镁铝类水滑石/阳离子淀粉分散体系流变学振荡行为研究

采用稳态剪切和小振幅振荡剪切实验研究了镁铝类水滑石化合物(Mg-Al HTlc)/阳离子淀粉(CS)分散体系(HTlc与CS质量之比R分别为0, 0.02, 0.05和0.08)的流变学性质．实验结果表明: 上述体系在实验pH值(5～11)范围内均为剪切稀释非牛顿流体, 其中, Mg-Al HTlc/CS (R＝0, 0.02和0.05)分散体系的流变曲线符合幂律模型, 而Mg-Al HTlc/CS (R＝0.08)体系符合Herschel-Bulkley模型. 上述体系先于1000 s^－1剪切180 s, 再于1 s^－1(或者3 s^－1)低速剪切时均表观出粘度随时间周期变化的振荡现象. 振荡现象缘于CS分子结构的周期变化. pH值、剪切速率和HTlc含量的变化可以改变振荡周期(频率)和振幅. 低pH值条件下, Mg-Al HTlc/CS (R＝0.08)体系先于1000 s^－1剪切180 s, 再于小振幅振荡剪切(剪切应力0.03 Pa, 频率0.5 Hz)时储能模量G?和损耗模量G?也表现出随时间周期变化的振荡现象.     

Elution-extrusion counter-current chromatography separation of five bioactive compounds from Dendrobium chrysototxum Lindl

The elution-extrusion counter-current chromatography (EECCC) method was firstly developed by Berthod in 2003 and has been used in natural products separation in recent years. The advantages of this method have been well documented such as reducing the separation time and solvent consumption. In the EECCC method, the time point of the extrusion step is very important during the whole separation process as it directly affects the resolutions, separation time and solvent consumption. However, how to choose a suitable time point to perform the extrusion step without decreasing the resolution has not been studied yet. In the present study, a strategy for systematically calculating the time point for extrusion was developed in theory and five bioactive compounds from the extract of Dendrobium chrysototxum Lindl. were separated and compared using normal CCC and EECCC method. Our results demonstrated that the accurate time point to perform the extrusion could be calculated and reduced both separation time and solvent consumption without losing separation performance. Using this EECCC method, five bioactive compounds were separated and purified with high purity. The separation time and solvent consumption were decreased from 200 min to 100 min and 5-2.5L during the separation process while the resolutions were still acceptable. Finally, 63 mg, 48 mg, 97 mg, 162 mg and 43 mg of hydroxyl phenanthrenes and bibenzyls with the purity of 98.7%, 98.0%, 98.2%, 99.0% and 98.7%, respectively were isolated from 1.2 g crude extract of D. chrysototxum Lindl. initially purified by column chromatography in one step separation. The purities of compounds were determined by HPLC. Their structures were identified by electrospray ionization-mass spectrometry (ESI-MS) and NMR.     

爆轰加载下金属材料的微层裂现象

通过在LiF窗口撞击镀膜面增加一薄层LiF和对LiF窗口反光面进行漫反射面镀膜处理的方法，对传统Asay窗诊断技术进行了改进，获得了微层裂物质高质量的实验信号。将改进后Asay窗技术与中能X射线照相及激光干涉测速技术相结合，实验给出了熔化状态下Sn材料微层裂物质不同时刻的密度空间分布图像及演化特征，且不同测试技术诊断结果半定量吻合。得到Sn材料微层裂物质的清晰物理图像，可为微层裂物理机理的认识和物理建模提供实验数据。     

新型有机光电开关器件

结合有机发光和光电二极管器件,制作了一种新型的有机光电开关器件。器件结构为：ITO／NPB／Alq3／CuPc／C60／NPB／Alq3／LiF／Al。其中,ITO(indium tin oxide,氧化铟锡)为正极,NPB[N,N′-di(naphthaleneyl)N,N′-diphenylbenzidine]／Alq3[tris-(8-hydro--xyquinoline,8-羟基喹啉铝)aluminum]作为电致发光层,CuPc(Copper Phthalocyanine,酞菁铜)／C60为光电转换层,LiF／Al为器件负极。即两个电致发光层和一个光电转换层组成的三明治型结构。从低向高施加电压和从高向低施加电压时,该器件呈现出不同的电流密度-电压(J-V)和功率密度-电压(P-V)曲线,即器件在相同的电压下可得到不同的电流密度值和功率密度值(亮度值),利用高亮度状态(ON)到低亮度状态(OFF)的转变,可实现开关型有机电致发光器件。器件的光电转换层吸收效率为0．153％。     

Discovery of New Thioviridamide‐Like Compounds with Antitumor Activities

Thioviridamide is a structurally unique compound with potent antitumor activity. The biosynthesis of thioviridamide follows a typical pathway as ribosomally synthesized and post‐translationally modified peptides, making the genome mining‐based discovery of thioviridamide‐like compounds rational. Taking advantage of the linkage between the precursor peptide and the metabolite skeleton, we identified a new biosynthetic gene cluster in Streptomyces sp. NRRL S‐87 that could encode thioviridamide analogues. Overexpression of the whole gene cluster led to the isolation and structure elucidation of TVA‐YJ‐4 and TVA‐YJ‐5, two novel thioviridamide‐like compounds featuring N‐terminal capping groups. Chemical screening of the fermentation extracts also detected TVA‐YJ‐6, another new thioviridamide‐like compound with representative methionine sulfoxide. Detailed analysis further revealed that these structural modifications were introduced during the compound extraction process instead of through genuine enzymatic reactions. TVA‐YJ‐4 and TVA‐YJ‐5 display slightly reduced cytotoxic activities against a panel of tumor cell lines in comparison with their parental natural product, TVA‐YJ‐2. Our work will expand the membership of this rare class of compounds and promote related biosynthetic studies.     

