Stretching Deformation Mechanism of Polyacrylonitrile-based Carbon Fiber Structure at High Temperatures

In a high-temperature environment, polyacrylonitrile-based carbon fiber (PAN-CF) can be deformed by stretching, where the stretching deformation ability of PAN-CF is enhanced with the increase of the temperature. Further, the hightemperature stretching deformation of PAN-CF directly affects the control of the carbon crystalline orientation. Based on the techniques of high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, X-ray diffraction and in situ tension testing, the variation regularity and the intrinsic mechanism of high-temperature stretching deformation ability of PAN-CF obtained at different preparation temperatures were systematically studied in a high-temperature environment. The results indicated that the essence of PAN-CF high-temperature deformation was the relative motion of the carbon crystallite. Further, the main structural parameters that affected the high-temperature stretching deformation ability of PAN-CF were the degree of cross-linking between the carbon crystallites, the orientation angle(OA) of the carbon crystallite and the nitrogen content. When the testing temperature was lower than the preparation temperature, only physical structure changes were observed in the PAN-CF. For the PAN-CF tested undergoing physical structure changes, as the degree of cross-linking between the crystallites and the orientation angle decreased, the slipping of crystallites became easier. In the same environment, as the stretching tension decreased, the stretching deformation ability improved. When PAN-CF was tested under temperatures higher than the preparation temperature, the microcrystalline cross-linking in the PAN-CF was prone to fracture and slipping, and the high-temperature stretching deformation ability was enhanced. Also, for PAN-CF of lower preparation temperatures in PAN-CF containing no nitrogen (i.e., <0.15 wt%), the cross-linkages increased and the structures were more unstable, inducing an increase in the fracture of weak bonds and a reduction of the stretching tension. For nitrogen-containing PAN-CF, the removal of nitrogen led to severe shrinkage in the graphite layer and interlayer, and the fiber tension was thus increased, causing the high-temperature stretching deformation ability of the PAN-CF with less nitrogen content to be improved.     

Tensile,Thermal, and Electrical Conductivity Properties of Carbon Fiber Reinforced Composites Using Itaconic Acid Based Dispersants

We prepared itaconic acid based dispersants (IBDs) by the copolymerization of itaconic acid with acrylic acid, acrylamide, or vinyl sulfonic acid, and compared the efficacy of the IBDs on carbon fiber (CF) dispersion in a water-based system, against that of sodium dodecyl sulphate (SDS) which is widely used as a dispersing agent. The procedure to fabricate nonwoven CF (NCF)/PP composites using IBDs includes the following steps: the synthesis of IBDs, the dispersion of CFs in water by the IBDs, the formation of a NCF, and hot pressing of NCF with polypropylene (PP) layer. We determined the tensile, thermal properties, and the electrical conductivity of non-woven CF/PP composites. It was found that using IBDs as a CF dispersing agent led to the CF/PP composites having better tensile, thermal, and electrical properties, as compared to when SDS was used as a dispersing agent.     

大豆乳清蛋白的热促凝聚及其对分离蛋白功能性的影响

分别在pH8.0和pH4.5对"碱提酸沉"法制备大豆分离蛋白过程中所得提取液进行热处理,研究了大豆乳清蛋白的热促凝聚效果及其对所制备分离蛋白功能性的影响。结果表明:加热处理可降低大豆乳清中乳清蛋白的含量,在pH8.0和pH4.5时提取液经70℃加热10 min分别使25.7%和40%乳清蛋白转移到分离蛋白产品中。以普通分离蛋白为对照,对3种分离蛋白产品进行功能性分析,发现3种产品均在pH4.5~4.8的范围内溶解度最小,70℃加热10 min所制备分离蛋白的持水性明显高于普通分离蛋白,但其持油性、起泡性、泡沫稳定性和乳化性均低于普通分离蛋白,而乳化稳定性无显著差异。     

Effect of Thermal Processing on Potato Sensory Profile and off-Odours Detection during Storage

