Film condensation on horizontal tube with wall suction effects

This study performs a theoretical investigation into the problem of two-dimensional steady filmwise condensation flow on a horizontal tube with suction effects at the tube surface. An effective suction function is introduced to model the effect of the wall suction on the thickness of the liquid condensate film. The local condensate film thickness and the local Nusselt number are then derived using a simple series numerical method. The results show that the Nusselt number varies as a function of the Jakob number Ja, the Rayleigh number Ra, and the suction parameter Sw. It is found that the wall suction effect has a significant influence on the heat transfer performance. An analytical solution is derived for the mean Nusselt number for the case in which the wall suction effect is ignored. Finally, a closed-form correlation is presented for the mean Nusselt number subject to a wall suction effect.     

多媒体教学与传统教学在高职教学中的利弊分析

随着计算机技术的迅速发展,高职教育的发展也受到影响．多媒体教学手段的广泛应用,使传统教学方法受到很大冲击,本文阐述了多媒体教学的特点和传统教学的特点及缺陷,寻找一种结合两种教学方法的新型的合适高职的教学方法。     

Effects of Ge Dopant on Thermoelectric Properties of Barium and Indium Double-Filled p-Type Skutterudites

A series of Ge-doped and (Ba,In) double-filled p-type skutterudite materials with nominal composition Ba_0.3In_0.2FeCo₃Sb_12?x Ge _x (x = 0 to 0.4, Δx = 0.1) have been prepared by melting, quenching, annealing, and spark plasma sintering methods. The effects of Ge dopant on the phase composition, microstructure, and thermoelectric properties of these materials were investigated in this work. A single-phase skutterudite material was obtained in the samples with 0 < x ≤ 0.2, and trace Fe₃Ge₂ was detected in the samples with x ≥ 0.3. The electrical conductivity increased and Seebeck coefficient decreased with increasing x in the range of 0 to 0.2, while the inverse behaviors of electrical conductivity and Seebeck coefficient were observed in the samples with x ≥ 0.3. The variations of electrical conductivity and Seebeck coefficient are attributed to the significant increase in the carrier concentration in the x range of 0 to 0.2 and the intensive impact of Fe₃Ge₂ when x ≥ 0.3. The lattice thermal conductivity of all the Ge-doped samples was considerably reduced as compared with the undoped Ba_0.3In_0.2FeCo₃Sb₁₂ sample, and the lowest value of lattice thermal conductivity of the Ba_0.3In_0.2FeCo₃Sb_11.8Ge_0.2 sample reached 1.0 W m^?1 K^?1 at 700 K. The highest ZT value of 0.54 was obtained at 800 K for the Ba_0.3In_0.2FeCo₃Sb_11.7Ge_0.3 sample, increased by 10% as compared with that of Ba_0.3In_0.2FeCo₃Sb₁₂.     

Ultrasonic Degradation Studies and Its Effect on Thermal Properties of Polypropylene

In this article, the ultrasonic degradation of polypropylene (PP) melt was conducted in a specially designed reactor. Dynamic stress rheometer and gel permeation chromatography (GPC) were used to study the degradation behavior of PP melt. Thermal properties of ultrasonically treated PP were further discussed. The results showed the decrease of complex viscosity, zero shear viscosity, representative relaxation time, viscoelastic moduli as well as cross-over modulus, but an increase of cross-over frequency with introduction of ultrasonic irradiation, due to reduction of weight average molecular weight and increase of molecular weight distribution index of the polymer. The ultrasonic chain scissions of PP melt mainly occurred at the initial 3 min of irradiation and subsequently tended to terminate under our experimental conditions. In addition, the crystallization temperature and melting temperature of PP together got decreased in the presence of ultrasonic irradiation due to the occurrence of lower molecular weight components and some chemical irregularities in PP chain, along with the slight increase of crystallinity.     

Hydroxygenkwanin Increases the Sensitivity of Liver Cancer Cells to Chemotherapy by Inhibiting DNA Damage Response in Mouse Xenograft Models

Molecules involved in DNA damage response (DDR) are often overexpressed in cancer cells, resulting in poor responses to chemotherapy and radiotherapy. Although treatment efficacy can be improved with the concomitant use of DNA repair inhibitors, the accompanying side effects can compromise the quality of life of patients. Therefore, in this study, we identified a natural compound that could inhibit DDR, using the single-strand annealing yeast-cell analysis system, and explored its mechanisms of action and potential as a chemotherapy adjuvant in hepatocellular carcinoma (HCC) cell lines using comet assay, flow cytometry, Western blotting, immunofluorescence staining, and functional analyses. We developed a mouse model to verify the in vitro findings. We found that hydroxygenkwanin (HGK) inhibited the expression of RAD51 and progression of homologous recombination, thereby suppressing the ability of the HCC cell lines to repair DNA damage and enhancing their sensitivity to doxorubicin. HGK inhibited the phosphorylation of DNA damage checkpoint proteins, leading to apoptosis in the HCC cell lines. In the mouse xenograft model, HGK enhanced the sensitivity of liver cancer cells to doxorubicin without any physiological toxicity. Thus, HGK can inhibit DDR in liver cancer cells and mouse models, making it suitable for use as a chemotherapy adjuvant.     

