从反应步数推导缩聚反应聚合度计算公式

聚合度计算是缩聚反应学习的重要内容之一.本文从聚合度的定义出发,根据反应步数与聚合物分子数之间的关系,简易地推导了线型缩聚2-2型单体体系a-A-a+b-B-6、2-2+1型单体体系a-A-a+b-B-b+C-b以及2+1型单体体系a-A-b+C-6达到一定反应程度时统一形式的数均聚合度计算公式:n=(1+r)/(1+...     

Network growth with preferential attachment for high indegree and low outdegree

We study the growth of a directed transportation network, such as a food web, in which links carry resources. We propose a growth process in which new nodes (or species) preferentially attach to existing nodes with high indegree (in food-web language, number of prey) and low outdegree (or number of predators). This scheme, which we call inverse preferential attachment, is intended to maximize the amount of resources available to each new node. We show that the outdegree (predator) distribution decays at least exponentially fast for large outdegree and is continuously tunable between an exponential distribution and a delta function. The indegree (prey) distribution is poissonian in the large-network limit.     

复合酶水解云南白鱼制备生物活性肽类物质

研究了复合蛋白酶对云南土著白鱼水解的工艺条件。考察了酶用量、温度、pH值、反应时间、底物浓度、复合酶比例等因素对白鱼水解的影响。确定了最佳酶解条件为:复合酶用量(木瓜蛋白酶+风味蛋白酶1∶1)16000U/g,底物浓度30%,温度55℃,pH值7.5,时间4h。在此条件下,水解度达34.12%,氮回收率90.05%。该结果为云南白鱼生产功能食品提供科学依据。     

云南盘鮈酶水解条件研究

采用动物蛋白水解酶对云南盘鮈进行酶水解,通过正交实验法确定了酶水解条件。结果表明,酶水解的最适条件为:温度50℃,pH7.0,时间3h,加酶量0.5%,固液比1∶2.5。在该条件下盘鮈肉蛋白的水解度为32.85%。氨基酸分析表明,游离氨基酸含量36.47mg/mL,必需氨基酸14.42mg/mL,占39.54%。尤其是亮氨酸、缬氨酸、苏氨酸、赖氨酸含量丰富,为低值鱼深加工研究提供理论依据。     

Jamming in complex networks with degree correlation

We study the effects of the degree-degree correlations on the pressure congestion J when we apply a dynamical process on scale free complex networks using the gradient network approach. We find that the pressure congestion for disassortative (assortative) networks is lower (bigger) than the one for uncorrelated networks which allow us to affirm that disassortative networks enhance transport through them. This result agree with the fact that many real world transportation networks naturally evolve to this kind of correlation. We explain our results showing that for the disassortative case the clusters in the gradient network turn out to be as much elongated as possible, reducing the pressure congestion J and observing the opposite behavior for the assortative case. Finally we apply our model to real world networks, and the results agree with our theoretical model.     

A network model of the interbank market

This work introduces a network model of an interbank market based on interbank credit lending relationships. It generates some network features identified through empirical analysis. The critical issue to construct an interbank network is to decide the edges among banks, which is realized in this paper based on the interbank’s degree of trust. Through simulation analysis of the interbank network model, some typical structural features are identified in our interbank network, which are also proved to exist in real interbank networks. They are namely, a low clustering coefficient and a relatively short average path length, community structures, and a two-power-law distribution of out-degree and in-degree.     

