Effects of Adenine Methylation on the Structure and Thermodynamic Stability of a DNA Minidumbbell

DNA methylation is a prevalent regulatory modification in prokaryotes and eukaryotes. N¹-methyladenine (m¹A) and N⁶-methyladenine (m⁶A) have been found to be capable of altering DNA structures via disturbing Watson–Crick base pairing. However, little has been known about their influences on non-B DNA structures, which are associated with genetic instabilities. In this work, we investigated the effects of m¹A and m⁶A on both the structure and thermodynamic stability of a newly reported DNA minidumbbell formed by two TTTA tetranucleotide repeats. As revealed by the results of nuclear magnetic resonance spectroscopic studies, both m¹A and m⁶A favored the formation of a T·m¹A and T·m⁶A Hoogsteen base pair, respectively. More intriguingly, the m¹A and m⁶A modifications brought about stabilization and destabilization effects on the DNA minidumbbell, respectively. This work provides new biophysical insights into the effects of adenine methylation on the structure and thermodynamic stability of DNA.     

光热电站容量效益评估及影响因素研究

光热发电作为一种清洁能源,配置储热后具有良好的调节性能,近年得到大力发展。依据自身经济性,光热电站往往配备较大的储热装置,能够平移所吸收的光热能,且具有跨日调节能力,使得光热机组有一定替代常规机组带负荷的能力,即容量效益。本文提出一种基于等可靠性的光热电站容量效益评估方法,考虑了调峰方式、储热时长、新能源规模、光热电站规模对光热电站容量效益发挥的影响,采用基于数学优化的生产模拟仿真程序,以周为尺度,计算全年8760 h的系统运行状态,计及了机组启停、水电跨日调节、抽蓄跨日调节、光热电站的跨日调节等因素。最后通过对西北地区实际电网的仿真,验证了所提方法的有效性。     

基于ANSYS Workbench下芯片的耦合研究

为了研究电子设备在温度较高的环境下电路板元器件散热和在温度载荷下引起的变形,通过ANSYS数值模拟的方法建立流热耦合的电路芯片散热模型,对芯片与电路板表面形成冲击压力进而导致热疲劳进行研究,分析与讨论温度对流场与静力学结构的影响.通过数值模拟分析得出:电路板为铝材质的变形很大,变形从中间凸起;而PCB材料电路板的变形不是局部变形,属于扩散式变形.     

模具型腔加工参数的优化问题

首先阐述了在CAD CAM集成环境下编制数控加工工艺的过程以及优化加工参数的必要性 ,接着 ,分析了需要优化的加工参数。文章详细阐述了优化模型的建立和算法设计问题     

超声波条件下除油技术的研究

在超声波条件下,研究确定了除油技术的清洗介质配方及运行条件,并对超声波、化学(声化)协同除油机理进行了分析讨论.研究结果表明,在声化条件下,研究确定的低浓度的碱性除油介质可在较低温度下,快速有效去除试样表面的油污;升高清洗液温度,可提高除油效率.     

An experimental investigation into soft-pad grinding of wire-sawn silicon wafers

Silicon is the primary semiconductor material used to fabricate microchips. A series of processes are required to manufacture high-quality silicon wafers. Surface grinding is one of the processes used to flatten wire-sawn wafers. A major issue in grinding of wire-sawn wafers is reduction and elimination of wire-sawing induced waviness. Results of finite element analysis have shown that soft-pad grinding is very effective in reducing the waviness. This paper presents an experimental investigation into soft-pad grinding of wire-sawn silicon wafers. Wire-sawn wafers from a same silicon ingot were used for the study to ensure that these wafers have similar waviness. These wafers were ground using two different soft pads. As a comparison, some wafers were also ground on a rigid chuck. Effectiveness of soft-pad grinding in removing waviness has been clearly demonstrated.     

用于气体保护焊的自动混气设备

介绍了一种用于焊接现场的气体保护焊的自动混气设备，该设备能精确控制气体混合比例。设备主要由气体传输、气体混合、信号检测和电气控制几大部分组成。计算机适时采集、显示混合气体的混合比例、输出压力、气体湿度等信息，超限发出声光报警。混气设备通过气体分析仪、比例阀和计算机形成闭环控制，从而实现气体混合比例的精确控制。     

碳氮共渗提高空心圆柱滚子轴承寿命的研究

通过GCr15钢碳氮共渗,在表层获得大量的残余奥氏体。磨损中,马氏体组织剥落,残余奥氏体则成小岛状,进而在表面迁移发生形变诱发马氏体相变,使耐磨性得以提高。同时,共渗在空心滚子内表面造成的压应力对改善弯曲疲劳性能有利。     

丙烯酸树脂在医用黏合剂中的应用

讨论了丙烯酸树脂在医用黏合剂中的应用及进展。     

气相色谱——质谱法对土壤中多种农药残留的测定方法

用GC -MS法测定土壤中的农药残留物 ,快速准确 ,回收率 83 %～ 112 %,平均变异系数在 4.8%～ 15 .2 %之间。为科学监测、合理利用土壤资源提供了依据