It is shown that high-energy astrophysics can provide information on the small-scale structure of spacetime.

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...

We study the photon axion mixing in the presence of large extra dimensions. The eigenvalues and eigenstates of the mixing matrix are analyzed and we establish the resonance condition for the total conversion of a high energy photon into a Kaluza-Klein (KK) axion state. This resonant transition, a photon transformed into a KK axion travelling freely through the bulk and converting back into a ph...

I discuss the recent exciting results of discovery of TeV photons from several galactic and extra-galactic sources, and highlight some objectives of VHE gamma ray astronomy that can be achieved in the near future by means of new generation ground-based detectors.

introduction in this study, we aimed to assess the medium-term energy stability of a 6mv elekta compacttm linear accelerator. to the best of our knowledge, this is the first published article to evaluate this linear accelerator in terms of energy stability. as well as investigating the stability of the linear accelerator energy over a period of several weeks, the results will be useful for esti...

introduction: scatter radiation is one of the major sources of error in nuclear medicine data processing. different methods of scatter correction have been introduced in order to improve the quality of data. however the best method is to avoid recording of scatter photons in acquisition. the only difference between scattered and non-scattered photons is the energy. pulse height analyzer is the ...

An important radiative process, used in several astrophysical contexts to generate high energy photons, is the inverse compton scattering. In this process, relativistic electrons transfer part of their kinetic energy to low energy photons thereby creating high energy photons. Conventional text book derivation (Rybicki & Lightman 1979) of this process uses the photon picture, kinematics of elect...

It has been speculated earlier that Gamma Ray Bursts are sources of ultrahigh energy cosmic rays. Recently, the search for high energy photons from Gamma Ray Bursts by Milagro group has put limits on the isotropic luminosity of these transient sources in very high energy photons. The implications of the results obtained by Milagro to our understanding of the ultrahigh energy cosmic ray spectrum...