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21.
Flow-mode static and dynamic laser light scattering (SLS/DLS) studies of polymers, including polystyrene, polyethylene, polypropylene and poly(dimethylsiloxane) (PDMS), in 1,2,4-trichlorobenzene (TCB) at 150 °C were performed on a high temperature gel permeation chromatography (GPC) coupled with a SLS/DLS detector. Both absolute molecular weight (M) and molecular sizes (radius of gyration, Rg and hydrodynamic radius, Rh) of polymers eluting from the GPC columns were obtained simultaneously. The conformation of different polymers in TCB at 150 °C were discussed according to the scaling relationships between Rg, Rh and M and the ρ-ratio (ρ=Rg/Rh). Flow-mode DLS results of PDMS were verified by batch-mode DLS study of the same sample. The presented technique was proved to be a convenient and quick method to study the shape and conformation of polymers in solution at high temperature. However, the flow-mode DLS was only applicable for high molecular weight polymers with a higher refractive index increment such as PDMS. 相似文献
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低光照和抗晕CCD的设计和制作 总被引:2,自引:1,他引:1
针对帧转移可见光CCD低光照响应、抗电晕能力和动态范围,较详细讨论了CCD光响应灵敏度、动态范围和抗电晕的设计与计算。设计的具有抗晕功能CCD,采用2μm工艺制作,达到了设计技术指标要求,满足了工程应用需求。 相似文献
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Shizuo Arichi Noriyuki Sakamoto Shozo Himuro Mayumi Miki Masafumi Yoshida 《Polymer》1985,26(8):1175-1180
In order to obtain the additional data concerning the unperturbed dimension of poly-4-substituted styrene, light scattering measurements are performed on the twenty-two fractions with molecular weight of (0.91–352)·104 of poly(4-acetoxystyrene) in dioxan at 25°C, from which the molecular weight obtained was found easily to be evaluated with the gel permeation chromatography using THF. Phase separation experiments for this polymer indicate that the theta state is attained in isopropyl acetate at 19.7°C and butyl acetate at 26.8°C. By making viscosity measurements at that state, the value of KΘ is directly evaluated as 5.4·10?4 dl g?1. The limiting viscosity number is also obtained in good solvents, THF and dioxan, at 25°C and constants of the Mark-Houwink-Sakurada equation in each solvent are determined. Further, approximately the same KΘ as above is obtained from these data with the Stockmayer-Fixman plot. The calculated value of steric factor, 2.37, on this polymer may be plausible, compared with those of polyvinylaromatic derivatives. 相似文献
27.
Critical-point drying and freeze drying were compared both quantitatively and qualitatively as preparative procedures for scanning electron microscopy. Isolated hepatocytes were used as model cells. Nomarski differential interference contrast microscopy was used for light microscopic measurements of the hepatocytes in the unfixed, the glutaraldehyde fixed, the glutaraldehyde + OsO4 fixed, the critical-point dried and the freeze dried states. Critical-point dried hepatocytes were found to shrink to 38% of glutaraldehyde + OsO4 fixed volume, whereas optimal freeze dried hepatocytes (frozen in water saturated with chloroform and freeze dried at 183 K for 84 h) were found to shrink to 51% of glutaraldehyde + OsO4 fixed volume. Transmission and scanning electron micrographs of the critical-point dried cells showed well-preserved ultrastructure and surface structure. Micrographs of the freeze dried cells showed ultrastructure destroyed by internal ice crystals and surface structure destroyed by external ice crystals. Double-fixed isolated hepatocytes were shown to swell during storage in buffer and to shrink during storage after critical-point drying. For low magnification scanning electron microscopy (up to about 3000 times) both critical-point drying and freeze drying can be used. However, for high magnification scanning electron microscopy, critical-point drying is superior to freeze drying. 相似文献
28.
介绍了以菱锌矿为原料生产轻质氧化锌的方法,论述了反应酸浓度,煅烧温度,溶液PH值对实验的影响,并对生产工艺条件进行了研究。其工艺流程是将粉碎后的菱锌矿进行循环酸浸,净化后再直接和碳化母液反应,经沉降后再煅烧分解为轻质氧化锌,产品质量符合国家标准,视比容大,活性强,成本低,经济效益显著。 相似文献
29.
In this paper we suggest a new statistical method of correcting the results of hot-line experiments for the effects of background sources and we use the new method to reassess the adequacy of three probability distributions proposed in the literature for image spread from line sources. The data are from sources labelled with 125I in semi-thin resin sections 0·4-0·8 μm in thickness. The new method reveals that two of the models describe the empirical distributions more closely than earlier analysis had suggested, and it confirms an increasing relationship between half distance of image spread and the thickness of the source. However, it also confirms that considerable ‘inter hot-line’ experimental variation remains, even after background correction. This suggests that multiple experiments are needed to produce reliable estimates of half distance. 相似文献
30.
首先介绍了光幕测量高度的原理 ,给出了高度测量光幕的一种实现方法 ,分析了由该方法设计的系统结构和主要性能。从而彻底解决了相邻通路间的干扰 ,提高了测量精度。 相似文献