利用对系统误差修正的逆测法测量电表的内阻

本文在伏安法测电阻实验的基础上,将系统误差修正方法进行逆运用,介绍一种测量电表内阻的方法。     

低温热管传热性能的实验研究

热管是一种高效的传热元件,低温热管可望在超导磁体冷却、空间探索方面获得广泛应用.本文对热虹吸管的传热特性进行了实验研究.研究结果表明,在同样加热功率的条件下,与相同形状和尺寸的紫铜导热棒相比,在加热功率较高的条件下,低温热管的传热性能远远优于紫铜棒的传热性能,完全能够满足超导磁体的冷却要求.     

Investigation of the Uptake and Transport of Two Novel Camptothecin Derivatives in Caco-2 Cell Monolayers

Irinotecan and Topotecan are two Camptothecin derivatives (CPTs) whose resistance is associated with the high expression of breast cancer resistance protein (BCRP) and P-glycoprotein (P-gp). To reverse this resistance, two novel CPTs, FL77-28 (7-(3-Fluoro-4-methylphenyl)-10,11-methylenedioxy-20(S)-CPT) and FL77-29 (7-(4-Fluoro-3-methylphenyl)-10,11-methylenedioxy-20(S)-CPT), were synthesized by our group. In this study, the anti-tumor activities of FL77-28, FL77-29, and their parent, FL118 (10,11-methylenedioxy-20(S)-CPT), were evaluated and the results showed that FL77-28 and FL77-29 had stronger anti-tumor activities than FL118. The transport and uptake of FL118, FL77-28, and FL77-29 were investigated in Caco-2 cells for the preliminary prediction of intestinal absorption. The apparent permeability coefficient from apical to basolateral (P_{app AP-BL}) values of FL77-28 and FL77-29 were (2.32 ± 0.04) × 10⁻⁶ cm/s and (2.48 ± 0.18) × 10⁻⁶ cm/s, respectively, suggesting that the compounds had moderate absorption. Since the transport property of FL77-28 was passive diffusion and the efflux ratio (ER) was less than 2, two chemical inhibitors were added to further confirm the involvement of efflux proteins. The results showed that FL77-28 was not a substrate of P-gp or BCRP, but FL77-29 was mediated by P-gp. In conclusion, FL77-28 might be a promising candidate to overcome drug resistance induced by multiple efflux proteins.     

Natural Products in Preventing Tumor Drug Resistance and Related Signaling Pathways

Drug resistance is still an obstacle in cancer therapy, leading to the failure of tumor treatment. The emergence of tumor drug resistance has always been a main concern of oncologists. Therefore, overcoming tumor drug resistance and looking for new strategies for tumor treatment is a major focus in the field of tumor research. Natural products serve as effective substances against drug resistance because of their diverse chemical structures and pharmacological effects. We reviewed the signaling pathways involved in the development of tumor drug resistance, including Epidermal growth factor receptor (EGFR), Renin-angiotensin system (Ras), Phosphatidylinositol-3-kinase/protein kinase B (PI3K/Akt), Wnt, Notch, Transforming growth factor-beta (TGF-β), and their specific signaling pathway inhibitors derived from natural products. This can provide new ideas for the prevention of drug resistance in cancer therapy.     

孔梯度陶瓷纤维复合膜管的制备及特性

陶瓷过滤管具有孔隙率高、耐腐蚀、耐高温、机械强度高、便于清洗、使用寿命长等优点,是高温烟尘处理用的高效过滤元件.本文研制了一种具有梯度孔结构堇青石陶瓷纤维复合膜过滤元件,该过滤元件是由多孔支撑体、过渡层和分离膜层组成.其中支撑体、过渡层和分离层的气孔率分别为35～40;、50～60;和60～70;.文中主要分析了孔梯度陶瓷纤维复合膜管的材料结构和抗热震性能,同时对复合膜管进行含尘气体过滤的冷态模拟试验.对于烟气中粒径大于或等于0.1μm的颗粒,复合膜管的截留率达到99.8;以上.     

