| Term | Definition | | Thimerosal | Thimerosal is a mercury-containing organic compound that has been used since the 1930s as a preservative in vaccines and other medical products. It is added to vials of vaccine that contain more than one dose (multi-dose vials) to prevent growth of germs, like bacteria and fungi. |
| Token | A token is the unit that a language model processes. While all data, including images and audio, are also broken down into tokens, the concept is simplest to grasp with text, where a token is typically a word fragment (though it can be whole words, punctuation marks, and other things too). |
| Trace Gas | Any one of the less common gases found in the Earth's atmosphere. Nitrogen, oxygen, and argon make up more than 99 percent of the Earth's atmosphere. Other gases, such as carbon dioxide, water vapor, methane, oxides of nitrogen, ozone, and ammonia, are considered trace gases. |
| Transgenic Organism | Organisms that have had genes from other species inserted into their genome. Transgenic means that one or more DNA sequences from another species have been introduced by artificial means. Transgenic plants can be made by introducing foreign DNA into a variety of different tissues. |
| Troposphere | The lowest part of the atmosphere from the surface to about 10 km in altitude in mid-latitudes (ranging from 9 km in high latitudes to 16 km in the tropics on average) where clouds and "weather" phenomena occur. |
| Ultraviolet Radiation (UV) | The energy range just beyond the violet end of the visible spectrum. Although ultraviolet radiation constitutes only about 5 percent of the total energy emitted from the sun, it is the major energy source for the stratosphere and mesosphere, playing a dominant role in both energy balance and chemical composition. |
| Vaccination | The physical act of administering any vaccine. |
| Vaccine | A vaccine is a biological preparation that provides active acquired immunity to a particular infectious or malignant disease. The safety and effectiveness of vaccines has been widely studied and verified. A vaccine typically contains an agent that resembles a disease-causing microorganism and is often made from weakened or killed forms of the microbe, its toxins, or one of its surface proteins. The agent stimulates the immune system to recognize the agent as a threat, destroy it, and destroy any of the microorganisms associated with that agent that it may encounter in the future. |
| Validation | Checking the accuracy of something. For example, to validate a climate model, scientists run the model to ?predict? the weather patterns over the past 20 years. Then they compare the output with the actual measurements and observations we have collected for that time. |
| Variable | In scientific or mathematical models, a factor whose value may vary (e.g., average air temperature, amount of solar radiation, etc.) |
