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1.
Front Psychol ; 12: 757059, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34777160

RESUMO

The current study focuses on a novel and recently popular internet phenomenon - celebrity livestreaming marketing. As one of the primary advantages of livestreaming marketing by Internet celebrities, we propose that the timely interactivity of Internet celebrities plays an important role in consumers' purchase intention. Based on stimulus-organism-response theory, this paper further identifies social presence and flow experience as mediators and the consistency of Internet celebrities' image and product image as a moderator and constructs an influence model of Internet celebrities' interactivity on consumers' purchase intention. The responses of a sample of 277 participants were collected by a questionnaire survey. SPSS and Amos were used to analyse the data. The results show that consumers' social presence and flow experience mediate the positive impact of the interactivity of Internet celebrity anchors on influencing consumers' purchase intention. However, there is no significant moderating effect of the consistency of Internet celebrities' image and product image on the relationship between social presence or flow experience and purchase intention. A discussion and implications are offered.

2.
Sci Rep ; 11(1): 22090, 2021 Nov 11.
Artigo em Inglês | MEDLINE | ID: mdl-34764365

RESUMO

[Formula: see text] is a layered transition-metal dichalcogenide (TMD) with outstanding electronic and optical properties, which is widely used in field-effect transistor (FET). Here the structural evolution and phase transition of [Formula: see text] under high pressure are systematically studied by CALYPSO structural search method and first-principles calculations. The structural evolutions of [Formula: see text] show that the ground state structure under ambient pressure is the experimentally observed P6[Formula: see text]/mmc phase, which transfers to R3m phase at 1.9 GPa. The trigonal R3m phase of [Formula: see text] is stable up to 72.1 GPa, then, it transforms into a new P6[Formula: see text]/mmc phase with different atomic coordinates of Se atoms. This phase is extremely robust under ultrahigh pressure and finally changes to another trigonal R-3m phase under 491.1 GPa. The elastic constants and phonon dispersion curves indicate that the ambient pressure phase and three new high-pressure phases are all stable. The electronic band structure and projected density of states analyses reveal a pressure induced semiconducting to metallic transition under 72.1 GPa. These results offer a detailed structural evolution and phase diagram of [Formula: see text] under high pressure, which may also provide insights for exploration other TMDs under ultrahigh pressure.

3.
Immun Inflamm Dis ; 9(3): 702-709, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-34077992

RESUMO

BACKGROUND: Destruction of melanocytes mediated by autoimmunity is currently believed as the main cause of vitiligo. This article aims to identify the role of CC chemokine ligand 17 (CCL17)-CC chemokine receptor 4 (CCR4) axis in vitiligo and provide new possibilities for the clinical treatment of vitiligo. METHODS: A total of 30 patients with vitiligo from Affiliated Huaian No. 1 People's Hospital of Nanjing Medical University were recruited based on the inclusion and exclusion criteria. Trephine was used to obtain skin samples from the lesion area and its surrounding normal areas, and the expression levels of CCL17, CCR4, Tbx21, Eomes, and Blimp1 were determined by quantitative reverse transcription polymerase chain reaction. Vitiligo mouse model was established by adoptively transferring CFP-PMEL CD8+ T cells into sublethally irradiated Krt14-Kitl* mice. Recipient mice received intraperitoneal injection of 1 × 106 plaque-forming units of rVV-hPMEL on the same day of transfer. The degree of depigmentation was scored blindly by one observer 5 weeks after vitiligo induction. CFP-PMEL CD8+ T cells migration to skin, draining lymph nodes, spleen, and blood were detected by flow cytometry. CCR4 blockade was performed by intraperitoneal injection of neutralizing antibody. RESULTS: The expression levels of CCL17, CCR4, Tbx21, Eomes, and Blimp1 in skin lesions were significantly increased compared with that in surrounding normal areas. CCL17-/- and CCR4-/- mice exhibited significantly lower disease scores than WT mice. The CFP-PMEL CD8+ T cells accumulation was significantly decreased in the skin of CCL17-/- and CCR4-/- mice, but was not changed in draining lymph nodes, spleen, and blood. Administration of CCR4 neutralizing antibody decreased the degree of depigmentation and the recruitment of CFP-PMEL CD8+ T cells to the skin, while keeping the number of T cells in draining lymph nodes unchanged. CONCLUSION: Targeting CCL17-CCR4 axis might inhibit T cell migrating to skin and alleviate vitiligo progression.


