Productivity Growth and Convergence in U.S. Agriculture: New Cointegration Panel Data Results

Dynamic effects of health and inter-state and inter-industry knowledge spillovers, total factor productivity (TFP) growth and convergence in U.S. agriculture are examined using recently developed procedures for panel data and a growth accounting model. Strong evidence is found to support the hypothesis that TFP converges to a steady-state. Health care supply in rural areas and research spillovers from other states and from nonagricultural sectors are found to have significant impacts on the productivity growth rate both in the short-run and long-run. These results suggest richer opportunities for policymakers to enhance productivity growth.convergence, growth, pooled mean group estimator, total factor productivity

Hydrogenation of Magnesium Nickel Boride for Reversible Hydrogen Storage

We report that a ternary magnesium nickel boride (MgNi_(2.5)B_2) mixed with LiH and MgH_2 can be hydrogenated reversibly forming LiBH_4 and Mg_2NiH_4 at temperatures below 300 °C. The ternary boride was prepared by sintering a mechanically milled mixture of MgB_2 and Ni precursors at 975 °C under inert atmosphere. Hydrogenation of the ternary, milled with LiH and MgH_2, was performed under 100 to 160 bar H_2 at temperatures up to 350 °C. Analysis using X-ray diffraction, Fourier transform infrared, and ^(11)B magic angle spinning NMR confirmed that the ternary boride was hydrogenated forming borohydride anions. The reaction was reversible with hydrogenation kinetics that improved over three cycles. This work suggests that there may be other ternary or higher order boride phases useful for reversible hydrogen storage

High Quality Ultrathin Bi2Se3 Films on CaF2 and CaF2/Si by Molecular Beam Epitaxy with a Radio Frequency Cracker Cell

Here we report a method to fabricate high quality Bi2Se3 thin films using molecular beam epitaxy with a radio frequency cracker cell as an atomic selenium source. With rates close to exact stoichiometry, optimal layer-by-layer growth of high quality Bi2Se3 thin films with smooth surfaces, has been achieved on CaF2(111) substrates and Si(111) substrates with a thin CaF2 buffer layer(CaF2/Si). Transport measurements show a characteristic weak antilocalization mangnetoresistance, with emergence of weak localization in the ultrathin film limit. Quantum Oscillations attributed to the topological surface states have been observed, including in films on CaF2/Si