Bayesian Approach to Find a Long-Term Trend in Erratic Polarization Variations Observed in Blazars

We developed a method to separate a long-term trend from observed temporal variations of polarization in blazars using a Bayesian approach. The temporal variation of the polarization vector is apparently erratic in most blazars, while several objects occasionally exhibited systematic variations, for example, an increase of the polarization degree associated with a flare of the total flux. We assume that the observed polarization vector is a superposition of distinct two components, a long-term trend and a short-term variation component responsible for short flares. Our Bayesian model estimates the long-term trend which satisfies the condition that the total flux correlates with the polarized flux of the short-term component. We demonstrate that assumed long-term polarization components are successfully separated by the Bayesian model for artificial data. We applied this method to photopolarimetric data of OJ 287, S5 0716+714, and S2 0109+224. Simple and systematic long-term trends were obtained in OJ 287 and S2 0109+224, while no such a trend was identified in S5 0716+714. We propose that the apparently erratic variations of polarization in OJ 287 and S2 0109+224 are due to the presence of the long-term polarization component. The behavior of polarization in S5 0716+714 during our observation period implies the presence of a number of polarization components having a quite short time-scale of variations.Comment: 12 pages, 7 figures, accepted for publication in PAS

Photopolarimetric Monitoring of Blazars in the Optical and Near-Infrared Bands with the Kanata Telescope. I. Correlations between Flux, Color, and Polarization

We report on the correlation between the flux, color and polarization variations on time scales of days--months in blazars, and discuss their universal aspects. We performed monitoring of 42 blazars in the optical and near-infrared bands from 2008 to 2010 using TRISPEC attached to the "Kanata" 1.5-m telescope. We found that 28 blazars exhibited "bluer-when-brighter" trends in their whole or a part of time-series data sets. This corresponds to 88% of objects that were observed for >10 days. Thus, our observation unambiguously confirmed that the "bluer-when-brighter" trend is common in the emission from blazar jets. This trend was apparently generated by a variation component with a constant and relatively blue color and an underlying red component. Prominent short-term flares on time scales of days--weeks tended to exhibit a spectral hysteresis; their rising phases were bluer than their decay phases around the flare maxima. In contrast to the strong flux--color correlation, the correlation of the flux and polarization degree was relatively weak; only 10 objects showed significant positive correlations. Rotations of polarization were detected only in three objects: PKS 1510-089, 3C 454.3, and PKS 1749+096, and possibly in S5 0716+714. We also investigated the dependence of the degree of variability on the luminosity and the synchrotron peak frequency, \nu_peak. As a result, we found that lower luminosity and higher \nu_peak objects had smaller variations in their amplitudes both in the flux, color, and polarization degree. Our observation suggests the presence of several distinct emitting sources, which have different variation time-scales, colors, and polarizations. We propose that the energy injection by, for example, internal shocks in relativistic shells is a major factor for blazar variations on time scales of both days and months.Comment: 39 pages, accepted for publication in PAS

Cigarette smoking, genetic polymorphisms and colorectal cancer risk: the Fukuoka Colorectal Cancer Study

Background: It is uncertain whether smoking is related to colorectal cancer risk. Cytochrome P-450 CYP1A1, glutathione-S-transferase (GST) and NAD(P)H:quinone oxidoreductase 1 (NQO1) are important enzymes in the metabolism of tobacco carcinogens, and functional genetic polymorphisms are known for these enzymes. We investigated the relation of cigarette smoking and related genetic polymorphisms to colorectal cancer risk, with special reference to the interaction between smoking and genetic polymorphism. Methods: We used data from the Fukuoka Colorectal Cancer Study, a population-based case-control study, including 685 cases and 778 controls who gave informed consent to genetic analysis. Interview was conducted to assess lifestyle factors, and DNA was extracted from buffy coat. Results: In comparison with lifelong nonsmokers, the odds ratios (OR) of colorectal cancer for <400, 400-799 and ≥800 cigarette-years were 0.65 (95 % confidence interval [CI], 0.45-0.89), 1.16 (0.83-1.62) and 1.14 (0.73-1.77), respectively. A decreased risk associated with light smoking was observed only for colon cancer, and rectal cancer showed an increased risk among those with ≥400 cigarette-years (OR 1.60, 95 % CI 1.04-2.45). None of the polymorphisms under study was singly associated with colorectal cancer risk. Of the gene-gene interactions studied, the composite genotype of CYP1A1*2A or CYP1A1*2C and GSTT1 polymorphisms was associated with a decreased risk of colorecta

