The Role of Cytochrome P450 1B1 in Dibenzo[ a,l ]pyrene-induced Carcinogenesis

In human cells, the most carcinogenic polycyclic aromatic hydrocarbon dibenzo[ a,l ]pyrene (DB[ a,l ]P) forms high levels of DNA adducts through formation of the ( m )- anti -(11 R ,12 S )-diol (13 S ,14 R )-epoxide (DB[ a,l ]PDE) and its metabolic precursor, the ( m )-(11 R ,12 R )-diol. Generation of these adducts results from the catalytic activity of cytochrome P450 (P450) 1A1 and 1B1. Additional adducts such as (+)- syn -DB[ a,l ]PDE-DNA or more polar DNA adducts were detected only after increasing exposure doses of the parent compound or in cells that express P450 1A1. At low concentrations (·;100 nM) exclusively ( m )- anti -DB[ a,l ]PDE-DNA adducts were formed by P450 1B1, which is constitutively expressed in many mammalian tissues. Measurement of DNA binding and mutagenicity of DB[ a,l ]P in V79 cells expressing human P450 enzymes revealed a higher activity of P450 1B1 compared to 1A1 at low concentrations. Treatment of P450 1B1 knockout mice and DNA binding studies with fibroblasts isolated from these animals provided further evidence for the central role of P450 1B1-catalyzed formation of ( m )- anti -DB[ a,l ]PDE-DNA adducts in DB[ a,l ]P-induced carcinogenesis.     

天然高分子絮凝剂仙人掌絮凝性能的初步研究

研究了天然高分子絮凝剂仙人掌的絮凝性能,标准水样用高岭土配制。分别处理较高浊度(100~200NTU)和低浊度(20~50NTU)的标准水样,结果表明,仙人掌絮凝剂对浊度的去除率比较高,最终的出水浊度可以达到5NTU。仙人掌絮凝剂的最佳用量与AlCl3·6H2O相比仅仅高一点。可以推测,仙人掌组分中的非极性成分在絮凝过程中起了重要的作用。     

Crystallization behavior,heat resistance,and mechanical performances of PLLA/myo‐inositol blends

In this work, use of <i>myo</i>‐inositol as a biobased nucleating agent (NA) for PLLA was researched. Effects of <i>myo</i>‐inositol on non‐isothermal and isothermal crystallization behaviors of PLLA at temperatures ranged from 85 °C to 130 °C were studied by using DSC, POM and WAXD. Isothermal crystallization kinetics results showed that the incorporation of <i>myo</i>‐inositol enhanced significantly the crystallization rate of the PLLA samples. It was confirmed that the optimum isothermal crystallization temperature range was 100 to 110 °C. The above results were instructive to confirm proper heat treatment time and temperature for compression or injection molding to fabricate highly crystallized PLLA articles. The relations among heat treatment time, crystallinity, heat resistance, and mechanical performances of the neat PLLA and PLLA/1% <i>myo</i>‐inositol specimens prepared by compression molding were investigated. Compared with the PLLA specimens, the PLLA/1% <i>myo</i>‐inositol specimens showed a shorter heat treatment time to reach the maximum crystallinity. Vicat softening temperature, as well as tensile strength, modulus, and toughness of the PLLA/1% <i>myo</i>‐inositol specimens was improved when crystallinity increased from 5.4% to 38.1%. Considering the nontoxicity and biocompatibility of <i>myo</i>‐inositol, PLLA/<i>myo</i>‐inositol blends would be potential to prepare some products, which are required higher health standard and can be used in elevated temperature environments. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , <i>134</i>, 44732.     

界面接触热阻影响因素的实验研究

通过自制的接触热阻实验装置分别对接触热阻的主要影响因素-接触表面温度、接触压力以及表面均方根粗糙度等进行了较为深入的实验研究。同时，实验还对热流方向的改变以及中间介质（石墨）对接触热阻的影响进行了研究，结果证实了热流方向的改变会导致接触热阻值的变化，热流方向由钢到铝的接触热阻值较由铝到钢的小。     

基于平面五杆闭环结构的空间并联机构类型综合与拓扑分析

分析了五杆闭环结构的类型、拓扑描述、组成形式和运动性能 ,重点研究了基于 5R闭环结构与RPRPR闭环结构在空间并联机构中的应用 ,给出了基于五杆闭环结构的空间并联机构的类型综合方法及步骤 ,并综合出了九种空间并联机构的构型。     

