Testing phenanthrene distribution properties of virgin plastic pellets and plastic eroded pellets found on Lesvos island beaches (Greece)     

Karapanagioti HK  Klontza I 《Marine environmental research》2008,65(4):283-290

Plastic pellets have been characterized as toxic pollutant carriers throughout the world oceans and coastal zones. However, their sorptive properties are not yet well understood. In the present study, virgin pellets and plastic eroded pellets (PEP) are used to elucidate their distribution characteristics through distribution kinetic studies. Distribution occurs through diffusion into the pellet for all materials (polyethylene, polyoxymethylene, and PEP) except polypropylene (PP). Although diffusion into the polymer happens with similar rates for both freshwater and saltwater external solutions, apparent diffusion is dependent on the solution salinity because it results in higher equilibrium distribution coefficients. Distribution coefficient into the PEP is higher and diffusion is slower than into the virgin materials. This is attributed to increased crystallinity of the PEP due to weathering. PP demonstrates diffusion rates that are increased by salinity and is apparently faster than into the other polymers suggesting a surface diffusion process.  相似文献   

A symbolic analysis of Vermeille and Borkowski polynomials for transforming 3D Cartesian to geodetic coordinates     

Laureano Gonzalez-Vega  Irene Polo-Blanco 《Journal of Geodesy》2009,83(11):1071-1081

Closed form solutions for transforming 3D Cartesian to geodetic coordinates reduce the problem to finding the real solutions of the fourth degree latitude equation or variations of it. By using symbolic tools (Sturm–Habicht coefficients and subresultants mainly) we study the methods (and polynomials) proposed by Vermeille and Borkowski to solve this problem. For Vermeille approach, the region where it cannot be applied is completely characterized. For those points it is shown how to transform 3D Cartesian to geodetic coordinates and a new method for solving Vermeille equation for those cases not yet covered is introduced. Concerning Borkowski’s approach, the symbolic analysis produces a complete characterization of the singular cases (i.e. where multiple roots appear).  相似文献