电磁场法向边值关系的严密数学理论

阐述了矢量场穿过2阶无穷小平面的通量虽然也是2阶无穷小量,但特殊情况下要求计算精度必须达到3阶无穷小量,为此目的需要把2阶无穷小平面分成无穷多个4阶无穷小面元来计算通量,并且给出如此计算所得结果遵循的规律——3阶无穷小精度下矢量场穿过2阶无穷小平面的通量定理.最后介绍了这个定理在散度理论和电磁场法向边值关系理论中的应用.     

极端中和表型HIV包膜蛋白gp120的高温分子动力学模拟研究

作为HIV侵染细胞的蛋白质机器,包膜蛋白gp120利用序列变异和结构柔性等策略逃避宿主免疫识别,是病毒呈现出不同中和表型的主要原因.尽管HIV中和表型的分子机制已被初步探索,但其热力学相关的分子基础仍待进一步阐明.本研究利用同源模建的方法构建了极端中和表型HIV毒株(中和抵抗毒株H061.14与中和敏感毒株R2)的gp120结构模型,在逐渐升高的温度梯度下进行了高温分子动力学模拟,以研究二者在结构稳定性、解折叠和构象柔性上的差异.结果表明,HIV中和表型与gp120的热力学性质呈正相关,与解折叠程度无必然关联.各温度下gp120的结构偏差、天然接触含量、构象群体分布,以及单残基柔性的比较清楚地说明,中和敏感比中和抵抗gp120表现出更大的结构偏差、更多的构象状态和更高的构象柔性,但两者具有相似的解折叠程度.由极端中和表型HIV包膜蛋白gp120显著不同的热力学性质可以推断,HIV很可能利用gp120的热力学性质来调节其构象,进而平衡病毒侵染和免疫逃避之间的矛盾.我们的研究不仅揭示了极端中和表型HIV包膜蛋白gp120的在构象柔性和结构稳定性上的差异,同时还从高温解折叠热力学的角度明确了...     

Vibrational spectroscopy of platinum(0) complexes—III. An improved normal coordinate analysis for Pt(O)(C2H4) and other M(C2H4) systems

The availability of new infrared and Raman data for metal-ethene complexes, has prompted a new normal coordinate analysis of the M(C₂H₄) fragment, using a larger data set than in previous studies. Assuming local C_2ν symmetry, M(C₂H₄) is treated in identical fashion to ethene oxide, C₂H₄O. Thus, a set of generalised valence force field (GVFF) force constants is obtained by fitting all of the a₁ and b₁ wavenumbers of C₂H₄O, C₂D₄O, C₂H₄Pt^II, C₂D₄Pt^II, C₂H₄Fe^(o), C₂D₄Fe^(o) and C₂H₄Pt^(o). The trends in CC and MC stretching force constants indicate an increasing tendency towards a metallocyclopropane form, in the order: C₂H₄Pt^II < C₂H₄Fe^(o) ≲ C₂H₄Pt^(o) < C₂H₄O. These, and other force constants, suggest that Zeise's salt is exceptional in not adopting a metallocyclopropane structure.     

A simplified and reliable LC–tandem mass spectrometry method for determination of ulipristal acetate in human plasma and its application to a pharmacokinetic study in healthy Chinese volunteers

In this study, a simplified, sensitive and reliable LC–tandem mass spectrometry method was established and validated for the quantification of ulipristal acetate (UPA) in human plasma and for the investigation of pharmacokinetic profile of UPA following a single oral administration of ella (UPA 30-mg tablet) in healthy Chinese volunteers. Plasma samples were analyzed after being processed by protein precipitation with methanol. Chromatographic separation was performed on a Kinetex EVO C₁₈ column (2.1 × 50 mm, 2.6 μm) using gradient elution with a mobile phase composed of methanol and water containing 2 mm ammonium acetate and 0.3% formic acid at a flow rate of 0.3 mL/min. The chromatographic running time was 4.0 min per sample. The MS detection was performed via an LC system with the positive ion electrospray ionization interface in multiple reaction monitoring mode using the transition of m/z 476.2 → 134.1 for UPA and m/z 479.3 → 416.2 for UPA-d3 [internal standard (IS)], respectively. UPA and IS were monitored without severe interference from the biological matrices. The method was linear over the wide concentration range of 0.300–300 ng/mL. The intra- and inter-day precision and accuracy were well within the limits required for bioanalytical assays. The method was first used to describe the pharmacokinetic characteristic of UPA after a single oral administration of ella in healthy Chinese volunteers. Based on a between-study comparison, there were statistically significant differences (p < .05) between Chinese and Caucasian volunteers for the systemic exposure of UPA, suggesting that race seems to significantly impact the systemic exposure of UPA.     