One of the most used thermal treatments in potatoes to inactivate enzymes and prevent their oxidation is the boiling process. This treatment significantly decreases the taste of the potato and causes “off-odours” during storage, whatsoever, represents a big problem for the production of potato-based foodstuffs. This study focused on evaluating the sensory profile of potato slices subjected to a boiling process of three Mexican potato varieties (Alpha, Chica and Gallo) and on off-odours detection in potato produced during storage. According to the examined parameters through PanelCheck, the trained panel had a good performance, resulting 8 of the 12 attributes evaluated were significant. The formation of “cardboard-like off-odour” was detected in the Alpha and Chica varieties at the 24 and 33 h of storage, respectively. Chica potato presented this off-odours with at level significantly lower than Alpha potato (about 30% lower). With respect of Gallo variety, this presented different oxidation olfactory perceptions described by the assessors as “burnt note”, detected after 5 h of refrigerated storage. An adequate election of the variety of potato according to processing will allow an effective utilization of this vegetable and the obtention of potato-based foodstuffs much more stable.     

大豆脂氧酶的热失活动力学与其二级结构的圆二色谱表现

应用大豆脂氧酶的变温圆二色谱图研究了大豆脂氧酶(LOX)的热失活与二级结构变化过程.结果表明:在50一65℃条件下,10 min内,LOX的酶活随热处理时间延长而下降,其热失活过程遵循一级动力学,活化能Ea值为217 kJ.mol-1.在相同的热处理条件下,LOX中二级结构a-螺旋和β-折叠的相对含量均在20%左右浮动...     

Spectroscopic Analyses on Chain Structure and Thermal Stabilization Behavior of Acrylonitrile/Methyl Acrylate/Itaconic Acid-based Copolymers Synthesized by Aqueous Suspension Polymerization

We have synthesized a series of copolymers with different compositions of acrylonitrile (AN, 80–100 wt%), methyl acrylate (MA, 4–20 wt%) and itaconic acid (IA, 0–3 wt%) by using an efficient aqueous suspension polymerization, and have investigated the molecular structure and thermal stabilization behavior of PAN homopolymer, AN/MA-based bipolymers, and AN/MA/IA-based terpolymers by adopting ¹H/¹³C-NMR and thermal FT-IR analyses. The viscosity-average molecular weight of the synthesized polymers were measured to be ~263,000 g/mol. The reactivity ratios of AN and MA for all the copolymers were evaluated to be 0.99 and 1.05, respectively. Accordingly, the output compositions of the synthesized copolymers were quite consistent with the input monomer compositions. The ¹³C NMR analysis revealed that all the synthesized polymers have an atactic chain configuration, regardless of the feed composition. The structural evolutions during the thermal stabilization process of the copolymers in air environment were characterized by monitoring the temperature-dependent changes of characteristic absorbance bands at 2240 cm^-1 (C≡N), 1595 cm^-1 (C=N) and 1660 cm^-1 (C=O) with aid of thermal FT-IR spectroscopy. It was found that the IA unit in the terpolymers accelerated the oxidation and cyclization reactions, unlike the retarding effect of MA unit, and that the onset temperatures of the oxidation reaction of the copolymers with IA unit was lower than that of the cyclization reaction.     

镉离子对茶叶光合机构及性能的影响

对水培在镉污染下的茶叶光合机构进行连续观察和光合性能测定。结果表明镉离子（0.5βmmol/L）伤害茶苗叶片叶绿体超微结构。在毒害初期,表现为基粒减少,排列不规则,类囊体减少,垛叠紧密度下降;而后,叶绿体逐渐变圆并与质膜分离,类囊体腔膨胀,垛叠疏松;到后期叶绿体结构更加混乱,类囊体大幅度降解,有些叶绿体外膜局部破裂,基质外泄。随Cd²⁺处理时间的延长,茶叶叶绿素含量减少,叶绿素a/b值下降 ,叶绿素荧光动力学参数Fv/Fo和Fv/Fm值降低。镉离子对光合作用有多方面影响,而且对细胞的毒害具有明显的累积效应。     

Effect of Chemical Modifications on Surface Morphological,Structural, Mechanical,and Thermal Properties of Sponge-gourd Natural Fiber

