海洋微生物抗肿瘤活性物质的研究进展

从海洋微生物中寻找和开发抗肿瘤药物是前途广阔的新领域。近年来,从海洋微生物中分离到许多结构新颖的抗肿瘤活性物质。本文按微生物种类,综述近几年海洋细菌、海洋放线菌及海洋真菌抗肿瘤活性物质的研究进展。     

低分子量聚丙烯酸钠的合成

采用自由基溶液聚合方法制备了低分子量聚丙烯酸钠,研究了链转移剂用量、单体浓度、温度、反应时间及引发剂用量、加料方式等因素对聚丙烯酸钠分子量的影响。实验结果表明,合成了低分子量(500-10000)聚丙烯酸钠。     

低相对分子质量阳离子聚丙烯酰胺的合成研究

以丙烯酰胺(AM)、二甲基二烯丙基氯化铵(DMDAAC)为原料采用水溶液聚合法制备了一种阳离子度为50%,相对分子质量100000～200000的低相对分子质量阳离子聚丙烯酰胺水溶液,研究了单体配比、投加浓度、聚合温度、引发体系等对反应的转化率和产物相对分子质量的影响.通过加入质量分数0.5%的抗交联剂CPL和螯合剂EDTA·2Na.采用三元复合引发体系可以将聚合反应不饱和单体的转化率提高到96%以上,并且通过控制分子质量调节剂SF的用量可以得到不同相对分子质量分布范围的阳离子聚合物.该产品对高含水原油采出液有独特的预脱水性能,可提高油田采出液油水分离设备的效率和油水分离效果,与反相破乳剂、净水剂等配合使用还可以提高其对含油污水的处理效果.     

Partial draining of low-molecular weight polymers with flexible chains

The results of the theory of intrinsic viscosity based on the model of a worm-like chain have been used in analyses of the [η]-M correlation under theta conditions, and of the Stockmayer—Fixman plot for polymers with flexible chains at molecular weights M < 10⁵. Their viscosity behaviour appears to be influenced by the chain thickness d. An analysis of the available data allowed us to obtain reasonable d values for several polymers: polyethylene; poly(ethylene oxide); polystyrene; poly(methyl methacrylate), and poly(vinyl acetate). The effect of solvent on d was ascertained. The analysis shows that the reliability of the results obtained by the Stockmayer—Fixman method is the higher, the larger the proportion of data used which reside in the region M > 10⁵.     

Density and viscosity of low-molecular weight triglycerides and their mixtures

The viscosities of tributyrin (C4∶0) and binary mixtures of this triglyceride with a diesel fuel, tricaproin (C6∶0), and tricaprylin (C8∶0) were determined for the temperature range −5 to 85°C and for shear rates of 1.62–64.7 s⁻¹. The resulting dynamic viscosities were fit to a power law model to obtain values for the consistency coefficient and the flow behavior index. These results indicated slightly pseudoplastic flow behavior (indices ranged from 0.94 to 0.99) for tributyrin and its mixtures. The calculated consistency coefficients for tributyrin and those previously obtained for tricaproin, tricaprylin and tricaprin were fit by a least-squares method to the three-parameter Vogel model to account for the effect of temperature. An ideal solution relationship and the Kendall-Monroe model were used to predict the density and consistency coefficients, respectively, for binary and quaternary mixtures of these low-molecular weight triglycerides.     

Release of lipoprotein lipase from cardiac myocytes by low-molecular weight heparin

Incubation of cardiac myocytes from rat heart with low-molecular weight heparin (LMWH; Mr approx. 3 kDa) for 30 min resulted in a concentration-dependent release of lipoprotein lipase (LPL) activity into the incubation medium. The release of lipoprotein lipase from cardiac myocytes isolated from both control and diabetic rat hearts induced by LMWH (10 μg/mL) following incubation times of 10 or 30 min was significantly greater than that produced by unfractionated heparin (10 and 30 μg/mL) or decavanadate (1 mM). Since LMWH released more LPL activity into the incubation medium than unfractionated heparin following a short (10 min) incubation time, LMWH is probably more effective in displacing LPL bound to heparan sulfate proteoglycan binding sites on the cell surface of cardiac myocytes.     

