Nmr spectral characteristics of N-H protons in purine derivatives

Proton chemical shifts are examined in a series of twelve purine and three 5-azapurine derivatives. The assignment of N-H signals in the xanthine and thioxanthine series, as well as the effects of moisture, concentration and temperature on the N-H and C-H nmr spectral characteristics are discussed.     

Supramolecular hydrogels induced rapidly by inclusion complexation of poly(epsilon-caprolactone)-poly(ethylene glycol)-poly(epsilon-caprolactone) block copolymers with alpha-cyclodextrin in aqueous solutions

On the basis of the synthesis of water-soluble poly(epsilon-caprolactone)-poly(ethylene glycol)-poly(epsilon-caprolactone) (PCL-PEG-PCL) block copolymers, the supramolecular hydrogels were fabricated rapidly in aqueous solutions by their inclusion complexation with alpha-cyclodextrin. X-ray diffraction (XRD) analyses confirmed the supramolecular self-assemblies of alpha-cyclodextrin threaded onto amphiphilic PCL-PEG-PCL block copolymers. The resulting hydrogels display a high degree of elasticity, with the storage modulus (G') greater than the loss modulus (G') over the entire range of frequency. Moreover, their viscosity greatly diminished as they were sheared. By controlling the molecular weight of the PEG component in the block copolymers and the content of the block copolymer, their rheological properties could be modulated. Such hydrogel materials have the potential to be used as tissue engineered scaffolds, biosensors in the human body, and carriers for controlled drug delivery.     

Quantum Mechanical Study on Tunnelling and Ballistic Transport of Nanometer Si MOSFETs

Using self-consistent calculations of million-atom SchrSdinger-Poisson equations, we investigate the I-V characteristics of tunnelling and ballistic transport of nanometer metal oxide semiconductor field effect transistors （MOSFET） based on a full 3-D quantum mechanical simulation under nonequilibtium condition. Atomistic empirical pseudopotentials are used to describe the device Hamiltonian and the underlying bulk band structure. We find that the ballistic transport dominates the I-V characteristics, whereas the effects of tunnelling cannot be neglected with the maximal value up to 0.8mA/μm when the channel length of MOSFET scales down to 25 nm. The effects of tunnelling transport lower the threshold voltage Vt. The ballistic current based on fully 3-D quantum mechanical simulation is relatively large and has small on-off ratio compared with results derived from the calculation methods of Luo et al.     

Ab initio study of I<Subscript>2</Subscript> and T<Subscript>2</Subscript> stacking faults in C14 Laves phase MgZn<Subscript>2</Subscript>

Based on the synchroshear mechanism, the formation of intrinsic stacking fault I ₂ and twin-like stacking fault T ₂ in C14 Laves phases has been modeled in detail and the generalised stacking fault energy curve of I ₂ and T ₂ for C14 Laves phase MgZn₂ has been calculated from first-principles. The results demonstrate that the unstable stacking fault energy of I ₂ by synchroshear is still very large, and the stable stacking fault energy of I ₂ is higher in comparison with pure Mg implying that the formation of I ₂ stacking fault in MgZn₂ is difficult. Starting with the I ₂ configuration, the T ₂ stacking fault can be formed by an additional synchroshear. The unstable and stable stacking fault energies of T ₂ are only slightly larger than those of I ₂, implying that the formation of T ₂ may be essentially similar to that of I ₂. From the obtained generalised stacking fault energy, the relevant deformation mechanism of MgZn₂ is also discussed. Finally, the electronic structure during synchroshear process is further studied.     

Submicrosized rods, cables, and tubes of ZnE (E = S, Se, Te): exterior-interior boron-chalcogen conversions and optical properties

The submicrosized ZnE rods, ZnO/ZnE cables, and ZnE tubes (E = S, Se, Te) have been synthesized via exterior-to-interior boron-chalcogen corrosions on the initial ZnO rods. The products are well characterized by XRD, SEM, TEM, and elemental analyses. The morphologies of both ZnE rods and ZnO/ZnE cables are roughly comparable to that of ZnO. The measured optical gaps of the ZnE rods are in agreement with those of the corresponding bulk materials, and the ZnO/ZnE cables exhibit type-I excitonic localization that is restrained in the region of the narrower band gap component.     

气相色谱中特殊混合固定相的协同效应研究

在气相色谱中,组份在混合固定液上的保留值具有加和性［１～３］．我们在研究一些特殊选择性固定液进行混合固定相保留行为时,发现存在一定的协同效应［４,５］．本文在以全戊基β－环糊精／ＴｌＮＯ３、有机皂土－３４／ＡｇＮＯ３、全戊基β－环糊精／ＡｇＮＯ３为混...     

C_4S_4~(m-)(m=0,1,2,3,4)的从头算研究2.成键状况、电离势和振动频率

在ＲＨＦ（基离子在ＵＨＦ）／６－３１Ｇ,６－３１Ｇ＊和６－３１＋Ｇ水平用从头算和Ｂｏｙｓ定域化方法计算了Ｃ４Ｓ４ｍ－（ｍ＝０,１,２,３,４）的电子结构、电离势和定域化分子轨道。讨论了其成键特征和电离势与ΔＥＳＣＦ的关系。在６－３１Ｇ水平用ａｂｉｎｉｔｉｏ解析方法计算它们的谐振动频率。电子结构计算结果和Ｂｏｙｓ定域化分子轨道及振动分析结果与优化的平衡几何和相对稳定性相一致     

Simultaneous Determination and Pharmacokinetics of Magnolol and Honokiol in Body Fluid and Tissue of Wistar Rat by A Reversed Phase High Performance Liquid Chromatography

A reversed phase high performance liquid chromatography method for simultaneous determined magnolol and honokiol in serum and urine of rat were builted.     

甲烷-二氧化碳重整制合成气与现代分析技术应用于探究性化工专业实验的设计与探索

以甲烷-二氧化碳重整制合成气为实例,设计探究性实验,将合成气的制备和现代分析技术应用于化工专业实验的教学实践中以提高学生的创新和实践能力。实验包括催化剂的制备,催化剂的性能评价和催化剂的表征等3大部分。采用工业最常用的浸渍法制备含有不同助剂的Ni/X/γ-Al2O3（X为Co,Fe,MgO,CeO2）催化剂,以甲烷-二氧化碳重整反应评价其催化性能,并采用XRD、H2-TPR、BET和TG对催化剂的微观结构进行表征。结合催化剂的性能评价结果和表征结果,探讨不同助剂对镍基催化剂性能的改善效果及机制。通过开设该实验,可以让学生了解化工学科的前沿知识以及现代分析技术的基本原理和用途,掌握专业的实验操作、数据处理和谱图绘制方法,提高学生的专业素养和综合能力。     

Experimental investigation of effects of airflows on plasma-assisted combustion actuator characteristics

The effects of the airflow on plasma-assisted combustion actuator(PACA) characteristics are studied in detail. The plasma is characterized electrically, as well as optically with a spectrometer. Our results show that the airflow has an obvious influence on the PACA characteristics. The breakdown voltage and vibrational temperature decrease, while the discharge power increases compared with the stationary airflow. The memory effect of metastable state species and the transportation characteristics of charged particles in microdischarge channel are the dominant causes for the variations of the breakdown voltage and discharge power, respectively, and the vibrational temperature calculated in this work can describe the electron energy of the dielectric barrier discharge plasma in PACA. These results offer new perspectives for the use of PACA in plasma-assisted combustion.