Telomere-telomere recombination provides an express pathway for telomere acquisition

DNA termini from Tetrahymena and Oxytricha, which bear C4A2 and C4A4 repeats respectively, can support telomere formation in Saccharomyces cerevisiae by serving as substrates for the addition of yeast telomeric C1-3A repeats. Previously, we showed that linear plasmids with 108 base pairs of C4A4 DNA (YLp108CA) efficiently acquired telomeres, whereas plasmids containing 28-64 base pairs of C4A4 DNA also promoted telomere formation, but with reduced efficiency. Although many of the C4A4 termini on these plasmids underwent recombination with a C4A2 terminus, the mechanism of telomere-telomere recombination was not established. We now report the sequence of the C4A4 ends from the linear plasmids. The results provide strong evidence for a novel recombination process involving a gene conversion event that requires little homology, occurs at or near the boundary of telomeric and nontelomeric DNA, and resembles the recombination process involved in bacteriophage T4 DNA replication.     

Structural differences between a ras oncogene protein and the normal protein

One of the most commonly found transforming ras oncogenes in human tumours has a valine codon replacing the glycine codon at position 12 of the normal c-Ha-ras gene. To understand the structural reasons behind cell transformation arising from this single amino acid substitution, we have determined the crystal structure of the GDP-bound form of the mutant protein, p21(Val-12), encoded by this oncogene. We report here the overall structure of p21(Val-12) at 2.2 A resolution and compare it with the structure of the normal c-Ha-ras protein. One of the major differences is that the loop of the transforming ras protein that binds the beta-phosphate of the guanine nucleotide is enlarged. Such a change in the 'catalytic site' conformation could explain the reduced GTPase activity of the mutant, which keeps the protein in the GTP bound 'signal on' state for a prolonged period time, ultimately causing cell transformation.     

Green公式及其证明

首先指出数学分析中反映二重积分和第二类平面线积分联系的Green公式可以看成是散度定理的一种特殊情形，然后利用散度定理给出广义分部积分公式、第一Green公式和第二Green公式的证明．     

第9届意大利传感器及微系统会议会议录

本书是由意大利传感器及微系统学会（AISFM）组织的第9届意大利传感器及微系统会议的会议录。这次会议于2004年2月8—11日在意大利北部城市费拉拉举行。它是由费拉拉大学物理系主办的。整个会议被分成了11个口头宣读分组会和2个书面张贴分组会。这本会议录收录了来自103个研究单位的83篇论文，充分表明了意大利当前在该领域中进行着非常活跃的研究，     

Interaction between the effects of centrally administered arecoline and leucocyte pyrogen on the activity of posterior hypothalamic neurons in the rabbit

Summary In experiments with urethane-anesthetized rabbits, the alteration in the activity of posterior hypothalamic neurons resulting from intracerebroventricular injection of leucocyte pyrogen was attentuated by subsequent administration of arecoline. Atropine failed to alter the neuronal response to leucocyte pyrogen but abolished the effect of arecoline. The neuronal response to arecoline was reversed in the absence of leucocyte pyrogen.     

Research on the Angular Glint of Targets in the Near-Zone

This paper presents a method to analyze and calculate the angular glint of targets. By parting the target to very small size cells, using high-frequency approximation, the near-field radar cross section （RCS） is calculated based on the scattering from complex targets and environments （SCTE） system, and the angular glint is calculated by the phase grads. The results show that the angular glint can be calculated exactly in the SCTE system, and this method is correct and efficient. In the near-zone, the far-field theory is not applicable and the angular glint should be calculated by the near-field theory.     

三类Schottky群的Jorgensen数

Sato H定义了八类经典Schottky群以及Jorgensen数，通过讨论第Ⅲ，第Ⅵ和第Ⅷ类的Jorgensen数的不同形式，给出了这三种类型的相关定理及其证明。