Assuntos
Receptores CCR4 , Vitiligo , Animais , Quimiocina CCL17 , Humanos , Ligantes , Camundongos , Pele
4.
J Phys Chem A ; 125(19): 4126-4132, 2021 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-33961432

RESUMO

Since the discovery of metal-doped boron clusters attracted great significance to create a new class of materials, research interests have been directed to chemical bonding and structural evolution of lanthanide boride clusters. Here, we perform an extensive ground-state structure search for the CeBn and CeBn- clusters in the size range from 9 to 18 using the Crystal structure AnaLYsis by Particle Swarm Optimization method and density functional theory optimization. It is found that the ground-state structures in both neutral and anionic series possess half-sandwich geometry. The host boron moiety in neutral series has a tendency to form borophene-like geometry. The pentagonal and hexagonal holes are more common in the larger anionic CeBn- series. The theoretical photoelectron spectroscopy has been simulated by applying time-dependent density functional theory calculations. The neutral CeB14 cluster is identified as a magic cluster on the basis of its robust relative stability with respect to its neighbors. Electronic structure and chemical bonding analyses reveal that the CeB14 cluster possesses a large HOMO-LUMO gap and enhanced stability with strong delocalized π and δ bonding via interactions between the Ce 5d- and B 2p-AOs.

5.
Genes Genomics ; 43(5): 491-501, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33709381

RESUMO

BACKGROUND: Cutaneous squamous cell carcinoma (CSCC) is a severe malignancy derived from skin. Dysregulated circular RNAs (circRNAs) might play vital roles in tumor development. OBJECTIVE: Here, we aimed to explore the function of a novel circRNA circ_0067772 in CSCC. METHODS: Quantitative real-time PCR (qRT-PCR) or Western blot assay was performed to determine the expression of circ_0067772, microRNA (miR)-1238-3p and forkhead box protein G1 (FOXG1). Cell proliferation was assessed by Cell Counting Kit-8 (CCK-8) assay and colony formation assay. Transwell assay and wound healing assay were employed to examine cell metastasis. Flow cytometry was employed to monitor cell cycle and apoptosis. The target association between miR-1238-3p and circ_0067772 or FOXG1 was validated by dual-luciferase reporter assay. Moreover, role of circ_0067772 in vivo was investigated via xenograft model in nude mice. RESULTS: Circ_0067772 and FOXG1 were upregulated, while miR-1238-3p was downregulated in CSCC tissues and cells. Circ_0067772 knockdown conferred inhibitory effects on cell proliferation, migration and invasion of CSCC cells. MiR-1238-3p served as a target of circ_0067772, whose silencing could reverse circ_0067772 knockdown-induced inhibitory impact on the malignant cellular behaviors. Circ_0067772 positively regulated FOXG1 expression by antagonizing miR-1238-3p. Additionally, miR-1238-3p could repress CSCC cell proliferation, migration and invasion by targeting FOXG1. Also, circ_0067772 knockdown hindered CSCC tumor growth in vivo. CONCLUSION: Our study identified a novel oncogenic circRNA and the involvement of circ_0067772/miR-1238-3p/FOXG1 axis in CSCC development, providing a target for CSCC therapy.

6.
Dermatol Ther ; 34(3): e14923, 2021 05.
Artigo em Inglês | MEDLINE | ID: mdl-33651436

RESUMO

Melanocyte-specific CD8+ T cells enrichment correlates with the severity of vitiligo, and the role of A20 derived from myeloid cells in the enrichment of pathogenic T cells is unknown. Premelanosome (PMEL)-specific transgenic CD8+ T cells were adoptive transferred into Krt14-Kitl* mice to construct the vitiligo model, which was further mated with A20MKO mice and IKK2fl/fl mice. Bone marrow cells were stimulated with 30% L929 cell-conditioned medium, Fc-human tumor necrosis factor, and lipopolysaccharides to induce bone marrow-derived macrophages (BMDMs). The relative expression of CCL2, CCL5, and IL12A was detected with real-time PCR, and nuclear factor kappa B (NFκB) related molecules were detected with Western blots. Fluorescence-activated cell sorting (FACS) was utilized to assay the percent of innate and adaptive immune cells in the spleen and bone marrow, and CD45+ T in the skin. Down-regulated A20 was detected in the skin biopsies of vitiligo patients. A20 deficiency did not affect the development of T cells, B cells, macrophages, and neutrophils. A20 negatively regulated the induction of proinflammatory chemokines (CCL2, CCL5, and IL12A) and NFκB-related molecule expression in BMDMs, which could be blocked by NFκB knockout. It further revealed that A20 negatively regulated the onset of vitiligo in mice with diminished CD45+ cells enrichment, which could also be reversed by NFκB knockout. A20 deficiency in myeloid cells could deteriorate the onset of vitiligo in mice, and A20 can be considered as a treatment target.


