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.
Greenhouse Covering. Whether you're replacing existing greenhouse coverings or building a greenhouse you're sure to find the best greenhouse covering at FarmTek. Greenhouse glazing is the material that covers the greenhouse frame and the most widely used materials are polycarbonate and poly film.
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.