热处理工艺对新型轻质奥氏体耐磨钢的组织与力学性能的影响

以新型轻质高锰、高铝的奥氏体耐磨钢为研究对象,利用XRD,OM,SEM,EDS观察显微组织和析出物,研究不同的热处理工艺对新型钢种的组织与力学性能影响。结果表明:该新型轻质奥氏体耐磨钢的最佳优化热处理工艺为1050℃保温1h水韧,550℃时效2h,空冷。在最佳热处理工艺条件下奥氏体基体内弥散析出细小的钙钛矿结构(Fe,Mn)3AlC的κ-碳化物颗粒,不仅强化了奥氏体基体,其力学性能也得到明显改善;最优工艺处理后实验钢的硬度、强度、冲击韧度达到了最佳匹配,其抗拉强度为825MPa,屈服强度为574MPa,冲击韧度值为156J/cm2(V型缺口),硬度为271HB;与只进行水韧处理相比实验钢的屈服强度提高40.0%,硬度提高32.2%。     

纳米卡拉胶微球的制备

利用 Span 80作表面活性剂 ,正丁醇作助表面活性剂制得反相微乳液。将天然海洋高分子κ-卡拉胶进行酸水解使其分子量降低 ,通过反相乳液法对水解后的κ-卡拉胶进行分散并用甲醛和戊二醛进行交联 ,制备卡拉胶微球 ,利用 TEM、IR研究了卡拉胶微球的粒度和分子结构变化。 TEM显示 :低分子量的卡拉胶能够得到纳米级的卡拉胶微球 ,粒径约为 40 nm,添加正丁醇有助于卡拉胶的分散。 IR光谱证明了甲醛和戊二醛在卡拉胶微球内部发生了羟醛缩合反应 ,产生了交联     

认知双向中继网络在κ-μ衰落信道下的中断性能分析

针对认知双向中继网络在进行数据传输时面临的复杂无线信道场景问题,采用广义κ-μ分布构建认知双向中继网络中的视距和非视距无线传输信道,推导次网络在κ-μ衰落信道下的统一中断概率,并分析次网络在多种单一和混合衰落信道情况下的中断性能.仿真结果表明,无线信道的衰落程度对次网络的中断概率影响显著,依据衰落信道类型合理设置网络参...     

Cooperative learning neural network output feedback control of uncertain nonlinear multi-agent systems under directed topologies

Without assuming that the communication topologies among the neural network (NN) weights are to be undirected and the states of each agent are measurable, the cooperative learning NN output feedback control is addressed for uncertain nonlinear multi-agent systems with identical structures in strict-feedback form. By establishing directed communication topologies among NN weights to share their learned knowledge, NNs with cooperative learning laws are employed to identify the uncertainties. By designing NN-based κ-filter observers to estimate the unmeasurable states, a new cooperative learning output feedback control scheme is proposed to guarantee that the system outputs can track nonidentical reference signals with bounded tracking errors. A simulation example is given to demonstrate the effectiveness of the theoretical results.     

Isolation of recombinant antibody fragments (scFv) by phage display technology for detection of almond allergens in food products

Tree nut allergies are considered an important health issue in developed countries. To comply with the regulations on food labeling, reliable allergen detection methods are required. In this work we isolated almond-specific recombinant antibody fragments (scFv) from a commercial phage display library bypassing the use of live animals, hence being consistent with the latest policies on animal welfare. To this end an iterative selection procedure employing the Tomlinson I phage display library and a crude almond protein extract was carried out. Two different almond-specific scFv (named PD1F6 and PD2C9) were isolated after two rounds of biopanning, and an indirect phage ELISA was implemented to detect the presence of almond protein in foodstuffs. The isolated scFvs demonstrated to be highly specific and allowed detection of 40 ng mL⁻¹ and 100 ng mL⁻¹ of raw and roasted almond protein, respectively. The practical detection limit of the assay in almond spiked food products was 0.1 mg g⁻¹ (110–120 ppm). The developed indirect phage ELISA was validated by analysis of 92 commercial food products, showing good correlation with the results obtained by a previously developed real-time PCR method for the detection of almond in foodstuffs. The selected phage clones can be affinity maturated to improve their sensitivity and genetically engineered to be employed in different assay formats.     

