2,741 research outputs found

    Polytypism and Unexpected Strong Interlayer Coupling of two-Dimensional Layered ReS2

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    The anisotropic two-dimensional (2D) van der Waals (vdW) layered materials, with both scientific interest and potential application, have one more dimension to tune the properties than the isotropic 2D materials. The interlayer vdW coupling determines the properties of 2D multi-layer materials by varying stacking orders. As an important representative anisotropic 2D materials, multilayer rhenium disulfide (ReS2) was expected to be random stacking and lack of interlayer coupling. Here, we demonstrate two stable stacking orders (aa and a-b) of N layer (NL, N>1) ReS2 from ultralow-frequency and high-frequency Raman spectroscopy, photoluminescence spectroscopy and first-principles density functional theory calculation. Two interlayer shear modes are observed in aa-stacked NL-ReS2 while only one interlayer shear mode appears in a-b-stacked NL-ReS2, suggesting anisotropic-like and isotropic-like stacking orders in aa- and a-b-stacked NL-ReS2, respectively. The frequency of the interlayer shear and breathing modes reveals unexpected strong interlayer coupling in aa- and a-b-NL-ReS2, the force constants of which are 55-90% to those of multilayer MoS2. The observation of strong interlayer coupling and polytypism in multi-layer ReS2 stimulate future studies on the structure, electronic and optical properties of other 2D anisotropic materials

    Determining layer number of two dimensional flakes of transition-metal dichalcogenides by the Raman intensity from substrate

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    Transition-metal dichalcogenide (TMD) semiconductors have been widely studied due to their distinctive electronic and optical properties. The property of TMD flakes is a function of its thickness, or layer number (N). How to determine N of ultrathin TMDs materials is of primary importance for fundamental study and practical applications. Raman mode intensity from substrates has been used to identify N of intrinsic and defective multilayer graphenes up to N=100. However, such analysis is not applicable for ultrathin TMD flakes due to the lack of a unified complex refractive index (n~\tilde{n}) from monolayer to bulk TMDs. Here, we discuss the N identification of TMD flakes on the SiO2_2/Si substrate by the intensity ratio between the Si peak from 100-nm (or 89-nm) SiO2_2/Si substrates underneath TMD flakes and that from bare SiO2_2/Si substrates. We assume the real part of n~\tilde{n} of TMD flakes as that of monolayer TMD and treat the imaginary part of n~\tilde{n} as a fitting parameter to fit the experimental intensity ratio. An empirical n~\tilde{n}, namely, n~eff\tilde{n}_{eff}, of ultrathin MoS2_{2}, WS2_{2} and WSe2_{2} flakes from monolayer to multilayer is obtained for typical laser excitations (2.54 eV, 2.34 eV, or 2.09 eV). The fitted n~eff\tilde{n}_{eff} of MoS2_{2} has been used to identify N of MoS2_{2} flakes deposited on 302-nm SiO2_2/Si substrate, which agrees well with that determined from their shear and layer-breathing modes. This technique by measuring Raman intensity from the substrate can be extended to identify N of ultrathin 2D flakes with N-dependent n~\tilde{n} . For the application purpose, the intensity ratio excited by specific laser excitations has been provided for MoS2_{2}, WS2_{2} and WSe2_{2} flakes and multilayer graphene flakes deposited on Si substrates covered by 80-110 nm or 280-310 nm SiO2_2 layer.Comment: 10 pages, 4 figures. Accepted by Nanotechnolog

    PO-187 Exercise reduced the extracellular Glu concentration of striatum neurons in PD model rats by up-regulating mGluR2/3 expression

