量子线/铁基超导隧道结中隧道谱的研究

考虑铁基超导中能带间的相互作用和界面对每一个能带的散射作用, 利用推广的Blonder-Tinkham-Klapwijk模型, 并通过求解Bogoliubov-de Gennes 方程研究了具有不同类型双能隙系统的量子线/铁基超导隧道结中准粒子的输运系数和隧道谱. 研究表明: 1)在弹道极限时, 随着带间相互作用的增大, s_± 波隧道谱中零偏压附近的平台演变成电导峰; s₊₊ 波的平台演变成凹陷; p波的零偏压电导峰被压低. 2)界面对两个能带的散射作用不为零时, 随着带间相互作用的增大, s_± 波和s₊₊ 波两能隙处的峰值将降低, 而两峰间的凹陷值将变大; p波的零偏压电导峰被压低, 非零偏压电导增大. 3)界面对每个能带的散射, 可使其产生的电导峰变得更加尖锐, 但可压低和抹平另一个带产生的电导峰值. 这些结果对于澄清铁基超导体的能隙结构和区别不同类型铁基超导体有所帮助.     

热迁移对Cu/Sn/Cu焊点液-固界面Cu6Sn5生长动力学的影响

电子封装技术中, 微互连焊点在一定温度梯度下将发生金属原子的热迁移现象, 显著影响界面金属间化合物的生长和基体金属的溶解行为. 采用Cu/Sn/Cu焊点在250℃和280℃下进行等温时效和热台回流, 对比研究了热迁移对液-固界面Cu₆Sn₅生长动力学的影响. 等温时效条件下, 界面Cu₆Sn₅生长服从抛物线规律, 由体扩散控制. 温度梯度作用下, 焊点冷、热端界面Cu₆Sn₅表现出非对称性生长, 冷端界面Cu₆Sn₅生长受到促进并服从直线规律, 由反应控制, 而热端界面Cu₆Sn₅生长受到抑制并服从抛物线规律, 由晶界扩散控制. 热端Cu 基体溶解到液态Sn中的Cu原子在温度梯度作用下不断向冷端热迁移, 为冷端界面Cu₆Sn₅的快速生长提供Cu 原子通量. 计算获得250℃和280℃下Cu原子在液态Sn中的摩尔传递热Q^*分别为14.11和14.44 kJ/mol, 热迁移驱动力F_L分别为1.62×10^-19和1.70×10^-19 N.     

双色场诱导气体产生相干可控的四次谐波

利用钛宝石飞秒激光器输出的基频脉冲ω及其倍频脉冲2ω所构成双色场作用空气, 实验中检测到了中心波长处于真空紫外波段的四阶谐波. 在气体未发生电离的情况下, 四次谐波强度对双色场的能力依赖关系显示其产生是参量过程2ω+ω+ω→4ω的贡献. 当气体发生电离, 四次谐波强度与双色场相对相位有关, 可通过双色场相干控制. 实验研究了四次谐波对双色场相位的依赖性以及与太赫兹波的关联性, 其结果与数值模拟结果相符, 分析发现当气体发生电离时四次谐波的产生过程存在太赫兹辐射Ω_THz的参与, 是参量过程2ω+2ω±Ω_THz→4ω和2ω+ω+ω→4ω的共同贡献.     

基于核各向异性扩散的红外小目标检测

为了减少红外图像中背景边缘对检测的影响,提出了一种具有鲁棒性的弱小目标检测算法,该算法利用核各向异性扩散模型进行背景预测,再与原图像差分实现弱小目标检测。为了提高算法的自适应能力,提出了一种鲁棒性扩散系数,能够根据图像背景的起伏程度自适应调整扩散系数曲线的陡峭程度。实验结果表明,与现有的检测算法相比,该算法能够在不同类型的复杂背景下有效抑制背景及其边缘,保留目标大小,降低虚警率,具有更强的鲁棒性。     

Lipid Raft Stationary Phase Chromatography for Screening Anti-tumor Components from Galla chinensis

For the first time, a novel biological affinity separating system called lipid raft stationary phase chromatography (LRSC) was developed. It was employed to screen bioactive components from Chinese gallnut, a traditional Chinese medicine (TCM). The LRSC was prepared by the addition of activated silica to Tris–HCl solution, which contains the isolated lipid rafts of U251 cells. This was followed by agitation, washing, centrifugation and then re-suspension of the residue in another Tris–HCl solution. The lipid rafts possess abundant receptor tyrosine kinase, specifically tropomyosin-related kinase A (TrkA), which is a widely researched anti-tumor drug target. Thus, TrkA provided the LRSC model with the ability to select fractions that specifically interact with it. Using a non-TrkA targeted anti-tumor drug (gemcitabine) and TrkA targeted anti-tumor drugs (lestaurtinib and gefitinib) as controls to evaluate the specific affinity of the LRSC column, the different fractions of Chinese gallnut were subjected to LRSC screening for the identification of anti-tumor components. As a result, the ether fraction of Chinese gallnut manifested desirable affinity properties. The methyl thiazolyl tetrazolium assay confirmed the anti-tumor effect of the screened ether fraction, and more importantly, the ether fraction failed woefully to exhibit its anti-proliferative activity in the presence of TrkA inhibitors (K252a and primary antibody). This further proves the selectivity of LRSC on TrkA-targeted drugs. The LRSC model has, therefore, shown to be of high efficiency and selectivity in screening bioactive components from the complex TCM extracts, thus offering an effective approach for the development of anticancer natural products.     

