When Nereis eggs are exposed to radiations from a tube of radium emanation, the walls of which absorb all the alpha-rays, the resulting physiological change is produced by rays having a coefficient of absorption of the order of 23.9 cm.(-1) This fact indicates that the physiological effect is due almost exclusively to beta-rays. The gamma-rays alone can produce the reaction. To produce equivale...

background: high density concrete is extensively used for efficient radiation attenuation in radiotherapy rooms and nuclear reactors. over the past eight years, some efficient galena-based concrete samples for shielding x or gamma rays was produced. the goal of this study was to produce a novel high density concrete against neutron and photon radiations using tourmaline and galena. materials an...

Both diffuse high energy gamma-rays and an extended electron-positron annihilation line emission have been observed in the Galactic Center (GC) region. Although X-ray observations indicate that the galactic black hole Sgr A is inactive now, we suggest that Sgr A can become active when a captured star is tidally disrupted and matter is accreted into the black hole. As a consequence the galactic ...

High energy gamma-ray emission has been observed above 100 MeV from at least 40 active galactic nuclei (AGN) by the EGRET instrument on the Compton Gamma Ray Observatory (CGRO), and above 300 GeV gamma rays have been detected by the Whipple observatory from two AGN. The sources detected so far are \blazars" indicating a jet origin for the gamma rays. They are seen to be variable on time scales ...

We propose generation of narrow-bandwidth GeV photons, gamma-rays, via Compton scattering of hard X-ray photons in X-ray free-electron laser oscillators [1]. The gamma-rays have a narrow-bandwidth spectrumwith a sharp peak, ∼0.1% (FWHM), due to the nature of Compton scattering in relativistic regime. Such gamma-rays will be a unique probe for studying hadron physics. In this paper, we discuss d...

We have compared the efficiency of cell-killing, DNA single-strand breakage and double-strand breakage in an Escherichia coli K-12 wild-type strain after irradiation with soft X-rays (50kVp) and hard gamma-rays (600 keV) under aerobic conditions. Irradiation with 50 kVP x-rays resulted in 1.47 times more cell killing than was observed with 137Cs gamma-rays based on a comparison of D0 values eva...

Human whole-blood was exposed to 137Cs gamma-rays or 50 keV/microm carbon ions in the presence or absence of glycine betaine, a beer component in vitro. The dicentrics of chromosome aberrations in human lymphocytes were significantly (p < 0.05) reduced by glycine betaine after irradiation with 4 Gy of either gamma-rays or carbon ions. The maximum protection by glycine betaine for gamma-rays or ...

When gamma-rays emerge from a central source they may undergo Compton scattering in surrounding matter. The resulting Compton-scattered electrons radiate. Coherent radiation by such Compton electrons follows nuclear explosions above the Earth's atmosphere. Particle acceleration in instabilities produced by Compton electron currents may explain the radio emission of SN1998bw. Bounds on coherent ...

LHAASO detected 12 gamma-ray sources above 100 TeV which are the possible origins of Galactic cosmic-rays. We summarize neutrino measurements by IceCube and ANTARES in vicinity to constrain contribution hadronic gamma-rays these sources. find that current observations contribute no more than ~60% from Crab Nebula. Gamma-rays two sources, J1825-1326 J1907+0626, dominated leptonic components up ~...