Introduction Most of the nuclear imaging systems require the use of a gamma (γ)-ray radiation shield to attenuate a stream of γ-rays so that only those traveling in a specified direction are allowed through and to absorb the scattered γ-rays from out of interest regions [1-2]. To meet those requirements, a γ-ray radiation shield is usually made out of lead (Pb) or some other high Z material suc...

background: the fatal effect of ionizing radiation on cells depends on linear energy transfer (let) level. the distribution of ionizing radiation is sparse and homogeneous for low let radiations such as x or γ, but it is dense and concentrated for high let radiation such as heavy-ions radiation. material and methods: chinese hamster ovary cells (cho-k1) were exposed to 4 gy fe-ion 2000 kev/m. ...

The overall dynamical evolution and radiation mechanism of γ-ray burst jets are briefly introduced. Various interesting topics concerning beaming in γ-ray bursts are discussed, including jet structures, orphan afterglows and cylindrical jets. The possible connection between γ-ray bursts and neutron stars is also addressed.

The attenuation of very high energy γ-rays by pair production on the Galactic interstellar radiation field has long been thought of as negligible. However, a new calculation of the interstellar radiation field consistent with multi-wavelength observations by DIRBE and FIRAS indicates that the Galactic interstellar radiation field is intense. We have made a calculation of the attenuation of very...

A quasi-classical method is developed to calculate the radiation damping of a relativistic particle in a straight, continuous focusing system. In one limiting case where the pitch angle of the particle θp is much larger than the radiation opening angle 1/γ , the radiation power spectrum is similar to synchrotron radiation and the relative damping rate of the transverse action is proportional to...

BACKGROUND There is a crucial shortage of methods capable of determining the extent of accidental exposures of human beings to ionizing radiation. However, knowledge of individual exposures is essential for early triage during radiological incidents to provide optimum possible life-sparing medical procedures to each person. METHODS AND FINDINGS We evaluated immunocytofluorescence-based quanti...

BACKGROUND γ-radiation is an effective treatment for cancer. There is evidence that radiotherapy supports tumor-specific immunity. It was described that irradiation induces de novo protein synthesis and enhances antigen presentation, we therefore investigated whether γ-radiation results in increased expression of cancer-testis (CT) antigens and MHC-I, thus allowing efficient immunological contr...

A prediction for the energy shift of the synchrotron spectrum of flat-spectrum radio quasars (FSRQs) during high-energy flares is presented. If the γ-ray emission of FSRQs is produced by Comptonization of external radiation, then the peak of the synchrotron spectrum is predicted to move to lower energies in the flare state. This is opposite to the well-known broadband spectral behavior of high-...

The beaming pattern of thermal annihilation radiation is broader than the beaming pattern produced by isotropic nonthermal electrons and positrons in the jets of radio-emitting active galactic nuclei which Compton scatter photons from an external isotropic radiation field. Thus blueshifted thermal annihilation radiation can provide the dominant contribution to the high-energy radiation spectrum...