mid- and late pregnancy. Women in group 2 showed sustained high GWG and high LGA prevalence than women in group 1 (48.24 vs. 21.56%, p < 0.0001). A catch-up in GWG after low weight gain did not result in significantly higher risk of LGA in group 3 compared to group 1. On the other hand, a rapid GWG in the first two-thirds of pregnancy followed by a strict weight control was associated with elevated risk of LGA in group 4 than group 1 (62.50 vs. 21.56%, p < 0.0001). CONCLUSIONS: Women affected by overweight or obesity combined with high GWG in early mid-pregnancy were at elevated risk of LGA. Early clinical recognition of a poor GWG trajectory will enable early intervention in high-risk groups.


Assuntos
Macrossomia Fetal/etiologia , Ganho de Peso na Gestação/fisiologia , Obesidade/fisiopatologia , Sobrepeso/fisiopatologia , Complicações na Gravidez/fisiopatologia , Adulto , Peso ao Nascer/fisiologia , Índice de Massa Corporal , Estudos de Coortes , Feminino , Macrossomia Fetal/epidemiologia , Macrossomia Fetal/fisiopatologia , Idade Gestacional , Humanos , Recém-Nascido , Obesidade/complicações , Obesidade/epidemiologia , Sobrepeso/complicações , Sobrepeso/epidemiologia , Gravidez , Complicações na Gravidez/epidemiologia , Prevalência , Fatores de Risco , Ganho de Peso/fisiologia , Adulto Jovem
15.
Endocrinol Metab Clin North Am ; 48(3): 569-581, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-31345524

RESUMO

Pituitary adenomas are common. The impact of pituitary tumors on fertility are mainly caused by oversecretion and/or undersecretion of pituitary hormones or compression of pituitary stalk and normal pituitary tissue by the tumor. Diagnosing and managing pituitary tumors during pregnancy involve many challenges, including the effect of hormone excess or deficiency on pregnancy outcome, changes in the pituitary or pituitary-related hormones, changes in tumor size, and the impact of various treatments of pituitary tumors on maternal and fetal outcomes. This article discusses the diagnosis and treatment of patients with prolactinomas, acromegaly, Cushing disease, and other pituitary tumors during pregnancy.


Assuntos
Neoplasias Hipofisárias/diagnóstico , Neoplasias Hipofisárias/terapia , Prolactinoma/diagnóstico , Prolactinoma/terapia , Acromegalia/diagnóstico , Acromegalia/epidemiologia , Acromegalia/etiologia , Acromegalia/terapia , Feminino , Humanos , Neoplasias Hipofisárias/complicações , Neoplasias Hipofisárias/epidemiologia , Gravidez , Prolactinoma/complicações , Prolactinoma/epidemiologia
16.
Nano Lett ; 19(8): 5102-5108, 2019 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-31271283

RESUMO

The design of efficient catalysts capable of delivering high currents at low overpotentials for hydrogen evolution reactions (HERs) is urgently needed to use catalysts in practical applications. Herein, we report platinum (Pt) alloyed with titanium (Ti) from the surface of Ti3C2Tx MXenes to form Pt3Ti intermetallic compound (IMC) nanoparticles (NPs) via in situ coreduction. In situ X-ray absorption spectroscopy (XAS) indicates that Pt undergoes a temperature-dependent transformation from single atoms to intermetallic compounds, and the catalyst reduced at 550 °C exhibits a superior HER performance in acidic media. The Pt/Ti3C2Tx-550 catalyst outperforms commercial Pt/Vulcan and has a small overpotential of 32.7 mV at 10 mA cm-2 and a low Tafel slope of 32.3 mV dec-1. The HER current was normalized by the mass and dispersion of Pt, and the mass activity and specific activity of Pt/Ti3C2Tx-550 are 4.4 and 13 times higher, respectively, than those of Pt/Vulcan at an overpotential of 70 mV. The density functional theory (DFT) calculations suggest that the (111)- and (100)-terminated Pt3Ti nanoparticles exhibit *H binding comparable to Pt(111), while the (110) termination has an *H adsorption that is too exergonic, thus poisoned in the low overpotential region. This work demonstrates the potential of MXenes as platforms for the design of electrocatalysts and may spur future research for other MXene-supported metal catalysts that can be used for a wide range of electrocatalytic reactions.

17.
BMC Gastroenterol ; 19(1): 119, 2019 Jul 08.
Artigo em Inglês | MEDLINE | ID: mdl-31286888

RESUMO

BACKGROUND: The effectiveness in surveillance colonoscopy largely depends on the quality of bowel preparation. We aimed to investigate the quality of bowel preparation segmentally and its effect on Adenoma Detection Rate (ADR) and Advanced Adenoma Detection Rate (AADR) at corresponding bowel segments. METHODS: This is a single-centered and cross-sectional study. A consecutive of 5798 patients who underwent colonoscopy examination were included. Bowel preparation was evaluated based on Bowel Bubble Scale (BBS) in general and Boston Bowel Preparation Scale (BBPS) in each segment (right side, transverse and left side of colon) and total BBPS scores. The quality of bowel preparation was correlated with ADR and AADR. RESULTS: Four thousand nine hundred forty colonoscopies (14,820 bowel segments) were included in the final analysis. In which 30.9% scored 3, 57.5% scored 2, 11.2% scored 1 and 0.4% scored 0 on basis of BBPS. For each score, ADR were 10.8, 7.7, 4.9 and 3.2%, respectively; whereas AADR were 4.5, 2.8,1.8 and 1.6% (P < 0.05). 36.9% of the colonoscopies showed presence of minimal bubbles and 34.3% with no bubble. For bowels without bubbles and with a large amount of bubbles, ADR were 28.3 and 20.0% respectively; and AADR were 13.3 and 7.1% respectively. CONCLUSIONS: Segmental bowels' cleanliness and the amount of bubbles in bowels significantly affect ADR and AADR. The better the bowel preparation at each segment is and the less bubbles in the bowel there are, the higher ADR and AADR we got. We suggest repeating colonoscopy if any segment of the bowel preparation is poor, or if there is more bubbles, even if the total score of BBPS indicates good or fair bowel preparation.


