Novel organotin‐containing shell‐cross‐linked knedel and core‐cross‐linked knedel: Synthesis and application in catalysis

A series of novel organotin‐containing core‐cross‐linked knedels and shell‐cross‐linked knedels were first synthesized facilely from poly(styrene)‐b‐poly(acrylate acid) nanoparticles in different selective solvents [Tetrahydrofuran (THF)/H₂O or THF/n‐octane] by using organotin compound 1,3‐dichloro‐tetra‐n‐butyl‐distannoxane as a new cross‐linker. The formation of the 1‐chloro‐3‐carboxylato‐tetra‐n‐butyl‐distannoxane layer in our cross‐linking reaction was supported by Fourier transform infrared (FT‐IR) and inductive coupled plasma emission spectrometer (ICP) analysis of the resulting shell‐cross‐linked knedels and core‐cross‐linked knedels. Transmission electron microscopy (TEM) study showed the spherical morphology and the size of the core‐cross‐linked knedels and shell‐cross‐linked knedel. Especially, the layer structure of the core‐cross‐linked knedels was clearly displayed in TEM image. The increase of extent of cross‐linking lead to the increasing of diameter for the shell‐cross‐linked knedels, whereas there was no significant effect on the core‐cross‐linked knedels. Dynamic light scattering (DLS) measurements gave hydrodynamic diameters of the core‐cross‐linked knedels that were in agreement with the TEM diameters. Moreover, the wall thickness of the shell layer of the core‐cross‐linked knedels could be easily modified by varying the block copolymer composition. Notably, the organotin‐containing core‐cross‐linked knedel exhibited highly efficient catalytic activity for the aqueous esterification reaction under nearly neutral conditions. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Recent advances in strontium tungstate scheelite material

Strontium tungstate is a well-known stimulated Raman scattering laser material. The unique structure of this crystal allows the usage of these crystals as matrices for laser active elements with nonlinear self-conversion of radiation to a new spectral range. The recent advances in crystal growth, particle and thin film fabrication, spectroscopy, and laser properties were reviewed. The demonstration of laser output of neat and Nd³⁺-doped SrWO₄ crystal shows that it is an efficient self-stimulated Raman scattering laser.     

Catalytic pyrolysis of Pubescens to phenols over Ni/C catalyst

The pyrolysis of Pubescens over Ni/C catalyst was studied at 350 °C in H₂ flow. The presence of Ni/C catalyst efficiently improved the degradation of raw materials, and produced bio-oil with high content of phenols but low contents of acetic acid, furfural and water. In the reaction, Ni/C catalyst plays the role of catalytic decomposition and catalytic hydrogenation. The existence of the carbon carrier favors the formation of active Ni in small sizes with more defects, which results in high catalytic activity of Ni in biomass decomposition and selective production of phenols.     

Photoresponsive nanocarriers based on PAMAM dendrimers with a o‐nitrobenzyl shell

Gn (n = 3, 4, and 5) poly(amidoamine) (PAMAM) dendrimers were synthesized and peripherally modified with photocleavable o‐nitrobenzyl (NB) groups by reacting o‐nitrobenzaldehyde with the terminal amine groups of PAMAM dendrimers, followed by reducing the imine to amine groups with NaBH₄. The NB‐modified dendrimers, Gn‐NB (n = 3, 4, and 5), were characterized by nuclear magnetic resonance and fourier transform infrared spectroscopy. The results showed that the NB groups were successfully attached on the periphery of the dendrimers with near 100% grafting efficiency. Such a photosensitive NB shell could be cut off on irradiation with 365 nm ultraviolet (UV) light. The encapsulation and release of guest molecules, that is, salicylic acid (SA) and adriamycin (ADR), by Gn‐NB were explored. The encapsulation capability of these dendrimers was found to increase as the guest molecular size was decreased and have dependence on the generation of dendrimers as well. For both of SA and ADR, the average encapsulation numbers per dendrimer decreased in the order of G4‐NB > G5‐NB > G3‐NB, indicating that the fourth generation dendrimer was a better container for the guest molecules. The rate of SA release was found to be greater with UV irradiation than that without, suggesting that the NB‐shelled PAMMAM dendrimers could function as a molecular container/box with photoresponsive characteristics. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 551–557, 2010     

HnRNP K and PDI marked response to chemotherapy to human colorectal cancer cells

5‐Fluorouracil has been the chemotherapy agent of first‐choice for colorectal cancer for many years, but since there are no proven predictors of a patient's response to therapy, all patients receive similar treatment. Consequently, identification of biomarkers for therapeutic effect is crucial for the development of novel therapeutic strategies. Two human colorectal cancer cell lines of different metastatic potential (LoVo and SW480) were studied. IC50 of 5‐FU for both cell lines were measured by 3‐(4,5‐dimethy‐lthiazol‐2‐yl)‐2,5‐diphenyltetrazolium assay and validated by cell cycle analysis. Then the cell lines were treated with 5‐FU at IC50 concentration and protein was extracted for 2‐DE. Differential protein spots were examined by MALDI‐TOF/TOF MS. The expression levels of the different proteins were further confirmed by Western blot and immunofluorescence analyses. Eleven proteins were identified. Expression of heterogeneous nuclear ribonucleoprotein K (hnRNP K) in LoVo cells was higher than in SW480 cells, while protein disulfide isomerase (PDI) displayed the opposite trend. After treatment with 5‐FU, the expression of hnRNP K in LoVo decreased more significantly than in SW480, while PDI in SW480 increased more significantly than in LoVo cells. Conclusion: hnRNP K and PDI in the two cell lines have different expression characteristics. The sensitivity to 5‐FU is not consistent in tumor progression. It may assist in development of novel treatment strategies for colorectal cancer metastasis.     

Uniform attractor for nonautonomous incompressible non-Newtonian fluid with a new class of external forces

This paper is joint with [27]. The authors prove in this article the existence and reveal its structure of uniform attractor for a two-dimensional nonautonomous incompressible non-Newtonian fluid with a new class of external forces.     

5-(5-氯-2-吡啶偶氮)-2,4-二氨基甲苯分光光度法测定微量钌(Ⅲ)

研究了 5- ( 5-氯 - 2 -吡啶偶氮 ) - 2 .4-二氨基甲苯 ( 5- Cl- PADAT)与钌 ( )的显色反应。在 p H4.0～ 6.5HAc- Na Ac缓冲溶液中 ,在加热的条件下 ,5- Cl-PADAT与 Ru( )形成稳定的配合物 ,加入无机酸 ( HCl,HCl O4 ,H2 SO4 ,H3 PO4 )酸化后 ,其最大吸收波长位于 50 5nm处 ,表观摩尔吸光系数为 8.5×1 0 4 L· mol-1· cm-1,钌浓度在 0～ 6μg/ 1 0 m L范围内服从比耳定律 ,Ru( )与 5- Cl- PADAT配合物的摩尔比为 1∶ 2。以 EDTA为掩蔽剂 ,方法具有良好的选择性 ,已应用于合成样中钌的测定。     

Highly Efficient Oxidative Bromination of Alkanes with the HBr-H2O2 System in the Presence of Catalyst

Various cycloalkanes and straight‐chain alkanes were efficiently brominated with an aqueous HBr‐H₂O₂ system. This oxidative brominating process was promoted by catalysis and irradiation with light. The cycloalkanes were converted to the corresponding bromo‐cycloalkanes in moderate yields and the straight‐chain alkanes produced dominantly secondary bromides. This simple but effective bromination method of alkanes is characterized by high atom efficiency, inexpensive reagents and the absence of organic waste, which make it a good alternative to the existing method for C? H activation through bromination.