单双液相下不同多酚氧化酶源对酶性合成茶黄素的影响

比较了单双液相条件下不同来源的多酚氧化酶对酶性合成茶黄素效率的影响。结果表明,在本试验体系下单双液相试验中,以不同的酶源合成茶黄素的试验效果不同,就茶鲜叶酶源而言,双液相明显比单液相的效果要显著,在单液相系统中总乙酸乙酯层茶黄素总含量达33.74%,合成率为14.245%,而在双液相系统中,其总含量达39.74%,合成率为31.792%;而就梨酶源处理而言,单液相的效果要比双液相稍好,在单液相系统中总乙酸乙酯层茶黄素总含量达45.73%,合成率为18.799%;而在双液相系统中,其总含量达40.20%,合成率为22.11%;就苹果酶源而言,单液相比双液相的效果要好些,在单液相系统中总乙酸乙酯层茶黄素总含量达18.22%,合成率为13.34%;而在双液相系统中,其总含量达11.56%,合成率为6.935%。     

混合沙粒对半开式叶轮离心泵磨损的影响

为了研究含有混合多种颗粒粒径的含沙水对离心泵过流部件磨损特性的影响,应用RN G k-ε湍流模型和SIMPLEC算法,基于颗粒离散相模型(DPM)和半经验的McLaury磨损模型,沙粒注入选用Rosin-Rammler分布的拟合方法,对1台半开式离心泵内固液两相流的磨损特性进行数值分析.研究结果表明:叶轮流道内沙粒组分...     

不同采收时间·花期及干燥方法对秀山金银花中绿原酸含量的影响

[目的]测定不同采收时间、花期和干燥方法制备的秀山金银花中的绿原酸含量。[方法]按2005年版《中国药典》规定的HPLC法测定样品中绿原酸。[结果]绿原酸的标准曲线为Y=3.6E＋7X-1.5E＋5,r=0.999 7。[结论]金银花的采摘时间、花期、干燥方法均是影响金银花药材绿原酸含量的重要因素,建议在7：00前采摘二白期金银花,采用杀青烘干。     

驱导辅助充种气吸式精量排种器设计与试验

针对现有气吸式排种器充种环节工作压力要求高、高速作业时充种性能不佳,导致排种质量下降的问题,采用主动驱导种群、减少局部种间接触的方法,提高排种器高速条件下的充种率,并基于此设计了一种驱导辅助充种气吸式精量排种器。分析了排种器充种过程中种子的受力状态,阐述了排种盘导种槽辅助充种的工作原理,以及在充种过程各阶段提高种子充填率的设计思路;对导种槽外形曲线方程、斜面倾角进行了理论计算,确定了曲线的基本参数;利用气固耦合数值分析方法 CFD-DEM,以型孔处局部空隙率为指标,进行了单因素仿真试验,确定了导种槽曲线方程的基圆半径最优值。为了验证设计结果,在工作压力-5、-6 kPa条件下,分别与其他2种气吸式排种器进行速度单因素对比试验,试验结果表明,所设计的排种器在高速条件下的漏充率优于其他排种器。对所设计的排种器进行了前进速度、工作压力的双因素试验,通过多目标优化方法,确定了排种器的最佳工作参数。将所设计的排种器安装在气力式玉米免耕播种机上,在3个工作速度下进行了单因素田间试验,结果表明,当作业速度为9. 11 km/h时,粒距合格指数为95. 48%,高速条件下充种性能较为稳定。     

Effects of continuous low dose infusion of lipopolysaccharide on inflammatory responses,milk production and milk quality in dairy cows

The objective of this study was to evaluate the effects of continuous low dose infusion of lipopolysaccharide (LPS) on inflammatory responses and milk production and quality in lactating dairy cows. Eight Holstein cows were assigned to two treatments in a cross‐over experimental design. Cows were infused intravenously either with saline solution or with saline solution containing LPS from Escherichia coli O111:B4 at a dose of 0.01 μg LPS/kg body weight for approximately 6 hr each day during a seven‐day trial. The clinical symptoms and milk production performance were observed. Milk samples were analysed for conventional components, fatty acids and amino acids. And jugular vein and mammary vein plasma samples were analysed for concentrations of cytokines and acute phase proteins. LPS infusion decreased feed intake and milk yield. An increase in body temperature was observed after LPS infusion. LPS infusion also increased plasma concentrations of interleukin‐1β, serum amyloid A, LPS‐binding protein, C‐reactive protein and haptoglobin. LPS infusion decreased the contents of some fatty acids, such as C17:1, C18:0, C18:1n9 (trans) and C18:2n6 (trans), and most amino acids except for methionine, threonine, histidine, cysteine, tyrosine and proline in the milk. The results indicated that a continued low dose infusion of LPS can induce an inflammatory response, decrease milk production and reduce milk quality.     

Analysis on the Effect of Moisture Migration through Walls on Heat Transfer

A dynamic mathematical model for simulating the coupled heat and moisture transfer through walls was proposed with variable material properties. Relative humidity and temperature were chosen as the driving potentials. The temperature and relative humidity and heat flux of wall surface were calculated under varying boundary conditions and compared with those without taking moisture transfer into account. The results show that without and with absorption and desorption processes, the wall interior surface temperature amplitude of the former case is lager than that of the latter, and the average difference temperature of two cases is 0.9℃. The phase change latent heat caused by absorption and desorption of wall surface takes up 27.5% of the total heat transfer quantity, which cant be neglected.     

浙江省主要畜禽产区养殖废水中抗生素残留研究

结合固相萃取、高效液相色谱—串联质谱分析,建立了适合畜禽养殖废水中磺胺类、氟喹诺酮类、四环素类、氯霉素类等共29种抗生素残留的测定方法,废水样品经盐酸调节pH 6.0、离心后经HLB固相萃取柱净化,液相色谱—串联质谱正离子模式测定磺胺类、氟喹诺酮类、四环素类,负离子模式测定氯霉素类。空白地表水中磺胺类和氟喹诺酮类添加浓度为0.02～1.0μg.L-1,四环素类和氯霉素类添加浓度为0.04～1.0μg.L-1,回收率范围为68.6%～95.0%(n=5),相对标准偏差(RSDs)为2.8%～12.3%,方法的定量限(LOQ)为0.02～0.04μg.L-1。利用该方法对养殖废水、养殖场附近河域20个水样进行测定,检出5种磺胺类化合物和氟苯尼考。     

THE SCINTIGRAPHIC EVALUATION OF SOLID PHASE GASTRIC EMPTYING IN NORMAL CATS

The gastric emptying half-time of solid food in normal cats was determined using a scintigraphic technique. ^99mTc-sulfur colloid was applied to dry food. Sequential images were acquired post prandial, and the gastric emptying half-time was determined for several different acquisition and processing parameters. Good correlation was found between different acquisition and processing methods, some of which made use of edge detection applications, while others used different views, or number of views from which the gastric emptying half-time was calculated. The mean ± standard deviation, (range) and median of the gastric emptying half-time determined using the geometric mean of total counts in hand-drawn regions of interest from the lateral and ventral images were 2.47 × 0.71, (1.42–3.61) and 2.37 hours respectably.     

光皮桦幼林生长节律的观察研究

光皮桦(Betuta luminifera H.Winkl)又称亮皮桦,系桦木科(Betulaceae)桦木属(Betula L)落叶乔木树种.木材呈淡黄或淡褐色,材质细致坚韧、切面光滑、不挠不裂,为优良的军工、航空、建筑、家具和室内装饰用材,也可用于造纸.