Evaluation of microfluidics-based droplet PCR combined with multiplex STR system in forensic science

Because of its excellent monodispersity, high throughput, and low volume, microfluidics-based droplet PCR has become the core technology of digital PCR, next-generation sequencing, and other technology platforms. This study constructed a microfluidic water-in-oil droplet PCR system and amplified a commercially available forensic 22-plex short tandem repeat detection system. We analyzed the sensitivity, concordance, amplification efficiency of the droplet PCR, and influence factors of the above aspects. The droplet PCR showed high concordance with conventional bulk PCR and had high sensitivity as 0.125 ng. Furthermore, we observed the performance of droplet PCR in high-order mixed DNA. As the mixture ratios from 10:1 to 30:1, droplet PCR presented more mixture proportion (Mx) increased loci from 11 (57.89%) to 17 (89.47%). In the mixture ratios 20:1, 25:1, and 30:1, significant Mx differences between droplet PCR and bulk PCR were observed (p < 0.05). The results showed that the droplet PCR could improve the identification of the minor contributor's DNA in a two-person mixture and alleviate the imbalanced amplification problem. This study provides a reference and basis for the wide application of droplet PCR in forensic science.     

A targeted ancestry informative InDels panel on capillary electrophoresis for ancestry inference in Asian populations

CE is the primary methodology used in forensic DNA typing. Alleles of commonly used types of genetic markers could be separated and detected via CE based on dye color and migration time. Insertion/deletion (InDel) is an ideal genetic marker for forensic DNA analysis due to their abundance in the human genome, low mutation rate, availability of their allele types via CE, and elimination of stutter peaks. Moreover, InDels could be used as ancestry informative markers since allele frequencies of InDels is different among geographically separated populations. Several ancestry informative insertion/deletion panels have been established based on CE platform to achieve the intercontinental populations distinction. However, improvements to differentiate intracontinental populations is few. In this study, 21 InDels with fixation index (F_ST) > 0.15 were selected and assembled into one ancestry informative insertion/deletion panel. Using well-designed primers, those 21 InDels could be amplified successfully and genotyped on the CE platform accurately and completely. The panel showed a large F_ST distance distinction among the ten Asian populations. Using clustering analysis, ten Asian populations were classified into three subgroups: East Asian, Southeast Asian, and South Asian subgroups. To evaluate the panel's capability in ancestry inference, a validation experiment was undertaken with 319 individuals from four geographically separated populations in China. Four Chinese populations were classified into different ancestry subgroups and 81.8% test individuals’ ancestry could be inferred correctly. Our result showed that development of high ancestry informative InDels panel based on CE platform is a potential for individual ancestry inference among intracontinental populations.     

基于超声射频信号的支持向量机双参量B线识别方法*

肺超声中的特殊征象B线对于临床诊断肺水肿等肺部疾病有重要意义,但诊断结果依赖于医生的主观判断,为了客观、自动地识别B线,提高诊断准确率,本文提出了一种基于超声回波射频信号的肺脏超声特殊征象B线识别方法。本文首先选取了射频信号的排列熵、信息熵、峰度、偏度、能量作为特征参数,利用独立样本t检验和单参数贝叶斯分类的方法检验超声射频数据中B线以及非B线所对应射频数据的各个参量的差异性以及各参数与B线识别的相关性。然后将不同的双参量组合输入非线性支持向量机（SVM）中进行分类,比较各个组合的分类效果。结果显示信息熵与排列熵参数组合基于射频信号的分类效果最好,分类灵敏度为90.521%,特异性为98.106%,准确率为96.328%,AUC等于0.95。在引入后处理算法后,B线识别效果有进一步提升,得到分类平均灵敏度为95.23%,平均特异性为97.22%,平均准确率为96.88%。研究结果表明基于射频数据的SVM双参量B线识别方法对辅助临床诊断具有重要价值,信息熵和排列熵的组合可以有效的对特殊征象B线进行高精度识别。     

Fe3O4@(SDS-HTlc)纳米复合物的制备及对甲基橙的吸附

采用离子交换法制备了具有核-壳结构的磁性十二烷基硫酸钠改性类水滑石Fe_3O_4@(SDSHTlc)纳米复合物,并利用透射电镜、粉末X-射线衍射、红外光谱、电感耦合等离子体发射光谱、元素分析等对其进行了表征。研究了Fe_3O_4@(SDS-HTlc)对甲基橙的吸附动力学和热力学。结果表明,Fe_3O_4@(SDSHTlc)对甲基橙有较好吸附效果,吸附动力学曲线符合准二级动力学方程;吸附等温线符合线性方程,吸附量随体系p H的增大和温度的升高均降低。在外部磁场下,30s内可从水溶液中分离出Fe_3O_4@(SDS-HTlc),这为去除水中疏水染料提供了简单的一步吸附处理方法。