Attrition patterns in a high ability programme for precollege students

Completion and performance data from 92 high ability seventh and eighth grade students in an eight‐week summer programme conducted in 1989 and sponsored by the GTE Service Corporation are examined.     

Tripyrrolidinophosphoric acid triamide as an activator in samarium diiodide reductions

The electrochemical and spectrophotometric characterization of the complex formed from samarium diiodide and 4 equiv of tripyrrolidinophosphoric acid triamide (TPPA) is presented. Kinetic studies indicate that the SmI(2)/TPPA complex possesses reactivity greater than the complex formed between samarium diiodide and 4 equiv of HMPA. Examples of the use of SmI(2)/TPPA in synthesis are presented.     

A note on the integration of competing psychophysical theories

Virtually from its inception psychophysics has been caught on the horns of the dilemma as to the proper form of the fundamental psychophysical law. This paper illustrates an integration of two competing theories.     

Characterization of the complex formed between samarium diiodide and the dehydro dimer of HMPA (diHMPA)

A new ligand that facilitates samarium diiodide-mediated reductions has been developed. Addition of a solution of samarium diiodide to the dehydro dimer of hexamethylphosphoramide results in a purple complex which is an excellent reductant for a variety of organic functionalities. The complex was characterized by the kinetics of reduction of 1-bromodecane, visible spectroscopy, and cyclic voltammetry.     

1H NMR study of cis-trans isomerization in two analogs of the thiol form of thiamine

Proton magnetic resonance (¹H NMR) was used to study cis-trans isomerization in N-methyl-N-(1-methylthio-2-propenyl)formamide and N-benzyl-N-(1-methylthio-2-propenyl)formamide, two analogs of the thiol form of thiamine. Benzene dilution studies and shift reagent studies were used to make resonance assignments, which indicate that the predominant isomer for each analog has the C? C bond trans to the carbonyl oxygen. Shift reagent studies, using Pr(fod)₃ in CCl₄ or CDCl₃, suggest that the reagent may be bonding to both the nitrogen and oxygen atoms of the substrate. For some of the systems studied, varying ρ at constant temperature had the same spectral effect as varying temperature at constant ρ.     

The Classification of Representations f Unramified Hecke Algebras

We give two characterizations of the isolated singularities of the local resolvent function of an operator T ε L(X) at a point ε of a complex Banach space X: in terms of a suitable decomposition of ε, and in terms of the existence of a sequence in X related with the Laurent series of the local resolvent function. Moreover, we introduce the locally chain-finite operators at a point ε and show that T is chain-finite if and only if T is locally chain-finite at every χ ε X.