Synthesis of Lactide from Lact-acid Oligmer

As dispensable material to prepare polylactide, the purity and cost of lactide effect the quality and price of polylactide. The oligomer dehydrated from oligomer in last reaction can be used as reaction stuff like fresh lactic acid, but the suitable react condition is not clear. This paper researches the difference between react system of lactic acid and oligomer, including the level of average molecular weight, relative content of composition and the influence of added catalyst. The maximal yield of lactide could reach 28%.     

Study on Synthesis of High Quality Lactide

Polylactide,a biodegradable polymer, is an important biomedical meaterial. The synthesis of lactide from lactic acid is the key dimer of polylactide,unevitably affacting the polymerized process and the quality. Present work improves synthesis process of lactide. The synthesized factors are discussed, the reactive time is shortened and the quality of resultant is also raised.     

环境友好型生物降解材料聚乳酸的性能研究

聚乳酸(PLA)是一类重要的绿色环保型可降解材料,正受到人们越来越多的关注,近年来被广泛应用。笔者简要论述了生物降解材料聚乳酸的物化性能、力学性能及生物降解性能,综述了聚乳酸的合成方法—乳酸直接缩聚法和丙交酯开环聚合法,分析了国内外的生产现状。最后,对聚乳酸的合成及应用前景进行了展望,并指出可生物降解材料聚乳酸一旦工业化,它在医用及降解塑料方面将会有难以估量的应用前景。     

棉花产量与品质改进新对策

世界经济形势对棉花作为主导的纺织纤维来源提出了挑战.过去10年中,世界棉花的丰产性育种进展不大,棉农种植棉花的收益较低,棉花生产效益不稳.从目前单产水平的这种停滞状态可看出在多年的育种进程中,棉花从种植到成熟过程中产量组分所受到的生理限制.就改进产量的育种对策而言,注重产量组分比之注重衣分或铃数更为重要,此外应注重的是棉株的生理特性,如种子的含油量.而在产量处于徘徊的这段时期,经济的竞争使世界纺纱与纺织技术加速改进,以满足棉纤维品质的需求.在棉纤维加工过程中,短绒(12.7mm及以下绒长)的问题往往是造成棉纱拉力降低,尤其是对气流纺织技术.随着乌斯特公司"高级纤维信息系统"R的问世,已可以在对棉纤维长度分类时直接对棉短绒含量进行测定.本文的目的是讨论如何在保持现有纤维品质的前提下,采用新的技术与对策进一步提高产量.     

中国鲜食玉米的研究脉络和趋势探析

为探明中国鲜食玉米研究领域的变迁轨迹,把握研究现状与热点内容,探析研究前沿与发展趋势,旨在为鲜食玉米研究提供理论参考。以中国知网(CNKI)数据库2010—2021年1588篇“鲜食玉米”研究文献为研究对象,基于CiteSpace软件进行可视化定量分析。近10年鲜食玉米领域研究发展稳定,年发表核心论文数保持在100篇以上;高产作者以陆卫平、刘春泉、李大婧、陆大雷等为代表,呈单线或辐射团队合作。作者所属机构以农业类高等院校和科研院所为主,在发文数量上农业类高等院校取得的成果更为显著,科研院所在新品种的研发上更有优势,科研机构和高等院校团队合作比较紧密。突现词分析表明,单倍体、超甜玉米、种子萌发、遗传多样性、营养品质、风味、叶酸、可溶性糖等为研究趋势。未来鲜食玉米研究的核心任务是扩大覆盖面,突破传统局限,拓展基因编辑技术、转基因技术、基因测序、单细胞测序、基因组、蛋白组、转录组等多种前沿生物技术手段辅助传统鲜食玉米育种研究,尤其是加强甜加糯型玉米和超甜玉米的研究,增强鲜食玉米品质和营养,提高其抗病虫、抗倒、抗旱等抗逆性研究;在食品加工、饲料研究领域多,注重延长鲜食玉米采收期、贮藏期,保证其...     

棉花纤维中苯丙烷类结构单体的检测方法

苯丙烷类化合物存在于棉花纤维中,并且与纤维品质的形成有关。为正确评价棉花纤维中存在的苯丙烷类结构单体,首先采用巯基乙酸法提取出棉花纤维中的苯丙烷类化合物,然后用衍生化后的还原裂解(DFRC,Derivatization followed by reductive cleavage)法结合气相色谱(GC,Gas chromatograph)对棉花纤维中的苯丙烷类单体进行测定。结果表明,利用该方法检测到棉花纤维苯丙烷类单体主要由愈创木基结构单体(G￣木质素)和紫丁香基结构单体(S￣木质素)组成。本研究为进一步揭示棉花纤维中苯丙烷类化合物的合成奠定了基础。     

