PC/EAA共混体系在加工过程中的反应

采用差示扫描量热法(DSC)和核磁共振氢谱法(1H-NMR)研究了不同聚碳酸酯(PC)/乙烯-丙烯酸共聚物(EAA)共混体系在加工过程中的大分子反应,考察了有机金属催化剂二丁基锡DBTO)含量和反应时间对体系的影响.采用哈克(Haake)转矩流变仪的混合器作反应釜,索氏抽提器分离产物.结果表明,PC和EAA在加工中反应剧烈,在共混体系的界面原位形成接枝或交联的PC-EAA共聚物,随催化剂用量增大、反应时间延长易生成共交联的PC-EAA共聚物.但混合时间过长,体系的断链反应会加剧,生成产物不稳定.     

反相高效液相色谱法测定葛根素和大豆苷元

利用反相高效液相色谱法,配以二极管阵列检测器测定了心可舒片中的葛根素和大豆苷元,建立了一种心可舒片的质量控制方法。色谱柱为C18柱,流动相为乙腈和0．02mol／L磷酸二氢钾,柱温为25℃,流速为0．8mL／min,梯度洗脱,检测波长为250nm。葛根素和大豆苷元的平均回收率分别为97．3％和101．4％：RSD为0．6％和1．9％。     

Investigation of tensile deformation behavior of PC,ABS, and PC/ABS blends from low to high strain rates

This paper experimentally studies the tensile deformation behavior of polycarbonate (PC), acrylonitrile-butadiene-styrene (ABS), and PC/ABS blends (with the blending ratios of PC to ABS being 80:20, 60:40, 50:50, and 40:60) from low to high strain rates. Using the universal MTS-810 machine and the split Hopkinson tension bar (SHTB) testing system, the quasi-static and impact tension tests are carried out at the room temperature. The curves of the true stress and the true strain are obtained. The deformation behaviors of PC, ABS, and PC/ABS blends are characterized in detail. The linear relationship between the strain rate and the yielding stress is given.     

核磁共振法测定片剂中西咪替丁

建立以核磁共振技术测定片剂中西咪替丁含量的方法。采用Agilent DD2-500型核磁共振波谱仪,以氘代甲醇为溶剂、对苯二甲酸二甲酯为内标,测试温度25℃,弛豫时间为20 s,脉冲角为45°,采集时间为2 s,扫描次数为16次,采集核磁共振氢谱。该方法线性范围为0.1~5.0 mg/mL,相关系数r=0.999 8,测定结果的相对标准偏差为0.11%(n=6),平均加标回收率在100.03%~100.58%之间。用该方法测定不同厂家片剂中西咪替丁的含量,测定结果与药典方法相吻合。该方法简单快速、样品用量少,适用于西咪替丁的质量控制。     

Detection of diminished response to cold pressor test in smokers: Assessment using phase-contrast cine magnetic resonance imaging of the coronary sinus

Purpose

The purposes of this study were to evaluate the reproducibility for measuring the cold pressor test (CPT)-induced myocardial blood flow (MBF) alteration using phase-contrast (PC) cine MRI, and to determine if this approach could detect altered MBF response to CPT in smokers.

Materials and methods

After obtaining informed consent, ten healthy male non-smokers (mean age: 28 ± 5 years) and ten age-matched male smokers (smoking duration ≥ 5 years, mean age: 28 ± 3 years) were examined in this institutional review board approved study. Breath-hold PC cine MR images of the coronary sinus were obtained with a 3 T MR imager with 32 channel coils at rest and during a CPT performed after immersing one foot in ice water. MBF was calculated as coronary sinus flow divided by the left ventricular (LV) mass which was given as a total LV myocardial volume measured on cine MRI multiplied by the specific gravity (1.05 g/mL).

