具有预防接种且带隔离项的传染病模型的定性分析

本文研究了一类具有预防接种且带隔离项的传染病模型,得到决定疾病流行与否的阈值,给出无病平衡点,地方病平衡点存在性的判定条件.利用Laslle不变原理证明了无病平衡点的全局渐近稳定.利用Hurwitz判别法得到地方病平衡点局部渐近稳定的充分条件,应用半流一致持久性的方法讨论解的一致持久性,应用复合矩阵得到了地方病平衡点的全局渐近稳定的充分条件.     

高强度轮毂的化学成分和熔炼处理工艺的研究

分析了轮毂的工作条件和基本性能要求,从保证其有良好强度和塑性韧性方面,采用强韧性较好的铸态铁素体球墨铸铁制造。对轮毂的化学成分进行设计,确定了其化学成分范围。选用低稀土镁合金的球化剂Re3Mg8,并采用冲入法进行球化处理,同时采用多次孕育处理及增加终硅量,强化孕育效果,使球墨铸铁的强度和塑性韧性得到提高。     

Improving chill control in iron powder treated slightly hypereutectic grey cast irons

Recent studies revealed that in eutectic to slightly hypereutectic grey irons (CE = 4.3%-4.5%) the presence of austenite dendrites provides an opportunity to improve the cast iron properties, as a high number of eutectic cells are "reinforced" by austenite dendrites. An iron powder addition proved to be important by promoting dendritic austenite in hypereutectic irons, but was accompanied by adverse effect on the characteristics of potential nuclei for graphite. The purpose of the present paper is to investigate the solidification pattern of these irons. Chill wedges with different cooling moduli (CM = 0.11 - 0.43 cm) were poured in resin bonded sand and metal moulds.Relative clear / mottled / total chill measurement criteria were applied. Iron powder additions led to a higher chill tendency, while single inoculation showed the strongest graphitizing effect. The various double treatments show an intermediate position, but the inoculant added after iron powder appears to be the most effective in reducing base iron chill tendency, for all cooling moduli and chill evaluation parameters. This performance reflects the improved properties of (Mn,X)S polygonal compounds as nucleation sites for graphite, especially in resin bonded sand mould castings. Both austenite and graphite nucleation benefit from a double addition of iron powder + inoculant,with positive effect on the final structure and chill tendency.     

Improvement of feed intake,digestibility, plasma metabolites,and lactation performance of dairy cows fed mixed silage of sugar beet pulp and rice straw inoculated with lactic acid bacteria

A study was conducted to investigate the inclusion effects of sugar beet pulp and rice straw mixture silage with inoculation (BRMS), in place of whole-plant corn silage (CS), on the dry matter intake, total-tract nutrient digestibility, plasma metabolites, rumen fermentation, and lactation performance in high-production dairy cows. Sixteen multiparous Holstein cows (body weight, 622 ± 35 kg; days in milk, 90 ± 11 d; mean ± standard deviation) were used in our experiments; the experiments were based on a repeated 4 × 4 Latin square design for 21 d, and each experimental period consisted of 14 d of adaptation, followed by 7 d of data collection. The 4 dietary treatments used were (dry matter basis): (1) 0% BRMS and 28.6% CS (0BRMS); (2) 4.3% BRMS and 24.3% CS (15BRMS); (3) 8.60% BRMS and 20.0% CS (30BRMS); and (4) 12.9% BRMS and 15.7% CS (45BRMS). The increasing inclusion of dietary BRMS was observed to linearly increase the total volatile fatty acids and the propionate concentration. The dry matter intake and digestibility values of neutral detergent fiber and acid detergent fiber increased linearly as the percentage of BRMS increased up to 45%. Milk yield linearly increased with the increase in the content of BRMS (39.0, 39.8, 40.9, and 40.3 kg/d for 0BRMS, 15BRMS, 30BRMS, and 45BRMS, respectively). The increasing inclusion of dietary BRMS induced a decrease in the ammonia nitrogen and milk urea nitrogen concentration, leading to a linear increase in milk protein production (1.15, 1.26, 1.35, and 1.27 kg/d for 0BRMS, 15BRMS, 30BRMS, and 45BRMS, respectively). In conclusion, the diets with the replacement of CS with BRMS up to 45% were beneficial to the production performance of high-production dairy cows, indicating that this method may be an appropriate use of sugar beet pulp and rice straw.     

