螺旋弯管内流动与传热特性的数值模拟

针对螺旋弯管内的流动与传热特性,以螺旋弯管传热试验中试验件模型为研究对象,基于Realizable k-ε湍流模型、第一类热边界条件下的薄壁热阻模型,对不同进口来流条件下,采用Fluent对螺旋弯管内水的流动与换热进行数值模拟.计算得到了螺旋弯管内速度场与温度场的分布,通过数值模拟结果与试验结果的比较,验证了数值模拟方法的正确性.结果表明:随着进口来流雷诺数的增大,螺旋弯管内的二次流迪恩涡核心向弯管管壁扩张;在螺旋弯管小曲率比、来流雷诺数2 280~6 000内,螺旋弯管的强化换热综合性能最佳;对模拟结果数据利用多元线性回归法,推导出螺旋弯管内换热努赛尔数、进出口压力降的准则关系式.研究结果可为螺旋管式换热器设计与优化提供一定的参考依据.     

低压电力系统配电母线N级联锁的算法

在电力系统中，由于开关容量及运行方式限制，通常在低压系统中多采用1段母线、1台变压器运行方式。为了避免这种运行方式在母线检修、故障时可能造成停电的缺点，因此可用断路器将单母线分段。母线经断路器分段后。对重要用户可以从不同段引出两个回路，有两个电源供电。母线分段的数目。可以根据电源数目和容量来分．段数越多，停电的范围越小，所需电气设备越多．一般以4～6段为宜。本文对此配电母线进行N级联锁推导其算法．有利于今后解决多级联锁的问题。     

超高压技术在粮食产品加工中的应用

超高压技术是一种非热加工技术,因具有杀菌、保持食品原有营养成分、护色等特点,在食品行业的应用已越来越广泛。目前,超高压技术在粮食产品加工方面的应用发展较快,随着对该技术研究的不断深入,其在粮食产品加工中所发挥的作用也越来越受关注。阐述了国内外超高压技术在粮食产品淀粉改性、蛋白质改性、成分提取、致敏性降低、贮藏(灭菌灭芽)等方面的研究进展,分析了各方面研究结果的意义、应用价值和前景,并对今后应重点关注的研究方向提出了建议。     

排水地段观测井与排水渠水质相关分析

根据田间实测的排水渠与观测井水质资料 ,分析了地下水中全盐量与其组分间的关系 ,以及排水渠与其邻近观测井地下水全盐量及主要离子含量之间的关系。为探讨观测井与排水渠水质间内在关系 ,研究观测井水质与排水渠水质相互转化关系 ,为简化水质监测工作提供指导。     

农机专业《机械制造工艺学》教学方法的探讨

《机械制造工艺学》是工科院校中一门实践性强、涉及面广、灵活性大又十分重要的专业课，对培养学生分析问题和解决问题的能力、创新能力、实践能力等起着重要的作用。为此对农机类专业的《机械制造工艺学》课程教学方法进行了探讨，提出了一些教学措施，并通过实践，取得较好效果。     

Effects of naringenin on PI3K/AKT signaling pathway and endoplasmic reticulum stress and its related apoptotic pathways in rats with myocardial ischemia/reperfusion injury

AIM To observe the effect of naringenin on cardiac injury in ischemia/reperfusion （I/R） rats, and to explore whether the role of naringenin is involved in PI3K/AKT signaling pathway and endoplasmic reticulum stress and its related apoptotic pathways. METHODS SD rats （n=48） were randomly divided into sham operation （sham） group, model （I/R） group, naringenin treatment （NAR） group and naringenin+LY294002 （NL） group. Myocardial I/R injury model was prepared by ligation of left anterior descending coronary artery of rats for 30 min followed by reperfusion for 120 min. After reperfusion, the serum levels of cardiac troponin I （cTnI） was measured by ELISA. HE staining, TTC staining and TUNEL staining were used to detect the myocardial histopathological changes, myocardial infarction area and myocardial cell apoptotic rate. The mRNA levels of endoplasmic reticulum stress-related indicators glucose-regulated protein 78 （GRP78）, C/EBP homologous protein （CHOP） and caspase-12 were detected by RT-qPCR. The protein levels of cleaved caspase-3, GRP78, CHOP, caspase-12, p-PI3K and p-AKT were determined by Western blot. RESULTS Compared with I/R group, the serum content of cTnI, myocardial pathological damage, myocardial infarction area and myocardial cell apoptotic rate were significantly reduced （P<0.05）, the protein levels of cleaved caspase-3, GRP78, CHOP and caspase-12 were decreased （P<0.05）, and the protein levels of p-PI3K and p-AKT were increased in NAR group （P<0.05）. LY294002 attenuated the protective effect of naringenin to some extent. CONCLUSION Naringenin reduces myocardial I/R injury in rats possibly by activating PI3K/AKT signaling pathway and subsequently regulating endoplasmic reticulum stress and its related apoptotic pathways.     

