Comparison of 80-keV D+ Ion Implantation with Thermal D2 Doping in Silica by FTIR and ESR Spectroscopy

Behavior of deuterium atoms in fused silica, which were implanted by 80-keV D⁺ (D₂⁺, D₃⁺) ions or doped thermally by D₂ (or D₂O), was studied by infrared Fourier transform spectroscopy (FTIR) and by ESR spectroscopy. When 80-keV deuteron ions are implanted into fused silica, OD bonds are formed. The OD bonds are also formed by thermal doping with D₂ or D₂O. When the deuterated silica is γ-ray irradiated at 77 K, D atoms are formed by rupture of the OD bonds. The efficiency of the OD bond rupture in the deuteron-implanted silica is much less than that in the D₂-doped silica. It is concluded from the results of thermal annealing that the low efficiency of the OD bond rupture in the deuteron-implanted silica is due to the radiation damage accompanying the implantation process. However, the decay rate and detrapping energy of deuterium atoms, once formed in the silica, are similar in both cases.     

快速无超调纳米定位

对于“直流电机＋滚珠丝杠”驱动机构,摩擦是实现大行程具有纳米级分辨率点位控制的主要障碍．通过设计高增益PID控制器,可以抑制摩擦的影响并在大范围内实现纳米定位,只是系统的性能受到执行机构饱和的影响．通过将时间优化的Bang—Bang控制器与该PID控制器结合在一起构成变结构控制系统,使用PID闭环控制跟踪Bang—Bang控制下的理论减速轨迹,并实现最终定位,从而消除了饱和所造成的超调．实验和仿真结果显示,该系统可以在较大摩擦力和模型参数变化的情况下获得大范围无超调的纳米定住,并且响应时间最优．     

色彩人生 源自ENZO

ENZO,就像一颗光芒四射的彩色宝石,镶嵌在6月香港珠宝首饰展览会香港艺粹馆,流光溢彩。     

Identification of Gene encoding a Putative RNA-Helicase,Homologous to SKI2, in Chromosome VII of Saccharomyces cerevisiae

We have determined the nucleotide sequence of a segment of chromosome VII of the yeast Saccharomyces cerevisiae contained in the cosmid clone pEGH101 for a total of 7 kbp. This sequence contains a large open reading frame (ORF) called G9365, coding for a protein of 1967 amino acids that shows a significant homology with the product of the SKI2 gene of S. cerevisiae and contains domains characteristic of RNA-helicases. The ORF is transcribed in vegetative cells but it is not essential for viability as demonstrated by gene disruption. The sequence has been deposited in the GenBank data library under Accession Number U35242. © 1997 John Wiley & Sons, Ltd.