部分还原氧化石墨烯的制备、 表征及对人宫颈癌HeLa细胞的体外杀伤作用

以氧化石墨烯(GO)为原料, 利用温和方法制备了3种不同还原程度的部分还原氧化石墨烯pRGO₁, pRGO₂和pRGO₃(pRGO_1—3)； 利用傅里叶变换红外光谱(FTIR)、 拉曼光谱(Raman)、 X 射线光电子能谱(XPS)、 紫外-可见光谱(UV-Vis)、 透射电子显微镜(TEM)和 EDS能谱对其结构和形貌进行了表征. 细胞实验结果表明, 无激光照射下pRGO_1—3本身的细胞毒性较低; 近红外(NIR)激光照射下pRGO_1—3通过光热和光毒性双重作用杀伤肿瘤细胞. 实验结果显示了pRGO 在肿瘤光热疗法和光动力疗法领域的应用潜力.     

Strong Pancake 2e/12c Bond in π-Stacking Phenalenyl Derivatives Avoiding Bond Conversion

The nature of the 2e/12c bond and its conversion to a carbon-carbon single bond in phenalenyl dimers have prompted a great deal of interests recently. In this work, we theoretically investigated a series of π-stacking phenalenyl derivatives with 2e/12c bonding character by density functional theory (DFT) calculations to elucidate origin of this unusual bond conversion. Results show that bond-conversion of the phenalenyl dimer easily occurs at room-temperature both dynamically and thermodynamically. However, bond-conversion of hetero π-stacking adducts, in which the two center carbon atoms were substituted by boron and nitrogen atoms, respectively, is much more difficult, because the 2e/12c bond is stabilized by its charge transfer character. Consequently, the bond-conversion is an endothermic process, albeit with a low conversion barrier. Interestingly, Lewis acid-base interactions would be induced by substitution of the center nitrogen atom to phosphorus atom. The 2e/12c bond is further stabilized by 5.9 kcal mol⁻¹ and its conversion is also thermodynamically unfavorable.     

Modelling heavy-tailedness in count time series

Count data frequently exhibit overdispersion, zero inflation and even heavy-tailedness (the tail probabilities are non-negligible or decrease very slowly) in practical applications. Many models have been proposed for modelling count data with overdispersion and zero inflation, but heavy-tailedness is less considered. The proposed model, a new integer-valued autoregressive process with generalized Poisson-inverse Gaussian innovations, is capable of capturing these features. The generalized Poisson-inverse Gaussian family is very flexible, which includes Poisson distribution, Poisson inverse Gaussian distribution, discrete stable distribution and so on. Stationarity and ergodicity of this model are investigated and the expressions of marginal mean and variance are provided. Conditional maximum likelihood is used for estimating the parameters, and consistency and asymptotic normality for the estimators are presented. Further, we consider the h-step forecast and diagnostics for the proposed model. The proposed model is applied to three real data examples. In the first example, we consider the monthly number of cases of Polio, which validates that the proposed model can take into account count data with excessive zeros. Then, we illustrate the use of the proposed model through an application to the numbers of National Science Foundation fundings. Finally, we apply the proposed model to the numbers of transactions in 5-min intervals for the stock traded at Empire District Electric Company. The second and third examples show that the proposed model has a good performance in modelling heavy-tailed count data.     

Stability analysis of switched fractional-order continuous-time systems

Nonlinear Dynamics - In this paper, a class of switched fractional-order continuous-time systems with order $$0<\alpha <1$$ is investigated. First, an interesting property of...     

正电子冲击下氦电离三重微分截面的理论计算

我们发展了一种正电子碰撞原子电离的畸变波Born近似方法， 在这个方法中，正负电子偶素通道通过一个ab initio的光学势附加到入射粒子和靶的相互作用势上，且通道对电离作用被第一次被考虑在正电子碰撞原子电离的过程中. 应用这个方法计算了在50 eV入射能量范围氦的电离的三重微分截面，计算结果和实验数据很好的符合.     