中国野生葡萄抗霜霉病相关基因VpPR4b及其启动子的克隆和功能分析

以中国野生葡萄(Vitis piasezkii)‘留坝-8’(抗霜霉病)和欧亚种葡萄(V.vinifera)‘黑比诺’(易感霜霉病)为材料,克隆得到抗霜霉病相关基因VpPR4b和VvPR4b。序列分析发现VpPR4b和VvPR4b核苷酸序列相似性为98.61%。VpPR4b编码区为432 bp,编码143个氨基酸,含有BARWIN保守结构域,属于典型的Ⅱ型PR4蛋白。VpPR4b和VvPR4b均可在霜霉菌侵染后诱导表达。亚细胞定位表明VpPR4b定位于细胞膜上。分别从‘留坝-8’和‘黑比诺’中克隆得到了VpPR4b和VvPR4b的启动子,其序列相似性高达95.65%,并且含有相似的顺式作用元件。通过酵母单杂交验证了转录因子WRKY40和WRKY75可以结合VpPR4b启动子。本研究的结果表明PR4b可能在葡萄抵御霜霉病侵染过程中发挥一定作用。     

MicroRNA-9-5p mediates sympathetic overactivity by targeting KCNN3 in paraventricular nucleus of rats with T2D

AIM To investigate whether microRNA-9-5p （miR-9-5p） mediates sympathetic overactivity by targeting KCNN3 （potassium intermediate/small conductance calcium-activated channel, subfamily N, member 3） gene,which encoded small-conductance calcium-activated potassium channel 3 （SK3） protein, in paraventricular nucleus （PVN） of rats with type 2 diabetes mellitus （T2D）. METHODS A rat model of T2D was established by high-fat diet combined with intraperitoneal injection of 30 mg/kg streptozotocin. The levels of miR-9-5p and KCNN3 mRNA in PVN were detected by real-time PCR. The relationship between KCNN3 and miR-9-5p was predicted by TargetScan. Recombinant adeno-associated virus （rAAV）-miR-9-5p or KCNN3 were bilaterally microinjected into the PVN to observe the changes in plasma glucose levels and sympathetic drive indicators. The number of FosB and SK3 positive cells was measured by immunofluorescence staining. The protein expression of SK3 was determined by Western blot. The relationship between KCNN3 and miR-9-5p were confirmed by cell transfection and dual-luciferase reporter assay. RESULTS Compared with the rats in diabetes control （DC） group, the blood glucose, sympathetic drive indexes and the level of miR-9-5p in PVN were significantly increased, while the SK3 expression in PVN was obviously reduced in the diabetes mellitus （DM） rats. After microinjecion of rAAV-miR-9-5p in PVN, the sympathetic drive indexes, blood glucose, and the number of FosB-positive cells were increased significantly, but the SK3 protein expression was significantly reduced （P<0.05）. However, up-regulation of KCNN3 in PVN had the opposite effect. These responses were obviously enhanced in DM rats compared with DC rats. The results of cell transfection and dual-luciferase reporter assay demonstrated that miR-9-5p bound to the 3’-UTR of KCNN3 and inhibit its expression. CONCLUSION miR-9-5p was up-regulated in PVN of the rats with T2D, and it may mediate sympathoexcitation by targeting KCNN3.     

美国梨产业概况及砧穗组合评价与利用

美国梨产量位居世界第2位,商业生产主要集中在美国西北部,其中华盛顿州和俄勒冈州占美国梨总产量的77%,但美国梨种植面积、单产和消费量都呈下降趋势。随着梨管理和劳动力成本的快速上涨,采用旧的栽培模式能够获得的利润已经很少,选育和利用早果、丰产和抗性强的矮化砧木,进行高密度栽植,才能保持美国梨产业的国内和国际市场竞争力。美国梨砧穗组合的评价研究主要集中于嫁接亲和性、产量效率、早果性、丰产性、矮化性、果实品质等方面,其他性状还包括抗盐碱、抗旱、抗寒以及对火疫病、衰退病和黑星病的抗性等。初步评价结果认为,美国最有发展前途的梨砧木是‘OH×F 87’‘OH×F 97’‘OH×F 69’和Pyro 2-33。