High-throughput retroviral tagging to identify components of specific signaling pathways in cancer

Genetic screens carried out in lower organisms such as yeast, Drosophila melanogaster and Caenorhabditis elegans have revealed many signaling pathways. For example, components of the RAS signaling cascade were identified using a mutant eye phenotype in D. melanogaster as a readout. Screening is usually based on enhancing or suppressing a phenotype by way of a known mutation in a particular signaling pathway. Such in vivo screens have been difficult to carry out in mammals, however, owing to their relatively long generation times and the limited number of animals that can be screened. Here we describe an in vivo mammalian genetic screen used to identify components of pathways contributing to oncogenic transformation. We applied retroviral insertional mutagenesis in Myc transgenic (E mu Myc) mice lacking expression of Pim1 and Pim2 to search for genes that can substitute for Pim1 and Pim2 in lymphomagenesis. We determined the chromosomal positions of 477 retroviral insertion sites (RISs) derived from 38 tumors from E mu Myc Pim1(-/-) Pim2(-/-) mice and 27 tumors from E mu Myc control mice using the Ensembl and Celera annotated mouse genome databases. There were 52 sites occupied by proviruses in more than one tumor. These common insertion sites (CISs) are likely to contain genes contributing to tumorigenesis. Comparison of the RISs in tumors of Pim-null mice with the RISs in tumors of E mu Myc control mice indicated that 10 of the 52 CISs belong to the Pim complementation group. In addition, we found that Pim3 is selectively activated in Pim-null tumor cells, which supports the validity of our approach.     

Driven coherent oscillations of a single electron spin in a quantum dot

The ability to control the quantum state of a single electron spin in a quantum dot is at the heart of recent developments towards a scalable spin-based quantum computer. In combination with the recently demonstrated controlled exchange gate between two neighbouring spins, driven coherent single spin rotations would permit universal quantum operations. Here, we report the experimental realization of single electron spin rotations in a double quantum dot. First, we apply a continuous-wave oscillating magnetic field, generated on-chip, and observe electron spin resonance in spin-dependent transport measurements through the two dots. Next, we coherently control the quantum state of the electron spin by applying short bursts of the oscillating magnetic field and observe about eight oscillations of the spin state (so-called Rabi oscillations) during a microsecond burst. These results demonstrate the feasibility of operating single-electron spins in a quantum dot as quantum bits.     

学生选购笔记本电脑的"八项注意"

关于学生应该如何选购笔记本电脑,已经有很多人士作过不同的评述。笔者结合学生用户的特点和需要总结出“八大注意”,仅供参考。第一,尽量以全内置机型为首选。因为学生不必经常携带笔记本电脑外出,体积和重量对学习生活影响不大。最重要的是全内置机型有功能齐全、接口丰富的特点,可以省却不必要的抽换,轻松插接外围周边设备。如并口打印机、USB扫描仪、鼠标、键盘、摄像头、外接显示器,甚至有S端子可外接显示到电视机上等充分满足学生的周边应用。注意处理器按需购买。第二,追求太高等级的处理器会带来不必要的价格成本。建议选购处理器…