加替沙星纯度标准物质研制

研制加替沙星纯度标准物质。采用质量平衡法和氢谱定量核磁法对加替沙星纯度标准物质候选物进行纯度定值,采用卡尔费休法和热重分析法准确测量了影响主成分纯度的水分含量,并考察了水分含量的稳定性。开展了加替沙星纯度定值、均匀性检验、稳定性考察以及不确定度评估。结果表明,加替沙星纯度标准物质的纯度值为93.1%,扩展不确定度为0.6%(k=2),水分含量为6.6%,特性量值均匀性良好,6个月稳定性可靠,被认定为国家二级标准物质,编号为GBW(E) 100476。研制的加替沙星纯度标准物质填补了国内空白,同时也为吸湿性较强的药物纯度标准物质研制过程中水分测定提供了参考与借鉴。     

Single‐Atom Cr−N4 Sites Designed for Durable Oxygen Reduction Catalysis in Acid Media

Single‐atom catalysts (SACs) are attracting widespread interest for the catalytic oxygen reduction reaction (ORR), with Fe?N_x SACs exhibiting the most promising activity. However, Fe‐based catalysts suffer serious stability issues as a result of oxidative corrosion through the Fenton reaction. Herein, using a metal‐organic framework as an anchoring matrix, we for the first time obtained pyrolyzed Cr/N/C SACs for the ORR, where the atomically dispersed Cr is confirmed to have a Cr?N₄ coordination structure. The Cr/N/C catalyst exhibits excellent ORR activity with an optimal half‐wave potential of 0.773 V versus RHE. More excitingly, the Fenton reaction is substantially reduced and, thus, the final catalysts show superb stability. The innovative and robust active site for the ORR opens a new possibility to circumvent the stability issue of the non‐noble metal ORR catalysts.     

Preparation and mesomorphic properties of 1-methyl-1H-benzimidazole-based compounds

A series of 1-methyl-1H-benzimidazole-based compounds, 2-(4?-alkoxy-1,1?-biphenyl-4-yl)-1-methyl- 1H-1,3-benzimidazole derivatives (nPPMx-M) with terminal hydrogen, methyl and nitro moieties (coded as nPPMH-M, nPPMM-M and nPPMN-M, respectively), were prepared and their structures were characterised. The compounds display enantiotropic smectic mesophases for hydrogen and methyl terminated compounds (nPPMH-M and nPPMM-M), and enantiotropic nematic mesophases for nitro terminated compounds (nPPMN-M) with short alkoxy chain below than 10 carbon atoms, where the mesophase ranges are 24–72°C and 74–104°C on heating and cooling processes for nPPMH-M, 90–119°C and 110–135°C for nPPMM-M, and 102–129°C and 113–207°C for nPPMN-M, respectively. It is noted that the compounds nPPMx-M exhibit much lower melting points and much wider mesophase range both in heating and cooling than non-1-methyl substituted analogs, which are ascribed to the disruption of hydrogen bonding among the molecules caused by methyl substitution at 1-position of benzimidazole. Meanwhile, among the compounds nPPMx-M, much wider mesophase ranges are obtained for nPPMM-M and nPPMN-M, indicating a much high mesophase stability for the compounds bearing terminal moiety (CH₃ and NO₂).     

Relations between cubic equation,stress tensor decomposition,and von Mises yield criterion

Inspired by Cardano's method for solving cubic scalar equations, the additive decomposition of spherical/deviatoric tensor (DSDT) is revisited from a new viewpoint. This decomposition simplifies the cubic tensor equation, decouples the spherical/deviatoric strain energy density, and lays the foundation for the von Mises yield criterion. Besides, it is verified that under the precondition of energy decoupling and the simplest form, the DSDT is the only possible form of the additive decomposition with physical meanings.     

非连续变形分析方法的改进及应用1）

首先,采用位移收敛判据对非连续变形的岩石断裂分析进行改进并程序实现. 其次,将非连续变形分析方法和裂隙网络渗流模型结合起来,建立了渗流应力耦合分析模型,研究了裂隙岩体变形对渗流的影响以及渗流与应力耦合作用下裂隙岩体的变形破坏特征. 研究发现,主干裂隙控制着渗流场分布,考虑耦合作用时的水头值比不考虑耦合作用时大,说明考虑耦合后坡体更容易变形失稳. 改进前后裂纹扩展形态基本不变,表明程序计算的收敛判据是有效的.     

A 12-bit current steering DAC with 2-dimensional gradient-error tolerant switching scheme

A 12-bit intrinsic accuracy digital-to-analog converter integrated into standard digital 0.18μm CMOS technology is proposed.It is based on a current steering segmented 6+6 architecture and requires no calibration.By dividing one most significant bit unary source into 16 elements located in 16 separated regions of the array,the linear gradient errors and quadratic errors can be averaged and eliminated effectively.A novel static performance testing method is proposed.The measured differential nonlinearity ...     

基于共耦合谐振单元结构的高温超导五工器

文章采用共耦合谐振单元结构设计制作了一款高温超导五工器,五工器五个信道的工作频率分别为807.5 MHz、810.5 MHz、813.5 MHz、816.5 MHz、819.5 MHz,每信道通带宽度均为1 MHz.滤波器电路用镝钡铜氧(DyBCO)双面超导薄膜制作,衬底为3英寸0.5 mm厚度的氧化镁(MgO)基片.文章给出了高温超导五工器的等效电路、理论曲线、耦合参数、Sonnet软件全波电磁场模拟仿真和实际测试曲线,取得较为理想的结果.     

Investigation of β-Ga2O3 thick films grown on c-plane sapphire via carbothermal reduction

We investigated the influence of the growth temperature, O₂ flow, molar ratio between Ga₂O₃ powder and graphite powder on the structure and morphology of the films grown on the c-plane sapphire (0001) substrates by a carbothermal reduction method. Experimental results for the heteroepitaxial growth of β-Ga₂O₃ illustrate that β-Ga₂O₃ growth by the carbothermal reduction method can be controlled. The optimal result was obtained at a growth temperature of 1050 °C. The fastest growth rate of β-Ga₂O₃ films was produced when the O₂ flow was 20 sccm. To guarantee that β-Ga₂O₃ films with both high-quality crystal and morphology properties, the ideal molar ratio between graphite powder and Ga₂O₃ powder should be set at 10 : 1.     

Efficient and stable tin-based perovskite solar cells by introducing π-conjugated Lewis base

Science China Chemistry - Tin-based perovskite solar cells (TPSCs) as the most promising candidate for lead-free PSCs have incurred extensive researches all over the world. However, the...