Effect of molecular weight distribution on polymer diffusion during film formation of two-component high-/low-molecular weight latex particles

We describe fluorescence resonance energy transfer (FRET) studies of film formation by a new type of two-component latex particles. These particles consist of a miscible blend of two components that have a similar composition but very different molecular weights. In our approach, we used sequential seeded emulsion polymerization to generate (in situ) a fraction of oligomer in poly(butyl acrylate-co-methyl methacrylate) P(BA-MMA) seed particles that contained a relatively high molecular weight (high-M) dye-labeled polymer. In this way we could systematically change the molecular weight distribution of polymer inside the particles. We varied the amount and the molecular weight of the oligomers. For latex films cast from these two-component particles, we studied the diffusion rate of the high molecular weight polymer by FRET. These measurements revealed that oligomers promoted diffusion rate during latex film formation (oligoplasticization). We analyzed our diffusion data in terms of the Fujita–Doolittle free-volume model and showed that higher molecular weight oligomers are less efficient as plasticizers. In separate experiments, oligomers with similar molecular weights as those in the two-component particles were introduced via latex blending. We compared oligoplasticization in latex blends films with that in the two-component particles films. Finally, we investigated the rheological behavior of the two-component polymers with compositions adjusted to have a common T_g (2 °C). The higher the molecular weight of the oligomer, the more that had to be added to achieve T_g = 2 °C. All of the oligomers were much shorter than the entanglement length and act as diluents of the entanglements in the high-M polymer. We found that incorporating larger amounts of oligomers with a higher molecular weight resulted in a more pronounced drop in polymer viscosity, associated with the decrease in the entanglement density.     

Morphology and crystallization kinetics in a mixture of low-molecular weight aliphatic amide and polylactide

Polylactide (PLA)/N,N-ethylenebis(12-hydroxystearamide) mixture was prepared by using melt extrusion. The detailed crystallization kinetics and morphology of neat PLA and a mixture were studied by using polarized optical microscopy, light scattering, differential scanning calorimetry, and wide-angle X-ray diffraction analyses. The overall crystallization rate and spherulitic texture of PLA were strongly influenced in presence of the organic additive. The overall crystallization rate of matrix PLA increased with addition of WX1. These behaviors indicated that WX1 crystallites, which crystallized at the very early stage of PLA crystallization act as a nucleating agent for PLA crystallization.     

半纤维素的化学改性研究进展

简要介绍了半纤维素的结构及其化学改性原理和方法,综述了近几年国内外半纤维素化学改性的研究状况;详细介绍了非离子半纤维素、阳离子半纤维素、阴离子半纤维素的合成方法.为了满足不同需要,半纤维素通过化学改性改善了其水溶性、热塑性、表面活性等,从而扩大了半纤维素的应用领域,使得改性半纤维素广泛应用于医药、造纸助剂、塑料、污水处理等众多领域.     

Attraction of nematodes to metabolites of yeasts and fungi

The free-living nematodesPanagrellus redivivus andRhabditis oxycerca are strongly attracted to methyl, ethyl, propyl, butyl, and amyl acetate, to ethyl, propyl, and amyl formate and to ethyl propionate, but all the respective alcohols and acids are without effect. No loss of attraction is observed when the attractants are combined with lethal concentrations of the commercial nematicide sodium methyl dithiocarbamate.     

低分子量聚丙烯酸钠高效陶瓷减水剂的应用

把自制低分子量聚丙烯酸钠减水剂的减水效果与工业生产中常用的无机三聚磷酸钠减水剂的减水效果作了比较，结果表明，聚丙烯酸钠的减水效果明显优于三聚磷酸钠，并分析了聚丙烯酸钠的减水机理；把有机聚丙烯酸钠与无机三聚磷酸钠复合使用，能达到更好的减水效果，而且解决了单纯使用有机减水剂成本较高的难题。     

淫羊藿属木脂素类化学成分研究进展

目的是对淫羊藿属木脂素类成分研究进展进行综述,为其进一步开发研究提供参考;方法是对国内外相关文献进行分析、整理和归纳;结果是综述了近40种木脂素类成分,其中有10余种属于自然界首次发现的新化合物,文中均给出其英文名称、文献来源等内容;结论是以往淫羊藿木脂素类成分的报道相对较少,其化学成分和药理活性亟待进一步研究。     

