In DSM, nicotine dependence is included under the general definition of substance dependence.  The essential feature of Substance Dependence is a cluster of cognitive, behavioral, and physiologic symptoms indicating that the individual continues use of the substance despite significant substance-related problems.
The Best Materials to Cover your Greenhouse. 1  Glass: The traditional greenhouse covering, glass is the preferred material for permanence. 2  Film Plastic: Film plastic is one sixth to one tenth of the cost per square foot of a glass covered structure.
Types of Greenhouses. Generally speaking, there are three types of greenhouses: lean-to, detached, and ridge and furrow or gutter connected (Figure 1). Few lean-to greenhouses are used for commercial production because of limitations in size. This type of house is the most popular among hobbyists.