麦汁中啤酒酵母的最适接种量研究

在麦汁中添加的酵母量将影响到啤酒的风味和质量。设计了3个不同接种量,试验其对酵母代谢副产物含量的影响,结果表明,控制接种量在2.0×107个/ml时,对啤酒风味物质高级醇和双乙酰含量合适,并可使啤酒有适当的酒精度和发酵度。(丹妮)     

葡萄酒活性干酵母直投和活化工艺对酒精发酵的影响

选取了6种国内外不同的葡萄酒活性干酵母,分别采用活化与直投工艺,在15 ℃和25 ℃条件下,验证其酒精发酵的代谢动力学及甘油产量的差异。结果表明,在15 ℃发酵条件下,部分活性干酵母直投接种比活化接种晚一天结束发酵;F1酵母活化与直投处理间甘油产量没有显著差异（P＞0.05）,其他5种酵母活化工艺发酵的葡萄酒甘油产量显著高于直投工艺（P＜0.05）;在25 ℃发酵条件下,活化接种和直投接种均在同一天完成酒精发酵,最终残糖均＜4 g/L;F1酵母活化与直投接种之间的甘油产量没有显著的差异（P＞0.05）,A2酵母活化接种后葡萄酒的甘油产量显著低于直投工艺（P＜0.05）,其他4种葡萄酒活性干酵母活化后的甘油产量明显高于直投工艺（P＜0.05）。与活化后接种相比,直投接种可能延长发酵时间,降低甘油产量。     

细菌接种量对铀生物浸出的影响

以某难处理铀矿石为原料,开展了不同细菌接种量对铀生物浸出的影响研究。在相同浸出条件下,经84h浸出,5%、10%、20%和30%细菌接种量的铀浸出率分别为50.46%、56.42%、62.38%和67.05%,细菌接种量越大,铀浸出率也越高。在铀矿生物浸出工艺中,可以通过控制细菌接种量来获得适宜的浸铀效率。     

混合硫酸盐还原菌的筛选及其生理特性研究

从某尾矿坝下500m污泥处筛选得到混合硫酸盐还原菌(SRB),研究了接种量、温度、初始pH、ρ(Fe~(2+))、ρ(SO2-4)以及碳源种类对混合SRB生长的影响。结果表明,该混合SRB在接种量为10%、温度25℃、初始pH=6.5、Fe~(2+)质量浓度为200mg/L、并以乳酸钠为碳源时生长最好。     

烟草青枯病苗期抗性鉴定的漂浮池恒温水培接种法研究

通过建造加热保温漂浮池和池水接种,建立了烟草青枯病抗性的苗期鉴定方法,并评价了该方法的应用效果.结果表明,7个抗性已知的烟草品种通过漂浮池恒温水培接种法鉴定的结果与抗感品种本身的抗病性程度相吻合.漂浮池恒温水培接种抗性鉴定方法具有发病迅速、占地面积小、减少土传病害干扰、重复性高等优点.     

采后热空气处理对枇杷果实抗病性的诱导

研究热空气处理对枇杷果实腐烂和抗病相关酶活性及基因表达的影响。枇杷果实先用43 ℃热空气处理3 h,然后接种炭疽病菌,接种后的果实置于20 ℃条件下贮藏8 d。结果表明,热空气处理有效降低了枇杷果实的自然发病率,显著抑制了接种枇杷果实病斑直径的扩展,诱导了果实中几丁质酶、β-1,3-葡聚糖酶、苯丙氨酸解氨酶（PAL）和多酚氧化酶（PPO）等抗病相关酶活性的增强。热空气处理还可显著诱导接种枇杷果实PAL、PPO、过氧化物酶和热激蛋白基因的表达。同时,热空气处理对枇杷果实的硬度、可滴定酸和可溶性固形物含量等品质指标没有显著影响,但促进了类胡萝卜素的积累。以上结果表明,热空气处理可通过诱导抗病相关基因的表达和抗病相关酶活性的上升,提高枇杷果实的抗病能力。