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1.
Phys Rev Lett ; 124(2): 027203, 2020 Jan 17.
Artigo em Inglês | MEDLINE | ID: mdl-32004033

RESUMO

Spin waves can probe the Dzyaloshinskii-Moriya interaction (DMI), which gives rise to topological spin textures, such as skyrmions. However, the DMI has not yet been reported in yttrium iron garnet (YIG) with arguably the lowest damping for spin waves. In this work, we experimentally evidence the interfacial DMI in a 7-nm-thick YIG film by measuring the nonreciprocal spin-wave propagation in terms of frequency, amplitude, and most importantly group velocities using all electrical spin-wave spectroscopy. The velocities of propagating spin waves show chirality among three vectors, i.e., the film normal direction, applied field, and spin-wave wave vector. By measuring the asymmetric group velocities, we extract a DMI constant of 16 µJ/m^{2}, which we independently confirm by Brillouin light scattering. Thickness-dependent measurements reveal that the DMI originates from the oxide interface between the YIG and garnet substrate. The interfacial DMI discovered in the ultrathin YIG films is of key importance for functional chiral magnonics as ultralow spin-wave damping can be achieved.

2.
ChemSusChem ; 2020 Feb 03.
Artigo em Inglês | MEDLINE | ID: mdl-32011109

RESUMO

Highly efficient Ru-catalyzed selective C-C or C-O bond cleavage of polyols (eg. crude glycerol) for N -hydroxyethylation or acetonylation of amines was achieved unprecedentedly via the hydrogen-borrowing approach. A variety of amines were transformed to the desired amino alcohols/ketones in moderate to excellent yields, opening up new avenues for generation of oxygenated pharmaceuticals and fine chemicals from renewable raw materials. The use of new redox active catalysts containing bisphosphine/thienylmethylamine ligands allows this hydrogen borrowing system to be operated selectively under both basic and acidic conditions.

3.
Nat Commun ; 10(1): 5013, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31676774

RESUMO

For atomically thin two-dimensional materials, interfacial effects may dominate the entire response of devices, because most of the atoms are in the interface/surface. Graphene/sapphire has great application in electronic devices and semiconductor thin-film growth, but the nature of this interface is largely unknown. Here we find that the sapphire surface has a strong interaction with some of the carbon atoms in graphene to form a C-O-Al configuration, indicating that the interface interaction is no longer a simple van der Waals interaction. In addition, the structural relaxation of sapphire near the interface is significantly suppressed and very different from that of a bare sapphire surface. Such an interfacial C-O-Al bond is formed during graphene growth at high temperature. Our study provides valuable insights into understanding the electronic structures of graphene on sapphire and remote control of epitaxy growth of thin films by using a graphene-sapphire substrate.

4.
Sci Adv ; 5(11): eaav4355, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31700996

RESUMO

Recently, several captivating topological structures of electric dipole moments (e.g., vortex, flux closure) have been reported in ferroelectrics with reduced size/dimensions. However, accurate polarization distribution of these topological ferroelectric structures has never been experimentally obtained. We precisely measure the polarization distribution of an individual ferroelectric vortex in PbTiO3/SrTiO3 superlattices at the subunit cell level by using the atomically resolved integrated differential phase contrast imaging in an aberration-corrected scanning transmission electron microscope. We find, in vortices, that out-of-plane polarization is larger than in-plane polarization, and that downward polarization is larger than upward polarization. The polarization magnitude is closely related to tetragonality. Moreover, the contribution of the Pb─O bond to total polarization is highly inhomogeneous in vortices. Our precise measurement at the subunit cell scale provides a sound foundation for mechanistic understanding of the structure and properties of a ferroelectric vortex and lattice-charge coupling phenomena in these topological ferroelectric structures.

