锆对低温液相合成甲醇Cu-Cr催化剂性能的影响

Cu-Cr and Cu-Cr-Zr catalysts for the low temperature methanol synthesis slurry phase, with the surface area of 77.9 and 113.2 m2/g respectively, were prepared by the co precipitation approach. The activity and selectivity of these catalysts were evaluated in a stainless steel autoclave at 5.5 MPa and at different temperatures of 383 and 423 K separately. It was found that the activity of Cu-Cr-Zr catalyst was obviously higher than that of Cu-Cr catalyst, whereas the methanol selectivity of Cu-Cr-Zr catalyst was a little lower. The concentration of sodium compounds in the solution after reaction was also measured. The results showed that the concentration of sodium formate after reaction is much lower than that before reaction, which is quite different from the observations from the Cu-Cr catalyst previously. This implies that the conversion of sodium methoxide to sodium formate has been completely suppressed in the presence of zirconia in Cu-Cr-Zr catalyst. This finding is more beneficial to improve the performance of Cu-Cr catalyst and to increase the life of catalyst system as well.     

硅基图案化TiO2表面微结构的制备和表征

结合微接触印刷术和TiO₂沉积成膜技术,在单晶硅表面成功地制备了具有微米级图案结构的TiO₂薄膜,并利用XPS,SEM和AFM对其表面性质和结构进行了表征.该硅基图案化TiO₂微结构在光电转化、微机电和光催化等领域中的应用具有重要意义.     

Pt-CeO2/C催化剂对甲醇氧化的电催化活性

将CeO2溶胶与Pt/C催化剂机械混合制备了Pt-CeO2/C催化剂,研究了酸性条件下Pt-CeO2/C催化剂对甲醇氧化的电催化活性。结果表明,与Pt/C催化剂相比,Pt-CeO2/C催化剂对甲醇展现出更好的催化活性。XRD和TEM测试结果表明,Pt-CeO2/C催化剂中Pt与CeO2的平均粒径均为3~4 nm。对CeO2含量不同的Pt-CeO2/C催化剂在CH3OH-H2SO4中进行循环伏安测试发现,Pt-CeO2/C催化剂对甲醇氧化的电催化活性较高,其中Pt与CeO2质量比为1∶1时,催化剂的催化活性最高,对甲醇氧化的峰电流密度达到0.112 A/cm2。     

Theoretical Study on Effects of Salt and Temperature on Denaturation Transition of Double-stranded DNA

We investigate the statistical mechanics properties of a nonlinear dynamics model of the denaturation of the DNA double-helix and study the effects of salt concentration and temperature on denaturation transition of DNA. The specific heat, entropy, and denaturation temperature of the system versus salt concentration are obtained. These results show that the denaturation of DNA not only depends on the temperature but also is influenced by the salt concentration in the solution of DNA, which are in agreement with experimental measurement.     

端羧基芳脂型超支化聚酯自组装性能的研究

利用聚电解质逐层浸渍 ( layer- by- layer dipping)法制备自组装膜是最近发展起来的进行表面改性的新方法[1～ 3] .一方面 ,从理论上来说 ,只要是带电荷的聚合物都可以利用该技术制备具有优异性能的自组装膜 ;另一方面 ,还可以通过调节溶液的 p H值和离子强度等控制阴阳离子的组装过程 ,从而控制自组装膜的内部结构和表面形态 ,为在纳米级范围内设计和控制聚合物聚集态内部结构提供了可能性 .近年来 ,具有高度支化结构的超支化分子由于具有独特的物理和化学性能而受到了广泛的关注 [4 ,5] ,但以聚电解质逐层浸渍法制备超支化分子自组装膜…     

NaF饮水喂养的小白鼠肝脏线粒体代谢热化学研究

利用 L KB2 2 77生物活性检测系统 ,测定了用含不同浓度 Na F饮水喂养的小白鼠肝脏线粒体代谢热曲线 ,实验表明 ,饮水中 Na F浓度增加 ,最大热功率增大 ,代谢产热增加 ,停滞期和活性维持时间缩短 .热曲线测定完毕后的样品 ATP浓度分析表明 ,随着 Na F浓度增加 ,系统的 ATP浓度降低 .结合透射电镜对肝细胞超微结构研究结果 ,根据化学渗透假说对实验结果进行了比较完满的解释     

Electrospinning of Biomaterials for Vascular Regeneration

Cardiovascular diseases have been the leading cause of morbidity and mortality in the world recently. With the growing aging population accompanied by chronic diseases, such as uremia and diabetes, there is an increasing clinical demand for vascular grafts with proper performance. Although some achievements have been made in the development of tissue-engineered vascular grafts composed of natural and synthetic polymeric materials or decellularized vessels, clinical applications with a diameter of less than 6 mm are still principally derived from autografts, such as autologous saphenous veins. Many challenges remain in anti-thrombosis, rapid endothelialization, modulating the inflammatory response and inhibition of intimal hyperplasia and calcification. In the review, recent progress in the electrospinning of biodegradable polymers for vascular regeneration are summarized, especially from the view of biomechanical factors. Hybrid vascular grafts consisting of natural and synthetic polymers with multicomponent, di-or tri-layers are focused in order to provide novel experiences in biomaterials for applications in this field.     

A Comprehensive Review of Rosmarinic Acid: From Phytochemistry to Pharmacology and Its New Insight

Polyphenolic acids are the widely occurring natural products in almost each herbal plant, among which rosmarinic acid (RA, C₁₈H₁₆O₈) is well-known, and is present in over 160 species belonging to many families, especially the Lamiaceae. Aside from this herbal ingredient, dozens of its natural derivatives have also been isolated and characterized from many natural plants. In recent years, with the increasing focus on the natural products as alternative treatments, a large number of pharmacological studies have been carried out to demonstrate the various biological activities of RA such as anti-inflammation, anti-oxidation, anti-diabetes, anti-virus, anti-tumor, neuroprotection, hepatoprotection, etc. In addition, investigations concerning its biosynthesis, extraction, analysis, clinical applications, and pharmacokinetics have also been performed. Although many achievements have been made in various research aspects, there still exist some problems or issues to be answered, especially its toxicity and bioavailability. Thus, we hope that in the case of natural products, the present review can not only provide a comprehensive understanding on RA covering its miscellaneous research fields, but also highlight some of the present issues and future perspectives worth investigating later, in order to help us utilize this polyphenolic acid more efficiently, widely, and safely.     

Electrochemical Oxidative C—H Sulfenylation of Imidazopyridines with Hydrogen Evolution

Selective oxidative C—H sulfenylation of imidazopyridine heterocycles is achieved using an undivided electrolytic cell. The reaction avoids the use of stoichiometric amount of external chemical oxidant and produces hydrogen gas as the only byproduct. Both aryl and aliphatic thiols demonstrate good reactivity for C—S bond formation.     

A branch and bound algorithm for dynamic resource allocation in population disease management

We embed an approximate dynamic program into a branch-and-bound framework to solve sequential resource allocation problems in population disease management. The proposed algorithm is capable of providing an optimality guarantee and getting bounds on the optimality gap of healthcare interventions. A numerical study on screening and treatment policy implementation for chronic hepatitis C virus (HCV) infection provides useful insights regarding HCV elimination for baby boomers.