On the Homogeneity of Metallocene Ethylene–Propylene Copolymers as Investigated by Multiple Fractionation Techniques

The chemical heterogeneity of ethylene–propylene copolymers by multiple fractionation techniques is addressed. Three metallocene copolymer samples with different ethylene contents, ranging from 30 to 50 mol% are analyzed using bulk methods to confirm their molecular heterogeneity. In a second step, the samples are fractionated by temperature rising elution fractionation (TREF) to obtain fractions at 30, 60, 90, and 130 °C. These fractions are subsequently analyzed regarding their thermal and molecular properties. Differential scanning calorimetry, crystallization analysis fractionation, and high‐temperature high performance liquid chromatography (HT‐HPLC) results reveal that the TREF fractions collected at 130 °C are mainly due to polypropylene homopolymer, which is rather unexpected considering the high ethylene contents of the bulk samples. Most importantly, HT‐HPLC reveals a remarkably high chemical heterogeneity of the fractions and thus the bulk samples. Solution ¹³C NMR provides the comonomer contents and sequence distributions of the fractions. These indicate that the same TREF fractions from different samples have distinctively different chemical compositions.

     

辣椒碱-羟丙基-β-环糊精包合物制备鉴定及 热力学稳定性研究

目的:制备及鉴定辣椒碱-HP-β-CD包合物,并考察辣椒碱和HP-β-CD之间的包合摩尔比及包合过程的热力学常数.方法:采用饱和水溶液法制备辣椒碱-HP-β-CD包合物,以差示扫描量热法(DSC)、X射线衍射法(XRD)和红外光谱法(IR)对包合物进行鉴定,通过表观溶解度法考察包合物中主客分子之间的包合摩尔比及包合过程的热力学常数.结果:25,35,45℃下辣椒碱和HP-β-CD能形成1:1摩尔比包合物,相溶解度图呈A_L型.结论:辣椒碱-羟丙基-β-环糊精包合物能显著增大药物的溶解度.     

镍钛锉模拟根管预备后相变行为分析

目的：比较镍钛锉在模拟根管预备后相变行为的变化.方法：（1）选取30#/0.06锥度的TF和K3镍钛锉,制备样本（n=5）,使用差示扫描量热仪测量相变行为.（2）以上两种镍钛锉,每套预备10个树脂S形弯曲模拟根管,预备过程模拟临床使用条件.收集其中30#/.06锥度的器械,制备样本（n=5）,测量相变行为.分析模拟根管预备后,两种器械相变行为的变化.使用Student＇s t-test检验.结果：两种锉的相变温度和相变热焓均显著下降（P＜0.05）.结论：镍钛锉模拟根管预备后,呈现显著的工作硬化现象,是疲劳折断的微观组织基础.     

The utility of cerebrospinal fluid for the molecular diagnosis of toxoplasmic encephalitis

The aim of this study was to assess the efficacy of nested polymerase chain reaction (PCR) and the loop-mediated isothermal amplification (LAMP) assay, which were developed to detect and identify toxoplasma parasites in human cerebrospinal fluid (CSF). Nested PCR was performed using primers generated by Dr. L.D. Sibley to target the 18S rDNA instead of the conventionally used primers which target the B1 gene. We also designed Toxoplasma gondii–specific LAMP primers targeting both genes. In vitro detection sensitivity was evaluated using 10-fold serially diluted genomic DNA purified from RH tachyzoites, and clinical sensitivity and specificity were evaluated using clinical CSF samples from 16 patients with toxoplasmic encephalitis (TE) and from 12 patients with other diseases. The 18S rDNA nested PCR showed the highest detection sensitivity limit with a minimum of 1.0 × 10⁻⁸ ng/μL. However, sensitivity and specificity of nested PCR with clinical specimens were 50% and 100%, respectively. The sensitivity of molecular diagnosis of TE is not sufficient; therefore, patients clinically suspected of having TE should be treated promptly. Our molecular diagnostic tool would restrictively facilitate a definitive diagnosis of TE at an early stage in approximately 50% of patients.     

