Linear Unsaturated Polyamides: Nylons 6 u18 and 18 u18

Summary: Linear unsaturated nylons 6 u18 and 18 u18 have been made containing a double bond in the center of the diacid segment with potential for additional functionalization. Solution state NMR showed the presence of a small portion of cis amide units. Solid state NMR verified the presence of the double bond in the bulk, and that the polyamides were present in the α‐crystalline form. Thermal stability was comparable to linear saturated nylons, and the melting and crystallization temperatures of the unsaturated nylons were lower compared to the saturated analogs.

DSC heating and cooling thermograms for nylons 6 u18 and 18 u18.     

Drawn gelatin films with improved mechanical properties

Chain anisotropic distribution in gelatin films has been obtained by uniaxial stretching at constant relative humidity, followed by air drying and successive cross-linking with glutaraldehyde. The drawn samples have been characterized by mechanical tests, differential scanning calorimetry and scanning electron microscopy. The Young’s modulus, E, and the stress at break, σ_b, increase linearly with the draw ratio and reach values which are about five times those characteristic of undrawn samples. Furthermore, on stretching the alignment of the gelatin strands along the direction of deformation increases while the thickness of the layers decreases significantly. The renaturation level, that is the fraction of gelatin in a collagen-like structure, has been calculated as the ratio between the melting enthalpy of gelatin samples and that of tendon collagen. The results indicate that the improvement of mechanical properties achieved by drawn gelatin is closely related to the renaturation level. The experimental approach utilized to induce segmental orientation in gelatin films, allows to obtain anisotropic materials with improved mechanical properties in the direction of deformation, and can be usefully applied in the preparation of biomaterials.     

In Situ Thermal Denaturation of Proteins in Dunning AT-1 Prostate Cancer Cells: Implication for Hyperthermic Cell Injury

The in situ thermal protein denaturation and its correlation with direct hyperthermic cell injury in Dunning AT-1 prostate tumor cells were investigated in this study. The in situ thermal protein denaturation was studied using both Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The FTIR spectra at different temperatures show changes in protein secondary structure (from alpha helix to extended beta sheet) during in situ thermal protein denaturation within AT-1 cells. Calorimetric studies using DSC show that endothermic heat release is associated with the in situ thermal protein denaturation. Furthermore, both the secondary structure changes detected by FTIR and the calorimetric changes detected by DSC were quantified and the kinetics of the overall in situ thermal protein denaturation was derived under different heating conditions. The onset temperature where the overall in situ thermal protein denaturation is first detectable was found to be scanning rate dependent (approximately 41 degrees C at 2 degrees C min(-1) and approximately 44 degrees C at 5 degrees C min(-1)). The kinetics of the overall in situ thermal protein denaturation was derived from both DSC and FTIR measurements and was fit using kinetic and statistical models. The kinetic data determined by FTIR and DSC under the same heating conditions match well with each other. The activation energy of the overall in situ thermal protein denaturation is found to be strongly dependent on the temperature range considered (the activation energy ranges from approximately 110 kJ mol(-1) between 44 and 90 degrees C to approximately 750 kJ mol(-1) between 44 and 50 degrees C). However, its dependence on heating rate is negligible. Several denaturation peaks, including a dominant one between approximately 62 and 65 degrees C, are identifiable from both the DSC and the FTIR results. To investigate directly the relationship between thermally induced cell injury and the in situ thermal protein denaturation, both acute (propidium iodide dye exclusion, assessed 3-h postthermal treatment) and chronic (clonogenics, assessed 7-day postthermal treatment) cell injury were quantified using AT-1 cells prepared under the same conditions as for the DSC protein studies. Comparisons of the results from the cell injury studies and the DSC protein denaturation studies show that the overall in situ thermal protein denaturation correlates well with both the acute and the chronic cell injury, which suggests that overall in situ thermal protein denaturation is an important mechanism of direct hyperthermic cell injury in AT-1 cells at the macromolecular level.     

