一类递推方程的周期性和渐近性

本文考虑差分方程xn+1=α+βxpn-k/xpn-l解的周期性、渐近性质和渐近稳定性.其中α≥0,β＞0,p≠0,k,l是非负整数,μ=max{k,l},及初值x-μ,x1-μ,…,x0是任意正实数.     

阶星形的几种特性

证明了当ｎ≥２，ｐ≥２ｎ－ ２，且（ － １）ｎｓｇｎ（ Ｃ２ｎ－ １） ≥０ 时，ｅｘｐ（ｑ） 的ｐ 阶（ｎ ，ｎ） 有理逼近Ｒｎｎ（ ｑ） 的阶星形有ｎ 个齿弧完全含于右半复平面，并得到了齿弧分布的两条一般性质     

Cytoplasmic and nuclear genetic components of membrane stability of winter wheat plants exposed to sub‐zero temperatures

Winter wheat (Triticum aestivum L.) is seeded in the autumn and harvested the following summer, and therefore, must survive multiple episodes of subfreezing temperatures throughout the winter months. Cellular membrane stability following exposure to subfreezing temperatures contributes to the ability to survive these episodes. This study investigated the inheritance of the ability to tolerate subfreezing temperatures with a seven‐parent diallel cross analysis of cellular membrane integrity as measured by electrolyte leakage after exposure to ?10 or ?14 °C. Significant differences in membrane stability were found among the parent lines. The inheritance of the freezing tolerance as measured by electrolyte leakage was complex and characterized by significant additive, dominant and cytoplasmic effects. General combining ability, indicative of additive genetic effects, were significant at both test temperatures, but accounted for 25.5% of the variance at the ?10° C test temperature, and only 4% of the variance at the ?14 °C test temperature. Specific combining ability, indicative of genetic dominance effects, were significant at both test temperatures, but accounted for only 14.6% of the variance at the ?10 °C test temperature, and 38% of the variance at the ?14 °C test temperature. Reciprocal (cytoplasmic) effects were significant and accounted for about 20% of the variance at both test temperatures. Cytoplasmic effects contributing to greater membrane stability were especially apparent in the cultivar Tiber when crossed to Masami, Lewjain, or Hatton. These results suggest that efforts to improve freezing tolerance are complicated by differing gene action at different test temperatures and also may benefit from identifying specific combinations of nuclear and cytoplasm sources that are most conducive to membrane stability following freezing.     

Effects of wheat tempering and stone rotational speed on particle size,dough rheology and bread characteristics for a stone-milled weak flour

The poor technological performance of weak wheat flours means that they are usually considered difficult to be transformed into satisfactory bread. During milling, there are several settings that can affect flour characteristics. In this study, we tested two operative parameters that have the potential to affect flour quality – stone rotational speed and wheat tempering. Tempering moistures were set at 11%, 13%, 15%, and 17%, while stone rotational speeds were set at 173, 260, and 346 rpm. Both factors were found to affect operative milling parameters, notably flour yield, process productivity and specific energy consumption. Grain moisture had a significant effect on both dough rheology and bread characteristics (dough stability, tenacity, and extensibility). Dough stability was maximum at 13% moisture. Dough tenacity decreased as moisture increased, while extensibility increased as moisture increased. Bread specific volume and crumb specific volume were improved at 13% and 15% moisture. In conclusion, wheat tempering can be used to improve the potential of a weak flour and bread characteristics, while stone rotational speed affects operative parameters and white flour yield.     

Increasing oxidative stability in corn oils through extraction of γ-oryzanol from heat treated rice bran

Corn oil was mixed with heated rice bran with different extraction periods and ratios of rice bran to corn oil to extract γ-oryzanol from rice bran. Selected corn oils based on the content of γ-oryzanol were heated at 180 °C for 100 min or 60 °C for 16 days, and oxidative stability was evaluated. Corn oils recovered from the mixture of rice bran showed higher oxidative stability at both 60 and 180 °C treatment compared to control corn oils. At 180 °C, corn oils of a 1:5 ratio of rice bran to corn oil (w/w) showed higher oxidative stability than did those of 1:3 and 1:7 (w/w), whereas at 60 °C, corn oils of 1:7 (w/w) showed higher oxidative stability than did others. γ-Oryzanol can be extracted through a corn-oil mixture at 80–90 mg/100 g oil, which is about 4.0% recovery of 2244 mg/100 g crude rice-bran oil. Oxidative stability of corn oils increased significantly, partly because of the extraction of γ-oryzanol under current experimental conditions.     

