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.
Weight of Building Materials. The weight of materials for a DIY small project, hobby greenhouse is probably not going to be a deciding factor, but comparatively, wood and rebar are relatively heavy and PVC pipe is extremely light. Strength of Building Materials. 1  Lumber frame construction is the norm for most construction projects that are 3 stories tall or less and can be designed to meet most building requirements. 2  A greenhouse frame constructed from rebar could also be very strong if the framework were welded and used lots of cross bracing.