Heterogeneity primary surface

Poly(ortho esters) (XVII) contain acid-labile linkages in the polymer backbone. As with the polyanhydrides discussed above, poly(ortho esters) are a class of polymers that can degrade heterogeneously by surface erosion. These polymers lose material from the surface only, while retaining their original geometry. As such, their primary use is in drug delivery. 

Primary nucleation is the classical form of nucleation. It occurs mainly at high levels of supersaturation and is thus most prevalent during unseeded crystallization or precipitation. This mode of nucleation may be subdivided into either homogeneous viz. spontaneously from clear solution, or heterogeneous viz. in the presence of dust particles in suspension, or solid surfaces. 

The primary nucleation on the surface of the NA is a kind of heterogeneous nucleation [25]. NA is a so called heterogeneity . In this study, all nucleation is limited to the heterogeneous nucleation. The shape of a heterogeneous nucleus is assumed parallelepiped with length of a stem l and the number of stems m and n. Here /, m, and n are counted by the number of atom... 

A wide spectrum of heterogeneous processes can occur at solid surfaces exposed to a glow discharge (5,25,27). The primary processes of interest in plasma etching (and in plasma deposition) are summarized in Table II i20). These interactions result from the bombardment of surfaces by particles. Although vacuum UV photons and soft x-rays present in the plasma are sufficiently energetic to break chemical bonds, electron and particularly ion bombardment has been found to be the most effective method of promoting surface reactions (25). 

---