A new seeding and electroless approach to alloying,direct patterning,and self-forming barriers for Cu thin-film nanostructures

In contrast to the previous studies involving sputter deposition to form Cu-alloy thin films with several atomic percentages of incorporated metallic solutes, this work examines the feasibility of using electroless deposition in conjunction with a new site-selective seeding process for the alloying and direct patterning of Cu thin-film nanostructures on dielectric layers. Very minute amounts (0.4 at.%) of manganese can be incorporated into the constituting Cu and segregated to form an interfacial layer at the SiO₂/Cu interface upon annealing in an Ar–H₂ atmosphere. The interfacial layer made up of only a few atomic layers is identified based on synchrotron X-ray spectroscopy and serves as a barrier for advanced technology nodes.     

Density functional study on chirospectra of hydrogen-bonded systems X-（H2O）3（X=F,Cl,Br,I）

This paper calculates the molecular structures,infrared,Raman,circular dichroism spectra and optical rotatory powers of some hydrogen-bonded supramolecular systems as a cyclic water trimer,(H2O)3 and its pyramidal halide complexes,X-(H2O)3(X = F,Cl,Br,I) with the gradient-corrected density functional theory method at the B3LYP/6-311++G(2d,2p) and B3LYP/Aug-cc-pVTZ levels.It finds that the complexation of halide anions with the water trimer can efficiently modulate the chirally optical behaviors.The calculated vibrational circular dichroism spectrum illuminates that the vibrational rotational strength of S(+)-(H2O)3 mostly originates from the O-H rocking modes,whereas chirality of S(-)-X-(H2O)3(X = F,Cl,Br,I) has its important origin in the O-H stretching modes.The calculated optical rotatory power demonstrates that S(+)-(H2O)3 and S(+)-F(H2O)3 are positively chiral,whereas S(-)-X-(H2O)3(X = Cl,Br,I) are negatively chiral.With the polarizable continuum model,calculated bulk solvent effect in the solvents water and carbontetrachloride and argon shows that the positive chirality of S(+)-(H2O)3 is enhanced and the negative chirality of S(-)-X-(H2O)3(X = Cl,Br,I) and the positive chirality of S(+)-F(H2O)3 are reduced with an augmentation of the solvent dielectric constant.     

天登烟挥发性香气成分的聚类分析

为更为系统的了解天登烟的品质特点,采用同时蒸馏萃取-气相色谱/质谱法分析了烟叶样品中挥发性香气成分,并结合DSP软件对18个烟叶样品中13个成分峰按欧式距离类平均法进行了聚类分析。结果表明,各天登烟样品可以有效地聚为一类,特别是2003年的样品差异非常小,进一步说明,天登烟自身的香气特征风格突出,在烟草主要特征香气成分含量与组成方面同国产香料烟与烤烟较为接近,而与白肋烟、晒黄烟之间的差异均较大。     

超整函数族Julia集的Hausdorff维数

Stallard曾经用一族特殊的整函数说明了:超越整函数的Julia集的Hausdorff维数可以无限接近1.本文证明了该函数族的随机迭代的Julia集的Hausdorff维数也可无限接近于1.另一方面,对任意自然数M及任意实数d∈(1,2),本文给出了M个元素的整函数族其随机迭代的Julia集的Hausdorff维数等于d.