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1.
Nano Lett ; 20(1): 709-714, 2020 Jan 08.
Artigo em Inglês | MEDLINE | ID: mdl-31838853

RESUMO

Magnetic topological insulator, a platform for realizing quantum anomalous Hall effect, axion state, and other novel quantum transport phenomena, has attracted a lot of interest. Recently, it is proposed that MnBi2Te4 is an intrinsic magnetic topological insulator, which may overcome the disadvantages in the magnetic doped topological insulator, such as disorder. Here we report on the gate-reserved anomalous Hall effect (AHE) in the MnBi2Te4 thin film. By tuning the Fermi level using the top/bottom gate, the AHE loop gradually decreases to zero and the sign is reversed. The positive AHE exhibits distinct coercive fields compared with the negative AHE. It reaches a maximum inside the gap of the Dirac cone, and its amplitude exhibits a linear scaling with the longitudinal conductance. The positive AHE is attributed to the competition of the intrinsic Berry curvature and the extrinsic skew scattering. Its gate-controlled switching contributes a scheme for the topological spin field-effect transistors.

2.
Adv Mater ; : e1904593, 2019 Dec 16.
Artigo em Inglês | MEDLINE | ID: mdl-31840308

RESUMO

A topological insulator (TI) is a kind of novel material hosting a topological band structure and plenty of exotic topological quantum effects. Achieving quantized electrical transport, including the quantum Hall effect (QHE) and the quantum anomalous Hall effect (QAHE), is an important aspect of realizing quantum devices based on TI materials. Intense efforts are made in this field, in which the most essential research is based on the optimization of realistic TI materials. Herein, the TI material development process is reviewed, focusing on the realization of quantized transport. Especially, for QHE, the strategies to increase the surface transport ratio and decrease the threshold magnetic field of QHE are examined. For QAHE, the evolution history of magnetic TIs is introduced, and the recently discovered magnetic TI candidates with intrinsic magnetizations are discussed in detail. Moreover, future research perspectives on these novel topological quantum effects are also evaluated.

3.
Medicine (Baltimore) ; 98(52): e18523, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31876746

RESUMO

Prostate cancer (PCa) is a frequently diagnosed malignant solid tumor in men. The etiology of PCa has been attributed to both environmental and genetic factors. In recent years, many studies have reported that miRNA gene single-nucleotide polymorphisms (SNPs) influence the susceptibility to several diseases such as cancer. To date, the mechanisms of PCa have remained unknown. The main aim of this study was to evaluate the association between PCa susceptibility and miRNA gene SNPs. A total of 156 PCa cases and 188 control subjects were included in this case-control study. The data were collected from hospitalized cases. We collected the demographic characteristic information, which included age, body mass index, tobacco smoking, alcohol consumption, and family history of cancer. Polymorphisms were analyzed by the ligase detection reaction. Unconditional logistic and stratified analyses were used to analyze the association between these SNPs and PCa susceptibility and to calculate the adjusted odds ratios (ORs) and the 95% confidence intervals (CIs). Cox regression model and the log-rank test were used to test the association between genetic variants and the overall survival. We found that miR-23a gene polymorphism rs3745453 carrying CC homozygotes had a 4.16-fold increased risk (95% CI = 1.30-13.25) than those carrying the TT/CT genotypes (P = .02), and the C allele displayed a higher prevalence of PCa than the T allele (OR = 1.68, 95% CI = 1.16-2.45, P = .01). Moreover, miR-23a showed that the homozygous carriers of the C-variant significantly increased the risk of survival rate as compared to the carriers of the TT/CT genotype (OR = 9.67, 95% CI = 2.83-33.09, P = .001). The rs3745453 polymorphism was potentially associated with PCa in the Chinese Han population and had an interactive relationship with the environmental factors.