Digital imaging as a tool to study the structure of porous baked foods

Processing of images captured by a digital camera showed to be useful in studying the microstructure (porosity characteristics and fractal dimension) of leavened baked products. Five different samples were baked including a control and 4 other samples in which wheat flour was partially replaced with other plant flours. Pasting temperature (°C) ranged from 72.94 to 76.25 with chickpea flour showing the highest value. The sample containing amaranth flour presented high porosity (8.23%) with high number of large pores. Whereas, the number of pores was highest for teff flour with 209 pores. This is an indication of weak potential of amaranth flour in stabilizing gas cells. The fractal dimension ranged from 1.644 to 1.683, where amaranth flour showed the lowest fractal dimension. The pore characteristics evaluation, pore size distribution, number of pores, mean area and largest area of pores were influenced when gluten was reduced. Processed images proved that coalescence can be a cause of large pore development when gluten is partially removed.     

Evaluation of yield,stability and adaptability of national winter rapeseed regional trials in the upper Yangtze River region in 2017-2018

Rapeseed variety needs to be tested by regional trial in multiple sites for many years before being applied in market in China. Performants of rapeseed were affected by the interaction of sites and varieties. Evaluation of regional trials is very important for guiding rapeseed breeding. GGE (genotype main effects and genotype ​× ​environment interaction) biplot was used to evaluate yield, stability, adaptability, representativeness and discrimination of national winter rapeseed trials in the upper reaches of Yangtze River in 2017-2018. Results showed that the main effects of genotype (G), environment (E) and genotype ​× ​environment interaction (G × E) were significant (P ​< ​0.01) for yield. Among them, E accounted for 46.95% total variation on average, G and G × E accounted for 19.34% and 33.71% respectively. Eight varieties were found with high-yield, excellent stability and adaptability, including ‘Yiyou 29’, ‘Xiwang 920’, ‘Liyouza 108’, ‘Nanyou 546’, ‘Dadi 195’, ‘Jiayou 1’, ‘Huayouza 28’ and ‘Yuhua 2’. Test sites included Nanchong, Mianyang, Wanzhou, Shuangliu and Chengdu in Sichuan Province and Zunyi together with Guiyang in Guizhou Province were selected for their excellent representativeness and discrimination. These results would provide theoretical basis for rapeseed breeding.     

高蛋白饮用型酸乳体系中微粒化乳清蛋白和物理改性淀粉对稳定性的影响

将微粒化乳清蛋白和2 种物理改性淀粉（大麦物理改性淀粉和大米物理改性淀粉）作为酸乳清洁标签的高蛋白饮用型酸乳体系，研究微粒化乳清蛋白（0.5 g/100 mL）和2 种物理改性淀粉（0.5、1.0 g/100 mL）对酸乳体系的影响。结果表明：5 种不同酸乳体系均具有较好的持水性和较高的黏度，其中，大麦物理改性淀粉添加量为1.0 g/100 mL的酸乳体系持水力最高，达70.20%，该体系黏度也最高，为4 422 mPa·s；粒径分布和流变学特性分析结果均显示，大麦物理改性淀粉对酸乳体系的稳定性有较好的维持作用；微粒化乳清蛋白酸乳体系指标值略低于物理改性淀粉体系，但是差异并不明显。     

接装纸涂胶量对卷烟滤嘴通风率的影响

为使接装纸透气度及滤嘴通风率在指标范围内保持稳定,采用单因素试验法,研究接装纸涂胶量对接装纸透气度及滤嘴通风率的影响,以及接装纸涂胶量随接装机运转速度和接装纸包角的变化关系。结果表明,1接装纸涂胶量对接装纸透气度及滤嘴通风率的影响显著;2接装纸涂胶量随接装机运转速度的提高而减少;3接装纸涂胶量随接装纸包角的增大而增加。并建立了接装纸涂胶量与接装机运转速度和接装纸涂胶量与接装纸包角之间的函数关系,经过分析计算得到了接装纸包角与接装机运行速度的数学模型。当接装机运转速度发生变化时,该模型可通过调节接装纸包角使接装纸涂胶量保持稳定,进而使接装纸透气度及滤嘴通风率保持稳定。     

长白山芳香植物精油膏的研制

将黄花蒿等11种长白山特有药用草本植物精油与化妆品基质配制成植物精油膏,并对其进行了稳定性及安全性检测。结果表明,精油膏在10 000 r/min下离心10 min,在-5、25、40℃等不同温度下放置24 h并循环3次,均表现出牢固的稳定性;甲醇含量为0.081%;砷、汞、铅限定物质含量分别是0.011 81、0.000 85、0.035 50 mg/kg,均符合国家标准。利用长白山特有草本植物精油制得的芳香植物精油膏是一个安全、有效、无毒的绿色产品,具有良好的开发前景。