Isolation and Purification of Polysaccharides from Cordyceps minlitaris and Its Inhibition on the Proliferation of Rat Glomerular Mesangial Cells

The crude polysaccharide was obtained by means of the decolorization of porphyrized Cordyceps minlitaris stroma with organic solvent, extraction with hot water, precipitation in 80% ethanol, and protein removal with the Sevag method. After purification with Sephadex G-75, two of its components, CMP-1 and CMP-2, were obtained. Through the assay of gel chromatography and polarimetry, CMP-1 was identified as pure polysaccharide. The results demonstrated that CMP-1 had favorable oxidation resistance activity, which could scavenge not only oxygen-free radicals in the self-oxidation system of pyrogallic acid, but also the hydroxide-free radicals in the Fenton system. The study focused on the effects of low, medium, and high dosages of CMP-1 in rat blood serum on the proliferation of glomerular mesangial cells in vitro. Through MTT Colorimetric analysis, the activities were compared among the blank control group and the Niaoduqing positive control group CMP-1 and CMP-2. The results shows that CMP-1 was able to inhibit the proliferation of rat glomerular mesangial cells effectively. Therefore, CMP-1, one component of polysaccharides of Cordyceps minlitaris, was certainly a potential remedy for hyperplastic glomerular nephritis, whose antioxidant activity could slow down the process of chronic renal failure（CRF） to some extent.     

一种超高耐久混凝土——梯度结构混凝土

分析超高耐久混凝土的研究现状,提出了一种高耐久、低成本的超高耐久混凝土--梯度结构混凝土(Gradient Structural Concrete,简称GSC),采用电量法和氯离子扩散系数法来评价梯度结构混凝土的抗氯离子渗透性能,最后进行梯度结构混凝土的寿命预测与成本分析.结果表明,高性能混凝土(High Performance Concrete,简称HPC)、无细观界面过渡区水泥基复合材料(Meso-interfacial transition zone-free cement-based materials,简称 MIF)和梯度结构混凝土MIF-HPC的6 h导电量和氯离子扩散系数的排列顺序均为:HPC>MIF-HPC>MIF,其抗氯离子渗透性能排列顺序为:MIF>MIF-HPC>HPC.梯度结构混凝土的成本会有所增加,但由于其氯离子渗透性能大幅降低,其使用寿命得到大幅延长,使得其年损耗费用大幅下降.     

用电阻定义式求特殊电容器直流电阻

在电子线路工程及其教学过程中,都需要对电容器的直流电阻进行计算.然而,对一些特殊形状的电容器的直流电阻计算,普遍采用的电流密度法是比较麻烦的.本文根据电阻定义式,结合电阻的串联和并联的简洁关系,简单明了地对球冠形电容器、柱冠形电容器和正多棱柱形电容器等的直流电阻进行了计算,并给出相应的定量表达式.     

Laser cladding of copper with molybdenum for wear resistance enhancement in electrical contacts

Laser cladding of Mo on Cu has been attempted with the aim of enhancing the wear resistance and hence increasing the service life of electrical contacts made of Cu. In order to overcome the difficulties arising from the large difference in thermal properties and the low mutual solubility between Cu and Mo, Ni was introduced as an intermediate layer between Mo and Cu. The Ni and Mo layers were laser clad one after the other to form a sandwich layer of Mo/Ni/Cu. Excellent bonding between the clad layer and the Cu substrate was ensured by strong metallurgical bonding. The hardness of the surface of the clad layer is seven times higher than that of the Cu substrate. Pin-on-disc wear tests consistently showed that the abrasive wear resistance of the clad layer was also improved by a factor of seven as compared with untreated Cu substrate. The specific electrical contact resistance of the clad surface was about 5.6 × 10⁻⁷ Ω cm².     

管内插新型自旋转子的流阻及抑垢特性

提出了一种新型自旋转子,并通过数值及实验方法研究了其流动阻力及抑垢特性.实验结果表明,在流速为0.76 m/s时转子转速仍可达100r/min,内插该转子的流动阻力比光管增加2倍左右,正反旋向转子组(每组4个转子)相问布置可防止沿流向转子转速递减,使转子转速基本恒定.数值分析表明,通过减小转子的旋转轴套外径并加前端导流...