Assuntos
Vitiligo , Animais , Linfócitos T CD8-Positivos , Humanos , Macrófagos , Camundongos , Células Mieloides , Proteína 3 Induzida por Fator de Necrose Tumoral alfa , Vitiligo/genética
7.
Phys Chem Chem Phys ; 23(3): 2166-2178, 2021 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-33438692

RESUMO

The coalescence of two Fe8N as well as the structure of the Fe16N2 cluster were studied using density functional theory with the generalized gradient approximation and a basis set of triple-zeta quality. It was found that the coalescence may proceed without an energy barrier and that the geometrical structures of the resulting clusters depend strongly on the mutual orientations of the initial moieties. The dissociation of N2 is energetically favorable on Fe16, and the nitrogen atoms share the same Fe atom in the lowest energy state of the Fe16N2 species. The attachment of two nitrogen atoms leads to a decrease in the total spin magnetic moment of the ground-state Fe16 host by 6 µB due to the peculiarities of chemical bonding in the magnetic clusters. In order to gain insight into the dependence of properties on charge and to estimate the bonding energies of both N atoms, we performed optimizations of Fe16N and the singly charged ions of both Fe16N2 and Fe16N. It was found that the electronic properties of the Fe16N2 cluster, such as electron affinity and ionization energy, do not appreciably depend on the attachment of nitrogen atoms but that the average binding energy per atom changes significantly. The lowering in total energy due to the attachment of two N atoms was found to be nearly independent of charge. The IR and Raman spectra were simulated for Fe16N2 and its ions, and it was found that the positions of the most intense peaks in the IR spectra strongly depend on charge and therefore present fingerprints of the charged states. The chemical bonding in the ground-state Fe16N20,±1 species was described in terms of the localized molecular orbitals.

8.
J Phys Chem A ; 124(44): 9187-9193, 2020 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-33085487

RESUMO

Transition metal-doped electronic deficiency boron clusters have led to a vast variety of electronic bonding properties in chemistry and materials science. We have determined the ground state structures of PdBn0/- (n = 10-20) clusters by performing CALYPSO search and density functional theory (DFT) optimization. The identified lowest energy structures for both neutral and anionic Pd-doped boron clusters follow the structure evolution from two dimensional (2D) planar configurations to 3D distorted Pd-centered drum-like or tubular structures. Photoelectron spectra are simulated by time-dependent DFT theoretical calculations, which is a powerful method to validate our obtained ground-state structures. More interestingly, two "magic" number clusters, PdB12 and PdB16, are found with enhanced stability in the middle size regime studied. Subsequently, molecular orbital and adaptive natural density partitioning analyses reveal that the high stability of the PdB16 cluster originates from doubly σ π aromatic and bonding interactions of d-type atomic orbitals of the Pd atom with tubular B16 units. The tubular C8v PdB16 cluster, with robust relative stability, is an ideal embryo for forming finite and infinite nanotube nanomaterials.

9.
J Phys Chem Lett ; 11(22): 9643-9648, 2020 Nov 19.
Artigo em Inglês | MEDLINE | ID: mdl-33125245

RESUMO

Low-dimensional materials with high stabilities and outstanding mechanical properties are essential for next generation microelectromechanical systems (MEMS). The successful synthesis of two-dimensional (2D) tungsten nitride makes it a promising candidate for the MEMS application. Here, we have confirmed the existence of experimentally synthesized W2N3 and predicted three additional new 2D monolayer tungsten nitrides: WN2, WN4, and W3N based on extensively structural searches by CALYPSO method and first-principle calculations. The calculations indicate that the nitrogen-rich WN4 monolayer possesses large in-plane negative Poisson ratios attributed to the 4-fold-coordinated WN4 νx = -0.103 and νy = -0.113, which are tetrahedron combined with the strong coupling between the 2p orbitals of N and 5d orbitals of W. Our findings not only enrich the family of 2D transition metal nitrides with excellent mechanical properties but also open avenues for design and synthesis of other novel 2D layered materials.

