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Loss of p15/Ink4b accompanies tumorigenesis triggered by complex DNA double-strand breaks
No full textDNA double-strand breaks (DSBs) are the most deleterious lesion inflicted by ionizing radiation. Although DSBs are potentially carcinogenic, it is not clear whether complex DSBs that are refractory to repair are more potently tumorigenic compared with simple breaks that can be rapidly repaired, correctly or incorrectly, by mammalian cells. We previously demonstrated that complex DSBs induced by high-linear energy transfer (LET) Fe ions are repaired slowly and incompletely, whereas those induced by low-LET gamma rays are repaired efficiently by mammalian cells. To determine whether Fe-induced DSBs are more potently tumorigenic than gamma ray-induced breaks, we irradiated 'sensitized' murine astrocytes that were deficient in Ink4a and Arf tumor suppressors and injected the surviving cells subcutaneously into nude mice. Using this model system, we find that Fe ions are potently tumorigenic, generating tumors with significantly higher frequency and shorter latency compared with tumors generated by gamma rays. Tumor formation by Fe-irradiated cells is accompanied by rampant genomic instability and multiple genomic changes, the most interesting of which is loss of the p15/Ink4b tumor suppressor due to deletion of a chromosomal region harboring the CDKN2A and CDKN2B loci. The additional loss of p15/Ink4b in tumors derived from cells that are already deficient in p16/Ink4a bolsters the hypothesis that p15 plays an important role in tumor suppression, especially in the absence of p16. Indeed, we find that reexpression of p15 in tumor-derived cells significantly attenuates the tumorigenic potential of these cells, indicating that p15 loss may be a critical event in tumorigenesis triggered by complex DSBs
The Study of Multi-Wires Proportional Chamber at RIBLLⅡ
No full text加速器及放射性束流装置是当今科学研究的重要装置。中国科学院近代物理研究所
新建成的高能重离子冷却存储环（CSR） 和第二条兰州重离子放射性束流线 （RIBLLⅡ），
可提供更高能量和更多种类的束流，极大拓展了核物理的实验范围，为我国在中高能核
物理领域的研究提供了条件。
为了更好的实现对 RIBLLⅡ中次级束流的位置监测，我们研制了气体位置探测器
——多丝正比室（MWPC）。MWPC给出的位置信息可以用于束流诊断，也可以用于靶
前入射粒子的径迹测量，对提高束流线的传输效率、更好的分离和鉴别束流组成有重要
意义。
本论文的工作主要有：
（1）详细调研了气体探测器和多丝正比室的工作原理。
（2）研究了 MWPC 在设计时考虑到的各种参数。经过测试，MWPC使用的阳极丝
间距为 2 mm，阳极面和阴极面间距 4 mm，使用 20 ns 的延迟块延迟时间读出位置信
号，工作气体使用 20% CO2 + 80% Ar 的混合气体。
（3）对MWPC的性能进行了全面的测试，并得到了很好的结果。其中典型位置分
辨 0.56 mm，时间分辨 37 ns，能量分辨 23.6%。
（4）最后，提出了下一步的工作方向,包括束流在线测试和双阳极 MWPC测试使用
Construction and Verification of Inducible Eukaryotic Expression Vector for Radiation Related Hsa-miR-663
No full text为了研究辐射相关的hsa-miR-663在肿瘤细胞辐射应答通路中的功能，本实验人工合成
其前体并构建入表达载体pcDNA™6.2-GW/EmGFP-miR-663，进一步通过BP/LR重组反应
将hsa-miR-663表达框转移至诱导型表达载体pT-REx-DEST30中。然后将hsa-miR-663的诱
导型载体pT-REx-DEST30-EmGFP-miR-663转染以HeLa细胞构建的四环素操纵子稳定表达
细胞系HeLa-TetR，通过抗生素筛选后获得了hsa-miR-663的稳定诱导型表达细胞系并通过
绿色荧光蛋白表达镜检和定量反转录聚合酶链式反应（qRT-PCR）进行了表达验证，结果
证明hsa-miR-663的诱导型表达载体及诱导型细胞系构建成功。本载体及细胞系的构建为深
入研究hsa-miR-663的功能奠定了基础
大功率开关电源整流桥与水冷板的加工方法
No full text本发明涉及一种大功率开关电源整流桥与IGBT水冷板的加工方法，其步骤为：a.选择25mm厚，190mm×990mm矩形紫铜板，用钻头分别从矩形铜板横向、纵向两端间隔对应打孔；b.纵向孔道分别与横向孔道贯通，纵孔内车成丝扣；c.将铜棒车成与纵孔径相应、丝扣相配合、长度不同螺杆堵头，将螺杆堵头旋入纵向不同长度的孔中，敲紧；d.将水冷板横向两端旋入螺杆堵头，鉚紧，完成后将所有堵头端面铣平；e.最后将整流桥模块和IGBT模块一起安装在加工的紫铜水冷板上。本发明克服了现有水冷板水路管道渗水、浇铸成本过高的缺陷，在铜板有限的空间内，设置了“S”形的水路通道。循环水畅通，使散热面积最大，达到很好的散热目的，满足了大功率开关电源性能要求，提高了电源的整体运行效率
EIGHTY YEARS OF CYCLOTRONS
No full textLawrence's invention of the cyclotron in 1930 not only<br />revolutionized nuclear physics, but proved the starting<br />point for a whole variety of recirculating accelerators,<br />from microtrons to FFAGs to synchrotrons, that have had<br />an enormous impact in almost every branch of science<br />and several areas of medicine and industry. Cyclotrons<br />(i.e. fixed-field accelerators) themselves have proved<br />remarkably adaptable, incorporating a variety of new<br />ideas and technologies over the years: frequency modulation,<br />edge focusing, AG focusing, axial and azimuthal<br />injection, ring geometries, stripping extraction, superconducting<br />magnets and rf... Long may they flourish
ECRIS DEVELOPMENT AT KVI*
No full textThis paper reports on work performed during the last<br />two years to improve the performance of the KVI-AECR<br />ion source, which is used as an injector for the AGOR<br />cyclotron. We have installed stainless-steel screens at the<br />injection and extraction sides and an additional collar<br />around the extraction aperture resulting in better plasma<br />stability and an increase of extracted ion currents. Source<br />tuning is aided by continuously observing the visible light<br />output of the plasma through the extraction aperture with<br />a CCD camera. We now routinely extract 700 μA of O6+<br />ions and 50 μA of Pb27+ ions.<br />Source optimization is supported by extensive<br />computational modelling of the ion transport in the lowenergy<br />beam line and measuring the transverse emittance<br />of the extracted ion beam with a pepperpot emittance<br />meter. These efforts have shown that second-order<br />aberrations in the analyzing magnet lead to a significant<br />increase of the effective beam emittance. Work is<br />underway to compensate these aberrations.IMP;Chinese Academy of Science