Assuntos
Predisposição Genética para Doença/genética , MicroRNAs/genética , Polimorfismo de Nucleotídeo Único/genética , Neoplasias da Próstata/genética , Idoso , Grupo com Ancestrais do Continente Asiático/genética , Estudos de Casos e Controles , China/epidemiologia , Homozigoto , Humanos , Masculino , Neoplasias da Próstata/epidemiologia , Fatores de Risco
4.
Nat Commun ; 10(1): 4469, 2019 10 02.
Artigo em Inglês | MEDLINE | ID: mdl-31578337

RESUMO

Magnetic topological insulators (MTIs) offer a combination of topologically nontrivial characteristics and magnetic order and show promise in terms of potentially interesting physical phenomena such as the quantum anomalous Hall (QAH) effect and topological axion insulating states. However, the understanding of their properties and potential applications have been limited due to a lack of suitable candidates for MTIs. Here, we grow two-dimensional single crystals of Mn(SbxBi(1-x))2Te4 bulk and exfoliate them into thin flakes in order to search for intrinsic MTIs. We perform angle-resolved photoemission spectroscopy, low-temperature transport measurements, and first-principles calculations to investigate the band structure, transport properties, and magnetism of this family of materials, as well as the evolution of their topological properties. We find that there exists an optimized MTI zone in the Mn(SbxBi(1-x))2Te4 phase diagram, which could possibly host a high-temperature QAH phase, offering a promising avenue for new device applications.

5.
Nat Commun ; 9(1): 2725, 2018 07 13.
Artigo em Inglês | MEDLINE | ID: mdl-30006515

RESUMO

Achieving a desirable combination of solid-like properties and fast self-healing is a great challenge due to slow diffusion dynamics. In this work, we describe a design concept that utilizes weak but abundant coordination bonds to achieve this objective. The designed PDMS polymer, crosslinked by abundant Zn(II)-carboxylate interactions, is very strong and rigid at room temperature. As the coordination equilibrium is sensitive to temperature, the mechanical strength of this polymer rapidly and reversibly changes upon heating or cooling. The soft-rigid switching ability σ, defined as G'max /G'min, can reach 8000 when ΔT = 100 °C. Based on these features, this polymer not only exhibits fast thermal-healing properties, but is also advantageous for various applications such as in orthopedic immobilization, conductive composites/adhesives, and 3D printing.

6.
Adv Mater ; 30(35): e1801556, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-30019415

RESUMO

The discovery of a new type-II Dirac semimetal in Ir1-x Ptx Te2 with optimized band structure is described. Pt dopants protect the crystal structure holding the Dirac cones and tune the Fermi level close to the Dirac point. The type-II Dirac dispersion in Ir1-x Ptx Te2 is confirmed by angle-resolved photoemission spectroscopy and first-principles calculations. Superconductivity is also observed and persists when the Fermi level aligns with the Dirac points. Ir1-x Ptx Te2 is an ideal platform for further studies on the exotic properties and potential applications of type-II DSMs, and opens up a new route for the investigation of the possible topological superconductivity and Majorana physics.

7.
Onco Targets Ther ; 11: 851-865, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29497317

RESUMO

Background: Although the relationship between several single nucleotide polymorphisms (SNPs) of the oncogene EZH2 and cancer risk has been assessed by some case-control studies, results of subsequent studies are controversial. Sample sizes from single-center studies are also limited, thereby providing unreliable findings. Hence, we conducted a comprehensive search and meta-analysis to evaluate the associations between EZH2 SNPs and cancer risk. Materials and methods: A comprehensive literature search for studies focusing on EZH2 SNPs and cancer risk was conducted on PubMed, Web of Science, Embase, and China National Knowledge Infrastructure online databases. Genotype data were extracted and examined through a meta-analysis, and pooled odds ratios (ORs) with 95% CIs were used to assess the corresponding associations. Sensitivity analysis, publication bias assessment, and heterogeneity test were performed using STATA 12.0. Results: Twelve eligible studies were included in this meta-analysis. The association of 4 SNPs, namely, rs887569, rs2302427, rs3757441, and rs41277434, in the EZH2 locus with cancer risk was evaluated. Five studies (1,794 cases and 1,878 controls) indicated that rs887569 was related to a decreased cancer risk (CTTT/CC: OR =0.849, 95% CI: [0.740 to 0.973], P=0.019; TT/CCCT: OR =0.793, 95% CI: [0.654 to 0.962], P=0.019). Seven studies (2,408 cases and 2,910 controls) showed that rs2302427 was linked to a decreased cancer risk (GG/CC: OR =0.562, 95% CI: [0.400 to 0.792], P=0.001; CGGG/CC: OR =0.856, 95% CI: [0.748 to 0.980], P=0.024; GG/CCCG: OR =0.733, 95% CI: [0.571 to 0.940], P=0.015). No relationships were observed between rs3757441 or rs41277434 and cancer risk. Conclusion: rs887569 and rs2302427 in EZH2 may be correlated with a decreased cancer risk. Although rs3757441 and rs41277434 are independent risk factors of cancer, further large-scale and functional studies are warranted to validate our findings.

