丁基罗丹明B-Bi(Ⅲ)-SCN~--PVA-Tween-80体系荧光熄灭法测定痕量铋

本文研究了在PVA和Tween 80存在下,铋离子与硫氰酸钾和丁基罗丹明B形成缔合型三元配合物,使丁基罗丹明B的荧光熄灭,建立了痕量铋的荧光分析新方法。工作曲线线性范围为0～5.0μg/25mL。方法灵敏度高,ε_(588)为3.5×10~5L·mol~(-1)·cm~(-1),操作简便。用于铸铁中痕量铋的测定,结果满意。     

丙烷在无机膜反应器中的芳构化

研究了在固定床反应器和膜反应器中的丙烷芳构化，考察了ＨＺＳＭ－５担载的Ｇａ和Ｐｔ－Ｇａ催化剂对反应的影响。结果表明，采用无机膜反应器可以提高丙烷芳构化选择性，从而提高芳烃收率达１０％以上。在膜反应器中，低碳烷烃选择性降低，烯烃选择性增强。固定床相比，膜反应器在低温时对芳构化反应的促进作用最为显著，但是随着温度升高，其促进作用减弱。     

Highly Ordered Superlattices from Self-assembly of Fe3O4 Nanocrystals

The nano materials often exhibit very interesting electrical, optical, magnetic, and chemical properties, which can not be achieved by their bulk counterparts. The development of uniform nanometer sized particles has been intensively pursued because of their technological and fundamental scientific importance. It is significant that nanostructured materials can be controllably assembled into the required geometry onto substrates, becoming the basis of the next generation of components and devices. The development of new methods and strategies for organizing the nanoparticle basic building blocks into the desired structures is required. Superlattices made from these building blocks give us the opportunity to study not only the properties of the individual building blocks, but also collective effects. The superparamagnetic iron oxide nanocrystals（NCs） have been used in the fields of bio-medicine, ferrofluids, refrigeration system, catalysis,     

含损伤黏弹性阻尼加筋层合板声功率和指向性变异*

该文旨在研究损伤位置和程度对自由阻尼加筋层合板声辐射功率和指向性的影响。基于Mindlin和Timoshenko梁理论,建立了自由阻尼层合板-梁组合结构有限元模型。数值求解四边简支边界条件自由阻尼加筋层合板振动响应,继而通过Rayleigh积分计算加筋层合板辐射声功率和指向性。将计算得到的前4阶模态固有频率、声辐射功率与指向性与已有文献进行了对比基本一致,验证了数值模型的正确性。最后,详细讨论了损伤位置和程度对自由阻尼加筋层合板固有频率、振型、声辐射功率和指向性的影响,结果表明：随着结构损伤程度的增大,声辐射功率峰值向低频移动,在更多角度上出现明显的指向性;声辐射功率和指向性对损伤位置比损伤程度更加敏感。     

Determination of Allosteric Effects and Interstrand Bidentate Interactions in DNA‐Peptide Molecular Recognition

To study DNA allostery, quantitative DNase I footprinting studies were carried out on a newly designed peptide His‐Hyp‐Lys‐Lys‐(Py)₄‐Lys‐Lys‐NH₂ (HypKK‐10) containing the XHypKK (Hyp = hydroxyproline) and polyamide motifs. The interconnection of DNA footprints of peptides HypKK‐10 and the parent peptide PyPro‐12 supports the proposal that interaction network cooperativity is preferred in DNA‐peptide interactions between multiple recognition sites. A simple method of determining interstrand bidentate interactions between the peptide moieties and DNA bases is introduced. It is envisaged that interstrand bidentate interactions also participate in the relay of conformational changes to recognition sites on the complementary strands. Circular dichroism studies of the titration of peptide HypKK‐10 with an oligonucleotide duplex indicate that this peptide binds in a dimeric fashion to DNA in the minor groove. This work may prompt the design of new DNA binding ligands for the study of DNA‐peptide allosteric interactions and DNA interaction network.     

Molecular dynamics simulations of hexahydro-1,3,5-trinitro-1,3,5-s-triazine (RDX) using a combined Sorescu-Rice-Thompson AMBER force field

We present the results of molecular dynamics simulations of crystalline hexahydro-1,3,5-trinitro-1,3,5-s-triazine (RDX) using the SRT-AMBER force field (P. M. Agrawal et al., J. Phys. Chem. B 2006, 110, 5721), which combines the rigid-molecule force field developed by Sorescu-Rice-Thompson (D. C. Sorescu, B. M. Rice, and D. L. Thompson, J. Phys. Chem. B 1997, 101, 798) with the intramolecular interactions obtained from the Generalized AMBER Force Field (Wang et al., J. Comput. Chem. 2004, 25, 1157). The calculated crystal density at room conditions is about 10% lower than the measured value, while the lattice parameters and thermodynamic melting point are within about 5% at ambient pressure. The chair and inverted chair conformation, bond lengths, and bond angles of the RDX molecule are accurately predicted; however, there are some inaccuracies in the calculated orientations of the NO2 groups. The SRT-AMBER force field predicts overall reasonable results, but modifications, probably in the torsional parameters, are needed for a more accurate force field.     

Molecular dynamics simulations of the melting of 1,3,3-trinitroazetidine

Physical properties of condensed-phase 1,3,3-trinitroazetidine (TNAZ) have been computed with molecular dynamics (MD) and a nonreactive, fully flexible force field formulated by combining the intramolecular interactions obtained from the Generalized AMBER Force Field and the rigid-molecule force field developed by Sorescu-Rice-Thompson [J. Phys. Chem. B 1997, 101, 798] (AMBER-SRT). The results are compared with MD calculations, using the AMBER force field. The predicted densities of crystalline TNAZ from both force fields are about 10% lower than the experimental value. The calculated thermodynamic melting point at 1 atm from the AMBER-SRT force field is 390 K, in good agreement with the measured value of 374 K, while the AMBER force field predicts a thermodynamic melting point of 462 K. The lattice parameters and the molecular and crystal structures calculated with the AMBER-SRT force field are in excellent agreement with experiment. Simulations with the AMBER-SRT force field were also used to generate the isotherm of TNAZ up to 4 GPa and the bulk modulus and its pressure derivative.