考虑水文变异的水库生态流量研究

为探讨水文变异对生态流量影响,确定最佳水库生态流量推求方法,针对尼尔基水库生态问题,采用Mann-kendall突变检测法、滑动T检验法和有序聚类法,结合序号总和理论和Spearman相关系数计算对水文时间序列作综合识别,确定水库发生水文变异年份为1963年和1999年。利用NGPRP法和逐月频率年内展布计算法分别计算天然状态、次天然状态、现状和不考虑水文变异条件下最小生态流量和适宜生态流量。参考Tennant法评价结果表明水库生态系统退化主要受人类扰动影响,观察次天然状态和不考虑变异状态下生态径流过程,最小生态流量占多年平均流量百分数相差9.21%和1.70%,适宜生态流量相差3.04%和1.47%。研究应更多考虑次天然生态径流过程,其最小生态流量仅可作为生态流量下限。     

叶片角度对输水泵站泵装置水力性能影响分析

为研究输水泵站泵装置水力性能受叶片角度变化的影响,采用CFD方法模拟全流道泵装置水力性能,分析设计流量工况下叶片角度变化对进水流道、出水流道流动及叶轮内部流动特性和水力性能的影响.结果表明:在设计流量工况下,叶片角度偏离设计工况角度,叶轮进口近轮毂区存在回流、脱流;叶片角度偏离设计工况角度越大,进水流道、出水流道内水流流态越差,水力损失越大.当叶片角度调节为-8°工况时,与叶片角度-0°工况比较,进水流道和出水流道水力损失相对值最大,分别为1.28和2.89.即叶片同等偏离角度下,出水流道水力损失增大幅度较进水流道更加明显.对比数值模拟结果与模型试验结果得出,在设计流量工况,叶片角度为0°时,扬程相对误差为1.2%,效率相对误差为2.1%,两者吻合较好.     

Effect of Plasticizers on Properties of Rice Straw Fiber Film

In order to improve the properties of rice straw fiber film, one factor contrast test method was employed. Plasticizer type was chosen as input variable, dry tension strength and elongation, wet tension strength and elongation, bursting strength and tearing strength were chosen as indexes. The results showed that there were significant differences among the means of dry tension strength, dry elongation and bursting strength of different plasticizers; there were not significant differences among the means of wet tension strength, wet elongation and tearing strength of different plasticizers; for dry tension strength and elongation, glycerol had a significant difference with sorbitol and PEG, no significant difference was observed between sorbitol and PEG, dry tension strength added glycerol had been reduced 6.8% compared with that added sorbitol, reduced 9.5% compared with that added PEG; elongation had been improved 6.1% and 9.4%, respectively; for bursting strength, sorbitol had a significant difference with glycerol and PEG, no significant difference was observed between glycerol and PEG; bursting strength added glycerol and added PEG had been improved 6.9% and 5.6%, respectively compared with that of the added sorbitol. The results provided a theoretical reference for further improving the straw fiber film manufacturing process.     

Phenotypic and genotypic characterization of canine pyoderma isolates of Staphylococcus pseudintermedius for biofilm formation

Biofilm-forming ability is increasingly being recognized as an important virulence factor in several Staphylococcus species. This study evaluated the biofilm-forming ability of sixty canine derived clinical isolates of S. pseudintermedius, using three phenotypic methods, microtiter plate test (MtP), Congo red agar method (CRA) and tube adherence test, and the presence and impact of biofilm-associated genes (icaA and icaD). The results showed that icaA and icaD genes were detected concomitantly in 55 (91.7%) of 60 isolates. A majority (88.3%) of the strains screened had matching results by the tube adherence test, MtP and PCR analysis. Better agreement (95%) was found between the PCR-based analysis and the CRA. Results of the icaA and icaD gene PCRs showed good agreement with CRA results, with a kappa of 0.7. Comparing the phenotypic methods, the statistical analysis showed that the agreement among the phenotypical tests using categorical data was generally good. Considering two classes (biofilm producer and biofilm non-producer), the percentage of matching results between the CRA method and the tube adherence test and between the CRA method and the MtP was 93.3%. A concordance of 100% was revealed between the MtP and the tube adherence test. The results indicate a high prevalence of the ica genes within S. pseudintermedius isolates, and their presence is associated with in vitro formation of a biofilm. A combination of phenotypic and genotypic tests is recommended for investigating biofilm formation in S. pseudintermedius.     

规模化养鸡场A型产气荚膜梭菌的分离鉴定及其对海南霉素敏感性的测定

为探究海南霉素对产气荚膜梭菌的敏感性,在某大型养鸡场采集了209份鸡肠道样本,采用选择性培养基和MALDI-TOF质谱仪微生物鉴定仪鉴定,并对鉴定的菌株进行分型。采用琼脂稀释法测定了海南霉素、恩拉霉素、盐霉素、丁酸甘油酯对临床分离的产气荚膜梭菌的抗菌活性,以期为当前限抗禁抗后养殖场选择合适的药物控制产气荚膜梭菌提供理论依据。试验结果表明：共分离出61株产气荚膜梭菌,分离率为29.2%;通过多重PCR对所分离的产气荚膜梭菌进行分型,结果分离株均为A型产气荚膜梭菌;4种药物均有不同程度的抑菌效果,其中海南霉素与恩拉霉素对鸡源产气荚膜梭菌的抑菌效果最好,且MIC值范围均为0.004～0.06μg/mL。海南霉素具有很好的抗梭菌效果。     

甘肃陇西黄芩灰霉病病原菌分离鉴定及田间药剂防治

为探明黄芩(Scutellaria baicalensis Georgi)茎基部和根部灰霉病的病原菌,本文于2019—2021年春季对甘肃陇西县采集的黄芩病样进行病原菌的分离培养,运用形态学和内转录间隔区(Internal transcribed spacer, ITS)、甘油醛-3-磷酸脱氢酶(Glyceraldehyde-3-phosphate dehydrogenase,G3PDH)、热激蛋白60(Heat shock protein 60,HSP60)和RNA聚合酶亚基II(The second largest subunit of the nuclear RNA polymerase enzyme II,RPB2)多基因方法鉴定,采用菌丝生长抑制法进行药剂室内毒力测定和田间药剂防治试验。结果表明：引起黄芩灰霉病的病原菌为灰葡萄孢(Botrytis cinerea),春季发病时表现为地上部分枯死不发芽,靠近地表的根表面呈暗绿色水渍状,随后地下根木质部变软呈黄褐色腐烂,病健交界明显;室内毒力测定表明,97%咯菌腈对灰葡萄孢菌的抑菌作用最强,EC₅₀为0.01...     

从六力互动模型角度分析天润乳业市场战略

以天润乳业为企业战略分析基点,利用六力互动模型分析天润乳业与供方、买方、替代品厂商、互补品厂商、同行业厂商、潜在进入者六种市场利益主体之间结成的动态竞争及合作关系。基于竞合共生的现实基础,分析天润乳业与六种市场利益主体间竞争与合作的前提条件及相互转换关系,为进一步探寻可持续发展之路,提出转变思维定式、坚持差异化战略、优化产品结构的建议。