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991.
碳酸二异十三酯是一种性能优良的合成润滑油基础油。在甲醇钠的催化作用下,以异十三醇和碳酸二甲酯为原料合成了碳酸二异十三酯。研究了催化剂用量、原料配比、反应时间及温度等因素对酯交换反应的影响。结果表明,较佳合成工艺条件是:催化剂甲醇钠∶碳酸二甲酯=0.02∶1(物质的量比),异十三醇∶碳酸二甲酯=2.4∶1(物质的量比),反应时间2 h,反应温度160℃。实验室产品收率达80%以上,产品黏度指数介于80~90,产品倾点低于-40℃,100℃黏度大于4 mm2/s,适合于做合成润滑油基础油。碳酸二异十三酯合成油应用于SL 5W-30汽油机油中,在低温性能方面表现良好,能够达到低温指标要求。用红外光谱和质谱对反应产品进行了结构确定。 相似文献
992.
Is rumen development in newborn calves affected by different liquid feeds and small intestine development? 总被引:1,自引:0,他引:1
Górka P Kowalski ZM Pietrzak P Kotunia A Jagusiak W Zabielski R 《Journal of dairy science》2011,94(6):3002-3013
The objective of the study was to determine the effect of different liquid feeds on calf small intestine and rumen development. Twenty-one bull calves (5 ± 1 d old) were randomly allocated to 3 groups and fed whole milk (WM), milk replacer (MR; 22% CP and 17.5% fat), or MR supplemented with sodium butyrate (MR+SB; 0.3% as fed). Liquid feed dry matter intake was equal between treatments and amounted to 1% of BW at the beginning of the trial. Starter diet was offered ad libitum. Animals were slaughtered at 26 (±1) d of age. Calves fed WM had higher average daily gain in the whole trial and higher starter diet dry matter intake between d 15 to 21 of the trial as compared with calves fed MR and MR+SB. Calves fed MR lost on average 1.4 kg of BW within first 14 d of the trial and their BW tended to be lower at d 7, 14, and 21 of the study as compared with calves fed MR+SB. The empty jejunum and ileum weight, crypt depth, mitotic index in the middle jejunum were higher, and apoptotic index tended to be lower in calves fed WM as compared with calves fed MR and MR+SB. Calves fed WM also had higher aminopeptidase N activity in the middle jejunum and tended to have higher maltase activity in the distal jejunum as compared with calves fed MR and MR+SB. The mitotic index was higher and apoptotic index was lower in the middle jejunum, and aminopeptidase A activity tended to be higher in the distal jejunum of calves fed MR+SB as compared with those fed MR. Calves fed WM had greater papillae length and width, and tended to have greater muscle layer thickness as compared with calves fed MR and MR+SB. Reticulorumen weight, reticulorumen weight expressed as percent of whole stomach weight, and papillae length and width were higher in calves fed MR+SB as compared with those fed MR. Additionally, calves fed WM had higher plasma glucose and urea in the whole trial period as compared with calves fed MR and MR+SB, and plasma glucose was higher in calves fed MR+SB as compared with those fed MR. Significant positive Pearson correlations were found between small intestine and reticulorumen weights as well as between activity of brush border lactase, maltase, aminopeptidase A, and aminopeptidase N and reticulorumen weight. Different liquid feeds affect small intestine development, animal growth, solid feed intake and metabolic status of calves and this effect can indirectly influence the development of forestomachs. 相似文献
993.
Milk production, rumen fermentation, and whole-tract apparent nutrient digestibility in response to feeding 20% steam-rolled wheat with or without sodium bicarbonate were evaluated in 12 Holstein cows averaging 165 ± 16 DIM. Cows were fed 1 of 2 isoenergetic and isonitrogenous diets containing either 0 or 0.75% sodium bicarbonate on a DM basis for 21 d in a crossover design. Rumen fluid samples were obtained 18 times during the last 2 d of each period, and fecal samples were collected on 12 occasions from d 18 to 21 of each period. Removal of sodium bicarbonate from the diet did not affect DMI (21.0 kg/d), yields of milk (30.8 kg/d), or milk components (1.16, 1.01, and 1.40 kg/d for fat, protein, and lactose, respectively). Whole-tract apparent digestibility of DM, CP, ADF, and NDF did not differ between the 2 treatments (75.3, 76.6, 67.2, and 63.6%, respectively). The mean rumen pH was 6.24 and was not affected by excluding sodium bicarbonate from the diet. Rumen NH3-N (12.31 mg/dL) and lactic acid (3.63 mM) concentrations were not different, whereas total volatile fatty acids concentration tended to increase when sodium bicarbonate was present in the diet (110 vs. 116 mM). However, average concentrations of the individual volatile fatty acids, as a proportion of total volatile fatty acids, were not affected by treatment. In conclusion, dairy cow diets can include up to 20% steam-rolled wheat without the need for added sodium bicarbonate as long as the diets are formulated to meet the fiber requirements of the cow. 相似文献
994.