10.
Front Chem ; 8: 338, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32411670

RESUMO

Trivalent Cerium (Ce3+) doped Yttrium Oxide (Y2O3) host crystal has drawn considerable interest due to its popular optical 5d-4f transition. The outstanding optical properties of Y2O3:Ce system have been demonstrated by previous studies but the microstructures still remain unclear. The lacks of Y2O3:Ce microstructures could constitute a problem to further exploit its potential applications. In this sense, we have comprehensively investigated the structural evolutions of Y2O3:Ce crystals based on the CALYPSO structure search method in conjunction with density functional theory calculations. Our result uncovers a new rhombohedral phase of Y2O3:Ce with R-3 group symmetry. In the host crystal, the Y3+ ion at central site can be naturally replaced by the doped Ce3+, resulting in a perfect cage-like configuration. We find an interesting phase transition that the crystallographic symmetry of Y2O3 changes from cubic to rhombohedral when the impurity Ce3+ is doped into the host crystal. With the nominal concentration of Ce3+ at 3.125%, many metastable structures are also identified due to the different occupying points in the host crystal. The X-ray diffraction patterns of Y2O3:Ce are simulated and the theoretical result is comparable to experimental data, thus demonstrating the validity of the lowest energy structure. The result of phonon dispersions shows that the ground state structure is dynamically stable. The analysis of electronic properties indicate that the Y2O3:Ce possesses a band gap of 4.20 eV which suggests that the incorporation of impurity Ce3+ ion into Y2O3 host crystal leads to an insulator to semiconductor transition. Meanwhile, the strong covalent bonds of O atoms in the crystal, which may greatly contribute to the stability of ground state structure, are evidenced by electron localization function. These obtained results elucidate the structural and bonding characters of Y2O3:Ce and could also provide useful insights for understanding the experimental phenomena.

11.
Phys Chem Chem Phys ; 22(9): 5018-5023, 2020 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-32073074

RESUMO

As a member of the refractory metal carbide family of materials, TaC is a promising candidate for ultra-high temperature ceramics (UHTC) with desirable mechanical strength. TaC sample quality and therefore mechanical properties are strongly dependent on synthesis method, and atomistic origins of mechanical failure are difficult to assign. Here, we have successfully synthesized high quality densified TaC samples at 5.5 GPa and 1400 °C using the high pressure and high temperature (HPHT) sintering method, with Vickers hardness determined to be 20.9 GPa. First-principles calculations based on the recently developed strain-stress method show that the ideal indentation strength of TaC is about 23.3 GPa in the (11[combining macron]0)[001] direction, in excellent agreement with experimental results. The detailed indentation shear deformation analysis and structural snapshots from the calculations indicate that the slip dislocations of TaC layers are the main structural deformation mode during the Vickers indentation process, and that the strong directional Ta-C bonds are responsible for the high mechanical strength of TaC. HPHT synthesis is shown to produce TaC samples with superior strength, and together with accurate first-principles calculations offers crucial insights for rational design and synthesis of novel and advanced UHTC materials.

12.
Front Biosci (Landmark Ed) ; 25: 463-479, 2020 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-31585897

RESUMO

Quercetin-3-O-ß-D-galactopyranoside, is a hyperoside flavonol glycoside with anti-cancer, anti-inflammatory, and anti-oxidant activities that is derived from Hypericum and Crataegus plants. To this end, we examined the effect of this hyperoside in skin cancer cells lines and in DMBA/TPA induced skin tumors in vivo. In vitro treatment of cancer cells with hyperoside significantly inhibited phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR)/p38 MAPK axis, concomitantly activated the 5'AMP-activated protein kinase (AMPK) signaling, inhibited proliferation, and induced apoptosis and autophagy. Hyperoside markedly inhibited diffuse epidermal hyperplasia and significantly reduced the changes in phosphorylated levels of PI3K, AKT, mTOR and AMPK while reducing p38 phosphorylation as well as of tumor burden in vivo in DMBA/TPA induced skin tumors. These data suggest that hyperoside might be of therapeutic value in chemoprevention of skin cancer.


