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.     

Angular-Multiplexing Optical Multiple-Image Encryption Based on Digital Holography and Random Amplitude Mask

We propose an improved optical image encryption scheme. By illuminating original images positioned in the input plane of the 4-f correlator and introducing reference waves with different incident angles in the output plane, we accomplish multiple-image encryption. To enhance the feasibility of the system and decrease the coding compliance for random phase mask, we apply the random amplitude masks and some digital manipulations in the encryption and decryption procedure. We also analyze the encryption and decryption quality of the method proposed together with the influence of different random number generators. Numerical simulation has proved the validity of the architecture suggested.     

Pollution characteristics and risk assessment of uranium and heavy metals of agricultural soil around the uranium tailing reservoir in Southern China

For the first time the pollution of the paddy soil within 2 km around the uranium tailing reservoir was investigated. The concentrations of U, Cd, Cr, Pb, Cu, Zn, Hg and As were determined by ICP-MS. The study showed that there was severe pollution in the first area (within 0–1 km of the tailing reservoir), which was caused by Cd, As, U and Hg. The pollution level of the second area (within 1–2 km) was relatively low. Hg and As were the main pollutants. In the first area, the contamination degree and risk of elements were positively correlated with the distance from the tailing reservoir. The second area was less polluted and influenced by mining and human activities because of mountain barriers.     

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。     

Chemoselective hydrogenation of α,β-unsaturated aldehydes with modified Pd/C catalyst

Selective hydrogenation of α, β-unsaturated aldehydes with modified Pd/C catalyst was developed.The reduction of C=O bond could be efficiently inhibited by the addition of carbonates,and high selectivity to the corresponding saturated aldehydes was achieved under mild conditions.This protocol provides an alternative for efficient preparation of saturated aldehydes.