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Search Results: 1 - 10 of 25593 matches for " CHENG Rongshi "
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SOLVATION EFFECT OF POLY(VINYL ALCOHOL) IN AQUEOUS SOLUTION via REPEATING FREEZING-THAWING CYCLES
聚乙烯醇水溶液反复冷冻过程中的溶剂化效应

LI Wenbo,XUE Feng,CHENG Rongshi,
李文波
,薛锋,程镕时

高分子学报 , 2008,
Abstract: The article is devoted to the study on solvation effect of poly(vinyl alcohol) (PVA) in aqueous solution via repeating freezing-thawing cycles using differential scanning calorimetry (DSC) technique.A straightforward method for determination of the hydration number,a parameter characterizing the extent of solvation effect,of polymers in aqueous solutions based on ice-melting technique of DSC is proposed.The simple yet precise method has been applied to determine the hydration number of PVA in aqueous solution covering a wide range of concentrations,from 0.005 to 0.3 g/g.The results indicate that the melting enthalpies and hydration numbers of PVA aqueous solutions differentiate greatly at different concentration regimes,i.e.dilute,semi-dilute,concentrated concentration region,which is attributed to the differences of intra-and inter-chain entanglements in their influence on the participation of solvent molecules in the solvation-desolvation process.The inter-chain entanglement points increase with increasing freezing cycles,which leads to part of solvent molecules entrapped in loops produced by inter-chain contact and forming a portion of polymer chain.Apparent change of solvation effect is a complex influence of desolvation and entrapped solvents.
Theoretical Analysis of the Relationship Between Solvated Polymer Peak and Solvent Peak in Chromatograms from Size-Exclusion Chromatography with Mixed Eluents
混合溶剂作淋洗剂的体积排除色谱谱图中溶剂化高分子峰和溶剂峰之间内在关系的理论分析

WANG Qingguo,LI Xiaowen,CHENG Rongshi,
王庆国
,李小文,程镕时

高分子学报 , 2008,
Abstract: 根据体积排除色谱(SEC)研究高分子溶质优先溶剂化的基本原理,证明在SEC色谱图中被束缚溶剂产生的面积与自由溶剂产生的面积大小相等方向相反,在研究优先溶剂化时从高分子峰入手和从自由溶剂峰入手在理论上具有等价性.分析表明,通过对溶剂化高分子峰的研究,还可以得到另一个重要物理参数——恒化学位时高分子溶液的折光指数增量.
Marinopyrrole Derivatives as Potential Antibiotic Agents against Methicillin-Resistant Staphylococcus aureus (II)
Chunwei Cheng,Yan Liu,Hao Song,Lili Pan,Jerry Li,Yong Qin,Rongshi Li
Marine Drugs , 2013, DOI: 10.3390/md11082927
Abstract: Methicillin-resistant Staphylococcus aureus (MRSA) continues to be a major problem, causing severe and intractable infections worldwide. MRSA is resistant to all beta-lactam antibiotics, and alternative treatments are limited. A very limited number of new antibiotics have been discovered over the last half-century, novel agents for the treatment of MRSA infections are urgently needed. Marinopyrrole A was reported to show antibiotic activity against MRSA in 2008. After we reported the first total synthesis of (±)-marinopyrrole A, we designed and synthesized a series of marinopyrrole derivatives. Our structure activity relationship (SAR) studies of these novel derivatives against a panel of Gram-positive pathogens in antibacterial assays have revealed that a para-trifluoromethyl analog ( 33) of marinopyrrole A is ≥63-, 8-, and 4-fold more potent than vancomycin against methicillin-resistant Staphylococcus epidermidis (MRSE), methicillin-susceptible Staphylococcus aureus (MSSA) and MRSA, respectively. The results provide valuable information in the search for new-generation antibiotics.
STUDY ON THE DEGREE OF CHAIN OVERLAP OF POLYMER IN SOLUTIONS
高分子在溶液中的链叠加度