Assuntos
Antineoplásicos/farmacologia , Apoptose/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Quercetina/análogos & derivados , Neoplasias Cutâneas/tratamento farmacológico , Animais , Antracenos , Proteínas Reguladoras de Apoptose/metabolismo , Linhagem Celular , Linhagem Celular Tumoral , Feminino , Humanos , Camundongos , Ésteres de Forbol , Fosfatidilinositol 3-Quinases/metabolismo , Piperidinas , Proteínas Proto-Oncogênicas c-akt/metabolismo , Quercetina/farmacologia , Transdução de Sinais/efeitos dos fármacos , Neoplasias Cutâneas/induzido quimicamente , Neoplasias Cutâneas/metabolismo , Serina-Treonina Quinases TOR/metabolismo
13.
Artigo em Inglês | MEDLINE | ID: mdl-31781265

RESUMO

Background: Kang-bai-ling (KBL), a Chinese patent medicine, has been demonstrated as an effective therapy for vitiligo in China. However, the pharmacological mechanisms of KBL have not been completely elucidated. Methods: In this study, the potential multicomponent, multitarget, and multipathway mechanism of KBL against vitiligo was clarified by using network pharmacology-based strategy. In brief, potential targets of KBL were collected based on TCMSP databases, followed by network establishment concerning the interactions of potential targets of KBL with well-known therapeutic targets of vitiligo by using protein-protein interaction (PPI) data. As a result, key nodes with higher level of seven topological parameters, including "degree centrality (DC)," "betweenness centrality (BC)," "closeness centrality (CC)," "eigenvector centrality (EC)," "network centrality (NC)," and "local average connectivity (LAC)" were identified as the main targets in the network, followed by subsequent incorporation into the ClueGO for GO and KEGG signaling pathway enrichment analysis. Results: In accordance with the topological importance, a total of 23 potential targets of KBL on vitiligo were identified as main hubs. Additionally, enrichment analysis suggested that targets of KBL on vitiligo were mainly clustered into multiple biological processes (associated with DNA translation, lymphocyte differentiation and activation, steroid biosynthesis, autoimmune and systemic inflammatory reaction, neuron apoptosis, and vitamin deficiency) and related pathways (TNF, JAK-STAT, ILs, TLRs, prolactin, and NF-κB), indicating the underlying mechanisms of KBL on vitiligo. Conclusion: In this work, we successfully illuminated the "multicompounds, multitargets" therapeutic action of KBL on vitiligo by using network pharmacology. Moreover, our present outcomes might shed light on the further clinical application of KBL on vitiligo treatment.

14.
Sci Rep ; 9(1): 14367, 2019 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-31591442

RESUMO

Beryllium-doped boron clusters display essential similarities to borophene (boron sheet) with a molecular structure characterized by remarkable properties, such as anisotropy, metallicity and high conductivity. Here we have determined low-energy structures of BeBn0/- (n = 10-20) clusters by utilizing CALYPSO searching program and DFT optimization. The results indicated that most ground states of clusters prefer plane or quasi-plane structures by doped Be atom. A novel unexpected fascinating planar BeB16- cluster with C2v symmetry is uncovered which possesses robust relative stability. Furthermore, planar BeB16- offers a possibility to construct metallo-borophene nano-materials. Molecular orbital and chemical bonding analysis reveal the peculiarities of BeB16- cluster brings forth the aromaticity and the strong interaction of B-B σ-bonds in boron network.

15.
ACS Appl Mater Interfaces ; 11(11): 10745-10750, 2019 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-30789696

RESUMO

There has been considerable research interest paid to rare-earth transition-metal-doped Y3Al5O12, which has great potential for application as a laser crystal of new-type laser devices because of its unique optoelectronic and photophysical properties. Here, we present new research conducted on the structural evolution and crystal-field characteristics of a rare-earth Nd-doped Y3Al5O12 laser crystal by using the CALYPSO structure search method and our newly developed WEPMD method. A novel cage-like structure with a Nd3+ concentration of 4.16% is uncovered, which belongs to the standardized C222 space group. Our results indicate that the impurity Nd3+ ions are likely to substitute the Y3+ at the central site of the host Y3Al5O12 crystal lattice. The laser emission 4F3/2 → 4I11/2 occurring at 1077 nm is in accord with that of the experimental data. By introducing the proper correlation crystal field, three transitions, 4G5/2 → 4I9/2, 4F7/2 → 4I9/2, and 4S3/2 → 4I9/2, are predicted to be good candidates for laser action. These findings can provide powerful guidelines for further experiments of rare-earth-metal-doped laser crystals.

