N-Monomethyl-arginine and nicotinamide prevent streptozotocin-induced double strand DNA break formation in pancreatic rat islets

The impact of short term in vitro exposure to the diabetogenic drug streptozotocin on pancreatic islet glucose metabolism, insulin secretion, DNA fragmentation and cell viability, was studied. Streptozotocin impaired cell viability as well as insulin secretion and the oxidation of glucose. These effects were partially counteracted by inhibition of the inducible form of nitric oxide synthase with N-monomethyl-arginine and by scavenging oxygen free radicals with nicotinamide. Isolated islets underwent double strand DNA fragmentation after 24 h in culture. The degree of DNA breakdown was strongly enhanced by exposure of the islet DNA was obtained with N-monomethyl-arginine and nicotinamide. These data suggest that the generation of reactive oxygen and nitrogen species is involved in the deleterious action of streptozotocin on pancreatic islet tissue. A role for oxygen radicals generated during streptozotocin-induced islet cell damage as possible mediators of the expression of the inducible form of nitric oxide synthase and the scavenging action of nicotinamide on these radicals, is then proposed.     

Degradation of the antibiotic sulfamonomethoxine sodium in aqueous solution by photo-Fenton oxidation

In this study, photo-Fenton oxidation was applied to degradation of sulfamonomethoxine sodium (SMMS) in aqueous solution. The operation parameters of pH, temperature, and concentrations of H2O2, Fe2+ and SMMS were investigated. The optimum conditions for the photo-Fenton process were determined as follows: [SMMS]=4.53 mg/L, pH 4.0, [H2O2]=0.49 mmol/L, [Fe2+]= 19.51 μmol/L and T=25°C. Under these conditions 98.5% of the SMMS degraded. The kinetics were also studied, and degradation of SMMS by the photo-Fenton process could be described by first-order kinetics. The apparent activation energy was calculated as 23.95 kJ/mol. Mineralization of the process was investigated by measuring the chemical oxygen demand (COD), and the COD decreased by 99% after 120 min. This process could be used as a pretreatment method for wastewater containing sulfamonomethoxine sodium.     

冷轧机穿带试验的分析和研究

通过对某钢厂冷轧机穿带试验过程及结果的分析和研究,得出了一些有助于生产实践的结论,进一步证明了新的穿带工艺在此轧机上应用的有效性.     

处理旋转运动图象模糊问题的一种算法

提出了处理旋转体图象运动模糊现象的一种算法。该算法取决于图象退化过程的先验知识。在先求出匀速直线运动模糊处理算法的基础上,推导出匀速旋转体的运动模糊处理算法。实验结果表明,该算法较好地解决了图象运动模糊问题。     

1700轧钢机接轴叉头失效分析

以实测为根据,应用断裂理论对滑块式联接轴叉头进行了失效分析,并提出了提高疲劳寿命的措施。     

南京造纸厂投入产出模型的编制与应用分析

<正>根据南京造纸厂经营管理的实际情况,运用现代数学方法编制了各类投入产出模型。并用电子计算机进行了优化处理及制定了优化结构的控制边界,并进行了成本牵动分析。     

含羧酸共生稀土光敏剂的高密度聚乙烯购物袋降解效果研究

通过ＵＶ光谱,ＴＧ－ＴＤＡ,ＩＲ等方法测定了羧酸共生稀土配合物光敏剂对高密度聚乙烯膜的光敏化效果,实验结果表明,含ＲＥＣａｒ３的ＨＤＰＥ膜光照诱导后掩埋能继续氧化降解,按筛选的配方可生产出符合标准的ＨＤＰＥ降解购物袋。     

再生纸生产废水治理技术应用

本文介绍了安徽省阜阳市涡阳县义门镇卫生纸厂再生纸废水处理工程工艺技术,此项技术运用动态膜过滤原理,用聚合氯化铝,聚丙烯酰胺和氯化铁为絮凝剂,以石子,砂子炉渣为滤料和承托层,取得较好的处理效果。     

基于逆高斯退化过程的面向任务系统CBM优化模型

针对现有单调退化系统视情维修(condition-based maintenance,CBM)优化模型中不完全维修影响考虑单一,且未同时融入可用度约束的问题,提出一种考虑不完全维修双重影响与可用度约束的单调退化系统CBM优化模型.首先,基于具有随机漂移系数的逆高斯过程,建立系统退化模型并得到相关概率分布;其次,描述任务...     

三种网孔结构组织工程肌腱支架增强体的性能

以聚乙交酯(PGA)复丝和聚丙交酯(PLA)复丝为原料进行合股编织,分别采用小口径圆纬机和手工编织的方法,制得纬平、方形和菱形3种网孔结构的组织工程肌腱支架增强体.探讨了3种支架增强体的延伸性、孔隙率、孔径、强力等性能,并研究了8星期体外降解试验过程中支架增强体的断裂强力、质量损失、厚度、口径及孔隙率等性能的变化规律.结果表明:方形网孔结构的支架增强体延伸性最小、孔隙率和孔径最大;3种支架增强体在降解过程中,前3星期断裂强力急剧下降,厚度有所增加;降解4~6星期后支架的质量损失显著增大,厚度迅速减小;孔隙率在降解过程中呈先减小后增大趋势,在3~4星期时孔隙率值最小;手工编织支架增强体的口径在降解过程中无明显变化,而纬平支架增强体的口径在降解前3星期逐渐减小,3星期后又逐渐增大.