Yes, nosebleeds do tend to occur more often during pregnancy. Pregnancy can cause the blood vessels in your nose to expand, and your increased blood supply puts more pressure on those delicate vessels, causing them to rupture more easily. Although it's unpleasant and inconvenient, an occasional minor nosebleed is generally harmless.
The higher the energy of the gamma rays, the thicker the shielding made from the same shielding material is required. Materials for shielding gamma rays are typically measured by the thickness required to reduce the intensity of the gamma rays by one half (the half value layer or HVL).
Gamma rays are electromagnetic waves of very short wavelength and high frequency. Gamma rays are emitted by most radioactive sources along with alpha or beta particles. After alpha or beta emission the remaining nucleus may still be in an excited energy state. By releasing a gamma photon it reduces to a lower energy state. Gamma rays have no electrical charge associated with them.