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To understand the biological effects of residual radioactivity after the atomic bomb explosion in Hiroshima and Nagasaki, we previously investigated the effects of [sup.56]Mn, a major residual radioisotope. Our rat study demonstrated that inhalation exposure to [sup.56]MnO[sub.2] microparticles affected gene expression in the lungs, testes, and liver, despite the low radiation doses. Because [sup.56]Mn is a β- and γ-emitter, the differential effects between β- and γ-rays should be clarified. In this study, [sup.31]Si, a β-emitter with a radioactive half-life similar to that of [sup.56]Mn, was used to determine its effects. Male Wistar rats were exposed to sprayed neutron-activated [sup.31]SiO[sub.2] microparticles, stable SiO[sub.2] microparticles, or X-rays. The animals were examined on days 3 and 14 after irradiation. The expression of radiation-inducible marker genes, including Ccng1, Cdkn1a, and Phlda3, was measured in the spleen, lungs, and liver. Furthermore, the expressions of pathophysiological marker genes, including Aqp1, Aqp5, and Smad7 in the lungs and Cth, Ccl2, and Nfkb1 in the liver, were determined. Impacts of [sup.31]SiO[sub.2] exposure were observed mainly in the liver, where the expression of Cth markedly increased on post-exposure days 3 and 14. Our data suggest that internal exposure to β-emitted microparticles has significant biological effects and its possible roles as residual radiation after atomic bombing.

To understand the biological effects of residual radioactivity after the atomic bomb explosion in Hiroshima and Nagasaki, we previously investigated the effects of 56Mn, a major residual radioisotope. Our rat study demonstrated that inhalation exposure to 56MnO2 microparticles affected gene expression in the lungs, testes, and liver, despite the low radiation doses. Because 56Mn is a β- and γ-emitter, the differential effects between β- and γ-rays should be clarified. In this study, 31Si, a β-emitter with a radioactive half-life similar to that of 56Mn, was used to determine its effects. Male Wistar rats were exposed to sprayed neutron-activated 31SiO2 microparticles, stable SiO2 microparticles, or X-rays. The animals were examined on days 3 and 14 after irradiation. The expression of radiation-inducible marker genes, including Ccng1, Cdkn1a, and Phlda3, was measured in the spleen, lungs, and liver. Furthermore, the expressions of pathophysiological marker genes, including Aqp1, Aqp5, and Smad7 in the lungs and Cth, Ccl2, and Nfkb1 in the liver, were determined. Impacts of 31SiO2 exposure were observed mainly in the liver, where the expression of Cth markedly increased on post-exposure days 3 and 14. Our data suggest that internal exposure to β-emitted microparticles has significant biological effects and its possible roles as residual radiation after atomic bombing.

To understand the biological effects of residual radioactivity after the atomic bomb explosion in Hiroshima and Nagasaki, we previously investigated the effects of Mn, a major residual radioisotope. Our rat study demonstrated that inhalation exposure to MnO microparticles affected gene expression in the lungs, testes, and liver, despite the low radiation doses. Because Mn is a β- and γ-emitter, the differential effects between β- and γ-rays should be clarified. In this study, Si, a β-emitter with a radioactive half-life similar to that of Mn, was used to determine its effects. Male Wistar rats were exposed to sprayed neutron-activated SiO microparticles, stable SiO microparticles, or X-rays. The animals were examined on days 3 and 14 after irradiation. The expression of radiation-inducible marker genes, including , , and , was measured in the spleen, lungs, and liver. Furthermore, the expressions of pathophysiological marker genes, including , , and in the lungs and , , and in the liver, were determined. Impacts of SiO exposure were observed mainly in the liver, where the expression of markedly increased on post-exposure days 3 and 14. Our data suggest that internal exposure to β-emitted microparticles has significant biological effects and its possible roles as residual radiation after atomic bombing.

Second Harmonic Generation induced by the electric field of a strong nearly single-cycle terahertz pulse with the peak amplitude of 300 kV/cm is studied in a classical inorganic ferroelectric thin film of (Ba 0.8 Sr 0.2 )TiO 3 . The dependences of the SHG intensity on the polarization of the incoming light is revealed and interpreted in terms of electric polarization induced in the plane of the film. As the THz pulse pumps the medium in the range of phononic excitations, the induced polarization is explained as a dynamical change of the ferrolectric order parameter. It is estimated that under action of the THz pulse the ferroelectric order parameter acquires an in-plane component up to 6% of the net polarization.

The ability to switch ferroics (magnets, ferroelectrics, multiferroics) between two stable bit states is the main principle of modern data storage technology. Due to many new ideas, originating from fundamental research during the last 50 years, this technology has developed in a breath-taking fashion. Ever increasing demands for faster and more energy efficient data storage strongly motivate fundamental studies of dynamics in ferroics triggered by ultrashort stimuli. It has been recently realized that nearly single cycle intense THz pulses and the phenomenon of the second harmonic generation are appealing tools for excitation and detection of poorly understood ultrafast dynamics of electric polarization in ferroelectrics at the picosecond timescale. Here we investigate picosecond dynamics of second harmonic from near-infrared pulse in ferroelectric heterostructure Ba 0.8 Sr 0.2 TiO 3 /MgO triggered by the electric field of a nearly single cycle intense THz pulse. The dynamics of the nonlinear optical signal is characterized by a step and oscillations at the frequency of about 1.67 THz. Although the observations can be mistakenly interpreted as oscillations of the electric polarization at the frequency of the soft mode and switching of the order parameter to another metastable state, here we show that the THz modulation of second harmonic generation in Ba 0.8 Sr 0.2 TiO 3 /MgO has a purely optical origin. The observation can be explained assuming that the THz pulse is a relativistically propagating inhomogeneity which induces center of symmetry breaking and linear birefringence. Our work reveals the role of propagation effects in interpretation of time-resolved non-linear optical experiments and thus it has important implications for experimental studies of ultrafast dynamics in ferroics.

The ability to switch ferroics (magnets, ferroelectrics, multiferroics) between two stable bit states is the main principle of modern data storage technology. Due to many new ideas, originating from fundamental research during the last 50 years, this technology has developed in a breath-taking fashion. Ever increasing demands for faster and more energy efficient data storage strongly motivate fundamental studies of dynamics in ferroics triggered by ultrashort stimuli. It has been recently realized that nearly single cycle intense THz pulses and the phenomenon of the second harmonic generation are appealing tools for excitation and detection of poorly understood ultrafast dynamics of electric polarization in ferroelectrics at the picosecond timescale. Here we investigate picosecond dynamics of second harmonic from near-infrared pulse in ferroelectric heterostructure Ba Sr TiO /MgO triggered by the electric field of a nearly single cycle intense THz pulse. The dynamics of the nonlinear optical signal is characterized by a step and oscillations at the frequency of about 1.67 THz. Although the observations can be mistakenly interpreted as oscillations of the electric polarization at the frequency of the soft mode and switching of the order parameter to another metastable state, here we show that the THz modulation of second harmonic generation in Ba Sr TiO /MgO has a purely optical origin. The observation can be explained assuming that the THz pulse is a relativistically propagating inhomogeneity which induces center of symmetry breaking and linear birefringence. Our work reveals the role of propagation effects in interpretation of time-resolved non-linear optical experiments and thus it has important implications for experimental studies of ultrafast dynamics in ferroics.