糯玉米改性淀粉的制备及其在速冻食品中的应用研究进展

糯玉米淀粉因独特的结构具有良好的冻融稳定性,在速冻食品中有着巨大的潜在利用价值,但原淀粉自身存在耐酸性、耐高温、耐剪切性较差等缺点,限制了其在食品工业中的应用。为了改善糯玉米淀粉的理化特性和加工性能,需要对原淀粉进行改性处理。概述了糯玉米淀粉常见的改性方法,介绍了糯玉米改性淀粉在速冻食品中的应用,并对糯玉米改性淀粉的研究现状和在速冻食品中的应用进行了分析和展望,为糯玉米改性淀粉在速冻食品中的应用提供一定的理论依据。     

以薯类为原料生产果葡糖浆的研究进展

薯类是一种很好的加工原料,以薯类为原料制备果葡糖浆可以很好的利用其中的淀粉,但目前我国薯类的加工与开发技术尚处于初始阶段。对薯类淀粉特性、利用其加工果葡糖浆的现状、加工工艺和目前存在的问题进行了研究和总结。     

玉米蛋白粉研究进展

玉米蛋白粉是湿式法玉米淀粉加工的副产物,可应用于各个领域。综述了玉米蛋白粉的组成、营养价值及其成分特点。利用玉米蛋白粉,可开发出玉米醇溶蛋白、玉米黄色素、谷氨酸、天然蛋白水解肽、可降解材料、膨化食品等深加工产品,具有成本低、无毒副作用的特点,提高了玉米蛋白粉的附加值,具有广阔的市场前景。     

Properties of Steel Fiber Asphalt Concrete and Its Application

To prevent asphalt pavement from cracking under low temperatures and prolong its fatigue life, we tested the properties of a new type of steel fiber asphalt pavement. The tests evaluated Marshall stability, dynamic ruts, and cleavage strength under both low and normal temperature conditions. We also analyzed the anti-corrosion property of steel fiber and the factors affecting the properties of the steel fiber asphalt mixture. The steel fiber asphalt pavement was installed on a highway in Chongqing, P. R. China to investigate the construction art of the steel fiber asphalt mixture and examine its effect in field use. The test results and concrete use in the field show that the cleavage strength and flexibility of steel fiber asphalt concrete increase due to the action of steel fiber. We conclude that the anti-cracking capacity of asphalt pavement under low temperature conditions can be improved by steel fiber. The construction art of steel fiber asphalt pavement is the same as common asphalt pavement without the necessity of anti-corrosion processing for steel fiber. The research results are useful for pavement material selection in low temperature regions and heavy traffic road pavement designs.     

Analysis for a Broken and Debonging Fiber in Ductile Matrix Composites

By studying the influence of the debonding fibers in composites under cyclical thermo mechanical load the distributions of fibers and matrixes stress are given around the debonding fiber. For illustrating the Boron/Al, continuous fiber composite is examined. Matrix around the debonding fiber only sustains shear stress. The constitution relationship of matrix is perfect elastical-plastical. The important conclusion is made, which lays a foundation for continuing studying the fatigue of composites.     

Synthesis of Lactide Using Zinc Lactate as a Catalyst

The catalytic efficiency of zinc lactate as a catalyst to prepare lactide from lactic acid was evaluated compared ose commonly used catalysts including zinc oxide, solid superacid and stannous octate, which indicated a much catalytic efficiency of zinc lactate than others. After mensurating the chemical structure and the crystal form of zinc lactate and recycled zinc lactate, the effects of catalyst and oligomerization time on the yield of crude lactide and the content of lactic acid in lactide product were studied. As a result, both zinc lactate and recycled zinc lactate showed same chemical structure and were comprised three crystal forms. Using zinc lactate and recycling zinc lactate as a cata- lyst, the yield of lactide were 75.7% ,72.1% , respectively. These indicate that zinc lactate is a kind of cheap, available, recyclable catalyst, which is significant in the industrial production of lactide.     

(甜)玉米澄清汁饮料加工工艺的研究

以甜玉米为原料,经提取玉米汁液,添加调配白砂糖和柠檬酸等,对甜玉米饮料的加工工艺(酶解,澄清)进行研究,研制出一种口味纯正的天然饮品。     

小麦-玉米轮作体系下长期定位秸秆还田对籽粒产量及品质的影响

以莱阳潮土区长期定位秸秆还田小麦-玉米轮作为研究对象,探讨秸秆还田条件下施用氮肥以及单施有机肥对小麦、玉米产量以及籽粒品质的影响。采用氨基酸组成分析法、半微量凯氏定氮法以及残余法,对不同秸秆还田施肥处理下籽粒品质做出分析,得出2季秸秆还田施氮肥(WCN)处理小麦、玉米籽粒粗脂肪含量较1季秸秆还田施氮肥(WN)处理显著提高5.72%和9.49%。秸秆所占比例越大越有利于提高籽粒粗脂肪含量。WCN处理小麦、玉米籽粒蛋白质含量较2季秸秆还田(WC)处理显著提高32.53%,72.44%,表明氮肥所占比例越大越有利于提高蛋白质含量。单施有机肥与2季秸秆还田施氮肥能显著提高小麦、玉米产量。不同秸秆还田处理对小麦籽粒赖氨酸、胱氨酸、丙氨酸影响较小,对玉米籽粒胱氨酸、谷氨酸、甘氨酸影响也较小,除天门冬氨酸、亮氨酸、缬氨酸、赖氨酸、胱氨酸、丙氨酸外,长期不同秸秆还田处理对其他氨基酸的影响趋势与氨基酸总量的变化规律类似。综上所述,在秸秆还田的基础上配施氮肥能够得到较高的产量,提高籽粒品质。     