Sponge-gourd (SG) natural fibers obtained from Luffa cylindrica plant were chemically treated separately using alkali (5, 10, and 15 wt%), acetic anhydride (5, 10, and 15 wt%), and benzoyl chloride (5, 10, and 15 wt%). Both untreated and chemically treated SG fibers (SGFs) were subsequently characterized using a field emission scanning electron microscope, a Fourier transform infrared spectrometer, an X-ray diffractometer, a universal testing machine, and a thermogravimetric analyzer. Surface analysis by scanning electron microscopy shows that the alkali treatments promote better outer surface layer than other treatments of the SGF with the exposition of inner fibrillar structure, thereby increasing roughness of the fiber surface. Alkali treatment also improves the crystallinity and exhibits new chemical bond formation in the SGF. The tensile strength and Young’s modulus have been analyzed through a two-parameter Weibull distribution model, where a significant increase in mechanical property of benzoylated fibers has been observed. The thermal stability of the modified fibers is also found to increase by acetic anhydride treatment.     

大豆秸秆粗纤维含量的测定及摘荚对其饲用品质的影响

大豆秸秆饲料利用率低,原因主要是其粗纤维含量高,粗蛋白含量低.提高作物秸秆饲用品质的农艺措施┅之一为抑制植株的生殖生长.在饲料粗纤维测定国家标准(GB/T 6434-94)的基础上,使用FOSS纤维测定仪1020,获得大豆秸秆粗纤维含量的测定方法.结果表明:参考国家标准测定大豆秸秆粗纤维含量需要调整3个参数,经调整的参数为:粉碎细度40目,样品称样量0.6-0.7 g,酸碱热浸提时间60 min.利用此方法测定了逐步抑制生殖生长后10组大豆品系秸秆粗纤维含量的变化,同时测定了相应的粗蛋白含量,结果表明:从鼓粒初期开始,随摘荚处理的时间逐步推后,大豆秸秆中粗纤维含量总体呈现上升趋势;粗蛋白含量总体呈现下降趋势.处理后,秸秆粗纤维含量基本低于对照,粗蛋白含量基本高于对照,在一定程度上提高大豆秸秆的饲用品质.     

竹纤维性能及发展展望

竹纤维是现今市场上极具经济开发价值的新型纺织原料,分为天然竹纤维和再生竹纤维。本文对这两类竹纤维从结构特点、生产流程、性能差异等角度进行了论述,指出了目前市场存在的问题以及未来的发展方向。     

竹纤维性能及发展展望

竹纤维是现今市场上极具经济开发价值的新型纺织原料.分为天然竹纤维和再生竹纤维.本文对这两类竹纤维从结构特点、生产流程、性能差异等角度进行了论述,指出了目前市场存在的问题以及未来的发展方向.     

尾煤泥施用的重金属安全性及其对土壤结构和燕麦生长的影响

为促进煤炭洗选加工废弃物尾煤泥在农业生产中的科学利用,以裸燕麦品种草莜1号和蒙农大燕1号为研究对象,尾煤泥基施量0(CK)、7 500、15 000、22 500kg·hm~(-2),在砂壤土田间进行随机试验,并对尾煤泥、土壤、燕麦茎叶的重金属和矿质营养成分进行了分析。结果表明,尾煤泥中的重金属镍(Ni)、铜(Cu)、锌(Zn)、铅(Pb)、铬(Cr)、镉(Cd)、汞(Hg)、砷(As)含量低于《城镇污水处理厂污泥处置:农用泥质》标准(CJ/T 309-2009)中的规定限量;尾煤泥显著(P0.01)提高了土壤与燕麦的氮(N)、钾(K)、钙(Ca)、镁(Mg)等养分含量及燕麦产量;两个燕麦品种对尾煤泥效应趋势一致;燕麦茎叶K含量与干草产量和籽粒产量的相关性最大,相关系数分别为0.446 8和0.571 1。综上所述,工业废弃物尾煤泥营养成分较高,可在土壤中安全施用,在燕麦种植中以15 000kg·hm~(-2)直接基施为宜,可提高砂壤土的容重10.48%,提高保水性(含水量提高16.84%),燕麦干草产量和籽粒产量两年平均提高42.79%和17.63%。     