AN Quanfu,QIAN Jinwen,WANG Meng,CHENG Rongshi,
安全福
,钱锦文,王猛,程镕时

高分子学报 , 2009,
Abstract: The radius of gyration is a good parameter for characterizing the dimensional distribution of a given polymer chain at perturbation conditions.But it is hard to give information about stack structures of polymer chains both in bulk and solution.It is highly desirable to establish the relationship between the micro-structure parameter and macroscopical properties of polymers in bulk or in solution.The degree of chain overlap is a good parameter for that,which has been defined and applied very well in bulk st...
ABSOLUTE QUANTIFICATION FOR SIZE EXCLUSION CHROMATOGRAPHY WITH DIFFERENTIAL REFRACTOMETRY AND LIGHT SCATTERING DUAL DETECTORS
示差折光和光散射双检测体积排除色谱的绝对定量化

LIU Chengguo,XIE Hongfeng,ZHENG Yun,CHENG Rongshi,
刘承果
,谢鸿峰,郑云,程镕时

高分子学报 , 2008,
Abstract: 讨论了示差折光和光散射联用双检测体积排除色谱的绝对定量化的原理,强调指出了试样注入量在数据处理中的重要作用.测量注入试样的这两种检测器的检测常数,可以同时得到试样的折光指数增量和重均分子量的绝对值.这一方法除了适用于各种均聚物外,还可以应用于高分子混合物的分析.此时,如将混合物看作为单一溶质,从所得折光指数增量和重均分子量,可对它们的组成作出定量分析,还可以判断共混物两个组分之间有无分子缔合等现象的产生.这一方法应用于聚甲基丙烯酸甲酯,聚苯乙烯(PMMA/PS)混合物的溶液,指明在四氢呋喃中两者产生缔合而形成了复合物.
Consideration of Castability and Formability for New Magnesium Alloys  [PDF]
Rongshi Chen, Songmao Liang, Di Wu, Enhou Han
Open Journal of Metal (OJMetal) , 2012, DOI: 10.4236/ojmetal.2012.21002
Abstract: A comprehensive consideration based on castability or plastic formability, as well as mechanical properties for development of either cast magnesium alloys or wrought magnesium alloys is a very important issue. To develop new magnesium alloy sheets with high formability at room temperature, the microstructure, texture, ductility and anisotropy of rolled Mg-Zn-Gd alloy sheets were investigated. The sheets exhibit an excellent ultimate elongation of nearly 50% and an uniform elongation greater than 30% with a very low planar anisotropy. The new sheet has a random basal texture and the basal pole is tilted by maximum 40° from the normal direction towards the transverse direction. The majority of grains in the tilted texture have an orientation favorable for both basal slip and tensile twining because of their high Schmid factor. The low planar anisotropy, the large uniform elongations and the high strain hardening rate observed in the Mg-Zn-Gd sheets result in excellent room temperature formability, the Erichsen values reach ~8, well comparable with the conventional aluminum alloys sheets at room temperature. The solidification pathways and phase equilibria of Mg-Al-Ca alloys have been profoundly investigated by using thermal analysis and thermodynamic calculations. The relationship between hot tearing tendency and alloy compositions were discussed in terms of strength of the mushy zone, solidification pathways and feeding mechanisms, et al. Thixoforming refers to as that metal components are formed in their semi-solid state. Criteria for thixoforming are summarized and then the thixoformability of Mg-Al-Ca based alloys (AC alloys) are evaluated using the thermodynamic calculations based on the consideration of metallurgical parameters.
Effect of Unsaturated Hydroxyl-Fatty Acid Modified Nano-CaCO3 on the Morphology and Rheology of PP
羟基不饱和脂肪酸改性纳米碳酸钙对聚丙烯微观形态和流变性能的影响

