background: sentinel node biopsy (slnb) is the standard of care for breast cancer treatment and it is getting wide acceptance in iran. the radiation safety of the procedure has been investigated under controlled conditions, but the standard dose of radiotracer and techniques are not always observed in the community setting. the aim of this study was to assess the magnitude of the absorbed doses...

Background: Humans beings are continuously exposed to ionizing radiation from natural sources. The main contributors to natural radiation are high-energy cosmic radiation and radioactive nuclides that originates in the earth’s crust. Exposure to high levels of radiation can cause serious health effects. In this study an attempt has been made to monitor the levels of environmental back...

People in some areas of Ramsar, a city in northern Iran, receive an annual radiation absorbed dose from background radiation that is up to 260 mSv y 1, substantially higher than the 20 mSv y 1 that is permitted for radiation workers. Inhabitants of Ramsar have lived for many generations in these high background areas. Cytogenetic studies show no significant differences between people in the hig...

People in some areas of Ramsar, a city in northern Iran, receive an annual radiation absorbed dose from background radiation that is up to 260 mSv y(-1), substantially higher than the 20 mSv y(-1) that is permitted for radiation workers. Inhabitants of Ramsar have lived for many generations in these high background areas. Cytogenetic studies show no significant differences between people in the...

The observed cosmic microwave background (CMB) radiation provides strong evidence for the hot big bang. The success of pri-mordial nucleosynthesis calculations (see Sec. 16, " Big-bang nucle-osynthesis ") requires a cosmic background radiation (CBR) characterized by a temperature kT ∼ 1 MeV at a redshift of z ≃ 10 9. In their pioneering work, Gamow, Alpher, and Herman [1] realized this and pred...

There have been great and rapid progresses in the field of γ-ray bursts (denoted as GRBs) since BeppoSAX and other telescopes discovered their afterglows in 1997. Here, we will first give a brief review on the observational facts of GRBs and direct understanding from these facts, which lead to the standard fireball model. The dynamical evolution of the fireball is discussed, especially a generi...