8.
Org Lett ; 20(3): 796-799, 2018 02 02.
Artigo em Inglês | MEDLINE | ID: mdl-29350043

RESUMO

A well-defined homogeneous silver precatalyst can be utilized for the direct C-H functionalization of a wide range of aromatic nitrogen heterocycles with cyclopropanols under acid-free conditions. This reaction can be conducted on gram-scale and with low catalyst loadings (as low as 1%), which is rare for silver-catalyzed Minisci-type reactions. Moreover, reactivity trends, as well as steric and calculated electronic properties of the heterocycles, strongly suggest that silver-heterocycle complexes formed in situ behave as redox active catalysts and as Lewis acid activators of the heterocycle and that the electronic nature of the heterocyclic substrates tunes the reactivity of the resulting complexes.

9.
ACS Nano ; 12(2): 1537-1543, 2018 02 27.
Artigo em Inglês | MEDLINE | ID: mdl-29294273

RESUMO

We report the study of a triaxial vector magnetoresistance (MR) in nonmagnetic (Bi1-xInx)2Se3 nanodevices at the composition of x = 0.08. We show a dumbbell-shaped in-plane negative MR up to room temperature as well as a large out-of-plane positive MR. MR at three directions is about in a -3%:-1%:225% ratio at 2 K. Through both the thickness and composition-dependent magnetotransport measurements, we show that the in-plane negative MR is due to the topological phase transition enhanced intersurface coupling near the topological critical point. Our devices suggest the great potential for room-temperature spintronic applications in, for example, vector magnetic sensors.

10.
Nanoscale ; 9(34): 12372-12378, 2017 Aug 31.
Artigo em Inglês | MEDLINE | ID: mdl-28612869

RESUMO

Time-reversal symmetry is broken by magnetic doping in topological insulators (TIs). An energy gap at the Dirac point opens and thus, generates numerous surface carriers. TI nanostructures are an ideal platform to investigate exotic surface transport behavior due to their large surface-to-volume ratio, which enhances the contribution of the TI surface states. However, magnetic doping into TI nanostructures has been challenging, and induced magnetic behavior has remained elusive. Herein, we have synthesized Fe-doped Bi2Se3 nanowires using a facile chemical vapor deposition with a doping concentration of ∼1 at%. The combined structural characterizations illustrate the homogeneous distribution of the Fe dopants. Cryogenic magnetic force microscopy gives direct evidence of the spontaneous magnetization with a Curie temperature of ∼40 K in a single nanowire. The transport measurements show a quantum transition from weak anti-localization to weak localization behavior. All the evidence indicates the existence of intrinsic ferromagnetism and gapped topological surface states in the TI nanowires, paving a way for future memory and magnetoelectric nanodevice applications.

11.
ScientificWorldJournal ; 2014: 897960, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24578665

RESUMO

The correlated color temperature (CCT) tunable white-light LED cluster with extrahigh color rendering property has been found by simulation and fabricated, which consists of three WW LEDs (CCT = 3183 K), one red LED (634.1 nm), one green LED (513.9 nm), and one blue LED (456.2 nm). The experimental results show that this cluster can realize the CCT tunable white-lights with a color rendering index (CRI) above 93, special CRI R9 for strong red above 90, average value of the special CRIs of R9 to R12 for the four saturated colors (red, yellow, green, and blue) above 83, and luminous efficacies above 70 lm/W at CCTs of 2719 K to 6497 K.