GU Ju,XIONG Qiang,JIA Demin,LUO Yuanfang,CHENG Rongshi,
古菊
,熊强,贾德民,罗远芳,程镕时

高分子学报 , 2008,
Abstract: 采用羟基不饱和脂肪酸,通过固相法对硬脂酸改性的工业纳米碳酸钙CCR进行表面改性制备了R-CCR,红外光谱(FTIR)显示改性剂已结合在碳酸钙表面.通过熔融共混法制备了聚丙烯(PP)/乙丙橡胶(EPDM)/纳米碳酸钙二元和三元复合材料.并利用扫描电子显微镜(SEM)和透射电子显微镜(TEM)观察复合材料的微观形态,发现R-CCR的加入,使PP复合材料的拉伸断面出现明显的拉丝状结构和大面积的屈服变形,与PP/EPDM/CCR相比,PP/EPDM/R-CCR冲击断面的空穴明显增加并细化,R-CCR在PP基体中分散均匀,且界面模糊,与基体的相容性明显优于CCR.复合材料流变行为的研究表明R-CCR的加入,体系储存模量G′和损耗模量G″随频率的增加而增加,对损耗因子和复数粘度的影响不大;但PP/EPDM/R-CCR复合材料的表观粘度,明显低于PP/EPDM/CCR和纯PP,同时,剪切速率的增加可有效降低体系的表观粘度.力学性能表明,R-CCR对PP同时起到增韧和增强的效果.且R-CCR和EPDM对PP具有协同增韧的效果.在保持聚丙烯的模量和强度基本不变的前提下,大幅度的改善聚丙烯的韧性,同时加工性能保持不变.
REINFORCEMENT OF NATURAL CELLULOSE WHISKER ON NATURAL RUBBER
天然微晶纤维素晶须补强天然橡胶的研究

GU Ju,LI Xionghui,JIA Demin,LUO Yuanfang,CHENG Rongshi,
古菊
,李雄辉,贾德民,罗远芳,程镕时

高分子学报 , 2009,
Abstract: .7%;断裂伸长率由594%下降至493%,变化率缩小至17.0%,而纯NR的拉伸强度由22.0 Mpa下降至2.4 Mpa,变化率为89.1%;断裂伸长率由579%下降至168%,变化率为71.0%.扫描电镜分析表明,RH-CW与NR基体的界面相容性较CW改善.热重分析表明,CW的加入使NR的5%失重温度降低,但残重增加,微分曲线在520℃处出现了一个小峰,RH-CW的加入,使该峰变大,残重进一步增加.
Cationic content effects of biodegradable amphoteric chitosan-based flocculants on the flocculation properties

Zhen Yang,Yabo Shang,Xin Huang,Yichun Chen,Yaobo Lu,Aimin Chen,Yuxiang Jiang,Wei Gu,Xiaozhi Qian,Hu Yang,Rongshi Cheng,

环境科学学报(英文版) , 2012,
Abstract: A series of biodegradable amphoteric chitosan-based flocculants (3-chloro-2-hydroxypropyl trimethyl ammonium chloride (CTA) modified carboxymethyl chitosan, denoted as CMC-CTA) with different substitution degrees of CTA were prepared successfully. The content of carboxymethyl groups in each CMC-CTA sample was kept almost constant. The solubility of the various flocculants showed that, higher cationic content of flocculants caused a better solubility. The flocculation experiments using kaolin suspension as synthetic water at the laboratory scale indicated that the substitution degree of CTA was one of the key factors for the flocculation properties. With the increase of cationic content, the flocculants were demonstrated better flocculation performance and lower dosage requirement. Flocculation kinetics model of particles collisions combining zeta potential and turbidity measurements was employed to investigate the effects of the cationic content of the flocculants on the flocculation properties from the viewpoint of flocculation mechanism in detail. Furthermore, flocculation performance using raw water from Zhenjiang part of Yangtze River at the pilot scale showed the similar effects to those at the laboratory scale.
Identification of concentration and brand for products using differential gel permeation chromatography
差减凝胶渗透色谱在产品浓度和品牌识别中的应用

WANG Qingguo,LI Xiaowen,LIU Bo,CAI Lixing,CHENG Rongshi,
王庆国
,李小文,刘波,蔡力行,程镕时

色谱 , 2008,
Abstract: In differential gel permeation chromatographic method (D-GPC), a standard solution and an analyzed solution are used as the eluent and injected solution, respectively. It can determine the minute differences between them. When the analyzed solution and the standard solution are identical, a null signal is given, otherwise the nonzero signal tells the detailed differences between them. Two examples, the concentration identification of five polyethylene glycol 200 (PEG200) solutions and the brand identification of three brands of beers, are given to show the application of the D-GPC method. The potential applications of the D-GPC method in quality control and the identification of counterfeit products are also discussed.
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