Results

In non-smokers, MBF was 0.86 ± 0.25 mL/min/g at rest, with a significant increase to 1.20 ± 0.36 mL/min/g seen during CPT (percentage change of MBF (?MBF (%)); 39.2% ± 14.4%, p < 0.001). Inter-study reproducibility for ?MBF (%) measurements by different MR technologist was good, as indicated by the intraclass correlation coefficient of 0.93 and reproducibility coefficient of 10.5%. There was no significant difference between smokers and non-smokers for resting MBF (0.85 ± 0.32 mL/min/g, p = 0.91). However, ?MBF (%) in smokers was significantly reduced (-4.0 ± 32.2% vs. 39.2 ± 14.4%, p = 0.011).

Conclusion

PC cine MRI can be used to reproducibly quantify MBF response to CPT and to detect impaired flow response in smokers. This MR approach may be useful for monitoring the sequential change of coronary blood flow in various potentially pathologic conditions and for investigating its relationship with cardiovascular risk.     

舰载导弹振动环境状态实时监测系统设计

为了全面监测舰上导弹贮存的振动环境,设计了对舰艇横摇、纵摇和升沉条件下的加速度信号实时监测系统;该系统采用一体化、模块化设计的思想,应用堆栈式结构总线PC104,提高了系统的便携性、可靠性;采用两种供电方式提高了系统适应性;文章详细阐述了硬件系统和软件系统的设计,并重点对数据采集存储和数据显示功能实现进行了论述;在1 000 Hz采样频率的实验条件下,采集数据准确可靠,精确度为99.75%,达到了系统设计的要求。     

不同应变率下PC,ABS和PC/ABS合金拉伸变形行为研究

采用实验方法研究了PC(聚碳酸酯)、ABS(丙烯腈-丁二烯-苯乙烯)和PC/ABS合金(PC与ABS共混率为80∶20,60∶40,50∶50和40∶60),在不同应变率条件下的拉伸变形行为.采用MTS-810万能材料试验机和分离式Hopkinson拉杆实验系统分别进行了PC,ABS和PC/ABS合金室温条件下的准静态和冲击拉伸实验,得到了上述材料在不同应变率条件下的真应力-真应变曲线;通过对其变形特点的详细分析,讨论了应变率和ABS含量对拉伸变形的影响,并且给出了10-4s-1～103s-1应变率范围内屈服应力与应变率的线性关系式.     

嵌入式PC／104主板在惯性导航系统中的应用

提出了用嵌入式PC／104主板为核心的新型结构对原有系统进行改造,在提高系统性能的同时确保与原有接口的兼容,使原有系统软件以最小的代价移植到新的系统中。详细叙述了改造中的关键技术及具体实现方法,并对系统的应用技术提出展望。     

Oxidative Dehydrogenation of Ethane to Ethylene over LiCl/MnOx/PC Catalysts

The catalytic stability of LiCl/MnO_x/PC catalyst have been investigated, the deactivation mechanism was discussed. The experimental results show that ethane conversion decreases and ethylene selectivity keeps about 90% as reaction time increases. The main deactivation reasons of LiCl/MnO_x/PC catalyst for oxidative dehydrogenation of ethane (ODHE) to ethylene are the transition of active species Mn₂O₃ to MnO species and the loss of active component Cl in catalyst. Instead of ethane with FCC tailed‐gas, the stability of LiCl/MnO_x/PC catalyst has been largely improved.     

Parallelization of multireference perturbation calculations with GAMESS

The quasi‐degenerate multireference second‐order perturbation theory (MRMP2) routines in the GAMESS suite of program codes have been parallelized using a distributed data interface (DDI). Two typical kinds of molecules were chosen for examination of parallelization speedup using one to eight PCs gathered as a cluster and connected by Fast Ethernet. The first example, in which total energies of several low‐lying electronic states have been obtained for niobium monohydride, give parallelization speedup of 7.15 when eight PCs were used as a cluster. The second example is the ground‐state total energy for a medium sized molecule, 4a,4b,8a,9a‐tetrahydro‐pyridino[1′,2′‐4,3]imidazo‐lidino[1,5‐a]pyridine. When distributed memory is employed, the parallelization speedup improves to 6.84 for the MRMP2 calculations when an eight‐PC cluster is used. These results demonstrate that our efforts to achieve the parallelization of MRMP2 routines have been successful. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1243–1251, 2001