Estimated Soft X-ray Spectrum And Ionization Of Molecular Hydrogen In The Central Molecular Zone Of The Galactic Center

From observed high H$_3^+$ column densities in the Central Molecular Zone (CMZ), a region with a radius of $\sim$150~pc at the center of our Milky Way Galaxy, H$_2$ ionization rates of $\zeta$~$\sim$~3~$\times$~10$^{-15}$~s$^{-1}$ have been reported.\footnote{Oka, T., Geballe, T. R., Goto, M., Usuda, T., and McCall, B. J. 2005, ApJ, \textbf{632} 882}\footnote{Geballe, T. R., and Oka, T. 2010, ApJ, \textbf{709} L70.} This ionization rate which is higher than those in dense clouds and diffuse clouds in the Galactic disk by $\sim$100 and $\sim$10, respectively, have been ascribed to high flux of cosmic rays due to the high density of supernova remnants in the region. We are studying the ionization rate due to X-rays intensely observed in the CMZ as a possible competing process. Last year we reported the estimated ionization rate due to observable X-rays with energy 1 - 10 keV as negligible compared to the observed $\zeta$. \vspace{0.1 in} However, just like cosmic ray ionization is dominated by low energy ($E\leq$~100~MeV) cosmic rays that are not directly observable because of deflection by solar magnetic field, the X-ray ionization is dominated by soft X-rays ($E\leq$~1~keV) that are not observable due to optical depth of the foreground gas. Our task therefore resembles those by Hayakawa et al. (1961)\footnote{Hayakawa,S.,Nishimura, S., Takayanagi, K. 1961, PASJ, \textbf{18} 184} and Spitzer and Tomasko (1968)\footnote{Spitzer,L. T., Tomasko, M. G. 1968, ApJ, \textbf{152} 971} who estimated the cosmic ray ionization rate $\zeta$ based on high energy ($>$~1 GeV) cosmic ray observations. \vspace{0.1 in} We use theoretical X-ray spectrum and interpolate the observed X-rays at 4 keV, which are observable nearly un-attenuated from the CMZ, to the low energy region. Two theoretical spectra are presented, one due to Bremsstrahlung with variable temperature and proper cut off and the other the advection-dominated accretion flow (ADAF) model.\footnote{Yuan, F., Quataert, E., Narayan, R. 2003, JPJ, \textbf{598} 301.}. Discussion of the calculations and the results will be presented

Study of the Hindrance Effect in Sub-barrier Fusion Reactions

We have measured the fusion cross sections of the 12C(13C, p)24Na reaction through off-line measurement of the beta-decay of 24Na using the beta-gamma coincidence method. Our new measurements in the energy range of Ec.m. = 2.6-3.0 MeV do not show an obvious S-factor maximum but a plateau. Comparison between this work and various models is presented.Comment: 3 pages, 3 figures, Talk at the "10th International Conference on Nucleus-Nucleus Collisions", Beijing, 16-21 August 200

IONIZATION OF H2_2 BY X-RAYS IN THE CENTRAL MOLECULAR ZONE OF THE GALACTIC CENTER

Author Institution: Department of Astronomy and Astrophysics and Department of Chemistry, the Enrico Fermi Institute, the University of Chicago, Chicago, Illinois, 60637, USARecent studies of the Galactic center using the infrared spectrum of H$_3^+$ have revealed a high ionization rate of H$_2$ on the order of $\zeta$~$\sim$~3$\times$10$^{-15}$~s$^{-1}$ in wide regions of the Central Molecular Zone (CMZ), a region with a radius of $\sim$~150~pc at the Galactic center. 882} L70.} So far we have ascribed this ionization rate, which is an order of magnitude higher than in the Galactic disk, to cosmic rays because of a high density of supernova remnants in the CMZ. In view of the abundant intense X-ray sources from 1 keV to several 10 keV in the region, however, there may be a significant ionization by X-rays also. \vspace{0.1 in} We estimate the ionization rate due to X-rays based on the large scale ART-P X-ray map of the Galactic center region. 116.} The calculations proceed in two steps. First we allow for the attenuation of the observed X-rays by the foreground gas to obtain the original intensities of the X-ray sources. 119.} We then use the corrected X-ray flux to calculate ionization rates of H$_2$ in the CMZ. The calculation is also related to the heating of the gas by X-rays. Discussion of the details of calculations and the results will be presented

A Gas-Filled Calorimeter for High Intensity Beam Environments

AbstractWe describe a novel gas-Cherenkov calorimeter, which detects Cherenkov light showers emitted in an array of thin metal tubes or channels filled with gas. The materials are not vulnerable to radiation damage, and the detector is inherently fast and able to operate in high rate environments. Future accelerators such as the ILC and a muon collider will need fast, radiation-tolerant detectors for monitoring beams and beam halos, and detectors are needed that can operate in the presence of high particle rates. Such detectors will also be useful for high rate environments at upgraded facilities such as RHIC, CEBAF II, and at Fermilab's Project X

前立腺癌ヨウ素125密封小線源永久挿入療法の初期経験

Initial clinical experience of radioactive iodine-125 permanent interstitial implantation for prostate cancer was presented. We reviewed dose volume histogram (DVH) data and prostate specific antigen (PSA) data, and adverse events of 53 patients who were treated by brachytherapy from October 2005 to March 2007. Twelve patients were treated with combined therapy of external body radiotherapy of 45 Gy because of intermediate risk (EBRT group), and 41 were treated only with brachytherapy (monotherapy group). Mean V100 was 93.1 %, D90 was 158.2 Gy in the monotherapy group, and 91.6 %, 115.6 Gy in the EBRT group. Migration of iodine-125 occurred in 21 patients (39.6%). DVH data of patients with migration were lower than that without migration (V100: 90.8 %, D90; 149.4 Gy vs. V100: 94.0%, D90: 161.5 Gy, respectively) (p<0.05), No severe early adverse event occurred. Serum PSA level in all patients began to decrease by 3 months after the implantation of the iodine. Our initial data of iodine-125 brachytherapy for prostate cancer is satisfactory, but longer follow up is required for further confirmation.2005年10月,当院は山陰で初めて前立腺癌のヨウ素125密封小線源永久挿入療法を導入した。2007年3月までに53例(単独治療41例,外照射併用12例)を経験したので初期成績を報告する。Dose volume histogram(DVH)のうちV100, D90の平均値は単独治療群93.1% 158.2Gy, 併用治療群91.6%, 115.6Gyだった。21例(39.6%)で線源の前立腺外移動が見られた。線源移動群のDVHデータ(V100: 90.8%, D90: 149.4Gy)は移動なし群(V100: 94.0%, D90: 161.5 Gy)に比べ不良であった(p<0.05)。重篤な急性期有害事象は認めず.前立腺特異抗原は全例低下を認めた。DVHデータおよび臨床データは満足できる結果であった。今後.線源移動の発生要因の検討に加え,さらに症例を重ねて長期成績を検討することが必要である