5.
Nano Lett ; 19(8): 5070-5076, 2019 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-31322902

RESUMO

Phonon polaritons hold potential prospects of nanophotonic applications at the mid- and far-infrared wavelengths. However, their experimental investigation in the far-infrared range has long been a technical challenge due to the lack of suitable light sources and detectors. To obviate these difficulties, here we use an electron probe with sub-10 meV energy resolution and subnanometer spatial resolution to study far-infrared surface phonon polaritons (∼50-70 meV) in ZnO nanostructures. We observe ultraslow propagation and interference fringes of propagating surface phonon polaritons and obtain their dispersion relation through measurements in the coordinate space. By mapping localized modes in nanowires and flakes, we reveal their localized nature and investigate geometry and size effects. Associated with simulation, we show that surface phonon polariton behaviors can be well described by the local continuum dielectric model. Our work paves the way for spatial-resolved investigation of surface phonon polaritons by electron probes and forwards polaritonics in the far-infrared range.

6.
J Org Chem ; 84(10): 6199-6206, 2019 May 17.
Artigo em Inglês | MEDLINE | ID: mdl-31016983

RESUMO

An efficient GaCl3-catalyzed direct cyanation of indoles and pyrroles using bench-stable electrophilic cyanating agent N-cyanosuccinimide was achieved and afforded 3-cyanoindoles and 2-cyanopyrroles in good yields and excellent regioselectivities. Notably, this protocol exhibited high reactivity for unprotected indoles and was applicable to a broad range of indole and pyrrole substrates.

7.
ChemSusChem ; 12(13): 3054-3059, 2019 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-30830999

RESUMO

Functionalization of amines by using CO2 is of fundamental importance considering the abundance of amines and CO2 . In this context, the catalytic formylation and methylation of amines represent convenient and successful protocols for selective CO2 utilization as a C1 building block. This study represents the first example of selective catalytic double N-formylation of aryl amines by using a dinuclear Mn complex in the presence of phenylsilane. This robust system also allows for selective formylation and methylation of amines under a range of conditions.

8.
Chem Commun (Camb) ; 55(19): 2797-2800, 2019 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-30758354

RESUMO

The presence of different aldehydes is found to have a significant influence on the catalytic performance when using PN(H)P type ligands for dehydrogenation of alcohols. Accordingly, hybrid multi-dentate ligands were discovered based on an oxygen-transfer alkylation of PNP ligands by aldehydes. The relevant Ru-PNN(PO) system provided the desired unsymmetrical esters in good yields via acceptorless dehydrogenation of alcohols. Hydrogen bonding interactions between the phosphine oxide moieties and alcohol substrates likely assisted the observed high chemoselectivity.

9.
Adv Sci (Weinh) ; 6(1): 1801182, 2019 Jan 09.
Artigo em Inglês | MEDLINE | ID: mdl-30643719

RESUMO

NH3 is a valuable chemical with a wide range of applications, but the conventional Haber-Bosch process for industrial-scale NH3 production is highly energy-intensive with serious greenhouse gas emission. Electrochemical reduction offers an environmentally benign and sustainable route to convert N2 to NH3 at ambient conditions, but its efficiency depends greatly on identifying earth-abundant catalysts with high activity for the N2 reduction reaction. Here, it is reported that MnO particles act as a highly active catalyst for electrocatalytic hydrogenation of N2 to NH3 with excellent selectivity. In 0.1 m Na2SO4, this catalyst achieves a high Faradaic efficiency up to 8.02% and a NH3 yield of 1.11 × 10-10 mol s-1 cm-2 at -0.39 V versus reversible hydrogen electrode, with great electrochemical and structural stability. On the basis of density functional theory calculations, MnO (200) surface has a smaller adsorption energy toward N than that of H with the *N2 → *N2H transformation being the potential-determining step in the nitrogen reduction reaction.

10.
ChemSusChem ; 11(13): 2077-2082, 2018 Jul 11.
Artigo em Inglês | MEDLINE | ID: mdl-29722204

RESUMO

Hydrogen is of fundamental importance for the construction of modern clean-energy supply systems. In this context, the catalytic dehydrogenation of formic acid (FA) is a convenient method to generate H2 gas from an easily available liquid. One of the issues associated with current catalytic dehydrogenation systems is insufficient stability. Here, we present a robust and recyclable system for FA dehydrogenation by combining a ruthenium 1,1,1-tris(diphenylphosphinomethyl)ethane complex and aluminum trifluoromethanesulfonate (Al(OTf)3 ). This robust system allows steady H2 production under pressure and recycling for an additional 14 runs without any apparent loss of activity (turnover frequencies up to 1920 h-1 , turnover numbers up to 20 000). Notably, the catalyst can also be used for the dehydrogenation of formates and the reverse hydrogenation of bicarbonates and CO2 .

