New progress on beam availability and reliability of PKU high intensity CW proton ECR ion source

The stability and reliability of an ion source and its beam availability are extremely significant for any accelerator,especially for those high current long term CW operation ones like ADS. Although the first high quality 306-hours continuous wave(CW) operating curve at 50 m A@35 ke V has been successfully obtained with a standard compact 2.45 GHz ECR ion source at Peking University(PKU), but the uncertainties that caused beam trips before are unacceptable during an accelerator real operation and should be eliminated. Meanwhile, no permission will be given when the beam power is upgraded from 50 m A@35 ke V to 50 m A@50 ke V. To improve the PKU CW proton source quality, several upgrades were done recently. After those improvements, a new long term CW proton beam experiment at 50 m A@50 ke V was carried out in June 2016. The total running time is 300.5 hours, including near 6 hours ion source preparation and 294 hours non-disturb continuous operation. Within the continuous 13 days operation, no beam-off happened, no spark was observed,no beam drop appeared, no interrupting action was needed, and only a few beam fluctuations caused by the air conditional failure occurred. Beam availability and reliability within the 294 hours is 100%. The root-mean-square(RMS) emittance of this 50 m A@50 ke V CW proton beam is about 0.186 π.mm.mrad. A careful inspection of the ion source was done after this long term operation and no obvious damage was found. The restart experimental results obtained after the ion source inspection prove the high repeatability of PKU PMECRIS. In addition, a 130-m A H+beam was obtained at 50 k V with duty factor of 10%(100 Hz/1 ms) with this source. Details will be presented in this paper.     

18Ni(300)钢高速干滑动摩擦磨损特性研究

利用销盘高速干滑动摩擦磨损试验机,对18Ni(300)马氏体时效钢的摩擦磨损性能进行了研究,应用JSM-6390A型扫描电子显微镜和X-衍射方法对摩擦磨损表面进行观察,表征其摩擦表面的微观形貌、摩擦磨损的磨屑以及由于摩擦产热而引起的氧化物,进而推断出磨损机制.结果表明:摩擦副的摩擦系数随载荷和速度的增加而下降;随着转速和载荷的增加,销表面氧化物逐渐由FeO转变为Fe_3O_4,其磨损机制由黏着磨损转变为严重的氧化磨损.     

A Chemical Inhibitor of the Skp2/p300 Interaction that Promotes p53‐Mediated Apoptosis

Skp2 is thought to have two critical roles in tumorigenesis. As part of the SCF^Skp2 ubiquitin ligase, Skp2 drives the cell cycle by mediating the degradation of cell cycle proteins. Besides the proteolytic activity, Skp2 also blocks p53‐mediated apoptosis by outcompeting p53 for binding p300. Herein, we exploit the Skp2/p300 interaction as a new target for Skp2 inhibition. An affinity‐based high‐throughput screen of a combinatorial cyclic peptoid library identified an inhibitor that binds to Skp2 and interferes with the Skp2/p300 interaction. We show that antagonism of the Skp2/p300 interaction by the inhibitor leads to p300‐mediated p53 acetylation, resulting in p53‐mediated apoptosis in cancer cells, without affecting Skp2 proteolytic activity. Our results suggest that inhibition of the Skp2/p300 interaction has a great potential as a new anticancer strategy, and our Skp2 inhibitor can be developed as a chemical probe to delineate Skp2 non‐proteolytic function in tumorigenesis.     

铝-钨丝混编阵的Z-箍缩实验研究

利用铝丝和钨丝混合编制的丝阵作为Z箍缩的负载，在俄罗斯Kurchatov研究所的S300强流装置上对其Z箍缩过程进行了实验研究，并与纯铝丝阵和纯钨丝阵的实验结果进行了比较.不同材料组成的丝阵的Z箍缩x射线能谱之间有明显差异，混编丝阵的铝K壳层的x射线辐射强度比纯铝丝阵的弱，在纯钨丝阵Z箍缩中没有发现波长小于1.6nm的线辐射.混编丝阵Z箍缩的x射线发光区域比纯铝丝阵的小，但比纯钨丝阵的大,混编丝阵的x射线产额比纯铝丝阵的大，但比纯钨丝阵的略低.在驱动电流为2.5—2.8MA条件下，Z箍缩的径向收缩比为4—5，x射线辐射脉冲脉宽为25ns左右，峰值为0.3—0.5TW，总能量为10—20kJ.激光探针的阴影像显示了丝阵等离子体形成的细致过程，还表明了等离子体的边界面不够清晰，其不稳定性有明显的发展，内部有丰富的结构. 关键词： Z箍缩 混编丝阵 S300强流装置     

Charge density distribution and electrostatic moments of N‐(4‐chloro‐3‐ trifluromethyl‐phenyl)‐2‐ethoxy‐benzamide molecule at the active site of p300 enzyme: A quantum chemical and theoretical charge density study

A Charge density analysis of CTB molecule in gas phase (Form I ) and the same present at the active site (Form II ) of p300 enzyme were performed for the wave functions obtained from the Density functional method (B3LYP) with the basis set 6‐311G**. This study has been carried out to understand the nature of conformational modification, charge redistribution and the change of electrostatic moments of the CTB molecule when present at the active site of p300. The difference of charge density distribution between both forms of CTB molecule explicitly indicates the effect of intermolecular interaction on CTB molecule in the active site. The dipole moment of CTB in the gas phase (9.6 D) has been significantly decreased (4.27 D) when it present at the active site of p300; this large variation is attributed to the charge redistribution in CTB, due to the intermolecular interaction between the CTB and the receptor p300 molecule. The electrostatic potential maps differentiate the difference of electrostatic potential between the two forms. A large electronegative region is found at the vicinity of oxygen and fluorine atoms. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012     