Experimental Studies on X-ray and Leukemia Part 3. Co-Leukemogenic Action of Croton Oil in the Onset of Leukemia induced by X-ray in RF Strain Mice

With the purpose of studying a possibility of the so-called "two-stage mechanism" in radiation leukemogenesis, a series of studies was conducted to compare the rate of leukemia development, using RF strain mice divided into a set of groups of mice that received one whole body X-irradiation of 150 r, 250 r, 350 r, respectively, and another set of groups similarly irradiated with respective doses and repeatedly painted with 5% croton oil in benzene solution after irradiation. 1. As a result it has been found that in the group receiving 350 r there was no significant difference in the rate of leukemia development between the group receiving the irradiation only and the group that was painted with croton oil solution in addition to the irradiation. 2. In the group that received 250 r, in the group that received croton oil painting immediately after the irradiation or one week after the irradition, there was observed a distinct increase in the rate of leukemia development, while there was no difference between the group that received croton oil painting before the irradiation and the group that received the X-irradiation only. 3. In the groups that received 150 r of the irradiation, leukemia did not develop but it developed only when croton oil was concurrently painted. This finding suggests that leukemia does not develop even when provirus is activated by X-irradiation, if the promoting agent, croton oil is not administered thereafter. 4. In the case when both X-irradiation and croton oil painting were given there could be recngnized leukemias of the so-called thymic type and the non-thymic type in about the same number. 5. In the group given one whoie body irradiation of 250 r and 100 mg of urethane in five separate doses, leukemia developed at a high rate, but in the group given urethane injection alone one of 8 mice developed leukemia. From these results it seems that the "two-stage mechanism" of cancer development as advocated by Berenblum is applicable to the radiation leukemogenesis, and it is thought that X-irradiation acts as an initiator and croton oil as its promotor. In addition, it is presumed that urethane as an initiator has ability to induce leukemia

Experimental Studies on X-ray and Leukemia Part 1. A. Comparative Study of the Effect of X-Irradiation on the Peripheral Blood Picture in Various Strains of Mice

As one of the series of studies on radiation leukemogenesis, changes in the peripheral blood picture occurring with lapse of time were pursued with the Cb, D103, StA, and Zb strains of mice (30-50 days old) after a single whole body X-irradiation of 350 r. The results are summarized as follows. 1. Both erythrocyte counts and hemoglobin contents showed the minimum values 2 weeks after the irradiation, and after recovering once they tended to decrease again. Reticulocytes decreased to about 2-4‰ immediately after the irradiation but by the second week they increased to about twice the number in normal condition, and thereafter they returned to the normal count. This change was most marked in the D103 strain, but ultimately the changes in the erythrocyte series presented similar curves in all the four strains mentioned above, and these changes did not differ from those observed in RF strain. 2. The number of leukocytes decressed rapidly to as low as 2,000 immediately after the X-irradiation. The susceptibility to X-ray irradiation was higher in the leukocyte series than in the erythrocyte series. 3. Lymphopoiesis was more sensitive to X-irradiation than myelogenous hematopoiesis, and the decrease of lymphocytes was greater than that of neutrophils, showing a relative neutrophilia for several weeks after the irradiation. 4. After once recovering, the leukocyte counts in the Cb, D103, StA, and Zb strains of mice all did not show such a transient decrease as observed in the preleukemic stage of RF strain about 13 weeks after the irradiation. In addition, lymphocytic leukemia did not develop. 5, In the Cb, D103, StA, and Zb strains irradiated with X-ray there could be recognized no severe eosinophilia such as observed in the RF strain that received X-irradiation. From these findings it has been confirmed that there can be recognized no marked differences in the peripheral blood picture immediately after a single whole body X-irradiation of 350 r between the RF strain of mice that develop leukemia by X-ray, and the Cb, D103, StA. and Zb strains that do not develop leukemia by X-irradiation, but in the observations conducted thereafter along with lapse of time there can be seen several distinct differences in the changes of the leukocyte series between them