11.
Chem Commun (Camb) ; 54(32): 3967-3970, 2018 Apr 17.
Artigo em Inglês | MEDLINE | ID: mdl-29610819

RESUMO

Impactful regioselectivity control is crucial for cost-effective chemical synthesis. By using cheap and abundant iron(iii) salts, the hydroxycarbonylations of both aromatic and aliphatic alkenes were significantly enhanced in both reactivity and selectivity (iso/n or n/iso up to >99 : 1). Moreover, Pd-catalyzed carbonylation selectivity can be switched from branched to linear by using different Fe(iii) salts. In addition, similar results were obtained for the carbonylation of secondary alcohols.

12.
ChemSusChem ; 11(2): 356-359, 2018 01 23.
Artigo em Inglês | MEDLINE | ID: mdl-29235723

RESUMO

An efficient strategy for the conversion of biomass derived 5-hydroxymethylfurfural (HMF) into 2-hydroxy-3-methylcyclopent-2-enone (MCP) by an intramolecular aldol condensation of 1-hydroxyhexane-2,5-dione (HHD) has been developed. Further transformations of MCP towards the diol, enol acetate, levulinic acid and N-heterocyclic compounds are also reported.


Assuntos
Ciclopentanos/química , Furaldeído/análogos & derivados , Hexanos/química , Biomassa , Catálise , Furaldeído/química , Ligações de Hidrogênio , Modelos Moleculares , Difração de Raios X
14.
Oncotarget ; 8(28): 46249-46261, 2017 Jul 11.
Artigo em Inglês | MEDLINE | ID: mdl-28545028

RESUMO

Stanniocalin-1 (STC1) is a secreted glycoprotein hormone and involved in various types of human malignancies. Our previous studies revealed that STC1 inhibited cell proliferation and invasion of cervical cancer cells through NF-κB P65 activation, but the mechanism is poorly understood. In our studies, we found overexpression of STC1 promoted cell apoptosis while silencing of STC1 promoted cell growth of cervical cancer. Phospho-protein profiling and Western blotting results showed the expression of NF-κB related phosphorylation sites including NF-κB P65 (Ser536), IκBα, IKKß, PI3K, and AKT was altered in STC1-overexpressed cervical cancer cells. Moreover, PI3K inhibitor LY294002, AKT-shRNA and IκBα-shRNA could decrease the protein content of phospho-P65 (Ser536), phospho-IκBα, phospho-AKT and phospho-IKKß while increasing the level of P65 compared to STC1 overexpression groups in cervical cancer cells. Also, PI3K inhibitor LY294002, AKT-shRNA and IκBα-shRNA elevated the percentage of apoptosis and suppressed the G1/S transition in those cells. Additionally, STC1 level was decreased in cervical cancer, especial in stage II and III. The results of immunohistochemistry for the cervical cancer microarray showed that a lower level of STC1, phospho-PI3K and P65 protein expression in tumor tissues than that in normal tissues, and a higher level of phospho-P65 protein expression in tumor tissues, which is consistent with the results of the Western blotting. These data demonstrated that STC1 can promote cell apoptosis via NF-κB phospho-P65 (Ser536) by PI3K/AKT, IκBα and IKK signaling in cervical cancer cells. Our results offer the first mechanism that explains the link between STC1 and cell apoptosis in cervical cancer.


