三元乙丙橡胶的13C-NMR定量分析

用13C核磁共振波谱法对三元乙丙橡胶进行了研究，通过图谱中各个峰的积分值，并用特定的计算公式测定了三元乙丙橡胶中乙烯及第三单体乙叉降冰片烯的含量，为红外光谱批量的定量分析建立了基准化的标定。     

NMR and structural investigations of a nonplanar iron corrolate: modified patterns of spin delocalization and coupling in a slightly saddled chloroiron(III) corrolate radical

An undecasubstituted chloroiron corrolate, octamethyltriphenylcorrolatoiron chloride, (OMTPCorr)FeCl, has been synthesized and studied by X-ray crystallography and (1)H and (13)C NMR spectroscopy. It is found that, although the structure is slightly saddled, the average methyl out-of-plane distance is only 0.63 Angstroms, while it is much greater for the dodecasubstituted porphyrinate analogue (OMTPP)FeCl (1.19 Angstroms) (Cheng, R.-J.; Chen, P.-Y.; Gau, P.-R.; Chen, C.-C.; Peng, S.-M. J. Am. Chem. Soc. 1997, 119, 2563-2569). In addition, the distance of iron from the mean plane of the four macrocycle nitrogens is also smaller for (OMTPCorr)FeCl (0.387 Angstroms) than for (OMTPP)FeCl (0.46 Angstroms). The (1)H and (13)C NMR spectra of (OMTPCorr)FeCl, as well as the chloroiron complexes of triphenylcorrolate, (TPCorr)FeCl; 7,13-dimethyl-2,3,8,12,17,18-hexaethylcorrolate, (DMHECorr)FeCl; 7,8,12,13-tetramethyl-2,3,17,18-tetraethylcorrolate, (TMTECorr)FeCl; and the phenyliron complex of 7,13-dimethyl-2,3,8,12,17,18-hexaethylcorrolate, (DMHECorr)FePh, have been assigned, and the spin densities at the carbons that are part of the aromatic ring of the corrole macrocycle have been divided into the part due to spin delocalization by corrole --> Fe pi donation and the part due to the unpaired electron present on the corrole ring. It is found that although the spin density at the beta-pyrrole positions is fairly similar to that of (TPCorr)FeCl, the meso-phenyl-carbon shift differences delta(m) - delta(p) are opposite in sign of those of (TPCorr)FeCl. This finding suggests that the radical electron is ferromagnetically coupled to the unpaired electrons on iron, rather than antiferromagnetically coupled, as in all of the other chloroiron corrolates. The solution magnetic moment was measured for (OMTPCorr)FeCl and found to be mu(eff) = 4.7 +/- 0.5 micro(B), consistent with S = 2 and ferromagnetic coupling. From this study, two conclusions may be reached about iron corrolates: (1) the spin states of chloroiron corrolates are extremely sensitive to the out-of-plane distance of iron, and (2) pyrrole-H or -C shifts are not useful in delineating the spin state and electron configuration of (anion)iron corrolates.     

基于周期极化KTiOPO4晶体的高亮度纠缠源研制

量子纠缠是量子信息领域的核心资源,目前利用β型硼酸钡(BBO)晶体参量下转换制备的纠缠光子对的亮度较低,它直接制约了量子通信的最远距离,已无法满足星地实用化量子通信的发展需求.利用周期极化KTiOPO4晶体,采用准相位匹配技术设计产生了一种后选择的纠缠源,测得的符合计数达到了16×103s-1 mW-1,极化对比度达到27∶1,在亮度上比基于BBO的量子纠缠光源提高了一个数量级以上.这一高亮度的纠缠源可以广泛应用于量子密钥分发、量子隐形传态以及量子计算等新兴量子信息领域,为实现全球化量子通信提供了有力的保障.     

声发射特性与材料断裂韧性相关性研究

以高强度铝合金的断裂过程为研究对象，利用先进的声发射试验系统，考察了拉伸试样和带有预制疲劳裂纹的DCB试样在断裂时的声发射事件特性，揭示了材料断裂韧性和声发射特性 间的关系.试验结果表明，材料稳态裂纹扩展起始于K_1C并发射出许多幅值超过 阈值35 dB的信号，材料裂纹失稳扩展时爆发出强烈的声发射信号，材料断裂的累积声发射能与宏 观断裂能呈线性关系. 关键词： 声发射 断裂韧性 铝合金     

Effect of moisture content on conveying characteristics of pulverized coal for pressurized entrained flow gasification