16.
Brain Behav Immun ; 76: 48-60, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30414952

RESUMO

Germinal centers (GC) are vital to adaptive immunity. BCL6 and miR-155 are implicated in control of GC reaction and lymphomagenesis. FBXO11 causes BCL6 degradation through ubiquitination in B-cell lymphomas. Chronic psychological stress is known to drive immunosuppression. Corticosterone (CORT) is an adrenal hormone expressed in response to stress and can similarly impair immune functions. However, whether GC formation is disrupted by chronic psychological stress and its molecular mechanism remain to be elucidated. To address this issue, we established a GC formation model in vivo, and a GC B cell differentiation model in vitro. Comparing Naive B cells to GC B cells in vivo and in vitro, the differences of BCL6 and FBXO11 mRNA do not match the changes at the protein level and miR-155 levels that were observed. Next we demonstrated that CORT increase, induced by chronic psychological stress, reduced GC response, IgG1 antibody production and miR-155 level in vivo. The effect of chronic psychological stress can be blocked by a glucocorticoid receptor (GR) antagonist. Similarly, impaired GC B cell generation and isotope class switching were observed. Furthermore, we found that miR-155 and BCL6 expression were downregulated, but FBXO11 expression was upregulated in GC B cells treated with CORT in vitro. In addition, we demonstrated that miR-155 directly down-regulated FBXO11 expression by binding to its 3́-untranslated region. The subsequent overexpression of miR-155 significantly blocked the stress-induced impairment of GC response, due to changes in FBXO11 and BCL6 expression, as well as increased apoptosis in B cells both in vivo and in vitro. Our findings suggest perturbation of GC reaction may play a role in chronic psychological stress-induced immunosuppression through a glucocorticoid pathway, and miR-155-mediated post-transcriptional regulation of FBXO11 and BCL6 expression may contribute to the impaired GC response.


Assuntos
Centro Germinativo/metabolismo , MicroRNAs/metabolismo , Estresse Psicológico/metabolismo , Animais , Apoptose/fisiologia , Linfócitos B/imunologia , Linfócitos B/metabolismo , Diferenciação Celular/imunologia , Proteínas de Ligação a DNA/genética , Proteínas F-Box/metabolismo , Feminino , Centro Germinativo/fisiologia , Ativação Linfocitária , Masculino , Camundongos , Camundongos Endogâmicos C57BL , MicroRNAs/genética , Proteínas Proto-Oncogênicas c-bcl-6/metabolismo , Estresse Psicológico/fisiopatologia
17.
Phys Chem Chem Phys ; 21(2): 617-622, 2019 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-30540305

RESUMO

Two-dimensional (2D) Dirac materials have attracted extensive research interest due to their high carrier mobility and ballistic charge transport, and they hold great promise for next-generation nanoscale devices. Here, we report a computational discovery of a stable 2D Dirac material, an NiB6 monolayer, which is identified by an extensive structure search, and its dynamic and thermal stabilities are confirmed by phonon and ab initio molecular dynamics (AIMD) simulations. This monolayer structure possesses anisotropic elastic properties with a Young's modulus of 189 N m-1, which is higher than that of phosphorene or silicene. Electronic band calculations reveal a double Dirac cone feature near the Fermi level with a high Fermi velocity of 8.5 × 105 m s-1, and the results are robust against external strains. We also propose two possible synthesis approaches based on a stable Ni4B8+ precursor or by embedding Ni atoms into the δ4 boron framework. The present findings offer a strong physics basis for the design and synthesis of a novel 2D Dirac material.

18.
Tuberculosis (Edinb) ; 113: 189-199, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30514502

RESUMO

The role of primary subsets of DCs in Mycobacterium tuberculosis infection in humans is incompletely understood. In this study, we identified a CD1c DC subset with phenotype of CD1c+CD11c+CD19-CD11b+ that was significantly increased in tuberculous pleural effusions and in peripheral blood from patients with TB compared with that from healthy controls (p < 0.0001). Sputum smear/culture-positive patients with tuberculosis had significantly higher frequency of CD1c+CD11b+ DC subset than sputum smear/culture-negative patients (p < 0.0001). After effective anti-TB chemotherapy, the frequency of CD1c+CD11b+ DC subset in peripheral blood and tuberculous pleural effusions was decreased. CD1c+CD11b+ DC subset from tuberculous pleural effusions expressed higher levels of TLR2, TLR4, CD172a, CD206 and FcεRⅠ, but lower levels of CD80, CD83 and CD86 compared with CD1c+CD11b- DC subset. Expression of IL-1ß, IL-6, IL-8, IL-23, TNF-α, IFN-γ and TGF-ß mRNA in CD1c+CD11b+ DCs was higher than in CD1c+CD11b- DC subset. Co-culture of autologous naive CD4+ T cells with sorted CD1c+CD11b+ DCs expressed significantly increased levels of IL-17A and RORγt transcripts as compared with those co-cultured with CD11b- subset. In conclusion, a CD1c+CD11b+ DC subset with elevated frequency in patients with tuberculosis was identified and it promoted Th17 cell differentiation.