聚合物共混物对水泥石-石英界面结构影响的机理

就聚合物共混物对水泥石－石英界面结构的影响机理进行了研究,结果表明：在聚合物共混物改性水泥砂浆中,石英表面的水化离解反应因聚合物分子链活性基因的电性作用而失去平衡,导致其表面出现大量带负电荷的「ＨＳｉＯ３」＾－和「ＳｉＯ３」＾２－离子;「ＨＳｉＯ３」＾－和「ＳｉＯ３」＾２－离子与水泥水化阳离子相互作用,在石英表面产生如水化硅酸钙等凝胶状粘结物,从而形成水泥石－石英粘附性界面。     

盐酸埃他卡林对小鼠脑组织缺氧的保护作用

目的: 研究盐酸埃他卡林(Ipt) 对脑组织缺氧的保护作用。方法: 小鼠给予Ipt 0.5, 2.0, 8.0 mg·kg^-1 3个剂量(n =12, ig), 连续给药3 wk, 并设生理盐水组和维生素E 组作为对照, 采用断头制备脑缺氧模型。活性采用化学比色法测定脑组织过氧化脂质(MDA) 含量、谷胱甘肽过氧化物酶(GSH-PX) 和超氧化物歧化酶(SOD) 活性。外周红细胞膜脂流动性以DPH 为荧光探针, 采用荧光偏振法测定。结果: Ipt0.5, 2.0, 8.0 mg·kg^-1 3 个剂量组延长小鼠断头后喘息持续时间, 增加外周红细胞膜脂流动性, 降低微粘度, 且呈现量效关系。相同条件下, Ipt 对MDA 含量,GSH-PX 活性及SOD 活性的影响不明显。结论: Ipt 对脑组织缺氧有显著保护作用, 其作用可能与其改变血液流变学特性有关。     

新型抗高血压药物盐酸埃他卡林对小动脉的选择性扩张作用及其药理学机制

目的: 研究新型抗高血压药物盐酸埃他卡林(Ipt) 对小动脉的作用特性及其药理学机制。方法: 采用大鼠尾动脉螺旋状血管条和主动脉离体血管环两种组织, 对比观察盐酸埃他卡林对大、小动脉扩张作用的药理学特性, 并且利用膜片钳技术观察盐酸埃他卡林对大鼠尾动脉平滑肌细胞钾电流的影响。结果: Ipt 在10^-7 ~ 10^-3 mol·L^-1 范围内对KCl 预致收缩的大鼠尾动脉血管条产生剂量依赖性舒张反应, 且具有部分内皮依赖性, 但对主动脉离体血管环无明显的舒张反应, 该作用在高血压状态时显著增强, 能被ATP 敏感性钾通道特异性阻断剂格列苯脲阻断, 并且对大鼠尾动脉平滑肌细胞的钾电流具有显著增强作用。结论: 盐酸埃他卡林具有选择性舒张小动脉作用, 具有ATP 敏感性钾通道开放剂的主要药理学特征。     

胆碱酯酶抑制剂类神经性毒剂诱导的犬循环衰竭救治前后血流动力学及血液内血管活性物质的变化

目的: 在胆碱酯酶抑制剂中毒诱发犬循环衰竭的模型上, 研究循环衰竭前后及N 受体拮抗剂美加明与M 受体拮抗剂阿托品救治后, 动物血流动力学及血液中血管活性物质的变化规律。方法: 健康成年雄性杂种犬, 体重12 ~ 16 kg 。随机分为4 组:对照组、美加明组、阿托品组、阿托品和美加明(剂量比10∶1) 联用组。肌肉注射敌敌畏诱发循环衰竭模型, 观察染毒前、循环衰竭时、救治15 、60 min 等时点平均动脉压(MAP) 、心室内压最大上升速率(+dp/dt_max) 、心室内压最大下降速率(-dp/dt_max) 、心肌纤维缩短速度(Vpm) 等血流动力学指标的变化及血液中一氧化氮(NO) 、内皮素(ET) 、6-酮-前列腺素F1α(6-Keto-PGF1α) 等血管活性物质的变化。结果: 与染毒前相比, 犬循环衰竭时, MAP 以及反映心脏收缩功能的指标(+dp/dt_max 、Vpm) 和反映心脏舒张功能的指标(-dp/dt_max) 均显著下降(P<0.01), 此时NO 、ET 和6-Keto-PGF1α等血管活性物质则显著升高(P<0.01) ;美加明与阿托品合用治疗15 min 时上述血流动力学指标及血管活性物质即显著好转,60 min 时基本恢复正常, 疗效均明显好于单用阿托品、美加明组。结论: 血浆NO 、ET 、6-Keto-PGF1α等血管活性物质的升高水平与胆碱酯酶抑制剂类神经性毒剂诱导的犬循环衰竭程度及病情转归相关, 美加明与阿托品之间存在协同增强作用。     

SHW46—1．6／150／90—AⅡ（65吨）型热水锅炉研制

介绍了大型往复炉排（65t）锅炉的研制过程及一些设计经验,为今后设计制造更大自然循环热水锅炉提供了一种借鉴。