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    Objective To investigate the effects of motor intervention on the extracellular Glu concentration and mGluR2/3 mRNA and mGluR2/3 protein expression levels of striatum neurons in PD model rats. Methods Rat model of unilateral injury was established by injecting neurotoxin 6-hydroxydopamine (6-OHDA) into the right brain medial forebrain bundle (MFB),the sham operation group was given the same dose of normal saline at the same site.Apomorphine (APO) induced rotation behavior test with substantia nigra and striatum TH immunohistochemical staining used to evaluate the reliability of the model. The exercise group began to exercise the treadmill training intervention (11m/min,30min/day,5day/week) at 1 weeks after the operation. Open field experiment and climbing pole experiment used to evaluate the ability of autonomous activity and movement coordination in rats.Western blotting used to detect tyrosine hydroxylase and  mGluR2/3 expression level. RT-PCR was used to detect the expression level of mGluR2 and mGluR3 mRNA in the striatum;In vivo microdialysis combined with high performance liquid chromatography (HPLC) used to detect extracellular Glu concentration in striatal neurons.  Results The results of the microdialysis combined with high performance liquid chromatography (HPLC) showed that,compared with control group,in PD group,Glu concentration of the extracellular of striatal neurons was significantly increased at third and fifth weeks,and the difference was very significant (P<0.01);Compared with PD group,in PD+Ex group,Glu concentration of the extracellular of striatal neurons was significantly decreased at third and fifth weeks,and the difference was very significant (P<0.05,P<0.01);Compared with the PD+Ex group,in PD+Ex+ APICA group,Glu concentration of the extracellular of striatal neurons was significantly increased at third and fifth weeks,and the difference was very significant (P<0.05, P<0.01). RT-PCR test results indicated that,the expression level of striatal mGluR3 mRNA of PD group decreased compared with the control group,and the difference was significant (P<0.01);Compared with the PD group,in the PD+Ex group,the expression level of striatal mGluR3 mRNA increased,a the difference was very significant (P<0.01);6-OHDA damage and exercise intervention had no effect on the expression of striatum mGluR2 mRNA,and the difference was was not significant (P>0.05). Western blotting results indicated that,the expression level of striatum mGluR2/3 protein of PD group was decreased compared with the control group,and the difference was vey significant (P<0.01),compared with the PD group,in PD+Ex group,the expression level of striatum mGluR2/3 protein was increased,and the difference significant (P<0.05) . The correlation between the extracellular Glu concentration of the striatum neurons and the total moving distance in PD rats showed that,at third weeks,the extracellular Glu concentration of striatal neurons was negatively correlated with the total movement distance (r=-0.82,P<0.05),at fifth weeks,the extracellular Glu concentration of striatal neurons was negatively correlated with the total movement distance (r=-0.91,P<0.01). Conclusions The expression level of mGluR2/3 decreased in rats with PD model with increased Gu concentration. The decrease of Gulu concentration and the increase of expression level of mGluR2/3 in the striatum striatum of PD model rats could be induced by the training intervention of running platform, which promoted the improvement of motor dysfunction in PD model rats.&nbsp

    Fractalkine is expressed in the human ovary and increases progesterone biosynthesis in human luteinised granulosa cells

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    Background: Recent evidence from rodent ovaries has demonstrated expression of fractalkine and the existence of fractalkine receptor, and showed that there is a significant increase in steroidogenesis in response to fractalkine, yet the role of fractalkine and CX3CR1 in the human ovary is still unknown. This study aimed to determine the expression levels of fractalkine and CX3CR1 in the human ovary and to investigate their roles in sexual hormone biosynthesis by human luteinising granulosa cells. This is the first detailed report of fractalkine and CX3CR1 expression and function in the human ovary. Methods: Fractalkine and CX3CR1 expression levels were measured by immunohistochemistry using ovarian tissue from pathological specimens from five individuals. Granulosa cells were obtained from patients during IVF treatment. They were cultured and treated with increasing doses of hCG with or without fractalkine. Media were collected to detect estradiol and progesterone by chemiluminescence. StAR, 3 beta HSD and CYP11A expression were determined in granulosa cells treated with or without fractalkine by real-time RT-PCR. Results: Fractalkine and CX3CR1 were expressed in the human ovary and in luteinising granulosa cells. However, fractalkine expression was stronger in luteinising granulosa cells. Treatment with fractalkine augmented hCG stimulation of progesterone production in a dose-dependent manner with concomitant increases in transcript levels for key steroidogenic enzymes (StAR, 3-beta HSD and CYP11A) but had no effect on estradiol biosynthesis(P < 0.05). Conclusions: Fractalkine and CX3CR1 were found to express in human ovary and luteinising granulosa cells. Fractalkine can increase the biosynthesis of progesterone in a dose-dependent manner by enhancing transcript levels of key steroidogenic enzymes.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000292939500001&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Endocrinology & MetabolismReproductive BiologySCI(E)PubMed2ARTICLE95

