Atomic Bomb Survivor Studies and their Current Significance: Comparison between the Practices of the ABCC-RERF and the RIRBM

Medical research spurred by radiation exposure is a critically important theme for modern society. Accordingly, studies of this contemporary problem should be based on a perspective that is focused on that origin, medical investigations into the effects of radiation exposure on survivors of the atomic bombs. Therefore, we organized and evaluated survey programs and research of atomic bomb survivors that have been conducted by ABCC (Atomic Bomb Casualty Commission) –RERF (Radiation Effects Research Foundation) and RIRBM (Research Institute for Radiation Biology and Medicine) between 1949 and 1975. ABCC established a set of carefully defined cohorts and launched an integrated research program based on three phases of pure research. That work has formed the foundation for the research that the RERF is engaged in today. And among surveys and studies worldwide that have generated fundamental data on radiation protection standards, the findings of ABCC-RERF surveys and studies have provided important information. It has thus provided various international research organizations (WHO (World Health Organization), ICRP (International Commission on Radiological Protection), UNSCEAR (United Nations Scientific Committee on the Effects of Atomic Radiation), etc.) with important information and indicators. RIRBM has pursued studies and surveys that are distinct from the undertakings led by ABCC-RERF. RIRBM was able to do something that ABCC-RERF would have found difficult to implement: namely, flexibly launching projects on themes that directly met the needs of the local society at the time. Atomic bomb survivors’ medical data continue to grow, from the bombing to the present, and to the future. Data sharing, joint research, and collaboration by research institutions in this field will be effective ways to foster rationally coordinated surveys and studies

Suzaku and Optical Spectroscopic Observations of SS 433 in the 2006 April Multiwavelength Campaign

We report results of the 2006 April multi-wavelengths campaign of SS 433, focusing on X-ray data observed with Suzaku at two orbital phases (in- and out-of- eclipse) and simultaneous optical spectroscopic observations. By analyzing the Fe25 K_alpha lines originating from the jets, we detect rapid variability of the Doppler shifts, dz/dt ~ 0.019/0.33 day^-1, which is larger than those expected from the precession and/or nodding motion. This phenomenon probably corresponding to "jitter" motions observed for the first time in X-rays, for which significant variability both in the jet angle and intrinsic speed is required. From the time lag of optical Doppler curves from those of X-rays, we estimate the distance of the optical jets from the base to be ~(3-4) \times 10^14 cm. Based on the radiatively cooling jet model, we determine the innermost temperature of the jets to be T_0 = 13 +/- 2 keV and 16 +/- 3 keV (the average of the blue and red jets) for the out-of-eclipse and in-eclipse phase, respectively, from the line intensity ratio of Fe25 K_alpha and Fe26 K_alpha. While the broad band continuum spectra over the 5--40 keV band in eclipse is consistent with a multi-temperature bremsstrahlung emission expected from the jets, and its reflection component from cold matter, the out-of-eclipse spectrum is harder than the jet emission with the base temperature determined above, implying the presence of an additional hard component.Comment: 12 pages, 15 figures, accepted for publication in PAS

Discovery of a new dwarf nova, TSS J022216.4+412259.9: WZ Sge-type dwarf novae breaking the shortest superhump period record

We report on the time-resolved CCD photometry of a newly discovered variable star, TSS J022216.4+412259.9 during the outburst in 2005 November-December brightening. The obtained light curves unambiguously showed 0.2-0.3 mag modulations, which we confirmed to be the superhump observed among SU UMa-type dwarf novae. We also performed a period search for the data obtained during the outburst plateau phase, and revealed the existence of the two periodicities: 0.054868(98) days for the first two nights and 0.055544(26) days for the following plateau phase. This bi-periodicity is hardly observed in usual SU UMa-type dwarf novae, but characteristic of WZ Sge-type stars. We undoubtedly detected a rebrightening in the post-outburst stage, which is typical of short-period SU UMa-type dwarf novae including WZ Sge-type stars. These observations suggests that TSS J022216.4+412259.9 may be a new WZ Sge stars breaking the shortest superhump period of 0.05648 days for V592 Her among this class with a known superhump period so far.Comment: 5 pages, 6 figures, accepted for PASJ lette

Long-term monitoring of the short period SU UMa-type dwarf nova, V844 Herculis

We report on time-resolved CCD photometry of four outbursts of a short-period SU UMa-type dwarf nova, V844 Herculis. We successfully determined the mean superhump periods to be 0.05584(64) days, and 0.055883(3) for the 2002 May superoutburst, and the 2006 April-May superoutburst, respectively. During the 2002 October observations, we confirmed that the outburst is a normal outburst, which is the first recorded normal outburst in V844 Her. We also examined superhump period changes during 2002 May and 2006 April-May superoutbursts, both of which showed increasing superhump period over the course of the plateau stage. In order to examine the long-term behavior of V844 Her, we analyzed archival data over the past ten years since the discovery of this binary. Although photometry is not satisfactory in some superoutbursts, we found that V844 Her showed no precursors and rebrightenings. Based on the long-term light curve, we further confirmed V844 Her has shown almost no normal outbursts despite the fact that the supercycle of the system is estimated to be about 300 days. In order to explain the long-term light curves of V844 Her, evaporation in the accretion disk may play a role in the avoidance of several normal outbursts, which does not contradict with the relatively large X-ray luminosity of V844 Her.Comment: 10 pages, 11 figures, accepted for PAS