Assuntos
Adenoma/diagnóstico , Catárticos/normas , Colonoscopia/estatística & dados numéricos , Neoplasias Colorretais/diagnóstico , Detecção Precoce de Câncer/estatística & dados numéricos , Vigilância da População/métodos , Idoso , Catárticos/uso terapêutico , Colo/efeitos dos fármacos , Estudos Transversais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade
18.
ACS Appl Mater Interfaces ; 11(26): 23254-23260, 2019 Jul 03.
Artigo em Inglês | MEDLINE | ID: mdl-31252478

RESUMO

Research and development in bimetallic nanoparticles have gained great interest over their monometallic counterparts because of their distinct and unique properties in a wide range of applications such as catalysis, energy storage, and bio/plasmonic imaging. Identification and characterization of these bimetallic surfaces for application in heterogeneous catalysis remain a challenge and heavily rely on advanced characterization techniques such as aberration-corrected electron microscopy and synchrotron X-ray absorption studies. In this article, we have reported a strategy to prepare sub-2 nm bimetallic Pt-Sn nanoclusters confined in the pores of a Zr-based metal-organic framework (MOF). The Pt-Sn nanoclusters encapsulated in the Zr-MOF pores show enhanced chemoselectivity from 51 to 93% in an industrially relevant reaction, furfural hydrogenation to furfuryl alcohol. The presence of bimetallic Pt-Sn surfaces was investigated by a surface-sensitive characterization technique utilizing diffuse reflectance infrared Fourier transform spectroscopy of adsorbed CO to probe the bimetallic surface of the encapsulated ultrafine Pt-Sn nanocluster. Complementary techniques such as aberration-corrected high-angle annular dark-field scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy were also used to characterize the Pt-Sn nanoclusters.

19.
Digestion ; : 1-8, 2019 Jun 14.
Artigo em Inglês | MEDLINE | ID: mdl-31203287

RESUMO

INTRODUCTION: Asia-Pacific Colorectal Screening (APCS) score has been implemented for colorectal cancer screening in asymptomatic cohort in many regions. However, no study has validated its efficiency in Asian outpatients with mild-self-limited gastrointestinal symptoms yet. The purpose of this study was to validate its efficiency in asymptomatic subjects and outpatients in Ningxia. METHODS: The records of 329 asymptomatic participants and 300 outpatients were collected and analyzed from database in the General Hospital of Ningxia Medical University from September 2017 to April 2018. These 2 main groups were divided into 3 tiers based on the scores calculated by the category of APCS score. The detection rates of advanced colorectal neoplasia (ACRN) were further compared according to histopathological classifications of tissues acquired during colonoscopy. RESULTS: Among the 329 participants screened in the asymptomatic cohort, 78 subjects (23.7%) were in the low-risk (LR) tier, 187 subjects (56.8%) in the moderate-risk (MR) tier, and 64 subjects (19.5%) in the high-risk (HR) tier. The percentage of ACRN in the LR, MR, and HR groups was 1.3, 8.6, and 20.3%, respectively. In the 300 outpatient cohorts, 78 patients (26%) were in the LR tier, 140 patients (46.7%) in the MR tier, and 82 patients (27.3%) in the HR tier. The detection rates of ACRN in the LR, MR, and HR groups were 0, 10, and 39%, respectively. CONCLUSION: APCS score is an effective method for ACRN screening in asymptomatic and also the outpatient subjects. Individuals with HR scores should be given priority for colonoscopy.

20.
Chem Rev ; 119(11): 6670-6768, 2019 06 12.
Artigo em Inglês | MEDLINE | ID: mdl-31181906

RESUMO

Self-assembly of supported 2D or 3D nanocrystals (NCs) by vacuum deposition and of 3D NCs by solution-phase synthesis (with possible subsequent transfer to a support) produces intrinsically nonequilibrium systems. Individual NCs can have far-from-equilibrium shapes and composition profiles. The free energy of NC ensembles is lowered by coarsening which can involve Ostwald ripening or Smoluchowski ripening (NC diffusion and coalescence). Preservation of individual NC structure and inhibition of coarsening are key, e.g., for avoiding catalyst degradation. This review focuses on postsynthesis evolution of metallic NCs. Atomistic-level modeling typically utilizes stochastic lattice-gas models to access appropriate time and length scales. However, predictive modeling requires incorporation of realistic rates for relaxation mechanisms, e.g., periphery diffusion and intermixing, in numerous local environments (rather than the use of generic prescriptions). Alternative coarse-grained modeling must also incorporate appropriate mechanisms and kinetics. At the level of individual NCs, we present analyses of reshaping, including sintering and pinch-off, and of compositional evolution in a vacuum environment. We also discuss modeling of coarsening including diffusion and decay of individual NCs and unconventional coarsening processes. We describe high-level modeling integrated with scanning tunneling microscopy (STM) studies for supported 2D epitaxial nanoclusters and developments in modeling for 3D NCs motivated by in situ transmission electron microscopy (TEM) studies.

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