Thermodynamic properties of hydrated sodium l-threonate Na(C4H7O5)·H2O(s)

Low-temperature heat capacities of the compound Na(C₄H₇O₅)·H₂O(s) have been measured with an automated adiabatic calorimeter. A solid-solid phase transition and dehydration occur at 290-318 K and 367-373 K, respectively. The enthalpy and entropy of the solid-solid transition are Δ_transH_m = (5.75 ± 0.01) kJ mol⁻¹ and Δ_transS_m = (18.47 ± 0.02) J K⁻¹ mol⁻¹. The enthalpy and entropy of the dehydration are Δ_dH_m = (15.35 ± 0.03) kJ mol⁻¹ and Δ_dS_m = (41.35 ± 0.08) J K⁻¹ mol⁻¹. Experimental values of heat capacities for the solids (I and II) and the solid-liquid mixture (III) have been fitted to polynomial equations.     

Detection of antisperm antibody in human serum using a piezoelectric immunosensor based on mixed self-assembled monolayers

A novel piezoelectric immunosensor based on mixed self-assembled monolayers (mixed SAMs) formed by short-chain amine- and carboxyl-terminated thiols has been developed to immobilize antigens onto gold electrodes for detecting antisperm antibody (AsAb) in human serum samples. The properties and the enhanced performance of the affinity biosensor interface based on mixed SAMs are investigated. Most importantly, analytical results of several human serum samples using the developed technique are in satisfactory agreement with those given by the enzyme-linked immunosorbent assay (ELISA) method in the concentration ranging from 32.3 to 300.0 mU/ml. It means the procedure proposed in this paper is likely to have a great potential in research and may play an important clinical role in a few years later.     

Poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide)-g-poly(vinylpyrrolidone): association behavior in aqueous solution and interaction with anionic surfactants

In this work, we aimed to study the association and interaction behavior of poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) block copolymers grafted with poly(vinylpyrrolidone). Critical micellization concentrations were determined using fluorescent probes (pyrene) and critical micellization temperatures characterizing temperature-dependent transitions from monomers to multimolecular micelles were measured. The thermal responsiveness of the copolymer is not affected by the grafting. The hydrodynamic radius of the graft copolymer micelles is found to be greater than that of the original copolymer micelles. The graft copolymer is found to form anisotropic aggregates. The structure of the graft copolymer micelles is less disrupted by the anionic surfactant sodium dodecyl sulfate, compared to the ungraft copolymer.     

室温离子液体EMIES的标准生成焓

在(298.15 ±0.01) K下用转动弹热量计测定了离子液体硫酸乙酯-1-甲基-3-乙基咪唑(EMIES)及合成它的原料1-甲基咪唑的恒容燃烧热,通过计算得到它们的标准燃烧焓 分别为(－2671±2) 和(－286.3±0.5) kJ·mol－1;标准生成焓 分别为(－3060±3) kJ·mol－1和(－2145±4) kJ·mol－1.结合文献上硫酸二乙酯的标准生成焓数据,得到了合成离子液体EMIES的反应热(－102.3±1.0) kJ·mol－1,与合成实验中观察到的强烈放热现象是一致的.根据离子液体EMIES的热容数据,计算了不同温度下EMIES的标准生成焓.     

Lycopodine‐Type Lycopodium Alkaloids from Huperzia serrata

Eleven Lycopodium alkaloids with a lycopodine‐type skeleton were isolated from the basic material of the whole plant of Huperzia serrata (Thunb .) Trev. (Huperziaceae). Among them, 12‐epilycodoline N‐oxide (=(12α,15R)‐12‐hydroxy‐15‐methyllycopodan‐5‐one N‐oxide; 1 ), 7‐hydroxylycopodine (=(15S)‐7‐hydroxy‐15‐methyllycopodan‐5‐one; 2 ), and 4,6α‐dihydroxylycopodine (=(6α,15R)‐4,6‐dihydroxy‐15‐methyllycopodan‐5‐one; 3 ) are new compounds. Their structures were identified spectroscopically, especially by means of 1D‐ and 2D‐NMR.     

