Derailleur gears by 13 drive-train. Most road bicycles have two chainrings, and touring bicycles commonly have three. The rear derailleur serves double duty: moving the chain between rear sprockets and taking up chain slack caused by moving to a smaller sprocket at the rear or a smaller chainring by the front derailleur. In order to accomplish this second task, it is positioned in the path of the bottom, slack portion of chain. Sometimes the rear-derailleurs are re-purposed as chain tensioners for single-speed bicycles that cannot adjust chain tension by a different method. Although variations exist, as noted below, most rear derailleurs have
Mechanism of action inflammation. This mechanism of action is specific to aspirin, and is not constant for all nonsteroidal anti-inflammatory drugs (NSAIDs). Rather, aspirin is the only NSAID that irreversibly inhibits COX-1. Some drug mechanisms of action are still unknown. However, even though the mechanism of action of a certain drug is unknown, the drug still functions; it is just unknown or unclear how the drug interacts with receptors and produces its therapeutic effect. In some literature articles, the term mechanism of action and mode of action (MoA) are used interchangeably; typically referring to the way in which the drug interacts and produces