Combining ability of upland cotton, <Emphasis Type="Italic">Gossypium hirsutum </Emphasis>L., with traits associated with sticky fiber

Sticky cotton causes severe processing problems at textile mills and can be caused by plant sugars deposited directly from the plant to the lint in the absence of insects. A partial diallel design was used to investigate the combining ability of six upland cotton, Gossypium hirsutum L., genotypes in Lubbock, Texas. Sucrose and glucose on fibers were measured as well as more mechanical fiber properties including stickiness ratings. Variance component analysis indicated significant differences among genotypes for all fiber traits and for sugar content. The greatest differentiation occurred in samples taken from more immature fruiting forms. Moreover, significant GCA and SCA differences were determined among parental lines for fiber traits including stickiness ratings. Findings suggest that breeding efforts could be directed toward lines with a low likelihood of producing sticky cotton.     

玉米皮天然水溶性膳食纤维提取的研究

以玉米加工副产物——玉米皮为试材,采用单因素实验和组合正交试验,最终研究出超声波辅助水提取玉米皮天然水溶性膳食纤维的工艺参数,并对提取样品进行了检测。     

膳食纤维对肠道菌群影响的研究进展

膳食纤维不能被人体小肠消化吸收,可在大肠中完全或部分发酵,是肠道微生物的主要能量来源。膳食纤维具有不同的结构特征,其降解受一系列碳水化合物活性酶(CAZymes)的控制。肠道微生物则是通过编码的碳水化合物活性酶利用膳食纤维,而其表达该酶的基因数量和基因类型具有差异,膳食纤维的选择性消耗决定了肠道中哪个细菌类群受到青睐并可以影响结肠中菌种和菌株的平衡。因此,膳食纤维的类型会影响菌群的种类和数量。介绍了膳食纤维和碳水化合物活性酶的定义和分类,并总结了特定的膳食纤维类型(抗性淀粉、果胶、纤维素、半纤维素和菊粉)对肠道微生物组成的影响,旨在为膳食纤维对肠道菌群和健康的研究提供理论参考。     

Mechanical Properties and Durability of Extruded Fiber Reinforced Cement Mortar Board and Its Composite Beam

The effect of water to cement ratio, fiber types and content, cement types on the bending performance of the extruded fiber reinforced cementitious board were studied. And it was found that polyvinyl alcohol (PVA) fibers can significantly improve the ductility of the board compared with polypropylene (PP) fibers. As PVA fiber content achieved 1.7%, the strain hardening and multiple cracking were occurred on the extruded board, while strain softening were shown on PP fiber reinforced cement board. The difference between the two kinds of board was from the differences of the mechanical properties of the two fibers. In addition, taking the fiber reinforced extruded board as base, the ultimate bending strength, as well as and the corresponded deflection and the resistant to chloride iron penetrating, was improved for a composite beam with fiber board and concrete compared with those of traditional concrete beam.     

从葛根渣中酶法制备膳食纤维

以采自湖南省临湘市、张家界市的家葛和野葛为材料,对葛渣中的膳食纤维的酶法制备工艺进行了试验研究。通过单因素试验、正交试验和极差分析,得出了最佳工艺参数。结果表明,在混合酶(α-淀粉酶与糖化酶质量之比为1∶2)用量0.2%、70℃处理80 min,蛋白酶用量0.4%、50℃处理60 min时,膳食纤维得率较高,张家界家葛、岳阳野葛、张家界野葛和岳阳家葛膳食纤维中的酸性洗涤纤维含量分别达78.69% \78。74% 、76.34% 和73.11%。因此,该酶法工艺为葛根膳食纤维的制备提供了依据。     

基于GIS的我国玉米秸秆纤维生产潜力研究

基于农作物生产潜力研究基础,利用GIS建立了我国玉米生产的空间数据库和属性数据库。通过对玉米生长期所需有效光和辐射进行光、温、水、土逐级修正后,计算得出玉米的生产潜力,根据一定的谷草比折算出玉米的秸秆生产潜力,以2006年我国各省玉米种植面积最终得出我国玉米秸秆纤维的潜力产量。我国玉米秸秆纤维生产潜力在2447.832-14079.55 kg&#8226;hm2之间,本研究为将来可用于生物燃料乙醇生产的纤维素资源的研究提供了基础。