First principles study on the structural,electronic and phonon properties of monolayer B2Si

Using first principles density functional theory, we predict a monolayer B₂Si structure with space group Pmm2 in the present work. This structure is confirmed to be dynamically stable. Based on the plane wave pseudopotential approach, the charge density, electron localization function, density of states, energy band, phonon property and thermal conductivity of Pmm2-B₂Si are systematically studied. It is interesting that the sp² hybridization and coordination bond of Si are found in Pmm2-B₂Si, which is the most important factor for its structural stability. The density of states and energy band analysis reveals that Pmm2-B₂Si is metallic because of the partial occupied Si 3pz and B 2pz states. Moreover, the acoustic-optical coupling is important for phonon transport in Pmm2-B₂Si, and the contribution of optical modes to the lattice thermal conductivity along the [100] and [010] directions is 13% and 12%, respectively. This study gives a fundamental understanding of the structural, electronic and phonon properties in Pmm2-B₂Si.     

Dialkoxymethano[60]fullerenes as electron acceptors in thin-film organic solar cells

This study presents the synthesis, characterization, and electrochemical properties of four new dialkoxymethanofullerenes, as well as their performance in organic solar cells (OSCs) devices. Dialkoxymethanofullerenes were synthesized in 27%–32% yield by thermolysis of dialkoxyoxadiazolines and reaction with C₆₀ under reflux in toluene. The prepared compounds were then characterized and used for the first time as electron-acceptor materials in thin-film bulk heterojunction OSCs with PBTZT-stat-BDTT-8 as the electron donor material. The devices made with ethoxy-hexyloxymethanofullerene and methoxy-hexyloxymethanofullerene exhibited optimal power conversion efficiencies (PCEs) of 3.79% and 4.65%, with open-circuit voltage of 0.832 and 0.831 V, respectively. In contrast, the devices made with ethoxy-ethoxymethanofullerene and methoxy-ethoxymethanofullerene exhibited very low PCEs of <0.01% for both, indicating a large impact of the substituents on device performance.     

An Optical Sensing Platform for Beta-Glucosidase Activity Using Protein-Inorganic Hybrid Nanoflowers

In this work, a convenient and dual-signal readout optical sensing platform for the sensitively and selectively determination of beta-glucosidase (β-Glu) activity was reported using protein-inorganic hybrid nanoflowers [BSA-Cu₃(PO₄)₂·3H₂O] possessing peroxidase-mimicking activity. The nanoflowers (NFs) were facilely synthesized through a self-assembled synthesis strategy at room temperature. The as-prepared NFs could catalytically convert the colorless and non-fluorescent Amplex Red into colored and highly fluorescent resorufin in the presence of hydrogen peroxide via electron transfer process. β-Glu could hydrolyze cyanogenic glycoside, using amygdalin (Amy) as a model, into cyanide ions (CN^?), which can subsequently efficiently suppress the catalytic activity of NFs, accompanied with the fluorescence decrease and the color fading. The concentration of CN^? was controlled by β-Glu-triggered enzymatic reaction of Amy. Thus, a sensing system was established for fluorescent and visual determination of β-Glu activity. Under the optimum conditions, the present fluorescent and visual bimodal sensing platform exhibited good sensitivity for β-Glu activity assay with a detection limit of 0.33 U·L^?1. The sensing platform was further applied to determinate β-Glu in real samples and satisfactory results were attained. Additionally, the optical sensing system can potentially be a promising candidate for β-Glu inhibitors screening.

     

High-order total variation-based Poissonian image deconvolution with spatially adapted regularization parameter

Images captured by image acquisition systems using photon-counting devices such as astronomical imaging, positron emission tomography and confocal microscopy imaging, are often contaminated by Poisson noise. Total variation (TV) regularization, which is a classic regularization technique in image restoration, is well-known for recovering sharp edges of an image. Since the regularization parameter is important for a good recovery, Chen and Cheng (2012) proposed an effective TV-based Poissonian image deblurring model with a spatially adapted regularization parameter. However, it has drawbacks since the TV regularization produces staircase artifacts. In this paper, in order to remedy the shortcoming of TV of their model, we introduce an extra high-order total variation (HTV) regularization term. Furthermore, to balance the trade-off between edges and the smooth regions in the images, we also incorporate a weighting parameter to discriminate the TV and the HTV penalty. The proposed model is solved by an iterative algorithm under the framework of the well-known alternating direction method of multipliers. Our numerical results demonstrate the effectiveness and efficiency of the proposed method, in terms of signal-to-noise ratio (SNR) and relative error (RelRrr).