THEORETICAL ANALYSIS AND FABRICATION OF COUPLING CAPACITOR FOR K500 SUPERCONDUCTING CYCLOTRON AT KOLKATA
No full textK500 SC cyclotron has already been constructed and<br />commissioned after spiralling Ne3+ internal beam with 70<br />nA up to extraction radius (670mm) at variable Energy<br />Cyclotron Centre at Kolkata, India. Several problems<br />have been experienced related to the coupling capacitor of<br />the radio frequency system including its sever burning<br />during commissioning of the cyclotron. Making of the<br />dissimilar joints between alumina ceramic and copper of<br />the coupling capacitor demands the usage of vacuum<br />furnace to avoid the cracking of the ceramic. Therefore<br />exhaustive analysis has been carried out to facilitate the<br />in-house fabrication of the coupling capacitor without<br />using the vacuum furnace in case of emergency. The<br />maximum allowable rate of temperature rise of the<br />ceramic and the optimum thickness ratio of the copper to<br />ceramic have been estimated. Finally, fabrication of the<br />coupling capacitor has been carried out in-house without<br />employing vacuum furnace. At present the coupling<br />capacitor is performing well as maximum 57 KV DEE<br />voltage were been achieved till date. This paper presents<br />the details of the analysis and experiences gained during<br />the fabrication of the coupling capacitor.IMP;Chinese Academy of Science
CLOSED LOOP RF TUNING FOR SUPERCONDUCITNG CYCLOTRON AT VECC
No full textThe RF system of Superconducting cyclotron has been
operational within 9 - 27 MHz frequency. It has three
tunable half-wave coaxial cavities as main resonators and
three tunable RF amplifier cavities. A PC-based system
takes care of stepper motor driven coarse tuning of
cavities with positional accuracy ~20μm and
hydraulically driven three couplers and three trimmers.
The couplers, in open loop, match the cavity impedance
to 50 Ohm in order to feed power from RF amplifier.
Trimmers operate in closed loop for fine tuning the cavity,
if detuned thermally at high RF power. The control logic
has been simulated and finally implemented with
Programmable Logic Controller (PLC). Precision control
of trimmer (~20μm) is essential to achieve the
accelerating (Dee) voltage stability better than 100 ppm.
and also minimizing the RF power to maintain it. Phase
difference between Dee-in and Dee-pick-off signals and
the reflected power signals (from cavity) together act in
closed loop for fine tuning of the cavity. The closed loop
PID control determines the final positioning of the
trimmer in each power level and achieved the required
voltage stability.IMP;Chinese Academy of Science
28GHZ SC-ECRIS AT RIBF
No full textThe next generation heavy ion accelerator facility at
RIKEN, requires an intense beam of high charged heavy
ions. To meet the requirements, we constructed and tested
the RIKEN new SC-ECRIS. After producing the first
beam in the spring of 2009, we tried to optimize the ion
source condition for maximizing the beam intensity with
18GHz microwave. We observed that the gentler field
gradient and lager ECR zone size give higher beam
intensity. Based on these studies, we produced 500μA of
Ar11+ and 350μA of Ar12+ at the RF power of 1.8kW. We
also produced highly charged U ion beam with sputtering
method for RIBF. In this article, we describe the structure
of the ion source, test experiment and future plan.IMP;Chinese Academy of Science
End Optimization of Dipole Magnet of Super-FRS for FAIR
No full text介绍了Super-FRS超导二极磁铁的磁场优化和端部削斜方案,采用OPERA软件对活极头进行削斜计算,得出合理的活极头尺寸,使各场下的积分均匀度在要求范围内达到了2*10-4.最后将计算的积分场均匀度与磁场测量的结果进行比较,结果吻合得较好,验证了这种端部活极头优化计算方法的正确性The end optimization of dipole magnet of Super-FRS for FAIR by OPERA-3D has been introduced in this paper.By using a complicated chamfer,the integral field homogeneity which is better than 2*10-4 can be obtained.In addition,the paper also introduced the comparison between the magnetic field measurement result and calculation one,which confirms the method of the removable pole end chamfer very well国家重点基础研究发展规划(973计划); 中国科学院近代物理研究所推进项