Absolute space and timeAbsolute space and time is a concept in physics and philosophy about the properties of the universe. In physics, absolute space and time may be a preferred frame. A version of the concept of absolute space (in the sense of a preferred frame) can be seen in Aristotelian physics. Robert S. Westman writes that a "whiff" of absolute space can be observed in Copernicus's De revolutionibus orbium coelestium, where Copernicus uses the concept of an immobile sphere of stars.
Elimination reactionAn elimination reaction is a type of organic reaction in which two substituents are removed from a molecule in either a one- or two-step mechanism. The one-step mechanism is known as the E2 reaction, and the two-step mechanism is known as the E1 reaction. The numbers refer not to the number of steps in the mechanism, but rather to the kinetics of the reaction: E2 is bimolecular (second-order) while E1 is unimolecular (first-order). In cases where the molecule is able to stabilize an anion but possesses a poor leaving group, a third type of reaction, E1CB, exists.
CarbamateIn organic chemistry, a carbamate is a category of organic compounds with the general formula and structure , which are formally derived from carbamic acid (). The term includes organic compounds (e.g., the ester ethyl carbamate), formally obtained by replacing one or more of the hydrogen atoms by other organic functional groups; as well as salts with the carbamate anion (e.g. ammonium carbamate). Polymers whose repeat units are joined by carbamate like groups are an important family of plastics, the polyurethanes.
NorgestimateNorgestimate, sold under the brand names Ortho Tri-Cyclen and Previfem among others, is a progestin medication which is used in birth control pills for women and in menopausal hormone therapy. The medication is available in combination with an estrogen and is not available alone. It is taken by mouth. Side effects of the combination of an estrogen and norgestimate include menstrual irregularities, headaches, nausea, abdominal pain, breast tenderness, mood changes, and others.
SarinSarin (NATO designation GB [short for G-series, "B"]) is an extremely toxic synthetic organophosphorus compound. A colourless, odourless liquid, it is used as a chemical weapon due to its extreme potency as a nerve agent. Exposure is lethal even at very low concentrations, where death can occur within one to ten minutes after direct inhalation of a lethal dose, due to suffocation from respiratory paralysis, unless antidotes are quickly administered.
LevonorgestrelLevonorgestrel is a hormonal medication which is used in a number of birth control methods. It is combined with an estrogen to make combination birth control pills. As an emergency birth control, sold under the brand names Plan B One-Step and Julie, among others, it is useful within 72 hours of unprotected sex. The more time that has passed since sex, the less effective the medication becomes, and it does not work after pregnancy (implantation) has occurred. Levonorgestrel works by preventing ovulation or fertilization from occurring.
