珠江隧道沉管管节制作中裂缝原因分析与治理

广州珠江隧道是我国首次采用沉管法施工的长达１２６７ｍ的大型过江隧道，为使隧道达到抗渗的设计要求，管节预制时裂缝的防治是关键的一个环节。本文主要介绍Ｅ１管节在干坞内制作中产生的裂缝，根据裂缝的部位和形状，对管节裂缝的原因作了详细分析。     

面板堆石坝集中渗流研究

采用电模拟了方法研究了堆石坝的面板和防渗墙产生裂缝时发生的集中渗流，研究结果表明，面权下的基垫层阻断集中渗流，降低坝内浸润线作用显著，实验表明，当防渗墙基础产生裂缝，发生集中渗流时，在坝基设置一定长度的水平防渗板，可以有效地阻隔集中渗流，降低坝内的浸润线。     

Human Genome and Diseases:¶Double-strand breaks and translocations in cancer

The correct repair of double-strand breaks (DSBs) is essential for the genomic integrity of a cell, as inappropriate repair can lead to chromosomal rearrangements such as translocations. In many hematologic cancers and sarcomas, translocations are the etiological factor in tumorigenesis, resulting in either the deregulation of a proto-oncogene or the expression of a fusion protein with transforming properties. Mammalian cells are able to repair DSBs by pathways involving homologous recombination and nonhomologous end-joining. The analysis of translocation breakpoints in a number of cancers and the development of model translocation systems are beginning to shed light on specific DSB repair pathway(s) responsible for the improper repair of broken chromosomes. Received 19 June 2001; received after revision 6 September 2001; accepted 11 September 2001     

Determination of DNA single-strand breaks by low-energy heavy ion and analysis of dose-effect curves

Calf thymus DNA was exposed to low-energy heavy ions (N+) and 60Co-γ-rays, and the dose-effect on DNA single-strand breaks (SSB) has been investigated. The results indicate that the dose-effect curve by N+ irradiation is different from that of conventional ionizing radiation. While the curve from γ-irradiation follows exponential type, the effect curve produced by N+ ion is of "saddle type". The yield of DNASSB per dose unit per DNA unit remained at a certain level under different doses of γ-rays. In contrast, the DNASSB at low dosage region of N+ showed an obvious peak before it decreased rapidly to a lower level.