Status Report and Beam Time Request for Experiment AD-4

Summary of current status and plans for October 200

Analytical expressions for stopping-power ratios relevant for accurate dosimetry in particle therapy

In particle therapy, knowledge of the stopping-power ratios (STPRs) of the ion beam for air and water is necessary for accurate ionization chamber dosimetry. Earlier work has investigated the STPRs for pristine carbon ion beams, but here we expand the calculations to a range of ions (1 <= z <= 18) as well as spread out Bragg peaks (SOBPs) and provide a theoretical in-depth study with a special focus on the parameter regime relevant for particle therapy. The Monte Carlo transport code SHIELD-HIT is used to calculate complete particle-fluence spectra which are required for determining STPRs according to the recommendations of the International Atomic Energy Agency (IAEA). We confirm that the STPR depends primarily on the current energy of the ions rather than on their charge z or absolute position in the medium. However, STPRs for different sets of stopping-power data for water and air recommended by the International Commission on Radiation Units & Measurements (ICRU) are compared, including also the recently revised data for water, yielding deviations up to 2% in the plateau region. In comparison, the influence of the secondary particle spectra on the STPR is about two orders of magnitude smaller in the whole region up till the practical range. The gained insights enable us to propose an analytic approximation for the STPR for both pristine and SOBPs as a function of penetration depth, which parametrically depend only on the initial energy and the residual range of the ion, respectively.Comment: 21 pages, 5 figures, fixed bug with figures in v

Mode-locking in driven vortex lattices with transverse ac-drive and random pinning

We find mode-locking steps in simulated current-voltage characteristics of driven vortex lattices with {\it random} pinning when an applied ac-current is {\it perpendicular} to the dc-current. For low frequencies there is mode-locking only above a non-zero threshold ac force amplitude, while for large frequencies there is mode-locking for any small ac force. This is consistent with the nature of {\it transverse} temporal order in the different regimes in the absence of an applied ac-drive. For large frequencies the magnitude of the fundamental mode-locked step depends linearly with the ac force amplitude.Comment: 4 pages, 4 figures, .tar.gz fil

Transverse phase-locking in fully frustrated Josephson junction arrays: a new type of fractional giant steps

We study, analytically and numerically, phase locking of driven vortex lattices in fully-frustrated Josephson junction arrays at zero temperature. We consider the case when an ac current is applied {\it perpendicular} to a dc current. We observe phase locking, steps in the current-voltage characteristics, with a dependence on external ac-drive amplitude and frequency qualitatively different from the Shapiro steps, observed when the ac and dc currents are applied in parallel. Further, the critical current increases with increasing transverse ac-drive amplitude, while it decreases for longitudinal ac-drive. The critical current and the phase-locked current step width, increase quadratically with (small) amplitudes of the ac-drive. For larger amplitudes of the transverse ac-signal, we find windows where the critical current is hysteretic, and windows where phase locking is suppressed due to dynamical instabilities. We characterize the dynamical states around the phase-locking interference condition in the $IV$ curve with voltage noise, Lyapunov exponents and Poincar\'e sections. We find that zero temperature phase-locking behavior in large fully frustrated arrays is well described by an effective four plaquette model.Comment: 12 pages, 11 figure

Biological Effects of Antiprotons Are Antiprotons a Candidate for Cancer Therapy?

2009 Status Report of AD-4 Experimen

A Study On The Model Of Profit And Risk In Xiamen’s Commercial Banks

随着相对滞后的金融体制改革提上议事日程，金融业中的银行业的风险和效益的矛盾对立统一日益成为讨论的焦点、热点。加入WTO对金融业意味着拥有先进管理技术和经验的外资银行抢滩国内银行业务，其对国内中资银行的竞争和生存环境的影响是巨大且不可预测的。作者认为国内中资银行是缺乏效率的，为避免银行命脉被外资控制，国内中资银行不能讳疾忌医，而要以有容乃大、自省的态度积极寻求市场经济下的解决之道，最可取的莫过于解剖一只麻雀。 按照这一思路，本文选取了厦门8家经营较稳定的商业银行进行收益风险模式比较，为国内其他中资商业银行的经营管理提供实证参考。 第一章导言。对银行经营活动的一般特点进行描述。提出银行作为经济...Owing to the combination between banking and economics , influencing factor is increasingly complicated. Banker needs to design one macroanalysis model to logically judge different kinds of income chance and danger all banks faced with，through which banker may supply effective diagnose for banking operating management. The theses takes banking 'data in Xiamen as an example .It exists that huge c...学位：工商管理硕士院系专业：管理学院工商管理教育中心_工商管理硕士(MBA)学号：19981505

Calculated LET spectrum from antiproton beams stopping in water

Antiprotons have been proposed as a potential modality for radiotherapy because the annihilation at the end of range leads to roughly a doubling of physical dose in the Bragg peak region. So far it has been anticipated that the radiobiology of antiproton beams is similar to that of protons in the entry region of the beam, but very different in the annihilation region, due to the expected high-LET components resulting from the annihilation. On closer inspection we find that calculations of dose averaged LET in the entry region may suggest that the RBE of antiprotons in the plateau region could significantly differ from unity, which seems to warrant closer inspection of the radiobiology in this region. Materials and Methods. Monte Carlo simulations using FLUKA were performed for calculating the entire particle spectrum of a beam of 126 MeV antiprotons hitting a water phantom. Results and Discussion. In the plateau region of the simulated antiproton beam we observe a dose-averaged unrestricted LET of about 4 keV/ m m, which is very different from the expected 0.6 keV/ m m of an equivalent primary proton beam. Even though the fluence of secondaries is a magnitude less than the fluence of primary particles, the increased stopping power of the secondary particles causes an increase in the dose averaged LET which is expected to result in a RBE different from unity