    The relationship between marital adjustment and personality characteristics, medical coping style of infertile patients

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    目的  探讨不孕不育患者婚姻调适状况与人格特征和医学应对方式的关系,为临床开展心理健康干预提供依据。方法  选取2012年8月—2015年1月某三级甲等医院生殖医学中心治疗的156例已婚不孕不育症患者。采用艾森克人格问卷表(EPQ)、Locke-Wollance婚姻调适测定量表和医学应对问卷(MCMQ),对患者进行调查,分别测评患者婚姻调适状况、人格特征和医学应对方式及其相关性。结果  患者婚姻调适状况与EPQ的P、N及MCMQ屈服呈显著负相关,与EPQ 的E和MCMQ面对则呈显著正相关;EPQ的P、N与MCMQ面对呈负相关,与MCMQ的屈服呈正相关;EPQ的E则与MCMQ面对呈显著正相关。EPQ的P、E、N和MCMQ面对、屈服在婚姻调适状况高中低分组中的比较,差异均有统计学意义(均P<0.01)。多元逐步回归分析:面对、回避,屈服及精神质(P)等4个因素共解释了不孕不育症患者婚姻调适总变异的26.4%。结论  人格特征、医学应对方式是影响不孕不育症患者婚姻调适的重要因素。Objective: To explore the relationship between marital adjustment and personality characteristics and coping styles of patients with infertility, and to provide evidence for clinical intervention. Methods: A total of 156 patients with infertility were selected from August 2012 to January 2015 in a grade a hospital of reproductive medicine center. This research is a cross - sectional survey. The Eysenck Personality Questionnaire (EPQ), Locke-Wollance marital adjustment test scale and Medical Coping Questionnaire (MCMQ), were investigated, respectively, to evaluate the patient status, marital adjustment and personality characteristics and coping style and their relationship. Results: Patients marital adjustment status and EPQ P, N and MCMQ yield was significantly negative correlated, and EPQ E and MCMQ was significantly positively related; EPQ P, N and MCMQ showed a negative correlation, and MCMQ yield positively correlated; EPQ E, and MCMQ face was significantly positively related, EPQ P, E, N and MCMQ, yield in the marital adjustment the conditions of grouping, the differences were statistically significant (all P < 0.01). Multiple stepwise regression analysis: 4 factors, such as confrontation, avoidance, yield and psychoticism (P), were used to explain the total variation of the adjustment of marriage in infertile patients (26.4%). Conclusion: Personality characteristics, medical coping styles are the important factors influencing the marital adjustment for infertility patients

    Invasive Fresh Water Snail, China

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    Modeling Multi-wavelength Pulse Profiles of Millisecond Pulsar PSR B1821-24

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    PSR B1821-24 is a solitary millisecond pulsar (MSP) which radiates multi-wavelength pulsed photons. It has complex radio, X-ray and γ\gamma-ray pulse profiles with distinct peak phase-separations that challenge the traditional caustic emission models. Using the single-pole annular gap model with suitable magnetic inclination angle (α=40\alpha=40^\circ) and viewing angle (ζ=75\zeta=75^\circ), we managed to reproduce its pulse profiles of three wavebands. It is found that the middle radio peak is originated from the core gap region at high altitudes, and the other two radio peaks are originated from the annular gap region at relatively low altitudes. Two peaks of both X-ray and γ\gamma-ray wavebands are fundamentally originated from annular gap region, while the γ\gamma-ray emission generated from the core gap region contributes somewhat to the first γ\gamma-ray peak. Precisely reproducing the multi-wavelength pulse profiles of PSR B1821-24 enables us to understand emission regions of distinct wavebands and justify pulsar emission models.Comment: Accepted for publication in Ap
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