First-principles calculations of the stibnite at the level of modified Becke–Johnson exchange potential

The demand for cheaper, nontoxic and earth-abundant materials as absorbing layer for solar cell is immensely needed to replace scarce, toxic and expensive one. In this regard, chalcogenide materials have considerably attracted the attention of a lot of researchers because of showing a great potential for different applications. Stibnite (Sb₂S₃), a chalcogenide binary material is considerably investigated for exploiting its potential for different energy technologies being a less toxic, abundantly available, stable and efficient, which are the fundamentals for sustainability as well as to realize the dream of green energy. In this study, theoretical calculations of the structural, electronic and optical properties of stibnite (Sb₂S₃) crystal structure are presented using the full potential (FP) linearized augmented plane wave (LAPW) framed within density functional theory (DFT). To incorporate the exchange-correlation part in the total energy functional, besides the local density approximation (LDA), Wu-Cohen parameterized generalized gradient approximation (WC-GGA), Perdew–Burke–Ernzerhof parameterized generalized gradient approximation (PBE-GGA), and Perdew–Burke–Ernzerhof generalized gradient approximation for solids and surfaces (PBEsol-GGA) are used for the calculations of the structural parameters, where the Trans-Blaha approach of the modified Becke–Johnson (TB-mBJ) potential is used to get more reliable results for the fundamental band gap energy value. These calculations are performed by involving spin-orbit coupling (SOC) contribution. Additionally, optical properties, such as imaginary and real parts of the dielectric function, optical conductivity, absorption coefficient, refractive index, reflectivity, and electron energy loss function are analyzed. Our first-principles calculations show that Wu-Cohen GGA (WC-GGA) reproduces results for lattice parameters comparable to the experimental measurements. The obtained results of the band gap energy and optical properties with TB-mBJ potential are also closer to the experimental data and, endorse its potentiality for the photovoltaics applications.     

Effect of ZnCl<Subscript>2</Subscript> impregnation concentration on the microstructure and electrical performance of ramie-based activated carbon hollow fiber

Activated carbon hollow fibers (ACHFs) with high surface area were prepared from natural ramie fibers (RFs) by one-step activation under different ZnCl₂ impregnation concentrations. The results showed that the morphology and pore structure development of ACHFs depend greatly on ZnCl₂ concentration because ZnCl₂ not only can swell and dissolve cellulose but also can serve as skeleton of newborn pores. It obtained granular activated carbons (ACs) instead of ACHFs when ZnCl₂ concentration was over a suitable range. As supercapacitor electrode, the ACHFs possessed the maximum capacity of 287 F g^?1 and showed excellent stability with more than 93 % efficiency after 1000 cycles. Besides, ACHFs showed higher electrochemical performance than granular ACs even if their microstructure was similar, indicating the morphology of material is also important to the electrochemical properties. Therefore, supercapacitors using ramie-based ACHFs as electrodes possess high comprehensive properties to serve for the need of backup energy storage and high pulse power applications.     

Discovery of a new biphenyl derivative by epigenetic manipulation of marine-derived fungus Aspergillus versicolor

Cultivation of the marine-derived Aspergillus versicolor MCCC 3A00080 with the addition of a histone deacetylase inhibitor, suberoylanilide hydroxamic acid (SAHA), significantly enhanced the diversity of secondary metabolites. From the culture treated, a new biphenyl derivative, named versiperol A (1), along with two known compounds, 2,4-dimethoxyphenol (2) and diorcinol (3) were isolated. The structures of 1–3 were established based on spectroscopic analysis and comparison with literature data. Among the isolates, versiperol A (1) exhibited modest inhibition of Staphylococcus aureus growth with MIC value of 8 μg/mL.     

混合型随机变量期望的求法及应用

讨论了混合型随机变量的数学期望的一般求法,并给出了其在保险精算中的应用.     

可见-近红外光谱的螺旋藻生长品质指标快速无损检测

为了实现微藻生长过程品质指标的快速无损检测，提出了可见-近红外光谱技术检测不同红蓝光源组合培养条件下螺旋藻中叶绿素a和蛋白质的含量。采集不同含量红光和蓝光组合下螺旋藻在325～1 075 nm波段范围内的光谱信息，其中红光与蓝光的含量组合分别是(100%，0%)，(90%, 10%)，(70%，30%)，(50%, 50%)。同时测量叶绿素a和蛋白质的含量，建立偏最小二乘(PLS)预测模型。分别基于连续投影算法(SPA)选择了用于叶绿素a和蛋白质预测的特征波长，分别得到5个(404，440，518，662和875 nm)和4个(411，531，602和1 047 nm)特征波长。基于特征波长建立了PLS和多元线性回归(MLR)预测模型，SPA-MLR模型中叶绿素a和蛋白质预测集相关系数(correlation coefficient, R_p)分别是0.949和0.974，均方根误差(RMSEP)分别是0.018 8和0.006 74。结果表明：可见-近红外光谱检测螺旋藻藻体中叶绿素a和蛋白质含量是可行的，通过测量螺旋藻的光谱结合化学计量学方法可以实现对螺旋藻生长状况的检测。     

岩体节理刚度系数的现场声波测试

Ｇｏｏｄｍａｎ教授提出的节理单元模型被广泛地应用于岩石力学与工程实践。然而该模型的分析精度却依赖于对节理的法向刚度ｋｎ切向刚度ｋｓ的准确确定。但这项工作在实验室几乎是不可能的。文中提出了一种在现场利用声波测试ｋｎ和ｋｓ的方法，并讨论了影响ｋｎ、ｋｓ测试精度的因素。     

Scaling of the viscoelastic shell properties of phospholipid encapsulated microbubbles with ultrasound frequency

Phospholipid encapsulated microbubbles are widely employed as clinical diagnostic ultrasound contrast agents in the 1–5 MHz range, and are increasingly employed at higher ultrasound transmit frequencies. The stiffness and viscosity of the encapsulating “shells” have been shown to play a central role in determining both the linear and nonlinear response of microbubbles to ultrasound. At lower frequencies, recent studies have suggested that shell properties can be frequency dependent. At present, there is only limited knowledge of how the viscoelastic properties of phospholipid shells scale at higher frequencies. In this study, four batches of in-house phospholipid encapsulated microbubbles were fabricated with decreasing volume-weighted mean diameters of 3.20, 2.07, 1.82 and 1.61 μm. Attenuation experiments were conducted in order to assess the frequency-dependent response of each batch, resulting in resonant peaks in response at 4.2, 8.9, 12.6 and 19.5 MHz, respectively. With knowledge of the size measurements, the attenuation spectra were then fitted with a standard linearized bubble model in order to estimate the microbubble shell stiffness S_p and shell viscosity S_f, resulting in a slight increase in S_p (1.53–1.76 N/m) and a substantial decrease in S_f (0.29 × 10⁻⁶–0.08 × 10⁻⁶ kg/s) with increasing frequency. These results performed on a single phospholipid agent show that frequency dependent shell properties persist at high frequencies (up to 19.5 MHz).