The Effect of Various Catalyst on In-situ Synthesis of Carbon Nanotubes on the Glass Mat Using Thermal Chemical Vapor Deposition Method

The main aim of this research work is in situ synthesis of carbon nano tube (CNT) on nonwoven glass mat. Different types of catalyst were used and the effect of them on growth of carbon nanotubes on glass mat was investigated. The process was considered as variable catalysts to achieve optimal conditions for CNT deposition on glass mat. In this research, iron, cobalt, copper and nickel were used as catalysts and acetylene gas was used as the hydrocarbon source. Also, argon was used as a carrier gas. In first step, samples were coated by mentioned catalyst using plasma sputtering method. The thickness of the catalyst on the surface of samples was fixed at 100 nm. In second part, thermal chemical vapor deposition (TCVD) system was used for growth of carbon nano tubes. Scanning electron microscopy (SEM) and raman spectroscopy, thermogravimetric analysis (TGA-DTG) and transmission electron microscopy (TEM) were used for investigating the morphology and quality of produced CNT. Electrical conductivity was observed and compared on both untreated and coated glass mat. The results show that, by pre sputtering of samples with nickel, the quality of CNT on the surface of glass mat will be improved and the resistivity of samples reach to 610 Ω.     

普洱茶发酵过程中不同添加物对茶褐素及其形成机制的影响

以云南大叶种晒青绿毛茶为原料,通过潮水和添加一定量不同外源物质进行固态发酵。结果表明,不同处理的茶叶外观色泽以及汤色均发生了显著的变化;添加葡萄糖、没食子酸、焦性没食子酸、邻苯二酚、甘氨酸以及混合使用葡萄糖与没食子酸处理的茶叶中,茶褐素的含量分别达到了6.99%、11.29%、10.22%、6.31%、9.25%和7.30%,显著高于对照干茶样（1.76%）和仅添加水的处理样（2.87%）;但有山梨酸钾存在时,样品中茶褐素的含量与对照差异极小。结果还表明,抗坏血酸氧化反应和茶叶内含成分对茶褐素的形成也有较大作用。     

根际氧环境对水稻幼苗根系微形态结构的影响及其生理机制

【目的】研究根际氧环境对水稻幼苗根系微形态建成的影响及其生理机制,以期为水稻幼苗理想根型的构建提供理论依据。【方法】以春优84和秀水09为材料,用国际水稻所营养液配方进行水培试验。秧苗移栽一周后用在线溶氧仪(氮气、氧气调节)设定低氧(0~1.0 mg/L)、中氧(2.5~3.5 mg/L)和高氧(>6.0 mg/L,饱和溶解氧处理,在水稻生长过程中用充气泵连续向水体中充入空气)和常规水培(CK,不进行氧调节,水稻移栽一周后水中氧含量约为0.3~2.5 mg/L) 4个氧处理,研究水稻幼苗生物量、根系微形态结构、根系分泌有机酸、呼吸强度等指标。【结果】1）各处理水稻幼苗根系直径为d₁(0~0.50 mm)、d₂(0.51~1.00 mm)和d₃(1.01~1.50 mm)的细根占总根的比例均超过90%,对水稻苗期根系形态构建尤为重要。中氧处理后,春优84直径为d₁、d₂和秀水09直径为d₁、d₃的根的根长和根表面积均明显高于对照。2）低氧处理减少地上部和地下部生物量,抑制细根(d₁)生长,促进粗根(d₅, 2.01~2.50 mm)的生长,降低呼吸强度,增加有机酸分泌量。中氧和高氧处理后水稻植株的生物量均有增加,但生理反应不尽相同。中氧处理后水稻根系呼吸强度上升,而高氧处理后根系呼吸强度降低。各氧处理均减少水稻幼苗根系生长素(IAA)含量,中氧和高氧处理与对照间差异达显著水平。高氧处理显著增加根系一氧化氮(NO)含量,其他处理间差异不显著。3）相关分析结果表明,两供试品种总根和细根(d₂)的各形态指标(根长、表面积和体积)均与根系有机酸分泌量、呼吸强度、NO含量正相关,与生长素(IAA)含量负相关。【结论】适当增氧(中氧)处理增加水稻幼苗根系呼吸强度和有机酸分泌量,根系生理活性增强;增加细根(直径为0~1.50 mm)的根长、吸收面积的占比,优化其根系形态结构。因此,生产上可以通过栽培措施改变根际氧环境调控分蘖期水稻根系微形态结构,增强根系功能。     