化学链催化甲烷氧化反应研究进展

甲烷作为天然气的主要组成成分,其有效利用具有重要的现实意义。本文首先介绍了甲烷转化工艺,系统地比较了传统甲烷氧化与化学链催化甲烷氧化工艺,提出化学链重整技术作为一种应用于甲烷氧化反应的新技术,提供了一个多功能平台,以清洁及有效的方式转换燃料。然后,介绍了应用于此技术的催化剂研究现状,重点关注具有高储氧性能、催化性能以及低合成成本特点的钙钛矿复合氧化物,特别综述了利用机器学习方法高通量筛选钙钛矿氧化物催化剂的理论计算工作。最后,系统讨论了钙钛矿氧化物对化学链催化甲烷氧化反应性能的影响规律,依据实验和密度泛函理论计算研究结果,对催化剂颗粒尺寸、金属离子价态、氧空穴形成能以及氧浓度同催化性能之间的关系进行了分析,提出钙钛矿氧化物催化甲烷氧化反应的关键影响因素,为钙钛矿氧化物催化剂的筛选提供理论支撑。     

化学法处理含油污泥研究进展

综述了各类含油污泥化学法处理办法,包括:热解法、氧化法、热洗及萃取法、电化学法。概述了这4类处理方法的概念、作用机理、研究进展,并对化学法处理含油污泥研究方向进行展望。     

新型化学热泵的研究进展

阐述了化学热泵中反应体系应具备的条件，介绍了新型的有机系、无机系化学热泵的研究动向及化学热泵的研究进展。     

正构烷烃加氢异构化反应机理的研究进展

综述了近年来正构烷烃在分子筛为载体的双功能催化剂上加氢异构化反应机理的研究进展,介绍了单分子机理、双分子机理、孔口机理及锁匙机理,并展望了反应机理在制备新型催化剂领域的应用前景。     

淫羊藿属植物黄酮类化学成分研究进展

综述了淫羊藿属植物中几乎所有已发现的黄酮类成分,并对其进行系统分类整理,可为该类成分的深入研究与开发提供参考。     

苯乙烯-丁二烯类热塑性弹性体的应用及研究进展

综述了苯乙烯-丁二烯-苯乙烯嵌段共聚物(SBS)在塑料垃圾回收、塑料改牲等方面的应用进展,并介绍了SBS薄膜在生物高分子材料和光记忆材料方面的应用。SBS的引入不同程度地改善了材料体系的综合性能,具有广阔的技术开发前景。     

Top coating of low-molecular weight polymer MALPB used for enhanced protection on anodized AZ31B Mg alloys

A protective composite coating on an AZ31B magnesium alloy was prepared by anodic oxidation to form an oxide layer, followed by single immersion in maleic anhydride-g-liquid polybutadiene (MALPB) solution to cover a polymer coating on top. As a low-molecular weight polymer with low viscosity, MALPB had a tendency to infiltrate into the pores and cracks in the anodic layer to fill the defects among oxides so that a compact layer could be formed after it was cured by its hardeners, as observed by scanning electron microscopy (SEM). This compact layer, which was composed of anodic oxides integrated with solidified MALPB, possessed thickness around 0.7 μm as detected by energy dispersive X-ray (EDX). The anodized, MALPB-coated AZ31B alloy exhibited enhancement in corrosion resistance superior to that separately coated by anodizing oxides or MALPB, as reflected by its much higher corrosion potentials (E _ccor) and lower corrosion current density (i _corr) in DC polarization tests. Based on electrochemical impedance spectroscopy (EIS) data, we conclude that the anticorrosive performance of the composite coating can be attributed to the barrier effects provided by different layers when the electrolyte passed through the MALPB layer, compact layer, and then the inner anodic layer before it reached the surface of Mg alloy, and that among them, the compact layer acted as a much more effective barrier to the electrolyte. The appearance of damaged areas on the composite coating surface after a much longer duration in a salt spray environment revealed that the life-span of the AZ31B Mg alloy could be greatly prolonged if the pores and cracks on the anodizing films were properly sealed by suitable polymers.