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41.
Der‐Jang Liaw Ching‐Cheng Huang En‐Tang Kang 《Journal of polymer science. Part A, Polymer chemistry》2006,44(9):2901-2911
Diblock copolymers of 5‐(methylphthalimide)bicyclo[2.2.1]hept‐2‐ene (NBMPI) and 1,5‐cyclooctadiene were synthesized by living ring‐opening metathesis polymerization with a well‐defined catalyst {RuCl2(CHPh)[P(C6H11)3]2}. Unhydrogenated diblock copolymers showed two glass transitions due to poly(NBMPI) and polybutadiene segments, such as two glass‐transition temperatures at ?86.5 and 115.3 °C for poly 1a and ?87.2 and 115.3 °C for poly 1b . However, only one melting temperature could be observed for hydrogenated copolymers, such as 119.8 °C for poly 2a and 121.7 °C for poly 2b . The unhydrogenated diblock copolymer with the longer poly(NBMPI) chain (poly 1a ; temperature at 10% mass loss = 400 °C) exhibited better thermal stability than the one with the shorter poly(NBMPI) chain (poly 1b ; temperature at 10% mass loss = 385 °C). Two kinds of hydrogenated diblock copolymers, poly 2a and poly 2b , exhibited relatively poor solubility but better thermal stability than unhydrogenated diblock copolymers because of the polyethylene segments. Poly[(hydrochloride quaternized 2‐norbornene‐5‐methyleneamine)‐b‐butadiene]‐1 (poly 3a ) was obtained after the hydrolysis and quaternization of poly 1a . Dynamic light scattering measurements indicated that the hydrodynamic diameters of the cationic copolymer (poly 3a ) in water (hydrodynamic diameter = 1580 nm without salt), methanol/water (4/96 v/v; hydrodynamic diameter = 1500 nm without salt), and tetrahydrofuran/water (4/96 v/v; hydrodynamic diameter = 1200 nm without salt) decreased with increasing salt (NaCl) concentration. The effect of temperature on the hydrodynamic diameter of hydrophobically modified poly 3a was also studied. The inflection point of the hydrodynamic diameter of poly 3a was observed at various polymer concentrations around 30 °C. The critical micelle concentration of hydrophobically modified poly 3a was observed at 0.018 g dL?1. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2901–2911, 2006 相似文献
42.
For every ?>0 and every positive integers Δ and r, there exists C=C(?,Δ,r) such that the Ramsey number, R(H,H) of any r-uniform hypergraph H with maximum degree at most Δ is at most C|V(H)|1+?. 相似文献
43.
符号几何规划的一种分解方法 总被引:1,自引:0,他引:1
针对符号几何规划提出了一种直接的分解方法,将难于求解的符号几何规划问题等价地转化为一个非线性程度很低的可分离规划,为寻求困难度高且规模较大的符号几何规划问题的求解提供了一种方法,特别是经此方法分解后的每个子问题均易于求解,最后给出了数值实例,验证了此方法的有效性. 相似文献
44.
用马来酸二丁酯(DBM)为接枝单体,过氧化二枯基(DCPO)为引发剂,对低密度聚乙烯(LDPE)进行了熔融接枝功能化。样品的红外光谱表明接枝反应确已发生。通过对样品中酯基的皂化水解测定产物的接枝率,对产物进行萃取,用凝胶量间接表征产物的交联程度;用溶液的特性粘度从侧面显示样品的支化或降解情况。实验结果表明,产物的接枝率和凝胶量可以通过选择反应条件(温度、时间及反应混合物的组成)来控制;过量的DCPO是引起交联产生凝胶的主要原因;向体系中添加DMF可阻止交联反应的发生,但产物的接枝率也有所下降,以自由基机理对上述结果进行了讨论。 相似文献
45.
Effects of sugar inhibition on cellulases and β-glucosidase during enzymatic hydrolysis of softwood substrates 总被引:1,自引:0,他引:1
Zhizhuang Xiao Xiao Zhang David J. Gregg John N. Saddler 《Applied biochemistry and biotechnology》2004,115(1-3):1115-1126
A quantitative approach was taken to determine the inhibition effects of glucose and other sugar monomers during cellulase
and β-Glucosidase hydrolysis of two types of cellulosic material: Avicel and acetic acid-pretreated softwood. The increased
glucose content in the hydrolysate resulted in a dramatic increase in the degrees of inhibition on both β-Glucosidase and
cellulase activities. Supplementation of mannose, xylose, and galactose during cellobiose hydrolysis did not show any inhibitory
effects on β-Glucosidase activity. However, these sugars were shown to have significant inhibitory effects on cellulase activity
during cellulose hydrolysis. Our study suggests that high-substrate consistency hydrolysis with supplementation of hemicellulose
is likely to be a practical solution to minimizing end-product inhibition effects while producing hydrolysate with high glucose
concentration. 相似文献
46.
