管线钢管局部屈曲应变分析与计算

针对基于应变的管线设计所使用的管线钢管进行变形能力评价,为基于应变设计地区用的钢管产品标准的指标制订提供技术基础。本文以精确建模的数值仿真计算作为钢管全尺寸弯曲变形试验的有效补充,对钢管进行了屈曲变形行为的研究;针对钢管产品试制中不同的材料性能进行了仿真计算,最终提出:两个与钢管临界屈曲应变相关的应力比指标Rt5.0/Rt1.0和Rt2.0/Rt1.0分别为1.04和1.08。该研究结果为基于应变设计地区使用的钢管标准的制订提供了技术支持。     

Hydrazone-based hydrogel hydrolytically degradable in acidic environment

We describe the synthesis of new crosslinker N′-{3-[2-(4-{2-[3-(methacryloylamino)propanoyl]hydrazono}cyclohexyliden)hydrazino]-3-oxopropyl}-2-methylacrylamide, which is stable at physiological pH, but is hydrolytically cleaved in acidic pH. Study of acid hydrolysis showed that the crosslinker is hydrolyzed into two N′-(3-hydrazino-3-oxopropyl)-2-methylacrylamide molecules and one 1,4-cyclohexanedione molecule. Hydrogels based on poly[N-(2-hydroxypropyl)methacrylamide] crosslinked with this crosslinker were prepared and their degradation rate was studied as a function of pH (in the range of pH 1.5-7.4). The hydrogel is cleaved within 8-27 days at pH between 1.5 and 6 and is stable at pH 7.4 making it promising for the construction of oesophageal stents.     

An efficient and convenient method for preparation of disulfides from thiols using air as oxidant catalyzed by Co-Salophen

Disulfides have been synthesized by oxidation of thiols using air as oxidant catalyzed by Co-Salophen with high yields,mild and neutral conditions,and easy procedures of the catalyst.The products were confirmed by ~1H NMR and IR.     

Miscible blends of nitro‐substituted polybenzimidazole and polyetherimide

A novel blend system was prepared by blending organosoluble nitro‐substituted polybenzimidazole (NO₂‐PBI) and polyetherimide (PEI) in a cosolvent at a moderate condition. It was shown that the NO₂‐PBI/PEI blends not only possess tractable processability owing to the enhanced solubility of NO₂‐PBI but also retain the desirable features of unmodified PBI/PEI blends. Apparent miscibility in the blends was observed and attributed to hydrogen‐bonding interactions between N? H groups in NO₂‐PBI and carbonyl groups in PEI. It was revealed that the NO₂‐PBI/PEI blends phase‐separate upon heating above the glass‐transition temperatures. The observed mixing of NO₂‐PBI and PEI in a molecular level, although sustainable only in the glassy region, was shown to lend synergy effects to the physical properties of the blends. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1778–1783, 2001     

Synthesis of New Near-infrared Fluorescent Dyes

Inrecentyears,agrowingnumberofscientistsareIookingforpr0cedurestolabelbiologicallyimp0rtantmolecules(suchasDNA,Proteins,etc.)'-'.Oneefficientwaycurrentlyexploitedistheuseofnear-infraredfluorescentdyesasfluorogeniclabels.AIthoughtherearemanyfluorescentdyescommerciallyavailable,onlyseveralclassesofm0lecuIescanbe0peratedinthefar-visibleornear-infraredregion(6O0-lO00nm)whicharetheareas0flowinterference.Inanattemptt0lookfornewnear-infraredfluorescentmolecules,0urgroupsynthesizedaseriesofbenzo[a…     

Coupling Reaction of 4-Chloro-7-H-Pyrrolo[2,3-d]Pyrimidine with 2,3,5-Tri-O-Acetyl-β-D-Ribofuranosyl Chloride

Tubercidin (4-amino-7--D-riobofuranosyl-7-H-pyrrolo[2,3-d]pyrimidine) 1, an antibio-tic substance produced in the culture broth of Streptomyces tubericidus1, is an adenosine analog in which N-7 is replaced by a carbon atom. It has attracted much attention due to the biological activities for the growth inhibition of certain tumors, and many derivatives of tubercidin have been synthesized2-5.For the synthesis of tubercidin analogs, 4-chloro-7-H-pyrrolo[2,3-d]pyrimidine-2,3,5-tri-O-acetyl--D-r…     

Preparation of planar‐chiral multidonor phosphanylferrocene carboxamides and their application as ligands for palladium‐catalysed asymmetric allylic alkylation

Amide coupling of (S_p)‐2‐(diphenylphosphanyl)ferrocene‐1‐carboxylic acid with appropriate terminal amines mediated by 1‐hydroxybenzotriazole and a carbodiimide affords multi‐donor amides terminally functionalized with planar‐chiral (S_p)‐2‐(diphenylphosphanyl)ferrocen‐1‐yl moieties in good to excellent yields. Palladium catalysts based on these ligands efficiently promote asymmetric allylic alkylation of 1,3‐diphenylallyl acetate with in situ generated dimethyl malonate anion to give the C‐alkylated product with ees up to 93% at room temperature. Copyright © 2010 John Wiley & Sons, Ltd.