Assuntos
Antígenos CD1/imunologia , Células Dendríticas/imunologia , Glicoproteínas/imunologia , Imunidade Inata , Pulmão/imunologia , Mycobacterium tuberculosis/imunologia , Células Th17/imunologia , Tuberculose Pulmonar/imunologia , Antituberculosos/uso terapêutico , Estudos de Casos e Controles , Diferenciação Celular , Células Cultivadas , Técnicas de Cocultura , Células Dendríticas/efeitos dos fármacos , Células Dendríticas/microbiologia , Interações Hospedeiro-Patógeno , Humanos , Imunidade Inata/efeitos dos fármacos , Pulmão/efeitos dos fármacos , Pulmão/microbiologia , Mycobacterium tuberculosis/efeitos dos fármacos , Mycobacterium tuberculosis/patogenicidade , Fenótipo , Derrame Pleural/imunologia , Derrame Pleural/microbiologia , Células Th17/efeitos dos fármacos , Células Th17/microbiologia , Resultado do Tratamento , Tuberculose Pulmonar/sangue , Tuberculose Pulmonar/tratamento farmacológico , Tuberculose Pulmonar/microbiologia
19.
Phys Chem Chem Phys ; 20(48): 30376-30383, 2018 Dec 12.
Artigo em Inglês | MEDLINE | ID: mdl-30489588

RESUMO

Modification of properties of boron nanoparticles by doping with transition metals presents a challenging problem because the number of isomers of both doped and un-doped nanoparticles rapidly increases with the nanoparticle size. Here, we perform a study of neutral and anionic Ru-doped boron clusters RuBn (n = 9-20) using the unbiased CALYPSO structural search method in combination with density functional theory calculations. Our results show that the neutral RuB9 cluster possesses a perfect planar wheel-like geometrical structure, whereas the RuBn clusters prefer structures of the half-sandwich type in the range of 10 ≤ n ≤ 14, drum-like type in the range of 15 ≤ n ≤ 18 and cage-like structures for larger n values. The geometrical structures of the lowest total energy states of the RuBn- anions are similar to those of the corresponding neutrals, except for RuB10-, RuB11-, RuB14-, RuB15- and RuB20-. The neutral RuB12 and RuB14 clusters are found to exhibit enhanced stability with respect to the rest of the RuBn clusters due to the delocalized bonding between the Ru atom and the boron host.

20.
Phys Chem Chem Phys ; 20(36): 23740-23746, 2018 Sep 19.
Artigo em Inglês | MEDLINE | ID: mdl-30198528

RESUMO

As an extension of boron based materials, transition-metal doped boron clusters deserve interest in controlling size-dependent structural and electronic properties. Herein, using the Crystal structure AnaLYsis by Particle Swarm Optimization (CALYPSO) method and density functional theory (DFT) calculations, we have performed a global search for the lowest-energy structures of ZrBQn (Q = 0, -1) clusters with n = 10-20. The results show that the ground-state structures of the obtained clusters feature a distinctive structural evolution pattern, from half-sandwich bowl to distorted drum-like and then to Zr-centered distorted tubular motifs. For the sake of validating the current ground-state structures, photoelectron spectra are predicted from time-dependent DFT calculations. More interestingly, the neutral and anionic ZrB12 clusters are found to possess enhanced stability in the size regime studied here. The stability of the closed shell half-sandwich ZrB12 cluster is analyzed by intrinsic bond orbital (IBO) and Adaptive Natural Density Partitioning (AdNDP) methods, which indicates that the stability mechanism is caused by the dopant Zr atom breaking the boron bowl's triangle B3 unit to form a quasi-linear B3 unit in B12 and strengthen both the interaction of the B-B σ-bonds and the Zr-B π-bonds.

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