Assuntos
Glicoproteínas/genética , Fator de Transcrição RelA/metabolismo , Neoplasias do Colo do Útero/genética , Apoptose , Linhagem Celular Tumoral , Movimento Celular , Proliferação de Células , Feminino , Regulação Neoplásica da Expressão Gênica , Glicoproteínas/metabolismo , Células HeLa , Humanos , Quinase I-kappa B/metabolismo , Inibidor de NF-kappaB alfa/metabolismo , Estadiamento de Neoplasias , Fosfatidilinositol 3-Quinases/metabolismo , Fosforilação , RNA Interferente Pequeno/genética , Transdução de Sinais , Fator de Transcrição RelA/genética
15.
Top Curr Chem (Cham) ; 375(2): 49, 2017 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-28397187

RESUMO

Ureas are an important class of bioactive organic compounds in organic chemistry and exist widely in natural products, agricultural pesticides, uron herbicides, pharmaceuticals. Even though urea itself has been synthesized from CO2 and ammonia for a long time, the selective and efficient synthesis of substituted ureas is still challenging due to the difficulty of dehydration processes. Efficient and economic fixation of CO2 is of great importance in solving the problems of resource shortages, environmental issues, global warming, etc. During recent decades, chemists have developed different catalytic systems to synthesize ureas from CO2 and amines. Herein, we focus on catalytic synthesis of ureas using CO2 and amines.


Assuntos
Dióxido de Carbono/química , Ureia/síntese química , Aminas/química , Catálise , Estrutura Molecular , Ureia/química
16.
Oncotarget ; 8(1): 1655-1667, 2017 Jan 03.
Artigo em Inglês | MEDLINE | ID: mdl-27926484

RESUMO

Upregulation of lncRNA H19 expression is associated with an unfavorable prognosis in some cancers. However, the prognostic value of H19 in female-specific cancers has remained uncharacterized. In this study, the prognostic power of high H19 expression in female cancer patients from the TCGA datasets was analyzed using Kaplan-Meier survival curves and Cox's proportional hazard modeling. In addition, in a meta-analysis of non-female cancer patients from TCGA datasets and 12 independent studies, hazard ratios (HRs) with 95% confidence interval (CI) for overall survival (OS) and disease-free survival (DFS)/relapse-free survival (RFS)/metastasis-free survival (MFS)/progression-free survival (PFS) were pooled to assess the prognostic value of high H19 expression. Kaplan-Meier analysis revealed that patients with uterine corpus cancer and higher H19 expression had a shorter OS (HR=2.710, p<0.05), while females with cervical cancer and increased H19 expression had a shorter RFS (HR=2.261, p<0.05). Multivariate Cox regression analysis showed that high H19 expression could independently predict a poorer prognosis in cervical cancer patients (HR=4.099, p<0.05). In the meta-analysis, patients with high H19 expression showed a poorer outcome in non-female cancer (p<0.05). These results suggest that high lncRNA H19 expression is predictive of an unfavorable prognosis in two female cancers (uterine corpus endometrioid cancer and cervical cancer) as well as in non-female cancer patients.


Assuntos
Biomarcadores Tumorais/genética , Neoplasias da Mama/genética , Carcinoma Endometrioide/genética , RNA Longo não Codificante/genética , Neoplasias do Colo do Útero/genética , Neoplasias da Mama/mortalidade , Neoplasias da Mama/patologia , Carcinoma Endometrioide/mortalidade , Carcinoma Endometrioide/patologia , Intervalo Livre de Doença , Feminino , Humanos , Estimativa de Kaplan-Meier , Masculino , Pessoa de Meia-Idade , Recidiva Local de Neoplasia/genética , RNA Longo não Codificante/biossíntese , Neoplasias do Colo do Útero/mortalidade , Neoplasias do Colo do Útero/patologia
17.
Nat Commun ; 7: 12075, 2016 07 05.
Artigo em Inglês | MEDLINE | ID: mdl-27377550

RESUMO

Upgrading C1 chemicals (for example, CO, CO/H2, MeOH and CO2) with C-C bond formation is essential for the synthesis of bulk chemicals. In general, these industrially important processes (for example, Fischer Tropsch) proceed at drastic reaction conditions (>250 °C; high pressure) and suffer from low selectivity, which makes high capital investment necessary and requires additional purifications. Here, a different strategy for the preparation of ethylene glycol (EG) via initial oxidative coupling and subsequent reduction is presented. Separating coupling and reduction steps allows for a completely selective formation of EG (99%) from CO. This two-step catalytic procedure makes use of a Pd-catalysed oxycarbonylation of amines to oxamides at room temperature (RT) and subsequent Ru- or Fe-catalysed hydrogenation to EG. Notably, in the first step the required amines can be efficiently reused. The presented stepwise oxamide-mediated coupling provides the basis for a new strategy for selective upgrading of C1 chemicals.

