在美国破产保护法第十一章下公司债券的定价和最佳破产边界研究

为了更好地处理公司破产重组问题,综合采用结构化方法和最优停时技巧,基于美国破产保护法第十一章,分析了有限到期日公司债券的定价问题,本质上为最优停时问题.用偏微分方程法证明了最佳破产边界的存在唯一性和单调性,得到了公司策略债务支付息票的显式表达式.数值结果表明：在美国破产保护法第十一章下,公司的破产率更高,股东可通过提前宣布破产而获益,而债权人能否获益依赖于谈判因子和谈判费用.     

基于磺胺掺杂氮硫的碳点制备及对Hg2+的光化学识别

为提高碳点对汞离子光化学识别的选择性及检测方法的可行性,以柠檬酸和磺胺为原材料采用热解法制备一种新型氮、硫共掺杂碳点（NS-CDs）。用红外光谱仪、紫外-可见光吸收光谱仪、透射电镜、元素分析仪和荧光光谱仪等对其结构和光学性能进行表征。结果表明：该量子点水溶性和分散性高,平均粒径4.78 nm左右,具有类石墨结构;其在3 446和3 261 cm-1处存在N-C和O-H键振动吸收峰;2 966和2 923 cm-1处为C-H键振动吸收带;1 630和1 570 cm-1处吸收峰归属于苯环骨架C═C双键振动;1 388 cm-1处为-CH₃剪式振动峰;1 268,1 192,1 146及1 071 cm-1处的振动吸收峰表明存在为C-N,C-S,C-O,C-O-C及-SO-₃键,912 cm-1处为环氧基的特征吸收峰,739 cm-1处吸收带归属于N-H键变形振动,可见,该碳点不仅含有苯环骨架结构,还有N和S等元素参与的成键结构存在。其在21.4°处出现一个明显且宽的(002)晶面衍射特征峰,晶格间距为0.41 nm,稍大于石墨晶格间距（0.34 nm）。NS-CDs的C,N,S和O元素含量分别为68.72%,7.37%,6.24%及17.67%,与红外分析结果吻合。NS-CDs在309 nm处有一个由C═C键的π→π*电子跃迁产生的较强吸收峰,且在可见光区域内有一个很长的拖尾;同时在335 nm处出现了一个由C═O键的n→π*电子跃迁而产生的吸收肩峰。当激发波长小于390 nm时,NS-CDs原液荧光发射峰值随激发波长增大而逐渐增大,且在390 nm时,荧光强度最强;大于390 nm时,随激发波长增大而逐渐减弱。同时发现随激发波长增加,发射峰逐渐红移。当NS-CDs溶液逐渐稀释时,其最佳激发峰也由390 nm蓝移至360 nm;当pH值＜11.0时,NS-CDs的荧光强度变化很小,在pH值为7.0时荧光峰最强;在pH＞12.0时,荧光强度急剧下降,故选用PBS缓冲溶液（pH 7）进行金属离子检测实验。在16种金属离子中只有Hg2+对NS-CDs荧光强度具有极其显著的影响,使碳点荧光完全猝灭,基于NS-CDs对Hg2+具有高选择性及Hg2+对NS-CDs强荧光猝灭作用,建立了其对Hg2+的荧光化学识别方法。该识别方法的线性方程为y=5.559 02x-13.860 39,其线性范围为1×10-3~1×10-9 mol·L-1,R2为0.9947,检出限为7.11×10-3 nmol·L-1,相对标准偏差小于2.5%,对实际样品检测精度和回收率高,可用于实际水样中Hg2+的检测,在生物和环境分析领域具有良好的应用前景。     

Inequalities involving Khatri-Rao products of Hermitian matrices

Recently, several inequalities involving Khatri-Rao products of two four partitioned blocks positive definite real symmetry matrices are established by Liu in [Lin. Alg. Appl. 289(1999):267-277]. We extend these results in two ways. First, the results are extended to two any partitioned blocks Hermitian matrices. Second, necessary and sufficient conditions under which these inequalities become equalities are presented.     

三维有序金纳米壳结构的可控制备及其SERS性能

采用金种子原位生长法,以SiO_2胶体晶体为模板,H_2O_2为还原剂实现了三维有序金纳米壳(GNSs)结构的可控制备,并对其生长过程中表面增强拉曼光谱(SERS)性能进行了研究。实验结果表明,通过控制反应时间、反应温度、还原剂H_2O_2及生长液K_2CO_3-HAuCl_4的量等参数实现了三维有序GNSs阵列的可控批量制备,并可根据需要去除SiO_2内核得到中空有序GNSs结构。通过对其SERS性能的研究,发现SiO_2表面完全被Au纳米粒子覆盖的粗糙结构具有最佳的SERS性能,且对应的中空有序GNSs结构显示出更优异的SERS活性。     

Improved cell morphology and reduced shrinkage ratio of ETPU beads by reactive blending

Thermoplastic polyurethane foam beads (ETPU) have attracted attention of researchers in recent years due to their wide use in industrial applications. In this study, a small amount of acrylonitrile-butadiene-styrene copolymer (ABS) was blended with TPU under the assistance of dicumyl peroxide (DCP) and maleic anhydride (MAH) to improve the cell morphology and reduce shrinkage ratio of the resulting blends. These blends were then foamed to prepare TPU/ABS blends foam beads in an autoclave using supercritical CO₂ as the blowing agent at different temperatures and FTIR spectra, and rheological and foaming properties of the samples were evaluated. The melt viscosity, melt strength and elasticity of TPU/ABS were improved with the increase of the ABS content. These results were attributed to the grafting and heterogeneous nucleation points provided by the ABS. These enhanced properties were used to produce foams with better cell morphology and increased expansion ratio. Furthermore, the TPU/ABS blends foam beads showed lower shrinkage ratios with increasing ABS content. Thus, the addition of ABS is a facile method for improving the cell morphology and anti-shrinkage properties of ETPU.     

荧光法快速测定邻苯二甲酸酯的总量

基于邻苯二甲酸酯在浓硫酸下荧光增强的原理构建了一种测定邻苯二甲酸酯总量的荧光分析新方法。 体系的荧光强度与邻苯二甲酸酯的浓度在5.00~600 μg/L的范围内呈线性关系,方法的检出限为0.57 μg/L,回收率在91.6%~105.1%之间。 该方法简单、快速、灵敏度高、线性范围宽。 用于塑料水杯和聚氯乙烯水管中邻苯二甲酸酯总量的测定,结果令人满意。     

Ultrasound Assisted Synthesis of Nanoscale NH_2-MIL-53(Fe) for the Adsorption of Dye

Nanometer blocks of amide-functionalized Fe(Ⅲ)-based metal-organic frameworks,NH2-MIL-53(Fe),were prepared via ultrasonic method without any surfactants at room temperature and atmospheric pressure.The characterization for the as-prepared nano-structured MOFs was established by XRD,SEM,TEM,XPS and N2 adsorption-desorption.The as-prepared sample with high specific surface area(179.9 m²·g^-1)showed excellent adsorption for methylene blue in the liquid phase.The as-prepared NH₂-MIL-53(Fe)adsorbent seems to be a promising material in practice for organic dye removal from aqueous solution.