This physics video tutorial explains how to calculate the average translational kinetic energy of molecules using Boltzmann’s constant. It also discusses how to calculate the average kinetic energy of multiple moles of molecules using another formula.
1960 Atomic Energy Commission U.S. War Dept. Film Food Irradiation Farm Fresh to You “Cobalt-60 On Food”
“Farm Fresh to You: Radiation Pasteurization of Fresh Fruits and Vegetables” On the preservation of food by irradiation with Gamma rays from Cobalt-60.
Food irradiation is the process of exposing foodstuffs to a source of energy capable of stripping electrons from individual atoms in the targeted material (ionizing radiation). This ionizing radiation is emitted by a radioactive substance or generated by high-energy accelerators including X-ray converters. Irradiation (in this context “ionizing radiation” is implied) is also used for non-food applications, such as medical devices, plastics, tubes for gas pipelines, hoses for floor heating, shrink-foils for food packaging, automobile parts, wires and cables (isolation), tires, and even gemstones.
As the energetic particles or waves pass through the target material they collide with particles. Around the sites of these collisions chemical bonds are broken. When collisions damage DNA or RNA effective reproduction becomes unlikely, also when collisions occur in cells, cell division is often suppressed. This treatment is used to preserve food, reduce the risk of food borne illness, prevent the spread of invasive pests, delay or eliminate sprouting or ripening, increase juice yield, and improve re-hydration.
Irradiated food does not become radioactive, as the radioactive source is never in contact with the foodstuffs and energy of radiation is limited below the threshold of induction of radioactivity (neutron radiation is not used). There is some controversy in the application of irradiation possibly due to it being confused with radioactive contamination or an association with the nuclear industry. Some may also think that chemical changes will be different from the chemical changes due to heating food (as higher energy transfer per collision occurs). However, research has found that this is not a major concern.
Food irradiation is currently permitted by over 50 countries, and the volume of food treated is estimated to exceed 500,000 metric tons annually worldwide…
When the irradiating energy collides with the target material electrons are stripped from their atoms, creating short lived radicals (e.g. the Hydroxyl radical, the hydrogen atom and solvated electrons) that damage DNA and cellular structures. This can damage DNA beyond its ability to repair, break down cell membranes, and interrupt enzymic pathways. Because of the inability for cells to divide, the target ceases all processes related to maturation or reproduction.
Depending on the dose, some or all of the microorganisms, bacteria, viruses, or insects present are destroyed or rendered incapable of reproduction, reducing or eliminating the risk of food borne illness…
Gamma irradiation involves exposing the target material to highly energetic packets of light (Gamma rays). The sources for this radiation in the processing of food are radioactive materials (radioisotopes). A pallet or tote is typically exposed for several minutes to hours depending on dose.
Radioactive material must be monitored and carefully stored to shield workers and the environment from its gamma rays. With most designs the radioisotope can be lowered into a water-filled source storage pool to allow maintenance personnel to enter the radiation shield. In this mode the water in the pool absorbs the radiation. In some gamma irradiators the radioactive source is under water at all times, and the hermetically sealed product is lowered into the water. No further shielding is required for such designs. Other uncommonly used designs feature dry storage by providing movable shields that reduce radiation levels in areas of the irradiation chamber.
Generally cobalt-60 is used as a radioactive source for food irradiation, because the deeper penetration enables administering treatment to entire industrial pallets or totes, reducing the need for material handling. Cobalt-60 is bred from cobalt-59 using neutron irradiation in specifically designed nuclear reactors…
Fifty years since construction of its first observatory commenced in 1967, the field of Very High Energy gamma-ray astronomy has truly entered a golden age. Astrophysicists using third-generation facilities such as VERITAS have grown the VHE source catalog to hundreds of sources, and a world-wide consortium of approximately 1400 scientists are poised to begin construction of a $400 million, next-generation VHE gamma-ray observatory (CTA) in 2018. Clearly there were many causes for celebration as VERITAS, the world’s most sensitive VHE gamma-ray observatory completed its tenth season of operation in July 2017. Highlights from the past decade of the VERITAS scientific program will be presented. In addition, an overview of CTA and the latest news concerning its development, including the potential US contribution, will be discussed.
Video Keyword – and astronomical physics
Video Title – The Golden Anniversary of Very High Energy Gamma-ray Astronomy
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