18.
Oncotarget ; 7(27): 41650-41661, 2016 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-27223436

RESUMO

Although screening has reduced mortality rates, metastasis still results in poor survival and prognosis in cervical cancer patients. We compared cervical cancer ESTs libraries with other ESTs libraries to identify candidate genes and cloned a novel cervical cancer-associated lncRNA, lnc-CC3. Overexpression of lnc-CC3 promoted migration and invasion by SiHa cervical cancer cells in vitro and in vivo, increased Slug expression, and reduced the expression of the epithelial cell marker E-cadherin. Conversely, lnc-CC3 knockdown altered SiHa cell morphology and increased the expression of E-cadherin, thereby suppressing migration and invasion. These results suggest lnc-CC3 may be a useful marker of metastasis in cervical cancer.


Assuntos
Movimento Celular/genética , RNA Longo não Codificante/fisiologia , Neoplasias do Colo do Útero/genética , Neoplasias do Colo do Útero/patologia , Animais , Biomarcadores Tumorais/genética , Biomarcadores Tumorais/fisiologia , Células Cultivadas , Feminino , Regulação Neoplásica da Expressão Gênica , Células HeLa , Células Hep G2 , Células Endoteliais da Veia Umbilical Humana , Humanos , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Nus , Invasividade Neoplásica , Metástase Neoplásica
19.
PeerJ ; 4: e1756, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27019775

RESUMO

Background. Understanding species distribution, especially areas of overlapping habitat between sympatric species, is essential for informing conservation through natural habitat protection. New protection strategies should simultaneously consider conservation efforts for multiple species that exist within the same landscape, which requires studies that include habitat overlap analysis. Methods. We estimated the potential habitat of cervids, which are typical ungulates in northern China, using the present locations of red deer (Cervus elaphus; N = 90) and roe deer (Capreolus capreolus; N = 106) in a Maximum Entropy (MaxEnt) model. Our study area was a human-dominated landscape in the Tieli Forestry Bureau located at the southern slope of the Lesser Xing'an Mountains. We grouped 17 environmental predictor variables into five predictor classes (terrain, habitat accessibility, land cover, vegetation feature, and interference), which were used to build habitat suitability models. Results. Habitat accessibility and human interferences were found to have the strongest influence on habitat suitability among the five variable classes. Among the environmental factors, distance to farmland (26.8%), distance to bush-grass land (14.6%), elevation (13.5%), and distance to water source (12.2%) were most important for red deer, distance to farmland (22.9%), distance to settlement (21.4%), elevation (11.6%), and coverage of shrub-grass (8%) were most important for roe deer. Model accuracy was high for both species (mean area under the curve (AUC) = 0.936 for red deer and 0.924 for roe deer). The overlapping habitat comprised 89.93 km(2) within the study area, which occupied 94% of potentially suitable habitat for red deer and 27% for roe deer. Conclusions. In terms of habitat suitability, roe deer showed greater selectivity than red deer. The overlapping habitat was mostly located in the eastern mountains. The southwestern plain was not a suitable habitat for deer because it was close to Tieli City. Regarding management measures, we suggest that priority protection should be given to the potential areas of overlapping deer habitats found in this study.

20.
Chemistry ; 22(21): 7050-3, 2016 05 17.
Artigo em Inglês | MEDLINE | ID: mdl-26991132

RESUMO

This article describes a selective reduction of functionalized amides, including N-acyl amino esters and dipeptides, to the corresponding amines using simple [Rh(acac)(cod)]. The catalyst shows excellent chemoselectivity in the presence of different sensitive functional moieties.


Assuntos
Amidas/química , Aminas/química , Dipeptídeos/química , Ródio/química , Silanos/química , Catálise , Ésteres/química , Oxirredução
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