Carbon-13 nuclear magnetic resonance spectra and mechanism of bridge–terminal carbonyl exchange in di-µ-carbonyl-bis[carbonyl(η-cyclopentadienyl)iron](Fe–Fe)[{(η-C5H5)Fe(CO)2}2]; cd-di-µ-carbonyl-f-carbonyl-ae-di(η-cyclopentadienyl)-b-(triethyl -phosphite)di-iron(Fe–Fe)[(η-C5H5)2Fe2(CO)3P(OEt)3], and some related complexes

A mechanism involving carbonyl-bridge breaking, rotation about the Fe–Fe bond, and bridge reformation is shown to account qualitatively for changes in the carbonyl region of the 13C n.m.r spectrum of the complex [(cp)(OC)[graphic omitted]e(cp){P(OEt)3}] and quantitatively for [(cp)(OC)[graphic omitted]e(CO)(cp)](cp =η-cyclopentadienyl).The activation energy for this process, 49.0 ± 4 kJ mol^–1(11.7 ± 1 kcal mol^–1), is close to that reported for cis–trans-isomerization of the cp groups, in accord with this mechanism. Variable-temperature 13C n.m.r. spectra of the complexes [(cp)(OC)[graphic omitted]u(CO)(cp)] and [(cp)(OC)[graphic omitted]i(cp)] are also reported

The Efficiency of Private Universities As Measured By Graduation Rates

It is well known that human capital is enhanced by graduation from a college or university. How efficient are such institutions in conveying this mark of human capital? Efficiency and productivity in private higher education is measured by using undergraduate graduation rates as the output, and demographic variables, the quality of the students, and the annual expenditures (adjusted for academic mission) as inputs. Tests of several models using OLS and stochastic frontier analysis confirm that private schools can increase their graduation rates by increasing focused expenditures and through more selective admissions. Estimated elasticities are reported and point toward increasing expenditures as the most responsive method. Estimate graduation efficiencies of 93.0, 91.5, and near 100% are also reported for four, five and six year graduation rates respectively. A rank correlation with the U S News and World Report 2008 rankings is consistent with our measure of relative efficiencies

Estimation of Irrigation Water Demand: A Case Study for the Texas High Plains

On the Texas High Plains, water from the Ogallala aquifer is used to supplement irrigation requirements, since annual rainfall is below 20.5 in/ year. This study addresses land and water demand by testing the effects of water costs, crop prices, and technology on water use and crop production acreages.Ogallala, Irrigation, Water Demand, Technology, Agricultural and Food Policy, Production Economics,