Long-term storage stability of selected potato starch – Non-starchy hydrocolloid binary gels

All 3, 4 and 5% potato starch gels containing either κ-carrageenan, guar gum or xanthan gum were prepared and their stability in terms of rheological and textural properties was checked on 30 day storage. It was shown that rheology of these binary potato starch – non-starchy hydrocolloid mixtures could be controlled by anionic character of the admixed hydrocolloid. Depending on the hydrocolloid added, gels made of the tuber starch can either retain their pattern typical for tuber starches or turn into that typical for gels of cereal starches. Hydrocolloids added plasticity to the binary gels but it was lost to a significant extent within the first day of storage. Resulting gels with dominating elastic character are rheologically and texturally fairly stable for subsequent 30 days of storage. Generally, hydrocolloids stabilized potato starch gel on long-time storage to the extent dependent on the gel concentration.     

The anticarcinogenic potential of essential oil and aqueous infusion from caper (Capparis spinosa L.)

The present study assessed the influence of essential oil and aqueous infusion from wild-grown caper (Capparis spinosa L.) on cell growth, NF-κB activation, apoptosis and cell cycle in the human colon carcinoma cell line, HT-29. Methyl isothiocyanate (92.06%), a degradation product of glucosinolate glucocapparin, was detected as major component of essential oil from caper leaves and flower buds. Aqueous infusion of caper showed an interesting and variegate compositional pattern containing several phenolic compounds, among which a flavonol glycoside, rutin (quercetin 3-O-rutinoside, 50.7%) and 5-caffeoyl-quinic acid (chlorogenic acid, 17.5%) were detected as dominant. Caper essential oil and aqueous infusion showed time- and dose-dependent high inhibitory effect on HT-29 cell proliferation. In addition, they induced the inhibition on nuclear factor κB (NF-κB) activity in a dose-dependent manner, while they did not show any effect on apoptosis in HT-29 cells. Flow cytometric analysis indicated that treatment with caper essential oil and aqueous infusion resulted in G₂/M cell cycle arrest in a dose-dependent manner. Presented results suggest that caper contains volatile and non-volatile compounds which potentially can play an important role in colon cancer prevention.     

κ-卡拉胶影响大豆分离蛋白乳浊液稳定性的研究

研究了卡拉胶对大豆分离蛋白乳浊液粒度分布、乳析率和离心沉淀率的影响,在此基础上分析了静置过程中乳浊液粒径与乳析率、离心沉淀率之间相关性,结果表明:乳浊液粒径随卡拉胶浓度由小到大依次为0.03%<空白样<0.06%<0.09%;而体系的表观粘度随卡拉胶浓度的增大而升高;静置过程中乳浊液顶部粒径d3,2与乳析率有较好的相关性;乳浊液底部d3,2与离心沉淀率有很好的相关性。进一步分析了其可能的作用机理:卡拉胶低浓度时,卡拉胶分子被吸附到液滴的蛋白质正电荷区域,增加了液滴间的静电排斥,从而增加了体系的絮凝稳定性;随着卡拉胶浓度增大,卡拉胶会引起体系排斥絮凝。     

Heat-induced aggregation of whey proteins in the presence of κ-casein or sodium caseinate

Aggregates were formed by heating mixtures of whey protein isolate (WPI) and pure κ-casein or sodium caseinate at pH 7 and 0.1 M NaCl. The aggregates were characterized by static and dynamic light scattering and size exclusion chromatography. After extensive heat-treatment at 80 °C for 24 h, almost all whey proteins and κ-casein formed mixed aggregates, but a large proportion of the sodium caseinate did not aggregate. At a given WPI concentration the size of the aggregates decreased with increasing κ-casein or sodium caseinate concentration, but the overall self-similar structure of the aggregates was the same. The presence of κ-casein or caseinate therefore inhibited growth of the heat-induced whey protein aggregates. The results were discussed relative to the reported chaperone-like activity of casein molecules towards heat aggregation of globular proteins.