Dwarf Novae in the Shortest Orbital Period Regime: I. A New Short Period Dwarf Nova, OT J055717+683226

We report the observation of a new dwarf nova, OT J055717+683226, during its first-ever recorded superoutburst in December 2006. Our observation shows that this object is an SU UMa-type dwarf nova having a very short superhump period of 76.67+/- 0.03 min (0.05324+/-0.00002 d). The next superoutburst was observed in March 2008. The recurrence time of superoutbursts (supercycle) is, hence, estimated to be ~480 d. The supercycle is much shorter than those of WZ Sge-type dwarf novae having supercycles of >~ 10 yr, which are a major population of dwarf novae in the shortest orbital period regime (<~85 min). Using a hierarchical cluster analysis, we identified seven groups of dwarf novae in the shortest orbital period regime. We identified a small group of objects that have short supercycles, small outburst amplitudes, and large superhump period excesses, compared with those of WZ Sge stars. OT J055717+683226 probably belongs to this group.Comment: 14 pages, 11 figures, accepted for publication in PAS

Breast cancer metastasis to the stomach: A case report

The stomach is an infrequent site of breast cancer metastasis. It may prove very difficult to distinguish a breast cancer metastasis to the stomach from a primary gastric cancer on the basis of clinical, endoscopic, radiological and histological features. We present a case of a 57-year-old woman of gastric metastasis from breast cancer by immunohistochemistry 6 years after mastectomy. Since no other lesions were observed in the image examination, she underwent laparoscopic gastrectomy and endocrine therapy. The patient remains well after 6 years from gastrectomy. Complete histopathological and immunohistochemical analysis of the gastric biopsies and comparison with the original breast cancer pathology is important

Spectral evolution of GRB 060904A observed with Swift and Suzaku -- Possibility of Inefficient Electron Acceleration

We observed an X-ray afterglow of GRB 060904A with the Swift and Suzaku satellites. We found rapid spectral softening during both the prompt tail phase and the decline phase of an X-ray flare in the BAT and XRT data. The observed spectra were fit by power-law photon indices which rapidly changed from $\Gamma = 1.51^{+0.04}_{-0.03}$ to $\Gamma = 5.30^{+0.69}_{-0.59}$ within a few hundred seconds in the prompt tail. This is one of the steepest X-ray spectra ever observed, making it quite difficult to explain by simple electron acceleration and synchrotron radiation. Then, we applied an alternative spectral fitting using a broken power-law with exponential cutoff (BPEC) model. It is valid to consider the situation that the cutoff energy is equivalent to the synchrotron frequency of the maximum energy electrons in their energy distribution. Since the spectral cutoff appears in the soft X-ray band, we conclude the electron acceleration has been inefficient in the internal shocks of GRB 060904A. These cutoff spectra suddenly disappeared at the transition time from the prompt tail phase to the shallow decay one. After that, typical afterglow spectra with the photon indices of 2.0 are continuously and preciously monitored by both XRT and Suzaku/XIS up to 1 day since the burst trigger time. We could successfully trace the temporal history of two characteristic break energies (peak energy and cutoff energy) and they show the time dependence of $\propto t^{-3} \sim t^{-4}$ while the following afterglow spectra are quite stable. This fact indicates that the emitting material of prompt tail is due to completely different dynamics from the shallow decay component. Therefore we conclude the emission sites of two distinct phenomena obviously differ from each other.Comment: 19 pages, 9 figures, accepted for publication in PASJ (Suzaku 2nd Special Issue

The 2006 November outburst of EG Aquarii: the SU UMa nature revealed

We report time-resolved CCD photometry of the cataclysmic variable EG Aquarii during the 2006 November outburst During the outburst, superhumps were unambiguously detected with a mean period of 0.078828(6) days, firstly classifying the object as an SU UMa-type dwarf nova. It also turned out that the outburst contained a precursor. At the end of the precursor, immature profiles of humps were observed. By a phase analysis of these humps, we interpreted the features as superhumps. This is the second example that the superhumps were shown during a precursor. Near the maximum stage of the outburst, we discovered an abrupt shift of the superhump period by ${\sim}$ 0.002 days. After the supermaximum, the superhump period decreased at the rate of $\dot{P}/P$=$-8.2{\times}10^{-5}$, which is typical for SU UMa-type dwarf novae. Although the outburst light curve was characteristic of SU UMa-type dwarf novae, long-term monitoring of the variable shows no outbursts over the past decade. We note on the basic properties of long period and inactive SU UMa-type dwarf novae.Comment: 9 pages, 7 figures, accepted for PAS