Assuntos
Luz , Dispositivos Ópticos/normas , Cor
12.
Ann Clin Lab Sci ; 43(2): 154-62, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23694790

RESUMO

The beneficial effect of stem cells on several animal models of neuropathic pain has been recognized recently. However, there have been no studies on the effects of neural stem cell transplantation on neuropathic pain. In the present study, using the rat model of chronic constriction injury of the sciatic nerve, we observed the effect of intrathecal transplantation of extrinsic neural stem cells on the behavior and expression of neurotrophins such as brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF) in the spinal dorsal horn and dorsal root ganglia (DRG), and analyzed BDNF and GDNF protein levels secreted by neural stem cells in vitro before and after differentiation. We found that intrathecal administration of neural stem cells 3 days after injury could significantly attenuate mechanical and thermal hyperalgesia. Furthermore, real-time PCR and enzyme-linked immunosorbent assay (ELISA) results together showed that the expression of GDNF, rather than BDNF, was significantly elevated in the neural stem cell transplantation group. The in vitro ELISA results showed that after differentiation, GDNF secrection was dramatically increased, whereas BDNF expression was sharply down-regulated. We therefore concluded that the secretion of GDNF, but not BDNF, by the transplanted neural stem cells might contribute to the relief of neuropathic pain.


Assuntos
Fator Neurotrófico Derivado de Linhagem de Célula Glial/metabolismo , Células-Tronco Neurais/transplante , Neuralgia/terapia , Análise de Variância , Animais , Diferenciação Celular/fisiologia , Primers do DNA/genética , Ensaio de Imunoadsorção Enzimática , Hiperalgesia/fisiopatologia , Injeções Espinhais , Masculino , Células-Tronco Neurais/metabolismo , Ratos , Ratos Sprague-Dawley , Reação em Cadeia da Polimerase em Tempo Real
13.
Opt Express ; 20 Suppl 5: A684-93, 2012 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-23037535

RESUMO

The correlated color temperature (CCT) tunable white-light LED cluster, which consists of direct-emission blue and red LEDs as well as phosphor-conversion (PC) LEDs packaged by combining green and orange phosphors with a blue LED die, has been obtained by nonlinear program for maximizing luminous efficacy (LE) of radiation (LER) under conditions of both color rendering index (CRI) and special CRI of R9 for strong red above 90 at CCTs of 2700 K to 6500 K. The optimal peak wavelengths of blue LED, red LED, blue LED die, green and orange phosphors are 465 nm, 628 nm, 452 nm, 530 nm and 586 nm, respectively. The real CCT tunable PC/red/blue LED cluster with CRIs of 90~96, R9s of 90~96, CQSs of 89~94, LERs of 303~358 lm/W, and LEs of 105~119 lm/W has been realized at CCTs of 2722 K to 6464 K. The deviation of the peak wavelength should be less than ± 5 nm for blue LED die, ± 1 nm for red LED, and ± 2 nm for blue LED to achieve the PC/R/B LED cluster with high optical performance.

14.
Opt Express ; 20(8): 9122-34, 2012 Apr 09.
Artigo em Inglês | MEDLINE | ID: mdl-22513623

RESUMO

The relationship and trade-offs between the performance parameters including color rendering index (CRI), luminous efficacy of radiation (LER) and correlated color temperature (CCT) of white LEDs using quantum dot nanophosphors (QD-WLEDs) are investigated for CRI ≥ 80 and LER ≥ 300 lm/W at 1500 K ≤ CCT ≤ 6500 K. The optimal spectra of QD-WLEDs with CCTs of 2700-6500 K have been obtained with a nonlinear program for maximizing LER under conditions of both CRI and a special CRI of R9 strong red above 90 or 95. Furthermore, high performance QD-WLEDs with LER = 381 lm/W for CRI = R9 = 90 and LER = 371 lm/W for CRI = R9 = 95 at CCT = 3000 K, with LER = 361 lm/W for CRI = R9 = 90 and LER = 352 lm/W for CRI = R9 = 95 at CCT = 4500 K, and with LER = 346 lm/W for CRI = R9 = 90 and LER = 338 lm/W for CRI = R9 = 95 at CCT = 5700 K could be achieved. The LERs of high performance white LEDs using QD nanophosphors increase by 13% to 32% compared with that of white LEDs using traditional phosphors.

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