Lxx侵染甘蔗后在蔗茎中的积累及对蔗茎组织结构的影响

以接种病原菌 Leifsonia xyli subsp. Xyli（Lxx）的‘拔地拉’（‘Badila’）甘蔗为研究材料,利用实时定量PCR技术研究病原菌Lxx在蔗茎中的积累情况,采用半薄切片技术研究茎维管束的病变规律。结果表明,在接种Lxx的Badila中,Lxx菌量积累随蔗茎由基层到尾层呈现递减趋势。半薄切片结果表明,接种Lxx蔗茎基部维管组织中的韧皮部和木质部损坏严重,甘蔗茎节处相对茎间的基本细胞小得多,且具有木质部异形、细胞大小不一、细胞整体较为密集。接种Lxx蔗茎维管组织中的韧皮部和木质部损坏程度与Lxx菌量分布呈正相关。甘蔗茎节与茎间的组织结构差异是Lxx菌量由基层到尾层呈现递减的原因之一。本研究为进一步研究Lxx与甘蔗寄主的互作提供了理论依据。     

稻田种植结构的生物多样性及对害虫和天敌种群的影响

农田作物种植结构的调整必然导致益害生物多样性的变化。在永州冷水滩两年的试验结果表明：与常规种植相比较,西瓜、蔬菜或其他作物与大面积水稻镶嵌式或插花式种植,可使水稻主要害虫稻飞虱、二化螟、稻纵卷叶螟高峰期虫量分别减少314头／百丛,24300头／hm2,25800头／hm2,蜘蛛和捕食性天敌等高峰期数量增加64头／百丛;套间作辣椒的主要害虫茶黄螨危害率只有7．1％。合理的作物种植结构,可促使生物多样性向有利于作物高产稳产、降低农药使用量、改善生态环境的方向发展。     

盐碱土类型对花生种子萌发过程中种子际土壤菌群结构的影响

本研究以不同含盐量的滨海盐土、内陆盐碱土和中等肥力非盐碱土壤为实验对象,探讨花生种子在吸水膨胀与萌发过程中,不同类型盐碱土对种子际土壤微生物多样性变化的影响。本实验对不同土壤样品中细菌的16SrRNA基因的V3-V4区进行PCR扩增;利用高通量测序的方法对12份V3-V4高变区PCR产物进行测序,并对测序数据进行生物信息学分析。结果显示:(1)东营青坨滨海盐土种子际土壤细菌群落多样性大于聊城高唐内陆盐碱土花生种子际土壤细菌群落多样性。(2)不同类型土壤样本微生物群落结构在纲水平存在明显差异。4种土壤中的种子际细菌共分属于6个菌纲,分别为Proteobacteria、Actinobacteria、Actinobacteria、Bacteroidetes、Acidobacteria和Firmicutes菌纲,并均以Proteobacteria和Actinobacteria菌纲为主要菌纲。全样本菌落结构分析结果表明,4种类型土壤中不同吸胀时间内种子际微生物菌落在门、属水平上的类型和丰度差异最为显著(p0.05)。(3)beta多样性分析和各样本遗传距离(phylogenetic distances)聚类树图分析表明,4个土壤类型的12个土壤样本种子际土壤中微生物群落均可聚为2大类。上述研究结果为盐碱地花生保全苗、促早发提供了重要的理论依据。     

白茶多糖的提取与结构初探

白茶经热水浸提、浓缩、醇沉、透析等工序制得一种白茶多糖,这种多糖采用saveg法处理前后的IR谱图和单糖组成均无变化。结果表明,白茶多糖是一种由8个单糖组成的寡糖,分子量为1453～1468,其结构中含有1个鼠李糖基、2个阿拉伯糖基、1个未知单糖A基、1个葡萄糖基和3个半乳糖基,单糖通过苷键结合。白茶多糖结构中不含氨基酸或其他酸性基团。