Comparison of high-dose and low-dose corticosteroid therapy for refractory Mycoplasma pneumoniae pneumonia in children

Background

Mycoplasma pneumoniae pneumonia (MPP) is generally a self-limiting disease, but it may become refractory. It is thought that refractory MPP is linked to the excessive immunologic responses of the host. Consequently, the use of adjunctive systemic corticosteroids may have beneficial effects. In this study, we compared the effects of high- and low-dose corticosteroid therapy in a pediatric population with refractory MPP.

霍乱弧菌CT毒素环介导等温扩增技术快速检测方法的建立

目的将一种新颖的核酸扩增技术——环介导等温扩增技术(LAMP)应用于霍乱弧菌毒素基因ctxA的快速检测。方法针对霍乱弧菌毒素基因ctxA设计6条特异性引物(两条内引物、两条外引物和两条环引物)进行LAMP扩增,对扩增反应进行优化。并考核方法的敏感性和特异性。结果最佳反应时间为60 min,反应温度为65℃。对8种相关肠道细菌进行LAMP扩增,仅含毒素基因ctxA的霍乱弧菌得到阳性扩增结果,证明引物具有很高的特异性。霍乱弧菌基因组DNA和纯培养物的检测灵敏度分别约为68 fg和42 cfu/ml。对模拟样品进行直接检测,检测限为72 cfu/g。结论该方法检测霍乱弧菌毒素基因ctxA特异性强、灵敏度高,并且操作简便、检测成本低,1 h即可完成,适合基层检验部门使用。     

快速检测单核细胞增生李斯特菌LAMP方法的建立

目的:建立一种检测单核细胞增生李斯特菌核酸的快速、特异的环介导等温扩增(Loop-mediated isothermalamplification,LAMP)方法。方法:针对单核细胞增生李斯特菌的李斯特菌溶血素hlyA基因设计4条LAMP引物,在水浴箱内65℃保温约60 min,完成对单核细胞增生李斯特菌的扩增,扩增产物经肉眼、SYBR Green I染色和电泳鉴定。利用LAMP和PCR方法同时检测1株单核细胞增生李斯特菌和10株非单核细胞增生李斯特菌(对照组)来验证LAMP方法的特异性。用LAMP和PCR方法分别检测一系列稀释后的单核细胞增生李斯特菌菌液,比较两者的敏感性。结果:经肉眼、加染料和电泳均能观察到1株单核细胞增生李斯特菌LAMP扩增阳性反应,10株非单核细胞增生李斯特菌没有出现LAMP扩增。LAMP敏感度比PCR高,LAMP检测单核细胞增生李斯特菌的检测下限为3 cfu/ml,PCR检测下限>300 cfu/ml。LAMP检测速度比PCR更快,只需要60 min。结论:建立了一种检测单核细胞增生李斯特菌的快速、特异的LAMP方法。     

LAMP技术检测弓形虫感染方法的建立

目的建立一种快速、简便的检测弓形虫感染的环介导等温扩增方法(LAMP)。方法根据弓形虫RH株SAG1基因序列合成2对特异性LAMP引物,优化扩增体系与参数。通过与常规PCR方法的比较,评估优化后的LAMP反应的特异性和灵敏性。利用建立的LAMP初步检测人工感染弓形虫4 d后白兔与大鼠的肌肉组织。结果 LAMP法检测弓形虫基因组DNA的灵敏度是传统PCR方法的100倍。LAMP法检测与其他常见寄生原虫、寄生虫无非特异性阳性结果。LAMP法检测人工接种动物的肌肉组织,阳性率达到100%,对照组为0,差异有统计学意义(P0.01)。结论 LAMP法检测弓形虫感染快速简便、敏感性高、设备要求低,具有较好的应用前景。     

新型催化剂C302-2作用下的三相床甲醇合成过程Ⅲ.本征反应动力学

在等温积分反应器中，压力2．5～5．6MPa，温度210～255℃，空速6000～20000h^-1的实验条件下，对西南化工研究院研制的新型低温低压甲醇合成催化剂C302—2的CO、CO2加氢合成甲醇的本征动力学进行了研究。用改进的单纯形法和改进的高斯-牛顿法相结合对所采用的Langmuir—Hinshelwood型动力学模型进行参数估值，得到本征动力学方程。残差分析和统计检验结果表明，得到的本征动力学模型是适定的，可良好地适合于反应条件。实验结果可以为采用细颗粒催化剂的三相淤浆床甲醇合成反应器设计提供本征动力学数据。