Density functional theory study of p‐chloroaniline adsorption on Pd surfaces and clusters

The adsorption mode of aromatic molecules on transition metal surfaces plays a key role in their catalytic transformation. In this study, by means of density functional theory calculations, we systematically investigate the adsorption of p‐chloroaniline on a series of Pd surfaces, including stepped surfaces, flat surfaces, and clusters. The adsorption energies of p‐chloroaniline on these substrates [Pd(221), Pd(211), Pd(111), Pd(100), Pd₁₃‐icosahedral, Pd₁₃‐cubo‐octahedron, Pd₅₅] are ?1.90, ?2.13, ?1.70, ?2.11, ?2.53, ?2.65, ?2.23 eV, respectively. Benzene ring is adsorpted on catalyst rather than amine group in p‐chloroaniline molecular. A very good linear relationship is further found between the adsorption energies of p‐chloroaniline and the d‐band center of both Pd surfaces and clusters. The lower of d‐band center of Pd models, the stronger adsorption of p‐chloroaniline on catalysts. In addition, the frontier molecular orbital and density of states analysis explain the adsorption energy sequence: cluster Pd₁₃ > stepped Pd(221) surface > flat Pd(111) surface. © 2014 Wiley Periodicals, Inc.     

Novel 4-Aryl-2-amino-6-(naphthalene-1-yl)-3-cyanopyridine Derivates as Potential Organic Fluorescent Materials Prepared Under Microwave Irradiation via Three-Component Domino Reactions

A green and efficient method for direct preparation of 3-cyanopyridine from aromatic aldehydes is reported. A series of novel 4-aryl-2-amino-6-(naphthalene-1-yl)-3-cyanopyridine derivates were successfully prepared by one-pot synthesis of three-component domino reactions including aromatic aldehydes, 1-acetylnaphthalene, and dicyanomethane in the presence of ammonium acetate in a solution of ethanol under microwave irradiation. This synthetic method for these compounds possesses many advantages including greater yield and shorter reaction times compared with traditional methods. The structures of these compounds were confirmed by means of high-resolution mass spectrometry, ¹H NMR, ¹³C NMR, and infrared. Moreover, the results of their fluorescent spectra showed that these compounds have good fluorescence intensity excited by the visible light wavelength of 416 nm.     

用于高性能锂硫电池的二维氮硫共掺杂多孔碳纳米片的快速合成

本工作基于工业炼油产品沥青,开发了一种无金属、氮和硫共掺杂多孔碳纳米片（NSPC）的合成方法。获得的多孔碳纳米片具有高比表面积（339 m²·g^-1）和优异的固硫能力。同时,高含量氮、硫共掺杂可以有效增强碳材料的导电性,同时促进多硫化物的高效催化转化。通过熔融法固硫后,制备得到的NSPC/S电极具有较高的比容量和优异的循环稳定性（在0.6C电流密度下,200次循环后容量为762 mAh·g^-1）,实现了高含量氮和硫共掺杂的二维多孔碳材料的快速批量生产并用于高性能锂硫电池正极材料。     

Phosphine-mediated annulation of N-protected imines with DEAD

In the presence of triphenylphosphine, the reactions of N-protected imines or their precursors with DEAD proceeded smoothly to give the corresponding functionalized 1H-1,2,4-triazole-1,4(5H)-dicarboxylate derivatives in good to high yields under mild conditions. A plausible mechanism has been proposed on the basis of the control experiments.     

Isolation and bioactivities of organic acids and phenols from walnut shell pyroligneous acid

Based on differences in acidity, organic acids and phenols were enriched by pH gradient extraction method from walnut shell pyroligneous acid. Contents of organic acids and phenols were measured by acid-base titration method and Folin colorimetric assay, respectively to assess the effectiveness of the extraction. In addition, the antimicrobial activity of the organic acids and antioxidant activity of phenols extracted were investigated. Chemical components of the extracts that were from the optimal concentrations of NaHCO₃ and NaOH were measured by GC-MS. The results showed that 5% NaHCO₃ could enrich the highest amount of organic acids, whereas 4% NaOH could enrich the highest amount of phenols. The enriched organic acids exhibited high antimicrobial activity, and the enriched phenols exhibited antioxidant activity under low concentrations, and demonstrated dosage dependency.