Quantitative Correlation between Steric Defects and Thermal Behavior in Highly Syndiotactic Polystyrene: A Study Based on DSC and 13C NMR Spectroscopy

Several syndiotactic polystyrene (sPS) samples have been synthesized by using different catalytic systems. Their stereochemistry has been determined by ¹³C NMR spectra in both the aliphatic CH₂ and aromatic C₁ resonance regions. The observed peaks have been unambiguously assigned to specific hexads and heptads, respectively, and their intensities have been used to draw the percent of defects (meso dyads) in the polymer chains. On the hypothesis that chain defects are at the origin of chain folding and thus determine the thickness of crystalline lamellae, we performed differential scanning calorimetry (DSC) analysis on the same samples, and their thermal parameters were measured. A model was developed to determine the amount of steric defects from the DSC melting‐peak profiles, and the results obtained were compared with the NMR results. A satisfactory agreement was found (correlation factor 0.96) in the explored range of defect concentrations (up to 2.5% of meso dyads). The possible influence of the extraction procedure of the amorphous fraction was found to be negligible. Thus, information on stereochemistry can be obtained from DSC experiments starting from as‐prepared (not extracted) samples.

     

CORDIC算法在B超数字扫描变换器中的应用

数字扫描变换器在B型超声诊断仪的应用，能使现代实时B型超声诊断仪实现一些新的诸如图像冻结、多帧贮存、数据测量计算和TV显示等功能。在设计B型超声诊断仪中数字扫描变化器的过程中，直角坐标到极坐标变换是一个关键的技术，本研究论述了应用在数字扫描变化器中的一种新的算法——CORDIC算法，对该算法的原理进行了简介，将CORDIC算法应用到直角——极坐标变换中，并进行了算法修正和公式计算。根据其具体的应用对该算法进行了优化，并给出了算法的硬件实现结构。最后，对算法进行了软件仿真，并给出了结果分析。     

马鞭草提取液对体外培养人早孕蜕膜细胞的影响

目的：探讨马鞭草及米非司酮抗早孕的细胞学作用机理，初步确定马鞭草抗生育的有效部位。方法：实验选用早孕人工流产蜕膜组织进行体外培养，观察马鞭草提取液A、B、C、D及米非司酮对蜕膜细胞形态，增殖，细胞凋亡及细胞周期动力学的影响。结果：高于12．5mg／na的A、B、C及80ug／na的米非司同酮均可明显改变蜕膜基质细胞(DSC)的形态，并对其增殖产生显著的抑制作用。25mg／ml的A、B、C及米非司酮(80μg／na)均促进细胞凋亡，对细胞周期无明显影响。D均无明显作用。结论：马鞭草、米非司酮均有抗早孕作用。抑制蜕膜细胞生长，促进凋亡为其抗早孕机制之一。     

差示扫描量热法测定7种药物纯度

目的用差示扫描量热(DSC)法测定药物纯度及探讨影响测定结果的因素。方法用DSC法测定吲哚美辛等7种不同类别药物的纯度,并与《中国药典》规定方法结果进行对照。结果DSC法测定药物纯度的准确性好;试药的用量、纯度、升温速度对测定结果产生影响。结论本法测定高纯度药物简便、结果准确。     

热熔挤出技术提高安宫牛黄固体分散体中黄芩苷溶出速率的研究

目的研究热熔挤出技术制备的固体分散体提高安宫牛黄固体分散体中黄芩苷的溶出速率。方法分别以泊洛沙姆-188、聚乙二醇6000为亲水性载体,与处方中栀子、黄芩、黄连、郁金提取物粉末按1∶4比例混合均匀,采用热熔挤出技术制备固体分散体。比较两者差示扫描量热图谱和累积溶出曲线。结果溶出结果显示,两种固体分散体中难溶性成分黄芩苷20 min累积溶出度均达到90%以上,溶出速率显著优于物理混合物。结论 热熔挤出技术制备的固体分散体中溶解度差、溶出速率较慢成分累积溶出速率显著提高。     

阿魏酸壳聚糖缓释微球的工艺优化及释药机制研究

 目的 优化离子凝聚法制备阿魏酸壳聚糖微球的工艺,并研究其缓释机制。方法 运用Doehlert设计、多重相应的渴求函数优化法对阿魏酸壳聚糖微球的工艺进行优化。通过显微镜观察和差示热分析研究微球结构和药物状态,探讨释药机制。结果 投药量和交联液pH值对包封率有很大影响。在优化条件下,阿魏酸壳聚糖微球的平均包封率为73.77％,平均载药量为8.08％,药物释放符合Higuchi方程和Weibull分布。药物以微晶状态分布于微球的骨架结构中,未与壳聚糖发生作用。结论 离子凝聚法制备的壳聚糖微球的缓释行为与其网状骨架结构相关。     

差示扫描量热法测定丁氧普鲁卡因的纯度

应用DSC测定丁氧普鲁卡因的纯度,操作迅速,精密度高,适用于不同批号产品间进行质量对比。