聚酰亚胺液晶定向膜(IP-300B)中微量钠的测定

应用原子吸收光谱法测定聚酰亚胺液晶定向膜 (IP -30 0B)中的微量钠。样品经硫酸消化 -炭化 ,再经马福炉灰化后 ,溶液上机测定。结果表明 ,钠的浓度与吸光度的线性关系 ( 0 1 0～ 2 0 0 μg/mL)、特征浓度 ( 3 5× 1 0 - 3 μg/mL/1 % )、精度 (S :0 0 0 6 8;CV % :3 0 )、和标准添加回收率 ( 92 3%～ 1 0 6 2 % )均达到要求 ,为液晶印刷电路板生产建立质控方法。     

Nuclear magnetic resonance spectroscopy of rat ventricles following chronic hypoxia: A model of right ventricular hypertrophy

Nuclear magnetic resonance spectroscopy was used to study the effect of chronic hypoxia on both right (RV) and left ventricular and septal (LV + S) muscle. Rats in the hypoxic group, kept in a hypobaric chamber at $\text{1}\text{2}$ atm pressure for 2 weeks, developed right, but not left, ventricular hypertrophy (p < 0.001). Tissues were studied within 2.5 h of return to air. T₁ and T₂ relaxation times of RV, LV + S and thigh muscle (Th) from hypoxic and control rats were compared. The T₂ value distinguished hypoxic from control RV (p < 0.002), but not hypoxic from control LV + S or Th, indicating that the change in relaxation time reflects cellular hypertrophy, and not hypoxemia. For hypoxic rats only the T₂ value distinguished each muscle type: RV from LV + S (p < 0.009), RV from Th (p < 0.001) and LV + S from Th (p < 0001). The T₁ value did not identify either the hypoxic or control group or the type of muscle. Percent water content was similar for all tissues. For hypoxic RV, T₂ correlated with the percent water content (r = 0.89; p < 0.01). The sensitivity of T₂ to the cellular changes associated with hypoxic RV hypertrophy could provide a means of detecting right ventricular hypertrophy.     

基于熵算法的股票指数高频数据复杂度测算与评价

在日内高频环境下检验基于兼容法的柯尔莫哥洛夫熵、样本熵和模糊熵等复杂度测算方法对我国沪深300股票指数的测算效率,并运用筛选后的有效算法分阶段研究和比较了序列复杂度的变化过程与变化幅度.结果表明,模糊熵算法是一种更适用于我国沪深300股票指数的有效复杂度测算方法,其对相似容忍度的敏感性更低,测度值连续性更好.随时间推移,我国沪深300股票指数复杂度整体呈上升趋势,而相较于发达市场甚至周边新兴市场其复杂度偏低.     

沪深300股指期货日内绝对收益率与成交量之间动态关系研究

均值为零的观测样本绝对收益率可以看作波动率的无偏估计量,因此本文选取连续20个交易日的日内高频数据来研究沪深300股指期货日内绝对收益率和成交量之间的动态关系。在检验了样本稳定性后,文章采用格兰杰检验方法检验了股指期货日内绝对收益率和成交量之间的因果关系,检验结果表明:所有样本的成交量均不是绝对收益率的格兰杰原因,而20个样本中的15个样本的绝对收益率是成交量的格兰杰原因。随后我们使用向量自回归模型分别对15个模型的系数做估计,并对模型估计结果做了脉冲响应分析。研究发现,在此高频抽样条件下,与以往研究不同,沪深300股指期货绝对收益率的变化会明显降低其观测期的成交量。因此,在股指期货日内成交量与绝对收益率的研究中,历史成交量与收益率都对当前成交量有着重要影响;而绝对收益率只受历史绝对收益率的影响。     

Separation of pectin methylesterase isoenzymes from tomato fruits using short monolithic columns

One of the main forms of tomato pectin methylesterase (PME; EC 3.1.1.1.1) that is applicable to the food industry was isolated from fresh tomato fruit. The extraction of the PME isoenzymes involved washing the fresh tomato flesh with water in order to remove sugars and than solubilizing the enzymes with a diluted HCl solution at pH 1.6. The extract was then neutralized to pH 7.4 using buffer solution. After filtration, the solution was directly fractioned using Convective Interaction Media (CIM) short monolithic disk column bearing sulfonyl (SO3) groups and using a linear gradient from 0 to 700 mM NaCl. The injection volume was 3 ml and the diameter of the column was 12 mm and length 3 mm. The isolated fractions were monitored for protein content and PME activity. The fraction with the targeted enzyme, which showed NaCl independent activity, was further purified and concentrated by ultrafiltration and finally purified by a second semi-preparative cation-exchange chromatography step using a CIM carboxymethyl (CM) disk monolithic column consisting of two disks and applying a step gradient. From 1 kg of fresh tomato fruits, 7.5 mg of purified PME with molecular mass estimated to be 26 000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was obtained. A fraction with mixed PME and polygalacturonase activity was also obtained. Compared to the published procedures for the isolation and purification of PME from plant materials, this new procedure is much faster and more efficient. The potential application of CIM disk short monolithic columns in the analysis and semi-preparative extraction and isolation of the PME isoenzyme is presented.