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The antioxidant mechanism of nitroxide TEMPO: scavenging with glutathionyl radicals
No full textA rhodamine-nitroxide probe (R-NOc), combining rhodamine fluorophore with a 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO) receptor unit was introduced to probe glutathionyl radicals (GSc) with high sensitivity and selectivity. The R-NOc probe could effectively scavenge GSc radicals with fluorescence enhancement since the nitroxide group restored the fluorescence properties. In this work, horseradish peroxidase (HRP)-catalyzed and metal-catalyzed oxidation systems were selected as the model of simulating the generation of GSc, and we found that the metal-catalyzed system had the same experimental results with the HRP-catalyzed system, which provided a new approach to demonstrate the strong oxidant ability of the hydroxyl radical (cOH) to initiate toxic GSc. Furthermore, we confirmed that the production of GSc abided by a radical-initiated peroxidation mechanism of GSH with the mass spectrometry (MS) analysis and fluorescence spectroscopy. By using combined high-performance liquid chromatography (HPLC) detection and MS analysis, we also demonstrated that the R-NOc was converted into fluorescent secondary amine derivative (R-NH). The application of the probe in biological system was explored to monitor GSc in HL-60 cells and secondary amine fluorescence was observed upon stimulation by hydrogen peroxide and phenol. Development of fluorescence was prevented via preincubation with the thiol-blocking reagent N-ethylmaleimide (NEM)
Instability research of 53.667 MHz heavy ion RFQ
No full text采用多粒子跟踪程序BEAMPATH对53.667 MHz RFQ进行模拟计算,基于RFQ腔体冷测、机械测量的结果,在考虑其入口束流不稳定性、电压不平整度、高频系统稳定度、加工误差、安装误差等因素的情况下,对RFQ的出口束流品质和不稳定性进行了系统分析。结果表明,在现有的加工、安装水平下,提高RFQ入口束流稳定度和高频系统稳定度对束流在RFQ中的传输十分必要。<div>
Based on the database from RFQ cavity cold model test and tip-pole geometry measurement,53.667 MHz RFQ was simulated by BEAMPATH code.The RFQ output beam quality and instability were analyzed as functions of input beam instability, voltage roughness,stability of RF control system,RFQ manufacturing error,and misalignment. According to these results,it shows that it is essential for beam transmission in RFQ to improve input beam stability and RF control system stability at the pre-sent level of machining and alignment.</div>
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Electromagnetic characteristics of the CH cavity
No full textIn this paper, we present the RF simulation, the fabrication and the normal RF test of a six-cell copper model cross bar H mode (CH) cavity. The CH cavity was researched and developed at the Institute of Modern Physics for Injector II of the superconducting linac of the accelerator driven system of China, operating at a frequency 162.5 MHz, beta=0.065. The deep drawing and electron beam welding were employed to fabricate this cavity, which would be used to develop the superconducting CH cavity in the future. The results of the normal RF test agree with the simulation of the electromagnetic properties, such as the electric field distribution on the cavity axis, frequency and Q factor
Investigation on the energy loss in low energy protons interacting with hydrogen plasma
No full text<span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">Energy loss of protons with energy 100 keV penetrating the partially ionized hydrogen plasma target was measured. The plasma target was created by electric discharge in the hydrogen gas, the state of the plasma target was diagnosed by using the laser interferometry method: the free electron density is up to 10(16) cm(-3), temperature is about 1-2 eV, and the plasma target may exist at the microsecond level. It is found that the energy loss of protons is closely related to the free electron density, and the energy loss data enable us to infer the value of the Coulomb logarithm (10.8) for the stopping power of the free electrons. This agrees well with the theoretical prediction which is 4.3 times higher than that given by the Bethe formula for neutral hydrogen, which is a little bigger than Hoffmann's result but much smaller than Jacoby's result. Comparing our result with Hoffmann's, the energy we used is only 100 keV, much lower than 1.4 MeV/u, and the low-energy regime we applied could be the cause of the increase in the enhancement factor. However, in the comparison between our result and the Jacoby's, the effective charge for protons is almost constant, unlike the Kr+ impact in wihch the enhanced ion charge state induces the giant enhancement factor. Compared to the gas target, the energy loss enhancement factor in plasma target is 2.9.</span
Energy dependence of H2+ ions guided through tapered capillaries in PC
No full text<span style="color: rgb(51, 51, 51); font-family: arial, helvetica, sans-serif; font-size: 13px; line-height: 22px; background-color: rgb(248, 248, 248);">Transmission of H-2(+) ions through tapered capillaries in insulating polycarbonate (PC) foil is reported. Guiding, focusing effects and multi-peaks phenomena on ions through capillaries have been studied</span