Shrinkage allowance takes into account only the solid shrinkage. There is almost no gradual shrinkage nor shrinkage due to molecular-level deformation. Sand is added to improve compressive strength, hardness and reduce shrinkage. This is due to shrinkage and possible part warping. Quality in this context means resistance to cracking, breaking, shrinkage, twisting and warping. The application of tensile stress opposes the reduction in energy gained by void shrinkage. It supplies liquid metal to the solidifying casting to compensate for solidification shrinkage. The AlO prevents dispersion and pellet shrinkage. Diffusion rates are high leading to high shrinkage and densification. A xerogel is a solid formed from a gel by drying with unhindered shrinkage. Particular attention is paid to the shrinkage induced by the curing. Composite inlays are cured by polymerisation shrinkage. It can withstand high temperatures, and has only moderate initial shrinkage. They may also be known as a "shrinkage" or "shrink" rule. The administration of cytotoxic drugs often results in initial tumour shrinkage.