Novel Route for Preparation of 7‐Methyl‐camptothecin and Its Possible Mechanism

A novel route for preparation of 7‐methyl‐camptothecin is described. Its possible mechanism is discussed.     

火焰原子吸收分光光度法测定维血康颗粒中总铁

建立火焰原子吸收分光光度法测定维血康颗粒中总铁的含量,火焰类型选择空气–乙炔,测定波长为248.3 nm,测定时间为4.0 s,燃气流量为0.9 L/min,以氘灯作为背景校正。铁的质量浓度在2.4~28.8μg/mL范围内与吸光度呈良好的线性,线性相关系数r~2=0.999 8。6次测定结果的相对标准偏差小于1.0%,样品加样回收率为93.89%,方法检出限为0.011 3μg/mL。该方法具有准确度高,稳定性、重复性好等优点,可用于维血康颗粒中总铁含量的测定。     

N-heterocyclic carbene-mediated formal [3+3] annulation of isatin-derived α, β-unsaturated acids: Access to functionalized 3,4′-spirooxindole δ-lactones

An in situ activation of isatin-derived α,β-unsaturated acids 2 for the generation of isatin-derived α,β-unsaturated acyl azoliums II was described. The acyl azoliums II were successfully applied to undergo a formal [3 + 3] annulation with 1,3-dicarbonyl compounds to access functionalized 3,4′-spirooxindole δ-lactones 4. A scale-up synthesis and an enantioselective variant of this protocol were also investigated. The stable and easily prepared acids 2 may be further utilized as promising versatile electrophilic 1,3-synthons for divergent synthesis of spirooxindoles.     

线型光束可燃气体探测器的校准

介绍线型光束可燃气体探测器的的校准方法。对线型光束可燃气体探测器的示值误差、报警功能、响应时间、光强衰减性能和抗日光干扰性能等主要计量特性及技术指标进行校准,给出了各主要计量特性的校准条件、试验设备和具体校准方法。对两台线型光束可燃气体探测器进行了校准,其示值误差用相对误差表示分别为–5%和4%,用引用误差表示分别为–4%FS和3%FS。经验证,上述结果均未超出设定指标,响应时间等其它主要计量特性也符合方法要求。该方法校准后的计量特性及技术指标较为合理,校准方法切实可行,可以用于线型光束可燃气体探测器的校准。     

Spin frustration-related behavior of mixed spin diamond chain

The magnetization of mixed spin-1/2, 1 Ising diamond chain with antiferromagnetic spin exchange interaction has been investigated by using the Monte Carlo simulation. Magnetization behaviors with different antiferromagnetic interactions are simulated under magnetic field at low temperature. The behaviors are studied in two different cases. In one case the absolute value of the interaction between two spin-1/2 atoms is the largest and in the other case it is not the largest. Multiple plateaus of magnetization M, such as plateaus at M=±1, M=0 and M=±0.566 are obtained. The plateaus at M=±0.566 correspond to two metastable states. The M=0 plateau may disappear at some specific values of spin exchange interactions. The spin configurations were checked when the plateaus appear. The dimmer and trimmer states are found.     

Inhibiting effect of carbonate on the photoinduced flatband potential shifts during water photooxidation at TiO2/solution interface

Journal of Solid State Electrochemistry - The TiO2/solution interfacial junction is of scientific and practical importance in the field of photoelectrochemical water splitting. Illumination of this...