Correlation of rheology and light scattering in isotactic polypropylene during early stages of crystallization

ABSTRACT: Structure development during crystallization of isotactic polypropylene (iPP) at low undercooling is studied by small-angle light scattering (SALS) and light transmission. The structure development is related to network formation (gelation) as previously measured on the same sample in dynamic mechanical experiments. Close to the rheologically measured gel point, small-angle light scattering (SALS) patterns in both Hv and Vv modes show circular symmetry; density fluctuations (maximum in Vv invariant) as determined by SALS go through a maximum. Orientation fluctuations develop much more slowly and appear at much later stages of the crystallization process. Growing clusters are characterized by very low anisotropy and low internal crystallinity. The characteristic length scale associated with the cluster at early stages is about 1 ím. At later times, evolution of 2-fold and 4-fold symmetry patterns suggests the development of the anisotropic superstructures. The growth of crystalline clusters leads to a strong increase in turbidity as monitored by light transmission in the Vv mode

Leadership and Collaborative Governance in Managing Emergencies and Crises

Leadership and governance are two concepts very central to disaster management. This chapter analyzes disaster and crisis management in two mega-disasters of 2010: the Haiti Earthquake and Pakistan Floods. These two cases are compared and contrasted from collaborative governance, international coordination, and multi-layered leadership perspectives. Findings indicate that leadership is a multi-layered and multi-dimensional phenomenon and concept in disasters and collaborative settings. Leadership layers comprise presidential and political leadership, civilian government leadership, military leadership, international humanitarian leadership which is primarily UN centric, and also community leadership. Comparative governance and leadership structures in the two countries show that the Pakistan military response and their leadership stand out because of their commendable efforts in the flood response and relief phases. On the other hand, Haiti has no military forces and had to rely heavily on the US military. Overall political leadership seems to be very weak in the two countries. The issue of competitive elections in Haiti, the deaths of many government officials and the destruction of government offices in the capital city contributed to worsening Haiti’s government response. Findings also indicate that the International humanitarian leadership which is UN centric, and follows a UN cluster approach, has ample shortcomings and needs to be revamped and improved