TixNy团簇结构的密度泛函研究

采用杂化密度泛函方法(B3LYP)和有效核势基组预测了Ti_xN_y (x≤3, y≤2)团簇的结构及稳定性, 并分析了可能存在构型的电子结构. 结果表明Ti₂N中体系的自旋多重度由Ti原子决定. Ti₃N中随着N的配位数增加, N的负电荷增加, 平均每个Ti向N提供约0.3个电子. 从Ti₂N₂可能稳定构型分析, 成键数目越多, 能量上越有利, 且Ti—N键的数目的增加, 将削弱N—N间的成键.     

Orientational dynamics of water confined on a nanometer length scale in reverse micelles

The time-resolved orientational anisotropies of the OD hydroxyl stretch of dilute HOD in H(2)O confined on a nanometer length scale in sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelles are studied using ultrafast infrared polarization and spectrally resolved pump-probe spectroscopy, and the results are compared to the same experiments on bulk water. The orientational anisotropy data for three water nanopool sizes (4.0, 2.4, and 1.7 nm) can be fitted well with biexponential decays. The biexponential decays are analyzed using a wobbling-in-a-cone model that involves fast orientational diffusion within a cone followed by slower, full orientational relaxation. The data provide the cone angles, the diffusion constants for motion within the cones, and the final diffusion constants as a function of the nanopool size. The two processes can be interpreted as a local angular fluctuation of the OD and a global hydrogen bond network rearrangement process. The trend in the relative amplitudes of the long and short exponential decays suggest an increasing rigidity as the nanopool size decreases. The trend in the long decay constants indicates a longer hydrogen bond network rearrangement time with decreasing reverse micelle size. The anisotropy measurements for the reverse micelles studied extrapolate to approximately 0.33 rather than the ideal value of 0.4, suggesting the presence of an initial inertial component in the anisotropy decay that is too fast to resolve. The very fast decay component is consistent with initial inertial orientational motion that is seen in published molecular-dynamics simulations of water in AOT reverse micelles. The angle over which the inertial orientational motion occurs is determined. The results are in semiquantitative agreement with the molecular-dynamics simulations.     

Effect of carbon nanotubes on the crystallization and properties of polypropylene

The effect of different concentrations of single‐walled carbon nanotubes (SWNTs) on the nonisothermal crystallization kinetics, morphology, and mechanical properties of polypropylene (PP) matrix composites obtained by melt compounding was investigated by means of X‐ray diffraction, differential scanning calorimetry, optical and scanning electron microscopy, and dynamic mechanical thermal analysis. Microscopy showed well‐dispersed nanotube ropes together with small and large aggregates. The modulus was found to increase by about 75% at a level of 0.5 wt % nanotubes. The SWNTs displayed a clear nucleating effect on the PP crystallization, favoring the α crystalline form rather than the β form. The crystallization kinetics analysis showed a significant increase in activation energy on incorporating nanotubes. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2445–2453, 2005     

A convenient catalytic approach to synthesize straight boron nitride nanotubes using synergic nitrogen source

Straight boron nitride nanotubes (BNNTs) with pure hexagonal phase were conveniently prepared by heating the mixture of Mg(BO₂)₂ · H₂O, NH₄Cl, NaN₃ and Mg powder in an autoclave at 600 °C for 20–60 h. These BNNTs had diameters mainly ranging 30–300 nm and lengths up to 5 μm, and a majority of them had at least one closed end. Besides the traditional end tips, additional cone-like tips were frequently found to be attached on the BNNTs. The effects of temperature, reactants and the possible mechanism of the catalytic formation of the BNNTs are discussed.     

Two New Cyclopeptides from Arenaria oreophila (Caryophyllaceae)

Two new cyclopeptides, named arenariphilin A ( 1 ) and arenariphilin B ( 2 ), were isolated from the whole plants of Arenaria oreophila. Their structures were determined as cyclo‐(Thr‐Gly) ( 1 ) and cyclo‐(Ser₁‐Gly ‐Ser₂‐Ile ‐Phe₁‐Phe₂) ( 2 ) on the basis of spectral data, especially by 2D‐NMR.