总结毛者提出的线型缩聚中当量系数的新定义及引入缩聚体系单体平均官能度的新方法,本文总结出了一套讲授数均聚合度计算问题的简单方法。 相似文献
47.
A comparison of different nebulisers for direct hyphenation of capillary and nano liquid chromatography (Cap-LC, Nano-LC) and quadrupole-based collision cell inductively coupled plasma mass spectrometry (CC-ICP–MS) for phosphorylation profiling of tryptic protein digests is described. Helium was used as cell gas and specially tuned instrumental conditions were used to achieve background minimisation at the mass of phosphorus, because of kinetic energy discrimination of the interfering polyatomic ions. The proposed set-up is based on a modified capillary electrophoresis interface and a home-made 4 mL spray chamber. It enables the use of gradient conditions with a highly concentrated organic mobile phase as often used in protein phosphorylation analysis, without the need to apply membrane desolvation for removal of the organic phase or further background minimisation. No significant signal suppression or other negative effects caused by the organic mobile phase occur, because of the low flow rates used in Cap-LC and the robust plasma conditions of the CC-ICP–MS instrument. A tryptic digest of beta-casein was investigated as model compound to demonstrate the applicability of the proposed set-up for phosphorylation profiling in protein analysis using quadrupole based collision-cell ICP–MS as phosphorus-specific detector. Detection limits for phosphorylated peptides down to the sub picomole level were obtained. As a complementary technique, electrospray ionisation tandem mass spectrometry (ESI–MS–MS) with data base searching was used for further characterisation of the phosphorylated peptides detected. 相似文献
48.
本文采用家兔肺泡巨噬细胞(AM)存活率和细胞过氧化脂质(LPO)值为测定指标,研究了硅氧的聚合度对其细胞毒性的影响。结果表明:各种聚合度的硅氧都有一定的细胞毒性,聚合度愈大,细胞毒性也愈大。胶体SiO_2的粒径增大,其细胞毒性降低。十硅酸盐及粒径小于5nm的硅溶胶的细胞毒性大于α-石英。聚合度小于6的低聚硅酸及其盐、粒径18nm以上的硅溶胶以及硅胶H的毒性皆小于α-石英。本实验细胞存活率降低和过氧化脂质值升高的趋势基本一致,这表明硅氧可能主要与细胞表面膜作用,膜上磷脂等表面活性物质被氧化和变性,从而导致细胞损伤。 相似文献
49.
The overall stability constantsK
1 andK
2 of NdNO
3
2+
and Nd(NO3)
2
+
complexes were determined (K
1=1.77;K
2=1.28) using an extraction method with tri-n-butyl phosphate as the extractant. The ratio 1/2 of the stepwise stability constants is discussed. It was established that the Nd(NO3)
2
+
complex was an outer-sphere ion pair.
Die Assoziation von Nitrat-Ion mit Nd3+
Zusammenfassung Mittels einer Extraktionsmethode wurden die StabilitätskonstantenK 1 undK 2 von NdNO 3 2+ - und Nd(NO3)+-Komplexen bestimmt (K 1=1.77;K 2=1.28; Tri-n-butylphosphat als Extraktionsmittel). Das Verhältnis 1/2 der stufenweisen Stabilitätskonstanten wird diskutiert. Es stellte sich heraus, daß der Nd(NO3)+-Komplex als ein Outer-Shere-Ionenpaar vorliegt.相似文献
50.
提出了在四氢呋喃(THF)、H2O和乙醇三元体系中用一般的化学还原法在室温下制备高合金化Pt-Ru/CMK-3催化剂的新方法. 与在纯水中制得的商品化ETEK催化剂相比, 其Pt-Ru粒子的合金化程度高、平均粒径较小且相对结晶度低, 因此, 该催化剂对甲醇氧化的电催化活性远高于在纯水中制得的Pt-Ru催化剂. 高合金化程度的原因是H2PtCl6和RuCl3在THF、H2O和乙醇三元溶液体系中的起始还原电位相近. 此外, CMK-3以其规整的二维有序孔道结构, 为直接甲醇燃烧电池(DMFC)中电子和物质的传输提供了方便的路径, 其巨大的比表面积也为Pt-Ru 纳米粒子的均匀分散提供了良好的载体. 相似文献