Martins JP Policelli RK Neuder LM Raphael W Pursley JR 《Journal of dairy science》2011,94(6):2815-2824
Luteolysis is a key event in Ovsynch programs of lactating dairy cows. Studies indicate that as many as 20% of cows treated with a Presynch/Ovsynch program have delayed or incomplete luteolysis using dinoprost tromethamine. Cows must have complete luteolysis to have a chance to become pregnant. Dinoprost tromethamine has a short half-life of approximately 7 to 8 min. Cloprostenol sodium is more resistant to endogenous metabolism and is maintained in circulation for a longer time (half-life = 3 h). The objective was to determine if cloprostenol sodium could increase the percentage of cows with complete luteolysis and subsequent pregnancy per artificial insemination (P/AI) in lactating dairy cows compared with dinoprost tromethamine when administered within a presynchronization plus Ovsynch program for first artificial insemination (n = 652) and an Ovsynch resynchronization program for second or later AI (second+; n = 394). Blood samples were collected daily for 5 d beginning at the PGF2α of Ovsynch in a subset of cows (n = 680) for first and second+ AI to measure circulating concentrations of progesterone (P4) and estradiol (E2). Complete luteolysis was defined as cows with functional corpus luteum (CL) at time of treatment and serum concentrations of P4 <0.5 ng/mL at 56, 72, and 96 h after treatment. Percentage of cows with functional CL that had complete luteolysis after treatment was not greater for cloprostenol sodium compared with dinoprost tromethamine in first (79 vs. 80%, respectively) or second+ AI (70 vs. 72%, respectively). In addition, mean serum concentrations of P4 were not less for cows treated with cloprostenol sodium following treatment. Pregnancy per AI of cows treated with cloprostenol sodium tended to be greater than dinoprost tromethamine for first (40 vs. 35%; respectively) but not second+ AI (23 vs. 21%, respectively). Cows with greater serum P4 concentrations at time of PGF2α of Ovsynch had a greater probability of undergoing complete luteolysis after PGF2α of Ovsynch and pregnancy at 39 d after timed AI (i.e., 50% pregnant at 8 vs. 28% pregnant at 4 ng/mL P4). Serum concentrations of E2 at 56 h after PGF2α of Ovsynch were a positive predictor of pregnancy at 39 d after timed AI. In summary, cloprostenol sodium tended to improve P/AI. Cows with greater serum concentrations of P4 at time of PGF2α of Ovsynch had a greater chance of luteolysis and pregnancy. 相似文献
995.
996.
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998.
乙酸钠浓度对AZ91D镁合金锡酸盐转化膜的影响 总被引:1,自引:0,他引:1
镁合金的无铬化学转化处理已成为其防护技术研究的一个重要方向,为此,开发了一种以乙酸钠为主要成分的镁合金锡酸盐转化工艺,采用全浸腐蚀试验、扫描电镜(SEM)、X射线衍射(XRD)等方法研究了AZ91D镁合金在含不同乙酸钠浓度成膜液中所形成膜层的结构,并比较了膜层的耐腐蚀性能.结果表明:成膜过程中,随着成膜液中乙酸钠浓度的... 相似文献
999.
1000.
采用聚乙二醇单甲醚(1000、2000)、甲基丙烯酸、阻聚剂、催化剂、引发剂、苯乙烯、丙烯酰胺和对苯乙烯磺酸钠合成了用于水泥沥青砂浆的聚羧酸减水剂.研究了酸醇摩尔比和苯乙烯、丙烯酰胺、对苯乙烯磺酸钠的用量对合成减水剂性能的影响.对聚羧酸减水剂配比进行了优化,进行了中试,制备了CA砂浆样板,并进行性能测试.用GPC对中试聚羧酸减水剂进行了表征.结果表明:大单体的制备及减水剂聚合工艺是可行的.最佳酸醇摩尔比为4.0:1.0,苯乙烯和丙烯酰胺的最佳用量均为3%,对苯乙烯磺酸钠用量以不超过3%为宜.掺该合成聚羧酸减水剂的CA砂浆性能良好,制备的CA砂浆样板基本无缺陷. 相似文献