It is well known that cigarette tobaccos contain naturally occurring radioactive nuclides such as (210)Pb and (210)Po. In many countries, the radioactivity of tobaccos has been measured to estimate the effective dose from smoking inhalation. The present study covered 24 cigarette brands including the top 20 of sales in Japan between April 2008 and March 2009. The activity concentrations of (210)Pb were measured by gamma-ray spectrometry, and then those of its progeny ((210)Po) were evaluated assuming the radioactive equilibrium between the two nuclides. Their concentrations were in the range of 2-14 mBq cigarette(-1) with an arithmetic mean of 8±3 mBq cigarette(-1). The annual committed effective doses were also calculated, based on the scenario that a smoker consumes 20 cigarettes a day. The average doses from (210)Pb and (210)Po inhalations were 22±9 and 68±27 μSv y(-1), respectively.
A phantom has previously been developed containing carrageenan, agarose and gadolinium chloride (called CAG phantom) for MRI with 1.5 T. T(1) and T(2) relaxation times of this phantom are independently changeable by varying concentrations of relaxation-time modifiers to simulate relaxation times of the various types of human tissues. The CAG phantom has a T(1) value of 202-1904 ms and a T(2) value of 38-423 ms, when the GdCl(3) concentration is varied from 0-140 micromol/kg and the agarose concentration is varied from 0-1.6%. A new phantom has now been developed (called CAGN phantom), made by adding an electric conductive agent, NaCl, to the CAG phantom for use in the areas of MRI and hyperthermia research. Dielectric properties of the CAGN phantom were measured and the results of experiments were expressed by the Cole-Cole equation in the frequency range of 5-130 MHz. The relationship between the conductivity of the CAGN phantom and the concentration of NaCl was expressed by a linear function in the frequency range of 1-130 MHz. The linear function involves a parameter of frequency and, when the frequency is 10 MHz, the conductivity of the CAGN phantom can be changed from 0.27-1.26 Sm(-1) by increasing the NaCl concentration from 0-0.7%. The CAGN phantom developed can be employed in basic experiments for non-invasive temperature measurement using MRI and as a loading phantom for MRI with up to 3 T.
Recently, the high mortality rate resulting from the reactivation of hepatitis B virus (HBV) through the use of immunosuppressive therapy or chemotherapy for fulminant hepatitis patients has been recognized as one of the most critical medical issues.
Intensities of x-ray microbeams formed by the 250-mm-long hollow glass pipes of inner diameters of 27.4, 23.0, and 18.8 μm have been theoretically investigated, by taking account of the slope distribution of microprojections (surface roughness) on the pipe inner wall, using the Monte Carlo method. The intensities for all the pipes calculated on the supposition that each pipe inner wall is perfect (i.e., zero rms of the slope distribution) have been much greater than the experimental values in the x-ray energy region from 6.93 to 19.6 keV. Assuming the slope rms from 2.5×10−4 rad to 3.3×10−3 rad, the calculated results have agreed with the experimental values. Discussions on the results for all the pipes are given in relation to the x-ray anomalous dispersion, the penetration of x rays, the intensity distribution on the x-ray sources used, undulation of the pipes, and the presence of microdust in the pipes.
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