感潮河段交汇区水流特性数值模拟 --以宁波三江口为例

河流交汇为城市的发展提供了便利,对区域防洪、航运及河道演变影响重大。针对感潮河段交汇区域特有的非恒定往复流条件,以宁波三江口为例,运用Delft-3D建立二维水动力数学模型。基于实测水文和地形资料,引入四种评估参数对模型进行了率定与验证。重点分析了洪、枯两季涨、落急时刻,交汇区流速分布及水面形态等水流特性。结果表明:涨潮时,交汇区流场可类比分叉水流;落潮时,则为交汇水流;交汇区顶点及左支入汇侧下游存在两个低流速区,并可形成分离区;汇流区流速整体呈落潮大于涨潮的趋势,洪、枯季间最大流速相近。此外,涨、落急时刻典型特征断面水面呈单一横比降,且落急时刻比降明显大于涨急时刻;落急时,交汇口水面呈混合层附近高,两侧低的"马鞍形"分布。     

©��ʽ���ܼ�⼼���ڹܵ��е�����

天然气输送管道在长期运行过程中，存在介质对管道的内部腐蚀，此外，施工质量，绝缘层的缺陷，土壤，阴极保护不足等诸多因素还会引起外腐蚀，且内、外腐蚀会随着管道运行年限的增加而逐年加重，事故隐患逐渐增大。因此，如何对管道内、外腐蚀进行检测、评价，确保管道安全平稳运行便成为了管道输送企业所面临的重大课题。西南油气田分公司在国内首次引进国外漏磁式智能检测技术，对所属的部分管道进行了智能检测。章分析了该项技术的原理、检测参数、准确性、置信度、经济效果和存在的不足，论述了管道内、外腐蚀的原因，提出了减缓腐蚀的各项建议和措施。     

基于形态学与多尺度空间聚类的SAR图像变化检测方法研究

介绍了一种形态学模型(morphological profile,MP)工具,这种工具运用在合 成孔径雷达(synthetic aperture radar,SAR) 图像中,增强了对SAR图像的多角度细节处理,提高了图像检测精度。在图像检测中加入算 法可被应用于遥感图像变化检测 领域。本文提出的SAR图像变化检测方法是在多尺度子空间融合谱聚类的基础上进行的,这 种方法是对不同时刻得到的同图 进行对数比和均值比处理,从而构成多个子空间获取图像的结构特征,并结合随机采样谱聚 类的子空间融合算法得到的变化 的图像。本文方法所得的SAR图可以检测到很多单一的像素点,误检像素点数目明显减小,优 于其他算法结果。检测结果抑制 了图像变化中的缺失问题,因此具备较高的检测精度。     

基于四元极谐变换矩与显著特征的图像鲁棒哈希算法

为了增强哈希序列对各种几何变换攻击的鲁棒性,设计基于四元极谐变换矩与显著特征的图像鲁棒哈希算法。引入线性插值与自适应Wiener滤波器,实现初始图像的预处理;计算预处理图像的颜色向量角度,并基于Fourier变换,得到其对应的幅度信息,以获取两个不同的频谱;计算两个频谱的残差,确定图像中的局部显著性区域;通过LBP算子,提取显著特征;基于四元极谐变换(Quaternion Polar Harmonic Transform,QPHT),获取预处理图像的QPHT矩;联合显著特征与QPHT矩,形成过渡哈希数组。引入Logistic映射,定义加密函数,实现对过渡哈希数组的加密,输出最终的哈希序列,以增强其抗碰撞性能。测量源图像与可疑图像之间的哈希序列所对应的l₂范数距离,并将其与优化阈值比较,对图像的真实性做出判断。在多种几何变换攻击下完成测试,输出数据显示:较当前准确性较高的哈希方法而言,该算法具有更理想的鲁棒性与识别准确率。     

水热法合成羟基磷灰石

本文进行了水热法合成羟基磷灰石的实验室研究,研究了配料比,反应温度和时间的影响,确定了适宜工艺条件。化学分析和红外光谱测定结果表明合成产品以羟基磷灰石为主;经洗涤的产品可达到较高的纯度。