高支化聚合物的合成与表征

介绍了近年来在高分子化学领域内十分活跃的高支化聚合物研究的状况。指出了通过ＡＢｘ型单体的缩聚反应和Ａ＝Ｂ－Ｃ＾８型单体的自缩合乙烯都可获得高支化聚合物。目前用以表征高支化聚合物支化度和分子量的方法主要为核心共振法和凝胶渗透色谱法,在实际应用中都存在局限性。     

人工神经网络用于化学数据解析的研究(Ⅰ)──逼近规律与过拟合

对多层前传网络的过拟合问题进行了探讨。定义了逼近误差和逼近度作为人工神经网络(ANN)的建模评价指标。通过应用于多元非线性校正的数值模拟和实际药物光度分析数据解析,表明该指标意义明确,便于掌握,且能较好地定量表述ANN逼近规律的程度。     

Synthesising injectable molecular self-curing polymer from monomer derived from lignocellulosic oil palm empty fruit bunch biomass: A review on treating Osteoarthritis

Osteoarthritis (OA) is a chronic and irreversible degenerative joint disease that most commonly affects individuals in their forties and fifties worldwide due to the continuously increasing life expectancy. Although joint replacement is an effective remedy for severe end-stage OA, the functional outcomes could be unsatisfactory, while the implants might have a limited lifespan. Due to the drawbacks and limitations of the joint replacement approach, bone Tissue Engineering (TE) is one of the promising bone tissue regeneration technologies that aid in cartilage repair and regeneration and has attracted the attention of experts. The advanced development of biopolymers, in particular biopolymer derived from Oil Palm Empty Fruit Bunch (OPEFB), has been utilised in the fabrication of scaffolds that serve as a crucial component in bone TE. The abundant supply of OPEFB biomass and the increasing trend of converting waste into wealth for environmental sustainability have also provided the opportunity and interest to fully apply biopolymer-derived materials for bone scaffolding and other applications. Therefore, this paper aimed to provide a review of the biopolymers derived from OPEFB for the treatment of OA and other related applications. A brief overview of the biomass sources in Malaysia was presented, followed by a discussion on the chemical compositions and pre-treatment methods of OPEFB by using organosolv pre-treatment and enzymatic hydrolysis for maximum glucose recovery, monomer derived from cellulose OPEFB and synthesizing self-curing polymer scaffold. Additionally, a detailed review of the polymeric biomaterials in bone TE for the fabrication of scaffolds were included in this review. Most importantly, the paper described the potential use of injectable polymeric biomaterials that provide a significant benefit in orthopaedic applications. Overall, this paper provides a perspective on the potential of OPEFB-derived injectable scaffolds as an alternative OA treatment and future bone TE applications.     

Synthesis and characterization of copolymers of β-cyclodextrin derivatives

Cyclodextrins (CDs) are cyclic oligosaccharides made up of d-glucose units connected by 1,4-glucosidic linkages. β-CD is a cyclical starch derivative containing seven glucopyranose units. β-CD derivatives have characteristic property of larger surface area, robust mechanical strength, high surface to volume ratio, electrical and optical properties for analyte determination, good dispersion, easy removal of the template, surface modification, functionalization and handling capacity. In this work, an attempt is made to prepare succinyl-β-CD-acrylamide (S-β-CD-AA) copolymer and β-CD-malic anhydride (β-CD-MAH) copolymer. For the synthesis of S-β-CD-AA, S-β-CD derivative is prepared and further, acrylamide (AA) along with cross-linker undergoes free radical copolymerization for the formation of gel like product. The degree of succinylation (DS) of β-CD derivative is estimated. S-β-CD-AA copolymer showed potential swelling, and deswelling characteristic. Another copolymer is prepared from β-CD malic anhydride derivative. Further, the derivative is treated with cellulose and ethylene diamine tetra acetate (EDTA) to form β-CD-MAH copolymer. The two derivatives are characterized by several techniques. Thermal stability of these copolymers is estimated with the help of thermogravimetric analysis. The basic characterization of the presence of functional groups is done using UV–visible spectroscopy, and infrared spectroscopy. The elemental analysis helped to estimate C, H, N, S in the synthesized compounds. The surface morphology characterization is done with the help of scanning electron microscopy. X-ray diffraction analysis helped in determination of crystal structure of β-CD-MAH. β-CD derivatives prepared may be potential candidate to prepare inclusion complex, in drug delivery, drug loading and several similar applications.