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Carbon ions induce autophagy effectively through stimulating the unfolded protein response and subsequent inhibiting Akt phosphorylation in tumor cells
No full textHeavy ion beams have advantages over conventional radiation in radiotherapy due to their superb biological effectiveness and dose conformity. However, little information is currently available concerning the cellular and molecular basis for heavy ion radiation-induced autophagy. In this study, human glioblastoma SHG44 and cervical cancer HeLa cells were irradiated with carbon ions of different linear energy transfers (LETs) and X-rays. Our results revealed increased LC3-II and decreased p62 levels in SHG44 and HeLa cells post-irradiation, indicating marked induction of autophagy. The autophagic level of tumor cells after irradiation increased in a LET-dependent manner and was inversely correlated with the sensitivity to radiations of various qualities. Furthermore, we demonstrated that high-LET carbon ions stimulated the unfolded protein response (UPR) and mediated autophagy via the UPR-eIF2 alpha-CHOP-Akt signaling axis. High-LET carbon ions more severely inhibited Akt-mTOR through UPR to effectively induce autophagy. Thus, the present data could serve as an important radiobiological basis to further understand the molecular mechanisms by which high-LET radiation induces cell death
Development and test of ADS injector II RFQ accelerator
No full textThe injector II RFQ accelerator of ADS is used to accelerate protons of 10 mA from 35 keV to 2.1 MeV. The cavity structure of the RFQ is the same as that of the SNS RFQ which has a square cross section, and it adopts π-mode rods to enhance the RF (radio frequency) stability of the cavity. Low power tests show that the flatness of the cavity is better than ±0.01 and the unloaded Q value is 13000. CW (continuous wave) working condition was realized after a long time conditioning of the cavity. Beam tests were conducted with a current of 10 mA in pulse mode and CW mode, respectively, and it indicates that the transmission efficiency is 95.3%, output energy is 2.165 MeV, energy spread is 1.9%, and the transverse and longitudinal emittances are all 0.33 πmm·mrad. ©, 2015, Atomic Energy Press. All right reserved
Adjusting the accelerating field distribution of a superconducting CH cavity
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);">In a superconducting CH (cross bar H mode) cavity, the method of regulating the length of a drift tube is employed to adjust the distribution of the accelerating field. In this article, we simulate the electromagnetic field of a CH structure to illustrate the reason for adjusting the field distribution by varying drift tube length. Meanwhile, that the presence of the drift tube will cause a sharp rise in the maximum electric field is also shown. This phenomenon is contrary to superconducting cavity design principles in which the cavity geometry needs to be optimized to reduce the maximum electric field to avoid field emission. We propose a variable diameter superconducting CH cavity design to solve this conflict. The simulation of the variable diameter superconducting CH cavity shows that this method is feasible.</span
Study of dielectronic recombination at the CSRm using lithium-like Ar15+ ions
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);">The main cooler storage ring (CSRm) of the HIRFL facility in Lanzhou, China is equipped with an electron-cooler and denotes an ideal platform for dielectronic recombination (DR) experiments. In order to fully understand our DR experimental setup and especially the electron energy detuning system, we have performed a DR calibration experiment using the Li-like argon ions at the CSRm because Ar15+ has a simple electronic structure and the DR spectrum can be calculated with an ultra-high precision and be compared with the existing experimental data. The experiment was carried out over the center-of-mass energy range 0-32 eV that includes all DR resonance associated with 2S(1/2) -> 2p(1/2) and most of the 2S(1/2) -> 2p(3/2) excitations. We present the details of the experimental technique and the DR experimental resonance spectrum of the Ar15+.</span
Rydberg-to-M-shell x-ray emission of hollow Xeq+ (q=27-30) atoms or ions above metallic surfaces
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);">X rays originating from transitions from high Rydberg states to the M shell (here called Rydberg-to-M-shell x rays) have been measured in the interaction of Xeq+ (q = 27-30) ions with aluminum, molybdenum, and beryllium surfaces in the energy range of 350-600 keV, by using a Si(Li) detector. The transition energy calculation by Cowan's program with relativistic correlation indicates that such x rays are mainly from the transition of the higher quantum states, with the principal quantum number from 6 up to 30, directly to M shell of xenon. The yield of the x ray per vacancy in M shell decreases slightly with increasing the projectile energies and is inversely proportional to the work functions of metallic surfaces used. However, it increases rapidly with the increase of the projectile charge states. All of these experimental facts combined with the transition rate calculations indicate that the measured Rydberg-to-M-shell x rays come from the "above the surface" hollow Xe atoms or ions deexcitation, when the inner shells such as N and O have not been filled.</span
Study of X-ray spectrum emitted due to the impact of Xe-129(q+) on different ion's charge on Au
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);">We report the experiment data of X-ray spectra produced by the impact of Xeq+ (q = 1 0, 15, 20, 26) with 2.4 MeV kinetic energy on Au surface in the National Laboratory of Heavy Ion Research Facility in Lanzhou. Results show that there is different broadening of Au M X-ray owing to multiply ionized effect in the collision with heavy ions, the degree of ionization mainly depends on the distribution of the electronic states in the ions' outer shell. The yield of X-ray is calculated and compared with BEA (binary encounter approximation) model, and the effect of ion charge state on the X-ray yield is also discussed.</span
Analytical model for describing ion guiding through capillaries in insulating polymers
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);">An analytical description for guiding of ions through nanocapillaries is given on the basis of previous work. The current entering into the capillary is assumed to be divided into a current fraction transmitted through the capillary, a current fraction flowing away via the capillary conductivity and a current fraction remaining within the capillary, which is responsible for its charge-up. The discharging current is assumed to be governed by the Frenkel-Poole process. At higher conductivities the analytical model shows a blocking of the ion transmission, which is in agreement with recent simulations. Also, it is shown that ion blocking observed in experiments is well reproduced by the analytical formula. Furthermore, the asymptotic fraction of transmitted ions is determined. Apart from the key controlling parameter (charge-to-energy ratio), the ratio of the capillary conductivity to the incident current is included in the model. Differences resulting from the nonlinear and linear limits of the Frenkel-Poole discharge are pointed out.</span