Summary. 1  Algae are a necessary component of any healthy natural pond ecosystem. 2  However, excessive inputs of nutrients can lead to an overabundance of algae. 3  Excessive growth of filamentous algae, referred to as mats, moss, or scum, is one of the most common problems encountered by pond owners.
From Wikipedia, the free encyclopedia. The history of radiation therapy or radiotherapy can be traced back to experiments made soon after the discovery of x-rays (1895), when it was shown that exposure to radiation produced cutaneous burns.ases sprung up of the development of carcinoma in patients who had used conventional radium therapy up to 40 years after the original treatments. Robley D. Evans made the first measurements of exhaled radon and radium excretion from a former dial painter in 1933.
Radiation therapy is a cancer treatment that uses concentrated radiation beams to kill cancer cells. The most common type of radiation therapy is external beam radiation. This type involves a machine that directs high-energy beams of radiation at cancer cells.