During the pneumatic conveying, pulverized coal with different moisture contents may develop substantial difference in flow characteristics, whose cause is not fully understood. This study focused on influence of moisture content on conveying characteristics in an experimental test facility with the conveying pressure up to 4 MPa. The experiments included soft coal and lignite with similar density and particle size. With the increase in moisture content, the mass flow rate decreased for lignite (3.24% < M < 8.18%) but increased at first and then decreased for soft coal (0.4% < M < 6.18%) at same operating parameters. The flowability of soft coal was worse than that of lignite at similar operating parameters and external moisture content. The extremal conveying moisture contents of two coal types were obtained. The particle charge and surface moisture content were investigated to indicate influence mechanism of moisture content on mass flow rate in pneumatic conveying at high pressure. Pressure drop of soft coal was greater than that of lignite for same test section. The conveying phase diagram of dense-phase pulverized coal at high pressure was obtained and the pressure drops through different test sections were compared and analyzed. The bend loss factor rose with the increase in moisture content and was independent of conveying velocity and solid-gas ratio in dense-phase pneumatic conveying at high pressure.     

An effective sequence characterized amplified region‐PCR method derived from restriction site‐amplified polymorphism for the identification of female Schistosoma japonicum of zoonotic significance

In the present study, restriction site‐amplified polymorphism (RSAP) markers were used to examine the genetic variability of Schistosoma japonicum isolates from different endemic provinces in mainland China. Of the 45 pairs of primers screened, 10 RSAP markers showed a clear banding pattern with good resolution; however, only six exhibited a polymorphism among different isolates. Among six RSAP markers, one pair of primers (R8+R10) was able to differentiate male and female parasites, and amplified one constant specific band for female S. japonicum isolates. The specific band was recovered, re‐amplified and sequenced, and a sequence of 162 bp was obtained. Based on this sequence, a pair of specific primers was designed and used to develop sequence characterized amplified region (SCAR)‐PCR assay for identification and differentiation of female S. japonicum isolates. The SCAR‐PCR assay allowed the specific identification of female S. japonicum, with no amplicons being amplified from male S. japonicum, Fasciola hepatica, Clonorchis sinensis, S. mansoni (male and female parasite). DNA sequencing confirmed the identity of the amplified products. The minimum amount of DNA detectable using SCAR‐PCR assay was 0.3 ng for female S. japonicum. The SCAR‐PCR was able to differentiate effectively the male and female S. japonicum worms collected from 12 geographical origins in eight endemic provinces, the gender of which was known based on the morphological and biological features. These results showed that SCAR‐PCR provides an effective tool for the sex differentiation studies of S. japonicum, identification of female S. japonicum, diagnosis and epidemiological survey of S. japonicum infections in animals and human.     

Switching in Metal–Organic Frameworks

In recent years, metal–organic frameworks (MOFs) have become an area of intense research interest because of their adjustable pores and nearly limitless structural diversity deriving from the design of different organic linkers and metal structural building units (SBUs). Among the recent great challenges for scientists include switchable MOFs and their corresponding applications. Switchable MOFs are a type of smart material that undergo distinct, reversible, chemical changes in their structure upon exposure to external stimuli, yielding interesting technological applicability. Although the process of switching shares similarities with flexibility, very limited studies have been devoted specifically to switching, while a fairly large amount of research and a number of Reviews have covered flexibility in MOFs. This Review focuses on the properties and general design of switchable MOFs. The switching activity has been delineated based on the cause of the switching: light, spin crossover (SCO), redox, temperature, and wettability.     

Steep pulsed electric fields modulate cell apoptosis through the change of intracellular calcium concentration

A steep electric pulsed field with low intensity (150–250 V/cm) and relative long time (10 min) was applied to adherent liver cancer cell line SMMC-7721 and the liver cell line HL-7702. Results showed that the electric field with intensity of 200 and 250 V/cm could trigger cell apoptosis, whereas the SMMC-7721 cell was more sensitive to the electric stimulation than the HL-7702 cell. Laser Scanning Confocal Microscope (LSCM) was used to measuring the real-time change of cytosolic free Ca²⁺ concentration. When cells were exposed electric pulses with 100 V/cm intensity for 10 min, there was no significant change of intracellular calcium concentration. With the intensity increased to 200 and 250 V/cm, intracellular calcium concentration decreased significantly. Results demonstrated the relationship between the apoptosis and change of intracellular calcium concentration. And the steep electric pulsed field can be used to the cancer therapy.     

Experimental and FEM study of windshield subjected to high speed bird impact

Both experimental and finite element model (FEM) results are presented for the dynamic strength behavior of windshield subjected to bird impact. The experimental data taken from a series of high speed photographs are compared with the numerical results predicted by using FEM in which the windshield was modeled entirely with solid elements and the bird body was approximately simulated by an elastic-plastic material with failure element behavior. Effective plastic strain and element pressure were adopted as the failure criteria and once the pressure or the effective plastic strain of an element reached the critical value, the element would lose the tensile resistance capability completely. The deflection and stress distribution in the windshield were obtained. It is shown that the result from the finite element analysis agrees with those from the full-scale bird impact test. The project supported by the National Natural Science Foundation of China (10272011)