MEASURING AND EXPLAINING THE DECLINE IN U.S. COTTON PRODUCTIVITY GROWTH

Tornquist input quantity indices were used to derive total and partial factor productivity measures for U.S. cotton across time, region, and scale. Total factor productivity for U.S. cotton increased .2 percent per year between 1974 and 1982. Partial productivity measures revealed that yield growth was about .6 percent and input use grew about .4 percent per year. Cotton enterprises in Alabama and Mississippi gained and those in the Texas High Plains lost competitive advantage relative to California. In 1982, very large (1750-5900 acres) and large (950-1749 acres) cotton enterprises were 2 percent more productive than medium-size enterprises (570-949 acres).Productivity Analysis,

ECONOMIES OF SIZE IN U.S. CROP PRODUCTION

Crop Production/Industries,

Rare Transition Events in Nonequilibrium Systems with State-Dependent Noise: Application to Stochastic Current Switching in Semiconductor Superlattices

Using recent mathematical advances, a geometric approach to rare noise-driven transition events in nonequilibrium systems is given, and an algorithm for computing the maximum likelihood transition curve is generalized to the case of state-dependent noise. It is applied to a model of electronic transport in semiconductor superlattices to investigate transitions between metastable electric field distributions. When the applied voltage $V$ is varied near a saddle-node bifurcation at $V_th$, the mean life time $$ of the initial metastable state is shown to scale like $log \propto |V_th - V|^{3/2}$ as $V\to V_th$

The Academy of Dental Materials: Providing roots and wings.

ObjectivesThe long history of the Academy of Dental Materials (ADM) is documented with its strategies (a) to rapidly communicate science among its members, (b) to establish special awards to stimulate new science, and (c) to develop new dental materials scientists.MethodsWe searched the history of the last 35 years of the ADM newsletters, transactions, journals, and officer notes. We document the (a) presidents, (b) meeting history, (c) membership growth, and (d) development of special awards through 2019 with the recent creation of the ADM Marshall Post-Doctoral Award.ResultsThere are 36 years of recent ADM history, 42 international meetings, membership growth to 400 individuals from 15 countries, service of 19 presidents, Paffenbarger annual Awardees since 1989, induction of >200 fellows, and recognition of the first winner of Marshall Post-Doctoral Award in 2018. New directions for recruiting members are suggested. Three potential new thrusts for the organization are presented: artificial intelligence, genetic engineering, and intensive member mentoring.SignificanceThese suggestions for the ADM provide a path for the ADM to continue to adapt to the ever changing scientific landscape