Post-contrast 3D T1-weighted TSE MR sequences (SPACE,CUBE, VISTA/BRAINVIEW,isoFSE, 3D MVOX): Technical aspects and clinical applications

Post-contrast three-dimensional T1-weighted imaging of the brain is widely used for a broad range of vascular, inflammatory or tumoral diseases. The variable flip angle 3D TSE sequence is now available from several manufacturers (CUBE, General Electric; SPACE, Siemens; VISTA/BRAINVIEW, Philips; isoFSE, Itachi; 3D MVOX, Canon). Compared to gradient-echo (GRE) techniques, 3D TSE offers the advantages of useful image contrasts and reduction of artifacts from static field inhomogeneity. However, the respective role of 3D TSE and GRE MR sequences remains to be elucidated, particularly in the setting of post-contrast imaging. The purpose of this review was (1) to describe the technical aspects of 3D TSE sequences, (2) to illustrate the main clinical applications of the post-contrast 3D T1-w TSE sequence through clinical cases, (3) to discuss the respective role of post-contrast 3D TSE and GRE imaging in the field of neuroimaging.     

重酒石酸长春瑞滨长循环脂质体的制备与表征

目的采用pH梯度法制备重酒石酸长春瑞滨长循环脂质体并进行表征。方法以粒径为指标,考察水化温度和挤出次数对空白脂质体粒径的影响;以粒径及包封率为指标,考察孵化温度和孵化时间对载药脂质体粒径和包封率的影响。并采用Malvern粒度仪测定脂质体的粒径分布、多分散系数及Zeta电位,透射电镜考察其形态,并考察脂质体稳定性。结果重酒石酸长春瑞滨长循环脂质体粒径（96.4±27.2） nm,多分散系数（0.162±0.042）,Zeta电位（－26.7±3.5） mV;透射电镜显示脂质体粒径均一,成单层膜球状分布;长期稳定性研究显示,脂质体在5 ℃条件下放置3个月稳定。结论pH梯度法可以用于重酒石酸长春瑞滨长循环脂质体的制备。     

HPLC法测定奥卡西平及其制剂中有关物质

目的:建立使用C₁₈色谱柱同时测定奥卡西平及其制剂中8个杂质的高效液相色谱法。方法:采用ACE Excel C₁₈(4.6 mm×150 mm, 3μm)色谱柱,流速1.0 mL·min^-1,以6.8 g·L^-1磷酸二氢钾溶液(每1 000 mL加三乙胺2 mL,用磷酸调pH 6.0)为流动相A,乙腈-甲醇(11∶8)为流动相B,梯度洗脱,检测波长240 nm,柱温45℃。结果:奥卡西平与8个杂质分离度良好,奥卡西平和卡马西平分别在0.05～4.0μg·mL^-1和0.08～40μg·mL^-1浓度范围内呈现良好线性(r≥0.999 9),奥卡西平和卡马西平的定量限分别为1.03、0.65 ng,检测限分别为0.34、0.33 ng。共测定奥卡西平原料2个企业5批样品、奥卡西平片2个企业6批样品,其中1批原料检出杂质E,含量为0.004%;3批片剂检出卡马西平,含量分别为0.008%、0.005%、0.006%;1批片剂检出杂质C和杂质D,含量为0.006%、...     

The elution and breakdown behavior of constituents from various light-cured composites

Objectives

Constituents of dental composites can be released from dental fillings after polymerization. The aim of this study was to examine the time-related elution and breakdown of separable constituents of polymerized composites using deuterated solvents.

Method

Elution and breakdown of constituents were investigated with deuterated solvents methanol and water by gas chromatography/mass spectrometry of following composites for 180 days: Filtek™ Supreme XT, Filtek™ Supreme XT Flow, Tetric Ceram^®, Tetric Flow^®, Grandio^®, Grandio^® Flow.

Results

Within 180 days no compounds were formed as the products of breakdown. 19 compounds were identified as elution products: Bis-EMA, TEGDMA, DDDMA, EGDMA, MAA, BPA, CQ, HQME, DMABEE, CSA, BL, TEG, BHT, TINP, TPP, TPSB, DEDHTP, DCHP, ß-PHEA.The highest concentration of Bis-EMA was measured for Tetric Flow^® in deuterated methanol on day 90 at 36.993 mmol/l and in deuterated water also on day 90 at 0.031 mmol/l.The highest TEGDMA concentrations were measured for Grandio^® Flow in deuterated methanol on day 60 at 1.322 mmol/l and for Filtek™ Supreme XT Flow in deuterated water on day 3 at 0.689 mmol/l. The highest BPA concentration was measured for Tetric Flow^® in deuterated methanol on day 90 at 1.469 mmol/l. The highest BPA concentration was measured for Grandio^® in deuterated water on day 180 at 0.007 mmol/l.Significance Examination of time-related elution indicates that various elution products (e.g. Bis-EMA, BPA) were only released in small quantities during the first 90 days, but in high quantities between day 90 and day 180.     

Mathematical Modeling of Crystallization Elution Fractionation of Ethylene/1‐Octene Copolymers

Crystallization elution fractionation (CEF) is a relatively new polyolefin characterization technique used to estimate the chemical composition distribution (CCD) of semicrystalline copolymers. CEF is developed to enhance the resolution and reduce the analysis time of temperature rising elution fractionation (TREF) by separating polymer samples in both the crystallization and elution steps. A model based on the concept of population balance, crystallization/dissolution kinetics, and dispersion model is developed to understand the CEF fractionation mechanisms. The proposed CEF model is found to describe well the experimental CEF profiles of a series of ethylene/1‐octene copolymers with different comonomer contents.

     

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.

     

HPLC-DAD法测定“武当三号金银花”不同部位中芦丁和木犀草苷的含量

目的：建立HPLC－DAD法测定“武当三号金银花”不同部位中芦丁和木犀草苷的含量。方法采用Fortis Xi Phenyl柱（250 mm ×4．6 mm,5μm）;流动相为乙腈（A）—0．5％冰醋酸溶液（B）进行线性梯度洗脱;检测波长为354 nm;柱温：30℃。结果芦丁和木犀草苷在各自测定的范围内均呈良好的线性关系（r≥0．9994）,平均回收率分别为99．4％、99．3％。结论该法操作简单,灵敏度高,重现性好,为控制“武当三号金银花”不同部位芦丁和木犀草苷的质量提供了一种可靠的方法。